fix(responses): backfill output[] when missing, not only when empty

[williamjameshandley]

Summary

The non-streaming /v1/responses collector (collectPassthrough in src/routes/responses.ts) backfills response.output from accumulated stream events when the upstream response.completed event omits it. The current guard only matches the empty array case:

if (Array.isArray(resp.output) && resp.output.length === 0) {

But upstream (observed on gpt-5.5 via ChatGPT subscription, 2026-05-27) frequently emits response.completed with the output field missing entirely, not as []. Array.isArray(undefined) returns false, the backfill is skipped, and the final non-stream JSON returned to the client has no output field at all.

Symptom

Clients using the official openai Python SDK get TypeError: 'NoneType' object is not iterable when their code accesses response.output_text — the SDK's @property iterates self.output without a None check:

File "openai/types/responses/response.py", line 315, in output_text
    for output in self.output:
TypeError: 'NoneType' object is not iterable

Fix

One-line: loosen the guard to also fire when output is missing:

-        if (Array.isArray(resp.output) && resp.output.length === 0) {
+        if (!Array.isArray(resp.output) || resp.output.length === 0) {

The body of the branch is unchanged — it only runs when there's no upstream output to copy through, so widening the trigger is safe.

Verification

End-to-end on lovelace (Arch Linux, codex-proxy 2.0.76 with this patch applied):

curl -sS http://localhost:8080/v1/responses \
  -H 'Authorization: Bearer pwd' \
  -H 'Content-Type: application/json' \
  -d '{"model":"gpt-5.5","input":[{"role":"user","content":[{"type":"input_text","text":"Reply ok"}]}],"max_output_tokens":50,"stream":false}'

Before: response JSON has no output field (33 top-level keys, output absent). usage.output_tokens=5 but generated text is dropped.

After: response JSON contains

"output": [{"id":"msg_...","type":"message","status":"completed",
            "content":[{"type":"output_text","text":"ok"}],
            "role":"assistant"}],
"output_text": "ok"

mcp-handley-lab's openai adapter (which calls responses.create(stream=False)) recovers from the 'NoneType' is not iterable crash and returns normal text.

Notes

• The accompanying Chinese comment also updated to reflect the new condition ("为空" → "为空或缺失").
• No tests added — this is a one-line guard change in a code path already covered by existing non-stream collect tests; the upstream-shape variation is the trigger, which would need a separate fixture to reproduce.

[xcqwan]

+1

[icebear0828]

Thanks! The fix and two additional tests covering the missing-output path have been landed on dev (7f6765d). Addresses this PR's change with test coverage.