Custos
Custos is an open-source safety control layer for AI agents that evaluates tool calls against YAML policies before execution.
Open productWhat it does
About Custos
Custos provides an open-source safety and governance control layer designed for AI agents. Operating in-process without requiring an external proxy, its SDK embeds policy evaluation and cryptographic auditing directly into application code across Python and Node environments. Every tool execution is evaluated before running against a deny-by-default YAML policy. All tool executions are recorded in an Ed25519-signed and SHA-256 hash-chained JSONL ledger, ensuring instant detection of any record modification, reordering, or deletion.
- Availability:
- unknown
- Access:
- free
- Format:
- software
- Platform:
- api
- Platform:
- cli
Pricing at launch: Released as open-source software under the Apache 2.0 license.
Core capabilities
YAML Policy Evaluation
Evaluates every tool call against a user-defined YAML policy before execution using deny-by-default authorization rules.
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