Dynamically selecting the model that claude-code-action should run with

[tobiasbueschel]

Hi 👋 thanks a lot for this great project - it's a really nice use case to be able to run Claude Code in a repository!

Is there a way to dynamically select the model that Claude Code should use by specifying it in the comment? For example like so:

@claude opus please fix this bug

I've tried the following configuration but without success:

name: Claude Code

on:
  issue_comment:
    types: [created]
  pull_request_review_comment:
    types: [created]
  issues:
    types: [opened, assigned]
  pull_request_review:
    types: [submitted]

jobs:
  claude:
    if: |
      (github.event_name == 'issue_comment' && contains(github.event.comment.body, '@claude')) ||
      (github.event_name == 'pull_request_review_comment' && contains(github.event.comment.body, '@claude')) ||
      (github.event_name == 'pull_request_review' && contains(github.event.review.body, '@claude')) ||
      (github.event_name == 'issues' && (contains(github.event.issue.body, '@claude') || contains(github.event.issue.title, '@claude')))
    runs-on: ubuntu-latest
    needs: install-dependencies
    permissions:
      contents: read
      pull-requests: read
      issues: read
      id-token: write
      actions: read
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 1

      - name: Parse model from comment
        id: parse-model
        run: |
          COMMENT_BODY="${{ github.event.comment.body || github.event.review.body || github.event.issue.body || github.event.issue.title }}"

          # Simple syntax: @claude opus @claude sonnet
          if echo "$COMMENT_BODY" | grep -qi "\b@claude\s+opus\b"; then
            MODEL="claude-opus-4-20250514"
            echo "model=$MODEL" >> $GITHUB_OUTPUT
            echo "Using model: $MODEL"
          elif echo "$COMMENT_BODY" | grep -qi "\b@claude\s+sonnet\b"; then
            MODEL="claude-sonnet-4-20250514"
            echo "model=$MODEL" >> $GITHUB_OUTPUT
            echo "Using model: $MODEL"
          fi

      - name: Run Claude Code
        id: claude
        uses: anthropics/claude-code-action@beta
        with:
          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}

          model: ${{ steps.parse-model.outputs.model }}

          additional_permissions: |
            actions: read

          claude_env: |
            ANTHROPIC_BASE_URL: ${{ vars.ANTHROPIC_BASE_URL }}

When I then comment and see Claude Code running in GH, it defaults back to Sonnet:

[halfstack-dev]

For anyone looking for something that does this, this code snippet below works for me.
You can invoke a model by writing opus or sonnet as the first word after claude.

Only downside to this is that user-message passed to the model includes the word opus or sonnet. It would be an improvement if this was supported OOTB.

name: Claude Code

on:
  issue_comment:
    types: [created]
  pull_request_review_comment:
    types: [created]
  issues:
    types: [opened, assigned]
  pull_request_review:
    types: [submitted]

jobs:
  claude:
    if: |
      (github.event_name == 'issue_comment' && contains(github.event.comment.body, '@claude')) ||
      (github.event_name == 'pull_request_review_comment' && contains(github.event.comment.body, '@claude')) ||
      (github.event_name == 'pull_request_review' && contains(github.event.review.body, '@claude')) ||
      (github.event_name == 'issues' && (contains(github.event.issue.body, '@claude') || contains(github.event.issue.title, '@claude')))
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: read
      issues: read
      id-token: write
      actions: read # Required for Claude to read CI results on PRs
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 1

      - name: Pick model from trigger body
        id: model
        env:
          COMMENT_BODY: ${{ github.event.comment.body }}
          REVIEW_BODY: ${{ github.event.review.body }}
          ISSUE_BODY: ${{ github.event.issue.body }}
          ISSUE_TITLE: ${{ github.event.issue.title }}
        run: |
          body=$(printf '%s\n%s\n%s\n%s\n' "$COMMENT_BODY" "$REVIEW_BODY" "$ISSUE_BODY" "$ISSUE_TITLE" | tr '[:upper:]' '[:lower:]')
          if printf '%s' "$body" | grep -Eq '@claude[[:space:]]+opus\b'; then
            echo "model=opus" >> "$GITHUB_OUTPUT"
          elif printf '%s' "$body" | grep -Eq '@claude[[:space:]]+sonnet\b'; then
            echo "model=sonnet" >> "$GITHUB_OUTPUT"
          else
            echo "model=" >> "$GITHUB_OUTPUT"
          fi

      - name: Run Claude Code
        id: claude
        uses: anthropics/claude-code-action@v1
        with:
          claude_code_oauth_token: ${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}

          # This is an optional setting that allows Claude to read CI results on PRs
          additional_permissions: |
            actions: read

          # Optional: Give a custom prompt to Claude. If this is not specified, Claude will perform the instructions specified in the comment that tagged it.
          # prompt: 'Update the pull request description to include a summary of changes.'

          # Pass --model when the trigger body mentions "opus" or "sonnet"; otherwise use the action default.
          claude_args: ${{ steps.model.outputs.model != '' && format('--model {0}', steps.model.outputs.model) || '' }}