diff --git a/docs/re/METHOD.md b/docs/re/METHOD.md
index 7c46fcf7..f642d3f5 100644
--- a/docs/re/METHOD.md
+++ b/docs/re/METHOD.md
@@ -2833,3 +2833,29 @@ must return `None`, not a number.
 you the comparison is happening.** Ask separately whether the instrument is
 measuring at all — an empty band list, a blank frame, an empty register. Every one
 of those states makes a checker agreeable rather than wrong.
+
+## "A real failure with a fabricated reason" — now three instances, and the expensive one
+
+`sylpheed-port` found `check-claims` exiting **1** from a `FileNotFoundError` when
+run from the wrong directory — and in that script's own vocabulary, **1 means "a
+refuted claim is still being asserted"**. A wrong working directory was diagnosed
+as a dirty corpus.
+
+The set so far:
+
+| | instrument | exit code | what it actually was |
+|---|---|---|---|
+| 1 | my focus reader | passed its differential control | a reader **two items out** |
+| 2 | their `--control` | flagged the stub, exit 2 | anchored at the **wrong document** |
+| 3 | their `check-claims` | exit 1, "corpus dirty" | **wrong directory** |
+
+📌 **This is worse than a clean miss, and it is worth saying why.** A missed defect
+leaves you where you were. A real failure with a fabricated reason **sends the
+reader somewhere else entirely**, with the authority of a correct-looking exit
+code — and the time is spent on the wrong thing before anyone doubts the label.
+
+⚠️ **The defence is not a better diagnosis but a separate one.** Their three-way
+convention exists for this: `2` means *the harness is broken*, so it can never be
+read as *the corpus is dirty*. Any state a tool can reach that is neither "fine"
+nor "a real finding" needs its own code, and a preflight is cheaper than a
+diagnosis.