diff --git a/packages/shared/src/markdownLinks.test.ts b/packages/shared/src/markdownLinks.test.ts
index aba5a74c01d3b..788424168bbe7 100644
--- a/packages/shared/src/markdownLinks.test.ts
+++ b/packages/shared/src/markdownLinks.test.ts
@@ -40,6 +40,13 @@ describe("inlineCodeFilePathCandidate", () => {
     ["/tmp/.../scratchpad/notes.md", null],
     ["~/projects/…/notes.md", null],
     ["src/.../main.ts", null],
+    // regression: #22181 a `:line` suffix does not make an extensionless basename a file
+    ["I/W217:220", null],
+    ["bin/run:12", null],
+    ["docs/README:12", "docs/README:12"],
+    ["./bin/run:12", "./bin/run:12"],
+    ["src/資料.備份:12", "src/資料.備份:12"],
+    ["src/foo.c++:12", "src/foo.c++:12"],
   ])("distinguishes file paths from code and hostnames in %s", (source, candidate) => {
     expect(inlineCodeFilePathCandidate(source)).toBe(candidate);
   });
diff --git a/packages/shared/src/markdownLinks.ts b/packages/shared/src/markdownLinks.ts
index edcc2cc5060d5..b0408486c8f04 100644
--- a/packages/shared/src/markdownLinks.ts
+++ b/packages/shared/src/markdownLinks.ts
@@ -37,6 +37,7 @@ const PATH_SEPARATOR_PATTERN = /[\\/]/;
 const ELIDED_PATH_SEGMENT_PATTERN = /(?:^|[\\/])(?:\.{3,}|…)(?:[\\/]|$)/;
 
 const FILE_EXTENSION_PATTERN = /\.[A-Za-z0-9_-]+$/;
+const ANY_FILE_EXTENSION_PATTERN = /\.[^./\\]+$/;
 const VERSION_SUFFIX_PATTERN = /\d\.\d[^.]*$/;
 const NUMERIC_DOTTED_PATTERN = /^\d+(?:\.\d+)+$/;
 
@@ -200,7 +201,17 @@ export function inlineCodeFilePathCandidate(codeText: string): string | null {
         .split(/[\\/]/)
         .at(-1) ?? "";
     if (VERSION_SUFFIX_PATTERN.test(basename)) return null;
-    if (!hasPosition && !FILE_EXTENSION_PATTERN.test(basename)) return null;
+    if (!FILE_EXTENSION_PATTERN.test(basename)) {
+      if (!hasPosition) return null;
+      // A `:line` suffix alone does not make `I/W217:220` a file reference.
+      if (
+        withoutPosition.includes("/") &&
+        !ANY_FILE_EXTENSION_PATTERN.test(basename) &&
+        !EXTENSIONLESS_FILE_NAMES.has(basename)
+      ) {
+        return null;
+      }
+    }
   }
   return candidate;
 }