diff --git a/apps/ai-game-creator-shell/src-tauri/src/agent/codex_app_server/mod.rs b/apps/ai-game-creator-shell/src-tauri/src/agent/codex_app_server/mod.rs
index 27f81fc6b..a5db418f6 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/agent/codex_app_server/mod.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/agent/codex_app_server/mod.rs
@@ -3013,7 +3013,12 @@ impl CodexAppServerConnection {
                                     turn_id: turn_id.clone(),
                                     item_id: Some(item_id.clone()),
                                     call_id: None,
-                                    payload: serde_json::json!({ "delta": delta.clone() }),
+                                    // 事件自足：增量也要说明它是哪类条目的正文，
+                                    // 前端 reducer 不允许靠猜 itemId 的来源决定 kind。
+                                    payload: serde_json::json!({
+                                        "delta": delta.clone(),
+                                        "kind": "message",
+                                    }),
                                 },
                             );
                         }
diff --git a/apps/ai-game-creator-shell/src/features/project-workspace/directThreadChat.ts b/apps/ai-game-creator-shell/src/features/project-workspace/directThreadChat.ts
new file mode 100644
index 000000000..e2764e51e
--- /dev/null
+++ b/apps/ai-game-creator-shell/src/features/project-workspace/directThreadChat.ts
@@ -0,0 +1,253 @@
+/**
+ * DirectProject 聊天 reducer：把运行态 raw event 与历史切片归并成同一份聊天条目。
+ *
+ * 事实源只有一个——项目对话历史；运行态事件只负责"当前回合"。这里不判断哪些条目
+ * 要显示，也不决定顺序策略之外的任何东西：顺序 = 历史文件顺序 + 运行态独有条目。
+ */
+
+import type { GameCreatorDirectToolCall } from '../../app/types';
+import type {
+  DirectThreadRawEvent,
+  DirectThreadSubscriptionBootstrap,
+} from './directThreadEvents';
+
+export type DirectChatEntryKind = 'message' | 'reasoning' | 'tool';
+
+/** 与 Rust `DirectChatEntry` 同形：运行态事件与历史切片共用的唯一形状。 */
+export type DirectChatEntry = {
+  itemId: string;
+  callId?: string | null;
+  turnId?: string | null;
+  kind: DirectChatEntryKind;
+  role?: 'user' | 'assistant' | null;
+  text?: string | null;
+  toolCall?: GameCreatorDirectToolCall | null;
+  at?: number;
+};
+
+export type DirectThreadChatState = {
+  subscriptionId: string | null;
+  /** 首屏历史锚点：`subscribe` 给出的最后一个完成条目 id。 */
+  lastCompletedItemId: string | null;
+  /** 活动回合：只有出现 `turn.started` 且没有对应 `turn.completed` 才有值。 */
+  activeTurnId: string | null;
+  /** 历史切片条目，保持文件顺序。 */
+  history: DirectChatEntry[];
+  /** 运行态条目，保持到达顺序。 */
+  live: DirectChatEntry[];
+  /** 流式正文累计（itemId → text）。 */
+  deltaText: Record<string, string>;
+};
+
+export function emptyDirectThreadChatState(): DirectThreadChatState {
+  return {
+    subscriptionId: null,
+    lastCompletedItemId: null,
+    activeTurnId: null,
+    history: [],
+    live: [],
+    deltaText: {},
+  };
+}
+
+/** 合并身份：工具条目的 app-server itemId 与原始 item 的 callId 是同一个值。 */
+export function directChatEntryIdentity(entry: DirectChatEntry): string {
+  return (entry.callId ?? '').trim() || entry.itemId;
+}
+
+function mergeToolCall(
+  left: GameCreatorDirectToolCall,
+  right: GameCreatorDirectToolCall,
+): GameCreatorDirectToolCall {
+  return {
+    ...left,
+    ...right,
+    title: right.title?.trim() ? right.title : left.title,
+    summary: right.summary?.trim() ? right.summary : left.summary,
+    kind: right.kind && right.kind !== 'other' ? right.kind : left.kind,
+    detail: {
+      command: right.detail?.command ?? left.detail?.command,
+      output: right.detail?.output ?? left.detail?.output,
+      changes: right.detail?.changes?.length
+        ? right.detail.changes
+        : left.detail?.changes,
+    },
+    startedAt: Math.min(
+      left.startedAt > 0 ? left.startedAt : right.startedAt,
+      right.startedAt > 0 ? right.startedAt : left.startedAt,
+    ),
+  };
+}
+
+/** 后到的快照只补空字段：结果快照不能抹掉先到的命令与标题。 */
+export function mergeDirectChatEntry(
+  existing: DirectChatEntry,
+  incoming: DirectChatEntry,
+): DirectChatEntry {
+  const merged: DirectChatEntry = {
+    ...existing,
+    ...incoming,
+    itemId: existing.itemId || incoming.itemId,
+    kind:
+      incoming.kind === 'tool' || existing.kind === 'tool'
+        ? 'tool'
+        : incoming.kind,
+    text: incoming.text ?? existing.text,
+    role: incoming.role ?? existing.role,
+    turnId: incoming.turnId ?? existing.turnId,
+  };
+  const left = existing.toolCall ?? null;
+  const right = incoming.toolCall ?? null;
+  merged.toolCall =
+    left && right ? mergeToolCall(left, right) : (right ?? left);
+  return merged;
+}
+
+function upsertLiveEntry(
+  state: DirectThreadChatState,
+  entry: DirectChatEntry,
+): DirectThreadChatState {
+  const identity = directChatEntryIdentity(entry);
+  const index = state.live.findIndex(
+    (existing) => directChatEntryIdentity(existing) === identity,
+  );
+  if (index < 0) {
+    return { ...state, live: [...state.live, entry] };
+  }
+  const existing = state.live[index];
+  if (!existing) {
+    return { ...state, live: [...state.live, entry] };
+  }
+  const live = [...state.live];
+  live[index] = mergeDirectChatEntry(existing, entry);
+  return { ...state, live };
+}
+
+/** 事件载荷就是聊天条目；不是聊天条目（例如纯工具输出之外的内部 item）返回 null。 */
+export function directChatEntryFromEventPayload(
+  payload: unknown,
+): DirectChatEntry | null {
+  if (!payload || typeof payload !== 'object') return null;
+  const entry = payload as DirectChatEntry;
+  if (typeof entry.itemId !== 'string' || !entry.itemId.trim()) return null;
+  if (!entry.kind) return null;
+  return entry;
+}
+
+function reduceDirectThreadEvent(
+  state: DirectThreadChatState,
+  event: DirectThreadRawEvent,
+): DirectThreadChatState {
+  switch (event.type) {
+    case 'turn.started':
+      return { ...state, activeTurnId: event.turnId };
+    case 'turn.completed':
+      return {
+        ...state,
+        activeTurnId:
+          state.activeTurnId === event.turnId ? null : state.activeTurnId,
+      };
+    case 'item.delta': {
+      const itemId = event.itemId?.trim();
+      if (!itemId) return state;
+      const payload = event.payload as { delta?: unknown; kind?: unknown };
+      const delta = typeof payload?.delta === 'string' ? payload.delta : '';
+      if (!delta) return state;
+      const text = `${state.deltaText[itemId] ?? ''}${delta}`;
+      const reasoning = payload?.kind === 'reasoning';
+      return upsertLiveEntry(
+        { ...state, deltaText: { ...state.deltaText, [itemId]: text } },
+        {
+          itemId,
+          kind: reasoning ? 'reasoning' : 'message',
+          role: reasoning ? null : 'assistant',
+          turnId: event.turnId,
+          text,
+        },
+      );
+    }
+    case 'item.started':
+    case 'item.completed': {
+      const entry = directChatEntryFromEventPayload(event.payload);
+      if (!entry) return state;
+      return upsertLiveEntry(state, {
+        ...entry,
+        turnId: entry.turnId ?? event.turnId,
+      });
+    }
+    default:
+      return state;
+  }
+}
+
+export function reduceDirectThreadEvents(
+  state: DirectThreadChatState,
+  events: readonly DirectThreadRawEvent[],
+): DirectThreadChatState {
+  return events.reduce(reduceDirectThreadEvent, state);
+}
+
+/** bootstrap 是运行态的唯一权威：原子替换运行态，历史窗口保留。 */
+export function resolveDirectThreadBootstrap(
+  state: DirectThreadChatState,
+  bootstrap: DirectThreadSubscriptionBootstrap,
+): DirectThreadChatState {
+  return reduceDirectThreadEvents(
+    {
+      ...emptyDirectThreadChatState(),
+      history: state.history,
+      subscriptionId: bootstrap.subscriptionId,
+      lastCompletedItemId: bootstrap.lastCompletedItemId ?? null,
+    },
+    bootstrap.events,
+  );
+}
+
+/** 历史切片并入：重叠条目按身份去重，新切片在前、已有历史在后。 */
+export function mergeDirectHistoryEntries(
+  state: DirectThreadChatState,
+  entries: readonly DirectChatEntry[],
+): DirectThreadChatState {
+  const byIdentity = new Map<string, DirectChatEntry>();
+  const order: string[] = [];
+  for (const entry of [...entries, ...state.history]) {
+    const identity = directChatEntryIdentity(entry);
+    const existing = byIdentity.get(identity);
+    if (existing) {
+      byIdentity.set(identity, mergeDirectChatEntry(existing, entry));
+      continue;
+    }
+    byIdentity.set(identity, entry);
+    order.push(identity);
+  }
+  return {
+    ...state,
+    history: order
+      .map((identity) => byIdentity.get(identity))
+      .filter((entry): entry is DirectChatEntry => Boolean(entry)),
+  };
+}
+
+/** 聊天投影输入：历史顺序 + 运行态覆盖；运行态独有条目排在最后。 */
+export function selectDirectChatEntries(
+  state: DirectThreadChatState,
+): DirectChatEntry[] {
+  const liveByIdentity = new Map(
+    state.live.map((entry) => [directChatEntryIdentity(entry), entry]),
+  );
+  const seen = new Set<string>();
+  const entries: DirectChatEntry[] = [];
+  for (const entry of state.history) {
+    const identity = directChatEntryIdentity(entry);
+    seen.add(identity);
+    const live = liveByIdentity.get(identity);
+    entries.push(live ? mergeDirectChatEntry(entry, live) : entry);
+  }
+  for (const entry of state.live) {
+    const identity = directChatEntryIdentity(entry);
+    if (seen.has(identity)) continue;
+    seen.add(identity);
+    entries.push(entry);
+  }
+  return entries;
+}
diff --git a/apps/ai-game-creator-shell/tests/directThreadChat.test.ts b/apps/ai-game-creator-shell/tests/directThreadChat.test.ts
new file mode 100644
index 000000000..912e645c7
--- /dev/null
+++ b/apps/ai-game-creator-shell/tests/directThreadChat.test.ts
@@ -0,0 +1,170 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+  type DirectChatEntry,
+  directChatEntryIdentity,
+  emptyDirectThreadChatState,
+  mergeDirectHistoryEntries,
+  reduceDirectThreadEvents,
+  resolveDirectThreadBootstrap,
+  selectDirectChatEntries,
+} from '../src/features/project-workspace/directThreadChat';
+import type { DirectThreadRawEvent } from '../src/features/project-workspace/directThreadEvents';
+
+function event(
+  partial: Partial<DirectThreadRawEvent> &
+    Pick<DirectThreadRawEvent, 'type' | 'turnId'>,
+): DirectThreadRawEvent {
+  return { seq: 1, payload: {}, ...partial };
+}
+
+function toolEntry(
+  overrides: Partial<DirectChatEntry & { status?: string }> = {},
+): DirectChatEntry {
+  return {
+    itemId: 'call-1',
+    callId: 'call-1',
+    turnId: 'turn-1',
+    kind: 'tool',
+    toolCall: {
+      schemaVersion: 'agc-tool-call.v1',
+      id: 'call-1',
+      turnId: 'turn-1',
+      kind: 'command',
+      title: '执行命令',
+      summary: 'ls',
+      status: 'running',
+      detail: { command: 'ls', output: undefined, changes: [] },
+      startedAt: 1000,
+      updatedAt: 1000,
+    },
+    ...overrides,
+  };
+}
+
+describe('DirectProject 聊天 reducer', () => {
+  it('只有 turn.started 且未完成的回合才是活动回合', () => {
+    const started = reduceDirectThreadEvents(emptyDirectThreadChatState(), [
+      event({ type: 'turn.started', turnId: 'turn-1' }),
+    ]);
+    expect(started.activeTurnId).toBe('turn-1');
+
+    const completed = reduceDirectThreadEvents(started, [
+      event({ type: 'turn.completed', turnId: 'turn-1' }),
+    ]);
+    expect(completed.activeTurnId).toBeNull();
+  });
+
+  it('bootstrap 原子替换运行态，没有生命周期事件就没有活动回合', () => {
+    const stale = reduceDirectThreadEvents(emptyDirectThreadChatState(), [
+      event({ type: 'turn.started', turnId: 'turn-old' }),
+    ]);
+    const bootstrapped = resolveDirectThreadBootstrap(stale, {
+      subscriptionId: 'sub-1',
+      lastCompletedItemId: 'msg-9',
+      events: [],
+    });
+    expect(bootstrapped.activeTurnId).toBeNull();
+    expect(bootstrapped.subscriptionId).toBe('sub-1');
+    expect(bootstrapped.lastCompletedItemId).toBe('msg-9');
+  });
+
+  it('增量正文按条目累计，完成快照覆盖同一段', () => {
+    const streamed = reduceDirectThreadEvents(emptyDirectThreadChatState(), [
+      event({
+        type: 'item.delta',
+        turnId: 'turn-1',
+        itemId: 'msg-1',
+        payload: { delta: '你', kind: 'message' },
+      }),
+      event({
+        type: 'item.delta',
+        turnId: 'turn-1',
+        itemId: 'msg-1',
+        payload: { delta: '好', kind: 'message' },
+      }),
+    ]);
+    expect(selectDirectChatEntries(streamed)).toHaveLength(1);
+    expect(selectDirectChatEntries(streamed)[0]?.text).toBe('你好');
+
+    const done = reduceDirectThreadEvents(streamed, [
+      event({
+        type: 'item.completed',
+        turnId: 'turn-1',
+        itemId: 'msg-1',
+        payload: {
+          itemId: 'msg-1',
+          turnId: 'turn-1',
+          kind: 'message',
+          role: 'assistant',
+          text: '你好，我是陶泥儿。',
+        },
+      }),
+    ]);
+    const entries = selectDirectChatEntries(done);
+    expect(entries).toHaveLength(1);
+    expect(entries[0]?.text).toBe('你好，我是陶泥儿。');
+  });
+
+  it('工具条目 started/completed 归并成一张卡片', () => {
+    const state = reduceDirectThreadEvents(emptyDirectThreadChatState(), [
+      event({
+        type: 'item.started',
+        turnId: 'turn-1',
+        itemId: 'call-1',
+        payload: toolEntry(),
+      }),
+      event({
+        type: 'item.completed',
+        turnId: 'turn-1',
+        itemId: 'call-1',
+        payload: {
+          ...toolEntry(),
+          toolCall: {
+            ...toolEntry().toolCall!,
+            status: 'completed',
+            detail: { command: 'ls', output: 'assets\ngame', changes: [] },
+            updatedAt: 2000,
+          },
+        },
+      }),
+    ]);
+    const entries = selectDirectChatEntries(state);
+    expect(entries).toHaveLength(1);
+    expect(entries[0]?.toolCall?.status).toBe('completed');
+    expect(entries[0]?.toolCall?.detail.output).toBe('assets\ngame');
+    expect(entries[0]?.toolCall?.detail.command).toBe('ls');
+  });
+
+  it('历史条目与运行态按 callId 合并，重复条目只出现一次', () => {
+    const historical = mergeDirectHistoryEntries(emptyDirectThreadChatState(), [
+      toolEntry(),
+      {
+        itemId: 'msg-user',
+        kind: 'message',
+        role: 'user',
+        text: '做一个拼图游戏',
+      },
+    ]);
+    const live = reduceDirectThreadEvents(historical, [
+      event({
+        type: 'item.completed',
+        turnId: 'turn-1',
+        itemId: 'call-1',
+        payload: {
+          ...toolEntry(),
+          itemId: 'call-1',
+          toolCall: {
+            ...toolEntry().toolCall!,
+            status: 'completed',
+            detail: { command: 'ls', output: 'assets', changes: [] },
+          },
+        },
+      }),
+    ]);
+    const entries = selectDirectChatEntries(live);
+    expect(entries).toHaveLength(2);
+    expect(entries[0]?.toolCall?.status).toBe('completed');
+    expect(directChatEntryIdentity(entries[0]!)).toBe('call-1');
+  });
+});