> Solana Developer Platform docs, served as Markdown. The [docs index](https://platform-beta.solana.com/docs.md) lists every page and [llms.txt](https://platform-beta.solana.com/docs/ai/llms.txt) the key ones; [SKILL.md](https://platform-beta.solana.com/SKILL.md) has the rules for building on SDP.

# External Co-Signers

Host provider-specific signing services outside the default self-hosted SDP stack.

Some signing providers need a co-signer or automation process that you run beside the SDP API. Run it outside `compose.yml`, which starts only SDP's own services: a co-signer has its own secrets, identity, ingress, and availability needs.

## Production pattern

Run each co-signer on a managed container service, such as Google Cloud Run or your cloud's equivalent.

- Use the image and runtime the provider or your operator team supplies.
- Store co-signer secrets in a cloud secret manager, never in the SDP `.env`.
- Give the co-signer a dedicated service account that can read only the secrets it needs.
- Set ingress and invoker IAM for the provider's flow. Keep ingress private or authenticated unless the provider needs a public callback.
- Keep at least one instance running (`minScale: 1` on Cloud Run) when callback latency or availability matters. Scale to zero only when cold starts are acceptable.
- Separate development, staging, and production co-signers by provider account, cloud project, service account, and secrets.
- Alert on failed signing attempts, container restarts, authentication failures, and stale or expired key material.

## Utila

SDP signs with Utila directly: select `utila` in the configurator and fill in its `UTILA_*` credentials. SDP submits each transaction to Utila and polls until it's signed, up to `UTILA_MAX_POLL_ATTEMPTS` times every `UTILA_POLL_INTERVAL_MS` (60 tries, a second apart, by default). Like the local signer, Utila needs a per-organization activation.

`UTILA_DESIGNATED_SIGNERS` lists the Utila users asked to sign each transaction. Left empty, it's the service account itself.

If your Utila setup runs an automated co-signer, host it outside the stack. `infra/utila/cloud-run/` in the repository has Cloud Run scaffolding for one: a service template and a deploy script for an image you supply.