agent: builder model: opus max_turns: 110 budget_usd: 22 —
Target and the two check switches into Nikaia (Part #125)Score: self-hosting lane (docs/priorities.md, owner’s direction 2026-10-27: moves first; #125, docs/selfhosting-plan.md C-7 rest and E12, row E12-4, the last E12 row). S=2 (a slice, ~250 Rust lines), C~3-5 M (comparable: e12-4a). Architect’s decision (2026-10-27, after d6318de): Build stays Rust for now. Its Default names Target::default(), which is Target::host() = env!("NIKAIA_HOST_TRIPLE"), a value of the compiler’s own build, not a build-time value a Nikaia field default (ADR-331 D5) can hold; and impl Default for a type of nikaia_std cannot be written in crates/nikaia (orphan rule). So e12-4b0 (lowered impl Default) is not needed by this move and waits.
crates/nikaia/src/emit/mod.rs: enum Target (:51, derives Debug, Clone, Copy, PartialEq, Eq; variants X86_64Linux, Aarch64Linux, Wasm32Unknown, Rust(&'static str)), impl Default for Target (:61, stays Rust as a free fn, see step 1), impl Target (:218-345: parse -> Result, is_bare_metal, name, triple, host, has_threads, has_runtime, unbuildable -> Option<&'static str>). 8 Target::Rust( sites in crates/.crates/nikaia/src/bounds.rs: BoundsChecks (:43), OverflowChecks (:72), each Debug, Clone, Copy, PartialEq, Eq, Default, PartialOrd, Ord with #[default], parse(word) -> Option, name() -> &'static str; 28 uses in crates/nikaia/src.crates/nikaia-std/src/tools/emit_build.nika (426 lines, from E12-4a): UserParallelism, ReentrancyCheck, emit_build_rust_targets() -> Vec[ref String], lowered to Vec<&'static str>; Target::parse reads it for Target::Rust(known). How 4a kept the Default of its enums (a hand impl Default for Build in Rust) is the model.parse throws in Nikaia with the refused! text byte for byte; the Rust adapter maps it back (fn switch, emit/mod.rs:135).Target into emit_build.nika with parse, is_bare_metal, name, triple, has_threads, has_runtime, unbuildable; emit re-exports it (pub use, as 4a did). Target::Rust keeps a 'static triple and Copy: probe first how Rust(ref String) lowers; if it does not lower to Rust(&'static str) without a lifetime parameter on Target, carry an index into emit_build_rust_targets() instead and let triple/name read the list (your choice, say which in Body:). host() and the Default stay in Rust as free functions in emit/mod.rs (host_target(), and Build::default() calls it); the lowered Target gets no Default, and callers of Target::default() / Target::host() (grep them) call the free functions. A lowering defect met is fixed in the compiler as its own commit with a test (Fix, do not work around).BoundsChecks and OverflowChecks with parse/name into emit_build.nika; bounds.rs re-exports them. Their Default: as 4a did for its enums (callers name the variant; Build’s hand impl Default already does). If PartialOrd/Ord are used (grep <, max, cmp on them) and the lowering does not derive them for a data-less enum, that is a compiler step: stop and report it under Needs: rather than writing the comparison by hand.lower-std: only emit_build’s lowered file and the index line change. Run the converter on the moved Rust first (rs2nika --profile emit --file on a file holding the Rust you move) and report --score under Rs2nika:. Update docs/selfhosting-plan.md row E12-4 (4b built; Build stays Rust and why, one line) and run python3 scripts/self_hosting.py (report the % under Tests:).it tests filtered on target parallelism bounds overflow optimization; nikaia --lib emit:: bounds::; nikaia test tests/compiler --both-settings; the guard set of .claude/agents/builder.md; clippy clean. Commits emit: the build target into Nikaia (E12-4b) and emit: the bounds and overflow switches into Nikaia (E12-4b), Part: #125. Changelog: none (a move).
An open design choice beyond the one left to you in step 1; an error in another agent’s file.
Read docs/builder-facts.md.
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; commit after each step; git push origin develop fast-forward, no rebase (rejected: report Pushed: rejected, go on committing).cargo fmt, cargo clippy --all-targets -- -D warnings, scripts/pre-push-check.sh, and the gate of .claude/agents/builder.md (#852).CHANGELOG.md, badges; no new NK code. New tests in Nikaia only; never the full suite. No foreground sleep, no polling; scripts in files.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./home/user/Nikaia/docs/briefs/e12-4b-target.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 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); 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:); 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