test(api): add recent activity hydration regression coverage

[phernandez]

Summary

• add regression tests for batched recent_activity hydration in to_graph_context()
• prove entities, observations, and relations share one find_by_ids(...) lookup
• verify empty context results skip entity hydration entirely

Why

Issue #710 described an N+1 lookup pattern in recent_activity hydration. The batching logic is already present on main, so this PR adds regression coverage to make sure that behavior stays in place.

Refs #710.

Test plan

• uv run pytest -q tests/api/v2/test_search_hydration.py tests/api/v2/test_memory_hydration.py tests/api/v2/test_utils_telemetry.py

[github-actions]

Claude finished @phernandez's task in 2m 23s —— View job

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PR Review: test(api): add recent activity hydration regression coverage

• Gather context (PR metadata, changed files)
• Read the new test file (tests/api/v2/test_memory_hydration.py)
• Read relevant source files (api/v2/utils.py, context_service.py, search.py)
• Review against team checklist
• Post final review

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Summary

This PR adds clean regression coverage for the N+1 fix from #710. The test structure mirrors the existing test_search_hydration.py and correctly verifies both the batching invariant and the hydrated data.

Code Quality Checklist

Item	Status	Notes
Follows coding conventions (CLAUDE.md)	✅	Consistent style, good section headers
Python 3.12+ type annotations	✅	from __future__ import annotations, proper hints
100-char line length	✅	No violations observed
No commented-out code	✅
Unit tests for new logic	✅	Two tests with distinct scenarios
Edge case coverage	✅	Empty results path tested
100% coverage maintained	✅	PR only adds tests, no new uncovered production code
No hardcoded secrets	✅
No emojis/unicode in output	✅
Windows-compatible paths	N/A	No os.path comparisons
DB changes / Alembic	N/A	No schema changes
MCP / architecture concerns	N/A	Pure unit test

Review Observations

The good:

1. SpyEntityRepository pattern (line 45-54) — clean duck-typed spy that mirrors SpyEntityService in test_search_hydration.py. Consistent with established test conventions.

2. Batch assertion is precise (line 158-159) — assert len(repo.calls) == 1 followed by assert set(repo.calls[0]) == {1, 2, 3} verifies both the call count (eliminates N+1) and that all three entity types (entity, observation parent, relation from/to) contribute IDs to the single lookup. This is the right invariant to lock down.

3. Data hydration correctness is also verified (lines 161-175) — not just the call count but the actual populated fields (external_id, entity_external_id, from_entity, to_entity_external_id). This prevents silent regressions where the batch fires but data is wired incorrectly.

4. SearchItemType is str, Enum — passing type="entity" string literals in _make_row compares correctly to SearchItemType.ENTITY in production code. No test brittleness here.

Minor observations (no blockers):

1. root_id=11 for child_observation and peer_entity (lines 108, 121) — 11 is the ID of child_observation itself, used as the grouping key for the second ContextResultItem. This is valid since root_id is just a grouping anchor, but it's a subtle choice. A brief inline comment would help future readers understand why the grouping key is 11 (the observation's own ID) rather than an entity ID.

2. SpyEntityRepository does not inherit EntityRepository — to_graph_context is typed entity_repository: EntityRepository, so pyright would flag the test call at line 156. This follows the same pattern as SpyEntityService, so it's consistent with project convention, but worth noting if type-checking tests becomes a goal.

3. _make_row defaults.update(kwargs) ordering (line 41) — kwargs override defaults, which is the correct behavior. Just confirming: this means callers must pass created_at via kwargs if they want to override the default datetime.now(). The tests all pass created_at=now via kwargs.pop("created_at", ...) → but wait, created_at is popped from kwargs first and then placed into defaults. That means passing created_at=now in _make_row(created_at=now, ...) correctly controls the timestamp. ✓

Verdict

Approve. The tests are well-structured, clearly express their intent, and lock down the right invariants for the N+1 fix. No functional issues found.