round-trip/ — <name>.json + <name>.md: the markdown adfToMarkdown must emit for that document, byte for byte, and that markdownToAdf must read back to it (AGENTS.md §2). Grouped by what the fixture exercises.
normalization/ — <name>.md + <name>.json: markdown input, and the document markdownToAdf must build from it, which must in turn emit and read back to itself. The markdown is not canonical.
errors/ — <name>.md: markdown input that must not convert. A <name>.error beside it pins which error.
real-payloads/ — <name>.json: sanitized live ADF, round-tripped ADF→markdown→ADF. No expected markdown.
commonmark-spec/ — the CommonMark suite run against markdownToAdf by three checks. spec.json (0.31.2, vendored byte-exact) is the suite; refusals.json pins each refusing example to its error code; exceptions.json pins each known divergence by check, example, kind and the exact divergence, with a reason. kind is mark-model (the permanent count divergence from ADF's mark-per-text-node model), unspellable (parses but the flavour has no spelling) or pending (a parser gap a later milestone may close). The two lists are derived and labelled, not hand-picked — regenerate them rather than hand-edit when re-pinning.

JSON is editor-normal (AGENTS.md §2), two-space indent, keys sorted. spec.json is the vendored, upstream machine-readable suite (CommonMark 0.31.2, CC-BY-SA-4.0, © John MacFarlane) and is not re-serialized by the corpus gate.