Follow-up to the #90972 salvage:
- strip loop: copy.deepcopy(msg) -> dict(msg). strip_anthropic_cache_control
is copy-on-write on content parts by contract (pops the top-level key,
rebuilds content lists/part dicts fresh), so a shallow top-level copy
preserves the caller-non-mutation guarantee — verified for all four
marker shapes — and removes the redundant second deepcopy the re-mark
path paid on already-decorated input. Docstring updated to match.
- tests: moved the surviving idempotency tests into
tests/agent/test_prompt_caching.py (where this module's tests live) as
TestApplyIdempotency; dropped the three tests that duplicated existing
coverage (dynamic_tool_accounting ~= TestPromptCachePlan::
test_copies_sections_and_keeps_canonical_tools_plain which already
asserts == 4; can_carry_marker_envelope_vs_native ~= TestCanCarryMarker;
never_exceeds_four_markers subsumed by the idempotency test).
- exact-count assertions per review: idempotency fixture pins == 4,
no-tools fallback pins == 3 (marker loss can no longer masquerade as
safety); added the one new _can_carry_marker assertion (native=True
empty assistant) to TestCanCarryMarker.
- new part-level stale-marker mutation guard (the other detection branch,
where part-dict aliasing is the risk); fails on pre-fix base with
marker accumulation (9 > 4), passes with the fix.
kshitijk4poor
c26357ad6a