diff --git a/packages/plugins/runtime-tmux/src/__tests__/index.test.ts b/packages/plugins/runtime-tmux/src/__tests__/index.test.ts
index fbacba905..8c8722540 100644
--- a/packages/plugins/runtime-tmux/src/__tests__/index.test.ts
+++ b/packages/plugins/runtime-tmux/src/__tests__/index.test.ts
@@ -238,7 +238,7 @@ describe("runtime.create()", () => {
         launchCommand: "bad-command",
         environment: {},
       }),
-    ).rejects.toThrow('Failed to send launch command to session "fail-session"');
+    ).rejects.toThrow('Failed to configure or launch session "fail-session"');
 
     // Verify kill-session was called for cleanup
     expect(mockExecFileCustom).toHaveBeenCalledWith(
@@ -248,6 +248,33 @@ describe("runtime.create()", () => {
     );
   });
 
+  it("cleans up session if set-option fails", async () => {
+    const runtime = create();
+
+    // 1: new-session succeeds
+    mockTmuxSuccess();
+    // 2: set-option fails (e.g. tmux command timeout on a slow host)
+    mockTmuxError("set-option timed out");
+    // 3: kill-session (cleanup attempt)
+    mockTmuxSuccess();
+
+    await expect(
+      runtime.create({
+        sessionId: "setopt-fail",
+        workspacePath: "/tmp/ws",
+        launchCommand: "echo hi",
+        environment: {},
+      }),
+    ).rejects.toThrow('Failed to configure or launch session "setopt-fail"');
+
+    // kill-session must run so we don't leave an orphaned tmux session
+    expect(mockExecFileCustom).toHaveBeenCalledWith(
+      "tmux",
+      ["kill-session", "-t", "setopt-fail"],
+      expectedTmuxOptions,
+    );
+  });
+
   it("rejects invalid session IDs with special characters", async () => {
     const runtime = create();
 
diff --git a/packages/plugins/runtime-tmux/src/index.ts b/packages/plugins/runtime-tmux/src/index.ts
index 57a67ce1a..9b05a2583 100644
--- a/packages/plugins/runtime-tmux/src/index.ts
+++ b/packages/plugins/runtime-tmux/src/index.ts
@@ -66,11 +66,6 @@ export function create(): Runtime {
       // Create tmux session in detached mode
       await tmux("new-session", "-d", "-s", sessionName, "-c", config.workspacePath, ...envArgs);
 
-      // Hide the tmux status bar — sessions are embedded in the web terminal,
-      // and the green bar at the bottom is visual noise (and racy with the
-      // web layer's own set-option call, which only fires on WebSocket connect).
-      await tmux("set-option", "-t", sessionName, "status", "off");
-
       // Re-export PATH inside the launch script. macOS zsh runs path_helper
       // during shell startup which resets PATH, wiping entries set via tmux -e.
       // Including the export in the script file (not send-keys) avoids terminal
@@ -83,10 +78,16 @@ export function create(): Runtime {
         launchCommand = `export PATH=$(printf '%s' ${JSON.stringify(pathValue)})\n${launchCommand}`;
       }
 
-      // Send the launch command — clean up the session if this fails.
-      // Use a temp script for long commands so the pane shows a short
+      // Configure the session and send the launch command — kill the session
+      // if any of these fail so we don't leave an orphaned tmux process.
+      // Use a temp script for long launch commands so the pane shows a short
       // invocation instead of a pasted wall of shell.
       try {
+        // Hide the tmux status bar — sessions are embedded in the web terminal,
+        // and the green bar at the bottom is visual noise (and racy with the
+        // web layer's own set-option call, which only fires on WebSocket connect).
+        await tmux("set-option", "-t", sessionName, "status", "off");
+
         if (launchCommand.length > 200) {
           const invocation = writeLaunchScript(launchCommand);
           await tmux("send-keys", "-t", sessionName, "-l", invocation);
@@ -102,7 +103,7 @@ export function create(): Runtime {
           // Best-effort cleanup
         }
         const msg = err instanceof Error ? err.message : String(err);
-        throw new Error(`Failed to send launch command to session "${sessionName}": ${msg}`, {
+        throw new Error(`Failed to configure or launch session "${sessionName}": ${msg}`, {
           cause: err,
         });
       }