diff --git a/cmd/mesh-controller/own_grants.go b/cmd/mesh-controller/own_grants.go
new file mode 100644
index 00000000..8964a078
--- /dev/null
+++ b/cmd/mesh-controller/own_grants.go
@@ -0,0 +1,69 @@
+package main
+
+import (
+	"context"
+	"fmt"
+)
+
+// A new controller's own grants reach the bus before it writes (novox/hq issue 1800).
+//
+// A controller's grants are composed by the controller binary itself (broker.PermissionsFor), so the controller that
+// walks a delivery cannot put its successor's grants in the bus's user list: the list that carries them was sent only
+// once the new controller passed its gate on its first machine (carryUserList). Until then the new controller wrote
+// buckets its account was not granted, and the bus refused them: plans-building on 2026-10-21, declared-packages on
+// 2026-10-22, and R4e's states-announced would be the third.
+//
+// So a controller that starts, holding the lease and before it starts anything that writes its buckets, sends the
+// machine holding the bus its user list when the list it composes is not the one that machine was last sent: the grants
+// step's send (release.go grantsStep), every build there kept at the one it runs, refused unsent when the declaration
+// would change more than the user list (errNotGrantsOnly). No build of a running plan reaches that machine before the
+// plan's own tier sends it (ADR 0503 §8). A send that cannot be made is said once, and the controller serves on.
+//
+// It does not ask heldMachines, as carryUserList does: every reason that gives is a build that would move with the
+// list (a policy, a plan not yet sent there, no gate passed), and here none can. The running plan that brought this
+// controller holds the bus's machine until its tier sends it; asking would leave the list behind exactly when 1800
+// meets it. The refusal unsent (errNotGrantsOnly) is the guard instead.
+
+// ownGrantsCarrier is what the start's send reads and does: whether the bus's list is behind and on which machine, and
+// the grants-only send to it. Variables so a test needs no store and no bus.
+type ownGrantsCarrier struct {
+	behind func(ctx context.Context) (holder string, behind bool, err error)
+	send   func(ctx context.Context, holder string) error
+}
+
+// carry sends the machine holding the bus the controller's own user list when it is behind, and says what it did.
+func (c ownGrantsCarrier) carry(ctx context.Context) string {
+	holder, behind, err := c.behind(ctx)
+	switch {
+	case err != nil:
+		return fmt.Sprintf("whether the bus's user list carries this controller's grants cannot be read, so it is not sent "+
+			"at start; a bucket it newly writes may be refused until the gate carries it: %v", err)
+	case holder == "" || !behind:
+		return ""
+	}
+	if err := c.send(ctx, holder); err != nil {
+		return fmt.Sprintf("this controller's grants could not be sent to %s, which holds the bus, at its start; a bucket "+
+			"it newly writes may be refused until the gate carries them: %v", holder, err)
+	}
+	return fmt.Sprintf("sent %s, which holds the bus, this controller's user list alone, every build there kept, "+
+		"before it writes", holder)
+}
+
+// startWithOwnGrants carries the controller's own grants to the bus and only then starts what writes (then).
+func startWithOwnGrants(ctx context.Context, c ownGrantsCarrier, then func()) {
+	if said := c.carry(ctx); said != "" {
+		fmt.Println(said)
+	}
+	then()
+}
+
+// ownGrantsOf is the carrier of the serving controller: the grants step's reading and its grants-only send.
+func ownGrantsOf(open *stores) ownGrantsCarrier {
+	return ownGrantsCarrier{
+		behind: func(ctx context.Context) (string, bool, error) { return brokerBehindOf(ctx, open, nil) },
+		send: func(ctx context.Context, holder string) error {
+			_, err := sendRollout(keepingEveryBuild(withScope(ctx, sendScope{}), holder), open, []string{holder})
+			return err
+		},
+	}
+}
diff --git a/cmd/mesh-controller/own_grants_test.go b/cmd/mesh-controller/own_grants_test.go
new file mode 100644
index 00000000..d7a8ea4f
--- /dev/null
+++ b/cmd/mesh-controller/own_grants_test.go
@@ -0,0 +1,73 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"testing"
+)
+
+// 1800 (1): a controller starting with the bus's list behind its own sends the bus's machine once, before anything
+// that writes its buckets starts.
+func TestAStartingControllerSendsItsGrantsBeforeItWrites(t *testing.T) {
+	var order []string
+	c := ownGrantsCarrier{
+		behind: func(context.Context) (string, bool, error) { return "novox", true, nil },
+		send:   func(_ context.Context, holder string) error { order = append(order, "send "+holder); return nil },
+	}
+	startWithOwnGrants(t.Context(), c, func() { order = append(order, "writers") })
+	if strings.Join(order, ", ") != "send novox, writers" {
+		t.Fatalf("the start did %v", order)
+	}
+}
+
+// 1800 (3), (4): no send when the list is current or there is no bus with a list; one that cannot be read or sent is
+// said once, and the controller goes on.
+func TestAStartingControllerSendsNothingWhenTheListIsCurrentAndGoesOnWhenRefused(t *testing.T) {
+	sends := 0
+	send := func(context.Context, string) error { sends++; return nil }
+	for _, c := range []ownGrantsCarrier{
+		{behind: func(context.Context) (string, bool, error) { return "novox", false, nil }, send: send},
+		{behind: func(context.Context) (string, bool, error) { return "", true, nil }, send: send},
+	} {
+		if said := c.carry(t.Context()); said != "" || sends != 0 {
+			t.Fatalf("a current list sent %d and said %q", sends, said)
+		}
+	}
+	refused := ownGrantsCarrier{behind: func(context.Context) (string, bool, error) { return "novox", true, nil },
+		send: func(context.Context, string) error { return errNotGrantsOnly }}
+	went := false
+	startWithOwnGrants(t.Context(), refused, func() { went = true })
+	if !went {
+		t.Fatal("a refused send stopped the controller")
+	}
+	if said := refused.carry(t.Context()); !strings.Contains(said, "could not be sent to novox") ||
+		!strings.Contains(said, errNotGrantsOnly.Error()) {
+		t.Fatalf("a refused send is said as %q", said)
+	}
+	unread := ownGrantsCarrier{behind: func(context.Context) (string, bool, error) { return "", false, errors.New("no store") },
+		send: send}
+	if said := unread.carry(t.Context()); !strings.Contains(said, "cannot be read") || sends != 0 {
+		t.Fatalf("an unread list: sent %d, said %q", sends, said)
+	}
+}
+
+// 1800 (2): the start's send is the grants step's: composed with every build of the bus's machine kept at the one it
+// runs, so the declaration differs from its last only by the user list (and is refused unsent otherwise,
+// errNotGrantsOnly, release.go), whatever a running plan registered since.
+func TestAStartingControllersSendKeepsEveryBuildOfTheBusMachine(t *testing.T) {
+	was := sendRollout
+	t.Cleanup(func() { sendRollout = was })
+	var kept bool
+	var named []string
+	sendRollout = func(ctx context.Context, _ *stores, names []string) ([]string, error) {
+		kept, named = everyBuildKept(ctx, "novox"), names
+		return names, nil
+	}
+	if err := ownGrantsOf(nil).send(t.Context(), "novox"); err != nil {
+		t.Fatal(err)
+	}
+	if !kept || len(named) != 1 || named[0] != "novox" {
+		t.Fatalf("the start's send keeps every build: %v, names %v", kept, named)
+	}
+}
diff --git a/cmd/mesh-controller/push.go b/cmd/mesh-controller/push.go
index 61cfcb9f..41d88d4f 100644
--- a/cmd/mesh-controller/push.go
+++ b/cmd/mesh-controller/push.go
@@ -189,7 +189,9 @@ func serve(ctx context.Context) (err error) {
 	// Open plans move on events (novox/hq ADR 0406 §5, issue 974): a tier is asked on the `built` and the send of the
 	// tier before it, a walk ends on its machines' reports, a silent machine is a key that expired, and a plan left
 	// by a replaced controller resumes from the first look, which this asks for. No timer looks every so often.
-	startRolloutEvents(ctx, open, server.JetStream())
+	// **Its own grants on the bus before it writes** (novox/hq issue 1800): a bucket this controller newly writes is
+	// granted before the first write, not after its gate.
+	startWithOwnGrants(ctx, ownGrantsOf(open), func() { startRolloutEvents(ctx, open, server.JetStream()) })
 	// And the merge window (novox/hq ADR 0276, ADR 0407): a batch is cut into its walk when the window closes,
 	// which no merge or outcome says. The window is two keys on the bus that expire and a watcher that hears it;
 	// nothing polls (issue 973).