chenhg5/cc-connect · error

tmux: invalid strip_pattern %q: %w

Error message

tmux: invalid strip_pattern %q: %w

What it means

newTmuxSession compiles each entry of the strip_pattern list; an invalid entry aborts construction with 'tmux: invalid strip_pattern %q: %w', naming the offending pattern. Strip patterns remove noise from captured tmux pane output, and each must be a valid RE2 expression.

Source

Thrown at agent/tmux/session.go:54

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,
		pollInt:         pollInt,
		stripInputBlock: stripInputBlock,
		stripPatterns:   stripPats,
		events:          make(chan core.Event, 128),
		ctx:             sessCtx,
		cancel:          cancel,
	}
	s.alive.Store(true)
	return s, nil

View on GitHub (pinned to 4000b2338a)

Solutions

1. Identify the failing pattern from the %q value in the error message
2. Validate it against Go RE2 rules (no backreferences, no lookaround) and fix the syntax
3. Remove or correct the bad strip_pattern entry in config.toml and restart

Example fix

// before (config.toml): backreference unsupported in RE2
strip_patterns = ["\1"]
// after
strip_patterns = ["\x1b\[[0-9;]*m"]

for _, p := range cfg.StripPatterns {
    if _, err := regexp.Compile(p); err != nil {
        return fmt.Errorf("bad strip_pattern %q: %w", p, err)
    }
}

// Go
if err != nil && strings.Contains(err.Error(), "invalid strip_pattern") {
    slog.Error("remove or fix the listed strip_pattern", "err", err)
}

When it happens

Trigger: StartSession with a strip_pattern element that regexp.Compile rejects — same failure modes as prompt_pattern: unbalanced groups, bad escapes, PCRE-only constructs.

Common situations: A strip pattern copied from a sed/PCRE tutorial containing backreferences (\1) or lookahead; an empty-string entry in the list; a typo introduced while adding a new ANSI-stripping pattern.

Related errors

• tmux: invalid prompt_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/beed334847efdb1a. Report an issue: GitHub.