LangDriver

中文

LangDriver is a lightweight Agent runtime implemented in under 500 lines of Ruby, with ReAct, context compaction, persistent memory, Skills, MCP, Hooks, sandboxing, and permission approvals.

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Install

Requires macOS and Ruby 3.0+ (uses Reline shipped with Ruby 3).

git clone https://github.com/kevin0x5/langdriver && cd langdriver
ruby --version    # expect ruby 3.0+

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Configure

1. API key

export DEEPSEEK_API_KEY="YOUR_DEEPSEEK_API_KEY"

2. langdriver.yaml

The default config is already tuned for DeepSeek:

runtime:
  model: deepseek-v4-pro                # or deepseek-v4-flash (cheaper / faster)
  compact_model: deepseek-v4-flash      # used for async chat compaction; falls back to model
  api_base: https://api.deepseek.com    # DeepSeek endpoint; other providers may require request-field changes
  api_key_env: DEEPSEEK_API_KEY
  max_steps: 50
  extra:                                # forwarded verbatim into chat/completions request body
    max_tokens: 384000                  # DeepSeek v4 single-call max output
    reasoning_effort: max               # recommended for complex agent tasks
    thinking: { type: enabled }         # chain-of-thought (DeepSeek-V3.2+ supports tool calls in thinking mode)

Notes:

• Model names: use deepseek-v4-pro or deepseek-v4-flash. The compatibility names deepseek-chat / deepseek-reasoner will be retired on July 24, 2026.
• Context limits: DeepSeek v4 provides a 1M context window without an extra request field. Other providers may use different limits and field names; follow that provider’s API documentation instead of copying DeepSeek values.
• Max thinking effort: declared via top-level reasoning_effort and thinking fields. LangDriver pipes the entire runtime.extra block into the request body verbatim.
• Switch provider: LangDriver uses the Chat Completions message/tool shape, but provider-specific models, fields, streaming details, and authentication may still require configuration or code changes. Remove unsupported DeepSeek-only fields such as thinking when appropriate.

3. Other declarative files (project root)

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First run

ruby langdriver.rb

In the REPL:

> read sample.txt and summarize it in one sentence