diff --git a/docs/development/agent-workflow.md b/docs/development/agent-workflow.md
index 32de7cd5b..301e3118e 100644
--- a/docs/development/agent-workflow.md
+++ b/docs/development/agent-workflow.md
@@ -71,7 +71,7 @@ HTML video, audio, source and track `src` assets and video posters use the same
 existence checks as images. Entity decoding uses full HTML text/attribute rules,
 including references whose semicolon may be omitted.
 Inline guidance imports are rejected after punctuation as well as whitespace.
-At-signs inside external URIs (including opaque schemes such as mailto) are excluded
+At-signs inside external URIs (including explicit opaque autolinks such as mailto) are excluded
 per HTML text node, preserving adjacent imports. A colon directly before an import
 does not make that import a URI.
 A closing bracket followed by punctuation and an at-sign terminates a bare URL exclusion.
diff --git a/tools/skills/agent-guidance-markdown.mjs b/tools/skills/agent-guidance-markdown.mjs
index ff3a34754..133a28b52 100644
--- a/tools/skills/agent-guidance-markdown.mjs
+++ b/tools/skills/agent-guidance-markdown.mjs
@@ -147,7 +147,7 @@ export function guidanceProse(markdown) {
             return ' ';
         if (node.nodeName === '#text')
             return node.value.replace(
-                /(?:\b[a-z][a-z\d+.-]*:(?![@\s])|\/\/)[^\s]*?(?=[)\]}>][.,;:!?]*@|\s|$)/giu,
+                /(?:(?<![@/\p{L}\p{N}_])[a-z][a-z\d+.-]*:(?![@\s])|\/\/)[^\s]*?(?=[)\]}>][.,;:!?]*@|\s|$)/giu,
                 ' '
             );
         const content = (node.childNodes ?? []).map(text).join('');
diff --git a/tools/skills/validate-agent-guidance.test.mjs b/tools/skills/validate-agent-guidance.test.mjs
index a463cebbe..d49b97bb3 100644
--- a/tools/skills/validate-agent-guidance.test.mjs
+++ b/tools/skills/validate-agent-guidance.test.mjs
@@ -1507,7 +1507,6 @@ for (const boundary of [').', '];', '}']) {
 
 for (const uri of [
     '<mailto:user@example.com?subject=@docs/guide.md>',
-    'mailto:user@example.com?subject=@docs/guide.md',
     '<urn:example:@docs/guide.md>',
 ]) {
     test(`opaque URI is not a guidance import: ${uri}`, async (t) => {