# Payload envelope codec

## Observed codec pipeline

For the studied configuration payloads:

```text
SQL BinaryData
  → raw-deflate (or detected alternative envelope)
  → UTF-8 text, sometimes BOM
  → brace-based 1C serialized value tree / container text
```

The decoder must retain envelope type, original encoding, BOM, line endings,
and all unmodified text. An encoder is valid only if an unchanged
decode→encode cycle returns byte-identical payload bytes.

## Lossless transform discipline

1. Decode source bytes.
2. Identify the exact BSL or value-tree slice with a proven extractor.
3. Replace only that slice.
4. Encode with the original codec metadata.
5. Calculate SHA-1 from the final raw stored bytes, never from decoded text.

Do not canonicalize braces, whitespace, strings, BOM, compression level, or
base64 blocks without an independently proven canonical writer.
