fix(adk): prevent session event duplication in KAgentSessionService

[onematchfox]

Fixes a session event duplication bug in KAgentSessionService.get_session where every event loaded from the database was appended twice to session.events. get_session constructed the Session with events=events (pre-populating the list), then immediately called super().append_event() for each event. BaseSessionService.append_event unconditionally calls session.events.append(event), so every event ended up in the list twice.

The bug was latent for normal usage because the LLM tolerates redundant history in simple Q&A flows. It was discovered while testing #1491 locally, where the duplicated context caused incorrect agent behaviour. However, it does cause context bloat since, ultimately, every conversation turn currently sends 2× the necessary history to the model. 😬

[Copilot]

Pull request overview

Fixes duplicated session events in KAgentSessionService.get_session by avoiding pre-populating Session.events before re-appending via BaseSessionService.append_event.

Changes:

• Initialize Session with an empty events list in get_session to prevent double-appends.
• Add unit tests covering 404/empty responses, event ID preservation, non-duplication, and state-delta expectations.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
python/packages/kagent-adk/src/kagent/adk/_session_service.py	Stops event duplication by constructing Session with events=[] before appending events via the base service.
python/packages/kagent-adk/tests/unittests/test_session_service.py	Adds regression tests to ensure events aren’t duplicated and basic session loading behavior is correct.

Comments suppressed due to low confidence (1)

python/packages/kagent-adk/tests/unittests/test_session_service.py:1

• These assertions won’t actually fail if the same state_delta is applied twice via dict.update(...) (applying {'counter': 7} twice still results in 7, and setting key_a/key_b twice is also indistinguishable). To make this a real regression test, consider asserting the number of base append_event / _update_session_state invocations (e.g., by spying/patching) equals len(events), or use a non-idempotent delta format if the ADK supports one.

"""Tests for KAgentSessionService."""

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