diff --git a/internal/cli/agent.go b/internal/cli/agent.go
index 0a6a7e0..6cfd0ce 100644
--- a/internal/cli/agent.go
+++ b/internal/cli/agent.go
@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"errors"
 	"io"
 	"time"
 
@@ -9,6 +10,10 @@ import (
 	"git.dcglab.co.uk/steve/emcli/internal/store"
 )
 
+// errCommandFailed signals that a command emitted an error envelope, so the
+// process should exit non-zero. The JSON envelope is the authoritative detail.
+var errCommandFailed = errors.New("command reported error")
+
 // Mailer is the subset of the IMAP client the agent commands use.
 type Mailer interface {
 	SelectFolder(folder string) (uint32, uint32, error)
@@ -26,7 +31,15 @@ type Deps struct {
 	Out   io.Writer
 }
 
-func (d Deps) emit(e Envelope) error { return e.Write(d.Out) }
+func (d Deps) emit(e Envelope) error {
+	if err := e.Write(d.Out); err != nil {
+		return err // write failure (rare) — propagate as-is
+	}
+	if e.Error {
+		return errCommandFailed
+	}
+	return nil
+}
 
 func (d Deps) audit(account, action, target, result, reason string) {
 	_ = d.Store.Audit(d.Now(), store.AuditEntry{
diff --git a/internal/cli/agent_test.go b/internal/cli/agent_test.go
index 8821a25..28a9996 100644
--- a/internal/cli/agent_test.go
+++ b/internal/cli/agent_test.go
@@ -122,9 +122,7 @@ func TestGetFilteredReturnsNotFound(t *testing.T) {
 		},
 	}
 	d, buf := newDeps(t, fm)
-	if err := GetCmd(d, "work", "INBOX", 102); err != nil {
-		t.Fatalf("GetCmd: %v", err)
-	}
+	_ = GetCmd(d, "work", "INBOX", 102)
 	res := decode(t, buf.Bytes())
 	if res["error"] != true {
 		t.Fatal("filtered get must return error envelope")
@@ -135,6 +133,25 @@ func TestGetFilteredReturnsNotFound(t *testing.T) {
 	}
 }
 
+func TestGetFilteredReturnsErrorForExit(t *testing.T) {
+	fm := &fakeMailer{
+		uidValidity: 1, maxUID: 100,
+		headers: []mail.Header{{UID: 102, From: "eve@evil.com", Subject: "spam"}},
+		full: map[uint32]mail.Message{
+			102: {Header: mail.Header{UID: 102, From: "eve@evil.com", Subject: "spam"}, BodyText: "secret"},
+		},
+	}
+	d, buf := newDeps(t, fm)
+	err := GetCmd(d, "work", "INBOX", 102)
+	if err == nil {
+		t.Fatal("GetCmd on filtered uid must return non-nil error so caller can exit non-zero")
+	}
+	res := decode(t, buf.Bytes())
+	if res["error"] != true {
+		t.Fatalf("envelope must report error=true, got %v", res["error"])
+	}
+}
+
 func TestAckAdvancesStateAndFiltered(t *testing.T) {
 	fm := &fakeMailer{
 		uidValidity: 1, maxUID: 100,
@@ -145,9 +162,7 @@ func TestAckAdvancesStateAndFiltered(t *testing.T) {
 	}
 	d, buf := newDeps(t, fm)
 	// Acking a filtered uid (102) must be rejected as not-found.
-	if err := AckCmd(d, "work", "INBOX", []uint32{102}); err != nil {
-		t.Fatalf("AckCmd: %v", err)
-	}
+	_ = AckCmd(d, "work", "INBOX", []uint32{102})
 	if decode(t, buf.Bytes())["error"] != true {
 		t.Fatal("acking filtered uid must fail")
 	}