determinism-tiers: a tier covers what the sink emits, not the decode alone #81

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2026-09-10

Transaction Science

determinism-tiers: a tier covers what the sink emits, not the decode alone ...

`decode-equivalence` claims "the whole decode to the final medium reproduces
byte-for-byte", and §3 makes it the precondition for a receipt carrying a
reproducible decoded-medium hash and for a hard provenance binding over the
RENDERED content. But the tier was defined over the decode stage only, and said
nothing about processing applied after a conformant decode.

Two mechanisms in force today walk through that gap, both arriving in the same
pipe as the codestream:

  * ITU-T H.274 (V4, 01/2026) `nnpfc`/`nnpfa` SEI activate a neural post-filter
    AFTER decoding, changing output pixels.
  * ISO/IEC 23001-11 decoding-operation-reduction metadata exists precisely to
    make a decoder spend fewer joules by doing less work — deliberate
    degradation, invisible to a conformance check that stops at the decoder.

So a capability could hold `decode-equivalence` honestly, emit a receipt with a
"reproducible decoded-medium hash", and have that hash describe something the
viewer never saw. The hash verifies. It attests the wrong artifact.

This is the same defect shape the proof ladder had: a claim that outruns what was
actually verified. There the fix was that an absent solver yields Unproved; here
it is that a tier claim is void if the sink alters the medium after decode.

Adds §2 "What a tier covers" with three rules — evaluate the tier over the
EMITTED medium; an object honouring a reduction hint MUST NOT claim
`decode-equivalence` nor carry a reproducible decoded-medium hash; a
registration SHOULD state whether its payload can carry post-decode directives at
all — plus a §3 cross-reference so the rule is visible where tiers are declared.

The second rule is the one with teeth for the energy work: reporting joules while
concealing the degradation that bought them states a cost without its
consideration.

No wire format change; vocabulary and conformance framing only, as the extension
already is. Found by the landscape survey in #80, then verified directly against
this file — it has no occurrence of post-decode, post-filter, SEI, or hint.

Co-Authored-By: Claude Opus 5 <[email protected]>

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