diff --git a/backend/cmd/tmmutate/main.go b/backend/cmd/tmmutate/main.go
index 92fb28b7..d9ef86ca 100644
--- a/backend/cmd/tmmutate/main.go
+++ b/backend/cmd/tmmutate/main.go
@@ -374,7 +374,14 @@ func one(root string, m Mutation, timeout time.Duration, logs string) (v verdict
 		path := filepath.Join(root, file)
 		body, rerr := os.ReadFile(path)
 		if rerr != nil {
-			return survivedTests, "", fmt.Errorf("%s: %w", m.ID, rerr)
+			// ROT, not a run failure. ⚠ AND IT DOES NOT CLOSE THE MOVED-FILE CASE, which is what a first
+			// draft of this comment claimed: the fingerprint pass above reads every file the catalogue names
+			// BEFORE any entry runs, so a renamed or deleted file still aborts the whole run there, ahead of
+			// this line. Measured: a catalogue with one entry naming a missing file printed
+			// «fingerprint …: no such file or directory» and ran nothing, the healthy entry behind it
+			// included. What this branch does cover is the narrow race — a file that disappears BETWEEN the
+			// fingerprint pass and this read. The moved-file abort is a live gap with a backlog row.
+			return rotted, fmt.Sprintf("%s: %v (the file moved or was deleted under the catalogue)", m.ID, rerr), nil
 		}
 		mu.Lock()
 		saved = append(saved, original{path: path, body: body, sum: hash(body)})
diff --git a/backend/cmd/tmmutate/mutations.json b/backend/cmd/tmmutate/mutations.json
index 7eda823c..b6271b29 100644
--- a/backend/cmd/tmmutate/mutations.json
+++ b/backend/cmd/tmmutate/mutations.json
@@ -1576,9 +1576,14 @@
  },
  {
   "id": "WB36-langscreen-version-literal",
-  "why": "the screen's version must be DERIVED from its calibrated constants: a literal lets the floor slide with no snapshot move, and a resumed chunk is re-verdicted by a rule nobody re-billed for",
+  "why": "the screen's version must be DERIVED from its constants. ⚠ TWO edits, and both are the entry: the literal ALONE is harmless (it prints what the derivation prints) and the slide alone moves the derived string honestly. Only together do they reproduce the finding — the floor slides 0.50→0.45 while the version stays byte-identical, so a resumed chunk is re-verdicted under a threshold nobody re-billed for. An earlier version of this entry carried the SLIDE ONLY under this name, and passed for a pin it was not: it reddened the boundary fixture, never the derivation",
   "package": "./internal/langscreen/",
   "edits": [
+   {
+    "file": "internal/langscreen/langscreen.go",
+    "find": "var Version = fmt.Sprintf(\"langscreen-v1-target-script-share+floor%.2f+min%d\", OnTargetFloor, MinLetters)",
+    "replace": "var Version = fmt.Sprint(\"langscreen-v1-target-script-share+floor0.50+min200\")"
+   },
    {
     "file": "internal/langscreen/langscreen.go",
     "find": "const OnTargetFloor = 0.50",