# D&D Combat-Turn Artifact Contract

This document defines the durable artifact and serialization boundary for
D&D combat turns. It does not define extraction, validation beyond the codec's
structural checks, normalization, prompts, or a selectable pipeline lane.

## Artifact identity

| Property | Value |
| --- | --- |
| Artifact kind | `dnd/combat-turn-list` |
| Schema ID | `notarius.dnd.combat_turns` |
| Schema name | `notarius_dnd_combat_turns_v1` |
| Schema version | `v1` |
| Media type | `application/json` |

The top-level JSON object contains the required `combat_turns` array, which
may be empty. Every object rejects unknown fields.

## JSON shape

Each combat turn contains these required fields:

| Field | Shape |
| --- | --- |
| `actor` | Non-empty string. |
| `turn_kind` | One of `turn`, `reaction`, `legendary_action`, `lair_action`, or `other`. |
| `round` | Required JSON field containing a positive integer or `null`. |
| `actions` | Required array with at least one action. |
| `summary` | Non-empty string. |
| `source_refs` | Required array with at least one source reference. |

Each action contains these required fields:

| Field | Shape |
| --- | --- |
| `category` | One of `attack`, `spell`, `movement`, `item`, `ability_check`, `saving_throw`, `condition`, or `other`. |
| `declaration` | Non-empty string describing what was declared. |
| `targets` | Required array of strings; the array may be empty, but entries may not be empty. |
| `resolution` | Required JSON field containing a non-empty string or `null`. |

Source references use the shared source-reference shape:

```json
{
  "source_id": "session-alpha",
  "start_unit_id": 1,
  "end_unit_id": 2
}
```

`source_id` must be non-empty and both unit IDs must be positive integers. The
codec does not resolve references against a source document or enforce source
range ordering; those checks belong to the later source-reference validation
boundary.

## Codec behavior

The codec exposes two representations of the same typed artifact:

- Candidate encode/decode preserves invalid enum values, nullable values,
  required-array presence, required strings, targets, and source references so
  later validators can report them. Candidate decoding still requires valid
  JSON, one JSON value, known fields, and the explicitly present `round` and
  `resolution` keys; `null` is distinct from a missing key.
- Approved encode/decode enforces the structural rules in this contract.

The codec owns the durable JSON Schema, whose object layers all set
`additionalProperties` to `false`. Codec metadata contains only
`combat_turn_count`.

The maintained compact fixture is
`internal/modules/dnd/codec/combatturns/testdata/dnd_combat_turns.v1.json`.