diff --git a/packages/web/package.json b/packages/web/package.json
index 946ee2a..7141107 100644
--- a/packages/web/package.json
+++ b/packages/web/package.json
@@ -39,6 +39,7 @@
 		"react": "catalog:",
 		"react-dom": "catalog:",
 		"react-markdown": "^10.1.0",
+		"remark-breaks": "^4.0.0",
 		"remark-gfm": "^4.0.1",
 		"tailwind-merge": "^3.5.0",
 		"tailwindcss": "^4.2.4",
diff --git a/packages/web/src/components/chat/ChatPage.tsx b/packages/web/src/components/chat/ChatPage.tsx
index 2b5ae78..a0b3a1e 100644
--- a/packages/web/src/components/chat/ChatPage.tsx
+++ b/packages/web/src/components/chat/ChatPage.tsx
@@ -4,6 +4,7 @@ import { Brain, Send } from "lucide-react";
 import { useEffect, useRef, useState } from "react";
 import { useChat } from "@/api/queries";
 import { LoadingSpinner } from "@/components/shared/LoadingSpinner";
+import { MessageMarkdown } from "@/components/shared/MessageMarkdown";
 import { Button } from "@/components/ui/button";
 import { Textarea } from "@/components/ui/input";
 import { SectionHeading } from "@/components/ui/typography";
@@ -146,7 +147,7 @@ export function ChatPage() {
 											}
 								}
 							>
-								<p className="whitespace-pre-wrap leading-relaxed">{mask(msg.content)}</p>
+								<MessageMarkdown content={mask(msg.content)} />
 							</div>
 						</motion.div>
 					))}
diff --git a/packages/web/src/components/sessions/SessionDetail.tsx b/packages/web/src/components/sessions/SessionDetail.tsx
index ed453af..6c22ebf 100644
--- a/packages/web/src/components/sessions/SessionDetail.tsx
+++ b/packages/web/src/components/sessions/SessionDetail.tsx
@@ -20,6 +20,7 @@ import { Badge } from "@/components/shared/Badge";
 import { ConfirmDialog } from "@/components/shared/ConfirmDialog";
 import { JsonViewer } from "@/components/shared/JsonViewer";
 import { PageLoader } from "@/components/shared/LoadingSpinner";
+import { MessageMarkdown } from "@/components/shared/MessageMarkdown";
 import { Pagination } from "@/components/shared/Pagination";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
@@ -263,7 +264,7 @@ export function SessionDetail() {
 														<Caption>{new Date(msg.created_at).toLocaleString()}</Caption>
 													)}
 												</div>
-												<Body className="whitespace-pre-wrap">{mask(msg.content)}</Body>
+												<MessageMarkdown content={mask(msg.content)} />
 											</div>
 										))}
 									</div>
diff --git a/packages/web/src/components/shared/MessageMarkdown.tsx b/packages/web/src/components/shared/MessageMarkdown.tsx
new file mode 100644
index 0000000..2d9b846
--- /dev/null
+++ b/packages/web/src/components/shared/MessageMarkdown.tsx
@@ -0,0 +1,29 @@
+import ReactMarkdown, { type Components } from "react-markdown";
+import remarkBreaks from "remark-breaks";
+import remarkGfm from "remark-gfm";
+
+const REMARK_PLUGINS = [remarkGfm, remarkBreaks];
+
+const COMPONENTS: Components = {
+	h1: ({ children }) => <h1 className="text-base font-semibold mt-3 mb-2">{children}</h1>,
+	h2: ({ children }) => <h2 className="text-sm font-semibold mt-3 mb-2">{children}</h2>,
+	h3: ({ children }) => <h3 className="text-sm font-medium mt-2 mb-1">{children}</h3>,
+	p: ({ children }) => <p className="leading-relaxed mb-2 last:mb-0">{children}</p>,
+	ul: ({ children }) => <ul className="list-disc pl-4 my-2 space-y-1">{children}</ul>,
+	ol: ({ children }) => <ol className="list-decimal pl-4 my-2 space-y-1">{children}</ol>,
+	pre: ({ children }) => <pre className="overflow-x-auto my-2 text-xs font-mono">{children}</pre>,
+};
+
+interface MessageMarkdownProps {
+	content: string;
+}
+
+export function MessageMarkdown({ content }: MessageMarkdownProps) {
+	return (
+		<div className="min-w-0 overflow-x-auto break-words text-sm">
+			<ReactMarkdown remarkPlugins={REMARK_PLUGINS} components={COMPONENTS}>
+				{content}
+			</ReactMarkdown>
+		</div>
+	);
+}
diff --git a/packages/web/src/test/message-markdown.test.tsx b/packages/web/src/test/message-markdown.test.tsx
new file mode 100644
index 0000000..7a37cd0
--- /dev/null
+++ b/packages/web/src/test/message-markdown.test.tsx
@@ -0,0 +1,249 @@
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { createMemoryHistory, createRouter, RouterProvider } from "@tanstack/react-router";
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { DemoProvider } from "@/context/DemoContext";
+import { MetadataProvider } from "@/context/MetadataContext";
+import { saveStore } from "@/lib/config";
+import { routeTree } from "@/routeTree.gen";
+
+const { httpFetch } = vi.hoisted(() => ({ httpFetch: vi.fn() }));
+vi.mock("@/lib/http", () => ({ httpFetch }));
+
+const WORKSPACE_ID = "ws-alpha";
+const SESSION_ID = "sess-1";
+const PEER_ID = "peer-bot";
+const INSTANCE = {
+	id: "inst-1",
+	name: "Local",
+	baseUrl: "http://localhost:8000",
+	token: "",
+};
+
+function json(body: unknown, status = 200) {
+	return new Response(JSON.stringify(body), {
+		status,
+		headers: { "Content-Type": "application/json" },
+	});
+}
+
+function requestOf(input: Request | string, init?: RequestInit) {
+	return typeof input === "string" ? new Request(input, init) : input;
+}
+
+function message(content: string) {
+	return {
+		id: "msg-1",
+		content,
+		peer_id: PEER_ID,
+		session_id: SESSION_ID,
+		workspace_id: WORKSPACE_ID,
+		created_at: "2026-01-01T00:00:00Z",
+		token_count: 12,
+	};
+}
+
+function mockHoncho(options: { messageContent?: string; chatContent?: string } = {}) {
+	httpFetch.mockImplementation(async (input: Request | string, init?: RequestInit) => {
+		const req = requestOf(input, init);
+		const url = req.url;
+		if (url.includes("/messages/list")) {
+			return json({
+				items: [message(options.messageContent ?? "hello")],
+				total: 1,
+				page: 1,
+				size: 50,
+				pages: 1,
+			});
+		}
+		if (url.includes("/chat")) {
+			return json({ content: options.chatContent ?? "ok" });
+		}
+		return json({ items: [], total: 0, page: 1, size: 20, pages: 0 });
+	});
+}
+
+function renderAt(path: string) {
+	saveStore({ instances: [INSTANCE], activeId: INSTANCE.id });
+	const router = createRouter({
+		routeTree,
+		history: createMemoryHistory({ initialEntries: [path] }),
+	});
+	const qc = new QueryClient({
+		defaultOptions: { queries: { retry: false }, mutations: { retry: false } },
+	});
+	return render(
+		<QueryClientProvider client={qc}>
+			<DemoProvider>
+				<MetadataProvider>
+					{/* biome-ignore lint/suspicious/noExplicitAny: test router type */}
+					<RouterProvider router={router as any} />
+				</MetadataProvider>
+			</DemoProvider>
+		</QueryClientProvider>,
+	);
+}
+
+function sessionPath() {
+	return `/workspaces/${WORKSPACE_ID}/sessions/${SESSION_ID}`;
+}
+
+function chatPath() {
+	return `/workspaces/${WORKSPACE_ID}/peers/${PEER_ID}/chat`;
+}
+
+describe("session message markdown", () => {
+	afterEach(() => {
+		httpFetch.mockReset();
+		localStorage.clear();
+	});
+
+	it("renders a heading instead of raw markdown syntax", async () => {
+		mockHoncho({ messageContent: "# Status update" });
+		renderAt(sessionPath());
+		expect(await screen.findByRole("heading", { name: "Status update" })).toBeInTheDocument();
+	});
+
+	it("renders a list item from markdown bullets", async () => {
+		mockHoncho({ messageContent: "- first item\n- second item" });
+		renderAt(sessionPath());
+		expect(await screen.findByText("first item")).toBeInTheDocument();
+	});
+
+	it("renders fenced code as a code block", async () => {
+		mockHoncho({ messageContent: "```\nconst x = 1\n```" });
+		renderAt(sessionPath());
+		expect(await screen.findByText("const x = 1")).toBeInTheDocument();
+	});
+
+	it("renders a GFM table header", async () => {
+		mockHoncho({ messageContent: "| Name | Value |\n| --- | --- |\n| alpha | 1 |" });
+		renderAt(sessionPath());
+		expect(await screen.findByRole("columnheader", { name: "Name" })).toBeInTheDocument();
+	});
+
+	it("keeps a plain-text message readable", async () => {
+		mockHoncho({ messageContent: "just a normal sentence" });
+		renderAt(sessionPath());
+		expect(await screen.findByText("just a normal sentence")).toBeInTheDocument();
+	});
+
+	it("does not execute raw HTML in message content", async () => {
+		mockHoncho({ messageContent: '<script>window.__md_xss = true</script><img src="x" />' });
+		renderAt(sessionPath());
+		await screen.findByText(/script/i);
+		expect(document.querySelector("script")).toBeNull();
+	});
+
+	it("does not turn a javascript URL into an executable link", async () => {
+		mockHoncho({ messageContent: "[click me](javascript:alert(1))" });
+		renderAt(sessionPath());
+		await screen.findByText("click me");
+		expect(document.querySelector('a[href^="javascript:"]')).toBeNull();
+	});
+
+	it("masks private message text in demo mode before rendering", async () => {
+		localStorage.setItem("openconcho:demo", "true");
+		mockHoncho({ messageContent: "secret-token-value" });
+		renderAt(sessionPath());
+		await screen.findByText("Session detail");
+		expect(screen.queryByText("secret-token-value")).not.toBeInTheDocument();
+	});
+
+	it("still shows message token count beside the rendered body", async () => {
+		mockHoncho({ messageContent: "**bold** note" });
+		renderAt(sessionPath());
+		expect(await screen.findByText("12 tokens")).toBeInTheDocument();
+	});
+
+	it("keeps a single newline in a plain-text message", async () => {
+		mockHoncho({ messageContent: "line one\nline two" });
+		renderAt(sessionPath());
+		const line = await screen.findByText(/line one/);
+		expect(line.querySelector("br")).not.toBeNull();
+	});
+
+	it("keeps timestamp lines in source order", async () => {
+		mockHoncho({
+			messageContent: "[2026-01-01 00:00:00] alpha-ts\n[2026-01-02 00:00:00] beta-ts",
+		});
+		renderAt(sessionPath());
+		await screen.findByText(/alpha-ts/);
+		const text = document.body.textContent ?? "";
+		expect(text.indexOf("alpha-ts")).toBeLessThan(text.indexOf("beta-ts"));
+	});
+
+	it("keeps a nested list nested", async () => {
+		mockHoncho({ messageContent: "- outer-md\n   - nested-md" });
+		renderAt(sessionPath());
+		const nested = await screen.findByText("nested-md");
+		expect(nested.closest("li")?.parentElement?.closest("li")).not.toBeNull();
+	});
+
+	it("keeps an indented code block as a code block", async () => {
+		mockHoncho({ messageContent: "Intro line.\n\n    const indented = 1\n" });
+		renderAt(sessionPath());
+		expect((await screen.findByText("const indented = 1")).closest("pre")).not.toBeNull();
+	});
+
+	it("leaves a bracketed token as literal text", async () => {
+		mockHoncho({
+			messageContent: "## Contradictions\n\n**CONTRADICTION**: See [abcdefghijklmn] here",
+		});
+		renderAt(sessionPath());
+		expect(await screen.findByText(/abcdefghijklmn/)).toBeInTheDocument();
+	});
+
+	it("renders representation-like headings as ordinary headings", async () => {
+		mockHoncho({
+			messageContent: "## Inductive Observations\n\n**Pattern** [high]: user likes cats",
+		});
+		renderAt(sessionPath());
+		await screen.findByText(/user likes cats/);
+		expect(screen.queryByText("high")).toBeNull();
+	});
+});
+
+describe("chat message markdown", () => {
+	afterEach(() => {
+		httpFetch.mockReset();
+		localStorage.clear();
+	});
+
+	it("renders assistant markdown as a heading in chat", async () => {
+		const user = userEvent.setup();
+		Element.prototype.scrollIntoView = vi.fn();
+		mockHoncho({ chatContent: "# Assistant heading" });
+		renderAt(chatPath());
+		await user.type(await screen.findByPlaceholderText(/Message this peer/i), "hello{Enter}");
+		expect(await screen.findByRole("heading", { name: "Assistant heading" })).toBeInTheDocument();
+	});
+
+	it("does not override user bubble paragraph color", async () => {
+		const user = userEvent.setup();
+		Element.prototype.scrollIntoView = vi.fn();
+		mockHoncho({ chatContent: "ok" });
+		renderAt(chatPath());
+		await user.type(
+			await screen.findByPlaceholderText(/Message this peer/i),
+			"Contrast check{Enter}",
+		);
+		const text = await screen.findByText("Contrast check");
+		const paragraph = text.closest("p") ?? text;
+		expect(paragraph.getAttribute("style") ?? "").not.toMatch(/--text-2/);
+	});
+
+	it("does not override user bubble list color", async () => {
+		const user = userEvent.setup();
+		Element.prototype.scrollIntoView = vi.fn();
+		mockHoncho({ chatContent: "ok" });
+		renderAt(chatPath());
+		await user.type(
+			await screen.findByPlaceholderText(/Message this peer/i),
+			"- bubble-item{Enter}",
+		);
+		const item = await screen.findByText("bubble-item");
+		expect(item.closest("ul")?.getAttribute("style") ?? "").not.toMatch(/--text-2/);
+	});
+});
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 2060c0a..57d0ed3 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -188,6 +188,9 @@ importers:
       react-markdown:
         specifier: ^10.1.0
         version: 10.1.0(@types/react@19.2.14)(react@19.2.5)
+      remark-breaks:
+        specifier: ^4.0.0
+        version: 4.0.0
       remark-gfm:
         specifier: ^4.0.1
         version: 4.0.1
@@ -2904,6 +2907,9 @@ packages:
   mdast-util-mdxjs-esm@2.0.1:
     resolution: {integrity: sha512-EcmOpxsZ96CvlP03NghtH1EsLtr0n9Tm4lPUJUBccV9RwUOneqSycg19n5HGzCf+10LozMRSObtVr3ee1WoHtg==}
 
+  mdast-util-newline-to-break@2.0.0:
+    resolution: {integrity: sha512-MbgeFca0hLYIEx/2zGsszCSEJJ1JSCdiY5xQxRcLDDGa8EPvlLPupJ4DSajbMPAnC0je8jfb9TiUATnxxrHUog==}
+
   mdast-util-phrasing@4.1.0:
     resolution: {integrity: sha512-TqICwyvJJpBwvGAMZjj4J2n0X8QWp21b9l0o7eXyVJ25YNWYbJDVIyD1bZXE6WtV6RmKJVYmQAKWa0zWOABz2w==}
 
@@ -3445,6 +3451,9 @@ packages:
     resolution: {integrity: sha512-P7B4+jq8DeD2nMsAcdfaqHbssgHtZ7Z5+++a5ask90fvmJ8p5je4mOa+wzu+DB4vQ5tdJV/xywY+UnVFeQLV5Q==}
     engines: {node: '>=14'}
 
+  remark-breaks@4.0.0:
+    resolution: {integrity: sha512-IjEjJOkH4FuJvHZVIW0QCDWxcG96kCq7An/KVH2NfJe6rKZU2AsHeB3OEjPNRxi4QC34Xdx7I2KGYn6IpT7gxQ==}
+
   remark-gfm@4.0.1:
     resolution: {integrity: sha512-1quofZ2RQ9EWdeN34S79+KExV1764+wCUGop5CPL1WGdD0ocPpu91lzPGbwWMECpEpd42kJGQwzRfyov9j4yNg==}
 
@@ -6722,6 +6731,11 @@ snapshots:
     transitivePeerDependencies:
       - supports-color
 
+  mdast-util-newline-to-break@2.0.0:
+    dependencies:
+      '@types/mdast': 4.0.4
+      mdast-util-find-and-replace: 3.0.2
+
   mdast-util-phrasing@4.1.0:
     dependencies:
       '@types/mdast': 4.0.4
@@ -7310,6 +7324,12 @@ snapshots:
     dependencies:
       '@pnpm/npm-conf': 3.0.2
 
+  remark-breaks@4.0.0:
+    dependencies:
+      '@types/mdast': 4.0.4
+      mdast-util-newline-to-break: 2.0.0
+      unified: 11.0.5
+
   remark-gfm@4.0.1:
     dependencies:
       '@types/mdast': 4.0.4