diff --git a/src/lib/upgrade.ts b/src/lib/upgrade.ts
index 78194a8b9..48ddaacc6 100644
--- a/src/lib/upgrade.ts
+++ b/src/lib/upgrade.ts
@@ -31,6 +31,7 @@ import { attemptDeltaUpgrade, type DeltaResult } from "./delta-upgrade.js";
 import { AbortError, UpgradeError } from "./errors.js";
 import {
   downloadNightlyBlob,
+  fetchManifest,
   fetchNightlyManifest,
   findLayerByFilename,
   getAnonymousToken,
@@ -384,9 +385,41 @@ export function fetchLatestVersion(
     : fetchLatestFromNpm();
 }
 
+/**
+ * Check if a versioned nightly tag exists in GHCR.
+ *
+ * Nightly builds are published to GHCR with tags like `nightly-0.14.0-dev.1772661724`.
+ * This performs an anonymous token exchange + manifest fetch (2 HTTP requests).
+ * Returns false only for 404/403 (tag not found); network errors propagate as
+ * UpgradeError to match stable version check behavior.
+ *
+ * @param version - Nightly version string (e.g., "0.14.0-dev.1772661724")
+ * @returns true if the nightly tag exists in GHCR, false if not found
+ * @throws {UpgradeError} On network failure or GHCR unavailability
+ */
+async function nightlyVersionExists(version: string): Promise<boolean> {
+  const token = await getAnonymousToken();
+  try {
+    await fetchManifest(token, `nightly-${version}`);
+    return true;
+  } catch (error) {
+    // 404 = tag doesn't exist; 403 = token lacks access to non-existent tag
+    if (
+      error instanceof UpgradeError &&
+      (error.message.includes("HTTP 404") || error.message.includes("HTTP 403"))
+    ) {
+      return false;
+    }
+    throw error;
+  }
+}
+
 /**
  * Check if a specific version exists in the appropriate registry.
- * curl installations check GitHub releases; package managers check npm.
+ *
+ * Nightly versions are checked against GHCR (where they are published as
+ * versioned tags like `nightly-0.14.0-dev.1772661724`). Stable versions
+ * are checked against GitHub Releases (curl/brew) or npm (package managers).
  *
  * @param method - How the CLI was installed
  * @param version - Version to check (without 'v' prefix)
@@ -397,6 +430,11 @@ export async function versionExists(
   method: InstallationMethod,
   version: string
 ): Promise<boolean> {
+  // Nightly versions are published to GHCR, not GitHub Releases or npm
+  if (isNightlyVersion(version)) {
+    return nightlyVersionExists(version);
+  }
+
   if (method === "curl" || method === "brew") {
     const response = await fetchWithUpgradeError(
       `${GITHUB_RELEASES_URL}/tags/${version}`,
@@ -470,12 +508,21 @@ function getNightlyGzFilename(): string {
  * matching this platform's `.gz` filename, then downloads and decompresses
  * the blob in-stream.
  *
+ * When `version` is provided, fetches the pinned versioned tag
+ * (`nightly-{version}`). Otherwise fetches the rolling `:nightly` tag.
+ *
  * @param destPath - File path to write the decompressed binary
+ * @param version - Specific nightly version to download (omit for latest)
  * @throws {UpgradeError} When GHCR fetch or blob download fails
  */
-async function downloadNightlyToPath(destPath: string): Promise<void> {
+async function downloadNightlyToPath(
+  destPath: string,
+  version?: string
+): Promise<void> {
   const token = await getAnonymousToken();
-  const manifest = await fetchNightlyManifest(token);
+  const manifest = version
+    ? await fetchManifest(token, `nightly-${version}`)
+    : await fetchNightlyManifest(token);
   const filename = getNightlyGzFilename();
   const layer = findLayerByFilename(manifest, filename);
   const response = await downloadNightlyBlob(token, layer.digest);
@@ -635,7 +682,7 @@ async function downloadFullBinary(
   destPath: string
 ): Promise<void> {
   if (isNightlyVersion(version)) {
-    await downloadNightlyToPath(destPath);
+    await downloadNightlyToPath(destPath, version);
   } else {
     await downloadStableToPath(downloadTag ?? version, destPath);
   }
diff --git a/test/lib/upgrade.test.ts b/test/lib/upgrade.test.ts
index 586d9c241..ed7565164 100644
--- a/test/lib/upgrade.test.ts
+++ b/test/lib/upgrade.test.ts
@@ -510,6 +510,79 @@ describe("versionExists", () => {
       "Failed to connect to npm registry"
     );
   });
+
+  test("checks GHCR for nightly version - version exists", async () => {
+    const manifest = { schemaVersion: 2, layers: [], annotations: {} };
+    mockFetch(async (url) => {
+      const u = String(url);
+      if (u.includes("ghcr.io/token")) {
+        return new Response(JSON.stringify({ token: "tok" }), { status: 200 });
+      }
+      if (u.includes("/manifests/nightly-")) {
+        return new Response(JSON.stringify(manifest), { status: 200 });
+      }
+      return new Response(null, { status: 404 });
+    });
+
+    const exists = await versionExists("curl", "0.14.0-dev.1772661724");
+    expect(exists).toBe(true);
+  });
+
+  test("checks GHCR for nightly version - version does not exist", async () => {
+    mockFetch(async (url) => {
+      const u = String(url);
+      if (u.includes("ghcr.io/token")) {
+        return new Response(JSON.stringify({ token: "tok" }), { status: 200 });
+      }
+      if (u.includes("/manifests/nightly-")) {
+        return new Response(null, { status: 404 });
+      }
+      return new Response(null, { status: 404 });
+    });
+
+    const exists = await versionExists("curl", "0.14.0-dev.9999999999");
+    expect(exists).toBe(false);
+  });
+
+  test("checks GHCR for nightly version regardless of install method", async () => {
+    const manifest = { schemaVersion: 2, layers: [], annotations: {} };
+    mockFetch(async (url) => {
+      const u = String(url);
+      if (u.includes("ghcr.io/token")) {
+        return new Response(JSON.stringify({ token: "tok" }), { status: 200 });
+      }
+      if (u.includes("/manifests/nightly-")) {
+        return new Response(JSON.stringify(manifest), { status: 200 });
+      }
+      return new Response(null, { status: 404 });
+    });
+
+    const exists = await versionExists("npm", "0.14.0-dev.1772661724");
+    expect(exists).toBe(true);
+  });
+
+  test("throws on network failure for nightly version", async () => {
+    mockFetch(async () => {
+      throw new TypeError("fetch failed");
+    });
+    await expect(
+      versionExists("curl", "0.14.0-dev.1772661724")
+    ).rejects.toThrow(UpgradeError);
+  });
+
+  test("throws on GHCR server error for nightly version", async () => {
+    mockFetch(async (url) => {
+      const u = String(url);
+      if (u.includes("ghcr.io/token")) {
+        return new Response(JSON.stringify({ token: "tok" }), { status: 200 });
+      }
+      // Manifest returns 500 (server error, not 404)
+      return new Response(null, { status: 500 });
+    });
+    await expect(
+      versionExists("curl", "0.14.0-dev.1772661724")
+    ).rejects.toThrow(UpgradeError);
+  });
 });
 
 describe("executeUpgrade", () => {