diff --git a/wasm/app/app.js b/wasm/app/app.js
index 1f9d71e..67a172e 100644
--- a/wasm/app/app.js
+++ b/wasm/app/app.js
@@ -261,27 +261,63 @@ function startLiveBlock(tierName) {
     pre.textContent = "";
     block.appendChild(pre);
     outputEl.appendChild(block);
+
+    // Each chunk gets split on \n: every completed line becomes its
+    // own block-level <div>, the trailing fragment without a newline
+    // accumulates in a pending div that's updated in place until the
+    // next \n closes it. display:block + white-space:pre set INLINE
+    // so a stale cached stylesheet can't suppress the fix — we kept
+    // chasing what turned out to be CSS not reloading.
+    const makeLine = () => {
+        const d = document.createElement("div");
+        d.style.display = "block";
+        d.style.whiteSpace = "pre";
+        return d;
+    };
+    let pendingLine = makeLine();
+    pre.appendChild(pendingLine);
+    let pendingText = "";
+
     return {
         append(chunk) {
-            // Append a TextNode rather than `pre.textContent += chunk`
-            // — the latter re-reads + restringifies + re-sets all
-            // existing children on every chunk, which under a fast
-            // C-tier loop (one chunk per (newline) printf) was
-            // dropping line breaks and rendering "tick 0tick 10000…"
-            // horizontally instead of stacking vertically. TextNode
-            // append preserves every byte verbatim.
-            pre.appendChild(document.createTextNode(chunk));
+            if (!chunk) return;
+            let start = 0;
+            for (let i = 0; i < chunk.length; i++) {
+                if (chunk.charCodeAt(i) === 10) {
+                    pendingText += chunk.slice(start, i);
+                    pendingLine.textContent = pendingText || " ";
+                    pendingText = "";
+                    pendingLine = makeLine();
+                    pre.appendChild(pendingLine);
+                    start = i + 1;
+                }
+            }
+            if (start < chunk.length) {
+                pendingText += chunk.slice(start);
+                pendingLine.textContent = pendingText;
+            }
             outputEl.scrollTop = outputEl.scrollHeight;
         },
         finalize(elapsedMs, kind, fullOutput) {
             if (kind === "cancelled") t.textContent = `  (cancelled @ ${elapsedMs.toFixed(0)} ms)`;
             else t.textContent = `  (${elapsedMs.toFixed(0)} ms)`;
             if (kind === "error") pre.className = "err";
-            // If the streamed chunks miss anything (e.g. asm tier
-            // which doesn't stream yet), reconcile with the full
-            // output. No-op when streaming captured everything.
-            if (fullOutput && pre.textContent !== fullOutput) {
-                pre.textContent = fullOutput;
+            // Reconcile against the full output if the streamed
+            // per-line divs don't add up — e.g. asm-tier fallback
+            // where streaming isn't wired yet. Otherwise the joined
+            // per-line text should match the eval's full output.
+            if (fullOutput) {
+                const got = Array.from(pre.children).map((d) =>
+                    d.textContent === " " ? "" : d.textContent).join("\n");
+                if (got !== fullOutput.replace(/\n$/, "")) {
+                    pre.textContent = "";
+                    const lines = fullOutput.split("\n");
+                    for (const ln of lines) {
+                        const d = makeLine();
+                        d.textContent = ln || " ";
+                        pre.appendChild(d);
+                    }
+                }
             }
         },
     };
diff --git a/www/playground/app.js b/www/playground/app.js
index 1f9d71e..67a172e 100644
--- a/www/playground/app.js
+++ b/www/playground/app.js
@@ -261,27 +261,63 @@ function startLiveBlock(tierName) {
     pre.textContent = "";
     block.appendChild(pre);
     outputEl.appendChild(block);
+
+    // Each chunk gets split on \n: every completed line becomes its
+    // own block-level <div>, the trailing fragment without a newline
+    // accumulates in a pending div that's updated in place until the
+    // next \n closes it. display:block + white-space:pre set INLINE
+    // so a stale cached stylesheet can't suppress the fix — we kept
+    // chasing what turned out to be CSS not reloading.
+    const makeLine = () => {
+        const d = document.createElement("div");
+        d.style.display = "block";
+        d.style.whiteSpace = "pre";
+        return d;
+    };
+    let pendingLine = makeLine();
+    pre.appendChild(pendingLine);
+    let pendingText = "";
+
     return {
         append(chunk) {
-            // Append a TextNode rather than `pre.textContent += chunk`
-            // — the latter re-reads + restringifies + re-sets all
-            // existing children on every chunk, which under a fast
-            // C-tier loop (one chunk per (newline) printf) was
-            // dropping line breaks and rendering "tick 0tick 10000…"
-            // horizontally instead of stacking vertically. TextNode
-            // append preserves every byte verbatim.
-            pre.appendChild(document.createTextNode(chunk));
+            if (!chunk) return;
+            let start = 0;
+            for (let i = 0; i < chunk.length; i++) {
+                if (chunk.charCodeAt(i) === 10) {
+                    pendingText += chunk.slice(start, i);
+                    pendingLine.textContent = pendingText || " ";
+                    pendingText = "";
+                    pendingLine = makeLine();
+                    pre.appendChild(pendingLine);
+                    start = i + 1;
+                }
+            }
+            if (start < chunk.length) {
+                pendingText += chunk.slice(start);
+                pendingLine.textContent = pendingText;
+            }
             outputEl.scrollTop = outputEl.scrollHeight;
         },
         finalize(elapsedMs, kind, fullOutput) {
             if (kind === "cancelled") t.textContent = `  (cancelled @ ${elapsedMs.toFixed(0)} ms)`;
             else t.textContent = `  (${elapsedMs.toFixed(0)} ms)`;
             if (kind === "error") pre.className = "err";
-            // If the streamed chunks miss anything (e.g. asm tier
-            // which doesn't stream yet), reconcile with the full
-            // output. No-op when streaming captured everything.
-            if (fullOutput && pre.textContent !== fullOutput) {
-                pre.textContent = fullOutput;
+            // Reconcile against the full output if the streamed
+            // per-line divs don't add up — e.g. asm-tier fallback
+            // where streaming isn't wired yet. Otherwise the joined
+            // per-line text should match the eval's full output.
+            if (fullOutput) {
+                const got = Array.from(pre.children).map((d) =>
+                    d.textContent === " " ? "" : d.textContent).join("\n");
+                if (got !== fullOutput.replace(/\n$/, "")) {
+                    pre.textContent = "";
+                    const lines = fullOutput.split("\n");
+                    for (const ln of lines) {
+                        const d = makeLine();
+                        d.textContent = ln || " ";
+                        pre.appendChild(d);
+                    }
+                }
             }
         },
     };