SecretLeakGuardrail

Detects and redacts secrets / credentials in LLM input and output.

Prevents two classes of leak:

• Input leak: a user accidentally pastes an API key into a prompt that is then logged, cached, or forwarded to third-party LLM providers.
• Output leak: the LLM echoes a secret back in its response (e.g. when asked to summarise a config file that contains credentials).

Detected credential types (defaults):

• OpenAI API keys (sk-... / sk-proj-...)
• Anthropic API keys (sk-ant-...)
• Google API keys (AIza...)
• Voyage API keys (pa-...)
• Langfuse keys (pk-lf-... / sk-lf-...)
• AWS Access Key IDs (AKIA...)
• JWT tokens (eyJ...eyJ...sig)

Behaviour is controlled by GuardrailAction:

• Block (default) – reject the text and return a Left error.
• Fix – replace secrets with typed placeholders and continue (e.g. [REDACTED_OPENAI_KEY]).
• Warn – allow the text through unchanged; the caller may inspect the Right and decide what to log.

Example usage:

// Block any input that contains a credential
agent.run(
 query          = userInput,
 tools          = tools,
 inputGuardrails = Seq(SecretLeakGuardrail())
)

// Mask secrets automatically and let the query proceed
agent.run(
 query          = userInput,
 tools          = tools,
 inputGuardrails = Seq(SecretLeakGuardrail.masking)
)

// Also scrub LLM responses
agent.run(
 query           = userInput,
 tools           = tools,
 outputGuardrails = Seq(SecretLeakGuardrail.masking)
)