v0.27.0 (#44): LLM-placed named map point markers

- shared: 8 MarkerTypes + MARKER_TYPE_INFO (label/color/glyph); MapMarker;
  GameState.markers (required, [] at init); TurnResult.markers {add,remove};
  MarkerSpec/MarkerInfo; FNV-1a 4-char markerId; MAX_MARKERS=400.
- data: new public/region-centroids.json (1,800 anchors = largest-part centroid
  + spread ~0.1x min-bbox) built by new idempotent scripts/build-region-centroids.mjs.
- server: regions.ts centroid loader (public/ then dist/); engine applyTurnResult
  marker ops (remove -> owner-recompute -> add, jitter, cap, never throws);
  prompt documents the contract; buildUserPrompt carries markers; stub marker-free.
- client: WorldMap symbol layer rendered as canvas per-type icons (glyph CDN dead);
  hover tooltip shows name; click focuses owning nation.
- tests: 168 -> 189 (centroids script, regions centroids, db legacy, engine markers).

server/db.test.ts

@@ -25,6 +25,7 @@ function makeState(id: string): GameState {
     version: 1,
     unowned: [],
     pendingNationOps: [],
+    markers: [],
   };
 }
 
@@ -97,6 +98,17 @@ describe('openDb', () => {
     db.close();
   });
 
+  it('(v0.27 #44) a legacy row saved before the markers field existed loads with it defaulted to []', () => {
+    const db = openDb(':memory:');
+    const legacy = makeState('legacy');
+    delete (legacy as { markers?: unknown[] }).markers; // a pre-v0.27 save (field absent)
+    db.save(legacy);
+    const loaded = db.load('legacy');
+    expect(loaded).not.toBeNull();
+    expect(loaded!.markers).toEqual([]);
+    db.close();
+  });
+
   it('delete removes a game by id and reports absence otherwise', () => {
     const db = openDb(':memory:');
     db.save(makeState('a'));

server/db.ts

@@ -46,6 +46,8 @@ export function openDb(filePath: string): Db {
         // (v0.23, #16 P4a) Same for pending nation-op proposals: a legacy game
         // has none awaiting confirm/reject.
         if (state.pendingNationOps === undefined) state.pendingNationOps = [];
+        // (v0.27, #44) Same for map markers: a legacy game has none placed.
+        if (state.markers === undefined) state.markers = [];
         return state;
       } catch {
         return null;

server/engine.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
-import type { GameState, Preset, RoundItem } from '../shared/types';
-import { makeEvent, type NationOp, type TurnResult } from '../shared/protocol';
+import type { GameState, MarkerType, Preset, RoundItem } from '../shared/types';
+import { makeEvent, markerId, MAX_MARKERS, type MarkerSpec, type NationOp, type TurnResult } from '../shared/protocol';
 import type { LlmClient, ToolDefinition, WireMessage } from './llm';
 import { makeStubLlmClient } from './stub';
 import {
@@ -21,6 +21,7 @@ import {
   removeRoundItem,
   resolveNationRef,
   runTurn,
+  validateMarkerOps,
   validateNationOps,
   validateTurnResult,
 } from './engine';
@@ -87,6 +88,7 @@ function baseState(): GameState {
     version: 1,
     unowned: [],
     pendingNationOps: [],
+    markers: [],
   };
 }
 
@@ -524,7 +526,7 @@ describe('validateNationOps (v0.23 #16 P4a)', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [{ kind: 'rename', nationRef: 'France', to: 'French Republic' }],
+      nationOps: [{ kind: 'rename', nationRef: 'France', to: 'French Republic' }], markers: { add: [], remove: [] },
     });
     expect(withOps).not.toBeNull();
     expect(withOps!.nationOps).toEqual([{ kind: 'rename', nationRef: 'France', to: 'French Republic' }]);
@@ -545,7 +547,7 @@ describe('applyTurnResult (nation-op proposals, v0.23 #16 P4a)', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }],
+      nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], markers: { add: [], remove: [] },
     });
     expect(next.nations.de.name).toBe('DE'); // still the old name
     expect(next.pendingNationOps).toEqual([{ kind: 'rename', nationRef: 'de', to: 'Reich' }]);
@@ -565,7 +567,7 @@ describe('applyTurnResult (nation-op proposals, v0.23 #16 P4a)', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [{ kind: 'rename', nationRef: 'us', to: 'USA' }], // new proposal this turn
+      nationOps: [{ kind: 'rename', nationRef: 'us', to: 'USA' }], markers: { add: [], remove: [] }, // new proposal this turn
     });
     expect(next.pendingNationOps).toEqual([
       { kind: 'rename', nationRef: 'de', to: 'Reich' }, // the old one survived
@@ -583,7 +585,7 @@ describe('applyTurnResult (nation-op proposals, v0.23 #16 P4a)', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }],
+      nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], markers: { add: [], remove: [] },
     });
     expect(next.pendingNationOps).toEqual([{ kind: 'rename', nationRef: 'de', to: 'Reich' }]);
   });
@@ -1039,7 +1041,7 @@ describe('applyTurnResult', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [],
+      nationOps: [], markers: { add: [], remove: [] },
     };
     applyTurnResult(state, result);
     expect(JSON.stringify(state)).toBe(snapshot);
@@ -1055,7 +1057,7 @@ describe('applyTurnResult', () => {
       relations: [],
       territoryChanges: [],
       unowned: [],
-      nationOps: [],
+      nationOps: [], markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result);
     expect(next.pending).toEqual([]);
@@ -1077,7 +1079,7 @@ 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: [],
+      nationOps: [], 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
@@ -1102,7 +1104,7 @@ describe('applyTurnResult', () => {
       // released (not in state.unowned), so it does not enter GameState.unowned.
       territoryChanges: [{ nation: 'de', gain: ['POL', 'wales-bbbb'], lose: [] }],
       unowned: [],
-      nationOps: [],
+      nationOps: [], markers: { add: [], remove: [] },
     };
     const next = applyTurnResult(state, result); // no validKeys -> nothing filtered
     expect(next.nations.de.territory).toContain('wales-bbbb');
@@ -1119,7 +1121,7 @@ describe('applyTurnResult (sole-ownership invariants, v0.21 #16 P2)', () => {
     stateChanges: [],
     relations: [],
     unowned: [],
-    nationOps: [],
+    nationOps: [], markers: { add: [], remove: [] },
   };
 
   it('a double claim (two different gainers, one key) is rejected: the key stays with its original owner', () => {
@@ -1208,7 +1210,7 @@ describe('applyTurnResult (no man\'s land, v0.22 #16 P3)', () => {
     relations: [],
     territoryChanges: [],
     unowned: [],
-    nationOps: [],
+    nationOps: [], markers: { add: [], remove: [] },
   };
 
   it('a release removes the key from its sole owner and marks it in GameState.unowned', () => {
@@ -1323,7 +1325,7 @@ 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: [], relations: [], territoryChanges: [], unowned: ['GBR'], nationOps: [] }),
+      isMeaningful({ date: 'x', events: [], stateChanges: [], relations: [], territoryChanges: [], unowned: ['GBR'], nationOps: [], markers: { add: [], remove: [] } }),
     ).toBe(true);
   });
 
@@ -1630,9 +1632,9 @@ 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: [], relations: [], territoryChanges: [], unowned: [], nationOps: [] })).toBe(true);
-    expect(isMeaningful({ date: 'x', events: [], stateChanges: [{ nation: 'uk', stat: 'military', op: 'set', value: 5 }], relations: [], territoryChanges: [], unowned: [], nationOps: [] })).toBe(true);
-    expect(isMeaningful({ date: 'x', events: [], stateChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [] })).toBe(false);
+    expect(isMeaningful({ date: 'x', events: [{ nation: 'uk', type: 'military', title: 't', text: 'b', outcome: 'neutral' }], stateChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [], markers: { add: [], remove: [] } })).toBe(true);
+    expect(isMeaningful({ date: 'x', events: [], stateChanges: [{ nation: 'uk', stat: 'military', op: 'set', value: 5 }], relations: [], territoryChanges: [], unowned: [], nationOps: [], markers: { add: [], remove: [] } })).toBe(true);
+    expect(isMeaningful({ date: 'x', events: [], stateChanges: [], relations: [], territoryChanges: [], unowned: [], nationOps: [], 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)', () => {
@@ -1644,8 +1646,265 @@ describe('isMeaningful', () => {
         relations: [],
         territoryChanges: [],
         unowned: [],
-        nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }],
+        nationOps: [{ kind: 'rename', nationRef: 'de', to: 'Reich' }], markers: { add: [], remove: [] },
+      }),
+    ).toBe(true);
+  });
+
+  it('(v0.27 #44) a turn that only adds a marker is meaningful (it survives the retry/nudge path)', () => {
+    expect(
+      isMeaningful({
+        date: 'x',
+        events: [],
+        stateChanges: [],
+        relations: [],
+        territoryChanges: [],
+        unowned: [],
+        nationOps: [],
+        markers: { add: [{ type: 'city', name: 'Lyon', regionKey: 'rhone-rhne' }], remove: [] },
       }),
     ).toBe(true);
   });
 });
+
+describe('markers (point placement, v0.27 #44)', () => {
+  // a deterministic centroid for one region key, undefined for everything else
+  const centroidOf = (key: string) =>
+    key === 'moselle-rygy' ? { lat: 48, lon: 6, spread: 1 } : undefined;
+
+  // build a MarkerSpec from a (possibly invalid, for the guard tests) type string
+  const mk = (type: string, name: string, regionKey: string): MarkerSpec =>
+    ({ type: type as MarkerType, name, regionKey });
+
+  it('adds a valid marker with a stable id, a jittered position within the spread, the region owner, and the placed turn', () => {
+    const state = baseState();
+    state.turn = 4; // placedTurn should equal the resolved turn
+    state.nations.uk.territory = ['GBR', 'moselle-rygy']; // the region is owned by uk
+    const result: TurnResult = {
+      date: '1939-09-03',
+      events: [],
+      stateChanges: [],
+      relations: [],
+      territoryChanges: [],
+      unowned: [],
+      nationOps: [],
+      markers: { add: [mk('city', 'Strasbourg', 'moselle-rygy')], remove: [] },
+    };
+    const next = applyTurnResult(state, result, undefined, centroidOf);
+    expect(next.markers).toHaveLength(1);
+    const m = next.markers[0];
+    expect(m.id).toBe(markerId('city', 'Strasbourg', 'moselle-rygy'));
+    expect(m.type).toBe('city');
+    expect(m.name).toBe('Strasbourg');
+    expect(m.regionKey).toBe('moselle-rygy');
+    expect(m.ownerNationId).toBe('uk'); // the region's sole owner
+    expect(m.placedTurn).toBe(4);
+    // the position is the centroid jittered within ±spread/2
+    expect(m.lat).toBeGreaterThanOrEqual(47.5);
+    expect(m.lat).toBeLessThanOrEqual(48.5);
+    expect(m.lon).toBeGreaterThanOrEqual(5.5);
+    expect(m.lon).toBeLessThanOrEqual(6.5);
+  });
+
+  it('is idempotent: re-adding the same (type, name, regionKey) does not duplicate the marker', () => {
+    const state = baseState();
+    state.nations.uk.territory = ['moselle-rygy'];
+    const add = [mk('city', 'Strasbourg', 'moselle-rygy')];
+    const first = applyTurnResult(state, {
+      date: '1939-09-03', events: [], stateChanges: [], relations: [], territoryChanges: [],
+      unowned: [], nationOps: [], 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: [], relations: [], territoryChanges: [],
+      unowned: [], nationOps: [], 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
+  });
+
+  it('applyTurnResult drops a new add whose region is unknown or has no centroid, but keeps a valid one', () => {
+    const state = baseState();
+    state.nations.uk.territory = ['moselle-rygy'];
+    // validKeys knows two keys; the centroid resolves only the first.
+    const validKeys = new Set(['moselle-rygy', 'other-key']);
+    const centroidOf2 = (k: string) =>
+      k === 'moselle-rygy' ? { lat: 48, lon: 6, spread: 1 } : undefined;
+    const result: TurnResult = {
+      date: '1939-09-03',
+      events: [],
+      stateChanges: [],
+      relations: [],
+      territoryChanges: [],
+      unowned: [],
+      nationOps: [],
+      markers: {
+        add: [
+          { type: 'city', name: 'Good', regionKey: 'moselle-rygy' }, // valid + centroid → kept
+          { type: 'city', name: 'NoCent', regionKey: 'other-key' }, // in validKeys, no centroid → dropped
+          { type: 'city', name: 'Unknown', regionKey: 'zzz-not-a-key' }, // not in validKeys → dropped
+        ],
+        remove: [],
+      },
+    };
+    const next = applyTurnResult(state, result, validKeys, centroidOf2);
+    expect(next.markers).toHaveLength(1);
+    expect(next.markers[0].name).toBe('Good');
+  });
+
+  it('caps the total marker count at MAX_MARKERS, dropping the newest add that exceeds the cap', () => {
+    const state = baseState();
+    // pre-seed the state with MAX_MARKERS - 1 distinct markers
+    const seeded: typeof state.markers = [];
+    for (let i = 0; i < MAX_MARKERS - 1; i++) {
+      const k = `seed-${i}`;
+      seeded.push({
+        id: markerId('city', `S${i}`, k),
+        type: 'city',
+        name: `S${i}`,
+        regionKey: k,
+        lat: 0, lon: 0,
+        ownerNationId: null,
+        placedTurn: 1,
+      });
+    }
+    state.markers = seeded;
+    // a permissive centroid: every region key resolves
+    const anyCentroid = () => ({ lat: 0, lon: 0, spread: 0 });
+    const result: TurnResult = {
+      date: '1939-09-03',
+      events: [],
+      stateChanges: [],
+      relations: [],
+      territoryChanges: [],
+      unowned: [],
+      nationOps: [],
+      markers: {
+        add: [
+          { type: 'city', name: 'NewA', regionKey: 'new-a' },
+          { type: 'city', name: 'NewB', regionKey: 'new-b' },
+        ],
+        remove: [],
+      },
+    };
+    const next = applyTurnResult(state, result, undefined, anyCentroid);
+    expect(next.markers).toHaveLength(MAX_MARKERS); // capped, not MAX_MARKERS + 1
+    expect(next.markers.some((m) => m.name === 'NewA')).toBe(true); // the 1st new one kept
+    expect(next.markers.some((m) => m.name === 'NewB')).toBe(false); // the 2nd (over cap) dropped
+  });
+
+  it('removes a marker by id; removing an absent id is a no-op', () => {
+    const state = baseState();
+    state.nations.uk.territory = ['moselle-rygy'];
+    const idA = markerId('city', 'Strasbourg', 'moselle-rygy');
+    const idB = markerId('port', 'Dunkirk', 'moselle-rygy');
+    state.markers = [
+      { id: idA, type: 'city', name: 'Strasbourg', regionKey: 'moselle-rygy', lat: 48, lon: 6, ownerNationId: 'uk', placedTurn: 1 },
+      { id: idB, type: 'port', name: 'Dunkirk', regionKey: 'moselle-rygy', lat: 48, lon: 6, ownerNationId: 'uk', placedTurn: 1 },
+    ];
+    const next = applyTurnResult(state, {
+      date: '1939-09-03', events: [], stateChanges: [], relations: [], territoryChanges: [],
+      unowned: [], nationOps: [], 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
+  });
+
+  it('a marker owner follows its region: released to no man\'s land → null; re-claimed → the new owner', () => {
+    const state = baseState();
+    state.nations.uk.territory = ['moselle-rygy'];
+    const idA = markerId('city', 'Strasbourg', 'moselle-rygy');
+    state.markers = [
+      { id: idA, type: 'city', name: 'Strasbourg', regionKey: 'moselle-rygy', lat: 48, lon: 6, ownerNationId: 'uk', placedTurn: 1 },
+    ];
+    // 1) uk releases the region → the marker becomes ownerless
+    const released = applyTurnResult(state, {
+      date: '1939-09-03', events: [], stateChanges: [], relations: [], territoryChanges: [],
+      unowned: ['moselle-rygy'], nationOps: [], 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: [], relations: [],
+      territoryChanges: [{ nation: 'de', gain: ['moselle-rygy'], lose: [] }],
+      unowned: [], nationOps: [], markers: { add: [], remove: [] },
+    }, undefined, centroidOf);
+    expect(reclaimed.markers[0].ownerNationId).toBe('de');
+  });
+
+  it('the user prompt carries the existing markers when provided (and omits the field otherwise)', () => {
+    const state = baseState();
+    const info = {
+      id: markerId('city', 'Strasbourg', 'moselle-rygy'),
+      type: 'city' as MarkerType,
+      name: 'Strasbourg',
+      regionKey: 'moselle-rygy',
+      owner: 'uk',
+    };
+    const payload = JSON.parse(
+      buildUserPrompt(state, [], undefined, undefined, undefined, [info]),
+    ) as { markers?: Array<Record<string, unknown>> };
+    expect(payload.markers).toHaveLength(1);
+    expect(payload.markers![0].name).toBe('Strasbourg');
+    expect(payload.markers![0].owner).toBe('uk');
+    // a bare call (no markers arg) omits the field entirely
+    const bare = JSON.parse(buildUserPrompt(state, [])) as { markers?: unknown };
+    expect(bare.markers).toBeUndefined();
+  });
+
+  it('the system prompt documents the markers contract (field + placement rule + a type)', () => {
+    const prompt = buildSystemPrompt(preset);
+    expect(prompt).toMatch(/named points on the map/i);
+    expect(prompt).toMatch(/"markers"/);
+    expect(prompt).toMatch(/"add"/);
+    expect(prompt).toMatch(/"remove"/);
+    expect(prompt).toMatch(/gathering/);
+    expect(prompt).toMatch(/no man's land/); // owner recompute on release
+  });
+
+  it('validateMarkerOps cleans a raw markers field: drops bad types/empty names, dedupes, trims removes', () => {
+    const raw = {
+      add: [
+        { type: 'city', name: 'X', regionKey: 'a' },
+        { type: 'not-a-type', name: 'Y', regionKey: 'a' }, // invalid type -> dropped
+        { type: 'city', name: '   ', regionKey: 'a' }, // empty name -> dropped
+        { type: 'city', name: 'X', regionKey: 'a' }, // duplicate (same id) -> deduped
+        { type: 'port', name: 'Z', regionKey: 'b' }, // valid
+      ],
+      remove: ['id-1', 42, '', '  id-2  ', 'id-1'], // number/empty dropped, trimmed, deduped
+    };
+    const out = validateMarkerOps(raw);
+    expect(out.add.map((m) => m.name).sort()).toEqual(['X', 'Z']);
+    expect(out.remove).toEqual(['id-1', 'id-2']);
+  });
+
+  it('validateMarkerOps returns empty ops for a non-object raw value (a string, an array, null)', () => {
+    for (const bad of ['oops', [{ type: 'city', name: 'X', regionKey: 'a' }], null, undefined]) {
+      expect(validateMarkerOps(bad)).toEqual({ add: [], remove: [] });
+    }
+  });
+
+  it('runTurn wires the centroid through: a marker added over the LLM path is placed (owner = region owner)', async () => {
+    const result = JSON.stringify({
+      date: '1939-09-03',
+      events: [],
+      stateChanges: [],
+      relations: [],
+      territoryChanges: [{ nation: 'uk', gain: ['moselle-rygy'], lose: [] }],
+      unowned: [],
+      nationOps: [],
+      markers: { add: [{ type: 'city', name: 'Strasbourg', regionKey: 'moselle-rygy' }], remove: [] },
+    });
+    const { state } = await runTurn({
+      llm: fakeLlm([result]),
+      preset,
+      state: baseState(),
+      items: [],
+      centroidOf,
+    });
+    expect(state.markers).toHaveLength(1);
+    expect(state.markers[0].name).toBe('Strasbourg');
+    expect(state.markers[0].ownerNationId).toBe('uk'); // uk gained the region this turn
+  });
+});

server/engine.ts

@@ -7,6 +7,7 @@ import type {
   EventOutcome,
   EventType,
   GameState,
+  MapMarker,
   Nation,
   NationStats,
   Preset,
@@ -18,9 +19,15 @@ import { EVENT_TYPES, RELATION_STATUSES } from '../shared/types';
 import {
   addDays,
   clampStat,
+  fnv1a32,
   isDateLike,
+  isMarkerType,
   makeEvent,
+  markerId,
+  MAX_MARKERS,
   nationForPrompt,
+  type MarkerInfo,
+  type MarkerSpec,
   type NationOp,
   type TurnEventSpec,
   type TurnResult,
@@ -187,12 +194,14 @@ export function buildSystemPrompt(preset: Preset, withNeighboursTool = false): s
     '    {"kind":"split","nationRef":"<nation id or name>","parts":[{"name":"<new name>","territory":["<region key>"]}]}',
     '    {"kind":"merge","nationRefs":["<id>","<id>"],"survivingRef":"<id of the surviving nation>","into":"<new name>"}',
     '  ],',
+    '  "markers": {"add":[{"type":"<city|factory|army|port|capital|fleet|rocket|gathering>","name":"<short name>","regionKey":"<region key>"}],"remove":["<marker id>"]}',
     '}',
     '',
     'HARD CONSTRAINTS',
     '- Use only nation ids and region keys that exist in the provided state.',
     '- A region key identifies one sub-region; the "regions" table in the user message maps each key to "<region name> (<parent country ISO_A3>)". Use those keys in territoryChanges and unowned.',
     '- List in "unowned" only region keys that a nation currently owns, and narrate each release in "events".',
+    '- Map markers ("markers") are named points on the map, anchored to a region key you own or that the narrative justifies: a capital (a nation\'s main seat of power — at most one per nation), major cities, factory complexes, army deployments, ports, fleet concentrations, rocket launch sites, or a gathering (a large political/social mass event that can enable a non-military takeover). Use only region keys from the "regions" table, keep each name under 40 characters, and place at most a handful of new markers per turn — only where the narrative justifies it. List a marker id from the user message\'s "markers" field in "remove" when it ceases to exist (a city razed, an army dispersed, a site destroyed).',
     '- Nation-management ops ("nationOps") are PROPOSALS: they only take effect if the player confirms them afterwards. Propose at most 1-2 per turn, only when the narrative justifies it, and narrate each one in "events".',
     '- Rename: add {"kind":"rename","nationRef":"<nation id or name>","to":"<new name>"} for a revolution, regime change or reunification that changes a nation\'s name.',
     '- Split: add {"kind":"split","nationRef":"<nation id or name>","parts":[{"name":"<new name>","territory":["<region key>"]}, ...]} when a state breaks up (dissolution, secession). Use at least 2 parts and assign each of the nation\'s region keys to at most one part — any key you leave unassigned goes to the first part.',
@@ -232,6 +241,14 @@ export function buildUserPrompt(
    * Omitted entirely when undefined.
    */
   noMansLand?: string[],
+  /**
+   * (v0.27, #44) The game's current map markers, as the model sees them:
+   * stable id, type, name, region key and current owner. Emitted verbatim
+   * (even when empty) so the model can reference a marker's id in
+   * `TurnResult.markers.remove` or leave an existing marker untouched.
+   * Omitted entirely when undefined.
+   */
+  markers?: MarkerInfo[],
 ): string {
   const player = state.nations[state.playerNationId];
   const playerName = player?.name ?? state.playerNationId;
@@ -270,6 +287,7 @@ export function buildUserPrompt(
   if (regionReference) payload.regions = regionReference;
   if (frontier !== undefined) payload.frontier = frontier;
   if (noMansLand !== undefined) payload.unowned = noMansLand;
+  if (markers !== undefined) payload.markers = markers;
   return JSON.stringify(payload, null, 2);
 }
 
@@ -393,6 +411,7 @@ export function validateTurnResult(input: unknown): TurnResult | null {
     territoryChanges: [],
     unowned: [],
     nationOps: [],
+    markers: { add: [], remove: [] },
   };
 
   if (Array.isArray(o.events)) {
@@ -482,9 +501,51 @@ export function validateTurnResult(input: unknown): TurnResult | null {
   // list for the player to confirm/reject.
   result.nationOps = validateNationOps(o.nationOps);
 
+  // (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).
+  result.markers = validateMarkerOps(o.markers);
+
   return result;
 }
 
+/**
+ * (v0.27, #44) Validate the raw `markers` object of a turn into a safe
+ * `{ add, remove }` shape. Defensive like the rest of the parser — never
+ * throws. `add`: each spec needs a known marker type, a non-empty `name`
+ * (capped at 120 chars) and a non-empty `regionKey` (capped at 120 chars);
+ * specs whose derived id collides with an earlier one in the same batch
+ * collapse to the first (re-adding is idempotent). `remove`: deduped,
+ * non-empty marker ids (capped at 120 chars).
+ */
+export function validateMarkerOps(raw: unknown): { add: MarkerSpec[]; remove: string[] } {
+  const out: { add: MarkerSpec[]; remove: string[] } = { add: [], remove: [] };
+  if (!raw || typeof raw !== 'object' || Array.isArray(raw)) return out;
+  const o = raw as Record<string, unknown>;
+  if (Array.isArray(o.add)) {
+    const seen = new Set<string>();
+    for (const e of o.add) {
+      if (!e || typeof e !== 'object') continue;
+      const s = e as Record<string, unknown>;
+      if (!isMarkerType(s.type)) continue;
+      const name = str(s.name, 120);
+      const regionKey = str(s.regionKey, 120);
+      if (!name || !regionKey) continue;
+      const id = markerId(s.type, name, regionKey);
+      if (seen.has(id)) continue;
+      seen.add(id);
+      out.add.push({ type: s.type, name, regionKey });
+    }
+  }
+  if (Array.isArray(o.remove)) {
+    for (const k of o.remove) {
+      const s = typeof k === 'string' ? k.trim() : '';
+      if (s && !out.remove.includes(s)) out.remove.push(s.slice(0, 120));
+    }
+  }
+  return out;
+}
+
 /**
  * A turn is "meaningful" if it produced at least an event, a stat change, a
  * no-man's-land release (v0.22 #16 P3: a release is a real world change even
@@ -498,7 +559,10 @@ export function isMeaningful(result: TurnResult): boolean {
     result.events.length > 0 ||
     result.stateChanges.length > 0 ||
     result.unowned.length > 0 ||
-    result.nationOps.length > 0
+    result.nationOps.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
   );
 }
 
@@ -516,13 +580,25 @@ function genericUnclearEvent(state: GameState): TurnEventSpec {
 
 /**
  * Apply a TurnResult to a GameState immutably: advance the date/turn, append
- * events, apply stat changes (clamped), symmetric relations, and territory
- * moves (including no-man's-land releases, v0.22 #16 P3). It also appends any
- * proposed nation-ops to the pending list (v0.23 #16 P4a) without applying
- * them — see the doc comment on `pendingNationOps` for why that list
- * deliberately survives across turns.
+ * events, apply stat changes (clamped), symmetric relations, territory moves
+ * (including no-man's-land releases, v0.22 #16 P3) and map markers (v0.27
+ * #44). It also appends any proposed nation-ops to the pending list (v0.23
+ * #16 P4a) without applying them — see the doc comment on `pendingNationOps`
+ * for why that list deliberately survives across turns.
+ *
+ * `centroidOf` (v0.27, #44) resolves a region key to its precomputed centroid
+ * (`{ lat, lon, spread }`, from public/region-centroids.json via
+ * server/regions.ts). New markers are positioned at that centroid plus a small
+ * deterministic offset; a spec whose key has no known centroid is dropped.
+ * Without it no marker can be placed (all adds are dropped), which keeps the
+ * engine pure and lets tests inject their own data.
  */
-export function applyTurnResult(state: GameState, result: TurnResult, validKeys?: ReadonlySet<string>): GameState {
+export function applyTurnResult(
+  state: GameState,
+  result: TurnResult,
+  validKeys?: ReadonlySet<string>,
+  centroidOf?: (key: string) => { lat: number; lon: number; spread: number } | undefined,
+): GameState {
   const next: GameState = JSON.parse(JSON.stringify(state));
   next.version = (state.version ?? 0) + 1; // every mutation is a new revision
   const actingTurn = state.turn; // this action resolves the current turn
@@ -636,6 +712,73 @@ export function applyTurnResult(state: GameState, result: TurnResult, validKeys?
   }
 
   next.unowned = [...unowned];
+
+  // --- Map markers (v0.27, #44) ---
+  //
+  // Markers are anchored to a region key and are processed against the FINAL
+  // post-claim ownership, in this order:
+  //   (1) REMOVE: a marker whose id is in result.markers.remove is dropped
+  //       (a listed-but-absent id is a no-op).
+  //   (2) OWNER RECOMPUTE: every surviving marker's ownerNationId is set to
+  //       its region's current owner — a captured region follows the new
+  //       owner, a region released to no man's land (or a key with 0 or 2+
+  //       owners) becomes `null`. A marker always follows its region.
+  //   (3) ADD: each new spec (in order) is placed at its region's centroid
+  //       (injected via centroidOf) plus a small deterministic per-axis
+  //       offset, owned by the region's post-turn owner, and stamped with
+  //       the acting turn. Dropped (never throws): a region key that is not
+  //       in validKeys or has no known centroid, an id that already exists
+  //       (a re-add is idempotent — the existing marker stays), and any adds
+  //       beyond MAX_MARKERS (the later ones).
+  {
+    const finalOwner = new Map<string, string | null>();
+    {
+      const owners = new Map<string, string[]>();
+      for (const n of Object.values(next.nations)) {
+        for (const key of n.territory) {
+          if (!valid(key)) continue;
+          const list = owners.get(key);
+          if (list) list.push(n.id);
+          else owners.set(key, [n.id]);
+        }
+      }
+      for (const [key, list] of owners) finalOwner.set(key, list.length === 1 ? list[0] : null);
+    }
+    const removeIds = new Set(result.markers.remove);
+    const markers: MapMarker[] = [];
+    for (const m of next.markers ?? []) {
+      if (removeIds.has(m.id)) continue;
+      markers.push({ ...m, ownerNationId: finalOwner.get(m.regionKey) ?? null });
+    }
+    // Deterministic ±(spread/2) offset per axis: a FNV-1a-derived unit
+    // fraction of the marker id (stable across runs and platforms), so
+    // markers of one region scatter naturally instead of stacking.
+    const jitter = (id: string, axis: 'lat' | 'lon', spread: number): number => {
+      const frac = (fnv1a32(`${id}#${axis}`) >>> 8) / 0x00ffffff;
+      return (frac * 2 - 1) * (spread / 2);
+    };
+    const round6 = (v: number): number => Math.round(v * 1e6) / 1e6;
+    for (const spec of result.markers.add) {
+      const id = markerId(spec.type, spec.name, spec.regionKey);
+      if (markers.some((m) => m.id === id)) continue; // re-add: idempotent, keep the existing
+      if (markers.length >= MAX_MARKERS) continue; // hard cap: drop the excess
+      if (!valid(spec.regionKey)) continue; // unknown region key
+      const c = centroidOf?.(spec.regionKey);
+      if (!c) continue; // no centroid data for this key
+      markers.push({
+        id,
+        type: spec.type,
+        name: spec.name,
+        regionKey: spec.regionKey,
+        lat: round6(c.lat + jitter(id, 'lat', c.spread)),
+        lon: round6(c.lon + jitter(id, 'lon', c.spread)),
+        ownerNationId: finalOwner.get(spec.regionKey) ?? null,
+        placedTurn: actingTurn,
+      });
+    }
+    next.markers = markers;
+  }
+
   // (v0.23, #16 P4a) Nation-op proposals are NOT applied by the turn — they
   // are appended to the pending list, which (unlike `pending`) SURVIVES
   // across turns until the player confirms or rejects each one. `next` is a
@@ -965,15 +1108,31 @@ export async function runTurn(opts: {
    * switches the turn onto the getNeighbours tool path.
    */
   getNeighbours?: (keys: string[]) => string[];
+  /**
+   * (v0.27, #44) Region-key -> precomputed centroid resolver (from
+   * public/region-centroids.json). Present, the turn's new markers can be
+   * placed at their region's centroid; absent, marker adds are dropped and
+   * the existing markers' owners still get recomputed.
+   */
+  centroidOf?: (key: string) => { lat: number; lon: number; spread: number } | undefined;
 }): Promise<{ state: GameState; result: TurnResult }> {
-  const { llm, preset, state, items, regionReference, validRegionKeys, getNeighbours } = opts;
+  const { llm, preset, state, items, regionReference, validRegionKeys, getNeighbours, centroidOf } = opts;
   const chatWithTools = llm.chatWithTools;
   const useTools = getNeighbours !== undefined && chatWithTools !== undefined;
   const system = buildSystemPrompt(preset, useTools);
   const frontier = getNeighbours ? playerFrontier(state, getNeighbours) : undefined;
   // (v0.22, #16 P3) the model always sees the current no-man's-land keys (empty
   // list on a fresh game) so it knows which unowned regions can be re-claimed.
-  const user = buildUserPrompt(state, items, regionReference, frontier, state.unowned ?? []);
+  // (v0.27, #44) likewise the current map markers, so it can reference their
+  // stable ids in `markers.remove` (or leave them untouched).
+  const markers = (state.markers ?? []).map((m) => ({
+    id: m.id,
+    type: m.type,
+    name: m.name,
+    regionKey: m.regionKey,
+    owner: m.ownerNationId,
+  }));
+  const user = buildUserPrompt(state, items, regionReference, frontier, state.unowned ?? [], markers);
   const nudge =
     'Your previous output was invalid. Respond with ONLY the JSON object described above for this batch — no prose, no fences.';
 
@@ -1018,10 +1177,11 @@ export async function runTurn(opts: {
       territoryChanges: [],
       unowned: [],
       nationOps: [],
+      markers: { add: [], remove: [] },
     };
   }
 
-  return { state: applyTurnResult(state, result, validRegionKeys), result };
+  return { state: applyTurnResult(state, result, validRegionKeys, centroidOf), result };
 }
 
 // --- Advisor (brainstorm) -----------------------------------------------------

server/index.ts

@@ -22,7 +22,7 @@ import { createLlmClient } from './llm';
 import { makeStubLlmClient } from './stub';
 import { askAdvisor, confirmNationOp, queueRoundItem, rejectNationOp, removeRoundItem, runTurn } from './engine';
 import { buildRegionMap } from './map';
-import { allTerritoryKeys, expandCountriesToKeys, hasAdjacency, loadRegions, neighboursOf, referenceForKeys, validKeys } from './regions';
+import { allTerritoryKeys, centroidOf, expandCountriesToKeys, hasAdjacency, hasCentroids, loadRegions, neighboursOf, referenceForKeys, validKeys } from './regions';
 import { createPresetStore } from './presets';
 import { openDb, type Db } from './db';
 
@@ -134,6 +134,8 @@ app.post('/api/games', (req: Request, res) => {
     // list grows as the LLM proposes renames (and, later, splits/merges) and
     // shrinks as the player confirms or rejects them.
     pendingNationOps: [],
+    // (v0.27, #44) No markers on a fresh game; the LLM places them over time.
+    markers: [],
   };
   // 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
@@ -288,6 +290,11 @@ app.post('/api/games/:id/jump', async (req, res) => {
       // engine the resolver — the turn then runs with the LLM's getNeighbours
       // tool and the player-frontier prompt field (both switch off without it).
       getNeighbours: hasAdjacency() ? (keys) => neighboursOf(keys) : undefined,
+      // (v0.27, #44) when the centroid manifest loaded, hand the engine the
+      // resolver so a turn can place new map markers at their region's
+      // centroid (without it, marker adds are dropped; existing markers are
+      // still maintained).
+      centroidOf: hasCentroids() ? (key) => centroidOf(key) : undefined,
     });
     db.save(state);
     broadcast(id, 'turn', { state, result });

server/map.test.ts

@@ -49,6 +49,7 @@ const state: GameState = {
   version: 1,
   unowned: [],
   pendingNationOps: [],
+  markers: [],
 };
 
 // The RegionMap built from the fixture: the authoritative region key → owner source.

server/regions.test.ts

@@ -5,8 +5,10 @@ import { tmpdir } from 'node:os';
 import path from 'node:path';
 import {
   allTerritoryKeys,
+  centroidOf,
   expandCountriesToKeys,
   hasAdjacency,
+  hasCentroids,
   hasRegionData,
   loadRegions,
   neighboursOf,
@@ -103,6 +105,7 @@ describe('regions (region-key loader, v0.19 #16 P1)', () => {
       version: 1,
       unowned: [],
       pendingNationOps: [],
+      markers: [],
     };
     // 16 GBR sub-regions + 42 FRA sub-regions, no overlap between the two.
     expect(allTerritoryKeys(state).size).toBe(58);
@@ -133,6 +136,19 @@ describe('regions (region-key loader, v0.19 #16 P1)', () => {
     expect(neighboursOf([])).toEqual([]);
   });
 
+  it('(v0.27 #44) hasCentroids() is true and centroidOf resolves a real key to a plausible location', () => {
+    expect(hasCentroids()).toBe(true);
+    const ain = centroidOf('ain-lqtt');
+    expect(ain).toBeDefined();
+    expect(ain!.lat).toBeCloseTo(46.16, 1);
+    expect(ain!.lon).toBeCloseTo(4.8, 1);
+    expect(ain!.spread).toBeGreaterThan(0);
+  });
+
+  it('(v0.27 #44) centroidOf returns undefined for an unknown key', () => {
+    expect(centroidOf('not-a-real-key-xyz')).toBeUndefined();
+  });
+
   describe('graceful degradation with no region data', () => {
     beforeEach(() => resetRegions());
 
@@ -146,6 +162,9 @@ describe('regions (region-key loader, v0.19 #16 P1)', () => {
       // and no adjacency: the LLM tool / frontier field switch off
       expect(hasAdjacency()).toBe(false);
       expect(neighboursOf(['moselle-rygy'])).toEqual([]);
+      // and no centroids: the marker-placement path degrades to a no-op
+      expect(hasCentroids()).toBe(false);
+      expect(centroidOf('ain-lqtt')).toBeUndefined();
     });
   });
 
@@ -197,6 +216,21 @@ describe('loadRegions resolves the manifest per environment (dev public/ vs prod
     expect(loadRegions(prodRoot)).toBe(true);
     expect(hasAdjacency()).toBe(false);
     expect(neighboursOf(['moselle-rygy'])).toEqual([]);
+    // and no centroids (not copied into this dist/) -> marker placement degrades
+    expect(hasCentroids()).toBe(false);
+    expect(centroidOf('ain-lqtt')).toBeUndefined();
+  });
+
+  it('(v0.27 #44) a dist/ WITH the centroids manifest loads them (prod layout)', () => {
+    copyFileSync(
+      path.join(realRoot, 'public', 'region-centroids.json'),
+      path.join(prodRoot, 'dist', 'region-centroids.json'),
+    );
+    expect(loadRegions(prodRoot)).toBe(true);
+    expect(hasCentroids()).toBe(true);
+    const ain = centroidOf('ain-lqtt');
+    expect(ain).toBeDefined();
+    expect(ain!.lat).toBeCloseTo(46.16, 1);
   });
 
   it('returns false and no data when neither public/ nor dist/ holds the files', () => {

server/regions.ts

@@ -2,7 +2,9 @@
 // (region-keys.json: stable feature id -> region key), the sub-national geo
 // (regions.geo.json: feature id -> { name, parent }), and — optionally — the
 // precomputed region-adjacency manifest (region-adjacency.json: region key ->
-// bordering region keys, built by scripts/build-region-adjacency.mjs) — all
+// bordering region keys, built by scripts/build-region-adjacency.mjs) and the
+// precomputed region-centroid manifest (region-centroids.json: region key ->
+// { lat, lon, spread }, built by scripts/build-region-centroids.mjs) — all
 // from public/ in dev (Vite serves it) or dist/ in prod (Vite copies
 // public/* -> dist/ at build, and the Docker image keeps only dist/) — and
 // joins them into the lookups the region-level ownership model needs:
@@ -13,6 +15,8 @@
 //   - neighboursOf(): the union of the bordering keys for a set of keys — the
 //     data behind the LLM's getNeighbours tool and the player-frontier prompt
 //     field (v0.21, #16 P2)
+//   - centroidOf(): a region key's precomputed anchor point ({ lat, lon, spread })
+//     — the data behind LLM-placed map markers (v0.27, #44)
 //
 // Deliberately turf-free: it reads the JSON files with plain JSON.parse and
 // never imports @turf/@types/geojson (importing one pulls @types/geojson into
@@ -39,12 +43,15 @@ interface RegionData {
   validKeys: Set<string>;
   /** region key -> bordering region keys (from public/region-adjacency.json). */
   adjacency: Record<string, string[]>;
+  /** region key -> anchor point (from public/region-centroids.json). */
+  centroids: Record<string, { lat: number; lon: number; spread: number }>;
 }
 
 let data: RegionData | null = null;
 
 /**
- * Load (or reload) the region-key manifest, geo, and adjacency. Idempotent.
+ * Load (or reload) the region-key manifest, geo, adjacency, and centroids.
+ * Idempotent.
  * The files are served to the client from `public/` in dev (Vite serves it
  * directly) and from `dist/` in prod (Vite copies `public/*` → `dist/` at build
  * and the Docker image keeps only `dist/`), so probe `public/` then `dist/`
@@ -52,7 +59,10 @@ let data: RegionData | null = null;
  * key manifest + geo. The adjacency manifest is OPTIONAL: when it is missing
  * or broken, `adjacency` stays empty and `neighboursOf`/`hasAdjacency` simply
  * report "no adjacency" (the LLM tool and the frontier prompt field switch
- * off; everything else keeps working). Returns true when the core pair loaded
+ * off; everything else keeps working). The centroid manifest is likewise
+ * OPTIONAL (v0.27, #44): when missing or broken, `centroids` stays empty and
+ * `centroidOf`/`hasCentroids` report "no centroids" (new map markers can't be
+ * placed, but everything else keeps working). Returns true when the core pair loaded
  * cleanly; a missing/broken pair clears the data and returns false so the
  * server still boots and degrades gracefully (expansion becomes a no-op,
  * ownership falls back to the raw input keys).
@@ -61,6 +71,7 @@ export function loadRegions(root: string): boolean {
   const keyFile = 'region-keys.json';
   const geoFile = 'regions.geo.json';
   const adjacencyFile = 'region-adjacency.json';
+  const centroidsFile = 'region-centroids.json';
   const base = [
     path.join(root, 'public'), // dev: Vite serves public/ at /
     path.join(root, 'dist'), // prod: Vite copies public/* -> dist/ (== clientDir)
@@ -105,7 +116,38 @@ export function loadRegions(root: string): boolean {
       }
     }
 
-    data = { idToKey, keyToInfo, keysByCountry, validKeys, adjacency };
+    // Centroids are optional too (v0.27, #44): a missing/broken file means
+    // "no centroid data" — new markers can't be placed (their adds are
+    // dropped), but everything else keeps working.
+    let centroids: Record<string, { lat: number; lon: number; spread: number }> = {};
+    const centroidsPath = path.join(base, centroidsFile);
+    if (existsSync(centroidsPath)) {
+      try {
+        const raw = JSON.parse(readFileSync(centroidsPath, 'utf8')) as Record<
+          string,
+          { lat?: unknown; lon?: unknown; spread?: unknown }
+        >;
+        // Keep only well-formed entries; a corrupt file degrades to "none".
+        for (const [k, v] of Object.entries(raw)) {
+          if (
+            v &&
+            typeof v.lat === 'number' &&
+            typeof v.lon === 'number' &&
+            typeof v.spread === 'number' &&
+            Number.isFinite(v.lat) &&
+            Number.isFinite(v.lon) &&
+            Number.isFinite(v.spread)
+          ) {
+            centroids[k] = { lat: v.lat, lon: v.lon, spread: v.spread };
+          }
+        }
+      } catch (err) {
+        console.error('[regions] failed to load region-centroids.json, continuing without it', err);
+        centroids = {};
+      }
+    }
+
+    data = { idToKey, keyToInfo, keysByCountry, validKeys, adjacency, centroids };
     return validKeys.size > 0;
   } catch (err) {
     console.error('[regions] failed to load region data', err);
@@ -189,6 +231,27 @@ export function hasAdjacency(): boolean {
   return data !== null && Object.keys(data.adjacency).length > 0;
 }
 
+/**
+ * True when the region-centroid manifest loaded with at least one entry
+ * (v0.27, #44). The server's jump route uses this to decide whether to hand
+ * the engine a centroid resolver (which lets a turn place new map markers)
+ * or skip marker placement (existing markers are still maintained).
+ */
+export function hasCentroids(): boolean {
+  return data !== null && Object.keys(data.centroids).length > 0;
+}
+
+/**
+ * The precomputed anchor point for a region key: the centroid of its
+ * largest-area part, plus a `spread` (≈ 0.1 × that part's smallest bbox
+ * dimension, in degrees) the engine scatters markers within
+ * ±(spread/2) of the centroid. `undefined` for an unknown key or when no
+ * centroid data is loaded (v0.27, #44).
+ */
+export function centroidOf(key: string): { lat: number; lon: number; spread: number } | undefined {
+  return data?.centroids[key];
+}
+
 /**
  * The union of the region keys that share a land border with any of the given
  * keys — deduplicated, the queried keys themselves excluded, and sorted for

server/stub.ts

@@ -31,6 +31,13 @@ export interface StubPayload {
    * is covered by unit tests against applyTurnResult, not by the stub.
    */
   unowned?: string[];
+  /**
+   * (v0.27, #44) Current map markers (`{ id, type, name, regionKey, owner }`),
+   * emitted by the engine's user prompt. The stub ignores this field — it
+   * never places or removes a marker (see deterministicTurn), so the marker
+   * path is covered by unit tests against applyTurnResult, not by the stub.
+   */
+  markers?: Array<{ id: string; type: string; name: string; regionKey: string; owner: string | null }>;
 }
 
 function truncate(s: string, n: number): string {
@@ -61,6 +68,10 @@ function truncate(s: string, n: number): string {
  * (v0.23, #16 P4a) The stub likewise NEVER proposes nation-management ops (it
  * always returns `nationOps: []`) — the propose→confirm/reject flow is
  * covered by unit tests only, keeping the e2e assertions untouched.
+ *
+ * (v0.27, #44) The stub likewise NEVER places or removes a map marker (it
+ * always returns `markers: { add: [], remove: [] }`) — the marker path is
+ * covered by unit tests only, keeping the e2e assertions untouched.
  */
 export function deterministicTurn(p: StubPayload): TurnResult {
   const state = p.state;
@@ -126,6 +137,7 @@ export function deterministicTurn(p: StubPayload): TurnResult {
     territoryChanges,
     unowned: [], // the stub never creates no man's land (see doc comment)
     nationOps: [], // the stub never proposes nation ops (see doc comment)
+    markers: { add: [], remove: [] }, // the stub never touches markers (see doc comment)
   };
 }