diff --git a/.configs/vitest.config.mjs b/.configs/vitest.config.mjs
index ce71ffb..e283d93 100644
--- a/.configs/vitest.config.mjs
+++ b/.configs/vitest.config.mjs
@@ -11,6 +11,7 @@
  *	@Copyright: Copyright (c) 2026-2026 Catalyzed Motivation Inc. All rights reserved.
  */
 
+import { fileURLToPath } from "node:url";
 import { defineConfig } from "vitest/config";
 
 /**
@@ -22,6 +23,10 @@ export default defineConfig({
 	test: {
 		environment: "node",
 		include: ["tests/**/*.test.vitest.mjs"],
+		// Wipe the fixture root before/after the run so orphaned fixtures from a
+		// crashed/interrupted run self-heal (see tests/helpers/workspace.mjs).
+		// Absolute path so it resolves regardless of vitest's root.
+		globalSetup: [fileURLToPath(new URL("./vitest.globalSetup.mjs", import.meta.url))],
 		// "dot" keeps CI logs to one character per test file instead of a full
 		// "RUN vX.Y.Z" + per-file pass/fail block for every file — vitest's
 		// non-interactive fallback (no TTY to redraw) otherwise reprints that
diff --git a/.configs/vitest.globalSetup.mjs b/.configs/vitest.globalSetup.mjs
new file mode 100644
index 0000000..d3f8b4c
--- /dev/null
+++ b/.configs/vitest.globalSetup.mjs
@@ -0,0 +1,23 @@
+/**
+ * @fileoverview Vitest global setup for the fix-headers test suite.
+ *
+ * Reaps ONLY stale fixture directories (see reapStaleWorkspaces in
+ * tests/helpers/workspace.mjs) before and after the run, so orphans from a
+ * previously crashed/interrupted run self-heal WITHOUT touching fixtures a
+ * concurrent, still-running suite (another shard, or CI + local at once) is
+ * actively using — those have a fresh mtime and are left alone. Per-test cleanup
+ * (cleanupWorkspace) still handles the happy path; this is the crash-path backstop.
+ * @module fix-headers/vitest-global-setup
+ */
+
+import { reapStaleWorkspaces } from "../tests/helpers/workspace.mjs";
+
+/** Reap orphans left by a prior aborted run (age-guarded). @returns {Promise<void>} */
+export async function setup() {
+	await reapStaleWorkspaces();
+}
+
+/** Reap any now-stale orphans on the way out (never this run's or a peer's live fixtures). @returns {Promise<void>} */
+export async function teardown() {
+	await reapStaleWorkspaces();
+}
diff --git a/tests/helpers/workspace.mjs b/tests/helpers/workspace.mjs
index 4de9a09..aeb8a02 100644
--- a/tests/helpers/workspace.mjs
+++ b/tests/helpers/workspace.mjs
@@ -11,7 +11,7 @@
  *	@Copyright: Copyright (c) 2026-2026 Catalyzed Motivation Inc. All rights reserved.
  */
 
-import { mkdir, rm, writeFile } from "node:fs/promises";
+import { mkdir, readdir, rm, stat, writeFile } from "node:fs/promises";
 import { join, resolve } from "node:path";
 
 /**
@@ -19,6 +19,20 @@ import { join, resolve } from "node:path";
  * @module fix-headers/tests/helpers/workspace
  */
 
+/**
+ * Root for every test fixture: the repo's OWN gitignored `tmp/` directory.
+ * Anchored to this file's location (not `process.cwd()`) so it's cwd-independent.
+ *
+ * Previously this was `join(resolve(process.cwd(), ".."), "tmp-fix-headers-tests")`,
+ * which resolved to the repo's PARENT (the shared repos root). Combined with
+ * unique-per-run names and cleanup that only runs on the happy path, every
+ * failed/interrupted run leaked its fixtures there, sprawling hundreds of orphaned
+ * git repos into the repos root. Keeping fixtures inside the gitignored `tmp/`
+ * contains any leak to a spot that's invisible to git and wiped by cleanup below.
+ * @type {string}
+ */
+export const FIXTURE_ROOT = resolve(import.meta.dirname, "..", "..", "tmp", "fix-headers-tests");
+
 /**
  * Creates an isolated test workspace under the project-local tmp directory.
  * @param {string} name - Workspace name suffix.
@@ -26,7 +40,7 @@ import { join, resolve } from "node:path";
  */
 export async function createWorkspace(name) {
 	const directoryName = `${name}-${Date.now()}-${Math.random().toString(16).slice(2)}`;
-	const workspacePath = join(resolve(process.cwd(), ".."), "tmp-fix-headers-tests", directoryName);
+	const workspacePath = join(FIXTURE_ROOT, directoryName);
 	await mkdir(workspacePath, { recursive: true });
 	return workspacePath;
 }
@@ -53,3 +67,39 @@ export async function writeWorkspaceFile(filePath, content) {
 export async function cleanupWorkspace(workspacePath) {
 	await rm(workspacePath, { recursive: true, force: true });
 }
+
+/**
+ * Reaps only STALE fixture directories under {@link FIXTURE_ROOT} — those whose
+ * mtime is older than `maxAgeMs`. This self-heals orphans from a crashed/interrupted
+ * run WITHOUT deleting fixtures a concurrent, still-running suite is actively using
+ * (an in-flight run's fixtures have a fresh mtime, so they're never reaped). A
+ * whole-root wipe would corrupt overlapping runs — CI + local, or two shards — so
+ * age is the guard. Per-test {@link cleanupWorkspace} still removes each fixture on
+ * the happy path; this is only the backstop for the crash/timeout path.
+ *
+ * The default 1h threshold is far longer than any real run of this suite (seconds)
+ * yet short enough to keep orphans from piling up; override for slower environments.
+ * Missing root and races (a dir removed mid-sweep by another run) are ignored.
+ * @param {number} [maxAgeMs=3600000] - Age past which a fixture counts as orphaned (default 1h).
+ * @returns {Promise<void>} Completion promise.
+ */
+export async function reapStaleWorkspaces(maxAgeMs = 60 * 60 * 1000) {
+	let entries;
+	try {
+		entries = await readdir(FIXTURE_ROOT, { withFileTypes: true });
+	} catch {
+		return; // fixture root doesn't exist yet — nothing to reap
+	}
+	const cutoff = Date.now() - maxAgeMs;
+	await Promise.all(
+		entries.map(async (entry) => {
+			const full = join(FIXTURE_ROOT, entry.name);
+			try {
+				const info = await stat(full);
+				if (info.mtimeMs < cutoff) await rm(full, { recursive: true, force: true });
+			} catch {
+				/* vanished mid-sweep (a concurrent run cleaned it) — fine */
+			}
+		})
+	);
+}