🤖 feat: fast-forward to latest origin on workspace creation (#800)

Fetch and fast-forward merge origin/<trunk> when creating workspaces.
Failures are logged but never block workspace creation.

_Generated with `mux`_

Author: ibetitsmike

src/node/runtime/LocalRuntime.ts

@@ -365,6 +365,9 @@ export class LocalRuntime implements Runtime {
 
       initLogger.logStep("Worktree created successfully");
 
+      // Pull latest from origin (best-effort, non-blocking on failure)
+      await this.pullLatestFromOrigin(workspacePath, trunkBranch, initLogger);
+
       return { success: true, workspacePath };
     } catch (error) {
       return {
@@ -374,6 +377,45 @@ export class LocalRuntime implements Runtime {
     }
   }
 
+  /**
+   * Fetch and rebase on latest origin/<trunkBranch>
+   * Best-effort operation - logs status but doesn't fail workspace creation
+   */
+  private async pullLatestFromOrigin(
+    workspacePath: string,
+    trunkBranch: string,
+    initLogger: InitLogger
+  ): Promise<void> {
+    try {
+      initLogger.logStep(`Fetching latest from origin/${trunkBranch}...`);
+
+      // Fetch the trunk branch from origin
+      using fetchProc = execAsync(`git -C "${workspacePath}" fetch origin "${trunkBranch}"`);
+      await fetchProc.result;
+
+      initLogger.logStep("Fast-forward merging...");
+
+      // Attempt fast-forward merge from origin/<trunkBranch>
+      try {
+        using mergeProc = execAsync(
+          `git -C "${workspacePath}" merge --ff-only "origin/${trunkBranch}"`
+        );
+        await mergeProc.result;
+        initLogger.logStep("Fast-forwarded to latest origin successfully");
+      } catch (mergeError) {
+        // Fast-forward not possible (diverged branches) - just warn
+        const errorMsg = getErrorMessage(mergeError);
+        initLogger.logStderr(`Note: Fast-forward skipped (${errorMsg}), using local branch state`);
+      }
+    } catch (error) {
+      // Fetch failed - log and continue (common for repos without remote)
+      const errorMsg = getErrorMessage(error);
+      initLogger.logStderr(
+        `Note: Could not fetch from origin (${errorMsg}), using local branch state`
+      );
+    }
+  }
+
   async initWorkspace(params: WorkspaceInitParams): Promise<WorkspaceInitResult> {
     const { projectPath, workspacePath, initLogger } = params;
 

src/node/runtime/SSHRuntime.ts

@@ -906,7 +906,10 @@ export class SSHRuntime implements Runtime {
       }
       initLogger.logStep("Branch checked out successfully");
 
-      // 3. Run .mux/init hook if it exists
+      // 3. Pull latest from origin (best-effort, non-blocking on failure)
+      await this.pullLatestFromOrigin(workspacePath, trunkBranch, initLogger, abortSignal);
+
+      // 4. Run .mux/init hook if it exists
       // Note: runInitHook calls logComplete() internally if hook exists
       const hookExists = await checkInitHookExists(projectPath);
       if (hookExists) {
@@ -928,6 +931,68 @@ export class SSHRuntime implements Runtime {
     }
   }
 
+  /**
+   * Fetch and rebase on latest origin/<trunkBranch> on remote
+   * Best-effort operation - logs status but doesn't fail workspace initialization
+   */
+  private async pullLatestFromOrigin(
+    workspacePath: string,
+    trunkBranch: string,
+    initLogger: InitLogger,
+    abortSignal?: AbortSignal
+  ): Promise<void> {
+    try {
+      initLogger.logStep(`Fetching latest from origin/${trunkBranch}...`);
+
+      // Fetch the trunk branch from origin
+      const fetchCmd = `git fetch origin ${shescape.quote(trunkBranch)}`;
+      const fetchStream = await this.exec(fetchCmd, {
+        cwd: workspacePath,
+        timeout: 120, // 2 minutes for network operation
+        abortSignal,
+      });
+
+      const fetchExitCode = await fetchStream.exitCode;
+      if (fetchExitCode !== 0) {
+        const fetchStderr = await streamToString(fetchStream.stderr);
+        initLogger.logStderr(
+          `Note: Could not fetch from origin (${fetchStderr}), using local branch state`
+        );
+        return;
+      }
+
+      initLogger.logStep("Fast-forward merging...");
+
+      // Attempt fast-forward merge from origin/<trunkBranch>
+      const mergeCmd = `git merge --ff-only origin/${shescape.quote(trunkBranch)}`;
+      const mergeStream = await this.exec(mergeCmd, {
+        cwd: workspacePath,
+        timeout: 60, // 1 minute for fast-forward merge
+        abortSignal,
+      });
+
+      const [mergeStderr, mergeExitCode] = await Promise.all([
+        streamToString(mergeStream.stderr),
+        mergeStream.exitCode,
+      ]);
+
+      if (mergeExitCode !== 0) {
+        // Fast-forward not possible (diverged branches) - just warn
+        initLogger.logStderr(
+          `Note: Fast-forward skipped (${mergeStderr || "branches diverged"}), using local branch state`
+        );
+      } else {
+        initLogger.logStep("Fast-forwarded to latest origin successfully");
+      }
+    } catch (error) {
+      // Non-fatal: log and continue
+      const errorMsg = getErrorMessage(error);
+      initLogger.logStderr(
+        `Note: Could not fetch from origin (${errorMsg}), using local branch state`
+      );
+    }
+  }
+
   async renameWorkspace(
     projectPath: string,
     oldName: string,

tests/ipcMain/initWorkspace.test.ts

@@ -174,8 +174,10 @@ describeIntegration("IpcMain workspace init hook integration tests", () => {
         expect(outputLines).toContain("Installing dependencies...");
         expect(outputLines).toContain("Build complete!");
 
-        expect(errorEvents.length).toBe(1);
-        expect(errorEvents[0].line).toBe("Warning: deprecated package");
+        // Should have at least the hook's stderr message
+        // (may also have pull-latest notes if fetch/rebase fails, which is expected)
+        const hookErrorEvent = errorEvents.find((e) => e.line === "Warning: deprecated package");
+        expect(hookErrorEvent).toBeDefined();
 
         // Last event should be end with exitCode 0
         const finalEvent = initEvents[initEvents.length - 1];