fix(develop): #1440's locals rule broke four CI jobs: FV runs stage 1; two probes and one fixture mark their locals

[shd101wyy]

Summary

Develop has been red since #1440 (00eddd3e4, battery 39087983359), and that blocks v0.2.65. Four jobs fail. All four come from #1440's new syntax or its locals rule reaching Yo source that its sweep and its tree-binary gate could not see:

1. "Formal verification (pinned Z3)": the seed runs migrated test files. Explained below.
2. "Static musl Linux bundle": the probe in scripts/bootstrap/probe-stack-sizing.sh lends &mut local from an unmarked binding (E0917).
3. "Docker default-seccomp epoll fallback": test.yml's inline probe calls &mut self as_ptr() on the unmarked sv_uninit and b_uninit (E0917).
4. "Compiler internal tests, shard 5": tests/internal/compile.test.yo embeds a fixture program in a string, and its k/i counters are reassigned (E0917). A yo subprocess on PATH compiles it. Locally that was the seed, so VBD decision 47 step 2, Generation A: bindings are immutable unless declared mut(name) (locals, patterns, comptime) #1440's gate passed it.

Items 2–4 mark the written locals. Those three programs are compiled only by tree-built binaries.

Item 1 in detail.

Root cause. The verify job ran tests/internal/verifier*.test.yo with the v0.2.64 seed. #1440's Generation A sweep marked those files' written locals mut(cfg) := …, and the seed cannot parse that: mut(x) is its deleted borrow word. The error is Invalid binding to "mut", expected identifier or operator, and 0 of 29 tests ran. I reproduced it locally with the seed and the job's environment.

The markers cannot be reverted. The tree compiler would then reject those files with E0917, and every other job runs tests/internal on the tree compiler. A tests/internal file is written in the tree's syntax, so only the tree compiler can run it.

Fix:

• verify now needs stage1. Its five yo test steps download yo-stage1 and run /tmp/yo-stage1 test …, the same pattern compiler-internal-tests-selfhosted uses. The tests and their assertions are unchanged.
• The yo verify steps stay on the seed, because their inputs (std/spec, std/collections, tests/spec) carry no new syntax. The verify-src comment that said "like every other step in the verify job" is corrected.
• AGENTS.md's Tier 1 list gains the lesson: when a change gives tests/ syntax the seed cannot parse, run every seed-run yo test step with the seed. A tree-binary Tier 1 cannot see this, and that is how VBD decision 47 step 2, Generation A: bindings are immutable unless declared mut(name) (locals, patterns, comptime) #1440's gate missed it.
• issues/fixed/2026-10-18-the-fv-job-runs-generation-a-test-files-with-the-seed.md (S2) covers all four.
• AGENTS.md's Tier 1 lesson names the three blind spots: seed-run yo test steps, workflow and shell-embedded probes, and test-embedded programs compiled through PATH.

Verification

• Reproduced the failure locally: the v0.2.64 seed with YO_STD=$PWD/std and YO_TEST_Z3=1 on verifier.test.yo fails to compile the batch (log ~/Workspace/Yo-wt/vbd-logs/fixfv/vt2.log).
• Ran the five files on the tree compiler (yo-d47loc-3d1afa693, whose src/std match 00eddd3e4) with the pinned Z3 5.1.0 and the job's leak-verdict settings. This is also the first run of these files under a real solver since VBD decision 47 step 2, Generation A: bindings are immutable unless declared mut(name) (locals, patterns, comptime) #1440: on this machine, Z3 was missing during its gate. All five passed: verifier 29/29, verifier_negative 10/10, verifier_assumed 5/5, verifier_refine 6/6, verifier_list_len 25/25 (logs ~/Workspace/Yo-wt/vbd-logs/fixfv/s1-*.log).
• CI, first run (b8fdc7acd): the verify job passed every step on stage 1, including the five verifier test steps and the four yo verify steps.
• Sweep for items 2–4: I extracted all 124 multi-line Yo programs embedded in tests/ string literals and checked each with the tree compiler. The only other E0917 is a formatter.test.yo input, which is formatted and never compiled. scripts/check-embedded-yo.sh passes 7 of 7 sites with the tree compiler, and both probes and the fixture now pass check.
• Workflow YAML parses. scripts/check-issue-refs.sh is green. No .yo file changed, so no fmt or check run was needed.
• yo check ./src --std-path ./std — not needed, no src change
• yo check ./std --std-path ./std — not needed, no std change
• Tests covering the change: this PR's own verify job runs the new steps; it must be green before merge
• yo fmt --check on tests/internal/compile.test.yo (tree binary)
• Bug has an issues/ entry with a severity
• Docs — not user-facing

LLM attribution

• Model: Claude Opus 5.5
• Agent harness (optional): Claude Code

Deferred

Nothing.

🤖 Generated with Claude Code