Beside every TypeScript entrypoint the builder writes an executable launcher; the runtime is told it (hq ADR 0193)

The runtime knows no language: the build makes each served entrypoint executable. For a TypeScript
bundle that is <entry>.serve.mjs, which imports the entrypoint and serves what it registered over
MCP on stdio through the bundle's own SDK. The build records its launchers on the bundle, and the
composer names the launcher where a build wrote one and the entrypoint where it did not, so bundles
built before this keep serving until they are rebuilt.

internal/builder/builder.go

@@ -587,6 +587,12 @@ func one(ctx context.Context, run Runner, publish Publisher,
 		if err != nil {
 			return catalogue.Built{}, fmt.Errorf("%s: compiling %s failed: %w", module, a.Name, err)
 		}
+		// **Every entrypoint the runtime may serve is executable** (novox/hq ADR 0193). The runtime
+		// knows no language; for one that runs through an interpreter the build writes the launcher.
+		launchers, err := writeLaunchers(compiled, chain, a)
+		if err != nil {
+			return catalogue.Built{}, fmt.Errorf("%s: writing %s's launchers failed: %w", module, a.Name, err)
+		}
 		say("bundle", "compiled, packing")
 		body, err := pack(compiled)
 		if err != nil {
@@ -598,7 +604,7 @@ func one(ctx context.Context, run Runner, publish Publisher,
 		if err != nil {
 			return catalogue.Built{}, err
 		}
-		return catalogue.Built{Name: a.Name, Kind: a.Kind, Reference: where, Digest: digest}, nil
+		return catalogue.Built{Name: a.Name, Kind: a.Kind, Reference: where, Digest: digest, Launchers: launchers}, nil
 
 	case catalogue.ArtifactPackage:
 		// Built and published on a public base, to the mesh's package registry, by version
@@ -1173,3 +1179,45 @@ func binaryName(a catalogue.Artifact) string {
 	}
 	return a.Name
 }
+
+// launcherSuffix is what a TypeScript entrypoint's launcher is called beside it: index.js is
+// started as index.serve.mjs (novox/hq ADR 0193). An ES module by its own extension, whatever the
+// bundle's package.json says.
+const launcherSuffix = ".serve.mjs"
+
+// writeLaunchers writes, beside every entrypoint of a TypeScript bundle, an executable that
+// imports the entrypoint and serves what it registered over MCP on stdio — through the bundle's
+// own copy of the SDK, so registering and serving meet in one registry (novox/hq ADR 0193). Its
+// answer is each entrypoint's launcher, by entrypoint, relative to the bundle's root; nothing for
+// a language whose build is already executable.
+func writeLaunchers(root string, chain Toolchain, a catalogue.Artifact) (map[string]string, error) {
+	if chain.Language != "typescript" {
+		return nil, nil
+	}
+	out := map[string]string{}
+	for _, entry := range a.Entrypoints {
+		if !strings.HasSuffix(entry, ".js") {
+			continue
+		}
+		launcher := strings.TrimSuffix(entry, ".js") + launcherSuffix
+		body := "#!/usr/bin/env node\n" +
+			"// Written by the mesh's builder (novox/hq ADR 0193): serve what " + entry + " registers,\n" +
+			"// over MCP on stdio, as the module the node's runtime names in MESH_SERVED_MODULE.\n" +
+			"import { serveRegisteredOverStdio } from \"@novox/mesh-sdk/stdio\";\n" +
+			"await import(\"./" + filepath.Base(entry) + "\");\n" +
+			"await serveRegisteredOverStdio();\n"
+		path := filepath.Join(root, filepath.FromSlash(launcher))
+		if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+			return nil, err
+		}
+		if err := os.WriteFile(path, []byte(body), 0o755); err != nil {
+			return nil, err
+		}
+		// WriteFile honours the umask; the mode a machine unpacks is the one packed, so it is set.
+		if err := os.Chmod(path, 0o755); err != nil {
+			return nil, err
+		}
+		out[entry] = launcher
+	}
+	return out, nil
+}