diff --git a/packages/opencode/src/account/account.ts b/packages/opencode/src/account/account.ts
index 4b49d2a74890..ac216deb3f4b 100644
--- a/packages/opencode/src/account/account.ts
+++ b/packages/opencode/src/account/account.ts
@@ -396,10 +396,22 @@ const layer: Layer.Layer<Service, never, AccountRepo.Service | HttpClient.HttpCl
       const parsed = yield* HttpClientResponse.schemaBodyJson(DeviceAuth)(response).pipe(
         mapAccountServiceError("Failed to decode response"),
       )
+      const verification = yield* Effect.try({
+        try: () => {
+          const url = new URL(parsed.verification_uri_complete, `${normalizedServer}/`)
+          if (url.protocol !== "http:" && url.protocol !== "https:") throw new Error("expected HTTP(S)")
+          return url
+        },
+        catch: (cause) =>
+          new AccountServiceError({
+            message: `Invalid device verification URL: ${cause instanceof Error ? cause.message : String(cause)}`,
+            cause,
+          }),
+      })
       return new Login({
         code: parsed.device_code,
         user: parsed.user_code,
-        url: `${normalizedServer}${parsed.verification_uri_complete}`,
+        url: verification.href,
         server: normalizedServer,
         expiry: parsed.expires_in,
         interval: parsed.interval,
diff --git a/packages/opencode/test/account/service.test.ts b/packages/opencode/test/account/service.test.ts
index 672d54971623..d6e3018e575b 100644
--- a/packages/opencode/test/account/service.test.ts
+++ b/packages/opencode/test/account/service.test.ts
@@ -10,6 +10,7 @@ import { Account } from "../../src/account/account"
 import {
   AccessToken,
   AccountID,
+  AccountServiceError,
   AccountTransportError,
   DeviceCode,
   Login,
@@ -100,6 +101,93 @@ it.live("login normalizes trailing slashes in the provided server URL", () =>
   }),
 )
 
+it.live("login resolves the verification URL against the server origin", () =>
+  Effect.gen(function* () {
+    const client = HttpClient.make((req) =>
+      Effect.succeed(
+        json(req, {
+          device_code: "device-code",
+          user_code: "user-code",
+          verification_uri_complete: "/console/device?user_code=user-code",
+          expires_in: 600,
+          interval: 5,
+        }),
+      ),
+    )
+
+    const result = yield* Account.use.login("https://one.example.com/console").pipe(Effect.provide(live(client)))
+
+    expect(result.server).toBe("https://one.example.com/console")
+    expect(result.url).toBe("https://one.example.com/console/device?user_code=user-code")
+  }),
+)
+
+it.live("login resolves relative verification URLs beneath the server path", () =>
+  Effect.gen(function* () {
+    const client = HttpClient.make((req) =>
+      Effect.succeed(
+        json(req, {
+          device_code: "device-code",
+          user_code: "user-code",
+          verification_uri_complete: "device?user_code=user-code",
+          expires_in: 600,
+          interval: 5,
+        }),
+      ),
+    )
+
+    const result = yield* Account.use.login("https://one.example.com/console").pipe(Effect.provide(live(client)))
+
+    expect(result.url).toBe("https://one.example.com/console/device?user_code=user-code")
+  }),
+)
+
+it.live("login rejects malformed verification URLs", () =>
+  Effect.gen(function* () {
+    const client = HttpClient.make((req) =>
+      Effect.succeed(
+        json(req, {
+          device_code: "device-code",
+          user_code: "user-code",
+          verification_uri_complete: "http://[::1",
+          expires_in: 600,
+          interval: 5,
+        }),
+      ),
+    )
+
+    const error = yield* Effect.flip(
+      Account.use.login("https://one.example.com/console").pipe(Effect.provide(live(client))),
+    )
+
+    expect(error).toBeInstanceOf(AccountServiceError)
+    expect(error.message).toContain("Invalid device verification URL")
+  }),
+)
+
+it.live("login rejects non-HTTP verification URLs", () =>
+  Effect.gen(function* () {
+    const client = HttpClient.make((req) =>
+      Effect.succeed(
+        json(req, {
+          device_code: "device-code",
+          user_code: "user-code",
+          verification_uri_complete: "file:///tmp/device",
+          expires_in: 600,
+          interval: 5,
+        }),
+      ),
+    )
+
+    const error = yield* Effect.flip(
+      Account.use.login("https://one.example.com/console").pipe(Effect.provide(live(client))),
+    )
+
+    expect(error).toBeInstanceOf(AccountServiceError)
+    expect(error.message).toContain("Invalid device verification URL: expected HTTP(S)")
+  }),
+)
+
 it.live("login maps transport failures to account transport errors", () =>
   Effect.gen(function* () {
     const client = HttpClient.make((req) =>