Description

Summary
The edit tool silently deleted approximately 50% of a LaTeX document (~190 lines) when attempting a simple string replacement. The oldString parameter matched a much larger block than intended, replacing it with a 10-character snippet and destroying everything in between.
What happened
I was making a targeted spacing adjustment to a .tex file. I issued an edit command with an oldString intended to match a single figure/table boundary (e.g., \end{figure} followed by a section header). Instead, the tool matched a spanning boundary that started at the end of Table 1 and ended somewhere before the Conclusion section. The replacement deleted:

• Table 1 content and caption
• All Taxonomy subsections (3.1–3.6)
• Section 4 (Training and Adaptation) + Table 2
• Section 5 (Applications to PdM) + Table 3
• Section 6 (Challenges and Future Directions)
  File dropped from 453 lines → 266 lines without any warning.
  Root cause
  The edit tool performs exact string replacement using the first match found. When the oldString is constructed from multi-line context, it can accidentally match a boundary that spans much more content than the user intended. There is:
• No preview/diff before applying
• No "match too large" safeguard
• No confirmation prompt for multi-line replacements exceeding a threshold

Plugins

No response

OpenCode version

1.3.17

Steps to reproduce

1. Open any multi-section .tex or .md file with repeating patterns (e.g., multiple \end{table} blocks)
2. Issue an edit with an oldString that includes context lines before and after a target
3. If that context happens to appear earlier in the file with a wider span, the tool replaces the first and largest match
4. Result: everything between the matched start and end is deleted

Screenshot and/or share link

No response

Operating System

Windows 11

Terminal

WSL