Close three variant bypasses adjacent to VERIA-28 found during post-fix
variant audit:
1. _guardrail_modification_check had the same isinstance(dict) bypass
Veria-AI just flagged on the pre-call strip. A caller sending
`{"metadata": "{…}"}` as a JSON-encoded string (multipart/form-data
or extra_body) skipped the guard, got parsed to dict downstream, and
reached guardrail logic with bypass flags intact. Coerce strings via
safe_json_loads before evaluating.
2. The allow_client_tags strip only covered body metadata.tags and
litellm_metadata.tags — caller-supplied tags arriving via the
x-litellm-tags header or root-level data["tags"] bypassed it. Gate
add_request_tag_to_metadata's result on the same flag.
3. requester_metadata was deepcopied BEFORE the strip, so attacker
injections (user_api_key_metadata shadows, disallowed tags,
_pipeline_managed_guardrails) persisted in the snapshot. The PANW
guardrail (and any future consumer) trusting requester_metadata
would see forged values. Move the deepcopy to after the strip.
Regression tests added for each.
user
76aa97f77b