docs(guardrails): document the flag() verdict for custom code guardrails

[devin-ai-integration]

Summary

Companion to BerriAI/litellm#39728 (Resolves LIT-6894). Adds flag(reason, metadata={}) to the custom code guardrail return-value table and a "Flagging without blocking" section: the request or response continues unchanged, a guardrail_flagged entry is recorded with the guardrail name, configured mode, input_type, reason and metadata, the Monitor counts it as flagged rather than passed or blocked, Request Logs shows flagged (most severe phase wins when a guardrail runs on both pre_call and post_call), and the request-level guardrail_status becomes guardrail_flagged unless another guardrail blocked or failed. Includes an audit-only config example and the resulting logging entry.

npm run build passes locally.

Link to Devin session: https://app.devin.ai/sessions/1b006929b7a3436797ef22a7ce2e3ef4
Open in Devin Desktop: https://app.devin.ai/desktop/session/1b006929b7a3436797ef22a7ce2e3ef4?variant=devin
Requested by: @yassin-berriai

[devin-ai-integration]

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Project	Deployment	Actions	Updated
litellm	Ready	Preview	Sep 4, 2026 9:55am UTC