plat 421

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PLAT-421 — Every confined Muse launch ended at once: the sweep prelude could not find muse

Coordination	Value
State	fixed on main (provider a3ecd73, pinned here); deployed to Excellence and RTS once the deploy below is done
Severity	P1 (Muse unusable in Code on Excellence after the deploy that carried PLAT-417)
Date	2026-10-04
Owner	coding-agent-bridge
Related	PLAT-417 (Muse fixes that introduced the prelude)

Problem

After the Excellence deploy of 2026-10-04 (agents-c584adde) every Muse message in Code failed with muse tmux session "mlp-muse-product-..." died while waiting for muse TUI to settle, about 185 ms after the start. Muse itself is unchanged (1.4.2, installed 2026-10-01) and runs fine inside the slot's sandbox.

Cause

A trace of the live launch (execve only) showed the chain bash -ilc → sudo -n -u slot03 slotctl exec → video-studio-landlock-runner → env GIT_CONFIG_... sh -c <sweep script> muse-sweep <tmp> muse --trust-workspace .... The sweep's exec "$@" looked for a bare muse in sudo's secure PATH (/usr/local/sbin ... /bin:/snap/bin, not /srv/agents/tools/bin), found nothing, and the tmux pane command exited, so the session never existed. A second effect: the Landlock launcher grants the CLI's install folder by looking at the first real argument, which was now sh. The failure message ("died while waiting for the TUI") hid a plain command-not-found.

Fix

• musePreludeArgv passes the path this process resolves for muse (the service's PATH has the install folder); unchanged when it cannot be found.
• clisandbox.executableDirs looks past a leading sh -c <script> <name> <arg> prelude. Tests: musecli_prelude_path_test.go (PATH without the muse folder), clisandbox/executable_dirs_test.go.

Left

• Verify on Excellence and RTS after the deploy: a Muse message in Code answers; New chat then an immediate message works.
• The error text still says "died while waiting for muse TUI to settle" for any launch failure; including the first line of last-launch.stderr would have named the cause at once.
• A temporary forwarding script in /usr/local/bin/muse was considered and not installed.