Vercel AI Sdk Knowledge Patch

Vercel AI SDK Knowledge Patch

Use this skill for TypeScript applications built with the ai package, AI SDK UI, provider packages, agents, workflows, generated media, or @ai-sdk/mcp. Confirm the application's installed core and provider versions before applying version-dependent names. Start with migrations and breaking changes, then load the topic reference for the work at hand.

Reference index

Breaking changes first

Runtime and packages

For the v7 API line, require Node.js 22 or newer and ESM imports. CommonJS require() is unsupported. Upgrade ai and every provider package together, run the codemod, and manually review semantic changes:

npx @ai-sdk/codemod v7

Version 4.0 also removed deprecated APIs. Its codemods handle much of the mechanical migration, but consult the migration guide for manual work.

Current names and deprecations

Use these names in v7-targeted code:

The repair options retain deprecated experimental aliases. System messages embedded in prompt or messages require allowSystemInMessages: true. Tool-level needsApproval, result-instance response methods, and Vue's Chat class are deprecated; use call-level toolApproval, top-level response helpers, and useChat.

Multi-step result scope

Top-level multi-step results accumulate content, tool calls and results, files, sources, warnings, and usage for the whole run. Use finalStep for last-step-only values. Request and response bodies are retained only when explicitly requested.

const totalUsage = await result.usage;
const finalStep = await result.finalStep;
console.log(totalUsage, finalStep.usage);

Agent control quick reference

Bound every loop

ToolLoopAgent defaults to isStepCount(20). stopWhen runs after a step that produced tool results, and arrays have OR semantics. A loop also stops after normal completion without tool calls, a tool call with no execute, or an approval request. Use isLoopFinished() only when uncapped natural completion is intentional.

const agent = new ToolLoopAgent({
  model,
  tools,
  stopWhen: [isStepCount(50), hasToolCall('publish')],
});

Reconfigure steps and calls

prepareStep sees the current model, zero-based stepNumber, previous steps, outgoing messages, and runtime context. It may replace the model or messages, restrict activeTools, choose tools, and override per-call settings; return {} to retain constructor settings. ToolLoopAgent.prepareCall can inspect and override the top-level reasoning setting.

For explicit completion, combine toolChoice: 'required' with a terminal tool that has no execute. Read its typed payload from staticToolCalls.

Typed state and output

Declare output: Output.object(...) on an agent for validated, inferred generate().output. Derive UI and persistence types with InferAgentUIMessage<typeof agent> and serve them with createAgentUIStreamResponse.

Use runtimeContext for typed orchestration state shared across preparation, approvals, callbacks, telemetry, and agents. Use a tool's contextSchema with toolsContext for private, tool-scoped values; only that tool receives validated context.

Constructor-level and call-level lifecycle callbacks compose. When both define the same callback, the constructor callback runs first.

Approvals return, then replay

Approval does not suspend generation. Preserve result.response.messages, append matching tool-approval-response parts in a tool message, then invoke generation again. Call-level toolApproval can request user review, decide automatically, or use a typed policy. Sign approvals and revalidate input and policy when replay crosses a trust boundary.

Tool execution quick reference

• execute(input, context) can read toolCallId, conversation messages, the request abortSignal, scoped context, and an optional sandbox session.
• dynamicTool retains static inference for known tools while marking runtime-loaded calls and results with dynamic: true; validate or cast their unknown values.
• An async-generator execute streams preliminary values; its last value is final.
• onInputStart runs before validated onInputAvailable in streaming and non-streaming calls; onInputDelta observes streaming argument chunks.
• Media returned from execute does not automatically reach the model. Implement toModelOutput, favoring inline bytes when provider URL support is uncertain.
• Use repairToolCall to replace malformed calls or return null; distinguish NoSuchToolError, InvalidToolArgumentsError, ToolExecutionError, and ToolCallRepairError.

Generation and agents accept total, step, first-content, idle-chunk, default-tool, and per-tool timeouts. Timeouts surface as TimeoutError; first-content and idle-chunk budgets apply only to streaming. A supplied SandboxSession reaches tools as experimental_sandbox and supports working directories, environment values, streaming output, and abort signals.

Use WorkflowAgent when execution must survive restarts, deployments, interruptions, or delayed approvals. Use experimental HarnessAgent to adapt an external runtime to the standard Agent interface and resume sessions or interrupted turns.

Streaming and structured output quick reference

streamText begins immediately but advances under consumer backpressure. Always consume a returned stream. Generation errors arrive through onError or in-band error parts; tool failures become tool-error parts. Non-streaming schema and generation failures still throw. Await response-piping helpers to catch both stream read and write errors.

Transforms run in order before callbacks and result promises. A transform that calls stopStream must emit synthetic finish-step and finish events. Exceptions in experimental lifecycle observer hooks are swallowed and do not fail generation.

For structured results:

• Agents can own an Output.object schema.
• Text generation can combine tools with a final validated output in a multi-step run.
• NoObjectGeneratedError preserves raw text, response metadata, usage, and cause.
• Array mode preserves transforms, coercions, defaults, and pipes.
• JSON extraction and repair can recover malformed structured output and tool calls.

UI and MCP quick reference

useChat can send client chat IDs, receive server-assigned response message IDs, and persist with appendResponseMessages. createDataStreamResponse emits custom data and annotations before or beside generation; merge streamText with mergeIntoDataStream. DirectChatTransport connects useChat directly to an agent.

Create MCP clients with @ai-sdk/mcp. Prefer HTTP in deployments and stdio locally. Keep the client open through generation and close it afterward. Passing schemas to client.tools() limits discovery and types inputs. An outputSchema validates structuredContent, falls back to JSON parsed from text, and throws if neither is valid; without it the tool returns raw CallToolResult.

Treat MCP resources as application-selected context and prompts as user-selected templates. Elicitation requires an advertised capability and a handler returning accept, decline, or cancel. Before exposing remotely described tools, persist a trusted fingerprintTools snapshot and compare later definitions with detectToolDrift.

Media, providers, and telemetry quick reference

• Compatible providers accept PDFs as file message parts with mimeType: 'application/pdf'.
• uploadFile and uploadSkill create reusable provider references.
• generateSpeech, transcribe, SpeechResult, TranscriptionResult, and generateImage are stable; canonical file parts support bytes, URLs, provider references, or text content.
• Streaming transcription has one consumer: read fullStream before awaiting result promises when both incremental and final values are required.
• Experimental video supports aborts, bounded downloads, image and video references, polling or webhooks, durable polling delays, and provider-specific adaptive ratios.
• Top-level reasoning supplies portable effort control; keep providerOptions for provider-specific settings.

Register one telemetry integration with registerTelemetry; OpenTelemetry is in @ai-sdk/otel. Runtime and tool context is excluded unless explicitly selected. Portable lifecycle hooks are onStart, onStepEnd, and onEnd; Node.js instrumentation can subscribe to the ai:telemetry tracing channel. Include only context fields safe to export.

Implementation checklist

1. Confirm the installed API line before selecting stable, deprecated, or experimental names.
2. Bound loops and long-running tools with stop rules, timeouts, and abort signals.
3. Consume streams, await piping helpers, and handle in-band failures.
4. Persist complete response messages before replaying approvals.
5. Validate runtime-defined tools, MCP outputs, and remotely supplied definitions.
6. Keep secrets in tool-scoped context and opt telemetry fields in deliberately.
7. Use durable workflows for operations that must survive process boundaries.