unimem no_std prerequisite — independent CODE review

Verdict: APPROVE for the reviewed source delta. No blocking source findings.

Reviewer: independent Codex agent /root/xtask_code_review, 2026-10-16. Parent: 9cbd48070a136e24711896c930670fcff8a147fc. Checkout: /Users/master/cyber/honeycrisp/.worktrees/unimem-core/honeycrisp. This is a Codex CODE review, not a different-vendor or council review. No source, documentation or refs were edited; no tests were rerun by this reviewer.

Correctness

• Default behavior is preserved: unimem/default -> std -> crossbeam-queue/std enables the queue's alloc and crossbeam-utils/std features. Inspection of the locked queue 0.3.12 and utils 0.8.21 source confirms the omitted queue default marker has no separate implementation effect. The std backoff still calls std::thread::yield_now() under prolonged contention.
• The isolated default-features = false mode selects alloc without runtime std. Its spinning backoff and allocator requirement are documented. Cargo's additive feature unification can restore std through another consumer; owning no-default tests therefore cannot by themselves establish the dependency boundary.
• Runtime edits replace standard-library reexports with their core definitions. Public signatures, layouts, FFI symbols, ownership, lock/unlock, native creation, access safety requirements and queue algorithms are unchanged. MemError keeps the same Error trait identity. Test changes import prelude items explicitly; existing expectations and test bodies are retained.
• The durable Nu gate compiles a separate workspace with its own panic handler, detecting an accidental transitive runtime std dependency. It checks normal dependency names, workspace package version and locked registry identities; uses the frozen lock with --locked --offline; derives the dependency path from the script; and uses a fresh temporary target. The inert allocator and native driver are never executed. Fixture and workspace locks are not rewritten.

Evidence inspected and limits

Records are under audit/2026-10-16-unimem-core/records/, anchored to the source epochs hashed below. parent-no-std.json records the durable gate failing E0152; candidate-no-std.json records the identical gate succeeding. Candidate owner default and no-default cargo test -p unimem ... --locked --offline each pass 53 tests plus 13 doctests. candidate-isolated.json records 44 native tests passing in the separate consumer. Candidate owner formatting passes. Recorded before/after source identities agree. These observations were read from actual command receipts and output, not inferred from the implementation.

Workspace formatting and strict Clippy already fail on the parent; the inspected Clippy output starts with error: duplicated attribute in acpu. The plan also retains a blocked historical-tag API gate and unverified product/dependent gates. Remaining candidate workspace/build/API/feature-graph records were still being collected when this source review was issued. This approval does not classify those gates as green, authorize a release, or establish Kadek Image completion. Preserve their actual results and the required wip: treatment of red gates.

Nonblocking record correction: the retained task plan says “production unchanged” and requires a fresh different-vendor review. In finalization, identify those as the planning-era state/policy and state the actual current source/review lineage; the implementation must not inherit a vendor-review claim from that stale text.

Reviewed SHA-256 identities