Claude Code: cross-session IPC split across Opus, Sonnet and Haiku
Opus, Sonnet and Haiku sessions message each other over local sockets without context bloat, while Jev handles the forks that need no thinker in milliseconds.
Boris Cherny, Head of Claude Code at Anthropic, just shared an official tip before Fable 5.5 ships The setup: split your workload across Opus 5.5, Sonnet 5.5, and Haiku 5.5, and let them talk directly across your open terminals Zero context pollution between windows: independent sessions ping each other via plain-text IPC over local sockets without burning a single token on conversation history You just launch Claude Code like this: claude --model sonnet --settings '{"crossSessionInbound":"accept"}' here's the split: → Opus 5.5 architects session permissions: audits ListAgents discovery, enforces inbound message policies, and signs off on multi-terminal diffs → Sonnet 5.5 executes code fixes: builds endpoints, updates schemas, and patches dependent code whenever a peer session reports a breaking change → Haiku 5.5 relays inter-session messages: processes SendMessage pings across terminals at 340 tok/s with zero history bloat and sub-millisecond local socket latency → you stop burning Opus context on manual copy-pasting between terminals and keep your sessions lean Opus only steps in at three moments: → setting up cross-session topology and inbound security rules before launch → evaluating contract diffs when a peer message signals an API schema update → signing off on synchronized multi-session PRs before merging to main Opus architects · Haiku relays · Sonnet executes JEV engineering is the same move one layer down: the forks that need no thinker (which peer, which tool, forward or drop) go to JEV in milliseconds, and the big models only see the ones that split the full tree > Opus 5.5 architects session permissions and audits cross-session topology > Haiku 5.5 relays SendMessage pings between terminals at 340 tok/s > Sonnet 5.5 patches code across workspaces when a peer signals a change > Sessions discover each other automatically via ListAgents and /peers > Messages travel as isolated plain text over local IPC sockets with 0 context dump > JEV routes micro-forks in milliseconds paste the tree and this prompt into Claude Code ↓ "Rebuild my Claude Code setup around this tree: 1. Configure cross-session discovery using /peers and set crossSessionInbound to accept 2. Delegate all peer-to-peer message routing and notification triage to Haiku 5.5 at 340 tok/s 3. Spawn Sonnet 5.5 to execute code edits and synchronize types whenever a peer session reports an update 4. Restrict all cross-session payload traffic to lightweight plain text via SendMessage with zero history transfer 5. Reserve Opus 5.5 for inter-session capability authorization and final sign-off before committing Show me every change as a diff first. No edits until I say go" ↳ http://code.claude.com/docs/en/cross-session-messaging bookmark this, your terminals now talk to each other
This post quotes another post: x.com/mirku21/status/2098836008468992471