Summary

Telegram DM topic mode can keep a topic binding pointed at a session that has already been superseded by a compression child. The gateway route may advance to the child, but the Telegram topic binding can still resolve to the parent on a later inbound message.

Impact

A later message in the same topic can load the parent-sized transcript again instead of the compressed continuation. That can trigger repeated preflight compression, slow responses, stale cached agents, and apparent infinite compression loops for topic lanes.

Reproduction Shape

1. Enable Telegram DM topic mode.
2. Process a topic lane until context compression splits parent -> child.
3. Leave the topic binding pointing at parent while the route or session lineage points at child.
4. Send another message in the same topic.
5. The gateway may load parent history instead of the current compression continuation.

Expected Behavior

Before transcript load, the gateway should canonicalize topic bindings through the compression tip or current descendant, rebind the topic to the current child, and evict any cached agent whose session id no longer matches the canonical route.

Related

• Earlier issue: Gateway can reuse parent-sized history after compression split, causing infinite preflight compression #25921
• Earlier PR on the same topic: fix(gateway): publish compression route advances #26204
• Related competing fix: fix(gateway): publish compression tip before reusing session history #26088

Notes

This report intentionally uses synthetic identifiers only; no production chat ids, user names, session ids, or logs are included.