diff --git a/bin/lib/launcher-utils.mjs b/bin/lib/launcher-utils.mjs
index 1e6d6bce..ac14c3ee 100644
--- a/bin/lib/launcher-utils.mjs
+++ b/bin/lib/launcher-utils.mjs
@@ -10,6 +10,22 @@ import { createHash } from "node:crypto";
 import { createReadStream, existsSync, renameSync, rmSync } from "node:fs";
 import * as path from "node:path";
 
+export const DEFAULT_PORT = "3000";
+
+/**
+ * Format a local startup link without changing the server's bind address.
+ * @param {string | null | undefined} hostname
+ * @param {string | number | null | undefined} port
+ * @returns {string}
+ */
+export function startupUrl(hostname, port) {
+  let host = hostname || "127.0.0.1";
+  if (host === "0.0.0.0") host = "127.0.0.1";
+  else if (host === "::" || host === "[::]") host = "[::1]";
+  else if (host.includes(":") && !host.startsWith("[")) host = `[${host}]`;
+  return `http://${host}:${port || DEFAULT_PORT}`;
+}
+
 /**
  * Platform/arch pairs the release workflow builds standalone payloads for
  * (must mirror the build jobs in .github/workflows/release-artifacts.yml).
diff --git a/bin/studio.js b/bin/studio.js
index a6090e91..3638f3b0 100644
--- a/bin/studio.js
+++ b/bin/studio.js
@@ -38,6 +38,8 @@ import {
   assessNodeRuntime,
   assessProvenance,
   extractArchive,
+  DEFAULT_PORT,
+  startupUrl,
   LauncherUsageError,
   parseLauncherArgs,
   parseSha256Sums,
@@ -67,7 +69,7 @@ network only prints a warning; an archive whose provenance is actively
 rejected stops the launcher (override: LIBREDB_STUDIO_SKIP_PROVENANCE=1).
 
 Options:
-  --port <n>        Port to listen on (default: $PORT or 3000)
+  --port <n>        Port to listen on (default: $PORT or ${DEFAULT_PORT})
   --host <addr>     Address to bind (default: $HOSTNAME or 127.0.0.1;
                     use --host 0.0.0.0 to expose on the network)
   --archive <path>  Start from a local standalone archive instead of
@@ -316,7 +318,7 @@ function startServer(payloadDir, port, host) {
   if (!env.WORKFLOW_LOCAL_DATA_DIR) env.WORKFLOW_LOCAL_DATA_DIR = resolveLedgerDir(os.homedir());
   // Log-line contract: npx-engine-smoke.yml parses the resolved version from
   // "Starting LibreDB Studio <version> " - keep the prefix stable.
-  console.log(`Starting LibreDB Studio ${pkg.version} on http://${env.HOSTNAME}:${env.PORT || "3000"}`);
+  console.log(`Starting LibreDB Studio ${pkg.version} on ${startupUrl(env.HOSTNAME, env.PORT)}`);
   const child = spawn(process.execPath, ["server.js"], { cwd: payloadDir, env, stdio: "inherit" });
   child.on("error", (error) => fail(`Could not start server.js: ${error.message}`));
   for (const signal of /** @type {const} */ (["SIGINT", "SIGTERM"])) {
diff --git a/tests/unit/launcher-utils.test.ts b/tests/unit/launcher-utils.test.ts
index b368af18..93c45067 100644
--- a/tests/unit/launcher-utils.test.ts
+++ b/tests/unit/launcher-utils.test.ts
@@ -8,6 +8,7 @@ import * as os from "os";
 import * as path from "path";
 import {
   artifactName,
+  startupUrl,
   assertReleaseVersion,
   assessNodeRuntime,
   assessProvenance,
@@ -566,3 +567,22 @@ describe("assessProvenance", () => {
     expect(result.message).toContain(ARTIFACT);
   });
 });
+
+describe("startupUrl", () => {
+  test.each([
+    ["0.0.0.0", "4000", "http://127.0.0.1:4000"],
+    ["::", "4000", "http://[::1]:4000"],
+    ["[::]", "4000", "http://[::1]:4000"],
+    ["fe80::1", "4000", "http://[fe80::1]:4000"],
+    ["[fe80::1]", "4000", "http://[fe80::1]:4000"],
+    ["127.0.0.1", "4000", "http://127.0.0.1:4000"],
+    ["example.internal", "4000", "http://example.internal:4000"],
+    ["", "4000", "http://127.0.0.1:4000"],
+    [undefined, undefined, "http://127.0.0.1:3000"],
+    [null, null, "http://127.0.0.1:3000"],
+    ["127.0.0.1", "", "http://127.0.0.1:3000"],
+    ["127.0.0.1", 4000, "http://127.0.0.1:4000"],
+  ])("formats host %s and port %s", (host, port, expected) => {
+    expect(startupUrl(host, port)).toBe(expected);
+  });
+});