agent: builder model: opus max_turns: 80 budget_usd: 20 —
match as it joins an if (ADR-361 D9) (Fixes #1021)Score: a prover defect y7b found (bugs before moving); small, one file family (prover_walk.nika), and it runs after y4c so the two never touch the same files at once. Not needed by json or yaml today.
Read first: docs/builder-facts.md, ADR-361 D9 (docs/specification/adr/adr-361.md: “after a branch that changes it on one side or both, it is one side’s value or the other’s”), then in crates/nikaia-std/src/tools/prover_walk.nika: the statement walk’s Expr::If arm (about line 1271) to prover_if, prover_join (about 1372) and prover_side (about 1455, renames a branch’s own names apart, y7b 65d86e57). Expr::Match falls through to prover_expr and is never joined. Facts y7b paid for: prover_follow_mutables decides whether a let mut is followed; scope.rebind clears; flatten nested if in tools/*.nika up front (clippy collapsible_if fires on the lowered code; grep clippy’s output with -A3 to see the --> line).
Before your first build: cp target/fast/nikaia $S/nikaia.before (a scratch dir), so “fails on the unfixed compiler” is one command per test.
Probe (refused NK1300 “not a whole number the prover reads”; the if form of the same body is proved):
fn f(first: i64) -> i64 {
assert(first >= 0 && first <= 10)
let mut cp = first
match cp > 5 {
true => { cp = cp + 1 },
false => {},
}
assert(cp >= 0 && cp <= 11)
return cp
}match on a bool (arms true, false, else, in either order, one arm missing allowed when else covers it) is walked as the if it is: the scrutinee is the condition, each arm a side, joined by prover_join. Test tests/compiler/tests/prove_a_match_on_a_bool_joins_like_an_if.nika + .stdout (the probe, and the false arm first).match joins what its arms assign: n sides instead of two (generalise prover_join/prover_side, or fold pairwise, your choice: say which in Body:); an arm that leaves (return, throw, break, continue) drops out as a leaving side does in prover_join; an arm’s pattern gives a fact only where it is a whole-number literal or range and the prover reads the matched value, else none. Tests prove_a_match_arm_assignment_reaches_the_join.nika + .stdout (an enum match whose arms assign different bounded values), and prove_a_match_arm_that_breaks_a_bound_is_refused.nika + .stderr (NK1300). The last commit says Fixes #1021.If n-way joining needs something the ADR does not say (for instance what a guard if on an arm gives), build without it and name it under Found:.
.claude/agents/builder.md (#852): a tools/prover_*.nika change, so lower-std, target/fast/nikaia test --both-settings --project tests/compiler, the it filters prove unproved_claims bounds plus the guard set, and the package gate below. The sequences guard: your change must not raise it.sync (#1014).Changelog: one sentence (a crates/ change); the version raise is the supervisor’s.Files this brief may touch (beyond its report): crates/nikaia-std/src/tools/prover_*.nika, bounds_body.nika, their lowered files and lowered.rs, the files lower-std rewrites, the new tests.
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.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: owner 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.Pushed: line names the pushed sha. 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).NIKAIA_CACHE_LIMIT=2G target/fast/nikaia test --project packages/yaml green, and cargo test --profile fast -p nikaia --test it -- fmt::every_nika_file (it formats every .nika under packages/). For a change only under packages/yaml/ this is the gate the line above asks for; a change under crates/ runs the gate of .claude/agents/builder.md (#852) as well. target/fast/nikaia is built by the session hook; if it is missing, cargo build --profile fast -p nikaia once.Changelog: none, unless the brief changes crates/.Files not to touch: anything outside packages/yaml/ and the brief’s own report, unless the brief names it; never docs/briefs/batch.txt or a brief of another lane.
max_turns: commit and push every finished step, then report Result: partial with what is left under Needs:. Uncommitted work at the end is lost work (y4 ran out at 110)./home/user/Nikaia/docs/briefs/yaml/y7c-match-join.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 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:); 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_01UVxJDveRM5qKZKyCqq6Y24