Twilight AI

When To Use

Use this skill when the task involves twilight-ai, especially:

• implementing or refactoring SDK APIs in sdk/
• adding or updating providers under provider/
• working on GenerateText, GenerateTextResult, StreamText, Embed, or EmbedMany
• adding tool-calling, streaming, reasoning, or embedding support
• writing examples, docs, or usage guidance for this library

Project Snapshot

Twilight AI is a lightweight Go AI SDK with a provider-agnostic core API.

• Text generation: sdk.GenerateText, sdk.GenerateTextResult, sdk.StreamText
• Embeddings: sdk.Embed, sdk.EmbedMany
• Tool calling: sdk.Tool, sdk.NewTool[T], WithMaxSteps, approval flow
• MCP tool integration: sdk.CreateMCPClient, sdk.MCPClient, sdk.MCPClientConfig
• Streaming: typed StreamPart events over Go channels
• Current providers:
  • provider/openai/completions
  • provider/openai/responses
  • provider/anthropic/messages
  • provider/google/generativeai
  • provider/openai/embedding
  • provider/google/embedding

Default Mental Model

Prefer the high-level SDK API first, then drop to provider details only when needed.

• sdk.Model binds a chat model to a sdk.Provider
• sdk.EmbeddingModel binds an embedding model to an sdk.EmbeddingProvider
• The client orchestrates tool loops, callbacks, approvals, and streaming lifecycle
• MCP clients can load remote MCP tools and turn them into ordinary sdk.Tool values
• Providers handle backend-specific HTTP, request mapping, response parsing, and SSE translation

Core API Guidance

Choose the narrowest API that matches the task:

• Need only final text: use sdk.GenerateText
• Need usage, finish reason, steps, sources, files, or tool details: use sdk.GenerateTextResult
• Need live output: use sdk.StreamText
• Need one vector: use sdk.Embed
• Need multiple vectors or embedding token usage: use sdk.EmbedMany

If the task introduces examples or docs, prefer simple end-to-end snippets that start with:

1. construct provider
2. get model
3. call SDK API
4. handle error

Provider Selection Rules

• Use openai/completions for broad OpenAI-compatible support such as DeepSeek, Groq, Ollama, Azure-style compatible endpoints, and generic /chat/completions backends.
• Use openai/responses when the task needs OpenAI Responses API features such as first-class reasoning models, reasoning summaries, URL citation annotations, or flat input mapping.
• Use anthropic/messages for Claude and Anthropic extended thinking via WithThinking.
• Use google/generativeai for Gemini chat, tool calling, vision, streaming, and Gemini reasoning.
• Use openai/embedding or google/embedding for embeddings. Keep embedding-provider work separate from chat-provider work.

Implementation Rules

Chat Providers

If adding or changing a chat provider, preserve the sdk.Provider contract:

• Name()
• ListModels(ctx)
• Test(ctx)
• TestModel(ctx, modelID)
• DoGenerate(ctx, params)
• DoStream(ctx, params)

Keep provider responsibilities focused:

• translate SDK messages/options into backend request format
• parse backend responses into sdk.GenerateResult
• map backend streaming events into typed sdk.StreamPart values
• report usage, finish reasons, reasoning, tool calls, sources, and files when supported

Embedding Providers

Embedding providers are separate from chat providers. Use sdk.EmbeddingProvider and return an sdk.EmbeddingModel via EmbeddingModel(id).

When updating embeddings:

• keep sdk.Embed for single-string convenience
• keep sdk.EmbedMany for batched requests
• preserve Usage.Tokens
• only expose dimensions/task-type behavior when the backend supports it

Tool Calling

Prefer sdk.NewTool[T] for new tool examples and integrations. It gives typed input and inferred JSON Schema.

Use these defaults unless the task requires something else:

• WithToolChoice("auto") for normal use
• WithMaxSteps(0) for inspection-only tool calls
• WithMaxSteps(N) for automatic execution loops
• RequireApproval: true only for sensitive side effects

When streaming with tools, ensure the implementation can emit:

• tool input construction parts
• tool execution parts
• progress updates
• denial/error events when applicable

MCP Tool Calling

Use MCP when the task needs remote tools exposed by an MCP server rather than locally implemented Execute handlers.

Default guidance:

• use sdk.CreateMCPClient(ctx, &sdk.MCPClientConfig{...})
• use sdk.MCPTransportHTTP for streamable HTTP MCP servers
• use sdk.MCPTransportSSE only when the server exposes legacy SSE transport
• for stdio, build the transport with the official MCP Go SDK and pass Transport: ...
• call mcpClient.Tools(ctx) and pass the result into sdk.WithTools(...)
• call defer mcpClient.Close() after successful creation

Important behavior:

• MCP tools become ordinary sdk.Tool values from the caller's perspective
• Twilight AI converts MCP InputSchema into *jsonschema.Schema
• MCP tool execution is delegated to tools/call on the remote server
• remote MCP text output becomes the tool result visible to the model

Streaming

Twilight AI streaming is channel-first and type-safe. Prefer type switches over loosely typed event parsing.

Important expectations:

• StreamText returns *sdk.StreamResult
• sr.Stream must be consumed before relying on sr.Steps or sr.Messages
• Text() and ToResult() are the convenience paths when callers do not want manual event handling

Messages And Results

Preserve the SDK message model and avoid backend-specific shapes leaking into public usage.

• user, assistant, system, and tool messages should stay in SDK types
• support rich parts where relevant: text, image, file, reasoning, tool call, tool result
• keep finish reason mapping aligned with SDK constants such as stop, length, content-filter, and tool-calls

Common Task Patterns

Add A New Usage Example

Use this structure:

1. pick the correct provider package
2. create provider with explicit options
3. create model via ChatModel or EmbeddingModel
4. call the top-level sdk function
5. show minimal but idiomatic result handling

Add Or Update A Provider Feature

Check all affected layers:

1. request mapping
2. non-streaming response mapping
3. streaming event mapping
4. finish-reason and usage mapping
5. reasoning/tool/source/file support if the backend exposes them
6. model discovery and provider health checks if endpoints exist

Add A Custom Provider

Use the built-in providers as the template. A custom provider should feel identical to existing ones from the caller's perspective.

Minimum behavior:

1. return a provider-bound model from ChatModel
2. implement discovery and health-check methods
3. support DoGenerate
4. support DoStream with correct lifecycle parts

Documentation Rules

When writing Twilight AI docs or README content:

• prefer provider-agnostic phrasing first, provider-specific details second
• use Go examples, not pseudocode, unless explaining an interface contract
• keep examples small and runnable in spirit
• mention exact package paths for imports
• explain when to choose Completions vs Responses when OpenAI is involved
• keep embeddings, tool calling, and streaming as separate concerns unless the example truly combines them

Terminology

Use these terms consistently:

• Provider: backend implementation for chat generation
• Embedding provider: backend implementation for embeddings
• Model: provider-bound chat model
• Embedding model: provider-bound embedding model
• Tool calling: model requests a tool invocation
• Multi-step execution: automatic tool loop controlled by WithMaxSteps
• Stream part: a typed event from StreamText

Quick Checklist

Before finishing work in this repo, verify:

• the chosen provider package matches the intended backend capabilities
• chat and embedding concerns are not mixed accidentally
• public examples use top-level sdk APIs unless lower-level behavior is the point
• streaming logic uses typed StreamPart handling
• tool-calling changes cover both inspection mode and multi-step mode when relevant
• MCP examples show both transport setup and normal WithTools(...) usage when relevant
• provider work includes health checks or model discovery behavior if the backend supports them

Additional Resources

• For exported APIs, signatures, provider options, and stream/event types, see reference.md