diff --git a/docs/adr/0019-session-start-hook-keeps-the-apm-install-current.md b/docs/adr/0019-session-start-hook-keeps-the-apm-install-current.md
index 9a9ca61..34e44d1 100644
--- a/docs/adr/0019-session-start-hook-keeps-the-apm-install-current.md
+++ b/docs/adr/0019-session-start-hook-keeps-the-apm-install-current.md
@@ -115,8 +115,9 @@ A test pins the reference.
 > emptied it. `tests/test-apm-current-hook.sh` still pins the literal string.
 
 **Session startup gets slower when the install is stale.** Measured: ~0.7 s for the `apm outdated`
-check when everything is current, ~10.4 s when six packages are behind and the refresh runs. The
-hook declares `timeout: 380` to cover a cold multi-package fetch. That number is not free-standing:
+check when everything is current, ~10.4 s when six packages are behind and the refresh runs
+(re-measured 2026-09-16: ~24–26 s for the same six-behind refresh, warm, on a LAN remote — still
+well inside the budget below). The hook declares `timeout: 380` to cover a cold multi-package fetch. That number is not free-standing:
 the script imposes its own `timeout 60` on `apm outdated` and `timeout 300` on `apm update`, so the
 host-side timeout has to exceed their sum or the host kills the hook mid-update and leaves
 `.claude/skills/` half-deployed with no notice emitted. An earlier revision declared `320`, which
@@ -145,6 +146,21 @@ to plural-only fails it.
 deploy until this change is merged and `apm update` has run once against the new default branch.
 Until then the repo has the mechanism in source and not in effect.
 
+**On a feature branch, the refresh installs `main`, not the branch.** Added 2026-09-16, after it
+happened. The dependencies resolve against the remote default branch, so a session opened on a
+branch that changes `plugins/` loads `main`'s content, refreshed or not — the branch's own edits
+are never live until merged. Two visible effects follow. Content the branch *removes* comes back in
+the deployed install: on `docs/simplification-audit` a refresh redeployed `main`'s `skill-audit`
+and `agent-audit` over the branch's merged `factory-audit`, and re-materialised `main`'s
+`plugins/bin/.mcp.json` into `apm_modules/`, so the gitignored root `.mcp.json` regained the
+`obsidian` server the branch deleted — invisible to `git status`. And the rewritten
+`apm.lock.yaml` records `main`'s commit, so on a branch it should be discarded
+(`git checkout -- apm.lock.yaml`, then `apm install` to bring the deployed tree back in line with
+the lock, or `apm pack --check-clean` refuses to run), not committed. Skipping the refresh off the
+default branch was considered and rejected: it would not make the branch live, only freeze the
+session on an older `main` — the silent staleness this ADR exists to prevent. Both effects end when
+the branch merges; apm removes a server that is no longer declared on its next update.
+
 **`.claude/settings.json` stops being `{"hooks": {}}`.** apm merges the hook into it and tracks
 ownership in a `.claude/apm-hooks.json` sidecar, with the script copied to
 `.claude/hooks/<pkg>/`. The sidecar and the script directory are gitignored install output; the