[Bug] Microsoft 365 connector OAuth generates duplicate `prompt` parameter

Bug Description
Title: Microsoft 365 connector OAuth fails with AADSTS9000411 — duplicate prompt parameter Description The official Microsoft 365 connector (https://microsoft365.mcp.claude.com/mcp) generates an OAuth authorization URL containing the prompt query parameter twice, causing Azure AD to reject the request. Steps to reproduce 1. claude mcp add --transport http microsoft365 https://microsoft365.mcp.claude.com/mcp 2. /mcp → Authenticate microsoft365 3. Browser opens login.microsoftonline.com 4. Azure AD returns error Error AADSTS9000411: The request is not properly formatted. The parameter 'prompt' is duplicated. Generated URL (redacted) https://login.microsoftonline.com/common/oauth2/v2.0/authorize ?prompt=select_account &response_type=code &client_id=08ad6f98-a4f8-4635-bb8d-f1a3044760f0 &code_challenge=... &code_challenge_method=S256 &redirect_uri=http%3A%2F%2Flocalhost%3A64501%2Fcallback &state=... &scope=api%3A%2F%2F07c030f6-5743-41b7-ba00-0a6e85f37c17%2F.default+offline_access+openid+email &prompt=consent ← duplicate Note both prompt=select_account and prompt=consent are present. Expected behavior Only one prompt parameter should be emitted. Environment - Claude Code CLI - macOS Darwin 23.1.0 - Connector: Microsoft 365 (Anthropic-developed, hosted at microsoft365.mcp.claude.com) - Tenant: work/school account Reference IDs (from one failed attempt) - Request Id: fa6da355-b660-49b1-a0ca-ff6acfb54100 - Correlation Id: 3b5be975-d2c3-40be-b3fb-010dcf1b179e - Timestamp: 2026-05-18T08:30:24Z Impact Authentication completely blocked. The connector is unusable until fixed.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.112
• Feedback ID: 0a3d5ec2-6e33-4d60-b140-0359be8f2fed

Errors

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