diff --git a/client/js/app.js b/client/js/app.js
index c9837a3..4723f71 100644
--- a/client/js/app.js
+++ b/client/js/app.js
@@ -334,7 +334,7 @@
       break;
 
     case 'context_compressed':
-      appendCompressionNotice(messagesEl);
+      appendCompressionNotice(messagesEl, event.messages_before, event.messages_after, event.summary);
       scrollToBottom(messagesEl);
       break;
 
diff --git a/client/js/chat.js b/client/js/chat.js
index 6a9a818..59baf41 100644
--- a/client/js/chat.js
+++ b/client/js/chat.js
@@ -404,11 +404,28 @@
 /**
  * Inline notice that compression ran — appended to the message list.
  */
-export function appendCompressionNotice(el) {
-  const div = document.createElement('div');
-  div.className = 'compression-notice';
-  div.textContent = '↑ Older messages summarized to free context space';
-  el.appendChild(div);
+export function appendCompressionNotice(el, before, after, summary) {
+  const label = (before != null && after != null)
+    ? `↑ Context compressed: ${before} → ${after} messages`
+    : '↑ Older messages summarized to free context space';
+
+  if (summary) {
+    const details = document.createElement('details');
+    details.className = 'compression-notice compression-notice--expandable';
+    const sumEl = document.createElement('summary');
+    sumEl.textContent = label;
+    details.appendChild(sumEl);
+    const body = document.createElement('div');
+    body.className = 'compression-summary-body';
+    body.innerHTML = marked.parse(summary);
+    details.appendChild(body);
+    el.appendChild(details);
+  } else {
+    const div = document.createElement('div');
+    div.className = 'compression-notice';
+    div.textContent = label;
+    el.appendChild(div);
+  }
 }
 
 /**
diff --git a/client/style.css b/client/style.css
index d99b020..28b3499 100644
--- a/client/style.css
+++ b/client/style.css
@@ -484,6 +484,39 @@
   opacity: 0.7;
 }
 
+.compression-notice--expandable {
+  border-radius: 8px;
+  padding: 6px 12px;
+  cursor: pointer;
+  opacity: 0.85;
+  max-width: 680px;
+}
+
+.compression-notice--expandable > summary {
+  cursor: pointer;
+  list-style: none;
+  user-select: none;
+}
+
+.compression-notice--expandable > summary::before {
+  content: '▶ ';
+  font-size: 9px;
+}
+
+.compression-notice--expandable[open] > summary::before {
+  content: '▼ ';
+}
+
+.compression-summary-body {
+  margin-top: 8px;
+  padding-top: 8px;
+  border-top: 1px solid #30363d;
+  font-size: 12px;
+  line-height: 1.5;
+  color: var(--text-secondary);
+  white-space: normal;
+}
+
 /* ── Agent note — model text between tool calls ──────── */
 
 .agent-note {
diff --git a/navi/api/websocket.py b/navi/api/websocket.py
index 4a2c103..67a666a 100644
--- a/navi/api/websocket.py
+++ b/navi/api/websocket.py
@@ -98,6 +98,7 @@
             "type": "context_compressed",
             "messages_before": event.messages_before,
             "messages_after": event.messages_after,
+            "summary": event.summary,
         }
     if isinstance(event, TurnThinking):
         return {"type": "turn_thinking", "thinking": event.thinking, "is_subagent": event.is_subagent}
diff --git a/navi/core/compressor.py b/navi/core/compressor.py
index 0276dff..9560003 100644
--- a/navi/core/compressor.py
+++ b/navi/core/compressor.py
@@ -128,7 +128,7 @@
     model: str,
     temperature: float,
     keep_recent: int,
-) -> list[Message] | None:
+) -> tuple[list[Message], str] | None:
     """
     Summarize old messages in the LLM context and return a shorter context list.
     Only operates on `context` — the full display history (session.messages) is never touched.
@@ -171,4 +171,4 @@
         created_at=datetime.now(timezone.utc),
     )
 
-    return system_msgs + [summary_msg] + to_keep
+    return system_msgs + [summary_msg] + to_keep, summary_text
diff --git a/navi/core/events.py b/navi/core/events.py
index 4f994a1..358c688 100644
--- a/navi/core/events.py
+++ b/navi/core/events.py
@@ -62,6 +62,7 @@
 
     messages_before: int
     messages_after: int
+    summary: str = ""  # the actual summary text produced by the LLM
 
 
 @dataclass
diff --git a/navi/workers/compressor.py b/navi/workers/compressor.py
index bb23249..2eb2845 100644
--- a/navi/workers/compressor.py
+++ b/navi/workers/compressor.py
@@ -28,7 +28,7 @@
 
         count_before = len(session.context)
         try:
-            new_context = await compress_context(
+            result = await compress_context(
                 context=session.context,
                 llm=ctx.llm,
                 model=ctx.model,
@@ -39,9 +39,10 @@
             log.warning("compression_worker.llm_failed", session_id=ctx.session_id, exc_info=True)
             return WorkerResult()
 
-        if new_context is None:
+        if result is None:
             return WorkerResult()
 
+        new_context, summary_text = result
         session.context = new_context
         session.context_token_count = 0  # reset so next turn doesn't re-compress pre-call
         await ctx.session_store.save(session)
@@ -56,4 +57,5 @@
         return WorkerResult(events=[ContextCompressed(
             messages_before=count_before,
             messages_after=len(session.context),
+            summary=summary_text,
         )])