refactor!(gui): Refactor simulation.ts

apps/gui/next-env.d.ts

@@ -1,6 +1,6 @@
 /// <reference types="next" />
 /// <reference types="next/image-types/global" />
-import "./.next/dev/types/routes.d.ts";
+import "./.next/types/routes.d.ts";
 
 // NOTE: This file should not be edited
 // see https://nextjs.org/docs/app/api-reference/config/typescript for more information.

apps/gui/src/app/builder/page.tsx

@@ -1,18 +1,5 @@
-"use client";
+import { BuilderView } from "@/components/builder/BuilderView";
 
 export default function BuilderPage() {
-  return (
-    <div className="flex-1 overflow-y-auto w-full">
-      <div className="mx-auto max-w-[800px] px-10 py-12">
-        <h1 className="mb-6 text-headline-lg text-primary animate-fade-in">
-          Scenario Builder
-        </h1>
-        <div className="border border-border/30 bg-card p-6 shadow-[2px_2px_0_0_var(--border)] min-h-[300px] flex flex-col items-center justify-center">
-          <p className="text-body-md text-muted-foreground font-mono text-center">
-            Scenario builder interface coming soon...
-          </p>
-        </div>
-      </div>
-    </div>
-  );
+  return <BuilderView />;
 }

apps/gui/src/app/page.tsx

@@ -1,5 +1,5 @@
-import { DashboardView } from "@/components/play/DashboardView";
+import { HomeView } from "@/components/home/HomeView";
 
 export default function Home() {
-  return <DashboardView />;
+  return <HomeView />;
 }

apps/gui/src/components/builder/BuilderView.tsx

@@ -0,0 +1,18 @@
+"use client";
+
+export function BuilderView() {
+  return (
+    <div className="flex-1 overflow-y-auto w-full">
+      <div className="mx-auto max-w-[800px] px-10 py-12">
+        <h1 className="mb-6 text-headline-lg text-primary animate-fade-in">
+          Scenario Builder
+        </h1>
+        <div className="border border-border/30 bg-card p-6 shadow-[2px_2px_0_0_var(--border)] min-h-[300px] flex flex-col items-center justify-center">
+          <p className="text-body-md text-muted-foreground font-mono text-center">
+            Scenario builder interface coming soon...
+          </p>
+        </div>
+      </div>
+    </div>
+  );
+}

apps/gui/src/components/home/HomeView.tsx

@@ -34,7 +34,7 @@ import {
   SelectValue,
 } from "@/components/ui/select";
 
-export function DashboardView() {
+export function HomeView() {
   const router = useRouter();
   const [loading, setLoading] = useState(false);
   const [loadingData, setLoadingData] = useState(true);

apps/gui/src/lib/simulation/alias-handoff.ts

@@ -0,0 +1,71 @@
+import { HandoffEngine, checkHandoffTrigger } from "@omnia/memory";
+import type { SimSession } from "./types";
+
+/**
+ * Runs the HandoffEngine for every agent entity that has accumulated enough
+ * buffer entries to warrant a handoff (compression to long-term memory).
+ */
+export async function runHandoffResolution(session: SimSession): Promise<void> {
+  const worldState = session.coreRepo.loadWorldState(session.worldInstanceId);
+  if (!worldState) throw new Error("World state lost");
+
+  const handoffEngine = new HandoffEngine(
+    session.handoffProvider,
+    session.embeddingProvider,
+    session.bufferRepo,
+    session.ledgerRepo,
+  );
+
+  const entities = Array.from(worldState.entities.values());
+  for (const entity of entities) {
+    if (!entity.isAgent) continue;
+
+    const bufferEntries = session.bufferRepo.listForOwner(entity.id);
+    const maxContext =
+      session.handoffProvider.maxContext !== undefined
+        ? session.handoffProvider.maxContext
+        : 32768;
+
+    const trigger = checkHandoffTrigger(
+      entity,
+      bufferEntries,
+      worldState.clock.get(),
+      maxContext,
+    );
+    if (trigger !== "none") {
+      await handoffEngine.runHandoff(
+        entity,
+        bufferEntries,
+        worldState.clock.get(),
+      );
+    }
+  }
+}
+
+/**
+ * For every agent that shares a location with another entity they haven't
+ * previously encountered, generates a first-person alias description and
+ * persists it on the viewing entity.
+ */
+export async function runAliasResolution(session: SimSession): Promise<void> {
+  const worldState = session.coreRepo.loadWorldState(session.worldInstanceId);
+  if (!worldState) throw new Error("World state lost");
+
+  const entities = Array.from(worldState.entities.values());
+  for (const viewer of entities) {
+    if (!viewer.isAgent) continue;
+    if (!viewer.locationId) continue;
+
+    for (const target of entities) {
+      if (viewer.id === target.id) continue;
+      if (
+        target.locationId === viewer.locationId &&
+        !viewer.aliases.has(target.id)
+      ) {
+        const alias = await session.aliasGenerator.generate(viewer, target);
+        viewer.aliases.set(target.id, alias);
+        session.coreRepo.saveEntity(viewer, worldState.id);
+      }
+    }
+  }
+}

apps/gui/src/lib/simulation/env.ts

@@ -0,0 +1,16 @@
+import dotenv from "dotenv";
+import path from "path";
+import fs from "fs";
+
+// Load .env from monorepo root or apps/gui/
+const cwd = process.cwd();
+const envCandidates = [
+  path.resolve(cwd, ".env"),
+  path.resolve(cwd, "../../.env"),
+];
+for (const c of envCandidates) {
+  if (fs.existsSync(c) && fs.statSync(c).isFile()) {
+    dotenv.config({ path: c });
+    break;
+  }
+}

apps/gui/src/lib/simulation/index.ts

@@ -0,0 +1,17 @@
+/**
+ * Barrel entry point for the simulation module.
+ *
+ * Consumers import from "@/lib/simulation" exactly as before — no import
+ * paths need to change anywhere in the codebase.
+ */
+import { SimulationManager } from "./simulation-manager";
+
+export const simulationManager = new SimulationManager();
+
+export type {
+  SimSnapshot,
+  EntityInfo,
+  LogEntry,
+  IntentInfo,
+  WaitingContext,
+} from "../simulation-types";

apps/gui/src/lib/simulation/provider-resolver.ts

@@ -0,0 +1,175 @@
+import {
+  GeminiProvider,
+  MockLLMProvider,
+  ProviderManager,
+  OpenRouterProvider,
+  GeminiEmbeddingProvider,
+  MockEmbeddingProvider,
+} from "@omnia/llm";
+import type {
+  ILLMProvider,
+  IEmbeddingProvider,
+  ModelProviderInstance,
+} from "@omnia/llm";
+
+// ---------------------------------------------------------------------------
+// Public types
+// ---------------------------------------------------------------------------
+
+export interface ResolvedProviders {
+  actorProvider: ILLMProvider;
+  validatorProvider: ILLMProvider;
+  decoderProvider: ILLMProvider;
+  timedeltaProvider: ILLMProvider;
+  handoffProvider: ILLMProvider;
+  embeddingProvider: IEmbeddingProvider;
+}
+
+export interface ProviderResolverOptions {
+  /**
+   * Pre-resolved generative instance to fall back to when ProviderManager has
+   * no active generative provider (e.g. when the caller already validated a
+   * specific provider during session creation).
+   */
+  fallbackInstance?: ModelProviderInstance | null;
+  /**
+   * When true, throws an Error if no provider can be resolved for a task.
+   * When false (default), falls back silently to MockLLMProvider / MockEmbeddingProvider.
+   */
+  required?: boolean;
+}
+
+// ---------------------------------------------------------------------------
+// Private builders
+// ---------------------------------------------------------------------------
+
+function buildLLMProvider(inst: ModelProviderInstance): ILLMProvider {
+  if (inst.providerName === "google-genai") {
+    return new GeminiProvider(
+      inst.apiKey,
+      inst.modelName,
+      inst.name,
+      inst.maxContext,
+    );
+  } else if (inst.providerName === "openrouter") {
+    return new OpenRouterProvider(
+      inst.apiKey,
+      inst.modelName,
+      inst.name,
+      inst.maxContext,
+    );
+  }
+  return new MockLLMProvider([]);
+}
+
+function buildEmbeddingProvider(
+  inst: ModelProviderInstance,
+): IEmbeddingProvider {
+  if (inst.providerName === "google-genai") {
+    return new GeminiEmbeddingProvider(inst.apiKey, inst.modelName);
+  }
+  return new MockEmbeddingProvider(inst.modelName);
+}
+
+// ---------------------------------------------------------------------------
+// Public API
+// ---------------------------------------------------------------------------
+
+/**
+ * Resolves all six LLM + embedding providers needed for a simulation session.
+ *
+ * Resolution order for each generative task:
+ *  1. Task-specific mapping from ProviderManager (via `mappings[task]`)
+ *  2. ProviderManager active generative instance
+ *  3. `fallbackInstance` (if supplied)
+ *  4. GOOGLE_API_KEY env var → auto-creates a temporary GeminiProvider
+ *  5. Throws (if `required`) or returns MockLLMProvider
+ */
+export function resolveProviders(
+  mappings: Record<string, string>,
+  options: ProviderResolverOptions = {},
+): ResolvedProviders {
+  const { fallbackInstance = null, required = false } = options;
+  const list = ProviderManager.list();
+  const activeGenerative =
+    ProviderManager.getActive("generative") ?? fallbackInstance ?? null;
+
+  const resolveGenerative = (task: string): ILLMProvider => {
+    const mappedId = mappings[task];
+    let inst: ModelProviderInstance | null = mappedId
+      ? (list.find((p) => p.id === mappedId) ?? null)
+      : null;
+
+    if (!inst || inst.type !== "generative") {
+      inst = activeGenerative;
+    }
+
+    if (!inst) {
+      const envKey = process.env.GOOGLE_API_KEY;
+      if (envKey) {
+        inst = ProviderManager.create(
+          "Default (Env)",
+          "google-genai",
+          envKey,
+          undefined,
+          "generative",
+        );
+      }
+    }
+
+    if (!inst) {
+      if (required) {
+        throw new Error(
+          `No active LLM Provider Instance found for task "${task}". Please configure a key in Settings first.`,
+        );
+      }
+      return new MockLLMProvider([]);
+    }
+
+    return buildLLMProvider(inst);
+  };
+
+  const resolveEmbedding = (): IEmbeddingProvider => {
+    const mappedId = mappings["embeddings"];
+    let inst: ModelProviderInstance | null = mappedId
+      ? (list.find((p) => p.id === mappedId) ?? null)
+      : null;
+
+    if (!inst || inst.type !== "embedding") {
+      inst = ProviderManager.getActive("embedding");
+    }
+
+    if (!inst) {
+      const envKey = process.env.GOOGLE_API_KEY;
+      if (envKey) {
+        inst = ProviderManager.create(
+          "Default Embed (Env)",
+          "google-genai",
+          envKey,
+          "gemini-embedding-001",
+          "embedding",
+        );
+      }
+    }
+
+    if (!inst) {
+      if (required) {
+        throw new Error(
+          `No active Embedding Provider Instance found. Please configure an embedding key in Settings first.`,
+        );
+      }
+      return new MockEmbeddingProvider(undefined);
+    }
+
+    return buildEmbeddingProvider(inst);
+  };
+
+  return {
+    actorProvider: resolveGenerative("actor-prose"),
+    validatorProvider: resolveGenerative("llm-validator"),
+    decoderProvider: resolveGenerative("intent-decoder"),
+    timedeltaProvider: resolveGenerative("timedelta"),
+    handoffProvider: resolveGenerative("handoff"),
+    embeddingProvider: resolveEmbedding(),
+  };
+}

apps/gui/src/lib/simulation/session-store.ts

@@ -0,0 +1,139 @@
+import Database from "better-sqlite3";
+import path from "path";
+import fs from "fs";
+import type { SimSession, SavedState } from "./types";
+import type { SimSnapshot } from "../simulation-types";
+
+export const DATA_DIR = path.resolve(process.cwd(), "data");
+
+// ---------------------------------------------------------------------------
+// Low-level read/write helpers
+// ---------------------------------------------------------------------------
+
+export function loadSessionState(
+  db: Database.Database,
+  id: string,
+): SavedState | null {
+  try {
+    db.prepare(
+      `CREATE TABLE IF NOT EXISTS gui_meta (
+        id TEXT PRIMARY KEY,
+        state_json TEXT
+      )`,
+    ).run();
+    const row = db
+      .prepare(`SELECT state_json FROM gui_meta WHERE id = ?`)
+      .get(id) as { state_json: string } | undefined;
+    return row ? (JSON.parse(row.state_json) as SavedState) : null;
+  } catch {
+    return null;
+  }
+}
+
+export function saveSession(session: SimSession): void {
+  const state: SavedState = {
+    scenarioName: session.scenarioName,
+    scenarioDescription: session.scenarioDescription,
+    turn: session.turn,
+    maxTurns: session.maxTurns,
+    entities: session.entities,
+    playerEntityId: session.playerEntityId,
+    entityIndex: session.entityIndex,
+    status: session.status,
+    error: session.error,
+    waitingEntity: session.waitingEntity,
+    aliasDoneForTurn: session.aliasDoneForTurn,
+    log: session.log,
+    providerMappings: session.providerMappings,
+  };
+
+  session.db
+    .prepare(
+      `CREATE TABLE IF NOT EXISTS gui_meta (
+        id TEXT PRIMARY KEY,
+        state_json TEXT
+      )`,
+    )
+    .run();
+
+  session.db
+    .prepare(
+      `INSERT INTO gui_meta (id, state_json)
+       VALUES (?, ?)
+       ON CONFLICT(id) DO UPDATE SET state_json = excluded.state_json`,
+    )
+    .run(session.worldInstanceId, JSON.stringify(state));
+}
+
+// ---------------------------------------------------------------------------
+// Session file management
+// ---------------------------------------------------------------------------
+
+export function deleteSessionFile(id: string): void {
+  const dbPath = path.join(DATA_DIR, `${id}.db`);
+  if (fs.existsSync(dbPath)) {
+    try {
+      fs.unlinkSync(dbPath);
+    } catch (err) {
+      console.error(`Failed to delete session file ${dbPath}:`, err);
+    }
+  }
+}
+
+/**
+ * Lists all saved simulation snapshots by scanning the data directory.
+ * Active in-memory sessions are snapshotted via the provided callback;
+ * inactive ones are read directly from their `.db` files.
+ */
+export function listSavedSessions(
+  activeSessions: Map<string, SimSession>,
+  snapshotFn: (session: SimSession) => SimSnapshot,
+): SimSnapshot[] {
+  if (!fs.existsSync(DATA_DIR)) return [];
+
+  const snapshots: SimSnapshot[] = [];
+  const files = fs
+    .readdirSync(DATA_DIR)
+    .filter((f) => f.startsWith("sim-") && f.endsWith(".db"));
+
+  for (const file of files) {
+    const id = file.replace(".db", "");
+    const dbPath = path.join(DATA_DIR, file);
+
+    const active = activeSessions.get(id);
+    if (active) {
+      snapshots.push(snapshotFn(active));
+      continue;
+    }
+
+    try {
+      const db = new Database(dbPath);
+      const state = loadSessionState(db, id);
+      db.close();
+
+      if (state) {
+        snapshots.push({
+          id,
+          status: state.status,
+          turn: state.turn,
+          maxTurns: state.maxTurns,
+          scenarioName: state.scenarioName,
+          scenarioDescription: state.scenarioDescription,
+          entities: state.entities || [],
+          log: state.log || [],
+          entityIndex: state.entityIndex,
+          waitingEntity: state.waitingEntity,
+          error: state.error,
+        });
+      }
+    } catch {
+      /* skip corrupt / in-use db files */
+    }
+  }
+
+  return snapshots.sort((a, b) => {
+    const tsA = parseInt(a.id.replace("sim-", ""), 10) || 0;
+    const tsB = parseInt(b.id.replace("sim-", ""), 10) || 0;
+    return tsB - tsA;
+  });
+}

apps/gui/src/lib/simulation/simulation-manager.ts

@@ -0,0 +1,455 @@
+import "./env"; // Must be first — loads .env before any code reads process.env
+import Database from "better-sqlite3";
+import path from "path";
+import fs from "fs";
+import { SQLiteRepository } from "@omnia/core";
+import { BufferRepository, LedgerRepository } from "@omnia/memory";
+import { Architect, AliasDeltaGenerator } from "@omnia/architect";
+import {
+  ProviderManager,
+  GeminiEmbeddingProvider,
+  MockEmbeddingProvider,
+} from "@omnia/llm";
+import type { ModelProviderInstance, IEmbeddingProvider } from "@omnia/llm";
+import { ScenarioLoader } from "@omnia/scenario";
+import type { SimSnapshot } from "../simulation-types";
+import type { SimSession, EntityInfo } from "./types";
+import { resolveProviders } from "./provider-resolver";
+import {
+  DATA_DIR,
+  loadSessionState,
+  saveSession,
+  listSavedSessions,
+  deleteSessionFile,
+} from "./session-store";
+import {
+  preparePlayerTurn,
+  processNpcTurn,
+  executePlayerAction,
+} from "./turn-executor";
+import { runAliasResolution, runHandoffResolution } from "./alias-handoff";
+
+export class SimulationManager {
+  private sessions = new Map<string, SimSession>();
+
+  // ---------------------------------------------------------------------------
+  // Session lifecycle
+  // ---------------------------------------------------------------------------
+
+  async create(
+    scenarioPath: string,
+    playEntityName?: string,
+    providerInstanceId?: string,
+  ): Promise<SimSnapshot> {
+    // Resolve or validate the active generative provider upfront so we can
+    // return a clean error snapshot before touching the filesystem.
+    let activeInstance: ModelProviderInstance | null = providerInstanceId
+      ? ProviderManager.list().find((p) => p.id === providerInstanceId) || null
+      : ProviderManager.getActive("generative");
+
+    if (!activeInstance) {
+      const envKey = process.env.GOOGLE_API_KEY;
+      if (envKey) {
+        activeInstance = ProviderManager.create(
+          "Default (Env)",
+          "google-genai",
+          envKey,
+          undefined,
+          "generative",
+        );
+      }
+    }
+    if (!activeInstance) {
+      return {
+        id: "",
+        status: "error",
+        turn: 0,
+        maxTurns: 20,
+        scenarioName: "",
+        scenarioDescription: "",
+        entities: [],
+        log: [],
+        entityIndex: 0,
+        error:
+          "No active LLM Provider Instance found. Please configure a key in Settings first.",
+      };
+    }
+
+    const scenarioJson = JSON.parse(fs.readFileSync(scenarioPath, "utf-8"));
+    const id = `sim-${Date.now()}`;
+
+    fs.mkdirSync(DATA_DIR, { recursive: true });
+    const dbPath = path.join(DATA_DIR, `${id}.db`);
+    const db = new Database(dbPath);
+    const coreRepo = new SQLiteRepository(db);
+    const bufferRepo = new BufferRepository(db);
+    const ledgerRepo = new LedgerRepository(db);
+    const loader = new ScenarioLoader(coreRepo, bufferRepo);
+
+    const worldInstanceId = id;
+    await loader.initializeWorld(scenarioJson, worldInstanceId);
+
+    const worldState = coreRepo.loadWorldState(worldInstanceId);
+    if (!worldState) {
+      db.close();
+      return {
+        id: "",
+        status: "error",
+        turn: 0,
+        maxTurns: 20,
+        scenarioName: "",
+        scenarioDescription: "",
+        entities: [],
+        log: [],
+        entityIndex: 0,
+        error: "Failed to load world state after initialization.",
+      };
+    }
+
+    // Build entity list
+    const rawEntities = Array.from(worldState.entities.values());
+    const entityInfos: EntityInfo[] = rawEntities.map((e) => ({
+      id: e.id,
+      name: (e.attributes.get("name")?.getValue() as string) || e.id,
+      isPlayer: false,
+      isAgent: e.isAgent,
+    }));
+
+    // Resolve player entity (exact match → name match → fuzzy)
+    let playerEntityId: string | undefined;
+    if (playEntityName) {
+      let matched = worldState.getEntity(playEntityName);
+      if (!matched) {
+        for (const ent of rawEntities) {
+          const nameAttr = ent.attributes.get("name")?.getValue() as
+            string | undefined;
+          if (nameAttr?.toLowerCase() === playEntityName.toLowerCase()) {
+            matched = ent;
+            break;
+          }
+        }
+      }
+      if (!matched) {
+        for (const ent of rawEntities) {
+          const nameAttr = ent.attributes.get("name")?.getValue() as
+            string | undefined;
+          if (
+            nameAttr?.toLowerCase().includes(playEntityName.toLowerCase()) ||
+            ent.id.toLowerCase().includes(playEntityName.toLowerCase())
+          ) {
+            matched = ent;
+            break;
+          }
+        }
+      }
+      if (matched) {
+        playerEntityId = matched.id;
+        const info = entityInfos.find((e) => e.id === matched!.id);
+        if (info) info.isPlayer = true;
+      }
+    }
+
+    const mappings = ProviderManager.getMappings();
+    const {
+      actorProvider,
+      validatorProvider,
+      decoderProvider,
+      timedeltaProvider,
+      handoffProvider,
+      embeddingProvider,
+    } = resolveProviders(mappings, { fallbackInstance: activeInstance });
+
+    const architect = new Architect(
+      { validator: validatorProvider, timedelta: timedeltaProvider },
+      coreRepo,
+    );
+    const aliasGenerator = new AliasDeltaGenerator(actorProvider);
+
+    const session: SimSession = {
+      db,
+      dbPath,
+      coreRepo,
+      bufferRepo,
+      ledgerRepo,
+      worldInstanceId,
+      scenarioName: scenarioJson.name,
+      scenarioDescription: scenarioJson.description || "",
+      turn: 1,
+      maxTurns: 20,
+      entities: entityInfos,
+      playerEntityId,
+      entityIndex: 0,
+      actorProvider,
+      validatorProvider,
+      decoderProvider,
+      timedeltaProvider,
+      handoffProvider,
+      embeddingProvider,
+      architect,
+      aliasGenerator,
+      log: [],
+      status: "running",
+      aliasDoneForTurn: false,
+      providerMappings: mappings,
+    };
+
+    this.sessions.set(id, session);
+    return this.snapshot(session);
+  }
+
+  async load(id: string): Promise<SimSnapshot | null> {
+    const active = this.sessions.get(id);
+    if (active) return this.snapshot(active);
+
+    const dbPath = path.join(DATA_DIR, `${id}.db`);
+    if (!fs.existsSync(dbPath)) return null;
+
+    try {
+      const db = new Database(dbPath);
+      const state = loadSessionState(db, id);
+      if (!state) {
+        db.close();
+        return null;
+      }
+
+      const mappings = state.providerMappings || {};
+      const {
+        actorProvider,
+        validatorProvider,
+        decoderProvider,
+        timedeltaProvider,
+        handoffProvider,
+        embeddingProvider,
+      } = resolveProviders(mappings, { required: true });
+
+      const coreRepo = new SQLiteRepository(db);
+      const bufferRepo = new BufferRepository(db);
+      const ledgerRepo = new LedgerRepository(db);
+      const architect = new Architect(
+        { validator: validatorProvider, timedelta: timedeltaProvider },
+        coreRepo,
+      );
+      const aliasGenerator = new AliasDeltaGenerator(actorProvider);
+
+      const session: SimSession = {
+        db,
+        dbPath,
+        coreRepo,
+        bufferRepo,
+        ledgerRepo,
+        worldInstanceId: id,
+        scenarioName: state.scenarioName,
+        scenarioDescription: state.scenarioDescription,
+        turn: state.turn,
+        maxTurns: state.maxTurns,
+        entities: state.entities || [],
+        playerEntityId: state.playerEntityId,
+        entityIndex: state.entityIndex,
+        actorProvider,
+        validatorProvider,
+        decoderProvider,
+        timedeltaProvider,
+        handoffProvider,
+        embeddingProvider,
+        architect,
+        aliasGenerator,
+        log: state.log || [],
+        status: state.status,
+        error: state.error,
+        waitingEntity: state.waitingEntity,
+        aliasDoneForTurn: state.aliasDoneForTurn || false,
+        providerMappings: mappings,
+      };
+
+      this.sessions.set(id, session);
+      return this.snapshot(session);
+    } catch (err) {
+      console.error(`Failed to load session ${id}:`, err);
+      return null;
+    }
+  }
+
+  close(id: string): void {
+    const session = this.sessions.get(id);
+    if (session) {
+      session.db.close();
+      this.sessions.delete(id);
+    }
+  }
+
+  deleteSession(id: string): void {
+    const session = this.sessions.get(id);
+    if (session) {
+      session.db.close();
+      this.sessions.delete(id);
+    }
+    deleteSessionFile(id);
+  }
+
+  listSavedSessions(): SimSnapshot[] {
+    return listSavedSessions(this.sessions, (s) => this.snapshot(s));
+  }
+
+  getSnapshot(id: string): SimSnapshot | null {
+    const session = this.sessions.get(id);
+    return session ? this.snapshot(session) : null;
+  }
+
+  // ---------------------------------------------------------------------------
+  // Simulation stepping
+  // ---------------------------------------------------------------------------
+
+  async step(id: string): Promise<SimSnapshot | null> {
+    const session = this.sessions.get(id);
+    if (!session) return null;
+    if (session.status !== "running") return this.snapshot(session);
+
+    try {
+      if (session.turn > session.maxTurns) {
+        session.status = "done";
+        saveSession(session);
+        return this.snapshot(session);
+      }
+
+      // Start of turn: alias + handoff resolution before any entity acts
+      if (!session.aliasDoneForTurn && session.entityIndex === 0) {
+        await runAliasResolution(session);
+        await runHandoffResolution(session);
+        session.aliasDoneForTurn = true;
+        saveSession(session);
+        return this.snapshot(session);
+      }
+
+      // End of turn: advance to next turn
+      if (session.entityIndex >= session.entities.length) {
+        session.turn++;
+        session.entityIndex = 0;
+        session.aliasDoneForTurn = false;
+        saveSession(session);
+        return this.snapshot(session);
+      }
+
+      const info = session.entities[session.entityIndex];
+
+      if (!info.isAgent) {
+        session.entityIndex++;
+        saveSession(session);
+        return this.snapshot(session);
+      }
+
+      if (info.isPlayer) {
+        await preparePlayerTurn(session, info);
+        saveSession(session);
+        return this.snapshot(session);
+      }
+
+      await processNpcTurn(session, info);
+      session.entityIndex++;
+    } catch (err) {
+      session.status = "error";
+      session.error = err instanceof Error ? err.message : String(err);
+    }
+
+    saveSession(session);
+    return this.snapshot(session);
+  }
+
+  async submitPlayerAction(
+    id: string,
+    prose: string,
+  ): Promise<SimSnapshot | null> {
+    const session = this.sessions.get(id);
+    if (!session) return null;
+    if (session.status !== "waiting_player") return this.snapshot(session);
+    if (!session.waitingEntity) return this.snapshot(session);
+
+    const ctx = session.waitingEntity;
+    session.waitingEntity = undefined;
+    session.status = "running";
+
+    try {
+      await executePlayerAction(session, ctx, prose);
+      session.entityIndex++;
+    } catch (err) {
+      session.status = "error";
+      session.error = err instanceof Error ? err.message : String(err);
+    }
+
+    saveSession(session);
+    return this.snapshot(session);
+  }
+
+  // ---------------------------------------------------------------------------
+  // Utility
+  // ---------------------------------------------------------------------------
+
+  async regenerateAllEmbeddings(newProviderInstanceId?: string): Promise<void> {
+    if (!fs.existsSync(DATA_DIR)) return;
+
+    const files = fs
+      .readdirSync(DATA_DIR)
+      .filter((f) => f.startsWith("sim-") && f.endsWith(".db"));
+
+    const list = ProviderManager.list();
+    let inst = newProviderInstanceId
+      ? (list.find((p) => p.id === newProviderInstanceId) ?? null)
+      : null;
+    if (!inst || inst.type !== "embedding") {
+      inst = ProviderManager.getActive("embedding");
+    }
+
+    const key = inst ? inst.apiKey : process.env.GOOGLE_API_KEY || "";
+    const providerName = inst ? inst.providerName : "google-genai";
+    const modelName = inst ? inst.modelName : undefined;
+
+    const embeddingProvider: IEmbeddingProvider =
+      providerName === "google-genai"
+        ? new GeminiEmbeddingProvider(key, modelName)
+        : new MockEmbeddingProvider(modelName);
+
+    for (const file of files) {
+      const dbPath = path.join(DATA_DIR, file);
+      const fileId = file.replace(".db", "");
+      const activeSession = this.sessions.get(fileId);
+      const db = activeSession ? activeSession.db : new Database(dbPath);
+
+      try {
+        const rows = db
+          .prepare(`SELECT id, content FROM ledger_entries`)
+          .all() as { id: string; content: string }[];
+
+        for (const row of rows) {
+          const vector = await embeddingProvider.embed(row.content);
+          const buffer = Buffer.from(new Float32Array(vector).buffer);
+          db.prepare(
+            `UPDATE ledger_entries SET embedding = ? WHERE id = ?`,
+          ).run(buffer, row.id);
+        }
+      } catch (err) {
+        console.error(`Failed to regenerate embeddings for ${file}:`, err);
+      } finally {
+        if (!activeSession) db.close();
+      }
+    }
+  }
+
+  // ---------------------------------------------------------------------------
+  // Private
+  // ---------------------------------------------------------------------------
+
+  private snapshot(session: SimSession): SimSnapshot {
+    return {
+      id: session.worldInstanceId,
+      status: session.status,
+      turn: session.turn,
+      maxTurns: session.maxTurns,
+      scenarioName: session.scenarioName,
+      scenarioDescription: session.scenarioDescription,
+      entities: session.entities,
+      log: session.log,
+      entityIndex: session.entityIndex,
+      waitingEntity: session.waitingEntity,
+      error: session.error,
+    };
+  }
+}

apps/gui/src/lib/simulation/turn-executor.ts

@@ -0,0 +1,277 @@
+import {
+  ActorAgent,
+  ActorPromptBuilder,
+  buildBufferEntryForIntent,
+} from "@omnia/actor";
+import type { IActorProseGenerator } from "@omnia/actor";
+import type { SimSession } from "./types";
+import type {
+  EntityInfo,
+  IntentInfo,
+  LogEntry,
+  WaitingContext,
+} from "../simulation-types";
+
+// ---------------------------------------------------------------------------
+// Internal helpers
+// ---------------------------------------------------------------------------
+
+/** Prose generator that returns a fixed player-supplied string verbatim. */
+class FixedProseGenerator implements IActorProseGenerator {
+  constructor(private prose: string) {}
+
+  async generate(
+    entityId: string,
+    systemPrompt: string,
+    userContext: string,
+  ): Promise<string> {
+    void entityId;
+    void systemPrompt;
+    void userContext;
+    return this.prose;
+  }
+}
+
+/**
+ * Processes every intent produced by an actor turn:
+ * - Validates via Architect
+ * - Appends to actor's own buffer
+ * - Fan-outs to co-located observers for dialogue/action intents
+ *
+ * Extracted to eliminate verbatim duplication between NPC and player paths.
+ */
+async function processIntents(
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  intents: any[],
+  actorEntityId: string,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  entity: any,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  worldState: any,
+  session: SimSession,
+): Promise<IntentInfo[]> {
+  const intentInfos: IntentInfo[] = [];
+
+  for (const intent of intents) {
+    const outcome = await session.architect.processIntent(worldState, intent);
+    const ts = worldState.clock.get().toISOString();
+
+    intentInfos.push({
+      type: intent.type,
+      description: intent.description,
+      selfDescription: intent.selfDescription,
+      modifiers: intent.modifiers || [],
+      targetIds: intent.targetIds,
+      isValid: outcome.isValid,
+      reason: outcome.reason,
+      minutesToAdvance: outcome.timeDelta?.minutesToAdvance,
+    });
+
+    const actorEntry = buildBufferEntryForIntent(intent, ts, entity.locationId);
+    if (intent.type === "action") {
+      actorEntry.outcome = { isValid: outcome.isValid, reason: outcome.reason };
+    }
+    session.bufferRepo.save(actorEntry);
+
+    // Fan-out observable events to co-located entities
+    if (
+      entity.locationId &&
+      (intent.type === "dialogue" || intent.type === "action")
+    ) {
+      for (const [, other] of worldState.entities) {
+        if (
+          other.id !== actorEntityId &&
+          other.locationId === entity.locationId
+        ) {
+          const observerEntry = buildBufferEntryForIntent(
+            intent,
+            ts,
+            entity.locationId,
+          );
+          if (intent.type === "action") {
+            observerEntry.outcome = {
+              isValid: outcome.isValid,
+              reason: outcome.reason,
+            };
+          }
+          session.bufferRepo.save({ ...observerEntry, ownerId: other.id });
+        }
+      }
+    }
+  }
+
+  return intentInfos;
+}
+
+// ---------------------------------------------------------------------------
+// Exported turn functions
+// ---------------------------------------------------------------------------
+
+/**
+ * Builds the prompt for the player entity and sets the session to
+ * `waiting_player` so the next client call can supply the prose.
+ */
+export async function preparePlayerTurn(
+  session: SimSession,
+  info: EntityInfo,
+): Promise<void> {
+  const worldState = session.coreRepo.loadWorldState(session.worldInstanceId);
+  if (!worldState) throw new Error("World state lost");
+
+  const entity = worldState.getEntity(info.id);
+  if (!entity) throw new Error(`Entity "${info.id}" not found`);
+
+  const promptBuilder = new ActorPromptBuilder(
+    session.bufferRepo,
+    session.ledgerRepo,
+    20,
+  );
+  const { systemPrompt, userContext } = promptBuilder.build(worldState, entity);
+
+  session.waitingEntity = {
+    entityId: info.id,
+    name: info.name,
+    systemPrompt,
+    userContext,
+  };
+  session.status = "waiting_player";
+}
+
+/**
+ * Runs an autonomous NPC turn: generates prose via ActorAgent, validates
+ * and persists all intents, and appends a LogEntry to the session.
+ */
+export async function processNpcTurn(
+  session: SimSession,
+  info: EntityInfo,
+): Promise<void> {
+  const worldState = session.coreRepo.loadWorldState(session.worldInstanceId);
+  if (!worldState) throw new Error("World state lost");
+
+  const entity = worldState.getEntity(info.id);
+  if (!entity) throw new Error(`Entity "${info.id}" not found`);
+
+  const actor = new ActorAgent(
+    { actor: session.actorProvider, decoder: session.decoderProvider },
+    session.bufferRepo,
+    session.ledgerRepo,
+    20,
+  );
+  const result = await actor.act(worldState, entity);
+
+  const entry: LogEntry = {
+    turn: session.turn,
+    entityId: info.id,
+    entityName: info.name,
+    narrativeProse: result.narrativeProse,
+    intents: [],
+    timestamp: worldState.clock.get().toISOString(),
+  };
+
+  if (
+    session.actorProvider.lastCalls &&
+    session.actorProvider.lastCalls.length > 0
+  ) {
+    const actorCall =
+      session.actorProvider.lastCalls[
+        session.actorProvider.lastCalls.length - 1
+      ];
+    entry.rawPrompt = {
+      systemPrompt: actorCall.systemPrompt,
+      userContext: actorCall.userContext,
+    };
+    entry.usage = actorCall.usage;
+  }
+
+  if (
+    session.decoderProvider.lastCalls &&
+    session.decoderProvider.lastCalls.length > 0
+  ) {
+    const decoderCall =
+      session.decoderProvider.lastCalls[
+        session.decoderProvider.lastCalls.length - 1
+      ];
+    entry.decoderPrompt = {
+      systemPrompt: decoderCall.systemPrompt,
+      userContext: decoderCall.userContext,
+    };
+    entry.decoderUsage = decoderCall.usage;
+  }
+
+  entry.intents = await processIntents(
+    result.intents.intents,
+    info.id,
+    entity,
+    worldState,
+    session,
+  );
+
+  session.log.push(entry);
+  session.coreRepo.saveWorldState(worldState);
+}
+
+/**
+ * Executes the player's turn using the prose they supplied.
+ * Uses a `FixedProseGenerator` so the ActorAgent bypasses its LLM call and
+ * returns the player's text directly.
+ */
+export async function executePlayerAction(
+  session: SimSession,
+  ctx: WaitingContext,
+  prose: string,
+): Promise<void> {
+  const worldState = session.coreRepo.loadWorldState(session.worldInstanceId);
+  if (!worldState) throw new Error("World state lost");
+
+  const entity = worldState.getEntity(ctx.entityId);
+  if (!entity) throw new Error(`Player entity "${ctx.entityId}" not found`);
+
+  const playerActor = new ActorAgent(
+    { actor: session.actorProvider, decoder: session.decoderProvider },
+    session.bufferRepo,
+    session.ledgerRepo,
+    20,
+    new FixedProseGenerator(prose),
+  );
+
+  const result = await playerActor.act(worldState, entity);
+
+  const entry: LogEntry = {
+    turn: session.turn,
+    entityId: ctx.entityId,
+    entityName: ctx.name,
+    narrativeProse: result.narrativeProse,
+    intents: [],
+    timestamp: worldState.clock.get().toISOString(),
+    rawPrompt: {
+      systemPrompt: ctx.systemPrompt,
+      userContext: ctx.userContext,
+    },
+  };
+
+  if (
+    session.decoderProvider.lastCalls &&
+    session.decoderProvider.lastCalls.length > 0
+  ) {
+    const call =
+      session.decoderProvider.lastCalls[
+        session.decoderProvider.lastCalls.length - 1
+      ];
+    entry.decoderPrompt = {
+      systemPrompt: call.systemPrompt,
+      userContext: call.userContext,
+    };
+    entry.decoderUsage = call.usage;
+  }
+
+  entry.intents = await processIntents(
+    result.intents.intents,
+    ctx.entityId,
+    entity,
+    worldState,
+    session,
+  );
+
+  session.log.push(entry);
+  session.coreRepo.saveWorldState(worldState);
+}

apps/gui/src/lib/simulation/types.ts

@@ -0,0 +1,68 @@
+import type Database from "better-sqlite3";
+import type { SQLiteRepository } from "@omnia/core";
+import type { BufferRepository, LedgerRepository } from "@omnia/memory";
+import type { Architect, AliasDeltaGenerator } from "@omnia/architect";
+import type { ILLMProvider, IEmbeddingProvider } from "@omnia/llm";
+import type { EntityInfo, LogEntry, WaitingContext } from "../simulation-types";
+
+export type {
+  EntityInfo,
+  IntentInfo,
+  LogEntry,
+  SimSnapshot,
+  WaitingContext,
+} from "../simulation-types";
+
+// ---------------------------------------------------------------------------
+// Persisted state (written to sqlite gui_meta table as JSON)
+// ---------------------------------------------------------------------------
+
+export interface SavedState {
+  scenarioName: string;
+  scenarioDescription: string;
+  turn: number;
+  maxTurns: number;
+  entities: EntityInfo[];
+  playerEntityId: string | undefined;
+  entityIndex: number;
+  status: "running" | "waiting_player" | "done" | "error";
+  error?: string;
+  waitingEntity?: WaitingContext;
+  aliasDoneForTurn: boolean;
+  log: LogEntry[];
+  providerMappings: Record<string, string>;
+}
+
+// ---------------------------------------------------------------------------
+// In-memory session (held in SimulationManager.sessions Map)
+// ---------------------------------------------------------------------------
+
+export interface SimSession {
+  db: Database.Database;
+  dbPath: string;
+  coreRepo: SQLiteRepository;
+  bufferRepo: BufferRepository;
+  ledgerRepo: LedgerRepository;
+  worldInstanceId: string;
+  scenarioName: string;
+  scenarioDescription: string;
+  turn: number;
+  maxTurns: number;
+  entities: EntityInfo[];
+  playerEntityId: string | undefined;
+  entityIndex: number;
+  actorProvider: ILLMProvider;
+  validatorProvider: ILLMProvider;
+  decoderProvider: ILLMProvider;
+  timedeltaProvider: ILLMProvider;
+  handoffProvider: ILLMProvider;
+  embeddingProvider: IEmbeddingProvider;
+  architect: Architect;
+  aliasGenerator: AliasDeltaGenerator;
+  log: LogEntry[];
+  status: "running" | "waiting_player" | "done" | "error";
+  error?: string;
+  waitingEntity?: WaitingContext;
+  aliasDoneForTurn: boolean;
+  providerMappings: Record<string, string>;
+}