diff --git a/.changeset/rude-seas-guess.md b/.changeset/rude-seas-guess.md
new file mode 100644
index 000000000..8fe0a26ae
--- /dev/null
+++ b/.changeset/rude-seas-guess.md
@@ -0,0 +1,5 @@
+---
+"emdash": patch
+---
+
+fix: exclude unused @tiptap collaboration deps from optimizeDeps so fresh installs do not fail
diff --git a/packages/core/src/astro/integration/vite-config.ts b/packages/core/src/astro/integration/vite-config.ts
index 480a8ab01..ff724d96c 100644
--- a/packages/core/src/astro/integration/vite-config.ts
+++ b/packages/core/src/astro/integration/vite-config.ts
@@ -366,7 +366,8 @@ export function createViteConfig(
 						// during pre-bundling and can't resolve them. Vite's exclude
 						// uses prefix matching (id.startsWith(m + "/")), so
 						// "virtual:emdash" matches all "virtual:emdash/*" imports.
-						exclude: ["virtual:emdash"],
+						// tiptap deps not used in this repo; excluded so optimizeDeps does not fail to resolve them on fresh installs (issue #771).
+						exclude: ["virtual:emdash", "@tiptap/extension-collaboration", "@tiptap/y-tiptap"],
 						include: [
 							// EmDash direct deps
 							"emdash > @portabletext/toolkit",
@@ -424,7 +425,20 @@ export function createViteConfig(
 			include: useSource
 				? ["@astrojs/react/client.js"]
 				: ["@emdash-cms/admin", "@astrojs/react/client.js"],
-			exclude: cloudflare ? ["virtual:emdash"] : [...NODE_NATIVE_EXTERNALS, "virtual:emdash"],
+			exclude: cloudflare
+				? [
+						// tiptap deps not used in this repo; excluded so optimizeDeps does not fail to resolve them on fresh installs (issue #771).
+						"virtual:emdash",
+						"@tiptap/extension-collaboration",
+						"@tiptap/y-tiptap",
+					]
+				: [
+						...NODE_NATIVE_EXTERNALS,
+						// tiptap deps not used in this repo; excluded so optimizeDeps does not fail to resolve them on fresh installs (issue #771).
+						"virtual:emdash",
+						"@tiptap/extension-collaboration",
+						"@tiptap/y-tiptap",
+					],
 		},
 	};
 }
diff --git a/packages/core/tests/unit/astro/vite-config-optimizedeps.test.ts b/packages/core/tests/unit/astro/vite-config-optimizedeps.test.ts
new file mode 100644
index 000000000..b5358cd27
--- /dev/null
+++ b/packages/core/tests/unit/astro/vite-config-optimizedeps.test.ts
@@ -0,0 +1,76 @@
+import type { AstroConfig } from "astro";
+import { describe, expect, it } from "vitest";
+
+import type { EmDashConfig } from "../../../src/astro/integration/runtime.js";
+import { createViteConfig } from "../../../src/astro/integration/vite-config.js";
+
+/**
+ * Regression for #771: a fresh `npm create emdash@latest && yarn dev` failed
+ * dependency optimization on `@tiptap/extension-collaboration` and
+ * `@tiptap/y-tiptap`. Neither package is imported in source code or declared
+ * as a dependency, but Vite's esbuild dep scanner follows non-static
+ * `import()` calls inside `@tiptap/react` / `@tiptap/starter-kit` and tries
+ * to resolve them. The fix: list both packages in `optimizeDeps.exclude` so
+ * the scanner skips them.
+ *
+ * Both branches of the integration's vite config (Cloudflare and non-
+ * Cloudflare) need the exclusion. The test pins both branches so a future
+ * refactor can't quietly drop the entries from one path.
+ */
+describe("vite-config optimizeDeps exclude (#771)", () => {
+	function makeOptions(adapter: "cloudflare" | "node") {
+		const astroConfig: Partial<AstroConfig> = {
+			adapter:
+				adapter === "cloudflare"
+					? { name: "@astrojs/cloudflare", hooks: {} }
+					: { name: "@astrojs/node", hooks: {} },
+		};
+		const emdashConfig: Partial<EmDashConfig> = {};
+		return {
+			astroConfig: astroConfig as AstroConfig,
+			emdashConfig: emdashConfig as EmDashConfig,
+			plugins: [] as PluginDescriptor[],
+		};
+	}
+
+	it("excludes @tiptap/extension-collaboration and @tiptap/y-tiptap on the Node path", () => {
+		const config = createViteConfig(
+			makeOptions("node") as Parameters<typeof createViteConfig>[0],
+			"dev",
+		);
+		const exclude = config.optimizeDeps?.exclude ?? [];
+		expect(exclude).toContain("@tiptap/extension-collaboration");
+		expect(exclude).toContain("@tiptap/y-tiptap");
+		// Sanity-check existing entries are still present so we did not
+		// regress the original optimizeDeps shape.
+		expect(exclude).toContain("virtual:emdash");
+	});
+
+	it("excludes @tiptap/extension-collaboration and @tiptap/y-tiptap on the Cloudflare ssr path", () => {
+		const config = createViteConfig(
+			makeOptions("cloudflare") as Parameters<typeof createViteConfig>[0],
+			"dev",
+		);
+		// On Cloudflare the exclusion shows up in two places: the
+		// adapter-specific ssr.optimizeDeps block, and the top-level
+		// optimizeDeps.exclude ternary. Both must carry the entries so a
+		// future refactor that drops one path is still caught.
+		const ssr = config.ssr as { optimizeDeps?: { exclude?: string[] } } | undefined;
+		const ssrExclude = ssr?.optimizeDeps?.exclude ?? [];
+		expect(ssrExclude).toContain("@tiptap/extension-collaboration");
+		expect(ssrExclude).toContain("@tiptap/y-tiptap");
+		expect(ssrExclude).toContain("virtual:emdash");
+
+		const topLevelExclude = config.optimizeDeps?.exclude ?? [];
+		expect(topLevelExclude).toContain("@tiptap/extension-collaboration");
+		expect(topLevelExclude).toContain("@tiptap/y-tiptap");
+	});
+});
+
+// Re-declare here to avoid pulling the runtime module's broader type surface
+// into a test file. The shape only needs to be assignable; the test does not
+// inspect the plugins list.
+type PluginDescriptor = {
+	name?: string;
+	package?: string;
+};