The Desktop's Update button hands off to the staged Tauri binary
(HERMES_HOME/hermes-setup.exe). That binary has no self-update path
(copy_self_to_hermes_home no-ops during --update), so every updater-side
fix only reaches users when a new installer is built, signed, and
published. In practice the published binary lags main by months and
users hit long-fixed bugs on every GUI update: the 2026-08-09 incident
chain was four distinct failures (stale install.ps1 cache resolver
pre-#67369, marker adoption pre-#74782, straggler teardown) all caused
by a June 4 binary running against an August repo.
This inverts ownership: scripts/desktop-update.ps1 lives in the repo
checkout, so every `hermes update` refreshes the code that drives the
NEXT update. Only PowerShell itself - an OS component - stays frozen.
Desktop side (apps/desktop/electron):
- resolveUpdateScriptHandoff() (updater-process.ts): returns the spawn
recipe when scripts/desktop-update.ps1 exists in the checkout;
Windows-only (POSIX updates in place via applyUpdatesPosixInApp);
null on old checkouts -> caller falls back to the staged binary path
completely unchanged.
- applyUpdates() prefers the script hand-off. The marker pre-write is
ALWAYS safe on this path - no stagedUpdaterSupportsPrewrittenMarker()
mtime heuristics - because hermes_cli/update_lock.py's UpdateLock
adopts a live marker held by a process ANCESTOR, and the script is
the `hermes update` child's parent. This closes the unguarded
marker-gap window that pre-#74782 binaries force today (the 23:56
failure in the incident: 'skipping marker pre-write: staged updater
predates self-adopt' -> renderer respawned a backend into the gap ->
update refused).
- CLI-installed users (no staged binary) now get the script hand-off
too instead of the manual `hermes update` card, when the script
exists.
Script (scripts/desktop-update.ps1): waits for the Desktop pid to exit
(bounded 30s), waits for the venv shim to unlock (mirrors the Rust
is_locked probe, bounded 20s), runs `hermes update --yes --gateway
--force --branch <ref>` from the CURRENT checkout with one retry for
the update-boundary class (skipped for exit 2), removes the marker on
every exit path, relaunches the Desktop. ASCII-only (the #67193
lesson), logs to logs/desktop-update-handoff.log.
Verification (real Windows box):
- apps/desktop: typecheck (3 projects) clean, eslint clean, vitest
updater-process.test.ts 12/12 (3 new resolver tests).
- Script E2E against a sandbox HERMES_HOME with a compiled fake
hermes.exe: correct argv (update --yes --gateway --force --branch
main), stale marker removed, exit code propagated (0 and 1 paths),
retry-once fires exactly once on failure, PS 5.1 parse + windows
footguns check clean.
- Contract E2E with the real UpdateLock: ancestor-owned marker adopted
(True), left in place on release, foreign live holder still refused.
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