fix(spawn): bootstrap tmux session when cold-starting with --new-window by namastex888 · Pull Request #1168 · automagik-si/genie

namastex888 · 2026-04-17T21:40:25Z

Summary

genie spawn <agent> --session <name> --new-window failed silently when the target tmux session didn't exist yet — tmux rejects new-window -t <session>: with can't find session.
This is the cold-start path used by the TUI (Nav.tsx → spawnAgent → genie spawn … --new-window) to launch an offline agent. The TUI invokes the child with stdio: 'ignore', so the error was swallowed and the user saw nothing happen when clicking "start" on an offline agent.
Patch checks has-session first; if the session doesn't exist, bootstraps with new-session -d -s <name> (creates session + first pane in one call). Existing behaviour preserved when the session is already present.

Repro (before fix)

$ tmux -L genie new-window -d -t 'khal-os:' -P -F '#{pane_id}' 'echo'
can't find session: khal-os
exit=1

After the fix, the same cold-start path takes the new-session branch and the pane is created correctly.

Test plan

`bun run typecheck` — clean
`bun run lint` — no new warnings in `createTmuxPane` (12 pre-existing complexity warnings unchanged)
`bun test` — 2501 pass / 0 fail
Manual: launch TUI, click start on an offline agent whose tmux session doesn't exist, confirm a new window/session appears

`genie spawn <agent> --session <name> --new-window` failed silently when the target tmux session did not yet exist. `createTmuxPane` ran `tmux new-window -t <session>:` which tmux rejects with "can't find session" when the session has not been created. This is the cold-start path the TUI uses to launch an offline agent (Nav.tsx spawnAgent → `genie spawn … --new-window`). Because the TUI fires the child with `stdio: 'ignore'`, the error was swallowed and the user saw nothing happen. Check `has-session` first; if the session does not exist, bootstrap with `new-session -d -s <name>` which creates the session and its first pane in one call. Existing behaviour is preserved when the session is already present. Reproduced before fix: $ tmux -L genie new-window -d -t 'khal-os:' -P -F '#{pane_id}' 'echo' can't find session: khal-os exit=1

coderabbitai · 2026-04-17T21:40:31Z

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chatgpt-codex-connector · 2026-04-17T21:45:18Z

-    const cmd = `${tmuxPrefix}new-window -a -d -t ${shellQuote(`${session}:`)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`;
+    let sessionExists = false;
+    try {
+      execSync(`${tmuxPrefix}has-session -t ${shellQuote(`=${session}`)}`, { stdio: 'ignore' });


Use real session name for cold-start existence check

The new has-session probe treats session as a tmux session name, but in this code path session can come from teamWindow.windowId (from ensureTeamWindow), which is a window id (@...), not a session identifier. That makes has-session -t '=…' mis-targeted and pushes --new-window spawns into the new-session -s ... fallback with an invalid/wrong name, causing failures or spawning into the wrong session when --session is not provided. Resolve the actual session name (not window id) before the existence check.

Useful? React with 👍 / 👎.

chatgpt-codex-connector · 2026-04-17T21:45:18Z

+    const cmd = sessionExists
+      ? `${tmuxPrefix}new-window -a -d -t ${shellQuote(`${session}:`)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`
+      : `${tmuxPrefix}new-session -d -s ${shellQuote(session)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`;


Make session bootstrap atomic under concurrent spawns

This introduces a check-then-create sequence (has-session followed by new-session) without handling duplicate session on create. If two genie spawn ... --new-window commands cold-start the same missing session concurrently, both can observe "missing" and one will fail on new-session, aborting that spawn. The tmux helpers elsewhere already avoid this TOCTOU by treating duplicate session as success; this branch should do the same.

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gemini-code-assist

Code Review

This pull request updates the tmux pane creation logic to handle cold-start scenarios by checking for session existence and using new-session when necessary. The review identifies several issues, including incorrect session naming using window IDs, redundant session checks when a window is already present, and the omission of standard UTF-8 environment variables, providing a comprehensive refactoring suggestion to address these concerns.

gemini-code-assist · 2026-04-17T21:45:20Z

    const session = ctx.sessionOverride ?? teamWindow?.windowId?.split(':')[0] ?? ctx.validated.team;
    const cwdFlag = ctx.cwd ? ` -c ${shellQuote(ctx.cwd)}` : '';
-    const cmd = `${tmuxPrefix}new-window -a -d -t ${shellQuote(`${session}:`)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`;
+    let sessionExists = false;
+    try {
+      execSync(`${tmuxPrefix}has-session -t ${shellQuote(`=${session}`)}`, { stdio: 'ignore' });
+      sessionExists = true;
+    } catch {
+      sessionExists = false;
+    }
+    const cmd = sessionExists
+      ? `${tmuxPrefix}new-window -a -d -t ${shellQuote(`${session}:`)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`
+      : `${tmuxPrefix}new-session -d -s ${shellQuote(session)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`;


The logic for deriving the session name and checking its existence has a few issues:

Window ID vs Session Name: teamWindow.windowId is a tmux window ID (e.g., @0). The expression teamWindow?.windowId?.split(':')[0] results in @0. Using this as a session name in has-session -t '=@0' will fail (as it looks for a session literally named @0), and new-session -s '@0' will then attempt to create a session with that ID as a name, which is likely unintended and will fail if the session already exists under its real name.

Redundant Check: If teamWindow is present, the session is already guaranteed to exist because resolveSpawnTeamWindow (which calls ensureTeamWindow) was successful. The has-session check can be skipped in this case.

Redundant Assignment: The sessionExists = false in the catch block is redundant as it's already initialized to false.

Consistency: Other session creation logic in src/lib/tmux.ts sets UTF-8 environment variables (-e LC_ALL=C.UTF-8 -e LANG=C.UTF-8). It's recommended to include them here as well for a consistent environment in cold-started sessions.

Suggested refactoring to use the team name as a fallback and leverage teamWindow presence:

Suggested change

const session = ctx.sessionOverride ?? teamWindow?.windowId?.split(':')[0] ?? ctx.validated.team;

const cwdFlag = ctx.cwd ? ` -c ${shellQuote(ctx.cwd)}` : '';

const cmd = `${tmuxPrefix}new-window -a -d -t ${shellQuote(`${session}:`)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`;

let sessionExists = false;

try {

execSync(`${tmuxPrefix}has-session -t ${shellQuote(`=${session}`)}`, { stdio: 'ignore' });

sessionExists = true;

} catch {

sessionExists = false;

}

const cmd = sessionExists

? `${tmuxPrefix}new-window -a -d -t ${shellQuote(`${session}:`)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`

: `${tmuxPrefix}new-session -d -s ${shellQuote(session)}${cwdFlag} -P -F '#{pane_id}' ${tmuxCommand}`;

const sessionName = ctx.sessionOverride ?? ctx.validated.team;

const cwdFlag = ctx.cwd ? " -c " + shellQuote(ctx.cwd) : "";

let sessionExists = !!teamWindow;

if (!sessionExists) {

try {

execSync(tmuxPrefix + "has-session -t " + shellQuote("=" + sessionName), { stdio: "ignore" });

sessionExists = true;

} catch {

// sessionExists remains false

}

}

const target = teamWindow ? teamWindow.windowId : sessionName + ":";

const cmd = sessionExists

? tmuxPrefix + "new-window -a -d -t " + shellQuote(target) + cwdFlag + " -P -F '#{pane_id}' " + tmuxCommand

: tmuxPrefix + "new-session -d -s " + shellQuote(sessionName) + " -e LC_ALL=C.UTF-8 -e LANG=C.UTF-8" + cwdFlag + " -P -F '#{pane_id}' " + tmuxCommand;

chatgpt-codex-connector Bot reviewed Apr 17, 2026

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gemini-code-assist Bot reviewed Apr 17, 2026

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namastex888 merged commit ef90931 into dev Apr 17, 2026
6 checks passed

This was referenced Apr 17, 2026

fix(spawn): fall back to on-disk team config when GENIE_TEAM unresolved #1170

Merged

fix(spawn): eliminate cruft windows for isolated-session --new-window #1173

Merged

automagik-genie mentioned this pull request Apr 18, 2026

release: spawn/team resolver hardening + TUI CLI-symmetric surfaces (v4.260417.1 → v4.260418.1) #1162

Closed

4 of 6 tasks

automagik-genie deleted the fix/tui-cold-start-session-bootstrap branch September 25, 2026 04:51

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fix(spawn): bootstrap tmux session when cold-starting with --new-window - #1168

fix(spawn): bootstrap tmux session when cold-starting with --new-window#1168
namastex888 merged 1 commit into
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namastex888 commented Apr 17, 2026

Summary

Repro (before fix)

Test plan

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