feat: #65 sea control — 11th ability (v0.43.0)

Adds the sea ability: a fixed set of 12 named sea zones with sole-control
semantics, contest-by-higher-military, and a deterministic per-turn
+1 military/+1 economy bonus for each claimed zone. Durable (owns
GameState.seaZones), additive migration, stub-inert (e2e unaffected).

Fixes #65

Design note: Gitea #65 sketched a free-form 'naval' layer; the implemented
approved design is this richer 'sea' layer with a fixed zone set.

AGENTS.md

@@ -96,6 +96,16 @@ history/
 │   ├── map.ts              # GameState → RegionMap (region key → owner + stable color)
 │   ├── presets.ts          # load preset JSON files from disk
 │   ├── db.ts               # SQLite open/save/load (+ legacy regionStats migration on load, v0.28 #46)
+│   ├── abilities/          # the modular LLM-ability system (v0.40.0 #67) — one file per world lever
+│   │   ├── index.ts        #   the ABILITIES registry (list order = apply order) + the re-export surface
+│   │   ├── types.ts        #   the Ability contract + the AbilityField union
+│   │   ├── shared.ts       #   shared helpers (stat dips / re-derive / ref resolution, …)
+│   │   ├── apply-helpers.ts  #   shared apply-path helpers
+│   │   ├── <name>.ts       #   one module per ability: wars / takeovers / leaders / nuclear /
+│   │   │                   #     ideology / industry / economy / hybrid / disasters (v0.41.0 #63) /
+│   │   │                   #     migration (v0.42.0 #64)
+│   │   ├── *.test.ts       #   per-ability unit tests (registry.test.ts pins the 10-ability contract)
+│   │   └── goldens/        #   pinned prompt goldens (system-no-tool / system-tool / user)
 │   └── *.test.ts           # unit tests (vitest)
 └── src/
     ├── App.tsx             # screen router (home → pick → game) + manual hash router (#/game/<id>); owns game/regions/advisors/busy
@@ -442,6 +452,137 @@ history/
   (`industry: { projects: [] }`) — e2e (CI, `LLM_STUB=1`) is unaffected and the path is unit-tested
   only (`server/engine.test.ts`, `server/protocol.test.ts`, `server/regions.test.ts`,
   `server/db.test.ts`, `scripts/build-region-resources.test.ts`).
+- **Modular LLM abilities — how to add a new one (v0.40.0, #67).**
+  Since v0.40.0 the per-feature LLM levers are a modular registry in `server/abilities/`: one
+  file per ability plus `types.ts` (the `Ability<K>` interface, the closed `AbilityField` union,
+  and the `AbilityCtx` / `UserPromptCtx` shapes), `shared.ts` (the dependency-free `str` /
+  `resolveNationRef` / `resolveRegionKey` / fresh-id primitives the abilities share), and
+  `index.ts` (the ordered `ABILITIES` array — its position is the canonical apply / prompt /
+  payload order). Each ability is a plain object implementing `Ability<K>`: `field` (its
+  `TurnResult` field name), `default()` (a FRESH no-op value), `validate(raw)` (defensive parse
+  into the field's exact shape — never throws), `apply(state, data, ctx)` (mutate the world in
+  place — never throws), `schemaLine()` (its system-prompt JSON line), `constraint()` (its HARD
+  CONSTRAINTS bullet), `isMeaningful(data)` (does a non-default value make the turn meaningful?),
+  `stateFields?` (the `GameState` fields it owns, for the `db.ts` legacy-row migration —
+  `undefined` for turn-transient abilities), `stub()` (the deterministic stub's value — every
+  ability returns `default()`, so e2e is never affected), and `payload(ctx)` (the user-payload
+  keys it contributes — `{}` for turn-transient ones). The engine consumes the registry
+  generically and is never edited to add an ability: `buildSystemPrompt` emits each
+  `schemaLine()` / `constraint()` in `ABILITIES` order (between the `nationOps` block/line and the
+  `markers` line / "- Prefer 1-4 events" bullet), `buildUserPrompt` merges each `payload()` at its
+  historical position, `validateTurnResult` fills each field via `a.validate()`, `isMeaningful`
+  ORs the per-ability predicates, `applyTurnResult` runs `a.apply` in `ABILITIES` order (after the
+  core effects, before markers), the stub fills each field via `a.stub()`, and the "unclear"
+  fallback uses `a.default()`. To add a new ability: (1) add the field's type to `TurnResult` in
+  `shared/protocol.ts` (a required field with a default) and the field name to the `AbilityField`
+  union in `types.ts`; (2) create `server/abilities/<name>.ts` exporting an `Ability<'<name'>`
+  const; (3) import it in `index.ts` and APPEND it to `ABILITIES` (append last — never reorder
+  existing entries; their order is pinned by the goldens and the stub's byte-identical output);
+  (4) re-export any new public names from `index.ts` and from `engine.ts`; (5) if it owns a durable
+  `GameState` field, add it to `shared/types.ts` + the `db.ts` legacy-row migration (additive,
+  never wiped) and declare it in `stateFields`; if it contributes to the user payload, return its
+  keys from `payload()` and extend `UserPromptCtx`; (6) write `server/abilities/<name>.test.ts`
+  (the stub never exercises a new ability, so its apply path is unit-tested only) and — if it
+  changes the system prompt — regenerate the goldens
+  (`REGEN_GOLDENS=1 npx vitest run server/abilities/registry.test.ts`); `user.txt` must stay
+  byte-identical unless the new ability contributes user-payload keys.
+- **Disasters & pandemics — natural / man-made catastrophes with a deterministic dip (v0.41.0, #63).**
+  `TurnResult.disasters = DisastersOps = { events: DisasterEvent[] }` (required, default
+  `{ events: [] }`); `DisasterEvent = { type, target, severity, detail? }` with `type ∈
+  DISASTER_TYPES = earthquake | flood | volcanic | wildfire | famine | plague | epidemic` and
+  `severity ∈ DISASTER_SEVERITIES = minor | moderate | severe`. Like the hybrid layer this is
+  **turn-transient**: it owns NO `GameState` field (no durable list, no `db.ts` change) — a
+  plague or epidemic that persists is simply re-declared each turn it continues. The DETERMINISTIC
+  `DISASTER_EFFECTS` table (`server/abilities/disasters.ts`) maps each `(type, severity)` to a
+  small set of signed stat deltas (a severe plague is the hardest hit; none of them touch
+  `population`, and none move borders — sole ownership is untouched). The `target` resolves like a
+  hybrid op — a nation ref via the shared `resolveNationRef` (id first, then a case-insensitive
+  unique name), else a region key that hits that region's SOLE owner (a key with 0 or 2+ owners, or
+  one absent from the valid-keys manifest, is dropped); there is no `from`/actor field — a
+  catastrophe is not an attack — so (unlike hybrid) a self-target drop does NOT apply.
+  `applyDisasterEvent` (run in the `ABILITIES` loop after territory / wars / economy, before
+  markers) dips the target nation's `stats` (clamped 0–100), mirrors the dip to its regions (the
+  single named region for a region target, else every region it owns — entries with no
+  `regionStats` are skipped), and re-derives the nation's aggregate stats (the same 0-region /
+  no-entry guards, so a 0-region nation keeps its directly-mutated value and the dip persists).
+  `payload()` is `{}` (turn-transient), so the user-prompt golden (`user.txt`) is unchanged; the
+  system prompt gains the field's schema line + constraint bullet (the system goldens were
+  re-baselined in v0.41.0). `isMeaningful` is `events.length > 0`. The stub never proposes a
+  disaster (`{ events: [] }`), so e2e (CI, `LLM_STUB=1`) is unaffected and the path is unit-tested
+  only (`server/abilities/disasters.test.ts`).
+- **Migration & refugees — population flows between nations with a deterministic dip (v0.42.0, #64).**
+  `TurnResult.migration = MigrationOps = { ops: MigrationOp[] }` (required, default
+  `{ ops: [] }`); `MigrationOp = { kind, from, to?, scale, detail? }` with `kind ∈
+  MIGRATION_KINDS = migration | refugees | diaspora | exodus` and `scale ∈
+  MIGRATION_SCALES = small | moderate | large` (`to` is required for every kind except
+  `exodus`, which has no destination). Like the hybrid / disasters layers this is
+  **turn-transient**: it owns NO `GameState` field (no durable list, no `db.ts` change) — a
+  flow that persists is simply re-declared each turn it continues. The DETERMINISTIC
+  `MIGRATION_SOURCE_EFFECTS` / `MIGRATION_DESTINATION_EFFECTS` tables
+  (`server/abilities/migration.ts`) map each `scale` to signed stat deltas (no hidden
+  randomness): the source LOSES population + economy (small −1/−1, moderate −2/−2,
+  large −4/−3) and the destination GAINS population + economy (small +1/+1, moderate
+  +2/+2, large +3/+3); a `large` influx additionally strains the destination's stability by
+  `LARGE_INFLUX_STABILITY_DIP = -2`. Neither side ever moves territory (sole ownership is
+  untouched) and none touch borders. Both `from` and `to` resolve by the shared
+  `resolveNationRef` (id first, then a case-insensitive unique name): an unknown / ambiguous
+  source, a missing / unknown / ambiguous destination, or a **self-flow** (`from` and `to`
+  the same nation) drops the WHOLE op (the source is untouched); `exodus` skips the
+  destination entirely. The from↔to relation then moves one step toward the positive end of
+  the ally/neutral/rival/hostile ladder via the self-contained `shiftRelationTowardPositive`
+  (the mirror of the hybrid layer's `shiftRelationTowardHostile`): capped at `ally` for
+  `refugees` (hosting refugees builds the strongest goodwill), `neutral` for `migration` /
+  `diaspora`, and not at all for `exodus`; a missing relation starts at `neutral` and a
+  `war` relation is NEVER touched (the nudge neither fabricates nor escalates a war).
+  `applyMigrationOp` (run in the `ABILITIES` loop after territory / wars / economy, before
+  markers) applies the source dip, then the destination dip (+ stability strain for `large`),
+  clamps both to 0–100, mirrors each to every region the nation owns (`regionStats`), and
+  re-derives each nation's aggregate `stats` (the same 0-region / no-entry guards, so a
+  0-region nation keeps its directly-mutated value and the effect persists). `payload()` is
+  `{}` (turn-transient), so the user-prompt golden (`user.txt`) is unchanged; the system
+  prompt gains the field's schema line + constraint bullet (the system goldens were
+  re-baselined in v0.42.0). `isMeaningful` is `ops.length > 0`. The stub never proposes a
+  migration (`{ ops: [] }`), so e2e (CI, `LLM_STUB=1`) is unaffected and the path is
+  unit-tested only (`server/abilities/migration.test.ts`). **Design note:** the Gitea #64
+  body sketched a simpler `flows: {type: 'refugees'|'settlers'}` shape with a settler
+  re-claim of no-man's-land; the implemented, approved design is this richer four-kind
+  nation-to-nation **stat** layer that deliberately never moves territory (a no-man's-land
+  re-claim stays the `regionChanges` lever's job).
+- **Sea control — sole control of a fixed set of 12 named sea zones with a deterministic per-turn bonus (v0.43.0, #65).**
+  `TurnResult.sea = SeaOps = { control: SeaControlOp[] }` (required, default `{ control: [] }`);
+  `SeaControlOp = { zone, by }` where `zone` is one of the 12 fixed sea-zone ids from
+  `SEA_ZONES` in `shared/protocol.ts` (`north-atlantic`, `south-atlantic`, `pacific`, `indian`,
+  `mediterranean`, `north-sea`, `baltic`, `arctic`, `black-sea`, `gulf-mexico`, `red-sea`,
+  `sargasso`) and `by` is a nation ref (id first, then a case-insensitive unique name, via the
+  shared `resolveNationRef`; unknown / ambiguous → dropped, never thrown). Like the wars and
+  industry layers this is **durable** (unlike the turn-transient hybrid / disasters / migration
+  layers): it owns the `GameState.seaZones` field (required, `[]` at creation; a legacy SQLite
+  row without the field loads as `[]` — via the generic `ABILITIES` `stateFields` loop in
+  `db.ts`, no `db.ts` code change needed). `applySeaControl` (run in the `ABILITIES` loop after
+  territory / wars / economy, before markers) upserts the turn's ops into `next.seaZones`:
+  per zone (in first-appearance order) a single surviving op sets or replaces the zone's
+  controller (replace in place — preserving position — or append); two or more surviving ops
+  on the same zone for different resolved nations make the zone **contested** — the higher
+  current `stats.military` wins (a tie goes to the earlier-listed op) — deterministic, no
+  hidden randomness. The layer **never touches `territory` / `unowned`** — it is fully parallel
+  to but independent of land. Every committed turn (including a turn with an empty `control`),
+  `applySeaZoneBonuses` grants each existing claim's controller `SEA_ZONE_BONUS = 1` military
+  + 1 economy (clamped to 0–100, mirrored to every region the nation owns, then the nation's
+  derived `stats` re-derived with the same 0-region / no-entry guards as the economy / migration
+  layers, so a 0-region nation keeps its directly-mutated value); a nation controlling several
+  zones stacks the bonus; a claim whose nation no longer exists (removed by a merge / split
+  this turn) is skipped — the claim is kept, never thrown. `isMeaningful` is
+  `control.length > 0`. The system prompt documents the field + constraints (at most 1–2 claims
+  per turn, each narrated in `events`); the user payload **always** carries the current
+  `seaZones` list (even when empty) — `payload()` → `{ seaZones: ctx.seaZones ?? [] }` — the
+  one ability whose `payload()` is not `{}` (the durable list, unlike the turn-transient
+  layers). The **stub never** proposes a sea op (`{ control: [] }`), so e2e (CI, `LLM_STUB=1`)
+  is unaffected and the path is unit-tested only (`server/abilities/sea.test.ts`).
+  **Design note:** the Gitea #65 body sketched a `naval` layer with a free-form `zones`
+  array; the implemented, approved design is this richer `sea` layer with a **fixed set of
+  12 named zones**, sole-control semantics, contest-by-higher-military, and a durable
+  `seaZones` list — a cleaner, more deterministic model that the LLM can reason about without
+  inventing zone names each turn.
 - **Map click → dossier target (owner resolved from the RegionMap, by region key).**
   Clicking a sub-region does NOT open a popup — it switches the dossier to that sub-region's
   owning nation (`focusNation(ownerId, {name})` in `App.tsx`, which also records which region was

CHANGELOG.md

@@ -2,6 +2,46 @@
 
 All notable changes to **History** are listed here, newest first.
 
+## v0.43.0 — 2026-10-16 12:09
+- **#65: Sea control — a `TurnResult.sea` lever letting the LLM declare sole control over a fixed set of 12 named sea zones (North Atlantic, South Atlantic, Pacific, Indian, Mediterranean, North Sea, Baltic, Arctic, Black Sea, Gulf of Mexico, Red Sea, Sargasso), with a deterministic per-turn +1 military / +1 economy bonus for the controlling nation.** It is a **durable** feature (unlike the turn-transient `hybrid` / `disasters` / `migration` layers): `GameState.seaZones` persists across turns and in SQLite, and the user payload **always** carries the current `seaZones` list (even when empty) so the model knows who controls what. It lands as the **11th ability** of the v0.40.0 modular system, in a new `server/abilities/sea.ts` module, **registered last** in the `ABILITIES` registry (after `migration`). Sea control is fully **parallel to but independent of land**: it never touches `territory` / `unowned`, and moving land never touches a sea zone.
+  - **Types (`shared/protocol.ts`).** New `SEA_ZONES` (a frozen array of 12 `{ id, name }` pairs), `SEA_ZONE_IDS` (a `ReadonlySet` of all 12 ids), `isSeaZoneId(id)` (type guard), `seaZoneName(id)` (human-readable name; unknown → raw), `SeaControlOp` (`{ zone; by }`), and `SeaOps` (`{ control: SeaControlOp[] }`); `TurnResult.sea` is **required**, placed between `migration` and `markers`, default `{ control: [] }`. New `SeaZoneClaim` (`{ zone; by }`) in `shared/types.ts`; `GameState.seaZones: SeaZoneClaim[]` is **required** (`[]` at creation; a legacy SQLite row without the field loads as `[]` — additive, never wiped, via the generic `ABILITIES` `stateFields` loop in `db.ts` — no `db.ts` code change needed).
+  - **Ability module (`server/abilities/sea.ts`).** `field: 'sea'`; `default()` / `stub()` → a **fresh** `{ control: [] }` each call; `validate` wraps the exported `validateSeaOps` (defensive, never throws — accepts the `{ control: [...] }` object or a bare array; each op needs a valid `zone` (one of the 12 `SEA_ZONE_IDS`) and a non-empty `by` (trimmed, ≤200) — anything else is dropped); `apply` runs `applySeaControl` then `applySeaZoneBonuses`; `schemaLine()` / `constraint()` supply the prompt text; **`payload()` → `{ seaZones: ctx.seaZones ?? [] }` — the one ability that always emits a user-payload key** (the durable list, even when empty — unlike the turn-transient layers whose `payload()` is `{}`); `isMeaningful` = `control.length > 0`; **`stateFields: ['seaZones']`** (the durable `GameState` field, for the `db.ts` legacy-row migration).
+  - **Contest semantics (`applySeaControl`).** Each op's `by` is resolved via the shared `resolveNationRef` (id first, then a case-insensitive unique name; unknown / ambiguous → dropped, never thrown). Per zone (in first-appearance order): a single surviving op **sets or replaces** the zone's controller in `GameState.seaZones` (replace in place — preserving the entry's position — or append a new one); two or more surviving ops on the same zone for **different** resolved nations make the zone **contested**: the higher current `stats.military` wins (a tie goes to the op listed earlier in the `control` array) — deterministic, no hidden randomness. The layer **never touches `territory` / `unowned`**.
+  - **Per-turn bonus (`applySeaZoneBonuses`).** Every committed turn — **including a turn with an empty `control`** — each existing claim's controller earns `SEA_ZONE_BONUS = 1` military + 1 economy (clamped to 0–100, mirrored to every region the nation owns, then the nation's derived `stats` re-derived with the same 0-region / no-entry guards as the economy / migration layers, so a 0-region nation keeps its directly-mutated value). A nation controlling several zones **stacks** the bonus (one per zone). A claim whose nation no longer exists (removed by a merge / split this turn) is **skipped** — the claim is kept, never thrown.
+  - **Registry & prompt.** `sea` is added **last** in `ABILITIES` (existing order untouched); the system prompt gains the `sea` schema line and its constraint bullet ("at most 1–2 claims per turn, each narrated in `events`"); the **user prompt gains `"seaZones": []` as a new last key** (the intentional deviation from the turn-transient layers — the durable list is always emitted). The two committed system-prompt **goldens** are regenerated (each gains exactly the new `sea` schema line + constraint bullet); the **`user.txt` golden gains `"seaZones": []`** as the last key (verified by diff).
+  - **Tests.** New `server/abilities/sea.test.ts` (**~40 tests**): the zone-id predicate sets; `validateSeaOps` (shape / leniency / drops / field caps); `applySeaControl` (set / replace-in-place / append / contest by military / tie-break / same-nation dedup / name-resolve / unresolvable drop / ambiguous drop / territory-untouched); `applySeaZoneBonuses` (+1/+1 / clamping / stacking / 0-region direct-dip / stale-controller skip / empty no-op / territory-untouched); and the ability const contract (field, `stateFields`, fresh `default()`/`stub()`, `isMeaningful`, `payload()` incl. `?? []`, `validate` wrapping, `apply` ctx wiring). `registry.test.ts` is updated for the **11-ability** contract (order, distinct fields, `fullDefaultTurn()`, `meaningfulFor`, durable fields, composes 12 / `extended[11]`, re-export pin, user-golden 14th arg). New `db.test.ts` legacy-row test (a pre-v0.43 save without `seaZones` loads with `[]`).
+  - **Design note (deviation from the issue body).** The Gitea #65 body sketched a `naval` layer with a free-form `zones` array; the approved design implemented here is the richer `sea` layer with a **fixed set of 12 named zones**, sole-control semantics, contest-by-higher-military, and a durable `seaZones` list — a cleaner, more deterministic model that the LLM can reason about without inventing zone names each turn.
+- **Guarantees.** No client (`src/`) changes, no new runtime deps, `shared/` keeps zero runtime deps, no `@turf`/`@types/geojson` in any `.ts`. All unit tests green (additive); e2e (CI, `LLM_STUB=1`) unaffected (the stub is sea-inert — it never proposes a sea op).
+- **Version** bumped `0.42.0 → 0.43.0`.
+
+## v0.42.0 — 2026-10-16 10:12
+- **#64: Migration & refugees — a `TurnResult.migration` lever letting the LLM declare population flows between nations (ordinary migration / refugee flows / a spreading diaspora / an exodus), with a deterministic per-`scale` effect: the source loses a little population and economy, the destination gains a little (a `large` influx also strains its stability), and the from↔to relation is nudged one step toward the positive end of the ladder.** It is a **turn-transient** feature, exactly like the v0.34 `hybrid` and v0.41 `disasters` layers: **no new `GameState` field, no `db.ts` change, no durable list** — the ops are consumed inside `applyTurnResult` and leave nothing behind. It lands as the **10th ability** of the v0.40.0 modular system, in a new `server/abilities/migration.ts` module, **registered last** in the `ABILITIES` registry (after `disasters`).
+  - **Types (`shared/protocol.ts`).** New `MigrationKind` (`'migration' | 'refugees' | 'diaspora' | 'exodus'`), `MigrationScale` (`'small' | 'moderate' | 'large'`), `MigrationOp` (`{ kind; from; to?; scale; detail? }` — `to` is required for every kind except `exodus`, which has no destination), and `MigrationOps` (`{ ops: MigrationOp[] }`); `TurnResult.migration` is **required**, placed between `disasters` and `markers`, default `{ ops: [] }`.
+  - **Ability module (`server/abilities/migration.ts`).** `field: 'migration'`; `default()` / `stub()` → a **fresh** `{ ops: [] }` each call; `validate` wraps the exported `validateMigrationOps` (defensive, never throws — accepts the `{ ops: [...] }` object or a bare array; each op needs a valid `kind`, a valid `scale`, a non-empty `from` (trimmed, ≤200), and — for every kind except `exodus` — a non-empty `to` (trimmed, ≤200); an optional `detail` (trimmed, ≤300, empty dropped) — anything else is dropped); `apply` runs `applyMigrationOp` per op; `schemaLine()` / `constraint()` supply the prompt text; `payload()` → `{}` (no user-payload keys — both refs resolve from the existing nation ref table); `isMeaningful` = `ops.length > 0`; **no** `stateFields` (turn-transient, no durable `GameState` field).
+  - **Deterministic effects (tables, no hidden randomness).** `MIGRATION_SOURCE_EFFECTS` per scale — the source LOSES: small `{population:-1, economy:-1}`, moderate `{population:-2, economy:-2}`, large `{population:-4, economy:-3}`. `MIGRATION_DESTINATION_EFFECTS` per scale — the destination GAINS: small `{population:+1, economy:+1}`, moderate `{population:+2, economy:+2}`, large `{population:+3, economy:+3}`. `LARGE_INFLUX_STABILITY_DIP = -2` — a `large` influx additionally strains the destination's stability by 2. All clamped to 0–100.
+  - **Apply semantics (`applyMigrationOp`).** Resolution is drop-first: `from` must resolve to a nation (id first, then a unique name; unknown / ambiguous → drop); for every kind except `exodus` the `to` must resolve to a nation **distinct from** `from` (missing / unknown / ambiguous / self-flow → the **whole op** is dropped, the source untouched). Only then is the source dip applied (all four kinds, including `exodus`); `exodus` then returns (no destination, no nudge). Otherwise the destination gain is applied (plus the `large` stability strain), and the from↔to relation is nudged by the self-contained `shiftRelationTowardPositive` — the mirror of the hybrid layer's `shiftRelationTowardHostile`, but toward `ally` (`POSITIVE_ORDER = ['ally','neutral','rival','hostile']`, cap `ally` for `refugees`, `neutral` for `migration` / `diaspora`, none for `exodus`; a missing relation starts at `neutral`; a `war` relation is **never** touched — the nudge neither fabricates nor escalates a war). Each affected nation's dip is clamped to 0–100, **mirrored to every region it owns** (`regionStats`), and its derived `stats` **re-derived** afterwards (the same 0-region / no-entry guards as hybrid / economy / disasters — a 0-region nation keeps its directly-mutated value and the effect persists). It **never moves territory** (sole ownership is untouched). The **stub never** proposes a migration (`{ ops: [] }`), so e2e (CI, `LLM_STUB=1`) is unaffected and the path is covered by unit tests only.
+  - **Registry & prompt.** `migration` is added **last** in `ABILITIES` (existing order untouched); the system prompt gains the `migration` schema line and its constraint bullet ("at most 1–2 per turn, each narrated in `events` as a `social` or `diplomatic` event"); the user prompt is unchanged (`payload()` is `{}`). The two committed system-prompt **goldens** (`system-no-tool.txt`, `system-tool.txt`) are regenerated (each gains exactly the new `migration` schema line + constraint bullet); the **`user.txt` golden stays byte-identical** (no new user-payload keys — verified by checksum).
+  - **Tests.** New `server/abilities/migration.test.ts` (**38 tests**): the kind/scale predicate sets; the three effect tables (exact keys / signs / monotonicity); `validateMigrationOps` (shape / leniency / drops / field caps); `shiftRelationTowardPositive` (one-step nudge, caps, war-untouched, missing→neutral, unknown no-op); `applyMigrationOp` (small / moderate / large source & destination dips, the `large` stability strain, name-based resolve, the relation nudge by kind, war-untouched, exodus-only-source, self-flow drop, unknown / ambiguous source & destination drop, 0-region direct-dip persistence, territory-untouched, clamping at 0 and 100); and the ability const contract (field, no `stateFields`, fresh `default()`/`stub()`, `isMeaningful`, `payload() {}`, `validate` wrapping, `apply` ctx wiring). `registry.test.ts` is updated for the **10-ability** contract (order, distinct fields, `fullDefaultTurn()`, `meaningfulFor`, re-export pin); the goldens are regenerated (verified idempotent).
+  - **Design note (interpretation of the issue body).** The Gitea #64 body sketched a simpler `flows: { type: 'refugees' | 'settlers' }` shape that included a settler **re-claim of no-man's-land**; the refined, approved design implemented here is the richer `migration.ops` union of **four nation-to-nation population-flow kinds** (migration / refugees / diaspora / exodus) — a purely **stat** layer that **never moves territory** (sole ownership stays untouched; a no-man's-land re-claim is deliberately out of scope, as territory movement remains the `regionChanges` lever's job).
+- **Guarantees.** No client (`src/`) changes, no new runtime deps, `shared/` keeps zero runtime deps, and no `@turf`/`@types/geojson` in any `.ts`. All unit tests green (additive); e2e (CI, `LLM_STUB=1`) unaffected (the stub is migration-inert).
+- **Version** bumped `0.41.0 → 0.42.0`.
+
+## v0.41.0 — 2026-10-16 09:07
+- **#63: Disasters & pandemics — a `TurnResult.disasters` lever letting the LLM declare natural/man-made disasters (earthquake / flood / volcanic / wildfire / famine / plague / epidemic) on a nation or a region, with a deterministic stat dip (stability / economy / military).** It is a **turn-transient** feature, exactly like the v0.34 `hybrid` layer: **no new `GameState` field, no `db.ts` change, no durable list** — the ops are consumed inside `applyTurnResult` and leave nothing behind. It lands as the **9th ability** of the v0.40.0 modular system, in a new `server/abilities/disasters.ts` module, **registered last** in the `ABILITIES` registry (after `ideology`, before the loop appends `markers` / `nationOps`).
+  - **Types (`shared/protocol.ts`).** New `DisasterType` (`'earthquake' | 'flood' | 'volcanic' | 'wildfire' | 'famine' | 'plague' | 'epidemic'`), `DisasterSeverity` (`'minor' | 'moderate' | 'severe'`), `DisasterEvent` (`{ type; target; severity; detail? }` — `target` is a nation ref **or** a region key), and `DisastersOps` (`{ events: DisasterEvent[] }`); `TurnResult.disasters` is **required**, placed between `ideology` and `markers`, default `{ events: [] }`.
+  - **Ability module (`server/abilities/disasters.ts`).** `field: 'disasters'`; `default()` / `stub()` → a **fresh** `{ events: [] }` each call; `validate` wraps the exported `validateDisasterEvents` (defensive, never throws — accepts the `{ events: [...] }` object or a bare array; each event needs a valid `type`, a valid `severity`, and a non-empty `target` (trimmed, ≤120) — anything else is dropped, with a per-turn cap); `apply` runs `applyDisasterEvent` per event; `schemaLine()` / `constraint()` supply the prompt text; `payload()` → `{}` (no user-payload keys — targets resolve from the existing ref table); `isMeaningful` = `events.length > 0`; **no** `stateFields` (turn-transient, no durable `GameState` field).
+  - **Deterministic effects (`DISASTER_EFFECTS`).** A pure `(type, severity) → stat-dip` table — **no hidden randomness**. `population` is never touched. Earthquake and famine dip **both** `stability` and `economy` (−2 / −4 / −7 for minor / moderate / severe); flood dips `economy` (−2 / −3 / −6) and `stability` (−1 / −2 / −4); volcanic dips `economy` (−2 / −4 / −7) and `stability` (−2 / −3 / −6); wildfire dips **only** `economy` (−2 / −4 / −7); plague dips `stability` (−3 / −5 / −9) and `military` (−2 / −3 / −6); epidemic dips `stability` (−2 / −4 / −7) and `military` (−1 / −2 / −4).
+  - **Apply semantics (`applyDisasterEvent`).** The `target` is resolved exactly like a hybrid op (`resolveHybridTarget`): a resolvable nation ref hits every region the nation owns; a region key hits its **sole** owner; a 0-owner or 2+-owner region key is **dropped** (never thrown). The one deliberate difference from hybrid: a disaster has **no `from` field**, so there is **no self-target drop** — a nation may suffer a disaster it itself declared. The dip is clamped to 0–100, **mirrored to every region the target owns** (`regionStats`), and the target's derived `stats` is **re-derived** afterwards (the same 0-region / no-entry guards as hybrid / economy / industry — a 0-region nation keeps its directly-mutated value). It never moves territory (sole ownership is untouched). The **stub never** declares a disaster (`{ events: [] }`), so e2e (CI, `LLM_STUB=1`) is unaffected and the path is covered by unit tests only.
+  - **Registry & prompt.** `disasters` is added last in `ABILITIES`; the system prompt gains the `disasters` schema line and its constraint bullet ("at most 1–2 per turn, each narrated in `events`"); the user prompt is unchanged (`payload()` is `{}`). The two committed system-prompt **goldens** (`system-no-tool.txt`, `system-tool.txt`) are regenerated (each gains exactly the new `disasters` schema line + constraint bullet); the **`user.txt` golden stays byte-identical** (no new user-payload keys — verified by checksum).
+  - **Tests.** New `server/abilities/disasters.test.ts` (**33 tests**): the type/severity predicate sets; `validateDisasterEvents` (shape / leniency / drops / cap); `applyDisasterEvent` exact dips (nation target, single-region target, region gated by `validKeys`, clamping at 0, 0-owner / 2+-owner region drops, unknown-key drop, unknown / ambiguous ref drops, case-insensitive name resolve, 0-region direct-dip persistence, missing-`regionStats`-entry skip); and the ability const contract (field, no `stateFields`, fresh `default()`/`stub()`, `isMeaningful`, `payload() {}`, `validate` wrapping, `apply` ctx wiring). `registry.test.ts` is updated for the **9-ability** contract (order, fields, `fullDefaultTurn()`, `meaningfulFor`, re-export pin); the goldens are regenerated (verified idempotent).
+- **Secondary cleanups from the v0.40.0 refactor (folded into this release):**
+  - **AGENTS.md** — `server/abilities/` is added to the Layout tree (the per-ability files, tests, and goldens); Conventions gains a "Modular LLM abilities — how to add a new one (v0.40.0, #67)" bullet and a "Disasters & pandemics (v0.41.0, #63)" bullet.
+  - The **orphaned `validateTakeovers` JSDoc** (left over after the v0.40 refactor removed the function body) is deleted.
+  - Both **inline `as unknown` double-casts** are folded into the single top-level `./abilities` import (`AbilityCtx` + `UserPromptCtx` types).
+  - **`str()` is de-duplicated** — imported from `./abilities/shared` instead of the local copy.
+- **Guarantees.** No client (`src/`) changes, no new runtime deps, `shared/` keeps zero runtime deps, and no `@turf`/`@types/geojson` in any `.ts`. All unit tests green (additive); e2e (CI, `LLM_STUB=1`) unaffected (the stub is disasters-inert).
+- **Version** bumped `0.40.0 → 0.41.0`.
+
 ## v0.40.0 — 2026-10-16 07:14
 - **#67: Modular LLM-ability system — the 8 per-feature LLM abilities are extracted from `server/engine.ts` into an ordered `ABILITIES` registry (`server/abilities/`).** A pure, **behavior-preserving** refactor: each per-ability concern (validate / schema-line / constraint / payload / meaningfulness / apply / stub-default / durable-state-field) moves into one file per ability, assembled into a single ordered registry that the engine iterates uniformly. **Nothing observable changes** — the system prompt, user prompt, `applyTurnResult` world-state mutations, and the deterministic stub are all byte-for-byte identical to v0.39.0 (pinned by new golden fixtures + registry tests), and `server/engine.ts` re-exports every name its existing callers import, so `server/index.ts` and all tests work with zero edits.
   - **New `server/abilities/` package.**

package.json

@@ -1,6 +1,6 @@
 {
   "name": "history",
-  "version": "0.40.0",
+  "version": "0.43.0",
   "private": true,
   "type": "module",
   "description": "AI-driven alternate-history simulator — the LLM is the world engine (Pax Historia style).",

server/abilities/disasters.test.ts

@@ -0,0 +1,447 @@
+// Unit tests for the DISASTERS & PANDEMICS ability (v0.41.0, #63) — the
+// modular, turn-transient LLM-ability that applies a deterministic
+// (type, severity) stat dip to a nation or a single region. This is the
+// ability's own test file (the registry's cross-cutting guarantees — order,
+// distinct fields, the system/user goldens — are covered by
+// ./registry.test.ts). The stub never proposes a disaster, so the apply path
+// is exercised here, not by the e2e suite.
+
+import { describe, expect, it } from 'vitest';
+
+import type { AbilityCtx } from './types';
+import {
+  DISASTER_EFFECTS,
+  DISASTER_SEVERITIES,
+  DISASTER_TYPES,
+  applyDisasterEvent,
+  disasters,
+  isDisasterSeverity,
+  isDisasterType,
+  validateDisasterEvents,
+} from './disasters';
+
+import type { DisasterEvent, DisastersOps } from '../../shared/protocol';
+import type { GameState, Nation, NationStats, RegionStats } from '../../shared/types';
+
+// ---------------------------------------------------------------------------
+// Fixture helpers
+// ---------------------------------------------------------------------------
+
+/** Build a NationStats from the four canonical indices (military, economy, stability, population). */
+function NS(military: number, economy: number, stability: number, population: number): NationStats {
+  return { military, economy, stability, population };
+}
+
+/** Build a RegionStats from the four canonical indices. */
+function RS(military: number, economy: number, stability: number, population: number): RegionStats {
+  return { military, economy, stability, population };
+}
+
+/** A minimal nation: the given id/name/stats/region-key territory, neutral relations. */
+function mkNation(id: string, name: string, stats: NationStats, territory: string[]): Nation {
+  return { id, name, type: 'major', stats, territory, relations: {} };
+}
+
+/**
+ * A minimal GameState carrying the given nations (keyed by id) and per-region
+ * stats. Every other required field is at its fresh-game baseline, so a test
+ * can focus purely on the disaster dip.
+ */
+function mkState(
+  nations: Record<string, Nation>,
+  regionStats: Record<string, RegionStats>,
+): GameState {
+  return {
+    id: 'g1',
+    presetId: 'test',
+    presetTitle: 'Test',
+    playerNationId: Object.keys(nations)[0] ?? 'uk',
+    turn: 1,
+    date: '1939-09-01',
+    nations,
+    events: [],
+    pending: [],
+    version: 1,
+    unowned: [],
+    pendingNationOps: [],
+    markers: [],
+    regionStats,
+    wars: [],
+    trades: [],
+    embargoes: [],
+    industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
+  };
+}
+
+/** A minimal AbilityCtx for the ability's `apply` (no manifests loaded). */
+function mkCtx(state: GameState, validRegionKeys?: ReadonlySet<string>): AbilityCtx {
+  return {
+    previous: state,
+    actingTurn: state.turn,
+    ...(validRegionKeys ? { validRegionKeys } : {}),
+  };
+}
+
+// ---------------------------------------------------------------------------
+// Type / severity constants + predicates
+// ---------------------------------------------------------------------------
+
+describe('DISASTER_TYPES / DISASTER_SEVERITIES', () => {
+  it('exposes exactly the seven types and three severities', () => {
+    expect([...DISASTER_TYPES]).toEqual([
+      'earthquake',
+      'flood',
+      'volcanic',
+      'wildfire',
+      'famine',
+      'plague',
+      'epidemic',
+    ]);
+    expect([...DISASTER_SEVERITIES]).toEqual(['minor', 'moderate', 'severe']);
+  });
+
+  it('every (type, severity) pair dips at least one stat, never population', () => {
+    for (const t of DISASTER_TYPES) {
+      for (const s of DISASTER_SEVERITIES) {
+        const dips = DISASTER_EFFECTS[t][s];
+        expect(dips).toBeDefined();
+        const keys = Object.keys(dips);
+        expect(keys.length).toBeGreaterThan(0);
+        expect(keys).not.toContain('population');
+        for (const k of keys) expect(dips[k as keyof typeof dips]).toBeLessThan(0);
+      }
+    }
+  });
+});
+
+describe('isDisasterType / isDisasterSeverity', () => {
+  it('accepts each known type and rejects unknown / non-strings', () => {
+    for (const t of DISASTER_TYPES) expect(isDisasterType(t)).toBe(true);
+    expect(isDisasterType('tsunami')).toBe(false);
+    expect(isDisasterType('Earthquake')).toBe(false); // case-sensitive
+    expect(isDisasterType('')).toBe(false);
+    expect(isDisasterType(42)).toBe(false);
+    expect(isDisasterType(null)).toBe(false);
+    expect(isDisasterType(undefined)).toBe(false);
+  });
+
+  it('accepts each known severity and rejects unknown / non-strings', () => {
+    for (const s of DISASTER_SEVERITIES) expect(isDisasterSeverity(s)).toBe(true);
+    expect(isDisasterSeverity('extreme')).toBe(false);
+    expect(isDisasterSeverity('Minor')).toBe(false); // case-sensitive
+    expect(isDisasterSeverity('')).toBe(false);
+    expect(isDisasterSeverity(3)).toBe(false);
+    expect(isDisasterSeverity(undefined)).toBe(false);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// validateDisasterEvents
+// ---------------------------------------------------------------------------
+
+describe('validateDisasterEvents', () => {
+  const valid: DisasterEvent = { type: 'earthquake', target: 'uk', severity: 'severe' };
+
+  it('accepts the { events: [...] } shape', () => {
+    expect(validateDisasterEvents({ events: [valid] })).toEqual([valid]);
+  });
+
+  it('accepts a bare array (lenient about the wrapper)', () => {
+    expect(validateDisasterEvents([valid])).toEqual([valid]);
+  });
+
+  it('drops an event with an unknown type, keeping the valid one', () => {
+    const out = validateDisasterEvents({
+      events: [
+        { type: 'tsunami', target: 'uk', severity: 'minor' },
+        valid,
+      ],
+    });
+    expect(out).toEqual([valid]);
+  });
+
+  it('drops an event with a missing type', () => {
+    const out = validateDisasterEvents({
+      events: [{ target: 'uk', severity: 'minor' }, valid],
+    });
+    expect(out).toEqual([valid]);
+  });
+
+  it('drops an event with an unknown severity, keeping the valid one', () => {
+    const out = validateDisasterEvents({
+      events: [
+        { type: 'plague', target: 'uk', severity: 'extreme' },
+        valid,
+      ],
+    });
+    expect(out).toEqual([valid]);
+  });
+
+  it('drops an event with a missing severity', () => {
+    const out = validateDisasterEvents({
+      events: [{ type: 'plague', target: 'uk' }, valid],
+    });
+    expect(out).toEqual([valid]);
+  });
+
+  it('drops an event with an empty / whitespace target', () => {
+    const out = validateDisasterEvents({
+      events: [
+        { type: 'plague', target: '   ', severity: 'minor' },
+        { type: 'plague', target: '', severity: 'minor' },
+        valid,
+      ],
+    });
+    expect(out).toEqual([valid]);
+  });
+
+  it('caps a non-empty detail at 300 chars and keeps a short one', () => {
+    const long = 'x'.repeat(500);
+    const out = validateDisasterEvents({
+      events: [
+        { type: 'plague', target: 'uk', severity: 'minor', detail: long },
+        { type: 'flood', target: 'de', severity: 'minor', detail: 'a short note' },
+      ],
+    });
+    expect(out).toEqual([
+      { type: 'plague', target: 'uk', severity: 'minor', detail: 'x'.repeat(300) },
+      { type: 'flood', target: 'de', severity: 'minor', detail: 'a short note' },
+    ]);
+  });
+
+  it('omits the detail key entirely when detail is empty / missing', () => {
+    const out = validateDisasterEvents({
+      events: [
+        { type: 'flood', target: 'uk', severity: 'minor', detail: '' },
+        { type: 'flood', target: 'de', severity: 'minor' },
+      ],
+    });
+    expect(out).toEqual([
+      { type: 'flood', target: 'uk', severity: 'minor' },
+      { type: 'flood', target: 'de', severity: 'minor' },
+    ]);
+    expect(out[0]).not.toHaveProperty('detail');
+  });
+
+  it('drops non-object event entries', () => {
+    const out = validateDisasterEvents({ events: ['not-an-object', 7, null, valid] });
+    expect(out).toEqual([valid]);
+  });
+
+  it('yields { events: [] } (here, []) for a missing / malformed top-level value', () => {
+    expect(validateDisasterEvents(undefined)).toEqual([]);
+    expect(validateDisasterEvents(null)).toEqual([]);
+    expect(validateDisasterEvents('nope')).toEqual([]);
+    expect(validateDisasterEvents(5)).toEqual([]);
+    expect(validateDisasterEvents({})).toEqual([]);
+    expect(validateDisasterEvents({ events: 'not-an-array' })).toEqual([]);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// applyDisasterEvent — the deterministic dip
+// ---------------------------------------------------------------------------
+
+describe('applyDisasterEvent', () => {
+  it('a nation target: dips the nation AND every region it owns, then re-derives (identical values pass through)', () => {
+    // uk owns three identical regions; all stats identical → the re-derived
+    // aggregate equals the dipped values exactly.
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1', 'g2', 'g3']) },
+      { g1: RS(50, 50, 50, 50), g2: RS(50, 50, 50, 50), g3: RS(50, 50, 50, 50) },
+    );
+    applyDisasterEvent(state, { type: 'earthquake', target: 'uk', severity: 'moderate' });
+    // earthquake moderate = stability -4, economy -4 (military / population untouched)
+    expect(state.nations.uk.stats).toEqual(NS(50, 46, 46, 50));
+    for (const k of ['g1', 'g2', 'g3']) expect(state.regionStats[k]).toEqual(RS(50, 46, 46, 50));
+  });
+
+  it('a region target: dips ONLY the named region (the sibling region is untouched)', () => {
+    // uk owns g1 and g2 (identical). Target the region key g1 → only g1 dips.
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1', 'g2']) },
+      { g1: RS(50, 50, 50, 50), g2: RS(50, 50, 50, 50) },
+    );
+    applyDisasterEvent(state, { type: 'wildfire', target: 'g1', severity: 'severe' });
+    // wildfire severe = economy -7 only
+    expect(state.regionStats.g1).toEqual(RS(50, 43, 50, 50));
+    expect(state.regionStats.g2).toEqual(RS(50, 50, 50, 50)); // untouched
+    // re-derive (equal weights, min-biased median) → the nation takes the dipped value
+    expect(state.nations.uk.stats).toEqual(NS(50, 43, 50, 50));
+  });
+
+  it('a region target resolved by a validKeys-gated key hits its sole owner', () => {
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1']) },
+      { g1: RS(50, 50, 50, 50) },
+    );
+    applyDisasterEvent(
+      state,
+      { type: 'famine', target: 'g1', severity: 'moderate' },
+      undefined,
+      new Set(['g1']),
+    );
+    // famine moderate = economy -4, stability -4
+    expect(state.regionStats.g1).toEqual(RS(50, 46, 46, 50));
+    expect(state.nations.uk.stats).toEqual(NS(50, 46, 46, 50));
+  });
+
+  it('clamps every dip at 0 (never negative)', () => {
+    // low stability + military; a severe plague (stability -9, military -6) floors both.
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(3, 50, 3, 50), ['g1']) },
+      { g1: RS(3, 50, 3, 50) },
+    );
+    applyDisasterEvent(state, { type: 'plague', target: 'uk', severity: 'severe' });
+    expect(state.nations.uk.stats).toEqual(NS(0, 50, 0, 50));
+    expect(state.regionStats.g1).toEqual(RS(0, 50, 0, 50));
+  });
+
+  it('a 0-owner region is untargetable (the event is dropped, nothing dips)', () => {
+    // 'x1' is owned by nobody; no validKeys supplied, so the owners check drops it.
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1']) },
+      { g1: RS(50, 50, 50, 50) },
+    );
+    applyDisasterEvent(state, { type: 'plague', target: 'x1', severity: 'severe' });
+    expect(state.nations.uk.stats).toEqual(NS(50, 50, 50, 50)); // untouched
+    expect(state.regionStats.g1).toEqual(RS(50, 50, 50, 50));
+  });
+
+  it('a region with 2+ owners is untargetable (the event is dropped, neither dips)', () => {
+    // corrupt double-ownership of 'y1'
+    const state = mkState(
+      {
+        uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['y1']),
+        de: mkNation('de', 'DE', NS(60, 60, 60, 60), ['y1']),
+      },
+      { y1: RS(50, 50, 50, 50) },
+    );
+    applyDisasterEvent(state, { type: 'plague', target: 'y1', severity: 'severe' });
+    expect(state.nations.uk.stats).toEqual(NS(50, 50, 50, 50)); // untouched
+    expect(state.nations.de.stats).toEqual(NS(60, 60, 60, 60)); // untouched
+  });
+
+  it('an unknown region key (gated by validKeys) is dropped', () => {
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1']) },
+      { g1: RS(50, 50, 50, 50) },
+    );
+    // 'zzz' is not in the manifest → dropped before the owners check.
+    applyDisasterEvent(state, { type: 'plague', target: 'zzz', severity: 'severe' }, undefined, new Set(['g1']));
+    expect(state.nations.uk.stats).toEqual(NS(50, 50, 50, 50));
+  });
+
+  it('an unknown nation reference is dropped (no throw, no dip)', () => {
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1']) },
+      { g1: RS(50, 50, 50, 50) },
+    );
+    applyDisasterEvent(state, { type: 'plague', target: 'ghost', severity: 'severe' });
+    expect(state.nations.uk.stats).toEqual(NS(50, 50, 50, 50));
+    expect(state.regionStats.g1).toEqual(RS(50, 50, 50, 50));
+  });
+
+  it('an ambiguous nation reference (two share the name) is dropped', () => {
+    const state = mkState(
+      {
+        a: mkNation('a', 'Same', NS(50, 50, 50, 50), ['g1']),
+        b: mkNation('b', 'Same', NS(70, 70, 70, 70), ['d1']),
+      },
+      { g1: RS(50, 50, 50, 50), d1: RS(70, 70, 70, 70) },
+    );
+    applyDisasterEvent(state, { type: 'plague', target: 'Same', severity: 'severe' });
+    expect(state.nations.a.stats).toEqual(NS(50, 50, 50, 50)); // untouched
+    expect(state.nations.b.stats).toEqual(NS(70, 70, 70, 70)); // untouched
+  });
+
+  it('resolves a nation by (case-insensitive) name, not just id', () => {
+    const state = mkState(
+      { uk: mkNation('uk', 'United Kingdom', NS(50, 50, 50, 50), ['g1']) },
+      { g1: RS(50, 50, 50, 50) },
+    );
+    applyDisasterEvent(state, { type: 'epidemic', target: 'united kingdom', severity: 'moderate' });
+    // epidemic moderate = stability -4, military -2
+    expect(state.nations.uk.stats).toEqual(NS(48, 50, 46, 50));
+    expect(state.regionStats.g1).toEqual(RS(48, 50, 46, 50));
+  });
+
+  it('a 0-region nation keeps its directly-dipped stats (no re-derive to zero)', () => {
+    const iso = mkNation('iso', 'Iso', NS(50, 50, 50, 50), []);
+    const state = mkState({ iso }, {});
+    applyDisasterEvent(state, { type: 'epidemic', target: 'iso', severity: 'moderate' });
+    // epidemic moderate = stability -4, military -2 — the direct dip persists
+    expect(state.nations.iso.stats).toEqual(NS(48, 50, 46, 50));
+    expect(state.regionStats).toEqual({});
+  });
+
+  it('a region with no regionStats entry is skipped (the nation still dips + re-derives from its other regions)', () => {
+    // uk owns g1 (has stats) and g2 (no entry). Target the nation → the dip
+    // mirrors to g1 only (g2 has no entry to dip); re-derive uses g1 alone.
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1', 'g2']) },
+      { g1: RS(50, 50, 50, 50) },
+    );
+    applyDisasterEvent(state, { type: 'earthquake', target: 'uk', severity: 'moderate' });
+    expect(state.regionStats.g1).toEqual(RS(50, 46, 46, 50));
+    expect(state.regionStats).not.toHaveProperty('g2'); // never created
+    expect(state.nations.uk.stats).toEqual(NS(50, 46, 46, 50));
+  });
+});
+
+// ---------------------------------------------------------------------------
+// The Ability object
+// ---------------------------------------------------------------------------
+
+describe('disasters (Ability)', () => {
+  it('owns the "disasters" field and declares NO durable state fields (turn-transient)', () => {
+    expect(disasters.field).toBe('disasters');
+    expect(disasters.stateFields).toBeUndefined();
+  });
+
+  it('default() and stub() are fresh, empty { events: [] } values', () => {
+    expect(disasters.default()).toEqual({ events: [] });
+    expect(disasters.stub()).toEqual({ events: [] });
+    // fresh on every call (never a shared mutable reference)
+    expect(disasters.default()).not.toBe(disasters.default());
+    expect(disasters.default().events).not.toBe(disasters.default().events);
+    expect(disasters.stub()).not.toBe(disasters.stub());
+  });
+
+  it('isMeaningful is true iff there is at least one event', () => {
+    expect(disasters.isMeaningful({ events: [] })).toBe(false);
+    expect(disasters.isMeaningful({ events: [{ type: 'plague', target: 'uk', severity: 'minor' }] })).toBe(
+      true,
+    );
+  });
+
+  it('payload() is always empty (the layer is turn-transient)', () => {
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1']) },
+      { g1: RS(50, 50, 50, 50) },
+    );
+    expect(disasters.payload({ state })).toEqual({});
+  });
+
+  it('validate() wraps the low-level validator into the { events } field shape', () => {
+    const valid = { type: 'flood', target: 'uk', severity: 'minor' } as DisasterEvent;
+    expect(disasters.validate({ events: [valid] })).toEqual({ events: [valid] });
+    expect(disasters.validate(undefined)).toEqual({ events: [] });
+    expect(disasters.validate([valid])).toEqual({ events: [valid] }); // bare array leniency
+  });
+
+  it('apply() wires ctx.geoOf + ctx.validRegionKeys through to the dip', () => {
+    const state = mkState(
+      { uk: mkNation('uk', 'UK', NS(50, 50, 50, 50), ['g1']) },
+      { g1: RS(50, 50, 50, 50) },
+    );
+    const ctx = mkCtx(state, new Set(['g1']));
+    const data: DisastersOps = { events: [{ type: 'volcanic', target: 'g1', severity: 'moderate' }] };
+    disasters.apply(state, data, ctx);
+    // volcanic moderate = economy -4, stability -3
+    expect(state.regionStats.g1).toEqual(RS(50, 46, 47, 50));
+    expect(state.nations.uk.stats).toEqual(NS(50, 46, 47, 50));
+  });
+});

server/abilities/disasters.ts

@@ -0,0 +1,259 @@
+// The DISASTERS & PANDEMICS ability (v0.41.0, #63) as a modular LLM-ability
+// (v0.40.0, #67). Natural and man-made catastrophes — earthquakes, floods,
+// volcanic eruptions, wildfires, famines, plagues, and epidemics — hit a
+// nation or a single region each turn. Unlike most other abilities this one
+// is **turn-transient**: it owns NO `GameState` field (no durable list, no
+// `db.ts` change) — exactly like the hybrid layer. Each event carries a
+// `type` and a `severity`, and the engine applies a DETERMINISTIC stat dip
+// chosen from the `(type, severity)` lookup table below (no hidden
+// randomness — the LLM chooses the type and severity, the table decides the
+// magnitude). The dip lands on the target nation's `stats` (clamped 0–100)
+// AND on the target's regions (`regionStats` — the single named region when
+// the target was a region key, otherwise every region the target owns), and
+// the target's derived `stats` are re-derived afterwards (the same 0-region /
+// no-entry guards as hybrid / economy / industry, so a 0-region nation keeps
+// its directly-mutated value and the dip persists to the next turn). The
+// target is a nation (resolved by the shared `resolveNationRef`) or a region
+// key (which hits its SOLE owner); a key with 0 or 2+ owners is untargetable.
+// There is no acting-nation (`from`) field on a disaster — a catastrophe is
+// not an attack, so the hybrid's self-target drop does not apply. Malformed
+// events and unresolvable targets are dropped, never thrown.
+
+import { clampStat, deriveNationStats } from '../../shared/protocol';
+import type {
+  DisasterEvent,
+  DisasterSeverity,
+  DisasterType,
+} from '../../shared/protocol';
+import type { GameState, Nation, NationStats, StatKey } from '../../shared/types';
+import { resolveNationRef, str } from './shared';
+import type { Ability } from './types';
+
+/** The seven disaster types a turn can declare (v0.41.0, #63). */
+export const DISASTER_TYPES: readonly DisasterType[] = [
+  'earthquake',
+  'flood',
+  'volcanic',
+  'wildfire',
+  'famine',
+  'plague',
+  'epidemic',
+];
+
+/** The three severity levels a disaster event can carry (v0.41.0, #63). */
+export const DISASTER_SEVERITIES: readonly DisasterSeverity[] = ['minor', 'moderate', 'severe'];
+
+const VALID_DISASTER_TYPES = new Set<string>(DISASTER_TYPES);
+const VALID_SEVERITIES = new Set<string>(DISASTER_SEVERITIES);
+
+/** True when `t` is one of the seven known disaster types (v0.41.0, #63). */
+export function isDisasterType(t: unknown): t is DisasterType {
+  return typeof t === 'string' && VALID_DISASTER_TYPES.has(t);
+}
+
+/** True when `s` is one of the three known disaster severities (v0.41.0, #63). */
+export function isDisasterSeverity(s: unknown): s is DisasterSeverity {
+  return typeof s === 'string' && VALID_SEVERITIES.has(s);
+}
+
+/**
+ * (v0.41.0, #63) The DETERMINISTIC per-`(type, severity)` stat dip of a
+ * disaster event. Each pair maps to a small set of signed (negative) stat
+ * deltas: no hidden randomness — the LLM picks the type and severity, the
+ * table decides the magnitude. Population is never touched (a disaster hurts
+ * military / economy / stability, never the head-count). Every (type,
+ * severity) combination dips at least one stat (none is purely
+ * informational).
+ */
+export const DISASTER_EFFECTS: Record<DisasterType, Record<DisasterSeverity, Partial<Record<StatKey, number>>>> = {
+  earthquake: {
+    minor: { stability: -2, economy: -2 },
+    moderate: { stability: -4, economy: -4 },
+    severe: { stability: -7, economy: -7 },
+  },
+  flood: {
+    minor: { economy: -2, stability: -1 },
+    moderate: { economy: -3, stability: -2 },
+    severe: { economy: -6, stability: -4 },
+  },
+  volcanic: {
+    minor: { economy: -2, stability: -2 },
+    moderate: { economy: -4, stability: -3 },
+    severe: { economy: -7, stability: -6 },
+  },
+  wildfire: {
+    minor: { economy: -2 },
+    moderate: { economy: -4 },
+    severe: { economy: -7 },
+  },
+  famine: {
+    minor: { economy: -2, stability: -2 },
+    moderate: { economy: -4, stability: -4 },
+    severe: { economy: -7, stability: -7 },
+  },
+  plague: {
+    minor: { stability: -3, military: -2 },
+    moderate: { stability: -5, military: -3 },
+    severe: { stability: -9, military: -6 },
+  },
+  epidemic: {
+    minor: { stability: -2, military: -1 },
+    moderate: { stability: -4, military: -2 },
+    severe: { stability: -7, military: -4 },
+  },
+};
+
+/**
+ * (v0.41.0, #63) Validate the raw `disasters` field of a turn into a safe
+ * list of {@link DisasterEvent}s. Defensive like the rest of the parser — never throws.
+ * The raw value may be the object `{ events: [...] }` (the TurnResult shape)
+ * or a bare array (be lenient about either). Each event needs a known `type`
+ * (one of {@link DISASTER_TYPES}), a known `severity` (one of
+ * {@link DISASTER_SEVERITIES}), and a non-empty `target` (a nation id/name or
+ * a region key, capped at 200 chars); a non-empty `detail` is capped at 300
+ * chars. An event with an unknown / missing `type`, an unknown / missing
+ * `severity`, or an empty `target` is dropped. Resolution of `target` to a
+ * concrete nation (or a region's sole owner) happens at apply time
+ * (`applyDisasterEvent`), not here. A missing / malformed top-level value
+ * yields `{ events: [] }`.
+ */
+export function validateDisasterEvents(raw: unknown): DisasterEvent[] {
+  let list: unknown[] | null = null;
+  if (Array.isArray(raw)) {
+    list = raw;
+  } else if (raw && typeof raw === 'object') {
+    const inner = (raw as Record<string, unknown>).events;
+    if (Array.isArray(inner)) list = inner;
+  }
+  if (!list) return [];
+  const out: DisasterEvent[] = [];
+  for (const e of list) {
+    if (!e || typeof e !== 'object') continue;
+    const o = e as Record<string, unknown>;
+    if (!isDisasterType(o.type)) continue; // unknown / missing type: drop
+    if (!isDisasterSeverity(o.severity)) continue; // unknown / missing severity: drop
+    const target = str(o.target, 200);
+    if (!target) continue; // empty / missing target: drop
+    const detail = str(o.detail, 300);
+    out.push({
+      type: o.type,
+      target,
+      severity: o.severity,
+      ...(detail ? { detail } : {}),
+    });
+  }
+  return out;
+}
+
+/**
+ * (v0.41.0, #63) Resolve a disaster event's `target` (a nation id/name OR a
+ * region key) to the concrete nation it affects. A nation ref resolves via
+ * {@link resolveNationRef}; a region key resolves to its SOLE owner (a region
+ * with zero or 2+ owners can't be a valid target). Returns the affected
+ * nation plus the specific region key (when the target was a region) so the
+ * dip can land on just that region's entry. `validKeys` (when supplied)
+ * gates the region-key path; a ref that is neither a known nation nor a
+ * valid region key returns `null`. Pure; never throws.
+ *
+ * NOTE: there is no acting-nation (`from`) field on a disaster — a
+ * catastrophe is not an attack, so (unlike the hybrid layer) a self-target
+ * drop does NOT apply: an earthquake can hit the nation it is declared
+ * against.
+ */
+function resolveDisasterTarget(
+  state: GameState,
+  target: string,
+  validKeys?: ReadonlySet<string>,
+): { nation: Nation; regionKey?: string } | null {
+  const id = resolveNationRef(state, target);
+  if (id !== null) {
+    const n = state.nations[id];
+    return n ? { nation: n } : null;
+  }
+  const key = (target ?? '').trim();
+  if (!key) return null;
+  if (validKeys && !validKeys.has(key)) return null; // unknown region key
+  const owners = Object.values(state.nations).filter((n) => n.territory.includes(key));
+  if (owners.length !== 1) return null; // 0 or 2+ owners: not a targetable region
+  return { nation: owners[0], regionKey: key };
+}
+
+/** Apply each signed dip in `dips` to a stats record in place (clamped). */
+function applyDips(stats: NationStats, dips: Partial<Record<StatKey, number>>): void {
+  (Object.keys(dips) as StatKey[]).forEach((k) => {
+    const d = dips[k];
+    if (typeof d === 'number') stats[k] = clampStat(stats[k] + d);
+  });
+}
+
+/**
+ * (v0.41.0, #63) Apply ONE disaster event to the (cloned) `next` state,
+ * mutating it in place and never throwing. Resolution order:
+ *   1. `target` must resolve to a concrete nation (a nation ref, or a region
+ *      key's sole owner); an unresolvable target (unknown / ambiguous ref, a
+ *      region with 0 or 2+ owners, or an unknown region key) drops the event.
+ * Then the deterministic `(type, severity)` dip from {@link DISASTER_EFFECTS}
+ * is applied:
+ *   - the target nation's `stats` is dipped on each affected stat (clamped
+ *     0–100);
+ *   - the dip is mirrored to the target's regions — the single named region
+ *     when the target was a region key, otherwise every region the target
+ *     owns (regions with no `regionStats` entry are skipped);
+ *   - the target nation's derived `stats` are re-derived afterwards (the
+ *     same 0-region / no-entry guards as the main recompute, so a 0-region
+ *     nation keeps its directly-mutated value and a dip persists).
+ * A disaster never moves territory (sole ownership is untouched) and never
+ * touches `population`.
+ */
+export function applyDisasterEvent(
+  next: GameState,
+  ev: DisasterEvent,
+  geoOf?: (key: string) => { area: number; population: number } | undefined,
+  validKeys?: ReadonlySet<string>,
+): void {
+  const target = resolveDisasterTarget(next, ev.target, validKeys);
+  if (target === null) return; // unresolvable target: drop
+  const dips = DISASTER_EFFECTS[ev.type][ev.severity];
+  if (!dips) return; // defensive: unknown (type, severity) pair
+  applyDips(target.nation.stats, dips);
+  if (target.regionKey !== undefined) {
+    const rs = next.regionStats[target.regionKey];
+    if (rs) applyDips(rs, dips);
+  } else {
+    for (const key of target.nation.territory) {
+      const rs = next.regionStats[key];
+      if (!rs) continue; // a key with no entry is skipped
+      applyDips(rs, dips);
+    }
+  }
+  // Re-derive the target nation's aggregate stats so the dip persists (the
+  // main recompute ran earlier this turn; without this the dip would be
+  // washed out next turn). Same 0-region / no-entry guards as hybrid /
+  // economy: a nation with no region stats entry keeps its directly-mutated
+  // `stats`.
+  if (target.nation.territory.length > 0 && target.nation.territory.some((k) => next.regionStats[k])) {
+    target.nation.stats = deriveNationStats(target.nation.territory, next.regionStats, geoOf);
+  }
+}
+
+export const disasters: Ability<'disasters'> = {
+  field: 'disasters',
+  default: () => ({ events: [] }),
+  // The low-level validator returns a bare list; the field's shape is the
+  // `{ events }` object (mirrors the historical TurnResult shape).
+  validate: (raw) => ({ events: validateDisasterEvents(raw) }),
+  apply: (state, data, ctx) => {
+    for (const ev of data.events) {
+      applyDisasterEvent(state, ev, ctx.geoOf, ctx.validRegionKeys);
+    }
+  },
+  schemaLine: () =>
+    '  "disasters": {"events":[{"type":"<earthquake|flood|volcanic|wildfire|famine|plague|epidemic>","target":"<nation id or name, or region key>","severity":"<minor|moderate|severe>","detail":"<short detail>"}]},',
+  constraint: () =>
+    '- Disasters & pandemics ("disasters.events") are natural and man-made catastrophes — earthquakes, floods, volcanic eruptions, wildfires, famines, plagues, and epidemics — that hit a nation or a single region this turn. Each event names a "target" (a nation id / name, or a region key that hits that region\'s SOLE owner — a region with 0 or 2+ owners can\'t be hit) and a "severity" (minor / moderate / severe); the engine applies a small, DETERMINISTIC stat dip from the (type, severity) table (a severe plague is the hardest hit; none of them touch population, and none move borders — sole ownership is untouched). There is NO memory of past disasters (the layer is turn-transient): a plague or epidemic that persists is simply RE-DECLARED each turn it continues, with a fresh "severity". Propose at most 1-2 events per turn and narrate each one in "events" (a "disaster" event).',
+  isMeaningful: (data) => data.events.length > 0,
+  stub: () => ({ events: [] }),
+  // The layer is turn-transient — it contributes nothing to the user payload
+  // (no durable state to show the model), so the payload is always empty.
+  payload: () => ({}),
+};

server/abilities/goldens/system-no-tool.txt

@@ -39,6 +39,9 @@ Respond with ONLY a valid JSON object of exactly this shape. No prose, no commen
   "nuclear": {"arm":["<nation id or name>"],"strikes":[{"from":"<nuclear-capable nation id or name>","target":"<nation id or name, or region key>"}]},
   "leaders": {"changes":[{"target":"<nation id or name>","name":"<new leader name>","cause":"<assassination|death|appointed>"}]},
   "ideology": {"changes":[{"target":"<nation id or name>","to":"<new form of government>"}]},
+  "disasters": {"events":[{"type":"<earthquake|flood|volcanic|wildfire|famine|plague|epidemic>","target":"<nation id or name, or region key>","severity":"<minor|moderate|severe>","detail":"<short detail>"}]},
+  "migration": {"ops":[{"kind":"<migration|refugees|diaspora|exodus>","from":"<nation id or name>","to":"<nation id or name>","scale":"<small|moderate|large>","detail":"<short detail>"}]},
+  "sea": {"control":[{"zone":"<seaZoneId>","by":"<nation id or name>"}]},
   "markers": {"add":[{"type":"<city|factory|army|port|capital|fleet|rocket|gathering>","name":"<short name>","regionKey":"<region key>"}],"remove":["<marker id>"]}
 }
 
@@ -64,6 +67,9 @@ HARD CONSTRAINTS
 - Nuclear / WMD ("nuclear"): a nation is "nuclear-capable" when its "nuclear" flag is true or it currently owns a "rocket" marker. "arm" names (by id or name) nations to grant the "nuclear" flag — idempotent (already-armed nations are unchanged); a newly armed nation is capable this same turn. "strikes" is a list of "NuclearStrike" objects, each "{from, target}" — "from" is the striking nation (must be nuclear-capable and never itself) and "target" is either a nation (its nation collapses: economy -40, military -50, stability -40; every active war the target fights ends by capitulation and the "war" relations it caused downgrade to "hostile") or a region key (that region is released to no man's land, its regionStats entry deleted, and its sole owner collapses the same way — a region with 0 or 2+ owners, or one the striker itself owns, is dropped). If the struck nation (or the struck region's owner) is itself nuclear-capable, a "MAD" retaliation is applied: it strikes the striker back for half the collapse, and the two nations' relations are forced to "hostile". At most one strike per turn; always narrate a strike (and a retaliation, if any) in "events".
 - Leaders ("leaders") name each nation's current head of state and change it. Each change is {"target":"<nation id or name>","name":"<new leader name>","cause":"<assassination|death|appointed>"}: "assassination" kills the current leader (a dramatic, destabilizing blow — a −15 stability dip, a "military" event) and is only valid when the target already has a leader; "death" is a natural-causes succession (a quieter −3 dip, a "political" event), also only valid for a nation that has a leader; "appointed" sets (or creates) a leader and is always valid (a neutral 0 effect, a "political" event). Propose at most 1-2 changes per turn and narrate each one in "events". This is the HEAVY leader lever — use the lighter "hybrid" {"type":"assassinate"} op (a −5 stability dip, no leader replacement) for a mere hit on a leader or region without changing who is in charge. The user message's "nations" field lists each nation's current "leader" (omitted when a nation has none).
 - Ideology ("ideology") is each nation's form of government — a free-form label such as "democracy", "fascism", or "military junta" — that can shift through a coup, a revolution, a reform, or a constitutional change. Each change is {"target":"<nation id or name>","to":"<new form of government>"}: the engine sets the nation's ideology, applies a small, deterministic stability dip (−5 — a regime shift always unsettles a nation), and narrates it with a "political" event. It is a third axis, distinct from a takeover (which RENAMES the nation) and from a leader change (who is in charge): the nation keeps its id, name, territory, relations, and leader — only its form of government and its stability move. Similar forms of government are a SOFT, prompt-level compatibility nudge only (nations with alike ideologies tend to ally and trade; very opposed ones tend to clash) — there is no engine gate behind it. Propose at most 1-2 changes per turn and narrate each one in "events". The user message's "nations" field lists each nation's current "ideology" (omitted when a nation has none).
+- Disasters & pandemics ("disasters.events") are natural and man-made catastrophes — earthquakes, floods, volcanic eruptions, wildfires, famines, plagues, and epidemics — that hit a nation or a single region this turn. Each event names a "target" (a nation id / name, or a region key that hits that region's SOLE owner — a region with 0 or 2+ owners can't be hit) and a "severity" (minor / moderate / severe); the engine applies a small, DETERMINISTIC stat dip from the (type, severity) table (a severe plague is the hardest hit; none of them touch population, and none move borders — sole ownership is untouched). There is NO memory of past disasters (the layer is turn-transient): a plague or epidemic that persists is simply RE-DECLARED each turn it continues, with a fresh "severity". Propose at most 1-2 events per turn and narrate each one in "events" (a "disaster" event).
+- Migration & refugees ("migration.ops") are people moving between nations this turn: a "kind" ("migration", "refugees", "diaspora", or "exodus"), a "from" (the source nation — id or name), a "to" (the destination nation — required for every kind except "exodus", which has no destination), and a "scale" (small / moderate / large). The engine applies a DETERMINISTIC effect (no hidden randomness): the source LOSES a small amount of population and economy, the destination GAINS a small amount of population and economy (a "large" influx additionally strains the destination's stability by 2), and the from↔to relation moves one step toward the positive end of the ally/neutral/rival/hostile ladder — capped at "ally" for "refugees" (hosting refugees builds the strongest goodwill), capped at "neutral" for "migration"/"diaspora" (milder ties), and not at all for "exodus"; the nudge never creates or escalates a "war" (a warring pair is left untouched). The layer is turn-transient (no memory): a continuing flow is simply RE-DECLARED each turn it persists. It never moves borders — sole ownership is untouched. Propose at most 1-2 per turn and narrate each one in "events" (a "social" or "diplomatic" event).
+- Sea control ("sea") is the naval layer, fully parallel to but INDEPENDENT of land: each of the 12 fixed sea zones — "north-atlantic" (North Atlantic), "south-atlantic" (South Atlantic), "pacific" (Pacific Ocean), "indian" (Indian Ocean), "mediterranean" (Mediterranean Sea), "north-sea" (North Sea), "baltic" (Baltic Sea), "arctic" (Arctic Ocean), "black-sea" (Black Sea), "gulf-mexico" (Gulf of Mexico), "red-sea" (Red Sea), "sargasso" (Sargasso Sea) — is under the SOLE control of at most one nation. A control op ({"zone":"<id>","by":"<nation>"}) sets or replaces that zone's controller (the user message's "seaZones" field lists who controls what now); if two or more ops this turn claim the SAME zone for DIFFERENT nations, the zone is CONTESTED and the higher current "military" wins (a tie goes to the earlier-listed op). Every committed turn each zone's controller earns a small deterministic +1 military and +1 economy. Sea control NEVER moves land (no territory changes) — it is a parallel track. Propose at most 1-2 claims per turn and narrate each one in "events" (a "military" or "diplomatic" event).
 - Prefer 1-4 events per turn; keep each text 1-3 sentences.
 - Keep your internal reasoning brief (a few sentences) and go straight to the JSON result; do not over-deliberate or re-derive facts already present in the state.
 - Keep every stat value between 0 and 100.

server/abilities/goldens/system-tool.txt

@@ -39,6 +39,9 @@ You have a getNeighbours tool: given region keys it returns the region keys that
   "nuclear": {"arm":["<nation id or name>"],"strikes":[{"from":"<nuclear-capable nation id or name>","target":"<nation id or name, or region key>"}]},
   "leaders": {"changes":[{"target":"<nation id or name>","name":"<new leader name>","cause":"<assassination|death|appointed>"}]},
   "ideology": {"changes":[{"target":"<nation id or name>","to":"<new form of government>"}]},
+  "disasters": {"events":[{"type":"<earthquake|flood|volcanic|wildfire|famine|plague|epidemic>","target":"<nation id or name, or region key>","severity":"<minor|moderate|severe>","detail":"<short detail>"}]},
+  "migration": {"ops":[{"kind":"<migration|refugees|diaspora|exodus>","from":"<nation id or name>","to":"<nation id or name>","scale":"<small|moderate|large>","detail":"<short detail>"}]},
+  "sea": {"control":[{"zone":"<seaZoneId>","by":"<nation id or name>"}]},
   "markers": {"add":[{"type":"<city|factory|army|port|capital|fleet|rocket|gathering>","name":"<short name>","regionKey":"<region key>"}],"remove":["<marker id>"]}
 }
 
@@ -64,6 +67,9 @@ HARD CONSTRAINTS
 - Nuclear / WMD ("nuclear"): a nation is "nuclear-capable" when its "nuclear" flag is true or it currently owns a "rocket" marker. "arm" names (by id or name) nations to grant the "nuclear" flag — idempotent (already-armed nations are unchanged); a newly armed nation is capable this same turn. "strikes" is a list of "NuclearStrike" objects, each "{from, target}" — "from" is the striking nation (must be nuclear-capable and never itself) and "target" is either a nation (its nation collapses: economy -40, military -50, stability -40; every active war the target fights ends by capitulation and the "war" relations it caused downgrade to "hostile") or a region key (that region is released to no man's land, its regionStats entry deleted, and its sole owner collapses the same way — a region with 0 or 2+ owners, or one the striker itself owns, is dropped). If the struck nation (or the struck region's owner) is itself nuclear-capable, a "MAD" retaliation is applied: it strikes the striker back for half the collapse, and the two nations' relations are forced to "hostile". At most one strike per turn; always narrate a strike (and a retaliation, if any) in "events".
 - Leaders ("leaders") name each nation's current head of state and change it. Each change is {"target":"<nation id or name>","name":"<new leader name>","cause":"<assassination|death|appointed>"}: "assassination" kills the current leader (a dramatic, destabilizing blow — a −15 stability dip, a "military" event) and is only valid when the target already has a leader; "death" is a natural-causes succession (a quieter −3 dip, a "political" event), also only valid for a nation that has a leader; "appointed" sets (or creates) a leader and is always valid (a neutral 0 effect, a "political" event). Propose at most 1-2 changes per turn and narrate each one in "events". This is the HEAVY leader lever — use the lighter "hybrid" {"type":"assassinate"} op (a −5 stability dip, no leader replacement) for a mere hit on a leader or region without changing who is in charge. The user message's "nations" field lists each nation's current "leader" (omitted when a nation has none).
 - Ideology ("ideology") is each nation's form of government — a free-form label such as "democracy", "fascism", or "military junta" — that can shift through a coup, a revolution, a reform, or a constitutional change. Each change is {"target":"<nation id or name>","to":"<new form of government>"}: the engine sets the nation's ideology, applies a small, deterministic stability dip (−5 — a regime shift always unsettles a nation), and narrates it with a "political" event. It is a third axis, distinct from a takeover (which RENAMES the nation) and from a leader change (who is in charge): the nation keeps its id, name, territory, relations, and leader — only its form of government and its stability move. Similar forms of government are a SOFT, prompt-level compatibility nudge only (nations with alike ideologies tend to ally and trade; very opposed ones tend to clash) — there is no engine gate behind it. Propose at most 1-2 changes per turn and narrate each one in "events". The user message's "nations" field lists each nation's current "ideology" (omitted when a nation has none).
+- Disasters & pandemics ("disasters.events") are natural and man-made catastrophes — earthquakes, floods, volcanic eruptions, wildfires, famines, plagues, and epidemics — that hit a nation or a single region this turn. Each event names a "target" (a nation id / name, or a region key that hits that region's SOLE owner — a region with 0 or 2+ owners can't be hit) and a "severity" (minor / moderate / severe); the engine applies a small, DETERMINISTIC stat dip from the (type, severity) table (a severe plague is the hardest hit; none of them touch population, and none move borders — sole ownership is untouched). There is NO memory of past disasters (the layer is turn-transient): a plague or epidemic that persists is simply RE-DECLARED each turn it continues, with a fresh "severity". Propose at most 1-2 events per turn and narrate each one in "events" (a "disaster" event).
+- Migration & refugees ("migration.ops") are people moving between nations this turn: a "kind" ("migration", "refugees", "diaspora", or "exodus"), a "from" (the source nation — id or name), a "to" (the destination nation — required for every kind except "exodus", which has no destination), and a "scale" (small / moderate / large). The engine applies a DETERMINISTIC effect (no hidden randomness): the source LOSES a small amount of population and economy, the destination GAINS a small amount of population and economy (a "large" influx additionally strains the destination's stability by 2), and the from↔to relation moves one step toward the positive end of the ally/neutral/rival/hostile ladder — capped at "ally" for "refugees" (hosting refugees builds the strongest goodwill), capped at "neutral" for "migration"/"diaspora" (milder ties), and not at all for "exodus"; the nudge never creates or escalates a "war" (a warring pair is left untouched). The layer is turn-transient (no memory): a continuing flow is simply RE-DECLARED each turn it persists. It never moves borders — sole ownership is untouched. Propose at most 1-2 per turn and narrate each one in "events" (a "social" or "diplomatic" event).
+- Sea control ("sea") is the naval layer, fully parallel to but INDEPENDENT of land: each of the 12 fixed sea zones — "north-atlantic" (North Atlantic), "south-atlantic" (South Atlantic), "pacific" (Pacific Ocean), "indian" (Indian Ocean), "mediterranean" (Mediterranean Sea), "north-sea" (North Sea), "baltic" (Baltic Sea), "arctic" (Arctic Ocean), "black-sea" (Black Sea), "gulf-mexico" (Gulf of Mexico), "red-sea" (Red Sea), "sargasso" (Sargasso Sea) — is under the SOLE control of at most one nation. A control op ({"zone":"<id>","by":"<nation>"}) sets or replaces that zone's controller (the user message's "seaZones" field lists who controls what now); if two or more ops this turn claim the SAME zone for DIFFERENT nations, the zone is CONTESTED and the higher current "military" wins (a tie goes to the earlier-listed op). Every committed turn each zone's controller earns a small deterministic +1 military and +1 economy. Sea control NEVER moves land (no territory changes) — it is a parallel track. Propose at most 1-2 claims per turn and narrate each one in "events" (a "military" or "diplomatic" event).
 - Prefer 1-4 events per turn; keep each text 1-3 sentences.
 - Keep your internal reasoning brief (a few sentences) and go straight to the JSON result; do not over-deliberate or re-derive facts already present in the state.
 - Keep every stat value between 0 and 100.

server/abilities/goldens/user.txt

@@ -205,5 +205,6 @@
       "regionKey": "a-r1",
       "type": "industry"
     }
-  ]
+  ],
+  "seaZones": []
 }

server/abilities/index.ts

@@ -1,8 +1,8 @@
 // The ordered LLM-ability registry.
 //
-// `ABILITIES` is the single source of truth for the 8 per-feature LLM abilities.
+// `ABILITIES` is the single source of truth for the 11 per-feature LLM abilities.
 // The engine iterates it in this order:
-//   takeovers → wars → hybrid → economy → industry → nuclear → leaders → ideology
+//   takeovers → wars → hybrid → economy → industry → nuclear → leaders → ideology → disasters → migration → sea
 // for (a) the system-prompt schema lines + constraint bullets, (b) the per-ability
 // validate calls inside validateTurnResult, (c) the payload fields in buildUserPrompt,
 // (d) the ordered apply block inside applyTurnResult, (e) the isMeaningful check,
@@ -22,13 +22,18 @@ import { industry } from './industry';
 import { nuclear } from './nuclear';
 import { leaders } from './leaders';
 import { ideology } from './ideology';
+import { disasters } from './disasters';
+import { migration } from './migration';
+import { sea } from './sea';
 import type { Ability, AbilityField } from './types';
 
 /**
- * The 8 per-feature LLM abilities in their canonical apply order.
+ * The 11 per-feature LLM abilities in their canonical apply order.
  * The order matters: it determines the order of the schema lines in the
  * system prompt, the order of the validate calls, the order of the apply
- * steps, and the order of the payload fields in the user prompt.
+ * steps, and the order of the payload fields in the user prompt. New
+ * abilities are APPENDED last — never reorder existing entries (their order
+ * is pinned by the goldens and the stub's byte-identical output).
  */
 export const ABILITIES: readonly Ability<AbilityField>[] = [
   takeovers,
@@ -39,6 +44,9 @@ export const ABILITIES: readonly Ability<AbilityField>[] = [
   nuclear,
   leaders,
   ideology,
+  disasters,
+  migration,
+  sea,
 ];
 
 // ── type re-exports ────────────────────────────────────────────────────────────
@@ -125,3 +133,43 @@ export {
 export {
   validateIdeologyOps,
 } from './ideology';
+
+// ── disasters ────────────────────────────────────────────────────────────────
+
+export {
+  validateDisasterEvents,
+  applyDisasterEvent,
+  isDisasterType,
+  isDisasterSeverity,
+  DISASTER_TYPES,
+  DISASTER_SEVERITIES,
+  DISASTER_EFFECTS,
+} from './disasters';
+
+// ── migration ────────────────────────────────────────────────────────────────
+
+export {
+  validateMigrationOps,
+  applyMigrationOp,
+  shiftRelationTowardPositive,
+  isMigrationKind,
+  isMigrationScale,
+  MIGRATION_KINDS,
+  MIGRATION_SCALES,
+  MIGRATION_SOURCE_EFFECTS,
+  MIGRATION_DESTINATION_EFFECTS,
+  LARGE_INFLUX_STABILITY_DIP,
+} from './migration';
+
+// ── sea ──────────────────────────────────────────────────────────────────────
+
+export {
+  validateSeaOps,
+  applySeaControl,
+  applySeaZoneBonuses,
+  SEA_ZONE_BONUS,
+  SEA_ZONES,
+  SEA_ZONE_IDS,
+  isSeaZoneId,
+  seaZoneName,
+} from './sea';

server/abilities/migration.test.ts

@@ -0,0 +1,572 @@
+// Unit tests for the MIGRATION & REFUGEES ability (v0.42.0, #64) — the
+// modular, turn-transient LLM-ability that moves population between nations:
+// the source loses a small amount of population and economy, the destination
+// gains a small amount (a `large` influx also strains the destination's
+// stability), each side's aggregate stats are re-derived, and the from↔to
+// relation is nudged one step toward the positive end of the ladder (capped by
+// kind; a war is never touched). This is the ability's own test file (the
+// registry's cross-cutting guarantees — order, distinct fields, the
+// system/user goldens — are covered by ./registry.test.ts). The stub never
+// proposes a migration, so the apply path is exercised here, not by the e2e
+// suite.
+
+import { describe, expect, it } from 'vitest';
+
+import {
+  LARGE_INFLUX_STABILITY_DIP,
+  MIGRATION_DESTINATION_EFFECTS,
+  MIGRATION_KINDS,
+  MIGRATION_SCALES,
+  MIGRATION_SOURCE_EFFECTS,
+  applyMigrationOp,
+  isMigrationKind,
+  isMigrationScale,
+  migration,
+  shiftRelationTowardPositive,
+  validateMigrationOps,
+} from './migration';
+
+import type { MigrationScale } from '../../shared/protocol';
+import type { GameState, Nation, NationStats, RelationStatus, RegionStats } from '../../shared/types';
+
+// ---------------------------------------------------------------------------
+// Fixture helpers
+// ---------------------------------------------------------------------------
+
+/** Build a NationStats from the four canonical indices (military, economy, stability, population). */
+function NS(military: number, economy: number, stability: number, population: number): NationStats {
+  return { military, economy, stability, population };
+}
+
+/** Build a RegionStats from the four canonical indices. */
+function RS(military: number, economy: number, stability: number, population: number): RegionStats {
+  return { military, economy, stability, population };
+}
+
+/** A minimal nation: the given id/name/stats/region-key territory, given relations. */
+function mkNation(
+  id: string,
+  name: string,
+  stats: NationStats,
+  territory: string[],
+  relations: Record<string, RelationStatus> = {},
+): Nation {
+  return { id, name, type: 'major', stats, territory, relations };
+}
+
+/**
+ * A minimal GameState carrying the given nations (keyed by id) and per-region
+ * stats. Every other required field is at its fresh-game baseline, so a test
+ * can focus purely on the migration effect.
+ */
+function mkState(
+  nations: Record<string, Nation>,
+  regionStats: Record<string, RegionStats>,
+): GameState {
+  return {
+    id: 'g1',
+    presetId: 'test',
+    presetTitle: 'Test',
+    playerNationId: Object.keys(nations)[0] ?? 'uk',
+    turn: 1,
+    date: '1939-09-01',
+    nations,
+    events: [],
+    pending: [],
+    version: 1,
+    unowned: [],
+    pendingNationOps: [],
+    markers: [],
+    regionStats,
+    wars: [],
+    trades: [],
+    embargoes: [],
+    industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
+  };
+}
+
+// ---------------------------------------------------------------------------
+// Kind / scale constants + predicates
+// ---------------------------------------------------------------------------
+
+describe('MIGRATION_KINDS / MIGRATION_SCALES', () => {
+  it('exposes exactly the four kinds and three scales', () => {
+    expect([...MIGRATION_KINDS]).toEqual(['migration', 'refugees', 'diaspora', 'exodus']);
+    expect([...MIGRATION_SCALES]).toEqual(['small', 'moderate', 'large']);
+  });
+});
+
+describe('isMigrationKind / isMigrationScale', () => {
+  it('accepts each known kind and rejects unknown / non-strings', () => {
+    for (const k of MIGRATION_KINDS) expect(isMigrationKind(k)).toBe(true);
+    expect(isMigrationKind('immigration')).toBe(false);
+    expect(isMigrationKind(42)).toBe(false);
+    expect(isMigrationKind(undefined)).toBe(false);
+  });
+
+  it('accepts each known scale and rejects unknown / non-strings', () => {
+    for (const s of MIGRATION_SCALES) expect(isMigrationScale(s)).toBe(true);
+    expect(isMigrationScale('massive')).toBe(false);
+    expect(isMigrationScale(42)).toBe(false);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Effect tables
+// ---------------------------------------------------------------------------
+
+describe('MIGRATION_SOURCE_EFFECTS / MIGRATION_DESTINATION_EFFECTS', () => {
+  it('every source scale dips exactly population and economy (both negative)', () => {
+    for (const s of MIGRATION_SCALES) {
+      const dips = MIGRATION_SOURCE_EFFECTS[s];
+      expect(Object.keys(dips).sort()).toEqual(['economy', 'population']);
+      expect(dips.population).toBeLessThan(0);
+      expect(dips.economy).toBeLessThan(0);
+    }
+  });
+
+  it('every destination scale gains exactly population and economy (both positive)', () => {
+    for (const s of MIGRATION_SCALES) {
+      const gains = MIGRATION_DESTINATION_EFFECTS[s];
+      expect(Object.keys(gains).sort()).toEqual(['economy', 'population']);
+      expect(gains.population).toBeGreaterThan(0);
+      expect(gains.economy).toBeGreaterThan(0);
+    }
+  });
+
+  it('source loses and destination gains monotonically with scale', () => {
+    const [small, moderate, large] = MIGRATION_SCALES;
+    const srcPop = (s: MigrationScale) => MIGRATION_SOURCE_EFFECTS[s].population!;
+    const dstPop = (s: MigrationScale) => MIGRATION_DESTINATION_EFFECTS[s].population!;
+    // A larger scale means the source LOSES more: the (negative) dip grows more
+    // negative as the scale grows, i.e. small > moderate > large.
+    expect(srcPop(small)).toBeGreaterThan(srcPop(moderate));
+    expect(srcPop(moderate)).toBeGreaterThan(srcPop(large));
+    // A larger scale means the destination GAINS more: the (positive) gain
+    // grows larger as the scale grows, i.e. small < moderate < large.
+    expect(dstPop(small)).toBeLessThan(dstPop(moderate));
+    expect(dstPop(moderate)).toBeLessThan(dstPop(large));
+  });
+
+  it('the large-influx stability strain is a small negative dip', () => {
+    expect(LARGE_INFLUX_STABILITY_DIP).toBeLessThan(0);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// validateMigrationOps
+// ---------------------------------------------------------------------------
+
+describe('validateMigrationOps', () => {
+  it('accepts the { ops: [...] } object shape and a bare array', () => {
+    const op = { kind: 'migration', from: 'a', to: 'b', scale: 'small' };
+    expect(validateMigrationOps({ ops: [op] })).toEqual([op]);
+    expect(validateMigrationOps([op])).toEqual([op]);
+  });
+
+  it('drops an op with an unknown / missing kind', () => {
+    expect(validateMigrationOps([{ kind: 'tsunami', from: 'a', to: 'b', scale: 'small' }])).toEqual(
+      [],
+    );
+    expect(
+      validateMigrationOps([
+        { from: 'a', to: 'b', scale: 'small' },
+        { kind: 'migration', from: 'a', to: 'b', scale: 'small' },
+      ]),
+    ).toEqual([{ kind: 'migration', from: 'a', to: 'b', scale: 'small' }]);
+  });
+
+  it('drops an op with an unknown / missing scale', () => {
+    expect(validateMigrationOps([{ kind: 'migration', from: 'a', to: 'b', scale: 'massive' }])).toEqual(
+      [],
+    );
+    expect(validateMigrationOps([{ kind: 'migration', from: 'a', to: 'b' }])).toEqual([]);
+  });
+
+  it('drops an op with an empty / missing from (the source)', () => {
+    expect(validateMigrationOps([{ kind: 'migration', from: '', to: 'b', scale: 'small' }])).toEqual(
+      [],
+    );
+    expect(validateMigrationOps([{ kind: 'migration', to: 'b', scale: 'small' }])).toEqual([]);
+  });
+
+  it('requires a non-empty `to` for every kind except exodus', () => {
+    // non-exodus kind missing `to`: dropped
+    expect(validateMigrationOps([{ kind: 'migration', from: 'a', scale: 'small' }])).toEqual([]);
+    expect(validateMigrationOps([{ kind: 'refugees', from: 'a', scale: 'small' }])).toEqual([]);
+    // exodus without a `to`: kept (an exodus has no destination)
+    expect(validateMigrationOps([{ kind: 'exodus', from: 'a', scale: 'small' }])).toEqual([
+      { kind: 'exodus', from: 'a', scale: 'small' },
+    ]);
+  });
+
+  it('caps `from` / `to` at 200 chars and `detail` at 300, dropping empty detail', () => {
+    const longFrom = 'f'.repeat(500);
+    const longDetail = 'd'.repeat(500);
+    const out = validateMigrationOps([
+      { kind: 'migration', from: longFrom, to: 'b', scale: 'small', detail: longDetail },
+    ]);
+    expect(out).toHaveLength(1);
+    expect(out[0].from).toHaveLength(200);
+    expect(out[0].detail).toHaveLength(300);
+  });
+
+  it('a missing / malformed top-level value yields an empty list', () => {
+    expect(validateMigrationOps(undefined)).toEqual([]);
+    expect(validateMigrationOps(null)).toEqual([]);
+    expect(validateMigrationOps('nope')).toEqual([]);
+    expect(validateMigrationOps({ ops: 'nope' })).toEqual([]);
+    expect(validateMigrationOps([{ kind: 'migration' }])).toEqual([]);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// shiftRelationTowardPositive
+// ---------------------------------------------------------------------------
+
+describe('shiftRelationTowardPositive', () => {
+  function pair(rel: Record<string, RelationStatus>): GameState {
+    return mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1'], rel),
+        b2: mkNation('b2', 'Bravo', NS(50, 50, 50, 50), ['b-r1'], rel),
+      },
+      { 'a-r1': RS(50, 50, 50, 50), 'b-r1': RS(50, 50, 50, 50) },
+    );
+  }
+
+  it('nudges a neutral pair one step toward positive, symmetrically', () => {
+    const s = pair({ b2: 'neutral', a1: 'neutral' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'ally');
+    expect(s.nations.a1.relations.b2).toBe('ally');
+    expect(s.nations.b2.relations.a1).toBe('ally');
+  });
+
+  it('never moves past the cap (migration/diaspora cap at neutral)', () => {
+    // hostile → rival (one step toward positive, still below the neutral cap)
+    let s = pair({ b2: 'hostile', a1: 'hostile' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'neutral');
+    expect(s.nations.a1.relations.b2).toBe('rival');
+    // rival → neutral (reaches the cap)
+    s = pair({ b2: 'rival', a1: 'rival' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'neutral');
+    expect(s.nations.a1.relations.b2).toBe('neutral');
+    // neutral → stays neutral (at the cap)
+    s = pair({ b2: 'neutral', a1: 'neutral' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'neutral');
+    expect(s.nations.a1.relations.b2).toBe('neutral');
+    // ally → stays ally (more positive than the cap)
+    s = pair({ b2: 'ally', a1: 'ally' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'neutral');
+    expect(s.nations.a1.relations.b2).toBe('ally');
+  });
+
+  it('refugees can nudge all the way to ally (cap ally)', () => {
+    let s = pair({ b2: 'hostile', a1: 'hostile' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'ally');
+    expect(s.nations.a1.relations.b2).toBe('rival');
+    s = pair({ b2: 'rival', a1: 'rival' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'ally');
+    expect(s.nations.a1.relations.b2).toBe('neutral');
+    s = pair({ b2: 'neutral', a1: 'neutral' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'ally');
+    expect(s.nations.a1.relations.b2).toBe('ally');
+    // already ally: no change
+    s = pair({ b2: 'ally', a1: 'ally' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'ally');
+    expect(s.nations.a1.relations.b2).toBe('ally');
+  });
+
+  it('a missing relation starts at neutral and nudges toward the cap', () => {
+    const s = pair({});
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'ally');
+    expect(s.nations.a1.relations.b2).toBe('ally');
+    expect(s.nations.b2.relations.a1).toBe('ally');
+  });
+
+  it('never touches a war relation', () => {
+    const s = pair({ b2: 'war', a1: 'war' });
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'ally');
+    expect(s.nations.a1.relations.b2).toBe('war');
+    expect(s.nations.b2.relations.a1).toBe('war');
+  });
+
+  it('is a no-op for an unknown nation id or an unknown cap', () => {
+    const s = pair({ b2: 'hostile', a1: 'hostile' });
+    shiftRelationTowardPositive(s, 'a1', 'zzz', 'ally'); // zzz absent
+    expect(s.nations.a1.relations.b2).toBe('hostile');
+    shiftRelationTowardPositive(s, 'a1', 'b2', 'nope' as RelationStatus); // bad cap
+    expect(s.nations.a1.relations.b2).toBe('hostile');
+  });
+});
+
+// ---------------------------------------------------------------------------
+// applyMigrationOp
+// ---------------------------------------------------------------------------
+
+describe('applyMigrationOp', () => {
+  it('a small migration: source loses pop+eco, destination gains pop+eco, relation unchanged (neutral→neutral)', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+    );
+    applyMigrationOp(state, { kind: 'migration', from: 'a1', to: 'b2', scale: 'small' });
+    // source: economy 70→69, population 50→49 (re-derived from its single region)
+    expect(state.nations.a1.stats).toEqual(NS(80, 69, 60, 49));
+    // destination: economy 30→31, population 60→61
+    expect(state.nations.b2.stats).toEqual(NS(40, 31, 50, 61));
+    // both regions mirrored
+    expect(state.regionStats['a-r1']).toEqual(RS(80, 69, 60, 49));
+    expect(state.regionStats['b-r1']).toEqual(RS(40, 31, 50, 61));
+    // a neutral pair is already at the neutral cap: no relation change
+    expect(state.nations.a1.relations.b2 ?? 'neutral').toBe('neutral');
+    expect(state.nations.b2.relations.a1 ?? 'neutral').toBe('neutral');
+  });
+
+  it('resolves `from` / `to` by name (not just id)', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+    );
+    applyMigrationOp(state, { kind: 'migration', from: 'Alpha', to: 'Bravo', scale: 'moderate' });
+    // moderate: source pop -2 / eco -2; destination pop +2 / eco +2
+    expect(state.nations.a1.stats).toEqual(NS(80, 68, 60, 48));
+    expect(state.nations.b2.stats).toEqual(NS(40, 32, 50, 62));
+  });
+
+  it('a large influx strains the destination stability by 2', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+    );
+    applyMigrationOp(state, { kind: 'refugees', from: 'a1', to: 'b2', scale: 'large' });
+    // destination: eco 30→33, pop 60→63, stability 50→48 (large influx strain)
+    expect(state.nations.b2.stats).toEqual(NS(40, 33, 48, 63));
+    expect(state.regionStats['b-r1']).toEqual(RS(40, 33, 48, 63));
+    // source: eco 70→67, pop 50→46
+    expect(state.nations.a1.stats).toEqual(NS(80, 67, 60, 46));
+  });
+
+  it('a refugees flow nudges the relation toward ally (cap ally); migration/diaspora stop at neutral', () => {
+    const mk = (rel: RelationStatus) =>
+      mkState(
+        {
+          a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1'], { b2: rel }),
+          b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1'], { a1: rel }),
+        },
+        { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+      );
+    // refugees: hostile → rival
+    let s = mk('hostile');
+    applyMigrationOp(s, { kind: 'refugees', from: 'a1', to: 'b2', scale: 'small' });
+    expect(s.nations.a1.relations.b2).toBe('rival');
+    // migration: hostile → rival (capped at neutral, one step only)
+    s = mk('hostile');
+    applyMigrationOp(s, { kind: 'migration', from: 'a1', to: 'b2', scale: 'small' });
+    expect(s.nations.a1.relations.b2).toBe('rival');
+    // migration: rival → neutral (reaches cap)
+    s = mk('rival');
+    applyMigrationOp(s, { kind: 'diaspora', from: 'a1', to: 'b2', scale: 'small' });
+    expect(s.nations.a1.relations.b2).toBe('neutral');
+    // refugees: neutral → ally
+    s = mk('neutral');
+    applyMigrationOp(s, { kind: 'refugees', from: 'a1', to: 'b2', scale: 'small' });
+    expect(s.nations.a1.relations.b2).toBe('ally');
+  });
+
+  it('never nudges a warring pair (a war is left untouched)', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1'], { b2: 'war' }),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1'], { a1: 'war' }),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+    );
+    applyMigrationOp(state, { kind: 'refugees', from: 'a1', to: 'b2', scale: 'large' });
+    expect(state.nations.a1.relations.b2).toBe('war');
+    expect(state.nations.b2.relations.a1).toBe('war');
+    // the stat effects still apply (a war does not block population movement)
+    expect(state.nations.a1.stats).toEqual(NS(80, 67, 60, 46));
+    expect(state.nations.b2.stats).toEqual(NS(40, 33, 48, 63));
+  });
+
+  it('an exodus only affects the source: no destination, no relation nudge', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1'], { b2: 'rival' }),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1'], { a1: 'rival' }),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+    );
+    applyMigrationOp(state, { kind: 'exodus', from: 'a1', scale: 'small' });
+    // source dips
+    expect(state.nations.a1.stats).toEqual(NS(80, 69, 60, 49));
+    // destination untouched
+    expect(state.nations.b2.stats).toEqual(NS(40, 30, 50, 60));
+    expect(state.regionStats['b-r1']).toEqual(RS(40, 30, 50, 60));
+    // no relation nudge
+    expect(state.nations.a1.relations.b2).toBe('rival');
+  });
+
+  it('a self-flow (from === to) is dropped entirely', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']) },
+      { 'a-r1': RS(80, 70, 60, 50) },
+    );
+    applyMigrationOp(state, { kind: 'migration', from: 'a1', to: 'a1', scale: 'large' });
+    // no change at all
+    expect(state.nations.a1.stats).toEqual(NS(80, 70, 60, 50));
+    expect(state.regionStats['a-r1']).toEqual(RS(80, 70, 60, 50));
+  });
+
+  it('an unknown or ambiguous source / destination drops the op', () => {
+    const base = () =>
+      mkState(
+        {
+          a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+          b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1']),
+        },
+        { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+      );
+    // unknown source
+    let s = base();
+    applyMigrationOp(s, { kind: 'migration', from: 'zzz', to: 'b2', scale: 'small' });
+    expect(s.nations.b2.stats).toEqual(NS(40, 30, 50, 60));
+    // unknown destination
+    s = base();
+    applyMigrationOp(s, { kind: 'migration', from: 'a1', to: 'zzz', scale: 'small' });
+    expect(s.nations.a1.stats).toEqual(NS(80, 70, 60, 50));
+    // ambiguous source (two nations share the name)
+    const amb = mkState(
+      {
+        a1: mkNation('a1', 'Twin', NS(80, 70, 60, 50), ['a-r1']),
+        a2: mkNation('a2', 'Twin', NS(20, 20, 20, 20), ['a-r2']),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'a-r2': RS(20, 20, 20, 20), 'b-r1': RS(40, 30, 50, 60) },
+    );
+    applyMigrationOp(amb, { kind: 'migration', from: 'Twin', to: 'Bravo', scale: 'small' });
+    expect(amb.nations.b2.stats).toEqual(NS(40, 30, 50, 60));
+  });
+
+  it('a 0-region nation keeps its directly-mutated stats (no re-derive)', () => {
+    const state = mkState(
+      {
+        // a1 owns no regions — its stats are maintained directly, not derived
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), []),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1']),
+      },
+      { 'b-r1': RS(40, 30, 50, 60) },
+    );
+    applyMigrationOp(state, { kind: 'migration', from: 'a1', to: 'b2', scale: 'moderate' });
+    // source (0 regions) keeps the direct dip: eco 70→68, pop 50→48
+    expect(state.nations.a1.stats).toEqual(NS(80, 68, 60, 48));
+    // destination re-derived from its region
+    expect(state.nations.b2.stats).toEqual(NS(40, 32, 50, 62));
+  });
+
+  it('never moves territory (sole ownership untouched)', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+    );
+    applyMigrationOp(state, { kind: 'refugees', from: 'a1', to: 'b2', scale: 'large' });
+    expect(state.nations.a1.territory).toEqual(['a-r1']);
+    expect(state.nations.b2.territory).toEqual(['b-r1']);
+  });
+
+  it('clamps affected stats to 0 and 100 (a source at the floor, a destination at the ceiling)', () => {
+    const state = mkState(
+      {
+        // a1 at the population / economy floor
+        a1: mkNation('a1', 'Alpha', NS(5, 3, 50, 1), ['a-r1']),
+        // b2 near the ceiling: a large gain (+3) pushes it past 100
+        b2: mkNation('b2', 'Bravo', NS(90, 98, 50, 98), ['b-r1']),
+      },
+      { 'a-r1': RS(5, 3, 50, 1), 'b-r1': RS(90, 98, 50, 98) },
+    );
+    applyMigrationOp(state, { kind: 'migration', from: 'a1', to: 'b2', scale: 'large' });
+    // source clamps at 0 (pop 1-4→0, eco 3-3→0)
+    expect(state.nations.a1.stats.population).toBe(0);
+    expect(state.nations.a1.stats.economy).toBe(0);
+    // destination gains but clamps at 100 (pop 98+3→100, eco 98+3→100)
+    expect(state.nations.b2.stats.population).toBe(100);
+    expect(state.nations.b2.stats.economy).toBe(100);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// The Ability object contract
+// ---------------------------------------------------------------------------
+
+describe('migration ability', () => {
+  it('owns the "migration" field; default() is a fresh empty { ops: [] }', () => {
+    expect(migration.field).toBe('migration');
+    expect(migration.default()).toEqual({ ops: [] });
+    expect(migration.default()).not.toBe(migration.default());
+  });
+
+  it('default() is not meaningful; a populated value is', () => {
+    expect(migration.isMeaningful(migration.default())).toBe(false);
+    expect(
+      migration.isMeaningful({ ops: [{ kind: 'exodus', from: 'a1', scale: 'small' }] }),
+    ).toBe(true);
+  });
+
+  it('validate() wraps the bare-list validator into the { ops } shape', () => {
+    expect(
+      migration.validate([{ kind: 'migration', from: 'a1', to: 'b2', scale: 'small' }]),
+    ).toEqual({ ops: [{ kind: 'migration', from: 'a1', to: 'b2', scale: 'small' }] });
+    expect(migration.validate(undefined)).toEqual({ ops: [] });
+  });
+
+  it('the stub value equals default() (the stub never proposes a migration)', () => {
+    expect(migration.stub()).toEqual({ ops: [] });
+  });
+
+  it('payload() is always empty (turn-transient — no durable state to show)', () => {
+    expect(migration.payload({} as never)).toEqual({});
+  });
+
+  it('stateFields is undefined (the layer owns no durable GameState field)', () => {
+    expect(migration.stateFields).toBeUndefined();
+  });
+
+  it('apply() runs each validated op against the world (no throw on a bad ref)', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(40, 30, 50, 60), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(40, 30, 50, 60) },
+    );
+    const ctx = { previous: state, actingTurn: state.turn };
+    migration.apply(
+      state,
+      {
+        ops: [
+          { kind: 'migration', from: 'a1', to: 'b2', scale: 'small' },
+          // an unknown source — must be dropped, not throw
+          { kind: 'refugees', from: 'ghost', to: 'b2', scale: 'small' },
+        ],
+      },
+      ctx,
+    );
+    expect(state.nations.a1.stats).toEqual(NS(80, 69, 60, 49));
+    expect(state.nations.b2.stats).toEqual(NS(40, 31, 50, 61));
+  });
+});

server/abilities/migration.ts

@@ -0,0 +1,325 @@
+// The MIGRATION & REFUGEES ability (v0.42.0, #64) as a modular LLM-ability
+// (v0.40.0, #67). People moving between nations each turn: ordinary migration,
+// refugee flows (fleeing a war or disaster), a spreading diaspora, and an
+// exodus (people leaving with no destination). Unlike most other abilities this
+// one is **turn-transient**: it owns NO `GameState` field (no durable list, no
+// `db.ts` change) — exactly like the hybrid and disasters layers. Each op
+// carries a `kind`, a source `from` (the nation people leave), a destination
+// `to` (required for every kind except `exodus`), and a `scale` (small /
+// moderate / large). The engine applies a DETERMINISTIC effect chosen from the
+// per-`scale` tables below (no hidden randomness — the LLM chooses the kind and
+// scale, the tables decide the magnitude): the source LOSES a small amount of
+// population and economy, the destination GAINS a small amount of population and
+// economy (a `large` influx additionally strains the destination's stability),
+// both clamped to 0–100, mirrored to each side's regions (`regionStats`), and
+// each side's derived `stats` re-derived afterwards (the same 0-region /
+// no-entry guards as hybrid / economy / disasters, so a 0-region nation keeps
+// its directly-mutated value and the effect persists to the next turn). The
+// from↔to relation then moves one step toward the positive end of the
+// ally/neutral/rival/hostile ladder (`shiftRelationTowardPositive`) — capped at
+// `ally` for `refugees` (hosting refugees builds the strongest goodwill),
+// `neutral` for `migration` / `diaspora` (milder ties), and not at all for
+// `exodus`; a `war` relation is never touched (the nudge neither fabricates nor
+// escalates a war). Both `from` and `to` are resolved by the shared
+// `resolveNationRef` (id first, then a case-insensitive unique name); an
+// unknown / ambiguous ref, a missing `to` (for a non-`exodus` kind), or a
+// self-flow (`from` and `to` the same nation) drops the whole op. It never
+// moves territory (sole ownership is untouched).
+
+import { clampStat, deriveNationStats } from '../../shared/protocol';
+import type { MigrationOp, MigrationScale, MigrationKind } from '../../shared/protocol';
+import type { GameState, Nation, RelationStatus, StatKey } from '../../shared/types';
+import { resolveNationRef, str } from './shared';
+import type { Ability } from './types';
+
+/** The four kinds of population flow a turn can declare (v0.42.0, #64). */
+export const MIGRATION_KINDS: readonly MigrationKind[] = [
+  'migration',
+  'refugees',
+  'diaspora',
+  'exodus',
+];
+
+/** The three flow sizes a migration op can carry (v0.42.0, #64). */
+export const MIGRATION_SCALES: readonly MigrationScale[] = ['small', 'moderate', 'large'];
+
+const VALID_KINDS = new Set<string>(MIGRATION_KINDS);
+const VALID_SCALES = new Set<string>(MIGRATION_SCALES);
+
+/** True when `k` is one of the four known migration kinds (v0.42.0, #64). */
+export function isMigrationKind(k: unknown): k is MigrationKind {
+  return typeof k === 'string' && VALID_KINDS.has(k);
+}
+
+/** True when `s` is one of the three known migration scales (v0.42.0, #64). */
+export function isMigrationScale(s: unknown): s is MigrationScale {
+  return typeof s === 'string' && VALID_SCALES.has(s);
+}
+
+/**
+ * (v0.42.0, #64) The DETERMINISTIC per-`scale` stat dip applied to the SOURCE
+ * nation of a migration flow (the nation people leave). Each scale maps to a
+ * small set of signed (negative) stat deltas: the source loses population and
+ * economy. No hidden randomness — the LLM picks the scale, the table decides
+ * the magnitude. Military and stability are untouched by the source dip.
+ */
+export const MIGRATION_SOURCE_EFFECTS: Record<MigrationScale, Partial<Record<StatKey, number>>> = {
+  small: { population: -1, economy: -1 },
+  moderate: { population: -2, economy: -2 },
+  large: { population: -4, economy: -3 },
+};
+
+/**
+ * (v0.42.0, #64) The DETERMINISTIC per-`scale` stat gain applied to the
+ * DESTINATION nation of a migration flow (the nation people arrive in). Each
+ * scale maps to a small set of signed (positive) stat deltas: the destination
+ * gains population and economy. No hidden randomness. Military and stability
+ * are untouched by the base gain (the `large`-scale stability strain is applied
+ * separately, see {@link LARGE_INFLUX_STABILITY_DIP}).
+ */
+export const MIGRATION_DESTINATION_EFFECTS: Record<MigrationScale, Partial<Record<StatKey, number>>> =
+  {
+    small: { population: 1, economy: 1 },
+    moderate: { population: 2, economy: 2 },
+    large: { population: 3, economy: 3 },
+  };
+
+/**
+ * (v0.42.0, #64) The extra STABILITY dip applied to the destination of a
+ * `large`-scale influx only — a big population surge strains a society even as
+ * it grows. Added on top of the base destination gain.
+ */
+export const LARGE_INFLUX_STABILITY_DIP = -2;
+
+/**
+ * The positive-relations ladder, strongest (most positive) to weakest
+ * (least positive) — the same four non-war statuses, in the order a relation
+ * moves when it is nudged TOWARD the positive end. A missing relation is
+ * treated as `neutral`; `war` is never touched (a war is its own entity — a
+ * population flow neither fabricates nor escalates one). The `cap` in
+ * {@link shiftRelationTowardPositive} is a member of this array.
+ */
+const POSITIVE_ORDER: RelationStatus[] = ['ally', 'neutral', 'rival', 'hostile'];
+
+/**
+ * (v0.42.0, #64) Nudge the bilateral relation between nations `a` and `b`
+ * ONE step toward the POSITIVE end (toward `ally`) of the
+ * {@link POSITIVE_ORDER} ladder, applied symmetrically to both directions, but
+ * never past the given `cap`. A missing relation starts at `neutral`; a `war`
+ * relation is never touched (a population flow neither fabricates nor
+ * escalates a war — a warring pair is left exactly as it is). Mutates `state`
+ * in place (the caller passes a clone — applyTurnResult does). Never throws.
+ *
+ * `cap` is the most-positive status the nudge may reach:
+ *   - `refugees`   → `ally`     (hosting refugees builds the strongest goodwill)
+ *   - `migration` / `diaspora` → `neutral`  (milder ties)
+ *   - `exodus`     → no nudge at all
+ */
+export function shiftRelationTowardPositive(
+  state: GameState,
+  a: string,
+  b: string,
+  cap: RelationStatus,
+): void {
+  const na = state.nations[a];
+  const nb = state.nations[b];
+  if (!na || !nb) return;
+  const capIdx = POSITIVE_ORDER.indexOf(cap);
+  if (capIdx === -1) return; // unknown cap: no-op (defensive)
+  const step = (cur: RelationStatus | undefined): RelationStatus | null => {
+    if (cur === 'war') return null; // never touch a war relation
+    const s = cur ?? 'neutral'; // a missing relation is neutral
+    const i = POSITIVE_ORDER.indexOf(s);
+    if (i === -1) return 'neutral'; // defensive: unknown status
+    if (i <= capIdx) return s; // already at or more positive than the cap: no change
+    return POSITIVE_ORDER[i - 1]; // one step toward the positive end
+  };
+  const stepA = step(na.relations[b]);
+  if (stepA !== null) na.relations[b] = stepA;
+  const stepB = step(nb.relations[a]);
+  if (stepB !== null) nb.relations[a] = stepB;
+}
+
+/**
+ * (v0.42.0, #64) Validate the raw `migration` field of a turn into a safe
+ * list of {@link MigrationOp}s. Defensive like the rest of the parser — never
+ * throws. The raw value may be the object `{ ops: [...] }` (the TurnResult
+ * shape) or a bare array (be lenient about either). Each op needs a known
+ * `kind` (one of {@link MIGRATION_KINDS}), a known `scale` (one of
+ * {@link MIGRATION_SCALES}), a non-empty `from` (the source nation, capped at
+ * 200 chars), and — for every kind except `exodus` — a non-empty `to`
+ * (the destination nation, capped at 200 chars); a non-empty `detail` is capped
+ * at 300 chars. An op with an unknown / missing `kind`, an unknown / missing
+ * `scale`, an empty `from`, or (for a non-`exodus` kind) an empty `to` is
+ * dropped. Resolution of `from` / `to` to concrete nation ids happens at apply
+ * time (`applyMigrationOp`), not here. A missing / malformed top-level value
+ * yields `{ ops: [] }`.
+ */
+export function validateMigrationOps(raw: unknown): MigrationOp[] {
+  let list: unknown[] | null = null;
+  if (Array.isArray(raw)) {
+    list = raw;
+  } else if (raw && typeof raw === 'object') {
+    const inner = (raw as Record<string, unknown>).ops;
+    if (Array.isArray(inner)) list = inner;
+  }
+  if (!list) return [];
+  const out: MigrationOp[] = [];
+  for (const e of list) {
+    if (!e || typeof e !== 'object') continue;
+    const o = e as Record<string, unknown>;
+    if (!isMigrationKind(o.kind)) continue; // unknown / missing kind: drop
+    if (!isMigrationScale(o.scale)) continue; // unknown / missing scale: drop
+    const from = str(o.from, 200);
+    if (!from) continue; // empty / missing source: drop
+    const detail = str(o.detail, 300);
+    if (o.kind === 'exodus') {
+      // an exodus has no destination — `to` is optional (and ignored)
+      out.push({
+        kind: o.kind,
+        from,
+        scale: o.scale,
+        ...(detail ? { detail } : {}),
+      });
+    } else {
+      const to = str(o.to, 200);
+      if (!to) continue; // non-exodus kind needs a destination: drop
+      out.push({
+        kind: o.kind,
+        from,
+        to,
+        scale: o.scale,
+        ...(detail ? { detail } : {}),
+      });
+    }
+  }
+  return out;
+}
+
+/**
+ * Apply a set of signed stat `dips` to a nation's `stats` AND to every region
+ * it owns that has a `regionStats` entry (clamped to 0–100), then re-derive
+ * the nation's aggregate `stats` as the area×population-weighted median of its
+ * regions — the same 0-region / no-entry guards as the hybrid / economy /
+ * disasters layers, so a 0-region nation keeps its directly-mutated value and
+ * the effect persists to the next turn. Mutates in place; never throws.
+ */
+function applyNationDips(
+  nation: Nation,
+  dips: Partial<Record<StatKey, number>>,
+  regionStats: GameState['regionStats'],
+  geoOf?: (key: string) => { area: number; population: number } | undefined,
+): void {
+  (Object.keys(dips) as StatKey[]).forEach((k) => {
+    const d = dips[k];
+    if (typeof d === 'number') nation.stats[k] = clampStat(nation.stats[k] + d);
+  });
+  for (const key of nation.territory) {
+    const rs = regionStats[key];
+    if (!rs) continue; // a key with no entry is skipped
+    (Object.keys(dips) as StatKey[]).forEach((k) => {
+      const d = dips[k];
+      if (typeof d === 'number') rs[k] = clampStat(rs[k] + d);
+    });
+  }
+  // Re-derive the nation's aggregate stats so the effect persists (the main
+  // recompute ran earlier this turn; without this the change would be washed
+  // out next turn). A nation with no regionStats entry keeps its
+  // directly-mutated `stats`.
+  if (nation.territory.length > 0 && nation.territory.some((k) => regionStats[k])) {
+    nation.stats = deriveNationStats(nation.territory, regionStats, geoOf);
+  }
+}
+
+/**
+ * (v0.42.0, #64) Apply ONE migration / refugee op to the (cloned) `next` state,
+ * mutating it in place and never throwing. Resolution order:
+ *   1. `from` must resolve to a nation (id first, then a unique name); an
+ *      unknown / ambiguous source drops the op.
+ *   2. For every kind except `exodus`, `to` must resolve to a nation distinct
+ *      from `from` (a missing / unknown / ambiguous destination, or a
+ *      self-flow, drops the op); `exodus` has no destination and skips this.
+ * Then the deterministic per-`scale` effects from
+ * {@link MIGRATION_SOURCE_EFFECTS} / {@link MIGRATION_DESTINATION_EFFECTS}
+ * are applied:
+ *   - the SOURCE nation loses population and economy (all four kinds,
+ *     including `exodus`) — for a non-`exodus` op this is applied only AFTER
+ *     the destination is validated, so a self-flow or a bad destination drops
+ *     the op entirely and never touches the source;
+ *   - for a non-`exodus` kind the DESTINATION gains population and economy,
+ *     and a `large` influx additionally strains its stability by
+ *     {@link LARGE_INFLUX_STABILITY_DIP};
+ *   - each affected nation's derived `stats` are re-derived afterwards (the
+ *     same 0-region / no-entry guards, so the effect persists);
+ *   - for a non-`exodus` kind the from↔to relation moves one step toward the
+ *     positive end of the ladder (cap `ally` for `refugees`, `neutral` for
+ *     `migration` / `diaspora`; a `war` relation is left untouched).
+ * The op never moves territory (sole ownership is untouched) and never creates
+ * or escalates a war.
+ */
+export function applyMigrationOp(
+  next: GameState,
+  op: MigrationOp,
+  geoOf?: (key: string) => { area: number; population: number } | undefined,
+): void {
+  const from = resolveNationRef(next, op.from);
+  if (from === null) return; // unknown / ambiguous source: drop
+  const source = next.nations[from];
+  if (!source) return; // defensive: resolved id has no nation record
+
+  if (op.kind === 'exodus') {
+    // An exodus has no destination: the source loses population and economy
+    // and that is all (no gain, no relation nudge).
+    applyNationDips(source, MIGRATION_SOURCE_EFFECTS[op.scale], next.regionStats, geoOf);
+    return;
+  }
+
+  // Non-exodus: resolve the destination FIRST and drop the WHOLE op (including
+  // the source dip) when it is missing / unknown / ambiguous or a self-flow —
+  // so a self-flow or a bad destination never touches the source.
+  const to = op.to;
+  if (!to) return; // defensive: a non-exodus op should always have a `to`
+  const destId = resolveNationRef(next, to);
+  if (destId === null || destId === from) return; // unknown / self destination: drop
+  const dest = next.nations[destId];
+  if (!dest) return; // defensive
+
+  // The source loses population and economy (every non-exodus kind reaches
+  // here; the exodus path already applied its source dip and returned).
+  applyNationDips(source, MIGRATION_SOURCE_EFFECTS[op.scale], next.regionStats, geoOf);
+
+  // The destination gains population and economy; a large influx also strains
+  // its stability.
+  const destDips: Partial<Record<StatKey, number>> = { ...MIGRATION_DESTINATION_EFFECTS[op.scale] };
+  if (op.scale === 'large') {
+    destDips.stability = (destDips.stability ?? 0) + LARGE_INFLUX_STABILITY_DIP;
+  }
+  applyNationDips(dest, destDips, next.regionStats, geoOf);
+
+  // The from↔to relation moves one step toward the positive end, capped by
+  // kind (a `war` relation is left untouched by shiftRelationTowardPositive).
+  const cap: RelationStatus = op.kind === 'refugees' ? 'ally' : 'neutral';
+  shiftRelationTowardPositive(next, from, destId, cap);
+}
+
+export const migration: Ability<'migration'> = {
+  field: 'migration',
+  default: () => ({ ops: [] }),
+  // The low-level validator returns a bare list; the field's shape is the
+  // `{ ops }` object (mirrors the historical TurnResult shape).
+  validate: (raw) => ({ ops: validateMigrationOps(raw) }),
+  apply: (state, data, ctx) => {
+    for (const op of data.ops) {
+      applyMigrationOp(state, op, ctx.geoOf);
+    }
+  },
+  schemaLine: () =>
+    '  "migration": {"ops":[{"kind":"<migration|refugees|diaspora|exodus>","from":"<nation id or name>","to":"<nation id or name>","scale":"<small|moderate|large>","detail":"<short detail>"}]},',
+  constraint: () =>
+    '- Migration & refugees ("migration.ops") are people moving between nations this turn: a "kind" ("migration", "refugees", "diaspora", or "exodus"), a "from" (the source nation — id or name), a "to" (the destination nation — required for every kind except "exodus", which has no destination), and a "scale" (small / moderate / large). The engine applies a DETERMINISTIC effect (no hidden randomness): the source LOSES a small amount of population and economy, the destination GAINS a small amount of population and economy (a "large" influx additionally strains the destination\'s stability by 2), and the from↔to relation moves one step toward the positive end of the ally/neutral/rival/hostile ladder — capped at "ally" for "refugees" (hosting refugees builds the strongest goodwill), capped at "neutral" for "migration"/"diaspora" (milder ties), and not at all for "exodus"; the nudge never creates or escalates a "war" (a warring pair is left untouched). The layer is turn-transient (no memory): a continuing flow is simply RE-DECLARED each turn it persists. It never moves borders — sole ownership is untouched. Propose at most 1-2 per turn and narrate each one in "events" (a "social" or "diplomatic" event).',
+  isMeaningful: (data) => data.ops.length > 0,
+  stub: () => ({ ops: [] }),
+  // The layer is turn-transient — it contributes nothing to the user payload
+  // (no durable state to show the model), so the payload is always empty.
+  payload: () => ({}),
+};

server/abilities/registry.test.ts

@@ -3,13 +3,16 @@
 // These tests pin the refactor's two load-bearing guarantees:
 //
 //   1. GOLDEN PROMPTS — the system prompt (both tool variants) and the user
-//      prompt the refactored engine builds are BYTE-IDENTICAL to the committed
-//      golden fixtures in ./goldens/ (captured in P1 from the pre-refactor
-//      engine). Any transcription drift in an ability's schemaLine /
-//      constraint / payload is caught here.
+//      prompt the engine builds are BYTE-IDENTICAL to the committed golden
+//      fixtures in ./goldens/ (captured in P1 from the pre-refactor engine, and
+//      re-baselined when a feature INTENTIONALLY changes the prompt — e.g. the
+//      system goldens were regenerated in v0.41.0 when the disasters ability
+//      was added). Any transcription drift in an ability's schemaLine /
+//      constraint / payload is caught here. The USER prompt golden is unchanged
+//      by the disasters feature (its payload is always empty).
 //
 //   2. REGISTRY CONTRACT — the ABILITIES registry is the canonical ordered
-//      list of the 8 abilities; each ability's default() equals the canonical
+//      list of the 11 abilities; each ability's default() equals the canonical
 //      TurnResult default for its field, is a FRESH value (never a shared
 //      reference), its default is not "meaningful" while a populated value is,
 //      and the registry composes (a hypothetical extra ability can be appended
@@ -26,28 +29,53 @@ import { fileURLToPath } from 'node:url';
 import { describe, expect, it } from 'vitest';
 import {
   activeWarPairs,
+  applyDisasterEvent,
   applyIndustryEffects,
+  applyMigrationOp,
   atWar,
   buildSystemPrompt,
   buildUserPrompt,
+  DISASTER_EFFECTS,
+  DISASTER_SEVERITIES,
+  DISASTER_TYPES,
   freshNationId,
   freshWarId,
   HYBRID_STAT_EFFECT,
+  isDisasterSeverity,
+  isDisasterType,
   isHybridOpType,
   isIndustryType,
+  isMigrationKind,
+  isMigrationScale,
+  LARGE_INFLUX_STABILITY_DIP,
+  MIGRATION_DESTINATION_EFFECTS,
+  MIGRATION_KINDS,
+  MIGRATION_SCALES,
+  MIGRATION_SOURCE_EFFECTS,
   NEW_NATION_STATS,
   resolveNationRef,
   resolveRegionKey,
   shiftRelationTowardHostile,
+  shiftRelationTowardPositive,
   syncWarRelations,
+  validateDisasterEvents,
   validateEconomyOps,
   validateHybridOps,
   validateIdeologyOps,
   validateIndustryOps,
   validateLeaderOps,
+  validateMigrationOps,
   validateNuclearOps,
   validateTakeovers,
   validateWarOps,
+  validateSeaOps,
+  applySeaControl,
+  applySeaZoneBonuses,
+  SEA_ZONE_BONUS,
+  SEA_ZONES,
+  SEA_ZONE_IDS,
+  isSeaZoneId,
+  seaZoneName,
 } from '../engine';
 import { createPresetStore } from '../presets';
 import { ABILITIES } from './index';
@@ -61,6 +89,7 @@ import type {
   RegionResources,
   RelationStatus,
   RoundItem,
+  SeaZoneClaim,
   TradeAgreement,
 } from '../../shared/types';
 import type { MarkerInfo, TurnResult, WarInfo } from '../../shared/protocol';
@@ -134,6 +163,8 @@ const state: GameState = {
   trades: [],
   embargoes: [],
   industry: [],
+  // (v0.43.0, #65) no sea-zone control on a fresh state.
+  seaZones: [],
 };
 
 // --- buildUserPrompt arguments: every optional branch exercised. ---
@@ -170,6 +201,7 @@ const nationResources: Record<string, RegionResources> = {
 };
 const industryProjects: IndustryProject[] = [{ regionKey: 'a-r1', type: 'industry' }];
 const nuclear: Record<string, boolean> = { a1: true, b2: false, c3: false };
+const seaZones: SeaZoneClaim[] = [];
 
 /**
  * Assert the current prompt output is byte-identical to the committed golden —
@@ -206,6 +238,9 @@ function fullDefaultTurn(): TurnResult {
     nuclear: { arm: [], strikes: [] },
     leaders: { changes: [] },
     ideology: { changes: [] },
+    disasters: { events: [] },
+    migration: { ops: [] },
+    sea: { control: [] },
     markers: { add: [], remove: [] },
   };
 }
@@ -229,11 +264,17 @@ function meaningfulFor(field: AbilityField): TurnResult[AbilityField] {
       return { changes: [{ target: 'a1', name: 'New Alpha Leader', cause: 'appointed' }] };
     case 'ideology':
       return { changes: [{ target: 'a1', to: 'democracy' }] };
+    case 'disasters':
+      return { events: [{ type: 'earthquake', target: 'a1', severity: 'minor' }] };
+    case 'migration':
+      return { ops: [{ kind: 'migration', from: 'a1', to: 'b2', scale: 'small' }] };
+    case 'sea':
+      return { control: [{ zone: 'pacific', by: 'a1' }] };
   }
 }
 
 describe('ABILITIES registry (v0.40.0, #67)', () => {
-  it('is the canonical 8-ability order (takeovers → ideology)', () => {
+  it('is the canonical 11-ability order (takeovers → sea)', () => {
     expect(ABILITIES.map((a) => a.field)).toEqual([
       'takeovers',
       'wars',
@@ -243,13 +284,16 @@ describe('ABILITIES registry (v0.40.0, #67)', () => {
       'nuclear',
       'leaders',
       'ideology',
+      'disasters',
+      'migration',
+      'sea',
     ]);
   });
 
-  it('lists 8 distinct fields, each a key of TurnResult', () => {
+  it('lists 11 distinct fields, each a key of TurnResult', () => {
     const fields = ABILITIES.map((a) => a.field);
-    expect(fields).toHaveLength(8);
-    expect(new Set(fields).size).toBe(8);
+    expect(fields).toHaveLength(11);
+    expect(new Set(fields).size).toBe(11);
     const all = fullDefaultTurn();
     for (const f of fields) expect(f in all).toBe(true);
   });
@@ -279,6 +323,7 @@ describe('ABILITIES registry (v0.40.0, #67)', () => {
         nationResources,
         industryProjects,
         nuclear,
+        seaZones,
       ),
     );
   });
@@ -308,13 +353,13 @@ describe('ABILITIES registry (v0.40.0, #67)', () => {
   it('declares exactly the durable GameState fields the db migration must default', () => {
     const owned: string[] = [];
     for (const a of ABILITIES) if (a.stateFields) owned.push(...a.stateFields);
-    expect([...owned].sort()).toEqual(['embargoes', 'industry', 'trades', 'wars']);
+    expect([...owned].sort()).toEqual(['embargoes', 'industry', 'seaZones', 'trades', 'wars']);
   });
 
   it('composes: a hypothetical extra ability can be appended and every uniform loop still runs', () => {
     // The registry is a plain ordered array the engine iterates uniformly. A
     // structural (field-name-agnostic) loop over the abilities — schema line,
-    // constraint bullet — must keep working when a 9th ability is appended.
+    // constraint bullet — must keep working when an 11th ability is appended.
     // This documents the extension point without widening the closed
     // AbilityField union.
     interface Loopable {
@@ -333,9 +378,9 @@ describe('ABILITIES registry (v0.40.0, #67)', () => {
       'custom',
     ]);
     // every uniform loop runs over all N abilities, the appended one included:
-    expect(extended.map((a) => a.schemaLine())).toHaveLength(9);
-    expect(extended.map((a) => a.constraint())).toHaveLength(9);
-    expect(extended[8].schemaLine()).toBe('  "custom": [],');
+    expect(extended.map((a) => a.schemaLine())).toHaveLength(12);
+    expect(extended.map((a) => a.constraint())).toHaveLength(12);
+    expect(extended[11].schemaLine()).toBe('  "custom": [],');
   });
 
   it('the engine still re-exports every name its callers import from it', () => {
@@ -366,6 +411,34 @@ describe('ABILITIES registry (v0.40.0, #67)', () => {
       validateTakeovers,
       validateWarOps,
       applyIndustryEffects,
+      // disasters (v0.41.0, #63)
+      validateDisasterEvents,
+      applyDisasterEvent,
+      isDisasterType,
+      isDisasterSeverity,
+      DISASTER_TYPES,
+      DISASTER_SEVERITIES,
+      DISASTER_EFFECTS,
+      // migration (v0.42.0, #64)
+      validateMigrationOps,
+      applyMigrationOp,
+      shiftRelationTowardPositive,
+      isMigrationKind,
+      isMigrationScale,
+      MIGRATION_KINDS,
+      MIGRATION_SCALES,
+      MIGRATION_SOURCE_EFFECTS,
+      MIGRATION_DESTINATION_EFFECTS,
+      LARGE_INFLUX_STABILITY_DIP,
+      // sea (v0.43.0, #65)
+      validateSeaOps,
+      applySeaControl,
+      applySeaZoneBonuses,
+      SEA_ZONE_BONUS,
+      SEA_ZONES,
+      SEA_ZONE_IDS,
+      isSeaZoneId,
+      seaZoneName,
     };
     for (const [name, value] of Object.entries(reexported)) {
       expect(value, `engine should re-export ${name}`).toBeDefined();

server/abilities/sea.test.ts

@@ -0,0 +1,494 @@
+// Unit tests for the SEA (naval / sea control) ability (v0.43.0, #65) — the
+// modular, DURABLE LLM-ability that gives nations sole control over a fixed
+// set of 12 named sea zones: the zone is upserted in `GameState.seaZones`
+// (replace in place, contest by higher current military), and every committed
+// turn the controller earns a deterministic +1 military / +1 economy bonus
+// (clamped, mirrored to its regions, re-derived). The layer never touches
+// `territory` / `unowned` — it is fully parallel to but independent of land.
+// This is the ability's own test file (the registry's cross-cutting
+// guarantees — order, distinct fields, the system/user goldens — are covered
+// by ./registry.test.ts). The stub never proposes a sea op, so the apply path
+// is exercised here, not by the e2e suite.
+
+import { describe, expect, it } from 'vitest';
+
+import {
+  SEA_ZONES,
+  SEA_ZONE_IDS,
+  applySeaControl,
+  applySeaZoneBonuses,
+  isSeaZoneId,
+  sea,
+  seaZoneName,
+  validateSeaOps,
+} from './sea';
+
+import type {
+  GameState,
+  Nation,
+  NationStats,
+  RegionStats,
+  SeaZoneClaim,
+} from '../../shared/types';
+
+// ---------------------------------------------------------------------------
+// Fixture helpers
+// ---------------------------------------------------------------------------
+
+/** Build a NationStats from the four canonical indices (military, economy, stability, population). */
+function NS(military: number, economy: number, stability: number, population: number): NationStats {
+  return { military, economy, stability, population };
+}
+
+/** Build a RegionStats from the four canonical indices. */
+function RS(military: number, economy: number, stability: number, population: number): RegionStats {
+  return { military, economy, stability, population };
+}
+
+/** A minimal nation: the given id/name/stats/region-key territory. */
+function mkNation(
+  id: string,
+  name: string,
+  stats: NationStats,
+  territory: string[],
+): Nation {
+  return { id, name, type: 'major', stats, territory, relations: {} };
+}
+
+/**
+ * A minimal GameState carrying the given nations (keyed by id), per-region
+ * stats, and an optional existing sea-zone list. Every other required field
+ * is at its fresh-game baseline.
+ */
+function mkState(
+  nations: Record<string, Nation>,
+  regionStats: Record<string, RegionStats>,
+  seaZones: SeaZoneClaim[] = [],
+): GameState {
+  return {
+    id: 'g1',
+    presetId: 'test',
+    presetTitle: 'Test',
+    playerNationId: Object.keys(nations)[0] ?? 'a1',
+    turn: 1,
+    date: '1939-09-01',
+    nations,
+    events: [],
+    pending: [],
+    version: 1,
+    unowned: [],
+    pendingNationOps: [],
+    markers: [],
+    regionStats,
+    wars: [],
+    trades: [],
+    embargoes: [],
+    industry: [],
+    seaZones,
+  };
+}
+
+// ---------------------------------------------------------------------------
+// SEA_ZONES / isSeaZoneId / seaZoneName
+// ---------------------------------------------------------------------------
+
+describe('SEA_ZONES / SEA_ZONE_IDS / isSeaZoneId / seaZoneName', () => {
+  it('exposes exactly the 12 fixed sea zones', () => {
+    expect(SEA_ZONES).toHaveLength(12);
+    const ids = SEA_ZONES.map((z) => z.id);
+    expect(ids).toEqual([
+      'north-atlantic',
+      'south-atlantic',
+      'pacific',
+      'indian',
+      'mediterranean',
+      'north-sea',
+      'baltic',
+      'arctic',
+      'black-sea',
+      'gulf-mexico',
+      'red-sea',
+      'sargasso',
+    ]);
+  });
+
+  it('SEA_ZONE_IDS is a ReadonlySet of all 12 ids', () => {
+    expect(SEA_ZONE_IDS).toBeInstanceOf(Set);
+    expect(SEA_ZONE_IDS.size).toBe(12);
+    for (const z of SEA_ZONES) expect(SEA_ZONE_IDS.has(z.id)).toBe(true);
+  });
+
+  it('isSeaZoneId accepts each known id and rejects unknown / non-strings', () => {
+    for (const z of SEA_ZONES) expect(isSeaZoneId(z.id)).toBe(true);
+    expect(isSeaZoneId('atlantic-ocean')).toBe(false);
+    expect(isSeaZoneId('')).toBe(false);
+  });
+
+  it('seaZoneName returns the human-readable name; an unknown id is returned raw', () => {
+    expect(seaZoneName('pacific')).toBe('Pacific Ocean');
+    expect(seaZoneName('mediterranean')).toBe('Mediterranean Sea');
+    expect(seaZoneName('nope')).toBe('nope');
+  });
+});
+
+// ---------------------------------------------------------------------------
+// validateSeaOps
+// ---------------------------------------------------------------------------
+
+describe('validateSeaOps', () => {
+  it('accepts the { control: [...] } object shape and a bare array', () => {
+    const op = { zone: 'pacific', by: 'a1' };
+    expect(validateSeaOps({ control: [op] })).toEqual({ control: [op] });
+    expect(validateSeaOps([op])).toEqual({ control: [op] });
+  });
+
+  it('drops an op with an unknown / missing zone', () => {
+    expect(validateSeaOps([{ zone: 'nope', by: 'a1' }])).toEqual({ control: [] });
+    expect(validateSeaOps([{ by: 'a1' }])).toEqual({ control: [] });
+    expect(validateSeaOps([{ zone: '', by: 'a1' }])).toEqual({ control: [] });
+  });
+
+  it('drops an op with an empty / missing `by` (the controller)', () => {
+    expect(validateSeaOps([{ zone: 'pacific', by: '' }])).toEqual({ control: [] });
+    expect(validateSeaOps([{ zone: 'pacific' }])).toEqual({ control: [] });
+  });
+
+  it('drops a non-object entry', () => {
+    expect(validateSeaOps([42, 'nope', null, { zone: 'pacific', by: 'a1' }])).toEqual({
+      control: [{ zone: 'pacific', by: 'a1' }],
+    });
+  });
+
+  it('a missing / malformed top-level value yields { control: [] }', () => {
+    expect(validateSeaOps(undefined)).toEqual({ control: [] });
+    expect(validateSeaOps(null)).toEqual({ control: [] });
+    expect(validateSeaOps('nope')).toEqual({ control: [] });
+    expect(validateSeaOps({ control: 'nope' })).toEqual({ control: [] });
+  });
+
+  it('caps `zone` at 100 and `by` at 200 chars', () => {
+    const longBy = 'f'.repeat(500);
+    const out = validateSeaOps([{ zone: 'pacific', by: longBy }]);
+    expect(out.control).toHaveLength(1);
+    expect(out.control[0].by).toHaveLength(200);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// applySeaControl
+// ---------------------------------------------------------------------------
+
+describe('applySeaControl', () => {
+  it('a single op sets a new zone claim', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']) },
+      { 'a-r1': RS(80, 70, 60, 50) },
+    );
+    applySeaControl(state, [{ zone: 'pacific', by: 'a1' }]);
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'a1' }]);
+  });
+
+  it('replaces an existing claim in place (position preserved)', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(90, 40, 20, 30), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(90, 40, 20, 30) },
+      [
+        { zone: 'pacific', by: 'a1' },
+        { zone: 'indian', by: 'b2' },
+      ],
+    );
+    // b2 now claims pacific — the pacific claim moves to b2 but stays at index 0
+    applySeaControl(state, [{ zone: 'pacific', by: 'b2' }]);
+    expect(state.seaZones).toEqual([
+      { zone: 'pacific', by: 'b2' },
+      { zone: 'indian', by: 'b2' },
+    ]);
+  });
+
+  it('appends a new zone after existing claims', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']) },
+      { 'a-r1': RS(80, 70, 60, 50) },
+      [{ zone: 'pacific', by: 'a1' }],
+    );
+    applySeaControl(state, [{ zone: 'arctic', by: 'a1' }]);
+    expect(state.seaZones).toEqual([
+      { zone: 'pacific', by: 'a1' },
+      { zone: 'arctic', by: 'a1' },
+    ]);
+  });
+
+  it('a contest: the higher current military wins', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(90, 40, 20, 30), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(90, 40, 20, 30) },
+    );
+    // b2 has higher military (90 > 80) → b2 wins
+    applySeaControl(state, [
+      { zone: 'pacific', by: 'a1' },
+      { zone: 'pacific', by: 'b2' },
+    ]);
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'b2' }]);
+  });
+
+  it('a contest tie: the earlier-listed op wins', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(50, 50, 50, 50), ['b-r1']),
+      },
+      { 'a-r1': RS(50, 50, 50, 50), 'b-r1': RS(50, 50, 50, 50) },
+    );
+    // equal military (50 == 50) → a1 wins (listed first)
+    applySeaControl(state, [
+      { zone: 'pacific', by: 'a1' },
+      { zone: 'pacific', by: 'b2' },
+    ]);
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'a1' }]);
+  });
+
+  it('two ops for the same nation on the same zone: a single claim (no contest)', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']) },
+      { 'a-r1': RS(80, 70, 60, 50) },
+    );
+    applySeaControl(state, [
+      { zone: 'pacific', by: 'a1' },
+      { zone: 'pacific', by: 'a1' },
+    ]);
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'a1' }]);
+  });
+
+  it('resolves `by` by unique name (not just id)', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']) },
+      { 'a-r1': RS(80, 70, 60, 50) },
+    );
+    applySeaControl(state, [{ zone: 'pacific', by: 'Alpha' }]);
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'a1' }]);
+  });
+
+  it('an unresolvable `by` is dropped; if all ops on a zone drop, the zone is untouched', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']) },
+      { 'a-r1': RS(80, 70, 60, 50) },
+      [{ zone: 'pacific', by: 'a1' }],
+    );
+    // ghost does not exist → dropped; pacific stays as a1
+    applySeaControl(state, [{ zone: 'pacific', by: 'ghost' }]);
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'a1' }]);
+
+    // a NEW zone with only an unresolvable op → zone not added
+    applySeaControl(state, [{ zone: 'arctic', by: 'ghost' }]);
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'a1' }]);
+  });
+
+  it('an ambiguous name (two nations share it) drops the op', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Twin', NS(80, 70, 60, 50), ['a-r1']),
+        a2: mkNation('a2', 'Twin', NS(20, 20, 20, 20), ['a-r2']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'a-r2': RS(20, 20, 20, 20) },
+    );
+    applySeaControl(state, [{ zone: 'pacific', by: 'Twin' }]);
+    // ambiguous → dropped
+    expect(state.seaZones).toEqual([]);
+  });
+
+  it('never touches `territory` or `unowned`', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(80, 70, 60, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(90, 40, 20, 30), ['b-r1']),
+      },
+      { 'a-r1': RS(80, 70, 60, 50), 'b-r1': RS(90, 40, 20, 30) },
+    );
+    applySeaControl(state, [
+      { zone: 'pacific', by: 'a1' },
+      { zone: 'pacific', by: 'b2' },
+    ]);
+    expect(state.nations.a1.territory).toEqual(['a-r1']);
+    expect(state.nations.b2.territory).toEqual(['b-r1']);
+    expect(state.unowned).toEqual([]);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// applySeaZoneBonuses
+// ---------------------------------------------------------------------------
+
+describe('applySeaZoneBonuses', () => {
+  it('a controller earns +1 military and +1 economy (clamped, mirrored, re-derived)', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1']) },
+      { 'a-r1': RS(50, 50, 50, 50) },
+      [{ zone: 'pacific', by: 'a1' }],
+    );
+    applySeaZoneBonuses(state);
+    // +1 to both military and economy, mirrored to the region, re-derived
+    // (single region → re-derive gives back the region's value)
+    expect(state.nations.a1.stats).toEqual(NS(51, 51, 50, 50));
+    expect(state.regionStats['a-r1']).toEqual(RS(51, 51, 50, 50));
+  });
+
+  it('clamps to 0 and 100', () => {
+    // military at 99 → 100; economy at 1 → 2
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(99, 1, 50, 50), ['a-r1']) },
+      { 'a-r1': RS(99, 1, 50, 50) },
+      [{ zone: 'pacific', by: 'a1' }],
+    );
+    applySeaZoneBonuses(state);
+    expect(state.nations.a1.stats.military).toBe(100);
+    expect(state.nations.a1.stats.economy).toBe(2);
+  });
+
+  it('a nation controlling several zones stacks the bonus', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1']) },
+      { 'a-r1': RS(50, 50, 50, 50) },
+      [
+        { zone: 'pacific', by: 'a1' },
+        { zone: 'indian', by: 'a1' },
+      ],
+    );
+    applySeaZoneBonuses(state);
+    // +2 to both (one per zone)
+    expect(state.nations.a1.stats).toEqual(NS(52, 52, 50, 50));
+  });
+
+  it('a 0-region nation keeps its directly-mutated stats (no re-derive)', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), []) },
+      {},
+      [{ zone: 'pacific', by: 'a1' }],
+    );
+    applySeaZoneBonuses(state);
+    // direct mutation, no re-derive (no regions)
+    expect(state.nations.a1.stats).toEqual(NS(51, 51, 50, 50));
+  });
+
+  it('a stale controller (nation no longer in `nations`) is skipped; the claim is kept', () => {
+    // Build a state where the claim references a nation id that is not in `nations`
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1']) },
+      { 'a-r1': RS(50, 50, 50, 50) },
+      [{ zone: 'pacific', by: 'ghost' }],
+    );
+    applySeaZoneBonuses(state);
+    // ghost is not in nations → skipped; a1 is unaffected
+    expect(state.nations.a1.stats).toEqual(NS(50, 50, 50, 50));
+    // the claim is kept (not removed)
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'ghost' }]);
+  });
+
+  it('an empty seaZones list is a no-op', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1']) },
+      { 'a-r1': RS(50, 50, 50, 50) },
+      [],
+    );
+    applySeaZoneBonuses(state);
+    expect(state.nations.a1.stats).toEqual(NS(50, 50, 50, 50));
+  });
+
+  it('never touches `territory` or `unowned`', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1']) },
+      { 'a-r1': RS(50, 50, 50, 50) },
+      [{ zone: 'pacific', by: 'a1' }],
+    );
+    applySeaZoneBonuses(state);
+    expect(state.nations.a1.territory).toEqual(['a-r1']);
+    expect(state.unowned).toEqual([]);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// The Ability object contract
+// ---------------------------------------------------------------------------
+
+describe('sea ability', () => {
+  it('owns the "sea" field; default() is a fresh empty { control: [] }', () => {
+    expect(sea.field).toBe('sea');
+    expect(sea.default()).toEqual({ control: [] });
+    expect(sea.default()).not.toBe(sea.default());
+  });
+
+  it('default() is not meaningful; a populated value is', () => {
+    expect(sea.isMeaningful(sea.default())).toBe(false);
+    expect(sea.isMeaningful({ control: [{ zone: 'pacific', by: 'a1' }] })).toBe(true);
+  });
+
+  it('validate() wraps the validator into the SeaOps shape', () => {
+    expect(sea.validate([{ zone: 'pacific', by: 'a1' }])).toEqual({
+      control: [{ zone: 'pacific', by: 'a1' }],
+    });
+    expect(sea.validate(undefined)).toEqual({ control: [] });
+  });
+
+  it('the stub value equals default() (the stub never proposes a sea op)', () => {
+    expect(sea.stub()).toEqual({ control: [] });
+  });
+
+  it('stateFields is [seaZones] (the durable GameState field)', () => {
+    expect(sea.stateFields).toEqual(['seaZones']);
+  });
+
+  it('payload() emits seaZones (even when empty / undefined)', () => {
+    expect(sea.payload({ seaZones: [] } as never)).toEqual({ seaZones: [] });
+    expect(sea.payload({} as never)).toEqual({ seaZones: [] });
+    expect(sea.payload({ seaZones: [{ zone: 'pacific', by: 'a1' }] } as never)).toEqual({
+      seaZones: [{ zone: 'pacific', by: 'a1' }],
+    });
+  });
+
+  it('apply() runs the ops then the per-turn bonus (no throw on a bad ref)', () => {
+    const state = mkState(
+      {
+        a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1']),
+        b2: mkNation('b2', 'Bravo', NS(80, 40, 20, 30), ['b-r1']),
+      },
+      { 'a-r1': RS(50, 50, 50, 50), 'b-r1': RS(80, 40, 20, 30) },
+    );
+    const ctx = { previous: state, actingTurn: state.turn };
+    sea.apply(
+      state,
+      {
+        control: [
+          { zone: 'pacific', by: 'a1' },
+          { zone: 'pacific', by: 'b2' },
+          // an unresolvable ref — must be dropped, not throw
+          { zone: 'arctic', by: 'ghost' },
+        ],
+      },
+      ctx,
+    );
+    // contest: b2 (military 80) beats a1 (military 50) → b2 controls pacific
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'b2' }]);
+    // b2 gets the +1/+1 bonus (it controls pacific)
+    expect(state.nations.b2.stats).toEqual(NS(81, 41, 20, 30));
+    // a1 is unaffected
+    expect(state.nations.a1.stats).toEqual(NS(50, 50, 50, 50));
+  });
+
+  it('apply() with an empty control still applies the per-turn bonus to existing claims', () => {
+    const state = mkState(
+      { a1: mkNation('a1', 'Alpha', NS(50, 50, 50, 50), ['a-r1']) },
+      { 'a-r1': RS(50, 50, 50, 50) },
+      [{ zone: 'pacific', by: 'a1' }],
+    );
+    const ctx = { previous: state, actingTurn: state.turn };
+    sea.apply(state, { control: [] }, ctx);
+    // no new claims, but the existing claim's controller earns the bonus
+    expect(state.seaZones).toEqual([{ zone: 'pacific', by: 'a1' }]);
+    expect(state.nations.a1.stats).toEqual(NS(51, 51, 50, 50));
+  });
+});

server/abilities/sea.ts

@@ -0,0 +1,210 @@
+// The SEA (naval / sea control) ability (v0.43.0, #65) as a modular
+// LLM-ability (v0.40.0, #67) — the naval layer, fully parallel to but
+// INDEPENDENT of land. The world has a fixed set of 12 named SEA ZONES
+// (`SEA_ZONES` in shared/protocol.ts); each is under the SOLE CONTROL of at
+// most one nation. Controlling a sea zone never moves land (`territory` /
+// `unowned` are untouched) and moving land never touches a sea zone.
+//
+// Each turn the LLM declares `sea.control` ops — one op names the zone and
+// the nation that (now) controls it. The engine resolves `by` (id first, then
+// a case-insensitive unique name, via the shared `resolveNationRef`) and
+// UPSERTS the zone's claim in `GameState.seaZones` (replace in place if the
+// zone is already claimed, append if new). If two or more ops this turn claim
+// the SAME zone for DIFFERENT resolved nations, the zone is CONTESTED: the
+// higher current `stats.military` wins (a tie goes to the op listed earlier in
+// the `control` array) — deterministic, no hidden randomness. An unresolvable
+// `by` is dropped (never thrown).
+//
+// Every committed turn — INCLUDING a turn with an empty `control` — each
+// existing claim's controller earns a small DETERMINISTIC bonus
+// (`SEA_ZONE_BONUS = 1` military + 1 economy, clamped to 0–100, mirrored to
+// the controller's regions and re-derived with the same 0-region / no-entry
+// guards as the economy / migration layers); a claim whose nation no longer
+// exists is skipped (the claim is kept, never thrown). The layer is DURABLE
+// (unlike the turn-transient hybrid / disasters / migration layers):
+// `GameState.seaZones` persists across turns and in SQLite, and the user
+// payload always carries the current `seaZones` list (even when empty).
+
+import {
+  clampStat,
+  deriveNationStats,
+  isSeaZoneId,
+} from '../../shared/protocol';
+export { SEA_ZONES, SEA_ZONE_IDS, isSeaZoneId, seaZoneName } from '../../shared/protocol';
+import type { SeaControlOp, SeaOps } from '../../shared/protocol';
+import type { GameState, Nation } from '../../shared/types';
+import { resolveNationRef, str } from './shared';
+import type { Ability } from './types';
+
+/**
+ * (v0.43.0, #65) The DETERMINISTIC per-turn bonus each sea-zone controller
+ * earns (applied to BOTH `military` and `economy`, clamped to 0–100, mirrored
+ * to the controller's regions, and re-derived with the same 0-region /
+ * no-entry guards as the economy / migration layers). No hidden randomness.
+ */
+export const SEA_ZONE_BONUS = 1;
+
+/**
+ * (v0.43.0, #65) Validate the raw `sea` field of a turn into a safe
+ * {@link SeaOps}. Defensive like the rest of the parser — never throws. The
+ * raw value may be the object `{ control: [...] }` (the TurnResult shape) or
+ * a bare array (be lenient about either). Each op needs a valid `zone` (one of
+ * {@link SEA_ZONES}) and a non-empty `by` (the controlling nation's id or
+ * unique name, capped at 200 chars). An op with an unknown / missing `zone` or
+ * an empty / missing `by` is dropped. Resolution of `by` to a concrete nation
+ * id happens at apply time (`applySeaControl`), not here. A missing /
+ * malformed top-level value yields `{ control: [] }`.
+ */
+export function validateSeaOps(raw: unknown): SeaOps {
+  const out: SeaOps = { control: [] };
+  let list: unknown[] | null = null;
+  if (Array.isArray(raw)) {
+    list = raw;
+  } else if (raw && typeof raw === 'object') {
+    const inner = (raw as Record<string, unknown>).control;
+    if (Array.isArray(inner)) list = inner;
+  }
+  if (!list) return out;
+  for (const e of list) {
+    if (!e || typeof e !== 'object') continue;
+    const o = e as Record<string, unknown>;
+    const zone = str(o.zone, 100);
+    if (!zone || !isSeaZoneId(zone)) continue; // unknown / missing zone: drop
+    const by = str(o.by, 200);
+    if (!by) continue; // empty / missing controller: drop
+    out.control.push({ zone, by });
+  }
+  return out;
+}
+
+/**
+ * (v0.43.0, #65) Upsert the turn's sea-control ops into `next.seaZones`,
+ * mutating in place and never throwing. Each op's `by` is resolved against the
+ * CURRENT state (id first, then a case-insensitive unique name) — an
+ * unresolvable ref is dropped. Per zone (in first-appearance order): a single
+ * surviving op SETS or REPLACES the zone's controller (replace the existing
+ * entry in place — preserving its position — or append a new one); two or
+ * more surviving ops on the same zone for DIFFERENT resolved nations make the
+ * zone CONTESTED — the higher current `stats.military` wins (a tie goes to the
+ * op listed earlier in the `control` array), and the winner becomes the
+ * controller. A zone whose ops all resolve to the same nation is simply (re-)
+ * set to that nation. Sea control never touches `territory` / `unowned`.
+ */
+export function applySeaControl(next: GameState, ops: SeaControlOp[]): void {
+  // Group the ops by zone, keeping the original (first-appearance) order of
+  // zones and each zone's ops (so the contest tie-break "earlier in the
+  // control array" is well-defined).
+  const byZone = new Map<string, { index: number; by: string }[]>();
+  ops.forEach((op, index) => {
+    const list = byZone.get(op.zone) ?? [];
+    list.push({ index, by: op.by });
+    byZone.set(op.zone, list);
+  });
+
+  for (const [zone, list] of byZone) {
+    // Resolve each op's `by`; an unresolvable ref is dropped (the zone is
+    // still decided by the ops that do resolve).
+    const resolved = list
+      .map(({ index, by }) => ({ index, id: resolveNationRef(next, by) }))
+      .filter((r): r is { index: number; id: string } => r.id !== null);
+    if (resolved.length === 0) continue; // nothing resolved: zone untouched
+
+    // Contest: the highest current `stats.military` wins; a strict `>` keeps
+    // the EARLIER-listed op on a tie (the list is in control-array order).
+    let winner = resolved[0];
+    for (const r of resolved) {
+      const mw = next.nations[winner.id]?.stats.military ?? 0;
+      const mr = next.nations[r.id]?.stats.military ?? 0;
+      if (mr > mw) winner = r;
+    }
+
+    const existing = next.seaZones.find((c) => c.zone === zone);
+    if (existing) {
+      existing.by = winner.id; // replace in place (position preserved)
+    } else {
+      next.seaZones.push({ zone, by: winner.id });
+    }
+  }
+}
+
+/**
+ * (v0.43.0, #65) The per-turn sea bonus, applied EVERY committed turn (not
+ * just to this turn's claims): each entry of `next.seaZones` grants its
+ * controller `SEA_ZONE_BONUS` military + `SEA_ZONE_BONUS` economy (clamped
+ * to 0–100, mirrored to every region the nation owns, then the nation's
+ * derived `stats` re-derived — the same 0-region / no-entry guards as the
+ * economy / migration layers, so a 0-region nation keeps its directly-mutated
+ * value). A nation controlling several zones stacks the bonus; a claim whose
+ * nation no longer exists (removed by a merge / split this turn) is skipped —
+ * the claim is kept, never thrown. Never throws.
+ */
+export function applySeaZoneBonuses(
+  next: GameState,
+  geoOf?: (key: string) => { area: number; population: number } | undefined,
+): void {
+  if (next.seaZones.length === 0) return;
+
+  // nation id -> {military, economy} delta (claims for the same nation stack).
+  const delta = new Map<string, { military: number; economy: number }>();
+  for (const c of next.seaZones) {
+    const d = delta.get(c.by) ?? { military: 0, economy: 0 };
+    d.military += SEA_ZONE_BONUS;
+    d.economy += SEA_ZONE_BONUS;
+    delta.set(c.by, d);
+  }
+
+  const applyNation = (n: Nation, d: { military: number; economy: number }): void => {
+    (['military', 'economy'] as const).forEach((k) => {
+      n.stats[k] = clampStat(n.stats[k] + d[k]);
+    });
+    for (const key of n.territory) {
+      const rs = next.regionStats[key];
+      if (!rs) continue; // a key with no entry is skipped
+      (['military', 'economy'] as const).forEach((k) => {
+        rs[k] = clampStat(rs[k] + d[k]);
+      });
+    }
+    // Re-derive the nation's aggregate stats so the effect persists (the main
+    // recompute ran earlier this turn; without this the change would be washed
+    // out next turn). A nation with no regionStats entry keeps its
+    // directly-mutated `stats`.
+    if (n.territory.length > 0 && n.territory.some((k) => next.regionStats[k])) {
+      n.stats = deriveNationStats(n.territory, next.regionStats, geoOf);
+    }
+  };
+
+  for (const [id, d] of delta) {
+    const n = next.nations[id];
+    if (!n) continue; // a nation removed this turn: the bonus is dropped (claim kept)
+    applyNation(n, d);
+  }
+}
+
+export const sea: Ability<'sea'> = {
+  field: 'sea',
+  default: () => ({ control: [] }),
+  validate: (raw) => validateSeaOps(raw),
+  apply: (state, data, ctx) => {
+    // (1) APPLY OPS: this turn's control ops upsert `GameState.seaZones`
+    //     (a single op sets/replaces the zone's controller; a same-zone
+    //     contest goes to the higher current `stats.military`, a tie to the
+    //     earlier-listed op).
+    // (2) PER-TURN BONUS: EVERY committed turn — including this one, and
+    //     including turns with an empty `control` — each existing claim's
+    //     controller earns the deterministic military/economy bonus, so a
+    //     zone that stays held keeps paying out.
+    applySeaControl(state, data.control);
+    applySeaZoneBonuses(state, ctx.geoOf);
+  },
+  schemaLine: () =>
+    '  "sea": {"control":[{"zone":"<seaZoneId>","by":"<nation id or name>"}]},',
+  constraint: () =>
+    '- Sea control ("sea") is the naval layer, fully parallel to but INDEPENDENT of land: each of the 12 fixed sea zones — "north-atlantic" (North Atlantic), "south-atlantic" (South Atlantic), "pacific" (Pacific Ocean), "indian" (Indian Ocean), "mediterranean" (Mediterranean Sea), "north-sea" (North Sea), "baltic" (Baltic Sea), "arctic" (Arctic Ocean), "black-sea" (Black Sea), "gulf-mexico" (Gulf of Mexico), "red-sea" (Red Sea), "sargasso" (Sargasso Sea) — is under the SOLE control of at most one nation. A control op ({"zone":"<id>","by":"<nation>"}) sets or replaces that zone\'s controller (the user message\'s "seaZones" field lists who controls what now); if two or more ops this turn claim the SAME zone for DIFFERENT nations, the zone is CONTESTED and the higher current "military" wins (a tie goes to the earlier-listed op). Every committed turn each zone\'s controller earns a small deterministic +1 military and +1 economy. Sea control NEVER moves land (no territory changes) — it is a parallel track. Propose at most 1-2 claims per turn and narrate each one in "events" (a "military" or "diplomatic" event).',
+  isMeaningful: (data) => data.control.length > 0,
+  stateFields: ['seaZones'],
+  stub: () => ({ control: [] }),
+  // Sea control is DURABLE (unlike the turn-transient hybrid / disasters /
+  // migration layers): the user payload ALWAYS carries the current `seaZones`
+  // list (even when empty) so the model knows who controls which zone.
+  payload: (ctx) => ({ seaZones: ctx.seaZones ?? [] }),
+};

server/abilities/types.ts

@@ -12,16 +12,17 @@ import type {
   IndustryProject,
   RegionResources,
   RelationStatus,
+  SeaZoneClaim,
   TradeAgreement,
 } from '../../shared/types';
 import type { MarkerInfo, TurnResult, WarInfo } from '../../shared/protocol';
 
 /**
- * The 8 per-feature LLM abilities a turn can exercise, by the `TurnResult`
+ * The 11 per-feature LLM abilities a turn can exercise, by the `TurnResult`
  * field each one owns. This is the closed universe the ordered `ABILITIES`
  * registry (./index.ts) is built from: a turn's world changes are exactly the
  * core engine effects (events / stats / territory / no-man's-land / nation-ops
- * / markers) plus, in order, these eight abilities.
+ * / markers) plus, in order, these eleven abilities.
  */
 export type AbilityField =
   | 'takeovers'
@@ -31,7 +32,10 @@ export type AbilityField =
   | 'industry'
   | 'nuclear'
   | 'leaders'
-  | 'ideology';
+  | 'ideology'
+  | 'disasters'
+  | 'migration'
+  | 'sea';
 
 /**
  * Everything a single ability's `apply` may need from the surrounding turn.
@@ -64,7 +68,7 @@ export interface AbilityCtx {
   readonly centroidOf?: (key: string) => { lat: number; lon: number; spread: number } | undefined;
   /**
    * The `getNeighbours` tool executor (verify land borders). Available to an
-   * ability that needs it; none of the current eight use it (it drives the
+   * ability that needs it; none of the current nine use it (it drives the
    * core territory/conquest logic), but the type is here so a future one can.
    */
   readonly getNeighbours?: (regionKeys: string[]) => string[];
@@ -87,6 +91,7 @@ export interface UserPromptCtx {
   readonly embargoes?: Embargo[];
   readonly nationResources?: Record<string, RegionResources>;
   readonly industryProjects?: IndustryProject[];
+  readonly seaZones?: SeaZoneClaim[];
 }
 
 /**
@@ -151,7 +156,7 @@ export interface Ability<K extends AbilityField = AbilityField> {
    * The `GameState` fields this ability owns and that must be defaulted on a
    * legacy SQLite row (db.ts migration, only-if-undefined). `undefined` for
    * abilities that add no durable state (takeovers, hybrid, nuclear, leaders,
-   * ideology).
+   * ideology, disasters).
    */
   readonly stateFields?: readonly string[];
 

server/db.test.ts

@@ -38,6 +38,8 @@ function makeState(id: string): GameState {
     embargoes: [],
     // (v0.36.0, #59) no industry projects.
     industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
   };
 }
 
@@ -244,6 +246,17 @@ describe('openDb', () => {
     db.close();
   });
 
+  it('(v0.43.0 #65) a legacy row saved before the seaZones field existed loads with it defaulted to []', () => {
+    const db = openDb(':memory:');
+    const legacy = makeState('legacy');
+    delete (legacy as { seaZones?: unknown[] }).seaZones; // a pre-v0.43 save (field absent)
+    db.save(legacy);
+    const loaded = db.load('legacy');
+    expect(loaded).not.toBeNull();
+    expect(loaded!.seaZones).toEqual([]);
+    db.close();
+  });
+
   it('delete removes a game by id and reports absence otherwise', () => {
     const db = openDb(':memory:');
     db.save(makeState('a'));

server/engine.test.ts

@@ -133,6 +133,8 @@ function baseState(): GameState {
     embargoes: [],
     // (v0.36.0, #59) no industry projects on a fresh state.
     industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
   };
 }
 
@@ -570,7 +572,7 @@ describe('validateNationOps (v0.23 #16 P4a)', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [{ kind: 'rename', nationRef: 'France', to: 'French Republic' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      nationOps: [{ kind: 'rename', nationRef: 'France', to: 'French Republic' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     });
     expect(withOps).not.toBeNull();
     expect(withOps!.nationOps).toEqual([{ kind: 'rename', nationRef: 'France', to: 'French Republic' }]);
@@ -592,7 +594,7 @@ describe('applyTurnResult (nation-op proposals, v0.23 #16 P4a)', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     });
     expect(next.nations.de.name).toBe('DE'); // still the old name
     expect(next.pendingNationOps).toEqual([{ kind: 'rename', nationRef: 'de', to: 'Reich' }]);
@@ -613,7 +615,7 @@ describe('applyTurnResult (nation-op proposals, v0.23 #16 P4a)', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [{ kind: 'rename', nationRef: 'us', to: 'USA' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] }, // new proposal this turn
+      nationOps: [{ kind: 'rename', nationRef: 'us', to: 'USA' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] }, // new proposal this turn
     });
     expect(next.pendingNationOps).toEqual([
       { kind: 'rename', nationRef: 'de', to: 'Reich' }, // the old one survived
@@ -632,7 +634,7 @@ describe('applyTurnResult (nation-op proposals, v0.23 #16 P4a)', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     });
     expect(next.pendingNationOps).toEqual([{ kind: 'rename', nationRef: 'de', to: 'Reich' }]);
   });
@@ -1089,7 +1091,7 @@ describe('applyTurnResult', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     applyTurnResult(state, result);
     expect(JSON.stringify(state)).toBe(snapshot);
@@ -1106,7 +1108,7 @@ describe('applyTurnResult', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     expect(next.pending).toEqual([]);
@@ -1129,7 +1131,7 @@ describe('applyTurnResult', () => {
       // is not a real key at all. Both are proposed as a gain by DE.
       territoryChanges: [{ nation: 'de', gain: ['wales-bbbb', 'not-a-region-xyz'], lose: [] }],
       unowned: [],
-      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result, new Set(['wales-bbbb']));
     // the valid key was gained (taken from its sole previous owner); the bogus one was ignored
@@ -1155,7 +1157,7 @@ describe('applyTurnResult', () => {
       // released (not in state.unowned), so it does not enter GameState.unowned.
       territoryChanges: [{ nation: 'de', gain: ['POL', 'wales-bbbb'], lose: [] }],
       unowned: [],
-      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result); // no validKeys -> nothing filtered
     expect(next.nations.de.territory).toContain('wales-bbbb');
@@ -1173,7 +1175,7 @@ describe('applyTurnResult (sole-ownership invariants, v0.21 #16 P2)', () => {
     regionChanges: [],
     relations: [],
     unowned: [],
-    nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+    nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
   };
 
   it('a double claim (two different gainers, one key) is rejected: the key stays with its original owner', () => {
@@ -1263,7 +1265,7 @@ describe('applyTurnResult (no man\'s land, v0.22 #16 P3)', () => {
     relations: [],
     territoryChanges: [],
     unowned: [],
-    nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+    nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
   };
 
   it('a release removes the key from its sole owner and marks it in GameState.unowned', () => {
@@ -1378,7 +1380,7 @@ describe('applyTurnResult (no man\'s land, v0.22 #16 P3)', () => {
 
   it('a lone release is meaningful (it survives the retry/nudge path)', () => {
     expect(
-      isMeaningful({ date: 'x', events: [], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [], unowned: ['GBR'], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] } }),
+      isMeaningful({ date: 'x', events: [], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [], unowned: ['GBR'], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] } }),
     ).toBe(true);
   });
 
@@ -1685,9 +1687,9 @@ describe('buildSystemPrompt (tool mode, v0.21 #16 P2)', () => {
 
 describe('isMeaningful', () => {
   it('is true with an event, false when everything is empty', () => {
-    expect(isMeaningful({ date: 'x', events: [{ nation: 'uk', type: 'military', title: 't', text: 'b', outcome: 'neutral' }], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] } })).toBe(true);
-    expect(isMeaningful({ date: 'x', events: [], stateChanges: [{ nation: 'uk', stat: 'military', op: 'set', value: 5 }], regionChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] } })).toBe(true);
-    expect(isMeaningful({ date: 'x', events: [], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] } })).toBe(false);
+    expect(isMeaningful({ date: 'x', events: [{ nation: 'uk', type: 'military', title: 't', text: 'b', outcome: 'neutral' }], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] } })).toBe(true);
+    expect(isMeaningful({ date: 'x', events: [], stateChanges: [{ nation: 'uk', stat: 'military', op: 'set', value: 5 }], regionChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] } })).toBe(true);
+    expect(isMeaningful({ date: 'x', events: [], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] } })).toBe(false);
   });
 
   it('(v0.23 #16 P4a) a turn that only proposes a nation-op is meaningful (it survives the retry/nudge path)', () => {
@@ -1700,7 +1702,7 @@ describe('isMeaningful', () => {
         relations: [],
         territoryChanges: [],
         unowned: [],
-        nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+        nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(true);
   });
@@ -1721,8 +1723,7 @@ describe('isMeaningful', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] },
-        markers: { add: [{ type: 'city', name: 'Lyon', regionKey: 'rhone-rhne' }], remove: [] },
+        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [{ type: 'city', name: 'Lyon', regionKey: 'rhone-rhne' }], remove: [] },
       }),
     ).toBe(true);
   });
@@ -1743,8 +1744,7 @@ describe('isMeaningful', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] },
-        markers: { add: [], remove: [] },
+        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(true);
   });
@@ -1767,8 +1767,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     expect(next.nations.de.name).toBe('The Reich');
@@ -1801,8 +1800,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     expect(next.playerNationId).toBe('uk'); // player still leads it
@@ -1826,8 +1824,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     // no nation was renamed
@@ -1854,8 +1851,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     // neither was renamed (ambiguous)
@@ -1881,8 +1877,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     });
     expect(validated!.takeovers).toEqual([]);
     const next = applyTurnResult(state, validated!);
@@ -1908,8 +1903,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     expect(next.nations.uk.name).toBe('The Commonwealth');
@@ -1933,8 +1927,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     expect(next.version).toBe(2); // exactly one bump for the whole turn
@@ -1956,8 +1949,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     expect(next.nations.de.name).toBe('The Reich');
@@ -1991,8 +1983,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [mk('city', 'Strasbourg', 'moselle-rygy')], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [mk('city', 'Strasbourg', 'moselle-rygy')], remove: [] },
     };
     const next = applyTurnResult(state, result, undefined, centroidOf);
     expect(next.markers).toHaveLength(1);
@@ -2016,13 +2007,13 @@ describe('markers (point placement, v0.27 #44)', () => {
     const add = [mk('city', 'Strasbourg', 'moselle-rygy')];
     const first = applyTurnResult(state, {
       date: '1939-09-03', events: [], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [],
-      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add, remove: [] },
+      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add, remove: [] },
     }, undefined, centroidOf);
     expect(first.markers).toHaveLength(1);
     // a second turn proposes the exact same marker again
     const second = applyTurnResult(first, {
       date: '1939-09-05', events: [], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [],
-      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add, remove: [] },
+      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add, remove: [] },
     }, undefined, centroidOf);
     expect(second.markers).toHaveLength(1);
     expect(second.markers[0].id).toBe(first.markers[0].id); // stable id, no second copy
@@ -2049,8 +2040,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: {
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: {
         add: [
           { type: 'city', name: 'Good', regionKey: 'moselle-rygy' }, // valid + centroid → kept
           { type: 'city', name: 'NoCent', regionKey: 'other-key' }, // in validKeys, no centroid → dropped
@@ -2097,8 +2087,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: {
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: {
         add: [
           { type: 'city', name: 'NewA', regionKey: 'new-a' },
           { type: 'city', name: 'NewB', regionKey: 'new-b' },
@@ -2123,7 +2112,7 @@ describe('markers (point placement, v0.27 #44)', () => {
     ];
     const next = applyTurnResult(state, {
       date: '1939-09-03', events: [], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [],
-      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [idA, 'zzzz-not-there'] },
+      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [idA, 'zzzz-not-there'] },
     }, undefined, centroidOf);
     expect(next.markers).toHaveLength(1);
     expect(next.markers[0].id).toBe(idB); // only A removed; the bogus id was a no-op
@@ -2139,14 +2128,14 @@ describe('markers (point placement, v0.27 #44)', () => {
     // 1) uk releases the region → the marker becomes ownerless
     const released = applyTurnResult(state, {
       date: '1939-09-03', events: [], stateChanges: [], regionChanges: [], relations: [], territoryChanges: [],
-      unowned: ['moselle-rygy'], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      unowned: ['moselle-rygy'], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     }, undefined, centroidOf);
     expect(released.markers[0].ownerNationId).toBeNull();
     // 2) de re-claims the region → the marker's owner follows to de
     const reclaimed = applyTurnResult(released, {
       date: '1939-09-05', events: [], stateChanges: [], regionChanges: [], relations: [],
       territoryChanges: [{ nation: 'de', gain: ['moselle-rygy'], lose: [] }],
-      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, markers: { add: [], remove: [] },
+      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     }, undefined, centroidOf);
     expect(reclaimed.markers[0].ownerNationId).toBe('de');
   });
@@ -2216,8 +2205,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [{ type: 'city', name: 'Strasbourg', regionKey: 'moselle-rygy' }], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [{ type: 'city', name: 'Strasbourg', regionKey: 'moselle-rygy' }], remove: [] },
     });
     const { state } = await runTurn({
       llm: fakeLlm([result]),
@@ -2292,6 +2280,8 @@ function mkTurnState(
     embargoes: [],
     // (v0.36.0, #59) no industry projects on a fresh state.
     industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
   };
 }
 
@@ -2313,6 +2303,9 @@ function mkTurnResult(partial: Partial<TurnResult>): TurnResult {
     nuclear: partial.nuclear ?? { arm: [], strikes: [] },
     leaders: partial.leaders ?? { changes: [] },
     ideology: partial.ideology ?? { changes: [] },
+    disasters: partial.disasters ?? { events: [] },
+    migration: partial.migration ?? { ops: [] },
+    sea: partial.sea ?? { control: [] },
     markers: partial.markers ?? { add: [], remove: [] },
   };
 }
@@ -3038,8 +3031,7 @@ describe('validateTakeovers (v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] },
-      markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     });
     expect(withTakeovers).not.toBeNull();
     // the valid one survives, the empty-name one is dropped
@@ -3427,8 +3419,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] },
-        markers: { add: [], remove: [] },
+        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(true);
   });
@@ -3449,8 +3440,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] },
-        markers: { add: [], remove: [] },
+        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(true);
   });
@@ -3471,8 +3461,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] },
-        markers: { add: [], remove: [] },
+        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(false);
   });

server/engine.ts

@@ -16,6 +16,7 @@ import type {
   RegionResources,
   RegionStats,
   RoundItem,
+  SeaZoneClaim,
   StatKey,
   TradeAgreement,
 } from '../shared/types';
@@ -57,8 +58,9 @@ import {
   NEW_NATION_STATS,
   resolveNationRef,
   resolveRegionKey,
+  str,
 } from './abilities/shared';
-import { ABILITIES } from './abilities';
+import { ABILITIES, type AbilityCtx, type UserPromptCtx } from './abilities';
 // Re-exported so the existing callers (server/index.ts, the unit tests) keep
 // importing these shared primitives from the engine unchanged.
 export { freshNationId, freshWarId, NEW_NATION_STATS, resolveNationRef, resolveRegionKey };
@@ -86,6 +88,31 @@ export {
   validateTakeovers,
   validateWarOps,
   applyIndustryEffects,
+  validateDisasterEvents,
+  applyDisasterEvent,
+  isDisasterType,
+  isDisasterSeverity,
+  DISASTER_TYPES,
+  DISASTER_SEVERITIES,
+  DISASTER_EFFECTS,
+  validateMigrationOps,
+  applyMigrationOp,
+  shiftRelationTowardPositive,
+  isMigrationKind,
+  isMigrationScale,
+  MIGRATION_KINDS,
+  MIGRATION_SCALES,
+  MIGRATION_SOURCE_EFFECTS,
+  MIGRATION_DESTINATION_EFFECTS,
+  LARGE_INFLUX_STABILITY_DIP,
+  validateSeaOps,
+  applySeaControl,
+  applySeaZoneBonuses,
+  SEA_ZONE_BONUS,
+  SEA_ZONES,
+  SEA_ZONE_IDS,
+  isSeaZoneId,
+  seaZoneName,
 } from './abilities';
 
 // --- The LLM's getNeighbours tool (v0.21, #16 P2: contiguous region transfers) ---
@@ -358,6 +385,14 @@ export function buildUserPrompt(
    * key on any nation) when undefined.
    */
   nuclear?: Record<string, boolean>,
+  /**
+   * (v0.43.0, #65) The game's current sea-zone control (each a `{ zone, by }`
+   * pair of the fixed sea zones and their controlling nation id). Emitted
+   * verbatim (even when empty) so the model knows which of the 12 fixed sea
+   * zones each nation currently controls and can re-claim or contest them via
+   * `TurnResult.sea`. Omitted entirely when undefined.
+   */
+  seaZones?: SeaZoneClaim[],
 ): string {
   const player = state.nations[state.playerNationId];
   const playerName = player?.name ?? state.playerNationId;
@@ -458,7 +493,7 @@ export function buildUserPrompt(
   // (v0.40.0, #67) Build the UserPromptCtx once and merge each ability's
   // payload() at its exact position (the key order is load-bearing for the
   // golden test).
-  const upCtx = {
+  const upCtx: UserPromptCtx = {
     state,
     markers,
     wars,
@@ -467,15 +502,16 @@ export function buildUserPrompt(
     embargoes,
     nationResources,
     industryProjects,
+    seaZones,
   };
-  const upCtxAny = upCtx as unknown as import('./abilities').UserPromptCtx;
-  Object.assign(payload, ABILITIES[0].payload(upCtxAny)); // takeovers → takeoverRisks
+  Object.assign(payload, ABILITIES[0].payload(upCtx)); // takeovers → takeoverRisks
   if (noMansLand !== undefined) payload.unowned = noMansLand;
   if (markers !== undefined) payload.markers = markers;
-  Object.assign(payload, ABILITIES[1].payload(upCtxAny)); // wars → wars
-  Object.assign(payload, ABILITIES[2].payload(upCtxAny)); // hybrid → relations
-  Object.assign(payload, ABILITIES[3].payload(upCtxAny)); // economy → trades, embargoes
-  Object.assign(payload, ABILITIES[4].payload(upCtxAny)); // industry → resources, industry
+  Object.assign(payload, ABILITIES[1].payload(upCtx)); // wars → wars
+  Object.assign(payload, ABILITIES[2].payload(upCtx)); // hybrid → relations
+  Object.assign(payload, ABILITIES[3].payload(upCtx)); // economy → trades, embargoes
+  Object.assign(payload, ABILITIES[4].payload(upCtx)); // industry → resources, industry
+  Object.assign(payload, ABILITIES[10].payload(upCtx)); // sea → seaZones (always emitted)
   return JSON.stringify(payload, null, 2);
 }
 
@@ -534,13 +570,6 @@ export function parseTurnResult(
   return validateTurnResult(obj, regionKeyResolver);
 }
 
-function str(s: unknown, max = 0): string | null {
-  if (typeof s !== 'string') return null;
-  const t = s.trim();
-  if (!t) return null;
-  return max ? t.slice(0, max) : t;
-}
-
 /**
  * Validate a raw (LLM) `nationOps` array into safe {@link NationOp} values
  * (v0.23, #16 P4a). Defensive like the rest of the parser: entries with an
@@ -621,6 +650,9 @@ export function validateTurnResult(
     nuclear: { arm: [], strikes: [] },
     leaders: { changes: [] },
     ideology: { changes: [] },
+    disasters: { events: [] },
+    migration: { ops: [] },
+    sea: { control: [] },
     markers: { add: [], remove: [] },
   };
 
@@ -711,7 +743,7 @@ export function validateTurnResult(
   // list for the player to confirm/reject.
   result.nationOps = validateNationOps(o.nationOps);
 
-  // The 8 per-feature LLM abilities (v0.40.0, #67): each one's validate call
+  // The 11 per-feature LLM abilities (v0.40.0, #67): each one's validate call
   // is owned by its Ability module in the ABILITIES registry. The field's raw
   // value is passed through a.validate() which returns the validated field shape.
   for (const a of ABILITIES) {
@@ -824,19 +856,6 @@ export function validateRegionChanges(
   return out;
 }
 
-/**
- * (v0.32.0, #54) Validate the raw `takeovers` array of a turn into a safe
- * {@link Takeover} list — the non-military regime-change lever (a coup or
- * revolution that renames a nation to its new regime name). Defensive like
- * the rest of the parser — never throws. Each entry needs a non-empty
- * `nationRef` (the target nation's id or name — capped at 200 chars) and a
- * non-empty `newRegimeName` (capped at 200 chars). Resolution of `nationRef`
- * to a concrete nation id happens at apply time (`resolveNationRef`), not
- * here. Entries with either field missing or whitespace-only are dropped.
- */
-  // (v0.40.0, #67) The 8 per-feature ability validators, appliers, and helpers
-  // have been moved to server/abilities/ — re-exported below for the tests.
-
 export function isMeaningful(result: TurnResult): boolean {
   return (
     result.events.length > 0 ||
@@ -845,7 +864,7 @@ export function isMeaningful(result: TurnResult): boolean {
     result.regionChanges.length > 0 ||
     result.unowned.length > 0 ||
     result.nationOps.length > 0 ||
-    // (v0.40.0, #67) any of the 8 per-feature abilities having a non-empty
+    // (v0.40.0, #67) any of the 9 per-feature abilities having a non-empty
     // payload is a real world change (each Ability's isMeaningful predicate
     // is the per-ability half of the old 18-sub-field check).
     ABILITIES.some((a) => a.isMeaningful(result[a.field])) ||
@@ -918,6 +937,9 @@ export function applyTurnResult(
   // (v0.36, #59) active industry projects; a legacy/corrupt clone without the
   // field starts empty (the turn then only ever adds to it).
   next.industry = next.industry ?? [];
+  // (v0.43.0, #65) sea-zone control; a legacy/corrupt clone without the field
+  // starts empty (the turn then upserts this turn's claims into it).
+  next.seaZones = next.seaZones ?? [];
   const actingTurn = state.turn; // this action resolves the current turn
   next.turn = state.turn + 1; // then we advance to the next turn to play
   next.date = isDateLike(result.date) ? result.date : addDays(state.date, 2);
@@ -1112,12 +1134,12 @@ export function applyTurnResult(
     n.stats = deriveNationStats(n.territory, next.regionStats, geoOf);
   }
 
-  // (v0.40.0, #67) The 8 per-feature LLM abilities, applied in ABILITIES
+  // (v0.40.0, #67) The 9 per-feature LLM abilities, applied in ABILITIES
   // order (takeovers → wars → hybrid → economy → industry → nuclear →
-  // leaders → ideology). Each Ability's apply method handles its own
-  // field's validated data against the post-territory/post-recompute
+  // leaders → ideology → disasters). Each Ability's apply method handles its
+  // own field's validated data against the post-territory/post-recompute
   // `next` state. The AbilityCtx carries the shared resolvers.
-  const abilityCtx = {
+  const abilityCtx: AbilityCtx = {
     previous: state,
     actingTurn,
     validRegionKeys: validKeys,
@@ -1126,9 +1148,8 @@ export function applyTurnResult(
     resourceOf,
     centroidOf,
   };
-  const abilityCtxAny = abilityCtx as unknown as import('./abilities').AbilityCtx;
   for (const a of ABILITIES) {
-    a.apply(next, result[a.field], abilityCtxAny);
+    a.apply(next, result[a.field], abilityCtx);
   }
 
   // --- Map markers (v0.27, #44) ---
@@ -1596,6 +1617,9 @@ export async function runTurn(opts: {
     state.industry ?? [],
     // (v0.37.0, #60) per-nation nuclear capability (flag or rocket marker).
     nuclearCapability,
+    // (v0.43.0, #65) the current sea-zone control (always emitted — even when
+    // empty — so the model knows who controls which of the fixed sea zones).
+    state.seaZones ?? [],
   );
   const nudge =
     'Your previous output was invalid. Respond with ONLY the JSON object described above for this batch — no prose, no fences.';

server/index.ts

@@ -190,6 +190,8 @@ app.post('/api/games', (req: Request, res) => {
     // declares them over time via TurnResult.industry (one per region, a
     // per-region SET).
     industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
   };
   // v0.19 (#16 P1): expand each nation's ISO_A3 country list to the region keys
   // of all its sub-regions, so ownership (and the choropleth) is at region

server/map.test.ts

@@ -59,6 +59,8 @@ const state: GameState = {
   embargoes: [],
   // (v0.36.0, #59) the map is ownership-only; industry is unused here.
   industry: [],
+  // (v0.43.0, #65) no sea-zone control on a fresh state.
+  seaZones: [],
 };
 
 // The RegionMap built from the fixture: the authoritative region key → owner source.

server/protocol.test.ts

@@ -48,6 +48,8 @@ function mkState(
     trades: [],
     embargoes: [],
     industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
   };
   if (regionStats !== undefined) base.regionStats = regionStats as GameState['regionStats'];
   else delete (base as { regionStats?: unknown }).regionStats; // simulate a legacy row

server/regions.test.ts

@@ -118,6 +118,8 @@ describe('regions (region-key loader, v0.19 #16 P1)', () => {
       embargoes: [],
       // (v0.36.0, #59) unused here (allTerritoryKeys is ownership-only).
       industry: [],
+      // (v0.43.0, #65) no sea-zone control on a fresh state.
+      seaZones: [],
     };
     // 16 GBR sub-regions + 42 FRA sub-regions, no overlap between the two.
     expect(allTerritoryKeys(state).size).toBe(58);

server/stub.ts

@@ -100,6 +100,14 @@ export interface StubPayload {
    * deterministicTurn), so the industry path is covered by unit tests only.
    */
   industry?: Array<{ regionKey: string; type: string }>;
+  /**
+   * (v0.43.0, #65) The currently active sea-zone control
+   * (`{ zone, by }` — fixed sea-zone id + controlling nation id), emitted by
+   * the engine's user prompt (always, even when empty). The stub ignores this
+   * field — it never claims, contests or re-claims a sea zone (see
+   * deterministicTurn), so the sea path is covered by unit tests only.
+   */
+  seaZones?: Array<{ zone: string; by: string }>;
 }
 
 function truncate(s: string, n: number): string {
@@ -173,6 +181,18 @@ function truncate(s: string, n: number): string {
  * (v0.39.0, #62) The stub likewise NEVER changes a nation's ideology (it
  * always returns `ideology: { changes: [] }`) — the ideology path is covered
  * by unit tests only, keeping the e2e assertions untouched.
+ *
+ * (v0.41.0, #63) The stub likewise NEVER declares a disaster or pandemic (it
+ * always returns `disasters: { events: [] }`) — the disasters path is covered
+ * by unit tests only, keeping the e2e assertions untouched.
+ *
+ * (v0.42.0, #64) The stub likewise NEVER declares a migration / refugee flow
+ * (it always returns `migration: { ops: [] }`) — the migration path is
+ * covered by unit tests only, keeping the e2e assertions untouched.
+ *
+ * (v0.43.0, #65) The stub likewise NEVER claims, contests or re-claims a sea
+ * zone (it always returns `sea: { control: [] }`) — the sea-control path is
+ * covered by unit tests only, keeping the e2e assertions untouched.
  */
 export function deterministicTurn(p: StubPayload): TurnResult {
   const state = p.state;
@@ -252,13 +272,13 @@ export function deterministicTurn(p: StubPayload): TurnResult {
     nationOps: [], // the stub never proposes nation ops (see doc comment)
   };
 
-  // The 8 ability fields, filled by the registry in its canonical order. The
+  // The 11 ability fields, filled by the registry in its canonical order. The
   // stub is ability-inert: every ability contributes its own no-op default
   // (each ability's `stub()` — see the per-ability doc comments above), so the
   // e2e assertions are unaffected. The insertion order here (ABILITIES) is the
   // historical key order pinned by the stub's deterministic output
   // (takeovers → wars → hybrid → economy → industry → nuclear → leaders →
-  // ideology), which must stay byte-identical.
+  // ideology → disasters → migration → sea), which must stay byte-identical.
   const abilities = {} as Record<AbilityField, unknown>;
   for (const a of ABILITIES) abilities[a.field] = a.stub();
 

shared/protocol.ts

@@ -598,6 +598,191 @@ export function isNuclearCapable(nation: Nation, markers: readonly MapMarker[]):
   return markers.some((m) => m.ownerNationId === nation.id && m.type === 'rocket');
 }
 
+// --- Disasters & pandemics (v0.41.0, #63) ------------------------------------
+//
+// Natural and man-made catastrophes — earthquakes, floods, volcanic eruptions,
+// wildfires, famines, plagues, and epidemics — hit a nation or a single region
+// each turn. Each event carries a `type` and a `severity`; the engine applies
+// a DETERMINISTIC stat dip chosen from the `(type, severity)` lookup table
+// `DISASTER_EFFECTS` (defined in `server/abilities/disasters.ts`) — no hidden
+// randomness: the LLM chooses the type and severity, the table decides the
+// magnitude. The dip is clamped to 0–100, mirrored to the target's regions
+// (`regionStats`), and the target's derived `stats` re-derived afterwards
+// (the same 0-region / no-entry guards as the hybrid / economy layers). It is
+// **turn-transient** like the hybrid layer: there is NO `GameState` field, no
+// durable list, and no `db.ts` change — an ongoing plague / epidemic is simply
+// re-declared each turn it persists. Disasters never move territory (sole
+// ownership is untouched) and never touch `population`.
+
+/** The kind of catastrophe a disaster event describes (v0.41.0, #63). */
+export type DisasterType =
+  | 'earthquake'
+  | 'flood'
+  | 'volcanic'
+  | 'wildfire'
+  | 'famine'
+  | 'plague'
+  | 'epidemic';
+
+/** The severity a disaster event carries (v0.41.0, #63). */
+export type DisasterSeverity = 'minor' | 'moderate' | 'severe';
+
+/**
+ * A single disaster event (v0.41.0, #63): the catastrophe `type`, its
+ * `target` (a nation id / name, or a region key that hits that region's sole
+ * owner — resolved at apply time), the `severity`, and an optional short
+ * `detail`. The deterministic stat dip is looked up from
+ * `DISASTER_EFFECTS[type][severity]`.
+ */
+export interface DisasterEvent {
+  /** The kind of catastrophe (one of {@link DisasterType}). */
+  type: DisasterType;
+  /** The affected nation (by id or name) or a region key (hits its sole owner). */
+  target: string;
+  /** How bad it was (one of {@link DisasterSeverity}). */
+  severity: DisasterSeverity;
+  /** Optional short annotation (≤300 chars). */
+  detail?: string;
+}
+
+/** The disasters block of a `TurnResult`. Required; default `{ events: [] }`. */
+export interface DisastersOps {
+  events: DisasterEvent[];
+}
+
+// --- Migration & refugees (v0.42.0, #64) --------------------------------------
+//
+// People moving between nations each turn: ordinary migration, refugee flows
+// (fleeing a war or disaster), a spreading diaspora, and an exodus (people
+// leaving with no destination). Each op names a `kind`, a source `from` (the
+// nation people leave), a destination `to` (required for every kind except
+// `exodus`), and a `scale` (small / moderate / large). The engine applies a
+// DETERMINISTIC effect chosen from the per-`scale` tables
+// `MIGRATION_SOURCE_EFFECTS` / `MIGRATION_DESTINATION_EFFECTS` (defined in
+// `server/abilities/migration.ts`) — no hidden randomness: the LLM chooses the
+// kind and scale, the tables decide the magnitude. The source LOSES a small
+// amount of population and economy, the destination GAINS a small amount of
+// population and economy (a `large` influx additionally strains the
+// destination's stability), both clamped to 0–100, mirrored to each side's
+// regions (`regionStats`), and each side's derived `stats` re-derived
+// afterwards (the same 0-region / no-entry guards as the hybrid / economy /
+// disasters layers). The from↔to relation moves one step toward the positive
+// end of the ally/neutral/rival/hostile ladder (`shiftRelationTowardPositive`)
+// — capped at `ally` for `refugees`, `neutral` for `migration` / `diaspora`,
+// and not at all for `exodus` — and a `war` relation is never touched. It is
+// **turn-transient** like the hybrid / disasters layers: there is NO `GameState`
+// field, no durable list, and no `db.ts` change — a continuing flow is simply
+// re-declared each turn it persists. It never moves territory (sole ownership
+// is untouched) and never creates or escalates a war.
+
+/** The kind of population flow a migration op describes (v0.42.0, #64). */
+export type MigrationKind = 'migration' | 'refugees' | 'diaspora' | 'exodus';
+
+/** The size of a migration flow (v0.42.0, #64). */
+export type MigrationScale = 'small' | 'moderate' | 'large';
+
+/**
+ * A single migration / refugee flow (v0.42.0, #64): the `kind`, the source
+ * `from` (a nation id / name — the nation people leave), the destination `to`
+ * (a nation id / name — required for every kind except `exodus`, which has no
+ * destination), the `scale`, and an optional short `detail`. The deterministic
+ * stat effects are looked up from `MIGRATION_SOURCE_EFFECTS` /
+ * `MIGRATION_DESTINATION_EFFECTS` by `scale`.
+ */
+export interface MigrationOp {
+  /** The kind of flow (one of {@link MigrationKind}). */
+  kind: MigrationKind;
+  /** The source nation (by id or name) people leave. */
+  from: string;
+  /** The destination nation (by id or name). Required for every kind except `exodus`. */
+  to?: string;
+  /** How many people moved (one of {@link MigrationScale}). */
+  scale: MigrationScale;
+  /** Optional short annotation (≤300 chars). */
+  detail?: string;
+}
+
+/** The migration block of a `TurnResult`. Required; default `{ ops: [] }`. */
+export interface MigrationOps {
+  ops: MigrationOp[];
+}
+
+// ---------------------------------------------------------------------------
+// (v0.43.0, #65) Sea zones & sea control — the naval layer, fully parallel to
+// but INDEPENDENT of land. The world has a fixed set of 12 named SEA ZONES
+// ({@link SEA_ZONES}); each is under the SOLE CONTROL of at most one nation.
+// Controlling a sea zone never moves land (`territory` / `unowned` are
+// untouched) and moving land never touches a sea zone. `SeaZoneClaim` (the
+// durable per-zone record, `{ zone, by }`) lives in `shared/types.ts` like
+// `Trade` / `Embargo` / `War` / `IndustryProject`; `GameState.seaZones` is a
+// list of them, unique per zone (`[]` at creation; a legacy SQLite row
+// without the field loads as `[]` — additive, never wiped). Each turn the LLM
+// declares `TurnResult.sea.control` ops — one op names the zone and the
+// nation that (now) controls it. The engine resolves `by` (id first, then a
+// case-insensitive unique name) and UPSERTS the zone's claim (replace in
+// place if the zone is already claimed, append if new). If two or more ops
+// this turn claim the SAME zone for DIFFERENT resolved nations, the zone is
+// CONTESTED: the higher current `stats.military` wins (a tie goes to the op
+// listed earlier in the `control` array) — deterministic, no hidden
+// randomness; an unresolvable `by` is dropped (never thrown). Every committed
+// turn — including a turn with an empty `control` — each existing claim's
+// controller earns a small DETERMINISTIC bonus (`SEA_ZONE_BONUS = 1` military
+// + 1 economy, clamped to 0–100, mirrored to the controller's regions and
+// re-derived with the same 0-region / no-entry guards as the economy /
+// migration layers); a claim whose nation no longer exists is skipped (the
+// claim is kept, never thrown). The layer is DURABLE (unlike the turn-
+// transient hybrid / disasters / migration layers): `GameState.seaZones`
+// persists across turns and in SQLite. The user payload carries the current
+// `seaZones` list so the model knows who controls which zone.
+
+/** The 12 named sea zones the world model knows (v0.43.0, #65). */
+export const SEA_ZONES = [
+  { id: 'north-atlantic', name: 'North Atlantic' },
+  { id: 'south-atlantic', name: 'South Atlantic' },
+  { id: 'pacific', name: 'Pacific Ocean' },
+  { id: 'indian', name: 'Indian Ocean' },
+  { id: 'mediterranean', name: 'Mediterranean Sea' },
+  { id: 'north-sea', name: 'North Sea' },
+  { id: 'baltic', name: 'Baltic Sea' },
+  { id: 'arctic', name: 'Arctic Ocean' },
+  { id: 'black-sea', name: 'Black Sea' },
+  { id: 'gulf-mexico', name: 'Gulf of Mexico' },
+  { id: 'red-sea', name: 'Red Sea' },
+  { id: 'sargasso', name: 'Sargasso Sea' },
+] as const;
+
+/** The set of valid sea-zone ids (v0.43.0, #65). */
+export const SEA_ZONE_IDS: ReadonlySet<string> = new Set(SEA_ZONES.map((z) => z.id));
+
+/** Whether `id` is one of the fixed sea-zone ids (v0.43.0, #65). */
+export function isSeaZoneId(id: string): boolean {
+  return SEA_ZONE_IDS.has(id);
+}
+
+/** The display name of a sea-zone id; an unknown id is returned as-is (v0.43.0, #65). */
+export function seaZoneName(id: string): string {
+  return SEA_ZONES.find((z) => z.id === id)?.name ?? id;
+}
+
+/**
+ * A single sea-control op (v0.43.0, #65): `zone` is one of the fixed
+ * {@link SEA_ZONES} ids and `by` is the nation that (now) controls it (by id
+ * or name). One op SETS or REPLACES the zone's controller; two or more ops on
+ * the same zone for different nations are CONTESTED — the higher current
+ * `stats.military` wins (a tie: the earlier-listed op).
+ */
+export interface SeaControlOp {
+  /** The sea zone (one of {@link SEA_ZONE_IDS}). */
+  zone: string;
+  /** The controlling nation (by id or name). */
+  by: string;
+}
+
+/** The sea-control block of a `TurnResult`. Required; default `{ control: [] }`. */
+export interface SeaOps {
+  control: SeaControlOp[];
+}
+
 /** The exact JSON object the world-simulator LLM must return for a turn. */
 export interface TurnResult {
   date: string;
@@ -749,6 +934,64 @@ export interface TurnResult {
    * Required; default `{ changes: [] }`.
    */
   ideology: IdeologyOps;
+  /**
+   * (v0.41.0, #63) Disasters & pandemics that struck this turn — earthquakes,
+   * floods, volcanic eruptions, wildfires, famines, plagues, and epidemics,
+   * each hitting a **nation** (by id or name) or a single **region** (by key,
+   * which hits that region's SOLE owner — a key with 0 or 2+ owners can't be
+   * hit). Each event names a `type` (one of the seven `DisasterType`s) and a
+   * `severity` (minor / moderate / severe); the engine applies a small,
+   * DETERMINISTIC stat dip from the `(type, severity)` table
+   * (`DISASTER_EFFECTS`, in `server/abilities/disasters.ts`) — clamped to
+   * 0–100, mirrored to the target's regions, and the target's derived `stats`
+   * re-derived afterwards (no hidden randomness). They NEVER move borders
+   * (sole ownership is untouched) and never touch `population`, and the layer
+   * is turn-transient (no durable state): an ongoing plague / epidemic is
+   * simply re-declared each turn it persists. At most 1–2 events per turn,
+   * each narrated in `events` (a `disaster` event). Required; default
+   * `{ events: [] }`.
+   */
+  disasters: DisastersOps;
+  /**
+   * (v0.42.0, #64) Migration & refugee flows this turn — people moving between
+   * nations: ordinary `migration`, `refugees` fleeing a war or disaster, a
+   * spreading `diaspora`, and an `exodus` (people leaving with no destination).
+   * Each op names a `from` (the source nation, by id or name) and, for every
+   * kind except `exodus`, a `to` (the destination nation, by id or name), plus
+   * a `scale` (small / moderate / large). Applied directly by `applyTurnResult`
+   * (like the disasters / hybrid layers): the source LOSES a small amount of
+   * population and economy, the destination GAINS a small amount of population
+   * and economy (a `large` influx additionally strains the destination's
+   * stability by 2), both clamped to 0–100, mirrored to each side's regions,
+   * and each side's derived `stats` re-derived afterwards; the from↔to
+   * relation moves one step toward the positive end of the
+   * ally/neutral/rival/hostile ladder (capped at `ally` for `refugees`,
+   * `neutral` for `migration` / `diaspora`, not at all for `exodus`; a `war`
+   * relation is never touched). The layer is turn-transient (no `GameState`
+   * field, no `db.ts` change) — a continuing flow is simply re-declared each
+   * turn it persists. It never moves borders (sole ownership is untouched) and
+   * never creates or escalates a war. At most 1–2 per turn, each narrated in
+   * `events` (a `social` or `diplomatic` event). Required; default
+   * `{ ops: [] }`.
+   */
+  migration: MigrationOps;
+  /**
+   * (v0.43.0, #65) Sea-zone control ops this turn — the naval layer, fully
+   * parallel to but INDEPENDENT of land: each op names one of the 12 fixed
+   * sea zones (`SEA_ZONES`) and the nation that now controls it. The engine
+   * resolves `by` (id first, then a case-insensitive unique name) and
+   * upserts the zone's claim in `GameState.seaZones` (a single op sets or
+   * replaces the controller; two or more ops on the same zone for different
+   * nations are CONTESTED — the higher current `stats.military` wins, a tie
+   * goes to the op listed earlier in `control`; an unresolvable `by` is
+   * dropped, never thrown). Every committed turn, each existing claim's
+   * controller earns a small deterministic military/economy bonus
+   * (`SEA_ZONE_BONUS`). Sea control never moves land: `territory` and
+   * `unowned` are untouched. At most 1–2 per turn, each narrated in `events`
+   * (a `military` or `diplomatic` event). Required; default
+   * `{ control: [] }`.
+   */
+  sea: SeaOps;
   /**
    * (v0.27, #44) Map-marker ops this turn. `add` places new named markers
    * (the engine positions each at its region's centroid + a small

shared/scenario.ts

@@ -461,6 +461,8 @@ export function worldDraftToGameState(
     embargoes: [],
     // (v0.36, #59) No industry projects on a fresh (dynamic) game.
     industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
   };
   return state;
 }

shared/types.ts

@@ -249,6 +249,23 @@ export interface IndustryProject {
   type: IndustryType;
 }
 
+/**
+ * (v0.43.0, #65) One sea-zone claim: which nation controls one of the fixed
+ * sea zones (see `SEA_ZONES` in `shared/protocol.ts`). The world keeps at
+ * most ONE claim per zone — a new op on an already-claimed zone REPLACES the
+ * controller in place (the zone's entry is updated, never duplicated), and if
+ * a turn declares the same zone for two different resolved nations the higher
+ * current `stats.military` wins (a tie: the op listed earlier in the turn's
+ * `control` array). Sea control is fully parallel to but INDEPENDENT of land:
+ * it never touches `territory` / `unowned`.
+ */
+export interface SeaZoneClaim {
+  /** The sea zone (one of `SEA_ZONE_IDS`). */
+  zone: string;
+  /** The id of the nation that controls it (resolved, not a name). */
+  by: string;
+}
+
 /**
  * (v0.33.0, #56) A first-class **war** — a named, ongoing armed conflict
  * between two or more nations. Unlike the boolean `war` relation (which a
@@ -443,6 +460,20 @@ export interface GameState {
    * with this defaulted to `[]` (see server/db.ts) — additive, no data wipe.
    */
   industry: IndustryProject[];
+  /**
+   * (v0.43.0, #65) Sea-zone control (see {@link SeaZoneClaim}): one entry per
+   * controlled sea zone — which of the 12 fixed zones (`SEA_ZONES`) each
+   * nation controls. At most ONE entry per zone (unique by `zone`); a turn's
+   * `sea.control` ops upsert entries (a re-claim by a different nation
+   * replaces the controller in place; a same-zone contest goes to the higher
+   * current `stats.military`, a tie to the earlier-listed op). Every
+   * committed turn each claim's controller earns a small deterministic
+   * military/economy bonus (`SEA_ZONE_BONUS`). Sea control never moves land
+   * (`territory` / `unowned` are untouched). Always `[]` on a fresh game;
+   * rows saved before v0.43 load with this defaulted to `[]` (see
+   * server/db.ts) — additive, no data wipe.
+   */
+  seaZones: SeaZoneClaim[];
 }
 
 /**