Claude Code lets your independent sessions message each other to share findings, coordinate work, and report status without you manually copying information between terminals. Messages are delivered between tool calls and filtered through permission controls that prevent sessions from approving actions or changing configuration on each other's behalf. You can prompt Claude to send a message, or it'll detect when another session needs information and send it automatically.

• Claude Code sessions (v2.1.224+, macOS/Linux) can now message each other automatically or on request, using ListAgents/SendMessage tools, without interrupting running processes.
• Cross-machine messaging is one-way by default—remote or web sessions can only reply to existing threads, not initiate them, and replies from sessions without Remote Control arrive without a return address.
• Incoming messages are treated as system info, not user commands, so they can't approve permissions, change config, or run commands—permission prompts still trigger as normal.
• Inbound behavior is configurable per session via crossSessionInbound, with automatic naming (e.g. "myapp-3f") and /list-agents to see reachable sessions.

Anthropic investigated user reports of degraded performance in Claude Code, the Agent SDK, and Cowork, and traced them to three separate changes: a lowered default reasoning effort, a bug that cleared session context on every turn after idle, and a prompt tweak to limit verbosity. All issues were reverted or fixed by April 20 (v2.1.116), and Anthropic is adding stricter testing, broader internal dogfooding, and more targeted evals to prevent similar regressions.

• Three unrelated changes (lowered reasoning effort, a context-clearing bug, and a verbosity-limiting prompt tweak) independently degraded Claude Code quality, and all were rolled back or fixed by April 20 (v2.1.116).
• A March 26 bug meant to prune old reasoning after an hour of idle time instead cleared context on every turn, causing Claude to forget logic, repeat itself, and make bad tool calls—while also burning through users' rate limits faster via cache misses.
• The default reasoning effort was dropped from high to medium on March 4 to reduce latency, but users found it dumbed-down, so it was reverted on April 7 to x-high (Opus 4.7) or high (other models).
• Because the three issues hit different traffic subsets at different times, users experienced inconsistent symptoms—slowdowns, forgetfulness, quality drops—making the problem hard to diagnose until late April.