feat: Parallelize task startup and session creation (#958)

- Agent session: Run fetchMcpToolMetadata, getModelConfigOptions and getAvailableSlashCommands in parallel. Make trySetModel fire-and-forget. Same pattern for resumeSession
- Workspace setup: Parallelize loadConfig + buildWorkspaceEnv in local mode (worktree mode already did this)
- Reconnect: Batch config option restoration with Promise.allSettled instead of sequential awaits
- Task creation saga: Start folder registration in parallel with task creation for new tasks

Author: charlesvien

apps/twig/src/main/services/workspace/service.ts

@@ -376,21 +376,19 @@ export class WorkspaceService extends TypedEventEmitter<WorkspaceServiceEvents>
       }
       foldersStore.set("taskAssociations", associations);
 
-      // Load config and run scripts from main repo
-      const { config } = await loadConfig(
-        folderPath,
-        path.basename(folderPath),
-      );
+      // Load config and build env in parallel
+      const [{ config }, workspaceEnv] = await Promise.all([
+        loadConfig(folderPath, path.basename(folderPath)),
+        buildWorkspaceEnv({
+          taskId,
+          folderPath,
+          worktreePath: null,
+          worktreeName: null,
+          mode,
+        }),
+      ]);
       let terminalSessionIds: string[] = [];
 
-      const workspaceEnv = await buildWorkspaceEnv({
-        taskId,
-        folderPath,
-        worktreePath: null,
-        worktreeName: null,
-        mode,
-      });
-
       // Run init scripts
       const initScripts = normalizeScripts(config?.scripts?.init);
       if (initScripts.length > 0) {

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

@@ -63,7 +63,7 @@ interface AuthCredentials {
   client: ReturnType<typeof useAuthStore.getState>["client"];
 }
 
-interface ConnectParams {
+export interface ConnectParams {
   task: Task;
   repoPath: string;
   initialPrompt?: ContentBlock[];
@@ -179,17 +179,18 @@ export class SessionService {
       }
 
       if (latestRun?.id && latestRun?.log_url) {
-        const workspaceResult = await trpcVanilla.workspace.verify.query({
-          taskId,
-        });
+        // Start workspace verify and log fetch in parallel
+        const [workspaceResult, logResult] = await Promise.all([
+          trpcVanilla.workspace.verify.query({ taskId }),
+          this.fetchSessionLogs(latestRun.log_url),
+        ]);
 
         if (!workspaceResult.exists) {
           log.warn("Workspace no longer exists, showing error state", {
             taskId,
             missingPath: workspaceResult.missingPath,
           });
-          const { rawEntries } = await this.fetchSessionLogs(latestRun.log_url);
-          const events = convertStoredEntriesToEvents(rawEntries);
+          const events = convertStoredEntriesToEvents(logResult.rawEntries);
 
           const session = this.createBaseSession(
             latestRun.id,
@@ -206,29 +207,42 @@ export class SessionService {
           sessionStoreSetters.setSession(session);
           return;
         }
-      }
 
-      if (!getIsOnline()) {
-        log.info("Skipping connection attempt - offline", { taskId });
-        const taskRunId = latestRun?.id ?? `offline-${taskId}`;
-        const session = this.createBaseSession(taskRunId, taskId, taskTitle);
-        session.status = "disconnected";
-        session.errorMessage =
-          "No internet connection. Connect when you're back online.";
-        sessionStoreSetters.setSession(session);
-        return;
-      }
+        if (!getIsOnline()) {
+          log.info("Skipping connection attempt - offline", { taskId });
+          const session = this.createBaseSession(
+            latestRun.id,
+            taskId,
+            taskTitle,
+          );
+          session.status = "disconnected";
+          session.errorMessage =
+            "No internet connection. Connect when you're back online.";
+          sessionStoreSetters.setSession(session);
+          return;
+        }
 
-      if (latestRun?.id && latestRun?.log_url) {
         await this.reconnectToLocalSession(
           taskId,
           latestRun.id,
           taskTitle,
           latestRun.log_url,
           repoPath,
           auth,
+          logResult,
         );
       } else {
+        if (!getIsOnline()) {
+          log.info("Skipping connection attempt - offline", { taskId });
+          const taskRunId = latestRun?.id ?? `offline-${taskId}`;
+          const session = this.createBaseSession(taskRunId, taskId, taskTitle);
+          session.status = "disconnected";
+          session.errorMessage =
+            "No internet connection. Connect when you're back online.";
+          sessionStoreSetters.setSession(session);
+          return;
+        }
+
         await this.createNewLocalSession(
           taskId,
           taskTitle,
@@ -271,9 +285,14 @@ export class SessionService {
     logUrl: string,
     repoPath: string,
     auth: AuthCredentials,
+    prefetchedLogs?: {
+      rawEntries: StoredLogEntry[];
+      sessionId?: string;
+      adapter?: Adapter;
+    },
   ): Promise<void> {
     const { rawEntries, sessionId, adapter } =
-      await this.fetchSessionLogs(logUrl);
+      prefetchedLogs ?? (await this.fetchSessionLogs(logUrl));
     const events = convertStoredEntriesToEvents(rawEntries);
 
     // Resolve adapter from logs or persisted store
@@ -340,26 +359,28 @@ export class SessionService {
           setPersistedConfigOptions(taskRunId, configOptions);
         }
 
-        // Restore persisted config options to server
+        // Restore persisted config options to server in parallel
         if (persistedConfigOptions) {
-          for (const opt of persistedConfigOptions) {
-            try {
-              await trpcVanilla.agent.setConfigOption.mutate({
-                sessionId: taskRunId,
-                configId: opt.id,
-                value: opt.currentValue,
-              });
-            } catch (error) {
-              log.warn(
-                "Failed to restore persisted config option after reconnect",
-                {
-                  taskId,
+          await Promise.all(
+            persistedConfigOptions.map((opt) =>
+              trpcVanilla.agent.setConfigOption
+                .mutate({
+                  sessionId: taskRunId,
                   configId: opt.id,
-                  error,
-                },
-              );
-            }
-          }
+                  value: opt.currentValue,
+                })
+                .catch((error) => {
+                  log.warn(
+                    "Failed to restore persisted config option after reconnect",
+                    {
+                      taskId,
+                      configId: opt.id,
+                      error,
+                    },
+                  );
+                }),
+            ),
+          );
         }
       } else {
         log.warn("Reconnect returned null, falling back to new session", {
@@ -512,25 +533,33 @@ export class SessionService {
       execution_type: "local",
     });
 
-    // Set the model - use passed model if provided, otherwise use store's effective model
+    // Set model and reasoning level in parallel
     const preferredModel =
       model ?? useModelsStore.getState().getEffectiveModel();
+    const configPromises: Promise<void>[] = [];
     if (preferredModel) {
-      await this.setSessionConfigOptionByCategory(
-        taskId,
-        "model",
-        preferredModel,
+      configPromises.push(
+        this.setSessionConfigOptionByCategory(
+          taskId,
+          "model",
+          preferredModel,
+        ).catch((err) => log.warn("Failed to set model", { taskId, err })),
       );
     }
-
-    // Set reasoning level if provided (e.g., from Codex adapter's preview session)
     if (reasoningLevel) {
-      await this.setSessionConfigOptionByCategory(
-        taskId,
-        "thought_level",
-        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);

apps/twig/src/renderer/sagas/task/task-creation.ts

@@ -1,5 +1,8 @@
 import { buildPromptBlocks } from "@features/editor/utils/prompt-builder";
-import { getSessionService } from "@features/sessions/service/service";
+import {
+  type ConnectParams,
+  getSessionService,
+} from "@features/sessions/service/service";
 import { useWorkspaceStore } from "@features/workspace/stores/workspaceStore";
 import { Saga, type SagaLogger } from "@posthog/shared";
 import type { PostHogAPIClient } from "@renderer/api/posthogClient";
@@ -62,7 +65,14 @@ export class TaskCreationSaga extends Saga<
     input: TaskCreationInput,
   ): Promise<TaskCreationOutput> {
     // Step 1: Get or create task
+    // For new tasks, start folder registration in parallel with task creation
+    // since folder_registration only needs repoPath (from input), not task.id
     const taskId = input.taskId;
+    const folderPromise =
+      !taskId && input.repoPath
+        ? this.resolveFolder(input.repoPath)
+        : undefined;
+
     const task = taskId
       ? await this.readOnlyStep("fetch_task", () =>
           this.deps.posthogClient.getTask(taskId),
@@ -108,21 +118,12 @@ export class TaskCreationSaga extends Saga<
 
       const branch = input.branch ?? task.latest_run?.branch ?? null;
 
-      // Get or create folder registration first
-      const folder = await this.readOnlyStep(
-        "folder_registration",
-        async () => {
-          const folders = await trpcVanilla.folders.getFolders.query();
-          let existingFolder = folders.find((f) => f.path === repoPath);
-
-          if (!existingFolder) {
-            existingFolder = await trpcVanilla.folders.addFolder.mutate({
-              folderPath: repoPath,
-            });
-          }
-          return existingFolder;
-        },
-      );
+      // Use the pre-fetched folder if we started it in parallel, otherwise fetch now
+      const folder = folderPromise
+        ? await this.readOnlyStep("folder_registration", () => folderPromise)
+        : await this.readOnlyStep("folder_registration", () =>
+            this.resolveFolder(repoPath),
+          );
 
       const workspaceInfo = await this.step({
         name: "workspace_creation",
@@ -197,25 +198,22 @@ export class TaskCreationSaga extends Saga<
       await this.step({
         name: "agent_session",
         execute: async () => {
-          // For opening existing tasks, await to ensure chat history loads
-          // For creating new tasks, we can proceed without waiting
-          if (input.taskId) {
-            await getSessionService().connectToTask({
-              task,
-              repoPath: agentCwd ?? "",
-            });
-          } else {
-            // Don't await for create - allows faster navigation to task page
-            getSessionService().connectToTask({
-              task,
-              repoPath: agentCwd ?? "",
-              initialPrompt,
-              executionMode: input.executionMode,
-              adapter: input.adapter,
-              model: input.model,
-              reasoningLevel: input.reasoningLevel,
-            });
-          }
+          // Fire-and-forget for both open and create paths.
+          // The UI handles "connecting" state with a spinner (TaskLogsPanel),
+          // so we don't need to block the saga on the full reconnect chain.
+          const connectParams: ConnectParams = {
+            task,
+            repoPath: agentCwd ?? "",
+          };
+          if (initialPrompt) connectParams.initialPrompt = initialPrompt;
+          if (input.executionMode)
+            connectParams.executionMode = input.executionMode;
+          if (input.adapter) connectParams.adapter = input.adapter;
+          if (input.model) connectParams.model = input.model;
+          if (input.reasoningLevel)
+            connectParams.reasoningLevel = input.reasoningLevel;
+
+          getSessionService().connectToTask(connectParams);
           return { taskId: task.id };
         },
         rollback: async ({ taskId }) => {
@@ -246,6 +244,18 @@ export class TaskCreationSaga extends Saga<
     });
   }
 
+  private async resolveFolder(repoPath: string) {
+    const folders = await trpcVanilla.folders.getFolders.query();
+    let existingFolder = folders.find((f) => f.path === repoPath);
+
+    if (!existingFolder) {
+      existingFolder = await trpcVanilla.folders.addFolder.mutate({
+        folderPath: repoPath,
+      });
+    }
+    return existingFolder;
+  }
+
   private async createTask(input: TaskCreationInput): Promise<Task> {
     let repository = input.repository;