Live staging (2026-08-02): only the FIRST auto-thread in a channel got an
auto-title/rename. Root cause is a grouping-model mismatch — the connector
auto-threads per message (each channel message spawns its own thread), but the
gateway keyed sessions per PARENT CHANNEL, so every message after the first
reused the first message's already-titled session; auto-title short-circuited
and the rename lane never fired for later threads.
Intended model: a channel message INITIATES a session, the thread CONTINUES it.
A Discord thread created from a message reuses that message's id as the thread
id, so the connector can tell us the thread id at inbound (before the thread
exists). The paired connector change stamps it as source.prospective_thread_id;
this keys the session on it:
- SessionSource.prospective_thread_id (new field; to_dict/from_dict + the relay
ws_transport inbound source build read it off the wire).
- build_session_key: effective_thread_id = thread_id or prospective_thread_id.
The channel-initiating message (no thread_id, carries prospective) and the
later follow-ups that arrive IN that thread (real thread_id ==
prospective_thread_id) now produce the SAME key. A real thread_id always
wins. The chat_type slot is normalized to "thread" when keying on a
prospective id so the initiating "group"/"channel" event byte-matches the
follow-up "thread" event. Prospective-thread sessions are shared across
participants like any thread (not per-user).
Net effect: each distinct channel message is its own session/thread and gets
its own title + rename; follow-ups inside a thread continue that session with
full history. Additive and inert until the connector sends the field, so
non-relay and pre-deploy behaviour is byte-identical.
Tests: initiate-then-continue share one session; distinct channel messages get
distinct sessions; real thread_id wins over prospective; prospective sessions
shared across participants. Session suite 59 passed; relay suite green; ruff +
footguns clean.
Paired: gateway-gateway stamps prospective_thread_id per auto-threading instance.
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