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perf: launch sessions as initial tmux process to skip pane-ready poll #389

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perf: launch sessions as initial tmux process to skip pane-ready poll #389

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6 changes: 3 additions & 3 deletions internal/session/instance.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1923,7 +1923,7 @@ func (i *Instance) Start() error {
// Build tmux option overrides from config (e.g. allow-passthrough = "all").
// Sandbox sessions also get remain-on-exit for dead-pane detection.
i.tmuxSession.OptionOverrides = i.buildTmuxOptionOverrides()
i.tmuxSession.RunCommandAsInitialProcess = i.IsSandboxed()
i.tmuxSession.RunCommandAsInitialProcess = i.IsSandboxed() || i.Tool != "shell"

// Start the tmux session
if err := i.tmuxSession.Start(command); err != nil {
Expand Down Expand Up @@ -2039,7 +2039,7 @@ func (i *Instance) StartWithMessage(message string) error {
// Build tmux option overrides from config (e.g. allow-passthrough = "all").
// Sandbox sessions also get remain-on-exit for dead-pane detection.
i.tmuxSession.OptionOverrides = i.buildTmuxOptionOverrides()
i.tmuxSession.RunCommandAsInitialProcess = i.IsSandboxed()
i.tmuxSession.RunCommandAsInitialProcess = i.IsSandboxed() || i.Tool != "shell"

// Start the tmux session
if err := i.tmuxSession.Start(command); err != nil {
Expand Down Expand Up @@ -4042,7 +4042,7 @@ func (i *Instance) Restart() error {
// Build tmux option overrides from config (e.g. allow-passthrough = "all").
// Sandbox sessions also get remain-on-exit for dead-pane detection.
i.tmuxSession.OptionOverrides = i.buildTmuxOptionOverrides()
i.tmuxSession.RunCommandAsInitialProcess = i.IsSandboxed()
i.tmuxSession.RunCommandAsInitialProcess = i.IsSandboxed() || i.Tool != "shell"

mcpLog.Debug("restart_starting_new_session", slog.String("command", command))

Expand Down
15 changes: 10 additions & 5 deletions internal/tmux/tmux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1181,13 +1181,18 @@ func (s *Session) Start(command string) error {
workDir = os.Getenv("HOME")
}

// Create new tmux session in detached mode.
// Sandbox sessions launch command as the pane process for dead-pane restart.
// Non-sandbox sessions keep the legacy shell+send flow.
// Create new tmux session in detached mode with the command as the initial
// process. This avoids the slow shell-wait-sendkeys path (~2s pane ready poll).
// Commands containing bash-specific syntax are wrapped for fish compatibility.
startWithInitialProcess := command != "" && s.RunCommandAsInitialProcess
args := []string{"new-session", "-d", "-s", s.Name, "-c", workDir}
if startWithInitialProcess {
args = append(args, command)
cmdToStart := command
if strings.Contains(command, "$(") || strings.Contains(command, "session_id=") {
escapedCmd := strings.ReplaceAll(command, "'", "'\"'\"'")
cmdToStart = fmt.Sprintf("bash -c '%s'", escapedCmd)
}
Comment on lines +1191 to +1194
args = append(args, cmdToStart)
Comment on lines +1190 to +1195
Comment on lines +1184 to +1195
}
cmd := exec.Command("tmux", args...)
output, err := cmd.CombinedOutput()
Expand Down Expand Up @@ -1288,7 +1293,7 @@ func (s *Session) Start(command string) error {
}
}

// Legacy behavior for non-sandbox sessions: start shell first, then send command.
// Fallback: if RunCommandAsInitialProcess is false, send command via send-keys.
if command != "" && !startWithInitialProcess {
cmdToSend := command
// Commands containing bash-specific syntax must be wrapped for fish users.
Expand Down
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