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[Bugfix][Rust Frontend] Match DeepSeek-V4.1 renderer to the 1017 reference encoding - #62200
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robertgshaw2-redhat merged 3 commits intoOct 19, 2026
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…rence encoding Tool-result-only user-content blocks no longer start a new user turn, so drop_thinking keeps the reasoning that led to a tool call. Reject literal image placeholder tokens in message text and reasoning. Mirrors the Python encoder fix so both frontends render identical prompts. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: Robert Shaw <robertgshaw2@gmail.com>
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LGTM, cc @BugenZhao in case you want to take another look.
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…rence encoding (vllm-project#62200) Signed-off-by: Robert Shaw <robertgshaw2@gmail.com> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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Overview
Rust counterpart of #62199: match the DeepSeek V4.1 renderer to the updated reference
encoding/.Affects both V4.1-Flash checkpoints (launch and 1017). DeepSeek fixed the turn handling in both repos (launch
314113f, 1017 release); theirencoding/is now identical. The image-token check has been in the reference since launch.Claims
<｜deepseek_image｜>in message text or reasoning returns 400.Examples
1. Tool call in thinking mode, with no
toolsfield in the request[{"role": "user", "content": "What's the weather in Paris? Answer in Fahrenheit."}, {"role": "assistant", "content": "", "reasoning": "Tool returns Celsius; convert to Fahrenheit.", "tool_calls": [{"id": "c1", "type": "function", "function": {"name": "get_weather", "arguments": "{\"city\": \"Paris\"}"}}]}, {"role": "tool", "tool_call_id": "c1", "content": "{\"temp_c\": 20}"}]Before (reasoning dropped):
After (reasoning kept, same as the reference encoder):
2. Literal image token in text
[{"role": "user", "content": "hi <｜deepseek_image｜>"}]Before: accepted, so the prompt has an image placeholder with no image. After: 400.
Validation
cargo test -p vllm-chat --lib renderer::: 210 passed. The new tests fail on main. fmt and clippy are clean.vllm-rs renderon DeepSeek-V4.1-Flash-1017: token IDs now match the Python frontend (113 vs 97 on main); the literal image token returns 400.Details
Not a duplicate: open Rust renderer PRs (#62189, #56334) don't touch turn boundaries or placeholder validation.
Pull Request Checklist
I used vLLM's
/pr-checklistskill. (Mandatory for agents, optional for humans).AI assistance was used during the creation of this PR.
Design Fit: Minimizes impact on core components, reuses existing functionality, and justifies added complexity.
Testing and Validation: Validates the change and ensures any added tests are meaningful and reliable, with CI coverage or documented CI resource constraints and validation performed outside CI.
Code Quality and Style: Keeps code and comments clear and concise, and updates relevant documentation and examples.
Pull Request Contents: Includes a brief summary and relevant links, supports claims with evidence, explains root causes and implementation trade-offs, and follows the contributing guide.
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