ci(fpga): pipefail the conformance step so a failing runner fails the job

[gHashTag]

Closes #2415

What

fpga-build.yml's conformance step, landed by #2403, cannot fail. Line 772:

if python3 tools/run_conformance_vvp.py "$m" "$v" build/fpga/conformance | tee "build/fpga/conformance/${m}.log"; then
  echo "| $m | EXECUTED, all cases passed |" >> $GITHUB_STEP_SUMMARY
else
  echo "| $m | FAILED (see log) |" >> $GITHUB_STEP_SUMMARY
  fails=$((fails+1))
fi

Without pipefail the if tests tee's exit status. A failing runner takes the then
branch, fails stays 0, and the exit 1 at :784 never fires.

The step has no set -o pipefail, and the workflow has no defaults: run: shell: block, so
the default bash -e {0} applies — -o pipefail is added only for an explicit
shell: bash.

Measured, with a stub runner that fails the way a real mismatch would

$ cat runner.sh
#!/bin/sh
echo "case 3: MISMATCH expected 0x2a got 0x00"
exit 1

As landed on master:

case 3: MISMATCH expected 0x2a got 0x00
| mac | EXECUTED, all cases passed |
fails=0
STEP EXIT 0 — job green

With set -o pipefail, same runner:

case 3: MISMATCH expected 0x2a got 0x00
| mac | FAILED |
fails=1
::error::conformance execution failed
step exit 1

The gate reports "all cases passed" on the line directly below its own log saying
MISMATCH.

This is the defect #2242 removed, in the same file

#2242 fixed exactly this in fpga-formal, and the corrected pattern sits 115 lines
above the new one, at :638-640:

# Audit 2026-08-19: without pipefail the if tested tee's exit (always 0),
set -o pipefail

On the negative control

#2403's body reports a planted-fault control failing correctly, and I have no quarrel with
it: it demonstrates the runner detects a fault. It does not demonstrate the gate
fails, because the gate reads tee. Those are different claims and only the second is what
CI enforces. fpga-conformance going green is consistent with both a working gate and a
vacuous one — which is precisely why the control has to run through the workflow step, not
beside it.

Raised on the PR before merge (#2403 review comment) and merged unchanged; filing so it is
tracked rather than lost.

Not in dispute

The rest of #2403 is good and this issue does not touch it: registry-scoped execution with
the remainder printed as visible debt is the honest shape, and its own comment — "a thin
gate that is real beats a broad one that is vacuous" — is exactly the right doctrine.

Related: #2241, #2242, #2403, #2376.

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PR Dashboard

Generated at: 2026-08-22 12:10:24 UTC

• ci(fpga): pipefail the conformance step so a failing runner fails the job #2417 ci(fpga): pipefail the conformance step so a failing runner fails the job | Created: 2026-08-22 | Updated: 2026-08-22 | 12 failing / 25 total
• parser: accept generic type application in type positions; repair frozen corpus damage #2407 parser: accept generic type application in type positions; repair frozen corpus damage | Created: 2026-08-22 | Updated: 2026-08-22 | 0 failing / 3 total
• corpus: freeze the damage, patch one class at a time, and say where one rule stops #2161 corpus: freeze the damage, patch one class at a time, and say where one rule stops | Created: 2026-08-14 | Updated: 2026-08-21 | 0 failing / 9 total
• Unbreak FPGA CI and correct two unbacked hardware claims #2081 Unbreak FPGA CI and correct two unbacked hardware claims | Created: 2026-08-11 | Updated: 2026-08-20 | 5 failing / 27 total

Summary

Status	Count
Total Open PRs	4
PRs with Failing Checks	1
PRs with All Checks Green	3
READY	2
FAILING	1
PENDING	0

Seal Status

• ⚠️ STALE -- sha256(compiler.rs)=3ea6c4644e23 != manifest seal=87e5cbd3ad94.
  The committed NMSE numbers were certified against an older compiler.rs.
  Run scripts/reseal-check.sh locally for the two-step reseal command (advisory; not a merge gate).

[github-actions]

PR Dashboard

Generated at: 2026-08-22 12:15:52 UTC

• ci(fpga): pipefail the conformance step so a failing runner fails the job #2417 ci(fpga): pipefail the conformance step so a failing runner fails the job | Created: 2026-08-22 | Updated: 2026-08-22 | 15 failing / 26 total
• parser: accept generic type application in type positions; repair frozen corpus damage #2407 parser: accept generic type application in type positions; repair frozen corpus damage | Created: 2026-08-22 | Updated: 2026-08-22 | 0 failing / 3 total
• corpus: freeze the damage, patch one class at a time, and say where one rule stops #2161 corpus: freeze the damage, patch one class at a time, and say where one rule stops | Created: 2026-08-14 | Updated: 2026-08-21 | 0 failing / 9 total
• Unbreak FPGA CI and correct two unbacked hardware claims #2081 Unbreak FPGA CI and correct two unbacked hardware claims | Created: 2026-08-11 | Updated: 2026-08-20 | 5 failing / 27 total

Summary

Status	Count
Total Open PRs	4
PRs with Failing Checks	1
PRs with All Checks Green	3
READY	2
FAILING	1
PENDING	0

Seal Status

• ⚠️ STALE -- sha256(compiler.rs)=3ea6c4644e23 != manifest seal=87e5cbd3ad94.
  The committed NMSE numbers were certified against an older compiler.rs.
  Run scripts/reseal-check.sh locally for the two-step reseal command (advisory; not a merge gate).

[github-actions]

📓 NotebookLM Notebook linked to this PR

• Notebook ID: b83263109fb055dc
• URL: https://notebooklm.google.com/notebook/b83263109fb055dc

This notebook contains session context, decisions, and artifacts for this work.