Python: Read and write chat history files as UTF-8 - #14445
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ChatHistory.store_chat_history_to_file and load_chat_history_from_file opened the file in text mode without an encoding, so they used the locale encoding. On Windows that is cp1252, and storing a history with non-ASCII content raised UnicodeEncodeError; a history written as UTF-8 elsewhere also failed to load. Both now pass encoding="utf-8", matching how the rest of the package reads text files (KernelPlugin.from_directory and KernelFunctionFromPrompt.from_directory default to utf-8). Adds a regression test that round-trips a history with Chinese, accented and emoji content, which fails on the Windows CI legs before this change.
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🟢 Approval recommended
The UTF-8 changes are covered by regression testing, with no unresolved review comments.
Pull request overview
Updates chat history file I/O to use UTF-8 consistently across platforms.
Changes:
- Uses UTF-8 when reading and writing chat history files.
- Adds regression coverage for non-ASCII content.
File summaries
| File | Summary |
|---|---|
python/tests/unit/contents/test_chat_history.py |
Tests non-ASCII chat history round-tripping. |
python/semantic_kernel/contents/chat_history.py |
Applies UTF-8 encoding to file reads and writes. |
Review details
- Files reviewed: 2/2 changed files
- Comments generated: 0
- Review effort level: Lite
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Motivation and Context
ChatHistory.store_chat_history_to_file and load_chat_history_from_file were opening files in text mode without specifying an encoding. This meant Python used the system's default locale encoding, which is typically cp1252 on Windows.
As a result, saving chat history containing non-ASCII characters (such as Chinese characters, accented characters, or emojis) could raise a UnicodeEncodeError. Similarly, chat history files written as UTF-8 could fail to load correctly on Windows.
This change makes both methods explicitly use UTF-8, which is also consistent with how other parts of the package handle text files, such as KernelPlugin.from_directory and KernelFunctionFromPrompt.from_directory.
Description
Explicitly use encoding="utf-8" when saving chat history.
Explicitly use encoding="utf-8" when loading chat history.
Added a regression test that saves and loads chat history containing Chinese, accented, and emoji characters.
The regression test ensures that chat history can be safely round-tripped across platforms, including Windows.