fix(tui): arm a fence added under a stable block

Author: TheGreatAxios

src/tui/code-links.ts

@@ -431,12 +431,20 @@ function sameChildIdentity(
  * so a bare URL becomes an OSC-8 span and survives native wrap. Markdown
  * prose already sets both — do not replace those, or conceal regresses.
  * OpenTUI can swap the only block for a new CodeRenderable without growing
- * the child count, so the walk follows child identity, not the count.
+ * the child count, so the walk follows child identity, not the count. A
+ * list box can also stay the same object while a fence is inserted under
+ * it; that new code node still needs the walk.
  */
 export function armCodeLinks(node: Renderable): void {
   const children = node.getChildren();
   const previous = armedChildIdentity.get(node);
-  if (previous !== undefined && sameChildIdentity(previous, children)) return;
+  if (
+    previous !== undefined &&
+    sameChildIdentity(previous, children) &&
+    !hasUnarmedCode(node)
+  ) {
+    return;
+  }
   codeLinkWalkCount += 1;
   const walk = (current: Renderable): void => {
     if (current instanceof CodeRenderable) {
@@ -452,3 +460,17 @@ export function armCodeLinks(node: Renderable): void {
   walk(node);
   armedChildIdentity.set(node, children);
 }
+
+/** True when a code node under `node` was created without link callbacks. */
+function hasUnarmedCode(node: Renderable): boolean {
+  if (
+    node instanceof CodeRenderable &&
+    (node.onHighlight === undefined || node.onChunks === undefined)
+  ) {
+    return true;
+  }
+  for (const child of node.getChildren()) {
+    if (hasUnarmedCode(child)) return true;
+  }
+  return false;
+}

src/tui/stream-retext-work.test.ts

@@ -3,7 +3,11 @@
  * copy the transcript child list to find the open row.
  */
 import { describe, expect, test } from "bun:test";
-import { CodeRenderable, type BaseRenderable } from "@opentui/core";
+import {
+  CodeRenderable,
+  MarkdownRenderable,
+  type BaseRenderable,
+} from "@opentui/core";
 import { withTestRenderer } from "./harness";
 import { codeLinkArmWalks } from "./code-links";
 import { appendStreamRow, replaceStreamRowAt } from "./shell/chrome";
@@ -147,4 +151,59 @@ describe("streaming retext work", () => {
       { width: 80, height: 24 },
     );
   });
+
+  test("a fence added under a stable list still arms that code node", async () => {
+    await withTestRenderer(
+      async (h) => {
+        const shell = createAppShell(h.renderer, SHELL_OPTS);
+        try {
+          appendStreamRow(shell, {
+            role: "assistant",
+            streaming: true,
+            text: "- intro",
+          });
+          await h.renderOnce();
+          const row = transcriptRowChildren(shell)[0];
+          if (row === undefined) throw new Error("row missing");
+          const markdown = row
+            .getChildren()
+            .find((child) => child instanceof MarkdownRenderable);
+          if (!(markdown instanceof MarkdownRenderable)) {
+            throw new Error("markdown missing");
+          }
+          // OpenTUI keeps one list box and inserts the fence under it. The
+          // first retext arms that box; the fence must still be walked.
+          markdown.internalBlockMode = "top-level";
+          replaceStreamRowAt(shell, 0, {
+            role: "assistant",
+            streaming: true,
+            text: "- intro",
+          });
+          const list = markdown.getChildren()[0];
+          if (list === undefined || list instanceof CodeRenderable) {
+            throw new Error("list box missing");
+          }
+          const before = codeLinkArmWalks();
+          replaceStreamRowAt(shell, 0, {
+            role: "assistant",
+            streaming: true,
+            text: "- intro\n\n  ```\n  https://example.com\n  ```",
+          });
+          expect(markdown.getChildren()[0]).toBe(list);
+          const codes = codeNodes(row);
+          const fence = codes.find(
+            (code) =>
+              code.onChunks === undefined || code.filetype !== "markdown",
+          );
+          expect(fence).toBeDefined();
+          expect(fence?.onChunks).toBeDefined();
+          expect(fence?.onHighlight).toBeDefined();
+          expect(codeLinkArmWalks()).toBeGreaterThan(before);
+        } finally {
+          shell.dispose();
+        }
+      },
+      { width: 80, height: 24 },
+    );
+  });
 });