diff --git a/src/resources/extensions/sf/sm-client.js b/src/resources/extensions/sf/sm-client.js
index c5fb3c3cf..0f2b89739 100644
--- a/src/resources/extensions/sf/sm-client.js
+++ b/src/resources/extensions/sf/sm-client.js
@@ -21,6 +21,38 @@
  * SM is opt-in: set SM_ENABLED=true to activate. Disabled by default.
  */
 import { getErrorMessage } from "./error-utils.js";
+
+/**
+ * Resolve the explicit tenant/project boundary for Singularity Memory calls.
+ *
+ * Purpose: prevent `SM_ENABLED=true` from becoming an implicit all-tenant
+ * cross-project recall switch.
+ *
+ * Consumer: SM sync/query operations before sending data to the memory server.
+ */
+export function resolveSmScope(opts = {}) {
+	const tenantId =
+		typeof opts.tenantId === "string" && opts.tenantId.trim()
+			? opts.tenantId.trim()
+			: (
+					process.env.SM_TENANT_ID ||
+					process.env.SINGULARITY_MEMORY_TENANT_ID ||
+					""
+				).trim();
+	const projectId =
+		typeof opts.projectId === "string" && opts.projectId.trim()
+			? opts.projectId.trim()
+			: (
+					process.env.SM_PROJECT_ID ||
+					process.env.SINGULARITY_MEMORY_PROJECT_ID ||
+					""
+				).trim();
+	return {
+		tenantId: tenantId || null,
+		projectId: projectId || null,
+	};
+}
+
 export async function initializeSmClient() {
 	// SM is opt-in — disabled unless explicitly enabled
 	if (process.env.SM_ENABLED !== "true") {
@@ -89,6 +121,14 @@ export async function syncMemoryToSm(memory, opts = {}) {
 		opts.smAddr ||
 		process.env.SINGULARITY_MEMORY_ADDR ||
 		"http://localhost:8080";
+	const scope = resolveSmScope(opts);
+	if (!scope.tenantId) {
+		return {
+			queued: false,
+			reason:
+				"SM tenant scope missing (set SM_TENANT_ID or SINGULARITY_MEMORY_TENANT_ID)",
+		};
+	}
 
 	// Queue sync in background (fire-and-forget)
 	setImmediate(async () => {
@@ -101,6 +141,8 @@ export async function syncMemoryToSm(memory, opts = {}) {
 				body: JSON.stringify({
 					memory,
 					source: "sf", // Identify source as SF instance
+					tenantId: scope.tenantId,
+					...(scope.projectId ? { projectId: scope.projectId } : {}),
 				}),
 				signal: AbortSignal.timeout(5000),
 			});
@@ -135,6 +177,10 @@ export async function querySmMemories(query, opts = {}) {
 		process.env.SINGULARITY_MEMORY_ADDR ||
 		"http://localhost:8080";
 	const limit = opts.limit || 5; // Cross-project recall limit (smaller than local)
+	const scope = resolveSmScope(opts);
+	if (!scope.tenantId) {
+		return [];
+	}
 
 	try {
 		const response = await fetch(`${addr}/v1/memories/query`, {
@@ -142,7 +188,12 @@ export async function querySmMemories(query, opts = {}) {
 			headers: {
 				"Content-Type": "application/json",
 			},
-			body: JSON.stringify({ query, limit }),
+			body: JSON.stringify({
+				query,
+				limit,
+				tenantId: scope.tenantId,
+				...(scope.projectId ? { projectId: scope.projectId } : {}),
+			}),
 			signal: AbortSignal.timeout(5000),
 		});
 
@@ -173,6 +224,7 @@ export function getSmStatus() {
 	return {
 		configured: true,
 		addr,
+		tenantConfigured: Boolean(resolveSmScope().tenantId),
 		status: "unknown", // Status should be checked via initializeSmClient
 	};
 }
diff --git a/src/resources/extensions/sf/tests/sm-client.test.ts b/src/resources/extensions/sf/tests/sm-client.test.ts
index 36aeb33c6..d882293d3 100644
--- a/src/resources/extensions/sf/tests/sm-client.test.ts
+++ b/src/resources/extensions/sf/tests/sm-client.test.ts
@@ -9,16 +9,20 @@
  * - Environment variable controls
  */
 
-import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 describe("SM Client", () => {
 	let originalEnv: Record<string, string | undefined>;
+	let originalFetch: typeof globalThis.fetch;
 
 	beforeEach(() => {
 		originalEnv = { ...process.env };
+		originalFetch = globalThis.fetch;
 	});
 
 	afterEach(() => {
+		globalThis.fetch = originalFetch;
+		vi.restoreAllMocks();
 		// Restore env
 		for (const key of Object.keys(process.env)) {
 			if (!(key in originalEnv)) {
@@ -193,6 +197,52 @@ describe("SM Client", () => {
 
 			expect(Array.isArray(result)).toBe(true);
 		});
+
+		it("when_sm_enabled_without_tenant_scope_returns_empty_without_fetch", async () => {
+			process.env.SM_ENABLED = "true";
+			delete process.env.SM_TENANT_ID;
+			delete process.env.SINGULARITY_MEMORY_TENANT_ID;
+			const fetchMock = vi.fn();
+			globalThis.fetch = fetchMock;
+
+			const { querySmMemories } = await import("../sm-client.js");
+
+			const result = await querySmMemories("cross-project", {
+				smConnected: true,
+				limit: 3,
+			});
+
+			expect(result).toEqual([]);
+			expect(fetchMock).not.toHaveBeenCalled();
+		});
+
+		it("when_tenant_scope_configured_sends_tenant_and_project_filters", async () => {
+			process.env.SM_ENABLED = "true";
+			process.env.SM_TENANT_ID = "tenant-a";
+			process.env.SM_PROJECT_ID = "project-b";
+			const fetchMock = vi.fn().mockResolvedValue({
+				ok: true,
+				json: async () => ({ memories: [{ id: "mem-1", content: "hit" }] }),
+			});
+			globalThis.fetch = fetchMock;
+
+			const { querySmMemories } = await import("../sm-client.js");
+
+			const result = await querySmMemories("cross-project", {
+				smConnected: true,
+				limit: 3,
+			});
+
+			expect(result).toEqual([{ id: "mem-1", content: "hit" }]);
+			expect(fetchMock).toHaveBeenCalledTimes(1);
+			const body = JSON.parse(fetchMock.mock.calls[0][1].body);
+			expect(body).toEqual({
+				query: "cross-project",
+				limit: 3,
+				tenantId: "tenant-a",
+				projectId: "project-b",
+			});
+		});
 	});
 
 	describe("getSmStatus", () => {
@@ -220,6 +270,7 @@ describe("SM Client", () => {
 			expect(status).toEqual(
 				expect.objectContaining({
 					configured: true,
+					tenantConfigured: false,
 					status: "unknown", // Actual connection status requires initializeSmClient
 				}),
 			);