Rho JSONL session schema

Rho JSONL is a coding-host implementation of SessionJournal. It is neither the agent contract nor a general R object serializer.

File framing

The file begins with one session record and continues with committed entry records. Every record ends with LF.

{"schema":"rho.session.jsonl","type":"session","id":"...","parent_id":""}

Entry records add a committed position and an entry semantic document. Atomic values and lists retain their R storage mode, names, and missing positions through the JSON value codec.

Semantic records

A semantic record has a stable type and declared fields. It does not contain an R package name, S7 class name, or reflected property list.

RhoJsonSemanticAdapter maps:

• a stable wire tag;
• stable wire-field names;
• the current S7 value class;
• each wire field to one current S7 property.

The two names may differ. This permits an R property rename without changing stored records.

An extension registers an adapter explicitly:

adapter <- rho_json_semantic_adapter(
  "example.result",
  ExampleResult,
  c(value = "current_value")
)
codec <- rho_json_session_codec(adapters = list(adapter))

Unknown S7 values resolve to RhoSessionCodecErrorValue. They are never granted a durable representation by namespace discovery or property reflection.

Change discipline

There is no released reader or stored consumer, so the current schema has no invented migration history. Its tags and fields state the format Rho writes now. Once a real consumer exists, an incompatible change must be explicit and tested against that consumer’s fixture.

Pi, training, DuckDB, and other representations are import/export codecs. They do not add conditionals to this journal.