Claude Code v2.1.260 ships cross-session messaging and Fable 5.1 default

Anthropic shipped nine Claude Code versions between August 7 and September 3, from v2.1.224 to v2.1.260. The latest v2.1.260 introduces cross-session messaging: ListAgents discovers active sessions and SendMessage delivers text to a named session via an @name prompt. Only the message travels between sessions; no history or files are transmitted, and same-machine traffic uses a local socket or named pipe without passing through Anthropic servers.

Highlights since v2.1.252 include Fable 5.1 becoming the default Fable model, /effort s for session-only reasoning effort, /doctor warning about stale sandbox masks, /code-review --comment posting to GitLab MRs, a fullscreen /diff panel, and --permission-prompts none for unattended headless runs. Forked subagents have inherited full context plus prompt cache by default since v2.1.232, with five-level nesting and 20 concurrent by default.

Anthropic also announced that standard weekly limits for Claude Code will be raised by 25% over the original baseline starting September 14, replacing the temporary 50% boost, so effective capacity drops roughly 17% from current levels. The MCP protocol's July 28 spec revision made the protocol stateless, removing the initialize handshake and session IDs, with each request self-contained in _meta and servers scalable horizontally behind standard load balancers.