diff --git a/services/capture/src/capture-manager.js b/services/capture/src/capture-manager.js
index ffe40ba..89baa72 100644
--- a/services/capture/src/capture-manager.js
+++ b/services/capture/src/capture-manager.js
@@ -39,10 +39,18 @@ function toUncShare(raw) {
   if (!s.startsWith('//')) s = '//' + s.replace(/^\/+/, '');  // host/share -> //host/share
   return s;
 }
-const GROWING_SMB_MOUNT    = toUncShare(process.env.GROWING_SMB_MOUNT || '');
-const GROWING_SMB_USERNAME = process.env.GROWING_SMB_USERNAME || '';
-const GROWING_SMB_PASSWORD = process.env.GROWING_SMB_PASSWORD || '';
-const GROWING_SMB_VERS     = process.env.GROWING_SMB_VERS     || '3.0';
+// Growing SMB params are read FRESH from process.env at mount time, NOT cached
+// at module load. Standby capture containers boot with these unset and receive
+// them per-session over /capture/start (capture.js sets process.env before
+// captureManager.start()). Caching them in module-level consts at import time
+// captured the empty boot values, so the mount silently no-op'd and growing
+// fell back to S3 — producing .mov instead of the XDCAM HD422 .mxf.
+const growingSmbConfig = () => ({
+  mount:    toUncShare(process.env.GROWING_SMB_MOUNT || ''),
+  username: process.env.GROWING_SMB_USERNAME || '',
+  password: process.env.GROWING_SMB_PASSWORD || '',
+  vers:     process.env.GROWING_SMB_VERS     || '3.0',
+});
 const SMB_CREDS_FILE       = '/run/smb-creds';
 
 // True when GROWING_PATH is already a mountpoint (e.g. a prior session left it
@@ -57,7 +65,11 @@ function isMounted(path) {
 // Returns true on success (or if already mounted), false on failure — callers
 // fall back to S3 streaming so a recording is never lost.
 function mountGrowingShare() {
-  if (!GROWING_SMB_MOUNT) return false;
+  const cfg = growingSmbConfig();
+  if (!cfg.mount) {
+    console.warn('[capture] growing requested but GROWING_SMB_MOUNT is empty — falling back to S3');
+    return false;
+  }
   try {
     if (isMounted(GROWING_PATH)) {
       console.log('[capture] growing share already mounted at', GROWING_PATH);
@@ -70,14 +82,14 @@ function mountGrowingShare() {
     // username/password mount inline and smbclient lists the share fine. Inline
     // user=/password= is the reliable form here.
     const opts = [
-      `username=${GROWING_SMB_USERNAME}`,
-      `password=${GROWING_SMB_PASSWORD}`,
+      `username=${cfg.username}`,
+      `password=${cfg.password}`,
       'uid=0', 'gid=0', 'file_mode=0664', 'dir_mode=0775',
-      `vers=${GROWING_SMB_VERS}`,
+      `vers=${cfg.vers}`,
     ].join(',');
-    execFileSync('mount', ['-t', 'cifs', GROWING_SMB_MOUNT, GROWING_PATH, '-o', opts],
+    execFileSync('mount', ['-t', 'cifs', cfg.mount, GROWING_PATH, '-o', opts],
       { stdio: ['ignore', 'ignore', 'pipe'] });
-    console.log('[capture] mounted CIFS growing share', GROWING_SMB_MOUNT, '->', GROWING_PATH);
+    console.log('[capture] mounted CIFS growing share', cfg.mount, '->', GROWING_PATH);
     return true;
   } catch (err) {
     const stderr = err.stderr ? err.stderr.toString().trim() : err.message;
@@ -88,7 +100,6 @@ function mountGrowingShare() {
 
 // Best-effort unmount on session stop. Ignores "not mounted".
 function unmountGrowingShare() {
-  if (!GROWING_SMB_MOUNT) return;
   try {
     if (isMounted(GROWING_PATH)) {
       execFileSync('umount', [GROWING_PATH], { stdio: ['ignore', 'ignore', 'pipe'] });