feat(chain): Circle's Arc as a third x402 payment chain

CLAUDE.md

@@ -2,7 +2,7 @@
 
 Smart LLM router for autonomous agents. <!-- br:models.chatVisible -->90<!-- /br:models.chatVisible --> models. Two ways to pay:
 
-- **Wallet (default)** — x402 USDC micropayments signed per call, against `blockrun.ai/api` (Base) or `sol.blockrun.ai/api` (Solana). New installs default to Solana.
+- **Wallet (default)** — x402 USDC micropayments signed per call, against `blockrun.ai/api` (Base), `sol.blockrun.ai/api` (Solana) or `arc.blockrun.ai/api` (Circle's Arc, same EVM key as Base). New installs default to Solana. Per-chain facts (gateway, label, CAIP-2) live in `src/payment-chain.ts`.
 - **API key** — `brk_live_…` from [user.blockrun.ai](https://user.blockrun.ai), billed against card-funded account credit, against `api.blockrun.ai`. `src/api-key.ts` resolves it (env → `~/.blockrun/.api-key` → `~/.openclaw/blockrun/api-key`); a key present anywhere wins over a wallet, and no wallet is generated or read in that mode.
 
 ## Commands

README.md

@@ -113,14 +113,14 @@ Full walkthrough: [Paying with a credit card](#paying-with-a-credit-card-api-key
 
 **Two ways to pay for the paid ones — pick one, the rest of ClawRouter is identical:**
 
-|                   | Wallet (default)                                           | API key                                                                                                    |
-| ----------------- | ---------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------- |
-| **Who it is for** | Autonomous agents, and anyone happy holding USDC           | People who would rather pay with a card                                                                    |
-| **Setup**         | Nothing — a wallet is generated on first run               | Sign up at [user.blockrun.ai](https://user.blockrun.ai), top up, mint a key, `clawrouter login brk_live_…` |
-| **Auth**          | An x402 signature per request                              | `Authorization: Bearer brk_live_…`                                                                         |
-| **Gateway**       | `sol.blockrun.ai` (Solana, default) / `blockrun.ai` (Base) | `api.blockrun.ai`                                                                                          |
-| **Billing**       | USDC leaves your wallet per call, non-custodial            | Card-funded account credit, drawn down at exact usage                                                      |
-| **Fees**          | $0.001/tx settlement fee (covers on-chain gas)             | 5.5% + $0.30 on the top-up, then list price with **nothing per call**                                      |
+|                   | Wallet (default)                                                                     | API key                                                                                                    |
+| ----------------- | ------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------- |
+| **Who it is for** | Autonomous agents, and anyone happy holding USDC                                     | People who would rather pay with a card                                                                    |
+| **Setup**         | Nothing — a wallet is generated on first run                                         | Sign up at [user.blockrun.ai](https://user.blockrun.ai), top up, mint a key, `clawrouter login brk_live_…` |
+| **Auth**          | An x402 signature per request                                                        | `Authorization: Bearer brk_live_…`                                                                         |
+| **Gateway**       | `sol.blockrun.ai` (Solana, default) / `blockrun.ai` (Base) / `arc.blockrun.ai` (Arc) | `api.blockrun.ai`                                                                                          |
+| **Billing**       | USDC leaves your wallet per call, non-custodial                                      | Card-funded account credit, drawn down at exact usage                                                      |
+| **Fees**          | $0.001/tx settlement fee (covers on-chain gas)                                       | 5.5% + $0.30 on the top-up, then list price with **nothing per call**                                      |
 
 ClawRouter prefers the API key whenever one is configured, so `clawrouter login`
 is all it takes to switch and `clawrouter logout` is all it takes to switch back.
@@ -583,12 +583,15 @@ USDC stays in your wallet until spent — non-custodial. Price is visible in the
 
 **Dual-chain support:** Pay with **USDC on Solana** (the default) or **USDC on Base (EVM)**. Both wallets are derived from a single BIP-39 mnemonic on first run. New installs get **Solana**; an install that predates the Solana default keeps its **Base** wallet — its USDC is there — until you switch with `/wallet solana`.
 
+**Arc:** you can also pay with **USDC on [Circle's Arc](https://arc.network)** (`eip155:5042`) via `arc.blockrun.ai` — same models, same prices, same $0.001 per-call fee as Base. Arc uses the **same EVM key and address as Base**, so there is nothing new to back up: switch with `/wallet arc` (or `clawrouter chain arc`) and fund that address with USDC on Arc.
+
 ```bash
 /wallet              # Check balance and address (both chains)
 /wallet export       # Export mnemonic + keys for backup
 /wallet recover      # Restore wallet from mnemonic on a new machine
 /wallet solana       # Switch to Solana USDC payments
 /wallet base         # Switch to Base (EVM) USDC payments
+/wallet arc          # Switch to Arc (EVM) USDC payments — same address as Base
 /stats               # View usage and savings
 /stats clear         # Reset usage statistics
 /exclude             # Show excluded models
@@ -601,6 +604,7 @@ USDC stays in your wallet until spent — non-custodial. Price is visible in the
 
 - **Solana (default):** Send USDC on Solana to your Solana address
 - **Base (EVM):** Send USDC on Base to your EVM address
+- **Arc (EVM):** Send USDC on Arc to the same EVM address
 - **Coinbase/CEX:** Withdraw USDC to either network
 - **Credit card:** don't fund a wallet at all — [sign up at user.blockrun.ai](https://user.blockrun.ai) and use an API key instead (below)
 

apps/desktop/README.md

@@ -33,6 +33,11 @@ ClawRouter wallet under `~/.openclaw/blockrun/` is copied into the corresponding
 Core files only when those files do not already exist. The legacy files are
 retained for rollback; Desktop never overwrites an existing Core wallet.
 
+Payment chains are Base, Solana and Circle's Arc — Desktop takes the list from
+ClawRouter's own table (`src/payment-chain.ts`) rather than defining its own.
+Arc pays from the same EVM key and address as Base (`~/.blockrun/.session`);
+its USDC balance is read from `https://arc.blockrun.ai/api/v1/balance`.
+
 ## One-click contract
 
 Every adapter follows the same transaction:

apps/desktop/electron/core/chains.ts

@@ -0,0 +1,41 @@
+/**
+ * Desktop's view of the payment chains. The chain list, labels and type are
+ * NOT redefined here: they come from ClawRouter's own table
+ * (src/payment-chain.ts), the same one the CLI and proxy use, so a chain the
+ * proxy can pay on cannot be missing from Desktop. Imported by both the
+ * Electron main process and the renderer; keep it free of Node imports.
+ */
+import {
+  PAYMENT_CHAINS,
+  PAYMENT_CHAIN_LABELS,
+  isPaymentChain,
+  type PaymentChain,
+} from "../../../../src/payment-chain.js";
+
+export { PAYMENT_CHAINS, PAYMENT_CHAIN_LABELS, isPaymentChain };
+export type { PaymentChain };
+
+/**
+ * Which Core wallet pays on a chain. Base and Arc are both EVM and share ONE
+ * key (~/.blockrun/.session) and address; Solana has its own
+ * (~/.blockrun/.solana-session).
+ */
+export type WalletKind = "evm" | "solana";
+
+export function walletKindOf(chain: PaymentChain): WalletKind {
+  return chain === "solana" ? "solana" : "evm";
+}
+
+/** The Core wallet file a chain's key lives in. */
+export function coreWalletFileOf(chain: PaymentChain): ".session" | ".solana-session" {
+  return walletKindOf(chain) === "evm" ? ".session" : ".solana-session";
+}
+
+export function chainLabel(chain: PaymentChain): string {
+  return PAYMENT_CHAIN_LABELS[chain];
+}
+
+/** A chain from /health or a chain file; anything unrecognised is undefined, not Base. */
+export function paymentChainOrUndefined(value: unknown): PaymentChain | undefined {
+  return isPaymentChain(value) ? value : undefined;
+}

apps/desktop/electron/core/ipc-policy.ts

@@ -1,6 +1,7 @@
 import { fileURLToPath } from "node:url";
 import { resolve } from "node:path";
 
+import { isPaymentChain } from "./chains.js";
 import type { AgentId, InstallOptions, PaymentChain } from "./types.js";
 
 const AGENT_IDS = new Set<AgentId>(["openclaw", "codex", "hermes", "dsh", "pi"]);
@@ -39,7 +40,7 @@ export function parseInstallOptions(value: unknown): InstallOptions {
 }
 
 export function parsePaymentChain(value: unknown): PaymentChain {
-  if (value !== "base" && value !== "solana") throw new Error("Unsupported payment chain");
+  if (!isPaymentChain(value)) throw new Error("Unsupported payment chain");
   return value;
 }