From 2f11d9a4ba957645c3c37854d8237be1f15515c1 Mon Sep 17 00:00:00 2001
From: NullVoxPopuli-ai-agent
 <268630448+NullVoxPopuli-ai-agent@users.noreply.github.com>
Date: Sat, 15 Aug 2026 17:19:28 -0400
Subject: [PATCH 1/2] fix(repl-sdk): make {#custom-id} heading suffix actually
 set the id

Previously the suffix only suppressed the auto-generated id: the custom
id was never assigned and the literal {#custom-id} stayed in the
rendered heading text, despite kolay documenting the feature as working.

Now the suffix becomes the heading id and is stripped from the text.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 .../repl-sdk/src/compilers/markdown/heading-id.js  | 10 ++++++++++
 .../repl-sdk/src/compilers/markdown/parse.test.ts  | 14 ++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/packages/repl-sdk/src/compilers/markdown/heading-id.js b/packages/repl-sdk/src/compilers/markdown/heading-id.js
index f679ba029..4dba7ad25 100644
--- a/packages/repl-sdk/src/compilers/markdown/heading-id.js
+++ b/packages/repl-sdk/src/compilers/markdown/heading-id.js
@@ -65,6 +65,16 @@ export function headingId(options = { defaults: false }) {
         const matched = string.match(/ {#([^]+?)}$/);
 
         if (matched) {
+          const remaining = string.slice(0, -matched[0].length);
+
+          if (remaining) {
+            lastChild.value = remaining;
+          } else {
+            node.children.pop();
+          }
+
+          setNodeId(node, matched[1]);
+
           return;
         }
       }
diff --git a/packages/repl-sdk/src/compilers/markdown/parse.test.ts b/packages/repl-sdk/src/compilers/markdown/parse.test.ts
index ae952b93a..87815ba62 100644
--- a/packages/repl-sdk/src/compilers/markdown/parse.test.ts
+++ b/packages/repl-sdk/src/compilers/markdown/parse.test.ts
@@ -253,6 +253,20 @@ describe('heading ids', () => {
 
     expect(result.text).toContain('id="a-s-b"');
   });
+
+  it('uses a {#custom-id} suffix as the id and strips it from the text', async () => {
+    const result = await parseMarkdown(`## A very long heading {#short-id}`, { ...defaults });
+
+    expect(result.text).toBe('<h2 id="short-id">A very long heading</h2>');
+  });
+
+  it('supports {#custom-id} on a heading ending in formatting', async () => {
+    const result = await parseMarkdown(`## Use \`parseMarkdown\` here {#parse}`, {
+      ...defaults,
+    });
+
+    expect(result.text).toBe('<h2 id="parse">Use <code>parseMarkdown</code> here</h2>');
+  });
 });
 
 describe('options', () => {

From 9fa3c0ffd4dd55232fe00c5fc307163c1c9a265a Mon Sep 17 00:00:00 2001
From: NullVoxPopuli-ai-agent
 <268630448+NullVoxPopuli-ai-agent@users.noreply.github.com>
Date: Sat, 15 Aug 2026 18:05:04 -0400
Subject: [PATCH 2/2] fix types: guard indexed regex-match access

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 packages/repl-sdk/src/compilers/markdown/heading-id.js | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/packages/repl-sdk/src/compilers/markdown/heading-id.js b/packages/repl-sdk/src/compilers/markdown/heading-id.js
index 4dba7ad25..c60f4d14e 100644
--- a/packages/repl-sdk/src/compilers/markdown/heading-id.js
+++ b/packages/repl-sdk/src/compilers/markdown/heading-id.js
@@ -63,9 +63,11 @@ export function headingId(options = { defaults: false }) {
       if (lastChild && lastChild.type === 'text') {
         const string = lastChild.value.replace(/ +$/, '');
         const matched = string.match(/ {#([^]+?)}$/);
+        const suffix = matched?.[0];
+        const customId = matched?.[1];
 
-        if (matched) {
-          const remaining = string.slice(0, -matched[0].length);
+        if (suffix && customId) {
+          const remaining = string.slice(0, -suffix.length);
 
           if (remaining) {
             lastChild.value = remaining;
@@ -73,7 +75,7 @@ export function headingId(options = { defaults: false }) {
             node.children.pop();
           }
 
-          setNodeId(node, matched[1]);
+          setNodeId(node, customId);
 
           return;
         }