ai-sdk-core-v7

Skill: ai-sdk-core

Scope

• Applies to: Backend AI with Vercel AI SDK v7 (ai package)
• Does NOT cover: React chat UIs (see ai-sdk-ui)

Assumptions

• Folder major tracks the installed ai package in package.json, not a skill-file revision
• Node.js 22+, ESM; Zod 4 for inputSchema
• Never write AI SDK from memory. Grep node_modules/ai/docs/ and node_modules/ai/src/ for the installed version. Else https://ai-sdk.dev/docs (append .md) or https://ai-sdk.dev/api/search-docs?q=
• v6 leftovers: https://ai-sdk.dev/docs/migration-guides/migration-guide-7-0

Principles

• generateText / streamText for request handlers and one-shot API routes; instructions for system-style prompt
• Request-handler tool loops: stopWhen: isStepCount(n) on generateText / streamText — not maxSteps, not stepCountIs
• ToolLoopAgent + generate() / stream() for durable agents — not hand-rolled loops, not new Agent()
• UI streams: createUIMessageStreamResponse + toUIMessageStream({ stream: result.stream }) from 'ai'. Use these for new handlers and for dedicated stream/SDK updates
• result.toUIMessageStreamResponse() still works in v7 (deprecated). Leave it only when the task is unrelated to streaming or the SDK
• Tool results must be JSON-serializable (no Date)
• System prompt lives in instructions. Client messages must not include { role: 'system' } unless the server fully trusts the payload

Constraints

MUST

• Read bundled docs before writing calls
• convertToModelMessages when the client sends UI messages
• Reject untrusted { role: 'system' } in messages. Do not set allowSystemInMessages: true for client-supplied chat

AVOID

• toDataStreamResponse / pipeDataStreamToResponse
• stepCountIs / maxSteps / result.fullStream / top-level system: (use isStepCount, result.stream, instructions)
• Guessing model IDs

Interactions

• Complements ai-sdk-ui, fastify, next
• Upstream: vercel/ai use-ai-sdk

Templates

• generate-text-basic.ts
• stream-text-chat.ts
• agent-with-tools.ts

References

• Request handlers — tools + isStepCount, Fastify SSE, system-message reject