# migrating-vercel-ai-sdk-and-eve-to-pydantic-ai

Moves TypeScript Vercel AI SDK or Eve apps to Python with Pydantic AI. Useful when the goal is keeping behavior, not the source APIs.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 306 installs · ★ 145
- Author: pydantic
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/pydantic/skills/tree/HEAD/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai/SKILL.md
- Updated: 2026-10-16
- HTML: https://affpapa.org/en/nevibecode/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai

## What it does

The skill splits a source project into layers: model calls and tool loops, the UI wire protocol, Eve sessions and schedules, and the plain application shell around them — auth, storage, deployment. It starts by reading dependencies, lockfiles, tests and the runtime entrypoint, resolving `workspace:*` to concrete versions, then capturing a baseline test on one real request.

From there it picks the smallest target. A normal AI SDK migration becomes one `pydantic_ai.Agent` behind the existing caller. Reach for `pydantic_graph` only when explicit typed nodes, branches and joins still earn their keep. `pydantic-ai-harness` is added for observed reusable policy: Agent Skills, model-directed subagents, planning, guardrails, step persistence. Datasets and evaluators live in the separate `pydantic-evals` package.

The real risk is silent semantic drift. `generateText()` and `streamText()` are single-step by default, `ToolLoopAgent` runs a longer loop, and `WorkflowAgent` has no step ceiling unless you set one. If a TypeScript or React client already speaks AI SDK UI, keep it and serve its protocol through `VercelAIAdapter` — match the adapter to the installed SDK version, because frame formats between older and newer implementations are not interchangeable.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add pydantic/skills --skill migrating-vercel-ai-sdk-and-eve-to-pydantic-ai -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add pydantic/skills --skill migrating-vercel-ai-sdk-and-eve-to-pydantic-ai -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add pydantic/skills --skill migrating-vercel-ai-sdk-and-eve-to-pydantic-ai -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install pydantic/skills migrating-vercel-ai-sdk-and-eve-to-pydantic-ai
```

2. **Manually: put the files in place**
- File: `.github/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add pydantic/skills --skill migrating-vercel-ai-sdk-and-eve-to-pydantic-ai -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/pydantic/skills --path skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add pydantic/skills --skill migrating-vercel-ai-sdk-and-eve-to-pydantic-ai -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/pydantic/skills/tree/HEAD/skills/migrating-vercel-ai-sdk-and-eve-to-pydantic-ai/SKILL.md

## When to use it
- port `generateText` and `streamText` calls to Python without changing behavior
- sort AI SDK Core, AI SDK UI and Eve contracts by owner
- keep the AI SDK UI protocol for an existing React client
- separate Eve durable sessions from Pydantic AI message history
- decide whether `pydantic-ai-harness` is needed or core is enough

## Example prompts
- Trace this repo and tell me which contracts belong to AI SDK Core and which to the application
- Migrate the `streamText` calls to `pydantic_ai.Agent`, keep the stop conditions and usage limits
- We have a `useChat` client — keep it and configure `VercelAIAdapter` for the installed SDK version

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: fe1e283d560b5d18.

BEGIN THIRD-PARTY FILE fe1e283d560b5d18
```text
---
name: migrating-vercel-ai-sdk-and-eve-to-pydantic-ai
description: Migrate TypeScript Vercel AI SDK or Eve applications to Python with Pydantic AI and, only when needed, Pydantic AI Harness. Use when source code imports `ai`, `@ai-sdk/*`, or `eve`, or relies on `generateText`, `streamText`, `ToolLoopAgent`, `useChat`, Eve agents, tools, skills, subagents, approvals, sessions, channels, schedules, or sandboxes.
---

# Migrate Vercel AI SDK and Eve to Pydantic AI

Preserve the application's observable behavior, not the source APIs. Vercel AI SDK Core, AI SDK UI, and Eve have different responsibilities: identify which one owns each source behavior before choosing a target.

## Trace the source before choosing a target

1. Read repository instructions, dependencies, lockfiles, tests, and the runtime entrypoint. Resolve `workspace:*` dependencies to concrete package versions and record the installed AI SDK, Eve, Pydantic AI, and Harness versions.
2. Trace one real request from its public entrypoint through messages, model calls, tools, approvals, streams, persistence, side effects, and the result the caller consumes. Establish a focused baseline or characterization test.
3. Classify every observed contract:
   - **AI SDK Core:** model calls, step loops, tool execution, structured output, and provider routing;
   - **AI SDK UI:** `UIMessage`, `useChat`, transports, client tools, stream chunks, and reconnect behavior;
   - **Eve:** filesystem-defined agents, durable sessions, skills, subagents, state, connections, channels, schedules, and sandboxes;
   - **Application/platform:** authentication, authorization, storage, queues, deployment, credentials, product UI, and hosted Vercel services.
4. Record each contract, its owner, semantic difference, and executable proof. An unused feature is not migration scope.
```
END THIRD-PARTY FILE fe1e283d560b5d18

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