diff --git a/.github/workflows/regression.yml b/.github/workflows/regression.yml
index 007eac30c7..6388c912d2 100644
--- a/.github/workflows/regression.yml
+++ b/.github/workflows/regression.yml
@@ -8,6 +8,12 @@ permissions:
 env:
   HYPERFRAMES_NO_TELEMETRY: "1"
 
+# Graphite can update a branch and its PR base separately for the same head
+# SHA. Keep only the newest expensive regression run for each PR/ref.
+concurrency:
+  group: regression-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 on:
   pull_request:
   push:
@@ -111,7 +117,10 @@ jobs:
           load: true
           tags: hyperframes-producer:test
           cache-from: type=gha,scope=regression-test-image
-          cache-to: type=gha,mode=max,scope=regression-test-image
+          # PR matrices can fan out across many stacked branches at once. Let
+          # them consume the shared cache, but keep a single writer on main so
+          # concurrent exports cannot exhaust the Actions cache service.
+          cache-to: ${{ github.event_name == 'push' && 'type=gha,mode=max,scope=regression-test-image' || '' }}
 
       - name: "Run regression shard: ${{ matrix.shard }}"
         run: |
diff --git a/lefthook.yml b/lefthook.yml
index ac248273b5..3477e0df44 100644
--- a/lefthook.yml
+++ b/lefthook.yml
@@ -38,6 +38,11 @@ pre-commit:
       # split paths containing spaces. It skips files under the limit, anything
       # routed through LFS, and registry/ assets. Tune via HF_MAX_NONLFS_KB.
       run: ./scripts/check-large-files.sh
+    tracked-artifacts:
+      # Keep ignored dependency trees and platform metadata out of commits.
+      # `git ls-files` observes the staged index, so staged removals pass and
+      # an accidental force-add fails before the commit is created.
+      run: bun run check:tracked-artifacts
     filesize:
       # Scoped to packages/studio — the 600 LOC limit is a studio architecture
       # standard enforced as part of the App.tsx decomposition work. Player and
diff --git a/package.json b/package.json
index 33b4b16ce2..5535bb035e 100644
--- a/package.json
+++ b/package.json
@@ -24,15 +24,16 @@
     "changelog:weekly": "tsx scripts/changelog-weekly.ts",
     "sync-schemas": "tsx scripts/sync-schemas.ts",
     "sync-schemas:check": "tsx scripts/sync-schemas.ts --check",
-    "lint": "oxlint . && tsx scripts/lint-skills.ts",
+    "lint": "bun run check:tracked-artifacts && oxlint . && tsx scripts/lint-skills.ts",
     "lint:skills": "tsx scripts/lint-skills.ts",
     "lint:fix": "oxlint --fix .",
+    "check:tracked-artifacts": "node scripts/check-tracked-artifacts.mjs",
     "format": "oxfmt .",
     "test": "bun run --filter '*' test",
     "player:perf": "bun run --filter @hyperframes/player perf",
     "format:check": "oxfmt --check .",
     "knip": "knip",
-    "test:scripts": "node --import tsx --test scripts/validate-release-channel.test.mjs scripts/draft-changelog.test.ts scripts/set-version.test.ts scripts/release-prepare.test.ts scripts/cli-options.test.ts scripts/changelog-weekly.test.ts scripts/claude-plugin-compression.test.ts scripts/verify-packed-manifests.test.mjs",
+    "test:scripts": "node --import tsx --test scripts/check-tracked-artifacts.test.mjs scripts/validate-release-channel.test.mjs scripts/draft-changelog.test.ts scripts/set-version.test.ts scripts/release-prepare.test.ts scripts/cli-options.test.ts scripts/changelog-weekly.test.ts scripts/claude-plugin-compression.test.ts scripts/verify-packed-manifests.test.mjs",
     "test:skills": "node --test 'skills/**/*.test.mjs'",
     "generate:previews": "tsx scripts/generate-template-previews.ts",
     "generate:catalog-previews": "tsx scripts/generate-catalog-previews.ts",
diff --git a/packages/producer/.DS_Store b/packages/producer/.DS_Store
deleted file mode 100644
index 277ac7d4c4..0000000000
Binary files a/packages/producer/.DS_Store and /dev/null differ
diff --git a/packages/producer/tests/.DS_Store b/packages/producer/tests/.DS_Store
deleted file mode 100644
index cb1dcac253..0000000000
Binary files a/packages/producer/tests/.DS_Store and /dev/null differ
diff --git a/packages/producer/tests/style-1-prod/.DS_Store b/packages/producer/tests/style-1-prod/.DS_Store
deleted file mode 100644
index 9a874b5768..0000000000
Binary files a/packages/producer/tests/style-1-prod/.DS_Store and /dev/null differ
diff --git a/scripts/check-tracked-artifacts.mjs b/scripts/check-tracked-artifacts.mjs
new file mode 100644
index 0000000000..eba42909b4
--- /dev/null
+++ b/scripts/check-tracked-artifacts.mjs
@@ -0,0 +1,48 @@
+import { spawnSync } from "node:child_process";
+import { resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const FORBIDDEN_BASENAMES = new Set([".DS_Store"]);
+
+export function isForbiddenTrackedPath(filePath) {
+  const normalized = filePath.replaceAll("\\", "/");
+  const segments = normalized.split("/");
+  return segments.includes("node_modules") || FORBIDDEN_BASENAMES.has(segments.at(-1));
+}
+
+export function findForbiddenTrackedPaths(filePaths) {
+  return filePaths.filter(isForbiddenTrackedPath).sort();
+}
+
+export function readTrackedPaths(cwd = process.cwd()) {
+  const result = spawnSync("git", ["ls-files", "-z"], {
+    cwd,
+    encoding: "utf8",
+    maxBuffer: 16 * 1024 * 1024,
+  });
+  if (result.error) throw result.error;
+  if (result.status !== 0) {
+    throw new Error(result.stderr.trim() || `git ls-files exited with status ${result.status}`);
+  }
+  return result.stdout.split("\0").filter(Boolean);
+}
+
+export function checkTrackedArtifacts(cwd = process.cwd()) {
+  return findForbiddenTrackedPaths(readTrackedPaths(cwd));
+}
+
+function main() {
+  const forbidden = checkTrackedArtifacts();
+  if (forbidden.length === 0) {
+    console.log("Tracked artifact check passed.");
+    return;
+  }
+
+  console.error("Forbidden generated artifacts are tracked by Git:");
+  for (const filePath of forbidden) console.error(`- ${filePath}`);
+  console.error("Remove these paths from the index; .gitignore already excludes them.");
+  process.exitCode = 1;
+}
+
+const entryPath = process.argv[1] ? resolve(process.argv[1]) : null;
+if (entryPath === fileURLToPath(import.meta.url)) main();
diff --git a/scripts/check-tracked-artifacts.test.mjs b/scripts/check-tracked-artifacts.test.mjs
new file mode 100644
index 0000000000..4b9543c242
--- /dev/null
+++ b/scripts/check-tracked-artifacts.test.mjs
@@ -0,0 +1,32 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { findForbiddenTrackedPaths, isForbiddenTrackedPath } from "./check-tracked-artifacts.mjs";
+
+describe("tracked artifact check", () => {
+  it("rejects node_modules at any directory depth", () => {
+    assert.equal(isForbiddenTrackedPath("node_modules/pkg/index.js"), true);
+    assert.equal(isForbiddenTrackedPath("packages/producer/node_modules/pkg"), true);
+    assert.equal(isForbiddenTrackedPath("packages\\producer\\node_modules\\pkg"), true);
+  });
+
+  it("rejects platform metadata by basename", () => {
+    assert.equal(isForbiddenTrackedPath(".DS_Store"), true);
+    assert.equal(isForbiddenTrackedPath("packages/producer/tests/.DS_Store"), true);
+  });
+
+  it("does not reject similarly named source paths", () => {
+    assert.equal(isForbiddenTrackedPath("docs/node_modules-policy.md"), false);
+    assert.equal(isForbiddenTrackedPath("packages/producer/src/DS_Store.ts"), false);
+  });
+
+  it("returns a deterministic sorted list", () => {
+    assert.deepEqual(
+      findForbiddenTrackedPaths([
+        "packages/z/.DS_Store",
+        "packages/producer/src/index.ts",
+        "packages/a/node_modules/pkg",
+      ]),
+      ["packages/a/node_modules/pkg", "packages/z/.DS_Store"],
+    );
+  });
+});