* fix(rate-limit): stop v3 limiter from leaking internal stash to provider body
PR #27001 (atomic TPM rate limit) introduced a reservation flow that
writes four LiteLLM-internal keys onto the request data dict:
_litellm_rate_limit_descriptors
_litellm_tpm_reserved_tokens
_litellm_tpm_reserved_model
_litellm_tpm_reserved_scopes
_litellm_tpm_reservation_released
These keys are forwarded as request body params to the upstream provider,
which rejects them as unknown fields:
OpenAI -> 400 'Unknown parameter: _litellm_rate_limit_descriptors'
(mapped by litellm to RateLimitError / 429, hiding the bug
behind a misleading 'throttling_error' code)
Anthropic -> 400 '_litellm_rate_limit_descriptors: Extra inputs are
not permitted'
Net effect: every chat completion against any real provider fails the
moment a virtual key has any tpm_limit / rpm_limit set — i.e. v3-enforced
key-level TPM/RPM limits are broken end-to-end. The v3 RPM/TPM check
itself still runs (raises 429 on over-limit), but the success path
poisons the upstream body.
Reproduced on litellm_internal_staging HEAD (410ce761dc) against
gpt-4o-mini and claude-haiku-4-5 with a 1-RPM/1-TPM key — first request
fails with the provider's unknown-field error.
Fix: the stash is metadata only.
- Add RATE_LIMIT_DESCRIPTORS_KEY constant and a _LITELLM_STASH_KEYS
registry so we have a single source of truth for stash keys.
- New helper _stash_value_in_metadata_channels writes to
data['metadata'] / data['litellm_metadata'] without touching the
top level.
- _stash_reservation_in_data and the descriptor stash now route
through that helper. _mark_reservation_released stops writing
top-level.
- _lookup_stashed_value also checks kwargs['metadata'] /
kwargs['litellm_metadata'] (raw request_data shape) in addition to
kwargs['litellm_params']['metadata'] (completion kwargs shape).
- async_post_call_failure_hook now reads descriptors via the unified
metadata lookup instead of request_data.get(top-level).
- Defense in depth: async_pre_call_hook strips any stash key that
somehow surfaced at the top level (stale cache, future refactor,
test fixture) before returning.
Tests:
- New regression test asserts no _litellm_* stash key is present at
the top level of data after async_pre_call_hook, and that the
metadata channel still carries the reservation + descriptors so
success / failure reconciliation works.
- Existing test_tpm_concurrent.py tests that asserted top-level
presence are updated to read from data['metadata'] — the location
is an implementation detail; the spec is that post-call callbacks
can resolve the stash.
Verified end-to-end against OpenAI gpt-4o-mini and Anthropic
claude-haiku-4-5 via /v1/chat/completions on a low-rpm key:
- With limits not exceeded: HTTP 200, valid completion response,
no leaked fields in body.
- With RPM exceeded: HTTP 429 from v3 enforcement
('Rate limit exceeded ... Limit type: requests').
- With TPM exceeded: HTTP 429 from v3 enforcement
('Rate limit exceeded ... Limit type: tokens').
Full v3 hook test suite passes (171 tests).
Co-authored-by: Mateo Wang <mateo-berri@users.noreply.github.com>
* chore(rate-limit): use RATE_LIMIT_DESCRIPTORS_KEY constant in test, trim noisy comments
Address greptile P2: test fixture now uses the imported constant.
Drop comments that re-explain what well-named identifiers already convey.
* fix(rate-limit): reject caller-supplied stash values to prevent TPM-refund abuse
Strip _LITELLM_STASH_KEYS from data top-level and both metadata channels at
the start of async_pre_call_hook. Without this, an authenticated caller can
inject _litellm_rate_limit_descriptors plus _litellm_tpm_reserved_tokens in
body metadata, trigger a proxy-side rejection, and cause
async_post_call_failure_hook to refund TPM counters against attacker-named
scopes (e.g. another tenant's api_key).
---------
Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Mateo Wang <mateo-berri@users.noreply.github.com>
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