Typed error classes

export class LLMTimeoutError extends Error {
  constructor(
    public readonly provider: string,
    public readonly ms: number,
  ) {
    super(`LLM provider "${provider}" timed out after ${ms}ms`);
    this.name = 'LLMTimeoutError';
  }
}

export class RepositoryNotFoundError extends Error {
  constructor(public readonly root: string) {
    super(`Repository root not found: ${root}`);
    this.name = 'RepositoryNotFoundError';
  }
}

Rules: extend Error, set this.name, typed constructor args, readonly properties.

Discriminated unions for state

type AgentResult =
  | { status: 'success'; output: string; tokensUsed: number }
  | { status: 'error'; error: Error; retryable: boolean };

// Exhaustive switch — TS warns if a case is missing
function handleResult(result: AgentResult): string {
  switch (result.status) {
    case 'success': return result.output;
    case 'error': throw result.error;
  }
}

function isAgentResult(value: unknown): value is AgentResult {
  return (
    typeof value === 'object' &&
    value !== null &&
    'status' in value &&
    (value.status === 'success' || value.status === 'error')
  );
}

function parseAgentResult(raw: unknown): AgentResult {
  if (!isAgentResult(raw)) throw new TypeError('Invalid AgentResult shape');
  return raw;
}

interface AgentOptions {
  name: string;
  model: string;
  temperature?: number;    // optional with default
  maxTokens?: number;
  memory: MemoryStore;
}

export function createAgent(options: AgentOptions): Agent {
  const { name, model, temperature = 0.2, maxTokens = 4096, memory } = options;
  // ...
}

// packages/core/src/agents/index.ts
export { ArchitectAgent } from './architect-agent.js';
export { CoderAgent } from './coder-agent.js';
export type { AgentResult, AgentOptions } from './types.js';

import { readFile } from 'node:fs/promises';       // 1. node built-ins
import { Database } from 'better-sqlite3';          // 2. external packages
import { LLMProvider } from '@devagents/core';      // 3. internal packages
import { buildPrompt } from './prompt-builder.js';  // 4. relative (.js always)

Typescript Patterns | Skills Pool

Typescript Patterns

Typescript Patterns

Typed error classes

Discriminated unions for state

Type guards for `unknown`

Options objects (when >3 params)

Barrel exports (index.ts — re-exports only)

Import order

Pytorch Patterns

Regex Vs Llm Structured Text

Effect

Flags

WPF to WinUI 3 Migration Skill

At Dispatch V2

Typescript Patterns

Typescript Patterns

Typed error classes

Discriminated unions for state

Type guards for unknown

Options objects (when >3 params)

Barrel exports (index.ts — re-exports only)

Import order

Pytorch Patterns

Regex Vs Llm Structured Text

Effect

Flags

WPF to WinUI 3 Migration Skill

At Dispatch V2

Type guards for `unknown`