ACP writeTextFile fails with "invalid path" when target file does not exist

[yiliang114]

What happened?

When using ACP's writeTextFile to write to a file path that does not yet exist (i.e., creating a new file), the operation fails with an "invalid path" error instead of creating the file.

The CLI sends a writeTextFile request via ACP protocol to the IDE companion. If the target file does not exist on disk, the request is rejected with an error containing "invalid path" in the data or message field, preventing new file creation.

This means ACP writeTextFile can only overwrite existing files but cannot create new ones.

What did you expect to happen?

writeTextFile should create the file (and any missing parent directories) when the target path does not exist, similar to how the local filesystem fallback behaves using fs.mkdir(recursive) + fs.writeFile.

Client information

Client Information

• OS: Darwin 24.1.0 arm64
• Node: v22.22.0
• VSCode: 1.111.0

[Br1an67]

I have submitted a fix for this in PR #2483.

Root cause: AcpFileSystemService.writeTextFile() had no error handling — when the IDE companion rejected the request (e.g. for a non-existent file), the error propagated directly to the caller. The readTextFile method already had similar fallback logic, but writeTextFile was missing it.

Fix: Wrapped the ACP writeTextFile call in a try/catch that falls back to the local filesystem service on failure. The local path handles new file creation correctly since WriteFileTool creates parent directories before calling writeTextFile.

[yiliang114]

@Br1an67 Thanks a lot for digging into this so quickly, and really appreciate you opening PR #2483.

I’m going to double-check whether this issue is still reproducible on the latest main, since there have been some recent changes around the ACP / IDE companion file write flow and it may already have been fixed.

Either way, thanks again for the investigation and the proposed fallback approach. I’ll verify it on my side and follow up here shortly.

[tanzhenxin]

By design