Provider Architecture Refactoring Design

Issue: #283 Discussion: #122 Branch: feat/refactor-provider-by-protocol

1. Current Problems

1.1 Configuration Structure Issues

Current State: Each Provider requires a predefined field in ProvidersConfig

type ProvidersConfig struct {
    Anthropic     ProviderConfig `json:"anthropic"`
    OpenAI        ProviderConfig `json:"openai"`
    DeepSeek      ProviderConfig `json:"deepseek"`
    Qwen          ProviderConfig `json:"qwen"`
    Cerebras      ProviderConfig `json:"cerebras"`
    VolcEngine    ProviderConfig `json:"volcengine"`
    // ... every new provider requires changes here
}

Problems:

• Adding a new Provider requires modifying Go code (struct definition)
• CreateProvider function in http_provider.go has 200+ lines of switch-case
• Most Providers are OpenAI-compatible, but code is duplicated

1.2 Code Bloat Trend

Recent PRs demonstrate this issue:

PR	Provider	Code Changes
#365	Qwen	+17 lines to http_provider.go
#333	Cerebras	+17 lines to http_provider.go
#368	Volcengine	+18 lines to http_provider.go

Each OpenAI-compatible Provider requires:

1. Modify config.go to add configuration field
2. Modify http_provider.go to add switch case
3. Update documentation

1.3 Agent-Provider Coupling

{
  "agents": {
    "defaults": {
      "provider": "deepseek",  // need to know provider name
      "model": "deepseek-chat"
    }
  }
}

Problem: Agent needs to know both provider and model, adding complexity.

---

2. New Approach: model_list

2.1 Core Principles

Inspired by LiteLLM design:

1. Model-centric: Users care about models, not providers
2. Protocol prefix: Use protocol/model_name format, e.g., openai/gpt-5.2, anthropic/claude-sonnet-4.6
3. Configuration-driven: Adding new Providers only requires config changes, no code changes

2.2 New Configuration Structure

{
  "model_list": [
    {
      "model_name": "deepseek-chat",
      "model": "openai/deepseek-chat",
      "api_base": "https://api.deepseek.com/v1",
      "api_key": "sk-xxx"
    },
    {
      "model_name": "gpt-5.2",
      "model": "openai/gpt-5.2",
      "api_key": "sk-xxx"
    },
    {
      "model_name": "claude-sonnet-4.6",
      "model": "anthropic/claude-sonnet-4.6",
      "api_key": "sk-xxx"
    },
    {
      "model_name": "gemini-3-flash",
      "model": "antigravity/gemini-3-flash",
      "auth_method": "oauth"
    },
    {
      "model_name": "my-company-llm",
      "model": "openai/company-model-v1",
      "api_base": "https://llm.company.com/v1",
      "api_key": "xxx"
    }
  ],

  "agents": {
    "defaults": {
      "model": "deepseek-chat",
      "max_tokens": 8192,
      "temperature": 0.7
    }
  }
}

2.3 Go Struct Definition

type Config struct {
    ModelList []ModelConfig `json:"model_list"`  // new
    Providers ProvidersConfig `json:"providers"`  // old, deprecated

    Agents   AgentsConfig   `json:"agents"`
    Channels ChannelsConfig `json:"channels"`
    // ...
}

type ModelConfig struct {
    // Required
    ModelName string `json:"model_name"`  // user-facing name (alias)
    Model     string `json:"model"`       // protocol/model, e.g., openai/gpt-5.2

    // Common config
    APIBase   string `json:"api_base,omitempty"`
    APIKey    string `json:"api_key,omitempty"`
    Proxy     string `json:"proxy,omitempty"`

    // Special provider config
    AuthMethod  string `json:"auth_method,omitempty"`   // oauth, token
    ConnectMode string `json:"connect_mode,omitempty"`  // stdio, grpc

    // Optional optimizations
    RPM            int    `json:"rpm,omitempty"`              // rate limit
    MaxTokensField string `json:"max_tokens_field,omitempty"` // max_tokens or max_completion_tokens
}

2.4 Protocol Recognition

Identify protocol via prefix in model field:

Prefix	Protocol	Description
openai/	OpenAI-compatible	Most common, includes DeepSeek, Qwen, Groq, etc.
anthropic/	Anthropic	Claude series specific
antigravity/	Antigravity	Google Cloud Code Assist
gemini/	Gemini	Google Gemini native API (if needed)

---

3. Design Rationale

3.1 Problems Solved

Problem	Old Approach	New Approach
Add OpenAI-compatible Provider	Change 3 code locations	Add one config entry
Agent specifies model	Need provider + model	Only need model
Code duplication	Each Provider duplicates logic	Share protocol implementation
Multi-Agent support	Complex	Naturally compatible

3.2 Multi-Agent Compatibility

{
  "model_list": [...],

  "agents": {
    "defaults": {
      "model": "deepseek-chat"
    },
    "coder": {
      "model": "gpt-5.2",
      "system_prompt": "You are a coding assistant..."
    },
    "translator": {
      "model": "claude-sonnet-4.6"
    }
  }
}

Each Agent only needs to specify model (corresponds to model_name in model_list).

3.3 Industry Comparison

LiteLLM (most mature open-source LLM Proxy) uses similar design:

model_list:
  - model_name: gpt-4o
    litellm_params:
      model: openai/gpt-5.2
      api_key: xxx
  - model_name: my-custom
    litellm_params:
      model: openai/custom-model
      api_base: https://my-api.com/v1

---

4. Migration Plan

4.1 Phase 1: Compatibility Period (v1.x)

Support both providers and model_list:

func (c *Config) GetModelConfig(modelName string) (*ModelConfig, error) {
    // Prefer new config
    if len(c.ModelList) > 0 {
        return c.findModelByName(modelName)
    }

    // Backward compatibility with old config
    if !c.Providers.IsEmpty() {
        logger.Warn("'providers' config is deprecated, please migrate to 'model_list'")
        return c.convertFromProviders(modelName)
    }

    return nil, fmt.Errorf("model %s not found", modelName)
}

4.2 Phase 2: Warning Period (late v1.x)

• Print more prominent warnings at startup
• Provide automatic migration script
• Mark providers as deprecated in documentation

4.3 Phase 3: Removal Period (v2.0)

• Completely remove providers support
• Remove agents.defaults.provider field
• Only support model_list

4.4 Configuration Migration Example

Old Config:

{
  "providers": {
    "deepseek": {
      "api_key": "sk-xxx",
      "api_base": "https://api.deepseek.com/v1"
    }
  },
  "agents": {
    "defaults": {
      "provider": "deepseek",
      "model": "deepseek-chat"
    }
  }
}

New Config:

{
  "model_list": [
    {
      "model_name": "deepseek-chat",
      "model": "openai/deepseek-chat",
      "api_base": "https://api.deepseek.com/v1",
      "api_key": "sk-xxx"
    }
  ],
  "agents": {
    "defaults": {
      "model": "deepseek-chat"
    }
  }
}

---

5. Implementation Checklist

5.1 Configuration Layer

• Add ModelConfig struct
• Add Config.ModelList field
• Implement GetModelConfig(modelName) method
• Implement old config compatibility conversion
• Add model_name uniqueness validation

5.2 Provider Layer

• Create pkg/providers/factory/ directory
• Implement CreateProviderFromModelConfig()
• Refactor http_provider.go to openai/provider.go
• Maintain backward compatibility for old CreateProvider()

5.3 Testing

• New config unit tests
• Old config compatibility tests
• Integration tests

5.4 Documentation

• Update README
• Update config.example.json
• Write migration guide

---

6. Risks and Mitigations

Risk	Mitigation
Breaking existing configs	Compatibility period keeps old config working
User migration cost	Provide automatic migration script
Special Provider incompatibility	Keep auth_method and other extension fields

---

7. References

• LiteLLM Config Documentation
• One-API GitHub
• Discussion #122: Refactor Provider Architecture