From 59986ae7bf0d1dc46b8a4e6d3f2f958e9101c19a Mon Sep 17 00:00:00 2001
From: Aditya kumar singh <143548997+Adityakk9031@users.noreply.github.com>
Date: Sun, 12 Jul 2026 16:47:02 +0530
Subject: [PATCH 1/4] fix(lint): resolve snippet typechecking failures on
 Windows due to mixed path separators

---
 packages/leadtype/src/lint/snippet-typecheck.ts | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/packages/leadtype/src/lint/snippet-typecheck.ts b/packages/leadtype/src/lint/snippet-typecheck.ts
index 6af71669..aee5624a 100644
--- a/packages/leadtype/src/lint/snippet-typecheck.ts
+++ b/packages/leadtype/src/lint/snippet-typecheck.ts
@@ -3,6 +3,7 @@ import { resolve } from "node:path";
 import type { Root } from "mdast";
 import type * as TS from "typescript";
 import { visit } from "unist-util-visit";
+import { normalizeDocsPath } from "../internal/docs-url";
 import { loadTypeScript } from "./snippet-lint";
 
 /**
@@ -229,7 +230,7 @@ export function typecheckSnippets(
   for (const [index, snippet] of options.snippets.entries()) {
     const virtualDir = `${projectRoot}/.leadtype-snippet-${index}`;
     for (const file of toVirtualFiles(snippet, virtualDir)) {
-      virtualFiles.set(file.path, file);
+      virtualFiles.set(normalizeDocsPath(file.path), file);
     }
   }
 
@@ -245,16 +246,17 @@ export function typecheckSnippets(
   const baseGetSourceFile = host.getSourceFile.bind(host);
   const baseDirectoryExists = host.directoryExists?.bind(host);
   host.fileExists = (fileName) =>
-    virtualFiles.has(fileName) || baseFileExists(fileName);
+    virtualFiles.has(normalizeDocsPath(fileName)) || baseFileExists(fileName);
   host.readFile = (fileName) =>
-    virtualFiles.get(fileName)?.content ?? baseReadFile(fileName);
+    virtualFiles.get(normalizeDocsPath(fileName))?.content ??
+    baseReadFile(fileName);
   // Module resolution probes the containing directory; virtual dirs never
   // exist on disk, so sibling imports (`./helpers`) need this to resolve.
   host.directoryExists = (directoryName) =>
-    virtualDirs.has(directoryName) ||
+    virtualDirs.has(normalizeDocsPath(directoryName)) ||
     (baseDirectoryExists?.(directoryName) ?? false);
   host.getSourceFile = (fileName, languageVersion, ...rest) => {
-    const virtual = virtualFiles.get(fileName);
+    const virtual = virtualFiles.get(normalizeDocsPath(fileName));
     if (virtual) {
       return ts.createSourceFile(fileName, virtual.content, languageVersion);
     }
@@ -287,7 +289,9 @@ export function typecheckSnippets(
       continue;
     }
     const fileName = diagnostic.file?.fileName;
-    const virtual = fileName ? virtualFiles.get(fileName) : undefined;
+    const virtual = fileName
+      ? virtualFiles.get(normalizeDocsPath(fileName))
+      : undefined;
     if (!virtual) {
       continue; // diagnostics from real project files aren't lint's business
     }

From e1062ea68f3a707e902807d79446c5ebbb981532 Mon Sep 17 00:00:00 2001
From: Aditya kumar singh <143548997+Adityakk9031@users.noreply.github.com>
Date: Sun, 12 Jul 2026 18:22:26 +0530
Subject: [PATCH 2/4] refactor(lint): use local toPosixPath helper and add
 regression test

---
 .../src/lint/snippet-typecheck.test.ts         |  9 +++++++++
 .../leadtype/src/lint/snippet-typecheck.ts     | 18 ++++++++++--------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/packages/leadtype/src/lint/snippet-typecheck.test.ts b/packages/leadtype/src/lint/snippet-typecheck.test.ts
index 789343a0..63caf023 100644
--- a/packages/leadtype/src/lint/snippet-typecheck.test.ts
+++ b/packages/leadtype/src/lint/snippet-typecheck.test.ts
@@ -3,6 +3,7 @@ import { tmpdir } from "node:os";
 import path from "node:path";
 import { afterEach, describe, expect, it } from "vitest";
 import { lintDocs } from "./runner";
+import { toPosixPath } from "./snippet-typecheck";
 
 const tempDirs: string[] = [];
 
@@ -188,4 +189,12 @@ describe("snippet typechecking", () => {
     );
     expect(violations).toEqual([]);
   });
+
+  describe("toPosixPath", () => {
+    it("converts Windows backslash paths to POSIX forward slash paths", () => {
+      expect(
+        toPosixPath("C:\\project\\root\\.leadtype-snippet-0\\main.ts")
+      ).toBe("C:/project/root/.leadtype-snippet-0/main.ts");
+    });
+  });
 });
diff --git a/packages/leadtype/src/lint/snippet-typecheck.ts b/packages/leadtype/src/lint/snippet-typecheck.ts
index aee5624a..49268ab3 100644
--- a/packages/leadtype/src/lint/snippet-typecheck.ts
+++ b/packages/leadtype/src/lint/snippet-typecheck.ts
@@ -3,7 +3,6 @@ import { resolve } from "node:path";
 import type { Root } from "mdast";
 import type * as TS from "typescript";
 import { visit } from "unist-util-visit";
-import { normalizeDocsPath } from "../internal/docs-url";
 import { loadTypeScript } from "./snippet-lint";
 
 /**
@@ -218,6 +217,10 @@ function isUnresolvedPackageImport(
   return !(specifier.startsWith(".") || specifier.startsWith("/"));
 }
 
+export function toPosixPath(filePath: string): string {
+  return filePath.replace(/\\/g, "/");
+}
+
 export function typecheckSnippets(
   options: TypecheckSnippetsOptions
 ): SnippetTypecheckIssue[] {
@@ -230,7 +233,7 @@ export function typecheckSnippets(
   for (const [index, snippet] of options.snippets.entries()) {
     const virtualDir = `${projectRoot}/.leadtype-snippet-${index}`;
     for (const file of toVirtualFiles(snippet, virtualDir)) {
-      virtualFiles.set(normalizeDocsPath(file.path), file);
+      virtualFiles.set(toPosixPath(file.path), file);
     }
   }
 
@@ -246,17 +249,16 @@ export function typecheckSnippets(
   const baseGetSourceFile = host.getSourceFile.bind(host);
   const baseDirectoryExists = host.directoryExists?.bind(host);
   host.fileExists = (fileName) =>
-    virtualFiles.has(normalizeDocsPath(fileName)) || baseFileExists(fileName);
+    virtualFiles.has(toPosixPath(fileName)) || baseFileExists(fileName);
   host.readFile = (fileName) =>
-    virtualFiles.get(normalizeDocsPath(fileName))?.content ??
-    baseReadFile(fileName);
+    virtualFiles.get(toPosixPath(fileName))?.content ?? baseReadFile(fileName);
   // Module resolution probes the containing directory; virtual dirs never
   // exist on disk, so sibling imports (`./helpers`) need this to resolve.
   host.directoryExists = (directoryName) =>
-    virtualDirs.has(normalizeDocsPath(directoryName)) ||
+    virtualDirs.has(toPosixPath(directoryName)) ||
     (baseDirectoryExists?.(directoryName) ?? false);
   host.getSourceFile = (fileName, languageVersion, ...rest) => {
-    const virtual = virtualFiles.get(normalizeDocsPath(fileName));
+    const virtual = virtualFiles.get(toPosixPath(fileName));
     if (virtual) {
       return ts.createSourceFile(fileName, virtual.content, languageVersion);
     }
@@ -290,7 +292,7 @@ export function typecheckSnippets(
     }
     const fileName = diagnostic.file?.fileName;
     const virtual = fileName
-      ? virtualFiles.get(normalizeDocsPath(fileName))
+      ? virtualFiles.get(toPosixPath(fileName))
       : undefined;
     if (!virtual) {
       continue; // diagnostics from real project files aren't lint's business

From 4d861f59e10838db18f7edd90f4f788a3cc23a52 Mon Sep 17 00:00:00 2001
From: Aditya kumar singh <143548997+Adityakk9031@users.noreply.github.com>
Date: Sun, 12 Jul 2026 22:09:31 +0530
Subject: [PATCH 3/4] test(lint): add integration regression test for Windows
 path separator check

---
 .../src/lint/snippet-typecheck.test.ts        | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/packages/leadtype/src/lint/snippet-typecheck.test.ts b/packages/leadtype/src/lint/snippet-typecheck.test.ts
index 63caf023..fb3fde7a 100644
--- a/packages/leadtype/src/lint/snippet-typecheck.test.ts
+++ b/packages/leadtype/src/lint/snippet-typecheck.test.ts
@@ -190,6 +190,34 @@ describe("snippet typechecking", () => {
     expect(violations).toEqual([]);
   });
 
+  it("catches typecheck errors when projectRoot contains Windows-style backslashes (Windows regression integration test)", async () => {
+    const { projectRoot, srcDir } = await createTypecheckProject();
+
+    // Create a path containing backslashes to simulate a Windows environment path separator mismatch
+    const backslashedProjectRoot = `${projectRoot}${path.sep}subdir\\subsubdir`;
+
+    const violations = await lintWithTypecheck(
+      backslashedProjectRoot,
+      srcDir,
+      [
+        "```ts",
+        "// @check",
+        'const x: number = "this is a string";',
+        "```",
+        "",
+      ].join("\n")
+    );
+
+    // This should successfully detect the type error
+    expect(violations).toEqual([
+      expect.objectContaining({
+        rule: "snippet:types",
+        severity: "error",
+        message: expect.stringContaining("string"),
+      }),
+    ]);
+  });
+
   describe("toPosixPath", () => {
     it("converts Windows backslash paths to POSIX forward slash paths", () => {
       expect(

From 1c15bd014521d5bb91d86e80cf78dc67ad53d814 Mon Sep 17 00:00:00 2001
From: Kaylee <65376239+KayleeWilliams@users.noreply.github.com>
Date: Wed, 15 Jul 2026 11:03:55 +0100
Subject: [PATCH 4/4] chore: add changeset for Windows snippet typechecking fix

---
 .changeset/calm-paths-agree.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/calm-paths-agree.md

diff --git a/.changeset/calm-paths-agree.md b/.changeset/calm-paths-agree.md
new file mode 100644
index 00000000..3bf24900
--- /dev/null
+++ b/.changeset/calm-paths-agree.md
@@ -0,0 +1,5 @@
+---
+"leadtype": patch
+---
+
+Fix snippet typechecking on Windows by normalizing virtual file paths before TypeScript compiler host lookups.