diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e938441..a6cbfb66 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Show an elapsed timer on the running automatic-compression card so long WebUI context-compression pauses no longer look frozen while the browser waits for the `compressed` event.
+
 ## [v0.51.89] — 2026-05-18 — Release BM (stage-382 — 6-PR full sweep batch — runtime adapter approval/clarify seam + SOUL.md memory panel + #1855 resolve_model_provider fast-path + PWA sidebar spinner fix + /model active-provider preference + contributor contract docs index)
 
 ### Changed
diff --git a/static/messages.js b/static/messages.js
index ae7c6113..98c63daf 100644
--- a/static/messages.js
+++ b/static/messages.js
@@ -1785,6 +1785,7 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
           phase:'running',
           automatic:true,
           message:d.message||'Auto-compressing context...',
+          startedAt:Date.now()/1000,
         };
         setCompressionUi(state);
         const liveAnswerStarted=!!(assistantRow||String(((_parseStreamState&&_parseStreamState())||{}).displayText||'').trim());
diff --git a/static/ui.js b/static/ui.js
index 4fedd18e..b9bbe0a1 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -1970,6 +1970,45 @@ function _formatActiveElapsedTimer(seconds){
   const s=total%60;
   return`${String(m).padStart(2,'0')}:${String(s).padStart(2,'0')}`;
 }
+const _COMPRESSION_ELAPSED_MAX_SECONDS=5*60;
+let _compressionElapsedTimer=null;
+function _compressionElapsedStartedAt(state){const n=Number(state&&state.startedAt);return Number.isFinite(n)&&n>0?n:null;}
+function _compressionElapsedLabel(state){
+  const started=_compressionElapsedStartedAt(state);
+  if(!started)return'';
+  const elapsed=Math.min(Math.max(0,(Date.now()/1000)-started),_COMPRESSION_ELAPSED_MAX_SECONDS);
+  return _formatActiveElapsedTimer(elapsed);
+}
+function _compressionElapsedExpired(state){const started=_compressionElapsedStartedAt(state);return !!(started&&((Date.now()/1000)-started)>=_COMPRESSION_ELAPSED_MAX_SECONDS);}
+function _compressionLiveCardNode(){return document.querySelector('[data-live-compression-card="1"][data-compression-started-at]');}
+function _compressionLiveCardState(){
+  const node=_compressionLiveCardNode();
+  const started=Number(node&&node.getAttribute('data-compression-started-at'));
+  if(!node||!S.session||!Number.isFinite(started)||started<=0)return null;
+  return {sessionId:S.session.session_id,phase:'running',automatic:true,message:node.getAttribute('data-compression-message')||'Auto-compressing context...',startedAt:started};
+}
+function _updateCompressionElapsedCards(state){
+  if(!state)return false;
+  const preview=_autoCompressionPreviewText(state), detail=_autoCompressionDetailText(state);
+  let updated=false;
+  document.querySelectorAll('.tool-card-compress-auto.tool-card-compress-running').forEach(card=>{
+    const previewEl=card.querySelector('.tool-card-preview');
+    const detailEl=card.querySelector('.tool-card-result pre');
+    if(previewEl) previewEl.textContent=preview;
+    if(detailEl) detailEl.textContent=detail;
+    updated=true;
+  });
+  return updated;
+}
+function _updateCompressionElapsedTimer(){
+  const state=_compressionStateForCurrentSession()||_compressionLiveCardState();
+  if(state&&state.automatic&&state.phase==='running'){
+    _updateCompressionElapsedCards(state);
+    if(_compressionElapsedExpired(state)) _clearCompressionElapsedTimer();
+  }else _clearCompressionElapsedTimer();
+}
+function _startCompressionElapsedTimer(){if(!_compressionElapsedTimer)_compressionElapsedTimer=setInterval(_updateCompressionElapsedTimer,1000);}
+function _clearCompressionElapsedTimer(){if(_compressionElapsedTimer){clearInterval(_compressionElapsedTimer);_compressionElapsedTimer=null;}}
 let _activityElapsedTimer=null;
 let _activityElapsedTimerGroup=null;
 function _activityElapsedStartedAt(group){
@@ -4875,6 +4914,7 @@ function isCompressionUiRunning(){
 }
 function clearCompressionUi(){
   window._compressionUi=null;
+  _clearCompressionElapsedTimer();
   _setCompressionSessionLock(null);
   renderCompressionUi();
 }
@@ -4883,8 +4923,14 @@ function setCompressionUi(state){
     clearCompressionUi();
     return;
   }
-  window._compressionUi={...state};
-  if(state.sessionId) _setCompressionSessionLock(state.sessionId);
+  const nextState={...state};
+  if(nextState.automatic&&nextState.phase==='running'&&!_compressionElapsedStartedAt(nextState)){
+    nextState.startedAt=Date.now()/1000;
+  }
+  window._compressionUi=nextState;
+  if(nextState.sessionId) _setCompressionSessionLock(nextState.sessionId);
+  if(nextState.automatic&&nextState.phase==='running') _startCompressionElapsedTimer();
+  else _clearCompressionElapsedTimer();
   renderCompressionUi();
 }
 function _compressionCardsHtml(state){
@@ -4950,21 +4996,38 @@ function _compressionCardsHtml(state){
     </div>
     ${referenceHtml}`;
 }
-function _autoCompressionCardsHtml(state){
+function _autoCompressionBaseDetail(state){
   const fallback='Context auto-compressed to continue the conversation';
   const running=state&&state.phase==='running';
-  const detail=running
+  return running
     ? (String(state.message||'Auto-compressing context...').trim()||'Auto-compressing context...')
-    : (String(state.message||fallback).trim()||fallback);
-  const preview=running
-    ? detail
-    : (String(state.summary?.headline||detail).trim()||detail);
+    : (String(state&&state.message||fallback).trim()||fallback);
+}
+function _autoCompressionPreviewText(state){
+  const running=state&&state.phase==='running';
+  const detail=_autoCompressionBaseDetail(state);
+  if(!running) return (String(state&&state.summary?.headline||detail).trim()||detail);
+  const elapsedLabel=_compressionElapsedLabel(state);
+  return [detail, elapsedLabel].filter(Boolean).join(' · ');
+}
+function _autoCompressionDetailText(state){
+  const running=state&&state.phase==='running';
+  const detail=_autoCompressionBaseDetail(state);
+  const elapsedLabel=running?_compressionElapsedLabel(state):'';
+  return running&&elapsedLabel
+    ? `${detail}\nElapsed: ${elapsedLabel}`
+    : detail;
+}
+function _autoCompressionCardsHtml(state){
+  const running=state&&state.phase==='running';
+  const preview=_autoCompressionPreviewText(state);
+  const cardDetail=_autoCompressionDetailText(state);
   return `
     <div class="tool-card-row compression-card-row" data-compression-card="1">
       ${_compressionStatusCardHtml({
         statusLabel: t('auto_compress_label'),
         previewText: preview,
-        detail,
+        detail: cardDetail,
         icon: running ? '<span class="tool-card-running-dot"></span>' : li('check',13),
         open: running,
         variantClass: running
@@ -4994,6 +5057,12 @@ function appendLiveCompressionCard(state){
   const node=_compressionCardsNode(state);
   if(!node) return false;
   node.setAttribute('data-live-compression-card','1');
+  if(state.automatic&&state.phase==='running'){
+    const started=_compressionElapsedStartedAt(state)||Date.now()/1000;
+    node.setAttribute('data-compression-started-at',String(started));
+    node.setAttribute('data-compression-message',String(state.message||'Auto-compressing context...'));
+    _startCompressionElapsedTimer();
+  }
   const existing=inner.querySelector('[data-live-compression-card="1"]');
   if(existing) existing.replaceWith(node);
   else inner.appendChild(node);
diff --git a/tests/test_auto_compression_card.py b/tests/test_auto_compression_card.py
index d092f615..a94b318a 100644
--- a/tests/test_auto_compression_card.py
+++ b/tests/test_auto_compression_card.py
@@ -67,6 +67,48 @@ def test_auto_compression_completion_transition_is_preserved_after_running_liste
     assert "phase:'done'" in _compressed_listener_block()
 
 
+def test_auto_compression_running_sse_stamps_elapsed_timer_start():
+    block = _compressing_listener_block()
+
+    assert "startedAt:Date.now()/1000" in block
+    assert block.index("startedAt:Date.now()/1000") < block.index("setCompressionUi(state)")
+
+
+def test_auto_compression_running_card_renders_elapsed_timer_and_caps_updates():
+    src = _read("static/ui.js")
+    start = src.find("function _autoCompressionPreviewText")
+    assert start != -1, "auto compression preview helper not found"
+    end = src.find("function _compressionCardsNode", start)
+    assert end != -1, "compression cards node helper not found after auto helper"
+    helper = src[start:end]
+
+    assert "const _COMPRESSION_ELAPSED_MAX_SECONDS=5*60;" in src
+    assert "function _compressionElapsedLabel(state)" in src
+    assert "_formatActiveElapsedTimer" in src
+    assert "_compressionElapsedLabel(state)" in helper
+    assert "elapsedLabel" in helper
+    assert "_autoCompressionPreviewText(state)" in helper
+    assert "_autoCompressionDetailText(state)" in helper
+    assert "function _startCompressionElapsedTimer()" in src
+    assert "function _clearCompressionElapsedTimer()" in src
+    assert "function _updateCompressionElapsedCards(state)" in src
+    assert "_startCompressionElapsedTimer();" in src
+    assert "_clearCompressionElapsedTimer();" in src
+
+
+def test_auto_compression_live_card_keeps_elapsed_state_for_timer_refresh():
+    src = _read("static/ui.js")
+    start = src.find("function appendLiveCompressionCard")
+    assert start != -1, "live compression card append helper not found"
+    end = src.find("function _isHandoffSummaryToolPayload", start)
+    assert end != -1, "handoff helper not found after live compression helper"
+    helper = src[start:end]
+
+    assert "data-compression-started-at" in helper
+    assert "data-compression-message" in helper
+    assert "_compressionLiveCardState" in src
+
+
 def test_auto_compression_does_not_rerender_over_live_answer_text():
     block = _compressing_listener_block()
     src = _read("static/ui.js")