diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index c1b019efa..9c6c24593 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -45,6 +45,7 @@
 
 ### Fixed
 
+- Fixed Anthropic web search requests to include `metadata.user_id` from the active session id, matching the main Messages path for gateway attribution ([#2295](https://github.com/can1357/oh-my-pi/issues/2295)).
 - Fixed `irc` live message delivery so successfully handed-off messages are no longer enqueued as mailbox mail, so they do not inflate unread `irc` counts
 - Fixed `irc send` with `await: true` to wait for a fresh reply to the current call instead of consuming previously buffered messages
 - Fixed main-session chat output to stop duplicating outbound `irc` sends from the main agent as relay cards
diff --git a/packages/coding-agent/src/web/search/providers/anthropic.ts b/packages/coding-agent/src/web/search/providers/anthropic.ts
index a99a494f1..3e354373c 100644
--- a/packages/coding-agent/src/web/search/providers/anthropic.ts
+++ b/packages/coding-agent/src/web/search/providers/anthropic.ts
@@ -82,6 +82,7 @@ function buildSystemBlocks(
  * @param auth - Authentication configuration (API key or OAuth)
  * @param model - Model identifier to use
  * @param query - Search query from the user
+ * @param sessionId - Optional session id forwarded as Anthropic metadata.user_id
  * @param systemPrompt - Optional system prompt for guiding response style
  * @returns Raw API response from Anthropic
  * @throws {SearchProviderError} If the API request fails
@@ -90,6 +91,7 @@ async function callSearch(
 	auth: AnthropicAuthConfig,
 	model: string,
 	query: string,
+	sessionId?: string,
 	systemPrompt?: string,
 	maxTokens?: number,
 	temperature?: number,
@@ -113,6 +115,10 @@ async function callSearch(
 		],
 	};
 
+	if (sessionId) {
+		body.metadata = { user_id: sessionId };
+	}
+
 	if (temperature !== undefined) {
 		body.temperature = temperature;
 	}
@@ -280,6 +286,7 @@ export async function searchAnthropic(
 				buildAnthropicAuthConfig(key, searchBaseUrl),
 				model,
 				params.query,
+				"authStorage" in params ? params.sessionId : undefined,
 				systemPrompt,
 				maxTokens,
 				params.temperature,
diff --git a/packages/coding-agent/test/web/search/anthropic.test.ts b/packages/coding-agent/test/web/search/anthropic.test.ts
new file mode 100644
index 000000000..bbdd5a062
--- /dev/null
+++ b/packages/coding-agent/test/web/search/anthropic.test.ts
@@ -0,0 +1,42 @@
+import { describe, expect, it } from "bun:test";
+import * as path from "node:path";
+import type { FetchImpl } from "@oh-my-pi/pi-ai";
+import { AuthStorage } from "@oh-my-pi/pi-coding-agent/session/auth-storage";
+import { searchAnthropic } from "@oh-my-pi/pi-coding-agent/web/search/providers/anthropic";
+import { TempDir } from "@oh-my-pi/pi-utils";
+
+describe("Anthropic search request body", () => {
+	it("passes the session id as Messages metadata.user_id", async () => {
+		using tempDir = TempDir.createSync("@pi-anthropic-search-");
+		const authStorage = await AuthStorage.create(path.join(tempDir.path(), "auth.db"));
+		try {
+			authStorage.setRuntimeApiKey("anthropic", "test-key");
+
+			let capturedBody: Record<string, unknown> | undefined;
+			const fetchMock: FetchImpl = async (_input, init) => {
+				capturedBody = JSON.parse(String(init?.body));
+				return new Response(
+					JSON.stringify({
+						id: "msg_test",
+						model: "claude-haiku-4-5",
+						content: [],
+						usage: { input_tokens: 1, output_tokens: 2 },
+					}),
+					{ status: 200, headers: { "Content-Type": "application/json" } },
+				);
+			};
+
+			await searchAnthropic({
+				query: "gateway attribution requirements",
+				systemPrompt: "Use web search.",
+				sessionId: "session-2295",
+				authStorage,
+				fetch: fetchMock,
+			});
+
+			expect(capturedBody?.metadata).toEqual({ user_id: "session-2295" });
+		} finally {
+			authStorage.close();
+		}
+	});
+});