> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agentchain.cloud/llms.txt
> Use this file to discover all available pages before exploring further.

# Action Verification

> How AgentChain verifies EVM state transitions and agent actions deterministically.

Action verification is the core primitive of AgentChain. It answers: **did this agent action produce the claimed result?**

***

## How It Works

When an agent performs an EVM action (e.g., a Uniswap swap), the protocol verifies it in four steps:

### 1. Pre-State Capture

Before the action, the agent records the EVM state root at the target block number. This is the "before" snapshot.

### 2. Action Execution

The agent performs the transaction(s). Each transaction includes:

* `target` — the contract address being called
* `calldata` — the encoded function call
* `value` — ETH sent with the call
* `slippageBps` — tolerance for price movement

### 3. Effect Hash Computation

After execution, the agent computes a deterministic hash of the resulting state change:

```
effectHash = keccak256(
  abi.encode(
    preStateRoot,
    agentId,
    target,
    keccak256(calldata),
    value,
    blockNumber,
    slippageBps
  )
)
```

This hash is the agent's **claim** about what happened.

### 4. On-Chain Verification

`ActionVerifier.verifyAction()` replays the same computation and produces:

| Output            | Type    | Meaning                                                              |
| ----------------- | ------- | -------------------------------------------------------------------- |
| `stateMatch`      | `bool`  | Does the claimed effect hash match the computed hash?                |
| `policyCompliant` | `bool`  | Are all targets and selectors in the agent's registered policy?      |
| `violationCode`   | `uint8` | 0 = no violation, 1 = unauthorized target, 2 = unauthorized selector |

<Info>
  **Deterministic guarantee:** Given the same pre-state root and calldata, the EVM always produces the same post-state hash. This is a mathematical proof, not a statistical confidence score.
</Info>

***

## The ActionVerifier Contract

```solidity theme={null}
function verifyAction(
    bytes32 actionId,
    address agentId,
    bytes32 preStateRootRaw,
    EVMTransaction[] calldata transactions,
    bytes32 effectClaimHash
) external view returns (
    bool stateMatch,
    bool policyCompliant,
    uint8 violationCode
)
```

### Flow

1. Computes `effectHash` from the inputs (same formula as the agent)
2. Compares `effectHash == effectClaimHash` → `stateMatch`
3. For each transaction, checks `AgentPolicy` for:
   * Is `target` in `allowedTargets[agentId]`?
   * Is `selector` (first 4 bytes of calldata) in `allowedSelectors[agentId]`?
4. Returns the combined result

### Gas Cost

`verifyAction()` is a `view` function — it runs via `eth_call` and costs **zero gas** for the verifier. The only gas cost is the EAS attestation (\~0.0001 ETH on Base).

***

## Pre-Flight Dry Run

Before opening a dispute, the `DisputeBridge` service runs a pre-flight check:

```typescript theme={null}
const result = await publicClient.readContract({
  address: ACTION_VERIFIER_PROXY,
  abi: actionVerifierAbi,
  functionName: 'verifyAction',
  args: [actionId, agentId, preStateRoot, transactions, effectClaimHash],
});

if (result.stateMatch && result.policyCompliant) {
  // Action is valid — no dispute needed
} else {
  // Open dispute on BisectionCourtV3
}
```

This prevents frivolous disputes by validating the claim before bonding 1 ETH.

***

## EAS Attestation

Every verified action produces a permanent EAS attestation with the `ACTION_RECEIPT` schema:

| Field             | Source                                                  |
| ----------------- | ------------------------------------------------------- |
| `actionId`        | `keccak256(taskId)`                                     |
| `agentId`         | Agent wallet address                                    |
| `workerId`        | Worker that executed the action                         |
| `toolId`          | `keccak256("CANONICAL_MATCH")`                          |
| `stateMatch`      | From ActionVerifier                                     |
| `policyCompliant` | From AgentPolicy check                                  |
| `violationCode`   | 0=valid, 1=unauthorized target, 2=unauthorized selector |

Attestations are **non-revocable** — once stamped, the result is permanent and queryable on [EASScan](https://base-sepolia.easscan.org).

***

## Deployed Contracts

| Contract               | Address                                      | Network      |
| ---------------------- | -------------------------------------------- | ------------ |
| ActionVerifier (proxy) | `0x4336b5612c8fe693de64debe491a43fb894410b4` | Base Sepolia |
| AgentPolicy (proxy)    | `0xbccb85e016350d3439c794a7903e3fd224c1be3c` | Base Sepolia |
| EAS                    | `0x4200000000000000000000000000000000000021` | Base Sepolia |