From bbf29b3c92a3b6b9af81d8ef275f4bb3bed92977 Mon Sep 17 00:00:00 2001
From: Ingwannu <ingwannu@users.noreply.github.com>
Date: Thu, 20 Aug 2026 11:53:29 +0000
Subject: [PATCH] fix(responses): bound terminal guard delta retention

---
 src/server/responses/terminal-guard.ts | 21 ++++++++++++++-------
 tests/terminal-guard.test.ts           | 11 +++++++++++
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/server/responses/terminal-guard.ts b/src/server/responses/terminal-guard.ts
index 347a489f19..67a55c2bfe 100644
--- a/src/server/responses/terminal-guard.ts
+++ b/src/server/responses/terminal-guard.ts
@@ -153,6 +153,16 @@ export interface GuardedEventStreamOptions {
   maxAutoContinuations?: number;
 }
 
+/**
+ * Events that are useful to the downstream stream consumer but carry no state used by the
+ * terminal-continuation decision or its rebuilt request. Keep them out of the retained event
+ * list so adapter liveness markers and arbitrarily large tool-argument fragments cannot make
+ * the guard's per-turn memory grow without adding any continuation semantics.
+ */
+export function isTerminalGuardPassthroughOnly(event: AdapterEvent): boolean {
+  return event.type === "heartbeat" || event.type === "tool_call_delta";
+}
+
 function mergeUsage(first: OcxUsage | undefined, second: OcxUsage | undefined): OcxUsage | undefined {
   if (!first) return second;
   if (!second) return first;
@@ -193,13 +203,10 @@ export async function* guardTerminalEventStream(options: GuardedEventStreamOptio
     const seen: AdapterEvent[] = [];
     let terminalSeen = false;
     for await (const event of source) {
-      // A heartbeat is adapter liveness, not turn content: it exists so the bridge watchdog
-      // can tell a buffering adapter from a hung one. Retaining it here would put an
-      // unbounded number of empty markers into `seen`, which feeds both the continuation
-      // analysis and the rebuilt request — and the openai-chat adapter now emits one per
-      // tool-call delta, so a long argument payload alone could grow this array without
-      // limit. The empty-completion guard already passes them through unretained; match it.
-      if (event.type === "heartbeat") {
+      // Liveness markers and tool argument fragments are passed through to the bridge, but
+      // neither analyzeTerminalTurn nor buildContinuationRequest consumes them. Retaining the
+      // fragments would duplicate arbitrarily large argument payloads in `seen` for no effect.
+      if (isTerminalGuardPassthroughOnly(event)) {
         yield event;
         continue;
       }
diff --git a/tests/terminal-guard.test.ts b/tests/terminal-guard.test.ts
index 906c726997..356e54fb3d 100644
--- a/tests/terminal-guard.test.ts
+++ b/tests/terminal-guard.test.ts
@@ -3,6 +3,7 @@ import {
   analyzeTerminalTurn,
   buildContinuationRequest,
   guardTerminalEventStream,
+  isTerminalGuardPassthroughOnly,
 } from "../src/server/responses/terminal-guard";
 import { buildResponseJSON } from "../src/bridge";
 import type { AdapterEvent, OcxParsedRequest } from "../src/types";
@@ -236,6 +237,16 @@ describe("terminal guard", () => {
     expect(actual.filter(event => event.type === "done")).toHaveLength(1);
   });
 
+  test("does not retain passthrough-only liveness or tool argument fragments", () => {
+    expect(isTerminalGuardPassthroughOnly({ type: "heartbeat" })).toBe(true);
+    expect(isTerminalGuardPassthroughOnly({
+      type: "tool_call_delta",
+      arguments: "x".repeat(1024 * 1024),
+    })).toBe(true);
+    expect(isTerminalGuardPassthroughOnly({ type: "tool_call_start", id: "call_1", name: "exec_command" })).toBe(false);
+    expect(isTerminalGuardPassthroughOnly({ type: "text_delta", text: "working" })).toBe(false);
+  });
+
   test("stops after the configured continuation bound", async () => {
     let continuations = 0;
     const actual: AdapterEvent[] = [];