diff --git a/libs/types/package.json b/libs/types/package.json
new file mode 100644
index 00000000..032c8a19
--- /dev/null
+++ b/libs/types/package.json
@@ -0,0 +1,18 @@
+{
+  "name": "@automaker/types",
+  "version": "1.0.0",
+  "description": "Shared type definitions for AutoMaker",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "scripts": {
+    "build": "tsc",
+    "watch": "tsc --watch"
+  },
+  "keywords": ["automaker", "types"],
+  "author": "",
+  "license": "MIT",
+  "devDependencies": {
+    "@types/node": "^22.10.5",
+    "typescript": "^5.7.3"
+  }
+}
diff --git a/libs/types/src/error.ts b/libs/types/src/error.ts
new file mode 100644
index 00000000..6c0459a4
--- /dev/null
+++ b/libs/types/src/error.ts
@@ -0,0 +1,16 @@
+/**
+ * Error type classification
+ */
+export type ErrorType = "authentication" | "cancellation" | "abort" | "execution" | "unknown";
+
+/**
+ * Classified error information
+ */
+export interface ErrorInfo {
+  type: ErrorType;
+  message: string;
+  isAbort: boolean;
+  isAuth: boolean;
+  isCancellation: boolean;
+  originalError: unknown;
+}
diff --git a/libs/types/src/feature.ts b/libs/types/src/feature.ts
new file mode 100644
index 00000000..9d98eacb
--- /dev/null
+++ b/libs/types/src/feature.ts
@@ -0,0 +1,40 @@
+/**
+ * Feature types for AutoMaker feature management
+ */
+
+export interface Feature {
+  id: string;
+  category: string;
+  description: string;
+  steps?: string[];
+  passes?: boolean;
+  priority?: number;
+  status?: string;
+  dependencies?: string[];
+  spec?: string;
+  model?: string;
+  imagePaths?: Array<string | { path: string; [key: string]: unknown }>;
+  // Branch info - worktree path is derived at runtime from branchName
+  branchName?: string; // Name of the feature branch (undefined = use current worktree)
+  skipTests?: boolean;
+  thinkingLevel?: string;
+  planningMode?: 'skip' | 'lite' | 'spec' | 'full';
+  requirePlanApproval?: boolean;
+  planSpec?: {
+    status: 'pending' | 'generating' | 'generated' | 'approved' | 'rejected';
+    content?: string;
+    version: number;
+    generatedAt?: string;
+    approvedAt?: string;
+    reviewedByUser: boolean;
+    tasksCompleted?: number;
+    tasksTotal?: number;
+  };
+  error?: string;
+  summary?: string;
+  startedAt?: string;
+  [key: string]: unknown;  // Keep catch-all for extensibility
+}
+
+export type FeatureStatus = 'pending' | 'running' | 'completed' | 'failed' | 'verified';
+export type PlanningMode = 'skip' | 'lite' | 'spec' | 'full';
diff --git a/libs/types/src/image.ts b/libs/types/src/image.ts
new file mode 100644
index 00000000..3cf54db8
--- /dev/null
+++ b/libs/types/src/image.ts
@@ -0,0 +1,21 @@
+/**
+ * Image data with base64 encoding and metadata
+ */
+export interface ImageData {
+  base64: string;
+  mimeType: string;
+  filename: string;
+  originalPath: string;
+}
+
+/**
+ * Content block for image (Claude SDK format)
+ */
+export interface ImageContentBlock {
+  type: "image";
+  source: {
+    type: "base64";
+    media_type: string;
+    data: string;
+  };
+}
diff --git a/libs/types/src/index.ts b/libs/types/src/index.ts
new file mode 100644
index 00000000..1d533817
--- /dev/null
+++ b/libs/types/src/index.ts
@@ -0,0 +1,50 @@
+/**
+ * @automaker/types
+ * Shared type definitions for AutoMaker
+ */
+
+// Provider types
+export type {
+  ProviderConfig,
+  ConversationMessage,
+  ExecuteOptions,
+  ContentBlock,
+  ProviderMessage,
+  InstallationStatus,
+  ValidationResult,
+  ModelDefinition,
+} from './provider';
+
+// Feature types
+export type {
+  Feature,
+  FeatureStatus,
+  PlanningMode,
+} from './feature';
+
+// Session types
+export type {
+  AgentSession,
+  SessionListItem,
+  CreateSessionParams,
+  UpdateSessionParams,
+} from './session';
+
+// Error types
+export type {
+  ErrorType,
+  ErrorInfo,
+} from './error';
+
+// Image types
+export type {
+  ImageData,
+  ImageContentBlock,
+} from './image';
+
+// Model types and constants
+export {
+  CLAUDE_MODEL_MAP,
+  DEFAULT_MODELS,
+  type ModelAlias,
+} from './model';
diff --git a/libs/types/src/model.ts b/libs/types/src/model.ts
new file mode 100644
index 00000000..fe310e7a
--- /dev/null
+++ b/libs/types/src/model.ts
@@ -0,0 +1,17 @@
+/**
+ * Model alias mapping for Claude models
+ */
+export const CLAUDE_MODEL_MAP: Record<string, string> = {
+  haiku: "claude-haiku-4-5",
+  sonnet: "claude-sonnet-4-20250514",
+  opus: "claude-opus-4-5-20251101",
+} as const;
+
+/**
+ * Default models per provider
+ */
+export const DEFAULT_MODELS = {
+  claude: "claude-opus-4-5-20251101",
+} as const;
+
+export type ModelAlias = keyof typeof CLAUDE_MODEL_MAP;
diff --git a/libs/types/src/provider.ts b/libs/types/src/provider.ts
new file mode 100644
index 00000000..6a05b6df
--- /dev/null
+++ b/libs/types/src/provider.ts
@@ -0,0 +1,104 @@
+/**
+ * Shared types for AI model providers
+ */
+
+/**
+ * Configuration for a provider instance
+ */
+export interface ProviderConfig {
+  apiKey?: string;
+  cliPath?: string;
+  env?: Record<string, string>;
+}
+
+/**
+ * Message in conversation history
+ */
+export interface ConversationMessage {
+  role: "user" | "assistant";
+  content: string | Array<{ type: string; text?: string; source?: object }>;
+}
+
+/**
+ * Options for executing a query via a provider
+ */
+export interface ExecuteOptions {
+  prompt: string | Array<{ type: string; text?: string; source?: object }>;
+  model: string;
+  cwd: string;
+  systemPrompt?: string;
+  maxTurns?: number;
+  allowedTools?: string[];
+  mcpServers?: Record<string, unknown>;
+  abortController?: AbortController;
+  conversationHistory?: ConversationMessage[]; // Previous messages for context
+  sdkSessionId?: string; // Claude SDK session ID for resuming conversations
+}
+
+/**
+ * Content block in a provider message (matches Claude SDK format)
+ */
+export interface ContentBlock {
+  type: "text" | "tool_use" | "thinking" | "tool_result";
+  text?: string;
+  thinking?: string;
+  name?: string;
+  input?: unknown;
+  tool_use_id?: string;
+  content?: string;
+}
+
+/**
+ * Message returned by a provider (matches Claude SDK streaming format)
+ */
+export interface ProviderMessage {
+  type: "assistant" | "user" | "error" | "result";
+  subtype?: "success" | "error";
+  session_id?: string;
+  message?: {
+    role: "user" | "assistant";
+    content: ContentBlock[];
+  };
+  result?: string;
+  error?: string;
+  parent_tool_use_id?: string | null;
+}
+
+/**
+ * Installation status for a provider
+ */
+export interface InstallationStatus {
+  installed: boolean;
+  path?: string;
+  version?: string;
+  method?: "cli" | "npm" | "brew" | "sdk";
+  hasApiKey?: boolean;
+  authenticated?: boolean;
+  error?: string;
+}
+
+/**
+ * Validation result
+ */
+export interface ValidationResult {
+  valid: boolean;
+  errors: string[];
+  warnings?: string[];
+}
+
+/**
+ * Model definition
+ */
+export interface ModelDefinition {
+  id: string;
+  name: string;
+  modelString: string;
+  provider: string;
+  description: string;
+  contextWindow?: number;
+  maxOutputTokens?: number;
+  supportsVision?: boolean;
+  supportsTools?: boolean;
+  tier?: "basic" | "standard" | "premium";
+  default?: boolean;
+}
diff --git a/libs/types/src/session.ts b/libs/types/src/session.ts
new file mode 100644
index 00000000..a4fea93c
--- /dev/null
+++ b/libs/types/src/session.ts
@@ -0,0 +1,31 @@
+/**
+ * Session types for agent conversations
+ */
+
+export interface AgentSession {
+  id: string;
+  name: string;
+  projectPath: string;
+  createdAt: string;
+  updatedAt: string;
+  messageCount: number;
+  isArchived: boolean;
+  isDirty?: boolean; // Indicates session has completed work that needs review
+  tags?: string[];
+}
+
+export interface SessionListItem extends AgentSession {
+  preview?: string; // Last message preview
+}
+
+export interface CreateSessionParams {
+  name: string;
+  projectPath: string;
+  workingDirectory?: string;
+}
+
+export interface UpdateSessionParams {
+  id: string;
+  name?: string;
+  tags?: string[];
+}
diff --git a/libs/types/tsconfig.json b/libs/types/tsconfig.json
new file mode 100644
index 00000000..54e9774b
--- /dev/null
+++ b/libs/types/tsconfig.json
@@ -0,0 +1,20 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "commonjs",
+    "lib": ["ES2020"],
+    "types": ["node"],
+    "declaration": true,
+    "declarationMap": true,
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "moduleResolution": "node"
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist"]
+}