diff --git a/src/server/websocket.ts b/src/server/websocket.ts
index 17ffdae..503a0e8 100644
--- a/src/server/websocket.ts
+++ b/src/server/websocket.ts
@@ -181,6 +181,35 @@ function sendPtyReady(entry: { viewer: WebSocket | null; alive: boolean }): bool
   return true;
 }
 
+/** True when `entry` is still the live, current owner of `session` and `ws`
+ *  is still its active viewer. After every `await`, the entry may have been
+ *  torn down, replaced by a takeover, or had its viewer displaced — bail
+ *  if any of that happened. */
+function entryStillCurrent(
+  entry: { alive: boolean; viewer: WebSocket | null },
+  session: string,
+  ws: WebSocket,
+): boolean {
+  return entry.alive
+    && (activePtySessions.get(session) as unknown) === entry
+    && entry.viewer === ws;
+}
+
+/** Try-close a WebSocket and log failures at debug. The close codes used
+ *  here (DISPLACED/SESSION_UNAVAILABLE/PTY_TEARDOWN/SERVER_ERROR/NORMAL)
+ *  always succeed in practice; the try/catch exists to guard against the
+ *  socket already being in a non-OPEN state. */
+function tryWsClose(
+  target: WebSocket,
+  code: number,
+  reason: string,
+  logMsg: string,
+  session: string,
+): void {
+  try { target.close(code, reason); }
+  catch (e: unknown) { log.debug(logMsg, { session, error: errMsg(e) }); }
+}
+
 /** Send prefill buffer in 32KB chunks with short delays to avoid stalling mobile connections.
  *  Sends `prefill_done` message at the end so the client exits buffering state. */
 async function sendPrefillChunked(
@@ -231,11 +260,11 @@ export function teardownPty(session: string): void {
       entry.unsubscribeLifecycle = null;
     }
     if (entry.viewer) {
-      try { entry.viewer.close(CLOSE_CODE_NORMAL, WS_CLOSE_REASONS.PTY_TEARDOWN); } catch (e: unknown) { log.debug(`teardownPty: viewer close failed`, { session, error: errMsg(e) }); }
+      tryWsClose(entry.viewer, CLOSE_CODE_NORMAL, WS_CLOSE_REASONS.PTY_TEARDOWN, "teardownPty: viewer close failed", session);
       entry.viewer = null;
     }
     if (entry.pendingViewer) {
-      try { entry.pendingViewer.close(CLOSE_CODE_NORMAL, WS_CLOSE_REASONS.PTY_TEARDOWN); } catch (e: unknown) { log.debug(`teardownPty: pendingViewer close failed`, { session, error: errMsg(e) }); }
+      tryWsClose(entry.pendingViewer, CLOSE_CODE_NORMAL, WS_CLOSE_REASONS.PTY_TEARDOWN, "teardownPty: pendingViewer close failed", session);
       entry.pendingViewer = null;
     }
     if (entry.proc) {
@@ -271,7 +300,7 @@ export function handlePtyWs(ws: WebSocket, session: string, reset = false): void
       const oldViewer = existing.viewer;
       existing.viewer = null;
       if (oldViewer) {
-        try { oldViewer.close(CLOSE_CODE_DISPLACED, WS_CLOSE_REASONS.DISPLACED); } catch (e: unknown) { log.debug(`takeover: oldViewer close failed`, { session, error: errMsg(e) }); }
+        tryWsClose(oldViewer, CLOSE_CODE_DISPLACED, WS_CLOSE_REASONS.DISPLACED, "takeover: oldViewer close failed", session);
       }
       if (existing.unsubscribe) {
         existing.unsubscribe();
@@ -289,7 +318,7 @@ export function handlePtyWs(ws: WebSocket, session: string, reset = false): void
         try { oldProc.kill(); } catch (e: unknown) { log.debug(`takeover: proc kill failed`, { session, error: errMsg(e) }); }
       }
       if (existing.pendingViewer) {
-        try { existing.pendingViewer.close(CLOSE_CODE_DISPLACED, WS_CLOSE_REASONS.DISPLACED); } catch (e: unknown) { log.debug(`displaced pendingViewer close failed`, { session, error: errMsg(e) }); }
+        tryWsClose(existing.pendingViewer, CLOSE_CODE_DISPLACED, WS_CLOSE_REASONS.DISPLACED, "displaced pendingViewer close failed", session);
         existing.pendingViewer = null;
       }
       setupNewPtyEntry(ws, session, dims);
@@ -301,7 +330,7 @@ export function handlePtyWs(ws: WebSocket, session: string, reset = false): void
 
     // If there's already a pending viewer, close it
     if (existing.pendingViewer) {
-      try { existing.pendingViewer.close(CLOSE_CODE_DISPLACED, WS_CLOSE_REASONS.DISPLACED); } catch (e: unknown) { log.debug(`displaced pendingViewer close failed`, { session, error: errMsg(e) }); }
+      tryWsClose(existing.pendingViewer, CLOSE_CODE_DISPLACED, WS_CLOSE_REASONS.DISPLACED, "displaced pendingViewer close failed", session);
     }
     existing.pendingViewer = ws;
 
@@ -315,7 +344,7 @@ export function handlePtyWs(ws: WebSocket, session: string, reset = false): void
     function cleanupPending() {
       clearInterval(pingTimer);
       if (existing.pendingViewer && existing.pendingViewer !== ws) {
-        try { existing.pendingViewer.close(CLOSE_CODE_DISPLACED, WS_CLOSE_REASONS.DISPLACED); } catch (e: unknown) { log.debug(`cleanupPending: displaced other pending`, { session, error: errMsg(e) }); }
+        tryWsClose(existing.pendingViewer, CLOSE_CODE_DISPLACED, WS_CLOSE_REASONS.DISPLACED, "cleanupPending: displaced other pending", session);
       }
       ws.removeListener("message", pendingMessage);
       ws.removeListener("close", cleanup);
@@ -396,9 +425,7 @@ function setupNewPtyEntry(
 
   if (!streamingBackend) {
     log.warn("ws attach: streaming backend unavailable", { session });
-    try { ws.close(CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE); } catch (e: unknown) {
-      log.debug("streaming backend missing close failed", { session, error: errMsg(e) });
-    }
+    tryWsClose(ws, CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE, "streaming backend missing close failed", session);
     activePtySessions.delete(session);
     return;
   }
@@ -433,14 +460,14 @@ function setupNewPtyEntry(
           entry.alive = false;
           activePtySessions.delete(session);
           if (entry.viewer) {
-            try { entry.viewer.close(CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE); } catch (e: unknown) { log.debug(`session unavailable: viewer close failed`, { session, error: errMsg(e) }); }
+            tryWsClose(entry.viewer, CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE, "session unavailable: viewer close failed", session);
             entry.viewer = null;
           }
           return;
         }
       }
 
-      if (!entry.alive || activePtySessions.get(session) !== entry || entry.viewer !== ws) return;
+      if (!entryStillCurrent(entry, session, ws)) return;
 
       // Skip settle wait when there's no snapshot to take — the only purpose
       // of waiting is to capture the SIGWINCH redraw in the snapshot, but
@@ -478,7 +505,7 @@ function setupNewPtyEntry(
         const settleStart = Date.now();
         let lastChangeAt = -1;
         while (true) {
-          if (!entry.alive || activePtySessions.get(session) !== entry || entry.viewer !== ws) return;
+          if (!entryStillCurrent(entry, session, ws)) return;
           const elapsedTotal = Date.now() - settleStart;
           if (elapsedTotal >= PRE_SNAPSHOT_RESIZE_TIMEOUT_MS) break;
           if (lastChangeAt < 0) {
@@ -498,7 +525,7 @@ function setupNewPtyEntry(
         }
       }
 
-      if (!entry.alive || activePtySessions.get(session) !== entry || entry.viewer !== ws) return;
+      if (!entryStillCurrent(entry, session, ws)) return;
 
       // Apply settled dims and wait for the SIGWINCH-triggered redraw to
       // fully land in the broker output stream BEFORE snapshotting.
@@ -539,7 +566,7 @@ function setupNewPtyEntry(
           let lastResizeAt = Date.now();
           const settleStart = lastResizeAt;
           while (true) {
-            if (!entry.alive || activePtySessions.get(session) !== entry || entry.viewer !== ws) break;
+            if (!entryStillCurrent(entry, session, ws)) break;
             // Dim changed since we last applied? Re-resize and restart the
             // quiescence clock so we capture this redraw too.
             if (
@@ -600,7 +627,7 @@ function setupNewPtyEntry(
         }
       }
 
-      if (!entry.alive || activePtySessions.get(session) !== entry || entry.viewer !== ws) return;
+      if (!entryStillCurrent(entry, session, ws)) return;
 
       // Final reconciliation catches resize frames that arrived while the
       // snapshot bytes were being fetched/sent. The resulting SIGWINCH
@@ -613,7 +640,7 @@ function setupNewPtyEntry(
       ) {
         appliedSize = latestRequestedSize;
         await backend.resize(session, appliedSize.cols, appliedSize.rows);
-        if (!entry.alive || activePtySessions.get(session) !== entry || entry.viewer !== ws) return;
+        if (!entryStillCurrent(entry, session, ws)) return;
       }
 
       // Subscribe after prefill. sinceSeq: prefillSeq replays any broker output
@@ -671,9 +698,7 @@ function setupNewPtyEntry(
           log.warn("subscribe rpc failed — tearing down viewer", { session, error: errMsg(err) });
           if (!entry.alive) return;
           if (entry.viewer && entry.viewer.readyState === 1) {
-            try { entry.viewer.close(CLOSE_CODE_SERVER_ERROR, WS_CLOSE_REASONS.SUBSCRIBE_FAILED); } catch (e: unknown) {
-              log.debug("subscribe-error: viewer close failed", { session, error: errMsg(e) });
-            }
+            tryWsClose(entry.viewer, CLOSE_CODE_SERVER_ERROR, WS_CLOSE_REASONS.SUBSCRIBE_FAILED, "subscribe-error: viewer close failed", session);
           }
           teardownPty(session);
         },
@@ -683,7 +708,7 @@ function setupNewPtyEntry(
         entry.alive = false;
         activePtySessions.delete(session);
         if (entry.viewer) {
-          try { entry.viewer.close(CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE); } catch (e: unknown) { log.debug(`onSessionData null: viewer close failed`, { session, error: errMsg(e) }); }
+          tryWsClose(entry.viewer, CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE, "onSessionData null: viewer close failed", session);
           entry.viewer = null;
         }
         return;
@@ -709,9 +734,7 @@ function setupNewPtyEntry(
           if (!entry.alive) return;
           log.warn("replay_truncated — forcing client reconnect for fresh snapshot", { session });
           if (entry.viewer && entry.viewer.readyState === 1) {
-            try { entry.viewer.close(CLOSE_CODE_SERVER_ERROR, WS_CLOSE_REASONS.SUBSCRIBE_FAILED); } catch (e: unknown) {
-              log.debug(`replay_truncated: viewer close failed`, { session, error: errMsg(e) });
-            }
+            tryWsClose(entry.viewer, CLOSE_CODE_SERVER_ERROR, WS_CLOSE_REASONS.SUBSCRIBE_FAILED, "replay_truncated: viewer close failed", session);
           }
           teardownPty(session);
           return;
@@ -730,11 +753,11 @@ function setupNewPtyEntry(
         // exit anyway, and we're inside the callback. Just null the ref.
         entry.unsubscribeLifecycle = null;
         if (entry.viewer) {
-          try { entry.viewer.close(CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE); } catch (e: unknown) { log.debug(`lifecycle exit: viewer close failed`, { session, error: errMsg(e) }); }
+          tryWsClose(entry.viewer, CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE, "lifecycle exit: viewer close failed", session);
           entry.viewer = null;
         }
         if (entry.pendingViewer) {
-          try { entry.pendingViewer.close(CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE); } catch (e: unknown) { log.debug(`lifecycle exit: pendingViewer close failed`, { session, error: errMsg(e) }); }
+          tryWsClose(entry.pendingViewer, CLOSE_CODE_SESSION_UNAVAILABLE, WS_CLOSE_REASONS.SESSION_UNAVAILABLE, "lifecycle exit: pendingViewer close failed", session);
           entry.pendingViewer = null;
         }
       });
@@ -825,7 +848,7 @@ function setupNewPtyEntry(
 
   function detach() {
     clearInterval(pingTimer);
-    if (entry.alive && entry.viewer === ws && activePtySessions.get(session) === entry) {
+    if (entryStillCurrent(entry, session, ws)) {
       entry.viewer = null;
       teardownPty(session);
     }