fix(chat): finish with length when a Responses upstream reports incomplete reason "length" by hedging8563 · Pull Request #7392 · lidge-jun/opencodex

hedging8563 · 2026-10-19T21:32:20Z

Summary

Volcengine Ark Coding Plan /responses ends a capped turn with status: "incomplete", incomplete_details.reason: "length" (OpenAI uses max_output_tokens). chatCompletionsIncompleteOutcome and responsesJsonToChatCompletion only accept max_output_tokens and content_filter, so Chat Completions returns 502 upstream stream ended early (length) instead of a 200 with finish_reason: "length". Clients treat the 502 as a dead route and fail over although the provider answered.

Read the reason through the existing truncationReasonFor() table (src/responses/truncated-stop-reason.ts, already maps length, max_tokens, ...) in chatCompletionsIncompleteOutcome.
responsesJsonToChatCompletion now calls that same function instead of its own two-value check.
Proxy-synthesized reasons (adapter_eof, upstream_stall_timeout, missing_terminal_event) are not in the table and still fail.

Repro: POST /v1/chat/completions, model volcengine-coding-plan/glm-5.3-flash, max_tokens: 16, non-streaming -> 502 before, 200 finish_reason: "length" after.

Verification (on dev `bddd61f`, Bun 1.4.3)

New tests/chat/incomplete-length-reason.test.ts: 4 tests. Without the fix 3 fail with upstream stream ended early (length); with it all 4 pass.
bun test tests/chat tests/server: the same 21 tests fail on unpatched dev and on the patched tree (checked by diffing the fail lists); the patch adds no failures. Those pre-existing failures are in provider-management/account tests, unrelated.
tsc --noEmit: clean.
Not run: full bun run test.

We run OpenCodex as a shared gateway and hit this through the Volcengine Coding Plan.

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Summary by CodeRabbit

Bug Fixes
- Responses marked incomplete due to output limits now consistently report a length finish reason in both streaming and non-streaming chat completions. Content-filter outcomes and other incomplete failures remain unchanged.

…plete reason "length"

github-actions · 2026-10-19T21:32:34Z

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github-actions · 2026-10-19T21:32:46Z

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coderabbitai · 2026-10-19T21:32:55Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: lidge-jun/opencodex/.coderabbit.yaml
Review profile: ASSERTIVE
Plan: Advanced
Run ID: 6613caa4-dd6f-4866-b412-5b82a8cea125

📥 Commits

Reviewing files that changed from the base of the PR and between bddd61f and 45d08af.

📒 Files selected for processing: 2

src/chat/outbound.ts
tests/chat/incomplete-length-reason.test.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

📝 Walkthrough

Incomplete Responses API reasons now pass through shared truncation-reason normalization when selecting Chat Completions finish outcomes. Tests cover length, max_output_tokens, content_filter, unsupported reasons, and JSON and buffered SSE projections.

Changes: Incomplete reason mapping

Layer / File(s)	Summary
Normalize incomplete reasons and verify projections `src/chat/outbound.ts`, `tests/chat/incomplete-length-reason.test.ts`	The shared outcome normalizes incomplete reasons before selecting `length` or `content_filter`; unsupported reasons remain failures. The non-streaming path delegates to this outcome. Tests cover outcome selection and JSON and buffered SSE projections.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 45d08

The change is mergeable after normal checks; no actionable risk is identified in the supplied review context.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly identifies the main change: mapping a Responses upstream incomplete reason of "length" to a Chat Completions finish reason of "length". It is specific, concise, and directly matches …
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title clearly identifies the main change: mapping a Responses upstream incomplete reason of "length" to a Chat Completions finish reason of "length". It is specific, concise, and directly matches the implementation and tests.

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Ingwannu

The shared truncation vocabulary now recognizes the reported length alias in both SSE and JSON projections while proxy EOF/stall reasons remain failures. Two repository-contract items are missing at this exact head:

Register tests/chat/incomplete-length-reason.test.ts in BOTH the current layout explicit/domain map and its tests/fixtures/test-layout-expected*.json shard. The complete two-file diff contains neither registration. Regex placement does not replace the explicit expected map.
Update the mapped Chat/Responses owning contract for this change to accepted incomplete-reason vocabulary and its failure boundary. The complete diff has no structure/documentation update.

Retain the negative EOF/stall/missing-terminal cases, and add an explicit streamed wire assertion if the fixture currently only collects that stream into a buffered completion. Please refresh current-head validation/readiness after the push; do not weaken the test/layout gates.

lidge-jun · 2026-10-22T18:15:08Z

Carried onto current dev in #7539 with @hedging8563 credited via Co-authored-by. That PR addresses the review: the regression moves to tests/responses/chat-incomplete-length-reason.test.ts and is registered in both scripts/test-layout/layout.json and tests/fixtures/test-layout-expected.json. The Chat incomplete vocabulary and its failure boundary are documented in structure/transports/responses-wire-shapes.md, and explicit streamed-wire and handler cases were added. This PR is left open for the maintainer to close.

lidge-jun · 2026-10-22T20:07:16Z

Thank you for this work. It has been carried onto current dev in #7539, with your authorship kept as a Co-authored-by trailer, and review continues there. Closing this PR in favour of #7539.

…plete reason "length" (#7539) Carries #7392 onto current dev. Co-authored-by: hedging8563 <45883076+hedging8563@users.noreply.github.com>

fix(chat): finish with length when a Responses upstream reports incom…

45d08af

…plete reason "length"

hedging8563 requested review from Ingwannu and lidge-jun as code owners October 19, 2026 21:32

github-actions Bot added the bug Something isn't working label Oct 19, 2026

github-actions Bot marked this pull request as draft October 19, 2026 21:32

Ingwannu requested changes Oct 20, 2026

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lidge-jun mentioned this pull request Oct 22, 2026

fix(chat): finish with length when a Responses upstream reports incomplete reason "length" #7539

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lidge-jun closed this Oct 22, 2026

lidge-jun added a commit that referenced this pull request Oct 22, 2026

fix(chat): finish with length when a Responses upstream reports incom…

a0806af

…plete reason "length" (#7539) Carries #7392 onto current dev. Co-authored-by: hedging8563 <45883076+hedging8563@users.noreply.github.com>

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fix(chat): finish with length when a Responses upstream reports incomplete reason "length" - #7392

fix(chat): finish with length when a Responses upstream reports incomplete reason "length"#7392
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Summary

Verification (on dev bddd61f, Bun 1.4.3)

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Verification (on dev `bddd61f`, Bun 1.4.3)

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