diff --git a/packages/server/src/server/file-observer/internal/paths.ts b/packages/server/src/server/file-observer/internal/paths.ts
index 8d75156ca9..fd943e0a72 100644
--- a/packages/server/src/server/file-observer/internal/paths.ts
+++ b/packages/server/src/server/file-observer/internal/paths.ts
@@ -53,7 +53,7 @@ export function createObserverPaths(platform: NodeJS.Platform): ObserverPaths {
     isInside,
     collapse,
     createIgnoreMatcher(roots) {
-      return createPathContainmentMatcher(roots, platform === "win32");
+      return createPathContainmentMatcher({ roots, compareAsWindows: platform === "win32" });
     },
     normalizeIgnoredRoots(root, paths) {
       const inside = paths
diff --git a/packages/server/src/server/git-observation-paths.ts b/packages/server/src/server/git-observation-paths.ts
index e37f0539f9..9516402469 100644
--- a/packages/server/src/server/git-observation-paths.ts
+++ b/packages/server/src/server/git-observation-paths.ts
@@ -81,7 +81,10 @@ export class GitObservationPaths {
         excluded.push(this.windows ? subtree.toLowerCase() : subtree);
       }
     }
-    const isExcluded = createPathContainmentMatcher(excluded, this.windows);
+    const isExcluded = createPathContainmentMatcher({
+      roots: excluded,
+      compareAsWindows: this.windows,
+    });
     return (candidate) => {
       const normalized = this.normalizeEventPath(candidate);
       const comparable = this.windows ? normalized.toLowerCase() : normalized;
diff --git a/packages/server/src/server/workspace-git-service.ts b/packages/server/src/server/workspace-git-service.ts
index 40cc1b5c15..d822447af4 100644
--- a/packages/server/src/server/workspace-git-service.ts
+++ b/packages/server/src/server/workspace-git-service.ts
@@ -2045,10 +2045,10 @@ export class WorkspaceGitServiceImpl implements WorkspaceGitService {
   }
 
   private pruneKnownDirectories(target: WorkingTreeWatchTarget): void {
-    const isIgnored = createPathContainmentMatcher(
-      target.ignoredDirectories,
-      looksLikeDefiniteWindowsPath(target.watchPath),
-    );
+    const isIgnored = createPathContainmentMatcher({
+      roots: target.ignoredDirectories,
+      compareAsWindows: looksLikeDefiniteWindowsPath(target.watchPath),
+    });
     for (const directory of target.knownDirectories) {
       if (isIgnored(directory)) {
         target.knownDirectories.delete(directory);
diff --git a/packages/server/src/utils/path.test.ts b/packages/server/src/utils/path.test.ts
index 34399473c1..318f33e410 100644
--- a/packages/server/src/utils/path.test.ts
+++ b/packages/server/src/utils/path.test.ts
@@ -101,7 +101,10 @@ describe("path equivalence", () => {
 
 describe("indexed path containment", () => {
   test("preserves POSIX case and component boundaries", () => {
-    const matches = createPathContainmentMatcher(["/repo/Build/", "/repo/cache"], false);
+    const matches = createPathContainmentMatcher({
+      roots: ["/repo/Build/", "/repo/cache"],
+      compareAsWindows: false,
+    });
     expect(matches("/repo/Build/nested/file")).toBe(true);
     expect(matches("/repo/cache")).toBe(true);
     expect(matches("/repo/Build-sibling/file")).toBe(false);
@@ -110,10 +113,10 @@ describe("indexed path containment", () => {
   });
 
   test("normalizes Windows case, separators and extended namespaces", () => {
-    const matches = createPathContainmentMatcher(
-      ["C:/Repo/Build", String.raw`\\server\share\cache`],
-      true,
-    );
+    const matches = createPathContainmentMatcher({
+      roots: ["C:/Repo/Build", String.raw`\\server\share\cache`],
+      compareAsWindows: true,
+    });
     expect(matches(String.raw`\\?\C:\REPO\build\file`)).toBe(true);
     expect(matches(String.raw`\\?\UNC\SERVER\SHARE\Cache\file`)).toBe(true);
     expect(matches("C:/Repo/Build-Sibling/file")).toBe(false);
@@ -121,8 +124,14 @@ describe("indexed path containment", () => {
   });
 
   test("handles filesystem roots and empty sets", () => {
-    expect(createPathContainmentMatcher(["/"], false)("/repo/file")).toBe(true);
-    expect(createPathContainmentMatcher(["C:/"], true)("c:/repo/file")).toBe(true);
-    expect(createPathContainmentMatcher([], false)("/repo/file")).toBe(false);
+    expect(
+      createPathContainmentMatcher({ roots: ["/"], compareAsWindows: false })("/repo/file"),
+    ).toBe(true);
+    expect(
+      createPathContainmentMatcher({ roots: ["C:/"], compareAsWindows: true })("c:/repo/file"),
+    ).toBe(true);
+    expect(createPathContainmentMatcher({ roots: [], compareAsWindows: false })("/repo/file")).toBe(
+      false,
+    );
   });
 });
diff --git a/packages/server/src/utils/path.ts b/packages/server/src/utils/path.ts
index d21a6a16ee..b693956047 100644
--- a/packages/server/src/utils/path.ts
+++ b/packages/server/src/utils/path.ts
@@ -72,11 +72,16 @@ export function stopPathContainmentMetrics(): number {
   return checks;
 }
 
+interface PathContainmentOptions {
+  roots: Iterable<string>;
+  compareAsWindows: boolean;
+}
+
 /** Compile lexical subtree membership without scanning unrelated roots per candidate. */
-export function createPathContainmentMatcher(
-  roots: Iterable<string>,
-  compareAsWindows: boolean,
-): (candidate: string) => boolean {
+export function createPathContainmentMatcher({
+  roots,
+  compareAsWindows,
+}: PathContainmentOptions): (candidate: string) => boolean {
   const pathApi = compareAsWindows ? nodePath.win32 : nodePath.posix;
   const indexed = new Set(
     Array.from(roots, (root) => normalizePathForComparison(root, compareAsWindows)),