write_to_file truncates filenames at special characters before file extensions

[Sonic-Ninja]

Problem (one or two sentences)

The write_to_file tool truncates filenames when the filename includes certain characters before the extension (e.g., hyphens, capitalization/camel case, or hyphens in parent directory names). This results in files being created with incomplete names and/or missing file extensions.

Context (who is affected and when)

This prevents generating files that follow common naming conventions, especially in JS/TS ecosystems where the following are standard:

kebab-case (my-file.ts)

CamelCase/PascalCase (MyFile.ts)

snake_case (my_file.ts)

numeric prefixes + hyphens (09-testing.md)

In practice, it breaks scaffolding workflows and automation since file names become corrupted and missing extensions.

Reproduction steps

Pattern / Heuristics Observed

Truncation appears to occur at:

Hyphens (-) near the filename/extension boundary
worker-service.ts → worker-

Periods (.) with CamelCase filenames
WorkerService.ts → WorkerService.

Hyphens in directory segments near the filename
09-testing.md → 09

This suggests the path parsing may be incorrectly tokenizing on - or . (or performing unsafe sanitization) and failing to preserve the full basename + extension.

Files That Worked Correctly (Control Cases)

These appear to succeed because they use simple lowercase naming without special characters:

src/worker/types/index.ts ✅

terraform/shared/backend.tf ✅

Expected result

write_to_file should create files using the exact path and filename provided, including the complete base name and file extension.

Actual result

When the target filename contains specific characters before the extension, the created file name is truncated.

Variations tried (optional)

No response

App Version

3.37.1

API Provider (optional)

Amazon Bedrock

Model Used (optional)

Claude Sonnet 4.5 and Opus 4.5

Roo Code Task Links (optional)

No response

Relevant logs or errors (optional)

[roomote]

Hi @Sonic-Ninja, thank you for the detailed bug report! I'd like to help investigate this issue, but I need some additional information to reproduce it:

1. Can you confirm the actual file on disk is truncated? When you navigate to the created file in VS Code's file explorer, is the filename actually truncated (e.g., worker- instead of worker-service.ts), or is this just how it appears in the Roo Code UI?

2. Could you share the exact prompt or tool call JSON? If you can expand the tool call in the chat history and share what path value was actually passed to write_to_file, that would help identify whether the truncation happens before or after the tool is called.

3. Are you using XML protocol or native tool calling? This can be found in your API provider settings.

4. Is this reproducible? If you try to create a file like test-file.ts or TestFile.ts again, does the same truncation occur?

5. Could you share the specific task/prompt that led to this issue? Understanding the context might help identify if the model itself is truncating the path.

This information will help me determine whether:

• The model is generating truncated paths
• The XML/native parser is mishandling the path
• The file system is having issues with certain characters
• This is a display issue in the UI

Please mention @roomote in your response with these details, and I'll be happy to investigate further and propose a fix.

[mrubens]

Interesting, can you repro this reliably? I thought I saw it yesterday.

[nabilfreeman]

I'm also having serious issues with native tool calling on Bedrock. Very interesting that you are having it too. The versions of Anthropic models on Bedrock are a special version so it could be that they implement native tool calling differently.

My issue specifically is when Claude Sonnet/Opus tries to write an index.ts file - it omits the index part and tries to write the directory path.

For example:

1. Try to write foo/bar/index.ts
2. Native tool calls write foo/bar
3. Error EISDIR - this soft locks Roo and leaves it frozen in Save/Reject buttons greyed out state. The only solution is Restart Extension Host

I have reverted back to 3.36.16 where I can still switch to XML tool calls.

Edit: Actually, thinking more carefully about this, I've seen issues where long file paths have been truncated as well. Not necessarily omitting index.ts only but better matching your description:

foo/bar/baz/index.ts write_file instead writes to foo/bar, omitting much of the later part of the path.

Usually after I restart extension host, I say to Roo: "Looks like there is a tool problem, please try to write the file using cat command." Then, it actually tries to write to the bad path, gets a recoverable error this time, and finally fixes itself.

The most frustrating thing about this is the soft locking of Roo. So, ideally EISDIR does not result in such a bad fail state.

[mrubens]

I'm seeing this too. We'll dig in.