Edit

Replace an exact substring in a file. On Go projects, lint findings for the edited file are appended to the success message. On Python / Node / Rust projects, a single-file format check (ruff format --check --diff, prettier --check, rustfmt --check) is appended under --- format ---.

Schema

Param	Type	Required	Default	Notes
file_path	string	yes	—	Absolute or workspace-relative path.
old_string	string	yes	—	Must be non-empty.
new_string	string	yes	—	May be empty (deletes the match).
replace_all	boolean	no	false	If false and old_string appears more than once, call is rejected.

Behaviour

1. Resolve the path (containment check).
2. Verify the file exists and isn’t a directory.
3. Verify the file has been Read in the current session — otherwise refusing to edit %s: Read it first.
4. Verify old_string is non-empty (prevents an os.WriteFile-shaped corruption path).
5. Count occurrences of old_string:
   • 0 → error old_string not found in %s
   • 1 → replace, atomic write.
   • >1 with replace_all=false → error old_string matched N times in %s; add context to make it unique or set replace_all=true
   • >1 with replace_all=true → replace all, atomic write.
6. On success, run the project’s linter with a 30s timeout. If any findings apply to the edited file, append them to the response.
7. If the detected language declares a per-file format check (Detector.FormatCheckCmd) and its binary is on PATH, run it with a 10s timeout and append any output under a --- format --- header. Go’s FormatCheckCmd is nil (its lint path already covers gofmt), so Go edits never render a format section.

Post-edit lint feedback

The “single biggest quality win” per the project proposal. On Go projects, after every successful Edit:

1. verify.Lint runs golangci-lint run ./... from the workspace root.
2. Findings are parsed into structured file:line:col:rule: message records.
3. Findings whose file matches the edited path are appended to the success body.

Best-effort: if the linter times out, isn’t installed, or the project isn’t Go, the base success message is unchanged.

See Post-edit lint feedback.

Post-edit format check

On non-Go projects, after the lint section (if any), Edit runs the detector’s FormatCheckCmd against the edited file with a 10s timeout. Per language:

Language	Command	Notes
Go	(nil)	Skipped — the lint path already covers gofmt / gofumpt coverage.
Python	ruff format --check --diff <file>	--diff prints the fix ruff would apply; --check keeps it non-destructive.
Node	prettier --check <file>	Assumes prettier is on PATH directly; projects installing it locally shadow via a wrapper script.
Rust	rustfmt --check <file>	Edition is inherited from the enclosing Cargo.toml.

Output rules:

• Formatter exit 0 (file is formatted) → no section rendered.
• Formatter exit non-zero with output → appended under --- format ---, truncated to 500 lines.
• Detector declares a formatter but the binary isn’t on PATH → a single line post-edit format: <binary> not found on PATH is appended (Edit never fails on format feedback).

Example output

Clean edit:

replaced 1 occurrence(s) in probe.go

Edit that introduces a lint violation:

replaced 1 occurrence(s) in probe.go

post-edit lint findings (1):
probe.go:5:3:errcheck: Error return value of `os.WriteFile` is not checked

Edit on a Python file that’s not formatted (rendered under --- format ---):

replaced 1 occurrence(s) in app.py

--- format ---
--- app.py
+++ app.py
@@ -1 +1 @@
-x=1
+x = 1

Related

• Read — prerequisite.
• Write — for whole-file replacement.
• run_lint — explicit whole-project lint run.