diff --git a/apps/api/src/cutover-orchestrator.ts b/apps/api/src/cutover-orchestrator.ts
index 8f466d4..19901e5 100644
--- a/apps/api/src/cutover-orchestrator.ts
+++ b/apps/api/src/cutover-orchestrator.ts
@@ -289,11 +289,14 @@ async function durableState(plan: CutoverPlan, state: CutoverState): Promise<voi
     await handle.close();
   }
   await rename(temporary, target);
-  const directory = await open(plan.stateDir, constants.O_RDONLY);
-  try {
-    await directory.sync();
-  } finally {
-    await directory.close();
+  if (process.platform !== 'win32') {
+    // directory fsync only exists on POSIX
+    const directory = await open(plan.stateDir, constants.O_RDONLY);
+    try {
+      await directory.sync();
+    } finally {
+      await directory.close();
+    }
   }
 }
 
diff --git a/apps/api/src/infrastructure/database/backup.ts b/apps/api/src/infrastructure/database/backup.ts
index 51cc391..9656e21 100644
--- a/apps/api/src/infrastructure/database/backup.ts
+++ b/apps/api/src/infrastructure/database/backup.ts
@@ -159,7 +159,8 @@ async function digestFileHandle(handle: FileHandle): Promise<string> {
 }
 
 async function syncFile(path: string): Promise<void> {
-  const handle = await open(path, 'r');
+  // Windows FlushFileBuffers requires a writable handle; POSIX allows fsync on 'r'.
+  const handle = await open(path, process.platform === 'win32' ? 'r+' : 'r');
   try {
     await handle.sync();
   } finally {
@@ -168,6 +169,7 @@ async function syncFile(path: string): Promise<void> {
 }
 
 async function syncDirectory(path: string): Promise<void> {
+  if (process.platform === 'win32') return; // directory fsync only exists on POSIX
   const handle = await open(path, 'r');
   try {
     await handle.sync();
diff --git a/apps/api/src/release-evidence.ts b/apps/api/src/release-evidence.ts
index aafecbe..71f8bdc 100644
--- a/apps/api/src/release-evidence.ts
+++ b/apps/api/src/release-evidence.ts
@@ -254,11 +254,14 @@ export async function appendReleaseEvidence(
       await handle.close();
     }
     await rename(temporary, absolute);
-    const directory = await open(parent, 'r');
-    try {
-      await directory.sync();
-    } finally {
-      await directory.close();
+    if (process.platform !== 'win32') {
+      // directory fsync only exists on POSIX
+      const directory = await open(parent, 'r');
+      try {
+        await directory.sync();
+      } finally {
+        await directory.close();
+      }
     }
     return Object.freeze(record);
   } finally {
diff --git a/eslint.config.js b/eslint.config.js
index d03bf4d..8d5259d 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -30,6 +30,14 @@ export default defineConfig(
     },
     rules: {
       'no-undef': 'off',
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        {
+          argsIgnorePattern: '^_',
+          varsIgnorePattern: '^_',
+          caughtErrorsIgnorePattern: '^_',
+        },
+      ],
     },
   },
 );
diff --git a/test/phase-one-blockers.test.js b/test/phase-one-blockers.test.js
index ec21915..7bf5424 100644
--- a/test/phase-one-blockers.test.js
+++ b/test/phase-one-blockers.test.js
@@ -14,7 +14,7 @@ import { RequestCoordinator } from '../public/state/request-coordinator.js'
 import { createApiClient } from '../public/infrastructure/api-client.js'
 import { createViewRouter } from '../public/router/view-router.js'
 
-const projectRoot = path.resolve(path.dirname(new URL(import.meta.url).pathname), '..')
+const projectRoot = path.resolve(import.meta.dirname, '..')
 
 async function files(instances = []) {
   const dir = await mkdtemp(path.join(tmpdir(), 'msa-blockers-'))