diff --git a/scripts/lib/shell-substitution.js b/scripts/lib/shell-substitution.js
index 5b747f0d0..efe6a9be1 100644
--- a/scripts/lib/shell-substitution.js
+++ b/scripts/lib/shell-substitution.js
@@ -120,23 +120,21 @@ function escapesActive(quotes) {
 }
 
 /**
- * Toggle quote state for the quote character at `source[i]`.
- * Returns true when it opened or closed a quote. Callers consume escapes
+ * Quote state after the quote character at `source[i]`, as a new object, or
+ * null when it neither opens nor closes a quote. Callers consume escapes
  * first, so a quote after a backslash here still closes (`'C:\'`, `"C:\\"`),
  * while `\'` inside `$'...'` is consumed before it can close the string.
  */
 function toggleQuote(source, i, quotes) {
   const ch = source[i];
   if (ch === "'" && !quotes.inDouble) {
-    quotes.inSingle = !quotes.inSingle;
-    quotes.ansiC = quotes.inSingle && opensAnsiC(source, i);
-    return true;
+    const inSingle = !quotes.inSingle;
+    return { ...quotes, inSingle, ansiC: inSingle && opensAnsiC(source, i) };
   }
   if (ch === '"' && !quotes.inSingle) {
-    quotes.inDouble = !quotes.inDouble;
-    return true;
+    return { ...quotes, inDouble: !quotes.inDouble };
   }
-  return false;
+  return null;
 }
 
 /**
@@ -144,7 +142,7 @@ function toggleQuote(source, i, quotes) {
  * is at `start`, honoring quotes and escapes inside the span.
  */
 function findParenSpanEnd(source, start) {
-  const quotes = { inSingle: false, inDouble: false, ansiC: false };
+  let quotes = { inSingle: false, inDouble: false, ansiC: false };
   let depth = 1;
   let i = start;
   while (i < source.length && depth > 0) {
@@ -153,7 +151,10 @@ function findParenSpanEnd(source, start) {
       i += 2;
       continue;
     }
-    if (!toggleQuote(source, i, quotes) && !quotes.inSingle && !quotes.inDouble) {
+    const toggled = toggleQuote(source, i, quotes);
+    if (toggled) {
+      quotes = toggled;
+    } else if (!quotes.inSingle && !quotes.inDouble) {
       depth += parenDelta(inner);
     }
     i += 1;
@@ -179,17 +180,19 @@ function findBacktickEnd(source, start) {
 
 /**
  * Top-level scan step shared by the group extractors: escapes, quote state,
- * `$(...)` and backtick spans. Returns the last index consumed so a `for`
- * loop's `i++` resumes after it, or -1 when the caller must inspect `source[i]`.
+ * `$(...)` and backtick spans. Returns the quote state after `source[i]` and
+ * `skipped`, the last index consumed so a `for` loop's `i++` resumes after it,
+ * or -1 when the caller must inspect `source[i]`.
  */
 function skipOuterSpan(source, i, quotes) {
   const ch = source[i];
-  if (ch === '\\' && escapesActive(quotes)) return i + 1;
-  if (toggleQuote(source, i, quotes)) return i;
-  if (quotes.inSingle || quotes.inDouble) return i;
-  if (ch === '$' && source[i + 1] === '(') return findParenSpanEnd(source, i + 2) - 1;
-  if (ch === '`') return findBacktickEnd(source, i + 1);
-  return -1;
+  if (ch === '\\' && escapesActive(quotes)) return { skipped: i + 1, quotes };
+  const toggled = toggleQuote(source, i, quotes);
+  if (toggled) return { skipped: i, quotes: toggled };
+  if (quotes.inSingle || quotes.inDouble) return { skipped: i, quotes };
+  if (ch === '$' && source[i + 1] === '(') return { skipped: findParenSpanEnd(source, i + 2) - 1, quotes };
+  if (ch === '`') return { skipped: findBacktickEnd(source, i + 1), quotes };
+  return { skipped: -1, quotes };
 }
 
 /**
@@ -197,7 +200,7 @@ function skipOuterSpan(source, i, quotes) {
  * the body text and the index of the closing paren (or where input ran out).
  */
 function readSubshellBody(source, start) {
-  const quotes = { inSingle: false, inDouble: false, ansiC: false };
+  let quotes = { inSingle: false, inDouble: false, ansiC: false };
   let depth = 1;
   let body = '';
   let i = start;
@@ -210,7 +213,10 @@ function readSubshellBody(source, start) {
       i = Math.min(i + 2, source.length);
       continue;
     }
-    if (!toggleQuote(source, i, quotes) && !quotes.inSingle && !quotes.inDouble) {
+    const toggled = toggleQuote(source, i, quotes);
+    if (toggled) {
+      quotes = toggled;
+    } else if (!quotes.inSingle && !quotes.inDouble) {
       depth += parenDelta(inner);
       if (depth === 0) break;
     }
@@ -240,12 +246,13 @@ function readSubshellBody(source, start) {
 function extractSubshellGroups(input) {
   const source = String(input || '');
   const groups = [];
-  const quotes = { inSingle: false, inDouble: false, ansiC: false };
+  let quotes = { inSingle: false, inDouble: false, ansiC: false };
 
   for (let i = 0; i < source.length; i++) {
-    const skipped = skipOuterSpan(source, i, quotes);
-    if (skipped !== -1) {
-      i = skipped;
+    const step = skipOuterSpan(source, i, quotes);
+    quotes = step.quotes;
+    if (step.skipped !== -1) {
+      i = step.skipped;
       continue;
     }
     if (source[i] !== '(') continue;
@@ -285,7 +292,7 @@ function opensBraceGroup(source, i) {
  * the body text and the index of the closing brace (or where input ran out).
  */
 function readBraceBody(source, start) {
-  const quotes = { inSingle: false, inDouble: false, ansiC: false };
+  let quotes = { inSingle: false, inDouble: false, ansiC: false };
   let depth = 1;
   let body = '';
   let i = start;
@@ -297,7 +304,9 @@ function readBraceBody(source, start) {
       i = Math.min(i + 2, source.length);
       continue;
     }
-    if (toggleQuote(source, i, quotes) || quotes.inSingle || quotes.inDouble) {
+    const toggled = toggleQuote(source, i, quotes);
+    if (toggled) quotes = toggled;
+    if (toggled || quotes.inSingle || quotes.inDouble) {
       body += inner;
       i += 1;
       continue;
@@ -347,12 +356,13 @@ function readBraceBody(source, start) {
 function extractBraceGroups(input) {
   const source = String(input || '');
   const groups = [];
-  const quotes = { inSingle: false, inDouble: false, ansiC: false };
+  let quotes = { inSingle: false, inDouble: false, ansiC: false };
 
   for (let i = 0; i < source.length; i++) {
-    const skipped = skipOuterSpan(source, i, quotes);
-    if (skipped !== -1) {
-      i = skipped;
+    const step = skipOuterSpan(source, i, quotes);
+    quotes = step.quotes;
+    if (step.skipped !== -1) {
+      i = step.skipped;
       continue;
     }
     if (source[i] === '(') {