sylph-decoder aa9b7ef340 re: the forced-backdrop rule's pixel cost -- 38 screens go black without it ...

Follows the necessity census. 'The order moves' is a property of the sort; the
tie-break work already found reorders costing zero pixels, so the picture
moving is a separate claim. Rendered each of the 62 deciding builds twice and
diffed.

  38 .prm deciders: changed_px == ink_px in ALL 38. Without the rule the
                    primitive sorts last, paints over everything, and the
                    screen composites to pure black. The port's original
                    contradiction argument, measured on 38 builds across seven
                    archives instead of argued on two.
  24 .tbm deciders: zero -- and that is MY INSTRUMENT, not a finding.

The control asked whether the composite had ink; it always does. The question
was whether the reordered ELEMENT has ink, and compose draws no pixels at all
for a .tbm. So those 24 zeros measure our renderer's blindness by construction.
tie_break_pixel_cost.rs already had the per-element ink_mask this needed.
Reported rather than quietly patched: a control that cannot fail is the shape
this corpus keeps paying for.

Also corrects two things the port agent caught:

  - 'Two renderers, same answer' was true of the six GP_TITLE instances and not
    of the other 74. The port's re-run of my probe is my code executed twice;
    its independent leg was removing its own exporter post-pass, which covers
    GP_TITLE only. The disc-wide 62 has one witness and the page now says so.
  - forced_backdrop_necessity.rs defaulted to GP_TITLE with no argument, so a
    bare run printed 6 instances in the same format as 80. It now walks every
    dat/*.pak and reports the archive count.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v

2026-08-30 07:04:05 +00:00

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