session_capacity
This code is registered so the envelope contract and its
docs_url
anchor stay stable, but nothing emits it. The MCP server caps a
workspace at 100 concurrent sessions and enforces that by evicting
the oldest session rather than refusing the new one, so the caller
that hits the cap gets a normal successful response — it’s an older
session elsewhere that is dropped. Do not write retry logic against
this code.
If sessions are being evicted under you, the fix is not a retry: audit
how many MCP hosts are connected to the workspace and disconnect the
ones you don’t need (Settings → Developer → Connected apps).