subagent-tuner

subagent-tuner is an open-source Claude Code mod published under the MIT license by Kruhlikau. When the agent starts a subagent, it settles that subagent's model and reasoning effort by asking the user, by a recommendation based on the kind of task, or by a saved default. The latest listed release is v0.1.4, and it requires Claude Code 2.1.287 or later.

What It Is

subagent-tuner is a plugin (mod) for Claude Code that intercepts Agent calls and sets only their model and effort fields. The aim is for a review to run on Opus while a file search runs on a cheaper, faster model. It shows a band above the prompt with the current mode and saved default, and it stores both in Claude Code's own plugin store so they persist across sessions.

How the modes work

Manual is the default after install and asks before a subagent starts. On terminals 144 columns wide or more the question appears as a pane beside the transcript, with model and effort selectors and options to run, run and save as default, or cancel. On narrower terminals it uses a short chain of dialogs. A dismissed question starts the subagent with what was shown.

Auto never asks. The saved default wins, even over a model or effort the agent set itself, such as a CLAUDE.md rule that passes model: "opus". A field left at the recommendation setting keeps what the call set, otherwise takes the recommendation. A toast reports what was applied.

The recommendation

The task kind is inferred from the subagent's type, else its description. Review, audit, verify, adversarial and security tasks map to opus with high effort. Implement, build and fix map to sonnet with medium effort. Explore, search and research map to haiku with low effort. Prompts longer than 4,000 characters get one step more effort, and other tasks inherit the session's model and effort.

Scope and safeguards

It leaves claude -p and SDK-hosted runs unchanged and never touches forks. In the VS Code extension it cannot show the band, so it behaves as Auto. The README states it reads each Agent call's subagent type, description, model, effort and prompt length, and makes no network calls. It runs sh or powershell.exe only to wait for the pane answer, and writes an empty sentinel file in its own .waits/ folder.

Setup path

Install inside Claude Code with /plugin install subagent-tuner --marketplace Kruhlikau/subagent-tuner, choose the user scope, and it works in that session. Alternatives include a two-step marketplace add, a shell command, or loading a local clone with --plugin-dir. The README reports testing on Claude Code 2.1.295 and 2.1.296 on macOS and Windows 11.