Lesson 1006 of 1455
Why Claude Doesn't Know What Happened Last Week
Models have a 'knowledge cutoff' — a date after which they know nothing without web search.
Builders · Model Families · ~4 min read
The big idea
Every model was trained on data up to a specific date — its 'knowledge cutoff.' After that date, the model knows nothing on its own. Ask it about today's news and it'll either say 'I don't know' or (worse) hallucinate. The fix: use a model with web search turned on (Perplexity, ChatGPT with search, Claude with web).
Some examples
- Claude Opus 4.5 cutoff: ~April 2024. Anything from after is unknown without search.
- GPT-5 cutoff: ~April 2025. Slightly newer, same problem.
- Gemini 2.5 cutoff: ~mid-2024. Same problem.
- Web search turns this off — Perplexity, ChatGPT 'Search', Claude 'Web Search' are all 2026-current.
Try it!
Ask Claude or ChatGPT (without search) about a news story from this week. Watch what it does. Then turn on search and ask again.
Key terms in this lesson
End-of-lesson quiz
Check what stuck
8 questions · Score saves to your progress.
Lesson help
Questions are best handled with a grown-up here.
For this age range, Tendril keeps freeform AI chat paused until parent/guardian consent and child-safe moderation are fully verified. Use the quiz, notes, and related lessons below, or ask a parent, guardian, teacher, or librarian to work through the question with you.
Progress saved locally in this browser. Sign in to sync across devices.
Related lessons
Keep going
Creators · 40 min
When to Fine-Tune vs When to Just Prompt: A Decision Framework
Fine-tuning is expensive and slow to iterate on. Prompting is fast and free. Knowing when fine-tuning actually pays off saves teams from premature optimization.
Builders · 28 min
ElevenLabs v3 — voice cloning without causing a disaster
ElevenLabs voices are indistinguishable from humans. That is a feature and a fraud vector. Here is the production checklist before you clone anyone.
Builders · 40 min
Claude vs ChatGPT for Teens: Quick Comparison
Both are great chatbots but they have different vibes. Knowing which to pick saves time.