TYPE 0x0907 · LEGACY FAMILY

P2TR_SCRIPT_LEGACY

Legacy P2TR script-path (Taproot) wrapped as a typed Ladder Script block. This is the critical block — taproot script-path is the primary inscription/data-embedding vector today. The revealed script leaf must be valid Ladder Script conditions.

Legacy Non-Invertible

Ladder Diagram

Fields

Field	Data Type	Size	Side	Description
hash256	HASH256	32 B	Conditions	Merkle root of the script tree. Node-computed — the node derives this from the PREIMAGE (script leaf). Raw hash input is rejected.
preimage	PREIMAGE	var	Witness	Revealed script leaf (serialised Ladder Script conditions) — provided by the user. The node derives HASH256 from this data at creation time.
[inner witness]	var	var	Witness	Witness fields required to satisfy the revealed leaf conditions

Public key folded into Merkle leaf via merkle_pub_key (PubkeyCountForBlock = 1). No key field in conditions.

Wire Format Breakdown

Conditions side (in scriptPubKey):

0x0907 0 2 HASH256 · 32B = 38 bytes

Witness side (in input witness):

0x0907 0 n PREIMAGE · varB [inner witness fields] = variable

Total (conditions + witness) variable

Witness size depends on the revealed script leaf and its witness fields.

Evaluation Logic

1. Compute SHA256(PREIMAGE) to get the leaf hash.

2. Verify leaf hash is included in the Merkle tree with root HASH256. If proof invalid → UNSATISFIED

3. Deserialize revealed leaf (PREIMAGE) as Ladder Script conditions. If invalid → UNSATISFIED

4. Evaluate inner conditions with remaining witness fields. Result → SATISFIED or UNSATISFIED

Return Values

Condition	Result
Missing HASH256 or PREIMAGE	ERROR
HASH256 wrong size or Merkle leaf pubkey count mismatch	ERROR
SHA256(PREIMAGE) != HASH256 (Merkle root)	UNSATISFIED
PREIMAGE fails to deserialize as Ladder conditions	ERROR
Inner conditions evaluation fails	UNSATISFIED
Recursion depth > 2	ERROR
Inner conditions satisfied	SATISFIED

JSON Wire Format

Conditions (scriptPubKey)

{
  "type": "P2TR_SCRIPT_LEGACY",
  "inverted": false,
  "fields": [
    { "type": "HASH256", "hex": "e3b0c4...32 bytes (Merkle root)" },
    { "type": "PUBKEY", "hex": "02abc1...33 bytes (internal key)" }
  ]
}

Witness (input)

{
  "type": "P2TR_SCRIPT_LEGACY",
  "inverted": false,
  "fields": [
    { "type": "PREIMAGE", "hex": "01020304...serialised Ladder conditions (revealed leaf)" },
    { "type": "PUBKEY", "hex": "02abc1...33 bytes" },
    { "type": "SIGNATURE", "hex": "e5f6a7...64 bytes" }
  ]
}

Notes

Closes the taproot inscription vector — the primary data-embedding surface in Bitcoin today.
Revealed script leaf must deserialize as valid Ladder Script conditions. Arbitrary data is rejected.
HASH256 is node-computed: the user provides PREIMAGE (script leaf) and the node derives the hash automatically. PUBKEY (internal key) is folded into the Merkle leaf via merkle_pub_key. Submitting raw hash values directly is rejected.
Recursion depth limited to 2.
The internal key is folded into the Merkle leaf, used for key-path/script-path binding.
For key-path-only spending, see P2TR_LEGACY (0x0906).

Use Cases

Anti-Inscription Protection

The primary inscription/data-embedding vector (taproot script-path) is closed. Revealed script leaf MUST be valid Ladder conditions.

Script Tree Migration

Taproot script tree with typed Ladder leaves instead of arbitrary scripts. Full anti-spam coverage.

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