> For the complete documentation index, see [llms.txt](https://123-87.gitbook.io/signgate-api/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://123-87.gitbook.io/signgate-api/documentation/overview.md).

# Security model

SignGate combines authenticated tenancy, strict request validation, action binding, short validity, single-use consume, and audit identifiers.

{% hint style="info" %}
**Primary constraint:** Security depends on the executor enforcing every check in order.
{% endhint %}

## Control layers

* Bearer authentication and scopes
* Organization isolation
* Strict schemas
* Mandates and evidence
* Action fingerprinting
* Expiry
* Atomic consume
* Redacted audit records

## Trust boundary

The client can propose an action; it cannot self-authorize. The executor can execute; it must first prove that SignGate authorized the same action.

## Preview boundary

See [Preview limitations](https://github.com/lukekwan/agent-payment-guard/tree/docs/doc-sg-001-api-docs/docs/gitbook/public/en/security/preview-limitations.md).


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