fix(attach): build the CLI command before creating the tmux session

changelog.d/fixed-372.md

@@ -0,0 +1 @@
+- `pluk attach` now validates the CLI command and arguments before creating the tmux session, so a bad `--cli-args` (e.g. an unterminated quote) is reported as a usage error (exit 2) instead of leaving an orphaned session with pipe-pane attached.

src/attach.ts

@@ -337,11 +337,6 @@ export function attach(opts: AttachOptions): void {
   log(`tmux session "${session}" exists: ${sessionExists}`);
 
   if (!sessionExists) {
-    console.error(`Creating tmux session: ${session}`);
-    log(`execFile: tmux new-session -d -s ${shellQuote(session)} -c ${shellQuote(workDir)}`);
-    tmuxNewSession(session, workDir);
-    wirePipePane();
-
     let fullCmd = buildCliCommand(cliCmd, opts.cliArgs);
     if (opts.dangerouslySkipPermissions) {
       const dangerFlag = resolveDangerousFlag(cli);
@@ -355,6 +350,11 @@ export function attach(opts: AttachOptions): void {
         console.error(`Warning: --dangerous has no known auto-approve flag for cli=${cli}; starting without it`);
       }
     }
+    console.error(`Creating tmux session: ${session}`);
+    log(`execFile: tmux new-session -d -s ${shellQuote(session)} -c ${shellQuote(workDir)}`);
+    tmuxNewSession(session, workDir);
+    wirePipePane();
+
     console.error(`Starting ${cli}: ${fullCmd}`);
     const sendArgs = ['send-keys', '-t', exactTarget(session), '--', fullCmd, 'Enter'];
     log(`execFile: tmux ${sendArgs.map(shellQuote).join(' ')}`);

src/cli.ts

@@ -8,7 +8,7 @@ import { PLUK_EVENT_TYPES, type PlukEventType } from './event.js';
 import { listAvailableCLIs, bundledPatternsDir, getPatterns, hasAnyPattern, BUILTIN_PATTERNS } from './patterns.js';
 import { discoverSessions } from './sessions.js';
 import { resolveRunDir, rotateLogFileIfNeeded, validateSessionName } from './run-dir.js';
-import { attach } from './attach.js';
+import { attach, splitShellWords } from './attach.js';
 import { send } from './send.js';
 import { ANSI_RED, ANSI_GREEN, ANSI_CYAN, ANSI_DIM, ANSI_BOLD, ANSI_RESET, paintStderr, paintStdout } from './ansi.js';
 import { packageVersion } from './version.js';
@@ -242,6 +242,17 @@ function cmdAttach(args: string[]): void {
     process.exit(2);
   }
 
+  for (const flag of ['command', 'cli-args']) {
+    const value = flags[flag];
+    if (value === undefined) continue;
+    try {
+      splitShellWords(value);
+    } catch (err) {
+      console.error(`${paintStderr(ANSI_RED, 'Error:')} --${flag}: ${(err as Error).message}`);
+      process.exit(2);
+    }
+  }
+
   if (flags['rationguard'] !== 'true') {
     for (const flag of ['rebuttal', 'rationguard-bin']) {
       if (flags[flag] !== undefined) {

test/attach-branch-gaps.test.js

@@ -301,3 +301,24 @@ test('--dir sets the tmux new-session working directory', () => {
   assert.equal(code, 0);
   assert.match(stubs.log('tmux'), new RegExp(`new-session -d -s agent-wd -c ${workDir}`));
 });
+
+test('attach() builds the CLI command before new-session so a bad --cli-args leaves no tmux session (#372)', () => {
+  // cli.js pre-validates --cli-args, so the CLI-level test cannot tell whether
+  // attach() itself still orders buildCliCommand() before tmux new-session.
+  // Call attach() directly to pin that ordering: has-session is the only tmux
+  // call allowed before the throw, and no new-session/pipe-pane may follow.
+  const stubs = makeStubs({ which: ['tmux', 'pluk'] });
+  const runDir = makeRunDir();
+  const script = `import { attach } from ${JSON.stringify(ATTACH)};
+attach({ session: 'agent-badargs', runDir: ${JSON.stringify(runDir)}, noOpen: true, cliArgs: "--model 'unterminated" });`;
+  const res = spawnSync(process.execPath, ['--input-type=module', '-e', script], {
+    encoding: 'utf-8',
+    timeout: 15000,
+    env: { ...process.env, PATH: `${stubs.dir}:${process.env.PATH}` },
+  });
+  assert.notEqual(res.status, 0, 'attach() must throw on an unterminated quote');
+  assert.match(res.stderr, /Unterminated quote in command arguments/);
+  const tmuxCalls = stubs.log('tmux').trim().split('\n').filter(Boolean);
+  assert.deepEqual(tmuxCalls, ['has-session -t =agent-badargs:'],
+    'only the existence probe may run before the command is validated');
+});

test/attach-orchestration.test.js

@@ -185,6 +185,17 @@ test('fresh session wires pipe-pane before send-keys so start-up output is captu
   assert.ok(pipePane < startCli, 'pipe-pane must precede the send-keys that starts the CLI');
 });
 
+test('attach rejects unterminated quote in --cli-args before creating tmux session', () => {
+  const stubs = makeStubs({ which: ['tmux', 'pluk'] });
+  const { code, stderr } = runAttach([
+    'bad-args', `--run-dir=${makeRunDir()}`, '--no-open',
+    "--cli-args=--model 'unterminated",
+  ], stubs);
+  assert.equal(code, 2);
+  assert.match(stderr, /Unterminated quote/);
+  assert.equal(stubs.log('tmux'), '', 'validation must precede all tmux calls');
+});
+
 // --- existing-session path ---------------------------------------------------------
 
 test('attach to an existing session skips create/send-keys and warns about --dangerous', () => {