agent: builder model: sonnet max_turns: 50 budget_usd: 8 —
Score: self-hosting lane, row BT of docs/selfhosting-plan.md: the one step BT left (Result: partial), now that its blocker #1055 is fixed (4de39626, b9). Small: one function body, one forward.
Facts: Moving Rust into Nikaia, Where things live, Traps already met, Commands
Cut: crates/nikaia/src/comptime_run.rs:642-660 Convert: –profile check-free –prefix bt_ Shape: faithful
tests/compiler/tests/a_field_of_a_coalesce_is_read_through_a_view.nika (b9’s test) has row_c, the exact chain this step writes. Run it: cd tests/compiler && ../../target/fast/nikaia run tests/a_field_of_a_coalesce_is_read_through_a_view.nika > $SCRATCH/out.txt 2>&1; diff $SCRATCH/out.txt tests/a_field_of_a_coalesce_is_read_through_a_view.stdout (after cargo build --profile fast -p nikaia if target/fast/nikaia is older than 4de39626). A diff or a rustc error: stop, Result: blocked, Found: with the output.
known_default’s body (comptime_run.rs:642, the KNOWN.with closure) becomes, in crates/nikaia-std/src/tools/build_eval.nika beside bt_may_not_run (:589):
pub fn bt_known_default(ledger: ref Ledger, package: String?, key: ref String, at: i64) -> String? syncThe key is f"{package}::{key}" where a package is given, else key; then let text = (((ledger.functions.get(k) ?? return null).signature ?? return null).config.get(at) ?? return null).default (the chain b9 fixed), and text where it is not empty, else null. Ledger, Signature, ConfigContract are ty.nika (:1233, FnContract.signature :1086, config :992); build_eval.nika already reads FnContract.
The Rust known_default keeps its signature and KNOWN (a thread_local, plan Stays Rust), and becomes one forward inside KNOWN.with: held.borrow().as_ref().and_then(|ledger| bt_known_default(ledger, package.map(str::to_string), &key.to_string(), at as i64)) (or what the lowered signature asks; crate::contracts::Ledger is the lowered ty::Ledger, contracts/mod.rs:55). Caller contracts/mod.rs:1217 (evaluate_defaults) unchanged.
target/fast/nikaia lower-std; the fixpoint changes only lowered/build_eval.rs (and its index line in lowered.rs if any). Check it first: cargo check --profile fast -p nikaia-std --features compiler --message-format short; a rustc error in lowered/build_eval.rs is a lowering defect: stop, Found: with the lowered line and a probe.cargo build --profile fast -p nikaia.cargo test --profile fast -p nikaia --test it -- comptime and -- build_time (singly; the defaults read is #468’s comptime path). No new test for a faithful move; no text a test compares may change.docs/selfhosting-plan.md: step 5 built (drop “except step 5” / the #1055 wait), the share as scripts/self_hosting.py counts it. Commit (Part: #125).known_default’s read is Nikaia, the Rust left is the KNOWN.with forward, the tests pass, committed. Commit subject: build time: the default read moves into Nikaia (BT step 5). Changelog: none (a move).
A text a test compares would change; a missing form (CLAUDE.md, A missing form stops the work); an edit needed outside comptime_run.rs, build_eval.nika, its lowered twin, lowered.rs’s index line, the plan row; an error in another agent’s file.
Not yours, never stage: every file git status shows modified or untracked at your start (today among them crates/nikaia-std/src/tools/lowered/project_members.rs, crates/rs2nika/convert/*, crates/rs2nika/facts/*, docs/briefs/*.report.md), and every docs/briefs/* file except your report. If lowered.rs or lowered/build_eval.rs shows another session’s hunk, stage only yours (builder-facts trap).
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/bt2-known-default.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