feat: add streaming markdown rendering with incremental output

src/render/index.ts

@@ -18,6 +18,8 @@ export default class Renderer {
   private lineCount = 0;
   private charsSinceNL = 0;
   private memOk = true;
+  private buffer = "";
+  private unsafeIndex = 0;
 
   constructor(
     private isPlain = false,
@@ -66,6 +68,33 @@ export default class Renderer {
     }
   }
 
+  private async bufferThenRender(text: string, pipe = process.stdout) {
+    this.buffer += text;
+
+    const idx = this.buffer.lastIndexOf("\n#");
+
+    const blockDelims = this.buffer.match(/```/g)?.length;
+    if (blockDelims && blockDelims % 2 !== 0) this.unsafeIndex = idx;
+
+    if (idx > this.unsafeIndex) {
+      const str = this.buffer.substring(0, idx) ?? "";
+      await this.render(str, pipe);
+      this.buffer = this.buffer.substring(idx);
+      this.unsafeIndex = 0;
+    }
+  }
+
+  private async render(str: string, pipe = process.stdout) {
+    this.moveCursor(-this.lineCount, pipe);
+    this.clearScreenDown(pipe);
+    this.resetCounts();
+
+    const [columns] = pipe.getWindowSize();
+    const rendered = await renderMarkdown(str, columns);
+    pipe.write(rendered);
+    pipe.write("\n");
+  }
+
   async renderStream(stream: AsyncIterableStream<TextStreamPart<ToolSet>>) {
     this.resetCounts();
 
@@ -113,16 +142,19 @@ export default class Renderer {
         }
         case "text-delta": {
           this.write(part.text);
-          if (!this.isPlain) this.checkContainment(part.text);
+          if (!this.isPlain) {
+            this.checkContainment(part.text);
+            await this.bufferThenRender(part.text);
+          }
           break;
         }
         case "text-end": {
-          if (!this.isPlain) {
-            this.moveCursor(-this.lineCount - 1);
-            this.clearScreenDown(process.stderr);
-            this.resetCounts();
+          if (this.buffer) {
+            await this.render(this.buffer);
+            this.buffer = "";
+            this.unsafeIndex = 0;
           } else {
-            this.write("\n\n");
+            this.write("\n");
           }
           break;
         }
@@ -144,20 +176,4 @@ export default class Renderer {
     const template = `Context: ${context.toFixed(1)}k, Output: ${output.toFixed(1)}k, Time: ${time.toFixed(2)}s\n`;
     process.stderr.write(chalkStderr.dim(template));
   }
-
-  async renderFinal(text: PromiseLike<string>) {
-    if (this.isPlain) return;
-
-    const [columns] = process.stdout.getWindowSize();
-
-    const start = Date.now();
-    const rendered = await renderMarkdown(text, columns);
-    const stop = Date.now();
-
-    this.write("\n");
-    this.write(rendered);
-    this.write("\n");
-
-    process.stderr.write(chalkStderr.dim(`Markdown: ${stop - start}ms, `));
-  }
 }

src/render/markdown.ts

@@ -47,7 +47,7 @@ import kanagawaLotus from "@shikijs/themes/kanagawa-lotus";
 import kanagawaWave from "@shikijs/themes/kanagawa-wave";
 
 export async function renderMarkdown(
-  text: PromiseLike<string>,
+  text: PromiseLike<string> | string,
   columns: number,
 ) {
   return render(await text, {