[zerafachris (zerafachris)]

Issue: #7971

Problem

MessageFilterAgent._apply_filter built its result by iterating per_source filters and appending matching messages in filter-config order. When multiple sources were configured, messages from a later-listed source that chronologically preceded messages from an earlier-listed source were emitted out of order, breaking the LLM agent's conversation timeline.

For example, given messages [user, A(old), B, A(new)] and a filter listing A before user:

• Before fix: [A(old), A(new), user] — config order, not chronological
• After fix: [user, A(old), A(new)] — original conversation order preserved (with position="last", count=1 → [user, A(new)])

Change

Track the original message index for each selected message and emit in original conversation order. The per-source count/position filtering logic is unchanged.

# Before
result: List[BaseChatMessage] = []
for source_filter in self._filter.per_source:
    msgs = [m for m in messages if m.source == source_filter.source]
    # ... slice by position/count ...
    result.extend(msgs)  # order follows filter-config, not timeline
return result

# After
selected: set[int] = set()
for source_filter in self._filter.per_source:
    indexed = [(i, m) for i, m in enumerate(messages) if m.source == source_filter.source]
    # ... slice by position/count ...
    for i, _ in indexed:
        selected.add(i)
return [m for i, m in enumerate(messages) if i in selected]  # original order

Tests

New regression test test_message_filter_agent_preserves_chronological_order in tests/test_group_chat_graph.py:

• Sets up per_source=[A-last(1), user-first(1)] (A listed before user)
• Messages arrive in order: user, A(first), A(second)
• Asserts the wrapped agent receives [user, A(second)] — original order — not [A(second), user] — config order

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Prepared with AI assistance (Claude Code, Anthropic), reviewed for correctness before submission.

[zerafachris (zerafachris)]

@microsoft-github-policy-service agree

[zerafachris (zerafachris)]

@microsoft-github-policy-service agree

[zerafachris (zerafachris)]

westey (@westey-m) The Microsoft CLA is now signed and green — ready for review when you get a chance!