feat(FN-3927): persist and restore durable chat recovery state

- Persist in-flight chat generation snapshots in core chat store types and DB plumbing
- Restore durable recovery state through dashboard chat manager and chat hooks on reload
- Add coverage for chat store persistence and chat/useQuickChat recovery behavior
- Document durable chat recovery architecture and dashboard behavior

Fusion-Task-Id: FN-3927

packages/core/src/__tests__/chat-store.test.ts

@@ -71,6 +71,7 @@ describe("ChatStore", () => {
         expect(session.modelId).toBeNull();
         expect(session.createdAt).toBeTruthy();
         expect(session.updatedAt).toBeTruthy();
+        expect(session.inFlightGeneration).toBeNull();
       });
 
       it("stores all provided fields", () => {
@@ -345,6 +346,27 @@ describe("ChatStore", () => {
       });
     });
 
+    describe("setInFlightGeneration", () => {
+      it("persists and clears in-flight generation snapshot", () => {
+        const session = createTestSession(store);
+
+        const updated = store.setInFlightGeneration(session.id, {
+          status: "generating",
+          streamingText: "partial",
+          streamingThinking: "thinking",
+          toolCalls: [{ toolName: "read", isError: false, status: "running" }],
+          replayFromEventId: 12,
+          updatedAt: new Date().toISOString(),
+        });
+
+        expect(updated?.inFlightGeneration?.streamingText).toBe("partial");
+        expect(store.getSession(session.id)?.inFlightGeneration?.replayFromEventId).toBe(12);
+
+        store.setInFlightGeneration(session.id, null);
+        expect(store.getSession(session.id)?.inFlightGeneration).toBeNull();
+      });
+    });
+
     describe("archiveSession", () => {
       it("sets status to archived", () => {
         const session = createTestSession(store);

packages/core/src/chat-store.ts

@@ -25,6 +25,7 @@ import type {
   ChatSessionUpdateInput,
   ChatMessagesFilter,
   ChatRoom,
+  ChatInFlightGenerationState,
   ChatRoomCreateInput,
   ChatRoomMember,
   ChatRoomMessage,
@@ -82,6 +83,7 @@ interface ChatSessionRow {
   createdAt: string;
   updatedAt: string;
   cliSessionFile: string | null;
+  inFlightGeneration: string | null;
 }
 
 /** Database row shape for chat_messages. */
@@ -156,6 +158,7 @@ export class ChatStore extends EventEmitter<ChatStoreEvents> {
       createdAt: row.createdAt,
       updatedAt: row.updatedAt,
       cliSessionFile: row.cliSessionFile ?? null,
+      inFlightGeneration: fromJson<ChatInFlightGenerationState>(row.inFlightGeneration) ?? null,
     };
   }
 
@@ -248,11 +251,12 @@ export class ChatStore extends EventEmitter<ChatStoreEvents> {
       createdAt: now,
       updatedAt: now,
       cliSessionFile: null,
+      inFlightGeneration: null,
     };
 
     this.db.prepare(`
-      INSERT INTO chat_sessions (id, agentId, title, status, projectId, modelProvider, modelId, createdAt, updatedAt)
-      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+      INSERT INTO chat_sessions (id, agentId, title, status, projectId, modelProvider, modelId, createdAt, updatedAt, inFlightGeneration)
+      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
     `).run(
       session.id,
       session.agentId,
@@ -263,6 +267,7 @@ export class ChatStore extends EventEmitter<ChatStoreEvents> {
       session.modelId,
       session.createdAt,
       session.updatedAt,
+      null,
     );
 
     this.db.bumpLastModified();
@@ -459,6 +464,20 @@ export class ChatStore extends EventEmitter<ChatStoreEvents> {
     this.db.bumpLastModified();
   }
 
+  setInFlightGeneration(id: string, inFlightGeneration: ChatInFlightGenerationState | null): ChatSession | undefined {
+    const existing = this.getSession(id);
+    if (!existing) return undefined;
+
+    this.db
+      .prepare("UPDATE chat_sessions SET inFlightGeneration = ? WHERE id = ?")
+      .run(toJsonNullable(inFlightGeneration), id);
+
+    const updated = this.getSession(id)!;
+    this.db.bumpLastModified();
+    this.emit("chat:session:updated", updated);
+    return updated;
+  }
+
   /**
    * Delete a chat session and all its messages.
    * Messages are cascade-deleted via foreign key constraint.

packages/core/src/chat-types.ts

@@ -19,6 +19,23 @@ export type ChatMessageRole = "user" | "assistant" | "system";
  * A chat session between a user and an agent.
  * Contains metadata about the conversation and references to the model used.
  */
+export interface ChatInFlightToolCall {
+  toolName: string;
+  args?: Record<string, unknown>;
+  isError: boolean;
+  result?: unknown;
+  status: "running" | "completed";
+}
+
+export interface ChatInFlightGenerationState {
+  status: "generating";
+  streamingText: string;
+  streamingThinking: string;
+  toolCalls: ChatInFlightToolCall[];
+  replayFromEventId: number;
+  updatedAt: string;
+}
+
 export interface ChatSession {
   id: string;
   /** Session routing kind; legacy sessions default to direct */
@@ -51,6 +68,8 @@ export interface ChatSession {
    * for sessions that have never produced an assistant reply.
    */
   cliSessionFile: string | null;
+  /** Durable in-flight assistant snapshot used to recover streaming UI after refresh. */
+  inFlightGeneration: ChatInFlightGenerationState | null;
 }
 
 /**

packages/core/src/db.ts

@@ -912,6 +912,7 @@ export const MIGRATION_ONLY_TABLE_SCHEMAS: Record<string, Record<string, string>
     createdAt: "TEXT NOT NULL",
     updatedAt: "TEXT NOT NULL",
     cliSessionFile: "TEXT",
+    inFlightGeneration: "TEXT",
   },
   chat_messages: {
     id: "TEXT PRIMARY KEY",
@@ -1828,7 +1829,8 @@ export class Database {
             modelProvider TEXT,
             modelId TEXT,
             createdAt TEXT NOT NULL,
-            updatedAt TEXT NOT NULL
+            updatedAt TEXT NOT NULL,
+            inFlightGeneration TEXT
           )
         `);
         this.db.exec(`CREATE INDEX IF NOT EXISTS idxChatSessionsAgentId ON chat_sessions(agentId)`);

packages/core/src/index.ts

@@ -890,6 +890,8 @@ export type {
 export type {
   ChatSessionStatus,
   ChatMessageRole,
+  ChatInFlightToolCall,
+  ChatInFlightGenerationState,
   ChatSession,
   ChatSessionSummary,
   EnrichedChatSession,