include rust binary in install script

install.sh

@@ -152,6 +152,33 @@ check_node() {
     return 1
 }
 
+# Download broker binary (Rust broker for workflow/SDK agent spawning)
+download_broker_binary() {
+    step "Downloading broker binary..."
+
+    local binary_name="agent-relay-broker-${PLATFORM}"
+    local download_url="https://github.com/$REPO_RELAY/releases/download/v${VERSION}/${binary_name}"
+    local target_path="$INSTALL_DIR/bin/agent-relay-broker"
+
+    mkdir -p "$INSTALL_DIR/bin"
+
+    if curl -fsSL "$download_url" -o "$target_path" 2>/dev/null; then
+        chmod +x "$target_path"
+        # Verify binary works (Rust clap binary supports --help)
+        if "$target_path" --help &>/dev/null; then
+            success "Downloaded broker binary (workflow agent spawning)"
+            return 0
+        else
+            warn "broker binary failed verification"
+            rm -f "$target_path"
+            return 1
+        fi
+    else
+        warn "No prebuilt broker binary for $PLATFORM"
+        return 1
+    fi
+}
+
 # Download relay-pty binary
 download_relay_pty() {
     step "Downloading relay-pty binary..."
@@ -602,6 +629,9 @@ Or use nvm: curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.0/instal
     # Install ACP bridge for Zed editor integration
     install_acp_bridge || true
 
+    # Download broker binary for workflow/SDK agent spawning
+    download_broker_binary || true
+
     success "Installed via npm"
 }
 
@@ -738,6 +768,8 @@ main() {
         INSTALL_METHOD="binary"
         # Also download relay-pty binary if available
         download_relay_pty || true
+        # Download broker binary for workflow/SDK agent spawning
+        download_broker_binary || true
         # Download dashboard-server binary if available
         download_dashboard_binary || true
         # Download dashboard UI files (required for standalone binary to serve the UI)

packages/broker-sdk/src/client.ts

@@ -486,10 +486,22 @@ function isExplicitPath(binaryPath: string): boolean {
 
 function resolveDefaultBinaryPath(): string {
   const exe = process.platform === "win32" ? "agent-relay.exe" : "agent-relay";
+  const brokerExe = process.platform === "win32" ? "agent-relay-broker.exe" : "agent-relay-broker";
+
+  // 1. Check for bundled broker binary in SDK package (npm install)
   const moduleDir = path.dirname(fileURLToPath(import.meta.url));
   const bundled = path.resolve(moduleDir, "..", "bin", exe);
   if (fs.existsSync(bundled)) {
     return bundled;
   }
+
+  // 2. Check for standalone broker binary in ~/.agent-relay/bin/ (install.sh)
+  const homeDir = process.env.HOME || process.env.USERPROFILE || "";
+  const standaloneBroker = path.join(homeDir, ".agent-relay", "bin", brokerExe);
+  if (fs.existsSync(standaloneBroker)) {
+    return standaloneBroker;
+  }
+
+  // 3. Fall back to agent-relay on PATH (may be Node CLI — will fail for broker ops)
   return "agent-relay";
 }