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…trict tools Since vllm-project#45600, get_model_structural_tag() returns None for tool_choice="auto" without any strict tool. Most OpenAI-compatible agentic clients send auto + non-strict tools, so DeepSeek-V4 gets no structural tag and is not constrained to valid DSML during generation. When the model emits partial/malformed DSML, DeepSeekV4ToolParser cannot extract it -- ｜DSML｜ fragments leak into content (non-streaming) or are dropped as an empty response with finish_reason="stop" (streaming). The parser-level fix vllm-project#40806 can't help because it can only extract well-formed DSML; the malformation originates at generation time. For deepseek_v4, keep the structural tag enabled for auto + non-strict. xgrammar's deepseek_v4 builtin returns a TriggeredTagsFormat that allows free text/reasoning and constrains DSML to valid grammar only when the model triggers <｜DSML｜tool_calls>, so it does not force a tool call and does not over-constrain generation (the concern from vllm-project#45600). Fixes vllm-project#40801. Signed-off-by: VickY0E <175975770+VickY0E@users.noreply.github.com>
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When auto + non-strict tools, it's expected that structural tag is not applied. |
2 participants
Purpose
Fixes the intermittent DSML fragment leakage / empty tool-call responses for DeepSeek-V4 with
tool_choice="auto"+ non-strict tools (#40801).Since #45600,
get_model_structural_tag()returnsNonefortool_choice="auto"without any strict tool. Most OpenAI-compatible agentic clients (e.g. opencode) sendauto+ non-strict tools, so DeepSeek-V4 never gets a structural tag and the model is not constrained to valid DSML during generation. When the model emits partial/malformed DSML,DeepSeekV4ToolParsercannot extract it —｜DSML｜fragments leak intocontent(non-streaming) or are dropped to an empty response withfinish_reason="stop"(streaming). The parser-level fix #40806 can't help here because it can only extract well-formed DSML; the malformation originates at generation time.Changes
get_model_structural_tag(): fordeepseek_v4, do not skip the structural tag forauto+ non-strict. xgrammar'sdeepseek_v4builtin returns aTriggeredTagsFormatthat allows free text/reasoning and constrains DSML to valid grammar only when the model triggers<｜DSML｜tool_calls>— so it does not force a tool call and does not over-constrain generation (the concern from [Frontend] Skip structural tags for auto tool_choice without strict mode #45600).get_model_structural_tag("deepseek_v4", non-strict tools, "auto")returns aStructuralTag.Test Plan
Verified on a DeepSeek-V4-Flash-NVFP4 deployment: tool calls extract cleanly with no DSML leakage, and an agentic workload (opencode subagents, many sequential tool calls) runs without the empty-response/leak failures.
Tradeoff
Re-introduces per-request xgrammar compilation for DSv4
autorequests (minor perf cost). Hardcodingdeepseek_v4is the minimal change; happy to generalize (model opt-in set / launch flag) if maintainers prefer.Fixes #40801.
Refs: #45600 · #40806 · #45862 · #45877