diff --git a/cmd/mesh-controller/seatverbs.go b/cmd/mesh-controller/seatverbs.go
index 90cf5afe..f56411c3 100644
--- a/cmd/mesh-controller/seatverbs.go
+++ b/cmd/mesh-controller/seatverbs.go
@@ -694,8 +694,19 @@ func (a *verbArguments) commandLine() ([]string, error) {
 		}
 		return []string{"module", "issue", str("module"), "--node", str("node")}, nil
 	case "build":
-		if err := need("repository"); err != nil {
-			return nil, err
+		// The command's three shapes (`build --on`, `build --behind`, `build <repository>`), one per
+		// call: each branch reads only its own argument, so another given beside it is refused as
+		// passed over rather than dropped. Asked and not waited for, the same as a single build.
+		if b := str("on"); b != "" {
+			return []string{"build", "--on", b, "--wait", "0"}, nil
+		}
+		if on("behind") {
+			return []string{"build", "--behind", "--wait", "0"}, nil
+		}
+		if a.given["repository"] == "" {
+			// No shape named: the command says its usage, which names all three — the answer the
+			// caller needs, and the same as `rotate` given neither of its shapes.
+			return []string{"build"}, nil
 		}
 		// Not waited for: a tool call cannot hold a connection for the minutes a build takes; the
 		// daemon takes the outcome in when it comes and the id follows the build (issue 176). A
diff --git a/cmd/mesh-controller/seatverbs_schema_test.go b/cmd/mesh-controller/seatverbs_schema_test.go
index 35656dce..61415039 100644
--- a/cmd/mesh-controller/seatverbs_schema_test.go
+++ b/cmd/mesh-controller/seatverbs_schema_test.go
@@ -263,8 +263,6 @@ var accountedFlags = map[string]map[string]string{
 		"wait":    "set by the verb to 0: the id follows the build (issue 176)",
 		"self":    "set by the verb from the repository's form: a path on the forge, or a URL",
 		"dry-run": "withheld: a dry run answers only when the build ends, which a call cannot wait for; `command` reaches it",
-		"behind":  "withheld: the named verb builds one named repository; `command` reaches the rest",
-		"on":      "withheld: the named verb builds one named repository; `command` reaches the rest",
 	},
 	"builds": {"n": "=limit"},
 	"plans":  {"n": "=limit", "what-if": "=repository"},
diff --git a/cmd/mesh-controller/seatverbs_test.go b/cmd/mesh-controller/seatverbs_test.go
index 0124c7d9..85f3ab76 100644
--- a/cmd/mesh-controller/seatverbs_test.go
+++ b/cmd/mesh-controller/seatverbs_test.go
@@ -36,6 +36,52 @@ func TestTheBuildToolTellsAForgePathFromAURL(t *testing.T) {
 	}
 }
 
+// The build tool has the command's three shapes: a repository, a base whose dependents are rebuilt
+// (`--on`), or everything behind its source (`--behind`) — each asked, not waited for, one per call.
+// Given neither, the command line is what it was: nothing new reaches it.
+func TestTheBuildToolTakesOnAndBehind(t *testing.T) {
+	cases := []struct {
+		args map[string]any
+		want string
+	}{
+		{map[string]any{"on": "mesh-tools"}, "build --on mesh-tools --wait 0"},
+		{map[string]any{"behind": "true"}, "build --behind --wait 0"},
+		{map[string]any{"behind": true}, "build --behind --wait 0"},
+		{map[string]any{"repository": "novox/x"}, "build novox/x --wait 0 --self"},
+		{map[string]any{"repository": "novox/x", "behind": "false"}, "build novox/x --wait 0 --self"},
+		{map[string]any{"repository": "novox/x", "path": "modules/x", "ref": "main"},
+			"build novox/x --wait 0 --self --path modules/x --ref main"},
+	}
+	for _, c := range cases {
+		argv, err := argvFor("build", c.args)
+		if err != nil {
+			t.Errorf("%v: %v", c.args, err)
+			continue
+		}
+		if got := strings.Join(argv, " "); got != c.want {
+			t.Errorf("%v became %q, not %q", c.args, got, c.want)
+		}
+	}
+	// Naming no shape runs the bare command, which answers its usage naming all three.
+	if argv, err := argvFor("build", map[string]any{}); err != nil || strings.Join(argv, " ") != "build" {
+		t.Errorf("a build naming nothing became %v, %v", argv, err)
+	}
+	// One shape per call: a second beside it is refused, not dropped, and so is half of one.
+	for _, refused := range []map[string]any{
+		{"path": "modules/x"},
+		{"on": "mesh-tools", "repository": "novox/x"},
+		{"on": "mesh-tools", "behind": "true"},
+		{"behind": "true", "repository": "novox/x"},
+		{"behind": "true", "path": "modules/x"},
+		{"on": "mesh-tools", "ref": "main"},
+		{"behind": "yes"},
+	} {
+		if argv, err := argvFor("build", refused); err == nil {
+			t.Errorf("%v was accepted as %v", refused, argv)
+		}
+	}
+}
+
 // `rotate` is one verb with two shapes (ADR 0114, issue 180): a pair credential by provision, or a
 // module's own secret by machine, module and name.
 func TestRotateTakesAProvisionOrAnOwnSecret(t *testing.T) {
diff --git a/internal/catalogue/verbs.go b/internal/catalogue/verbs.go
index 5e96e812..b99177e2 100644
--- a/internal/catalogue/verbs.go
+++ b/internal/catalogue/verbs.go
@@ -396,13 +396,22 @@ var ControllerVerbs = []Verb{
 			"machine": "one machine (optional)",
 			"retired": "\"true\": only what is retired",
 		}, nil, "retired")},
-	{Name: "build", Description: "Have the build machine build a repository. Answers at once with the build's id: " +
-		"`builds` with that id follows it line by line, and the module is registered when the outcome comes.",
+	// Three shapes, as the command has them: one repository, every module standing on a base (on), or
+	// every module behind its source (behind). One per call; a second is refused as passed over.
+	{Name: "build", Description: "Have the build machine build a repository — or, instead, every module that " +
+		"stands on a base (on), or every module behind its source (behind). Answers at once with each build's id: " +
+		"`builds` with an id follows it line by line, and a module is registered when its outcome comes.",
 		Input: schema(map[string]string{
-			"repository": "the repository's URL, or its path on the forge holding the git seat (owner/name)",
-			"path":       "the module's directory inside it (optional)",
-			"ref":        "the branch, tag or commit to build (optional)",
-		}, []string{"repository"})},
+			"repository": "the repository's URL, or its path on the forge holding the git seat (owner/name); " +
+				"needed unless on or behind is given",
+			"path": "with repository: the module's directory inside it (optional)",
+			"ref":  "with repository: the branch, tag or commit to build (optional)",
+			"on": "instead of a repository: a module's name. Every module the mesh holds that was built against " +
+				"its artifacts is built again from its own source, bases among them asked first — the rebuild a " +
+				"changed base needs, which behind does not see because their sources did not move",
+			"behind": "\"true\", instead of a repository: build every module the mesh holds whose source has moved " +
+				"past the commit it was built from, bases asked first",
+		}, nil, "behind")},
 }
 
 // schema is a JSON schema for an object of string properties, which is every argument the verbs
diff --git a/internal/inventory/seats_test.go b/internal/inventory/seats_test.go
index 0c1f2a38..916be433 100644
--- a/internal/inventory/seats_test.go
+++ b/internal/inventory/seats_test.go
@@ -227,3 +227,48 @@ func TestASeatsVerbGainsTheArgumentsTheBinaryNames(t *testing.T) {
 		}
 	}
 }
+
+// **A stored row's build verb takes on and behind** (novox/hq ADR 0246: arguments added to a verb are
+// additive): a row seeded before them described build with a repository it required, so the console
+// would refuse both and a call naming neither would be refused for want of a repository. Re-seeding
+// gives the row this binary's build.
+func TestAStoredRowsBuildVerbTakesOnAndBehind(t *testing.T) {
+	inv := ForTest(t)
+	ctx := t.Context()
+	if _, err := inv.SeedSeats(ctx, catalogue.DefaultSeats()); err != nil {
+		t.Fatal(err)
+	}
+	old := `[{"name":"build","description":"Have the build machine build a repository.","input":{"type":"object",
+	          "properties":{"repository":{"type":"string"},"path":{"type":"string"},"ref":{"type":"string"}},
+	          "required":["repository"]}}]`
+	if _, err := inv.store.Pool().Exec(ctx, `update seat set serves = $1 where name = $2`,
+		[]byte(old), catalogue.ControllerSeatName); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := inv.SeedSeats(ctx, catalogue.DefaultSeats()); err != nil {
+		t.Fatal(err)
+	}
+	seats, err := inv.Seats(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var build catalogue.Verb
+	for _, s := range seats {
+		if s.Name == catalogue.ControllerSeatName {
+			for _, v := range s.Serves {
+				if v.Name == "build" {
+					build = v
+				}
+			}
+		}
+	}
+	props, _ := build.Input["properties"].(map[string]any)
+	for _, arg := range []string{"repository", "path", "ref", "on", "behind"} {
+		if _, has := props[arg]; !has {
+			t.Errorf("build in the row does not take %s: %v", arg, props)
+		}
+	}
+	if req, _ := build.Input["required"].([]any); len(req) != 0 {
+		t.Errorf("build in the row still requires %v, so on and behind alone are refused", req)
+	}
+}