Cause (Documented platform behavior): Windows refuses to spawn the program (code with no standard name → EUNKNOWN); during reinstall the binary is briefly unexecutable.
Fix status: released_fix (fixed in v2.1.212 (PowerShell 7 / direct start fallback))
Workaround (not a fix): claude daemon run in a foreground terminal (service lives only while that terminal is open).
Other error fragments:
- Couldn't start the session — EUNKNOWN: unknown error, uv_spawn
- Couldn't start the background service — spawn background service: EACCES: permission denied, posix_spawn
Evidence (public sources, summarized; not reproduced by this contributor):
- https://code.claude.com/docs/en/errors.md (official_docs, unknown, documented_behavior): Sections 'EUNKNOWN when starting a background session' and 'EACCES when starting a background session' describe messages, causes (restriction policy, npm reinstall window) and version history.
Search phrasings: claude --bg EUNKNOWN uv_spawn windows; claude code background service applocker; claude daemon status couldn't reach background service
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Background sessions fail to start.
- Context
- Product: Claude Code Component: Background service / agent view (claude --bg, /background) Operation: Starting a background session Affected versions: PowerShell 7 fallback since v2.1.212 (earlier only Windows PowerShell 5.1) Environment: Windows with software restriction policies; npm installs being updated Trigger: Group Policy/AppLocker blocks PowerShell 5.1 or the Claude executable; npm install -g (manual or auto-updater) replacing the binary at that moment.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- Couldn't reach the background service (spawn background service: EUNKNOWN: unknown error, uv_spawn) — run 'claude daemon status'
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [Claude Code background sessions] 'Couldn't reach the background service (spawn background service: EUNKNOWN: unknown error, uv_spawn)' on Windows (AppLocker/Group Policy) or 'EACCES: pe
Recommended action: Upgrade to v2.1.212+; if an npm install is running wait and retry; otherwise ask admins to allow the Claude executable; workaround on older versions: run 'claude daemon run' in a separate terminal.
Option: Upgrade and retry after install [evidence: official_recommended_action]
Applies when: Windows / npm installs
Steps:
1. Update to >= v2.1.212
2. Retry after npm install finishes
3. Ask admin to allowlist the executable if persistent
Expected: Background service starts
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- f57e0b94-a74d-4a8f-b26b-cea3091a9c76
- Proposed action
- Recommended action: Upgrade to v2.1.212+; if an npm install is running wait and retry; otherwise ask admins to allow the Claude executable; workaround on older versions: run 'claude daemon run' in a separate terminal. Option: Upgrade and retry after install [evidence: official_recommended_action] Applies when: Windows / npm installs Steps: 1. Update to >= v2.1.212 2. Retry after npm install finishes 3. Ask admin to allowlist the executable if persistent Expected: Background service starts
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
Page 1 · 1 children total
Sources and related records
No source relations recorded.