fix(mcp): fix OAuth auto-connect failing on first connection (#15547)

Co-authored-by: Aiden Cline <63023139+rekram1-node@users.noreply.github.com>

packages/opencode/src/mcp/index.ts

@@ -396,8 +396,13 @@ export namespace MCP {
         } catch (error) {
           lastError = error instanceof Error ? error : new Error(String(error))
 
-          // Handle OAuth-specific errors
-          if (error instanceof UnauthorizedError) {
+          // Handle OAuth-specific errors.
+          // The SDK throws UnauthorizedError when auth() returns 'REDIRECT',
+          // but may also throw plain Errors when auth() fails internally
+          // (e.g. during discovery, registration, or state generation).
+          // When an authProvider is attached, treat both cases as auth-related.
+          const isAuthError = error instanceof UnauthorizedError || (authProvider && lastError.message.includes("OAuth"))
+          if (isAuthError) {
             log.info("mcp server requires authentication", { key, transport: name })
 
             // Check if this is a "needs registration" error

packages/opencode/src/mcp/oauth-provider.ts

@@ -144,10 +144,19 @@ export class McpOAuthProvider implements OAuthClientProvider {
 
   async state(): Promise<string> {
     const entry = await McpAuth.get(this.mcpName)
-    if (!entry?.oauthState) {
-      throw new Error(`No OAuth state saved for MCP server: ${this.mcpName}`)
+    if (entry?.oauthState) {
+      return entry.oauthState
     }
-    return entry.oauthState
+
+    // Generate a new state if none exists — the SDK calls state() as a
+    // generator, not just a reader, so we need to produce a value even when
+    // startAuth() hasn't pre-saved one (e.g. during automatic auth on first
+    // connect).
+    const newState = Array.from(crypto.getRandomValues(new Uint8Array(32)))
+      .map((b) => b.toString(16).padStart(2, "0"))
+      .join("")
+    await McpAuth.updateOAuthState(this.mcpName, newState)
+    return newState
   }
 
   async invalidateCredentials(type: "all" | "client" | "tokens"): Promise<void> {