diff --git a/browse/src/browser-manager.ts b/browse/src/browser-manager.ts
index 32f5ab769..c37b0f564 100644
--- a/browse/src/browser-manager.ts
+++ b/browse/src/browser-manager.ts
@@ -312,6 +312,12 @@ export class BrowserManager {
 
     this.browser = await chromium.launch({
       headless: useHeadless,
+      // Honor GSTACK_CHROMIUM_PATH on the headless launch path. The headed
+      // path (launchPersistentContext, below) already respects it; this keeps
+      // both modes consistent for custom Chromium builds — e.g. a NixOS system
+      // binary, where Playwright's bundled chrome-headless-shell can't run.
+      // No-op when the env var is unset.
+      ...(process.env.GSTACK_CHROMIUM_PATH ? { executablePath: process.env.GSTACK_CHROMIUM_PATH } : {}),
       // On Windows, Chromium's sandbox fails when the server is spawned through
       // the Bun→Node process chain (GitHub #276). Disable it — local daemon
       // browsing user-specified URLs has marginal sandbox benefit. Also disabled
diff --git a/setup b/setup
index 631b84003..eacfc1ef1 100755
--- a/setup
+++ b/setup
@@ -256,7 +256,13 @@ ensure_playwright_browser() {
   else
     (
       cd "$SOURCE_GSTACK_DIR"
-      bun --eval 'import { chromium } from "playwright"; const browser = await chromium.launch(); await browser.close();'
+      if [ -n "$GSTACK_CHROMIUM_PATH" ]; then
+        # GSTACK_CHROMIUM_PATH set: verify that custom Chromium instead (e.g. a
+        # NixOS system binary, where Playwright's bundled Chromium can't run).
+        bun --eval 'import { chromium } from "playwright"; const browser = await chromium.launch({ executablePath: process.env.GSTACK_CHROMIUM_PATH, args: ["--no-sandbox"] }); await browser.close();'
+      else
+        bun --eval 'import { chromium } from "playwright"; const browser = await chromium.launch(); await browser.close();'
+      fi
     ) >/dev/null 2>&1
   fi
 }