/weak-model
Switches the Weak Model responsible for commit messages and chat history summarization.
/weak-model <name> sets the so-called weak model: a cheaper/faster secondary model that Aider uses internally for side tasks like writing commit messages and summarizing older chat history, while the main model (/model) handles the actual code changes. On the command line this corresponds to --weak-model WEAK_MODEL.
✅ WHEN TO USE IT?
Cut costs without hurting the quality of the actual code answers
/weak-model anthropic/claude-haiku-4-5, while the main model stays a more capable model
Use a different model when the default doesn't produce good commit messages
Switch /weak-model to another model when the current weak model's generated commit messages are imprecise
⛔ WHEN NOT TO?
You want to improve the quality of the actual code answers
The weak model only affects side tasks (commit messages, history summarization), not the code suggestions themselves.
Better: Use /model to switch the main model
No deliberate reason for a second, weaker model (e.g. a solo setup with only one model available anyway)
An unnecessarily weak weak-model can, e.g., lead to worse commit messages without any real cost benefit if only one model is available anyway.
Better: Leave the weak model at Aider's sensible default
SOURCES
- Aider Docs — In-chat Commands ↗ aider.chat