Fix tmux agent send bracketed paste submission

packages/agent-manager/src/__tests__/terminal/TtyWriter.test.ts

@@ -19,6 +19,7 @@ function mockExecFileSuccess(stdout = '') {
     mockedExecFile.mockImplementation((...args: unknown[]) => {
         const cb = args[args.length - 1] as (err: Error | null, result: { stdout: string }, stderr: string) => void;
         cb(null, { stdout }, '');
+        return { stdin: { end: vi.fn() } };
     });
 }
 
@@ -41,22 +42,36 @@ describe('TtyWriter', () => {
             tty: '/dev/ttys030',
         };
 
-        it('sends message and Enter as separate tmux send-keys calls', async () => {
+        it('pastes message in bracketed paste mode and sends Enter separately', async () => {
             mockExecFileSuccess();
+            const message = 'line 1\nline 2\n';
 
-            await TtyWriter.send(location, 'continue');
+            await TtyWriter.send(location, message);
 
-            expect(mockedExecFile).toHaveBeenCalledWith(
+            const loadArgs = mockedExecFile.mock.calls[0]?.[1] as string[];
+            const bufferName = loadArgs[2];
+            expect(bufferName).toMatch(/^ai-devkit-send-/);
+            expect(mockedExecFile).toHaveBeenNthCalledWith(
+                1,
                 'tmux',
-                ['send-keys', '-t', 'main:0.1', '-l', 'continue'],
+                ['load-buffer', '-b', bufferName, '-'],
                 expect.any(Function),
             );
-            expect(mockedExecFile).toHaveBeenCalledWith(
+            expect(mockedExecFile.mock.results[0]?.value.stdin.end)
+                .toHaveBeenCalledWith(message);
+            expect(mockedExecFile).toHaveBeenNthCalledWith(
+                2,
+                'tmux',
+                ['paste-buffer', '-t', 'main:0.1', '-b', bufferName, '-p', '-d'],
+                expect.any(Function),
+            );
+            expect(mockedExecFile).toHaveBeenNthCalledWith(
+                3,
                 'tmux',
                 ['send-keys', '-t', 'main:0.1', 'Enter'],
                 expect.any(Function),
             );
-            expect(mockedExecFile).toHaveBeenCalledTimes(2);
+            expect(mockedExecFile).toHaveBeenCalledTimes(3);
         });
 
         it('throws on tmux failure', async () => {

packages/agent-manager/src/terminal/TtyWriter.ts

@@ -39,16 +39,33 @@ export class TtyWriter {
     }
 
     private static async sendViaTmux(identifier: string, message: string): Promise<void> {
-        // Send text and Enter as two separate calls so that Enter arrives
-        // outside of bracketed paste mode. When the inner application (e.g.
-        // Claude Code) has bracketed paste enabled, tmux wraps the send-keys
-        // payload in paste brackets — if Enter is included, it gets swallowed
-        // as part of the paste instead of acting as a submit action.
-        await execFileAsync('tmux', ['send-keys', '-t', identifier, '-l', message]);
+        // Paste the message body using tmux bracketed paste, then send Enter as
+        // a separate key so the inner TUI treats it as submission rather than
+        // pasted content.
+        const bufferName = `ai-devkit-send-${process.pid}-${Date.now()}-${Math.random().toString(36).slice(2)}`;
+        await TtyWriter.execFileWithInput('tmux', ['load-buffer', '-b', bufferName, '-'], message);
+        await execFileAsync('tmux', ['paste-buffer', '-t', identifier, '-b', bufferName, '-p', '-d']);
         await new Promise((resolve) => setTimeout(resolve, 150));
         await execFileAsync('tmux', ['send-keys', '-t', identifier, 'Enter']);
     }
 
+    private static async execFileWithInput(command: string, args: string[], input: string): Promise<void> {
+        await new Promise<void>((resolve, reject) => {
+            const child = execFile(command, args, (error) => {
+                if (error) {
+                    reject(error);
+                    return;
+                }
+                resolve();
+            });
+            if (!child.stdin) {
+                reject(new Error(`Cannot write stdin to ${command}`));
+                return;
+            }
+            child.stdin.end(input);
+        });
+    }
+
     /**
      * Build an AppleScript that finds an iTerm2 session by TTY and runs a
      * command against it. The `sessionCommand` is inserted inside a