Atlassian MCP Integration authentication failing: Existing OAuth client information is required when

[Saishiva K]

Atlassian MCP Integration authentication failing on Claude code with the following error.

Existing OAuth client information is required when exchanging an authorization code

Claude Code v2.1.212

[Viswanathan Ramachandran]

Hi @Saishiva K 

This is usually caused by stale OAuth/Dynamic Client Registration state after Atlassian’s auth-server migration. Claude Code starts the login with one client registration, then attempts to exchange the code without the matching client details.

Fix: remove and re-add the Atlassian MCP server using

https://mcp.atlassian.com/v1/mcp/authv2

Then run /mcp in Claude Code, clear the existing authentication, and sign in again using a private/incognito browser window. Also remove any manually configured Authorisation header or duplicate old Atlassian MCP entries.

If the organisation restricts MCP redirects, you/Atlassian admin can allowlist the Claude Code localhost callback in Rovo MCP Domain settings (typically http://:*/**).

 Note: Allowlist http://:*/** is the standard localhost OAuth callback pattern for desktop/CLI clients such as Claude Code. It does not expose Atlassian data to the public internet; the redirect remains local and the authorisation code is short-lived and PKCE-bound. As with any developer-tool integration, enable it only for approved clients on trusted/managed devices and keep access/audit controls in place.

FYI: Do not exchange the authorisation code manually or reuse a code from a prior browser attempt authorisation codes are one-time and bound to the original OAuth client and PKCE flow.

Happy to hear how it goes.