From 1de78f855f11b39f07db4aa9000945d539bde95d Mon Sep 17 00:00:00 2001
From: Nexus Dev <nexus@local>
Date: Sat, 11 Apr 2026 11:11:06 +0000
Subject: [PATCH] fix(nexus): tighten settings-route guard in ModeBreadcrumb
 (phase 8)

Code-quality review for Task 2 caught a startsWith false-positive:
`/instance/settings-foo` was matching the settings branch of
deriveBreadcrumbSegments and producing nonsense output like
["SETTINGS", "-FOO"]. Tightened the guard to require an exact
match or a literal trailing slash before entering the settings
branch.

Added three test cases to lock it in:
  - /instance/settings (exact, no trailing) -> ["SETTINGS"]
  - /instance/settings-foo -> ["HOME"]
  - /instance/settings-foo/bar -> ["HOME"]

22 tests pass. No behavior change for any previously-tested path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 ui/src/components/frame/ModeBreadcrumb.test.tsx | 3 +++
 ui/src/components/frame/ModeBreadcrumb.tsx      | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/ui/src/components/frame/ModeBreadcrumb.test.tsx b/ui/src/components/frame/ModeBreadcrumb.test.tsx
index 735b731b..68b28768 100644
--- a/ui/src/components/frame/ModeBreadcrumb.test.tsx
+++ b/ui/src/components/frame/ModeBreadcrumb.test.tsx
@@ -38,6 +38,9 @@ describe("deriveBreadcrumbSegments", () => {
     ["/NEX/routines", ["PROJECTS"]],
     ["/instance/settings/general", ["SETTINGS"]],
     ["/instance/settings/integrations", ["SETTINGS", "INTEGRATIONS"]],
+    ["/instance/settings", ["SETTINGS"]],
+    ["/instance/settings-foo", ["HOME"]],
+    ["/instance/settings-foo/bar", ["HOME"]],
     ["/", ["HOME"]],
     ["/unknown/path", ["HOME"]],
   ])("maps %s to %o", (input, expected) => {
diff --git a/ui/src/components/frame/ModeBreadcrumb.tsx b/ui/src/components/frame/ModeBreadcrumb.tsx
index 2112b992..237f7275 100644
--- a/ui/src/components/frame/ModeBreadcrumb.tsx
+++ b/ui/src/components/frame/ModeBreadcrumb.tsx
@@ -21,7 +21,7 @@ import { cn } from "@/lib/utils";
  */
 export function deriveBreadcrumbSegments(pathname: string): string[] {
   // /instance/settings/...
-  if (pathname.startsWith("/instance/settings")) {
+  if (pathname === "/instance/settings" || pathname.startsWith("/instance/settings/")) {
     const rest = pathname.replace(/^\/instance\/settings\/?/, "");
     if (!rest) return ["SETTINGS"];
     const leaf = rest.split("/")[0] ?? "";