What Claude is NOT (good at)

This is the lesson the hype skips.

Claude is sometimes confidently wrong. Treating its output as automatically correct will get you in trouble. The fix is a habit, not a feature.

Everything in this lesson is true today and may be less true in two years. But the habit it builds is the durable thing — it’ll outlast any particular model.

How Claude is wrong

A few flavors, in rough order of frequency:

• Hallucinated details. It cites a function that doesn’t exist. It references a flag that was renamed. It invents a file. The shape of the answer is plausible; the specifics are made up.
• Stale knowledge. Its training has a cutoff. New library versions, new APIs, recent changes to your own code from five minutes ago — it might miss those unless it actually looks.
• Confident wrong-ness. This is the dangerous one. It doesn’t always know when it’s guessing. You’ll get answers that sound certain but aren’t.
• Misreading scope. You asked it to change one thing; it also changed a related thing that looked related but wasn’t.

The good news: most of these are catchable in a couple of seconds, if you look.

The verify habit

Pick one thing to do every time Claude tells you something nontrivial:

• It says a file contains X? Ask it to show you the relevant lines. Or cat the file yourself.
• It made an edit? Read the diff before moving on.
• It ran a command and reported success? Re-run the test or check the output yourself.

The habit isn’t paranoia. It’s the same instinct that makes you glance in the rearview mirror before changing lanes — cheap, automatic, occasionally lifesaving.

Reading is safer than writing

A useful frame for the rest of this course:

• Asking Claude to read your code and explain something is low-risk. The worst case is a wrong explanation, which you spot when the next thing doesn’t make sense.
• Asking Claude to write or change your code is higher-risk. A wrong change persists silently. Now you have a bug you didn’t write.

The next level is Read with Claude for this exact reason: build the habit on the safe side first. Then you start writing.

What’s next

You know what Claude is, what it can see, what it asks before doing, and where it falls down. Time to put it all together on a real task.