diff --git a/web/package-lock.json b/web/package-lock.json
index 473d113..5bb7750 100644
--- a/web/package-lock.json
+++ b/web/package-lock.json
@@ -11,7 +11,8 @@
         "@fontsource/jetbrains-mono": "^5.3.0",
         "@xterm/addon-fit": "^0.10.0",
         "@xterm/addon-webgl": "^0.19.0",
-        "@xterm/xterm": "^5.5.0"
+        "@xterm/xterm": "^5.5.0",
+        "marked": "^18.0.11"
       },
       "devDependencies": {
         "happy-dom": "^20.11.6",
@@ -1222,6 +1223,18 @@
         "@jridgewell/sourcemap-codec": "^1.5.5"
       }
     },
+    "node_modules/marked": {
+      "version": "18.0.11",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-18.0.11.tgz",
+      "integrity": "sha512-HnslJfsZkRPBDJRHvVtAaWlZHEpSu7u8LgQuJCELjRKuWR+hpq4A7sLq3p8HaI9ypVoXDXxV34CsQJEe1+J5Aw==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 20"
+      }
+    },
     "node_modules/ms": {
       "version": "2.1.3",
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
diff --git a/web/package.json b/web/package.json
index ef2765d..f496bbf 100644
--- a/web/package.json
+++ b/web/package.json
@@ -16,7 +16,8 @@
     "@fontsource/jetbrains-mono": "^5.3.0",
     "@xterm/addon-fit": "^0.10.0",
     "@xterm/addon-webgl": "^0.19.0",
-    "@xterm/xterm": "^5.5.0"
+    "@xterm/xterm": "^5.5.0",
+    "marked": "^18.0.11"
   },
   "devDependencies": {
     "happy-dom": "^20.11.6",
diff --git a/web/pnpm-lock.yaml b/web/pnpm-lock.yaml
index 5219b6d..cc86f77 100644
--- a/web/pnpm-lock.yaml
+++ b/web/pnpm-lock.yaml
@@ -20,6 +20,9 @@ importers:
       '@xterm/xterm':
         specifier: ^5.5.0
         version: 5.5.0
+      marked:
+        specifier: ^18.0.11
+        version: 18.0.11
     devDependencies:
       happy-dom:
         specifier: ^20.11.6
@@ -424,6 +427,11 @@ packages:
   magic-string@0.30.21:
     resolution: {integrity: sha512-vd2F4YUyEXKGcLHoq+TEyCjxueSeHnFxyyjNp80yg0XV4vUhnDer/lvvlqM/arB5bXQN5K2/3oinyCRyx8T2CQ==}
 
+  marked@18.0.11:
+    resolution: {integrity: sha512-HnslJfsZkRPBDJRHvVtAaWlZHEpSu7u8LgQuJCELjRKuWR+hpq4A7sLq3p8HaI9ypVoXDXxV34CsQJEe1+J5Aw==}
+    engines: {node: '>= 20'}
+    hasBin: true
+
   ms@2.1.3:
     resolution: {integrity: sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==}
 
@@ -864,6 +872,8 @@ snapshots:
     dependencies:
       '@jridgewell/sourcemap-codec': 1.5.5
 
+  marked@18.0.11: {}
+
   ms@2.1.3: {}
 
   nanoid@3.3.12: {}
diff --git a/web/src/structuredRender.test.ts b/web/src/structuredRender.test.ts
index 7fce155..b85a388 100644
--- a/web/src/structuredRender.test.ts
+++ b/web/src/structuredRender.test.ts
@@ -5,6 +5,7 @@ import {
   buildToolGroup,
   buildTranscriptRow,
   renderInlineMarkdown,
+  renderMarkdown,
 } from "./structuredRender.js";
 import type { TranscriptRow } from "./types.js";
 
@@ -82,6 +83,24 @@ describe("renderInlineMarkdown", () => {
   });
 });
 
+describe("renderMarkdown", () => {
+  it("renders GFM tables as semantic table markup", () => {
+    const html = renderMarkdown("| Model | State |\n| --- | --- |\n| Opus | ready |");
+    expect(html).toContain("<table>");
+    expect(html).toContain("<th>Model</th>");
+    expect(html).toContain("<td>Opus</td>");
+  });
+
+  it("removes executable HTML and unsafe URLs", () => {
+    const html = renderMarkdown(
+      '<img src=x onerror="alert(1)"><script>alert(2)</script>[bad](javascript:alert(3))',
+    );
+    expect(html).not.toContain("<img");
+    expect(html).not.toContain("<script");
+    expect(html).not.toContain('href="javascript:');
+  });
+});
+
 describe("buildTranscriptRow: tool calls", () => {
   it("shows glyph, name, argument and no meta for a completed non-diff call", () => {
     const el = buildTranscriptRow(
diff --git a/web/src/structuredRender.ts b/web/src/structuredRender.ts
index 14a66ba..3513e34 100644
--- a/web/src/structuredRender.ts
+++ b/web/src/structuredRender.ts
@@ -4,6 +4,7 @@
 // unit-testable without a WebSocket.
 
 import { escapeHtml } from "./html.js";
+import { marked, Renderer } from "marked";
 import { computeDiffLines, diffStats } from "./structuredDiff.js";
 import type {
   AcpContentBlock,
@@ -95,10 +96,7 @@ function contentBlockText(block: AcpContentBlock | undefined): string {
   }
 }
 
-/** A tiny, dependency-free inline renderer: `**bold**`, `*italic*`, and
- *  `` `code` `` become real markup; everything else stays escaped plain
- *  text. No block-level markdown (lists, headings) — agent prose is
- *  paragraphs, not documents. */
+/** Small inline renderer retained for compact labels and focused tests. */
 export function renderInlineMarkdown(text: string): string {
   const escaped = escapeHtml(text);
   return escaped
@@ -107,15 +105,37 @@ export function renderInlineMarkdown(text: string): string {
     .replace(/(?<!\*)\*([^*]+)\*(?!\*)/g, "<em>$1</em>");
 }
 
+/** Render assistant output as GFM, then sanitize the complete result before it
+ * enters the DOM. This gives transcripts proper tables, lists, code blocks and
+ * links without trusting model-authored HTML or URL attributes. */
+export function renderMarkdown(text: string): string {
+  const renderer = new Renderer();
+  renderer.html = ({ text: raw }) => escapeHtml(raw);
+  renderer.image = ({ text: alt }) => escapeHtml(alt ? `[image: ${alt}]` : "[image]");
+  renderer.link = ({ href, title, tokens }) => {
+    const label = renderer.parser.parseInline(tokens);
+    const scheme = /^([a-z][a-z\d+.-]*):/i.exec(href.trim())?.[1]?.toLowerCase();
+    if (scheme && !["http", "https", "mailto"].includes(scheme)) return label;
+    const safeTitle = title ? ` title="${escapeHtml(title)}"` : "";
+    return `<a href="${escapeHtml(href)}"${safeTitle}>${label}</a>`;
+  };
+
+  return marked.parse(text, { async: false, gfm: true, renderer });
+}
+
 function renderProse(container: HTMLElement, text: string): void {
-  const paragraphs = text.split(/\n{2,}/);
-  for (const para of paragraphs) {
-    if (!para) continue;
-    const p = document.createElement("p");
-    p.innerHTML = renderInlineMarkdown(para);
-    container.appendChild(p);
+  container.innerHTML = renderMarkdown(text);
+
+  for (const table of Array.from(container.querySelectorAll("table"))) {
+    const scroller = el("div", "st-markdown-table-wrap");
+    table.replaceWith(scroller);
+    scroller.appendChild(table);
+  }
+
+  for (const link of container.querySelectorAll("a")) {
+    link.target = "_blank";
+    link.rel = "noopener noreferrer";
   }
-  if (container.children.length === 0) container.textContent = "";
 }
 
 async function writeClipboard(text: string): Promise<void> {
@@ -158,7 +178,10 @@ function makeCopyable(node: HTMLElement, text: string, label: string): void {
       },
     );
   };
-  node.addEventListener("click", copy);
+  node.addEventListener("click", (event) => {
+    if ((event.target as Element | null)?.closest("a")) return;
+    copy();
+  });
   node.addEventListener("keydown", (event) => {
     if (event.key !== "Enter" && event.key !== " ") return;
     event.preventDefault();
diff --git a/web/src/styles.css b/web/src/styles.css
index 28377db..618edb5 100644
--- a/web/src/styles.css
+++ b/web/src/styles.css
@@ -1892,6 +1892,7 @@ input.leaf-rename:focus {
   align-items: center;
   gap: var(--sp-2);
   height: var(--bar-h);
+  flex: 0 0 var(--bar-h);
   padding: 0 var(--sp-2);
   border-bottom: 1px solid var(--border);
   background: var(--surface);
@@ -2388,6 +2389,88 @@ input.leaf-rename:focus {
   margin-bottom: 0;
 }
 
+.st-row-agent .st-body > :first-child {
+  margin-top: 0;
+}
+
+.st-row-agent .st-body > :last-child {
+  margin-bottom: 0;
+}
+
+.st-row-agent .st-body h1,
+.st-row-agent .st-body h2,
+.st-row-agent .st-body h3,
+.st-row-agent .st-body h4 {
+  margin: var(--sp-4) 0 var(--sp-2);
+  color: var(--ink);
+  font-size: var(--fs-14);
+  line-height: 1.35;
+}
+
+.st-row-agent .st-body ul,
+.st-row-agent .st-body ol {
+  margin: var(--sp-2) 0;
+  padding-left: var(--sp-5);
+}
+
+.st-row-agent .st-body li + li {
+  margin-top: var(--sp-1);
+}
+
+.st-row-agent .st-body pre {
+  margin: var(--sp-2) 0;
+  padding: var(--sp-3);
+  overflow-x: auto;
+  border: 1px solid var(--border);
+  border-radius: var(--r-2);
+  background: var(--surface-2);
+}
+
+.st-row-agent .st-body pre code {
+  padding: 0;
+  border: 0;
+  background: transparent;
+}
+
+.st-row-agent .st-body a {
+  color: var(--ink);
+  text-decoration-color: var(--border-strong);
+  text-underline-offset: 2px;
+}
+
+.st-markdown-table-wrap {
+  max-width: 100%;
+  margin: var(--sp-2) 0;
+  overflow-x: auto;
+  border: 1px solid var(--border);
+  border-radius: var(--r-2);
+}
+
+.st-row-agent table {
+  width: 100%;
+  border-collapse: collapse;
+  font-size: var(--fs-12);
+}
+
+.st-row-agent th,
+.st-row-agent td {
+  padding: var(--sp-2) var(--sp-3);
+  border-bottom: 1px solid var(--border);
+  text-align: left;
+  vertical-align: top;
+  white-space: nowrap;
+}
+
+.st-row-agent th {
+  color: var(--ink);
+  background: var(--surface-2);
+  font-weight: 600;
+}
+
+.st-row-agent tr:last-child td {
+  border-bottom: 0;
+}
+
 .st-row-agent code {
   background: var(--surface-2);
   border: 1px solid var(--border);