re: the game surface is rendering BLACK -- check that before explaining absences

The named experiment was to attach the fast probe at t=0 so the boot
title could not be missed. Done, default config, English:

  2391 frames in 600.4 s = 3.98 fps; max glyph 0; hits 0

Ten minutes sampled four times a second FROM LAUNCH, no green-(A) glyph.
So "the plate only shows in an early boot window I keep missing" is mine
and refuted -- the third explanation refuted in three iterations.

Then the check that should have come first. Splitting the raw root grab
into bands:

  y   0- 44 (GTK menu bar)   100.00% non-black   mean 210.50
  y  45-719 (game surface)     0.08% non-black   mean   0.07

The game is rendering black, reproducibly across back-to-back samples,
while the guest is alive and polling input (XamInputGetKeystrokeEx past
1201 calls) and MEM-WATCH keeps reporting. The crop and every pixel
oracle were correct; there was nothing on the surface to detect.

What this does NOT do is retroactively explain the earlier failures, and
claiming so would be the fourth over-reach in a row. Those runs had
content: run 2 sampled mean 33.1, run 3's classifier measured real
frame-to-frame rmse, the gamma_type=0 run measured mean 122.8. The
failure mode CHANGED over the session; black is the newest and worst.

Hypothesis for the regression, untested: canary's shader/pipeline cache
is 47 MB and was last written 23:49 on Aug 28, during the failed runs,
and this session has kill -9'd the emulator repeatedly. The test is to
move cache* aside and boot again -- one line and one run, not done.

Two METHOD lines: ask whether the screen is drawing anything before
explaining why a feature of it is missing; and a newly found fault does
not retroactively explain older failures.

docs/re/METHOD.md

@@ -518,3 +518,17 @@ agent's loop prompt, i.e. nowhere durable. See [`README.md`](README.md) for the
   happened not to be the cause — the most seductive kind, because fixing it feels
   like confirmation. A plausible mechanism that explains a failure is a
   hypothesis, and the fix is its experiment, not its proof.
+* **Ask whether the screen is drawing anything before explaining why a feature of
+  it is missing.** Four iterations produced four explanations for "the title is
+  not detected" — a stale oracle, the locale, the sampling rate, a one-shot boot
+  window — and three of them were refuted in turn. Splitting a raw root grab into
+  bands then showed the game surface at **0.08 % non-black, mean 0.07**: it was
+  rendering black. The check costs one command and belongs at the *front* of that
+  sequence, not after the fourth hypothesis. A detector reporting absence is
+  ambiguous between "the feature is not there" and "nothing is there".
+* **A newly found fault does not retroactively explain older failures.** The
+  black surface is real and reproducible *in the run where it was measured*.
+  Earlier runs in the same session had measurable content (mean 33.1, mean 122.8,
+  non-zero frame-to-frame rmse), so the failure mode changed over the session.
+  Reaching back to re-explain earlier results with the newest cause would have
+  been the fourth over-reach in a row.

docs/re/REFUTED.md

@@ -446,3 +446,8 @@ neighbourhood, not just the line.
   withdrawn last iteration for want of evidence, now **reinstated as a
   measurement**: 1 674 dense samples over 420 s, English, zero glyph frames.
   ⚠️ Reach: a mid-run window only; it says nothing about the boot title.
+* "the PRESS Ⓐ plate appears only in the **boot** title window, which mid-run
+  sampling could never catch" → **mine, and refuted.** The fast probe was
+  attached at t=0: **2 391 frames over 600 s at 3.98 fps from launch**, max glyph
+  0. The plate did not appear at any point in the first ten minutes.
+  [`capture-harness-status.md`](capture-harness-status.md)

docs/re/capture-harness-status.md

@@ -118,3 +118,55 @@ region rather than the full surface, drop the ImageMagick `convert` round trip,
 or keep the glyph test in one long-lived process instead of re-importing numpy
 per sample. None of that is done — this page is the diagnosis, and it is what
 every remaining emulator-side question is waiting on.
+
+
+---
+
+## 🔴 The boot-window hypothesis is refuted too — and the surface is BLACK
+
+**2026-08-29, third explanation and third refutation.** The named experiment was
+to attach the fast probe at **t = 0** so the boot title could not be missed.
+Done, on the default config, English:
+
+```
+2391 frames in 600.4 s = 3.98 fps; max glyph 0; hits 0
+```
+
+Ten minutes, sampled four times a second **from launch**, and the green Ⓐ glyph
+never appeared. So "the plate only shows in an early boot window I keep missing"
+is **mine, and refuted**.
+
+Then the thing I should have checked first. Splitting the raw root grab by band:
+
+| band | non-black | mean |
+|---|---|---|
+| y 0–44 (the GTK menu bar) | **100 %** | 210.5 |
+| **y 45–719 (the game surface)** | **0.08 %** | **0.07** |
+
+**The game is rendering black**, reproducibly across back-to-back samples, while
+the guest is alive and polling input (`XamInputGetKeystrokeEx` past 1 201 calls)
+and `MEM-WATCH` keeps reporting. The crop and every pixel oracle were correct;
+there was nothing on the surface to detect.
+
+### ⚠️ What this does and does not explain
+
+**It does not retroactively explain the earlier failures**, and saying so would
+be the fourth over-reach in a row. Those runs had *content*: run 2 sampled frames
+at mean 33.1 (warm), run 3's classifier measured real frame-to-frame rmse, and
+the `gamma_type = 0` run measured mean 122.8. A black surface is **this run's**
+symptom.
+
+So the honest reading is that the failure mode **changed** over the session, and
+the black screen is a new and worse one.
+
+### 🟡 Hypothesis for the regression, untested
+
+Canary's shader/pipeline cache at `~/.local/share/Xenia/cache` is **47 MB** and
+was last written **23:49 on 2026-08-28** — during the failed runs. This session
+has `kill -9`'d the emulator repeatedly, which can leave a partially written
+cache. A corrupt pipeline cache is a plausible route to a guest that runs while
+nothing reaches the screen.
+
+**The test is one line and one run:** move `cache*` aside and boot again. Not
+done — it needs a fresh 10-minute run, and this iteration had spent its emulator
+budget proving the negative above.