Security

STACK places a runtime boundary between an agent and the systems it uses. The linked concept and API articles define each control in detail.

Hosting and data location

STACK's production applications run in Stockholm. The primary database region is Frankfurt. Production encryption uses AWS KMS in eu-north-1. Some configured providers can process data in other regions. Review the Privacy page and your selected provider before you send regulated data.

Runtime boundary

• Passports carry short-lived, signed authority and narrow through delegation.
• The proxy verifies authority and constraints before it injects a credential.
• Detectors can deny a request, redact a response, revoke authority, or record an event.
• The append-only audit log links each entry to the previous entry hash.
• Revocation rejects the next STACK-verified call and cascades through delegated children.

Credentials and encryption

• Production credentials use KMS envelope encryption at rest.
• Proxy-only agents do not receive the raw upstream credential.
• PII is not included in Passport JWTs. The Passport carries an opaque claim reference.
• Enterprise accounts can move supported operator ciphertext to a customer-managed AWS KMS key.

See Encryption and CMEK and Credentials API.

Authentication and governance

Human clients should use OAuth, which preserves the operator or member identity and applies the member's role and service restrictions. A headless service can use the long-lived operator API key when it cannot complete OAuth, but that key carries operator-wide access. A Passport or agent JWT creates an agent-bearing request, which STACK denies on human governance routes including scope expansion, encryption changes and Intent decisions.

See STACK Authentication, Agent Keys, and Intents and Governance.

Revocation boundary

STACK checks live revocation on each STACK-verified call. Offline signature verification proves signature and expiry but cannot see a later revocation. Use the online verification endpoint when current revocation status matters. See Revocation.

Audit boundary

Hash chaining makes later row changes detectable. Anchor the chain head outside STACK if you need evidence against a full chain rewrite. See Audit Log and Evidence API.

Operator responsibilities

• Grant the smallest service scopes, Intents, counterparties, and duration needed for the job.
• Keep interactive clients on OAuth. Keep headless keys in a service secret store.
• Rotate upstream credentials that have left STACK. Passport revocation cannot rotate them.
• Review detector events, failed governance actions, and the audit chain.
• Use the current limits in the Rate Limits reference. Do not retry 429 responses in a tight loop.

If a credential is compromised

• Revoke the affected STACK authority.
• Rotate the upstream credential with its provider.
• Review the audit log and security events for unexpected use.
• Reissue only the narrow authority that the agent still needs.

Report a vulnerability