diff --git a/package.json b/package.json
index d3ada198..8089d8e5 100644
--- a/package.json
+++ b/package.json
@@ -21,7 +21,6 @@
     "openpgp": "6.3.2",
     "react": "19.3.0",
     "react-dom": "19.3.0",
-    "typebox": "1.3.6",
     "web-ui-primitives": "1.1.4",
     "wire-mesh-core": "4.0.6",
     "ws": "8.21.1",
@@ -70,6 +69,7 @@
     "semantic-release": "25.0.7",
     "tsx": "^4.23.1",
     "turbo": "2.11.5",
+    "typebox": "1.3.6",
     "typescript": "^6.0.3",
     "typescript-eslint": "8.70.0",
     "vite": "8.3.2",
@@ -113,7 +113,8 @@
   "packageManager": "pnpm@12.4.1+sha512.2e81e399d73fe8390dab25e06aa788ab7a5908248d2f5a370f82b481147a6a7a367bf8048f9a6fdb6460f21a66f0542dedb8b94ca2c8723596741920b1656d4c",
   "peerDependencies": {
     "@earendil-works/pi-ai": ">=0.79.0",
-    "@earendil-works/pi-coding-agent": ">=0.79.0"
+    "@earendil-works/pi-coding-agent": ">=0.79.0",
+    "typebox": "*"
   },
   "pi": {
     "extensions": [
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index cc169bb5..963af2f7 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -221,9 +221,6 @@ importers:
       react-dom:
         specifier: 19.3.0
         version: 19.3.0(react@19.3.0)
-      typebox:
-        specifier: 1.3.6
-        version: 1.3.6
       web-ui-primitives:
         specifier: 1.1.4
         version: 1.1.4(@mantine/core@9.6.1(@mantine/hooks@9.6.1(react@19.3.0))(@types/react@19.3.0)(react-dom@19.3.0(react@19.3.0))(react@19.3.0))(react-dom@19.3.0(react@19.3.0))(react@19.3.0)
@@ -363,6 +360,9 @@ importers:
       turbo:
         specifier: 2.11.5
         version: 2.11.5
+      typebox:
+        specifier: 1.3.6
+        version: 1.3.6
       typescript:
         specifier: ^6.0.3
         version: 6.0.3
diff --git a/src/test/pi-manifest-packed.integration.test.ts b/src/test/pi-manifest-packed.integration.test.ts
index cf3233fe..832c57a7 100644
--- a/src/test/pi-manifest-packed.integration.test.ts
+++ b/src/test/pi-manifest-packed.integration.test.ts
@@ -2,6 +2,8 @@
  * Every extension the `pi` manifest in package.json names must ship in the published package. `pi install npm:agent-comms` reported success and then could not load the extension when the manifest pointed at `src/`, which `files` did not publish (ExaDev/agent-comms#412, #440); nothing in the suite noticed, because the manifest and the tarball were never compared.
  *
  * The tarball contents come from `npm pack --dry-run`, the same file selection a publish uses, so a `files` entry or an ignore rule that drops the manifest's path fails here and not in a user's install.
+ *
+ * The same manifest declares `typebox`, which the pi bridge imports directly. Pi supplies that package to extensions and maps the specifier to its own copy, so declaring it in `dependencies` installs a second physical copy that shadows the mapping and makes Pi warn on every start (ExaDev/agent-comms#455).
  */
 import { spawnSync } from "node:child_process";
 import * as fs from "node:fs";
@@ -10,6 +12,16 @@ import { describe, expect, it } from "vitest";
 
 const packageRoot = path.resolve(import.meta.dirname, "../..");
 
+// Packages Pi supplies to extensions, from the host-provided list in Pi's package docs.
+const HOST_PROVIDED_PACKAGES = [
+  "@earendil-works/pi-agent-core",
+  "@earendil-works/pi-ai",
+  "@earendil-works/pi-coding-agent",
+  "@earendil-works/pi-tui",
+  "@sinclair/typebox",
+  "typebox",
+];
+
 function isRecord(value: unknown): value is Record<string, unknown> {
   return typeof value === "object" && value !== null && !Array.isArray(value);
 }
@@ -81,4 +93,24 @@ describe("the pi manifest", () => {
       expect(packed.has(path.posix.normalize(extension)), extension).toBe(true);
     }
   });
+
+  it("declares host-provided packages as wildcard peers, never dependencies", () => {
+    const manifest = readJson(path.join(packageRoot, "package.json"));
+    if (!isRecord(manifest)) {
+      throw new Error("package.json is not an object");
+    }
+    const dependencies = isRecord(manifest.dependencies)
+      ? Object.keys(manifest.dependencies)
+      : [];
+    const peers = isRecord(manifest.peerDependencies)
+      ? manifest.peerDependencies
+      : {};
+    for (const name of HOST_PROVIDED_PACKAGES) {
+      expect(dependencies, `${name} must not be a dependency`).not.toContain(
+        name,
+      );
+    }
+    // The pi bridge imports `typebox`, so it must be declared as a peer, and `"*"` lets Pi's own copy satisfy it.
+    expect(peers.typebox).toBe("*");
+  });
 });