AI-generated conceptual illustration of separate coding sessions exchanging a limited text message; not a Claude Code screenshot or real session data.
Claude Code 2.1.224 adds a messaging channel between independently launched sessions, allowing them to exchange findings, decisions and status during parallel work. 9to5Mac reported the release on August 7, 2026, while Anthropic’s cross-session messaging documentation provides the implementation and availability details.
The feature is narrower than shared memory. Messages contain plain text, not conversation history or files, and the receiving session continues to apply its own permissions and configuration.
What moves between sessions
Claude Code uses ListAgents to discover reachable peers and SendMessage to address one by name. A message can summarize a breaking change, report that a migration finished, pass along a decision or request an update.
According to Anthropic’s delivery documentation, an active receiver reads an accepted message between tool calls, so a running tool is not interrupted. If the receiving session is idle, an accepted message starts a new turn.
Delivery is not guaranteed. The receiving session evaluates every incoming message under its inbound controls, producing one of three outcomes: delivered, held or refused. A held message reaches Claude only after approval or a later settings change permits it; a refused message is dropped.
Developers who need the complete working context must still resume the original session. Cross-session messaging does not clone prompts, tool results, files or the conversation into another terminal.
The receiver keeps its permission boundaries
A peer message does not make one session an authorization proxy for another. Anthropic’s incoming-message rules state that a message cannot approve a permission request, change permission settings or other configuration, or execute a slash command. Text such as /compact arrives as text.
If acting on a message requires permission, the receiving session follows its normal rules and can still prompt the user. The instruction may cross sessions; the sender’s authority does not.
Administrators and users can set crossSessionInbound to accept, hold or refuse. When no explicit value applies, Claude Code uses the permission-mode classes of the sending and receiving sessions to decide whether to deliver the message or hold it for approval.
That boundary matters for unattended or high-permission workflows. Teams should choose an inbound policy deliberately instead of assuming every peer message will arrive or be acted on.
Local delivery and remote replies use different paths
For sessions on the same machine, messages travel over per-session sockets and, according to Anthropic’s cross-machine routing table, do not pass through Anthropic servers. The inbox socket is restricted to the same operating-system user.
Local reachability also depends on filesystem visibility. Sessions find one another through registration files, so a session inside a container cannot automatically reach a session on the host. Two enabled sessions inside the same container can communicate.
Replies to one of the user’s sessions on another machine or in Claude Code on the web take a different route: they pass through Anthropic servers. The local session cannot initiate that cross-machine exchange; it can only reply after the remote or web session has contacted it.
Setting isolatePeerMachines to true adds an explicit approval step before any reply leaves the machine. This requirement also applies when ordinary permission prompts are bypassed.
Availability has platform and provider limits
Cross-session messaging requires Claude Code 2.1.224 or later. Anthropic’s availability requirements list support for macOS and Linux, including Linux under WSL 2, but not native Windows.
The feature is also unavailable through Amazon Bedrock, Claude Platform on AWS, Google Cloud’s Agent Platform and Microsoft Foundry.
A supported operating system and version are not sufficient in every configuration. Environment settings that disable the feature-flag evaluation Claude Code depends on can keep messaging off.
The quickest check is /list-agents, also available as /peers. When messaging is active, /status also shows the current session’s peer address.
Limits for parallel coding work
Delivered messages count toward usage like prompts typed by the user. Anthropic’s documented limits also throttle repeated message loops, drop identical repeats arriving within a short window and cap accepted unread messages waiting for a session at 50.
The practical benefit is reduced manual coordination. A session changing an API can notify another that is updating its client, while a long-running migration or test session can report progress to the session a developer is watching.
Cross-session messaging is not a replacement for subagents, agent teams or session resumption. It is a limited coordination channel between sessions that developers launch and steer independently. Teams adopting it should name sessions clearly, choose an inbound policy and treat cross-machine replies as a separate network path.
