fix(proxy/gemini): keep streaming-parity baseline so eligible_pct can't exceed 100 (#2824)

## Description

The non-streaming Gemini `generateContent` finalizer builds its
`RequestOutcome` with `optimized_tokens` set to Gemini's own
`promptTokenCount` (the provider's tokenizer scale, which correctly
feeds billing and the dashboard), while `original_tokens` stays a local
estimator count. Those two are on different rulers.

Every delta the beacon derives from the pair is a same-ruler difference:
`tokens_saved`, `tokens_inflated`, `attempted_input_tokens`, and the
beacon's `eligible_pct` / `yield_pct`. When Gemini counts the forwarded
prompt higher than our local estimator does, `attempted_input_tokens`
(which is `optimized_tokens + tokens_saved`) exceeds the local
`original_tokens`, and the request ships a structurally-impossible
`eligible_pct > 100` plus a phantom `tokens_inflated`. This is the exact
class of bug #2756 removed, on a path #2756 did not touch: it fixed the
non-streaming OpenAI handler, and the streaming finalizer
(`_finalize_stream_response`) already guards against it by lifting the
baseline onto the provider scale. The non-streaming Gemini path had
neither treatment.

The fix mirrors the streaming finalizer's already-tested handling: when
a provider count is present, lift the baseline to `max(original_tokens,
promptTokenCount + tokens_saved)` so `attempted_input_tokens <=
original_tokens` holds and `tokens_inflated` collapses to 0. It is
guarded on a present count, so a null or absent `promptTokenCount`
leaves the local baseline untouched and the existing zero-usage
preservation test still holds. `optimized_tokens` still carries the
provider count, so billing and the dashboard are unchanged.

Closes #

## Type of Change

- [x] Bug fix (non-breaking change that fixes an issue)
- [ ] New feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
- [ ] Performance improvement
- [ ] Code refactoring (no functional changes)

## Changes Made

- `headroom/proxy/handlers/gemini.py` (`handle_gemini_request`,
non-streaming `generateContent` branch): compute
`effective_original_tokens = max(original_tokens, total_input_tokens +
tokens_saved)` when `total_input_tokens > 0` (else keep
`original_tokens`), and pass it as the outcome's `original_tokens`.
Mirrors the streaming finalizer's provider-usage handling.
- `tests/test_proxy/test_gemini_savings_profile.py`: added
`test_gemini_provider_count_above_local_estimate_does_not_inflate_eligible`,
which drives a request where Gemini's `promptTokenCount` (150) exceeds
the local post-compression count (80), and asserts
`attempted_input_tokens <= original_tokens`, `tokens_inflated == 0`, the
provider count is still carried in `optimized_tokens`, and the baseline
is lifted to 170.

## Testing

- [x] Unit tests pass (`pytest`)
- [x] Linting passes (`ruff check .`)
- [x] Type checking passes (`mypy headroom`)
- [x] New tests added for new functionality
- [ ] Manual testing performed

### Test Output

```text
# Fail-before (source fix stashed, new test kept):
tests/test_proxy/test_gemini_savings_profile.py::test_gemini_provider_count_above_local_estimate_does_not_inflate_eligible FAILED
  assert outcome.attempted_input_tokens <= outcome.original_tokens
  AssertionError: assert 170 <= 100

# Pass-after (fix applied):
tests/test_proxy/test_gemini_savings_profile.py::test_gemini_provider_count_above_local_estimate_does_not_inflate_eligible PASSED

# Full file + related outcome suites:
tests/test_proxy/test_gemini_savings_profile.py tests/test_proxy_gemini_native_integration.py tests/test_request_outcome.py tests/test_outcome_token_scale.py
47 passed, 18 skipped

# uvx ruff@0.15.17 check  -> All checks passed!
# uvx mypy@1.20.2 headroom/proxy/handlers/gemini.py -> Success: no issues found in 1 source file
```

## Real Behavior Proof

- Environment: Windows 11, Python 3.12.11, project venv (litellm
installed), pytest 9.1.1 with pytest-asyncio 1.4.0 (asyncio_mode=auto
per pyproject), ruff 0.15.17 and mypy 1.20.2 via uvx.
- Exact command / steps: confirmed the streaming sibling already lifts
the baseline (`_finalize_stream_response` in
`headroom/proxy/handlers/streaming.py` sets `effective_original_tokens =
max(original_tokens, provider_input_tokens + tokens_saved)` for
openai/gemini), then fail-before with `git stash push
headroom/proxy/handlers/gemini.py` and `python -m pytest
tests/test_proxy/test_gemini_savings_profile.py -k inflate_eligible`
(the assertion fails with `170 <= 100`, i.e. eligible_pct 170%), then
pass-after with `git stash pop` and rerunning (passes), then the full
file plus the outcome suites (47 passed, 18 skipped).
- Observed result: with Gemini reporting `promptTokenCount=150` against
a local post-compression count of 80 (saved 20), the outcome now reports
`original_tokens=170`, `attempted_input_tokens=170` (so `eligible_pct <=
100`) and `tokens_inflated=0`, while `optimized_tokens` stays 150 so
billing and the dashboard are unchanged. Before the fix the same request
reported `original_tokens=100`, `attempted_input_tokens=170`
(eligible_pct 170%) and `tokens_inflated=50`.
- Not tested: a live streamed call to real Gemini/Vertex (no provider
credentials in this environment). The provider-count-above-local case is
reproduced with a mock response mirroring Gemini's `usageMetadata`
shape, and the baseline-lift it mirrors is existing, tested code on the
streaming path.

## Review Readiness

- [x] I have performed a self-review
- [x] This PR is ready for human review

## Checklist

- [x] My code follows the project's style guidelines
- [x] I have performed a self-review of my code
- [x] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] I did **not** edit `CHANGELOG.md`: it is generated by
release-please from my Conventional Commit PR title (a CI guard enforces
this)

## Additional Notes

Docs and manual testing are N/A: this aligns the non-streaming Gemini
finalizer with the already-correct streaming finalizer, no API surface
change. The baseline lift is guarded on a present provider count, so the
existing zero-usage preservation test
(`test_gemini_zero_usage_prompt_count_is_preserved`) is unaffected: a
null or zero `promptTokenCount` keeps the local baseline and leaves
`optimized_tokens` at 0.
This commit is contained in:
Abhay Singh
2026-08-07 07:51:56 +05:30
committed by GitHub
parent 01161fe019
commit b97c7c6e99
2 changed files with 92 additions and 1 deletions
+19 -1
View File
@@ -738,6 +738,24 @@ class GeminiHandlerMixin:
uncached_input_tokens = max(0, total_input_tokens - cache_read_tokens)
# optimized_tokens carries Gemini's own promptTokenCount, which is
# on the provider's tokenizer scale (it feeds billing/dashboard),
# while original_tokens is a LOCAL estimator count. When Gemini
# counts the forwarded prompt higher than our estimator does,
# attempted_input_tokens (optimized + saved) exceeded the local
# original_tokens and shipped a structurally-impossible
# eligible_pct > 100 plus a phantom tokens_inflated. Lift the
# baseline onto the provider scale when a provider count is
# present, mirroring the streaming finalizer's tested handling in
# _finalize_stream_response so the two Gemini paths agree. Guarded
# on a present count so a null/absent promptTokenCount leaves the
# local baseline untouched.
effective_original_tokens = (
max(original_tokens, total_input_tokens + tokens_saved)
if total_input_tokens > 0
else original_tokens
)
# Eligible-tracking is TODO for Gemini; pass the full
# pre-compression request size as the fallback denominator.
# This makes Gemini's contribution to the aggregate
@@ -757,7 +775,7 @@ class GeminiHandlerMixin:
provider=provider_name,
model=model,
status_code=response.status_code,
original_tokens=original_tokens,
original_tokens=effective_original_tokens,
optimized_tokens=total_input_tokens,
output_tokens=output_tokens,
tokens_saved=tokens_saved,
@@ -199,3 +199,76 @@ def test_gemini_zero_usage_prompt_count_is_preserved():
outcome = captured["outcome"]
assert outcome.optimized_tokens == 0
assert outcome.uncached_input_tokens == 0
def test_gemini_provider_count_above_local_estimate_does_not_inflate_eligible():
"""When Gemini's promptTokenCount exceeds our local estimate, the outcome must
not ship attempted_input_tokens > original_tokens (a structurally impossible
eligible_pct > 100) or a phantom tokens_inflated. The local baseline is lifted
onto the provider scale, matching the streaming finalizer's tested handling."""
config = ProxyConfig(
optimize=True,
cache_enabled=False,
rate_limit_enabled=False,
cost_tracking_enabled=False,
)
# Local pipeline count: 100 tokens before compression, 80 after (saved 20).
# Return genuinely-changed messages so the handler adopts the pipeline's
# tokens_before/after (the override only fires when messages actually change).
def passthrough_apply(**kwargs):
sent = kwargs["messages"]
compressed = [dict(m) for m in sent]
if compressed:
compressed[0] = {**compressed[0], "content": "compressed"}
return SimpleNamespace(
messages=compressed,
transforms_applied=["gemini_compress"],
timing={},
tokens_before=100,
tokens_after=80,
waste_signals=None,
)
# Gemini counts the forwarded prompt at 150 -- higher than our local 80, so
# attempted = 150 + 20 = 170 would exceed a local original of 100.
resp = MagicMock()
resp.status_code = 200
resp.headers = {"content-type": "application/json"}
resp.content = (
b'{"candidates":[{"content":{"parts":[{"text":"ok"}]}}],'
b'"usageMetadata":{"promptTokenCount":150,"candidatesTokenCount":2}}'
)
resp.json.return_value = {
"candidates": [{"content": {"parts": [{"text": "ok"}]}}],
"usageMetadata": {"promptTokenCount": 150, "candidatesTokenCount": 2},
}
captured: dict[str, object] = {}
async def recording_outcome(outcome): # noqa: ANN001
captured["outcome"] = outcome
big = "word " * 4000
app = create_app(config)
with TestClient(app) as client:
proxy = client.app.state.proxy
proxy.openai_pipeline.apply = MagicMock(side_effect=passthrough_apply)
proxy._retry_request = AsyncMock(return_value=resp)
proxy._record_request_outcome = AsyncMock(side_effect=recording_outcome)
r = client.post(
"/v1beta/models/gemini-2.0-flash:generateContent?key=test-key",
json={"contents": [{"parts": [{"text": big}]}]},
)
assert r.status_code == 200, r.text
outcome = captured["outcome"]
# The provider's own count is still carried for billing/dashboard.
assert outcome.optimized_tokens == 150
# The eligible ratio cannot exceed 100%: attempted must not exceed original.
assert outcome.attempted_input_tokens <= outcome.original_tokens
# No phantom growth (optimized - original clamped to >= 0 was 50 before).
assert outcome.tokens_inflated == 0
# Baseline lifted onto the provider scale: max(local 100, provider 150 + saved 20).
assert outcome.original_tokens == 170