Doppler vs Google Cloud Secret Manager

Doppler

Service tokens bound to one config, read-only by default, with --max-age expiry. Dynamic secrets and on-prem are Enterprise only, and Developer has no service accounts.

Google Cloud Secret Manager

Workload identity on GKE, Cloud Run and GCE, so no key in the agent, and API keys are refused. Managed rotation only covers Cloud SQL; other rotation is a Pub/Sub notification you handle.

Doppler

1. Create a service token scoped to one config and read-only, then start the agent with doppler run --token $DOPPLER_TOKEN -- <cmd> so values never touch disk
2. Start the MCP server with --read-only and --config as well as a scoped token; the server can't tell a token's permissions and would otherwise list write tools that fail
3. Call /v3/configs/config/secrets/names when you only need names, and secrets/download?format=json for every value in one call
4. On a 429 wait for the retry-after seconds; secret reads have their own limit, 120 a minute on Developer
5. Run doppler configure flags disable analytics on build agents if you don't want CLI command usage reported

Google Cloud Secret Manager

1. Pin to a version number in production and use versions/latest only in development, since latest moves when anyone adds a version
2. Grant roles/secretmanager.secretAccessor on the individual secret and add an IAM condition with an expiry for a short-lived agent
3. Turn on Data Access audit logs for secretmanager.googleapis.com if you need a record of each read
4. Read once per run and cache; accesses past 10,000 a month are metered
5. Use a regional secret (projects/*/locations/*/secrets/*) when the data must stay in one place, and note the higher write quota there