diff --git a/packages/coding-agent/test/model-catalog-protocol.test.ts b/packages/coding-agent/test/model-catalog-protocol.test.ts
index 9222af565..197cab282 100644
--- a/packages/coding-agent/test/model-catalog-protocol.test.ts
+++ b/packages/coding-agent/test/model-catalog-protocol.test.ts
@@ -61,8 +61,6 @@ function startCatalogServer(requests: string[]): Promise<Server> {
 		const catalogRequest = parseModelCatalogRequest(url, request.headers["user-agent"]);
 		if (!provider) {
 			response.writeHead(404).end();
-		} else if (catalogRequest.kind === "redirect") {
-			response.writeHead(307, { location: catalogRequest.location, "cache-control": "no-store" }).end();
 		} else if (catalogRequest.kind === "invalid") {
 			response.writeHead(400).end(catalogRequest.error);
 		} else {
@@ -120,7 +118,7 @@ describe("model catalog protocol with the current client", () => {
 		expect([...refresh.errors]).toEqual([]);
 
 		const catalogUrl = "/api/models/providers/openrouter?types=chat%2Cimage%2Cclassifier";
-		expect(requests).toEqual([catalogUrl, `${catalogUrl}&pi-version=${VERSION}`]);
+		expect(requests).toEqual([catalogUrl]);
 
 		const expectedModel =
 			selectModelCatalog(index, VERSION)?.revision === legacyRevision ? legacyModel : mixedApiModel;
diff --git a/scripts/model-catalog-protocol.test.ts b/scripts/model-catalog-protocol.test.ts
index cdfcc0d50..0a7e3af77 100644
--- a/scripts/model-catalog-protocol.test.ts
+++ b/scripts/model-catalog-protocol.test.ts
@@ -55,25 +55,23 @@ test("selects the newest catalog a Pi version supports", () => {
 	assert.equal(selectModelCatalog(index, undefined)?.revision, mixedApiRevision);
 });
 
-test("redirects Pi user agents to an explicit catalog version", () => {
+test("serves Pi user agents the catalog for their version", () => {
 	// Regression test for #9099: released clients identify themselves only by User-Agent.
 	assert.deepEqual(
 		parseModelCatalogRequest(
 			"https://pi.dev/api/models/providers/openrouter?types=chat%2Cimage",
 			"pi/0.84.4 (linux; node/v22.0.0; x64)",
 		),
-		{
-			kind: "redirect",
-			location: "https://pi.dev/api/models/providers/openrouter?types=chat%2Cimage&pi-version=0.84.4",
-		},
+		{ kind: "catalog", piVersion: "0.84.4", representation: "typed" },
 	);
 	assert.deepEqual(parseModelCatalogRequest("https://pi.dev/api/models", "pi/0.84.4"), {
-		kind: "redirect",
-		location: "https://pi.dev/api/models?pi-version=0.84.4",
+		kind: "catalog",
+		piVersion: "0.84.4",
+		representation: "legacy",
 	});
 });
 
-test("serves explicit and unversioned catalog requests without redirecting", () => {
+test("serves explicit and unversioned catalog requests", () => {
 	assert.deepEqual(
 		parseModelCatalogRequest("https://pi.dev/api/models?pi-version=0.83.0", "pi/0.85.1 (linux; node/v22.0.0; x64)"),
 		{ kind: "catalog", piVersion: "0.83.0", representation: "legacy" },
diff --git a/scripts/model-catalog-protocol.ts b/scripts/model-catalog-protocol.ts
index d151d36a5..173c62b19 100644
--- a/scripts/model-catalog-protocol.ts
+++ b/scripts/model-catalog-protocol.ts
@@ -53,7 +53,6 @@ export type ModelCatalogIndex = {
 
 export type ModelCatalogRequest =
 	| { kind: "catalog"; piVersion: string | undefined; representation: ModelCatalogRepresentation }
-	| { kind: "redirect"; location: string }
 	| { kind: "invalid"; error: string };
 
 export function getModelCatalogArtifactKey(revision: string, artifact: ModelCatalogArtifact): string {
@@ -97,10 +96,11 @@ export function parseModelCatalogRepresentation(
 /**
  * Decide how to answer a catalog request from its URL and User-Agent.
  *
- * Released clients do not send `pi-version`. Responses are cached by URL, so
- * instead of varying the response on the User-Agent, clients that identify
- * as Pi are redirected to the equivalent URL with an explicit `pi-version`.
- * Requests without a Pi User-Agent receive the default catalog.
+ * Released clients do not send `pi-version`, so clients that identify as Pi
+ * are served the catalog for the version in their User-Agent. The response
+ * therefore varies on the User-Agent, and the server must say so with `Vary`.
+ * An explicit `pi-version` takes precedence. Requests without a Pi User-Agent
+ * receive the default catalog.
  */
 export function parseModelCatalogRequest(url: string | URL, userAgent: string | null | undefined): ModelCatalogRequest {
 	const requestUrl = new URL(url);
@@ -113,8 +113,7 @@ export function parseModelCatalogRequest(url: string | URL, userAgent: string |
 	if (piVersion === null) {
 		const userAgentVersion = PI_USER_AGENT_RE.exec(userAgent ?? "")?.[1];
 		if (userAgentVersion !== undefined && isValidModelCatalogPiVersion(userAgentVersion)) {
-			requestUrl.searchParams.set("pi-version", userAgentVersion);
-			return { kind: "redirect", location: requestUrl.toString() };
+			return { kind: "catalog", piVersion: userAgentVersion, representation };
 		}
 		return { kind: "catalog", piVersion: undefined, representation };
 	}