mcp-server

T

ClaudeandClaude Fable 5 f089793218 feat(job_writer): reject code that is not valid UTF-8

write_job_file now validates that the incoming code string is encodable
as UTF-8 BEFORE doing any file I/O. A lone surrogate (U+D800..U+DFFF) —
typically the result of a broken decode somewhere upstream in the
agent's pipeline — cannot be represented in UTF-8, and would otherwise
either silently produce mojibake on disk or crash with an opaque
UnicodeEncodeError from open().

Behavior:
  - try: code.encode('utf-8')
  - on UnicodeEncodeError: log a warning and raise ValueError with a
    message that points the agent at 're-generate the code as plain
    Unicode'. ValueError -> HTTP 400 via the existing server.py
    exception handler, so the agent gets a clean error and no file is
    written.
  - normal CJK / emoji / accented Latin still work — the encode check
    is essentially free.

Tests:
  - test_write_accepts_valid_utf8_including_cjk_and_emoji: positive
    case for the common LLM output patterns.
  - test_write_rejects_lone_surrogate: negative case, also asserts
    that tmp_path is empty (no half-written .py left behind).

Full suite 246 passed (+2 from 244).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

2026-06-30 14:33:53 +08:00