[SDK] Claude Code provider for .harness()

[santoshkumarradha]

Overview

Implement the Claude Code provider using native SDKs (claude_agent_sdk for Python, @anthropic-ai/claude-agent-sdk for TypeScript). SDK-first approach — no subprocess.

Branch: feat/harness-v2
Design doc: docs/design/harness-v2-design.md (Sections 4, 10.1)

Scope

Python (sdk/python/agentfield/harness/providers/)

• claude.py — ClaudeCodeProvider implementing HarnessProvider:
  • Uses claude_agent_sdk.query() async generator
  • Maps HarnessOptions → ClaudeAgentOptions
  • Collects messages, extracts result text, builds metrics
  • Lazy import of claude_agent_sdk (optional dependency)
  • Graceful error if SDK not installed
• Register in _factory.py for provider name "claude-code"
• Tests with mocked claude_agent_sdk (mock the query generator)

TypeScript (sdk/typescript/src/harness/providers/)

• claude.ts — ClaudeCodeProvider implementing HarnessProvider:
  • Uses @anthropic-ai/claude-agent-sdk query function
  • Same mapping and collection logic
  • Optional peer dependency
• Register in factory.ts
• Tests with mocked SDK

Key Details

• claude_agent_sdk supports: model, cwd, max_turns, allowed_tools, system_prompt, max_budget_usd, permission_mode, env
• Output is async generator of messages — collect into list, extract final text
• Session ID from SDK response for potential resume
• Cost from usage metrics in response

Acceptance Criteria

• Provider correctly maps all HarnessOptions to Claude SDK options
• Handles SDK not installed (ImportError → clear error message)
• Collects all messages and extracts final text result
• Extracts cost/usage metrics
• Registered in factory under "claude-code"
• All tests pass with mocked SDK

Dependencies

• Depends on: [SDK] Core types & provider interface for .harness() #199 (types), [SDK] HarnessRunner with retry & schema orchestration for .harness() #201 (runner)
• Blocks: [SDK] Wire .harness() into Agent class #204

[github-actions]

Thanks for picking this up, @santoshkumarradha! 🎉

Here's what to expect:

• We'll check in after 7 days if we haven't heard an update
• After 14 days, we'll send a second reminder
• After 21 days without activity, we'll unassign to let others contribute

Tips for success:

• Drop a comment when you start working on it
• Share any blockers - we're here to help!
• Link your PR with Fixes #202 in the description

Happy coding! 🚀