Module validation 

Three-tier block validation pipeline (SPEC §5, §7).

Tiers

Tier	Module	SPEC	Requirements	External state	Chia crates used
1 — Structural	structural	§5	SVL-001 — SVL-006	None	chia-consensus::compute_merkle_set_root, chia-sdk-types::MerkleTree
2 — Execution	execution	§7.4	EXE-001 — EXE-009	clvmr::Allocator	dig-clvm::validate_spend_bundle (wraps chia-consensus, chia-bls, clvmr)
3 — State	state	§7.5	STV-001 — STV-007	crate::CoinLookup	chia-bls::verify

Validation flow

L2Block
  │
  ├─► Tier 1: validate_structure()     ← no external state; cheapest checks first
  │     ├── header version vs height (SVL-001)
  │     ├── DFSP roots pre-activation (SVL-002)
  │     ├── cost/size limits (SVL-003)
  │     ├── timestamp future bound (SVL-004)
  │     ├── count agreement (SVL-005)
  │     └── Merkle roots + integrity (SVL-006)
  │
  ├─► Tier 2: validate_execution()     ← needs CLVM allocator
  │     ├── puzzle hash verification (EXE-002)
  │     ├── CLVM execution via dig-clvm (EXE-003)
  │     ├── condition parsing + assertion checking (EXE-004)
  │     ├── BLS signature verification (EXE-005)
  │     ├── conservation + fee consistency (EXE-006)
  │     ├── cost consistency (EXE-007)
  │     └── → ExecutionResult (EXE-008) with PendingAssertion (EXE-009)
  │
  └─► Tier 3: validate_state()         ← needs CoinLookup
        ├── coin existence (STV-002)
        ├── puzzle hash cross-check (STV-003)
        ├── addition non-existence (STV-004)
        ├── height/time lock evaluation (STV-005)
        ├── proposer signature (STV-006)
        └── state root verification (STV-007)

Composite method (SPEC §10.3)

crate::L2Block::validate_full (SPEC §7.1, STV-001) chains all three tiers. If Tier 1 fails, Tiers 2 and 3 are never reached. If Tier 2 fails, Tier 3 is never reached. Returns the first error encountered or Ok(computed_state_root) on success.

Chia parity (SPEC §1.4)

The three-tier split mirrors Chia’s validation in block_body_validation.py:

• Checks 1-14 ≈ Tier 1 (structural: counts, roots, duplicates, size — SPEC §5.1–§5.2)
• Checks 15-22 ≈ Tier 2+3 (CLVM execution, coin existence, signatures, conservation — SPEC §7.4–§7.5)

DIG separates execution (CLVM) from state (coin lookups) for cleaner testing and partial validation (SPEC §1.1 Design Principle: Layered validation).

Modules

execution

Tier 2 execution validation (EXE-*): CLVM execution, condition parsing, signatures, conservation.

state

Tier 3 state validation (STV-*): coin existence, puzzle hash cross-checks, lock evaluation, proposer signature, and state root verification.

structural

Tier 1 structural validation (SVL-*): cheap, pure checks on headers and block bodies before CLVM or state.