docs: add Solver7702Delegate docs

docs/cow-protocol/tutorials/arbitrate/solver/driver.md

@@ -53,9 +53,10 @@ The auctions sent to the driver by the autopilot only contain the bare minimum o
 But usually a solver engine requires more information than that so the driver pre-processes the auction before forwarding it to the solver engine.
 We also want to reduce the overall workload of a solver engine, since it's usually expensive to match an order (in terms of time, RPC requests, API calls, etc.).
 That process includes:
-* fetching additional metadata (e.g. token decimals)
-* discarding orders that can definitely not be settled (e.g. user is missing balances)
-* very basic prioritization of remaining orders (e.g. orders below or close to the market price are most likely to settle)
+
+- fetching additional metadata (e.g. token decimals)
+- discarding orders that cannot be settled (e.g. user is missing balances)
+- very basic prioritization of remaining orders (e.g. orders below or close to the market price are most likely to settle)
 
 ### Fetching liquidity
 
@@ -92,11 +93,12 @@ The driver can be configured to use different submission strategies which it dyn
 If the settlement does not expose any MEV (e.g. it executes all trades without AMMs) it's safe and most efficient to directly submit to the public mempool.
 However, if a settlement exposes MEV the driver would submit to an MEV-protected RPC like [MEVBlocker](https://mevblocker.io).
 
+Production solvers using the reference driver should configure [Solver7702Delegate](../../solvers/solver-7702-delegate.md) during initial driver setup. A single pending solver EOA transaction can delay later settlements; auxiliary EOAs provide additional nonce lanes while `GPv2Settlement` still sees the solver EOA as the settlement caller.
+
 ### Flash Loans
 
 The user is able to create a flash loan order's hint by attaching to the `appData` the specified metadata. The autopilot reads the order and cuts it into a [fair combinatorial batch auction](../../../concepts/introduction/fair-combinatorial-auction). Then the driver fetches the `appData` by calling the orderbook with `GET /v1/app_data/<app_data_hash>` for every order and caches them in memory. The driver should include the flash loan information into the batch auction's order before sending it to the solver(s).
 
-
 ```mermaid
 sequenceDiagram
     actor User

docs/cow-protocol/tutorials/solvers/solver-7702-delegate.md

@@ -0,0 +1,98 @@
+---
+sidebar_position: 11
+description: Configure Solver7702Delegate and ERC-7702 auxiliary accounts for parallel settlement submission.
+keywords:
+  - Solver7702Delegate
+  - solver 7702 delegate
+  - ERC-7702
+  - EIP-7702
+  - parallel settlement submission
+---
+
+# Parallel Settlement Submission
+
+`Solver7702Delegate` lets a solver keep its existing allowlisted EOA and use auxiliary EOAs as additional nonce lanes for settlement submission.
+
+Solvers expecting production volume should set this up early. With one EOA, a pending transaction can block every settlement behind it. Auxiliary EOAs can submit in parallel, while `GPv2Settlement` still sees the solver EOA as `msg.sender`.
+
+:::warning
+
+Treat auxiliary EOAs as operationally sensitive accounts. Any approved auxiliary EOA can submit settlements through the solver EOA while the delegation is active. Keep their keys in the same security setup as the solver EOA, monitor their native-token balances, and make sure the team responsible for the solver EOA is also responsible for these accounts.
+
+If an auxiliary key is compromised, rotate the delegation by configuring a new approved caller set and re-delegating from the solver EOA.
+
+:::
+
+## Reference driver setup
+
+If you use the reference driver, add `submission-accounts` to the solver entry in your driver config. This is all most solvers need to configure.
+
+```toml
+[[solver]]
+name = "my-solver"
+endpoint = "https://solver.example"
+account = "<solver-private-key-or-signer-config>"
+max-solutions-to-propose = 6 # solver EOA + 5 auxiliary EOAs
+submission-accounts = [
+  "<auxiliary-private-key-or-signer-config-1>",
+  "<auxiliary-private-key-or-signer-config-2>",
+  "<auxiliary-private-key-or-signer-config-3>",
+  "<auxiliary-private-key-or-signer-config-4>",
+  "<auxiliary-private-key-or-signer-config-5>"
+]
+```
+
+The solver `account` must be able to sign the ERC-7702 authorization. Each `submission-accounts` entry must also include signing credentials, not only an address.
+
+Fund each auxiliary EOA with the chain's native token so it can pay gas.
+
+At startup, the reference driver deploys `Solver7702Delegate` at the expected CREATE2 address, or reuses the existing deployment at that address. When the solver EOA is busy, it uses the auxiliary accounts to submit settlements through separate nonce lanes.
+
+## What changes when submitting
+
+When the solver EOA is free, it submits directly to `GPv2Settlement`. If it already has a pending transaction, an auxiliary EOA can submit to the solver EOA instead. The solver EOA runs `Solver7702Delegate`, which forwards the call to `GPv2Settlement`.
+
+```mermaid
+flowchart LR
+    SolverEOA{"Solver EOA"}
+    DirectTx["tx.data = settle(...)"]
+    AuxEOAs{"Auxiliary EOAs<br/>0...N"}
+    DelegatedTx["tx.data = bytes20(target)<br/>|| targetCalldata"]
+    DelegatedSolver["Solver EOA<br/>delegated to Solver7702Delegate"]
+    TargetCall["target = GPv2Settlement<br/>targetCalldata = settle(...)"]
+    Settlement["GPv2Settlement"]
+
+    SolverEOA --> DirectTx --> Settlement
+    AuxEOAs --> DelegatedTx --> DelegatedSolver --> TargetCall --> Settlement
+
+    classDef eoa fill:#fff3bf,stroke:#b08900,color:#1f2937
+    classDef tx fill:#f3f0ff,stroke:#7048e8,color:#1f2937
+    classDef contract fill:#1864ab,stroke:#0b3558,stroke-width:3px,color:#ffffff,font-weight:bold
+    class SolverEOA,AuxEOAs eoa
+    class DirectTx,DelegatedTx,TargetCall tx
+    class DelegatedSolver,Settlement contract
+```
+
+The calldata format is packed on purpose. Use `abi.encodePacked(bytes20(target), targetCalldata)`. Do not use `abi.encode(target, targetCalldata)`.
+
+## Verification
+
+First, check that the solver EOA points to the expected delegate:
+
+```shell
+cast code <solver_eoa> --rpc-url <rpc_url>
+```
+
+For ERC-7702, the code has this form:
+
+```text
+0xef0100 || delegate_address
+```
+
+On a block explorer, the solver EOA may not have a normal contract code view. Confirm that its **Delegated to** banner points to the expected address, then open that address and verify its source as `Solver7702Delegate`.
+
+See the README's [verification steps](https://github.com/cowprotocol/solver-7702-delegate#verify-delegation) for details.
+
+## More details
+
+For manual deployment, authorization, revocation, verification, and operational details, use the [`Solver7702Delegate` README](https://github.com/cowprotocol/solver-7702-delegate#usage).