diff --git a/scripts/check-upstream-release.mjs b/scripts/check-upstream-release.mjs
index 7d459b809..dcf4599af 100644
--- a/scripts/check-upstream-release.mjs
+++ b/scripts/check-upstream-release.mjs
@@ -22,8 +22,9 @@
 import { execFileSync } from "node:child_process";
 import { appendFileSync, readFileSync } from "node:fs";
 
-const UPSTREAM_REMOTE = "upstream";
 const UPSTREAM_REPO = "badlogic/pi-mono";
+const UPSTREAM_REMOTE_URL = `https://github.com/${UPSTREAM_REPO}.git`;
+const UPSTREAM_MAIN_REF = "refs/remotes/pi-mono/main";
 const PIN_PATH = ".github/upstream.json";
 
 function log(message) {
@@ -55,7 +56,7 @@ function latestUpstreamReleaseTag() {
 		log("gh releases/latest unavailable; falling back to remote tags");
 	}
 
-	const lsRemote = run("git", ["ls-remote", "--tags", "--refs", UPSTREAM_REMOTE, "v*"]);
+	const lsRemote = run("git", ["ls-remote", "--tags", "--refs", UPSTREAM_REMOTE_URL, "v*"]);
 	const tags = lsRemote
 		.split("\n")
 		.filter(Boolean)
@@ -81,10 +82,16 @@ function compareSemver(a, b) {
 
 function resolveTagSha(tag) {
 	// Fetch the tag so the commit object exists locally for the ancestry check.
-	const fetch = tryRun("git", ["fetch", "--quiet", UPSTREAM_REMOTE, "--no-tags", `+refs/tags/${tag}:refs/upstream-tags/${tag}`]);
+	const fetch = tryRun("git", [
+		"fetch",
+		"--quiet",
+		UPSTREAM_REMOTE_URL,
+		"--no-tags",
+		`+refs/tags/${tag}:refs/upstream-tags/${tag}`,
+	]);
 	if (!fetch.ok) {
 		// Fall back to a full tag fetch.
-		tryRun("git", ["fetch", "--quiet", "--tags", UPSTREAM_REMOTE]);
+		tryRun("git", ["fetch", "--quiet", "--tags", UPSTREAM_REMOTE_URL]);
 	}
 	const peeled = tryRun("git", ["rev-parse", `refs/upstream-tags/${tag}^{commit}`]);
 	if (peeled.ok && peeled.stdout) {
@@ -94,7 +101,8 @@ function resolveTagSha(tag) {
 }
 
 function resolveUpstreamHeadSha() {
-	return run("git", ["rev-parse", `${UPSTREAM_REMOTE}/main`]);
+	run("git", ["fetch", "--quiet", UPSTREAM_REMOTE_URL, `+refs/heads/main:${UPSTREAM_MAIN_REF}`]);
+	return run("git", ["rev-parse", UPSTREAM_MAIN_REF]);
 }
 
 function currentPinTag() {
@@ -129,7 +137,7 @@ function main() {
 	const sha = resolveTagSha(tag);
 	log(`resolved ${tag} -> ${sha}`);
 	const upstreamHeadSha = resolveUpstreamHeadSha();
-	log(`resolved ${UPSTREAM_REMOTE}/main -> ${upstreamHeadSha}`);
+	log(`resolved ${UPSTREAM_REPO} main -> ${upstreamHeadSha}`);
 
 	if (force) {
 		log("--force set; proceeding regardless of merge state");
diff --git a/scripts/check-upstream-release.test.mjs b/scripts/check-upstream-release.test.mjs
index ec09d04cf..b9dc40455 100644
--- a/scripts/check-upstream-release.test.mjs
+++ b/scripts/check-upstream-release.test.mjs
@@ -2,9 +2,11 @@ import assert from "node:assert/strict";
 import { execFileSync } from "node:child_process";
 import { after, before, describe, it } from "node:test";
 
-const UPSTREAM_REMOTE_URL = "https://github.com/badlogic/pi-mono.git";
+const CONTRIBUTOR_UPSTREAM_URL = "https://github.com/code-yeongyu/senpi.git";
+const DETECTOR_UPSTREAM_URL = "https://github.com/badlogic/pi-mono.git";
 
 let addedUpstreamRemote = false;
+let originalUpstreamUrl = "";
 
 function git(args) {
 	return execFileSync("git", args, { encoding: "utf8", stdio: ["ignore", "pipe", "pipe"] }).trim();
@@ -18,28 +20,39 @@ function tryGit(args) {
 	}
 }
 
+function tryGitCommand(args) {
+	try {
+		execFileSync("git", args, { stdio: "ignore" });
+		return true;
+	} catch {
+		return false;
+	}
+}
+
 describe("upstream release detector outputs", () => {
 	let upstreamAvailable = false;
 
 	before(() => {
-		if (!tryGit(["remote", "get-url", "upstream"])) {
-			if (!tryGit(["remote", "add", "upstream", UPSTREAM_REMOTE_URL])) return;
+		originalUpstreamUrl = tryGit(["remote", "get-url", "upstream"]);
+		if (originalUpstreamUrl) {
+			if (!tryGitCommand(["remote", "set-url", "upstream", CONTRIBUTOR_UPSTREAM_URL])) return;
+		} else {
+			if (!tryGitCommand(["remote", "add", "upstream", CONTRIBUTOR_UPSTREAM_URL])) return;
 			addedUpstreamRemote = true;
 		}
-		// A real fetch of the upstream GitHub repo. On credential-less/offline
+		// Probe the repository the detector actually reads. On credential-less/offline
 		// runners (e.g. the release publish job checks out with
-		// persist-credentials:false) this cannot authenticate — skip rather than
+		// persist-credentials:false) this can be unreachable — skip rather than
 		// hard-fail the whole `test:scripts` suite, since this test inherently
 		// requires the external upstream repo.
-		if (tryGit(["fetch", "--quiet", "upstream", "+refs/heads/main:refs/remotes/upstream/main"]) === "" && !tryGit(["rev-parse", "upstream/main"])) {
-			return;
-		}
-		upstreamAvailable = tryGit(["rev-parse", "upstream/main"]) !== "";
+		upstreamAvailable = Boolean(tryGit(["ls-remote", DETECTOR_UPSTREAM_URL, "refs/heads/main"]));
 	});
 
 	after(() => {
 		if (addedUpstreamRemote) {
 			git(["remote", "remove", "upstream"]);
+		} else if (originalUpstreamUrl) {
+			git(["remote", "set-url", "upstream", originalUpstreamUrl]);
 		}
 	});
 
@@ -48,16 +61,27 @@ describe("upstream release detector outputs", () => {
 			t.skip("upstream remote unreachable (offline or no git credentials)");
 			return;
 		}
-		const stdout = execFileSync("node", ["scripts/check-upstream-release.mjs", "--force"], { encoding: "utf8" });
+		const stdout = execFileSync("node", ["scripts/check-upstream-release.mjs", "--force"], {
+			encoding: "utf8",
+			env: { ...process.env, GITHUB_OUTPUT: "" },
+		});
 		const output = Object.fromEntries(
 			stdout
 				.trim()
 				.split("\n")
 				.map((line) => line.split("=", 2)),
 		);
-		const upstreamMain = git(["rev-parse", "upstream/main"]);
+		const upstreamMain = git(["ls-remote", DETECTOR_UPSTREAM_URL, "refs/heads/main"]).split(/\s+/, 1)[0];
 		const releaseTag = output.tag;
-		const releaseSha = tryGit(["rev-parse", `refs/upstream-tags/${releaseTag}^{commit}`]) || git(["rev-parse", `${releaseTag}^{commit}`]);
+		const remoteTagRefs = git([
+			"ls-remote",
+			"--tags",
+			DETECTOR_UPSTREAM_URL,
+			`refs/tags/${releaseTag}`,
+			`refs/tags/${releaseTag}^{}`,
+		]).split("\n");
+		const peeledTag = remoteTagRefs.find((line) => line.endsWith(`refs/tags/${releaseTag}^{}`));
+		const releaseSha = (peeledTag ?? remoteTagRefs[0]).split(/\s+/, 1)[0];
 
 		assert.equal(output.proceed, "true");
 		assert.equal(output.sha, releaseSha);