fix(lens): refund failed model requests without a response

[moe-berri]

Superseded by merged #44431, which fixes the same budget-settlement bug. The extra regression assertion remains in #44428

TLDR

Problem this solves:

• Failed analysis requests crash while releasing reserved budget

How it solves it:

• Refund failed requests without reading a nonexistent response
• Record completion details only after a model responds

User Flow

Before: an analysis provider error becomes an internal error and leaves reserved spend behind

1. Run a Lens investigation using a provider that returns an error
2. The worker receives HTTP 500 with an undefined-response error
3. The investigation retains the request's estimated spend

After: the provider error is preserved and reserved spend is released

1. Run a Lens investigation using a provider that returns an error
2. The worker receives the provider's original error status
3. The investigation releases the estimated spend without recording a completion

Validation

Reproduced the regression on fe683ea139 against a fresh PostgreSQL database: a rate-limited request returned HTTP 500 instead of 429. The fixed database lifecycle suite passes all eight cases, including three repeated provider failures with zero retained budget and no fabricated model-completion steps

The full Lens suite passes 200 tests. make check passes on this branch and with the fix in the coordinated-release branch. Current-tip hosted checks pass, including Codecov coverage of every modified executable line. The eight PostgreSQL lifecycle cases also passed again against a fresh disposable database

Screenshots / Proof of Fix

Both runs used the same local proxy at http://127.0.0.1:4426, real PostgreSQL, and a real paid provider. Register an analysis model with explicit pricing and a limited worker key, create an investigation, and claim it. The IDs below are the values returned by those API calls. The success request body is {"purpose":"extract","prompt":"Return JSON only: {\"observations\":[]}"}. Then replace only that test deployment's provider credential with an invalid value and send the same request again

Before (fe683ea)

1. Send POST http://127.0.0.1:4426/lens/worker/<lens-id>/<job-id>/model with the worker token and request above: HTTP 200, actual cost $0.000274
2. Repeat after invalidating the test provider credential: HTTP 500, cannot access free variable 'response'
3. Read GET http://127.0.0.1:4426/lens/<lens-id>: spend increases to $0.041398 despite the failed request

After (91644ec)

1. Send POST http://127.0.0.1:4426/lens/worker/<lens-id>/<job-id>/model with the worker token and request above: HTTP 200, actual cost $0.000274
2. Repeat after invalidating the test provider credential: HTTP 401; two immediate retries return the router's HTTP 429 cooldown response
3. Read GET http://127.0.0.1:4426/lens/<lens-id> after each failure: spend stays $0.000274 and the one successful model step is preserved

Companion changes

Found during end-to-end release validation for #44428. This focused fix can merge independently; the release branch also contains it for combined validation

Pre-Submission checklist

• Meaningful regression tests pass locally
• Current-tip hosted tests and coverage pass
• The fix only changes failed-request budget settlement
• Greptile, Veria, and Bugbot reviews are available and acceptable

Caveats

Low

• Required automated reviews have not appeared; keeping this draft

Type

Bug fix

[codspeed]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing litellm_lens_budget_failure_fix (91644ec) with main (fe683ea)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[moe-berri]

@greptileai @veria-ai Please review the current tip for release regressions, incompatible worker versions, unsafe upgrades, and missed failure paths

[moe-berri]

bugbot run

Please review the current tip for release regressions, incompatible worker versions, unsafe upgrades, and missed failure paths

[greptile-apps]

Confidence Score: 5/5

[Medium risk] Changes how failed model requests record their lifecycle.

The PR appears safe to merge; no issue caused by the changed code was established.

Summary

The PR refunds Lens budget reservations when a model request fails without a response and records a model step only after a response exists.

• Adds a regression assertion that repeated provider failures leave no model-completion steps.

_{Reviews (1) · Last reviewed commit: "fix(lens): refund failed model requests ..."}

[cursor]

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^{Reviewed by Cursor Bugbot for commit 91644ec. Configure here.}