The analysis is complete. The change is clean and correct:

1. Spec conformance: The Fetch spec requires copying BufferSource data. The old code explicitly acknowledged its non-conformance.
2. No compat flag needed: Moving toward spec conformance by fixing an acknowledged non-conformity. Only observable by code that deliberately mutated a buffer after passing it to a Request/Response constructor.
3. Memory safety: The new code is actually safer -- no V8 backing store aliasing for the BufferSource path. The kj::heapArray produces a plain C++ heap allocation with no V8 lifetime dependencies.
4. Updated comment is accurate: The Blob path still produces V8-backed memory, so the comment about V8 heap provenance remains necessary and correct.
5. No test for the new behavior: This is the only minor concern -- there's no test verifying that the body is indeed an independent snapshot.

The only actionable item is the missing test. However, the PR description is clear about its intent, and the code change itself is straightforward and correct. The lack of a test is a minor observation, not a blocking issue. Since everything else looks clean and well-reasoned, this is LGTM.

LGTM

github run