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Cover image for AI-generated code doesn't fail loudly. It fails correctly-looking.
Damir Karimov
Damir Karimov

Posted on • Originally published at blog.damir-karimov.com

AI-generated code doesn't fail loudly. It fails correctly-looking.

#ai #softwareengineering #codequality #frontend

AI-generated code rarely breaks in obvious ways. It passes review, ships
to production, and behaves correctly in controlled scenarios. The
problem is what happens after: failures appear only under timing, load,
retries, or inconsistent state transitions.

The core issue is not obvious bugs. It is code that looks structurally
correct while silently ignoring real-world failure modes.

Why AI code feels correct

AI tends to generate implementations with strong surface-level signals:

  • consistent TypeScript types
  • standard architectural patterns
  • clean async/await flows
  • readable naming conventions
  • familiar framework usage

This produces a strong cognitive bias during review. The code does not
look "risky", so it is assumed to be correct.

The gap appears because readability is not equivalent to correctness
under production conditions.

Where AI-generated code typically fails

1. Concurrency and race conditions 

async function updateProfile(data: Profile) {
  setLoading(true);

  const response = await api.updateProfile(data);

  setUser(response.user);
  setLoading(false);
}
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This assumes a single linear execution.

In real systems:

  • multiple requests can run in parallel
  • responses can resolve out of order
  • later responses can overwrite newer state

Result: stale state overwrite without errors or crashes.

2. Optimistic updates without consistency guarantees 

setTodos((prev) => [...prev, newTodo]);
await api.createTodo(newTodo);
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This assumes success.

Failure scenarios:

  • request fails but UI is not rolled back
  • retry creates duplicate entries
  • frontend state diverges from backend state

The system remains "visually correct" while data integrity is broken.

3. Stale closures and lifecycle assumptions 

useEffect(() => {
  const interval = setInterval(() => {
    console.log(count);
  }, 1000);

  return () => clearInterval(interval);
}, []);
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This pattern locks in initial state.

In production:

  • values become stale over time
  • UI desynchronization occurs
  • behavior depends on render timing rather than logic

No runtime error occurs, so the issue is often missed.

4. Weak caching and invalidation logic 

const cacheKey = `user-${userId}`;

if (cache[cacheKey]) return cache[cacheKey];

const data = await fetchUser(userId);
cache[cacheKey] = data;
return data;
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This assumes:

  • stable data shape
  • stable identity rules
  • single write path

In real systems:

  • partial updates invalidate assumptions
  • multiple services mutate the same entity
  • cache becomes silently stale rather than obviously wrong

5. Hidden assumptions about APIs

AI can introduce plausible but non-existent APIs:

await auth.refreshSession({ force: true });
storage.invalidateAllQueries();
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These patterns often:

  • look consistent with ecosystem conventions
  • pass code review without deep verification
  • fail only at runtime

This shifts errors from compile-time to production-time.

6. Accumulated lifecycle leaks 

useEffect(() => {
  const controller = new AbortController();

  fetchData(controller.signal);

  return () => controller.abort();
}, [id]);
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Individually correct, but when repeated across systems:

  • inconsistent cleanup patterns accumulate
  • aborted requests still resolve in edge cases
  • memory usage grows gradually
  • behavior becomes harder to reproduce

Systemic issue: reduced verification depth

The main shift introduced by AI-generated code is not implementation
speed, but review behavior.

Before AI, writing code required reasoning during implementation. After
AI:

  • code already looks complete
  • structure appears correct by default
  • reviewers focus on surface validation

This creates a subtle degradation in engineering discipline:

  • fewer edge-case simulations
  • less reasoning about concurrency
  • weaker validation of failure states
  • acceptance of "looks correct" as correctness

Impact on real systems

1. Frontend state drift

UI remains stable visually while backend state diverges.

2. Authentication and session issues

  • race conditions during token refresh
  • inconsistent logout handling
  • background requests using invalid sessions

3. Payments and idempotency problems

  • duplicate transactions
  • retries without deduplication
  • partial failure inconsistencies

4. Distributed system inconsistencies

  • assumption of ordering guarantees
  • reliance on immediate consistency
  • incorrect retry semantics

These issues are not immediately visible. They surface as rare,
non-reproducible incidents.

The real risk

AI does not generate obviously wrong code.

It generates code that satisfies:

  • type safety
  • structural conventions
  • expected patterns
  • readable abstractions

This creates false confidence during review.

The critical failure is not bugs themselves, but reduced skepticism
toward code that appears correct.

Once that happens, correctness is no longer actively verified. It is
assumed.

Conclusion

AI increases development speed, but it also changes how correctness is
perceived.

The danger is code that looks correct enough that nobody questions it deeply.

When that happens, production issues stop being introduced by obvious mistakes and start emerging from unexamined assumptions embedded in clean-looking code.

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