diff --git a/core/archipelago/src/api/handler/mod.rs b/core/archipelago/src/api/handler/mod.rs
index 4c85d3c4..89977115 100644
--- a/core/archipelago/src/api/handler/mod.rs
+++ b/core/archipelago/src/api/handler/mod.rs
@@ -522,6 +522,15 @@ impl ApiHandler {
                 Self::handle_container_logs_http(self.rpc_handler.clone(), path, &origin).await
             }
 
+            // Peer content streaming proxy — Range-streams a peer's media file
+            // so <video>/<audio> can seek/play (B3). Same-origin, session-gated.
+            (Method::GET, p) if p.starts_with("/api/peer-content/") => {
+                if !self.is_authenticated(&headers).await {
+                    return Ok(Self::unauthorized());
+                }
+                self.handle_peer_content_stream(p, &headers).await
+            }
+
             // LND proxy — requires session. The LND wallet UI calls this
             // cross-origin from its own app port, so even the 401 must carry
             // CORS headers; otherwise the browser reports a bare CORS failure
diff --git a/core/archipelago/src/api/handler/proxy.rs b/core/archipelago/src/api/handler/proxy.rs
index 598605aa..1df9427c 100644
--- a/core/archipelago/src/api/handler/proxy.rs
+++ b/core/archipelago/src/api/handler/proxy.rs
@@ -185,4 +185,77 @@ impl ApiHandler {
             }
         }
     }
+
+    /// Range-streaming proxy for a peer's content file (B3). The browser's
+    /// `<video>`/`<audio>` element makes Range requests; we forward the Range
+    /// header to the peer's `/content/<id>` (which already returns 206 Partial
+    /// Content) and pass the bytes + Content-Range/Content-Type straight back.
+    /// This replaces the old path of downloading the whole file as base64 into
+    /// a non-seekable Blob URL, which broke playback/seeking for video and
+    /// large audio. Same-origin + session-authenticated (checked by caller).
+    /// Path: `/api/peer-content/<onion>/<content_id>`.
+    pub(super) async fn handle_peer_content_stream(
+        &self,
+        path: &str,
+        headers: &hyper::HeaderMap,
+    ) -> Result<Response<hyper::Body>> {
+        let bad = |msg: &str| {
+            Ok(build_response(
+                StatusCode::BAD_REQUEST,
+                "application/json",
+                hyper::Body::from(serde_json::json!({ "error": msg }).to_string()),
+            ))
+        };
+        let rest = path.strip_prefix("/api/peer-content/").unwrap_or("");
+        let (onion, content_id) = match rest.split_once('/') {
+            Some((o, c)) if !o.is_empty() && !c.is_empty() => (o, c),
+            _ => return bad("expected /api/peer-content/<onion>/<content_id>"),
+        };
+        // Validate to prevent SSRF / path traversal.
+        let onion_norm = onion.trim_end_matches(".onion");
+        let onion_ok = onion_norm.len() == 56
+            && onion_norm
+                .bytes()
+                .all(|b| b.is_ascii_lowercase() || b.is_ascii_digit());
+        let id_ok = !content_id.contains("..")
+            && content_id
+                .bytes()
+                .all(|b| b.is_ascii_alphanumeric() || matches!(b, b'-' | b'_' | b'.'));
+        if !onion_ok || !id_ok {
+            return bad("invalid onion or content id");
+        }
+
+        let fips_npub =
+            crate::federation::fips_npub_for_onion(&self.config.data_dir, onion).await;
+        let peer_path = format!("/content/{}", content_id);
+        let mut req = crate::fips::dial::PeerRequest::new(fips_npub.as_deref(), onion, &peer_path)
+            .service(crate::settings::transport::PeerService::PeerFiles)
+            .timeout(std::time::Duration::from_secs(60));
+        if let Some(r) = headers.get("range").and_then(|v| v.to_str().ok()) {
+            req = req.header("Range", r.to_string());
+        }
+        match req.send_get().await {
+            Ok((resp, _transport)) => {
+                let status = resp.status().as_u16();
+                let rh = resp.headers().clone();
+                let bytes = resp.bytes().await.unwrap_or_default();
+                let mut builder = Response::builder()
+                    .status(status)
+                    .header("Accept-Ranges", "bytes");
+                for h in ["content-type", "content-range", "content-length"] {
+                    if let Some(v) = rh.get(h).and_then(|v| v.to_str().ok()) {
+                        builder = builder.header(h, v);
+                    }
+                }
+                Ok(builder
+                    .body(hyper::Body::from(bytes))
+                    .unwrap_or_else(|_| Response::new(hyper::Body::empty())))
+            }
+            Err(e) => Ok(build_response(
+                StatusCode::BAD_GATEWAY,
+                "application/json",
+                hyper::Body::from(serde_json::json!({ "error": e.to_string() }).to_string()),
+            )),
+        }
+    }
 }
diff --git a/neode-ui/src/views/PeerFiles.vue b/neode-ui/src/views/PeerFiles.vue
index 3dfdcb4a..8af3c972 100644
--- a/neode-ui/src/views/PeerFiles.vue
+++ b/neode-ui/src/views/PeerFiles.vue
@@ -537,6 +537,22 @@ async function playMedia(item: CatalogItem) {
 
   const paid = isPaidItem(item.access)
 
+  // Free content: stream via the Range-capable proxy (B3) so the player can
+  // seek and start instantly, instead of downloading the whole file as a
+  // base64 blob into a non-seekable Blob URL (which broke video/large audio).
+  if (!paid) {
+    const streamUrl = `/api/peer-content/${encodeURIComponent(onion)}/${encodeURIComponent(item.id)}`
+    if (item.mime_type.startsWith('audio/')) {
+      audioPlayer.play(streamUrl, item.filename.split('/').pop() || item.filename)
+    } else if (item.mime_type.startsWith('video/')) {
+      videoPlayerItem.value = item
+      videoPlayerUrl.value = streamUrl
+      videoPlayerPaid.value = false
+    }
+    return
+  }
+
+  // Paid content: use the preview/download flow below.
   // If we already have a preview blob URL, use it
   const existingUrl = previewUrls[item.id]
   if (existingUrl) {
diff --git a/tests/production-quality/TRACKER.md b/tests/production-quality/TRACKER.md
index 1f202294..23408cb3 100644
--- a/tests/production-quality/TRACKER.md
+++ b/tests/production-quality/TRACKER.md
@@ -53,7 +53,7 @@ Dupes, erroneous names, and non-convergent group membership across nodes. Expect
 ### B2 — Duplicate chat contact for one node — PASSED (resolved by load-dedup feeding mesh seed; unit-tested). UI visual-confirm recommended.
 Federated peer "sapien" shows TWO chats: one "sapien" WITHOUT archy logo (looks non-federated) + one named by raw DID `did:key:z6MkoSbN5CM7fBaQg2nWbCymEkFXsHnuXvec9Mjo5RtJf9dQ`. Same node keyed by both federated identity and raw DID → merge to one. Code: core/archipelago/src/mesh + mesh/typed_messages.rs (note :233 — meshcore adverts don't carry archy pubkey).
 
-### B3 — Cloud peer media won't preview/play — ROOT-CAUSED (plan ready: streaming proxy endpoint)
+### B3 — Cloud peer media won't preview/play — FIXING (code done: /api/peer-content streaming proxy + playMedia streams free content)
 Music/video preview files on peer nodes' cloud don't play (streaming/range/content-type over mesh+Tor peer fetch).
 
 ### B4 — Cloud "my folders" fails (JSON parse / 502) — PASSED (content-type guard; built, guard in bundle, deployed .198). UI visual-confirm recommended.