kernc/backtesting.py

Chart Rendering seems incorrect

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#1327 opened on Oct 26, 2025

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help wanted

Description

Expected behavior

When I am testing my strategy, I noticed the strategy was placing order at odd places on the charts. On the closer inspection, I think the OHLC rendering on the chart is incorrect

If you checked the time 10/17 21:05 PM

Correct data: Close = 1072.25

I expect to see the same data on chart.

Code sample

Actual behavior

Incorrect data rendered on chart: Close = 1071.192

Any idea on why this is happening? Is it due to some misalignment issue?

Additional info, steps to reproduce, full crash traceback, screenshots

No response

Software versions

  • backtesting.__version__: 0.6.5
  • pandas.__version__: 2.3.2
  • numpy.__version__: 2.2.6
  • bokeh.__version__: 3.8.0
  • OS: MacOS

Contributor guide

Tech stack
python
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Python programmingUnderstanding of OHLC dataFamiliarity with bokeh
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Investigate the chart rendering code in the backtesting.py library, specifically how OHLC data is transformed and passed to bokeh. Check if there is a misalignment in data indexing or timezone conversion. Look at the relevant source files such as `backtesting/ plotting.py` or similar. Compare the actual data values from the user's screenshot with the data fed to the plot. Consider if there is a bug in the candlestick plot function (e.g., `plot candlesticks`).