diff --git a/src/resources/extensions/sf/doctor-config-checks.js b/src/resources/extensions/sf/doctor-config-checks.js
index c94db46fb..12b69300a 100644
--- a/src/resources/extensions/sf/doctor-config-checks.js
+++ b/src/resources/extensions/sf/doctor-config-checks.js
@@ -389,9 +389,8 @@ export function checkVaultHealth(issues, _shouldFix) {
  */
 export async function checkSmHealth(issues, _shouldFix) {
 	try {
-		// Check if explicitly disabled
-		if (process.env.SM_ENABLED === "false") {
-			// Not an issue — explicit opt-out
+		// SM is opt-in — only check when explicitly enabled
+		if (process.env.SM_ENABLED !== "true") {
 			return;
 		}
 
diff --git a/src/resources/extensions/sf/memory-store.js b/src/resources/extensions/sf/memory-store.js
index 772de921a..50a4c1f09 100644
--- a/src/resources/extensions/sf/memory-store.js
+++ b/src/resources/extensions/sf/memory-store.js
@@ -124,8 +124,8 @@ export async function getRelevantMemoriesRanked(query, limit = 10) {
 	let crossProjectMemories = [];
 	try {
 		const smResults = await querySmMemories(query, {
-			limit: Math.max(3, Math.ceil(limit * 0.3)), // Cross-project recall is 30% of local limit
-			smConnected: process.env.SM_ENABLED !== "false",
+			limit: Math.max(3, Math.ceil(limit * 0.3)),
+			smConnected: process.env.SM_ENABLED === "true",
 		});
 		// Convert SM results to local format (all cross-project memories tagged as such)
 		crossProjectMemories = (smResults || []).map((m) => ({
diff --git a/src/resources/extensions/sf/sm-client.js b/src/resources/extensions/sf/sm-client.js
index bf8bb7f77..57f38a123 100644
--- a/src/resources/extensions/sf/sm-client.js
+++ b/src/resources/extensions/sf/sm-client.js
@@ -18,15 +18,15 @@
  * Returns { connected: boolean, version: string | null, error?: string }
  *
  * Tries to connect to SM at SINGULARITY_MEMORY_ADDR (default: http://localhost:8080).
- * Respects SM_ENABLED=false env var to explicitly disable.
+ * SM is opt-in: set SM_ENABLED=true to activate. Disabled by default.
  */
 export async function initializeSmClient() {
-	// Check if explicitly disabled
-	if (process.env.SM_ENABLED === "false") {
+	// SM is opt-in — disabled unless explicitly enabled
+	if (process.env.SM_ENABLED !== "true") {
 		return {
 			connected: false,
 			version: null,
-			reason: "disabled via SM_ENABLED=false",
+			reason: "disabled (set SM_ENABLED=true to enable)",
 		};
 	}
 
@@ -161,10 +161,10 @@ export async function querySmMemories(query, opts = {}) {
  * Get SM client status for doctor checks.
  */
 export function getSmStatus() {
-	if (process.env.SM_ENABLED === "false") {
+	if (process.env.SM_ENABLED !== "true") {
 		return {
 			connected: false,
-			reason: "disabled via SM_ENABLED=false",
+			reason: "disabled (set SM_ENABLED=true to enable)",
 		};
 	}
 
diff --git a/src/resources/extensions/sf/tests/sm-client.test.ts b/src/resources/extensions/sf/tests/sm-client.test.ts
index b8087fce6..36aeb33c6 100644
--- a/src/resources/extensions/sf/tests/sm-client.test.ts
+++ b/src/resources/extensions/sf/tests/sm-client.test.ts
@@ -197,7 +197,7 @@ describe("SM Client", () => {
 
 	describe("getSmStatus", () => {
 		it("when_sm_disabled_returns_disconnected_status", async () => {
-			process.env.SM_ENABLED = "false";
+			delete process.env.SM_ENABLED; // SM is opt-in — absence means disabled
 
 			const { getSmStatus } = await import("../sm-client.js");
 
@@ -205,7 +205,7 @@ describe("SM Client", () => {
 
 			expect(status).toEqual({
 				connected: false,
-				reason: "disabled via SM_ENABLED=false",
+				reason: "disabled (set SM_ENABLED=true to enable)",
 			});
 		});