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agent: builder model: opus max_turns: 90 budget_usd: 18 effort: medium —

Brief: #1152 a struct with a ref field cannot be built from a local (NK1106) or a ref parameter (NK2302)

Blocks: t1-tools-test-blocks step 2 and t2-tests-ty-touch-manifest (the Rust unit tests move into Nikaia, #1147)

Score: a defect / obvious extension approved by the supervisor (2026-11-02): a ref field takes an owned local by lending it, as a ref parameter does. Found by T1.

Facts: Where things live, Traps already met, Commands

Problem

The probe is verbatim in #1152 (run it with target/fast/nikaia check): W { own: l, k: 1 } with own: ref L and a local l: L is NK1106; the same literal from a ref L parameter inside a function it never leaves is NK2302 (go keeps l ... doesn't say whose data).

To build

1. A struct literal lends an owned local to a ref T field (as a call argument is lent), and a struct value built from a ref parameter that does not leave the function is no keep. The existing keeps rules still refuse such a struct returned past the local. Tests tests/compiler/ref_field_from_local.nika + .stdout, and one refusal ref_field_outlives_local.nika + .stderr. Commit Fixes #1152. Run the tests your change touches (nikaia test on the new tests, the --test it filters of the files you change); lower-std and its fixpoint if a tools/*.nika changed.

Rules

• Read .claude/agents/builder.md and docs/builder-facts.md first. Commit locally with target/fast/nikaia run scripts/commit.nika -- REPORT; the driver pushes.
• Version lines, CHANGELOG.md, badges and NK codes are the supervisor’s.
• No cause after about 60 turns: stop, Result: partial with what you ruled out and the suspected file and function.

Report (at most 15 lines, to exactly /home/user/Nikaia/docs/briefs/bugs/b37-1152-ref-field-from-local.md.report.md)

Fields of docs/supervisor.md, Briefs and reports. Final answer, one line: done <sha>, report <path> (or BLOCKED: ...).

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