npm / @ai-sdk/mcp

@ai-sdk/mcp

What changed in @ai-sdk/mcp 1 to 2, from its official release notes, upgrade guides and advisories. Sources checked 2026-10-18.

5 breaking7 security9 new APIs and options3 behavior and defaults12 fixes and other

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@ai-sdk/mcp 233 changes

Breaking changes 5

Managed event subscription creation now requires ttlMs as a millisecond duration or null instead of accepting expiresAt; responses still include the backend-calculated expiresAt deadline.
2.0.76release notes
Rejects invalid or missing adapter operations, nullish results, and Promise or thenable results with MCPClientError before the transport starts.
2.0.73release notes
Pass an integration implementing createAdapter instead of passing subscription operations directly; existing operations can be wrapped with { createAdapter: () => operations }.
2.0.73release notes
The configured integration type is now Experimental_MCPEventAdapter and requires implementing createAdapter.
2.0.73release notes
The former subscription operations interface is renamed to Experimental_MCPEventOperations; update imports and operation type annotations.
2.0.73release notes

Security 6

Prevents authorization server paths beginning with repeated slashes from bypassing validation.
1.0.92, 2.0.70release notes release notes
Failed OAuth tokens are identified for conditional invalidation.
2.0.65release notes
Pre-registered OAuth clients are preserved after client authentication errors, and dynamically registered credentials are replaced only with explicit provider provenance.
1.0.85, 2.0.55release notes release notes
DNS validation and connection pinning remain in place when frameworks or instrumentation wrap global fetch before or after the SDK loads.
0.0.39, 1.0.90, 2.0.51release notes release notes release notes
Prevents SSRF in OAuth metadata discovery.
0.0.39, 1.0.90, 2.0.49release notes release notes release notes
OAuth client registration is hardened according to the latest protocol.
2.0.33release notes

New APIs and options 8

Experimental event adapters implement synchronous createAdapter({ transport }) to receive the configured transport description and return bound subscription operations, so applications no longer configure the endpoint twice.
2.0.73release notes
Adds experimental adapters for backend-owned subscription lifecycles without a local event store.
2.0.70release notes
Adds an exclusive configuration union that distinguishes managed and direct event APIs from a single MCPClientConfig.
2.0.70release notes
Adds compatibility for webhook-based MCP events.
2.0.70release notes
Exports MCPClientError for typed MCP failure handling.
2.0.67release notes
Adds an error for OAuth authorization server pin mismatches.
2.0.66release notes
Adds the foundation for the latest 2026 protocol discovery.
2.0.33release notes
Adds support for MCP 2026 streamable HTTP.
2.0.33release notes

Behavior and default changes 2

Renames the unreleased client event configuration to experimental_events.
2.0.70release notes
Server-provided tool annotations are now surfaced in tool metadata.
1.0.78, 2.0.45release notes release notes

Fixes and other changes 12

MCP tools can now execute without options.
0.0.40, 1.0.93, 2.0.74release notes release notes release notes
Preserves OAuth credentials when callback codes are rejected.
1.0.91, 2.0.67release notes release notes
Rejects startup when the connection closes before an endpoint is received.
2.0.67release notes
Preserves prototype-named tools, providers, and provider metadata as own properties without changing lookup object prototypes, preventing inherited names from resolving as registered providers or breaking image metadata aggregation.
0.0.38, 1.0.89, 2.0.62release notes release notes release notes
Explicit environment values for the stdio transport are now preserved.
0.0.36, 1.0.86, 2.0.58release notes release notes release notes
Avoids duplicate OAuth refreshes for stale 401 responses in legacy SSE.
1.0.82, 2.0.53release notes release notes
OAuth callbacks use the stored authorization server when protected resource metadata rediscovery fails.
1.0.81, 2.0.51release notes release notes
MCP tool results can return structuredContent without content; the serialized structured result is added as text.
2.0.45release notes
Origin-only OAuth issuers now accept trailing slashes.
1.0.79, 2.0.44release notes release notes
Creating an MCP tool set now fetches all paginated tool definitions.
1.0.74, 2.0.37release notes release notes
Command shims such as npx can now be spawned on Windows.
0.0.29, 1.0.73, 2.0.36release notes release notes release notes
Rejects SSE requests when POST responses are unsuccessful.
1.0.72, 2.0.35release notes release notes

@ai-sdk/mcp 13 changes

Security 1

Private OAuth endpoints are rejected before credentials are sent, preventing credential disclosure.
0.0.39, 1.0.75release notes release notes

New APIs and options 1

OAuthClientProvider.invalidateCredentials accepts optional token context so providers sharing storage can atomically delete only the rejected token generation and preserve tokens saved by a concurrent refresh.
1.0.91release notes

Behavior and default changes 1

MCP scope selection now applies to dynamic client registration as well as authorization.
1.0.75release notes