[Bugfix][Parser] Confirm reasoning end when an Inkling content block opens

[Vegetog]

Fixes the streaming text-then-tool half of #49865.

Rebased onto current main (including #51391) and narrowed to that one bug,
per @bbrowning's review.

Purpose

Inkling's reasoning pass leaves its reasoning phase only on an explicit
reasoning-end event. A response that opens with visible content and no thinking
block never emitted one, so DelegatingParser never entered its tool phase and
the tool pass never ran.

#51391 fixed marker ownership inside the reasoning pass, but not this phase
gating. With both Inkling parsers enabled, tools declared, and
tool_choice="auto", this still fails on current main:

<|content_text|>let me check<|end_message|>
<|message_model|>
<|content_invoke_tool_json|>{"name":"get_weather","args":{"city":"SF"}}<|end_message|>

Content comes back as

let me check<|content_invoke_tool_json|>{"name":"get_weather","args":{"city":"SF"}}<|end_message|>

and no tool call is parsed.

Fix

Emit REASONING_END from every transition that opens a block rendering as
visible content — TEXT_START, TOOL_TEXT and TOOL_ERROR, from both
CONTENT and MESSAGE_HEADER. Six one-line changes in inkling_config();
nothing else in the parser or engine is touched.

These openers are not tool terminals, so they do not interact with the
forwarded-tool-span tracking added in #51391.

Scope

Narrowed from the original PR, per review:

• passthrough_terminal_when_skipping_tools and its engine/config plumbing are
  dropped — [Bugfix][Parser] Prevent Inkling block-end leakage with tools #51391 owns shared block-closer handling now, and that plumbing
  was the source of the rebase conflict.
• The generic _extract_tool_calls cleaned-content fallback is dropped.
  [Bugfix][Parser] Prevent Inkling block-end leakage with tools #51391's own test_plain_text_non_streaming covers the non-streaming
  plain-text-with-tools case on current main, so there is no separate
  post-[Bugfix][Parser] Prevent Inkling block-end leakage with tools #51391 reproduction for it.
• The no-tools plain-text work is split out into a follow-up PR. Final
  content is correct on main; what remains there is the streaming-latency
  issue, which wants its own tests.
• The tool-first / no-thinking case is left to [Bugfix][Parser] Emit REASONING_END for Inkling tool calls that follow no thinking block #50528, which owns the
  TOOL_START → REASONING_END transition.

Test Plan

TestDelegatingTwoPass::test_visible_text_then_tool_streaming in
tests/parser/engine/test_inkling.py drives the served two-pass
DelegatingParser.parse_delta path with a real function tool declared and
tool_choice="auto", and asserts:

• visible content is exactly let me check
• the tool call is parsed as get_weather with arguments {"city": "SF"}
• neither <|content_invoke_tool_json|> nor <|end_message|> appears in content

Parameterized over chunk sizes 1 / 3 / 64 and over all three visible-content
openers (TEXT_START, TOOL_TEXT, TOOL_ERROR), since the same change lands
on all of them — nine cases.

_stream_delegating now also returns accumulated tool-call arguments so the
argument assertion is possible; its two existing callers are updated for the
extra return value.

Test Result

All nine cases fail on current main and pass with this change. On main the
content assertion fails as:

- let me check
+ let me check<|content_invoke_tool_json|>{"name":"get_weather","args":{"city":"SF"}}<|end_message|>

tests/parser/engine: 3767 passed (main reports 3758 in #51391; the
difference is exactly the nine cases added here).

ruff check and ruff format --check clean on both changed files.

Note for anyone reproducing locally: pytest tests/parser tests/reasoning
segfaults on current main in this environment, in the autouse cleanup_fixture
teardown after
tests/parser/mistral/test_reasoning.py::test_mistral_reasoning_v13[v13_basic]
(cleanup_dist_env_and_memory → torch.accelerator.empty_host_cache). It
reproduces identically with and without this change, so it is unrelated —
tests/parser/engine runs clean.

No live model evaluation was run; this is a parser-only change with
deterministic CPU-only coverage, and an Inkling model was not available.

AI assistance

The human submitter selected and claimed the underlying issue, controlled the
scope, reviewed the root cause and implementation, reviewed every changed line,
and approved publication. AI-assisted tooling supported implementation,
regression-test authoring, and validation orchestration.

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[Vegetog]

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Codex Review: Didn't find any major issues. 👍

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[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @Vegetog.

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[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @Vegetog.

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End reasoning for raw and error tool blocks

In streaming DelegatingParser configurations with tools declared, TOOL_TEXT and TOOL_ERROR also open visible-content blocks, but only TEXT_START now emits REASONING_END. Those transitions therefore leave the outer parser in its reasoning phase; when the normal block-end terminal arrives, skip_tool_parsing re-emits it as text and the downstream tool pass never runs, leaking the literal <|end_message|> or end-sampling marker. Emit the same reasoning-end event for both visible raw/error block transitions, including their MESSAGE_HEADER variants.

Useful? React with 👍 / 👎.

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @Vegetog.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[bbrowning]

Thanks for helping us get this fixed! I'm trying to land the various fixes around this area, and have some requests for this PR now that #51391 has now merged. Could you please rebase this PR onto current main and narrow it to the remaining streaming text→tool correctness bug?

I verified the following still fails on current main:

• both Inkling reasoning and tool parsers enabled
• tools declared with tool_choice="auto"
• streaming response containing:

<|content_text|>let me check<|end_message|>
<|message_model|>
<|content_invoke_tool_json|>{"name":"get_weather","args":{"city":"SF"}}<|end_message|>

Current behavior returns the entire tool block as assistant content and produces no parsed tool call. Adding REASONING_END to the visible-content opener transitions fixes it.

For this PR, please:

1. Rebase onto current main, including #51391.

2. Keep the REASONING_END events on:

   • (CONTENT, TEXT_START)
   • (MESSAGE_HEADER, TEXT_START)
   • (CONTENT, TOOL_TEXT)
   • (MESSAGE_HEADER, TOOL_TEXT)
   • (CONTENT, TOOL_ERROR)
   • (MESSAGE_HEADER, TOOL_ERROR)

3. Add a focused DelegatingParser.parse_delta regression test for streaming text→tool with tools declared. It should assert:

   • visible content is exactly "let me check"
   • the tool call is parsed with the expected name and arguments
   • CONTENT_INVOKE_TOOL_JSON and END_MESSAGE do not appear in content

4. If inexpensive, parameterize equivalent visible-prefix coverage for TOOL_TEXT and TOOL_ERROR, since those transitions receive the same change.

5. Drop passthrough_terminal_when_skipping_tools and its engine/config plumbing. #51391 now owns shared block-closer handling, and this is the source of the rebase conflict.

6. Drop the generic _extract_tool_calls cleaned-content fallback unless it has a separate post-#51391 reproduction.

7. Leave the tool-first/no-thinking case to #50528, which owns the TOOL_START → REASONING_END transition.

Please split the no-tools plain-text streaming-latency work into a follow-up PR. Final content is now correct on main, but the remaining latency issue is reproducible: with reasoning_effort=none|minimal, bare output fed one token at a time is buffered and returned as one final content delta instead of streaming incrementally. Splitting this out helps me ensure we land the correctness fixes properly layered and then when correctness is handled we can improve the incremental streaming no tools piece.

The follow-up should retain only the minimum Inkling-specific plain-text-mode/context plumbing needed to make those deltas incremental, with a test that:

• uses no tools and reasoning_effort of none and minimal
• feeds bare text one token per parse_delta call
• covers both an explicit END_MESSAGE and EOS without a closer
• asserts the content deltas arrive incrementally, not merely that their final concatenation is correct
• verifies tools-enabled requests continue using message-header parsing

[Vegetog]

Thanks for helping us get this fixed! I'm trying to land the various fixes around this area, and have some requests for this PR now that #51391 has now merged. Could you please rebase this PR onto current main and narrow it to the remaining streaming text→tool correctness bug?

I verified the following still fails on current main:

• both Inkling reasoning and tool parsers enabled
• tools declared with tool_choice="auto"
• streaming response containing:

<|content_text|>let me check<|end_message|>
<|message_model|>
<|content_invoke_tool_json|>{"name":"get_weather","args":{"city":"SF"}}<|end_message|>

Current behavior returns the entire tool block as assistant content and produces no parsed tool call. Adding REASONING_END to the visible-content opener transitions fixes it.

For this PR, please:

1. Rebase onto current main, including [Bugfix][Parser] Prevent Inkling block-end leakage with tools #51391.

2. Keep the REASONING_END events on:

   • (CONTENT, TEXT_START)
   • (MESSAGE_HEADER, TEXT_START)
   • (CONTENT, TOOL_TEXT)
   • (MESSAGE_HEADER, TOOL_TEXT)
   • (CONTENT, TOOL_ERROR)
   • (MESSAGE_HEADER, TOOL_ERROR)

3. Add a focused DelegatingParser.parse_delta regression test for streaming text→tool with tools declared. It should assert:

   • visible content is exactly "let me check"
   • the tool call is parsed with the expected name and arguments
   • CONTENT_INVOKE_TOOL_JSON and END_MESSAGE do not appear in content

4. If inexpensive, parameterize equivalent visible-prefix coverage for TOOL_TEXT and TOOL_ERROR, since those transitions receive the same change.

5. Drop passthrough_terminal_when_skipping_tools and its engine/config plumbing. [Bugfix][Parser] Prevent Inkling block-end leakage with tools #51391 now owns shared block-closer handling, and this is the source of the rebase conflict.

6. Drop the generic _extract_tool_calls cleaned-content fallback unless it has a separate post-[Bugfix][Parser] Prevent Inkling block-end leakage with tools #51391 reproduction.

7. Leave the tool-first/no-thinking case to [Bugfix][Parser] Emit REASONING_END for Inkling tool calls that follow no thinking block #50528, which owns the TOOL_START → REASONING_END transition.

Please split the no-tools plain-text streaming-latency work into a follow-up PR. Final content is now correct on main, but the remaining latency issue is reproducible: with reasoning_effort=none|minimal, bare output fed one token at a time is buffered and returned as one final content delta instead of streaming incrementally. Splitting this out helps me ensure we land the correctness fixes properly layered and then when correctness is handled we can improve the incremental streaming no tools piece.

The follow-up should retain only the minimum Inkling-specific plain-text-mode/context plumbing needed to make those deltas incremental, with a test that:

• uses no tools and reasoning_effort of none and minimal
• feeds bare text one token per parse_delta call
• covers both an explicit END_MESSAGE and EOS without a closer
• asserts the content deltas arrive incrementally, not merely that their final concatenation is correct
• verifies tools-enabled requests continue using message-header parsing

Thanks — #51391 landing made this much smaller. Rebased onto 75231eff2; now 2 files, +55/-11, one commit.

1–2. Rebased; all six REASONING_END openers kept.

3–4. Added TestDelegatingTwoPass::test_visible_text_then_tool_streaming, parameterized over the three openers and chunk sizes 1 / 3 / 64. Asserts content is exactly let me check, the call parses as get_weather with {"city": "SF"}, and neither <|content_invoke_tool_json|> nor <|end_message|> appears in content. I confirmed your repro first — all nine cases fail on unmodified main.

5. Dropped, along with forward_delegating_context / _delegating_tool_parser_enabled, which existed only to feed it.

6. Dropped — I could not produce a post-[Bugfix][Parser] Prevent Inkling block-end leakage with tools #51391 reproduction, and your test_plain_text_non_streaming already covers the non-streaming case on main. Happy to restore it if you have one.

7. Untouched.

One shared-test change worth flagging: _stream_delegating now also returns accumulated tool-call arguments, so the argument assertion is possible; its two existing callers are updated.

I'll open the plain-text streaming-latency follow-up with the test shape you specified.

tests/parser/engine: 3767 passed (3758 plus the nine added here). ruff check and format --check clean. FYI, tests/parser as a whole segfaults on current main here — autouse cleanup_fixture teardown after test_mistral_reasoning_v13[v13_basic], in cleanup_dist_env_and_memory → torch.accelerator.empty_host_cache. It reproduces on unmodified main, so it's unrelated, but it does scope what I could run locally.

[mergify]

Hi @Vegetog, the pre-commit checks have failed. Please run:

uv pip install pre-commit>=4.5.1
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

[bbrowning]

I'm doing some live testing of these changes before approval, but on the surface things look good. Note the pre-commit hook caught a mypy typing failure that will need to be fixed before merging:

Error: tests/parser/engine/test_inkling.py:173: error: Need type annotation for "args" (hint: "args: dict[<type>, <type>] = ...") [var-annotated]

[bbrowning]

I reviewed this manually and with the help of two different coding assistants, just to double-check the transitions here. I verified the new test properly reproduces the tool call leak to prevent regressing here.

It needs a small pre-commit fix but is otherwise good to merge.

Unit Tests

I ran the entire parser engine unit test suite as well as the reasoning and tool parser unit tests for a selection of other models that use the shared parser engine to ensure no regressions.

Command

pytest -sv \
  tests/parser/engine \
  tests/reasoning/test_deepseekv3_reasoning_parser.py \
  tests/reasoning/test_gemma4_reasoning_parser.py \
  tests/reasoning/test_glm4_moe_reasoning_parser.py \
  tests/reasoning/test_minimax_m2_reasoning_parser.py \
  tests/reasoning/test_qwen3_reasoning_parser.py \
  tests/tool_parsers/test_deepseekv4_tool_parser.py \
  tests/tool_parsers/test_gemma4_tool_parser.py \
  tests/tool_parsers/test_glm47_moe_tool_parser.py \
  tests/tool_parsers/test_minimax_m2_tool_parser.py \
  tests/tool_parsers/test_qwen3coder_tool_parser.py

Results

4073 passed, 17 warnings

Live model regression tests from 51391

Using the same reproduction script of various edge cases I used to review 51391 (https://gist.github.com/bbrowning/2ad70e0838630ffbcdaf0368ebd85764), I confirmed no regressions in the live model case from what 51391 fixed.

vLLM Server Args

VLLM_USE_V2_MODEL_RUNNER=1 \
FLASH_ATTENTION_CUTE_DSL_CACHE_ENABLED=1 \
vllm serve \
    --model thinkingmachines/Inkling-Small-NVFP4 \
    --trust-remote-code \
    --tokenizer-mode inkling \
    --kernel-config.enable_flashinfer_autotune=False \
    --tensor-parallel-size 4 \
    --gpu-memory-utilization 0.75 \
    --enable-auto-tool-choice \
    --tool-call-parser inkling \
    --reasoning-parser inkling \
    --port 8088

No regression of 51391 fixes

The specific fixes exercised by the new unit tests here were not entirely covered by my live reproduction, so this mostly serves as a test of no regressions in what 51391 just fixed. The inconclusive ones appear to just be actual model differences in output across turns. I'll dig into those separately, but I think those are actually behaving fine given what the model is generating. And, no changes from this PR in that department.

The 1 remaining failure in this reproduction script should be fixed by #50528, as the output shows.

$ python repro_inkling_marker_leak.py --base-url http://localhost:8088/v1 --repeats 10
model: thinkingmachines/Inkling-Small-NVFP4
[PASS] #49876 no-tools/none/non-stream (10 pass, 0 fail, 0 inconclusive)
[PASS] #49876 no-tools/none/stream (10 pass, 0 fail, 0 inconclusive)
[INCONCLUSIVE] #49876 no-tools/minimal/non-stream (4 pass, 0 fail, 6 inconclusive)
[INCONCLUSIVE] #49876 no-tools/minimal/stream (4 pass, 0 fail, 6 inconclusive)
[PASS] #51391 post-tool synthesis/non-stream (10 pass, 0 fail, 0 inconclusive)
[PASS] #51391 post-tool synthesis/stream (10 pass, 0 fail, 0 inconclusive)
[PASS] #50528 tool without thinking/non-stream (10 pass, 0 fail, 0 inconclusive)
[FAIL] #50528 tool without thinking/stream (0 pass, 10 fail, 0 inconclusive); exemplar: parser marker leaked; content='<|content_invoke_tool_json|>{"name":"get_info","args":{"query":"result count"}}<|end_message|>', tools=[]
summary: 5 passed, 1 failed, 2 inconclusive

[bbrowning]

/ci run

[github-actions]

✅ Triggered Buildkite CI #83017 for commit 1c77dac97d42.

[bbrowning]

Merged - thanks!