Track versions and .SI2

A track built for the modern engine can be hidden from a 1998 install that would render it wrong. The mechanism is the situation file's extension: .SIT is a normal track, .SI2 is one only newer engines see. An old engine does not recognise .SI2 and simply passes over it.

It is the same file under a different name, and it follows the same pattern as disabling: a disabled .SIT is .SIX, and a disabled .SI2 is .SIY. The engine ignores what it does not recognise, which is the whole trick.

The version record

Beside it sits DATA\<stem>.TXV, a small text record that asserts things about the pod around it — whether the legacy .RAW / .ACT pair was packed, and whether any texture is larger than 256×256. It is plain ASCII, key=value one per line, with # comments.

C-POD preserves it untouched through pack, unpack and rebuild — including keys it does not recognise. That is deliberate: unknown keys are the extension mechanism, so a record written by a newer Traxx has to survive a trip through an older tool unchanged.

When it starts to matter

It matters when you edit a pod. Strip the .RAW files to shrink one and the record now says something false — and the situation file has to become .SI2 at the same time. Those are one decision, not two.

Check Version Record on a track compares the record against the pod around it and reports three kinds of disagreement:

• the record says the legacy pair was packed and it was not, or the reverse;
• the hdTextures claim disagrees with the art actually present;
• the extension contradicts the fallback claim — HD-only content that is still .SIT, which is exactly the case a 1998 install would list and then render without textures.

A version record that contradicts its pod is worse than no record at all. Readers trust it, so the failure does not surface here — it surfaces later, on somebody else's machine, as missing art or a track that never appears.