Do not claim to know why subtraction ran over

Nine episodes subtracted against their publishers' masters land between 82% and
110% of what the declared-versus-served gap implies, and all but one are over.
The readout said the excess was advertising baked into what the publisher serves,
which the gap cannot see. That was a guess, and on inspection it is wrong at
least some of the time.

Heavyweight "#70 Cayden" is over by 46 seconds across four candidates. Its first
candidate opens on `Today's episode, "Caiton."` and `[MUSIC]` -- a title card
and a music sting, neither of which is advertising and neither of which appears
in a publisher's written transcript either. Subtraction answers "not in the
master", which is a superset of "advertising": whisper's own [MUSIC] and `>>`
markers qualify too.

So the readout now states the overrun and names both possible causes instead of
picking one. Tightening the edges is a separate piece of work and needs to be
measured in both directions -- the same lesson MinRunSamples taught, where
improving one show doubled a false positive on another.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018AwnALZL6bD4VBtATDVv3B

1 files changed, 10 insertions, 3 deletions

diff --git a/server/cmd/listend/main.go b/server/cmd/listend/main.go
index 6dd3c65..d45f890 100644
--- a/server/cmd/listend/main.go
+++ b/server/cmd/listend/main.go
@@ -589,9 +589,16 @@ func adAccounting(e *store.Episode, found []transcript.Candidate) string {
 			"so anything found is baked into what the publisher serves",
 			len(found), how, clock(total))
 	case total > gap:
-		return fmt.Sprintf("%d ad candidate(s) %s, %s against %s inserted -- the excess is "+
-			"advertising baked in rather than inserted, which the length gap cannot see",
-			len(found), how, clock(total), clock(gap))
+		// Deliberately does not say why it is over. Two causes look identical here and the
+		// first guess was the wrong one: advertising baked into what the publisher serves,
+		// which the gap cannot see, and candidate edges reaching past the advertisement.
+		// Subtraction answers "not in the master", which is a superset of "advertising" --
+		// a title card, a music sting and whisper's own [MUSIC] markers are all absent from a
+		// publisher's written transcript too. Checked on Heavyweight "#70 Cayden", where a
+		// 134-second candidate opens on `Today's episode, "Caiton."` and `[MUSIC]`.
+		return fmt.Sprintf("%d ad candidate(s) %s, %s against %s inserted -- over by %s, "+
+			"which is either baked-in advertising or candidate edges reaching too far",
+			len(found), how, clock(total), clock(gap), clock(total-gap))
 	default:
 		return fmt.Sprintf("%d ad candidate(s) %s, %s of the %s inserted (%d%%)",
 			len(found), how, clock(total), clock(gap), total*100/gap)