A TypeScript bundle is one file per entrypoint, bundled in the toolchain (hq ADR 0193); a toolchain follows the SDK it stands on (hq issue 212)

Every served bundle is its own process now, so each carries its own copy of what it imports: after
the compile and the launchers, the toolchain image's esbuild bundles every entrypoint in place and
every launcher under its own name into one ES module file, the SDK inlined, require provided to
inlined CommonJS, the launcher's shebang kept and its mode 0755. The toolchain's node_modules is
copied only for packages an artifact names external. An image without the bundler is refused by
name. Issue 212: build.on already passes a published package by its exact version and plans the
toolchain after it; tests say so.

internal/builder/builder.go

@@ -593,6 +593,12 @@ func one(ctx context.Context, run Runner, publish Publisher,
 		if err != nil {
 			return catalogue.Built{}, fmt.Errorf("%s: writing %s's launchers failed: %w", module, a.Name, err)
 		}
+		if chain.Bundler != "" {
+			say("bundle", "bundling each entrypoint into one file")
+			if compiled, err = bundled(ctx, run, tree, chain, base, a, launchers); err != nil {
+				return catalogue.Built{}, fmt.Errorf("%s: bundling %s failed: %w", module, a.Name, err)
+			}
+		}
 		say("bundle", "compiled, packing")
 		body, err := pack(compiled)
 		if err != nil {
@@ -974,7 +980,7 @@ func compile(ctx context.Context, run Runner, tree string, chain Toolchain,
 	if _, err := run(ctx, tree, "docker", invocation...); err != nil {
 		return "", err
 	}
-	if chain.Dependencies != "" {
+	if chain.Dependencies != "" && chain.Bundler == "" {
 		// **What the bundle runs with, from the image it was compiled in** (Toolchain.Dependencies).
 		// A second run in the same image rather than a shell wrapped around the compiler: the
 		// compile line stays a plain command a reader can run by hand, and the copy is one more
@@ -1224,3 +1230,94 @@ func writeLaunchers(root string, chain Toolchain, a catalogue.Artifact) (map[str
 	}
 	return out, nil
 }
+
+// bundledSuffix is where a bundle's one-file output is written, beside what the compiler wrote.
+const bundledSuffix = ".bundled"
+
+// bundled makes every entrypoint and every launcher of a compiled bundle ONE file, in the toolchain
+// image's bundler, and answers the directory to pack (novox/hq ADR 0193).
+//
+// **What a launched bundle runs is what it imports, and nothing else.** Every served bundle is its
+// own process, so it carries its own copy of the SDK and its own dependencies inlined — the
+// toolchain's whole node_modules no longer travels in every bundle. An entrypoint a process runs by
+// name (`node daemon/index.js`) is bundled in place under its own name; a launcher keeps its name
+// and its first line, and stays executable. A package the bundler cannot inline is named by the
+// artifact (`external`), kept as an import, and only then is the toolchain's runtime directory
+// copied beside the files. CommonJS inlined into an ES module still finds `require`.
+func bundled(ctx context.Context, run Runner, tree string, chain Toolchain, base string,
+	a catalogue.Artifact, launchers map[string]string) (string, error) {
+	const within = "/app/modules/module"
+	out, final := Out(a.Name), Out(a.Name)+bundledSuffix
+	if err := os.RemoveAll(filepath.Join(tree, final)); err != nil {
+		return "", err
+	}
+	if err := os.MkdirAll(filepath.Join(tree, final), 0o755); err != nil {
+		return "", err
+	}
+	common := []string{"--bundle", "--platform=node", "--format=esm", "--target=node22",
+		"--outbase=" + out, "--outdir=" + final, "--log-level=warning",
+		"--banner:js=import { createRequire as __meshRequire } from 'node:module'; const require = __meshRequire(import.meta.url);"}
+	for _, x := range a.External {
+		common = append(common, "--external:"+x)
+	}
+	var plain []string
+	for _, e := range a.Entrypoints {
+		if strings.HasSuffix(e, ".js") {
+			plain = append(plain, out+"/"+e)
+		}
+	}
+	var launch []string
+	for _, l := range sortedValues(launchers) {
+		launch = append(launch, out+"/"+l)
+	}
+	// Refused by name in an image that predates the bundler, as the dependencies copy is: a bundle
+	// packed without it would carry nothing it imports.
+	guard := `test -x "$0" || { echo "the toolchain image carries no bundler at $0: it predates one-file bundles, rebuild mesh-tools first" >&2; exit 1; }; exec node "$0" "$@"`
+	step := func(entries []string, extra ...string) error {
+		if len(entries) == 0 {
+			return nil
+		}
+		invocation := []string{"run", "--rm", "--volume", tree + ":" + within, "--workdir", within, base,
+			"sh", "-c", guard, chain.Bundler}
+		invocation = append(invocation, entries...)
+		invocation = append(invocation, common...)
+		invocation = append(invocation, extra...)
+		_, err := run(ctx, tree, "docker", invocation...)
+		return err
+	}
+	if err := step(plain); err != nil {
+		return "", err
+	}
+	if err := step(launch, "--out-extension:.js=.mjs"); err != nil {
+		return "", err
+	}
+	// Plain `.js` output is an ES module; said once, as the runtime directory used to say it.
+	if err := os.WriteFile(filepath.Join(tree, final, "package.json"), []byte(`{"type":"module","private":true}`+"\n"), 0o644); err != nil {
+		return "", err
+	}
+	for _, l := range launchers {
+		path := filepath.Join(tree, final, filepath.FromSlash(l))
+		if _, err := os.Stat(path); err == nil {
+			if err := os.Chmod(path, 0o755); err != nil {
+				return "", err
+			}
+		}
+	}
+	if len(a.External) > 0 && chain.Dependencies != "" {
+		copying := []string{"run", "--rm", "--volume", tree + ":" + within, "--workdir", within, base,
+			"sh", "-c", `cp -a "$0/node_modules" "$1/"`, chain.Dependencies, final}
+		if _, err := run(ctx, tree, "docker", copying...); err != nil {
+			return "", fmt.Errorf("copying the packages %s keeps external: %w", a.Name, err)
+		}
+	}
+	return filepath.Join(tree, final), nil
+}
+
+func sortedValues(m map[string]string) []string {
+	out := make([]string, 0, len(m))
+	for _, v := range m {
+		out = append(out, v)
+	}
+	sort.Strings(out)
+	return out
+}