diff --git a/internal/viewer/server_extra_test.go b/internal/viewer/server_extra_test.go
index db60459c2..3ed259380 100644
--- a/internal/viewer/server_extra_test.go
+++ b/internal/viewer/server_extra_test.go
@@ -156,6 +156,60 @@ func TestRenderTemplate_SessionPage(t *testing.T) {
 	}
 }
 
+func TestRenderTemplate_SecondarySectionsCollapsedByDefault(t *testing.T) {
+	rr := httptest.NewRecorder()
+	vs := &ViewSession{
+		Summary: SessionSummary{
+			SessionID:     "abc",
+			CWD:           "/test",
+			FilesReviewed: []string{"main.go"},
+		},
+		TokenUsage: TokenUsageSummary{
+			FileTokenBreakdown: []FileTokenUsage{{FilePath: "main.go"}},
+		},
+		Files: []*FileGroup{{FilePath: "main.go", Tasks: map[TaskType][]*TaskCard{}}},
+		Comments: []*ReviewComment{{
+			FilePath: "main.go",
+			Content:  "Keep this visible",
+		}},
+	}
+
+	renderTemplate(rr, "session.html", sessionPageData{
+		EncodedRepo: "repo",
+		RepoName:    "MyRepo",
+		Session:     vs,
+	})
+
+	body := rr.Body.String()
+	if count := strings.Count(body, `<details class="file-accordion section-accordion">`); count != 2 {
+		t.Fatalf("collapsed secondary section count = %d, want 2", count)
+	}
+	if strings.Contains(body, `<details class="file-accordion section-accordion" open>`) {
+		t.Fatal("secondary sections should be collapsed by default")
+	}
+	if !strings.Contains(body, `<details class="token-breakdown">`) || strings.Contains(body, `<details class="token-breakdown" open>`) {
+		t.Fatal("file token breakdown should be rendered and collapsed by default")
+	}
+	if !strings.Contains(body, `<details class="comment-file-group" open>`) {
+		t.Fatal("review comment groups should remain expanded")
+	}
+}
+
+func TestRenderTemplate_HidesEmptyConversationsSection(t *testing.T) {
+	rr := httptest.NewRecorder()
+	renderTemplate(rr, "session.html", sessionPageData{
+		EncodedRepo: "repo",
+		RepoName:    "MyRepo",
+		Session: &ViewSession{
+			Summary: SessionSummary{SessionID: "abc", CWD: "/test"},
+		},
+	})
+
+	if strings.Contains(rr.Body.String(), `<span class="section-title">Conversations</span>`) {
+		t.Fatal("empty conversations section should not be rendered")
+	}
+}
+
 func TestRenderTemplate_ExecutionError(t *testing.T) {
 	rr := httptest.NewRecorder()
 	// Pass wrong data type to trigger template execution error
diff --git a/internal/viewer/static/style.css b/internal/viewer/static/style.css
index 234ec757e..1fab6efcc 100644
--- a/internal/viewer/static/style.css
+++ b/internal/viewer/static/style.css
@@ -420,6 +420,26 @@ h3 {
 }
 .token-table tbody tr:hover { background: var(--accent-soft); }
 
+.token-breakdown-toggle {
+    display: flex;
+    align-items: center;
+    gap: 0.5rem;
+    color: var(--text-secondary);
+    cursor: pointer;
+    font-size: 0.82rem;
+    font-weight: 600;
+    list-style: none;
+    padding: 0.25rem 0 0.75rem;
+}
+.token-breakdown-toggle::-webkit-details-marker { display: none; }
+.token-breakdown-toggle::marker { content: none; }
+.token-breakdown-toggle .file-count-badge { margin-left: auto; }
+.token-breakdown[open] > .token-breakdown-toggle .chevron-sm { transform: rotate(45deg); }
+.token-breakdown-body {
+    overflow-x: auto;
+    padding-top: 0.25rem;
+}
+
 /* ── File List ── */
 .file-list {
     list-style: none;
@@ -548,6 +568,18 @@ h3 {
     padding: 1rem 1.25rem 1.25rem;
 }
 
+.section-accordion {
+    margin-top: 1.25rem;
+}
+.section-title {
+    flex: 1;
+    font-weight: 600;
+}
+.section-accordion .file-list,
+.section-accordion .conversations {
+    margin: 0;
+}
+
 /* Task Group */
 .task-group { margin-bottom: 1.25rem; }
 .task-group:last-child { margin-bottom: 0; }
diff --git a/internal/viewer/templates/session.html b/internal/viewer/templates/session.html
index 9858bcdaf..a6adfbce1 100644
--- a/internal/viewer/templates/session.html
+++ b/internal/viewer/templates/session.html
@@ -80,20 +80,29 @@ <h3>Token Usage</h3>
         {{end}}
     </div>
     {{with .Session.TokenUsage.FileTokenBreakdown}}
-    <table class="token-table">
-        <thead><tr><th>File</th><th>Prompt</th><th>Completion</th>{{if or $.Session.TokenUsage.TotalCacheReadTokens $.Session.TokenUsage.TotalCacheWriteTokens}}<th>Cache Read</th><th>Cache Write</th>{{end}}<th>Total</th></tr></thead>
-        <tbody>
-        {{range .}}
-            <tr>
-                <td title="{{.FilePath}}">{{.FilePath | truncate 60}}</td>
-                <td title="{{.PromptTokens}}">{{formatNumber .PromptTokens}}</td>
-                <td title="{{.CompletionTokens}}">{{formatNumber .CompletionTokens}}</td>
-                {{if or $.Session.TokenUsage.TotalCacheReadTokens $.Session.TokenUsage.TotalCacheWriteTokens}}<td title="{{.CacheReadTokens}}">{{formatNumber .CacheReadTokens}}</td><td title="{{.CacheWriteTokens}}">{{formatNumber .CacheWriteTokens}}</td>{{end}}
-                <td title="{{add .PromptTokens .CompletionTokens}}"><strong>{{formatNumber (add .PromptTokens .CompletionTokens)}}</strong></td>
-            </tr>
-        {{end}}
-        </tbody>
-    </table>
+    <details class="token-breakdown">
+        <summary class="token-breakdown-toggle">
+            <span class="chevron-sm"></span>
+            <span>File breakdown</span>
+            <span class="file-count-badge">{{len .}} files</span>
+        </summary>
+        <div class="token-breakdown-body">
+            <table class="token-table">
+                <thead><tr><th>File</th><th>Prompt</th><th>Completion</th>{{if or $.Session.TokenUsage.TotalCacheReadTokens $.Session.TokenUsage.TotalCacheWriteTokens}}<th>Cache Read</th><th>Cache Write</th>{{end}}<th>Total</th></tr></thead>
+                <tbody>
+                {{range .}}
+                    <tr>
+                        <td title="{{.FilePath}}">{{.FilePath | truncate 60}}</td>
+                        <td title="{{.PromptTokens}}">{{formatNumber .PromptTokens}}</td>
+                        <td title="{{.CompletionTokens}}">{{formatNumber .CompletionTokens}}</td>
+                        {{if or $.Session.TokenUsage.TotalCacheReadTokens $.Session.TokenUsage.TotalCacheWriteTokens}}<td title="{{.CacheReadTokens}}">{{formatNumber .CacheReadTokens}}</td><td title="{{.CacheWriteTokens}}">{{formatNumber .CacheWriteTokens}}</td>{{end}}
+                        <td title="{{add .PromptTokens .CompletionTokens}}"><strong>{{formatNumber (add .PromptTokens .CompletionTokens)}}</strong></td>
+                    </tr>
+                {{end}}
+                </tbody>
+            </table>
+        </div>
+    </details>
     {{end}}
 </div>
 
@@ -151,16 +160,31 @@ <h3>Review Comments ({{len .Session.Comments}} findings)</h3>
 {{end}}
 
 {{if .Session.Summary.FilesReviewed}}
-<h3>Files Reviewed</h3>
-<ul class="file-list">
-{{range .Session.Summary.FilesReviewed}}
-    <li>{{.}}</li>
-{{end}}
-</ul>
+<details class="file-accordion section-accordion">
+    <summary class="file-accordion-header">
+        <span class="chevron"></span>
+        <span class="section-title">Files Reviewed</span>
+        <span class="file-count-badge">{{len .Session.Summary.FilesReviewed}} files</span>
+    </summary>
+    <div class="file-accordion-body">
+        <ul class="file-list">
+        {{range .Session.Summary.FilesReviewed}}
+            <li>{{.}}</li>
+        {{end}}
+        </ul>
+    </div>
+</details>
 {{end}}
 
-<h3>Conversations ({{len .Session.Files}} files)</h3>
-<div class="conversations">
+{{if .Session.Files}}
+<details class="file-accordion section-accordion">
+    <summary class="file-accordion-header">
+        <span class="chevron"></span>
+        <span class="section-title">Conversations</span>
+        <span class="file-count-badge">{{len .Session.Files}} files</span>
+    </summary>
+    <div class="file-accordion-body">
+        <div class="conversations">
 {{range .Session.Files}}
 <details class="file-accordion">
     <summary class="file-accordion-header">
@@ -229,7 +253,10 @@ <h4 class="task-type-label">
     </div>
 </details>
 {{end}}
-</div>
+        </div>
+    </div>
+</details>
+{{end}}
 
 <script src="/static/session.js"></script>
 </main>