LA-62: Qualify callback-bearing native attribute mutation keys #757

Scope

Finite follow-up under exception owner #124 and Track A #600, exposed by LA-59–LA-61 (#756).

Native attribute mutation must account for string-subtype keys whose hash/equality overrides participate in native type lookup. On pinned CPython 3.14.7, a key's hash callback can run even when mutation ultimately raises AttributeError; a lookup callback error may be suppressed before missing-name metadata is selected. Earlier missing-name cases with a raising hash and no output do not certify callback ordering or absence of callbacks.

The reflective layouts adopted by #756 explicitly refuse keys with owned hash/equality overrides before callbacks or mutation. Reconcile the corresponding behavior and claims for the other fixed native mutation layouts, including scalar/container/callable/view/generator/iterator receivers and writable native fields.

Acceptance

• Exact CPython 3.14.7 reference matrix for hash/equality results, callback side effects, lookup failures, native data descriptors versus missing names, multiple mutation attempts, and any cache-dependent behavior.
• Preserve original key/receiver identity, error selection, actual callback order, partial mutations and native receiver validation.
• Owned execution through drain/step/parked Node and Chromium, collection/cancellation/close, shared resource budgets, composed modules/dynamic source and installed offline acceptance.
• Remove a refusal only when its exact callback contract is adopted; retain separately qualified cache/host differences outside successful differential counts.

No broader formatting, source admission, library/package certification, release or deployment is implied.

Accepted — 2026-11-02

#760 is squash merged into main at 5072ae1 after complete local validation. All 678 shared PR-check IDs and 223 isolated installed-wheel offline checks pass, including the full Node/Chromium driver/profile matrix, parked collection/cancellation/close, shared limits, composed modules/dynamic source, original frames and offline Stop/Restart. Four browser worker-startup interruptions passed isolated one-worker retries; unchanged passing evidence was retained. The duplicate PR workflow was cancelled before merge.

The corpus adds 615 cases and adopts six prior reflective-key refusals. The final 2,443 cases contain 2,387 supported semantic/error comparisons and 56 explicit refusals, with 267 shared core cases and seven separate qualifications. Successful/NotImplemented equality, truth conversion and suppressed lookup errors select the actual native descriptor or dictionary storage. The first false comparison retains an explicit refusal after its effects: 16 seeded probes produced two or three comparisons for the same input. #759 owns that separately qualified path and it earns no supported differential credit.

The 140-site refusal audit and all eight revision-22 resource observations pass. The exact contract is in docs/interpreter-exceptions.md; examples/interpreter_native_keys.py runs unchanged on the pinned reference and offline console. #600/#124 record the broader remaining gates.