TrustRecordSchema superRefine mutates record during validation

[flyingrobots]

Migrated from Method backlog

GitHub Issues are now the live work tracker. Repository docs remain Method evidence.

Field	Value
Source backlog	docs/method/backlog/bad-code/BND_schemas-refine-mutation.md
Archived source	docs/archive/backlog/github-issue-migration-2026-06-01/docs/method/backlog/bad-code/BND_schemas-refine-mutation.md
Original lane	bad-code
Original id	BND_schemas-refine-mutation
Original legend	BND
Original feature	merge-strands-worldlines
Original release home	v19.0.0

Original backlog card

TrustRecordSchema superRefine mutates record during validation

Effort: S

Problem

The Zod superRefine callback mutates record.subject, replacing it
with the parsed sub-schema result. Zod schemas should be pure validators;
mutation during refinement is surprising and fragile. It makes the
validation step order-dependent and hard to reason about.

Suggested Fix

Use .transform() instead of superRefine for the mutation step, or
parse the subject separately and merge the results. Keep refinement
callbacks pure.