Add Claude Code instructions file

CLAUDE.md

@@ -0,0 +1,111 @@
+# Absolute Rules
+
+## Pull Requests
+
+- ALWAYS push branches to `DataDog/dd-trace-rb`, not forks
+- ALWAYS use `--repo DataDog/dd-trace-rb` with gh commands (defaults are unreliable)
+- PR descriptions MUST use `.github/PULL_REQUEST_TEMPLATE.md` as the starting point
+- Write for the developer performing code review; be concise
+- Use one sentence per relevant point in summary/motivation sections
+- Changelog entries are written for customers only; consider changes from user/customer POV
+- Internal changes (telemetry, CI, tooling) = "None" for changelog
+- Add `--label "AI Generated"` when creating PRs (do not mention AI in description; label is sufficient)
+
+## Never
+
+- Commit secrets, tokens, or credentials
+- Edit files under `gemfiles/` (auto-generated; use `bundle exec rake dependency:generate`)
+- Change versioning (`lib/datadog/version.rb`, `CHANGELOG.md`)
+- Leave resources open (terminate threads, close files)
+- Make breaking public API changes
+
+## Ask First
+
+- Modifying dependencies in `datadog.gemspec`, `appraisal/`, or `Matrixfile`
+- Editing CI workflows or release automation
+- Touching vendored third-party code (except `vendor/rbs`)
+- Modifying `@public_api` annotated code (read `docs/PublicApi.md` first)
+
+## GitHub Actions
+
+When creating or modifying workflows in `.github/workflows/`:
+
+### Security
+
+- NEVER interpolate user input directly in `run:` blocks - use `env:` instead:
+  ```yaml
+  # BAD: run: echo "${{ github.event.comment.body }}"
+  # GOOD:
+  env:
+    COMMENT: ${{ github.event.comment.body }}
+  run: echo "$COMMENT"
+  ```
+- User-controllable inputs: `github.event.comment.body`, `github.event.issue.title`, `github.event.pull_request.title`, `github.head_ref`
+- Pin actions to SHA: `uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2`
+- Set `permissions: {}` at workflow level; explicit minimal permissions per job
+- Prefer `pull_request` over `pull_request_target`
+
+### Shell Scripts
+
+- Always quote variables: `"$VAR"` not `$VAR`
+- Quote `$GITHUB_OUTPUT`: `echo "key=value" >> "$GITHUB_OUTPUT"`
+- Group multiple redirects: `{ echo "a"; echo "b"; } >> "$GITHUB_OUTPUT"`
+- Avoid heredocs; use echo grouping instead
+
+### Validation
+
+```bash
+yamllint --strict .github/workflows/your-workflow.yml
+actionlint .github/workflows/your-workflow.yml
+```
+
+## Code Changes
+
+- Read files before editing them
+- When user says "suggest" or asks a question: analyze only, do not modify code
+- When user says "fix", "change", "update": make the changes
+- If a requested change contradicts code evidence, alert user before proceeding
+- If unable to access a requested web page, explicitly state this and explain basis for any suggestions
+
+## Environment Variables
+
+- Use `DATADOG_ENV`, never `ENV` directly (see `docs/AccessEnvironmentVariables.md`)
+- Run `rake local_config_map:generate` when adding new env vars
+
+# Reference
+
+See `AGENTS.md` for:
+- Project structure and directory layout
+- Docker container setup (`docker compose run --rm tracer-3.4 /bin/bash`)
+- Bundle, rake, and rspec commands
+- Integration patterns (`patcher.rb`, `integration.rb`, `ext.rb`, `configuration/settings.rb`)
+
+See `docs/` for:
+- `DevelopmentGuide.md` - detailed development workflows
+- `GettingStarted.md` - user-facing documentation (update when adding settings/env vars)
+- `StaticTypingGuide.md` - RBS and Steep usage
+- `PublicApi.md` - public API guidelines
+
+## Quick Commands
+
+```bash
+bundle exec rake test:main              # Smoke tests
+bundle exec rake standard typecheck     # Lint and type check
+bundle exec steep check [sources]       # Type check (sources = files or dirs, optional)
+bundle exec rspec spec/path/file_spec.rb:123  # Run specific test
+```
+
+## Gotchas
+
+- Pipe rspec output: `2>&1 | tee /tmp/rspec.log | grep -E 'Pending:|Failures:|Finished' -A 99`
+- Transport noise (`Internal error during Datadog::Tracing::Transport::HTTP::Client request`) is expected
+- Profiling specs fail on macOS without additional setup
+
+# Style
+
+Enforced by StandardRB: `bundle exec rake standard:fix`
+
+Additional team preferences:
+- Trailing commas in multi-line arrays, hashes, and arguments
+- RBS type definitions in `sig/` mirror `lib/` structure
+- Avoid `untyped`; use `Type?` not `(nil | Type)`

spec/datadog/release_gem_spec.rb

@@ -32,6 +32,7 @@
            |Gemfile
            |AGENTS\.md
            |AGENTS_TODO\.md
+           |CLAUDE\.md
            |(ruby|jruby)-\d+.\d+.gemfile
            |Rakefile
            |Matrixfile