CLAUDE_CODE_SYNC_SESSION_REFS Environment Variable / Claude Code v2.1.210

What

A new environment variable CLAUDE_CODE_SYNC_SESSION_REFS enables session-reference syncing when set alongside a CLAUDE_CODE_SESSION_ID that passes validation.

Details

Session-reference syncing is activated only when CLAUDE_CODE_SYNC_SESSION_REFS is truthy AND CLAUDE_CODE_SESSION_ID passes the format validator (Kae(e) !== e — the session ID must produce a different canonical form when normalized).
When active, both skills sync and plugin sync bypass the regular account-based sync APIs (oto() / nto()) and instead fetch a pre-assigned manifest from GET /worker/skill-manifest on the ccr-session host. That host resolves to the CCR Remote session URL supplied via --sdk-url; if no --sdk-url is provided the request throws "ccr-session host requires --sdk-url".
The manifest response is a JSON object { skills: [...], plugins: [...] } where each entry carries {id, name, description, version, directory}. Only entries with a non-empty id are used.
A single manifest fetch is shared across both skills and plugins via a lazy singleton (YKb()), so only one HTTP round-trip is made per sync cycle; the request carries a 30-second timeout.
If the manifest fetch fails (no auth, HTTP ≥ 300, 503 unavailable, or malformed body), sync silently returns {success: false} and emits tengu_skills_sync_manifest_failed or tengu_plugins_sync_manifest_failed telemetry rather than raising an error.
The jot() helper — which gates whether skill invocation waits for skill materialization — returns true when either CLAUDE_CODE_SYNC_SKILLS is set OR session-refs mode is active, so skill-wait logic applies to session-ref sessions as well.
CLAUDE_CODE_SYNC_SESSION_REFS is also forwarded to spawned worker processes by the CCR preload layer alongside CLAUDE_CODE_SESSION_ID, so child sessions inherit the same sync path.

Evidence

New constant check (search for "CLAUDE_CODE_SYNC_SESSION_REFS"); manifest fetch (search for "/worker/skill-manifest"); sync branch (search for "sync_session_refs_skills")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.