[BUG] Cowork custom instructions: stale version served to new sessions

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Resume FR : depuis la mise a jour des instructions Cowork (v2.6 → v2.10) le 17/07/2026, les nouvelles conversations recoivent de maniere intermittente l’ancienne v2.6, alors que le champ des Reglages affiche bien la v2.10 sur les 3 machines. Test d’isolement du 18/07 (toutes les autres machines eteintes, champ re-enregistre) : 5 conversations neuves sur 5 ont recu la v2.6. Cause locale exclue par deux fouilles independantes — le chemin serveur qui alimente les sessions ressert une copie perimee. Rapport a coller sur support.claude.com.

Summary

Custom Cowork instructions (Settings field, injected as global CLAUDE.md into every new session) were updated from v2.6 (saved Jul 11, 2026) to v2.10 on Jul 17, 2026 ~18:00. Since then, new conversations intermittently receive the OLD v2.6 content — 13 of 16 new sessions (81.2%) — even though the Settings UI consistently shows v2.10 when reopened, on all devices. An isolation test excludes any client-side or multi-device cause: the read path that provisions new sessions appears to serve a stale cached copy server-side (cache invalidation failure). This is the account’s 5th occurrence of instruction-version desync since deploying versioned instructions.

Environment

Account: m.roux@atypik-studio.com

App: Claude Desktop, Cowork mode, macOS — main machine Mac Mini M4 Pro

Other devices on the account: MacBook Pro M1 (macOS), PC (Windows), iPhone, iPad

All times below: Europe/Paris, 2026

Expected vs actual

Expected: after saving new instructions in Settings, every subsequently created conversation receives the new content.

Actual: newly created conversations receive either the new v2.10 or the old v2.6, unpredictably, for 24+ hours after the update. Existing conversations keeping their original instructions is understood to be by design; this report concerns newly created conversations only.

Evidence 1 — per-session snapshots (injected CLAUDE.md found in local session dirs)

Source: ~/Library/Application Support/Claude/local-agent-mode-sessions/…/local_*/.claude/CLAUDE.md (each new session stores the instructions it received at creation; file mtime = session creation).

Jul 12–17 (daytime): all sessions v2.6 (normal — v2.10 not yet deployed)

Jul 17 18:04 → v2.10 · 18:08 → v2.6 · 18:17 → v2.10 · 19:17 → v2.6 · 20:11 → v2.6

Jul 18 07:06 → v2.6 · 10:26 → v2.6 · 11:35 → v2.6 · 11:44 → v2.10 · 11:50 → v2.6 · 11:55 → v2.6

Evidence 2 — no local source of the stale content

Two independent forensic sweeps of the main machine (Jul 18 morning, then Jul 18 midday) found NO local copy of the instructions text outside the per-session snapshots: app storages (IndexedDB, Local Storage, Session Storage, WebStorage, Partitions) all negative for the instructions text; no ~/.claude/CLAUDE.md. The content is therefore fetched from the server at conversation creation.

Evidence 3 — isolation test (Jul 18, 12:10–12:31)

ALL other devices powered off: MacBook Pro, PC, iPhone, iPad (nothing else could write to the account).

v2.10 re-saved in the Settings field on the sole remaining machine (Mac Mini) at ~12:10. The field displayed v2.10 before and after saving.

Five new conversations created at 12:16:49, 12:20:17, 12:23:23, 12:26:29, 12:30:50.

Result: all five received v2.6 (verified in the on-disk snapshots listed above).

Conclusion

The write path works (Settings stores v2.10; the UI reads it back correctly on all three computers, verified Jul 18). The read path that provisions new Cowork sessions serves a stale v2.6 copy that should have been invalidated on Jul 17 ~18:00. Client-side and cross-device causes are excluded by Evidence 2 and 3.

Additional observation

Markdown formatting of the pasted instructions (leading # heading marks, bold, italics) is stripped/flattened in the content injected into sessions, compared to the originally pasted text. Possibly related to how the field content is stored or transformed.

Impact

The user operates with versioned custom instructions across three machines; since Jul 17, 81.2% of new sessions (13/16) were provisioned with the outdated v2.6, silently reverting behavior and routing rules introduced in v2.7–v2.10.

What Should Happen?

After saving updated custom instructions (v2.10) in Cowork Settings, every newly created conversation should receive the v2.10 content. Instead, most new conversations (13/16 over 24h) still receive the previous v2.6, even though the Settings field correctly displays v2.10 when reopened on all devices

Error Messages/Logs

o error message — silent failure. Per-session snapshots of the injected instructions (from ~/Library/Application Support/Claude/local-agent-mode-sessions/.../local_*/.claude/CLAUDE.md, mtime = session creation, Europe/Paris):

Jul 17 18:04 -> v2.10 | 18:08 -> v2.6 | 18:17 -> v2.10 | 19:17 -> v2.6 | 20:11 -> v2.6
Jul 18 07:06 -> v2.6 | 10:26 -> v2.6 | 11:35 -> v2.6 | 11:44 -> v2.10 | 11:50 -> v2.6 | 11:55 -> v2.6
Isolation test Jul 18 (all other devices OFF, field re-saved at ~12:10): 12:16 -> v2.6 | 12:20 -> v2.6 | 12:23 -> v2.6 | 12:26 -> v2.6 | 12:30 -> v2.6

Steps to Reproduce

1. On an account with custom Cowork instructions saved in Settings, replace the content with a new version and save. Reopen the field to confirm the new version is displayed.
2. Power off every other device signed in to the account (other computers, phone, tablet) to exclude cross-device writes.
3. Re-save the Settings field once on the sole remaining machine.
4. Create 5 new conversations over ~15 minutes.
5. Check which instructions each new session received (ask the session, or inspect local_*/.claude/CLAUDE.md in local-agent-mode-sessions).

Expected: all sessions receive the new version. Actual: all 5 received the OLD version. Local forensic sweeps (app storages, ~/.claude) found no local copy of the stale text: the stale content comes from the server-side path that provisions new sessions. Settings UI shows the new version throughout, so the write path works; the session-provisioning read path serves a stale cached copy.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Desktop app 1.22209.0 (Cowork mode) — no CLI installed; bug concerns the desktop app's Cowork custom instructions provisioning

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

N/A — Claude Desktop app (Cowork mode), not the CLI