chenhg5/cc-connect · error

tmux: invalid prompt_pattern %q: %w

Error message

tmux: invalid prompt_pattern %q: %w

What it means

newTmuxSession compiles the configured prompt_pattern as a regular expression. If regexp.Compile fails, the constructor cancels its context and returns 'tmux: invalid prompt_pattern %q: %w'. This is a fail-fast config validation error for the tmux agent's prompt-detection regex.

Source

Thrown at agent/tmux/session.go:45

	cancel          context.CancelFunc
	alive           atomic.Bool
	closeOnce       sync.Once

	mu              sync.Mutex
	pollCancel      context.CancelFunc
	baselineCapture string // full captureScrollback output at the time of the last Send()
}

func newTmuxSession(ctx context.Context, target, sessionID, promptPattern string, pollInt time.Duration, stripInputBlock bool, stripPatternStrs []string, workDir string) (*tmuxSession, error) {
	sessCtx, cancel := context.WithCancel(ctx)

	var pat *regexp.Regexp
	if promptPattern != "" {
		var err error
		pat, err = regexp.Compile(promptPattern)
		if err != nil {
			cancel()
			return nil, fmt.Errorf("tmux: invalid prompt_pattern %q: %w", promptPattern, err)
		}
	}

	var stripPats []*regexp.Regexp
	for _, s := range stripPatternStrs {
		re, err := regexp.Compile(s)
		if err != nil {
			cancel()
			return nil, fmt.Errorf("tmux: invalid strip_pattern %q: %w", s, err)
		}
		stripPats = append(stripPats, re)
	}

	s := &tmuxSession{
		target:          target,
		sessionID:       sessionID,
		workDir:         workDir,
		promptPat:       pat,

View on GitHub (pinned to 4000b2338a)

Solutions

1. Read the wrapped error for the exact character offset of the syntax problem
2. Test the pattern in Go RE2 (all Go regexp is RE2: no backreferences, no lookaround)
3. Fix prompt_pattern in config.toml — simplify or rewrite using RE2-compatible syntax

Example fix

// before (config.toml): lookbehind not supported by RE2
prompt_pattern = "(?<=\$ )$"
// after
prompt_pattern = "^\$ $"

// validate before constructing the session
if _, err := regexp.Compile(cfg.PromptPattern); err != nil {
    return fmt.Errorf("bad prompt_pattern: %w", err)
}

// Go
sess, err := agent.StartSession(ctx, opts)
if err != nil && strings.Contains(err.Error(), "invalid prompt_pattern") {
    slog.Error("fix prompt_pattern in config.toml (RE2 syntax)", "err", err)
}

When it happens

Trigger: Starting a tmux agent session (StartSession) with a prompt_pattern option that is not a valid RE2 expression — e.g. unbalanced parentheses, invalid escape like '\d' with a typo, or a trailing operator like 'a+'.*','+a'.

Common situations: User copies a PCRE-only pattern (lookbehind/lookahead, \d in wrong context) into config.toml; hand-edited regex with a missing bracket; pattern written for grep -P syntax rather than Go RE2.

Related errors

• tmux: invalid strip_pattern %q: %w
• tmux: 'session' option is required (name of the tmux session
• tmux: session %q does not exist and auto_create is disabled
• tmux: create session %q: %w
• cron project not found

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/a10df623f7b2b103. Report an issue: GitHub.