# RE backlog

Open items that are *not* being worked right now. Each entry says what is wrong or
unknown, what evidence exists, and what the first step would be. Move an item into
`INDEX.md` (with a `structures/…md` or a parser + test) once it is actually settled.

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## Capital ships assemble wrong in the viewer

**Reported:** 2026-07-30, by the user. **Status:** ❔ open, not investigated.

The reborn viewer builds capital ships from the split XBG7 parts via
`sylpheed-formats::ship::assemble_ship`, and they come out **wrong** — parts in the
wrong place / wrong orientation.

**Why this is a real finding and not a known limitation:** the RE write-up
[`ship-placement-runtime-capture.md`](ship-placement-runtime-capture.md) declares
static assembly ✅ **exact** as of 2026-07-26 — 9-channel joint tables
`[TX TY TZ RY RX RZ SX SY SZ]`, Euler `Ry·Rx·Rz`, with
`ship::tests::static_assembly_matches_runtime_capture` asserting static == runtime
capture (T < 1.0, R < 0.02). So either the viewer is not using that path, or the
claim generalises worse than the test suggests.

**The likely gap:** that test is **one ship** — the `e106` destroyer, 8 parts plus
two nacelles, two turrets and the hull mirror. Nothing pins the other classes.
Rules that were derived from `e106` and could easily be `e106`-specific:

- the engine cluster rig mounted at `GN_Engine_01` (two mirrored nacelles + centre);
- "X-reflect the shared-geometry twin whose lateral offset opposes the geometry's
  dominant side" — a heuristic, not a decoded flag;
- cross-id turret instancing (×2).

**First step (the oracle already exists):** re-run the runtime capture on a *different*
capital ship and diff static vs captured, exactly as `e106` was done — F10 in the
`capture-ship-placement` build of `xenia-canary-native` dumps the ship shader's
`c0..c2` WorldViewProjection rows per part; `WV_ref⁻¹ · WV_p` is the ship-space rigid
transform, which is ground truth. Pick a class whose rig differs from `e106`
(different engine count, a ship with no `sld`, a carrier). Then extend
`static_assembly_matches_runtime_capture` into a per-ship table so a regression in one
class cannot hide behind `e106` passing.

**Also worth ruling out first, cheaply:** that the viewer's own transform stack (scale,
handedness, node-instance recursion) is not re-breaking a correct assembly — compare
the viewer's placement against `assemble_ship`'s output directly before blaming the
format layer.