Polish: simplify formatTimestamp and tone down export button

Replace try/catch with isNaN guard in the HTML exporter's
formatTimestamp, matching the same cleanup applied client-side.

Downgrade the export button from btn-primary to btn-secondary so it
doesn't compete visually with the main content area. The primary blue
gradient was overly prominent for a utility action.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,16 @@
+node_modules/
+dist/
+*.tsbuildinfo
+
+# Environment
+.env
+.env.*
+
+# Editor / OS
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+.DS_Store
+Thumbs.db

src/client/components/ExportButton.tsx

@@ -65,7 +65,7 @@ export function ExportButton({
         btn btn-sm flex-shrink-0 gap-1.5 transition-all duration-200
         ${state === "success" ? "text-white shadow-glow-success" : ""}
         ${state === "error" ? "text-white" : ""}
-        ${state === "idle" || state === "exporting" ? "btn-primary" : ""}
+        ${state === "idle" || state === "exporting" ? "btn-secondary" : ""}
       `}
       style={
         state === "success"

src/client/components/MessageBubble.tsx

@@ -1,4 +1,4 @@
-import React, { useMemo } from "react";
+import React, { useMemo, useState } from "react";
 import type { ParsedMessage } from "../lib/types";
 import { CATEGORY_LABELS } from "../lib/types";
 import { CATEGORY_COLORS } from "../lib/constants";
@@ -33,7 +33,15 @@ export function MessageBubble({
   const colors = CATEGORY_COLORS[message.category];
   const label = CATEGORY_LABELS[message.category];
 
+  // Collapsible state for thinking blocks and tool calls/results
+  const isCollapsible = message.category === "thinking" || message.category === "tool_call" || message.category === "tool_result";
+  const [collapsed, setCollapsed] = useState(isCollapsible);
+  const [linkCopied, setLinkCopied] = useState(false);
+
   const renderedHtml = useMemo(() => {
+    // Skip expensive rendering when content is collapsed and not visible
+    if (collapsed) return "";
+
     const msg = autoRedactEnabled ? redactMessage(message) : message;
 
     if (msg.category === "tool_call") {
@@ -46,14 +54,41 @@ export function MessageBubble({
 
     // Structured data categories: render as preformatted text, not markdown.
     // Avoids expensive marked.parse() on large JSON/log blobs.
-    if (msg.category === "hook_progress" || msg.category === "tool_result" || msg.category === "file_snapshot") {
+    if (msg.category === "hook_progress" || msg.category === "file_snapshot") {
       const html = `<pre class="hljs"><code>${escapeHtml(msg.content)}</code></pre>`;
       return searchQuery ? highlightSearchText(html, searchQuery) : html;
     }
 
+    if (msg.category === "tool_result") {
+      const html = isDiffContent(msg.content)
+        ? renderDiffHtml(msg.content)
+        : `<pre class="hljs"><code>${escapeHtml(msg.content)}</code></pre>`;
+      return searchQuery ? highlightSearchText(html, searchQuery) : html;
+    }
+
     const html = renderMarkdown(msg.content);
     return searchQuery ? highlightSearchText(html, searchQuery) : html;
-  }, [message, searchQuery, autoRedactEnabled, colors.text]);
+  }, [message, searchQuery, autoRedactEnabled, colors.text, collapsed]);
+
+  // Generate preview for collapsed thinking blocks
+  const collapsedPreview = useMemo(() => {
+    if (!isCollapsible || !collapsed) return null;
+    if (message.category === "thinking") {
+      const lines = message.content.split("\n").filter(l => l.trim());
+      const preview = lines.slice(0, 2).join("\n");
+      const totalLines = lines.length;
+      return { preview, totalLines };
+    }
+    if (message.category === "tool_call") {
+      return { preview: message.toolName || "Unknown Tool", totalLines: 0 };
+    }
+    if (message.category === "tool_result") {
+      const lines = message.content.split("\n");
+      const preview = lines[0]?.substring(0, 120) || "Result";
+      return { preview, totalLines: lines.length };
+    }
+    return null;
+  }, [isCollapsible, collapsed, message]);
 
   const timestamp = message.timestamp
     ? formatTimestamp(message.timestamp)
@@ -61,14 +96,13 @@ export function MessageBubble({
 
   return (
     <div
-      onClick={onToggleRedactionSelection}
       className={`
-        group rounded-xl border bg-surface-raised cursor-pointer
+        group rounded-xl border bg-surface-raised
         transition-all duration-200 relative overflow-hidden
         ${colors.border}
         ${dimmed ? "message-dimmed" : ""}
         ${selectedForRedaction ? "redaction-selected" : ""}
-        hover:shadow-card-hover hover:-translate-y-px
+        hover:shadow-card-hover
         shadow-card
       `}
     >
@@ -76,39 +110,151 @@ export function MessageBubble({
       <div className={`absolute left-0 top-0 bottom-0 w-[3px] rounded-l-xl ${colors.dot}`} />
 
       {/* Header bar */}
-      <div className="flex items-center gap-2 px-4 pl-5 pt-3 pb-1">
+      <div className="flex items-center gap-2 px-4 pl-5 h-10">
+        {isCollapsible && (
+          <button
+            onClick={(e) => { e.stopPropagation(); setCollapsed(!collapsed); }}
+            className="flex items-center justify-center w-5 h-5 text-foreground-muted hover:text-foreground transition-colors flex-shrink-0"
+            aria-label={collapsed ? "Expand" : "Collapse"}
+          >
+            <svg
+              className={`w-3.5 h-3.5 transition-transform duration-150 ${collapsed ? "" : "rotate-90"}`}
+              fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2.5}
+            >
+              <path strokeLinecap="round" strokeLinejoin="round" d="M8.25 4.5l7.5 7.5-7.5 7.5" />
+            </svg>
+          </button>
+        )}
         <span className={`w-1.5 h-1.5 rounded-full flex-shrink-0 ${colors.dot}`} />
-        <span className="text-caption font-semibold uppercase tracking-wider text-foreground-muted">
+        <span className="text-caption font-semibold uppercase tracking-wider text-foreground-muted leading-none">
           {label}
         </span>
         {timestamp && (
           <>
-            <span className="text-border">·</span>
-            <span className="text-caption text-foreground-muted tabular-nums">
+            <span className="text-border leading-none">·</span>
+            <span className="text-caption text-foreground-muted tabular-nums leading-none">
               {timestamp}
             </span>
           </>
         )}
+        {isCollapsible && collapsed && collapsedPreview && (
+          <>
+            <span className="text-border leading-none">·</span>
+            <span className="text-caption text-foreground-muted truncate max-w-[300px] leading-none">
+              {message.category === "thinking" && collapsedPreview.totalLines > 2
+                ? `${collapsedPreview.totalLines} lines`
+                : collapsedPreview.preview}
+            </span>
+          </>
+        )}
+
+        {/* Right-aligned header actions */}
+        <div className="ml-auto flex items-center gap-0.5 opacity-0 group-hover:opacity-100 transition-opacity flex-shrink-0">
+          <button
+            onClick={(e) => {
+              e.stopPropagation();
+              const url = `${window.location.origin}${window.location.pathname}#msg-${message.uuid}`;
+              navigator.clipboard.writeText(url).then(() => {
+                setLinkCopied(true);
+                setTimeout(() => setLinkCopied(false), 1500);
+              }).catch(() => {});
+            }}
+            className="flex items-center justify-center w-7 h-7 rounded-md text-foreground-muted hover:text-foreground hover:bg-surface-overlay/60 transition-colors"
+            title="Copy link to message"
+          >
+            {linkCopied ? (
+              <svg className="w-4 h-4 text-green-400" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+                <path strokeLinecap="round" strokeLinejoin="round" d="M4.5 12.75l6 6 9-13.5" />
+              </svg>
+            ) : (
+              <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={1.5}>
+                <path strokeLinecap="round" strokeLinejoin="round" d="M15.75 17.25v3.375c0 .621-.504 1.125-1.125 1.125h-9.75a1.125 1.125 0 01-1.125-1.125V7.875c0-.621.504-1.125 1.125-1.125H6.75a9.06 9.06 0 011.5.124m7.5 10.376h3.375c.621 0 1.125-.504 1.125-1.125V11.25c0-4.46-3.243-8.161-7.5-8.876a9.06 9.06 0 00-1.5-.124H9.375c-.621 0-1.125.504-1.125 1.125v3.5m7.5 10.375H9.375a1.125 1.125 0 01-1.125-1.125v-9.25m0 0a2.625 2.625 0 115.25 0H12m-3.75 0h3.75" />
+              </svg>
+            )}
+          </button>
+          <button
+            onClick={(e) => {
+              e.stopPropagation();
+              onToggleRedactionSelection();
+            }}
+            className={`flex items-center justify-center w-7 h-7 rounded-md transition-colors ${
+              selectedForRedaction
+                ? "text-red-400 bg-red-500/15 hover:bg-red-500/25"
+                : "text-foreground-muted hover:text-red-400 hover:bg-red-500/10"
+            }`}
+            title={selectedForRedaction ? "Deselect for redaction" : "Select for redaction"}
+          >
+            <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={1.5}>
+              <path strokeLinecap="round" strokeLinejoin="round" d="M3.98 8.223A10.477 10.477 0 001.934 12C3.226 16.338 7.244 19.5 12 19.5c.993 0 1.953-.138 2.863-.395M6.228 6.228A10.45 10.45 0 0112 4.5c4.756 0 8.773 3.162 10.065 7.498a10.523 10.523 0 01-4.293 5.774M6.228 6.228L3 3m3.228 3.228l3.65 3.65m7.894 7.894L21 21m-3.228-3.228l-3.65-3.65m0 0a3 3 0 10-4.243-4.243m4.242 4.242L9.88 9.88" />
+            </svg>
+          </button>
+        </div>
       </div>
 
       {/* Content — sourced from local user-owned JSONL files, not external/untrusted input */}
+      {!collapsed && (
         <div
           className="prose-message text-body text-foreground px-4 pl-5 pb-4 pt-1 max-w-none break-words overflow-hidden"
           dangerouslySetInnerHTML={{ __html: renderedHtml }}
         />
+      )}
+      {collapsed && message.category === "thinking" && collapsedPreview && (
+        <div className="px-4 pl-5 pb-3 pt-1">
+          <pre className="text-caption text-foreground-muted whitespace-pre-wrap line-clamp-2 font-mono">{collapsedPreview.preview}</pre>
+        </div>
+      )}
     </div>
   );
 }
 
+function isDiffContent(content: string): boolean {
+  const lines = content.split("\n").slice(0, 30);
+  let hunkHeaders = 0;
+  let diffLines = 0;
+  for (const line of lines) {
+    if (line.startsWith("@@") || line.startsWith("diff --")) {
+      hunkHeaders++;
+    } else if (line.startsWith("+++") || line.startsWith("---")) {
+      hunkHeaders++;
+    } else if (line.startsWith("+") || line.startsWith("-")) {
+      diffLines++;
+    }
+  }
+  // Require at least one hunk header AND some +/- lines to avoid false positives
+  // on YAML lists, markdown lists, or other content with leading dashes
+  return hunkHeaders >= 1 && diffLines >= 2;
+}
+
+function renderDiffHtml(content: string): string {
+  const lines = content.split("\n");
+  const htmlLines = lines.map((line) => {
+    const escaped = escapeHtml(line);
+    if (line.startsWith("@@")) {
+      return `<span class="diff-hunk">${escaped}</span>`;
+    }
+    if (line.startsWith("+++") || line.startsWith("---")) {
+      return `<span class="diff-meta">${escaped}</span>`;
+    }
+    if (line.startsWith("diff --")) {
+      return `<span class="diff-header">${escaped}</span>`;
+    }
+    if (line.startsWith("+")) {
+      return `<span class="diff-add">${escaped}</span>`;
+    }
+    if (line.startsWith("-")) {
+      return `<span class="diff-del">${escaped}</span>`;
+    }
+    return escaped;
+  });
+  return `<pre class="hljs diff-view"><code>${htmlLines.join("\n")}</code></pre>`;
+}
+
 function formatTimestamp(ts: string): string {
-  try {
   const d = new Date(ts);
+  if (isNaN(d.getTime())) return "";
   return d.toLocaleTimeString(undefined, {
     hour: "2-digit",
     minute: "2-digit",
     second: "2-digit",
   });
-  } catch {
-    return "";
-  }
 }

src/client/components/SessionList.tsx

@@ -96,6 +96,12 @@ export function SessionList({ sessions, loading, selectedId, onSelect }: Props)
                   <span>{formatDate(session.modified || session.created)}</span>
                   <span className="text-border">·</span>
                   <span className="tabular-nums">{session.messageCount} msgs</span>
+                  {session.duration && session.duration > 0 && (
+                    <>
+                      <span className="text-border">·</span>
+                      <span className="tabular-nums">{formatSessionDuration(session.duration)}</span>
+                    </>
+                  )}
                 </div>
               </button>
             );
@@ -154,17 +160,24 @@ function formatProjectName(project: string): string {
   return project;
 }
 
+function formatSessionDuration(ms: number): string {
+  const minutes = Math.floor(ms / 60000);
+  if (minutes < 1) return "<1m";
+  if (minutes < 60) return `${minutes}m`;
+  const hours = Math.floor(minutes / 60);
+  const rem = minutes % 60;
+  if (rem === 0) return `${hours}h`;
+  return `${hours}h ${rem}m`;
+}
+
 function formatDate(dateStr: string): string {
   if (!dateStr) return "";
-  try {
   const d = new Date(dateStr);
+  if (isNaN(d.getTime())) return dateStr;
   return d.toLocaleDateString(undefined, {
     month: "short",
     day: "numeric",
     hour: "2-digit",
     minute: "2-digit",
   });
-  } catch {
-    return dateStr;
-  }
 }

src/client/components/SessionViewer.tsx

@@ -58,7 +58,22 @@ export function SessionViewer({
     }
   }, [focusedIndex]);
 
-  // Build display list with redacted dividers.
+  // Auto-scroll to hash anchor on load
+  useEffect(() => {
+    const hash = window.location.hash;
+    if (hash && hash.startsWith("#msg-") && messages.length > 0) {
+      requestAnimationFrame(() => {
+        const el = document.getElementById(hash.slice(1));
+        if (el) {
+          el.scrollIntoView({ behavior: "smooth", block: "center" });
+          el.classList.add("search-match-focused", "rounded-xl");
+          setTimeout(() => el.classList.remove("search-match-focused"), 3000);
+        }
+      });
+    }
+  }, [messages.length]);
+
+  // Build display list with redacted dividers and time gaps.
   // Must be called before any early returns to satisfy Rules of Hooks.
   const displayItems = useMemo(() => {
     if (messages.length === 0) return [];
@@ -67,9 +82,11 @@ export function SessionViewer({
     const items: Array<
       | { type: "message"; message: ParsedMessage; messageIndex: number }
       | { type: "redacted_divider"; key: string }
+      | { type: "time_gap"; key: string; duration: string }
     > = [];
 
     let prevWasRedactedGap = false;
+    let prevTimestamp: string | undefined;
     let messageIndex = 0;
     for (const msg of allMessages) {
       if (redactedUuids.has(msg.uuid)) {
@@ -86,6 +103,20 @@ export function SessionViewer({
         });
         prevWasRedactedGap = false;
       }
+      // Insert time gap indicator if > 5 minutes between visible messages
+      if (prevTimestamp && msg.timestamp) {
+        const currTime = new Date(msg.timestamp).getTime();
+        const prevTime = new Date(prevTimestamp).getTime();
+        const gap = currTime - prevTime;
+        if (!isNaN(gap) && gap > 5 * 60 * 1000) {
+          items.push({
+            type: "time_gap",
+            key: `gap-${msg.uuid}`,
+            duration: formatDuration(gap),
+          });
+        }
+      }
+      if (msg.timestamp) prevTimestamp = msg.timestamp;
       items.push({ type: "message", message: msg, messageIndex });
       messageIndex++;
     }
@@ -154,6 +185,17 @@ export function SessionViewer({
           if (item.type === "redacted_divider") {
             return <RedactedDivider key={item.key} />;
           }
+          if (item.type === "time_gap") {
+            return (
+              <div key={item.key} className="flex items-center gap-3 py-2">
+                <div className="flex-1 h-px bg-border-muted" />
+                <span className="text-caption text-foreground-muted tabular-nums flex-shrink-0">
+                  {item.duration} later
+                </span>
+                <div className="flex-1 h-px bg-border-muted" />
+              </div>
+            );
+          }
           const msg = item.message;
           const isMatch =
             searchQuery &&
@@ -163,6 +205,7 @@ export function SessionViewer({
           return (
             <div
               key={msg.uuid}
+              id={`msg-${msg.uuid}`}
               data-msg-index={item.messageIndex}
               className={`animate-fade-in ${isFocused ? "search-match-focused rounded-xl" : ""}`}
               style={{ animationDelay: `${Math.min(idx * 20, 300)}ms`, animationFillMode: "backwards" }}
@@ -184,3 +227,12 @@ export function SessionViewer({
     </div>
   );
 }
+
+function formatDuration(ms: number): string {
+  const minutes = Math.floor(ms / 60000);
+  if (minutes < 60) return `${minutes}m`;
+  const hours = Math.floor(minutes / 60);
+  const remainMinutes = minutes % 60;
+  if (remainMinutes === 0) return `${hours}h`;
+  return `${hours}h ${remainMinutes}m`;
+}

src/client/lib/markdown.ts

@@ -18,6 +18,15 @@ marked.use(
   })
 );
 
+// Custom renderer to wrap code blocks with copy button
+const renderer = new marked.Renderer();
+renderer.code = function ({ text, lang }: { text: string; lang?: string | undefined; escaped?: boolean }) {
+  const langLabel = lang ? `<span class="code-lang-label">${escapeHtml(lang)}</span>` : "";
+  return `<div class="code-block-wrapper">${langLabel}<button class="code-copy-btn" data-copy-code type="button">Copy</button><pre class="hljs"><code>${text}</code></pre></div>`;
+};
+
+marked.use({ renderer });
+
 export function renderMarkdown(text: string): string {
   if (!text) return "";
   try {

src/client/main.tsx

@@ -3,6 +3,23 @@ import ReactDOM from "react-dom/client";
 import { App } from "./app.js";
 import "./styles/main.css";
 
+// Delegated click handler for code block copy buttons
+document.addEventListener("click", (e) => {
+  const btn = (e.target as HTMLElement).closest("[data-copy-code]") as HTMLButtonElement | null;
+  if (!btn) return;
+  e.stopPropagation();
+  const wrapper = btn.closest(".code-block-wrapper");
+  const code = wrapper?.querySelector("code");
+  if (!code) return;
+  navigator.clipboard.writeText(code.textContent || "").then(() => {
+    btn.textContent = "Copied!";
+    setTimeout(() => { btn.textContent = "Copy"; }, 1500);
+  }).catch(() => {
+    btn.textContent = "Failed";
+    setTimeout(() => { btn.textContent = "Copy"; }, 1500);
+  });
+});
+
 ReactDOM.createRoot(document.getElementById("root")!).render(
   <React.StrictMode>
     <App />

src/client/styles/main.css

@@ -147,6 +147,12 @@
   transition: opacity 150ms, background-color 150ms, color 150ms;
 }
 
+/* When a language label is present, shift copy button below it */
+.code-block-wrapper .code-lang-label + .code-copy-btn,
+.code-block-wrapper:has(.code-lang-label) .code-copy-btn {
+  top: 2rem;
+}
+
 .code-block-wrapper:hover .code-copy-btn {
   opacity: 1;
 }
@@ -156,6 +162,54 @@
   background: var(--color-surface-overlay);
 }
 
+/* ═══════════════════════════════════════════════
+   Diff view — colored line-level highlighting
+   ═══════════════════════════════════════════════ */
+
+.diff-view {
+  font-size: 0.8125rem;
+  line-height: 1.6;
+}
+
+.diff-add {
+  background: rgba(63, 185, 80, 0.12);
+  color: #3fb950;
+  display: block;
+  margin: 0 -1rem;
+  padding: 0 1rem;
+}
+
+.diff-del {
+  background: rgba(248, 81, 73, 0.12);
+  color: #f85149;
+  display: block;
+  margin: 0 -1rem;
+  padding: 0 1rem;
+}
+
+.diff-hunk {
+  color: #79c0ff;
+  display: block;
+  margin: 0 -1rem;
+  padding: 0.25rem 1rem;
+  background: rgba(121, 192, 255, 0.06);
+}
+
+.diff-meta {
+  color: var(--color-foreground-muted);
+  font-weight: 600;
+  display: block;
+}
+
+.diff-header {
+  color: var(--color-foreground-secondary);
+  font-weight: 600;
+  display: block;
+  margin: 0 -1rem;
+  padding: 0.25rem 1rem;
+  background: rgba(136, 144, 245, 0.06);
+}
+
 /* ═══════════════════════════════════════════════
    Search highlight — warm amber glow
    ═══════════════════════════════════════════════ */
@@ -246,12 +300,12 @@ mark.search-highlight {
    ═══════════════════════════════════════════════ */
 
 .message-dimmed {
-  opacity: 0.2;
+  opacity: 0.35;
   transition: opacity 200ms ease;
 }
 
 .message-dimmed:hover {
-  opacity: 0.45;
+  opacity: 0.65;
 }
 
 /* ═══════════════════════════════════════════════
@@ -473,11 +527,15 @@ mark.search-highlight {
 
   .btn-secondary {
     @apply bg-surface-raised text-foreground-secondary border border-border;
-    @apply hover:bg-surface-overlay hover:text-foreground hover:border-foreground-muted/30;
+    @apply hover:bg-surface-overlay hover:text-foreground;
     @apply disabled:opacity-50 disabled:cursor-not-allowed;
     @apply focus-visible:ring-accent;
   }
 
+  .btn-secondary:hover {
+    border-color: rgba(80, 90, 110, 0.3);
+  }
+
   .btn-ghost {
     @apply text-foreground-secondary;
     @apply hover:bg-surface-overlay hover:text-foreground;

src/server/services/html-exporter.ts

@@ -170,16 +170,13 @@ function renderMarkdown(text: string): string {
 }
 
 function formatTimestamp(ts: string): string {
-  try {
   const d = new Date(ts);
+  if (isNaN(d.getTime())) return "";
   return d.toLocaleTimeString(undefined, {
     hour: "2-digit",
     minute: "2-digit",
     second: "2-digit",
   });
-  } catch {
-    return "";
-  }
 }
 
 function getHighlightCss(): string {

src/server/services/session-discovery.ts

@@ -80,6 +80,7 @@ export async function discoverSessions(
             modified: entry.modified || "",
             messageCount: entry.messageCount || 0,
             path: resolved,
+            duration: computeDuration(entry.created, entry.modified),
           });
         }
       } catch {
@@ -102,3 +103,12 @@ export async function discoverSessions(
 
   return sessions;
 }
+
+function computeDuration(created?: string, modified?: string): number {
+  if (!created || !modified) return 0;
+  const createdMs = new Date(created).getTime();
+  const modifiedMs = new Date(modified).getTime();
+  if (isNaN(createdMs) || isNaN(modifiedMs)) return 0;
+  const diff = modifiedMs - createdMs;
+  return diff > 0 ? diff : 0;
+}

src/shared/types.ts

@@ -28,6 +28,7 @@ export interface SessionEntry {
   modified: string;
   messageCount: number;
   path: string;
+  duration?: number; // Duration in milliseconds from first to last message
 }
 
 export interface SessionListResponse {