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

@@ -548,6 +548,41 @@ history/
   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 +2,18 @@
 
 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: [] }`.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "history",
-  "version": "0.42.0",
+  "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

@@ -70,6 +70,8 @@ function mkState(
     trades: [],
     embargoes: [],
     industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
   };
 }
 

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

@@ -41,6 +41,7 @@ Respond with ONLY a valid JSON object of exactly this shape. No prose, no commen
   "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>"]}
 }
 
@@ -68,6 +69,7 @@ HARD CONSTRAINTS
 - 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

@@ -41,6 +41,7 @@ You have a getNeighbours tool: given region keys it returns the region keys that
   "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>"]}
 }
 
@@ -68,6 +69,7 @@ HARD CONSTRAINTS
 - 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 10 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 → disasters → migration
+//   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,
@@ -24,10 +24,11 @@ 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 10 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. New
@@ -45,6 +46,7 @@ export const ABILITIES: readonly Ability<AbilityField>[] = [
   ideology,
   disasters,
   migration,
+  sea,
 ];
 
 // ── type re-exports ────────────────────────────────────────────────────────────
@@ -158,3 +160,16 @@ export {
   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

@@ -82,6 +82,8 @@ function mkState(
     trades: [],
     embargoes: [],
     industry: [],
+    // (v0.43.0, #65) no sea-zone control on a fresh state.
+    seaZones: [],
   };
 }
 

server/abilities/registry.test.ts

@@ -12,7 +12,7 @@
 //      by the disasters feature (its payload is always empty).
 //
 //   2. REGISTRY CONTRACT — the ABILITIES registry is the canonical ordered
-//      list of the 10 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
@@ -68,6 +68,14 @@ import {
   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';
@@ -81,6 +89,7 @@ import type {
   RegionResources,
   RelationStatus,
   RoundItem,
+  SeaZoneClaim,
   TradeAgreement,
 } from '../../shared/types';
 import type { MarkerInfo, TurnResult, WarInfo } from '../../shared/protocol';
@@ -154,6 +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. ---
@@ -190,6 +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 —
@@ -228,6 +240,7 @@ function fullDefaultTurn(): TurnResult {
     ideology: { changes: [] },
     disasters: { events: [] },
     migration: { ops: [] },
+    sea: { control: [] },
     markers: { add: [], remove: [] },
   };
 }
@@ -255,11 +268,13 @@ function meaningfulFor(field: AbilityField): TurnResult[AbilityField] {
       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 10-ability order (takeovers → migration)', () => {
+  it('is the canonical 11-ability order (takeovers → sea)', () => {
     expect(ABILITIES.map((a) => a.field)).toEqual([
       'takeovers',
       'wars',
@@ -271,13 +286,14 @@ describe('ABILITIES registry (v0.40.0, #67)', () => {
       'ideology',
       'disasters',
       'migration',
+      'sea',
     ]);
   });
 
-  it('lists 10 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(10);
-    expect(new Set(fields).size).toBe(10);
+    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);
   });
@@ -307,6 +323,7 @@ describe('ABILITIES registry (v0.40.0, #67)', () => {
         nationResources,
         industryProjects,
         nuclear,
+        seaZones,
       ),
     );
   });
@@ -336,7 +353,7 @@ 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', () => {
@@ -361,9 +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(11);
-    expect(extended.map((a) => a.constraint())).toHaveLength(11);
-    expect(extended[10].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', () => {
@@ -413,6 +430,15 @@ describe('ABILITIES registry (v0.40.0, #67)', () => {
       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 9 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 nine abilities.
+ * / markers) plus, in order, these eleven abilities.
  */
 export type AbilityField =
   | 'takeovers'
@@ -33,7 +34,8 @@ export type AbilityField =
   | 'leaders'
   | 'ideology'
   | 'disasters'
-  | 'migration';
+  | 'migration'
+  | 'sea';
 
 /**
  * Everything a single ability's `apply` may need from the surrounding turn.
@@ -89,6 +91,7 @@ export interface UserPromptCtx {
   readonly embargoes?: Embargo[];
   readonly nationResources?: Record<string, RegionResources>;
   readonly industryProjects?: IndustryProject[];
+  readonly seaZones?: SeaZoneClaim[];
 }
 
 /**

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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, 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: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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);
   });
@@ -1721,7 +1723,7 @@ describe('isMeaningful', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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);
   });
@@ -1742,7 +1744,7 @@ describe('isMeaningful', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, markers: { add: [], remove: [] },
+        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(true);
   });
@@ -1765,7 +1767,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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');
@@ -1798,7 +1800,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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
@@ -1822,7 +1824,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     // no nation was renamed
@@ -1849,7 +1851,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     // neither was renamed (ambiguous)
@@ -1875,7 +1877,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, markers: { add: [], remove: [] },
+      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
     });
     expect(validated!.takeovers).toEqual([]);
     const next = applyTurnResult(state, validated!);
@@ -1901,7 +1903,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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');
@@ -1925,7 +1927,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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
@@ -1947,7 +1949,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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');
@@ -1981,7 +1983,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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);
@@ -2005,13 +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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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
@@ -2038,7 +2040,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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
@@ -2085,7 +2087,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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' },
@@ -2110,7 +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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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
@@ -2126,14 +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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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: [] }, disasters: { events: [] }, migration: { ops: [] }, 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');
   });
@@ -2203,7 +2205,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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]),
@@ -2278,6 +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: [],
   };
 }
 
@@ -2301,6 +2305,7 @@ function mkTurnResult(partial: Partial<TurnResult>): TurnResult {
     ideology: partial.ideology ?? { changes: [] },
     disasters: partial.disasters ?? { events: [] },
     migration: partial.migration ?? { ops: [] },
+    sea: partial.sea ?? { control: [] },
     markers: partial.markers ?? { add: [], remove: [] },
   };
 }
@@ -3026,7 +3031,7 @@ describe('validateTakeovers (v0.32.0 #54)', () => {
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
       nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-      ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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
@@ -3414,7 +3419,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, markers: { add: [], remove: [] },
+        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(true);
   });
@@ -3435,7 +3440,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, markers: { add: [], remove: [] },
+        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, sea: { control: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(true);
   });
@@ -3456,7 +3461,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
         nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
-        ideology: { changes: [] }, disasters: { events: [] }, migration: { ops: [] }, 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';
@@ -104,6 +105,14 @@ export {
   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) ---
@@ -376,6 +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;
@@ -485,6 +502,7 @@ export function buildUserPrompt(
     embargoes,
     nationResources,
     industryProjects,
+    seaZones,
   };
   Object.assign(payload, ABILITIES[0].payload(upCtx)); // takeovers → takeoverRisks
   if (noMansLand !== undefined) payload.unowned = noMansLand;
@@ -493,6 +511,7 @@ export function buildUserPrompt(
   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);
 }
 
@@ -633,6 +652,7 @@ export function validateTurnResult(
     ideology: { changes: [] },
     disasters: { events: [] },
     migration: { ops: [] },
+    sea: { control: [] },
     markers: { add: [], remove: [] },
   };
 
@@ -723,7 +743,7 @@ export function validateTurnResult(
   // list for the player to confirm/reject.
   result.nationOps = validateNationOps(o.nationOps);
 
-  // The 9 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) {
@@ -917,6 +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);
@@ -1594,6 +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 9 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 → disasters), 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

@@ -707,6 +707,82 @@ 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;
@@ -899,6 +975,23 @@ export interface TurnResult {
    * `{ 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[];
 }
 
 /**