Add Sei payment method docs

src/components/cards.tsx

@@ -297,6 +297,28 @@ export function CardChargeCard() {
   );
 }
 
+export function SeiMethodCard() {
+  return (
+    <Card
+      description="ERC-20 stablecoin payments on Sei with sub-second finality"
+      icon="lucide:link"
+      title="Sei"
+      to="/payment-methods/sei"
+    />
+  );
+}
+
+export function SeiChargeCard() {
+  return (
+    <Card
+      description="One-time ERC-20 payments settled on Sei"
+      icon="lucide:link"
+      title="Sei charge"
+      to="/payment-methods/sei/charge"
+    />
+  );
+}
+
 export function CustomMethodCard() {
   return (
     <Card

src/pages/payment-methods/index.mdx

@@ -3,7 +3,7 @@ imageDescription: "Available payment methods in MPP and how to choose the right
 ---
 
 import { Cards, Tab, Tabs } from 'vocs'
-import { TempoMethodCard, CardMethodCard, LightningMethodCard, SolanaMethodCard, StripeMethodCard, CustomMethodCard } from '../../components/cards'
+import { TempoMethodCard, CardMethodCard, LightningMethodCard, SolanaMethodCard, SeiMethodCard, StripeMethodCard, CustomMethodCard } from '../../components/cards'
 
 # Payment methods [Available methods and how to choose one]
 
@@ -42,6 +42,12 @@ WWW-Authenticate: Payment method="lightning", intent="charge", ...
 ```http
 HTTP/1.1 402 Payment Required
 WWW-Authenticate: Payment method="solana", intent="charge", ...
+```
+  </Tab>
+  <Tab title="Sei">
+```http
+HTTP/1.1 402 Payment Required
+WWW-Authenticate: Payment method="sei", intent="charge", ...
 ```
   </Tab>
 </Tabs>
@@ -54,5 +60,6 @@ WWW-Authenticate: Payment method="solana", intent="charge", ...
   <CardMethodCard />
   <LightningMethodCard />
   <SolanaMethodCard />
+  <SeiMethodCard />
   <CustomMethodCard />
 </Cards>

src/pages/payment-methods/sei/charge.mdx

@@ -0,0 +1,79 @@
+---
+imageDescription: "One-time ERC-20 token transfers on Sei with sub-second on-chain settlement"
+---
+
+import { Cards } from 'vocs'
+import { SpecCard } from '../../../components/SpecCard'
+
+# Sei charge [One-time ERC-20 token transfers on Sei]
+
+The Sei implementation of the [charge](/intents/charge) intent.
+
+The client submits an ERC-20 `transfer` transaction on Sei. The server verifies the transfer on-chain and returns the resource with a receipt. Settlement completes in ~400ms.
+
+This method is best for single API calls, content access, or one-off purchases paid with USDC or USDT on Sei.
+
+## Server
+
+Use `sei.charge` to gate endpoints behind ERC-20 token payments on Sei.
+
+```ts
+import { Mppx } from 'mppx/server'
+import { sei } from '@sei/mpp/server'
+
+const mppx = Mppx.create({
+  methods: [sei.charge({
+    recipient: '0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266',
+    chainId: 1329,
+  })],
+  secretKey: process.env.MPP_SECRET_KEY!,
+})
+
+export async function handler(request: Request) {
+  const result = await mppx.charge({
+    amount: '1.00',
+    currency: '0xe15fc38f6d8c56af07bbcbe3baf5708a2bf42392', // USDC on Sei
+  })(request)
+
+  if (result.status === 402) return result.challenge
+
+  return result.withReceipt(Response.json({ data: '...' }))
+}
+```
+
+## Credential types
+
+Sei charge supports two credential types:
+
+### `transaction`
+
+The client signs but does not broadcast. The signed transaction is sent to the server, which broadcasts it and waits for confirmation.
+
+### `hash`
+
+The client broadcasts the transaction itself and presents the transaction hash. The server confirms the transfer on-chain before returning the resource.
+
+## Client
+
+Use `sei.charge` with `Mppx.create` to automatically handle Sei charge challenges. The client parses the challenge, signs an ERC-20 transfer, and retries with the credential.
+
+```ts
+import { Mppx } from 'mppx/client'
+import { sei } from '@sei/mpp/client'
+import { privateKeyToAccount } from 'viem/accounts'
+
+const account = privateKeyToAccount('0xabc…123')
+
+const mppx = Mppx.create({
+  methods: [sei.charge({ account })],
+  polyfill: false,
+})
+
+const response = await mppx.fetch('https://api.example.com/resource')
+```
+
+## Specification
+
+<Cards>
+  <SpecCard to="https://paymentauth.org/draft-sei-charge-00" />
+</Cards>

src/pages/payment-methods/sei/index.mdx

@@ -0,0 +1,37 @@
+---
+imageDescription: "ERC-20 stablecoin payments on Sei with sub-second finality"
+---
+
+# Sei [ERC-20 stablecoin payments on Sei]
+
+The Sei payment method enables MPP payments using ERC-20 stablecoins on [Sei](https://sei.io), an EVM-compatible L1 with ~400ms finality. Sei supports the **charge** intent for one-time payments settled directly on-chain.
+
+Because Sei is fully EVM-compatible, it works with standard Ethereum tooling—viem, ethers, and any ERC-20 wallet.
+
+## Why Sei
+
+Sei's architecture provides several properties useful for MPP:
+
+- **~400ms finality**—Deterministic confirmation in under half a second, no probabilistic waiting
+- **EVM compatibility**—Standard ERC-20 transfers using existing Ethereum tooling
+- **Low fees**—Transaction costs suitable for micropayments and per-request billing
+- **USDC and USDT support**—Pay with widely-held stablecoins
+
+## Chain IDs
+
+| Network | Chain ID |
+|---|---|
+| Mainnet | `1329` |
+| Testnet | `1238` |
+
+## Intents
+
+<div className="vocs:grid vocs:grid-cols-1 vocs:md:grid-cols-2 vocs:gap-4">
+  <a href="/payment-methods/sei/charge" className="vocs:relative vocs:flex vocs:flex-col vocs:space-y-2 vocs:rounded-md vocs:bg-surfaceTint/70 vocs:border vocs:border-primary vocs:p-4 vocs:no-underline vocs:transition-colors vocs:hover:bg-surfaceTint">
+    <div className="vocs:size-8 vocs:flex vocs:items-center vocs:justify-center vocs:rounded-lg vocs:border vocs:border-primary vocs:bg-surface vocs:text-accent">
+      <svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"/><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"/></svg>
+    </div>
+    <div className="vocs:text-[15px] vocs:font-medium vocs:text-heading">Sei charge</div>
+    <div className="vocs:text-sm vocs:leading-relaxed vocs:text-secondary">One-time ERC-20 payments settled on Sei</div>
+  </a>
+</div>

vocs.config.ts

@@ -367,6 +367,14 @@ export default defineConfig({
               { text: "Charge", link: "/payment-methods/solana/charge" },
             ],
           },
+          {
+            text: "Sei",
+            collapsed: true,
+            items: [
+              { text: "Overview", link: "/payment-methods/sei" },
+              { text: "Charge", link: "/payment-methods/sei/charge" },
+            ],
+          },
           { text: "Custom", link: "/payment-methods/custom" },
         ],
       },