LangChain Launches Decision Models with Open-Source SemIf Free for a Week
On September 21, LangChain founder Harrison Chase announced that decision models would become a first-class capability on LangSmith Gateway, with the open-source decision model SemIf free to use for one week starting immediately. Decision models do not generate chat replies; instead they perform structured classification or scoring on text and return structured results, offering developers a lightweight alternative to generative LLMs for use cases such as typed output and agent routing.
Confirmed
- Decision models were announced as first-class citizens on LangSmith Gateway by Harrison Chase on September 21, corroborated by official SemIf documentation from the LangChain account
- The open-source decision model is semif-qwen3.5-4b (built on qwen3.5), callable via the LangSmith LLM Gateway and System One API, compatible with the TypeSafe SDK—users can switch by changing a single string
- SemIf was formerly OpenJev, created by TheoLeeCJ; according to reposted threads it runs locally on a single RTX 3090
- LangChain engineer Hacubu published full integration documentation on the same day, covering both the hosted SemIf model and bring-your-own-Jev-key (BYOK) usage
Why it matters
- Decision models carve classification and scoring tasks away from conversational generation, returning structured results and reducing integration cost and uncertainty for such applications
- Open-sourcing plus a limited-time free offer and BYOK support signals LangChain's strategy of expanding its model catalog through LangSmith Gateway
2026-09-21 ~ 2026-09-22 · 7 related posts
Primary sources
- LangChain launches 'decision models' in LangSmith Gateway, hosts open-source SemIf free for a week — hwchase17 ·
- LangChain ships SemIf decision model: structured classification via LLM Gateway — LangChain ·
- LangChain docs detail calling SemIf decision models via LangSmith Gateway System One API — Hacubu ·
- [source] LangChain docs detail calling SemIf decision models via LangSmith Gateway System One API — Hacubu · 2026-09-21
- [source] LangChain launches 'decision models' in LangSmith Gateway, hosts open-source SemIf free for a week — hwchase17 · 2026-09-21
- [source] LangChain ships SemIf decision model: structured classification via LLM Gateway — LangChain · 2026-09-22
- LangChain offers open-source decision model SemIf free for a week in LangSmith Gateway — hwchase17 · 2026-09-22
- Open-source decision model SemIf lands on LangSmith Gateway free, runs locally on a 3090 — hwchase17 · 2026-09-22
- LangChain hosts open-source decision model SemIf free for a week via LangSmith Gateway — hwchase17 · 2026-09-22
1 near-duplicate retellings: Hacubu