--- a/crates/adom-aiflow/src/main.rs
+++ b/crates/adom-aiflow/src/main.rs
@@ -1720,8 +1720,19 @@
     if let Some(sheet) = contact_sheet(file) {
         r.log("artifact", json!({"step": step, "kind": "contact-sheet", "file": sheet}));
         eprintln!("contact sheet (look at it before you go on): {sheet}");
     }
+    // A clip rejected as blank or truncated is NOT suitable for video evidence.
+    // Keep its original recording, immutable fault ledger and contact sheet,
+    // but never spend engineer time compressing known-invalid footage.
+    // This guard applies to every shared clip-processing call site.
+    if let Some(why) = verdict.as_deref() {
+        r.log("clip-encode-skipped", json!({
+            "step": step, "file": file, "reason": why,
+            "policy": "invalid-video-no-encode", "originalPreserved": true
+        }));
+        return;
+    }
     let out = format!("{}-{speed}x.mp4", file.trim_end_matches(".mp4"));
     // the recorder's first frames are black before the window paints: they are cut off the head
     // of both cuts (never more than five seconds; longer black is a real clip problem, kept)
     let lead = leading_black(file);
@@ -7002,8 +7013,92 @@
         let e = clip_verdict("/nonexistent/clip.mp4", &["aiflow-no-such-ffprobe", "ffmpeg"]).unwrap_err();
         assert!(e.contains("aiflow-no-such-ffprobe") && !e.contains("no frames"), "{e}");
     }
 
+    /// Regression: a long flat recorder must never trigger
+    /// costly 10x/action FFmpeg conversion on ANY workflow step.
+    #[test]
+    fn invalid_blank_video_is_preserved_and_never_encoded() {
+        if std::process::Command::new("ffmpeg").arg("-version").output().is_err() { return; }
+        if std::process::Command::new("ffprobe").arg("-version").output().is_err() { return; }
+        let dir=std::env::temp_dir().join(format!("aiflow-blank-noencode-{}",std::process::id()));
+        let _=std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        let f=dir.join("routing-blank.mp4");
+        let status=std::process::Command::new("ffmpeg").args([
+          "-v","error","-y","-f","lavfi",
+          "-i","color=c=black:s=96x96:r=2",
+          "-t","4","-pix_fmt","yuv420p",
+          f.to_str().unwrap()
+        ]).status().unwrap();
+        assert!(status.success(),"test fixture video failed");
+        let source=f.display().to_string();
+        let mut r=Run{dir:dir.clone(),data:json!({
+          "captures":[{"file":source,"step":"routing","visit":1}],
+        })};
+        clip_artifacts_with(&mut r,&json!("routing-1"), &source,10, MEDIA_TOOLS);
+        assert!(f.is_file(),"raw evidence destroyed");
+        assert!(r.data["captures"][0]["suspect"].as_str().unwrap_or("").contains("flat colour"));
+        assert!(!dir.join("routing-blank-10x.mp4").exists(),"invalid clip was encoded");
+        assert!(!dir.join("routing-blank-action.mp4").exists(),"invalid clip produced an action derivative");
+        let ledger=r.ledger();
+        assert!(ledger.iter().any(|e| e["event"]=="clip-encode-skipped"));
+        assert!(ledger.iter().any(|e| e["event"]=="clip-suspect"));
+        assert!(ledger.iter().any(|e| e["event"]=="artifact" && e["kind"]=="clip"));
+        assert!(!ledger.iter().any(|e| e["event"]=="artifact" && e["kind"]=="clip10x"));
+        let _=std::fs::remove_dir_all(dir);
+    }
+
+    #[test]
+    fn invalid_truncated_video_has_no_encoded_derivatives() {
+        if std::process::Command::new("ffmpeg").arg("-version").output().is_err() { return; }
+        if std::process::Command::new("ffprobe").arg("-version").output().is_err() { return; }
+        let dir=std::env::temp_dir().join(format!("aiflow-truncated-noencode-{}",std::process::id()));
+        let _=std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        let f=dir.join("routing-truncated.mp4");
+        std::fs::write(&f,b"not a valid MP4").unwrap();
+        let source=f.display().to_string();
+        let mut r=Run{dir:dir.clone(),data:json!({
+           "captures":[{"file":source,"step":"routing","visit":1}],
+        })};
+        clip_artifacts_with(&mut r,&json!("routing-1"), &source,10,MEDIA_TOOLS);
+        let ledger=r.ledger();
+        assert!(f.is_file());
+        assert!(!dir.join("routing-truncated-10x.mp4").exists());
+        assert!(ledger.iter().any(|e| e["event"]=="clip-encode-skipped"));
+        let _=std::fs::remove_dir_all(dir);
+    }
+
+    /// Normal changing footage must still generate the same evidence derivatives.
+    #[test]
+    fn healthy_motion_clip_still_generates_video_derivatives() {
+        if std::process::Command::new("ffmpeg").arg("-version").output().is_err() { return; }
+        if std::process::Command::new("ffprobe").arg("-version").output().is_err() { return; }
+        let dir=std::env::temp_dir().join(format!("aiflow-motion-kept-{}",std::process::id()));
+        let _=std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        let f=dir.join("routing-motion.mp4");
+        let status=std::process::Command::new("ffmpeg").args([
+          "-v","error","-y","-f","lavfi",
+          "-i","testsrc2=size=128x128:rate=10",
+          "-t","6","-pix_fmt","yuv420p",
+          f.to_str().unwrap()
+        ]).status().unwrap();
+        assert!(status.success());
+        let source=f.display().to_string();
+        let mut r=Run{dir:dir.clone(),data:json!({
+          "captures":[{"file":source,"step":"routing","visit":1}]
+        })};
+        clip_artifacts_with(&mut r,&json!("routing-1"), &source,10,MEDIA_TOOLS);
+        let ledger=r.ledger();
+        assert!(f.is_file());
+        assert!(!ledger.iter().any(|e|e["event"]=="clip-encode-skipped"));
+        assert!(dir.join("routing-motion-10x.mp4").is_file(),"healthy video derivative missing");
+        assert!(ledger.iter().any(|e|e["event"]=="artifact" && e["kind"]=="clip10x"));
+        let _=std::fs::remove_dir_all(dir);
+    }
+
     #[test]
     fn a_clip_is_left_unjudged_when_the_tools_are_missing() {
         let dir = std::env::temp_dir().join(format!("aiflow-media-tools-{}", std::process::id()));
         let _ = std::fs::remove_dir_all(&dir);