ca61aab5f9
The era test left one element responsible for all 74 507 differing pixels on title_jp -- ptlogo_eff3.t32, the corpus's named plateau-less rest() discriminator -- with two candidate rest poses, (108,72) stale and (98,42) fixed. There is a capture of that exact screen, so the oracle can choose. Scored over the 388x423 box where the two renders differ, so the result is not diluted by the ~92 % of the frame that is identical: stale era rest (108,72) RMSE 58.412 fixed era rest (98,42) RMSE 41.690 <- the game agrees with the fixed era fixed era --settle t=213 RMSE 40.210 Until now the keyframe record-layout fix rested on internal consistency: 0 of 1 042 multi-segment alpha ramps constant-rate under the old reading against 857 of 1 540 under the new. Strong, but not a measurement of the game. It now has one, on the single screen where the two readings change pixels. Three controls, all run first. Alignment found by sweeping the vertical offset rather than assuming it -- 45 gives 32.41 against 56.37 and 53.08 either side, a sharp minimum at the known game-surface offset. The scoring box discriminates: the same box against a different screen's capture gives 98-103 against 40-58 here. And --black changes nothing (58.412/41.690 either way) because every pixel in that box is covered by an element -- recorded because the flag's help says a framebuffer capture must be compared against a black canvas, and here it happens not to matter. Sweeping the screen's own timeline with --at gives the noise scale: the capture sits on a plateau from t~135 to t~240, flat to 1.2 RMSE across 105 units, rising sharply outside (78 at t=0 and t=270). So the stale-vs-fixed margin of 16.7 is ~14x that flatness and decisive, while the settle-vs-rest margin of 1.5 is INSIDE it and is not. This capture separates the eras and cannot separate the policies; the settle-instant proposal stays unadopted. Refutation attempted: sylpheed-port's adjudication that their shipped pose is closer to the game than their reference. It SURVIVES, independently and by a different metric, in the same direction. Also concedes that my "your branch is the stale era" reasoning was invalid -- I inferred era from a line count, which is the error they named -- while recording that the conclusion holds for the ref I could see: origin/auto/port-p6-audio's ui_layout.rs is md5-identical to origin/main's. METHOD: two things that should differ producing identical output is a broken experiment until proven otherwise, and a zero is its most dangerous form. Four instances now. Verify the inputs differ before believing the outputs match, and do not infer that difference from a proxy -- line count is not era. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v
Reverse-engineering knowledge base
This directory is the spec-side of the clean-room: it records what the original Project Sylpheed binary does (behaviour) and how its data is laid out, so that the Rust port can be implemented from these specs without re-deriving anything and without ever copying original code.
It exists to answer one question fast: "do we already know how X works, and how sure are we?"
The one rule that matters
Never document a claim more confidently than the evidence supports, and never paste original code here.
A wrong-but-confident note is worse than no note: someone builds on it and the bug hides for weeks. Every entry therefore carries an explicit confidence and its evidence. This mirrors the project method — measure the oracle, never infer; refute before believing.
Clean-room firewall
- ✅ Allowed: behaviour descriptions, field offsets/types, formulas, state machines,
observed input→output pairs, and references to the original by address
(
sub_821B68C0) or toxenia-rs/sylpheed.db. - ❌ Forbidden here and in
crates/: pasted decompiled C/C++ or verbatim disassembled function bodies presented as the thing to reimplement. Cite the address; describe the behaviour in your own words. Disassembly is a tool for understanding, not a source to copy.
Confidence levels
| Level | Meaning | Bar to reach it |
|---|---|---|
CONFIRMED |
Behaviour verified against ground truth. | ≥2 independent observations or one observation cross-checked against an oracle (canary framebuffer, a known-correct value, a second code path). |
PROBABLE |
Strong single-source inference. | One clean observation, or an unambiguous static read of the disassembly. |
HYPOTHESIS |
Educated guess, not yet tested. | Anything else. Must say what would confirm/refute it. |
The status markers
The table above is the confidence scale. The markers that appear in
BACKLOG.md and the structures/ pages are a separate, and until now undefined,
vocabulary. They mean:
| Marker | Meaning |
|---|---|
| ✅ | Confirmed — verified against ground truth. |
| 🟡 | Partial: true as far as it goes, or true under a stated assumption. |
| ❔ | Open question. Nobody has answered it yet. |
| 🔴 | Refuted — shown false — or blocked by something the container cannot do. |
| ❌ | A specific claim that was tried and failed. Prefer 🔴. |
| 🚧 | Work started and not finished. |
🔴 never means "we have not run it yet." That is ❔ or 🚧. Reserve 🔴's "blocked" sense for a real limit of the box — no push credentials, no hardware Vulkan (lavapipe only), or a decision only the user can make. The box can run the emulator, script input, screenshot, read guest memory, and build and test Rust, so "needs a run" is never a blocker. This paragraph exists because the marker was undefined for 98 uses and three of them were mislabelled that way.
Promotion requires new evidence, not re-reading the old evidence. A HYPOTHESIS that
"looks right again" is still a HYPOTHESIS. Only an independent check promotes it.
If evidence later contradicts an entry, demote it and record the contradiction — do
not silently edit the conclusion.
When to document
- Right after a function/structure crosses from
HYPOTHESISto at leastPROBABLE— before moving to the next code path, so the knowledge isn't lost or re-derived. - Whenever confidence changes (up or down) — append to the Evidence log, don't overwrite.
- Not while it's still a pure guess with no evidence — a one-liner in the relevant backlog/plan is enough until there's something to stand on.
What to document
- Functions/code paths →
docs/re/functions/<name>.md(one file per function or tight cluster). - Data structures / formats →
docs/re/structures/<name>.md. - Keep the index in
INDEX.md(one line each: name · confidence · one-line summary).
Use the templates: _TEMPLATE.function.md,
_TEMPLATE.structure.md.
How we find and confirm code paths (the toolchain)
Everything joins on the guest virtual address (PC) — code addresses are fixed by the XEX load, identical across our emulator and canary.
- Static (cheap, try first):
xenia-rs/sylpheed.db(DuckDB: 25 481 functions, xrefs, strings, vtables, imports). Query withxenia-rs/zq.py—zq.py grep <str>,zq.py xref <addr>,zq.py dis <lo> <hi>,zq.py fn <pc>. Entry points are usually a string (zq.py grep MSG_DEMO) or an import (movie/XMA API) xref'd back to the loader. - Dynamic (when static is ambiguous): run
xenia-rswith its probe suite —--pc-probe/--audit-pc-probe-hex(fires at block entry),--mem-watch(mid-block reads/writes of a VA),--lr-trace(call/return chains),--trace-instructions,--dump-addr(read guest memory). These already exist; prefer them over hacking canary. - Oracle (correctness ground truth): canary — the Wine cross-build
xenia-canary/build-cross/bin/Windows/Debug/xenia_canary.exe(the native Linux ELF crashes / does not run — do not use it). This is the only emulator that reaches the in-game menu; ourxenia-rsnever got past the intro video. Use canary to observe output (capture its framebuffer for texture colours), not usually to instrument code — though itsbuild-crosstoolchain does compile, so small C++ probes + rebuild are possible when needed. Run muted, one emulator process at a time, point it at the real ISO (not the symlink).
⚠️ VA-equality caveat: join code by PC (fixed), but never assume a data VA holds the same bytes across emulators — allocators differ. Compare data by content/layout.