The three-layer model

This page is the single diagram you should print and pin to the wall. It shows who owns what, who computes what, who can dispute what, and how the future court path fits in. Every other page in this section zooms into one part of this picture.

The full picture

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flowchart TB
    subgraph OFF["Off-chain (producer / witness / DA)"]
        direction TB
        PR["Producer"]:::off
        WT["Witnesses<br/>(game tape, signed quote,<br/>sensor batch, agent task receipt)"]:::off
        DA["DA store<br/>+ optional external DA receipt"]:::off
    end

    subgraph L2["L2 — Myelin session runtime"]
        direction TB
        MP["Mempool<br/>(admission queue)"]:::l2
        SC["CellDAG scheduler"]:::l2
        EX["CKB-VM-style verifier<br/>(script groups, syscalls)"]:::l2
        ST["State store<br/>(live / consumed / created Cells<br/>+ state root)"]:::l2
        DM["DA manifest<br/>(Merkle SegmentProof)"]:::l2
        CO["Committee<br/>(static or Tendermint)"]:::l2
        BL["MyelinBlock<br/>+ committee certificate"]:::l2
        CB["Court bundle<br/>(per-chunk)"]:::l2
        SP["Settlement package<br/>(per-session)"]:::l2
        AP["Anchor package<br/>(per-DA-manifest)"]:::l2
    end

    subgraph L1["L1 — CKB mainnet / testnet / devnet"]
        direction TB
        CU["Asset custody Cells<br/>(session lock + participants)"]:::l1
        DA_L1["DA anchor CellTx<br/>(published on L1)"]:::l1
        ST_L1["Settlement CellTx<br/>(published on L1)"]:::l1
        CV["Court verifier<br/>(future CKB type script)"]:::l1
        VERDICT["Verdict<br/>(accept or slash)"]:::l1
    end

    %% Off-chain to L2
    PR --> WT --> MP
    MP --> SC --> EX --> ST
    ST --> BL
    CO --> BL
    EX --> DM
    DM --> AP
    AP --> DA_L1
    DM --> CB
    CB --> SP
    SP --> ST_L1

    %% L2 to L1 (custody + dispute)
    CU -. lock at session open .-> MP
    ST_L1 -. release / settle .-> CU
    DA_L1 -. fetch chunk payload .-> CV
    CB  -. dispute submission .- CV
    CV --> VERDICT

    classDef off fill:#CBD5E1,stroke:#334155,color:#1E293B;
    classDef l2  fill:#A5B4FC,stroke:#4F46E5,color:#1E293B;
    classDef l1  fill:#C7D2FE,stroke:#7C3AED,color:#1E293B;

The three layers are colour-coded:

• Off-chain — orange. Producer, witnesses, DA store, external DA provider.
• L2 (Myelin) — teal. Mempool, scheduler, verifier, state, committee, block, evidence packages.
• L1 (CKB) — cyan. Asset custody, DA anchor CellTx, settlement CellTx, future court verifier.

Who owns what

Concern	Owner	Where it lives
Long-lived asset custody	Producer + participants	CKB Cells (L1)
In-session state	Myelin runtime	myelin-state (L2)
Finality of Myelin blocks	Committee (configured set)	myelin-consensus (L2)
Chunk payload availability	DA store + external DA provider	Off-chain, with anchor CellTx (L1)
Dispute resolution	Future CKB court verifier	L1 type script

Who computes what

Computation	Layer	What it produces
CellTx execution	L2 (verifier)	MyelinExecutionReport (cycles, state root transition)
CKB-style projection	L2 (verifier)	CkbProjectionReport (with ckb_style_tx_hash)
Block finality	L2 (committee)	FinalisedBlock with committee certificate
DA sealing	L2 (myelin-state)	DA manifest with SegmentProof
Anchor package	L2 (CLI)	CKB-compatible CellTx package with l1_da_published = false
Settlement package	L2 (CLI)	CKB-compatible CellTx package for disputed close
Court verification	L1 (future)	Accept / slash verdict

Who can dispute what

A dispute happens when any participant believes a finalised Myelin block contains an invalid state-root transition. To dispute:

1. Fetch the disputed chunk payload from the DA store, or from the DA anchor CellTx on L1.
2. Replay the chunk in a CKB-VM-style verifier (off-chain, or on the future L1 court type script).
3. Compare the computed state_root_after against the one in the finalised block.

If they disagree, the disputer submits the court bundle to the L1 court verifier. The court replays the chunk, and the verdict is either "accept" (the committee was right, dispute bond refunded) or "slash" (the committee was wrong, dispute bond awarded, committee bond slashed).

The exact economics are in Settlement package — but the shape is the same: deterministic replay, deterministic verdict.

Where each piece lives across the layers

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flowchart LR
    A["CellTx"]:::l2
    B["MyelinExecutionReport"]:::l2
    C["CkbProjectionReport"]:::l2
    D["DA manifest<br/>(payload_hash, segment_root,<br/>segment_proof)"]:::l2
    E["Anchor package<br/>(DA CellTx)"]:::l2
    F["Settlement package<br/>(disputed-close CellTx)"]:::l2
    G["Court bundle<br/>(chunk payload + CKB Molecule tx<br/>+ projection + cert)"]:::l2

    H["DA anchor CellTx<br/>(published)"]:::l1
    I["Settlement CellTx<br/>(published)"]:::l1
    J["Court verifier<br/>(replay + verdict)"]:::l1

    E --> H
    F --> I
    G --> J
    D --> E
    D --> G

    classDef l2 fill:#C4B5FD,stroke:#4C1D95,color:#1E293B;
    classDef l1 fill:#A5B4FC,stroke:#312E81,color:#1E293B;

Solid arrows: produced on L2, optionally published to L1. Dotted arrows: an L1 verifier reads the L2 artefact from the published package.

Why this matters

Three patterns come up over and over in Myelin docs:

1. L1 is custody and court, not real-time execution. The CKB chain is where the assets live and where disputes are resolved. It is not where the high-throughput work happens.
2. L2 is finite, not infinite. Every Myelin session has an open, a sequence of finalised blocks, and a close. There is no "always-on global state." This is what makes the CellDAG and the state root meaningful.
3. Off-chain is what carries the bulk data. Game tapes, signed quotes, sensor batches, agent task receipts — none of these belong on-chain by default. They live in the DA store, with an anchor CellTx on L1 to prove their availability.

That three-layer split is what makes Myelin a CKB-aligned session runtime rather than a CKB re-implementation or a generic sidechain.

What's not in the picture

• No P2P layer. The current Myelin kernel is a single-process runtime driven by the CLI. The committee is a configured set; it is not a gossip network.
• No wallet. Wallets are L1 concerns. Myelin talks to CKB through the JSON-RPC; it doesn't manage keys beyond committee validator keys.
• No public RPC. The CKB node provides the public RPC; Myelin consumes it.

Where to go next

• Session lifecycle — see one full session walk through the layers.
• Court path — the dispute-resolution deep dive.
• Claim ladder — what each piece of evidence actually proves about the L2.