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fix(frontend): preserve chat token IDs and EOS logprobs - #17586
Preserve requested prompt/completion IDs and backend logprobs through SGLang processing and both Rust chat-parser routes. Buffered markers, queued reasoning and EOS-only chunks must not drop, duplicate or reorder token records.
Key Changes
SGLang retains the hidden EOS score, emits requested IDs, and truncates completion IDs at the token completing a local stop.
V2 transfers each source choice's scores once and preserves source order across queued Qwen reasoning.
V1 tracks scores per choice outside the jail and flushes remaining scores at EOF. The jail retains its original score inputs for Kimi's score-sensitive text handling.
Docs clarify that EOS can have literal text/bytes, concatenated bytes only approximate output, and V1 can emit a late score-only chunk.
Validation
One committed regression per parser path, plus one focused converter check:
SGLang: 48 ordered scores including hidden EOS, plus requested completion/prompt IDs.
V2: A/B/C/D/E score order across alternating raw input and queued Qwen reasoning.
V1: the swallowed EOS score reaches a final empty-delta choice after the finish.
Responses: a post-finish, score-only empty-delta choice emits no new events and leaves exactly one completed output item.
Local CPU validation: 445 Python unit cases and 3,760 Rust library cases passed; 13 existing Rust tests remain ignored. Rust checks used --no-default-features; Python checks used SGLang 0.5.23 and a rebuilt native runtime. Rustfmt, strict all-target Clippy for dynamo-llm, pinned Black/isort/Ruff and docs lint passed.
Earlier saved GLM-5.3 direct/HTTP replays preserved 48/48 scores and completion IDs, plus 187 prompt IDs once. That replay evidence remains private; the converter behavior now has its own small in-repo regression. No new GPU generation was run.
The SGLang CI job selects this module with pre_merge and sglang and gpu_0. Jobs named Unit tests in the PR issue-link workflow do not execute the frontend suite; remote SGLang CI for the new head still needs confirmation.
Score preservation copies V1 payloads and adds CPU/memory work. Earlier processor fixtures measured roughly 4–7% V1 CPU overhead; this is not a serving-latency or throughput claim. Existing SGLang explicit-stop logprob trimming is unchanged, so IDs and scores can differ in length at a local stop.
The change tracks local stop boundaries in SGLang streaming, includes requested token IDs in response metadata, preserves choice logprobs through the legacy tool-call jail and unified parser, and updates the troubleshooting guide’s descriptions of token and byte data.
Stop filtering records a stop position and preserves stop-token logprobs. The postprocessor exposes a count of generated token IDs beyond the local stop.
The streaming path accumulates requested completion token IDs, removes IDs withheld after a local stop, and attaches requested completion or prompt IDs to response metadata under the described conditions.
The jail adapter buffers content and refusal logprobs by choice, restores them to emitted choices, clears them on terminal errors, and emits remaining scores in empty choice carriers at EOF.
Parsed-choice logprobs and token guidance lib/llm/src/protocols/openai/chat_completions/unified_parser.rs, docs/fern/pages/use-cases/tool-calling-and-reasoning/troubleshooting-tool-calls.md
The unified parser attaches source logprobs to the last emitted choice, creating an empty choice when needed. The guide describes token-stream scope and the limits of decoded text and bytes.
Some chat responses can lose stop-token scores or report scores out of generation order. Fix those metadata errors before merging; also qualify the troubleshooting guide’s byte-reconstruction advice.
Pre-merge checks: 4 · 1
Failed checks: 1 inconclusive
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Resolution
Docstring Coverage
Docstring coverage is 71.43% 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
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Title check
The title clearly identifies the main change: preserving chat token IDs and EOS logprobs.
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.
Description check
The description follows the repository template. It has Overview, Key Changes, Validation, and Issues and Ongoing Work sections, plus the checklist. It gives specific validation: per-parser regression…
Full details: Description check
Explanation
The description follows the repository template. It has Overview, Key Changes, Validation, and Issues and Ongoing Work sections, plus the checklist. It gives specific validation: per-parser regression tests, Python and Rust case counts, and lint results. It also names the linked issue reference (#8548) and a related PR (#17467). The 'Closes #XXXX' line is replaced by 'Part of #8548', which is a non-closing reference. The Overview and Key Changes sections are detailed and specific. The checklist item is marked as complete.
Full details: Docstring Coverage
Explanation
Docstring coverage is 71.43% 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 7 functions across 2 files. (3 skipped: 1 unsupported, 2 too large.)
Resolution
Write docstrings for the functions missing them to satisfy the coverage threshold.
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Actionable comments posted: 3
🪄 Fix comments: Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @components/src/dynamo/frontend/sglang_prepost.py:
- Around line 1728-1730: Update process_output so stop_logprobs are appended to
self._pending_logprobs_content after stop-string suppression regardless of
whether stop_end is None; retain the EOS score when a local stop-string match
also occurs.
Review comments at
@docs/fern/pages/use-cases/tool-calling-and-reasoning/troubleshooting-tool-calls.md:
- Around line 101-103: Update the byte-reconstruction guidance in the
troubleshooting section to describe concatenated decoded bytes as approximate,
since per-token decoding may lose context-dependent spacing. Recommend using
completion token IDs for exact replay when available.
Review comments at
@lib/llm/src/protocols/openai/chat_completions/unified_parser.rs:
- Around line 2309-2310: Update the choice-processing branch guarded by
choices.is_empty() or last_is_queued to buffer scores for opener fragments that
emit no deltas; release those scores only after the queued reasoning scores,
preserving their order in the non-streaming response.
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Summary: The PR makes backend token records reach the response exactly once on three paths: the SGLang processor scores the stripped stop token and emits requested IDs, the V2 choices_for moves source logprobs onto one rebuilt choice while holding them behind queued Qwen reasoning, and the V1 jail wrapper tracks scores per choice index and reattaches them. I traced all three and could not construct a drop or a double emission, including n>1 on V1 and rmccorm4's alternating Qwen case. The blocker is that none of it is tested in-repo and the Python unit job never ran.
Blocking
No test files change; the PR body cites eight regression tests that are "not in this PR". A fix whose whole contract is "exactly once, in order" on three independent paths needs at least one in-repo test per path (SGLang EOS 48/48 + IDs, V2 choices_for with queued Qwen reasoning, V1 EOS-only final chunk). The Unit tests (Python) CI job is SKIPPED on every run of this PR, so even the existing test_sglang_processor_unit.py stop/logprob cases were not executed against this change.
Non-blocking
docs/fern/pages/use-cases/tool-calling-and-reasoning/troubleshooting-tool-calls.md:99 — "end-of-sequence can have empty text and bytes" is not what this PR produces on SGLang; _decode_logprob_token decodes with skip_special_tokens=False, so the new EOS entry carries the literal <|im_end|> text and bytes, and the "concatenate bytes" recipe appends it (P3).
lib/llm/src/preprocessor.rs:6985 — V1 now emits a delta: {} choice carrying only logprobs after the finish_reason chunk; the docs note explicitly excludes V1, so the wire shape is unspecified. q: has the Responses stream converter been checked against a post-finish choice with no delta? (P3)
Checked: diff read against main for all five files; V2 ordering traced for the A/B/D/C/E case fixed in 30bbc0a; V1 per-index BTreeMap replace + EOF leftovers; Rust consumed-prefix rule vs Python _count_tokens_through (both keep the stop-completing token); del completion_ids[...] cannot go negative; nvext field names match delta.rs; aggregator per-index extend, no double count; no new unwrap/index paths. Not run: tests. rmccorm4's perf thread is addressed by the bisect in 9f57ec1 but still open; coderabbit's EOS-after-local-stop thread awaits a human call (the code is self-consistent).
One in-repo test per path, each asserting identity and order rather than counts: SGLang hidden-EOS case (scores == logprobs, completion_token_ids per chunk, prompt_token_ids once on the final chunk), V2 qwen_queued_reasoning_keeps_source_logprob_order (exact A B C D E), V1 legacy_jail_delivers_swallowed_eos_score_after_finish (score-only carrier after finish_reason), and the Responses converter test for a post-finish score-only chunk (no events).
Docs now state that SGLang keeps the EOS literal and that concatenated bytes can include it.
Correction: the SKIPPED check I called "Unit tests" belongs to pr-issue-link.yml and is unrelated. The frontend Python tests run via pr.yamlsglang-test, which only triggers after copy-pr-bot mirrors the PR; no /ok to test has been issued, so test_sglang_processor_unit.py has not yet executed in CI for this PR. A vetter should trigger it before merge.
Checked: test delta diffed against 9f57ec1 (non-test code unchanged); CI green on f2be166, the earlier rust-tests (.) failure was the unrelated http-transcriptions connection-error flake and passed on rerun. Tests not run locally.
Preserve requested token metadata through Python and Rust chat parsing, including terminal tokens.
Signed-off-by: Jimmy Shong <69131491+Jiminator@users.noreply.github.com>
The dynamo-parsers-v2 version sentence is stale on main independently of this fix; leave it for a separate docs update.
Signed-off-by: Jimmy Shong <69131491+Jiminator@users.noreply.github.com>
While Qwen reasoning waits behind a split tool-call opener, a later chunk's
logprobs were emitted on a score-only choice ahead of that reasoning. Hold
them until the reasoning is released so scores stay in generation order.
Signed-off-by: Jimmy Shong <69131491+Jiminator@users.noreply.github.com>
Per-token decoding can drop context-dependent spacing, so concatenated bytes
only approximate the output. Point to completion_token_ids for exact replay.
Signed-off-by: Jimmy Shong <69131491+Jiminator@users.noreply.github.com>
Scores held behind queued Qwen reasoning were released only after every
queued reasoning chunk. With raw text and reasoning alternating behind a
split tool-call opener, a raw chunk's scores followed reasoning generated
after it. They now lead the next queued reasoning's source envelope.
Signed-off-by: Jimmy Shong <69131491+Jiminator@users.noreply.github.com>
Finding the token that completes a local stop string decoded every prefix
of the buffered IDs, which is quadratic in their count. Once a decoded
prefix covers the stop text every longer one does, so bisect instead.
Signed-off-by: Jimmy Shong <69131491+Jiminator@users.noreply.github.com>
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Re-approving at 9b2a74a: the rebase moved the held logprobs into QwenXmlStreamState::deferred_logprobs per #17719 with equivalent merge logic in choices_for; all other files are byte-identical to f2be166. CI green on this head, including the sglang-test run.
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Overview
Preserve requested prompt/completion IDs and backend logprobs through SGLang processing and both Rust chat-parser routes. Buffered markers, queued reasoning and EOS-only chunks must not drop, duplicate or reorder token records.
Key Changes
Validation
One committed regression per parser path, plus one focused converter check:
Local CPU validation: 445 Python unit cases and 3,760 Rust library cases passed; 13 existing Rust tests remain ignored. Rust checks used
--no-default-features; Python checks used SGLang 0.5.23 and a rebuilt native runtime. Rustfmt, strict all-target Clippy fordynamo-llm, pinned Black/isort/Ruff and docs lint passed.Earlier saved GLM-5.3 direct/HTTP replays preserved 48/48 scores and completion IDs, plus 187 prompt IDs once. That replay evidence remains private; the converter behavior now has its own small in-repo regression. No new GPU generation was run.
The SGLang CI job selects this module with
pre_merge and sglang and gpu_0. Jobs namedUnit testsin the PR issue-link workflow do not execute the frontend suite; remote SGLang CI for the new head still needs confirmation.Score preservation copies V1 payloads and adds CPU/memory work. Earlier processor fixtures measured roughly 4–7% V1 CPU overhead; this is not a serving-latency or throughput claim. Existing SGLang explicit-stop logprob trimming is unchanged, so IDs and scores can differ in length at a local stop.
Issues and Ongoing Work
Pull Request Checklist
/pr-checklistskill.