diff --git a/.gitattributes b/.gitattributes
index 147b6c96..205d162b 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -4,3 +4,6 @@
 # anything nested. Together they exclude all 3 bundles from language stats.
 backend/mcp-bundles/* linguist-vendored
 backend/mcp-bundles/**/* linguist-vendored
+
+# Source-pin tests read files and match on \n; a Windows checkout with autocrlf turned every one red. LF everywhere, on every OS.
+* text=auto eol=lf
diff --git a/.github/workflows/suites-matrix.yml b/.github/workflows/suites-matrix.yml
index 7050001d..4a42050a 100644
--- a/.github/workflows/suites-matrix.yml
+++ b/.github/workflows/suites-matrix.yml
@@ -11,7 +11,8 @@ on:
 
 concurrency:
   group: suites-matrix-${{ github.ref }}
-  cancel-in-progress: true
+  # A run in flight keeps its verdicts; a push mid-run queues behind it instead of cancelling the Mac legs.
+  cancel-in-progress: false
 
 permissions:
   contents: read
@@ -27,6 +28,8 @@ jobs:
     env:
       OSW_NEVER_KILL_ROUTER: '1'
       OSW_DISABLE_AUTO_RESUME: '1'
+      # The packaged app spawns its backend with PYTHONUTF8=1 (electron/main.js); the suite runs the way the product runs, or Windows' cp1252 default fails collection on the first source read.
+      PYTHONUTF8: '1'
       CSC_IDENTITY_AUTO_DISCOVERY: 'false'
     steps:
       - uses: actions/checkout@v4
diff --git a/electron/affiliateTracking.test.js b/electron/affiliateTracking.test.js
index cd809311..fd22d96c 100644
--- a/electron/affiliateTracking.test.js
+++ b/electron/affiliateTracking.test.js
@@ -630,9 +630,13 @@ test("poll loop respects max attempts and gives up", async () => {
     isPackaged: true,
   });
 
-  // Wait long enough for all attempts to fail. 20ms × 30 = 600ms.
-  await delay(900);
-  const state = readJson(path.join(userDataDir, "install.json"));
+  // Wait for the loop to record its last attempt, not for a clock: a fixed 900ms saw 29 of 30 on a loaded Mac.
+  let state = {};
+  for (let i = 0; i < 200; i++) {
+    state = readJson(path.join(userDataDir, "install.json"));
+    if (state.attempts === 30) break;
+    await delay(50);
+  }
   assert.equal(state.ref, null, "no ref after exhausted polls");
   assert.equal(state.attempts, 30, "all attempts recorded");
 });
diff --git a/electron/backendSpawnUtf8.test.js b/electron/backendSpawnUtf8.test.js
new file mode 100644
index 00000000..7cf66261
--- /dev/null
+++ b/electron/backendSpawnUtf8.test.js
@@ -0,0 +1,13 @@
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('fs');
+const path = require('path');
+
+// 46 reads in backend/apps open text files without naming an encoding; on Windows the default is
+// cp1252 and the first non-Latin byte raises. The packaged spawn declares UTF-8, and the CI suites
+// run under the same declaration (suites-matrix.yml), so the two must not drift apart.
+test('every backend spawn in main.js declares PYTHONUTF8=1', () => {
+  const main = fs.readFileSync(path.join(__dirname, 'main.js'), 'utf8');
+  const spawns = main.match(/PYTHONUTF8: '1'/g) || [];
+  assert.ok(spawns.length >= 2, `expected the dev and packaged spawn envs to carry PYTHONUTF8, found ${spawns.length}`);
+});
diff --git a/frontend/scripts/run-tests.mjs b/frontend/scripts/run-tests.mjs
index 559d7d62..e067d684 100644
--- a/frontend/scripts/run-tests.mjs
+++ b/frontend/scripts/run-tests.mjs
@@ -10,6 +10,7 @@ import { globSync } from 'node:fs';
 import { mkdirSync, rmSync } from 'node:fs';
 import path from 'node:path';
 import { spawnSync } from 'node:child_process';
+import { pathToFileURL } from 'node:url';
 import { fileURLToPath } from 'node:url';
 
 const root = path.dirname(fileURLToPath(import.meta.url)) + '/..';
@@ -47,7 +48,8 @@ try {
   });
   const built = globSync('**/*.mjs', { cwd: outDir }).concat(globSync('**/*.js', { cwd: outDir }));
   const setup = path.join(root, 'scripts/test-globals.mjs');
-  const res = spawnSync(process.execPath, ['--import', setup, '--test', ...built.map((f) => path.join(outDir, f))],
+  // --import takes a URL: a bare Windows path (D:\...) is read as protocol 'd:' and every test file fails before it starts.
+  const res = spawnSync(process.execPath, ['--import', pathToFileURL(setup).href, '--test', ...built.map((f) => path.join(outDir, f))],
     { stdio: 'inherit', cwd: root });
   status = res.status ?? 1;
 } finally {