Version 2.1.15

A new hidden --cowork flag enables an alternate plugin directory for development and testing workflows.

# Via CLI flag
claude plugins list --cowork
claude plugins install my-plugin --cowork

# Via environment variable
CLAUDE_CODE_USE_COWORK_PLUGINS=true claude

• When enabled, plugins are stored in cowork_plugins/ instead of plugins/
• Settings file changes to cowork_settings.json instead of settings.json
• The --cowork flag is hidden from help output (.hideHelp())
• Only available with user scope for certain commands; attempting to use with other scopes results in an error
• Can be enabled via CLAUDE_CODE_USE_COWORK_PLUGINS environment variable

Cn5() at line 90980 (plugin directory selector, contains "cowork_plugins"), CLI definitions at line 560985 (contains "--cowork", "Use cowork_plugins directory")

Claude Code now sends version and entrypoint information in API requests for better usage tracking and diagnostics.

• Header format: x-anthropic-billing-header: cc_version=2.1.15.{hash}; cc_entrypoint={entrypoint}
• The entrypoint is read from CLAUDE_CODE_ENTRYPOINT environment variable (defaults to "unknown")
• Previously this header was stubbed to always return an empty string (gated by tengu_ant_attribution_header_new flag)

X61() at line 158274 (attribution header generator, contains "x-anthropic-billing-header")

The entire UI layer has been updated to use React Compiler's automatic memoization through useMemoCache.

• In v2.1.14: Only 1 reference to react.memo_cache_sentinel (the definition in React internals)
• In v2.1.15: 736 usages across UI components
• A new shared e() function wraps useMemoCache for use across all components
• This provides automatic fine-grained memoization without manual useMemo/useCallback calls
• Should improve rendering performance by avoiding unnecessary re-renders

e = function(A) { return dn5.H.useMemoCache(A) } at line 92039, 736 occurrences of Symbol.for("react.memo_cache_sentinel") checks throughout UI code

Added internal state tracking for remote/teleport mode sessions.

• New isRemoteMode boolean state in the global state object
• Getter Hf1() and setter Fg6() functions added
• Used to modify behavior when running in remote session context (e.g., preventing empty input submission)

k6.isRemoteMode = A at line 2350, usage checks at lines 548372 and 548402

The --cowork flag and cowork plugins directory are hidden internal features, likely intended for Anthropic development and testing workflows. They are not documented in public help output and should be considered unsupported for general users.