Code-Interactive Candlestick Reasoning: Fin-Thinker Makes Evidence Verifiable
ORIGINAL / Code-Interactive Visual Reasoning for Financial Candlestick Understanding
Existing financial candlestick QA often measures answer accuracy alone, without checking whether predictions are supported by chart evidence. This work introduces code-interactive financial candlestick reasoning: the model generates and executes code to obtain observations and perform computations, then uses returned results to guide subsequent reasoning. It also builds 32K replay-verified trajectories and a 1,200-question benchmark that separately assesses answer correctness
01 ABSTRACT
The authors propose a code-interactive financial candlestick reasoning task and present Fin-Thinker, based on Qwen3.5-9B, which generates and executes code to obtain observations and perform calculations before continuing reasoning. To train this capability, they construct FinKLine-32K with 32,184 replay-verified code-observation trajectories and use three-stage training: foundational visual-code fine-tuning, financial process supervision, and execution-feedback reinforcement learning. On FinKLineBench, they report 13.1 percentage-point improvement in strict accuracy over the best direct-answer baseline and 33.2 points over its base model with sandbox access; however, all numbers come from the authors' own benchmark and self-reported experiments and need independent replication.
02 KEY FINDINGS
- The task requires locating visual elements in candlestick charts, aligning them across trading dates and panels, and combining numerical and financial reasoning to answer.
- Fin-Thinker uses code to obtain observations and computations; the FinKLine-32K training data includes successful solutions and error-recovery trajectories, emphasizing verifiable processes.
- FinKLineBench contains 1,200 questions across 138 financial task types and separately evaluates answer correctness, code execution, and evidence grounding; ablations show successive gains from process supervision and execution-feedback reinforcement learning.
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