Preserve GHES API compatibility

Author: maxffarrell

internal/ghmcp/oauth_test.go

@@ -602,7 +602,7 @@ func TestCreateGitHubClientsTokenProvider(t *testing.T) {
 
 	do()
 	assert.Equal(t, "", gotAuth, "no auth header before authorization")
-	assert.Equal(t, headers.GitHubAPIVersion, gotAPIVersion)
+	assert.Equal(t, headers.GitHubEnterpriseServerAPIVersion, gotAPIVersion)
 
 	current = "oauth-token"
 	do()

internal/githubapp/githubapp.go

@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/github/github-mcp-server/pkg/http/headers"
+	"github.com/github/github-mcp-server/pkg/http/transport"
 	"golang.org/x/oauth2"
 )
 
@@ -143,7 +144,7 @@ func (s *installationTokenSource) Token() (*oauth2.Token, error) {
 	}
 	req.Header.Set(headers.AuthorizationHeader, "Bearer "+jwt)
 	req.Header.Set(headers.AcceptHeader, "application/vnd.github+json")
-	req.Header.Set(headers.GitHubAPIVersionHeader, headers.GitHubAPIVersion)
+	transport.SetGitHubAPIVersionHeader(req)
 
 	resp, err := s.httpClient.Do(req)
 	if err != nil {

internal/githubapp/githubapp_test.go

@@ -12,6 +12,7 @@ import (
 	"encoding/json"
 	"encoding/pem"
 	"fmt"
+	"io"
 	"log/slog"
 	"net/http"
 	"net/http/httptest"
@@ -25,6 +26,12 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+type roundTripFunc func(*http.Request) (*http.Response, error)
+
+func (f roundTripFunc) RoundTrip(req *http.Request) (*http.Response, error) {
+	return f(req)
+}
+
 func newTestKey(t *testing.T) *rsa.PrivateKey {
 	t.Helper()
 	key, err := rsa.GenerateKey(rand.Reader, 2048)
@@ -156,7 +163,7 @@ func installationServer(t *testing.T, pub *rsa.PublicKey, token string, expiresA
 		calls.Add(1)
 		assert.Equal(t, http.MethodPost, r.Method)
 		assert.Equal(t, "/app/installations/456/access_tokens", r.URL.Path)
-		assert.Equal(t, headers.GitHubAPIVersion, r.Header.Get(headers.GitHubAPIVersionHeader))
+		assert.Equal(t, headers.GitHubEnterpriseServerAPIVersion, r.Header.Get(headers.GitHubAPIVersionHeader))
 
 		authz := r.Header.Get("Authorization")
 		require.True(t, strings.HasPrefix(authz, "Bearer "), "must send the app JWT as a bearer token")
@@ -187,6 +194,34 @@ func newTestTokenSource(t *testing.T, cfg Config, client *http.Client) *installa
 	return newInstallationTokenSource(cfg, privateKey, client)
 }
 
+func TestInstallationTokenSourceSetsAPIVersionForGitHubCloud(t *testing.T) {
+	key := newTestKey(t)
+	expiresAt := time.Now().Add(time.Hour).UTC().Format(time.RFC3339)
+
+	for _, baseURL := range []string{"https://api.github.com", "https://api.example.ghe.com"} {
+		t.Run(baseURL, func(t *testing.T) {
+			var gotVersion string
+			client := &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
+				gotVersion = req.Header.Get(headers.GitHubAPIVersionHeader)
+				body := fmt.Sprintf(`{"token":"ghs_test","expires_at":%q}`, expiresAt)
+				return &http.Response{
+					StatusCode: http.StatusCreated,
+					Status:     "201 Created",
+					Header:     make(http.Header),
+					Body:       io.NopCloser(strings.NewReader(body)),
+					Request:    req,
+				}, nil
+			})}
+			source := newTestTokenSource(t, newTestConfig(key, baseURL), client)
+
+			token, err := source.Token()
+			require.NoError(t, err)
+			assert.Equal(t, "ghs_test", token.AccessToken)
+			assert.Equal(t, headers.GitHubAPIVersion, gotVersion)
+		})
+	}
+}
+
 func TestProviderFetchesToken(t *testing.T) {
 	key := newTestKey(t)
 	srv, calls := installationServer(t, &key.PublicKey, "ghs_fresh", time.Now().Add(time.Hour))

pkg/github/__toolsnaps__/search_issues.snap

@@ -22,7 +22,6 @@
             "user",
             "author_association",
             "labels",
-            "assignee",
             "assignees",
             "milestone",
             "comments",

pkg/github/__toolsnaps__/search_pull_requests.snap

@@ -22,7 +22,6 @@
             "user",
             "author_association",
             "labels",
-            "assignee",
             "assignees",
             "milestone",
             "comments",

pkg/github/dependencies_test.go

@@ -36,7 +36,7 @@ func testExporters() observability.Exporters {
 	return obs
 }
 
-func TestRequestDepsGetClientSetsAPIVersion(t *testing.T) {
+func TestRequestDepsGetClientPreservesGHESAPIVersion(t *testing.T) {
 	t.Parallel()
 
 	var gotVersion string
@@ -60,7 +60,7 @@ func TestRequestDepsGetClientSetsAPIVersion(t *testing.T) {
 	require.NoError(t, err)
 	defer resp.Body.Close()
 
-	assert.Equal(t, headers.GitHubAPIVersion, gotVersion)
+	assert.Equal(t, headers.GitHubEnterpriseServerAPIVersion, gotVersion)
 }
 
 func TestIsFeatureEnabled_WithEnabledFlag(t *testing.T) {

pkg/github/minimal_types.go

@@ -75,7 +75,7 @@ var listReleasesItemFieldEnum = []any{
 // the main lever for shrinking large result sets.
 var searchIssuesItemFieldEnum = []any{
 	"number", "title", "body", "state", "state_reason", "draft", "locked",
-	"html_url", "user", "author_association", "labels", "assignee", "assignees",
+	"html_url", "user", "author_association", "labels", "assignees",
 	"milestone", "comments", "reactions", "created_at", "updated_at", "closed_at",
 	"closed_by", "type", "repository_url", "pull_request", "field_values",
 }
@@ -87,7 +87,7 @@ var searchIssuesItemFieldEnum = []any{
 // the main lever for shrinking large result sets.
 var searchPullRequestsItemFieldEnum = []any{
 	"number", "title", "body", "state", "state_reason", "draft", "locked",
-	"html_url", "user", "author_association", "labels", "assignee", "assignees",
+	"html_url", "user", "author_association", "labels", "assignees",
 	"milestone", "comments", "reactions", "created_at", "updated_at", "closed_at",
 	"closed_by", "pull_request", "repository_url",
 }

pkg/http/headers/headers.go

@@ -53,6 +53,10 @@ const (
 	GraphQLFeaturesHeader = "GraphQL-Features"
 	// GitHubAPIVersionHeader is the header used to specify the GitHub API version.
 	GitHubAPIVersionHeader = "X-GitHub-Api-Version"
-	// GitHubAPIVersion is the GitHub REST API version used by this server.
+	// GitHubAPIVersion is the GitHub REST API version used for GitHub.com and
+	// GitHub Enterprise Cloud requests.
 	GitHubAPIVersion = "2026-03-10"
+	// GitHubEnterpriseServerAPIVersion is the compatibility version used for
+	// GitHub Enterprise Server requests.
+	GitHubEnterpriseServerAPIVersion = "2022-11-28"
 )

pkg/http/transport/api_version.go

@@ -4,13 +4,38 @@ import (
 	"net/http"
 
 	"github.com/github/github-mcp-server/pkg/http/headers"
+	"github.com/github/github-mcp-server/pkg/utils"
 )
 
-// APIVersionTransport sets the GitHub REST API version on every request.
+// APIVersionTransport sets the GitHub REST API version on requests to
+// GitHub.com and GitHub Enterprise Cloud.
 type APIVersionTransport struct {
 	Transport http.RoundTripper
 }
 
+// SetGitHubAPIVersionHeader selects the REST API version supported by the
+// target deployment. GitHub Enterprise Server releases support API versions
+// independently, so they retain the established compatibility version.
+func SetGitHubAPIVersionHeader(req *http.Request) {
+	if req == nil || req.URL == nil {
+		return
+	}
+
+	hostType, err := utils.ParseHostType(req.URL.String())
+	if err != nil {
+		return
+	}
+
+	if req.Header == nil {
+		req.Header = make(http.Header)
+	}
+	version := headers.GitHubAPIVersion
+	if hostType == utils.HostTypeGHES {
+		version = headers.GitHubEnterpriseServerAPIVersion
+	}
+	req.Header.Set(headers.GitHubAPIVersionHeader, version)
+}
+
 // RoundTrip implements http.RoundTripper.
 func (t *APIVersionTransport) RoundTrip(req *http.Request) (*http.Response, error) {
 	underlying := t.Transport
@@ -19,6 +44,6 @@ func (t *APIVersionTransport) RoundTrip(req *http.Request) (*http.Response, erro
 	}
 
 	req = req.Clone(req.Context())
-	req.Header.Set(headers.GitHubAPIVersionHeader, headers.GitHubAPIVersion)
+	SetGitHubAPIVersionHeader(req)
 	return underlying.RoundTrip(req)
 }

pkg/http/transport/api_version_test.go

@@ -2,32 +2,91 @@ package transport
 
 import (
 	"net/http"
-	"net/http/httptest"
 	"testing"
 
 	"github.com/github/github-mcp-server/pkg/http/headers"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+type roundTripFunc func(*http.Request) (*http.Response, error)
+
+func (f roundTripFunc) RoundTrip(req *http.Request) (*http.Response, error) {
+	return f(req)
+}
+
 func TestAPIVersionTransport(t *testing.T) {
 	t.Parallel()
 
-	var gotVersion string
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		gotVersion = r.Header.Get(headers.GitHubAPIVersionHeader)
-		w.WriteHeader(http.StatusOK)
-	}))
-	defer server.Close()
+	tests := []struct {
+		name            string
+		url             string
+		existingVersion string
+		wantVersion     string
+	}{
+		{
+			name:            "GitHub.com overrides the default version",
+			url:             "https://api.github.com/repos/octo-org/octo-repo",
+			existingVersion: headers.GitHubEnterpriseServerAPIVersion,
+			wantVersion:     headers.GitHubAPIVersion,
+		},
+		{
+			name:        "GitHub Enterprise Cloud sets the new version",
+			url:         "https://api.example.ghe.com/repos/octo-org/octo-repo",
+			wantVersion: headers.GitHubAPIVersion,
+		},
+		{
+			name:            "GitHub Enterprise Server pins the compatibility version",
+			url:             "https://github.example.com/api/v3/repos/octo-org/octo-repo",
+			existingVersion: headers.GitHubAPIVersion,
+			wantVersion:     headers.GitHubEnterpriseServerAPIVersion,
+		},
+		{
+			name:        "GitHub Enterprise Server sets the compatibility version",
+			url:         "https://github.example.com/api/v3/repos/octo-org/octo-repo",
+			wantVersion: headers.GitHubEnterpriseServerAPIVersion,
+		},
+		{
+			name:        "host classification is case insensitive",
+			url:         "https://API.GITHUB.COM/repos/octo-org/octo-repo",
+			wantVersion: headers.GitHubAPIVersion,
+		},
+		{
+			name:        "lookalike domain is treated as GitHub Enterprise Server",
+			url:         "https://api.github.com.example.org/api/v3/",
+			wantVersion: headers.GitHubEnterpriseServerAPIVersion,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			var gotVersion string
+			underlying := roundTripFunc(func(req *http.Request) (*http.Response, error) {
+				gotVersion = req.Header.Get(headers.GitHubAPIVersionHeader)
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     make(http.Header),
+					Body:       http.NoBody,
+					Request:    req,
+				}, nil
+			})
 
-	req, err := http.NewRequest(http.MethodGet, server.URL, nil)
-	require.NoError(t, err)
-	req.Header.Set(headers.GitHubAPIVersionHeader, "2022-11-28")
+			req, err := http.NewRequest(http.MethodGet, tt.url, nil)
+			require.NoError(t, err)
+			if tt.existingVersion != "" {
+				req.Header.Set(headers.GitHubAPIVersionHeader, tt.existingVersion)
+			} else {
+				req.Header = nil
+			}
 
-	resp, err := (&APIVersionTransport{}).RoundTrip(req)
-	require.NoError(t, err)
-	defer resp.Body.Close()
+			resp, err := (&APIVersionTransport{Transport: underlying}).RoundTrip(req)
+			require.NoError(t, err)
+			defer resp.Body.Close()
 
-	assert.Equal(t, headers.GitHubAPIVersion, gotVersion)
-	assert.Equal(t, "2022-11-28", req.Header.Get(headers.GitHubAPIVersionHeader))
+			assert.Equal(t, tt.wantVersion, gotVersion)
+			assert.Equal(t, tt.existingVersion, req.Header.Get(headers.GitHubAPIVersionHeader), "the original request must not be mutated")
+		})
+	}
 }