Start by separating three settings: chat mode chooses the workflow, the architect model proposes a change, and the editor model plus its edit format turns that proposal into file edits. If Aider reports that a SEARCH block does not match, the editor's patch did not fit the file text it received; changing chat mode alone does not repair that mismatch. Aider's mode, edit-error, and option documentation was checked November 3, 2026.

What does architect mode do?

In architect mode, Aider sends the task to a main model for a proposed solution, then asks an editor model to produce concrete file edits. The editor can be selected with --editor-model; the editor's format is configured separately with --editor-edit-format. Aider documents editor-diff and editor-whole as recommended edit formats for this workflow. This is a two-request workflow and can take longer or cost more than one model request; it is not an approval-only mode.

Use /architect for one message, /chat-mode architect to switch the active session mode, or start Aider with --architect. Check the prompt indicator to see whether a message is in code, ask, or architect mode. For a discussion before you decide to edit, use /ask and then explicitly move to /code; Aider documents that as a separate workflow.

Why did a SEARCH/REPLACE block fail?

Aider's file-editing guide says this type of failure can happen when the model returns edits in a format the tool cannot apply. A SEARCH block must match the existing text, including whitespace, comments, and indentation. A GitHub issue reports this error with an architect/editor configuration, but it is an individual report, not evidence of how often it happens or proof of a current Aider defect.

1. Confirm which model and edit format Aider announced at startup. In architect mode, inspect both the main model and the editor model/format.
2. Check that the files to change are actually in the chat. Add only the relevant files; use /drop to remove unrelated ones.
3. For a SEARCH mismatch, inspect the current file and retry with a smaller, precisely scoped change. Do not paste a proposed replacement over a file without reviewing the diff.
4. If the editor repeatedly emits unusable patches, try the documented architect formats editor-diff or editor-whole, one at a time, and compare the result on a small task.
5. If you are using a local model, check its configured context window and whether it can follow the requested edit format. Aider's troubleshooting guide specifically flags context limits and model compliance as possible causes.

Which edit-format option should I change?

For architect mode's second step, the relevant setting is --editor-edit-format. The general --edit-format setting controls the normal editing path. The option names look similar, so verify the startup announcement and the current Aider options reference before changing one. A format choice is model-dependent: this guide does not prescribe one universal best format.

# Example: select an editor model and the documented editor-diff format
# Replace MODEL with a model identifier supported by your Aider setup.
aider --architect --editor-model MODEL --editor-edit-format editor-diff

Keep credentials in your existing provider configuration; do not paste API keys into a shared command history or report. The command above is a configuration shape, not a claim that every model/provider accepts every format.

Why did architect mode edit without asking me?

Architect mode divides reasoning and editing between models; that division does not itself promise a separate human approval step. A historical Aider issue documents user confusion about this distinction and the maintainer's explanation. Check the current option reference for the installed version's auto-accept setting, and make a clean Git checkpoint before trying a new mode or acceptance setting. Inspect git diff and run your normal checks before keeping the change.

If your goal is to review a plan before any edit, use ask mode to discuss it and then deliberately switch to code mode when ready. That makes the discussion/edit transition explicit in the workflow. It is still necessary to review any resulting changes.

How can I isolate the problem?

1. Record the Aider version and startup lines showing the main model, editor model, and formats.
2. Start from a clean Git diff and choose a small change in one file already added to the chat.
3. Try the same change in code mode and architect mode, changing one model or format setting per attempt.
4. Compare whether the proposed edit is relevant, whether it applies cleanly, and whether the project checks pass. This is a local troubleshooting trial, not a benchmark.
5. When asking for help, share the error and relevant startup details after removing secrets and private source code.

Public reports linked below are qualitative examples of user questions. They do not establish a failure rate. Check Aider's live docs for behavior that may have changed since this page was reviewed.

Related: Aider profile and Cline vs Aider workflow comparison.