diff --git a/internal/cli/broker_dial_other.go b/internal/cli/broker_dial_other.go
index d516138..0b7cb51 100644
--- a/internal/cli/broker_dial_other.go
+++ b/internal/cli/broker_dial_other.go
@@ -10,3 +10,9 @@ import (
 func newBrokerHTTPClient(int) *http.Client { return nil }
 
 var errBrokerUnsupported = errors.New("flashduty: broker mode is not supported on this platform")
+
+// brokerEgressCapable reports whether this build can act as a broker-mode client.
+// False on non-unix builds, which lack the FLASHDUTY_CRED_FD dial path. The
+// runner reads this (via `fduty version --json`) to decide whether to advertise
+// broker mode to safari. See broker_dial_unix.go for the rationale.
+const brokerEgressCapable = false
diff --git a/internal/cli/broker_dial_unix.go b/internal/cli/broker_dial_unix.go
index 7070ed7..4e631d2 100644
--- a/internal/cli/broker_dial_unix.go
+++ b/internal/cli/broker_dial_unix.go
@@ -19,6 +19,13 @@ import (
 // never returns nil), but defaultNewClient references it on every platform.
 var errBrokerUnsupported = errors.New("flashduty: broker mode is not supported on this platform")
 
+// brokerEgressCapable reports whether this build can act as a broker-mode client
+// (read FLASHDUTY_CRED_FD and dial over the inherited control fd). The runner
+// probes it via `fduty version --json` and only advertises broker mode to safari
+// when true — otherwise safari would deliver the per-person key out-of-band to an
+// fduty that can't read it. True on unix, where this file is built.
+const brokerEgressCapable = true
+
 // brokerDialer owns the inherited control fd and serializes per-dial handshakes.
 // Each Dial sends a 1-byte request datagram on the control channel and receives
 // one dedicated SOCK_STREAM fd back via SCM_RIGHTS.
diff --git a/internal/cli/version.go b/internal/cli/version.go
index 28bc276..e7c72c0 100644
--- a/internal/cli/version.go
+++ b/internal/cli/version.go
@@ -24,7 +24,28 @@ func newVersionCmd() *cobra.Command {
 		Use:   "version",
 		Short: "Print version information",
 		Run: func(cmd *cobra.Command, args []string) {
-			fmt.Printf("flashduty version %s (%s) built %s\n", versionStr, commitStr, dateStr)
+			out := cmd.OutOrStdout()
+			// A structured (--json / --output-format) request emits a
+			// machine-readable object that includes broker_egress, the capability
+			// the runner probes before advertising broker mode to safari. An older
+			// fduty ignores these flags and prints the plain line below, so the
+			// absence of the broker_egress field reads as "not capable". The plain
+			// human output is unchanged.
+			if currentOutputFormat().Structured() {
+				b, err := marshalStructured(map[string]any{
+					"version":       versionStr,
+					"commit":        commitStr,
+					"date":          dateStr,
+					"broker_egress": brokerEgressCapable,
+				})
+				if err != nil {
+					_, _ = fmt.Fprintln(cmd.ErrOrStderr(), err)
+					return
+				}
+				_, _ = fmt.Fprintln(out, string(b))
+				return
+			}
+			_, _ = fmt.Fprintf(out, "flashduty version %s (%s) built %s\n", versionStr, commitStr, dateStr)
 		},
 	}
 }
diff --git a/internal/cli/version_test.go b/internal/cli/version_test.go
new file mode 100644
index 0000000..7163b6b
--- /dev/null
+++ b/internal/cli/version_test.go
@@ -0,0 +1,48 @@
+package cli
+
+import (
+	"bytes"
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+// TestVersionPlainOutput keeps the human-readable line stable (the runner's
+// install scripts and humans rely on it).
+func TestVersionPlainOutput(t *testing.T) {
+	cmd := newVersionCmd()
+	var buf bytes.Buffer
+	cmd.SetOut(&buf)
+	cmd.Run(cmd, nil)
+	if got := buf.String(); !strings.HasPrefix(got, "flashduty version ") {
+		t.Fatalf("plain version output changed: %q", got)
+	}
+}
+
+// TestVersionJSONAdvertisesBrokerEgress locks the capability contract the runner
+// depends on: `fduty version --json` must emit a broker_egress field whose value
+// matches this build's compile-time capability (true on unix, false elsewhere).
+// If the field went missing, broker-capable runners would stop advertising
+// broker mode and silently fall back to the legacy env-key path.
+func TestVersionJSONAdvertisesBrokerEgress(t *testing.T) {
+	origJSON := flagJSON
+	flagJSON = true
+	defer func() { flagJSON = origJSON }()
+
+	cmd := newVersionCmd()
+	var buf bytes.Buffer
+	cmd.SetOut(&buf)
+	cmd.Run(cmd, nil)
+
+	var got map[string]any
+	if err := json.Unmarshal(buf.Bytes(), &got); err != nil {
+		t.Fatalf("version --json must be valid JSON, got %q: %v", buf.String(), err)
+	}
+	v, ok := got["broker_egress"]
+	if !ok {
+		t.Fatalf("version --json must include the broker_egress field, got: %q", buf.String())
+	}
+	if v != brokerEgressCapable {
+		t.Fatalf("broker_egress = %v, want %v (compile-time capability)", v, brokerEgressCapable)
+	}
+}