Scenario schema, version `1.0`

A scenario is one JSON object. All keys are required except description. Unknown keys are rejected at every level, so a typo cannot silently become a default. Numbers must be finite. Integers must be JSON integers (1, not 1.0 and not true).

{
  "schema_version": "1.0",
  "scenario_id": "one_person_one_exit",
  "description": "optional free text",
  "grid": {"width": 7, "height": 3},
  "obstacles": [[0, 0], [0, 1]],
  "exits": [{"id": "E1", "position": [1, 5]}],
  "people": [{"id": "P1", "position": [1, 1]}],
  "ignitions": [[1, 3]],
  "fire": {"model": "deterministic", "spread_interval": 1, "exits_flammable": true},
  "movement": {"conflict_resolution": "lowest_id_wins", "enter_fire": "casualty"},
  "termination": {"max_steps": 50},
  "seed": 1
}

Field	Type	Rules
`schema_version`	string	Must be `"1.0"`.
`scenario_id`	id	Matches `^[A-Za-z0-9_-]{1,64}$`.
`grid.width`, `grid.height`	int	1 to 1024.
`obstacles`	list of `[row, col]`	In bounds, no duplicates. These are walls: impassable and non-flammable.
`exits`	list of `{id, position}`	At least one. Unique IDs and positions. Not on an obstacle.
`people`	list of `{id, position}`	At least one. Unique IDs and positions. Not on an obstacle, exit or ignition point.
`ignitions`	list of `[row, col]`	Cells burning at step 0. May be empty. In bounds, no duplicates, not on an obstacle. On an exit only if `fire.exits_flammable` is true.
`fire.model`	`"deterministic"` \| `"stochastic"`	See the simulation contract.
`fire.spread_interval`	int ≥ 1	Fire spreads on steps where `step % interval == 0`.
`fire.exits_flammable`	bool	Whether exits can catch fire and become unusable.
`fire.spread_probability`	number in [0, 1]	Required for `stochastic`. Forbidden for `deterministic`.
`movement.conflict_resolution`	`"lowest_id_wins"`	The only V1 rule. It is stated explicitly.
`movement.enter_fire`	`"blocked"` \| `"casualty"`	What happens when someone moves into a burning cell.
`termination.max_steps`	int, 1 to 100000	Step limit.
`seed`	int, 0 to 2^64 − 1	Default run seed. A new simulator for the scenario and seed can override it, and the record stores the seed used. Evaluator-private: never shown to a model (see `v1-fairness-spec.md`).

Canonical form and identity

After parsing, the following lists are sorted: obstacles and ignitions by position, and exits and people by ID. The scenario JSON text emits canonical JSON (sorted keys, no whitespace). The scenario content hash is its SHA-256. Input order therefore never changes a scenario's identity. Run records store the hash, so a replay against a different scenario is rejected.

Fixtures

Each description starts with TEST FIXTURE. and ends with an ASCII layout. They are not benchmark scoring scenarios, and they are not the hidden evaluation set.

Fixture	Purpose
`one_person_one_exit`	Basic movement and evacuation, no fire.
`blocked_shortest_route`	The shortest route crosses fire. The safe route is longer. Exits are not flammable.
`multiple_exits`	Three people, two exits, fire in the middle.
`narrow_corridor`	A one-wide queue, chain moves and exit throughput.
`fire_threatening_exit`	Fire burns the near exit at step 1. The far exit stays usable.
`stochastic_room`	Seeded stochastic spread with the `blocked` fire-entry policy.

The canonical public V1 scenarios are a separate set in scenarios/public/v1/. See scenario-suite.md.

Scenario schema, version 1.0

Canonical form and identity

Fixtures

Scenario schema, version `1.0`