25Sekisho — Managed-Identity Gateway for Microsoft Foundry
Role: Creator & Maintainer
Executive summary
Built an experimental, stateless reverse-proxy gateway that exposes an Entra-only Microsoft Foundry deployment as an OpenAI-compatible endpoint, so any OpenAI-SDK-compatible client can use it without ever handling Entra tokens or a Foundry API key.
- FastAPI
- Microsoft Foundry
- Entra ID (Managed Identity)
- Azure Key Vault
- Azure Container Apps
- Bicep
Some Azure environments enforce policy that disables local/key auth on Microsoft Foundry (Entra-only access), which breaks any client expecting a standard OpenAI-compatible API key. I wanted a personal project to explore a clean way to bridge that gap without ever exposing a Foundry key.
- Design a thin, stateless proxy that authenticates inbound callers with its own key, then exchanges that for a managed-identity Entra token outbound to Foundry.
- Expose chat, responses and audio (speech-to-text / text-to-speech) endpoints in an OpenAI-compatible shape.
- Support key issuance, rotation and revocation, plus infrastructure-as-code and a deployment runbook.
I built a FastAPI app that accepts a "Sekisho Key" (`Authorization: Bearer`) from callers, calls Foundry using its system-assigned managed identity (Entra token, `https://ai.azure.com/.default` scope) with automatic 401 → refresh → retry, and exposes `/openai/v1/*` for chat, responses and audio models. Key lifecycle (issue/rotate/revoke) is backed by Azure Key Vault via an `/admin` UI protected by Entra Easy Auth. Infrastructure (Foundry + project, Key Vault, Container Apps, least-privilege RBAC) is defined in Bicep, with a multi-stage Docker build, a deployment runbook and ADRs.
A working experimental gateway with a pytest suite covering the proxy, auth, keys and token exchange. It is explicitly documented as an experiment, not for production use — the expected result is a working, personal proof of the managed-identity bridging pattern, not a shipped product.
Designing the inbound-key / outbound-managed-identity split clarified how to keep zero long-lived model credentials anywhere in the system, and labeling this clearly as an experiment (not a product) kept the scope tight enough to actually finish it.
Architecture diagram coming soon
Drop an image at assets/img/diagrams/sekisho-foundry-gateway.png