fix(server): keep a provider-side model switch across reload

A model_changed event from the provider updated runtimeInfo.model but
left config.model at the creation-time value. Reload and daemon restart
resume from config.model, so the resumed session was switched back to
the old model. model_changed now writes config.model, as
thinking_option_changed already does for config.thinkingOptionId.

Co-authored-by: Edo Sulaiman <edosulai@icloud.com>

packages/app/src/agent-stream/presentation.test.ts

@@ -210,6 +210,17 @@ describe("stream presentation through installed plugins", () => {
     expect(result.head).toMatchObject([{ text: "```ts\nconst a = 1;\n\nconst b = 2;" }]);
   });
 
+  // Codex streams a line break and the next line's indent as their own chunks.
+  it("keeps a line break when a chunk ends in the next line's indent", () => {
+    const harness = streamHarness();
+    harness.send(assistant("```mermaid\nflowchart TD\n    A[Start] --> B[Review]\n"));
+    harness.send(assistant("   "));
+    const result = harness.send(assistant(" B --> C[Finish]\n```"));
+    expect(result.head).toMatchObject([
+      { text: "```mermaid\nflowchart TD\n    A[Start] --> B[Review]\n    B --> C[Finish]\n```" },
+    ]);
+  });
+
   // One rendering path: a fetched message is the same block group as a streamed one,
   // which is what lets find, scroll-to-message and history reveal address it by id.
   // A link reference definition stays with the paragraph that uses it, so the split

packages/app/src/agent-stream/presentation.ts

@@ -112,8 +112,10 @@ export function createStreamPresentation() {
       const index = prefix.length + offset;
       let blockText = text;
       if (offset === textBlocks.length - 1) {
-        const trailingNewlines = /\n+$/.exec(item.text)?.[0] ?? "";
-        blockText += trailingNewlines;
+        // The split drops trailing blank lines, including a line break followed only
+        // by the next line's indent. Keep them so the next append continues that line.
+        const trailingBlankLines = /\n\s*$/.exec(item.text)?.[0] ?? "";
+        blockText += trailingBlankLines;
       }
       const existing = previous?.[index];
       const id = `${item.id}:block:${index}`;

packages/server/src/server/agent/agent-manager.test.ts

@@ -5066,6 +5066,42 @@ test("session config drift events update state through the stream channel", asyn
   expect(streams.map((event) => event.type)).toEqual([]);
 });
 
+test("provider-side model switch survives reload and daemon restart", async () => {
+  const workdir = mkdtempSync(join(tmpdir(), "agent-manager-provider-model-switch-"));
+  const storage = new AgentStorage(join(workdir, "agents"), logger);
+  let capturedSession: TestAgentSession | null = null;
+  class ModelSwitchClient extends TestAgentClient {
+    override async createSession(config: AgentSessionConfig): Promise<AgentSession> {
+      capturedSession = new TestAgentSession(config);
+      return capturedSession;
+    }
+  }
+  const client = new ModelSwitchClient();
+  const manager = new AgentManager({
+    clients: { codex: client },
+    registry: storage,
+    logger,
+    idFactory: () => "00000000-0000-4000-8000-000000000134",
+  });
+
+  const snapshot = await manager.createAgent(
+    { provider: "codex", cwd: workdir, model: "gpt-5.2-codex" },
+    undefined,
+    { workspaceId: undefined },
+  );
+  capturedSession!.pushEvent({
+    type: "model_changed",
+    provider: "codex",
+    runtimeInfo: { provider: "codex", sessionId: capturedSession!.id, model: "gpt-5.4" },
+  });
+  await manager.flush();
+
+  await manager.reloadAgentSession(snapshot.id);
+  expect(client.resumeOverrides.at(-1)?.model).toBe("gpt-5.4");
+  expect((await storage.get(snapshot.id))?.config?.model).toBe("gpt-5.4");
+  rmSync(workdir, { recursive: true, force: true });
+});
+
 test("setLabels merges and persists labels", async () => {
   const workdir = mkdtempSync(join(tmpdir(), "agent-manager-set-labels-"));
   const storagePath = join(workdir, "agents");

packages/server/src/server/agent/agent-manager.ts

@@ -4310,6 +4310,7 @@ export class AgentManager {
         return undefined;
       case "model_changed":
         agent.runtimeInfo = event.runtimeInfo;
+        agent.config.model = event.runtimeInfo.model ?? agent.config.model;
         if (!agent.persistence && event.runtimeInfo.sessionId) {
           agent.persistence = attachPersistenceCwd(
             { provider: agent.provider, sessionId: event.runtimeInfo.sessionId },