diff --git a/src/app/(protected)/workorders/_components/media/media-uploader.tsx b/src/app/(protected)/workorders/_components/media/media-uploader.tsx
index c87f430e..5364bd7b 100644
--- a/src/app/(protected)/workorders/_components/media/media-uploader.tsx
+++ b/src/app/(protected)/workorders/_components/media/media-uploader.tsx
@@ -45,7 +45,7 @@ const VIDEO_DURATION_MESSAGE = `Videos must be ${MAX_VIDEO_DURATION_SECONDS} sec
 
 async function isWithinContract(file: File, kind: WorkOrderUploadKind): Promise<boolean> {
   if (kind === "video") {
-    // SH-116: duration is checked client-side only; unreadable metadata never blocks.
+    // SH-116: pre-check only; the server enforces it too. Unreadable metadata never blocks.
     const duration = await probeVideoDurationSeconds(file);
     if (duration != null && duration > MAX_VIDEO_DURATION_SECONDS) {
       toast.error(VIDEO_DURATION_MESSAGE);
diff --git a/src/domain/vendor-portal/lib/document-validation.ts b/src/domain/vendor-portal/lib/document-validation.ts
index 81444abc..bf059bca 100644
--- a/src/domain/vendor-portal/lib/document-validation.ts
+++ b/src/domain/vendor-portal/lib/document-validation.ts
@@ -56,7 +56,7 @@ export async function validateVendorDocument(file: File): Promise<string | undef
     if (file.size > MAX_VIDEO_BYTES) {
       return "Videos must be 100 MB or smaller.";
     }
-    // Duration is checked client-side only; unreadable metadata never blocks.
+    // Pre-check; the server enforces it too. Unreadable metadata never blocks.
     const duration = await probeVideoDurationSeconds(file);
     if (duration != null && duration > MAX_VIDEO_DURATION_SECONDS) {
       return `Videos must be ${MAX_VIDEO_DURATION_SECONDS} seconds or shorter.`;
diff --git a/src/domain/work-orders/utils/work-order-media-limits.ts b/src/domain/work-orders/utils/work-order-media-limits.ts
index 77429d75..e19640d5 100644
--- a/src/domain/work-orders/utils/work-order-media-limits.ts
+++ b/src/domain/work-orders/utils/work-order-media-limits.ts
@@ -5,7 +5,8 @@ import { isWorkOrderCompletionSurfaceReadOnly } from "@/domain/work-orders/utils
  * (JPEG/PNG/HEIC), videos up to 100 MB and 90 seconds (MP4/MOV), at most
  * 10 photos and 3 videos per work order. Applies to the Photos & Videos modal,
  * the Completion Doc → Media tab and the vendor portal upload. Duration is
- * checked client-side only (the server cannot probe it cheaply). Documents
+ * pre-checked here and enforced by the server from the MP4/MOV header;
+ * unreadable metadata never blocks. Documents
  * keep the 50 MB document cap; the signed completion PDF keeps its own cap.
  */
 export const MAX_WORK_ORDER_PHOTO_BYTES = 10_000_000;
diff --git a/src/lib/probe-video-duration.ts b/src/lib/probe-video-duration.ts
index 61f047f6..d09bec1c 100644
--- a/src/lib/probe-video-duration.ts
+++ b/src/lib/probe-video-duration.ts
@@ -1,7 +1,8 @@
 /**
  * Best-effort client-side video duration probe. Resolves null when the browser
  * cannot decode the container's metadata — callers must not block the upload in
- * that case (SH-116: duration is a client-side check only).
+ * that case (SH-116: the server enforces the limit from the MP4/MOV header and
+ * also lets unreadable metadata through).
  */
 export const VIDEO_DURATION_PROBE_TIMEOUT_MS = 10_000;