I3239 — One job builds a run's executable and every other job of that run uses it

✕BLOCKED wave 6 · p1 · implementation profile · parallel safe

Part of a-change-is-judged-in-minutes — A change is derived in under a second and judged in minutes, and nothing that could have changed is skipped.

Objective

Build the debug executable once per validate run, upload it, and have suite-shard, evidence, ui, mesh-lab and the site jobs download it as MAJORDOMUS_BIN instead of running cargo build each. macOS keeps its own build.

Why

c228#3 and c195#2: build once and let consumers download products; every job otherwise pays restore, compile and link. It extends milestone ci-critical-path. Sources: chatgpt-majordomus:c195#2, chatgpt-majordomus:c228#3, chatgpt-majordomus:c019#0, chatgpt-majordomus:c019#4.

Current state

Measured on master 707a04c, 2026-10-18: validate.yml has five `cargo build --quiet --locked` steps, in the suite-shard, evidence, ui, mesh-lab and macos jobs (grep -c), and 18 suite cases call cargo build, run or test directly (grep -l over test/cases/*.sh). Only the plan artifact is shared.

Desired state

One Linux build per run; the artifact carries its generation, and a consumer refuses a mismatched one.

Scope

• .github/workflows/validate.yml
• test/lib.sh
• test/cases/3019_a_failed_branch_run_cancels_itself.sh
• lib/rust_bin.sh
• scripts/ci-plan
• .ai/repo/ci/plan.yaml
• scripts/ci/run-plan
• scripts/ci/evidence-collect
• scripts/ci/mesh-lab-evidence

Out of scope

• Uploading the whole target directory
• Release builds (I2353, rescue)

Dependencies

• I3242✕BLOCKED The pull-request critical path has a committed GitHub baseline and a budget per required job, and a run's summary names its critical path and every cache state

Acceptance criteria

• Exactly one Linux cargo build step per validate run (a case reads the workflow)
• Each consumer's job time falls by its former build time, measured on GitHub
• A consumer given an executable of another generation fails
• Validation runs bash test/run.sh 3019_a_failed_branch_run_cancels_itself (the case on disk) and the one-build case this issue adds
• test/lib.sh and the 18 suite cases that call cargo build/run/test directly use the downloaded MAJORDOMUS_BIN, or are listed as exempt with their measured compile cost
• Per-job time is compared with I3242's committed GitHub baseline, suite shards included

Validation

• scripts/ci-plan --check
• bash test/run.sh 3019_a_failed_branch_run_cancels_itself

Evidence required

• one_build_per_run_case
• per_job_time_before_after

Evidence

None recorded. Every token above needs a command or an artifact behind it before this issue can be completed; narrative is refused.

Timeline

started

—

verified

—

completed

—

Those three fields, the evidence above and the state of the dependencies are all the status is made of. There is no status field to disagree with them.

Canonical record: .ai/repo/project/issues/I3239.yaml. Read it back with majordomus plan show I3239.