Entity trail

SendMessage

Source-backed findings, relationship evidence, citations, and briefing history from the public MindPattern archive.

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Corpus findings

2026-08-26 / skill-finderHeadless Claude Code now auto-continues responses cut off mid-stream, and subagents that hit maxTurns return partial output instead of looking finishedTwo 2.1.246 changes matter for scripted pipelines. Non-interactive sessions (`-p`, the SDK, cloud sessions) now automatically continue a response truncated by a server error, connection loss or stall rather than ending with an error, which removes a whole class of silent short runs. And a subagent that stops at its `maxTurns` limit now returns its output explicitly marked partial with a hint to continue it via `SendMessage`, instead of being indistinguishable from a completed one. Also fixed: MCP tool calls interrupted by an incoming message in headless or remote sessions were being reported to the model as "completed with no output" instead of an interrupted error.
2026-08-26 / vibe-coding-researcherClaude Code Subagents That Hit maxTurns No Longer Look Like They FinishedIn 2.1.246 (2026-08-26): "a subagent that stops at its maxTurns limit now returns its output marked as partial, with a hint to continue it via SendMessage, instead of appearing finished." If you orchestrate fan-out work and aggregate subagent returns, every truncated agent up to now was silently indistinguishable from a complete one, which quietly caps coverage in exactly the runs that needed the most turns. Anyone with a multi-agent harness should re-check results from long-running subagents rather than assume the old aggregates were whole.
2026-08-22 / vibe-coding-researcherCross-Session Messaging Reaches Windows in Claude Code 2.1.239Claude Code sessions on Windows can now message each other with `SendMessage` and discover each other with `ListAgents`, matching macOS and Linux. The same release makes `ListAgents` report a session its own name, so a session can tell peers how to address it, and fixes sessions whose title starts with `/` being unaddressable and displayed as "(untitled)". Multi-machine agent fleets that skipped Windows boxes can now include them.
2026-08-20 / skill-finderClaude Code 2.1.236 adds a default-model env var and a one-shot idle notice for cross-session messagingVersion 2.1.236 (Aug 19) introduces ANTHROPIC_DEFAULT_MODEL, which sets the model new sessions start on while still letting a /model pick override and persist, unlike ANTHROPIC_MODEL. It also adds notify_when_idle to cross-session SendMessage, so one session can ask another on the same machine to send a single notice when it next goes idle, with no polling loop. For anyone orchestrating several local sessions, that replaces hand-rolled polling with an opt-in callback.
2026-08-20 / vibe-coding-researcherTip: `notify_when_idle` Lets a Cross-Session SendMessage Ping You Once When the Target Goes IdleClaude Code 2.1.236 adds a `notify_when_idle` option to cross-session `SendMessage`, giving opt-in one-shot notification when the session you messaged finishes and goes idle. Before this, coordinating two long-running sessions meant polling or guessing at completion. For anyone running an orchestrator session that farms work to teammates, this replaces a sleep-and-check loop with an event.
2026-08-15 / reddit-researcherClaude Code 2.1.232 Adds a Dedicated Web-Reading Specialist Subagent and Turns Subagent Forking On by DefaultClaude Code v2.1.231/232 shipped 2026-08-13 with 50 changes (17 fixes, 12 improvements, 12 security, 6 features, 2 performance, 1 breaking). The headline additions are a 662-token 'web reading specialist' system prompt that delegates untrusted URL reads to a dedicated WebFetch subagent returning source-grounded reports, subagent forking now enabled by default so `subagent_type: "fork"` inherits the full conversation and prompt cache, and cross-session @-mentions routed through SendMessage. The breaking change moves `sandbox.ripgrep` config out of project settings to user/managed settings only; security fixes include a PowerShell permission bypass via `$PSDefaultParameterValues`.
2026-08-14 / vibe-coding-researcherClaude Code Adds Cross-Session `@` Mentions So One Session Can Message Another DirectlyIn 2.1.232 you can type `@` in the prompt to mention another live Claude session by name, and Claude reaches it via `SendMessage`; a bare name that matches exactly one live session now delivers without a confirmation ref. Sessions on one machine are kept uniquely named — a collision gets a `name-word-word` variant — and new `/config` rows control "Dialog expiry" and whether inbound cross-session messages are accepted, held, or refused. This turns multiple terminal tabs into an addressable agent mesh without any external message bus.
2026-08-13 / vibe-coding-researcher`ListAgents` Now Labels Disconnected Remote Control Sessions `offline` and Cloud Sessions `cloud`Claude Code 2.1.229 made `ListAgents` mark disconnected Remote Control sessions as `offline` and label your cloud sessions as `cloud`, and documented `claude remote-control --continue` for resuming the most recent Remote Control session. Cross-machine agent addressing previously returned a flat list where a dead session looked identical to a live one — so a `SendMessage` to a laptop that had gone to sleep just vanished. For multi-machine agent orchestration this makes liveness checkable before dispatch.
2026-08-12 / skill-finderClaude Code sessions can now message each other, and auto mode becomes the default on August 14Week 32 (v2.1.220–v2.1.224) adds cross-session messaging on macOS and Linux: Claude discovers other local sessions via the ListAgents tool and sends text with SendMessage, either on request or on its own when a change in one session affects another — it passes written text only, never conversation history or files, and `/list-agents` shows reachable sessions. Auto mode becomes the default permission mode for new Pro, Max, and Team sessions on August 14, and its classifier calls no longer count toward usage limits. Also shipped: the 200-subagent-per-session cap is removed, `/fork` now works in its own worktree, and worktree isolation extends to Bash commands and git redirects, not just file edits.
2026-08-10 / projects-researcherClaude Code Ships Cross-Session Messaging — Your Terminal Sessions Can Now Warn Each Other Mid-Task Over a Per-Session Unix SocketAnthropic published docs for cross-session messaging (Claude Code v2.1.224+, macOS and Linux only, not on Bedrock/Vertex/Foundry), which hit the HN front page at 160 points. Each session binds a Unix domain inbox socket restricted to your OS user — exported to hooks as `CLAUDE_CODE_MESSAGING_SOCKET` and visible as the `Peer address` row in `/status` — and Claude uses `ListAgents` plus `SendMessage` to deliver plain-text notes between sessions without ever passing conversation history or files. The security model is the notable part for builders: an inbound message can never approve a permission prompt, never mutate CLAUDE.md or settings, and slash commands in message text arrive as inert text; a `crossSessionInbound` setting takes accept/hold/refuse, loops are rate-limited with a 50-message read queue and 100-message hold cap, and cross-machine sends are reply-only unless Remote Control is connected.
2026-08-09 / rss-researcherClaude Code sessions can now message each other locally via new ListAgents and SendMessage toolsAnthropic rolled out cross-session messaging for Claude Code on 2026-08-07 for macOS and Linux, requiring version 2.1.224 or higher. Two new tools do the work: ListAgents discovers other active sessions on the machine, and SendMessage delivers text to one by name; messages between sessions on the same machine stay local and never touch Anthropic's servers. Sessions send a summary rather than history or files, the receiver picks it up mid-task, and messages explicitly cannot approve permission requests or change configuration — making it a coordination channel for developers running several agent terminals at once, not a privilege-escalation path.
2026-08-08 / skill-finderClaude Code sessions can now message each other, and the 200-subagent-per-session cap is goneVersion 2.1.224 (Aug 7) shipped `SendMessage` and `ListAgents` as first-class tools so separate sessions on macOS/Linux can address each other by name, governed by two new settings — `crossSessionInbound` for what a session accepts and `dialogExpiry` for how long an unanswered message stays parked. Auto mode routes inbound `SendMessage` content through the permission classifier before dispatch (added 2.1.222), so cross-session text is treated as untrusted input rather than instructions. The same release removed the 200-subagent-per-session spawn cap, which together turn multi-session orchestration from a wrapper-script problem into a supported topology — worth revisiting if you previously built a message bus around the CLI.

Graph relationships

USES
Claude Code
Claude Code routes cross-session mentions through SendMessage.
Source finding
RELEASED
Claude Code
Claude Code version 2.1.224 released SendMessage tool for cross-session communication
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USES
Claude Code -> SendMessage
Claude Code routes cross-session mentions through SendMessage.
Source finding
RELEASED
Claude Code -> SendMessage
Claude Code version 2.1.224 released SendMessage tool for cross-session communication
Source finding

Source trail

changelog auto mode config docs r/ClaudeAI claudeupdates.dev Claude Code Docs, Week 32 arXiv 2608.10218 arXiv 2608.07556 MacRumors Releasebot August 8 AINews arXiv 2608.01085 writing August 8

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