[JianhaoYu (JianhaoYu-AI)]

Summary

Malformed upstream JSON and JSON values such as null or arrays currently raise before the gateway records a model-request event. Non-JSON HTTP 200 responses instead become empty successful responses.

This change returns a structured upstream-response error, maps invalid responses below HTTP 400 to 502, and preserves existing upstream HTTP error statuses. The existing event path records the error and retry count; the in-flight counter is released as before. Valid object responses retain their current behavior.

Fixes #655.

Validation

Windows, Python 3.12.14, pytest 9.1.1; local dependencies, not the frozen lockfile. No model calls or GPU use.

• Eight new endpoint cases fail on the unchanged source.
• python -m pytest -q tests/server/test_proxy_response.py tests/server/test_endpoints.py tests/test_client.py --tb=short: 51 passed.
• python -m pytest -q tests --tb=short: 117 passed, 9 failed, 3 skipped. The unchanged upstream baseline, excluding the new test file, gives 109 passed, the same 9 failed, 3 skipped. The failures reference POSIX os.killpg, unavailable on Windows; skips concern optional VERL dependencies.
• Ruff lint/format, diff whitespace checks and all applicable changed-file pre-commit hooks passed.

The new tests mock the upstream transport, call the public gateway endpoint, and inspect the returned error, stored event, retry count and in-flight counter. Existing tests cover valid completions and provider-error objects.

Scope and review status

This checks JSON decoding and the top-level object shape, not the entire provider schema. Linux CI, GPU training, frozen-lock validation and whole-project type checking were not run.

Duplicate-work checks found #587 (request-body validation) and #574 (triplet export), which address different paths. A refreshed open-PR search did not find this response-ingestion fix.

AI assistance was used for investigation, implementation and test execution. This is a draft; submitting-author review is still pending. No claim of completed human review is made.

[Copilot]

🟢 Approval recommended

The focused change preserves valid-response behavior and cleanup, with regression coverage for the reported failures and no identified blocking issues.

No open issues 🎉

What changed in this PR

Fixes #655 by turning invalid upstream responses into structured gateway errors so failed model requests remain observable.

Changes:

• Handles malformed JSON, non-object JSON, and non-JSON responses, mapping statuses below 400 to 502 while preserving upstream error statuses.
• Uses the resulting status for both the recorded event and gateway response, leaving valid-object handling unchanged.
• Adds eight endpoint regression cases covering errors, event recording, retry counts, and in-flight cleanup.

File	Description
tests/​server/​test_proxy_response.py	Adds endpoint coverage for invalid upstream responses and failure observability.
agentlightning/​server/​proxy.py	Normalizes invalid responses into structured errors before event capture.

_{Review effort: Balanced}

[JianhaoYu (JianhaoYu-AI)]

The Test workflow is waiting for approval for this fork, while license/cla is green. Could a maintainer approve the workflow when convenient? The local regression commands and results are in the PR description.