[BUG] Write/Update tool failures with backslash escape sequences

Open geoffreybennett opened this issue 2 weeks ago • 2 comments

Preflight Checklist

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

What's Wrong?

Claude Code attempted and failed 15 times to replace this line using the Update tool:

    "Inputs →\n<span size=\"4pt\"> </span>\nOutputs ↓"

with this line:

    "<span line_height=\"1.5\">Inputs →</span>\nOutputs ↓"

What Should Happen?

Simple string writes or replacement should succeed on the first attempt.

Error Messages/Logs

The user wants me to continue with the edit. I have the current content now.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I need to use the exact string from the file, using \n escape sequences rather than actual newlines.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  The string in the file is a single line with escape sequences like \n. Let me match that exactly.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  The string in the file uses literal \n characters in the C string, not actual newlines. Let me match
  the entire line.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I see - the issue is that in the source file, the \n is actually the two characters \ and n, not a
  real newline. Let me try matching the whole line as it appears in the file exactly.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I keep making the same mistake. The file contains the literal string on one line with escape
  sequences. I need to match the whole line with the literal backslash-n characters. Let me match the
  entire line including the quotes.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I keep failing because I'm not properly representing the string. Let me try matching the whole C
  string literal exactly as it appears on line 310.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I keep repeating the same approach. Let me try a different approach - match the whole line.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I need to match the entire line with the escaped newline characters. The file shows:
      "Inputs →\n<span size=4pt> \nOutputs ↓"

  Let me read the file as raw bytes to see exactly what's in there, or let me just match the entire
  line.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I think I need to match the C source line that contains literal \n (backslash-n) characters. Let me
  try a different approach - match the whole line including indentation.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I keep making the same error. The problem is my parameters are being interpreted differently than I
  expect. Let me try a completely different approach - using the full line from the source.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  Something strange is happening with my parameter escaping. Let me try with more context around the
  string.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  Let me try matching the entire function call including quotes and backslash escapes.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  Let me try matching the entire content of the gtk_label_set_markup call.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  I need to see the actual raw content. Let me try using the Bash tool to see what's really in the file.

● Bash(sed -n '310p' window-mixer.c | cat -A)
  ⎿      "Inputs M-bM-^FM-^R\n<span size=\"4pt\"> </span>\nOutputs M-bM-^FM-^S"$

∴ Thinking…

  I can see the file contains literal \n characters (backslash followed by n), not actual newlines. The
  M-b M-^F M-^R and M-^S are UTF-8 encoded arrows (→ and ↓).

  Let me try a different approach - match the whole line exactly as it appears.

● Update(window-mixer.c)
  ⎿  Error: String to replace not found in file.
     String: Inputs →
     <span size="4pt"> </span>
     Outputs ↓

∴ Thinking…

  It seems my inputs are being transformed - my literal \n characters are being converted to newlines.
  Let me try a sed command instead to directly modify the file.

● Bash(sed -i 's|"Inputs →\\n<span size=\\"4pt\\"> </span>\\nOutputs ↓"|"<span
      line_height=\\"1.5\\">Inputs →</span>\\nOutputs ↓"|'
      window-mixer.c)
  ⎿  (No content)

∴ Thinking…

  Let me verify it worked.

● Read(window-mixer.c · lines 308-312)
  ⎿  Read 5 lines

∴ Thinking…

  Done. The change has been made successfully.

● Done. The label now uses line_height="1.5" instead of the hacky small span.

Steps to Reproduce

Ask Claude to:

Create a file test.txt with this one line of content (include spaces and quotes and note that the \n is a literal backslash followed by n, not a newline):

    "Inputs →\n<span size=\"4pt\"> </span>\nOutputs ↓"

(I used triple-backticks in my prompt)

Note how it cannot write the file with the Write tool, and switches to Bash instead after some failed attempts.
Ask Claude to:

Use the update tool to replace:

    "Inputs →\n<span size=\"4pt\"> </span>\nOutputs ↓"

with:

    "<span line_height=\"1.5\">Inputs →</span>\nOutputs ↓"

Note how it cannot update the file with the Update tool, and switches to Bash instead after some failed attempts.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

No response

Claude Code Version

2.0.76 (Claude Code)

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Xterm

Additional Information

No response

Dec 24 '25 17:12 geoffreybennett