mcp: Deprecate roots, sampling and logging (SEP-2577) (#1017)

Fixes #1013

README.md

@@ -44,6 +44,13 @@ The following table shows which versions of the Go SDK support which versions of
 
 \*\* Partial support for 2025-11-25 (client side OAuth and Sampling with tools not available).
 
+The roots, sampling, and logging features are deprecated as of protocol version
+2026-07-28 by
+[SEP-2577](https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging).
+The SDK continues to support them for compatibility during the deprecation
+window (at least twelve months). See the individual feature documentation for
+migration guidance.
+
 New releases of the SDK target only supported versions of Go. See
 https://go.dev/doc/devel/release#policy for more information.
 

conformance/everything-server/main.go

@@ -5,6 +5,8 @@
 // The conformance server implements features required for MCP conformance testing.
 // It mirrors the functionality of the TypeScript conformance server at
 // https://github.com/modelcontextprotocol/conformance/blob/main/examples/servers/typescript/everything-server.ts
+//
+//lint:file-ignore SA1019 conformance server exercises deprecated SEP-2577 APIs (roots, sampling, logging).
 package main
 
 import (

docs/client.md

@@ -10,6 +10,13 @@
 
 ## Roots
 
+> **Note:** The roots feature is deprecated as of protocol version 2026-07-28
+> ([SEP-2577](https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging)).
+> It remains fully functional during the deprecation window (at least twelve
+> months). The SDK continues to support roots for compatibility. New code
+> should pass paths via tool parameters, resource URIs, or configuration
+> instead.
+
 MCP allows clients to specify a set of filesystem
 ["roots"](https://modelcontextprotocol.io/specification/2025-06-18/client/roots).
 The SDK supports this as follows:
@@ -77,6 +84,13 @@ func Example_roots() {
 
 ## Sampling
 
+> **Note:** The sampling feature is deprecated as of protocol version
+> 2026-07-28
+> ([SEP-2577](https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging)).
+> It remains fully functional during the deprecation window (at least twelve
+> months). The SDK continues to support sampling for compatibility. Servers
+> that need LLM completions should call LLM provider APIs directly.
+
 [Sampling](https://modelcontextprotocol.io/specification/2025-06-18/client/sampling)
 is a way for servers to leverage the client's AI capabilities. It is
 implemented in the SDK as follows:

docs/server.md

@@ -474,6 +474,13 @@ _ = mcp.NewServer(&mcp.Implementation{Name: "server"}, &mcp.ServerOptions{
 
 ### Logging
 
+> **Note:** The logging feature is deprecated as of protocol version
+> 2026-07-28
+> ([SEP-2577](https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging)).
+> It remains fully functional during the deprecation window (at least twelve
+> months). The SDK continues to support logging for compatibility. Servers
+> should migrate to stderr logging (for STDIO transports) or OpenTelemetry.
+
 MCP servers can send logging messages to MCP clients.
 (This form of logging is distinct from server-side logging, where the
 server produces logs that remain server-side, for use by server maintainers.)

examples/server/distributed/main.go

@@ -16,6 +16,8 @@
 // Example:
 //
 //	./distributed -http=localhost:8080 -child_ports=8081,8082
+//
+//lint:file-ignore SA1019 example server exercises deprecated SEP-2577 logging API for demonstration.
 package main
 
 import (

examples/server/everything/main.go

@@ -3,6 +3,8 @@
 // license that can be found in the LICENSE file.
 
 // The everything server implements all supported features of an MCP server.
+//
+//lint:file-ignore SA1019 example server exercises deprecated SEP-2577 APIs (roots, sampling, logging) for demonstration.
 package main
 
 import (

internal/docs/client.src.md

@@ -4,6 +4,13 @@
 
 ## Roots
 
+> **Note:** The roots feature is deprecated as of protocol version 2026-07-28
+> ([SEP-2577](https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging)).
+> It remains fully functional during the deprecation window (at least twelve
+> months). The SDK continues to support roots for compatibility. New code
+> should pass paths via tool parameters, resource URIs, or configuration
+> instead.
+
 MCP allows clients to specify a set of filesystem
 ["roots"](https://modelcontextprotocol.io/specification/2025-06-18/client/roots).
 The SDK supports this as follows:
@@ -26,6 +33,13 @@ method. To receive notifications about root changes, set
 
 ## Sampling
 
+> **Note:** The sampling feature is deprecated as of protocol version
+> 2026-07-28
+> ([SEP-2577](https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging)).
+> It remains fully functional during the deprecation window (at least twelve
+> months). The SDK continues to support sampling for compatibility. Servers
+> that need LLM completions should call LLM provider APIs directly.
+
 [Sampling](https://modelcontextprotocol.io/specification/2025-06-18/client/sampling)
 is a way for servers to leverage the client's AI capabilities. It is
 implemented in the SDK as follows:

internal/docs/server.src.md

@@ -236,6 +236,13 @@ requests.
 
 ### Logging
 
+> **Note:** The logging feature is deprecated as of protocol version
+> 2026-07-28
+> ([SEP-2577](https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging)).
+> It remains fully functional during the deprecation window (at least twelve
+> months). The SDK continues to support logging for compatibility. Servers
+> should migrate to stderr logging (for STDIO transports) or OpenTelemetry.
+
 MCP servers can send logging messages to MCP clients.
 (This form of logging is distinct from server-side logging, where the
 server produces logs that remain server-side, for use by server maintainers.)

internal/readme/README.src.md

@@ -43,6 +43,13 @@ The following table shows which versions of the Go SDK support which versions of
 
 \*\* Partial support for 2025-11-25 (client side OAuth and Sampling with tools not available).
 
+The roots, sampling, and logging features are deprecated as of protocol version
+2026-07-28 by
+[SEP-2577](https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging).
+The SDK continues to support them for compatibility during the deprecation
+window (at least twelve months). See the individual feature documentation for
+migration guidance.
+
 New releases of the SDK target only supported versions of Go. See
 https://go.dev/doc/devel/release#policy for more information.
 

mcp/capabilities_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by an MIT-style
 // license that can be found in the LICENSE file.
 
+//lint:file-ignore SA1019 tests exercise deprecated SEP-2577 APIs (roots, sampling, logging).
+
 package mcp
 
 import (

mcp/client.go

@@ -82,6 +82,12 @@ type ClientOptions struct {
 	// &SamplingCapabilities{}. If [ClientOptions.Capabilities] is set and has a
 	// non nil value for [ClientCapabilities.Sampling], that value overrides the
 	// inferred capability.
+	//
+	// Deprecated: the sampling feature is deprecated as of protocol version
+	// 2026-07-28 (SEP-2577). It remains functional during the deprecation
+	// window (at least twelve months). Migrate to calling LLM provider APIs
+	// directly from your server. See
+	// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 	CreateMessageHandler func(context.Context, *CreateMessageRequest) (*CreateMessageResult, error)
 	// CreateMessageWithToolsHandler handles incoming sampling/createMessage
 	// requests that may involve tool use. It returns
@@ -95,6 +101,12 @@ type ClientOptions struct {
 	//
 	// It is a panic to set both CreateMessageHandler and
 	// CreateMessageWithToolsHandler.
+	//
+	// Deprecated: the sampling feature is deprecated as of protocol version
+	// 2026-07-28 (SEP-2577). It remains functional during the deprecation
+	// window (at least twelve months). Migrate to calling LLM provider APIs
+	// directly from your server. See
+	// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 	CreateMessageWithToolsHandler func(context.Context, *CreateMessageWithToolsRequest) (*CreateMessageWithToolsResult, error)
 	// ElicitationHandler handles incoming requests for elicitation/create.
 	//
@@ -152,10 +164,17 @@ type ClientOptions struct {
 	// ElicitationCompleteHandler handles incoming notifications for notifications/elicitation/complete.
 	ElicitationCompleteHandler func(context.Context, *ElicitationCompleteNotificationRequest)
 	// Handlers for notifications from the server.
-	ToolListChangedHandler      func(context.Context, *ToolListChangedRequest)
+	ToolListChangedHandler     func(context.Context, *ToolListChangedRequest)
-	PromptListChangedHandler    func(context.Context, *PromptListChangedRequest)
+	PromptListChangedHandler   func(context.Context, *PromptListChangedRequest)
-	ResourceListChangedHandler  func(context.Context, *ResourceListChangedRequest)
+	ResourceListChangedHandler func(context.Context, *ResourceListChangedRequest)
-	ResourceUpdatedHandler      func(context.Context, *ResourceUpdatedNotificationRequest)
+	ResourceUpdatedHandler     func(context.Context, *ResourceUpdatedNotificationRequest)
+	// LoggingMessageHandler handles incoming notifications/message
+	// notifications from the server.
+	//
+	// Deprecated: the logging feature is deprecated as of protocol version
+	// 2026-07-28 (SEP-2577). It remains functional during the deprecation
+	// window (at least twelve months). See
+	// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 	LoggingMessageHandler       func(context.Context, *LoggingMessageRequest)
 	ProgressNotificationHandler func(context.Context, *ProgressNotificationClientRequest)
 	// MultiRoundTrip configures the automatic MultiRoundTrip (Multi Round-Trip Requests) middleware.
@@ -615,6 +634,12 @@ func (cs *ClientSession) startKeepalive(interval time.Duration) {
 // AddRoots adds the given roots to the client,
 // replacing any with the same URIs,
 // and notifies any connected servers.
+//
+// Deprecated: the roots feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). Migrate to passing paths via tool parameters,
+// resource URIs, or configuration. See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 func (c *Client) AddRoots(roots ...*Root) {
 	// Only notify if something could change.
 	if len(roots) == 0 {
@@ -627,6 +652,12 @@ func (c *Client) AddRoots(roots ...*Root) {
 // RemoveRoots removes the roots with the given URIs,
 // and notifies any connected servers if the list has changed.
 // It is not an error to remove a nonexistent root.
+//
+// Deprecated: the roots feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). Migrate to passing paths via tool parameters,
+// resource URIs, or configuration. See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 func (c *Client) RemoveRoots(uris ...string) {
 	changeAndNotify(c, notificationRootsListChanged, &RootsListChangedParams{},
 		func() bool { return c.roots.remove(uris...) })
@@ -1242,6 +1273,14 @@ func (cs *ClientSession) CallTool(ctx context.Context, params *CallToolParams) (
 	return handleSend[*CallToolResult](ctx, methodCallTool, newClientRequest(cs, orZero[Params](params)))
 }
 
+// SetLoggingLevel sets the minimum severity level for log messages sent by
+// the server.
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). Migrate to consuming stderr output (for STDIO
+// servers) or OpenTelemetry. See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 func (cs *ClientSession) SetLoggingLevel(ctx context.Context, params *SetLoggingLevelParams) error {
 	_, err := handleSend[*emptyResult](ctx, methodSetLevel, newClientRequest(cs, orZero[Params](params)))
 	return err

mcp/client_example_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by an MIT-style
 // license that can be found in the LICENSE file.
 
+//lint:file-ignore SA1019 examples exercise deprecated SEP-2577 APIs (roots, sampling) for demonstration.
+
 package mcp_test
 
 import (

mcp/client_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by an MIT-style
 // license that can be found in the LICENSE file.
 
+//lint:file-ignore SA1019 tests exercise deprecated SEP-2577 APIs (roots, sampling, logging).
+
 package mcp
 
 import (

mcp/content.go

@@ -189,6 +189,11 @@ func (c *EmbeddedResource) fromWire(wire *wireContent) {
 
 // ToolUseContent represents a request from the assistant to invoke a tool.
 // This content type is only valid in sampling messages.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type ToolUseContent struct {
 	// ID is a unique identifier for this tool use, used to match with ToolResultContent.
 	ID string
@@ -229,6 +234,11 @@ func (c *ToolUseContent) fromWire(wire *wireContent) {
 
 // ToolResultContent represents the result of a tool invocation.
 // This content type is only valid in sampling messages with role "user".
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type ToolResultContent struct {
 	// ToolUseID references the ID from the corresponding ToolUseContent.
 	ToolUseID string

mcp/logging.go

@@ -69,6 +69,11 @@ func compareLevels(l1, l2 LoggingLevel) int {
 }
 
 // LoggingHandlerOptions are options for a LoggingHandler.
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type LoggingHandlerOptions struct {
 	// The value for the "logger" field of logging notifications.
 	LoggerName string
@@ -79,6 +84,11 @@ type LoggingHandlerOptions struct {
 }
 
 // A LoggingHandler is a [slog.Handler] for MCP.
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type LoggingHandler struct {
 	opts LoggingHandlerOptions
 	ss   *ServerSession
@@ -101,6 +111,11 @@ func ensureLogger(l *slog.Logger) *slog.Logger {
 
 // NewLoggingHandler creates a [LoggingHandler] that logs to the given [ServerSession] using a
 // [slog.JSONHandler].
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 func NewLoggingHandler(ss *ServerSession, opts *LoggingHandlerOptions) *LoggingHandler {
 	var buf bytes.Buffer
 	jsonHandler := slog.NewJSONHandler(&buf, &slog.HandlerOptions{

mcp/mcp_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by an MIT-style
 // license that can be found in the LICENSE file.
 
+//lint:file-ignore SA1019 tests exercise deprecated SEP-2577 APIs (roots, sampling, logging).
+
 package mcp
 
 import (

mcp/mrtr_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by the license
 // that can be found in the LICENSE file.
 
+//lint:file-ignore SA1019 tests exercise deprecated SEP-2577 APIs (roots, sampling, logging).
+
 package mcp
 
 import (

mcp/protocol.go

@@ -439,6 +439,11 @@ func (x *CancelledParams) GetProgressToken() any  { return getProgressToken(x) }
 func (x *CancelledParams) SetProgressToken(t any) { setProgressToken(x, t) }
 
 // RootCapabilities describes a client's support for roots.
+//
+// Deprecated: the roots feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type RootCapabilities struct {
 	// ListChanged reports whether the client supports notifications for
 	// changes to the roots list.
@@ -466,14 +471,27 @@ type ClientCapabilities struct {
 	// Deprecated: use RootsV2. As described in #607, Roots should have been a
 	// pointer to a RootCapabilities value. Roots will be continue to be
 	// populated, but any new fields will only be added in the RootsV2 field.
+	//
+	// The roots feature itself is also deprecated by SEP-2577; see RootsV2.
 	Roots struct {
 		// ListChanged reports whether the client supports notifications for
 		// changes to the roots list.
 		ListChanged bool `json:"listChanged,omitempty"`
 	} `json:"roots,omitempty"`
-	// RootsV2 is present if the client supports roots. When capabilities are explicitly configured via [ClientOptions.Capabilities]
+	// RootsV2 is present if the client supports roots. When capabilities are
+	// explicitly configured via [ClientOptions.Capabilities].
+	//
+	// Deprecated: the roots feature is deprecated as of protocol version
+	// 2026-07-28 (SEP-2577). It remains functional during the deprecation
+	// window (at least twelve months). See
+	// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 	RootsV2 *RootCapabilities `json:"-"`
 	// Sampling is present if the client supports sampling from an LLM.
+	//
+	// Deprecated: the sampling feature is deprecated as of protocol version
+	// 2026-07-28 (SEP-2577). It remains functional during the deprecation
+	// window (at least twelve months). See
+	// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 	Sampling *SamplingCapabilities `json:"sampling,omitempty"`
 	// Elicitation is present if the client supports elicitation from the server.
 	Elicitation *ElicitationCapabilities `json:"elicitation,omitempty"`
@@ -641,6 +659,12 @@ type CompleteResult struct {
 
 func (*CompleteResult) isResult() {}
 
+// CreateMessageParams holds parameters for a sampling/createMessage request.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type CreateMessageParams struct {
 	// This property is reserved by the protocol to allow clients and servers to
 	// attach additional metadata to their responses.
@@ -648,10 +672,11 @@ type CreateMessageParams struct {
 	// A request to include context from one or more MCP servers (including the
 	// caller), to be attached to the prompt. The client may ignore this request.
 	//
-	// The default is "none". Values "thisServer" and
+	// The default is "none". The values "thisServer" and "allServers" are
-	// "allServers" are soft-deprecated. Servers SHOULD only use these values if
+	// deprecated as of protocol version 2025-11-25 (SEP-2596) and will be
-	// the client declares ClientCapabilities.sampling.context. These values may
+	// removed no later than the sampling feature itself (SEP-2577). Servers
-	// be removed in future spec releases.
+	// SHOULD omit this field or use "none". See
+	// https://modelcontextprotocol.io/seps/2596-feature-lifecycle-and-deprecation-policy.
 	IncludeContext string `json:"includeContext,omitempty"`
 	// The maximum number of tokens to sample, as requested by the server. The
 	// client may choose to sample fewer tokens than requested.
@@ -681,6 +706,11 @@ func (x *CreateMessageParams) SetProgressToken(t any) { setProgressToken(x, t) }
 // and messages that support array content (for parallel tool calls).
 //
 // Use with [ServerSession.CreateMessageWithTools].
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type CreateMessageWithToolsParams struct {
 	Meta           `json:"_meta,omitempty"`
 	IncludeContext string `json:"includeContext,omitempty"`
@@ -741,6 +771,11 @@ func (p *CreateMessageWithToolsParams) toBase() (*CreateMessageParams, error) {
 // object for compatibility with pre-2025-11-25 implementations. When
 // unmarshaling, a single JSON content object is accepted and wrapped in a
 // one-element slice.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type SamplingMessageV2 struct {
 	Content []Content `json:"content"`
 	Role    Role      `json:"role"`
@@ -782,6 +817,11 @@ func (m *SamplingMessageV2) UnmarshalJSON(data []byte) error {
 // The client should inform the user before returning the sampled message, to
 // allow them to inspect the response (human in the loop) and decide whether to
 // allow the server to see it.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type CreateMessageResult struct {
 	// This property is reserved by the protocol to allow clients and servers to
 	// attach additional metadata to their responses.
@@ -828,6 +868,11 @@ func (r *CreateMessageResult) UnmarshalJSON(data []byte) error {
 //
 // When unmarshaling, a single JSON content object is accepted and wrapped in a
 // one-element slice, for compatibility with clients that return a single block.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type CreateMessageWithToolsResult struct {
 	Meta    `json:"_meta,omitempty"`
 	Content []Content `json:"content"`
@@ -1218,6 +1263,12 @@ type ListResourcesResult struct {
 func (x *ListResourcesResult) isResult()              {}
 func (x *ListResourcesResult) nextCursorPtr() *string { return &x.NextCursor }
 
+// ListRootsParams holds parameters for a roots/list request.
+//
+// Deprecated: the roots feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type ListRootsParams struct {
 	// This property is reserved by the protocol to allow clients and servers to
 	// attach additional metadata to their responses.
@@ -1233,6 +1284,11 @@ func (x *ListRootsParams) SetProgressToken(t any) { setProgressToken(x, t) }
 // The client's response to a roots/list request from the server. This result
 // contains an array of Root objects, each representing a root directory or file
 // that the server can operate on.
+//
+// Deprecated: the roots feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type ListRootsResult struct {
 	// This property is reserved by the protocol to allow clients and servers to
 	// attach additional metadata to their responses.
@@ -1277,8 +1333,20 @@ func (x *ListToolsResult) nextCursorPtr() *string { return &x.NextCursor }
 //
 // These map to syslog message severities, as specified in RFC-5424:
 // https://datatracker.ietf.org/doc/html/rfc5424#section-6.2.1
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type LoggingLevel string
 
+// LoggingMessageParams holds the parameters for a notifications/message
+// notification.
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type LoggingMessageParams struct {
 	// This property is reserved by the protocol to allow clients and servers to
 	// attach additional metadata to their responses.
@@ -1301,6 +1369,11 @@ func (x *LoggingMessageParams) SetProgressToken(t any) { setProgressToken(x, t)
 //
 // Keys not declared here are currently left unspecified by the spec and are up
 // to the client to interpret.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type ModelHint struct {
 	// A hint for a model name.
 	//
@@ -1327,6 +1400,11 @@ type ModelHint struct {
 // These preferences are always advisory. The client may ignore them. It is also
 // up to the client to decide how to interpret these preferences and how to
 // balance them against other considerations.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type ModelPreferences struct {
 	// How much to prioritize cost when selecting a model. A value of 0 means cost
 	// is not important, while a value of 1 means cost is the most important factor.
@@ -1652,6 +1730,11 @@ type ResourceTemplate struct {
 type Role string
 
 // Represents a root directory or file that the server can operate on.
+//
+// Deprecated: the roots feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type Root struct {
 	// See [specification/2025-06-18/basic/index#general-fields] for notes on _meta
 	// usage.
@@ -1666,6 +1749,13 @@ type Root struct {
 	URI string `json:"uri"`
 }
 
+// RootsListChangedParams holds parameters for a notifications/roots/list_changed
+// notification.
+//
+// Deprecated: the roots feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type RootsListChangedParams struct {
 	// This property is reserved by the protocol to allow clients and servers to
 	// attach additional metadata to their responses.
@@ -1681,6 +1771,11 @@ func (x *RootsListChangedParams) SetProgressToken(t any) { setProgressToken(x, t
 // below directly above ClientCapabilities.
 
 // SamplingCapabilities describes the client's support for sampling.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type SamplingCapabilities struct {
 	// Context indicates the client supports includeContext values other than "none".
 	Context *SamplingContextCapabilities `json:"context,omitempty"`
@@ -1689,12 +1784,27 @@ type SamplingCapabilities struct {
 }
 
 // SamplingContextCapabilities indicates the client supports context inclusion.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type SamplingContextCapabilities struct{}
 
 // SamplingToolsCapabilities indicates the client supports tool use in sampling.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type SamplingToolsCapabilities struct{}
 
 // ToolChoice controls how the model uses tools during sampling.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type ToolChoice struct {
 	// Mode controls tool invocation behavior:
 	//  - "auto": Model decides whether to use tools (default)
@@ -1721,6 +1831,11 @@ type URLElicitationCapabilities struct{}
 //
 // For assistant messages, Content may be text, image, audio, or tool_use.
 // For user messages, Content may be text, image, audio, or tool_result.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type SamplingMessage struct {
 	Content Content `json:"content"`
 	Role    Role    `json:"role"`
@@ -1746,6 +1861,12 @@ func (m *SamplingMessage) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
+// SetLoggingLevelParams holds parameters for a logging/setLevel request.
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type SetLoggingLevelParams struct {
 	// This property is reserved by the protocol to allow clients and servers to
 	// attach additional metadata to their responses.
@@ -2071,6 +2192,11 @@ type Implementation struct {
 type CompletionCapabilities struct{}
 
 // LoggingCapabilities describes the server's support for sending log messages to the client.
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 type LoggingCapabilities struct{}
 
 // PromptCapabilities describes the server's support for prompts.
@@ -2114,6 +2240,11 @@ type ServerCapabilities struct {
 	// suggestions.
 	Completions *CompletionCapabilities `json:"completions,omitempty"`
 	// Logging is present if the server supports log messages.
+	//
+	// Deprecated: the logging feature is deprecated as of protocol version
+	// 2026-07-28 (SEP-2577). It remains functional during the deprecation
+	// window (at least twelve months). See
+	// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 	Logging *LoggingCapabilities `json:"logging,omitempty"`
 	// Prompts is present if the server supports prompts.
 	Prompts *PromptCapabilities `json:"prompts,omitempty"`
@@ -2196,6 +2327,11 @@ const (
 	// MetaKeyClientCapabilities carries the client's [ClientCapabilities].
 	MetaKeyClientCapabilities = "io.modelcontextprotocol/clientCapabilities"
 	// MetaKeyLogLevel identifies the desired log level for the request.
+	//
+	// Deprecated: the logging feature is deprecated as of protocol version
+	// 2026-07-28 (SEP-2577). It remains functional during the deprecation
+	// window (at least twelve months). See
+	// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 	MetaKeyLogLevel = "io.modelcontextprotocol/logLevel"
 	// MetaKeySubscriptionID identifies the subscriptions/listen request that an
 	// out-of-band notification belongs to.

mcp/sampling_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by an MIT-style
 // license that can be found in the LICENSE file.
 
+//lint:file-ignore SA1019 tests exercise deprecated SEP-2577 sampling APIs.
+
 package mcp
 
 // TODO: move other sampling-related tests to this file.

mcp/server.go

@@ -73,6 +73,12 @@ type ServerOptions struct {
 	// If zero, defaults to [DefaultPageSize].
 	PageSize int
 	// If non-nil, called when "notifications/roots/list_changed" is received.
+	//
+	// Deprecated: the roots feature is deprecated as of protocol version
+	// 2026-07-28 (SEP-2577). It remains functional during the deprecation
+	// window (at least twelve months). Migrate to passing paths via tool
+	// parameters, resource URIs, or configuration. See
+	// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 	RootsListChangedHandler func(context.Context, *RootsListChangedRequest)
 	// If non-nil, called when "notifications/progress" is received.
 	ProgressNotificationHandler func(context.Context, *ProgressNotificationServerRequest)
@@ -1474,6 +1480,12 @@ func (ss *ServerSession) Ping(ctx context.Context, params *PingParams) error {
 }
 
 // ListRoots lists the client roots.
+//
+// Deprecated: the roots feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). Migrate to passing paths via tool parameters,
+// resource URIs, or configuration. See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 func (ss *ServerSession) ListRoots(ctx context.Context, params *ListRootsParams) (*ListRootsResult, error) {
 	if err := ss.checkInitialized(methodListRoots); err != nil {
 		return nil, err
@@ -1486,6 +1498,12 @@ func (ss *ServerSession) ListRoots(ctx context.Context, params *ListRootsParams)
 // If the client returns multiple content blocks (e.g. parallel tool calls),
 // CreateMessage returns an error. Use [ServerSession.CreateMessageWithTools]
 // for tool-enabled sampling.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). Migrate to calling LLM provider APIs directly
+// from your server. See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 func (ss *ServerSession) CreateMessage(ctx context.Context, params *CreateMessageParams) (*CreateMessageResult, error) {
 	if err := ss.checkInitialized(methodCreateMessage); err != nil {
 		return nil, err
@@ -1523,6 +1541,12 @@ func (ss *ServerSession) CreateMessage(ctx context.Context, params *CreateMessag
 // returning a [CreateMessageWithToolsResult] that supports array content
 // (for parallel tool calls). Use this instead of [ServerSession.CreateMessage]
 // when the request includes tools.
+//
+// Deprecated: the sampling feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). Migrate to calling LLM provider APIs directly
+// from your server. See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 func (ss *ServerSession) CreateMessageWithTools(ctx context.Context, params *CreateMessageWithToolsParams) (*CreateMessageWithToolsResult, error) {
 	if err := ss.checkInitialized(methodCreateMessage); err != nil {
 		return nil, err
@@ -1609,28 +1633,21 @@ func (ss *ServerSession) Elicit(ctx context.Context, params *ElicitParams) (*Eli
 	return res, nil
 }
 
-// logLevelContextKey carries the per-request log level from
-// [ServerSession.handle] to [ServerSession.Log] for new-protocol
-// (>= 2026-07-28) requests. The level is scoped to a single in-flight request
-// — including handler goroutines that call [ServerSession.Log] concurrently —
-// rather than to the session, which avoids races between concurrent requests
-// and aligns with SEP-2575's per-request opt-in model. The value type is
-// [LoggingLevel]; an empty string means the request opted out of log messages.
-type logLevelContextKey struct{}
-
 // Log sends a log message to the client.
 //
 // For new-protocol (>= 2026-07-28) requests, the level is taken from the
 // originating request's `_meta` field (SEP-2575); an absent or empty value
 // suppresses the message per spec. For old-protocol requests, the level is
 // taken from the session state set via `logging/setLevel`.
+//
+// Deprecated: the logging feature is deprecated as of protocol version
+// 2026-07-28 (SEP-2577). It remains functional during the deprecation window
+// (at least twelve months). See
+// https://modelcontextprotocol.io/seps/2577-deprecate-roots-sampling-and-logging.
 func (ss *ServerSession) Log(ctx context.Context, params *LoggingMessageParams) error {
-	logLevel, ok := ctx.Value(logLevelContextKey{}).(LoggingLevel)
+	ss.mu.Lock()
-	if !ok {
+	logLevel := ss.state.LogLevel
-		ss.mu.Lock()
+	ss.mu.Unlock()
-		logLevel = ss.state.LogLevel
-		ss.mu.Unlock()
-	}
 	if logLevel == "" {
 		// The spec is unclear, but seems to imply that no log messages are sent until the client
 		// sets the level.
@@ -1806,7 +1823,7 @@ func (ss *ServerSession) handle(ctx context.Context, req *jsonrpc.Request) (any,
 	ctx = context.WithValue(ctx, idContextKey{}, req.ID)
 	// For new-protocol requests, propagate the per-request log level.
 	if validatedMeta.usesNewProtocol {
-		ctx = context.WithValue(ctx, logLevelContextKey{}, validatedMeta.logLevel)
+		ss.setLevel(ctx, &SetLoggingLevelParams{Level: validatedMeta.logLevel})
 	}
 	return handleReceive(ctx, ss, req)
 }