feat: Provider-agnostic LLM abstraction to support OpenAI, Bedrock, and Ollama

[Nanle-code]

Overview

The LLM enhancement layer is hardcoded to Anthropic Claude, blocking teams on OpenAI, AWS Bedrock, or self-hosted models from using AI-powered findings enhancement. A provider abstraction removes this vendor lock-in.

Proposed Abstraction

export interface LLMProvider {
  name: string;
  complete(prompt: string, systemPrompt?: string): Promise<string>;
}

export interface LLMProviderConfig {
  provider: 'anthropic' | 'openai' | 'bedrock' | 'ollama' | 'custom';
  model?: string;
  apiKey?: string;
  baseUrl?: string;        // for Ollama / self-hosted
  region?: string;         // for AWS Bedrock
  customProvider?: LLMProvider;
}

Provider Targets

Provider	Default Model
Anthropic	claude-sonnet-4-20250514
OpenAI	gpt-4o
AWS Bedrock	anthropic.claude-3-5-sonnet
Ollama	llama3 (localhost:11434)

Config File Support

{
  "llm": {
    "provider": "openai",
    "model": "gpt-4o",
    "apiKey": "${OPENAI_API_KEY}"
  }
}

Env variable interpolation supported in config values.

CLI Flags

chainproof scan contracts/ --llm-provider openai --llm-model gpt-4o --api-key sk-...

Acceptance Criteria

• LLMProvider interface and LLMProviderConfig type exported from core
• Anthropic, OpenAI, and Ollama provider implementations
• AWS Bedrock provider behind optional peer dependency
• customProvider field in ScanConfig
• --llm-provider and --llm-model CLI flags
• Config file llm block with env var interpolation
• Full backward compatibility with existing --api-key and ANTHROPIC_API_KEY
• Providers are lazy-loaded — no SDK imported if provider not used

[ZuLu0890]

I would like to work on this issue

[Vibeofkd]

Hi id love to work on this issue

[grantfox-oss]

🦊 GrantFox — @Vibeofkd has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #15)
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