CoW Protocol Solver Penalty & Slashing Framework
There are three enforcement layers: smart contract (on-chain), automated off-chain (autopilot/driver code), and governance (DAO social consensus).
Layer 1: Smart Contract Enforcement (On-Chain, Automatic)
Hard-coded in the settlement contract and cannot be bypassed.
| Rule | What Happens |
|---|---|
| Limit price violation | Transaction reverts — orders cannot execute at prices worse than the user's limit |
| Solver not whitelisted | Transaction reverts — only bonded, approved solvers can submit |
Layer 2: Automated Off-Chain Enforcement (Autopilot + Driver Code)
Enforced programmatically by the autopilot and driver services.
2a. Participation Guard — Solver Banning (Autopilot)
| Policy | Trigger | Default Threshold | Penalty | Duration |
|---|---|---|---|---|
| Non-settling | Won N consecutive auctions, settled none | 3 consecutive unsettled wins | Auction ban | 5 min |
| Low-settling | Settlement failure rate too high across window | >90% failure over 100 auctions (min 3 wins) | Auction ban | 5 min |
Both are configurable and enabled by default. Banned solvers receive HTTP notifications (Banned { reason, until }).
Configuration parameters:
| Parameter | Default | Purpose |
|---|---|---|
db_enabled | true | Master switch for participation guard |
solver_blacklist_cache_ttl | 5m | How long bans last |
non_settling_solvers_blacklisting_enabled | true | Enable non-settling policy |
non_settling_last_auctions_participation_count | 3 | Auction window for non-settling policy |
low_settling_solvers_blacklisting_enabled | true | Enable low-settling policy |
low_settling_last_auctions_participation_count | 100 | Auction window for low-settling policy |
low_settling_min_wins_threshold | 3 | Min wins before evaluation |
solver_max_settlement_failure_rate | 0.9 | Max acceptable failure rate (90%) |
2b. Settlement Validation (Driver)
Before any settlement hits the chain, the driver validates:
- Trusted token check — internalized interactions can only use trusted tokens; violation produces
NonBufferableTokensUsederror and settlement is blocked - Simulation — settlement must not revert in simulation
- Gas safety — sufficient gas parameters required
2c. Settlement Deadline Enforcement
Settlements must land within chain-specific block deadlines:
| Chain | Deadline |
|---|---|
| Ethereum | 3 blocks |
| Gnosis/Polygon/BNB/Avalanche | 10-20 blocks |
| Arbitrum/Base/Linea/Ink | 20-40 blocks |
Missing the deadline can trigger immediate denylisting pending manual inspection.
Layer 3: Governance / Social Consensus (DAO-Enforced, CIP-11+)
These rules are not automatically enforced by code. The core team monitors settlements with tooling, flags suspicious behavior, and the DAO votes on slashing via CIPs.
3a. Unfair Solutions (CIP-11)
- Violation: Providing clearing prices worse than what users would get on reference AMMs (Uniswap, Balancer, Curve, etc.), also called the EBBO rule (Ethereum Best Bid/Offer)
- Consequence: Monitoring flag, potential slashing at DAO discretion
3b. Score Inflation (CIP-11)
- Violation: Creating fake tokens or wash-trading to artificially inflate solution scores
- Consequence: Slashing
3c. Illegal Buffer Usage (CIP-11)
- Violation: Using internal buffers beyond legitimate AMM replacement; systematic trading with unsafe tokens; creating buffer attack vectors
- Consequence: Flagging, slashing
- Real-world example: CIP-22 — Barter Solver failed to revoke approvals on an old contract, a hacker drained ~$166K from the settlement contract. Bond was slashed to reimburse losses.
3d. Illegal Surplus Shifts / Local Token Conservation (CIP-11)
- Violation: Intentionally transferring surplus between orders that share common tokens (one user's surplus subsidizes another)
- Consequence: Slashing
3e. Overbidding / Pennying (CIP-13)
- Violation: Systematically inflating reported scores beyond
surplus + fees - gas, expecting rewards to cover losses - Detection formula:
avg(score) > avg(surplus + fees - gas) + epsilon - Consequence: Slashing (currently retroactive/manual, not automated)
3f. Pre/Post Hook Non-Execution (CIP-11)
- Violation: Intentionally excluding hooks specified in order app data
- Consequence: Slashing
3g. Catch-All: Other Malicious Behavior (CIP-11)
- Violation: Any intentional harm to users or the protocol not covered above
- Consequence: Slashing at DAO discretion
- Real-world example: CIP-55 — GlueX solver slashing (passed vote)
Layer 4: Economic Penalties (Reward Mechanism, CIP-38+)
Even without explicit "slashing," the reward formula itself penalizes poor behavior.
Performance Reward Formula
performanceReward_i = cap(totalScore - referenceScore_i - missingScore_i)Where:
totalScore= sum of all winning solutions' scoresreferenceScore_i= counterfactual total score if solver i hadn't participatedmissingScore_i= scores of solver i's solutions that reverted (failed settlements)
Failed settlements directly reduce rewards — and can make them negative.
Capping (Bounds)
cap(x) = max(-c_l, min(c_u, x))| Chain | Lower Bound (max loss per auction) | Upper Bound |
|---|---|---|
| Ethereum/Arbitrum/Base | 0.010 ETH | beta x protocol fees earned |
| Gnosis | 10 xDAI | beta x protocol fees earned |
| Polygon | 30 POL | beta x protocol fees earned |
| Avalanche | 0.3 AVAX | beta x protocol fees earned |
| BNB | 0.04 BNB | beta x protocol fees earned |
| Linea/Ink | 0.0015 ETH | beta x protocol fees earned |
| Plasma | 30 XPL | beta x protocol fees earned |
A solver can owe the protocol money if their reverted settlements drag down the total score.
Buffer Slippage Accounting
Positive/negative slippage from buffer usage is settled weekly. Negative slippage = solver pays.
Bonding Requirements (The Stake at Risk)
All DAO-enforced slashing ultimately hits the solver's bonding pool.
| Pool Type | Stablecoins | COW Tokens | Notes |
|---|---|---|---|
| Standard (CoW DAO pool) | $500,000 | 1,500,000 COW | CoW DAO safe is sole signer |
| Reduced pool (CIP-44) | $50,000 to $100,000 over 1 year | 500,000 to 1,000,000 COW over 1 year | Must already be vouched under main pool |
Solvers in the CoW DAO pool also pay a 15% service fee on weekly COW rewards (starting 6 months after joining).
Summary: What Can Go Wrong for a Solver
| Risk | Enforcement | Automated? | Financial Impact |
|---|---|---|---|
| Limit price violation | Smart contract | Yes | Tx reverts (gas wasted) |
| Not whitelisted | Smart contract | Yes | Tx reverts |
| Consecutive non-settlement | Autopilot | Yes | Temp ban (5 min) |
| High failure rate | Autopilot | Yes | Temp ban (5 min) |
| Untrusted token internalization | Driver | Yes | Settlement blocked |
| Settlement revert on-chain | Reward formula | Yes | Negative reward (pay protocol) |
| Missed deadline | Autopilot | Yes | Immediate denylist |
| Unfair prices (EBBO) | DAO governance | No | Bond slashing |
| Score inflation | DAO governance | No | Bond slashing |
| Illegal buffer usage | DAO governance | No | Bond slashing |
| Surplus shifting | DAO governance | No | Bond slashing |
| Overbidding | DAO governance | No | Bond slashing |
| Hook non-execution | DAO governance | No | Bond slashing |
| Security negligence | DAO governance | No | Bond slashing (e.g. $166K in CIP-22) |