feat(mcp)!: accept host implementation and logger options

CHANGELOG.md

@@ -1,5 +1,16 @@
 # Changelog
 
+## [Unreleased]
+
+
+### ⚠ BREAKING CHANGES
+
+* **mcp:** `mcpserver.New` requires an `Options` argument.
+
+### Features
+
+* **mcp:** let hosts set MCP implementation identity and a slog logger
+
 ## 0.1.0 (2026-08-26)
 
 

README.md

@@ -64,7 +64,7 @@ func main() {
 
 	// StaticSubject suits a single-user stdio server; multi-user hosts
 	// resolve each authenticated request with ContextSubject.
-	srv, err := mcpserver.New(server, mcpserver.StaticSubject(authz.Subject{ID: "local"}))
+	srv, err := mcpserver.New(server, mcpserver.StaticSubject(authz.Subject{ID: "local"}), mcpserver.Options{})
 	if err != nil {
 		log.Fatal(err)
 	}

docs/docs/reference/public-api.md

@@ -633,12 +633,21 @@ boundary, such as a local stdio server. Multi-user hosts must not use it.
 authentication middleware remains responsible for validating credentials and
 installing a subject for each request.
 
+### `Options`
+
+`Options` configures adapter construction:
+
+| Field | Contract |
+| --- | --- |
+| `Implementation *mcp.Implementation` | MCP application identity advertised to clients. Nil retains Name `codemode` and Version `2`. A non-nil value is borrowed and passed to the SDK without copying or validating fields. |
+| `Logger *slog.Logger` | Optional slog logger for SDK server diagnostics. Nil selects the SDK default logger, which discards records. |
+
 ### `New`
 
 ```text
-New(service Service, resolver InvocationResolver) (*mcp.Server, error)
+New(service Service, resolver InvocationResolver, options Options) (*mcp.Server, error)
 ```
 
-`New` rejects nil and typed-nil dependencies with `ErrInvalidRegistration`. The returned official SDK server exposes exactly `search_api`, `describe_api`, and `execute`. It does not own authentication, transport creation, listeners, cancellation, or shutdown. The host connects the returned server to an official MCP transport and owns that lifecycle.
+`New` rejects nil and typed-nil Service and InvocationResolver with `ErrInvalidRegistration`. Pass `Options{}` to keep the library identity. The returned official SDK server exposes exactly `search_api`, `describe_api`, and `execute`. It does not own authentication, transport creation, listeners, cancellation, or shutdown. The host connects the returned server to an official MCP transport and owns that lifecycle.
 
 See [MCP tool reference](mcp-tools.md) for the wire contracts and [Understanding CodeMode's security model](../explanation/security-model.md) for the trust boundary.

docs/docs/tutorials/first-server.md

@@ -82,7 +82,7 @@ func main() {
 		log.Fatal(err)
 	}
 
-	srv, err := mcpserver.New(server, mcpserver.StaticSubject(authz.Subject{ID: "local"}))
+	srv, err := mcpserver.New(server, mcpserver.StaticSubject(authz.Subject{ID: "local"}), mcpserver.Options{})
 	if err != nil {
 		log.Fatal(err)
 	}

mcpserver/e2e_test.go

@@ -325,7 +325,7 @@ func TestActualMCPSecureLoop(t *testing.T) {
 	root, err := builder.Build()
 	require.NoError(t, err)
 
-	mcpServer, err := mcpserver.New(root, contextResolver{})
+	mcpServer, err := mcpserver.New(root, contextResolver{}, mcpserver.Options{})
 	require.NoError(t, err)
 
 	trustedCtx := withInvocationIdentity(t.Context(), invocationIdentity{
@@ -344,6 +344,7 @@ func TestActualMCPSecureLoop(t *testing.T) {
 	initialized := session.InitializeResult()
 	require.NotNil(t, initialized)
 	require.NotNil(t, initialized.ServerInfo)
+	assert.Equal(t, "codemode", initialized.ServerInfo.Name)
 	assert.Equal(t, "2", initialized.ServerInfo.Version)
 
 	listed, err := session.ListTools(t.Context(), &mcp.ListToolsParams{})
@@ -538,7 +539,7 @@ func TestActualMCPCompositeProgram(t *testing.T) {
 	root, err := builder.Build()
 	require.NoError(t, err)
 
-	mcpServer, err := mcpserver.New(root, contextResolver{})
+	mcpServer, err := mcpserver.New(root, contextResolver{}, mcpserver.Options{})
 	require.NoError(t, err)
 
 	trustedCtx := withInvocationIdentity(t.Context(), invocationIdentity{
@@ -557,6 +558,7 @@ func TestActualMCPCompositeProgram(t *testing.T) {
 	initialized := session.InitializeResult()
 	require.NotNil(t, initialized)
 	require.NotNil(t, initialized.ServerInfo)
+	assert.Equal(t, "codemode", initialized.ServerInfo.Name)
 	assert.Equal(t, "2", initialized.ServerInfo.Version)
 
 	const (
@@ -668,7 +670,7 @@ func TestActualMCPPureComputeProgram(t *testing.T) {
 	root, err := builder.Build()
 	require.NoError(t, err)
 
-	mcpServer, err := mcpserver.New(root, contextResolver{})
+	mcpServer, err := mcpserver.New(root, contextResolver{}, mcpserver.Options{})
 	require.NoError(t, err)
 
 	trustedCtx := withInvocationIdentity(t.Context(), invocationIdentity{
@@ -726,7 +728,7 @@ func TestActualMCPModelDerivedDiagnostics(t *testing.T) {
 	root, err := builder.Build()
 	require.NoError(t, err)
 
-	mcpServer, err := mcpserver.New(root, contextResolver{})
+	mcpServer, err := mcpserver.New(root, contextResolver{}, mcpserver.Options{})
 	require.NoError(t, err)
 
 	trustedCtx := withInvocationIdentity(t.Context(), invocationIdentity{

mcpserver/example_test.go

@@ -55,7 +55,11 @@ func Example_officialTransport() {
 		panic(err)
 	}
 
-	mcpServer, err := mcpserver.New(root, mcpserver.StaticSubject(authz.Subject{ID: "example-user"}))
+	mcpServer, err := mcpserver.New(
+		root,
+		mcpserver.StaticSubject(authz.Subject{ID: "example-user"}),
+		mcpserver.Options{},
+	)
 	if err != nil {
 		panic(err)
 	}

mcpserver/server.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"reflect"
 
 	"github.com/google/jsonschema-go/jsonschema"
@@ -47,6 +48,17 @@ type operationResult[Value any] struct {
 	err error
 }
 
+// Options configures official MCP server construction.
+type Options struct {
+	// Implementation is the MCP application identity advertised to clients.
+	// Nil retains Name "codemode" and Version "2". A non-nil value is borrowed
+	// and passed to the SDK without copying or validating fields.
+	Implementation *mcp.Implementation
+
+	// Logger receives SDK server diagnostics. Nil selects the SDK default logger.
+	Logger *slog.Logger
+}
+
 // adapter binds a Service and InvocationResolver to the three official MCP tools.
 type adapter struct {
 	// service is the required CodeMode application port.
@@ -58,9 +70,11 @@ type adapter struct {
 
 // New constructs an official MCP server that exposes exactly search_api, describe_api, and execute.
 //
-// New rejects a nil or typed-nil Service or InvocationResolver. The returned server has no
-// generic downstream MCP forwarding path. Client request metadata is untrusted and ignored.
-func New(service Service, resolver InvocationResolver) (*mcp.Server, error) {
+// New rejects a nil or typed-nil Service or InvocationResolver. A nil Implementation
+// retains the library identity Name "codemode" and Version "2". Logger is optional.
+// The returned server has no generic downstream MCP forwarding path. Client request
+// metadata is untrusted and ignored.
+func New(service Service, resolver InvocationResolver, options Options) (*mcp.Server, error) {
 	if isNil(service) {
 		return nil, fmt.Errorf("%w: service is required", codemode.ErrInvalidRegistration)
 	}
@@ -114,7 +128,11 @@ func New(service Service, resolver InvocationResolver) (*mcp.Server, error) {
 	}
 
 	bound := &adapter{service: service, resolver: resolver}
-	server := mcp.NewServer(&mcp.Implementation{Name: "codemode", Version: "2"}, nil)
+	implementation := options.Implementation
+	if implementation == nil {
+		implementation = &mcp.Implementation{Name: "codemode", Version: "2"}
+	}
+	server := mcp.NewServer(implementation, &mcp.ServerOptions{Logger: options.Logger})
 	mcp.AddTool(server, &mcp.Tool{
 		Name:         "search_api",
 		Description:  "Search enabled capabilities using task, resource, or exact-name vocabulary. Results are relevance-ranked. Pass the exact returned name to describe_api. If truncated is true and no result fits, submit a more specific task/resource query.",

mcpserver/server_test.go

@@ -57,7 +57,7 @@ func TestNewRejectsMissingDependencies(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			server, err := mcpserver.New(tt.service, tt.resolver)
+			server, err := mcpserver.New(tt.service, tt.resolver, mcpserver.Options{})
 
 			require.ErrorIs(t, err, codemode.ErrInvalidRegistration)
 			assert.Nil(t, server)
@@ -132,6 +132,24 @@ func TestNewRegistersExactlyThreeTools(t *testing.T) {
 	}
 }
 
+// TestNewAdvertisesCustomImplementation proves initialize reports host-supplied application identity.
+func TestNewAdvertisesCustomImplementation(t *testing.T) {
+	session := connectTestSession(t, mocks.NewMockService(t), mocks.NewMockInvocationResolver(t), mcpserver.Options{
+		Implementation: &mcp.Implementation{
+			Name:    "inventory",
+			Title:   "Inventory server",
+			Version: "9",
+		},
+	})
+
+	initialized := session.client.InitializeResult()
+	require.NotNil(t, initialized)
+	require.NotNil(t, initialized.ServerInfo)
+	assert.Equal(t, "inventory", initialized.ServerInfo.Name)
+	assert.Equal(t, "Inventory server", initialized.ServerInfo.Title)
+	assert.Equal(t, "9", initialized.ServerInfo.Version)
+}
+
 // TestSDKRejectsMalformedArgumentsBeforeResolution proves schema validation owns malformed tool input.
 func TestSDKRejectsMalformedArgumentsBeforeResolution(t *testing.T) {
 	tests := []struct {
@@ -720,7 +738,19 @@ type testSession struct {
 func newTestSession(t *testing.T, service mcpserver.Service, resolver mcpserver.InvocationResolver) *testSession {
 	t.Helper()
 
-	server, err := mcpserver.New(service, resolver)
+	return connectTestSession(t, service, resolver, mcpserver.Options{})
+}
+
+// connectTestSession connects an official client to New with the supplied adapter options.
+func connectTestSession(
+	t *testing.T,
+	service mcpserver.Service,
+	resolver mcpserver.InvocationResolver,
+	options mcpserver.Options,
+) *testSession {
+	t.Helper()
+
+	server, err := mcpserver.New(service, resolver, options)
 	require.NoError(t, err)
 	serverTransport, clientTransport := mcp.NewInMemoryTransports()
 	serverSession, err := server.Connect(t.Context(), serverTransport, nil)
@@ -737,7 +767,10 @@ func newTestSession(t *testing.T, service mcpserver.Service, resolver mcpserver.
 	initialized := clientSession.InitializeResult()
 	require.NotNil(t, initialized)
 	require.NotNil(t, initialized.ServerInfo)
-	assert.Equal(t, "2", initialized.ServerInfo.Version)
+	if options.Implementation == nil {
+		assert.Equal(t, "codemode", initialized.ServerInfo.Name)
+		assert.Equal(t, "2", initialized.ServerInfo.Version)
+	}
 	return &testSession{client: clientSession}
 }