fix: add explicit encoding='utf-8' to text-mode open() calls

[avoronov-explyt]

Several open() calls in autogen-ext use text mode without specifying encoding='utf-8'. On systems where the default encoding is not UTF-8 (e.g., cp950 on Chinese Windows, cp1251 on Russian Windows), these calls will raise UnicodeDecodeError or produce mojibake.

Affected files:

• _docker_jupyter.py: HTML output writing
• chat_completion_client_recorder.py: session file read/write
• page_logger.py: hash file, call tree HTML, page HTML writing

This PR adds encoding='utf-8' to all text-mode open() calls in these files, ensuring consistent behavior across all platforms.

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[t0ugh-sys]

Code Review: fix: add explicit encoding='utf-8' to text-mode open() calls

Overall assessment: ✅ Looks good — this is a well-scoped and valuable fix.

Summary

This PR correctly addresses a real cross-platform issue. On systems where the default locale encoding is not UTF-8 (e.g., Windows with cp1252, cp950, cp1251, etc.), text-mode open() calls without an explicit encoding parameter can silently produce mojibake or raise UnicodeDecodeError. The changes are minimal, consistent, and targeted.

File-by-file observations

1. _docker_jupyter.py — open(path, "w", encoding="utf-8")

   • Writing HTML data that may contain non-ASCII characters. Correct fix.

2. chat_completion_client_recorder.py — Two changes:

   • Read (json.load): open(..., "r", encoding="utf-8") — ensures JSON round-trip fidelity regardless of system locale.
   • Write (json.dump): open(..., "w", encoding="utf-8") — ensures the session file is always written as UTF-8, which is the expected encoding for JSON.
   • ✅ Both directions are covered, preventing asymmetric encoding issues.

3. page_logger.py — Three changes:

   • Hash file writing, call tree HTML, and page HTML all now use encoding="utf-8".
   • These files may contain arbitrary user-generated text, so the fix is appropriate.

Minor suggestions (non-blocking)

• Consistency note: This PR covers files in autogen-ext. It might be worth a follow-up audit of other packages (autogen-core, autogen-agentchat, etc.) to ensure no similar open() calls are missing explicit encoding. A lint rule (e.g., pylint's unspecified-encoding / W1514) could help enforce this project-wide.

• pathlib consideration (optional, not a blocker): Some of these open() calls could alternatively use pathlib.Path(...).write_text(data, encoding="utf-8") / .read_text(encoding="utf-8") for slightly cleaner code, but that's a style preference and not required for this fix.

Verdict

LGTM. The changes are correct, safe, and well-motivated by the PR description. The fix prevents a class of bugs that only manifests on non-UTF-8 default locales, making this a meaningful improvement for international users.