diff --git a/scripts/__tests__/test-changed.test.mjs b/scripts/__tests__/test-changed.test.mjs
index a0c475b51b..3b53873e62 100644
--- a/scripts/__tests__/test-changed.test.mjs
+++ b/scripts/__tests__/test-changed.test.mjs
@@ -46,6 +46,7 @@ import {
   isTestFilePath,
   changedSourceFilesAffectingPackage,
   existingChangedTestFilesInPackage,
+  resolveRepoRoot,
   GATE_COVERED_MEMORY_ENVELOPE_PACKAGES,
   SCOPED_AFFECTED_MEMORY_ENVELOPES,
   CORE_SCOPED_AFFECTED_PACKAGE,
@@ -2032,6 +2033,26 @@ test("existingChangedTestFilesInPackage: default existence root anchors at the g
   assert.deepEqual(existingChangedTestFilesInPackage([selfRel], "scripts"), [selfRel]);
 });
 
+// FNXC:TestInfrastructure 2026-06-26-14:40: regression for the "subdirectory runs
+// skip" bug — rootDir (which drives ALL workspace discovery) must resolve to the
+// git toplevel, not process.cwd(), so a run launched from a package subdir without
+// FUSION_PROJECT_DIR still finds the workspace instead of exiting through the gate.
+test("resolveRepoRoot: honors FUSION_PROJECT_DIR else resolves the git toplevel (cwd-independent)", () => {
+  const saved = process.env.FUSION_PROJECT_DIR;
+  try {
+    process.env.FUSION_PROJECT_DIR = path.join(path.sep, "explicit", "root");
+    assert.equal(resolveRepoRoot(), path.resolve(path.join(path.sep, "explicit", "root")));
+    delete process.env.FUSION_PROJECT_DIR;
+    const top = resolveRepoRoot();
+    assert.ok(path.isAbsolute(top), "toplevel must be absolute");
+    // The resolved root must contain this workspace (cwd-independent), not a subdir.
+    assert.ok(existsSync(path.join(top, "scripts/test-changed.mjs")), "resolved root must be the repo root");
+  } finally {
+    if (saved === undefined) delete process.env.FUSION_PROJECT_DIR;
+    else process.env.FUSION_PROJECT_DIR = saved;
+  }
+});
+
 // FNXC:TestInfrastructure 2026-06-26-09:15: the merge gate re-covers a delegated
 // engine lane (curated engine-core subset) but runs NO dashboard tests. Lock that
 // asymmetry so the delegation messaging never overclaims dashboard gate coverage.
diff --git a/scripts/test-changed.mjs b/scripts/test-changed.mjs
index d5dcc86dc4..741708d282 100644
--- a/scripts/test-changed.mjs
+++ b/scripts/test-changed.mjs
@@ -96,9 +96,31 @@ function parseWorkspacePackagesFromYaml(rawYaml) {
   return packages;
 }
 
-const rootDir = process.env.FUSION_PROJECT_DIR
-  ? path.resolve(process.env.FUSION_PROJECT_DIR)
-  : process.cwd();
+/*
+FNXC:TestInfrastructure 2026-06-26-14:40:
+This is a workspace-wide test runner: it MUST anchor at the repo root, not the
+cwd. If launched from a package subdirectory without FUSION_PROJECT_DIR, a bare
+`process.cwd()` root made workspace discovery (readWorkspacePatterns /
+listWorkspacePackageInfos / packageHasVitestConfig) find no packages, so
+decideExecutionPlan saw "no affected package", ran only the gate, and exited
+SUCCESSFULLY without running the live changed package tests (greptile). Resolve
+the git toplevel as the fallback so every cwd inside the repo (including a git
+worktree, which is how the engine runs per-task verification) resolves to the
+correct root. FUSION_PROJECT_DIR remains the explicit override; fall back to cwd
+only when git can't report a toplevel (e.g. not a repo).
+*/
+export function resolveRepoRoot() {
+  if (process.env.FUSION_PROJECT_DIR) return path.resolve(process.env.FUSION_PROJECT_DIR);
+  try {
+    const r = spawnSync("git", ["rev-parse", "--show-toplevel"], { encoding: "utf8" });
+    const top = r.status === 0 ? (r.stdout ?? "").trim() : "";
+    if (top) return top;
+  } catch {
+    // git unavailable / not a repo — fall through to cwd
+  }
+  return process.cwd();
+}
+const rootDir = resolveRepoRoot();
 
 /** @type {string} Cache format version — bump when the shape or hash inputs change. */
 const CACHE_FORMAT_VERSION = 1;
@@ -1480,25 +1502,14 @@ handing Vitest an empty/garbage positional set.
  * @returns {string[]}
  */
 /*
-FNXC:TestInfrastructure 2026-06-26-13:40:
-Existence checks for changed test files must anchor at the GIT REPO ROOT, not
-`rootDir` (which falls back to `process.cwd()`). `git diff --name-only` returns
-repo-root-relative paths regardless of the cwd it runs from, so joining them
-against a `rootDir` that is a package SUBDIR (script run from a package without
-FUSION_PROJECT_DIR) would form a doubled path (packages/x/packages/x/...), make
-`existsSync` false, and silently DROP live changed tests into the delegate path.
-Resolve the toplevel once via git so the check is correct from any cwd inside the
-repo; fall back to rootDir if git can't report a toplevel.
+FNXC:TestInfrastructure 2026-06-26-14:40:
+Existence checks for changed test files join repo-root-relative `git diff` paths
+against `projectRoot` (default `rootDir`). `rootDir` is now resolved to the git
+toplevel (see resolveRepoRoot above), so this is correct from any cwd inside the
+repo — no doubled path, no silently-dropped live test. Deleted/renamed-away test
+paths correctly fail existsSync and fall into the delegate-to-gate path.
 */
-let _repoToplevelCache;
-function repoRootForExistence() {
-  if (_repoToplevelCache !== undefined) return _repoToplevelCache;
-  const top = gitOutput(["rev-parse", "--show-toplevel"]);
-  _repoToplevelCache = top && top.trim() ? top.trim() : rootDir;
-  return _repoToplevelCache;
-}
-
-export function existingChangedTestFilesInPackage(changedFiles, pkgDir, { projectRoot = repoRootForExistence() } = {}) {
+export function existingChangedTestFilesInPackage(changedFiles, pkgDir, { projectRoot = rootDir } = {}) {
   return (changedFiles ?? []).filter(
     (file) =>
       isTestFilePath(file) &&