MCP OAuth rejects Microsoft Entra multi-tenant issuer after successful authentication

What version of Codex CLI is running?

0.148.0-alpha.9

What subscription do you have?

ChatGPT Business

Which model were you using?

Not applicable. The failure occurs during MCP OAuth authentication, before any MCP tools become available.

What platform is your computer?

Windows x64

What terminal emulator and version are you using (if applicable)?

PowerShell, launched from Codex Desktop.

Codex doctor report

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}

What issue are you seeing?

Codex cannot complete OAuth authentication for Microsoft Fabric's FabricIQ remote MCP server.

The server advertises the Microsoft Entra multi-tenant authorization-server issuer:

https://login.microsoftonline.com/organizations/v2.0

Microsoft browser authentication completes successfully and redirects back to Codex's localhost callback. Codex then rejects the callback because Microsoft returns a tenant-specific issuer:

https://login.microsoftonline.com/<tenant-id>/v2.0

The resulting error is:

Error: Authorization server issuer mismatch:
expected https://login.microsoftonline.com/organizations/v2.0,
received https://login.microsoftonline.com/<tenant-id>/v2.0

The tenant ID has been redacted.

Because the OAuth result is rejected, the FabricIQ MCP server remains in an authentication-required state and its tools are absent from Codex.

This appears to be a strict issuer-comparison problem in Codex's MCP OAuth implementation. Codex treats the /organizations authority and the resulting tenant-specific Microsoft Entra issuer as unrelated, even though the browser authentication was initiated through that multi-tenant authority.

What steps can reproduce the bug?

1. Configure the Microsoft Fabric FabricIQ MCP server:

``toml
[mcp_servers.FabricIQ]
url = "https://api.fabric.microsoft.com/v1/mcp/fabricaihub/integrations/m365"
http_headers = { X-VARIANTS = "Fabric.Routing.PowerBIDataExploration" }
``

1. Start OAuth login using CIMD:

``powershell
codex mcp login FabricIQ --oauth-client-registration cimd
``

1. Complete the Microsoft browser-based authentication.

1. The browser returns to the localhost OAuth callback.

1. Codex fails while handling the callback:

``text
Authorization server issuer mismatch:
expected https://login.microsoftonline.com/organizations/v2.0,
received https://login.microsoftonline.com/<tenant-id>/v2.0
``

1. Restart or reload Codex. The FabricIQ MCP tools are still unavailable because authentication was not accepted.

What is the expected behavior?

Codex should successfully complete OAuth when Microsoft Entra's /organizations/v2.0 authority produces a valid tenant-specific issuer after the user authenticates.

Possible solutions could include:

• validating the returned issuer as a tenant-specific instance of the advertised Microsoft Entra multi-tenant authority;
• supporting Microsoft Entra issuer templates;
• allowing an explicit tenant-specific authorization-server or issuer override in the MCP configuration; or
• providing another documented way to configure the expected issuer.

After successful authentication, the FabricIQ MCP server should initialize and expose its tools.

Actual behavior

The browser sign-in succeeds, but Codex rejects the OAuth callback during issuer validation. The token cannot be used and the FabricIQ MCP server's tools remain absent.

Related open issues

These issues appear related, but none describes this exact Microsoft Entra /organizations versus tenant-specific issuer mismatch:

• https://github.com/openai/codex/issues/31573 — OAuth authentication fails at issuer validation. This concerns a missing RFC 9207 iss callback parameter rather than a Microsoft Entra multi-tenant/tenant-specific mismatch.
• https://github.com/openai/codex/issues/37373 — MCP app-server strips a trailing slash from the expected authorization-server issuer. This is another strict issuer-comparison failure, but involves URL canonicalization.
• https://github.com/openai/codex/issues/15818 — Remote HTTP MCP OAuth with Microsoft Entra fails when dynamic client registration is unavailable. It involves the same /organizations/v2.0 authority and remote MCP authentication, but fails during client registration rather than issuer validation.

Additional information

• Fabric skills plugin version: 0.3.12
• Power BI authoring plugin version: 0.3.12
• The FabricIQ endpoint is reachable and OAuth discovery successfully initiates Microsoft authentication.
• This failure occurs before Power BI/Fabric permissions or report access can be evaluated.
• No tokens, tenant IDs, account email addresses, or client secrets are included in this report.