diff --git a/lyra/chat.py b/lyra/chat.py
index 971bc7d..551d58f 100644
--- a/lyra/chat.py
+++ b/lyra/chat.py
@@ -30,6 +30,11 @@ def _detail_note(exchanges: list[memory.Exchange]) -> Message:
     return {"role": "system", "content": body}
 
 
+def _render(messages: list[Message]) -> str:
+    """Human-readable dump of the exact prompt, for the live-log inspector."""
+    return "\n\n".join(f"[{m['role']}]\n{m['content']}" for m in messages)
+
+
 def build_messages(session_id: str, user_msg: str) -> list[Message]:
     """Assemble the full, tiered message list for one turn."""
     messages: list[Message] = [{"role": "system", "content": persona.system_prompt()}]
@@ -51,16 +56,17 @@ def build_messages(session_id: str, user_msg: str) -> list[Message]:
     if recalled:
         messages.append(_detail_note(recalled))
 
-    logbus.log(
-        "debug", "context built",
-        recent=len(recent), summaries=len(summaries), details=len(recalled),
-    )
-
     # Tier 3: current session, full fidelity.
     for ex in recent:
         messages.append({"role": ex.role, "content": ex.content})
 
     messages.append({"role": "user", "content": user_msg})
+
+    logbus.log(
+        "debug", "context built",
+        recent=len(recent), summaries=len(summaries), details=len(recalled),
+        chars=sum(len(m["content"]) for m in messages), detail=_render(messages),
+    )
     return messages
 
 
diff --git a/lyra/web/static/index.html b/lyra/web/static/index.html
index 3cbb822..adb30a6 100644
--- a/lyra/web/static/index.html
+++ b/lyra/web/static/index.html
@@ -734,7 +734,10 @@
 
         const level = event.level || 'info';
         const time = new Date((event.ts || 0) * 1000).toLocaleTimeString();
-        const fields = event.fields || {};
+        const fields = Object.assign({}, event.fields || {});
+        // `detail` is rendered as an expandable block, not an inline field.
+        const detail = fields.detail;
+        delete fields.detail;
         const fieldStr = Object.keys(fields).length
           ? Object.entries(fields).map(([k, v]) => `${k}=${v}`).join('  ')
           : '';
@@ -746,6 +749,7 @@
           <span class="log-level log-level-${level}">${escapeHtml(level)}</span>
           <span class="log-msg">${escapeHtml(event.msg || '')}</span>
           ${fieldStr ? `<span class="log-fields">${escapeHtml(fieldStr)}</span>` : ''}
+          ${detail ? `<details class="log-detail"><summary>view full prompt</summary><pre>${escapeHtml(detail)}</pre></details>` : ''}
         `;
 
         thinkingContent.appendChild(eventDiv);
diff --git a/lyra/web/static/style.css b/lyra/web/static/style.css
index bdfbb46..a93bf8a 100644
--- a/lyra/web/static/style.css
+++ b/lyra/web/static/style.css
@@ -941,3 +941,25 @@ select:hover {
 .log-error .log-level, .log-error .log-msg { color: #fca5a5; }
 .log-system  { border-left-color: #00ff66; }
 .log-system .log-level { color: #00ff66; }
+
+.log-detail { width: 100%; margin-top: 4px; }
+.log-detail summary {
+  cursor: pointer;
+  color: var(--accent);
+  font-size: 0.72rem;
+  user-select: none;
+}
+.log-detail pre {
+  margin: 6px 0 0;
+  padding: 8px;
+  max-height: 340px;
+  overflow: auto;
+  background: rgba(0,0,0,0.25);
+  border-left: 2px solid var(--accent);
+  border-radius: 4px;
+  font-size: 0.72rem;
+  line-height: 1.4;
+  white-space: pre-wrap;
+  word-break: break-word;
+  color: var(--text);
+}