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agent: builder model: opus max_turns: 100 budget_usd: 20 —

Brief: GR - a grammar run’s build and run of its parser move into Nikaia (Part #125)

Score: self-hosting lane, row GR of docs/selfhosting-plan.md. It needs hash::sha256_hex and env::var (#922 steps 1-2, brief s922-sha256-env.md, the batch’s step before this one) and BT’s Wall = CheckWall (brief bt-build-time.md, the first step of the batch).

Facts: Moving Rust into Nikaia, Where things live, Traps already met, Commands

Cut: crates/nikaia/src/grammar_run.rs:185-262 Convert: –profile check-free –prefix grammar_run_ Shape: faithful

Line numbers at 042cee5d, before BT. BT deletes Wall (:43-64), so re-find fn compile_and_run, fn cargo, fn write_if_changed and cut those three items.

Pre-flight (before any edit; stop if one fails)

  1. hash::sha256_hex and env::var are on develop: grep -n 'hash::sha256_hex\|env::var' crates/nikaia-std/std.contracts. If absent: Result: blocked, Needs: s922 first.
  2. grammar_run::Wall is a pub use of CheckWall (BT built). If not: Result: blocked, Needs: BT first.

What moves (a new crates/nikaia-std/src/tools/grammar_run.nika, prefix grammar_run_)

  1. compile_and_run becomes pub fn grammar_run_compile_and_run(host: ref GrammarRunHost, at: ref fs::Path, input: ref String) -> String throwing CheckWall. Follow how build_eval.nika throws BtRefusal and how check_host.nika names CheckWall. The steps are the Rust ones, in order:
    • host.driver();
    • the key hash::sha256_hex(program bytes);
    • grammar_run_write_if_changed for src/main.rs, then for Cargo.toml with host.manifest(key, program);
    • process::run(env::var("CARGO") ?? "cargo", ["build", "--quiet", "--manifest-path", …, "--target-dir", …], dir: host.where_tools_start()). On a non-zero exit: DidNotBuild { detail: stderr }. A thrown io::IoError becomes DidNotBuild { detail: f"running cargo: {e}" };
    • write input;
    • run target/debug/p<key> over it. On success: the trimmed stdout. Otherwise: Refused { detail: stderr }. The texts stay byte for byte (creating …, writing …, running …).
  2. write_if_changed becomes grammar_run_write_if_changed(path: ref fs::Path, text: ref String) throwing CheckWall, over fs::create_dir_all, fs::read_to_string, fs::write with fs::Root::Anywhere (as sysroot_cache.nika uses them). cargo() is the one env::var line above, and goes.
  3. The host trait GrammarRunHost has four methods. Check the name with nikaia run scripts/where.nika -- GrammarRunHost.
    • driver(ref self) -> String, throwing CheckWall. The Rust impl holds parsed and ask and calls driver, which stays Rust: Parsed, emit.
    • manifest(ref self, key: ref String, program: ref String) -> String sync. It calls project::runtime_dependencies_for, which is Rust.
    • shared_target(ref self) -> fs::Path sync. It uses env! and the orchestrator cache, and moves with O1.
    • where_tools_start(ref self) -> fs::Path sync.
  4. Rust Workshop::run keeps the running guard: a Mutex, and the guard is lock glue. It calls the lowered function through nikaia_std::rt::exec::block_on, because process::run pauses (the pattern is in modules.rs:88). compile_and_run, cargo and write_if_changed are deleted from Rust.

Stays Rust (say so in the commit body)

Ask (it borrows Ty and Parsed), Workshop and its Mutex/OnceLock, run_comptime, driver, dumper, shapes (Ty::from_ast has no Nikaia counterpart), decode (a forward already), shared_target and manifest (as host methods).

Forms to watch (CLAUDE.md, A missing form stops the work)

Tests

The it filters grammar_at_build_time dsl_grammar build_time comptime, plus the guard set of .claude/agents/builder.md. Then the gate on the whole tests/compiler package, and the lower-std fixpoint: a new lowered/grammar_run.rs and its index line in lowered.rs, nothing else. No new test: the paths are the same as before. A text no existing test prints is named under Tests:, since a failing cargo cannot be staged offline.

To build

  1. Convert, read the draft against the cut, write grammar_run.nika, lower-std, check the lowered file.
  2. Rust: the host impl, Workshop::run calls the lowered function, delete the three items. Update GR’s row in docs/selfhosting-plan.md: built, what is left, and that shared_target and manifest move with O1.
  3. Commit grammar run: the parser's build and run move into Nikaia (GR), Part: #125.

Not yours

crates/rs2nika/convert/nikaia.{contracts,derived,proofs}, crates/nikaia-std/src/tools/check_core_{flow,leaves,stmt}.nika, check_takes.nika and their lowered twins (the bug lane’s b8), the other briefs and reports in docs/briefs/, and any file git status shows modified at your start.

Rules (CLAUDE.md; this block is pasted into every brief, also a fix-forward)

Report (at most 15 lines, to exactly /home/user/Nikaia/docs/briefs/gr-grammar-run.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

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