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fix(message-history): fall back within the requested session in get_relevant() - #765
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vishal-bala wants to merge 1 commit into
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vishal-bala wants to merge 1 commit into
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…elevant() get_relevant(session_tag=..., fall_back=True) searched the requested session but, when nothing was relevant, fell back to get_recent() without the session_tag. It therefore returned the recent messages of the instance's default session, letting a lookup for one conversation surface another's. The fall-back now passes session_tag through, so it reads the same session the search did. SemanticSessionManager inherits the fix; MessageHistory has no fall_back and is unaffected. The new integration test stores one exchange in the default session and one in another, then asks for the other session with distance_threshold=0 so the fall-back fires. On main it returns the default session's exchange; with this change it returns the requested one.
vishal-bala
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October 15, 2026 08:39
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Motivation
SemanticMessageHistory.get_relevant()accepts asession_tagand runs its vector search within that session. When nothing in the session is relevant andfall_back=True, it falls back toget_recent(), but without thesession_tag. The fall-back therefore returns the recent messages of the instance's default session, so a lookup for one conversation can surface another conversation's messages.SemanticSessionManagerinherits the same behaviour.Changes
The fall-back now passes
session_tagthrough toget_recent(), so it reads the same session the search did. When nosession_tagis given, both still use the default session, as before.MessageHistoryhas nofall_backoption and is unaffected.A new integration test,
test_semantic_get_relevant_falls_back_within_the_requested_session, stores one exchange in the default session and one in a second session. It then callsget_relevant()for the second session withdistance_threshold=0, which forces the fall-back. Againstmainthe test fails, returning the default session's exchange; with this change it returns the requested session's.Release Notes
SemanticMessageHistory.get_relevant()andSemanticSessionManager.get_relevant()called with bothsession_tagandfall_back=Truenow fall back to the recent messages of that session. Previously they returned the recent messages of the instance's default session.Note
Medium Risk
Changes multi-session context retrieval for semantic history fallback, which could affect LLM prompt assembly but is a targeted bugfix with a regression test.
Overview
Fixes a session leak when
SemanticMessageHistory.get_relevant()(andSemanticSessionManager, which subclasses it) runs with bothsession_tagandfall_back=True. Vector search was already scoped to that session, but the empty-result fallback calledget_recent()withoutsession_tag, so recent messages from the instance default session could appear in another conversation’s context.The fallback now forwards
session_tag(and existingrole/ formatting args) toget_recent(), so recent context stays in the same session; behavior whensession_tagis omitted is unchanged.Adds integration test
test_semantic_get_relevant_falls_back_within_the_requested_session(two sessions, forced fallback viadistance_threshold=0) to lock in session-scoped fallback.Reviewed by Cursor Bugbot for commit 3d972cc. Bugbot is set up for automated code reviews on this repo. Configure here.