[stanleys12]

Purpose

FunctionGemmaToolParser.extract_tool_calls_streaming dropped a tool call entirely when the whole
<start_function_call>call:name{...}<end_function_call> block arrived inside one streaming delta, which happens with
speculative decoding, multi-token prediction or stream_interval > 1.

A tool call was only opened in the branch guarded by start_count > prev_start_count and start_count > end_count. When a
complete block lands in a single delta, start_count == end_count for that step, so the call was never opened and
current_tool_id stayed at -1. The "call just ended" branch did run, but it was guarded by current_tool_id >= 0 and
so returned None. The client got nothing: no name, no arguments, no error, even though non-streaming
extract_tool_calls parses the same text correctly.

This fix moves the completion handling into _flush_completed_calls, which opens any completed call that was never
started (advancing current_tool_id and the streamed_args_for_tool / prev_tool_call_arr bookkeeping) before emitting
its name and arguments. It is called both when a call ends and when a delta closes one call while opening the next, so
trailing arguments of an in-flight call are not lost when a new <start_function_call> shows up in the same delta.

A delta that carries several calls now reports all of them in one update. That is how other parsers behave when tokens
are batched (see the assert_one_tool_per_delta=False tests for granite, olmo3, pythonic, kimi_k2 and others); the
alternative would be to hold back all but the first call, which is exactly the silent loss this PR fixes.

Related to #48020 (the FunctionGemma case reported there).

Not a duplicate: the only other open PR touching this streaming path is #48705, which changes how argument diffs are
computed (find_common_prefix, dropping the premature closing brace) and never touches the branches that open a call,
so it does not fix this bug. #57768, #57120 and #57989 are unrelated (regex timeout, trailing content, hyphenated
names). #48636 is the same bug class in the DeepSeek V3/V3.1 parser, a different file. Whichever of #48705 and this PR
lands second needs a trivial rebase, since both touch the argument-diff lines and add a TestExtractToolCallsStreaming
class; I am happy to rebase on top of #48705.

Test Plan

pytest tests/tool_parsers/test_functiongemma_tool_parser.py -v

Streaming tests:

• test_whole_tool_call_in_single_delta: the whole call in one delta reconstructs to the same name/arguments as
  extract_tool_calls.
• test_parallel_tool_calls_in_single_delta: two complete calls in one delta.
• test_second_tool_call_in_single_delta: one call streamed token by token, the second complete in its own delta.
• test_tool_call_closed_and_next_call_in_same_delta: one delta closes the first call's arguments and carries the whole
  second call.
• test_tool_call_split_across_deltas covers the pre-existing token-by-token path and keeps the one-tool-call-per-delta
  invariant.

Test Result

Before the parser change (tests only, on main):

4 failed, 16 passed
FAILED ...::TestExtractToolCallsStreaming::test_whole_tool_call_in_single_delta
FAILED ...::TestExtractToolCallsStreaming::test_parallel_tool_calls_in_single_delta
FAILED ...::TestExtractToolCallsStreaming::test_second_tool_call_in_single_delta
FAILED ...::TestExtractToolCallsStreaming::test_tool_call_closed_and_next_call_in_same_delta

After:

20 passed, 1 warning in 3.47s

pre-commit run --files vllm/tool_parsers/functiongemma_tool_parser.py tests/tool_parsers/test_functiongemma_tool_parser.py
passes (ruff, mypy, SPDX, test tethering).

No model evaluation: this only changes how already-generated text is turned into streaming deltas, not sampling or
model output, and the added tests pin the streaming result to the non-streaming parse of the same text.

I used AI help on this. I went through every changed line, traced the state machine by hand, and ran the tests locally.

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

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[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @stanleys12.

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