4 files changed, 135 insertions, 6 deletions
diff --git a/src/adapters/ws/logic.test.ts b/src/adapters/ws/logic.test.ts
index dd2b773..43cf8ff 100644
--- a/src/adapters/ws/logic.test.ts
+++ b/src/adapters/ws/logic.test.ts
@@ -232,6 +232,38 @@ describe("parseServerMessage", () => {
     });
   });
 
+  it("parses a conversation.open message with a persisted model", () => {
+    const data = JSON.stringify({
+      type: "conversation.open",
+      conversationId: "c1",
+      workspaceId: "w1",
+      model: "openrouter/stealth/ox-alpha",
+    });
+    const result = parseServerMessage(data);
+    expect(result).toEqual({
+      type: "conversation.open",
+      conversationId: "c1",
+      workspaceId: "w1",
+      model: "openrouter/stealth/ox-alpha",
+    });
+  });
+
+  it("omits the model when conversation.open carries a non-string/empty model", () => {
+    const result = parseServerMessage(
+      JSON.stringify({
+        type: "conversation.open",
+        conversationId: "c1",
+        workspaceId: "w1",
+        model: 42,
+      }),
+    );
+    expect(result).toEqual({
+      type: "conversation.open",
+      conversationId: "c1",
+      workspaceId: "w1",
+    });
+  });
+
   it("returns null for conversation.open with missing conversationId", () => {
     expect(
       parseServerMessage(JSON.stringify({ type: "conversation.open", workspaceId: "w1" })),
diff --git a/src/adapters/ws/logic.ts b/src/adapters/ws/logic.ts
index 03ef763..72a6338 100644
--- a/src/adapters/ws/logic.ts
+++ b/src/adapters/ws/logic.ts
@@ -116,10 +116,15 @@ export function parseServerMessage(data: string): WsServerMessage | null {
     case "conversation.open": {
       if (typeof parsed.conversationId !== "string") return null;
       if (typeof parsed.workspaceId !== "string") return null;
+      // Forward the persisted per-conversation model when the backend includes
+      // it, so a client can stamp the opened tab with the conversation's ACTUAL
+      // model (fix-toolcall-duplicate-keys plan Part 4).
+      const model = parsed.model;
       const msg: ConversationOpenMessage = {
         type: "conversation.open",
         conversationId: parsed.conversationId,
         workspaceId: parsed.workspaceId,
+        ...(typeof model === "string" && model.length > 0 ? { model } : {}),
       };
       return msg;
     }
diff --git a/src/app/store.svelte.ts b/src/app/store.svelte.ts
index 08a7cd8..52136ee 100644
--- a/src/app/store.svelte.ts
+++ b/src/app/store.svelte.ts
@@ -1077,15 +1077,20 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
    * stamped with the conversation's actual `workspaceId`, NOT the viewer's
    * currently active workspace.
    */
-  function openConversation(conversationId: string, workspaceId: string): void {
+  function openConversation(conversationId: string, workspaceId: string, model?: string): void {
     if (chatStores.has(conversationId)) return;
-    const store = createChatFor(conversationId, activeModel, workspaceId);
+    // Stamp the tab with the conversation's PERSISTED model when the open
+    // broadcast carries it (falling back to the current global selection) —
+    // never let the globally-active model overwrite a conversation's real one
+    // (fix-toolcall-duplicate-keys plan Part 4).
+    const tabModel = model ?? activeModel;
+    const store = createChatFor(conversationId, tabModel, workspaceId);
     chatStores.set(conversationId, store);
     void store.load();
     subscribeChat(conversationId);
     tabsStore.openTab({
       conversationId,
-      model: activeModel,
+      model: tabModel,
       title: "Conversation",
       workspaceId,
     });
@@ -1172,13 +1177,18 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
       const existingIds = new Set(chatStores.keys());
       for (const conv of data.conversations) {
         if (!existingIds.has(conv.id)) {
-          const store = createChatFor(conv.id, activeModel, conv.workspaceId);
+          // Stamp the tab with the conversation's PERSISTED model (when the
+          // list carries it) instead of the global active model — the fix for
+          // tabs showing/overwriting the wrong model
+          // (fix-toolcall-duplicate-keys plan Part 4).
+          const model = conv.model ?? activeModel;
+          const store = createChatFor(conv.id, model, conv.workspaceId);
           chatStores.set(conv.id, store);
           void store.load();
           subscribeChat(conv.id);
           tabsStore.openTab({
             conversationId: conv.id,
-            model: activeModel,
+            model,
             title: conv.title,
             workspaceId: conv.workspaceId,
           });
@@ -1218,7 +1228,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
     onMessage: handleServerMessage,
     onChat: handleChatMessage,
     onConversationOpen(msg: ConversationOpenMessage): void {
-      openConversation(msg.conversationId, msg.workspaceId);
+      openConversation(msg.conversationId, msg.workspaceId, msg.model);
     },
     onConversationStatusChanged(msg: ConversationStatusChangedMessage): void {
       const { conversationId, status, workspaceId } = msg;
diff --git a/src/app/store.test.ts b/src/app/store.test.ts
index c41efc2..f8b878a 100644
--- a/src/app/store.test.ts
+++ b/src/app/store.test.ts
@@ -799,6 +799,88 @@ describe("createAppStore", () => {
     store.dispose();
   });
 
+  it("fetchOpenConversations stamps tabs with the conversation's persisted model (not the global active model)", async () => {
+    const ws = fakeSocket();
+    const fetchImpl: typeof fetch = async (
+      input: string | URL | Request,
+      init?: RequestInit,
+    ): Promise<Response> => {
+      const url = typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
+      if (url.endsWith("/models")) {
+        return new Response(JSON.stringify({ models: ["opencode-1/deepseek-v4-flash"] }), {
+          status: 200,
+        });
+      }
+      // The authoritative open-conversation list — one conversation whose
+      // persisted model differs from the global activeModel.
+      if (url.includes("/conversations?status=")) {
+        return new Response(
+          JSON.stringify({
+            conversations: [
+              {
+                id: "conv-model",
+                createdAt: 1000,
+                lastActivityAt: 2000,
+                title: "Model conv",
+                status: "idle",
+                workspaceId: "default",
+                model: "openrouter/stealth/ox-alpha",
+              },
+            ],
+          }),
+          { status: 200 },
+        );
+      }
+      return new Response(JSON.stringify({ chunks: [], latestSeq: 0 }), { status: 200 });
+    };
+
+    const store = createAppStore({
+      socketFactory: () => ws,
+      fetchImpl,
+      localStorage: createFakeStorage(),
+    });
+    ws.resolveOpen();
+
+    // global activeModel is the default until anything changes it
+    expect(store.activeModel).toBe("opencode-1/deepseek-v4-flash");
+
+    // fetchOpenConversations (boot reconcile) opens the conversation's tab —
+    // stamped with the PERSISTED model from the list, not activeModel.
+    await vi.waitFor(() => {
+      const tab = store.tabs.find((t) => t.conversationId === "conv-model");
+      expect(tab?.model).toBe("openrouter/stealth/ox-alpha");
+    });
+
+    store.dispose();
+  });
+
+  it("conversation.open WS message carrying a model stamps the tab with it", async () => {
+    const ws = fakeSocket();
+    const store = createAppStore({
+      socketFactory: () => ws,
+      fetchImpl: fakeFetchImpl(),
+      localStorage: createFakeStorage(),
+    });
+    ws.resolveOpen();
+
+    // The user stays on their current (draft) tab; the backend broadcasts
+    // `conversation.open` with the conversation's persisted model.
+    ws.feedServerMessage({
+      type: "conversation.open",
+      conversationId: "conv-ws",
+      workspaceId: "default",
+      model: "openrouter/stealth/ox-alpha",
+    });
+
+    await vi.waitFor(() => {
+      const tab = store.tabs.find((t) => t.conversationId === "conv-ws");
+      expect(tab?.model).toBe("openrouter/stealth/ox-alpha");
+      expect(tab?.workspaceId).toBe("default");
+    });
+
+    store.dispose();
+  });
+
   it("chat.delta routes to the matching tab only", () => {
     const ws = fakeSocket();
     const store = createAppStore({