Show actual SEARCH/REPLACE content in diff summaries

[fangchenli]

Problem

When diff-based evolution is enabled, the "Previous Attempts" section of prompts shows changes like:

Change 1: Replace 15 lines with 18 lines

This gives the LLM no visibility into what the actual edits were, making it harder to:

• Learn from successful patterns
• Avoid repeating failed exact matches
• Understand what format produces valid SEARCH blocks

This contributes to the high rate of "apply diff fail" errors (see issue #346) where SEARCH patterns don't exactly match the original code.

Solution

Update format_diff_summary() to show actual content for multi-line blocks:

Change 1: Replace:
  def old_function():
      return False
with:
  def new_function():
      return True

Single-line changes remain compact:

Change 1: 'x = 1' to 'x = 2'

Add _format_block_lines() helper with configurable truncation limits.

Configuration

New options in prompt: config section:

prompt:
  diff_summary_max_line_len: 100  # Truncate lines longer than this
  diff_summary_max_lines: 30      # Max lines per SEARCH/REPLACE block

Files Changed

• openevolve/config.py - Add PromptConfig options
• openevolve/utils/code_utils.py - Update format_diff_summary
• openevolve/iteration.py - Pass config to format_diff_summary
• openevolve/process_parallel.py - Pass config to format_diff_summary
• tests/test_code_utils.py - Add tests for new behavior

Some files got reformatted, I'll leave those changes there.

[CLAassistant]

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