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docs: retract "reference renderer" -- sylpheed-cli is not the oracle

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A framing correction from the human, and it runs through everything I have
written, so it is a retraction rather than a silent edit.

Reborn "was/is just a GUI explorer and extraction CLI for verifying the decoding
of the various files. It may very well be wrong." The oracle is the Xenia Canary
capture and the game.

So verify-screen is a CONSISTENCY check between two decoders that share their
assumptions, plus a regression detector -- not a correctness check, and
agreement in it is not evidence of correctness. Its header now says so, it calls
the CLI the COMPARISON renderer, and DIFFERS means "we moved apart, find out
which of us moved".

The uncomfortable part, recorded because it is the actual failure mode: this
file already contained the sentence "two renderers reading one field through one
decoder agreeing is not evidence that the field is right", written after the
ptframe1 case -- and I then went on quoting 3/255 against sylpheed-cli as though
it meant the port was right. Having the principle written down did not stop me
leaning on the agreement.

Three times both renderers agreed and both were wrong, each caught only by a
capture: pteff05 (menu screens had no background), scale-0 (drawn full size
instead of collapsed), rest() (the menu bracket missing).

Correctness moves to the captures -- nine of them, indexed at
docs/re/captures/ORACLE-CAPTURES.md, covering all five screens in scope. Three
cautions travel with them: not gamma-neutral (there is a floor, don't chase it),
geometry IS sound (a positional disagreement is real), and each is one moment of
a still-animating screen.

verify-screen keeps running over all 16 screens every iteration. It is still
worth having -- total, cheap, and it catches a divergence introduced on the RE
side. It is just not a grade.
This commit is contained in:
Sylpheed port agent
2026-08-29 08:45:48 +00:00
parent 579c8096c1
commit 2fbcd59920
3 changed files with 94 additions and 10 deletions
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docs/DECISIONS.md
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@@ -750,3 +750,62 @@ transcode, is 2-channel, and decodes. Whether Godot emits it audibly is
unconfirmed and is stated as unconfirmed rather than assumed from the stream's
presence. It is a cheap check for anyone with a sound device and an impossible
one here.
---
## RETRACTION — `sylpheed-cli` is not the oracle, 2026-08-29
**This corrects a framing that runs through everything above, so it is a
retraction rather than an edit.** Every place this file called
`sylpheed-cli screen render` *"the reference renderer"* — and it does so
repeatedly, starting at P1 — overstated what it is.
The correction comes from the human, via the RE agent, in their words: Reborn
"was/is just a GUI explorer and extraction CLI for verifying the decoding of the
various files. It may very well be wrong." **The oracle is the Xenia Canary
capture and the game.**
So `tools/verify-screen` is a **consistency check between two decoders that
share their assumptions**, and a regression detector. It is not a correctness
check, and agreement in it is not evidence of correctness.
### The embarrassing part is that this file already knew
After the `ptframe1` case, P2's write-up says: *"Two renderers reading one field
through one decoder agreeing is not evidence that the field is right."* Then P1's
numbers kept being quoted as though 3/255 against `sylpheed-cli` meant the port
was right. Having the principle written down did not stop me leaning on the
agreement — which is worth recording, because that is the failure mode, not
ignorance of the principle.
**Three times** both renderers agreed and both were wrong, all three caught by a
capture and catchable by nothing else:
| | what both got wrong | how it surfaced |
|---|---|---|
| `pteff05` | the menu screens had **no background** | the RE agent decoded the RATC child name |
| scale 0 | drawn at full size instead of collapsed | RE agent's control run |
| `rest()` | `ptframe1`/`ptframe2` invisible; the menu bracket missing | `main-menu-oracle.png` |
### What changes
* `tools/verify-screen` says all of this in its own header, calls the CLI the
**comparison** renderer, and a `DIFFERS` row now means "we moved apart, find
out which of us moved" rather than "the port is wrong".
* The correctness question moves to the captures. The RE agent has committed
nine of them with an index at `docs/re/captures/ORACLE-CAPTURES.md`, covering
all five screens in scope — including a **main menu with `OPTIONS` focused**,
whose difference from the unfocused menu isolates exactly what focus changes.
* Three cautions travel with any capture comparison, and they are the RE agent's:
the captures are **not gamma-neutral** (γ ≈ 1.49 menu, 1.34 title — there is a
floor, do not chase it); **geometry is sound** (best alignment 0,0 at corr
0.9466, so a positional disagreement is real); and each is **one moment of a
still-animating screen**, so compare settled poses or regions known to be at
rest.
### What does not change
The port keeps running `verify-screen` over all 16 screens every iteration. A
consistency check is still worth having — it is total, it is cheap, and it is
what catches a divergence the RE agent introduces on their side. It is simply
not a grade, and this file will stop quoting it as one.