e803930e88
sylpheed-port's BLOCKED ask #2. The gap was the one quantity in the transition with no rule: measured at 0, 3 and 2 frames across three transitions, and I had proposed it might be a load, which would make it emulator- and storage-dependent and unauthorable. Leg 1, bundle size runs the wrong way. If the gap were the incoming bundle arriving, the biggest bundle would gap longest. Build 4 is 12 278 666 B and gaps ZERO frames; build 5 is 6 977 437 B and gaps 3 and 2. Leg 2, ran title->menu a second time from cold. The outgoing ramp is byte-identical (63, 127, 191, 255) and the gap is 3 frames in BOTH runs. Leg 3, and the two runs are not a null comparison -- which is the objection leg 2 invites. The captures refute it themselves: press-to-first-change differs by ~12 frames between them (~25 against ~10). Something in this transition really is cache-sensitive and moved by 0.4 s, while the gap did not move at all. The control comes from inside the measurement rather than from an assumption that conditions differed. So the gap is deterministic to the frame and not a load. It is also not constant across transitions (0, 3, 2, 3) and not in the fade group -- the port reports 866 keyframes across 16 screens with 0 untimed. A deterministic game quantity with no rule found; black_hold_units stays 0, and "not a load" must not become a reason to author a constant. The load proposal in screen-transitions.md is marked refuted rather than deleted. Also fills in docs/game/navigation.md, which the standing brief asks me to keep and which I had not touched while measuring four transitions: a player-side section on what a screen change looks like, and three scripting traps -- that `pkill -f xenia_canary` kills the shell that ran it (cost a launch today, and the same trap is already in METHOD for pgrep), that screen_id.py reports `menu` during the attract loop, and that it cannot tell EXTRAS from the main menu. 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.