{
  "handle": "CausalBarrier",
  "mechanism": "A middleware layer that buffers incoming messages and releases them to the agent ONLY when all their causal dependencies are met. Guarantees the agent never sees an 'impossible' state. It maintains a {{state_lock}} on the event processing queue, releasing it only when all causal predecessors have been observed.",
  "gloss": "Enforcing strict event ordering",
  "failure_modes": [
    "Buffer overflow if dependencies never arrive."
  ],
  "invariants": [
    "Causal Ordering: Event E cannot be processed until all Dependencies(E) are processed",
    "Events before barrier cannot affect events after.",
    "No Impossible States: {{agent}} state never violates causal consistency"
  ],
  "parameters": [
    {
      "name": "on_undeliverable",
      "type": "Enum",
      "range": "{block, drop, escalate}",
      "description": "What happens to a buffered message whose dependencies never arrive. The barrier never releases it out of order — that would breach causal ordering — so the choice is how long to hold it and what to do instead."
    },
    {
      "name": "party_count",
      "type": "Integer",
      "range": "[2, 100]",
      "description": "Participants tracked"
    },
    {
      "name": "timeout",
      "type": "Duration",
      "range": "[1s, 1h]",
      "description": "How long a message waits before on_undeliverable applies"
    }
  ],
  "_meta": {
    "tier": 1,
    "ring": 0,
    "supersedes": [
      "sema:CausalBarrier#mh:SHA-256:0904e3eb6ac5a36cfa3ec9d1c3fe374ad4eb817e1da35375ce8d32d8272b6128",
      "sema:CausalBarrier#mh:SHA-256:d1b20d964f273174495ad103b4c7b31ae747e4ad56de14d9e935ca1705088c5d",
      "sema:CausalBarrier#mh:SHA-256:9e178f07d754eefadad17a92a84f76badce58bd00571dca64b37e83176a57e94",
      "sema:CausalBarrier#mh:SHA-256:39b3168c5b9bad18505b7af584fbb24b80ba7c5bf90e6ff0611fc2cd405f0178",
      "sema:CausalBarrier#mh:SHA-256:a6d8167a05ffab8cf5fda4da7a81e2c196de8a182f0673b9a8a5cbf189222dfc"
    ],
    "path": [
      "Physics",
      "Time"
    ]
  },
  "sema_id": "sema:CausalBarrier#mh:SHA-256:cf54b35c9236d8fd2db3ca4f35ab5bdaac79c17052d9095aaa5fa6f143507809",
  "sema_ref": "CausalBarrier#cf54",
  "sema_stub": "cf54",
  "dependencies": {
    "references": {
      "agent": "sema:Agent#mh:SHA-256:e127459069739fffc96a71d54ef6e8c97ca53471d5349c16aa72a092a33756cd",
      "state_lock": "sema:StateLock#mh:SHA-256:c9c2809bdf97bb6ac17a8ffe428d4aa9a28294b99d64cc8a336a239d26a8afb8"
    }
  },
  "sema_layer": "Physics",
  "sema_category": "Time",
  "used_by": {
    "references": {
      "TimeWarpLog": "sema:TimeWarpLog#mh:SHA-256:755f480a60517d8e99807da674019db06ab0b7b2edabcc806d833947da4446e4"
    }
  }
}