agent: builder model: sonnet max_turns: 60 budget_usd: 10 —
Blocks: none (found by s1082, docs/briefs/s1082-or-default-cloned.md.report.md)
Score: compiler bug, a wrong output with no error, so it ranks above a refusal. One branch of one function, the cause traced and sure: cheap.
Facts: Where things live, Traps already met, Commands
Run 1 stopped partial on K3b’s then-untracked comptime_bundle.nika, which broke the build; K3b is committed (79e5571b) and develop builds. Run 1 left its edit uncommitted in the tree: crates/nikaia-std/src/tools/emit_core_leaves.nika (hole-less branch: format_of(parts).replace("{{", "{").replace("}}", "}")) and its twin lowered/emit_core_leaves.rs. These two files are yours: take the edit over, check it against step 2 (escaping as the LitString arm does it, not a second escaper), rebuild, test, commit. Old report: b22-1099-fstring-no-hole-braces.md.report.run1.md. Committing them moves the self-hosting share (83.2 to 83.3 %): the badge trap in Traps already met applies.
target/fast/nikaia at 0d8deb1f)fn main() {
let n = f"a {{ b }}".len()
print(n)
print(f"a {{ b }}".clone())
}Expected 7 and a { b }. Got 9 and a {{ b }}. With a hole, f"a {{ {x} }}".clone() is right; print(f"...") takes another path and is right.
Cause (traced, sure): crates/nikaia-std/src/tools/emit_core_leaves.nika, emit_core_string, the Expr::LitInterpolated arm, branch !emit_leaf_has_holes(parts): it writes "{format_of(parts)}".to_string(). format_of makes the text of a format! string, with { and } doubled; with no format! around it the doubling stays.
Tests:)." and \ and control characters escaped as the Expr::LitString arm just above does it (reuse its escaping, do not write a second one).lower-std and its fixpoint.tests/compiler/tests/fstring_no_hole_braces.nika + .stdout: the probe, f"{{}}".len() (2), and a hole-less f-string holding \" and \\ used as a receiver; failing on the unfixed binary.
Commit emit: an f-string with no hole writes its braces once (Fixes #1099).The new test fails on the unfixed compiler and passes through nikaia test --project tests/compiler --both-settings. Also: lower-std fixpoint clean; build, fmt, clippy, pre-push-check.sh; committed locally. Changelog: one line. Stop about 15 turns before max_turns: commit what is finished and report partial.
An edit is needed outside emit_core_leaves.nika, the file that defines format_of (read only unless the fix must go there; then say why in Body:), their lowered twins and the new test. Or you hit an error in another agent’s file.
Not yours, never stage: every file git status shows modified or untracked at your start except the two run-1 files above, 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/b22-1099-fstring-no-hole-braces.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 or red <check>: your cheap checks, never none, which cuts the batch, j4 2026-10-31), 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