fix: Fix model selection lost during task creation (#1437)

Author: charlesvien

apps/code/src/main/services/agent/schemas.ts

@@ -49,6 +49,7 @@ export const startSessionInput = z.object({
   additionalDirectories: z.array(z.string()).optional(),
   customInstructions: z.string().max(2000).optional(),
   effort: effortLevelSchema.optional(),
+  model: z.string().optional(),
 });
 
 export type StartSessionInput = z.infer<typeof startSessionInput>;

apps/code/src/main/services/agent/service.ts

@@ -189,6 +189,8 @@ interface SessionConfig {
   customInstructions?: string;
   /** Effort level for Claude sessions */
   effort?: EffortLevel;
+  /** Model to use for the session (e.g. "claude-sonnet-4-6") */
+  model?: string;
 }
 
 interface ManagedSession {
@@ -465,6 +467,7 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
       permissionMode,
       customInstructions,
       effort,
+      model,
     } = config;
 
     // Preview sessions don't need a real repo — use a temp directory
@@ -638,6 +641,7 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
             sessionId: existingSessionId,
             systemPrompt,
             ...(permissionMode && { permissionMode }),
+            ...(model != null && { model }),
             claudeCode: {
               options: {
                 ...(additionalDirectories?.length && {
@@ -669,6 +673,7 @@ export class AgentService extends TypedEventEmitter<AgentServiceEvents> {
             taskRunId,
             systemPrompt,
             ...(permissionMode && { permissionMode }),
+            ...(model != null && { model }),
             claudeCode: {
               options: {
                 ...(additionalDirectories?.length && { additionalDirectories }),
@@ -1362,6 +1367,7 @@ For git operations while detached:
       customInstructions:
         "customInstructions" in params ? params.customInstructions : undefined,
       effort: "effort" in params ? params.effort : undefined,
+      model: "model" in params ? params.model : undefined,
     };
   }
 

apps/code/src/renderer/features/sessions/hooks/useSessionConnection.ts

@@ -86,28 +86,24 @@ export function useSessionConnection({
       return;
     }
 
-    connectingTasks.add(taskId);
-
-    const isNewSession = !task.latest_run?.id;
-    const hasInitialPrompt = isNewSession && task.description;
+    // New sessions (no latest_run) are handled by the task creation saga,
+    // which passes model/adapter/executionMode. Only reconnect existing ones here.
+    if (!task.latest_run?.id) return;
 
-    if (hasInitialPrompt) {
-      markActivity(task.id);
-    }
+    connectingTasks.add(taskId);
 
-    log.info("Connecting to task session", {
+    log.info("Reconnecting to existing task session", {
       taskId: task.id,
       hasLatestRun: !!task.latest_run,
       sessionStatus: session?.status ?? "none",
     });
 
+    markActivity(task.id);
+
     getSessionService()
       .connectToTask({
         task,
         repoPath,
-        initialPrompt: hasInitialPrompt
-          ? [{ type: "text", text: task.description }]
-          : undefined,
       })
       .finally(() => {
         connectingTasks.delete(taskId);

apps/code/src/renderer/features/sessions/service/service.ts

@@ -536,6 +536,7 @@ export class SessionService {
 
     const { customInstructions: startCustomInstructions } =
       useSettingsStore.getState();
+    const preferredModel = model ?? DEFAULT_GATEWAY_MODEL;
     const result = await trpcClient.agent.start.mutate({
       taskId,
       taskRunId: taskRun.id,
@@ -548,6 +549,7 @@ export class SessionService {
       effort: effortLevelSchema.safeParse(reasoningLevel).success
         ? (reasoningLevel as EffortLevel)
         : undefined,
+      model: preferredModel,
     });
 
     const session = this.createBaseSession(taskRun.id, taskId, taskTitle);
@@ -586,32 +588,6 @@ export class SessionService {
       adapter,
     });
 
-    const preferredModel = model ?? DEFAULT_GATEWAY_MODEL;
-    const configPromises: Promise<void>[] = [];
-    if (preferredModel) {
-      configPromises.push(
-        this.setSessionConfigOptionByCategory(
-          taskId,
-          "model",
-          preferredModel,
-        ).catch((err) => log.warn("Failed to set model", { taskId, err })),
-      );
-    }
-    if (reasoningLevel) {
-      configPromises.push(
-        this.setSessionConfigOptionByCategory(
-          taskId,
-          "thought_level",
-          reasoningLevel,
-        ).catch((err) =>
-          log.warn("Failed to set reasoning level", { taskId, err }),
-        ),
-      );
-    }
-    if (configPromises.length > 0) {
-      await Promise.all(configPromises);
-    }
-
     if (initialPrompt?.length) {
       await this.sendPrompt(taskId, initialPrompt);
     }

packages/agent/src/adapters/claude/claude-agent.ts

@@ -876,58 +876,92 @@ export class ClaudeAcpAgent extends BaseAcpAgent {
       { sessionId, taskId, taskRunId: meta?.taskRunId },
     );
 
-    try {
-      const result = await withTimeout(
-        q.initializationResult(),
-        SESSION_VALIDATION_TIMEOUT_MS,
-      );
-      if (result.result === "timeout") {
-        throw new Error(
-          `Session ${isResume ? (forkSession ? "fork" : "resumption") : "initialization"} timed out for sessionId=${sessionId}`,
+    if (isResume) {
+      // Resume must block on initialization to validate the session is still alive.
+      // For stale sessions this throws (e.g. "No conversation found").
+      try {
+        const result = await withTimeout(
+          q.initializationResult(),
+          SESSION_VALIDATION_TIMEOUT_MS,
         );
+        if (result.result === "timeout") {
+          throw new Error(
+            `Session ${forkSession ? "fork" : "resumption"} timed out for sessionId=${sessionId}`,
+          );
+        }
+      } catch (err) {
+        settingsManager.dispose();
+        if (
+          err instanceof Error &&
+          err.message === "Query closed before response received"
+        ) {
+          throw RequestError.resourceNotFound(sessionId);
+        }
+        this.logger.error(
+          forkSession ? "Session fork failed" : "Session resumption failed",
+          {
+            sessionId,
+            taskId,
+            taskRunId: meta?.taskRunId,
+            error: err instanceof Error ? err.message : String(err),
+          },
+        );
+        throw err;
       }
-    } catch (err) {
-      settingsManager.dispose();
-      if (
-        isResume &&
-        err instanceof Error &&
-        err.message === "Query closed before response received"
-      ) {
-        throw RequestError.resourceNotFound(sessionId);
-      }
-      this.logger.error(
-        isResume
-          ? forkSession
-            ? "Session fork failed"
-            : "Session resumption failed"
-          : "Session initialization failed",
-        {
+    }
+
+    // Kick off SDK initialization for new sessions so it runs concurrently
+    // with the model config fetch below (the gateway REST call is independent).
+    const initPromise = !isResume
+      ? withTimeout(q.initializationResult(), SESSION_VALIDATION_TIMEOUT_MS)
+      : undefined;
+
+    const [modelOptions] = await Promise.all([
+      this.getModelConfigOptions(
+        settingsManager.getSettings().model || meta?.model || undefined,
+      ),
+      ...(meta?.taskRunId
+        ? [
+            this.client.extNotification("_posthog/sdk_session", {
+              taskRunId: meta.taskRunId,
+              sessionId,
+              adapter: "claude",
+            }),
+          ]
+        : []),
+    ]);
+
+    if (initPromise) {
+      try {
+        const initResult = await initPromise;
+        if (initResult.result === "timeout") {
+          settingsManager.dispose();
+          throw new Error(
+            `Session initialization timed out for sessionId=${sessionId}`,
+          );
+        }
+      } catch (err) {
+        settingsManager.dispose();
+        this.logger.error("Session initialization failed", {
           sessionId,
           taskId,
           taskRunId: meta?.taskRunId,
           error: err instanceof Error ? err.message : String(err),
-        },
-      );
-      throw err;
-    }
-
-    if (meta?.taskRunId) {
-      await this.client.extNotification("_posthog/sdk_session", {
-        taskRunId: meta.taskRunId,
-        sessionId,
-        adapter: "claude",
-      });
+        });
+        throw err;
+      }
     }
 
-    // Resolve model: settings model takes priority, then gateway
     const settingsModel = settingsManager.getSettings().model;
-    const modelOptions = await this.getModelConfigOptions();
-    const resolvedModelId = settingsModel || modelOptions.currentModelId;
+    const metaModel = meta?.model;
+    const resolvedModelId =
+      settingsModel || metaModel || modelOptions.currentModelId;
     session.modelId = resolvedModelId;
     session.lastContextWindowSize =
       this.getContextWindowForModel(resolvedModelId);
 
     const resolvedSdkModel = toSdkModelId(resolvedModelId);
+
     if (!isResume && resolvedSdkModel !== DEFAULT_MODEL) {
       await this.session.query.setModel(resolvedSdkModel);
     }

packages/agent/src/adapters/claude/types.ts

@@ -108,6 +108,8 @@ export type NewSessionMeta = {
   persistence?: { taskId?: string; runId?: string; logUrl?: string };
   additionalRoots?: string[];
   allowedDomains?: string[];
+  /** Model ID to use for this session (e.g. "claude-sonnet-4-6") */
+  model?: string;
   claudeCode?: {
     options?: Options;
   };