---
name: is-this-red-mine-delta-test
description: "Before saying a word about a CI red's cause, run the same job on the head WITHOUT your delta and check what files the delta actually touches — attribution first, mechanism never."
metadata: 
  node_type: memory
  type: feedback
  originSessionId: d1011551-1412-4921-bcda-e3142510bb8e
  modified: 2026-08-02T17:07:49.182Z
---

Golden 30754060525 on `a0b8d5f` reds looked like they landed on my lane's head. Two reads settled it in minutes: (1) the same `test` job on `7a3c08c` (the head without my four commits + hertz's fixtures) had SIX product rows red, all six green now — my delta fixed, not broke; (2) the two surviving reds were a Linux-only clippy lint in `crates/xtask/` and a Windows link-step file lock, neither in my delta's file scope. Next head `2138b16` red on one e2e row, and `git diff --stat a0b8d5f 2138b16` = 2 xtask files, 4 insertions — a delta that cannot reach a `spt` e2e binary, on a row that passed one run earlier.

**Why:** a red in a head that contains your commits is not evidence about your commits. Attribution is a cheap mechanical check (prior head's same job + `git diff --stat` + `git log -L <line>,<line>:<file>` for blame); mechanism is an expensive story that adopts the anomaly. Same discipline as [[refuse-mechanism-until-something-discriminates]], pointed at your own work.

**How to apply:** before reporting, run the prior head's same job, diff the delta's file scope, blame the flagged lines. Then report attribution + the discriminating check, and name what you are NOT claiming — one green after an intermittent is not a fix and one red after one green is not a defect ([[one-sample-is-not-a-negative]]). Flag a hypothesis that would convict you along with the check that would settle it; doyle ran mine (my refusals print reason + pid — zero refusal lines in the job log) and refuted it. See [[gh-run-poll-jobs-not-status]] for reading a job log mid-run.