[ShaiShmuel]

Problem

A request too long for a model's sequence window came back as HTTP 500 on /v1/extract, /v1/encode and /v1/generate on the SGLang path. A 500 says the server is broken, so a client may retry a request that can never succeed. We saw this while testing xiaomi-research/Xiaomi-OCR-0 (#875) and reproduced it on the published v0.11.0 images, on all three routes.

Fix

The engine reports these refusals as plain text, in a stream event, an abort finish reason or a 400 body, depending on where it noticed. adapters/sglang/_window.py recognises the four exact texts, and the adapters raise INPUT_TOO_LONG, which these routes already return as HTTP 400.

• Exact matches only. Other engine messages stay generic, and the caller sees a fixed message with the token counts: The request needs 24998 tokens, at or over this model's limit of 24576.
• Multi-item requests stay atomic. One over-window item fails the whole request with a 400.
• Shared batches can still isolate the request at fault. The new error is also an InvalidInputError, which is the type batch isolation retries on. Good requests sent alongside a bad one still succeeded on the real engine.
• Both pinned engines are covered. The texts are identical in SGLang 0.5.10 and 0.5.20. 0.5.20 adds fields beside message in its stream event, and there is a test for that shape.

Impact

Over-window requests now get 400 INPUT_TOO_LONG instead of 500, and the SDK raises InputTooLongError instead of ServerError. On /v1/generate, a refusal in the engine scheduler's margin was already a 400; its code changes from invalid_request to INPUT_TOO_LONG. There are no new settings or request fields.

Validation

Real engine on one L4 GPU, using the published v0.11.0 images, with this change's source files copied over the image's for the "after" column:

Route, model	Request	Before	After
/v1/extract, Xiaomi-OCR-0	Instruction past the window	500 INFERENCE_ERROR	400 INPUT_TOO_LONG
	max_new_tokens past the window	500	400
	Full page plus instruction past the window	500	400
	Two items, instruction past the window	500	400
	Full page past a 16K window (descriptor override)	500	400
	Over-window request beside three good ones	500 for it, others succeed	400 for it, others succeed
/v1/encode, Qwen3-Embedding-0.6B	Text past the window	500 INFERENCE_ERROR	400 INPUT_TOO_LONG
	Two items, one past the window	500	400
	Over-window request beside three good ones	500 for it, others succeed	400 for it, others succeed
/v1/generate, Qwen3.5-4B	Prompt far past the window	500 inference_error	400 INPUT_TOO_LONG
	Prompt plus output past the window	500	400
	Total exactly at the limit (8187 + 1, engine counts 8192)	500	400
	Inside the scheduler's margin (8186 + 1)	400 invalid_request	400 INPUT_TOO_LONG
	Fits (8185 + 1), and a normal request after the refusals	2xx	2xx

Tests fail without the fix:

• test_extract_engine_window_refusal_is_input_too_long and test_encode_engine_window_refusal_is_input_too_long fail against unfixed source with assert 500 == 400.
• With only the new module added and the adapters unfixed, 25 of the 48 tests in test_sglang_window_refusal.py fail. The other 23 test the new module itself or check that other engine errors stay failures.

mise run lint
# 1007 files already formatted, all checks passed
mise run typecheck
# all checks passed
git ls-files 'packages/sie_server/tests/adapters/test_sglang*' 'packages/sie_server/tests/api/test_generate*' 'packages/sie_server/tests/api/test_openai*' 'packages/sie_server/tests/processors/test_streaming*' 'packages/sie_server/tests/**/test_queue*' packages/sie_server/tests/api/test_extract.py packages/sie_server/tests/api/test_encode_endpoint.py | xargs mise exec -- uv run --no-sync pytest -q
# 1770 passed

Covered by unit tests only, not triggered on a real engine:

• SGLang 0.5.20: the texts and event shapes were compared from its source.
• The multimodal scheduler text: a page that is too long is refused earlier by the tokenizer check.
• An abort refusal on a request with a grammar: the served Qwen3.5-4B profile rejects grammars first.

Not in this PR

• /v1/chat/completions: over-window requests were already 400 before this change. The body is still a generic upstream_error.
• Corrupt images: still 500 on /v1/extract. The engine closes the stream mid-body, so the adapter cannot tell this from an engine failure. The engine stays healthy afterwards.
• The 10-second /generate write limit: unchanged. 64 concurrent full-size uploads with max_concurrent_requests raised to 64 had 24 of 64 fail as 500. All 64 passed with SIE_SGLANG_GENERATE_WRITE_TIMEOUT_S=120, and all 64 passed at the shipped cap of 32 (one run each).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Requests that exceed an SGLang model’s context window are now reported as input-too-long errors across embedding, generation, and vision extraction.
  • The encode and extract endpoints return a consistent input-too-long response for these requests.

[coderabbitai]

Walkthrough

SGLang context-window refusal messages are recognized and mapped to input-too-long errors in generation, embedding, and vision extraction. The added adapter and endpoint tests check error classification and HTTP 400 responses.

Changes: SGLang context-window refusal handling

Layer / File(s)	Summary
Refusal recognition and error type packages/sie_server/src/sie_server/adapters/sglang/_window.py, packages/sie_server/tests/adapters/test_sglang_window_refusal.py	Four known refusal formats map to fixed refusal text with token and limit counts. Other inputs remain unmatched.
Generation refusal classification packages/sie_server/src/sie_server/adapters/sglang/generation.py, packages/sie_server/tests/adapters/test_sglang_window_refusal.py	Generation HTTP 400 responses, in-band errors, and status-400 aborts classify recognized refusals as input-too-long errors. Tests cover streaming and non-streaming requests and unrelated errors.
Embedding refusal classification packages/sie_server/src/sie_server/adapters/sglang/embedding.py, packages/sie_server/tests/adapters/test_sglang_window_refusal.py, packages/sie_server/tests/api/test_encode_endpoint.py	Embedding HTTP 400 refusals raise the SGLang input-too-long error. Tests cover concurrent shards, other error responses, and the encode endpoint response.
Vision extraction error translation packages/sie_server/src/sie_server/adapters/sglang_vision_extract/adapter.py, packages/sie_server/tests/adapters/test_sglang_window_refusal.py, packages/sie_server/tests/api/test_extract.py	Vision extraction translates generation input-too-long errors into the SGLang error type. Tests cover adapter classification and the extract endpoint response.

Sequence Diagram(s)

sequenceDiagram
  participant SGLangEngine
  participant SGLangEmbeddingAdapter
  participant EncodeEndpoint
  SGLangEngine->>SGLangEmbeddingAdapter: HTTP 400 with context-window refusal
  SGLangEmbeddingAdapter-->>EncodeEndpoint: Raise SGLangInputTooLongError
  EncodeEndpoint-->>EncodeEndpoint: Return HTTP 400 with INPUT_TOO_LONG

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Suggested reviewers: svonava, krisztian-gajdar

Merge Risk: Minimal · up to 4d0bb

No confirmed issue remains that should prevent merging.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 44.44% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documenta…	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 and concisely describes the main change: mapping SGLang context-window refusals to client errors.
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: Docstring Coverage

Explanation

Docstring coverage is 44.44% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 9 functions across 7 files.

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

Finishing Touches

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Commits

Reviewing files that changed from the base of the PR and between e8aeb68 and 4d0bbfd.

Files selected for processing: 7

• packages/sie_server/src/sie_server/adapters/sglang/_window.py
• packages/sie_server/src/sie_server/adapters/sglang/embedding.py
• packages/sie_server/src/sie_server/adapters/sglang/generation.py
• packages/sie_server/src/sie_server/adapters/sglang_vision_extract/adapter.py
• packages/sie_server/tests/adapters/test_sglang_window_refusal.py
• packages/sie_server/tests/api/test_encode_endpoint.py
• packages/sie_server/tests/api/test_extract.py

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