fix(mcp): surface OAuth completion errors

packages/opencode/src/mcp/index.ts

@@ -28,7 +28,7 @@ import { McpAuth } from "./auth"
 import { EventV2Bridge } from "@/event-v2-bridge"
 import { TuiEvent } from "@/server/tui-event"
 import open from "open"
-import { Cause, Effect, Exit, Layer, Option, Context, Schema, Stream } from "effect"
+import { Cause, Effect, Exit, Layer, Context, Schema, Stream } from "effect"
 import { EffectBridge } from "@/effect/bridge"
 import { InstanceState } from "@/effect/instance-state"
 import { ChildProcess, ChildProcessSpawner } from "effect/unstable/process"
@@ -928,16 +928,17 @@ export const layer = Layer.effect(
       const pending = pendingOAuthTransports.get(mcpName)
       if (!pending) throw new Error(`No pending OAuth flow for MCP server: ${mcpName}`)
 
-      const result = yield* Effect.tryPromise({
-        try: () => pending.transport.finishAuth(authorizationCode).then(() => true as const),
-        catch: (error) => {
-          return error
-        },
-      }).pipe(Effect.option)
+      const error = yield* Effect.tryPromise({
+        try: () => pending.transport.finishAuth(authorizationCode),
+        catch: (error) => error,
+      }).pipe(
+        Effect.match({
+          onFailure: (error) => (error instanceof Error ? error.message : String(error)),
+          onSuccess: () => undefined,
+        }),
+      )
 
-      if (Option.isNone(result)) {
-        return { status: "failed", error: "OAuth completion failed" } satisfies Status
-      }
+      if (error) return { status: "failed", error: `OAuth completion failed: ${error}` } satisfies Status
 
       yield* Effect.promise(() => pending.provider?.commit() ?? Promise.resolve())
       yield* auth.clearCodeVerifier(mcpName)

packages/opencode/test/mcp/oauth-auto-connect.test.ts

@@ -263,7 +263,7 @@ mcpTest.instance(
 
       expect(yield* mcp.finishAuth(name, "invalid-code")).toEqual({
         status: "failed",
-        error: "OAuth completion failed",
+        error: "OAuth completion failed: Token exchange failed",
       })
       const entry = yield* auth.get(name)
       expect(entry?.tokens?.accessToken).toBe("working-token")