agent: builder model: opus max_turns: 80 budget_usd: 16 —
Score: compiler bug, a wrong lowering that reaches rustc (a list unborrowed, an owned text moved) where Part I and ADR-282 D2 say the compiler lends; found by b12, small and traced.
Facts: Where things live, Traps already met, Commands
A call through a field holding code (h.f(x)) does not lend its arguments; the same call through a let or a parameter (g(x), apply(count, x)) does. Not about pausing: sync or not, one view or two.
Probe (checked on 46e6179f’s binary, each fails in rustc):
struct H { f: fn(ref Vec[i64]) -> i64 }
fn count(a: ref Vec[i64]) -> i64 { a.len() }
fn main() {
let h = H { f: count }
let x = [1, 2, 3]
println(h.f(x)) // rustc: Mismatched types, expected `&[i64]`, found `Vec<{integer}>`
}struct H { f: fn(String) -> i64 }, fn count(a: String) -> i64 { a.len() }, let n = 3, let s = f"ab{n}", println(h.f(s)), then println(s): rustc Borrow of moved value: s.struct H { f: fn(ref Vec[i64], ref Vec[i64]) -> ref Vec[i64] }, fn first(a: ref Vec[i64], b: ref Vec[i64]) -> ref Vec[i64] { a }, let y = [4], println(h.f(x, y).len()): Arguments to this function are incorrect.
Expected output a 3, b 3 then ab3, c 3.check_core_a_called_field (crates/nikaia-std/src/tools/check_core_args.nika :791) calls check_core_arguments_given (:797) and drops its result. The kept-call path check_core_call_kept (check_core_call.nika :174) passes it to check_core_call_lent (:159), which records facts.lent_args. Make it reachable (it is a private fn in check_core_call.nika: pub, or a twin; say which) and call it on the field path.emit_core_a_field_call (emit_core_reads.nika :339, the loop at :362) writes each argument with bare emit_expr; it reads no lent_args. Lend as emit_core_args does (emit_core_args.nika :386: lent_args and the text-literal exception), ideally by reusing that writer rather than copying its rule; if you copy, name the rule’s other homes in Body:.
If the trace is wrong, find where the kept call gets its & and give the field call the same.Tests:.lower-std, fixpoint).tests/compiler/tests/a_field_call_lends.nika + .stdout holding rows a-c, failing on the unfixed binary.
Commit check, emit: a call through a field holding code lends its arguments (Fixes #1065).The new test fails on the unfixed compiler and passes through nikaia test --project tests/compiler --both-settings, with the tests whose names contain field, kept, code_param, function_type, lambda (by name); lower-std fixpoint clean; build, fmt, clippy, pre-push-check.sh; committed locally. Changelog: one line.
An edit is needed outside check_core_args.nika, check_core_call.nika, emit_core_reads.nika, emit_core_args.nika, their lowered twins and the new test; an error in another agent’s file.
Not yours, never stage: every file git status shows modified or untracked at your start (lowered/project_members.rs is uncommitted residue), and every docs/briefs/* file except your report.
docs/builder-facts.md first. develop in the main checkout; git status at start: other agents’ uncommitted files are not yours, never touch or stage them.git add <files> only (scripts/commit.nika -- REPORT does it); commit locally after each step and never push: the driver runs the complete suite and pushes (.claude/agents/builder.md, Cheap checks only; owner, 2026-10-31).cargo build --profile fast -p nikaia, lower-std and its fixpoint when a tools/*.nika changed, cargo fmt, cargo clippy --all-targets -- -D warnings, scripts/pre-push-check.sh, the tests the brief names and the ones your change touches. No gate.nika.CHANGELOG.md, badges; no new NK code. New tests in Nikaia only; never the full suite. No foreground sleep, no polling; scripts in files.std or the toolchain lacks stops the work: no code around it unless an ADR or Part I-III refuses it (name it). Else Result: blocked, Found: gap + probe, Needs: architect decision (CLAUDE.md, A missing form stops the work).NIKAIA_CACHE_LIMIT=2G; at most two clones with target/ in the machine; delete your own clone’s target/ and target/release/nikaia-scratch at the end; report GB freed.Result: partial with what you ruled out, the probe, and the suspected file and function (.claude/agents/builder.md).target/fast/nikaia run scripts/commit.nika -- REPORT, which writes Pushed: local <sha> into it. A report without a Pushed: line, or with a placeholder left in (TC, DISK), is not done and cuts the batch (k3a1 2026-10-29: Result: done, nothing committed)./home/user/Nikaia/docs/briefs/bugs/b16-1065-field-call-lends.md.report.md)Fields of docs/architect.md, Briefs and reports: Result: done|noop|partial|blocked (the bare word alone on that line: Result: done, never a summary after it, which cuts the batch, b869a 2026-10-27; Owner: is a question for the owner or none, never a role), Files, Commit, Body (optional, one paragraph for the commit message), Fixes, Pushed, Tests, Gate (green|red), Deviation, Found, Needs, Changelog, Owner, Disk freed, and for a move Rs2nika: (the kept N of M lines of rs2nika --score, then the three costliest hand edits; none for a task that moves no Rust, none (redesign) for a brief with Shape: redesign and no Convert: line). none where nothing, and then the bare word: Deviation: none (a note) cuts the batch (batch.nika compares exactly); a note goes into the commit message. Found: is only for a defect outside your change (it cuts the batch); a process event such as another session resetting or rewriting your files is no Found:, it goes under Needs: (m3a 2026-10-28); a converter draft that came out wrong is no Found:, it is one of the costliest edits under Rs2nika:, which the converter lane reads (e12-4b 2026-10-27); how you solved your own step goes into the commit message. Deviation: is only a step of the brief built otherwise than written or not built (a choice the brief left to you, such as keep what X needs and say so, is no deviation: it goes into the commit message; nor is building two steps in one commit when every step is built, e12-3a 2026-10-27, nor a step another commit on develop already built, shown by your test failing with that commit’s change reverted, b889 2026-10-27: name the commit in Body:, nor a test’s expected .stdout/.stderr taken from what the program really prints where the brief’s sketch of it was short or wrong, b934 2026-10-29: say so in Body:, nor a lowering that follows the ADR governing it where the brief’s expected lowering contradicts that ADR, b933 2026-10-29: name the ADR in Body:, nor a lowering other than the brief’s where rustc cannot take the brief’s, b1029 2026-10-31: say why in Body:, nor re-keying an allow-list entry (KNOWN) whose hash changed for the same program and the same reason, b-fixforward-sweep2 2026-10-28: say so in Body:, nor an existing test’s expected .stdout/.stderr updated because your change rightly changes the message it prints, b1012b 2026-10-31: name the test in Body:); how you verified (e.g. a test not run against the unfixed compiler) goes under Tests:. A noop says why under Tests: (what was probed), not under Deviation:. Final answer, one line: done <sha>, report <path> (or BLOCKED: ... / PUSH REJECTED ...).
Attribution: Co-Authored-By: Claude Opus 5.5 noreply@anthropic.com Claude-Session: https://claude.ai/code/session_01GFeMqxRbtUMiGVyDMxsvEq