A TypeScript bundle carries what it runs with: the toolchain's runtime directory is copied into it (hq to-be 38 WP3, ADR 0188)

A bundle that compiled was not yet a bundle that ran. The compiler resolved `import "nats"` from
the toolchain image's own node_modules and the pack took only what the compiler wrote, so what a
machine unpacked could not find a single dependency — and Node would have read the bare `.js` as
CommonJS besides. No TypeScript bundle had run live to show it; the runtime's own is the first that
must. A toolchain now names a Dependencies directory in its image, copied whole into the output's
root after the compile by a second run in the same image: for TypeScript /app/runtime, which the
runtime's image puts a `"type": "module"` package.json and its pruned node_modules at. An older
image without it fails the build by name rather than packing a bundle that starts nowhere. The
SDK's and the runtime's dependencies, nothing module-specific yet: a skeleton, by ADR 0188 §5.

internal/builder/builder.go

@@ -968,6 +968,26 @@ 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 != "" {
+		// **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
+		// plain command beside it. Refused by name when the image carries no such directory — an
+		// older toolchain image — because a bundle packed without its dependencies starts nowhere
+		// and says so three layers away from here.
+		copying := []string{
+			"run", "--rm",
+			"--volume", tree + ":" + within,
+			"--workdir", within,
+			base,
+			"sh", "-c",
+			`test -d "$1" || { echo "the toolchain image carries no $1: it predates the mesh shipping a bundle's dependencies, rebuild $2 first" >&2; exit 1; }; cp -a "$1/." "$3/"`,
+			"dependencies", chain.Dependencies, chain.Base, out,
+		}
+		if _, err := run(ctx, tree, "docker", copying...); err != nil {
+			return "", fmt.Errorf("copying the %s dependencies a bundle runs with: %w", chain.Language, err)
+		}
+	}
 	return filepath.Join(tree, out), nil
 }
 

internal/builder/bundle_test.go

@@ -82,6 +82,41 @@ func TestABundleIsCompiledAndPackedWithNoDockerfile(t *testing.T) {
 	if !strings.HasPrefix(digest, "sha256:") {
 		t.Fatalf("the bundle was not pinned: %v", got.Manifest.Resources[0])
 	}
+
+	// **And what it runs with, from the image it was compiled in** (novox/hq to-be 38 WP3). A
+	// second run in the same toolchain image copies the toolchain's runtime directory — the
+	// `"type": "module"` package.json and the pruned node_modules — into the output's root, and
+	// refuses by name when the image carries none rather than packing a bundle that starts nowhere.
+	var copied string
+	for _, line := range r.ran {
+		if strings.HasPrefix(line, "docker run") && strings.Contains(line, "/app/runtime") {
+			copied = line
+		}
+	}
+	if copied == "" {
+		t.Fatalf("the bundle's dependencies were not copied in after the compile:\n%s", strings.Join(r.ran, "\n"))
+	}
+	if !strings.Contains(copied, "mesh-tools/build@sha256:") || !strings.Contains(copied, "predates") ||
+		!strings.Contains(copied, Out("code")) {
+		t.Fatalf("the copy does not run in the same toolchain, refuse an older image by name, or land in the artifact's output: %s", copied)
+	}
+	if strings.Index(strings.Join(r.ran, "\n"), "--outDir") > strings.Index(strings.Join(r.ran, "\n"), "/app/runtime") {
+		t.Fatal("the dependencies were copied before the compile wrote its output")
+	}
+}
+
+// A language whose bundle carries its own dependencies copies nothing in: a Go binary is static.
+func TestOnlyALanguageWithARuntimeDirectoryCopiesDependenciesIn(t *testing.T) {
+	ts, _ := ToolchainFor("typescript")
+	if ts.Dependencies != "/app/runtime" {
+		t.Fatalf("typescript bundles run with %q", ts.Dependencies)
+	}
+	for _, language := range []string{"go", "python"} {
+		chain, _ := ToolchainFor(language)
+		if chain.Dependencies != "" {
+			t.Fatalf("%s copies %q into every bundle, and its bundles carry their own", language, chain.Dependencies)
+		}
+	}
 }
 
 // **Refused before anything is built, naming what to build first.** A base the mesh has not built
@@ -145,9 +180,13 @@ func TestTwoBundlesInOneModuleArePackedSeparately(t *testing.T) {
 		t.Fatalf("a module with two bundles did not build: %v", err)
 	}
 
-	// Compiled into two different places.
+	// Compiled into two different places. Only the compile lines: the copy of each bundle's
+	// dependencies names the same directory again, deliberately.
 	var outputs []string
 	for _, line := range r.ran {
+		if !strings.Contains(line, "--outDir") {
+			continue
+		}
 		for _, part := range strings.Fields(line) {
 			if strings.HasPrefix(part, ".mesh-build/") {
 				outputs = append(outputs, part)

internal/builder/toolchain.go

@@ -57,6 +57,23 @@ type Toolchain struct {
 	// carrying its debug info. The mistake was believing a comment rather than reading the file it
 	// produced (novox/hq 04-ISSUES/161).
 	LinkerFlags []string
+	// Dependencies is a directory inside the toolchain image whose contents a bundle in this
+	// language runs with, copied whole into the compiled output's root after the compile.
+	//
+	// **A bundle that compiles is not yet a bundle that runs.** The compiler resolves `import
+	// "nats"` from the toolchain image's own node_modules and the pack takes only what the compiler
+	// wrote, so what a machine unpacked could not find a single dependency — and no TypeScript bundle
+	// had ever run live to show it (novox/hq to-be 38 WP3). For TypeScript the directory holds a
+	// `package.json` saying `"type": "module"` — Node reads a bare `.js` as CommonJS otherwise, so a
+	// bundle with its dependencies and without that line still fails to start — and the pruned,
+	// production-only node_modules the runtime itself ships with: the SDK's and the runtime's
+	// dependencies, and nothing module-specific yet (novox/hq ADR 0188 §5: a skeleton; a module's
+	// own npm dependencies are a later step). Empty for a language whose bundle carries its own —
+	// a Go binary is static, a Python bundle is installed with its dependencies.
+	//
+	// A toolchain image without the directory fails the build by name rather than packing a bundle
+	// that starts nowhere: the image predates this and must be rebuilt first.
+	Dependencies string
 	// SystemStamp is the variable this language's linker fills with the artifact's declared system,
 	// for a language whose binaries are pinned to one at link time (novox/hq ADR 0005).
 	//
@@ -118,9 +135,10 @@ var toolchains = []Toolchain{
 			"--module", "NodeNext", "--moduleResolution", "NodeNext",
 			"--target", "ES2022", "--rootDir", ".",
 		},
-		OutputFlag: "--outDir",
+		OutputFlag:   "--outDir",
-		Unit:       UnitSources,
+		Unit:         UnitSources,
-		SourceExt:  ".ts",
+		SourceExt:    ".ts",
+		Dependencies: "/app/runtime",
 	},
 	{
 		Language: "go",