From 25663ed00fbe7e93cffb3295d7f8a217d5242ef3 Mon Sep 17 00:00:00 2001
From: r4iju <5772718+r4iju@users.noreply.github.com>
Date: Fri, 16 Oct 2026 12:46:02 +0900
Subject: [PATCH] fix(web): diffs that turn a file into a folder no longer
 crash the file tree

A diff that deletes a file (often a symlink) and adds files under the same
path as a folder handed Pierre's tree both a file and a directory at one
path, and resetPaths threw "Path collides with an existing file".

The tree now leaves out the replaced file; the folder's files carry the
change, and the diff body still shows the deletion.
---
 .../components/diffs/diffFileTree.logic.test.ts   | 15 +++++++++++++++
 .../src/components/diffs/diffFileTree.logic.ts    |  8 +++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/apps/web/src/components/diffs/diffFileTree.logic.test.ts b/apps/web/src/components/diffs/diffFileTree.logic.test.ts
index 170e84308069..f7d62350f575 100644
--- a/apps/web/src/components/diffs/diffFileTree.logic.test.ts
+++ b/apps/web/src/components/diffs/diffFileTree.logic.test.ts
@@ -51,6 +51,21 @@ describe("diffFileTreeEntries", () => {
   });
 });
 
+describe("diffFileTreeEntries", () => {
+  it("drops a file whose path became a directory in the same diff", () => {
+    const entries = diffFileTreeEntries([
+      file("deleted", "skills/react-composition"),
+      file("new", "skills/react-composition/SKILL.md"),
+      file("new", "skills/other.md"),
+    ]);
+    expect(entries).toEqual([
+      { path: "skills/react-composition/SKILL.md", status: "added" },
+      { path: "skills/other.md", status: "added" },
+    ]);
+    expect(() => preloadFileTree({ paths: entries.map((entry) => entry.path) })).not.toThrow();
+  });
+});
+
 describe("collectDirectoryPaths", () => {
   it("lists every ancestor once, parents first, with Pierre's trailing slash", () => {
     expect(collectDirectoryPaths(["apps/web/src/a.ts", "apps/web/b.ts", "README.md"])).toEqual([
diff --git a/apps/web/src/components/diffs/diffFileTree.logic.ts b/apps/web/src/components/diffs/diffFileTree.logic.ts
index b727c3ee3ffb..b14fc434e92f 100644
--- a/apps/web/src/components/diffs/diffFileTree.logic.ts
+++ b/apps/web/src/components/diffs/diffFileTree.logic.ts
@@ -27,6 +27,9 @@ function toGitStatus(file: FileDiffMetadata): GitStatus {
  * Maps parsed diff files to tree entries, keeping the diff's own order. A path
  * appears once: a type change (regular file to symlink) is a deletion plus an
  * addition of the same path, and the tree shows the surviving file as modified.
+ *
+ * A file whose path is also a directory in the same diff (a file or symlink replaced by a
+ * folder) is left out: the tree cannot hold both, and the folder's files carry the change.
  */
 export function diffFileTreeEntries(
   files: ReadonlyArray<FileDiffMetadata>,
@@ -38,7 +41,10 @@ export function diffFileTreeEntries(
     const previous = statusByPath.get(path);
     statusByPath.set(path, previous === undefined || previous === status ? status : "modified");
   }
-  return [...statusByPath].map(([path, status]) => ({ path, status }));
+  const directories = new Set(collectDirectoryPaths([...statusByPath.keys()]));
+  return [...statusByPath]
+    .filter(([path]) => !directories.has(`${path}/`))
+    .map(([path, status]) => ({ path, status }));
 }
 
 /**