From 6b3e9e4fbabcb265266a55a3593f02decdd18e98 Mon Sep 17 00:00:00 2001
From: Krystan HuffMenne <khuffmenne@optro.ai>
Date: Fri, 14 Aug 2026 16:03:57 -0700
Subject: [PATCH 1/2] fix(repl-sdk): correct the whitespace escape in
 formatDefaultId
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`/\\s+/g` matches a literal backslash followed by one or more `s`, not
whitespace. The intent reads as collapsing runs of whitespace before
kebab-casing the heading text.

In practice this is a no-op: `kebabCase` already splits on whitespace, so
every realistic heading slugs identically either way. The one input that
differs is a heading containing a literal `\s`:

  "a \s b"   before: a-b     after: a-s-b

Happy to close this in favour of dropping the `replaceAll` entirely, since
`kebabCase` makes it redundant — I went with the minimal change.
---
 packages/repl-sdk/src/compilers/markdown/heading-id.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/repl-sdk/src/compilers/markdown/heading-id.js b/packages/repl-sdk/src/compilers/markdown/heading-id.js
index 4f2647d9e..f679ba029 100644
--- a/packages/repl-sdk/src/compilers/markdown/heading-id.js
+++ b/packages/repl-sdk/src/compilers/markdown/heading-id.js
@@ -38,7 +38,7 @@ function extractText(children) {
  * @param {string} value
  */
 function formatDefaultId(value) {
-  return kebabCase(value.replaceAll(/\\s+/g, ' ').trim());
+  return kebabCase(value.replaceAll(/\s+/g, ' ').trim());
 }
 
 /**

From 4e57935810e2f9aa3ca89d77915aa89304d57c83 Mon Sep 17 00:00:00 2001
From: Krystan HuffMenne <khuffmenne@optro.ai>
Date: Fri, 14 Aug 2026 16:44:11 -0700
Subject: [PATCH 2/2] test(repl-sdk): cover the heading-id whitespace handling

Two cases for the escape fix:

- runs of whitespace in a heading collapse to a single `-` in the id (passes
  either way, since kebabCase also splits on whitespace -- pins the intent so a
  future refactor of formatDefaultId cannot quietly change it)
- a literal `\s` in a heading is text, not whitespace

The second is the actual regression test. With the old `/\\s+/g`,
`## a \s b` produced `id="a-b"` -- the `s` was consumed as part of the match.
---
 .../src/compilers/markdown/parse.test.ts       | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/packages/repl-sdk/src/compilers/markdown/parse.test.ts b/packages/repl-sdk/src/compilers/markdown/parse.test.ts
index 213679e87..ae952b93a 100644
--- a/packages/repl-sdk/src/compilers/markdown/parse.test.ts
+++ b/packages/repl-sdk/src/compilers/markdown/parse.test.ts
@@ -237,6 +237,24 @@ describe('default features', () => {
   });
 });
 
+describe('heading ids', () => {
+  it('collapses runs of whitespace in the heading text', async () => {
+    const result = await parseMarkdown(`##   Hello    World  `, { ...defaults });
+
+    // Only the id is normalized; the rendered text keeps the author's spacing.
+    expect(result.text).toContain('id="hello-world"');
+  });
+
+  it('treats a literal \\s in a heading as text, not as whitespace', async () => {
+    // The regex in formatDefaultId used to be /\\s+/g -- a literal backslash
+    // followed by `s`, rather than whitespace -- so `\s` here was replaced with
+    // a space and the `s` vanished from the id.
+    const result = await parseMarkdown(`## a \\s b`, { ...defaults });
+
+    expect(result.text).toContain('id="a-s-b"');
+  });
+});
+
 describe('options', () => {
   describe('remarkPlugins', () => {
     it('works', async () => {