Startup commands frequently don't run on launch (panes processed before PTY session is ready; background workspace never connects) #14

Summary

Per-pane startup commands frequently don't run when a workspace launches — intermittently for a single workspace, and almost always for the second workspace when two have launchOnStartup: true. On Windows the delivery rate I measured was only ~11% of panes on cold start.

I instrumented this fairly thoroughly (replaced startup commands with marker-file writes to measure per-pane delivery objectively, and captured the plugin's own console.log output from the renderer via the Chrome DevTools Protocol). There are three independent root causes, all timing/lifecycle related.

Environment

• TabbySpaces 0.2.7
• Tabby 1.0.2xx, Windows 11
• Profiles in use: clink, cmd, and PowerShell (default)
• Two workspaces with launchOnStartup: true, 6 panes total, each running a claude --rc "…" startup command

Steps to reproduce

1. Create two workspaces, each with multiple panes and a startupCommand, both launchOnStartup: true.
2. Start Tabby (cold).
3. Observe: many panes never execute their startup command. The second workspace's panes fail almost every time.

Root causes (with evidence)

1. Pane discovery is a single 300 ms shot.
StartupCommandService.onTabOpened() does setTimeout(() => this.processChildTabs(tab), 300) and calls getAllTabs() exactly once. If the split panes aren't constructed yet at 300 ms, getAllTabs() returns 0 and every command for that workspace is silently skipped — no retry.
Observed log: Found child tabs: 0.

2. The command is sent before the PTY session exists.
In processTerminalTab() the code checks terminalTab.session?.output$. At processing time the session is usually still null, so it takes the else branch and blind-fires setTimeout(sendCommand, 500) into a shell that isn't ready yet → the typed input is dropped (clink/conpty in particular drop input typed during shell init).
Observed log: No session.output$, falling back to timeout for every pane, followed by sends that never land.

3. Background-workspace panes never connect their session.
When two launchOnStartup workspaces open, only the active tab initializes its PTYs. The workspace that ends up in the background never gets a session at all, so there is nothing to send to.
Observed log: every background pane ends in a permanent "no session" state.

(Side note: the cwd-not-applied reports in #10/#12 may share root cause #2 — the pane isn't actually ready when the plugin acts on it.)

Proposed fix

Three coordinated changes (I have a working implementation and ~100% delivery after applying all three; happy to open a PR):

• src/services/startupCommand.service.ts — poll for panes. Replace the single 300 ms processChildTabs call with a short re-scan loop that processes panes as they appear and stops only when all pending commands are handled (or a sane cap). Fixes Welcome to TabbySpaces Discussions! #1.
• src/services/startupCommand.service.ts — wait for real readiness. Poll until session.output$ actually exists, then wait for the shell to be ready before sendInput. The most robust readiness signal I found is prompt detection: watch output$, strip ANSI, and fire once the output ends in a prompt char (> / $ / # / ❯), with an output-settle timeout only as a fallback. This replaces the blind 500 ms / first-output heuristic. Fixes The title and color set on Workspace Editor can be shown on tabs #2.
• src/providers/toolbar.provider.ts — serialize startup launches. Open launchOnStartup workspaces one at a time, keeping each foreground until its sessions are connected and its commands sent, then open the next. Fixes Release v0.2.0 #3.

A cleaner long-term option

The fundamental fragility is typing the command into the terminal after the prompt appears. The fully race-free approach is to pass the command via the shell's own launch arguments instead — e.g. cmd /k "<cmd>", pwsh -NoExit -Command "<cmd>", bash -c '<cmd>; exec bash' — so the shell runs it itself when it's ready. That removes the timing heuristics and the need to serialize launches. (clink makes the cmd case a bit trickier since it's already injected via args.)

Measured impact of the typing-based fix above: ~11% → 100% pane delivery across cold starts on Windows (clink/cmd/PowerShell), including under load.

Happy to submit a PR if this direction sounds good.