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Defined in: client/client.ts:72

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Properties

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auth?

Defined in: client/client.ts:77 Authentication to attach to HTTP requests. A plain string is treated as a Bearer token.

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autoInitialize?

Defined in: client/client.ts:89 When true (default), the MCP initialize handshake is performed automatically inside connect().

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cachePartition?

Defined in: client/client.ts:136 Opaque per-principal identifier for response-cache writes whose server-reported cacheScope is 'private'. Set this to a stable identity of the authorization context (e.g. the auth subject) when one responseCacheStore backs several principals. Passed through verbatim.

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defaultCacheTtlMs?

Defined in: client/client.ts:142 TTL (ms) applied when a cacheable result arrives without a ttlMs field. Default 0 (never served from cache, but still stored). Passed through verbatim.

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defaultOptions?

Defined in: client/client.ts:90

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handlers?

Defined in: client/client.ts:78

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inputRequired?

Defined in: client/client.ts:122 Multi-round-trip auto-fulfilment (protocol revision 2026-07-28). On the modern era, servers obtain client input (elicitation, sampling, roots) by answering a request with an input_required result instead of a server→client request. By default the client fulfils these automatically through the same handlers.sampling/handlers.elicitation callbacks, retrying up to maxRounds times. Set autoFulfill: false for manual mode. Has no effect on legacy-era connections. Passed through verbatim to the SDK client.

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legacySSE?

Defined in: client/client.ts:150 Allow the deprecated SSE transport when a target URL’s path indicates SSE (e.g. ends in /sse). Default false — such URLs throw a clear error pointing at Streamable HTTP and this flag, rather than silently connecting over a transport the MCP SDK itself marks @deprecated. When enabled, a one-time deprecation warning is logged via console.warn.

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prior?

Defined in: client/client.ts:111 A cached era verdict from a previous connection to the same server, so connect() can skip the server/discover probe entirely. Takes precedence over versionNegotiation. { kind: 'modern', discover } adopts a prior DiscoverResult with zero round trips; { kind: 'legacy' } skips the probe and runs the plain legacy initialize handshake. Freshness is the caller’s responsibility — a stale modern verdict fails loudly at the first request; a stale legacy verdict succeeds silently forever. Reuse only within one authorization context.

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responseCacheStore?

Defined in: client/client.ts:129 The response-cache store backing cacheable results (SEP-2549 ttlMs/ cacheScope hints on listTools/listResources/listResourceTemplates/ listPrompts/readResource). Defaults to a fresh in-memory store per client (the SDK’s own default) when omitted. Passed through verbatim.

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roots?

Defined in: client/client.ts:84 Filesystem roots to advertise to the server. Accepts a static array of strings / Root objects, or an async callback invoked on each roots/list request (useful for dynamic root sets).

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versionNegotiation?

Defined in: client/client.ts:100 Opt-in protocol version negotiation (protocol revision 2026-07-28 and later). The default is 'legacy': connect() runs the plain 2025 sequence, byte-identical to today’s behavior (no probe, no new headers). Pass { mode: 'auto' } to probe with server/discover and use the modern era when the server supports it (falling back to legacy otherwise), or { mode: { pin: '2026-07-28' } } to require the modern era outright. See getProtocolEra() to read the negotiated result after connecting.