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System 1 and System 2, for models
LangChain maps Kahneman's split onto models: System 1 as the fast automatic decision, System 2 as the slow deliberate one, with Jev in the first role.
- Format
- Video
- Published by
- Community
- Author
- LangChain
- Last verified
- Oct 2026
Works forJev for Routing
Used inJev for Software & DevTools
Highlights
- Uses Kahneman's System 1 and System 2 as the frame for which model to call.
- System 1 is described as fast, cheap, and automatic. System 2 is slow, expensive, and deliberate.
- Separate from LangChain's harness walkthrough and the short PII Noul clip.
Watch out
A conceptual clip. It does not publish a routing eval.
Questions about this entry
Short answers drawn from the linked project or page.
Not covered. The source does not document an escalation or fallback path, and the entry caveats call this a conceptual clip that publishes no routing eval. It frames which model to call, not how to recover from a bad fast answer.
No. The caveats state explicitly that no routing eval is published, and the captured source page is only the title plus YouTube boilerplate, so there are no accuracy, latency or cost figures to check.
No, it is vocabulary borrowed from psychology. The description uses the split to sort model roles, and the highlights describe System 1 as fast, cheap and automatic. Neither claim is backed by a measured comparison anywhere in the entry.
No. The entry copy separates this clip from LangChain's own harness walkthrough and its PII Noul demo, so nothing here shows a chain or code you can copy. The captured source page documents only the title.
LangChain published it, using Kahneman's System 1 and System 2 as the frame for which model to call.
System 1 is described as fast, cheap, and automatic; System 2 as slow, expensive, and deliberate. Jev is placed in the first role.
LangChain's harness walkthrough and the short PII Noul clip. The entry treats this one as a conceptual piece rather than either of those.
Reactions & coverage
Posts, threads, and videos about this entry from around the web.
YouTube: LangChain maps System 1 and System 2 onto fast decisions versus slow generation.
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FacebookClinicnotes
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