Escape MCP client metadata and preserve revision provenance

Encode upstream client comments as valid HTTP header data, keep explicit build revisions independent of embedded dirty state, and reject null source hashes. Cover protocol wire behaviour and document the version-source contract.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 6dde41da-ec25-4370-b26c-b036d0a53b3c

Author: jidicula

README.md

@@ -405,9 +405,9 @@ For a complete overview of all installation options, see our **[Installation Gui
 If you don't have Docker, you can use `go build` to build the binary in the
 `cmd/github-mcp-server` directory, and use the `github-mcp-server stdio` command with the `GITHUB_PERSONAL_ACCESS_TOKEN` environment variable set to your token. To specify the output location of the build, use the `-o` flag. You should configure your server to use the built executable as its `command`.
 
-STDIO API requests identify the server as `github-mcp-server/<version>` and retain the upstream MCP client's name/version in parentheses when available. Release builds keep their release version. Source and default Docker builds use `vcs-<full-commit-sha>` (with `-dirty` when embedded VCS metadata records modified source), rather than the placeholder `version` or `dev`. This is a VCS build identifier, not a release number.
+STDIO API requests identify the server as `github-mcp-server/<version>` and retain the upstream MCP client's name/version in parentheses when available. Control characters, quotes, backslashes and parentheses in client metadata are escaped so the HTTP header remains valid; ordinary names, versions, spaces and printable Unicode are preserved. Release builds keep their release version. Source and default Docker builds use `vcs-<full-commit-sha>`, rather than the placeholder `version` or `dev`. The `-dirty` marker applies only when both the revision and modified state come from embedded VCS metadata, never to an explicitly supplied `main.commit`. This is a VCS build identifier, not a release number.
 
-Build the complete package with `go build -o github-mcp-server ./cmd/github-mcp-server` from a Git checkout to embed its VCS revision. For builds without VCS metadata, supply the actual release with `-ldflags '-X main.version=<release>'` or the full source revision with `-ldflags '-X main.commit=<sha>'`. STDIO startup reports an error if neither a real release nor a valid revision is available.
+Build the complete package with `go build -o github-mcp-server ./cmd/github-mcp-server` from a Git checkout to embed its VCS revision. For builds without VCS metadata, supply the actual release with `-ldflags '-X main.version=<release>'` or the full source revision with `-ldflags '-X main.commit=<sha>'`. Explicit source revisions remain authoritative even if build-context filtering changes embedded VCS metadata. STDIO startup reports an error if neither a real release nor a valid, nonzero revision is available.
 
 For example:
 

cmd/github-mcp-server/version.go

@@ -41,7 +41,8 @@ func resolveServerVersion(release, revision string, info *debug.BuildInfo) (stri
 			}
 		}
 	}
-	if revision == "" || revision == "commit" {
+	revisionFromVCS := revision == "" || revision == "commit"
+	if revisionFromVCS {
 		revision = vcsRevision
 		if revision == "" && info != nil && !isPlaceholder(info.Main.Version) {
 			return validateRelease(info.Main.Version)
@@ -56,8 +57,11 @@ func resolveServerVersion(release, revision string, info *debug.BuildInfo) (stri
 	if _, err := hex.DecodeString(revision); err != nil {
 		return "", fmt.Errorf("invalid server build revision: %w", err)
 	}
+	if strings.Trim(revision, "0") == "" {
+		return "", fmt.Errorf("invalid server build revision: all-zero hashes do not identify source")
+	}
 	resolved := "vcs-" + strings.ToLower(revision)
-	if dirty {
+	if revisionFromVCS && dirty {
 		resolved += "-dirty"
 	}
 	return resolved, nil

cmd/github-mcp-server/version_test.go

@@ -46,6 +46,8 @@ func TestResolveServerVersion(t *testing.T) {
 		},
 		{name: "dirty source", release: "version", revision: "commit", info: dirty, want: "vcs-" + sha + "-dirty"},
 		{name: "Docker revision", release: "dev", revision: sha, want: "vcs-" + sha},
+		{name: "Docker revision ignores context dirty state", release: "dev", revision: sha, info: dirty, want: "vcs-" + sha},
+		{name: "linked revision ignores unrelated dirty state", release: "dev", revision: otherSHA, info: dirty, want: "vcs-" + otherSHA},
 		{name: "linked revision precedence", release: "dev", revision: otherSHA, info: source, want: "vcs-" + otherSHA},
 		{name: "SHA256", release: "dev", revision: strings.Repeat("ab", 32), want: "vcs-" + strings.Repeat("ab", 32)},
 		{name: "canonical hex", release: "dev", revision: strings.ToUpper(sha), want: "vcs-" + sha},
@@ -73,3 +75,31 @@ func TestResolveServerVersion(t *testing.T) {
 		})
 	}
 }
+
+func TestResolveServerVersionRejectsNullRevisions(t *testing.T) {
+	t.Parallel()
+	for _, revision := range []string{strings.Repeat("0", 40), strings.Repeat("0", 64)} {
+		for _, modified := range []string{"false", "true"} {
+			for _, linked := range []bool{false, true} {
+				name := revision + "/modified=" + modified
+				if linked {
+					name += "/linked"
+				}
+				t.Run(name, func(t *testing.T) {
+					info := &debug.BuildInfo{Settings: []debug.BuildSetting{
+						{Key: "vcs.revision", Value: revision},
+						{Key: "vcs.modified", Value: modified},
+					}}
+					commit := "commit"
+					if linked {
+						commit = revision
+						info.Settings[0].Value = strings.Repeat("ab", 20)
+					}
+					got, err := resolveServerVersion("dev", commit, info)
+					require.ErrorContains(t, err, "invalid server build revision")
+					assert.Empty(t, got)
+				})
+			}
+		}
+	}
+}

internal/ghmcp/server.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"strconv"
 	"strings"
 	"syscall"
 	"time"
@@ -443,7 +444,10 @@ func createFeatureChecker(enabledFeatures []string, insidersMode bool) inventory
 func stdioUserAgent(cfg github.MCPServerConfig, client *mcp.Implementation) string {
 	agent := fmt.Sprintf("github-mcp-server/%s", cfg.Version)
 	if client != nil {
-		agent += fmt.Sprintf(" (%s/%s)", client.Name, client.Version)
+		comment := strconv.Quote(client.Name + "/" + client.Version)
+		comment = comment[1 : len(comment)-1]
+		comment = strings.NewReplacer("(", `\(`, ")", `\)`).Replace(comment)
+		agent += " (" + comment + ")"
 	}
 	if cfg.InsidersMode {
 		agent += " (insiders)"

internal/ghmcp/server_test.go

@@ -88,6 +88,41 @@ func TestStdioGraphQLUserAgent(t *testing.T) {
 			clientInfo: &mcp.Implementation{Name: "test-client", Version: "4.5.6"},
 			want:       "github-mcp-server/v1.2.4 (test-client/4.5.6)",
 		},
+		{
+			name: "HTTP comment delimiters", version: "v1.2.3",
+			clientInfo: &mcp.Implementation{Name: `Editor (Preview) \client`, Version: `v(1)\build`},
+			want:       `github-mcp-server/v1.2.3 (Editor \(Preview\) \\client/v\(1\)\\build)`,
+		},
+		{
+			name: "modern control characters", version: "v1.2.3",
+			clientInfo: &mcp.Implementation{Name: "editor(\x00)\\client\r\nX-Fake:1", Version: "1.0\tbeta\x7f"},
+			want:       `github-mcp-server/v1.2.3 (editor\(\x00\)\\client\r\nX-Fake:1/1.0\tbeta\x7f)`,
+		},
+		{
+			name: "SDK control characters", handshake: "sdk", version: "v1.2.3", insiders: true,
+			clientInfo: &mcp.Implementation{Name: "editor(\x00)\\client\r\nX-Fake:1", Version: "1.0\tbeta\x7f"},
+			want:       `github-mcp-server/v1.2.3 (editor\(\x00\)\\client\r\nX-Fake:1/1.0\tbeta\x7f) (insiders)`,
+		},
+		{
+			name: "legacy control characters", handshake: "legacy", version: "v1.2.3",
+			clientInfo: &mcp.Implementation{Name: "editor(\x00)\\client\r\nX-Fake:1", Version: "1.0\tbeta\x7f"},
+			want:       `github-mcp-server/v1.2.3 (editor\(\x00\)\\client\r\nX-Fake:1/1.0\tbeta\x7f)`,
+		},
+		{
+			name: "spaces and Unicode preserved", version: "v1.2.3",
+			clientInfo: &mcp.Implementation{Name: "VS Code \u03b2", Version: "\u03b1 1.0"},
+			want:       "github-mcp-server/v1.2.3 (VS Code \u03b2/\u03b1 1.0)",
+		},
+		{
+			name: "empty client metadata", version: "v1.2.3",
+			clientInfo: &mcp.Implementation{},
+			want:       "github-mcp-server/v1.2.3 (/)",
+		},
+		{
+			name: "quoted client metadata", version: "v1.2.3",
+			clientInfo: &mcp.Implementation{Name: `"Editor"`, Version: `v"1`},
+			want:       `github-mcp-server/v1.2.3 (\"Editor\"/v\"1)`,
+		},
 	}
 
 	for _, tt := range tests {