[FEATURE] Allow configuring a separate model for auto mode classifier via environment variable

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Problem Statement

Currently, Claude Code's auto mode classifier automatically defaults to whichever main model is currently active in the session. For instance, when using a high-capability model like Claude 4.8 Opus as the primary model, the sub-task classification and routing decisions are also executed by Claude 4.8 Opus.

<img width="2019" height="1118" alt="Image" src="https://github.com/user-attachments/assets/f79cd40f-0345-4cab-b1f3-e0f5b5d8ea42" />

This behavior introduces two major pain points:

1. Performance Bottleneck (Slowness): Using a heavy, high-parameter model like Opus for simple intent classification or step routing drastically slows down the automated loop execution.
2. Exorbitant Costs: Running every minor classification check through Opus 4.8 rapidly consumes API tokens, making the workflow highly cost-inefficient.

Furthermore, Anthropic's own engineering blog post (https://www.anthropic.com/engineering/claude-code-auto-mode) highlights that Sonnet 4.6 already delivers highly effective and accurate results when acting as the auto mode permission classifier. Since Sonnet 4.6 is substantially faster and much more cost-effective, forcing the classifier to run on a heavy primary model like Opus 4.8 creates unnecessary overhead and prevents users from achieving the optimal balance of speed and cost outlined in your documentation.

Proposed Solution

We propose introducing a dedicated configuration option or environment variable—such as CLAUDE_CODE_AUTO_MODE_MODEL—to decouple the auto mode classifier from the main coding model.

For example, a user could configure their environment as follows:

export CLAUDE_CODE_AUTO_MODE_MODEL=claude-sonnet-4-6

Alternative Solutions

_No response_

Priority

High - Significant impact on productivity

Feature Category

CLI commands and flags

Use Case Example

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Additional Context

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