A tools bundle is given its words, composed per machine; what they name is the account's to read (hq ADR 0192)

build.artifacts[].env on a bundle: words and values written with ${dir:…} and ${port:…} only,
refused when a value carries any other reference (a secret's content, a binding) or names a word
the runtime sets for itself, and on any artifact that is not a bundle. Resolved per machine like a
container's environment and handed to the runtime as MESH_TOOL_ENV, module by module, in the unit
so a change restarts it. Every file and directory of the module a word names, or that holds one, is
owned by the account the runtime runs as where it says no owner, since a tool reads as that account.

internal/catalogue/build.go

@@ -92,7 +92,7 @@ func (m Manifest) Resolve(built []Built) (Manifest, error) {
 			out.Bundles = append(out.Bundles, Bundle{
 				Name: a.Name, Source: Recorded(made.Reference), Digest: made.Digest,
 				Language: a.Language, Entrypoints: append([]string(nil), a.Entrypoints...),
-				Loads: loads,
+				Loads: loads, Env: copyWords(a.Env),
 			})
 		}
 		sort.Slice(out.Bundles, func(i, j int) bool { return out.Bundles[i].Name < out.Bundles[j].Name })
@@ -203,6 +203,12 @@ func (b *Build) problems(module string) []string {
 		// A bundle's source is the module's own directory by definition, and what it needs to say
 		// is which compiler — because the mesh chooses that, and cannot choose for a module that
 		// has not said.
+		if len(a.Env) > 0 && a.Kind != ArtifactBundle {
+			problems = append(problems, fmt.Sprintf(
+				"%s: %q is a %q and says what it is given (env). Only a bundle the node's runtime "+
+					"serves is given words (novox/hq ADR 0192); a container says its own environment",
+				module, a.Name, a.Kind))
+		}
 		if a.Kind == ArtifactBundle || a.Kind == ArtifactPackage {
 			// **Except for a language that compiles to a binary, where it names which one**
 			// (novox/hq 04-ISSUES/142). A bundle in an interpreted language is the module's own
@@ -222,6 +228,7 @@ func (b *Build) problems(module string) []string {
 					"%s: %q is a bundle and says no language, so nothing can choose a compiler "+
 						"for it", module, a.Name))
 			}
+			problems = append(problems, bundleEnvProblems(module, a)...)
 			// What the runtime loads is among what was compiled (ADR 0175): a name here that is
 			// not an entrypoint is a file the bundle does not contain, and the runtime would
 			// fail to import it on every machine rather than here.
@@ -360,3 +367,50 @@ func versionOf(digest string) string {
 	}
 	return hex
 }
+
+// bundleEnvWords are the words the runtime sets for itself; a bundle that named one would be
+// telling the runtime what it is, which is the mesh's to say (novox/hq ADR 0192).
+var bundleEnvWords = map[string]bool{
+	RuntimeToolModules: true, RuntimeBrokerFile: true, RuntimeOperatorAccount: true,
+	RuntimeOperatorHome: true, RuntimeToolEnv: true,
+}
+
+// bundleEnvProblems says what is wrong with what a bundle says it is given (novox/hq ADR 0192):
+// a value is a path or a constant written with the references a container's environment may use
+// for a place or a port, and never a secret's content or another module's binding — a secret
+// reaches a tool as a file whose path is named.
+func bundleEnvProblems(module string, a Artifact) []string {
+	if len(a.Env) == 0 {
+		return nil
+	}
+	var problems []string
+	for _, word := range sortedKeys(a.Env) {
+		value := a.Env[word]
+		if bundleEnvWords[word] {
+			problems = append(problems, fmt.Sprintf(
+				"%s: %q gives itself %s, which the node's runtime sets for itself; a bundle is "+
+					"given its own words beside the runtime's, never in place of them (novox/hq ADR 0192)",
+				module, a.Name, word))
+		}
+		rest := ofPort.ReplaceAllString(dirRef.ReplaceAllString(value, ""), "")
+		if strings.Contains(rest, "${") {
+			problems = append(problems, fmt.Sprintf(
+				"%s: %q gives %s the value %q. A bundle's word is a path or a constant, written with "+
+					"${dir:…} and ${port:…} only; a secret reaches a tool as a file the mesh places, "+
+					"named by its path, never as its content (novox/hq ADR 0192)",
+				module, a.Name, word, value))
+		}
+	}
+	return problems
+}
+
+func copyWords(in map[string]string) map[string]string {
+	if len(in) == 0 {
+		return nil
+	}
+	out := make(map[string]string, len(in))
+	for k, v := range in {
+		out[k] = v
+	}
+	return out
+}