feat(FN-4075): repair room reply session creation

Fixes FN-4075: repairs room reply session creation logic in the chat module, with accompanying tests added to cover the fix.

Fusion-Task-Id: FN-4075

packages/dashboard/src/__tests__/chat.rooms.test.ts

@@ -263,6 +263,54 @@ describe("Chat orchestration — rooms (FN-3805..FN-3811 contract)", () => {
       );
     });
 
+    it("passes resolved-session runtime options when generating room replies", async () => {
+      mockChatStore.listRoomMembers.mockReturnValue([
+        { roomId: "room-1", agentId: "agent-a", role: "member", addedAt: "2026-01-01" },
+      ]);
+      mockAgentStore.listAgents.mockResolvedValue([
+        {
+          id: "agent-a",
+          name: "Alpha",
+          role: "executor",
+          runtimeConfig: { model: "anthropic/claude-sonnet-4-5", runtimeHint: "openclaw" },
+        },
+      ]);
+      mockAgentStore.getAgent.mockResolvedValue({
+        id: "agent-a",
+        name: "Alpha",
+        role: "executor",
+        runtimeConfig: { model: "anthropic/claude-sonnet-4-5", runtimeHint: "openclaw" },
+      });
+
+      const createResolvedSession = vi.fn().mockResolvedValue({
+        session: {
+          prompt: vi.fn().mockResolvedValue(undefined),
+          dispose: vi.fn(),
+          state: {
+            messages: [{ role: "assistant", content: "Room reply" }],
+          },
+        },
+      });
+      __setCreateResolvedAgentSession(createResolvedSession as any);
+
+      const manager = new ChatManager(mockChatStore as any, "/tmp", mockAgentStore as any);
+      await manager.sendRoomMessage("room-1", "hello @Alpha");
+
+      expect(createResolvedSession).toHaveBeenCalledWith(expect.objectContaining({
+        sessionPurpose: "heartbeat",
+        pluginRunner: undefined,
+        runtimeHint: "openclaw",
+        cwd: "/tmp",
+        systemPrompt: expect.any(String),
+        tools: "coding",
+        defaultProvider: "anthropic",
+        defaultModelId: "claude-sonnet-4-5",
+      }));
+      expect(createResolvedSession.mock.calls[0]?.[0]).not.toHaveProperty("createFnAgentArgs");
+      expect(createResolvedSession.mock.calls[0]?.[0]).not.toHaveProperty("resolvedProvider");
+      expect(createResolvedSession.mock.calls[0]?.[0]).not.toHaveProperty("resolvedModel");
+    });
+
     it("throws surfaced error when all room responders fail to reply", async () => {
       mockChatStore.listRoomMembers.mockReturnValue([
         { roomId: "room-1", agentId: "agent-a", role: "member", addedAt: "2026-01-01" },

packages/dashboard/src/chat.ts

@@ -1015,18 +1015,32 @@ export class ChatManager {
       input.content,
     ].join("\n\n");
 
+    const responderRuntimeModel = extractRuntimeModel(input.responder.runtimeConfig);
+    const effectiveModelProvider = input.modelProvider ?? responderRuntimeModel.provider;
+    const effectiveModelId = input.modelId ?? responderRuntimeModel.modelId;
+    const chatModelSettings = await this.getChatModelSettings();
+    const allowFallback = !(input.modelProvider && input.modelId)
+      && !(responderRuntimeModel.provider && responderRuntimeModel.modelId);
+
     const resolvedSession = await createResolvedAgentSession({
-      createFnAgent,
+      sessionPurpose: "heartbeat",
-      resolvedProvider: input.modelProvider,
+      pluginRunner: this.pluginRunner,
-      resolvedModel: input.modelId,
+      runtimeHint: extractRuntimeHint(input.responder.runtimeConfig),
-      defaultModelProvider: input.modelProvider,
+      cwd: this.rootDir,
-      defaultModelId: input.modelId,
+      systemPrompt,
-      createFnAgentArgs: {
+      tools: "coding",
-        rootDir: this.rootDir,
+      ...(effectiveModelProvider && effectiveModelId
-        modelProvider: input.modelProvider,
+        ? {
-        modelId: input.modelId,
+            defaultProvider: effectiveModelProvider,
-        systemPrompt,
+            defaultModelId: effectiveModelId,
-      },
+          }
+        : {}),
+      ...(allowFallback && chatModelSettings.fallbackProvider && chatModelSettings.fallbackModelId
+        ? {
+            fallbackProvider: chatModelSettings.fallbackProvider,
+            fallbackModelId: chatModelSettings.fallbackModelId,
+          }
+        : {}),
     });
 
     try {