* fix(proxy): strip LiteLLM policy tracking from OpenAI batch metadata
Batch create was failing with `Invalid type for 'metadata.applied_policies':
expected a string, but got an array instead` whenever a policy attachment
matched the request. The policy engine helpers wrote `applied_policies`,
`applied_guardrails`, and `policy_sources` into `data["metadata"]`
unconditionally, and `/v1/batches` forwarded that dict straight to OpenAI,
which only accepts string values.
- Route proxy-internal tracking into `litellm_metadata` for batch/file
routes via a shared `_get_or_create_proxy_metadata_bucket` helper.
- Sanitize `data["metadata"]` in `create_batch` to drop known internal
keys and non-string values before building the OpenAI request.
- Cover both behaviors with unit + endpoint tests.
Co-authored-by: Cursor <cursoragent@cursor.com>
* fix(proxy): merge metadata buckets for batch policy response headers
Ensure get_logging_caching_headers reads both metadata and litellm_metadata so policy/guardrail headers are emitted on batch routes with user metadata, and log dropped non-string OpenAI metadata at debug level.
Co-authored-by: Cursor <cursoragent@cursor.com>
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Co-authored-by: Cursor <cursoragent@cursor.com>
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