Add SDK documentation

- docs/sdk.md: comprehensive SDK reference - Core concepts (createAgentSession, AgentSession, Agent, events) - All options with examples - Discovery functions - Complete example - README.md: add SDK section with brief overview and links
2026-04-15 20:03:05 +00:00 · 2025-12-22 03:20:09 +01:00 · 2025-12-22 03:20:09 +01:00 · 05e1f31feb
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+# SDK
+
+The SDK provides programmatic access to pi's agent capabilities. Use it to embed pi in other applications, build custom interfaces, or integrate with automated workflows.
+
+**Example use cases:**
+- Build a custom UI (web, desktop, mobile)
+- Integrate agent capabilities into existing applications
+- Create automated pipelines with agent reasoning
+- Build custom tools that spawn sub-agents
+- Test agent behavior programmatically
+
+See [examples/sdk/](../examples/sdk/) for working examples from minimal to full control.
+
+## Quick Start
+
+```typescript
+import { createAgentSession, SessionManager } from "@mariozechner/pi-coding-agent";
+
+const { session } = await createAgentSession({
+  sessionManager: SessionManager.inMemory(),
+});
+
+session.subscribe((event) => {
+  if (event.type === "message_update" && event.assistantMessageEvent.type === "text_delta") {
+    process.stdout.write(event.assistantMessageEvent.delta);
+  }
+});
+
+await session.prompt("What files are in the current directory?");
+```
+
+## Installation
+
+```bash
+npm install @mariozechner/pi-coding-agent
+```
+
+The SDK is included in the main package. No separate installation needed.
+
+## Core Concepts
+
+### createAgentSession()
+
+The main factory function. Creates an `AgentSession` with configurable options.
+
+**Philosophy:** "Omit to discover, provide to override."
+- Omit an option → pi discovers/loads from standard locations
+- Provide an option → your value is used, discovery skipped for that option
+
+```typescript
+import { createAgentSession } from "@mariozechner/pi-coding-agent";
+
+// Minimal: all defaults (discovers everything from cwd and ~/.pi/agent)
+const { session } = await createAgentSession();
+
+// Custom: override specific options
+const { session } = await createAgentSession({
+  model: myModel,
+  systemPrompt: "You are helpful.",
+  tools: [readTool, bashTool],
+  sessionManager: SessionManager.inMemory(),
+});
+```
+
+### AgentSession
+
+The session manages the agent lifecycle, message history, and event streaming.
+
+```typescript
+interface AgentSession {
+  // Send a prompt and wait for completion
+  prompt(text: string, options?: PromptOptions): Promise<void>;
+  
+  // Subscribe to events (returns unsubscribe function)
+  subscribe(listener: (event: AgentSessionEvent) => void): () => void;
+  
+  // Session info
+  sessionFile: string | null;
+  sessionId: string;
+  
+  // Model control
+  setModel(model: Model, thinkingLevel?: ThinkingLevel): void;
+  setThinkingLevel(level: ThinkingLevel): void;
+  
+  // Access underlying agent
+  agent: Agent;
+  
+  // Session management
+  reset(): void;
+  branch(targetTurnIndex: number): Promise<void>;
+  
+  // Abort current operation
+  abort(): void;
+}
+```
+
+### Agent and AgentState
+
+The `Agent` class (from `@mariozechner/pi-agent-core`) handles the core LLM interaction. Access it via `session.agent`.
+
+```typescript
+// Access current state
+const state = session.agent.state;
+
+// state.messages: AppMessage[] - conversation history
+// state.model: Model - current model
+// state.thinkingLevel: ThinkingLevel - current thinking level
+// state.systemPrompt: string - system prompt
+// state.tools: Tool[] - available tools
+
+// Replace messages (useful for branching, restoration)
+session.agent.replaceMessages(messages);
+
+// Wait for agent to finish processing
+await session.agent.waitForIdle();
+```
+
+### Events
+
+Subscribe to events to receive streaming output and lifecycle notifications.
+
+```typescript
+session.subscribe((event) => {
+  switch (event.type) {
+    // Streaming text from assistant
+    case "message_update":
+      if (event.assistantMessageEvent.type === "text_delta") {
+        process.stdout.write(event.assistantMessageEvent.delta);
+      }
+      if (event.assistantMessageEvent.type === "thinking_delta") {
+        // Thinking output (if thinking enabled)
+      }
+      break;
+    
+    // Tool execution
+    case "tool_execution_start":
+      console.log(`Tool: ${event.toolName}`);
+      break;
+    case "tool_execution_update":
+      // Streaming tool output
+      break;
+    case "tool_execution_end":
+      console.log(`Result: ${event.isError ? "error" : "success"}`);
+      break;
+    
+    // Message lifecycle
+    case "message_start":
+      // New message starting
+      break;
+    case "message_end":
+      // Message complete
+      break;
+    
+    // Agent lifecycle
+    case "agent_start":
+      // Agent started processing prompt
+      break;
+    case "agent_end":
+      // Agent finished (event.messages contains new messages)
+      break;
+    
+    // Turn lifecycle (one LLM response + tool calls)
+    case "turn_start":
+      break;
+    case "turn_end":
+      // event.message: assistant response
+      // event.toolResults: tool results from this turn
+      break;
+    
+    // Session events (auto-compaction, retry)
+    case "auto_compaction_start":
+    case "auto_compaction_end":
+    case "auto_retry_start":
+    case "auto_retry_end":
+      break;
+  }
+});
+```
+
+## Options Reference
+
+### Directories
+
+```typescript
+const { session } = await createAgentSession({
+  // Working directory for project-local discovery
+  cwd: process.cwd(), // default
+  
+  // Global config directory
+  agentDir: "~/.pi/agent", // default (expands ~)
+});
+```
+
+`cwd` is used for:
+- Project hooks (`.pi/hooks/`)
+- Project tools (`.pi/tools/`)
+- Project skills (`.pi/skills/`)
+- Project commands (`.pi/commands/`)
+- Context files (`AGENTS.md` walking up from cwd)
+- Session directory naming
+
+`agentDir` is used for:
+- Global hooks (`hooks/`)
+- Global tools (`tools/`)
+- Global skills (`skills/`)
+- Global commands (`commands/`)
+- Global context file (`AGENTS.md`)
+- Settings (`settings.json`)
+- Models (`models.json`)
+- OAuth tokens (`oauth.json`)
+- Sessions (`sessions/`)
+
+### Model
+
+```typescript
+import { findModel, discoverAvailableModels } from "@mariozechner/pi-coding-agent";
+
+// Find specific model
+const { model } = findModel("anthropic", "claude-sonnet-4-20250514");
+
+// Or get all models with valid API keys
+const available = await discoverAvailableModels();
+
+const { session } = await createAgentSession({
+  model: model,
+  thinkingLevel: "medium", // off, low, medium, high
+  
+  // Models for cycling (Ctrl+P in interactive mode)
+  scopedModels: [
+    { model: sonnet, thinkingLevel: "high" },
+    { model: haiku, thinkingLevel: "off" },
+  ],
+});
+```
+
+If no model is provided:
+1. Tries to restore from session (if continuing)
+2. Uses default from settings
+3. Falls back to first available model
+
+### API Keys
+
+```typescript
+import { defaultGetApiKey, configureOAuthStorage } from "@mariozechner/pi-coding-agent";
+
+// Default: checks models.json, OAuth, environment variables
+const { session } = await createAgentSession();
+
+// Custom resolver
+const { session } = await createAgentSession({
+  getApiKey: async (model) => {
+    // Custom logic (secrets manager, database, etc.)
+    if (model.provider === "anthropic") {
+      return process.env.MY_ANTHROPIC_KEY;
+    }
+    // Fall back to default
+    return defaultGetApiKey()(model);
+  },
+});
+
+// Use OAuth from ~/.pi/agent with custom agentDir for everything else
+configureOAuthStorage(); // Must call before createAgentSession
+const { session } = await createAgentSession({
+  agentDir: "/custom/config",
+  // OAuth tokens still come from ~/.pi/agent/oauth.json
+});
+```
+
+### System Prompt
+
+```typescript
+const { session } = await createAgentSession({
+  // Replace entirely
+  systemPrompt: "You are a helpful assistant.",
+  
+  // Or modify default (receives default, returns modified)
+  systemPrompt: (defaultPrompt) => {
+    return `${defaultPrompt}\n\n## Additional Rules\n- Be concise`;
+  },
+});
+```
+
+### Tools
+
+```typescript
+import {
+  codingTools,   // read, bash, edit, write (default)
+  readOnlyTools, // read, bash
+  readTool, bashTool, editTool, writeTool,
+  grepTool, findTool, lsTool,
+} from "@mariozechner/pi-coding-agent";
+
+// Use built-in tool set
+const { session } = await createAgentSession({
+  tools: readOnlyTools,
+});
+
+// Pick specific tools
+const { session } = await createAgentSession({
+  tools: [readTool, bashTool, grepTool],
+});
+```
+
+### Custom Tools
+
+```typescript
+import { Type } from "@sinclair/typebox";
+import { createAgentSession, discoverCustomTools, type CustomAgentTool } from "@mariozechner/pi-coding-agent";
+
+// Inline custom tool
+const myTool: CustomAgentTool = {
+  name: "my_tool",
+  label: "My Tool",
+  description: "Does something useful",
+  parameters: Type.Object({
+    input: Type.String({ description: "Input value" }),
+  }),
+  execute: async (toolCallId, params) => ({
+    content: [{ type: "text", text: `Result: ${params.input}` }],
+    details: {},
+  }),
+};
+
+// Replace discovery with inline tools
+const { session } = await createAgentSession({
+  customTools: [{ tool: myTool }],
+});
+
+// Merge with discovered tools
+const discovered = await discoverCustomTools();
+const { session } = await createAgentSession({
+  customTools: [...discovered, { tool: myTool }],
+});
+
+// Add paths without replacing discovery
+const { session } = await createAgentSession({
+  additionalCustomToolPaths: ["/extra/tools"],
+});
+```
+
+### Hooks
+
+```typescript
+import { createAgentSession, discoverHooks, type HookFactory } from "@mariozechner/pi-coding-agent";
+
+// Inline hook
+const loggingHook: HookFactory = (api) => {
+  api.on("tool_call", async (event) => {
+    console.log(`Tool: ${event.toolName}`);
+    return undefined; // Don't block
+  });
+  
+  api.on("tool_call", async (event) => {
+    // Block dangerous commands
+    if (event.toolName === "bash" && event.input.command?.includes("rm -rf")) {
+      return { block: true, reason: "Dangerous command" };
+    }
+    return undefined;
+  });
+};
+
+// Replace discovery
+const { session } = await createAgentSession({
+  hooks: [{ factory: loggingHook }],
+});
+
+// Disable all hooks
+const { session } = await createAgentSession({
+  hooks: [],
+});
+
+// Merge with discovered
+const discovered = await discoverHooks();
+const { session } = await createAgentSession({
+  hooks: [...discovered, { factory: loggingHook }],
+});
+
+// Add paths without replacing
+const { session } = await createAgentSession({
+  additionalHookPaths: ["/extra/hooks"],
+});
+```
+
+### Skills
+
+```typescript
+import { createAgentSession, discoverSkills, type Skill } from "@mariozechner/pi-coding-agent";
+
+// Discover and filter
+const allSkills = discoverSkills();
+const filtered = allSkills.filter(s => s.name.includes("search"));
+
+// Custom skill
+const mySkill: Skill = {
+  name: "my-skill",
+  description: "Custom instructions",
+  filePath: "/path/to/SKILL.md",
+  baseDir: "/path/to",
+  source: "custom",
+};
+
+const { session } = await createAgentSession({
+  skills: [...filtered, mySkill],
+});
+
+// Disable skills
+const { session } = await createAgentSession({
+  skills: [],
+});
+
+// Discovery with settings filter
+const skills = discoverSkills(process.cwd(), undefined, {
+  ignoredSkills: ["browser-*"],  // glob patterns to exclude
+  includeSkills: ["search-*"],   // glob patterns to include (empty = all)
+});
+```
+
+### Context Files
+
+```typescript
+import { createAgentSession, discoverContextFiles } from "@mariozechner/pi-coding-agent";
+
+// Discover AGENTS.md files
+const discovered = discoverContextFiles();
+
+// Add custom context
+const { session } = await createAgentSession({
+  contextFiles: [
+    ...discovered,
+    {
+      path: "/virtual/AGENTS.md",
+      content: "# Guidelines\n\n- Be concise\n- Use TypeScript",
+    },
+  ],
+});
+
+// Disable context files
+const { session } = await createAgentSession({
+  contextFiles: [],
+});
+```
+
+### Slash Commands
+
+```typescript
+import { createAgentSession, discoverSlashCommands, type FileSlashCommand } from "@mariozechner/pi-coding-agent";
+
+const discovered = discoverSlashCommands();
+
+const customCommand: FileSlashCommand = {
+  name: "deploy",
+  description: "Deploy the application",
+  source: "(custom)",
+  content: "# Deploy\n\n1. Build\n2. Test\n3. Deploy",
+};
+
+const { session } = await createAgentSession({
+  slashCommands: [...discovered, customCommand],
+});
+```
+
+### Session Management
+
+```typescript
+import { createAgentSession, SessionManager } from "@mariozechner/pi-coding-agent";
+
+// In-memory (no persistence)
+const { session } = await createAgentSession({
+  sessionManager: SessionManager.inMemory(),
+});
+
+// New persistent session
+const { session } = await createAgentSession({
+  sessionManager: SessionManager.create(process.cwd()),
+});
+
+// Continue most recent
+const { session, modelFallbackMessage } = await createAgentSession({
+  sessionManager: SessionManager.continueRecent(process.cwd()),
+});
+if (modelFallbackMessage) {
+  console.log("Note:", modelFallbackMessage);
+}
+
+// Open specific file
+const { session } = await createAgentSession({
+  sessionManager: SessionManager.open("/path/to/session.jsonl"),
+});
+
+// List available sessions
+const sessions = SessionManager.list(process.cwd());
+for (const info of sessions) {
+  console.log(`${info.id}: ${info.firstMessage} (${info.messageCount} messages)`);
+}
+
+// Custom agentDir for sessions
+const { session } = await createAgentSession({
+  agentDir: "/custom/agent",
+  sessionManager: SessionManager.create(process.cwd(), "/custom/agent"),
+});
+```
+
+### Settings
+
+```typescript
+import { createAgentSession, loadSettings } from "@mariozechner/pi-coding-agent";
+
+// Load current settings
+const settings = loadSettings();
+
+// Override specific settings
+const { session } = await createAgentSession({
+  settings: {
+    compaction: { enabled: false },
+    retry: { enabled: true, maxRetries: 5, baseDelayMs: 1000 },
+    terminal: { showImages: true },
+    hideThinkingBlock: true,
+  },
+});
+```
+
+## Discovery Functions
+
+All discovery functions accept optional `cwd` and `agentDir` parameters.
+
+```typescript
+import {
+  discoverModels,
+  discoverAvailableModels,
+  findModel,
+  discoverSkills,
+  discoverHooks,
+  discoverCustomTools,
+  discoverContextFiles,
+  discoverSlashCommands,
+  loadSettings,
+  buildSystemPrompt,
+} from "@mariozechner/pi-coding-agent";
+
+// Models
+const allModels = discoverModels();
+const available = await discoverAvailableModels();
+const { model, error } = findModel("anthropic", "claude-sonnet-4-20250514");
+
+// Skills
+const skills = discoverSkills(cwd, agentDir, skillsSettings);
+
+// Hooks (async - loads TypeScript)
+const hooks = await discoverHooks(cwd, agentDir);
+
+// Custom tools (async - loads TypeScript)
+const tools = await discoverCustomTools(cwd, agentDir);
+
+// Context files
+const contextFiles = discoverContextFiles(cwd, agentDir);
+
+// Slash commands
+const commands = discoverSlashCommands(cwd, agentDir);
+
+// Settings
+const settings = loadSettings(agentDir);
+
+// Build system prompt manually
+const prompt = buildSystemPrompt({
+  skills,
+  contextFiles,
+  appendPrompt: "Additional instructions",
+  cwd,
+});
+```
+
+## Return Value
+
+`createAgentSession()` returns:
+
+```typescript
+interface CreateAgentSessionResult {
+  // The session
+  session: AgentSession;
+  
+  // Custom tools (for UI setup)
+  customToolsResult: {
+    tools: LoadedCustomTool[];
+    setUIContext: (ctx, hasUI) => void;
+  };
+  
+  // Warning if session model couldn't be restored
+  modelFallbackMessage?: string;
+}
+```
+
+## Complete Example
+
+```typescript
+import { Type } from "@sinclair/typebox";
+import {
+  createAgentSession,
+  configureOAuthStorage,
+  defaultGetApiKey,
+  findModel,
+  SessionManager,
+  readTool,
+  bashTool,
+  type HookFactory,
+  type CustomAgentTool,
+} from "@mariozechner/pi-coding-agent";
+import { getAgentDir } from "@mariozechner/pi-coding-agent/config";
+
+// Use OAuth from default location
+configureOAuthStorage(getAgentDir());
+
+// Custom API key with fallback
+const getApiKey = async (model: { provider: string }) => {
+  if (model.provider === "anthropic" && process.env.MY_KEY) {
+    return process.env.MY_KEY;
+  }
+  return defaultGetApiKey()(model as any);
+};
+
+// Inline hook
+const auditHook: HookFactory = (api) => {
+  api.on("tool_call", async (event) => {
+    console.log(`[Audit] ${event.toolName}`);
+    return undefined;
+  });
+};
+
+// Inline tool
+const statusTool: CustomAgentTool = {
+  name: "status",
+  label: "Status",
+  description: "Get system status",
+  parameters: Type.Object({}),
+  execute: async () => ({
+    content: [{ type: "text", text: `Uptime: ${process.uptime()}s` }],
+    details: {},
+  }),
+};
+
+const { model } = findModel("anthropic", "claude-sonnet-4-20250514");
+if (!model) throw new Error("Model not found");
+
+const { session } = await createAgentSession({
+  cwd: process.cwd(),
+  agentDir: "/custom/agent",
+  
+  model,
+  thinkingLevel: "off",
+  getApiKey,
+  
+  systemPrompt: "You are a minimal assistant. Be concise.",
+  
+  tools: [readTool, bashTool],
+  customTools: [{ tool: statusTool }],
+  hooks: [{ factory: auditHook }],
+  skills: [],
+  contextFiles: [],
+  slashCommands: [],
+  
+  sessionManager: SessionManager.inMemory(),
+  
+  settings: {
+    compaction: { enabled: false },
+    retry: { enabled: true, maxRetries: 2 },
+  },
+});
+
+session.subscribe((event) => {
+  if (event.type === "message_update" && event.assistantMessageEvent.type === "text_delta") {
+    process.stdout.write(event.assistantMessageEvent.delta);
+  }
+});
+
+await session.prompt("Get status and list files.");
+```
+
+## RPC Mode Alternative
+
+For subprocess-based integration, use RPC mode instead of the SDK:
+
+```bash
+pi --mode rpc --no-session
+```
+
+See [RPC documentation](rpc.md) for the JSON protocol.
+
+The SDK is preferred when:
+- You want type safety
+- You're in the same Node.js process
+- You need direct access to agent state
+- You want to customize tools/hooks programmatically
+
+RPC mode is preferred when:
+- You're integrating from another language
+- You want process isolation
+- You're building a language-agnostic client
+
+## Exports
+
+The main entry point exports:
+
+```typescript
+// Factory
+createAgentSession
+configureOAuthStorage
+
+// Discovery
+discoverModels
+discoverAvailableModels
+findModel
+discoverSkills
+discoverHooks
+discoverCustomTools
+discoverContextFiles
+discoverSlashCommands
+
+// Helpers
+defaultGetApiKey
+loadSettings
+buildSystemPrompt
+
+// Session management
+SessionManager
+
+// Built-in tools
+codingTools
+readOnlyTools
+readTool, bashTool, editTool, writeTool
+grepTool, findTool, lsTool
+
+// Types
+type CreateAgentSessionOptions
+type CreateAgentSessionResult
+type CustomAgentTool
+type HookFactory
+type Skill
+type FileSlashCommand
+type Settings
+type SkillsSettings
+type Tool
+```
+
+For hook types, import from the hooks subpath:
+
+```typescript
+import type { HookAPI, HookEvent, ToolCallEvent } from "@mariozechner/pi-coding-agent/hooks";
+```
+
+For config utilities:
+
+```typescript
+import { getAgentDir } from "@mariozechner/pi-coding-agent/config";
+```