langchain-typescript-quickstart

1# LangChain TypeScript quickstart
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3Follow the live docs — do not invent an alternate API from memory:
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5**https://docs.langchain.com/oss/javascript/langchain/quickstart**
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7Fetch that page (Docs MCP or HTTP) and implement what it shows (weather agent + `createAgent`). Requires Node 22+.
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9## Local setup constraints
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11Apply these on top of the quickstart (they keep setup minimal and model-agnostic):
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131. **Ask** which provider/model to use. Showcase that LangChain is model-agnostic. Suggested prompt:
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15   > Which model should this agent use? Pass a `provider:model` string — e.g. `openai:gpt-5.5`, `anthropic:claude-sonnet-5`, `google-genai:gemini-2.5-flash-lite`. Default if you're unsure: **`anthropic:claude-sonnet-5`**.
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17   Swap the quickstart's model string for their choice (or the default).
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192. Create a **new** directory (e.g. `langchain-agent/`) and do all work there — do not pollute the open project.
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213. Only secret: the provider API key in `.env` (gitignored). No LangSmith / Tavily unless they ask. Prefer they edit `.env` themselves — don't paste keys into chat.
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234. Install the provider package needed for their model if the quickstart's base install isn't enough.
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255. Run the example, show output, then stop. Point to `langchain-fundamentals` for next steps.