Edit an app file

<Info>This API is in beta. Endpoints, fields, and behavior may still change, so avoid depending on it in production.</Info>

Applies exact-string edits to a file in the app's sandbox and returns the diff.

Every sandbox-bridge endpoint runs against the app's live sandbox, the same filesystem the Base44 builder edits, so a change here is visible in the builder immediately.

Send up to 100 edits and Base44 applies them in order, all or nothing: if any one fails to match, the file is left untouched and the request answers 400. Each old_text has to match exactly, and has to be unique in the file unless you set replace_all on that edit.

Set dry_run: true to get the same diff back without writing. A dry run answers with applied as false and no warnings key at all, so read applied rather than checking for warnings. A dry run still needs write access, because it is the edit tool.

Prefer this over Write an app file for changing part of a file: you send only the strings involved, and the response shows exactly what changed.

This endpoint is limited to 60 requests per minute per app, shared with the other sandbox-bridge endpoints that change files.

<Warning>A write is committed, not checkpointed. Only checkpoints appear in the builder's version history, and a Restore or Revert there rolls the app back to the last checkpoint and discards everything written after it. Call Create a sandbox checkpoint when you finish a unit of work and before you stop.</Warning>

<Note>The sandbox bridge needs a Builder plan or higher on the app's workspace, and answers 402 below that. Workspace API keys are not authorized and are rejected with a 403, and it is unavailable for agent apps. A personal API key works as-is. An OAuth access token needs the sandbox:write scope.</Note>

<Tip>Every error response carries a stable extra_data.code alongside the human-readable message. Branch on the code rather than on the message text or the status.</Tip>

{
  "path": "src/pages/Home.jsx",
  "diff": "--- src/pages/Home.jsx\n+++ src/pages/Home.jsx\n@@ -1,3 +1,3 @@\n-  return <h1>Hello</h1>;\n+  return <h1>Welcome</h1>;\n",
  "applied": true,
  "warnings": []
}