diff --git a/src/agents/pi-embedded-subscribe.handlers.tools.test.ts b/src/agents/pi-embedded-subscribe.handlers.tools.test.ts
index c03eb00da57..96a988e5bc6 100644
--- a/src/agents/pi-embedded-subscribe.handlers.tools.test.ts
+++ b/src/agents/pi-embedded-subscribe.handlers.tools.test.ts
@@ -88,6 +88,37 @@ describe("handleToolExecutionStart read path checks", () => {
     expect(warn).toHaveBeenCalledTimes(1);
     expect(String(warn.mock.calls[0]?.[0] ?? "")).toContain("read tool called without path");
   });
+
+  it("awaits onBlockReplyFlush before continuing tool start processing", async () => {
+    const { ctx, onBlockReplyFlush } = createTestContext();
+    let releaseFlush: (() => void) | undefined;
+    onBlockReplyFlush.mockImplementation(
+      () =>
+        new Promise<void>((resolve) => {
+          releaseFlush = resolve;
+        }),
+    );
+
+    const evt: ToolExecutionStartEvent = {
+      type: "tool_execution_start",
+      toolName: "exec",
+      toolCallId: "tool-await-flush",
+      args: { command: "echo hi" },
+    };
+
+    const pending = handleToolExecutionStart(ctx, evt);
+    // Let the async function reach the awaited flush Promise.
+    await Promise.resolve();
+
+    // If flush isn't awaited, tool metadata would already be recorded here.
+    expect(ctx.state.toolMetaById.has("tool-await-flush")).toBe(false);
+    expect(releaseFlush).toBeTypeOf("function");
+
+    releaseFlush?.();
+    await pending;
+
+    expect(ctx.state.toolMetaById.has("tool-await-flush")).toBe(true);
+  });
 });
 
 describe("handleToolExecutionEnd cron.add commitment tracking", () => {
diff --git a/src/agents/pi-embedded-subscribe.handlers.tools.ts b/src/agents/pi-embedded-subscribe.handlers.tools.ts
index ea3031a6cc4..18dc11193f0 100644
--- a/src/agents/pi-embedded-subscribe.handlers.tools.ts
+++ b/src/agents/pi-embedded-subscribe.handlers.tools.ts
@@ -174,7 +174,7 @@ export async function handleToolExecutionStart(
   // Flush pending block replies to preserve message boundaries before tool execution.
   ctx.flushBlockReplyBuffer();
   if (ctx.params.onBlockReplyFlush) {
-    void ctx.params.onBlockReplyFlush();
+    await ctx.params.onBlockReplyFlush();
   }
 
   const rawToolName = String(evt.toolName);