663587f9b5
No Canary patch was needed: UpdateLoopStatus already logs loop_start/loop_end, they just need the Apu category (--log_mask=13 --log_level=3). Decoded, from the menu, 8734 records all after BGM_103's contexts appear: ctx0 (wave 3876864) loop_start 3605682 loop_end 25640423 loop_count 255 ctx1 (wave 3930112) loop_start 3539158 loop_end 26216351 loop_count 255 The movie's three ADV streams log NO loop records -- they do not loop. Semantics visible in the trajectory: read_offset runs from 32 upward and 20 % of samples sit below loop_start, so the stream plays from the beginning and loop_start is where it returns AFTER loop_end. No wrap was observed -- the 45 s hold ended with read_offset at 17 M against a loop_end of 25.6 M. Two registered predictions REFUTED. loop_start is not ~0 but 11.6 % in. And a linear bits-to-seconds conversion is invalid: it gives 62.34 s and 63.29 s for two stems that must play sample-synchronously, which is impossible, so the data refutes the assumption on its own. That leaves a conflict I am not resolving: the field implies a cycle of roughly [10 s, 72 s]; my audio tracking reported offsets 0.25..57.18 s. Recorded as contested, with the likely weak link named as mine -- that locator's control used slices cut from the wave itself, exact copies, which is an easier problem than matching a real capture, and a control easier than the measurement does not bound its error. The port is told to change nothing: its trimmed 61.93 s loop is verified in its own output, and the length survives better than the placement. 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.