diff --git a/src/gateway/chat-abort.test.ts b/src/gateway/chat-abort.test.ts
index 5a1d464022e..f7e262c5fd8 100644
--- a/src/gateway/chat-abort.test.ts
+++ b/src/gateway/chat-abort.test.ts
@@ -360,6 +360,7 @@ describe("resolveInFlightRunSnapshot", () => {
       aborted?: boolean;
       projectSessionActive?: boolean;
       startedAtMs?: number;
+      kind?: ChatAbortControllerEntry["kind"];
     },
   ): ChatAbortControllerEntry => {
     const now = Date.now();
@@ -376,6 +377,7 @@ describe("resolveInFlightRunSnapshot", () => {
       startedAtMs,
       expiresAtMs: startedAtMs + 10_000,
       projectSessionActive: opts?.projectSessionActive ?? true,
+      kind: opts?.kind,
     };
   };
 
@@ -446,6 +448,18 @@ describe("resolveInFlightRunSnapshot", () => {
     }
   });
 
+  it("ignores hidden agent runs that are not visible chat sends", () => {
+    expect(
+      snap({
+        chatAbortControllers: new Map([
+          ["run-agent", inFlightEntry("agent:main:s", { kind: "agent" })],
+        ]),
+        chatRunBuffers: new Map([["run-agent", "hidden partial"]]),
+        sessionKey: "agent:main:s",
+      }),
+    ).toBeUndefined();
+  });
+
   it("treats an entry with undefined projectSessionActive as active (sessions.list contract)", () => {
     const entry = inFlightEntry("agent:main:s");
     delete (entry as { projectSessionActive?: boolean }).projectSessionActive;
diff --git a/src/gateway/chat-abort.ts b/src/gateway/chat-abort.ts
index 7573480e0ca..d470eea332d 100644
--- a/src/gateway/chat-abort.ts
+++ b/src/gateway/chat-abort.ts
@@ -175,9 +175,10 @@ function normalizeActiveAgentId(agentId: string | undefined): string | undefined
  * key, so accept a match on EITHER `requestedSessionKey` or `canonicalSessionKey`,
  * scoping the shared "global" session by agent. Only runs still projected active
  * (`projectSessionActive !== false`, matching sessions.list; the terminal lifecycle
- * flips it to false) and not aborted are returned, so a finalized run — already in
- * persisted history — is not duplicated and a stale run cannot leave the client
- * stuck in `streaming`.
+ * flips it to false), not aborted, and visible chat-send runs are returned, so a
+ * finalized run — already in persisted history — is not duplicated and hidden
+ * agent runs cannot be adopted by chat clients that will not receive their final
+ * events.
  */
 export function resolveInFlightRunSnapshot(params: {
   chatAbortControllers: Map<string, ChatAbortControllerEntry>;
@@ -218,7 +219,11 @@ export function resolveInFlightRunSnapshot(params: {
     // Active unless explicitly projected inactive — mirrors sessions.list's
     // collectTrackedActiveSessionRuns (`projectSessionActive !== false`), so a run
     // that indicator shows active is never silently dropped here.
-    if (entry.projectSessionActive === false || entry.controller.signal.aborted) {
+    if (
+      entry.projectSessionActive === false ||
+      entry.controller.signal.aborted ||
+      entry.kind === "agent"
+    ) {
       continue;
     }
     if (