diff --git a/src/build.ts b/src/build.ts
index 539776d3f..96067b7a2 100644
--- a/src/build.ts
+++ b/src/build.ts
@@ -109,10 +109,11 @@ export async function build(
       const clientPath = getClientPath(entry);
       const outputPath = join("_observablehq", name);
       effects.output.write(`${faint("bundle")} ${clientPath} ${faint("→")} `);
-      const code = await (entry.endsWith(".css")
-        ? bundleStyles({path: clientPath})
+      const {text, sourcemap} = await (entry.endsWith(".css")
+        ? bundleStyles({path: clientPath, minify: true})
         : rollupClient(clientPath, {minify: true}));
-      await effects.writeFile(outputPath, code);
+      console.warn(sourcemap);
+      await effects.writeFile(outputPath, text);
     }
     if (config.search) {
       const outputPath = join("_observablehq", "minisearch.json");
@@ -125,13 +126,15 @@ export async function build(
         const outputPath = join("_import", style.path);
         const sourcePath = join(root, style.path);
         effects.output.write(`${faint("style")} ${sourcePath} ${faint("→")} `);
-        const code = await bundleStyles({path: sourcePath});
-        await effects.writeFile(outputPath, code);
+        const {text, sourcemap} = await bundleStyles({path: sourcePath, minify: true});
+        await effects.writeFile(outputPath, text);
+        console.warn(sourcemap);
       } else {
         const outputPath = join("_observablehq", `theme-${style.theme}.css`);
         effects.output.write(`${faint("bundle")} theme-${style.theme}.css ${faint("→")} `);
-        const code = await bundleStyles({theme: style.theme});
-        await effects.writeFile(outputPath, code);
+        const {text, sourcemap} = await bundleStyles({theme: style.theme, minify: true});
+        await effects.writeFile(outputPath, text);
+        console.warn(sourcemap);
       }
     }
   }
diff --git a/src/preview.ts b/src/preview.ts
index 93185dedf..052c2486e 100644
--- a/src/preview.ts
+++ b/src/preview.ts
@@ -103,7 +103,7 @@ export class PreviewServer {
         if (pathname.endsWith(".js")) {
           end(req, res, await rollupClient(path), "text/javascript");
         } else if (pathname.endsWith(".css")) {
-          end(req, res, await bundleStyles({path}), "text/css");
+          end(req, res, (await bundleStyles({path})).text, "text/css");
         } else {
           throw new HttpError(`Not found: ${pathname}`, 404);
         }
@@ -114,7 +114,7 @@ export class PreviewServer {
       } else if (pathname === "/_observablehq/minisearch.json") {
         end(req, res, await searchIndex(config), "application/json");
       } else if ((match = /^\/_observablehq\/theme-(?<theme>[\w-]+(,[\w-]+)*)?\.css$/.exec(pathname))) {
-        end(req, res, await bundleStyles({theme: match.groups!.theme?.split(",") ?? []}), "text/css");
+        end(req, res, (await bundleStyles({theme: match.groups!.theme?.split(",") ?? []})).text, "text/css");
       } else if (pathname.startsWith("/_observablehq/")) {
         send(req, pathname.slice("/_observablehq".length), {root: publicRoot}).pipe(res);
       } else if (pathname.startsWith("/_import/")) {
@@ -123,7 +123,7 @@ export class PreviewServer {
         try {
           if (pathname.endsWith(".css")) {
             await access(filepath, constants.R_OK);
-            end(req, res, await bundleStyles({path: filepath}), "text/css");
+            end(req, res, (await bundleStyles({path: filepath})).text, "text/css");
             return;
           } else if (pathname.endsWith(".js")) {
             const input = await readFile(filepath, "utf-8");
diff --git a/src/render.ts b/src/render.ts
index 906de4a5f..c25707772 100644
--- a/src/render.ts
+++ b/src/render.ts
@@ -117,7 +117,7 @@ async function renderSidebar(title = "Home", pages: (Page | Section)[], path: st
         )}"><input type="search" placeholder="Search"></div>
   <div id="observablehq-search-results"></div>
   <script>{${html.unsafe(
-    (await rollupClient(getClientPath("./src/client/search-init.ts"), {minify: true})).trim()
+    (await rollupClient(getClientPath("./src/client/search-init.ts"), {minify: true})).text.trim()
   )}}</script>`
       : ""
   }
@@ -142,7 +142,7 @@ async function renderSidebar(title = "Home", pages: (Page | Section)[], path: st
   </ol>
 </nav>
 <script>{${html.unsafe(
-    (await rollupClient(getClientPath("./src/client/sidebar-init.ts"), {minify: true})).trim()
+    (await rollupClient(getClientPath("./src/client/sidebar-init.ts"), {minify: true})).text.trim()
   )}}</script>`;
 }
 
diff --git a/src/rollup.ts b/src/rollup.ts
index 547a1126f..8418921f8 100644
--- a/src/rollup.ts
+++ b/src/rollup.ts
@@ -25,18 +25,42 @@ function rewriteInputsNamespace(code: string) {
   return code.replace(/\b__ns__\b/g, "inputs-3a86ea");
 }
 
-export async function bundleStyles({path, theme}: {path?: string; theme?: string[]}): Promise<string> {
+export async function bundleStyles({
+  minify = false,
+  path,
+  theme
+}: {
+  minify?: boolean;
+  path?: string;
+  theme?: string[];
+}): Promise<{text: string; sourcemap?: string}> {
   const result = await build({
     bundle: true,
     ...(path ? {entryPoints: [path]} : {stdin: {contents: renderTheme(theme!), loader: "css"}}),
     write: false,
+    minify,
+    sourcemap: !!path,
     alias: STYLE_MODULES
   });
-  const text = result.outputFiles[0].text;
-  return rewriteInputsNamespace(text); // TODO only for inputs
+  let text = result.outputFiles[0].text;
+  let sourcemap;
+  if (path) {
+    const groups = text.match(
+      /^(?<text>.*)[/][*]# sourceMappingURL=data:application[/]json;base64,(?<sourcemap>[a-zA-Z0-9+]+=) [*][/]$/m
+    )?.groups;
+    if (groups) {
+      ({text, sourcemap} = groups);
+      console.warn({path, sourcemap});
+    }
+  }
+  if (path === "src/client/stdlib/inputs.js") text = rewriteInputsNamespace(text);
+  return {text, sourcemap};
 }
 
-export async function rollupClient(clientPath: string, {minify = false} = {}): Promise<string> {
+export async function rollupClient(
+  clientPath: string,
+  {minify = false} = {}
+): Promise<{text: string; sourcemap?: string}> {
   const bundle = await rollup({
     input: clientPath,
     external: [/^https:/],
@@ -55,11 +79,11 @@ export async function rollupClient(clientPath: string, {minify = false} = {}): P
     ]
   });
   try {
-    const output = await bundle.generate({format: "es"});
+    const output = await bundle.generate({format: "es", sourcemap: "inline"});
     let code = output.output.find((o): o is OutputChunk => o.type === "chunk")!.code; // TODO don’t assume one chunk?
     code = rewriteTypeScriptImports(code);
-    code = rewriteInputsNamespace(code); // TODO only for inputs
-    return code;
+    if (clientPath === "src/client/stdlib/inputs.js") code = rewriteInputsNamespace(code); // TODO only for inputs
+    return {text: code};
   } finally {
     await bundle.close();
   }