diff --git a/npm/install.js b/npm/install.js
index 652daec..c3b6b43 100644
--- a/npm/install.js
+++ b/npm/install.js
@@ -39,25 +39,59 @@ function download(url, dest, cb) {
       return fail(`HTTP ${res.statusCode} downloading ${url}`);
     }
     res.pipe(file);
-    file.on("finish", () => file.close(cb));
+    // Wait for 'close' (not just 'finish'): on Windows the fd is not actually
+    // released until close completes, and subsequent extractors (PowerShell
+    // Expand-Archive in particular) will fail with a file-in-use error.
+    file.on("finish", () => file.close());
+    file.on("close", () => cb());
   }).on("error", (err) => fail(err.message));
 }
 
 // extractZip extracts a .zip archive into tmpDir.
-// Tries native tar first (Windows 10+); falls back to PowerShell Expand-Archive
-// with a retry loop to handle transient Antivirus file locks.
+//
+// On Windows, PATH under Git Bash (npm's postinstall shell) resolves `tar`
+// to GNU tar, which parses `C:\...` as `host:path` (rsh syntax), prints
+// "Cannot connect to C: resolve failed", and exits 0 with nothing extracted.
+// We explicitly call the native Windows bsdtar at %SystemRoot%\System32\tar.exe
+// (present on Windows 10+), which handles both Windows paths and the zip
+// format. On older Windows we fall back to PowerShell Expand-Archive with
+// retries for Defender/indexer file locks.
+//
+// After extraction we always verify tmpDir is non-empty — some extractors
+// (notably GNU tar in the failure mode above) exit 0 without writing anything.
 // Accepts an optional execFn for testing (defaults to execSync).
 function extractZip(archive, tmpDir, execFn) {
   const exec = execFn || execSync;
-  try {
-    exec(`tar -xf "${archive}" -C "${tmpDir}"`);
-  } catch {
-    const psCommand =
-      `$RetryCount = 0; while ($RetryCount -lt 10) { try { Expand-Archive` +
-      ` -Force -Path '${archive}' -DestinationPath '${tmpDir}'; break }` +
-      ` catch { Start-Sleep -Seconds 1; $RetryCount++ } }`;
-    exec(`powershell -NoProfile -Command "${psCommand}"`);
+  const attempts = [];
+
+  const bsdtar = path.join(process.env.SystemRoot || "C:\\Windows", "System32", "tar.exe");
+  if (process.platform === "win32" && fs.existsSync(bsdtar)) {
+    attempts.push({ cmd: `"${bsdtar}" -xf "${archive}" -C "${tmpDir}"`, label: "bsdtar" });
+  }
+  // PowerShell fallback. Retries handle transient locks from Windows Defender
+  // / Search Indexer on the freshly-written zip. Throws if all retries fail.
+  const psCommand =
+    `$ErrorActionPreference='Stop'; ` +
+    `$lastErr = $null; ` +
+    `for ($i=0; $i -lt 20; $i++) { ` +
+    `  try { Expand-Archive -Force -Path '${archive}' -DestinationPath '${tmpDir}'; exit 0 } ` +
+    `  catch { $lastErr = $_; Start-Sleep -Seconds 1 } ` +
+    `}; ` +
+    `throw $lastErr`;
+  attempts.push({ cmd: `powershell -NoProfile -Command "${psCommand}"`, label: "powershell" });
+
+  let lastErr = null;
+  for (const { cmd } of attempts) {
+    try {
+      exec(cmd);
+      let entries = [];
+      try { entries = fs.readdirSync(tmpDir); } catch { /* missing dir => failure */ }
+      if (entries.length > 0) return;
+    } catch (e) {
+      lastErr = e;
+    }
   }
+  throw lastErr || new Error(`[supermodel] extraction produced no files in ${tmpDir}`);
 }
 
 if (require.main === module) {
diff --git a/npm/install.test.js b/npm/install.test.js
index 6d29a02..8893f3f 100644
--- a/npm/install.test.js
+++ b/npm/install.test.js
@@ -11,123 +11,127 @@ const path = require("path");
 const { execSync } = require("child_process");
 const { extractZip } = require("./install");
 
-// createTestZip builds a real .zip containing a single file named "supermodel.exe"
-// using the system zip/tar command. Skips on platforms where neither is available.
-function createTestZip(t) {
-  const src = fs.mkdtempSync(path.join(os.tmpdir(), "supermodel-test-src-"));
-  const binary = path.join(src, "supermodel.exe");
-  fs.writeFileSync(binary, "fake binary");
+const isWindows = process.platform === "win32";
+const isTarCmd = (c) => /tar(\.exe)?["'\s]/.test(c.split(" ")[0]);
+const isPsCmd = (c) => c.includes("powershell");
 
-  const archive = path.join(os.tmpdir(), `supermodel-test-${process.pid}.zip`);
+// Make a fake extraction succeed by dropping a file into tmpDir so the
+// post-extract verification (readdirSync(tmpDir).length > 0) passes.
+const fakeExtract = (tmpDir) => () => {
+  fs.writeFileSync(path.join(tmpDir, "supermodel.exe"), "fake");
+};
+
+test("extractZip succeeds when the first extractor produces files", () => {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "smt-ok-"));
   try {
-    // Use system zip or tar to build the archive.
-    try {
-      execSync(`zip -j "${archive}" "${binary}"`, { stdio: "pipe" });
-    } catch {
-      execSync(`tar -cf "${archive}" --format=zip -C "${src}" supermodel.exe`, { stdio: "pipe" });
-    }
-  } catch {
-    fs.rmSync(src, { recursive: true, force: true });
-    return null; // zip tooling not available — caller should skip
+    const commands = [];
+    extractZip("/fake/archive.zip", tmpDir, (cmd) => {
+      commands.push(cmd);
+      fakeExtract(tmpDir)();
+    });
+    assert.equal(commands.length, 1, "stops at first successful extractor");
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
   }
-  fs.rmSync(src, { recursive: true, force: true });
-  return archive;
-}
+});
 
-test("extractZip extracts via tar when tar succeeds", () => {
-  const archive = createTestZip();
-  if (!archive) {
-    // Skip gracefully if zip tooling unavailable (e.g. minimal CI image).
-    console.log("  skipped: zip tooling not available");
-    return;
-  }
+test("extractZip falls back when first extractor throws", { skip: !isWindows }, () => {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "smt-throw-"));
   try {
-    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "supermodel-test-out-"));
-    try {
-      let called = null;
-      extractZip(archive, tmpDir, (cmd) => {
-        called = cmd;
-        // Only simulate tar; let the actual extraction happen via real execSync
-        // if this is the tar command.
-        if (cmd.startsWith("tar")) {
-          execSync(cmd, { stdio: "pipe" });
-        } else {
-          throw new Error("should not reach PowerShell");
-        }
-      });
-      assert.ok(called.startsWith("tar"), "should have called tar first");
-      const extracted = fs.readdirSync(tmpDir);
-      assert.ok(extracted.length > 0, "tmpDir should contain extracted files");
-    } finally {
-      fs.rmSync(tmpDir, { recursive: true, force: true });
-    }
+    const commands = [];
+    extractZip("/fake/archive.zip", tmpDir, (cmd) => {
+      commands.push(cmd);
+      if (isTarCmd(cmd)) throw new Error("tar unavailable");
+      fakeExtract(tmpDir)();
+    });
+    assert.equal(commands.length, 2, "tries tar then PowerShell");
+    assert.ok(isTarCmd(commands[0]), "first attempt is tar");
+    assert.ok(isPsCmd(commands[1]), "second attempt is PowerShell");
   } finally {
-    fs.unlinkSync(archive);
+    fs.rmSync(tmpDir, { recursive: true, force: true });
   }
 });
 
-test("extractZip falls back to PowerShell when tar fails", () => {
-  const commands = [];
-  // Simulate tar failing; PowerShell "succeeds" (no-op).
-  extractZip("/fake/archive.zip", "/fake/tmpdir", (cmd) => {
-    commands.push(cmd);
-    if (cmd.startsWith("tar")) throw new Error("tar not available");
-    // PowerShell call — just record it, don't execute.
-  });
-
-  assert.equal(commands.length, 2, "should have attempted tar then PowerShell");
-  assert.ok(commands[0].startsWith("tar"), "first call should be tar");
-  assert.ok(commands[1].includes("powershell"), "second call should be PowerShell");
-  assert.ok(commands[1].includes("Expand-Archive"), "PowerShell command should use Expand-Archive");
+test("extractZip falls back when first extractor exits 0 but writes nothing", { skip: !isWindows }, () => {
+  // Reproduces the GNU-tar-in-Git-Bash bug: tar prints "Cannot connect to C:"
+  // but still exits 0 without extracting anything.
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "smt-silent-"));
+  try {
+    const commands = [];
+    extractZip("/fake/archive.zip", tmpDir, (cmd) => {
+      commands.push(cmd);
+      if (isTarCmd(cmd)) return; // silent no-op "success"
+      fakeExtract(tmpDir)();
+    });
+    assert.equal(commands.length, 2, "falls back when tar produced no files");
+    assert.ok(isPsCmd(commands[1]), "fallback is PowerShell Expand-Archive");
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
 });
 
-test("extractZip PowerShell fallback includes retry loop", () => {
-  const commands = [];
-  extractZip("/fake/archive.zip", "/fake/tmpdir", (cmd) => {
-    commands.push(cmd);
-    if (cmd.startsWith("tar")) throw new Error("tar not available");
-  });
-
-  const psCmd = commands.find((c) => c.includes("powershell"));
-  assert.ok(psCmd, "PowerShell command should be present");
-  assert.ok(psCmd.includes("$RetryCount"), "should include retry counter");
-  assert.ok(psCmd.includes("Start-Sleep"), "should include sleep between retries");
-  assert.ok(psCmd.includes("-lt 10"), "should retry up to 10 times");
+test("extractZip throws when every extractor fails", () => {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "smt-fail-"));
+  try {
+    assert.throws(() => {
+      extractZip("/fake/archive.zip", tmpDir, () => {
+        throw new Error("boom");
+      });
+    }, /boom/);
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
 });
 
-test("extractZip uses tar when both succeed — tar wins", () => {
-  const commands = [];
-  extractZip("/fake/archive.zip", "/fake/tmpdir", (cmd) => {
-    commands.push(cmd);
-    // Both would succeed; tar is tried first and doesn't throw.
-  });
-
-  assert.equal(commands.length, 1, "should only call tar when it succeeds");
-  assert.ok(commands[0].startsWith("tar"), "the single call should be tar");
+test("extractZip throws when every extractor silently produces nothing", () => {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "smt-empty-"));
+  try {
+    assert.throws(() => {
+      extractZip("/fake/archive.zip", tmpDir, () => {
+        // no-op: exit 0, no files — the exact silent-failure mode we must catch
+      });
+    });
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
 });
 
-test("extractZip passes archive and tmpDir paths into tar command", () => {
-  const archive = "/tmp/test.zip";
-  const tmpDir = "/tmp/extract-dir";
-  let tarCmd = null;
-  extractZip(archive, tmpDir, (cmd) => {
-    tarCmd = cmd;
-  });
-
-  assert.ok(tarCmd.includes(archive), "tar command should include archive path");
-  assert.ok(tarCmd.includes(tmpDir), "tar command should include tmpDir path");
+test("extractZip PowerShell fallback uses Expand-Archive with a retry loop", () => {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "smt-ps-"));
+  try {
+    const commands = [];
+    try {
+      extractZip("/fake/archive.zip", tmpDir, (cmd) => {
+        commands.push(cmd);
+        throw new Error("all fail");
+      });
+    } catch {}
+    const psCmd = commands.find(isPsCmd);
+    assert.ok(psCmd, "PowerShell command should be attempted");
+    assert.ok(psCmd.includes("Expand-Archive"), "uses Expand-Archive");
+    assert.ok(psCmd.includes("Start-Sleep"), "sleeps between retries");
+    assert.match(psCmd, /-lt\s+\d+/, "has a retry counter");
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
 });
 
-test("extractZip passes archive and tmpDir paths into PowerShell fallback", () => {
+test("extractZip passes archive and tmpDir paths into every command", () => {
   const archive = "/tmp/test.zip";
-  const tmpDir = "/tmp/extract-dir";
-  const commands = [];
-  extractZip(archive, tmpDir, (cmd) => {
-    commands.push(cmd);
-    if (cmd.startsWith("tar")) throw new Error("tar failed");
-  });
-
-  const psCmd = commands[1];
-  assert.ok(psCmd.includes(archive), "PowerShell command should include archive path");
-  assert.ok(psCmd.includes(tmpDir), "PowerShell command should include tmpDir path");
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "smt-paths-"));
+  try {
+    const commands = [];
+    try {
+      extractZip(archive, tmpDir, (cmd) => {
+        commands.push(cmd);
+        throw new Error("fail all");
+      });
+    } catch {}
+    for (const cmd of commands) {
+      assert.ok(cmd.includes(archive), `archive path present: ${cmd}`);
+      assert.ok(cmd.includes(tmpDir), `tmpDir path present: ${cmd}`);
+    }
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
 });