Bulletproof TypeScript: Building a Self-Enforcing Framework for AI Development

by Engineering Team
typescriptaiarchitecturevalidationmonorepo

There's a paradox at the heart of AI-assisted development: AI agents can generate thousands of lines of working code in seconds, yet they're architecturally careless. They'll happily embed business logic in route handlers, create circular dependencies, and hand-write types that should be inferred. The code works, but it violates every architectural principle you've spent years establishing.

Traditional enforcement mechanisms—documentation, code review, team discipline—are too slow for AI development loops. By the time a human reviews AI-generated code and requests changes, you've lost the productivity advantage AI promised.

What if the architecture could enforce itself? What if violations were caught in under one second, automatically, with zero human intervention?

The Problem: AI Agents and Architectural Debt

AI agents excel at pattern matching but struggle with architectural judgment. Give an AI agent the task "create a user registration endpoint," and you'll get something like this:

// AI-generated code (works, but violates architecture)
app.post('/users', async (c) => {
  const body = await c.req.json()

  const user = {
    id: crypto.randomUUID(),        // ❌ Business logic
    ...body,
    emailVerified: false,           // ❌ Business logic
    createdAt: new Date(),          // ❌ Business logic
  }

  await db.insert(users).values(user) // ❌ Direct database access
  return c.json(user, 201)
})

This code works perfectly. Tests pass. The API responds correctly. But it's a maintenance nightmare:

  • Business logic (ID generation, defaults, timestamps) is in the HTTP layer
  • Direct database access couples the route to infrastructure
  • No service layer means this logic can't be reused
  • Testing requires mocking the entire HTTP stack

Traditional solutions don't scale. Documentation? AI agents might not read it. Code review? Takes 10-30 minutes per iteration, destroying the AI productivity advantage. Hope? Not a strategy.

The core issue is slow feedback loops. By the time you identify violations, the AI has moved on to the next task.

The Solution: Architecture as Code

Bulletproof TypeScript rests on three pillars: explicit layer separation, schema-first development, and automated validation.

Pillar 1: Thin-Client, 4-Layer Architecture

Every piece of code has exactly one correct location:

Layer 1: Pure Business Logic (packages/core)

  • Zod schemas and inferred types
  • Domain services with pure functions
  • Zero workspace dependencies (completely isolated)

Layer 2: Data Access (packages/db)

  • Drizzle ORM repositories
  • Database queries only, no business logic
  • Zero workspace dependencies (completely isolated)

Layer 3: Orchestration (packages/services)

  • Application services coordinate domain + database
  • Use case implementations
  • Depends on core + db (intentionally bridges layers)

Layer 4: Apps (apps/*)

  • Thin HTTP handlers (max 15 lines each)
  • Parse request → call service → return response
  • No business logic, no database access

Pillar 2: Schema-First Development

Types are never hand-written. Ever.

// Define schema once
export const userSchema = z.object({
  id: z.string().uuid(),
  email: z.string().email(),
  firstName: z.string().min(1),
  createdAt: z.date(),
})

// Types inferred automatically
export type User = z.infer<typeof userSchema>

Change the schema, and TypeScript compiler shows everywhere that needs updating. Single source of truth. No drift between runtime validation and compile-time types.

Pillar 3: Automated Validation Suite

Seven checks run in under three seconds:

  1. Package isolation - Core and DB have zero workspace dependencies
  2. Circular dependencies - No cycles in dependency graph
  3. Schema-first enforcement - All types use z.infer
  4. Workspace protocols - Dependencies use correct version syntax
  5. Route handler size - Max 15 lines (forces thin-client pattern)
  6. Test coverage - Critical packages have tests
  7. RPC alignment - RPC contracts reference Zod schemas

Run pnpm run check:all and get instant feedback on architectural violations.

How It Works: The AI Development Loop

The workflow is radically simple:

  1. AI reads explicit templates from docs/ai-agent-instructions.md
  2. AI generates code following the exact patterns
  3. Run validation with pnpm run check:all
  4. Two outcomes:
    • ✅ Pass → Done (30 seconds total)
    • ❌ Fail → AI sees error → self-corrects → repeat

Here's a real example:

AI: *generates route with business logic*

$ pnpm run check:all
❌ Business logic detected in route handler
   apps/api-v2/src/routes/user.ts:42
   Pattern: Date creation. Move to domain service.

AI: *moves logic to packages/core/src/domain/user/userService.ts*

$ pnpm run check:all
✅ All checks passed!

Time comparison:

  • Traditional (manual code review): 10-30 minutes per iteration
  • Automated (validation suite): 30-60 seconds per iteration

What Gets Caught: Real Examples

The validation suite is ruthless:

Business logic in routes? ESLint detects crypto.randomUUID(), new Date(), .map(), .filter() patterns and errors immediately.

Hand-written types? check:schema scans /types/ directories for files without z.infer usage.

Circular dependencies? check:circular analyzes the dependency graph and reports cycles.

Wrong package imports? check:isolation verifies core package has zero @workspace/* dependencies.

Fat route handlers? check:routes warns about handlers exceeding 15 lines.

The key insight: AI agents cannot commit broken architecture. Pre-commit hooks block it. The validation suite runs automatically before every commit. No bypassing (without --no-verify), no forgetting, no exceptions.

Why This Matters: The Bigger Picture

Bulletproof TypeScript isn't just faster linting—it's a fundamental shift in how we build software.

Speed AND Quality: These are no longer competing concerns. AI generates code in seconds. Validation confirms architectural correctness in seconds. Ship features in minutes with complete confidence.

Solo Developer Advantage: You don't need senior developers for architecture review. The validation suite IS the architecture review. A solo developer with AI agents can maintain architectural discipline that previously required entire teams.

AI as Force Multiplier: Instead of "AI writes messy code that humans clean up," we get "AI writes architecturally sound code that ships immediately." The AI isn't fighting the architecture—it's guided by it.

Framework Portability: Want to swap Hono for Fastify? Express for Deno HTTP? Your business logic (in isolated packages) doesn't change. Only the thin route handlers need updates.

The automation IS the architecture enforcement.

The Future of Development

We're entering an era where AI writes most code. But AI needs guardrails, not documentation.

Bulletproof TypeScript provides:

  • Explicit templates - AI knows exactly what to generate
  • Instant validation - Feedback in seconds, not hours
  • Self-enforcing patterns - Impossible to merge violations
  • Architectural confidence - Ship fast without technical debt

This isn't just better tooling—it's a new development paradigm. Architectures that enforce themselves. Code that can't break patterns. AI agents that generate production-ready features in minutes.

The future isn't AI replacing developers. It's developers using AI to build better software, faster, with architectural guarantees that were previously impossible.

The era of self-enforcing architecture has arrived. Your codebase should be bulletproof.

Try it yourself: