Symptom

QA filed an end-to-end smoke test asking the dev-krill / krill-blue-bot loop to prove the full pipeline still works: blue runner picks up an assigned issue, branches, makes a small repo edit, files a PR, and the QA-verify run on the ghost runner installs a deb whose Version: matches the just-built PR head.

This is intentionally not a code-fixing issue — there is no bug. The “change” is a marker comment in README.md that proves the round trip.

Root cause

N/A — this is a verification round trip, not a fix. The work is to exercise the path:

1. dev-krill (krill-blue-bot, blue runner) picks up #215 from its assigned-and-open queue.
2. Branches fix/215-…, edits one line, commits, pushes, opens a PR labelled needs-qa-verify.
3. Verify Agent Ghost.yml (ghost runner) builds the four debs from the PR head, version-stamps them, installs them, and hands off to the QA agent.
4. QA confirms dpkg-query -W -f='${Version}\n' krill ends in +qaPR215.r<run>.

Fix

• Added an HTML comment marker to README.md: <!-- e2e-test-marker: krill#215 — blue runner verification -->. No semantic change to any rendered docs; it is the smallest possible payload that still produces a non-empty diff for CI to chew on.

Prevention

• No realistic prevention — this is a verification artifact, not a bugfix. The “regression test” is the QA verify run itself: if dpkg-query reports the right +qaPR215.r<n> suffix and the deb contents come from this PR’s head, the loop is healthy.
• If a future round trip silently fails (e.g. PR opens but the verify workflow never fires), the first thing to check is the runner-label contract: blue runner picks up the dev side via ['self-hosted', 'Linux', 'X64', 'blue']; ghost runner picks up verify via ['self-hosted', 'Linux', 'ghost']. Mismatched labels = silent routing miss. (See 2026-05-03-verify-agent-ghost-workflow.md for the deeper writeup.)