diff --git a/extension/src/command-handler.ts b/extension/src/command-handler.ts
index ca9ee30..b0106e2 100644
--- a/extension/src/command-handler.ts
+++ b/extension/src/command-handler.ts
@@ -25,6 +25,8 @@ export interface CommandHandlerContext {
     onAutoApproveChanged: (enabled: boolean) => void;
     /** Track recently sent Discord→AG texts to avoid echo relay */
     recentDiscordSentTexts: Map<string, number>;
+    /** Get the active cascade/session ID from step-probe polling state */
+    getActiveSessionId: () => string;
 }
 
 // ─── File-based command watcher ───
@@ -127,10 +129,12 @@ export function handleWSCommand(ctx: CommandHandlerContext, data: { text?: strin
  * This is the same mechanism AG's native red ■ stop button uses.
  */
 async function _cancelCurrentCascade(ctx: CommandHandlerContext) {
-    // 1. Get the active cascade ID from SDK titles manager
-    const cascadeId = ctx.sdk?.titles?.getActiveCascadeId?.();
+    // 1. Get the active cascade ID from extension state (step-probe polling)
+    //    NOTE: ctx.sdk.titles.getActiveCascadeId() is renderer-only (DOM scraping)
+    //    and always returns undefined from extension host. Use activeSessionId instead.
+    const cascadeId = ctx.getActiveSessionId();
     if (!cascadeId) {
-        ctx.logToFile('[STOP] No active cascade to cancel (getActiveCascadeId returned null)');
+        ctx.logToFile('[STOP] No active cascade — no session tracked yet');
         return;
     }
 
diff --git a/extension/src/extension.ts b/extension/src/extension.ts
index 2fbe548..b33c407 100644
--- a/extension/src/extension.ts
+++ b/extension/src/extension.ts
@@ -430,6 +430,7 @@ export async function activate(context: vscode.ExtensionContext) {
                     bridgePath, projectName, sdk, ls: sdk?.ls, autoApproveEnabled, logToFile,
                     onAutoApproveChanged: (enabled: boolean) => { autoApproveEnabled = enabled; },
                     recentDiscordSentTexts,
+                    getActiveSessionId: () => activeSessionId,
                 }, data);
             },
             onInstanceUpdate: (count, instances) => {
@@ -559,6 +560,7 @@ export async function activate(context: vscode.ExtensionContext) {
         bridgePath, projectName, sdk, ls: sdk?.ls, autoApproveEnabled, logToFile,
         onAutoApproveChanged: (enabled: boolean) => { autoApproveEnabled = enabled; },
         recentDiscordSentTexts,
+        getActiveSessionId: () => activeSessionId,
     });
 
     // Response watcher is now initialized by initStepProbe() above