Merge pull request 'feat(#61): named leaders — assassination / death / appointment with succession (v0.38.0)' (#72) from feat/61-named-leaders into master

CHANGELOG.md

@@ -2,6 +2,22 @@
 
 All notable changes to **History** are listed here, newest first.
 
+## v0.38.0 — 2026-10-15 20:06
+- **#61: Named leaders — a per-nation `leader` + a `TurnResult.leaders` lever (assassination / death / appointment) with a deterministic stability effect and succession narration.** Each nation may carry a single named head of state (`Nation.leader`); the model changes it each turn via `leaders.changes`. The engine is **fully deterministic (no hidden randomness)** and **additive** (no `db.ts` change — `leader` is an optional `Nation` field; a pre-v0.38 row loads with it absent, i.e. "no leader").
+  - **Types (`shared/types.ts`).** `Nation.leader?: { name: string }` (optional; `undefined`/absent = the nation has no leader).
+  - **Protocol (`shared/protocol.ts`).** New `LeaderCause` (`'assassination' | 'death' | 'appointed'`), `LeaderChange` (`{ target; name; cause }` — `target` is a nation ref, `name` is the new leader's name), and `LeaderOps` (`{ changes: LeaderChange[] }`); `TurnResult.leaders` is **required**, placed between `nuclear` and `markers`, default `{ changes: [] }`. New exported **`LEADER_STABILITY_EFFECT = { assassination: −15, death: −3, appointed: 0 }`** (the deterministic stability dip by cause). `nationForPrompt` now includes the nation's `leader` (omitted when absent), so `buildUserPrompt` carries each nation's current leader with no separate wiring.
+  - **Engine (`server/engine.ts`).**
+    - `validateLeaderOps(raw)` — new exported, defensive validator (never throws): accepts a `{ changes: [...] }` object or a bare array; each change needs a non-empty `target` (≤120), a non-empty `name` (≤120), and a `cause` that is one of the three literals — anything else is dropped. Refs stay raw (resolved at apply time, like wars / hybrid / nuclear ops).
+    - `applyLeaderChange(next, op, geoOf?, actingTurn?)` — new, mirrors `applyHybridOp` (single-stat, nation-target). Resolves the target (unknown / ambiguous → dropped, never thrown). **GATE**: an `assassination`/`death` requires the target to already have a leader (a leaderless target is dropped); `appointed` is always valid (it creates the first leader). On a valid change it sets `n.leader = { name }` and applies `LEADER_STABILITY_EFFECT[cause]` to `n.stats.stability` (clamped 0–100) mirrored to every region the nation owns (`regionStats`), then re-derives the nation's stats (the same 0-region / no-entry guards as hybrid / economy / industry, so a 0-region nation keeps its directly-mutated value). Finally it appends a narration event: a dramatic **`military`** event for an assassination, a **`political`** succession event for a death or an appointment. The replacement never moves territory (sole ownership is untouched).
+    - `applyTurnResult` — the leader block runs **after `nuclear` and before `markers`** (order: events → relations → territory → stateChanges → recompute → takeovers → wars → hybrid → economy → industry → nuclear → **leaders** → markers → nationOps).
+    - `isMeaningful` — a non-empty `leaders.changes` makes a turn meaningful.
+    - `validateTurnResult` — initializes and validates `leaders` (default `{ changes: [] }`).
+    - `buildSystemPrompt` — documents the `leaders` field (the three causes, the stability effects, the leaderless-gate, the "at most 1–2 per turn, narrated" rule) and contrasts it with the lighter `hybrid.assassinate` op (a −5 dip, no leader replacement) in both tool and plain modes.
+    - `runTurn` — the "unclear" fallback carries `leaders: { changes: [] }`.
+  - **Stub (`server/stub.ts`).** `deterministicTurn` always returns `leaders: { changes: [] }` and the `StubPayload` nations type gains an optional `leader` — the stub **never** changes a leader, so the e2e (CI, `LLM_STUB=1`) is unaffected and the path is covered by unit tests only.
+  - **Tests.** New unit tests in `engine.test.ts`: `validateLeaderOps` (`{changes}` object, bare array, unknown-cause drop, missing target/name drop, malformed top-level, mixed batch keeps only valid); `isMeaningful` (a leader change is meaningful, empty leaders is not); `applyTurnResult` (assassination with a leader → replaced + −15 + `military` event; assassination / death on a leaderless nation → dropped, no stat change, no event; death → replaced + −3 + `political` succession event; appointment on a leader-having and on a leaderless nation → sets the leader, neutral (no dip); a multi-region nation → every region dipped and stats re-derived; an unknown target and an ambiguous (two-nation-same-name) target → dropped without throwing). Two `db.test.ts` round-trips: a legacy row with no leader loads with it absent, and a set leader round-trips through save/load.
+- **Version** bumped `0.37.0 → 0.38.0`.
+
 ## v0.37.0 — 2026-10-15 19:15
 - **#60: Nuclear / WMD — a per-nation `nuclear` capability flag + a `TurnResult.nuclear` lever (`arm` + `strikes`) with deterministic strikes and MAD retaliation.** A nation is *nuclear-capable* when its `nuclear` flag is `true` **or** it currently owns a `rocket` marker (a launch site is an arsenal). The model can **arm** nations (grant the flag — idempotent; a newly-armed nation is capable the same turn, since `arm` is applied before `strikes`) and fire **strikes** (`{ from, target }`). The engine is **fully deterministic (no hidden randomness)** and **additive** (a `db.ts` change is not needed — `nuclear` is an optional `Nation` field; a pre-v0.37 row loads with the flag absent).
   - **Capability (`shared/protocol.ts`).** `isNuclearCapable(nation, markers)` — exported pure helper: `nation.nuclear === true` **or** it owns a `rocket` marker (`marker.type === 'rocket' && marker.ownerNationId === nation.id`). Markers supply the *pre-turn* rocket set, so a rocket placed this turn makes the owner capable from the *next* turn.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "history",
-  "version": "0.37.0",
+  "version": "0.38.0",
   "private": true,
   "type": "module",
   "description": "AI-driven alternate-history simulator — the LLM is the world engine (Pax Historia style).",

server/db.test.ts

@@ -200,6 +200,28 @@ describe('openDb', () => {
     db.close();
   });
 
+  it('(v0.38.0 #61) a legacy row saved before the nation leader field existed loads with it absent (no leader)', () => {
+    const db = openDb(':memory:');
+    // makeState has no nation.leader field — a pre-v0.38 save. The field is
+    // optional and not re-stamped by load, so an absent leader stays absent.
+    db.save(makeState('legacy'));
+    const loaded = db.load('legacy');
+    expect(loaded).not.toBeNull();
+    expect(loaded!.nations.uk.leader).toBeUndefined();
+    db.close();
+  });
+
+  it('(v0.38.0 #61) a set nation leader round-trips through save/load', () => {
+    const db = openDb(':memory:');
+    const s = makeState('ldr');
+    s.nations.uk.leader = { name: 'Admiral Old' };
+    db.save(s);
+    const loaded = db.load('ldr');
+    expect(loaded).not.toBeNull();
+    expect(loaded!.nations.uk.leader).toEqual({ name: 'Admiral Old' });
+    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

@@ -48,6 +48,7 @@ import {
   validateEconomyOps,
   validateHybridOps,
   validateIndustryOps,
+  validateLeaderOps,
   validateMarkerOps,
   validateNuclearOps,
   validateNationOps,
@@ -568,7 +569,7 @@ 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: [] }, 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: [] }, markers: { add: [], remove: [] },
     });
     expect(withOps).not.toBeNull();
     expect(withOps!.nationOps).toEqual([{ kind: 'rename', nationRef: 'France', to: 'French Republic' }]);
@@ -590,7 +591,7 @@ 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: [] }, 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: [] }, markers: { add: [], remove: [] },
     });
     expect(next.nations.de.name).toBe('DE'); // still the old name
     expect(next.pendingNationOps).toEqual([{ kind: 'rename', nationRef: 'de', to: 'Reich' }]);
@@ -611,7 +612,7 @@ 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: [] }, 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: [] }, markers: { add: [], remove: [] }, // new proposal this turn
     });
     expect(next.pendingNationOps).toEqual([
       { kind: 'rename', nationRef: 'de', to: 'Reich' }, // the old one survived
@@ -630,7 +631,7 @@ 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: [] }, 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: [] }, markers: { add: [], remove: [] },
     });
     expect(next.pendingNationOps).toEqual([{ kind: 'rename', nationRef: 'de', to: 'Reich' }]);
   });
@@ -1087,7 +1088,7 @@ describe('applyTurnResult', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, markers: { add: [], remove: [] },
+      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, markers: { add: [], remove: [] },
     };
     applyTurnResult(state, result);
     expect(JSON.stringify(state)).toBe(snapshot);
@@ -1104,7 +1105,7 @@ describe('applyTurnResult', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, markers: { add: [], remove: [] },
+      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     expect(next.pending).toEqual([]);
@@ -1127,7 +1128,7 @@ 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: [] }, markers: { add: [], remove: [] },
+      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, 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
@@ -1153,7 +1154,7 @@ 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: [] }, markers: { add: [], remove: [] },
+      nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result); // no validKeys -> nothing filtered
     expect(next.nations.de.territory).toContain('wales-bbbb');
@@ -1171,7 +1172,7 @@ 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: [] }, markers: { add: [], remove: [] },
+    nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, markers: { add: [], remove: [] },
   };
 
   it('a double claim (two different gainers, one key) is rejected: the key stays with its original owner', () => {
@@ -1261,7 +1262,7 @@ 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: [] }, markers: { add: [], remove: [] },
+    nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, markers: { add: [], remove: [] },
   };
 
   it('a release removes the key from its sole owner and marks it in GameState.unowned', () => {
@@ -1376,7 +1377,7 @@ 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: [] }, 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: [] }, markers: { add: [], remove: [] } }),
     ).toBe(true);
   });
 
@@ -1683,9 +1684,9 @@ 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: [] }, 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: [] }, 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: [] }, 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: [] }, 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: [] }, 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: [] }, 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)', () => {
@@ -1698,7 +1699,7 @@ 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: [] }, 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: [] }, markers: { add: [], remove: [] },
       }),
     ).toBe(true);
   });
@@ -1718,7 +1719,7 @@ describe('isMeaningful', () => {
         wars: { declare: [], end: [] },
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
-        nuclear: { arm: [], strikes: [] },
+        nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
         markers: { add: [{ type: 'city', name: 'Lyon', regionKey: 'rhone-rhne' }], remove: [] },
       }),
     ).toBe(true);
@@ -1739,7 +1740,7 @@ describe('isMeaningful', () => {
         wars: { declare: [], end: [] },
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
-        nuclear: { arm: [], strikes: [] },
+        nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
         markers: { add: [], remove: [] },
       }),
     ).toBe(true);
@@ -1762,7 +1763,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
@@ -1795,7 +1796,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
@@ -1819,7 +1820,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
@@ -1846,7 +1847,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
@@ -1872,7 +1873,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     });
     expect(validated!.takeovers).toEqual([]);
@@ -1898,7 +1899,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
@@ -1922,7 +1923,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
@@ -1944,7 +1945,7 @@ describe('takeovers (regime change, v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
@@ -1978,7 +1979,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [mk('city', 'Strasbourg', 'moselle-rygy')], remove: [] },
     };
     const next = applyTurnResult(state, result, undefined, centroidOf);
@@ -2003,13 +2004,13 @@ 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: [] }, markers: { add, remove: [] },
+      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, 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: [] }, markers: { add, remove: [] },
+      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, 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
@@ -2035,7 +2036,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: {
         add: [
           { type: 'city', name: 'Good', regionKey: 'moselle-rygy' }, // valid + centroid → kept
@@ -2082,7 +2083,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: {
         add: [
           { type: 'city', name: 'NewA', regionKey: 'new-a' },
@@ -2108,7 +2109,7 @@ 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: [] }, 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: [] }, 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
@@ -2124,14 +2125,14 @@ 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: [] }, markers: { add: [], remove: [] },
+      unowned: ['moselle-rygy'], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, 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: [] }, markers: { add: [], remove: [] },
+      unowned: [], nationOps: [], takeovers: [], wars: { declare: [], end: [] }, hybrid: { ops: [] }, economy: { trade: [], embargo: [] }, industry: { projects: [] }, nuclear: { arm: [], strikes: [] }, leaders: { changes: [] }, markers: { add: [], remove: [] },
     }, undefined, centroidOf);
     expect(reclaimed.markers[0].ownerNationId).toBe('de');
   });
@@ -2200,7 +2201,7 @@ describe('markers (point placement, v0.27 #44)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [{ type: 'city', name: 'Strasbourg', regionKey: 'moselle-rygy' }], remove: [] },
     });
     const { state } = await runTurn({
@@ -2295,6 +2296,7 @@ function mkTurnResult(partial: Partial<TurnResult>): TurnResult {
     economy: partial.economy ?? { trade: [], embargo: [] },
     industry: partial.industry ?? { projects: [] },
     nuclear: partial.nuclear ?? { arm: [], strikes: [] },
+    leaders: partial.leaders ?? { changes: [] },
     markers: partial.markers ?? { add: [], remove: [] },
   };
 }
@@ -3019,7 +3021,7 @@ describe('validateTakeovers (v0.32.0 #54)', () => {
       wars: { declare: [], end: [] },
       hybrid: { ops: [] },
       economy: { trade: [], embargo: [] }, industry: { projects: [] },
-      nuclear: { arm: [], strikes: [] },
+      nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
       markers: { add: [], remove: [] },
     });
     expect(withTakeovers).not.toBeNull();
@@ -3407,7 +3409,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         wars: { declare: [{ sides: ['a', 'b'] }], end: [] },
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
-        nuclear: { arm: [], strikes: [] },
+        nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
         markers: { add: [], remove: [] },
       }),
     ).toBe(true);
@@ -3428,7 +3430,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         wars: { declare: [], end: [{ id: 'w1', outcome: 'armistice' }] },
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
-        nuclear: { arm: [], strikes: [] },
+        nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
         markers: { add: [], remove: [] },
       }),
     ).toBe(true);
@@ -3449,7 +3451,7 @@ describe('isMeaningful — wars (v0.33.0 #56)', () => {
         wars: { declare: [], end: [] },
         hybrid: { ops: [] },
         economy: { trade: [], embargo: [] }, industry: { projects: [] },
-        nuclear: { arm: [], strikes: [] },
+        nuclear: { arm: [], strikes: [] }, leaders: { changes: [] },
         markers: { add: [], remove: [] },
       }),
     ).toBe(false);
@@ -4611,7 +4613,7 @@ describe('isMeaningful — nuclear (v0.37.0 #60)', () => {
     expect(isMeaningful(mkTurnResult({ nuclear: { arm: [], strikes: [{ from: 'uk', target: 'de' }] } }))).toBe(true);
   });
   it('a turn with empty nuclear ops and nothing else is not meaningful', () => {
-    expect(isMeaningful(mkTurnResult({ nuclear: { arm: [], strikes: [] } }))).toBe(false);
+    expect(isMeaningful(mkTurnResult({ nuclear: { arm: [], strikes: [] }, leaders: { changes: [] } }))).toBe(false);
   });
 });
 
@@ -4644,3 +4646,177 @@ describe('buildUserPrompt — nuclear capability (v0.37.0 #60)', () => {
     expect(out.state.nations.de).not.toHaveProperty('nuclear');
   });
 });
+
+describe('named leaders (v0.38.0 #61)', () => {
+  // `uk` starts with a named leader; `de` has none. Each owns one region
+  // seeded to its stats (the fresh-state invariant), so a uniform dip leaves
+  // the derived median equal to the dipped value.
+  const leaderBase = (): GameState => {
+    const uk: Nation = { ...mkNation('uk', NS(50, 50, 50, 50), ['g1']), leader: { name: 'Admiral Old' } };
+    const de: Nation = { ...mkNation('de', NS(50, 50, 50, 50), ['d1']) };
+    return mkTurnState({ uk, de }, { g1: RS(50, 50, 50, 50), d1: RS(50, 50, 50, 50) });
+  };
+
+  describe('validateLeaderOps', () => {
+    it('accepts a {changes} object and a bare array of valid changes', () => {
+      const fromObj = validateLeaderOps({
+        changes: [
+          { target: 'uk', name: 'New Leader', cause: 'assassination' },
+          { target: 'de', name: 'Other', cause: 'death' },
+        ],
+      });
+      expect(fromObj).toEqual([
+        { target: 'uk', name: 'New Leader', cause: 'assassination' },
+        { target: 'de', name: 'Other', cause: 'death' },
+      ]);
+      expect(validateLeaderOps([{ target: 'uk', name: 'X', cause: 'appointed' }])).toEqual([
+        { target: 'uk', name: 'X', cause: 'appointed' },
+      ]);
+    });
+
+    it('drops a change with an unknown cause', () => {
+      expect(validateLeaderOps({ changes: [{ target: 'uk', name: 'X', cause: 'explosion' }] })).toEqual([]);
+    });
+
+    it('drops a change missing a target or a name', () => {
+      expect(
+        validateLeaderOps({
+          changes: [
+            { target: '', name: 'X', cause: 'appointed' },
+            { target: 'uk', name: '', cause: 'death' },
+          ],
+        }),
+      ).toEqual([]);
+    });
+
+    it('returns [] for undefined / non-object / non-array-changes input', () => {
+      expect(validateLeaderOps(undefined)).toEqual([]);
+      expect(validateLeaderOps('nope')).toEqual([]);
+      expect(validateLeaderOps({ changes: 'nope' })).toEqual([]);
+    });
+
+    it('keeps only the valid changes of a mixed batch', () => {
+      const out = validateLeaderOps({
+        changes: [
+          { target: 'uk', name: 'Good', cause: 'appointed' },
+          { target: 'uk', name: 'Bad', cause: 'nope' },
+          null,
+          { target: 'uk', name: 'Also Good', cause: 'death' },
+        ],
+      });
+      expect(out).toEqual([
+        { target: 'uk', name: 'Good', cause: 'appointed' },
+        { target: 'uk', name: 'Also Good', cause: 'death' },
+      ]);
+    });
+  });
+
+  describe('isMeaningful — leaders', () => {
+    it('a turn with only a leader change is meaningful', () => {
+      expect(isMeaningful(mkTurnResult({ leaders: { changes: [{ target: 'uk', name: 'X', cause: 'death' }] } }))).toBe(true);
+    });
+    it('a turn with empty leaders and nothing else is not meaningful', () => {
+      expect(isMeaningful(mkTurnResult({ leaders: { changes: [] } }))).toBe(false);
+    });
+  });
+
+  describe('applyTurnResult — leaders', () => {
+    it('assassinating a nation with a leader replaces it, dips stability, and adds a military event', () => {
+      const next = applyTurnResult(
+        leaderBase(),
+        mkTurnResult({ leaders: { changes: [{ target: 'uk', name: 'New Leader', cause: 'assassination' }] } }),
+      );
+      expect(next.nations.uk.leader).toEqual({ name: 'New Leader' });
+      expect(next.nations.uk.stats.stability).toBe(35); // 50 - 15
+      expect(next.regionStats.g1.stability).toBe(35); // mirrored to the region
+      expect(next.events).toHaveLength(1);
+      expect(next.events[0]!.type).toBe('military');
+    });
+
+    it('assassinating a leaderless nation is dropped (no leader, no stat change, no event)', () => {
+      const next = applyTurnResult(
+        leaderBase(),
+        mkTurnResult({ leaders: { changes: [{ target: 'de', name: 'New Leader', cause: 'assassination' }] } }),
+      );
+      expect(next.nations.de.leader).toBeUndefined();
+      expect(next.nations.de.stats).toEqual(NS(50, 50, 50, 50));
+      expect(next.events).toHaveLength(0);
+    });
+
+    it('a death of a leader replaces it, dips stability a little, and adds a political succession event', () => {
+      const next = applyTurnResult(
+        leaderBase(),
+        mkTurnResult({ leaders: { changes: [{ target: 'uk', name: 'Successor', cause: 'death' }] } }),
+      );
+      expect(next.nations.uk.leader).toEqual({ name: 'Successor' });
+      expect(next.nations.uk.stats.stability).toBe(47); // 50 - 3
+      expect(next.events).toHaveLength(1);
+      expect(next.events[0]!.type).toBe('political');
+    });
+
+    it('a death of a leaderless nation is dropped', () => {
+      const next = applyTurnResult(
+        leaderBase(),
+        mkTurnResult({ leaders: { changes: [{ target: 'de', name: 'X', cause: 'death' }] } }),
+      );
+      expect(next.nations.de.leader).toBeUndefined();
+      expect(next.nations.de.stats).toEqual(NS(50, 50, 50, 50));
+      expect(next.events).toHaveLength(0);
+    });
+
+    it('an appointment on a nation that has a leader replaces it with no stability dip', () => {
+      const next = applyTurnResult(
+        leaderBase(),
+        mkTurnResult({ leaders: { changes: [{ target: 'uk', name: 'New PM', cause: 'appointed' }] } }),
+      );
+      expect(next.nations.uk.leader).toEqual({ name: 'New PM' });
+      expect(next.nations.uk.stats).toEqual(NS(50, 50, 50, 50)); // neutral: no dip
+      expect(next.events).toHaveLength(1);
+      expect(next.events[0]!.type).toBe('political');
+    });
+
+    it('an appointment creates the first leader on a leaderless nation', () => {
+      const next = applyTurnResult(
+        leaderBase(),
+        mkTurnResult({ leaders: { changes: [{ target: 'de', name: 'First', cause: 'appointed' }] } }),
+      );
+      expect(next.nations.de.leader).toEqual({ name: 'First' });
+      expect(next.nations.de.stats).toEqual(NS(50, 50, 50, 50));
+    });
+
+    it('a leader change on a multi-region nation dips every region and re-derives its stats', () => {
+      const uk: Nation = { ...mkNation('uk', NS(50, 50, 50, 50), ['g1', 'g2']), leader: { name: 'Old' } };
+      const state = mkTurnState({ uk }, { g1: RS(50, 50, 50, 50), g2: RS(50, 50, 50, 50) });
+      const next = applyTurnResult(
+        state,
+        mkTurnResult({ leaders: { changes: [{ target: 'uk', name: 'New', cause: 'assassination' }] } }),
+      );
+      expect(next.regionStats.g1.stability).toBe(35);
+      expect(next.regionStats.g2.stability).toBe(35);
+      expect(next.nations.uk.stats.stability).toBe(35); // re-derived from the dipped regions
+    });
+
+    it('an unknown target is dropped without throwing (no leader change, no event, no crash)', () => {
+      const next = applyTurnResult(
+        leaderBase(),
+        mkTurnResult({ leaders: { changes: [{ target: 'ghost', name: 'X', cause: 'assassination' }] } }),
+      );
+      expect(next.nations.uk.leader).toEqual({ name: 'Admiral Old' }); // untouched
+      expect(next.events).toHaveLength(0);
+    });
+
+    it('an ambiguous target (two nations share the name) is dropped without throwing', () => {
+      const a: Nation = { ...mkNation('a', NS(50, 50, 50, 50), ['g1']), name: 'Same', leader: { name: 'Old' } };
+      const b: Nation = { ...mkNation('b', NS(50, 50, 50, 50), ['d1']), name: 'Same' };
+      const state = mkTurnState({ a, b }, { g1: RS(50, 50, 50, 50), d1: RS(50, 50, 50, 50) });
+      const next = applyTurnResult(
+        state,
+        mkTurnResult({ leaders: { changes: [{ target: 'Same', name: 'New', cause: 'assassination' }] } }),
+      );
+      // 'Same' matches two nations -> ambiguous -> dropped; neither leader changes.
+      expect(next.nations.a.leader).toEqual({ name: 'Old' });
+      expect(next.nations.b.leader).toBeUndefined();
+      expect(next.events).toHaveLength(0);
+    });
+  });
+});

server/engine.ts

@@ -34,6 +34,7 @@ import {
   isDateLike,
   isMarkerType,
   isNuclearCapable,
+  LEADER_STABILITY_EFFECT,
   makeEvent,
   markerId,
   MAX_MARKERS,
@@ -46,6 +47,8 @@ import {
   type HybridOp,
   type HybridOpType,
   type IndustryOps,
+  type LeaderCause,
+  type LeaderChange,
   type MarkerInfo,
   type MarkerSpec,
   type NationOp,
@@ -243,6 +246,7 @@ export function buildSystemPrompt(preset: Preset, withNeighboursTool = false): s
     '  "economy": {"trade":[{"a":"<nationId>","b":"<nationId>","lift":<true|false>}],"embargo":[{"from":"<nationId>","target":"<nationId>","lift":<true|false>}]},',
     '  "industry": {"projects":[{"regionKey":"<region key>","type":"<oil|iron|food|industry>"}]},',
     '  "nuclear": {"arm":["<nation id or name>"],"strikes":[{"from":"<nuclear-capable nation id or name>","target":"<nation id or name, or region key>"}]},',
+    '  "leaders": {"changes":[{"target":"<nation id or name>","name":"<new leader name>","cause":"<assassination|death|appointed>"}]},',
     '  "markers": {"add":[{"type":"<city|factory|army|port|capital|fleet|rocket|gathering>","name":"<short name>","regionKey":"<region key>"}],"remove":["<marker id>"]}',
     '}',
     '',
@@ -266,6 +270,7 @@ export function buildSystemPrompt(preset: Preset, withNeighboursTool = false): s
     '- Economy ("economy") is the trade & embargo layer: a bilateral trade (trade: {"a":"..","b":".."}) gives BOTH parties a small, deterministic economy gain every turn, while a unilateral embargo (embargo: {"from":"..","target":".."}) lowers only the TARGET\'s economy every turn. Omit "lift" to declare / impose, and set "lift":true to end or lift an existing one (the user message\'s "trades"/"embargoes" fields list what is currently active). Propose at most 1-2 operations per turn and narrate each one in "events". Trades and embargoes between nations at war are suspended automatically by the engine.',
     '- Industry ("industry") is the per-resource development lever: each project is a building in one region you (or a nation) controls — {"regionKey":"<region key>","type":"<oil|iron|food|industry>"} (an oil facility, an iron mine, a food operation, or a factory). Every committed turn each active project gives its region\'s owner a small, deterministic economy gain, the bigger the region\'s industry profile (see the "resources" field). A region holds at most one project — do not re-declare one on a region that already has one (the user message\'s "industry" field lists what is already built). Propose at most 1-2 new projects per turn and narrate each one in "events".',
     '- Nuclear / WMD ("nuclear"): a nation is "nuclear-capable" when its "nuclear" flag is true or it currently owns a "rocket" marker. "arm" names (by id or name) nations to grant the "nuclear" flag — idempotent (already-armed nations are unchanged); a newly armed nation is capable this same turn. "strikes" is a list of "NuclearStrike" objects, each "{from, target}" — "from" is the striking nation (must be nuclear-capable and never itself) and "target" is either a nation (its nation collapses: economy -40, military -50, stability -40; every active war the target fights ends by capitulation and the "war" relations it caused downgrade to "hostile") or a region key (that region is released to no man\'s land, its regionStats entry deleted, and its sole owner collapses the same way — a region with 0 or 2+ owners, or one the striker itself owns, is dropped). If the struck nation (or the struck region\'s owner) is itself nuclear-capable, a "MAD" retaliation is applied: it strikes the striker back for half the collapse, and the two nations\' relations are forced to "hostile". At most one strike per turn; always narrate a strike (and a retaliation, if any) in "events".',
+    '- Leaders ("leaders") name each nation\'s current head of state and change it. Each change is {"target":"<nation id or name>","name":"<new leader name>","cause":"<assassination|death|appointed>"}: "assassination" kills the current leader (a dramatic, destabilizing blow — a −15 stability dip, a "military" event) and is only valid when the target already has a leader; "death" is a natural-causes succession (a quieter −3 dip, a "political" event), also only valid for a nation that has a leader; "appointed" sets (or creates) a leader and is always valid (a neutral 0 effect, a "political" event). Propose at most 1-2 changes per turn and narrate each one in "events". This is the HEAVY leader lever — use the lighter "hybrid" {"type":"assassinate"} op (a −5 stability dip, no leader replacement) for a mere hit on a leader or region without changing who is in charge. The user message\'s "nations" field lists each nation\'s current "leader" (omitted when a nation has none).',
   '- 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.',
@@ -631,6 +636,7 @@ export function validateTurnResult(
     economy: { trade: [], embargo: [] },
     industry: { projects: [] },
     nuclear: { arm: [], strikes: [] },
+    leaders: { changes: [] },
     markers: { add: [], remove: [] },
   };
 
@@ -757,6 +763,13 @@ export function validateTurnResult(
   // (after industry, before markers).
   result.nuclear = validateNuclearOps(o.nuclear);
 
+  // (v0.38, #61) Leader changes: assassinations / deaths / appointments of
+  // named leaders. Refs stay raw here (resolved against the real state at
+  // apply time, like wars / hybrid / nuclear ops); an unresolvable target or a
+  // leaderless assassination/death is dropped at apply time, never thrown.
+  // Applied by applyTurnResult after nuclear, before markers.
+  result.leaders = { changes: validateLeaderOps(o.leaders) };
+
   // (v0.27, #44) Map-marker ops: new placements (validated here) and
   // removals by stable id. Applied by applyTurnResult after the territory
   // moves (a new marker's owner is the region's post-turn owner).
@@ -1093,6 +1106,39 @@ export function validateNuclearOps(raw: unknown): NuclearOps {
   return out;
 }
 
+/**
+ * (v0.38, #61) Validate the raw `leaders` object of a turn into a safe
+ * `LeaderChange[]`. Defensive like the rest of the parser — never throws.
+ * Accepts a `{ changes: [...] }` object or a bare array (lenient). Each change
+ * needs a non-empty `target` (a nation ref, capped at 120 chars), a non-empty
+ * `name` (the new leader's name, capped at 120 chars), and a `cause` that is
+ * one of the three known literals (assassination / death / appointed). Refs
+ * stay raw here (resolved against the real state at apply time, like the wars
+ * / hybrid / nuclear ops); a leaderless assassination/death is dropped at
+ * apply time, never thrown.
+ */
+export function validateLeaderOps(raw: unknown): LeaderChange[] {
+  const out: LeaderChange[] = [];
+  const list = Array.isArray(raw)
+    ? raw
+    : raw && typeof raw === 'object'
+      ? (raw as Record<string, unknown>).changes
+      : undefined;
+  if (!Array.isArray(list)) return out;
+  for (const e of list) {
+    if (!e || typeof e !== 'object') continue;
+    const s = e as Record<string, unknown>;
+    const target = str(s.target, 120);
+    const name = str(s.name, 120);
+    if (!target || !name) continue;
+    const cause = typeof s.cause === 'string' ? s.cause : '';
+    if (cause === 'assassination' || cause === 'death' || cause === 'appointed') {
+      out.push({ target, name, cause: cause as LeaderCause });
+    }
+  }
+  return out;
+}
+
 /**
  * (v0.33.0, #56) The UNORDERED pairs of belligerents of a set of ACTIVE
  * wars: a war with sides [a, b, c] contributes the pairs {a,b}, {a,c},
@@ -1377,6 +1423,85 @@ function applyHybridOp(
   else if (op.type === 'proxy') shiftRelationTowardHostile(next, from, target.nation.id, 'rival');
 }
 
+// --- Named leaders (v0.38, #61) -----------------------------------------------
+
+/**
+ * (v0.38, #61) Apply a single leader change to `next` (in place). The target
+ * nation is resolved by the shared resolver (id first, then a case-insensitive
+ * unique name; an unknown or ambiguous ref is dropped, never thrown). A GATE
+ * then applies: an `assassination` or `death` requires the target to already
+ * have a leader (a leaderless target is dropped); an `appointed` change is
+ * always valid (it creates the first leader). On a valid change the target's
+ * `leader` is set to the new name and a DETERMINISTIC stability dip
+ * (`LEADER_STABILITY_EFFECT[cause]`) is applied to its `stats.stability`
+ * (clamped 0–100) and mirrored to every region the nation owns
+ * (`regionStats`); the nation's derived stats are re-derived afterwards (the
+ * same 0-region / no-entry guards as the hybrid/economy/industry effects, so a
+ * 0-region nation keeps its directly-mutated value). Finally a narration event
+ * is appended: a dramatic `military` event for an assassination, a `political`
+ * succession event for a death or an appointment. The replacement never moves
+ * territory (sole ownership is untouched).
+ */
+function applyLeaderChange(
+  next: GameState,
+  op: LeaderChange,
+  geoOf?: (key: string) => { area: number; population: number } | undefined,
+  actingTurn?: number,
+): void {
+  const turn = actingTurn ?? next.turn;
+  const id = resolveNationRef(next, op.target);
+  if (id === null) return; // unknown / ambiguous target: drop, never throw
+  const n = next.nations[id];
+
+  // GATE: assassination / death require an existing leader; an appointment is
+  // always valid (it creates the first leader).
+  if (op.cause !== 'appointed' && !n.leader) return;
+
+  const prevName = n.leader?.name;
+  n.leader = { name: op.name };
+
+  const delta = LEADER_STABILITY_EFFECT[op.cause];
+  if (delta !== 0) {
+    n.stats.stability = clampStat(n.stats.stability + delta);
+    for (const key of n.territory) {
+      const rs = next.regionStats[key];
+      if (!rs) continue;
+      rs.stability = clampStat(rs.stability + delta);
+    }
+    // Re-derive the nation's aggregate stats (the main recompute ran earlier
+    // this turn, so without this the dip would be washed out next turn).
+    if (n.territory.length > 0 && n.territory.some((k) => next.regionStats[k])) {
+      n.stats = deriveNationStats(n.territory, next.regionStats, geoOf);
+    }
+  }
+
+  const title =
+    op.cause === 'assassination'
+      ? `${prevName ?? 'The leader'} of ${n.name} is assassinated`
+      : op.cause === 'death'
+        ? `${prevName ?? 'The leader'} of ${n.name} dies`
+        : `${n.name} appoints ${op.name}`;
+  const text =
+    op.cause === 'assassination'
+      ? `${n.name}'s leader ${prevName ?? ''} was assassinated; ${op.name} takes power amid turmoil.`
+      : op.cause === 'death'
+        ? `${n.name}'s leader ${prevName ?? ''} has died; ${op.name} succeeds to power.`
+        : `${n.name} has appointed ${op.name} as its new leader.`;
+  next.events.push(
+    makeEvent(
+      {
+        nation: n.id,
+        type: op.cause === 'assassination' ? 'military' : 'political',
+        title,
+        text,
+        outcome: 'success',
+      },
+      turn,
+      next.date,
+    ),
+  );
+}
+
 // --- Economy ops: trade + embargo (v0.35.0, #58) ------------------------------
 
 /**
@@ -1948,6 +2073,9 @@ export function isMeaningful(result: TurnResult): boolean {
     // this turn is a real world change.
     result.nuclear.arm.length > 0 ||
     result.nuclear.strikes.length > 0 ||
+    // (v0.38, #61) a leader assassinated / died / appointed this turn is a real
+    // world change (a nation's leader and stability moved).
+    result.leaders.changes.length > 0 ||
     // (v0.27, #44) a marker placed or removed this turn is a real world change.
     result.markers.add.length > 0 ||
     result.markers.remove.length > 0
@@ -2372,6 +2500,16 @@ export function applyTurnResult(
   // rocket-marker half of nuclear capability.
   applyNuclearOps(next, result.nuclear, state, geoOf, validKeys, regionNameOf, actingTurn);
 
+  // --- Named leaders (v0.38, #61) ---
+  //
+  // Placed AFTER the nuclear block (both are the "heavier" levers) and BEFORE
+  // the markers block (markers recompute their owner from the FINAL post-claim
+  // ownership; leaders only touch stats, so ordering w.r.t. markers is
+  // immaterial, but keeping the levers grouped is clearer). Each change sets
+  // the target's leader, applies a deterministic stability dip by cause, and
+  // appends a narration event. A leaderless assassination/death is dropped.
+  for (const op of result.leaders.changes) applyLeaderChange(next, op, geoOf, actingTurn);
+
   // --- Map markers (v0.27, #44) ---
   //
   // Markers are anchored to a region key and are processed against the FINAL
@@ -2983,6 +3121,7 @@ export async function runTurn(opts: {
       economy: { trade: [], embargo: [] },
       industry: { projects: [] },
       nuclear: { arm: [], strikes: [] },
+      leaders: { changes: [] },
       markers: { add: [], remove: [] },
     };
   }

server/stub.ts

@@ -16,9 +16,17 @@ export interface StubPayload {
     // `nuclear` (v0.37.0, #60) is the per-nation nuclear capability stamped by
     // the engine (its `nuclear` flag OR a `rocket` marker); the stub ignores
     // it — it never arms or strikes (see deterministicTurn).
+    // `leader` (v0.38.0, #61) is the per-nation named leader stamped by the
+    // engine; the stub ignores it — it never changes a leader (see
+    // deterministicTurn).
     nations: Record<
       string,
-      { stats: Record<string, number>; territory?: string[]; nuclear?: boolean }
+      {
+        stats: Record<string, number>;
+        territory?: string[];
+        nuclear?: boolean;
+        leader?: { name: string };
+      }
     >;
   };
   /** The raw pending round the engine emitted (one entry per queued item). */
@@ -224,6 +232,7 @@ export function deterministicTurn(p: StubPayload): TurnResult {
     economy: { trade: [], embargo: [] }, // the stub never touches trades/embargoes (see doc comment)
     industry: { projects: [] }, // the stub never declares industry projects (see doc comment)
     nuclear: { arm: [], strikes: [] }, // the stub never arms or strikes (see doc comment)
+    leaders: { changes: [] }, // the stub never changes leaders (see doc comment)
     markers: { add: [], remove: [] }, // the stub never touches markers (see doc comment)
   };
 }

shared/protocol.ts

@@ -468,6 +468,48 @@ export interface NuclearOps {
   strikes: NuclearStrike[];
 }
 
+// --- Named leaders (v0.38, #61) -----------------------------------------------
+//
+// Each nation may have a single named leader (`Nation.leader`). The LLM changes
+// it each turn via `TurnResult.leaders`. A change names a target nation (id or
+// name) and the outcome: an `assassination` (a leader killed — a dramatic,
+// destabilizing blow), a `death` (a leader dies of natural causes — a quieter
+// succession), or an `appointed` leader (a neutral succession / new head of
+// state). The engine sets the nation's leader to the new name and applies a
+// DETERMINISTIC stability dip (see `LEADER_STABILITY_EFFECT` below) — no hidden
+// randomness. A change whose target has no current leader may only *appoint*
+// one (an assassination/death of a leaderless nation is dropped, not thrown).
+
+/** How a nation's leader changed this turn (v0.38, #61). */
+export type LeaderCause = 'assassination' | 'death' | 'appointed';
+
+/** A single leader change: the target nation, the new leader's name, the cause. */
+export interface LeaderChange {
+  /** The target nation, by id or name (resolved by the shared resolver). */
+  target: string;
+  /** The new leader's name (the incoming / successor head of state). */
+  name: string;
+  /** What happened to the leader this turn. */
+  cause: LeaderCause;
+}
+
+/** The leader-ops block of a `TurnResult`. Required; default `{ changes: [] }`. */
+export interface LeaderOps {
+  changes: LeaderChange[];
+}
+
+/**
+ * The deterministic stability effect of each leader-cause (v0.38, #61).
+ * Assassination is the most destabilizing, a natural death a minor wobble, an
+ * appointment is neutral. Applied to the target's `stability` (clamped 0–100),
+ * mirrored to its `regionStats`, and its derived stats re-derived afterwards.
+ */
+export const LEADER_STABILITY_EFFECT: Record<LeaderCause, number> = {
+  assassination: -15,
+  death: -3,
+  appointed: 0,
+};
+
 // --- Nuclear / WMD effect math (v0.37, #60) ----------------------------------
 //
 // A nuclear strike is a DETERMINISTIC, devastating stat collapse — there is no
@@ -637,6 +679,21 @@ export interface TurnResult {
    * never queued. Required; default `{ arm: [], strikes: [] }`.
    */
   nuclear: NuclearOps;
+  /**
+   * (v0.38, #61) Leader changes this turn. Each change names a target nation
+   * (id or name) and sets its leader to the new name, applying a deterministic
+   * stability effect by cause: `assassination` (leader killed — a dramatic
+   * −15 to the target's stability, a `military` event), `death` (natural
+   * causes — a quieter −3 succession, a `political` event), or `appointed`
+   * (a neutral 0 succession, a `political` event). An assassination/death
+   * requires the target to already have a leader (a leaderless target is
+   * dropped, never thrown); an appointment is always valid (it creates the
+   * first leader). At most 1–2 per turn, each narrated in `events`. This is
+   * the *leader* lever — heavier and more destabilizing than the lighter
+   * `hybrid.assassinate` op (a −5 stability dip on a nation or region, with
+   * no leader replacement). Required; default `{ changes: [] }`.
+   */
+  leaders: LeaderOps;
   /**
    * (v0.27, #44) Map-marker ops this turn. `add` places new named markers
    * (the engine positions each at its region's centroid + a small
@@ -949,6 +1006,7 @@ export function nationForPrompt(n: Nation) {
     stats: n.stats,
     territory: n.territory,
     relations: n.relations,
+    leader: n.leader,
   };
 }
 

shared/types.ts

@@ -80,6 +80,14 @@ export interface Nation {
    * `isNuclearCapable` in `protocol.ts`).
    */
   nuclear?: boolean;
+  /**
+   * The nation's current named leader (v0.38, #61). Optional — a legacy game
+   * (or a nation the LLM has never given a leader to) has none, which is the
+   * "no leader" baseline. The LLM changes it via `TurnResult.leaders`
+   * (assassination / death / appointment, see `LeaderChange` in `protocol.ts`);
+   * each change carries a deterministic stability effect + a narration event.
+   */
+  leader?: { name: string };
 }
 
 /** Categories a narrative event can take. */