How to Stop AI From Hallucinating Code (2026 Fix)

TL;DR: AI hallucinations happen when the tool lacks context. Each hallucination type maps to a missing document. Add the right spec, and the hallucination stops.

Before you debug: Check your hallucination risk with the Spec Readiness Score.

Table of Contents

1. What Are AI Hallucinations in Code?
2. The 8 Hallucination Types
3. Type 1: Phantom APIs
4. Type 2: Wrong Columns
5. Type 3: Fake Imports
6. Type 4: Scope Creep
7. Type 5: Pattern Mismatch
8. Type 6: Wrong Tech
9. Type 7: Imagined Config
10. Type 8: Bonus Features
11. The Prevention Stack
12. Free Resources

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What Are AI Hallucinations in Code?

AI hallucinations occur when coding tools (Cursor, Cline, v0, Copilot) generate code that references things that don't exist:

• API endpoints that aren't defined
• Database columns that aren't in your schema
• Functions imported from packages that don't export them
• Configuration variables that don't exist

Why They Happen

AI tools are trained on millions of codebases. When prompted without context, they pattern-match against that training data and fill gaps with plausible inventions.

No Context + Pattern Matching = Confident Hallucination

The output looks real. It often compiles. But it doesn't work.

The Cost

Impact	Time Lost
Debug phantom import	1-2 hours
Rewrite wrong API call	2-4 hours
Fix schema mismatch	4-8 hours
Undo architecture confusion	1-2 days

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The 8 Hallucination Types

Every AI code hallucination falls into one of 8 categories:

Type	Example	Missing Doc
Phantom API	Calls /api/users/sync (doesn't exist)	API Spec
Wrong Columns	Queries user_name (column is name)	Database Schema
Fake Imports	import { useAuth } from '@/lib/auth' (doesn't exist)	Architecture Doc
Scope Creep	Adds real-time chat (not in requirements)	PRD with non-goals
Pattern Mismatch	Mixes REST + GraphQL	Architecture Doc
Wrong Tech	Uses MongoDB syntax in PostgreSQL	Tech Stack Doc
Imagined Config	References STRIPE_KEY (undefined)	Environment Spec
Bonus Features	Implements "nice to have" as required	PRD scope lock

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Type 1: Phantom APIs

Symptom

AI generates code calling an endpoint that doesn't exist:

// AI generated this
const response = await fetch("/api/users/sync", { method: "POST" });

But /api/users/sync was never created.

Root Cause

AI saw similar patterns in training data and assumed you have this endpoint.

Fix: API Spec

Create an OpenAPI spec listing every endpoint:

paths:
  /api/users:
    get: ...
    post: ...
  /api/users/{id}:
    get: ...

Reference in prompts:

Using @api-spec.yaml, implement user fetching.
ONLY use endpoints defined in the spec.

→ Download API Spec Template. Remember: PRD is only step one.

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Type 2: Wrong Columns

Symptom

AI queries columns that don't exist:

-- AI generated this
SELECT user_name FROM users WHERE active = true;

But your table has name not user_name, and no active column.

Root Cause

AI guessed column names based on common patterns.

Fix: Database Schema Doc

Document exact column names:

CREATE TABLE users (
  id UUID PRIMARY KEY,
  name TEXT NOT NULL,  -- Not "user_name"
  status TEXT,         -- Not "active"
  created_at TIMESTAMPTZ
);

Reference in prompts:

Using @schema.sql, write a query to get active users.
Check: the column is "status", not "active".

→ Download Schema Template

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Type 3: Fake Imports

Symptom

AI imports functions that don't exist:

// AI generated this
import { useAuth, usePermissions } from "@/lib/auth";

But @/lib/auth doesn't export usePermissions.

Root Cause

AI assumed common auth patterns from other codebases.

Fix: Architecture Doc

Document your actual exports:

## /lib/auth

Exports:

- `useAuth()` - Returns current user
- `signIn(email, password)` - Login
- `signOut()` - Logout

Does NOT export:

- `usePermissions` (does not exist)
- `useRoles` (does not exist)

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Type 4: Scope Creep

Symptom

AI adds features you didn't ask for:

// Prompt: "Add user profile editing"
// AI also creates:
// - Avatar upload system
// - Social links section
// - Activity feed

Root Cause

AI extrapolates from "profile" to include everything profiles usually have.

Fix: PRD with Non-Goals

Explicit non-goals stop this:

## Out of Scope (NOT Building)

- [ ] Avatar upload (use Gravatar for MVP)
- [ ] Social links
- [ ] Activity feeds
- [ ] Profile sharing

→ Download PRD Template or use the free PRD generator.

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Type 5: Pattern Mismatch

Symptom

AI mixes incompatible patterns:

// File 1: REST
const data = await fetch("/api/users");

// File 2: GraphQL (same project!)
const { data } = useQuery(GET_USERS);

Root Cause

AI doesn't know which pattern your project uses.

Fix: Architecture Doc

State your patterns explicitly:

## API Patterns

This project uses:

- REST (NOT GraphQL)
- Server components (NOT client-side fetching)
- tRPC for type-safe calls

NEVER use:

- GraphQL
- SWR or React Query (use Server Components)

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Type 6: Wrong Tech

Symptom

AI uses wrong technology syntax:

// Your stack: PostgreSQL
// AI generates MongoDB syntax:
await db.collection("users").insertOne({ name });

Root Cause

AI pattern-matched to a different database technology.

Fix: Tech Stack Doc

## Tech Stack

| Category | Technology           | Version |
| -------- | -------------------- | ------- |
| Database | PostgreSQL           | 15      |
| ORM      | Prisma               | 5.x     |
| Queries  | Raw SQL via Supabase | -       |

NOT using:

- MongoDB
- Mongoose
- Drizzle

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Type 7: Imagined Config

Symptom

AI references environment variables that don't exist:

// AI generated
const stripeKey = process.env.STRIPE_SECRET_KEY;

But STRIPE_SECRET_KEY isn't in your .env.

Fix: Environment Spec

Document your actual env vars:

## Environment Variables

| Variable       | Purpose             | Required |
| -------------- | ------------------- | -------- |
| DATABASE_URL   | Supabase connection | Yes      |
| OPENAI_API_KEY | LLM calls           | Yes      |
| RESEND_API_KEY | Email               | Yes      |

NOT defined:

- STRIPE\_\* (not using Stripe yet)

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Type 8: Bonus Features

Symptom

AI implements "nice to have" as if required:

// Prompt: "Create task list"
// AI implements:
// - Drag-and-drop reordering
// - Subtasks
// - Time tracking
// - Recurring tasks

Root Cause

AI doesn't distinguish MVP from full product.

Fix: Strict Scope Lock

## Scope Lock

### MVP (This Version)

- [x] Create tasks
- [x] Mark complete
- [x] Delete tasks

### NOT MVP

- Drag-and-drop (v2)
- Subtasks (v2)
- Time tracking (v3)
- Recurring (v3)

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The Prevention Stack

Each hallucination type requires a specific document:

Hallucination	Prevention Document
Phantom API	API Spec Template
Wrong Columns	Schema Template
Fake Imports	Architecture Doc
Scope Creep	PRD Template
Pattern Mismatch	Architecture Doc
Wrong Tech	Tech Stack Doc
Imagined Config	Environment Spec
Bonus Features	PRD Scope Lock

Minimum Viable Prevention

At minimum, create:

1. PRD with explicit non-goals
2. API Spec with all endpoints
3. Database Schema with all tables/columns

These three prevent 80% of hallucinations.

→ Full SDD Template Pack

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Free Resources

Templates

• Spec-Driven Development Pack
• PRD Template
• API Spec Template

Guides

• How to Build an App Without Hallucinations
• Spec-Driven Development Guide

Tools

• Spec Readiness Score — Check your hallucination risk
• PRD Generator — Create your first PRD for free
• PRD vs FRD vs BRD — Which requirement doc do you need?

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Zero hallucinations starts with complete specs. Generate yours →

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Last updated: January 2026