diff --git a/changes/274-launcher-runtime-fixes.md b/changes/274-launcher-runtime-fixes.md
new file mode 100644
index 00000000..ebe9bfc1
--- /dev/null
+++ b/changes/274-launcher-runtime-fixes.md
@@ -0,0 +1,5 @@
+type: fixed
+area: launcher
+
+- Kept the first-run setup window from navigating away on unexpected URLs.
+- Made Windows mpv honor an explicitly configured executable path instead of silently falling back to PATH.
diff --git a/launcher/smoke.e2e.test.ts b/launcher/smoke.e2e.test.ts
index 82798fd7..439e9955 100644
--- a/launcher/smoke.e2e.test.ts
+++ b/launcher/smoke.e2e.test.ts
@@ -79,7 +79,7 @@ function createSmokeCase(name: string): SmokeCase {
 
   writeExecutable(
     fakeMpvPath,
-    `#!/usr/bin/env node
+    `#!/usr/bin/env bun
 const fs = require('node:fs');
 const net = require('node:net');
 const path = require('node:path');
@@ -118,7 +118,7 @@ process.on('SIGTERM', closeAndExit);
 
   writeExecutable(
     fakeAppPath,
-    `#!/usr/bin/env node
+    `#!/usr/bin/env bun
 const fs = require('node:fs');
 
 const logPath = ${JSON.stringify(fakeAppLogPath)};
diff --git a/src/core/services/youtube/metadata-probe.test.ts b/src/core/services/youtube/metadata-probe.test.ts
index 5ae196e0..2c8f1ec7 100644
--- a/src/core/services/youtube/metadata-probe.test.ts
+++ b/src/core/services/youtube/metadata-probe.test.ts
@@ -17,7 +17,7 @@ async function withTempDir<T>(fn: (dir: string) => Promise<T>): Promise<T> {
 function makeFakeYtDlpScript(dir: string, payload: string): void {
   const scriptPath = path.join(dir, 'yt-dlp');
   const script = process.platform === 'win32'
-    ? `#!/usr/bin/env node
+    ? `#!/usr/bin/env bun
 process.stdout.write(${JSON.stringify(payload)});
 `
     : `#!/usr/bin/env sh
diff --git a/src/core/services/youtube/playback-resolve.test.ts b/src/core/services/youtube/playback-resolve.test.ts
index 1eee56d4..708ea6d2 100644
--- a/src/core/services/youtube/playback-resolve.test.ts
+++ b/src/core/services/youtube/playback-resolve.test.ts
@@ -17,7 +17,7 @@ async function withTempDir<T>(fn: (dir: string) => Promise<T>): Promise<T> {
 function makeFakeYtDlpScript(dir: string, payload: string): void {
   const scriptPath = path.join(dir, 'yt-dlp');
   const script = process.platform === 'win32'
-    ? `#!/usr/bin/env node
+    ? `#!/usr/bin/env bun
 process.stdout.write(${JSON.stringify(payload)});
 `
     : `#!/usr/bin/env sh
diff --git a/src/core/services/youtube/track-download.test.ts b/src/core/services/youtube/track-download.test.ts
index f340f714..54a4a85c 100644
--- a/src/core/services/youtube/track-download.test.ts
+++ b/src/core/services/youtube/track-download.test.ts
@@ -16,7 +16,7 @@ async function withTempDir<T>(fn: (dir: string) => Promise<T>): Promise<T> {
 
 function makeFakeYtDlpScript(dir: string): string {
   const scriptPath = path.join(dir, 'yt-dlp');
-  const script = `#!/usr/bin/env node
+  const script = `#!/usr/bin/env bun
 const fs = require('node:fs');
 const path = require('node:path');
 
diff --git a/src/core/services/youtube/track-probe.test.ts b/src/core/services/youtube/track-probe.test.ts
index b5460105..00891851 100644
--- a/src/core/services/youtube/track-probe.test.ts
+++ b/src/core/services/youtube/track-probe.test.ts
@@ -21,7 +21,7 @@ function makeFakeYtDlpScript(dir: string, payload: unknown, rawScript = false):
     process.platform === 'win32'
       ? rawScript
         ? stdoutBody
-        : `#!/usr/bin/env node
+        : `#!/usr/bin/env bun
 process.stdout.write(${JSON.stringify(stdoutBody)});
 `
       : `#!/usr/bin/env sh
diff --git a/src/main/runtime/first-run-setup-window.ts b/src/main/runtime/first-run-setup-window.ts
index fe31d358..c52199cb 100644
--- a/src/main/runtime/first-run-setup-window.ts
+++ b/src/main/runtime/first-run-setup-window.ts
@@ -396,7 +396,8 @@ export function createHandleFirstRunSetupNavigationHandler(deps: {
 }) {
   return (params: { url: string; preventDefault: () => void }): boolean => {
     if (!params.url.startsWith('subminer://first-run-setup')) {
-      return false;
+      params.preventDefault();
+      return true;
     }
     params.preventDefault();
     let submission: FirstRunSetupSubmission | null;
diff --git a/src/main/runtime/windows-mpv-launch.ts b/src/main/runtime/windows-mpv-launch.ts
index 0d966e86..681edc4b 100644
--- a/src/main/runtime/windows-mpv-launch.ts
+++ b/src/main/runtime/windows-mpv-launch.ts
@@ -18,8 +18,11 @@ export function resolveWindowsMpvPath(
   configuredMpvPath = '',
 ): string {
   const configPath = normalizeCandidate(configuredMpvPath);
-  if (configPath && deps.fileExists(configPath)) {
-    return configPath;
+  if (configPath) {
+    if (deps.fileExists(configPath)) {
+      return configPath;
+    }
+    return '';
   }
 
   const envPath = normalizeCandidate(deps.getEnv('SUBMINER_MPV_PATH'));
@@ -107,11 +110,14 @@ export function launchWindowsMpv(
   pluginEntrypointPath?: string,
   configuredMpvPath?: string,
 ): { ok: boolean; mpvPath: string } {
-  const mpvPath = resolveWindowsMpvPath(deps, configuredMpvPath);
+  const normalizedConfiguredPath = normalizeCandidate(configuredMpvPath);
+  const mpvPath = resolveWindowsMpvPath(deps, normalizedConfiguredPath);
   if (!mpvPath) {
     deps.showError(
       'SubMiner mpv launcher',
-      'Could not find mpv.exe. Set mpv.executablePath, set SUBMINER_MPV_PATH, or add mpv.exe to PATH.',
+      normalizedConfiguredPath
+        ? `Configured mpv.executablePath was not found: ${normalizedConfiguredPath}`
+        : 'Could not find mpv.exe. Set mpv.executablePath, set SUBMINER_MPV_PATH, or add mpv.exe to PATH.',
     );
     return { ok: false, mpvPath: '' };
   }