feat: automate changelog updates in release workflow (#231)

Replace GitHub API-based commits with local git workflow and integrate
claude-code-action to automatically generate changelog entries. The
workflow now:
- Creates release branch locally with version commits
- Uses Claude to review changes and update CHANGELOG.md
- Pushes complete branch with all commits together

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/publish.yml

@@ -104,66 +104,79 @@ jobs:
         echo "Package published to PyPI"
         echo "Install with: pip install claude-agent-sdk==${{ env.VERSION }}"
     
-    - name: Create version update PR
-      env:
-        GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    - name: Get previous release tag
+      id: previous_tag
+      run: |
+        PREVIOUS_TAG=$(git describe --tags --abbrev=0 2>/dev/null || echo "")
+        echo "previous_tag=$PREVIOUS_TAG" >> $GITHUB_OUTPUT
+        echo "Previous release: $PREVIOUS_TAG"
+
+    - name: Create release branch and commit version changes
       run: |
         # Create a new branch for the version update
         BRANCH_NAME="release/v${{ env.VERSION }}"
         echo "BRANCH_NAME=$BRANCH_NAME" >> $GITHUB_ENV
-        
-        # Create branch via API
-        BASE_SHA=$(git rev-parse HEAD)
-        gh api \
-          --method POST \
-          /repos/$GITHUB_REPOSITORY/git/refs \
-          -f ref="refs/heads/$BRANCH_NAME" \
-          -f sha="$BASE_SHA"
-        
-        # Get current SHA values of files
-        echo "Getting SHA for pyproject.toml"
-        PYPROJECT_SHA=$(gh api /repos/$GITHUB_REPOSITORY/contents/pyproject.toml --jq '.sha')
-        echo "Getting SHA for _version.py"
-        VERSION_SHA=$(gh api /repos/$GITHUB_REPOSITORY/contents/src/claude_agent_sdk/_version.py --jq '.sha')
 
-        # Commit pyproject.toml via GitHub API (this creates signed commits)
-        message="chore: bump version to ${{ env.VERSION }}"
-        base64 -i pyproject.toml > pyproject.toml.b64
-        gh api \
-          --method PUT \
-          /repos/$GITHUB_REPOSITORY/contents/pyproject.toml \
-          -f message="$message" \
-          -F content=@pyproject.toml.b64 \
-          -f sha="$PYPROJECT_SHA" \
-          -f branch="$BRANCH_NAME"
+        # Configure git
+        git config --local user.email "github-actions[bot]@users.noreply.github.com"
+        git config --local user.name "github-actions[bot]"
+
+        # Create and switch to new branch
+        git checkout -b "$BRANCH_NAME"
+
+        # Commit version changes
+        git add pyproject.toml src/claude_agent_sdk/_version.py
+        git commit -m "chore: bump version to ${{ env.VERSION }}"
+
+    - name: Update changelog with Claude
+      continue-on-error: true
+      uses: anthropics/claude-code-action@v1
+      with:
+        prompt: |
+          You are updating the changelog for the new release v${{ env.VERSION }}.
+
+          Update CHANGELOG.md to add a new section for version ${{ env.VERSION }} at the top of the file, right after the '# Changelog' heading.
+
+          Review the recent commits and merged pull requests since the last release (${{ steps.previous_tag.outputs.previous_tag }}) to generate meaningful changelog content for v${{ env.VERSION }}. Follow the existing format in CHANGELOG.md with sections like:
+          - Breaking Changes (if any)
+          - New Features
+          - Bug Fixes
+          - Documentation
+          - Internal/Other changes
+
+          Include only the sections that are relevant based on the actual changes. Write clear, user-focused descriptions.
+
+          After updating CHANGELOG.md, commit the changes with the message "docs: update changelog for v${{ env.VERSION }}".
+        anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+        claude_args: |
+          --allowedTools 'Bash(git add:*),Bash(git commit:*),Edit'
+
+    - name: Push branch and create PR
+      env:
+        GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      run: |
+        # Push the branch with all commits
+        git push origin "${{ env.BRANCH_NAME }}"
 
-        # Commit _version.py via GitHub API
-        base64 -i src/claude_agent_sdk/_version.py > version.py.b64
-        gh api \
-          --method PUT \
-          /repos/$GITHUB_REPOSITORY/contents/src/claude_agent_sdk/_version.py \
-          -f message="$message" \
-          -F content=@version.py.b64 \
-          -f sha="$VERSION_SHA" \
-          -f branch="$BRANCH_NAME"
-        
         # Create PR using GitHub CLI
         PR_BODY="This PR updates the version to ${{ env.VERSION }} after publishing to PyPI.
-        
+
         ## Changes
         - Updated version in \`pyproject.toml\`
         - Updated version in \`src/claude_agent_sdk/_version.py\`
-        
+        - Updated \`CHANGELOG.md\` with release notes
+
         ## Release Information
         - Published to PyPI: https://pypi.org/project/claude-agent-sdk/${{ env.VERSION }}/
         - Install with: \`pip install claude-agent-sdk==${{ env.VERSION }}\`
-        
+
         🤖 Generated by GitHub Actions"
-        
+
         PR_URL=$(gh pr create \
-          --title "chore: bump version to ${{ env.VERSION }}" \
+          --title "chore: release v${{ env.VERSION }}" \
           --body "$PR_BODY" \
           --base main \
-          --head "$BRANCH_NAME")
-        
+          --head "${{ env.BRANCH_NAME }}")
+
         echo "PR created: $PR_URL"