session.send
A Claude Code settings key, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
Plugin hooks can now listen for a new session.send event, alongside session.receive/detach/end
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.280.
In the changelogs
7Releases whose published page names session.send.
-
v2.1.304
Plugins can intercept queued messages, and session.send checks the input hold
Hook plugins can now intercept a queued message, and a plugin's session.send is refused if Claude Code cannot read whether plugin input is held
found in this entry's text, named in this entry
-
v2.1.293
Session append for code-based hooks, and several small permission and sandbox changes
Hook code can call session.append next to session.send, and file-write checks, the sandbox and hook reporting get small changes
found in this entry's text
-
v2.1.285
New names for MCP connections and appending to a session
Three new names appear for connecting to MCP, appending to a session and a plain MCP server call, next to existing ones
found in this entry's text
-
v2.1.280
New plugin-hookable event: session.send
Plugin hooks can now listen for a new session.send event, alongside session.receive/detach/end
named in this entry, found in this entry's text
-
v2.1.280
Plugin hooks can intercept and readdress SendMessage sends
Plugin hooks can now intercept SendMessage calls, rewriting or blocking who a message goes to
found in this entry's text
-
v2.1.280
Plugin/SDK host API: new
$.session.sendoperationPlugins and SDK integrations gain a session.send call to message a target by name, agent id, or session/agent address
found in this entry's text
-
v2.1.280
Plugin
$.session.messagesand$.session.usagenow accept an agentId/as parameterPlugin session.messages and session.send can now target a specific agent via an agentId/as parameter
found in this entry's text
First cited
7The earliest release whose published evidence quoted session.send was v2.1.280, 22 Sep 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
1 further span in the ledger name it. The list above is the earliest first and stops at 6.
Presence across releases
0The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the settings key does. All settings keys.