fix(corpus_search): pin DefaultAzureCredential to MI client id#200
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When the MCP server is configured with OAuth (`AZURE_CLIENT_ID` set to the App Registration's client id for JWT audience validation), `DefaultAzureCredential` picks up that same env var and tries to use it as the managed identity's client id. The MI step fails with "No User Assigned or Delegated Managed Identity found for specified ClientId" because that GUID isn't a managed identity. Accept an optional `managed_identity_client_id` kwarg on `AzureCorpusBackendRegistry` and a `CORPUS_AZURE_MANAGED_IDENTITY_CLIENT_ID` env var on `build_registry`. When set, pass through to `DefaultAzureCredential(managed_identity_client_id=...)` so only the MI step of the credential chain is pinned; other steps (env credential, workload identity, az CLI for local dev) are unaffected.
ancongui
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May 31, 2026
#200) When the MCP server is configured with OAuth (`AZURE_CLIENT_ID` set to the App Registration's client id for JWT audience validation), `DefaultAzureCredential` picks up that same env var and tries to use it as the managed identity's client id. The MI step fails with "No User Assigned or Delegated Managed Identity found for specified ClientId" because that GUID isn't a managed identity. Accept an optional `managed_identity_client_id` kwarg on `AzureCorpusBackendRegistry` and a `CORPUS_AZURE_MANAGED_IDENTITY_CLIENT_ID` env var on `build_registry`. When set, pass through to `DefaultAzureCredential(managed_identity_client_id=...)` so only the MI step of the credential chain is pinned; other steps (env credential, workload identity, az CLI for local dev) are unaffected. Co-authored-by: miguelgfierro <miguelgfierro@users.noreply.github.com>
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Summary
AzureCorpusBackendRegistrynow reads an optionalCORPUS_AZURE_MANAGED_IDENTITY_CLIENT_IDenv var and passes it toDefaultAzureCredential(managed_identity_client_id=...).Why
On the MCP server,
AZURE_CLIENT_IDis set to the OAuth App Registration's client id (used byOAuthJWTMiddlewarefor JWT audience validation).DefaultAzureCredentialpicks up that same env var and tries it as the MI's client id, so the MI step of the credential chain fails:Pinning the MI step to a separate, explicit env var sidesteps the collision without touching
AZURE_CLIENT_ID(which other layers depend on).Test plan
CORPUS_AZURE_MANAGED_IDENTITY_CLIENT_IDonfirefly-mcp,list_corporasucceeds against the blob container