Why does my AI-built app say everything worked when it did not?

Usually because the integration code cannot tell the difference. We ran five broken integrations through a generated-style order flow: it reported all five as successful, and the provider's own ledger showed none of them had happened. No exception was raised and no log line was written, because nothing in the code was ever looking at the result.

Does try/catch around fetch catch HTTP errors?

No, and this is the single most expensive misunderstanding here. fetch only rejects on a network-level failure, so a 410, a 401 and a 500 are all successful fetches as far as JavaScript is concerned. We measured it: four of our five failures never reached the catch block at all.

How do I find silently failing code in my app?

Search for every catch and read what it does — one that logs nothing is a decision never to find out. Then search for fetch and check whether anything inspects response.ok. Then find every call with no timeout, because a service that hangs is not covered by a catch either.

Why did my integration stop working after an API update?

Often because a field was renamed rather than anything being removed. Our inventory sync summed a field that no longer existed, which gives NaN; NaN is not greater than zero, so the next step was skipped and no error occurred anywhere. The response was a perfectly valid 200.

How does silent failure cause the AI doom loop?

Because the loop needs feedback to converge, and silence provides none. If a broken feature reports success, you cannot tell whether the last round of changes fixed anything, so you ask for another round against the same false picture. The fix is not better prompting; it is making the failure visible before you ask again.

What should an error handler actually do?

Keep the detail the provider sent you. In our run the provider replied with the exact remedy — the endpoint had moved and the new path was in the message — and the silent version received that body and discarded it. An error handler that preserves the status and the message turns a week of guessing into one line.

Silent Failures: Why Your App Says “Success” When the Request Failed

You fix one thing, two others break, and last week's bug returns. The loop runs because nothing is telling you the truth — and the most common failure is not an error message but silence.

You fix one thing, two others break, and a bug you killed last week comes back. Nobody has solved this, and no platform can stop a model from going round in circles.

But a loop needs something to converge on, and that is the part you control. If a broken feature reports success, you cannot tell whether the last round of changes helped — so you ask for another round against the same false picture.

The most common failure we hit was not an error at all. It was silence. So we measured how much a generated app’s error handling actually hides.

Watch it instead

The doom loop is number 4 in our countdown of what actually goes wrong for people building with AI.

Video: We Analyzed 130,000 Vibe Coder Posts. These Are the Problems That Actually Hurt. — From the Back4app channel. This guide is the long version of its fourth position; the countdown itself is in the companion post. Open on YouTube →

What did the app say, and what actually happened?

Two completely different stories, from the same run:

Five integrations compared: the app in its generated shape reported all five steps succeeded, the same five written honestly reported all five failed, and the provider's ledger shows none of the five actually happened

The right-hand column is not the app’s opinion. It is the provider’s own ledger — a count of receipts sent, inventory commits made and cards charged, kept on the other side of the network where the app cannot affect it.

Five features. Five green ticks. Nothing happened.

A green tick is only worth anything if something in the code could ever have produced a red one.

Why didn’t anything get logged?

Because there was nothing to log. This is the shape the code came in:

try {
  await fetch(`${BASE}/v1/messages`, { method: 'POST', body: JSON.stringify({ to: order.email }) });
  return { ok: true };
} catch (e) { console.log('could not send receipt'); return { ok: true }; }

Read it as the computer does. The request is made. A response comes back. Nothing looks at it. { ok: true } is returned because that is the only thing this function can return.

The catch is not even reached — and when it is, it returns { ok: true } anyway.

Does try/catch catch an HTTP error at all?

No, and that is the measurement worth carrying away from this article. We put each failure through a bare call and recorded whether it threw:

the failure             does it throw?  what the code gets back
endpoint removed (410)  no              returned a Response
field renamed (200)     no              returned NaN
key rotated (401)       no              returned a Response
never answers           YES             TimeoutError
ingest down (500)       no              returned a Response

fetch rejects only when the request never completed — DNS failure, connection refused, an abort. A server replying “this endpoint is gone” is a completed request, and therefore a success.

The quietest of the five is the renamed field. Summing a field that no longer exists gives NaN, and NaN > 0 is false, so the next step is skipped. Valid 200, valid JSON, no error anywhere, and the inventory never syncs.

What did the honest version say?

Exactly what was wrong, in five lines, including the remedy:

sendReceipt: HTTP 410 — POST /v1/messages was removed in v3. Use POST /v3/email with {to, template}.
syncInventory: inventory total is not a number — a field name changed
chargeCard: HTTP 401 — This key was rotated on 2026-09-30.
fetchRates: no answer within 3000 ms
logAnalytics: HTTP 500 — ingest_unavailable

Look at the first line again. The provider said the endpoint had moved and named its replacement. That body arrived in the silent run too — identical bytes, same response — and was discarded without being read.

The same five integrations

5 of 5reported ok by the generated version

→

0 of 5actually happened, per the provider's ledger

4 of 5failures that never reach a catch block

The ledger is kept by the provider, not the app. Identical across three runs.

What does this have to do with the loop?

It is the loop’s fuel. Round one asks for a fix, round two reports success, and nothing has changed — so round three is asked against the same false picture, and the model has no more information than it had at the start.

Making failures visible does not stop a model from going round in circles. What it does is let you see which round actually worked, which turns an argument with a machine into a sequence of checkable steps.

The other half of surviving the loop is being able to step back cleanly, which we measured separately in undoing what an AI assistant broke. Visible failures tell you that a round was bad; versioning lets you leave it behind in one command.

What should you change in the code?

Four things, and they are small. Check response.ok on every call, and put the provider’s status and message into the error you raise — that message is often the entire fix.

Give every outbound call a timeout, because a hang is not an exception and will not be caught by anything. And validate the shape of what came back, not just that something came back, which is the only thing that would have caught the renamed field.

What should you do first?

Search your code for catch and read every one out loud. A catch that logs nothing is a decision, made once, to never find out.

Then take your most important integration and ask what would look different if it silently did nothing. If the honest answer is “nothing visible”, then you do not currently know whether it works — and neither does whatever you are asking to fix it.

The lab is in the repo — five integrations, two ways of writing them, and a provider that keeps score independently of what the app believes.