{
  "profile": "cbor-det-v1",
  "spec": "Decode-tolerance proof. Every vector below is a byte string the reference encoder PRODUCED before the integer-widening rule, when an integer needing an 8-byte CBOR head fell through to a float64 (major type 7, additional info 27). Records anchored under that encoder are immutable, so the only thing that can break them is a decoder that stops understanding them. These bytes are unreachable from the post-the integer-widening rule encoder, which is what stops this file from becoming a self-referential re-recording of current behaviour: nothing here can be regenerated by running the encoder again.",
  "captured": "2026-08-11, two independent sources agreeing byte-for-byte: (1) the pre-fix build of the reference encoder, (2) an independent downstream measurement of the published reference encoder build.",
  "vectors": [
    {
      "name": "first-float64-value",
      "doc": "2^32. The first value the pre-fix encoder could not fit in a 4-byte head, and therefore the first it wrote as a float64. Post-fix this same value encodes as 1b0000000100000000; this vector proves the old bytes still read back.",
      "historical_hex": "fb41f0000000000000",
      "decodes_to": 4294967296
    },
    {
      "name": "first-float64-value-plus-one",
      "doc": "2^32 + 1. Guards against a decoder that special-cases only the round boundary value.",
      "historical_hex": "fb41f0000000100000",
      "decodes_to": 4294967297
    },
    {
      "name": "max-safe-integer",
      "doc": "2^53 - 1, the largest integer a JS number represents exactly and the top of this profile's integer value domain.",
      "historical_hex": "fb433fffffffffffff",
      "decodes_to": 9007199254740991
    },
    {
      "name": "negative-past-the-4-byte-head",
      "doc": "-(2^32) - 1. The negative side breaks one value further out than the positive side, because major type 1 encodes -1-n.",
      "historical_hex": "fbc1f0000000100000",
      "decodes_to": -4294967297
    },
    {
      "name": "min-safe-integer",
      "doc": "-(2^53 - 1), the bottom of the integer value domain.",
      "historical_hex": "fbc33fffffffffffff",
      "decodes_to": -9007199254740991
    },
    {
      "name": "action-time-timestamp",
      "doc": "A real Action.time value in milliseconds since the epoch. This is the case that made the defect universal: every Action ever written carries a timestamp above 2^32, so every anchored envelope contains one of these.",
      "historical_hex": "fb4279ff1610b3d000",
      "decodes_to": 1786461096765
    },
    {
      "name": "grant-expires-at-timestamp",
      "doc": "A GrantArgs.expiresAt value, a field the delegation grammar declares as an unsigned integer, historically pinned as a float64.",
      "historical_hex": "fb427a2ce84263d000",
      "decodes_to": 1798761096765
    },
    {
      "name": "round-timestamp-in-a-map",
      "doc": "A historical timestamp nested inside a map, so the tolerance proof covers a structural position and not only a bare top-level value.",
      "historical_hex": "a16474696d65fb4278bcfe56800000",
      "decodes_to": {
        "time": 1700000000000
      }
    }
  ]
}