[BUG] Claude can't edit files that use tabs for indentation

[d5ve]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

For some reason #9163 was closed with no resolution.

This is affecting me. Claude fails to edit files indented with tabs. PHP code in my case. It falls back to running ridiculous and fragile sed commands. See below.

What Should Happen?

The Update tool should be able to make changes to files that use tabs for indentation.

$ file application/views/user/layout/service-note-modal.php
application/views/user/layout/service-note-modal.php: HTML document, ASCII text, with very long lines (318)

Error Messages/Logs

● Read(application/views/user/layout/service-note-modal.php)
  ⎿  Read 25 lines

● Update(application/views/user/layout/service-note-modal.php)
  ⎿  Error editing file

● Bash(sed -i '88,109s/^\t\t\t\t\t\t/\t\t\t\t\t\t\t/' /home/anon/apps/portal/application/views/user/layout/service-note-modal.php && sed -i '109a\\t\t\t\t\t\t</div>' /h…)
  ⎿  Running…

Steps to Reproduce

Have a file with tabs.
Ask for an edit.
Watch Claude flail.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

No response

Claude Code Version

2.0.37 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

iTerm2

Additional Information

No response

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] Edit Tool Cannot Handle Files with Tabs #9163
2. [Bug] File editing fails due to indentation mismatch between Read tool output and actual file content #10332
3. [BUG] Golang replace calls more often than not fail (tabs vs spaces?) #753

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
• To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

[d5ve]

It is a duplicate with #9163 BUT that was closed with no resolution. So it's still an active bug.

It is probably a duplicate with #10332 BUT that was closed as a duplicate for the other one. So it's still an active bug.

It is probably a duplicate with #753 BUT that was closed mentioning a fix applied months ago. I am still seeing the issue today so it's still an active bug.

[d5ve]

This is ridiculous!

● Update(application/views/user/service-logs.php)
  ⎿  Error editing file

● Let me check the exact whitespace in that section:

● Bash(sed -n '137,157p' /home/anon/apps/portal/application/views/user/service-logs.php | cat -A)
  ⎿  ^I^I^I^I^I<div class="card-body scroll-y overflow-hidden p-0 d-none">$
     ^I^I^I^I^I^I<div class="p-4 p-xl-6 text-editor">$
     ^I^I^I^I^I^I^I<h5>Service notes</h5>$
     … +18 lines (ctrl+o to expand)

● Now I can see the exact whitespace (tabs). Let me update it correctly:

● Update(application/views/user/service-logs.php)
  ⎿  Error editing file

● I see there's a trailing space on one line. Let me match it exactly:

● Update(application/views/user/service-logs.php)
  ⎿  Error editing file

● Let me try a different approach - I'll edit just the content part:

● Update(application/views/user/service-logs.php)
  ⎿  Error editing file

● Let me use Write to rewrite the whole file with the changes:

● Bash(cp /home/anon/apps/portal/application/views/user/service-logs.php /home/anon/apps/portal/application/views/user/service-logs.php.backup)
  ⎿  Running…

 Bash command

   cp /home/anon/apps/portal/application/views/user/service-logs.php /home/anon/apps/portal/application/views/user/service-logs.php.backup
   Backup service-logs.php before editing

 Do you want to proceed?
 ❯ 1. Yes
   2. Yes, and don't ask again for cp commands in /home/anon/apps/portal
   3. Tell Claude what to do differently


● I'll continue by making smaller edits. Let me add the title and date fields to the panel:

● Update(application/views/user/service-logs.php)
  ⎿  File must be read first

● Read(application/views/user/service-logs.php)
  ⎿  Read 25 lines

● Update(application/views/user/service-logs.php)
  ⎿  Error editing file

● Bash(sed -i '139 i\\t\t\t\t\t\t\t<h5>Title</h5>\n\t\t\t\t\t\t\t<p id="serviceLogTitle"></p>\n\t\t\t\t\t\t\t<h5>Date</h5>\n\t\t\t\t\t\t\t<p id="serviceLogDate"></p>'…)
  ⎿  Running…

[d5ve]

Check out this command!

──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
 Bash command

   sed -i '337 a\\t\t\t\t\t\t\t\t\tif (response.service_log.vehicle_service_history_title != "" && response.service_log.vehicle_service_history_title !== null) {\n\t\t\t\t\t\t\t\t\t\t$("#serviceLogTitle").html("").html(utf8Decode(response.service_log.vehicle_service_history_title));\n\t\t\t\t\t\t\t\t\t} else
   {\n\t\t\t\t\t\t\t\t\t\t$("#serviceLogTitle").html("").html("N/A");\n\t\t\t\t\t\t\t\t\t}\n\t\t\t\t\t\t\t\t\tif (response.service_log.service_date != "" && response.service_log.service_date !== null)
   {\n\t\t\t\t\t\t\t\t\t\t$("#serviceLogDate").html("").html(response.service_log.service_date);\n\t\t\t\t\t\t\t\t\t} else {\n\t\t\t\t\t\t\t\t\t\t$("#serviceLogDate").html("").html("N/A");\n\t\t\t\t\t\t\t\t\t}' /home/anon/apps/portal/application/views/user/service-logs.php
   Add title and date population code

 Do you want to proceed?
 ❯ 1. Yes
   2. Yes, and don't ask again for sed commands in /home/anon/apps/portal
   3. Tell Claude what to do differently

[GlassBeaver]

I'm facing similar problems. If it's of any help, I asked claude to tell me what the problem is:

can you tell me what was causing your edits to fail and what I can do to fix it

To which it replied:

The issue was with how the Edit tool matches text - it requires exact whitespace matching, including:

1. Tabs vs Spaces: The codebase uses tabs, but when I copy text from the Read tool output, the line number prefix
   format obscures the actual indentation. The Read tool shows 340→ with the arrow, and everything after the tab
   following the arrow is the actual file content. I was mixing tabs and spaces in my search strings.
2. Line endings: Windows uses CRLF (\r\n), not LF (\n). When I construct multi-line strings in the tool
   parameters, they default to LF unless I'm careful.

What eventually worked:

• Reading the file first (required by Edit tool)
• Using smaller, unique snippets to match (less whitespace to get wrong)
• Matching the indentation exactly as shown AFTER the line number arrow in Read output
• The Edit tool automatically handles CRLF correctly when it reads/writes, so I didn't need to worry about that
  once I got the tabs right

What you could improve (if you control the tooling):

1. Make the Edit tool more lenient with whitespace matching (normalize tabs/spaces automatically)
2. Show the actual whitespace characters in Read output (like ^I for tab, $ for line end)
3. Add a parameter to Edit like normalize_whitespace: true that ignores differences in indentation
4. Better error messages - instead of just "String to replace not found", show what character position first
   differed

For now, the workaround is to use very small, unique code snippets when editing, so there's less whitespace to
match exactly.

I'm on Windows 11, in my case it's c++ and I'm using tabs instead of spaces for indentation. Line endings on Windows are CRLF and Claude mentions that its tooling was designed for LF so that's another problem.

[mj321]

Same here, using WSL/Windows 11. This is a serious issue for people who are affected.

[tskimmett]

This is still a problem and a massive time/token waster. Virtually every time I kick off an implementation after planning I'm hit with the dreaded Error editing file, followed by 2 minutes of claude trying to figure out how to insert a few lines of code in a file.

[d5ve]

I still run into this issue.

I have had some success with periodically adding the following to the chat.

This file uses tabs for indentation. Use Update() or Write() with tab support. You are forbidden to use Bash()/sed/awk/etc.

In most cases, the next few file edits do work.

[pdb0102]

I ran into the same problem and I added the following instruction to CLAUDE.md, which taught Claude how to not run into the issue:

## Edit Tool - Whitespace Handling

  The Read tool uses `→` to mark where line numbers end and file content begins.

  **Rule:** Copy the EXACT whitespace that appears after the `→` marker.
  - Whatever appears between `→` and the code text is what's actually in the file
  - That whitespace must be used EXACTLY in Edit tool's old_string
  - Don't count arrows, don't interpret - just copy what's after the `→`

  **Example:**
  14→		private byte tag;
  For Edit, use: `		private byte tag;` (copy everything after →, including the two tabs)

  **If Edit fails:** Stop and explain the problem. Do not attempt sed/awk/bash workarounds.

  **IMPORTANT**: Trust the Read tool output. Copy what's after `→` into Edit immediately. DO NOT verify with sed/od/grep first - that's wasting time and the instructions already tell you to stop if Edit fails, not to pre-verify.

[github-actions]

This issue has been inactive for 30 days. If the issue is still occurring, please comment to let us know. Otherwise, this issue will be automatically closed in 30 days for housekeeping purposes.