• Issue: #1793
• Branch: fix/issue-1793, three commits — 255c0d2f4 (restore + rulebook), 1e251f91b (docs + CHANGELOG), 6903f424e and the review-fix commit (harness
  • #1793 suite)
• Area: test-suite maintenance / ai/AGENTS.md rulebook (no application code touched)
• Severity: minor for the product, major for the safety net — a verification suite that guarded the 1.9.20-parity of the issue-tracker connection-check diagnostics was no longer re-runnable from the repository, so a regression on that path would have passed CI silently.

git show origin/sebiboga:tmp/TLU_Test_Cases.md | grep -c "Issue #1701" || true returns 0: the suite documenting a failed issue-tracker connection check must record why it failed, and the log row must name its source was missing from the tracked test file, while its sibling suite (#1740) was present.

$ grep -c "Issue #1701" tmp/TLU_Test_Cases.md      # before the fix
0
$ grep -c "Issue #1740" tmp/TLU_Test_Cases.md      # control: sibling present
1

$ git log --oneline origin/sebiboga -S"Issue #1701" -- tmp/TLU_Test_Cases.md
ce093fa54 docs(#1740): regression suite + screenshots for …   <-- removed it again
47905e3e8 test(#1701): regression suite for the issue-tracker connection-check diagnostic
30aeecd0d feat(opencode): leftover changes from a task-implementation run
861a74549 test(#1701): regression suite for the issue-tracker connection-check diagnostic

$ git show --stat ce093fa54 -- tmp/TLU_Test_Cases.md
 tmp/TLU_Test_Cases.md | 221 +++++++++++++++++++++++++++++---------------------
 1 file changed, 129 insertions(+), 92 deletions(-)

$ git show ce093fa54 -- tmp/TLU_Test_Cases.md | grep -m1 '^@@'
@@ -1626,103 +1626,140 @@ role 3 = read-only user tlu1037norights, only mgt_view_tc(6)

-S reports commits where the count of the string changes, so the four lines above read: added (861a74549) → lost (30aeecd0d) → re-added (47905e3e8) → lost again (ce093fa54).

git log -S"Issue #1740" returns ce093fa54, a2df484a8, 2f108e321: the same mechanism destroyed two suites in three consecutive commits. Only the newer one was ever restored.

tmp/TLU_Test_Cases.md is a single shared append-target for every concurrent CI agent (rule 9 of ai/AGENTS.md) and it sits under a git-ignored directory (.gitignore:47 = tmp/). Two consequences:

1. git add tmp/TLU_Test_Cases.md refuses the path ("use -f if you really want to add it"), so the file is force-added by every agent — the ignore applies to new paths only;
2. no CI job asserts anything about the file. It is tracked (git ls-files tmp/TLU_Test_Cases.md), so a review diff does show the 92-line deletion — the reason it shipped is the absence of a gate, not an invisible diff: the file is invisible to every automated check, and 3.6k lines of appended suites are not what a reviewer reads line by line.

The deletion itself: the agent working on issue #1740 built its copy of the suite file by re-serialising a stale read (its base predated the #1701 block) and then wrote the file wholesale instead of appending. Git had to realign the whole neighbourhood of the inserted suite, and the #1701 block fell inside the removed span — that single hunk (@@ -1626,103 +1626,140 @@, 129+/92-) is the deletion. This is a shared-file clobber, not a careless edit: the same agent pattern destroyed #1740 one commit later (a2df484a8).

1. Append, never regenerate. The #1701 block is the last section of 47905e3e8 (lines 1631→EOF of a 1728-line file), so it is self-contained and can be restored verbatim without touching a single existing line:

git show 47905e3e8:tmp/TLU_Test_Cases.md | sed -n '1631,1728p' >> tmp/TLU_Test_Cases.md

2. Make the obligation explicit where the agents read it — ai/AGENTS.md:

• rule 9 (Write Test Cases) is now APPEND-ONLY: the file is shared by all agents and lives under the git-ignored tmp/, so no CI gate can see a clobber; never regenerate it from your own copy, append with >>, and before committing verify git diff --cached --numstat -- tmp/TLU_Test_Cases.md shows 0 deletions (grep -cE "Issue #<n>" finds your suite, and grep -cE "^## (Regression|Suite|Task|Modernize) " did not drop). Both destroyed suites are cited by commit hash. The --cached is not cosmetic: git diff --numstat compares worktree to index, and rule 9 forces the agent to stage the file with -f — once staged that diff is empty, so the naive gate passes even on a clobber. The rule therefore names git diff --cached --numstat before the commit and git diff --numstat HEAD~1 HEAD after it.
• rules 5 of ai/FIX-ISSUE.md and ai/IMPLEMENT-TASK.md get the same gate — those are the two rulebooks whose runs actually produced ce093fa54 and a2df484a8, so hardening only ai/AGENTS.md would have left the hole open where it was dug.
• rule 7 (Update the GitHub Wiki) gains the mirror-image rule for the second shared artifact: never regenerate a page from a stale read — git pull --rebase first, then edit only your own section.
• rule 18 (Coordination etiquette) names both shared artifacts explicitly.

$ git diff --numstat origin/sebiboga...fix/issue-1793 -- tmp/TLU_Test_Cases.md
189	0	tmp/TLU_Test_Cases.md                    # additions only, nothing removed
$ git diff origin/sebiboga -- tmp/TLU_Test_Cases.md | grep -c '^-[^-]'
0                                               # zero removed lines, ever
$ grep -cE "^## Regression — Issue #1701:" tmp/TLU_Test_Cases.md
1
$ grep -cE "Issue #1701|Issue #1740" tmp/TLU_Test_Cases.md
2                                              # both suites coexist
$ tail -99 tmp/TLU_Test_Cases.md | sed '1d' | diff - <(git show 47905e3e8:tmp/TLU_Test_Cases.md | sed -n '1631,1728p')
                                               # byte-identical
$ diff <(git show origin/sebiboga:tmp/TLU_Test_Cases.md | grep '^## ') \
       <(grep '^## ' tmp/TLU_Test_Cases.md)
47a48,49
> ## Regression — Issue #1701: …               # only the two new suites
> ## Regression — Issue #1793: …

bash tmp/verify_1793.sh (exit 0 = PASS) — see the suite ## Regression — Issue #1793 in tmp/TLU_Test_Cases.md. It reads the tracked suite file (git show HEAD:tmp/TLU_Test_Cases.md), not the working copy, and asserts 8 invariants: the #1701 heading, its R1–R7 measured rows, its PASS verdicts, its 1.9.20 target line, "no suite lost vs 47905e3e8", balanced markdown fences, a non-truncated tail, and — when run on the repo — that the last commit touching the suite file deleted nothing.

$ bash tmp/verify_1793.sh
  PASS  Issue #1701 heading present (= 1)
  PASS  Issue #1701 measured rows R1-R7 intact (= 7)
  PASS  Issue #1701 records a PASS verdict (= 7)
  PASS  Issue #1701 keeps its 1.9.20 target (= 1)
  PASS  no suite lost vs 47905e3e8 (= 0)
  PASS  markdown fences balanced (= 0)
  PASS  file does not end mid-block (last line non-blank)
  PASS  last commit on the suite file deletes nothing (= 0)
G1793 result: 8 PASS / 0 FAIL      # exit 0

Negative controls — three, because "the #1701 suite is gone" is only part of the risk, and a gate that cannot run must not report success:

NC3 exists because the first version of the cross-check took its baseline only from 47905e3e8 and matched the issue number anywhere in the text: a later suite could vanish and the harness still reported 8 PASS / 0 FAIL — exactly the false negative a clobber would use. The cross-check now takes the union of 47905e3e8 and the last commit that touched the file (45 suite references) and matches the suite heading, not a prose mention. NC4 exists because the cross-checks used to skip() silently whenever they could not run (below the repo root, outside a clone); an unavailable cross-check is now a FAIL unless --allow-skip is passed explicitly.

The deletion gate itself compares against the merge-base with the default branch, not HEAD~1: the invariant that matters is "nothing that existed before this work can be missing", whereas HEAD~1 only sees the previous commit and would also flag a legitimate correction of a suite section that this branch added itself.

• Re-generate the whole file from a merged history — this is the exact operation that caused the bug (twice).
• Add a sixth CI workflow that fails when a commit touching tmp/TLU_Test_Cases.md contains deletions — attractive, but the path is git-ignored, so a git-level gate is unreliable there; and rule 18 forbids fighting the five existing workflows. The obligation is agent-side instead.
• Move the suite file out of tmp/ into a tracked path — this does remove the ignore problem, but it would break the reference contract of every Refs #<n> suite and every agent currently in flight. Recorded as the follow-up option, deliberately out of scope for a bug fix.

No application code, no API endpoint, no locale bundle and no DB schema was touched, so no Event Viewer / events entry can be produced by this change (verified: SELECT COUNT(*) FROM events; → 0).

Mirror. This page is mirrored verbatim in the GitHub Wiki (sebiboga/testlink-upgraded.wiki, page Bugfix-Issue-1793-TLU-Test-Cases-1701-Suite-Clobber.md, local clone tmp/wiki-repo/); the wiki copy additionally carries any screenshots, this defect being a repository-hygiene one with no UI surface.