diff --git a/packages/opencode/src/cli/cmd/auth.ts b/packages/opencode/src/cli/cmd/auth.ts
index 3dd7bcc35dd..991d12ab20c 100644
--- a/packages/opencode/src/cli/cmd/auth.ts
+++ b/packages/opencode/src/cli/cmd/auth.ts
@@ -295,6 +295,7 @@ export const AuthLoginCommand = cmd({
                   opencode: "recommended",
                   anthropic: "Claude Max or API key",
                   openai: "ChatGPT Plus/Pro or API key",
+                  openrouter: "OAuth or API key",
                 }[x.id],
               })),
             ),
diff --git a/packages/opencode/src/plugin/index.ts b/packages/opencode/src/plugin/index.ts
index f57b46a3521..8a84e1be42f 100644
--- a/packages/opencode/src/plugin/index.ts
+++ b/packages/opencode/src/plugin/index.ts
@@ -8,6 +8,7 @@ import { BunProc } from "../bun"
 import { Instance } from "../project/instance"
 import { Flag } from "../flag/flag"
 import { CodexAuthPlugin } from "./codex"
+import { OpenRouterAuthPlugin } from "./openrouter"
 
 export namespace Plugin {
   const log = Log.create({ service: "plugin" })
@@ -15,7 +16,7 @@ export namespace Plugin {
   const BUILTIN = ["opencode-copilot-auth@0.0.12", "opencode-anthropic-auth@0.0.8"]
 
   // Built-in plugins that are directly imported (not installed from npm)
-  const INTERNAL_PLUGINS: PluginInstance[] = [CodexAuthPlugin]
+  const INTERNAL_PLUGINS: PluginInstance[] = [CodexAuthPlugin, OpenRouterAuthPlugin]
 
   const state = Instance.state(async () => {
     const client = createOpencodeClient({
diff --git a/packages/opencode/src/plugin/openrouter.ts b/packages/opencode/src/plugin/openrouter.ts
new file mode 100644
index 00000000000..ad0b672d511
--- /dev/null
+++ b/packages/opencode/src/plugin/openrouter.ts
@@ -0,0 +1,321 @@
+/**
+ * OpenRouter OAuth PKCE authentication plugin.
+ * Allows users to authenticate with their OpenRouter account instead of manually entering an API key.
+ * See: https://openrouter.ai/docs/guides/overview/auth/oauth
+ */
+import type { Hooks, PluginInput } from "@opencode-ai/plugin"
+import { Log } from "../util/log"
+import open from "open"
+
+const log = Log.create({ service: "plugin.openrouter" })
+
+const OAUTH_PORT = 3000
+const OPENROUTER_AUTH_URL = "https://openrouter.ai/auth"
+const OPENROUTER_KEYS_URL = "https://openrouter.ai/api/v1/auth/keys"
+
+interface PkceCodes {
+  verifier: string
+  challenge: string
+}
+
+async function generatePKCE(): Promise<PkceCodes> {
+  const verifier = generateRandomString(43)
+  const encoder = new TextEncoder()
+  const data = encoder.encode(verifier)
+  const hash = await crypto.subtle.digest("SHA-256", data)
+  const challenge = base64UrlEncode(hash)
+  return { verifier, challenge }
+}
+
+function generateRandomString(length: number): string {
+  const chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~"
+  const bytes = crypto.getRandomValues(new Uint8Array(length))
+  return Array.from(bytes)
+    .map((b) => chars[b % chars.length])
+    .join("")
+}
+
+function base64UrlEncode(buffer: ArrayBuffer): string {
+  const bytes = new Uint8Array(buffer)
+  const binary = String.fromCharCode(...bytes)
+  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "")
+}
+
+function buildAuthorizeUrl(redirectUri: string, pkce: PkceCodes): string {
+  const params = new URLSearchParams({
+    callback_url: redirectUri,
+    code_challenge: pkce.challenge,
+    code_challenge_method: "S256",
+  })
+  return `${OPENROUTER_AUTH_URL}?${params.toString()}`
+}
+
+interface KeyResponse {
+  key: string
+}
+
+async function exchangeCodeForKey(code: string, pkce: PkceCodes): Promise<KeyResponse> {
+  const response = await fetch(OPENROUTER_KEYS_URL, {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/json",
+      "HTTP-Referer": "https://opencode.ai/",
+      "X-Title": "opencode",
+    },
+    body: JSON.stringify({
+      code,
+      code_verifier: pkce.verifier,
+      code_challenge_method: "S256",
+    }),
+  })
+  if (!response.ok) {
+    const text = await response.text()
+    throw new Error(`Key exchange failed: ${response.status} - ${text}`)
+  }
+  return response.json()
+}
+
+const HTML_SUCCESS = `<!doctype html>
+<html>
+  <head>
+    <title>OpenCode - OpenRouter Authorization Successful</title>
+    <style>
+      body {
+        font-family:
+          system-ui,
+          -apple-system,
+          sans-serif;
+        display: flex;
+        justify-content: center;
+        align-items: center;
+        height: 100vh;
+        margin: 0;
+        background: #131010;
+        color: #f1ecec;
+      }
+      .container {
+        text-align: center;
+        padding: 2rem;
+      }
+      h1 {
+        color: #f1ecec;
+        margin-bottom: 1rem;
+      }
+      p {
+        color: #b7b1b1;
+      }
+    </style>
+  </head>
+  <body>
+    <div class="container">
+      <h1>Authorization Successful</h1>
+      <p>You can close this window and return to OpenCode.</p>
+    </div>
+    <script>
+      setTimeout(() => window.close(), 2000)
+    </script>
+  </body>
+</html>`
+
+const HTML_ERROR = (error: string) => `<!doctype html>
+<html>
+  <head>
+    <title>OpenCode - OpenRouter Authorization Failed</title>
+    <style>
+      body {
+        font-family:
+          system-ui,
+          -apple-system,
+          sans-serif;
+        display: flex;
+        justify-content: center;
+        align-items: center;
+        height: 100vh;
+        margin: 0;
+        background: #131010;
+        color: #f1ecec;
+      }
+      .container {
+        text-align: center;
+        padding: 2rem;
+      }
+      h1 {
+        color: #fc533a;
+        margin-bottom: 1rem;
+      }
+      p {
+        color: #b7b1b1;
+      }
+      .error {
+        color: #ff917b;
+        font-family: monospace;
+        margin-top: 1rem;
+        padding: 1rem;
+        background: #3c140d;
+        border-radius: 0.5rem;
+      }
+    </style>
+  </head>
+  <body>
+    <div class="container">
+      <h1>Authorization Failed</h1>
+      <p>An error occurred during authorization.</p>
+      <div class="error">${error}</div>
+    </div>
+  </body>
+</html>`
+
+interface PendingOAuth {
+  pkce: PkceCodes
+  resolve: (key: string) => void
+  reject: (error: Error) => void
+}
+
+let oauthServer: ReturnType<typeof Bun.serve> | undefined
+let pendingOAuth: PendingOAuth | undefined
+
+async function startOAuthServer(): Promise<{ port: number; redirectUri: string }> {
+  if (oauthServer) {
+    return { port: OAUTH_PORT, redirectUri: `http://localhost:${OAUTH_PORT}/auth/callback` }
+  }
+
+  oauthServer = Bun.serve({
+    port: OAUTH_PORT,
+    fetch(req) {
+      const url = new URL(req.url)
+
+      if (url.pathname === "/auth/callback") {
+        const code = url.searchParams.get("code")
+        const error = url.searchParams.get("error")
+        const errorDescription = url.searchParams.get("error_description")
+
+        if (error) {
+          const errorMsg = errorDescription || error
+          pendingOAuth?.reject(new Error(errorMsg))
+          pendingOAuth = undefined
+          return new Response(HTML_ERROR(errorMsg), {
+            headers: { "Content-Type": "text/html" },
+          })
+        }
+
+        if (!code) {
+          const errorMsg = "Missing authorization code"
+          pendingOAuth?.reject(new Error(errorMsg))
+          pendingOAuth = undefined
+          return new Response(HTML_ERROR(errorMsg), {
+            status: 400,
+            headers: { "Content-Type": "text/html" },
+          })
+        }
+
+        if (!pendingOAuth) {
+          const errorMsg = "No pending OAuth request"
+          return new Response(HTML_ERROR(errorMsg), {
+            status: 400,
+            headers: { "Content-Type": "text/html" },
+          })
+        }
+
+        const current = pendingOAuth
+        pendingOAuth = undefined
+
+        exchangeCodeForKey(code, current.pkce)
+          .then((result) => current.resolve(result.key))
+          .catch((err) => current.reject(err))
+
+        return new Response(HTML_SUCCESS, {
+          headers: { "Content-Type": "text/html" },
+        })
+      }
+
+      return new Response("Not found", { status: 404 })
+    },
+  })
+
+  log.info("openrouter oauth server started", { port: OAUTH_PORT })
+  return { port: OAUTH_PORT, redirectUri: `http://localhost:${OAUTH_PORT}/auth/callback` }
+}
+
+function stopOAuthServer() {
+  if (oauthServer) {
+    oauthServer.stop()
+    oauthServer = undefined
+    log.info("openrouter oauth server stopped")
+  }
+}
+
+function waitForOAuthCallback(pkce: PkceCodes): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const timeout = setTimeout(
+      () => {
+        if (pendingOAuth) {
+          pendingOAuth = undefined
+          reject(new Error("OAuth callback timeout - authorization took too long"))
+        }
+      },
+      5 * 60 * 1000,
+    )
+
+    pendingOAuth = {
+      pkce,
+      resolve: (key) => {
+        clearTimeout(timeout)
+        resolve(key)
+      },
+      reject: (error) => {
+        clearTimeout(timeout)
+        reject(error)
+      },
+    }
+  })
+}
+
+export async function OpenRouterAuthPlugin(_input: PluginInput): Promise<Hooks> {
+  return {
+    auth: {
+      provider: "openrouter",
+      methods: [
+        {
+          label: "OpenRouter Account",
+          type: "oauth",
+          authorize: async () => {
+            const { redirectUri } = await startOAuthServer()
+            const pkce = await generatePKCE()
+            const authUrl = buildAuthorizeUrl(redirectUri, pkce)
+
+            const callbackPromise = waitForOAuthCallback(pkce)
+
+            log.info("opening browser for openrouter oauth", { url: authUrl })
+            open(authUrl).catch(() => {})
+
+            return {
+              url: authUrl,
+              instructions: "Complete authorization in your browser. This window will close automatically.",
+              method: "auto" as const,
+              callback: async () => {
+                try {
+                  const key = await callbackPromise
+                  stopOAuthServer()
+                  return {
+                    type: "success" as const,
+                    key,
+                  }
+                } catch (error) {
+                  stopOAuthServer()
+                  log.error("openrouter oauth failed", { error })
+                  return {
+                    type: "failed" as const,
+                  }
+                }
+              },
+            }
+          },
+        },
+        {
+          label: "Manually enter API Key",
+          type: "api",
+        },
+      ],
+    },
+  }
+}