- src/web/settings-writer.ts:110: export assertSettingsWritable(), the writer's own read-for-write rule run on its own
- src/web/routes/case-routes.ts:1860: an admin's rename checks settings.json before it ends any session or moves the folder, and answers 409 CONFLICT with the writer's message (placed before the session-starting check, so nothing is awaited between it and the lock)
- test/routes/case-rename-routes.test.ts:314: the torn-file pin now expects 409 CONFLICT (no stoppedSessions, like the other pre-checks)
- test/routes/case-rename-routes.test.ts:331: new test, a live session with stopSessions and a torn file: 409 CONFLICT, cleanupSession not called
- docs/api-reference.md: the Settings paragraph says an admin's rename answers this refusal as 409 CONFLICT before ending sessions
- src/hooks-config.ts:1161, src/prompt-cache-keepwarm.ts:341: comments describe the atomic writer, not an in-place rewrite
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Quick-start saved lastUsedCase with an un-awaited, non-atomic read-modify-write, and the settings PUT, model config, case order, case rename, Ralph start and the boot tunnel reset each ran their own. Two overlapping truncate-then-write calls left one write's bytes over the tail of the other (the CI flake in test/quick-start.test.ts), and most writers then read the torn file as {} and wrote back only its own keys, erasing the rest of the user's settings.
All of them now go through one writer that runs one change at a time, replaces the file atomically, and refuses (409 CONFLICT) to overwrite a file that does not parse.
The rename lock is checked once, in the Session constructor, but a session
reaches the server's map (where the rename route builds its list of open
sessions) only later, after the create awaits the owner's layout lock and a
fresh settings read (and, for POST /api/sessions, inferLocalCaseName). A
rename in that gap neither listed nor stopped the session, moved the folder,
and the create then registered a session whose pane starts with
`cd "<old path>"`, skipping the 409 requiresStop / stopSessions guarantee.
- case-rename.ts keeps a record of sessions constructed but not yet
registered (`noteCaseSessionStarting` / `caseSessionSettled` /
`isCaseSessionStarting`), with a 30 s TTL for one that never registers
(a failed create, a one-shot prompt), swept on every note and check.
- The Session constructor records itself (local sessions only, as the
route ignores remote ones); registerSessionWithLayout()'s register
callback, the boot-restore registration and stop() settle it.
- The rename route answers 409 CONFLICT with renameCode BUSY ("A session is
starting in this case") for a folder move while one is recorded at or
under the folder. The check runs in the same tick that takes the lock, so
every interleaving is either refused here or by the constructor. An
alias-only rename is not refused.
A create whose path was validated before the move but whose Session is
constructed after it is still the ordinary check-then-use race of any
create path; CLAUDE.md now says so instead of "nothing starts mid-move".
Tests: unit (record, settle, stop, TTL), route (BUSY, then requiresStop once
registered; alias-only unaffected) and an end-to-end WebServer test that
holds the create between constructor and registration (it fails without
the route check: the folder moves under the session).
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude history merges, never overwriting, into a project directory a deleted case of the new name left behind, instead of staying orphaned under the old key.
The free-target pre-check also refuses a dangling symlink (lstat), so stopSessions no longer ends sessions before a 409 EXISTS.
The rename dialog says stopped sessions are closed (their tabs go away) and, after a failed rename, how many were already closed.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Restore settings.json (caseOrder, lastUsedCase) when linked-cases.json cannot be written, with the rollback test extended
List Claude Code's per-project ~/.claude.json entry as not migrated in Core-Concepts.md and CLAUDE.md
Say in the 500 that the folder is now at the new path when moving it back fails
Describe the rename dialog's folder checkbox in Core-Concepts.md, carry stoppedSessions on errors, count 5 case SSE events
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Only an admin's rename touches the server-wide settings.json, which is now
written before linked-cases.json with the registry restored on failure. The
Resume list follows a renamed folder, the owner's default session group is
carried over, remote sessions are never listed or stopped, errorCode maps
EXISTS and BUSY, and the unmigrated items are documented.
Codeman maintainer