diff --git a/apps/desktop/README.md b/apps/desktop/README.md
index ac980b5e81..db89247542 100644
--- a/apps/desktop/README.md
+++ b/apps/desktop/README.md
@@ -60,10 +60,12 @@ signature seal. Write access to this repository is therefore a deliberate trust
 assumption of the development workflow — a separate matter from who may claim
 the bundle's identity.
 
-The default profile is `~/Library/Application Support/Maka Dev-<worktree-id>`,
-which keeps development isolated from the packaged Maka profile; an explicit
-`--user-data-dir` takes precedence. Shutdown matches this worktree's own bundle
-path, so a concurrent worktree's app is unaffected. Because that lock is keyed
+The default profile is `~/Library/Application Support/Maka Dev`, which keeps
+development isolated from the packaged Maka profile and is shared by the
+repository CLI (`npm run cli:dev`), the plain dev build, and the TCC dev build;
+an explicit `--user-data-dir` takes precedence. Shutdown matches this worktree's
+own bundle path, so a concurrent worktree's app survives — and then holds the
+single-instance lock for the shared profile. Because that lock is keyed
 on the profile, a launch first reclaims any app left over from a hard-killed
 session — otherwise the stale app would absorb the new launch and keep showing
 its old, dead Vite URL.
diff --git a/apps/desktop/scripts/dev-app-runtime.mjs b/apps/desktop/scripts/dev-app-runtime.mjs
index 2db7ddfc2f..bacdd08c8f 100644
--- a/apps/desktop/scripts/dev-app-runtime.mjs
+++ b/apps/desktop/scripts/dev-app-runtime.mjs
@@ -45,12 +45,13 @@ const MARKER = join(DEV_RUNTIME_DIR, 'runtime.json');
 const ELECTRON_PACKAGE = join(REPO_ROOT, 'node_modules', 'electron', 'package.json');
 const SOURCE_APP = join(REPO_ROOT, 'node_modules', 'electron', 'dist', 'Electron.app');
 const WORKTREE_ID = createHash('sha256').update(REPO_ROOT).digest('hex').slice(0, 12);
-const DEV_USER_DATA_DIR = join(
-  homedir(),
-  'Library',
-  'Application Support',
-  `Maka Dev-${WORKTREE_ID}`,
-);
+// Deliberately NOT worktree-scoped, unlike the bundle identifier above: the
+// profile is what `app.setName('Maka Dev')` already yields on the plain
+// `npm run dev` path and what `npm run cli:dev` writes to, so scoping it here
+// would only mean that turning MAKA_DEV_TCC on silently switched the
+// developer's database. TCC isolation is provided by DEV_BUNDLE_ID, not by the
+// data root. An explicit `--user-data-dir=` still takes precedence.
+const DEV_USER_DATA_DIR = join(homedir(), 'Library', 'Application Support', 'Maka Dev');
 
 /**
  * Per-worktree, and deliberately so. An ad-hoc signature designates a bare
@@ -484,6 +485,9 @@ export function createRuntimeMarker(electronVersion) {
     electronVersion,
     bundleId: DEV_BUNDLE_ID,
     desktopDir: DESKTOP_DIR,
+    // Burned into the generated bootstrap, so a change here must invalidate
+    // the cached bundle (isDevelopmentRuntimeCurrent compares every field).
+    userDataDir: DEV_USER_DATA_DIR,
   };
 }