diff --git a/config/quality/file-size-baseline.json b/config/quality/file-size-baseline.json
index 19b2a3e9c4..081460c833 100644
--- a/config/quality/file-size-baseline.json
+++ b/config/quality/file-size-baseline.json
@@ -364,7 +364,7 @@
     "open-sse/services/combo.ts": 3648,
     "open-sse/services/compression/strategySelector.ts": 1060,
     "open-sse/services/rateLimitManager.ts": 1167,
-    "open-sse/translator/response/openai-responses.ts": 1215,
+    "open-sse/translator/response/openai-responses.ts": 1224,
     "open-sse/utils/cursorAgentProtobuf.ts": 1505,
     "open-sse/utils/stream.ts": 2889,
     "src/app/(dashboard)/dashboard/HomePageClient.tsx": 1388,
@@ -401,7 +401,7 @@
     "src/shared/components/RequestLoggerV2.tsx": 1629,
     "src/shared/components/analytics/charts.tsx": 1035,
     "src/shared/services/cliRuntime.ts": 1122,
-    "src/sse/handlers/chat.ts": 1918,
+    "src/sse/handlers/chat.ts": 1904,
     "src/sse/services/auth.ts": 2520,
     "tests/unit/account-fallback-service.test.ts": 1572,
     "tests/unit/provider-validation-specialty.test.ts": 2985,
@@ -561,5 +561,6 @@
   "open-sse/translator/request/openai-to-kiro.ts": "1057",
   "open-sse/utils/sseHeartbeat.ts": "142",
   "_rebaseline_2026_08_04_9305_sse_comments": "#9305 fix: broadened sseCommentsEnabled()",
-  "_rebaseline_2026_08_09_v3850_release_close": "Release v3.8.50 close reconciliation on e0ce95c592: src/sse/handlers/chat.ts 1904->1918 is the irreducible request-pipeline wiring from #9759 that invokes the Modality Bridge guardrail without moving its implementation into the handler; covered by the 17 Vision Bridge canaries plus the PR-1 focused suite. open-sse/translator/response/openai-responses.ts 1204->1215 is #9168's Responses tool-call argument delta buffering/normalization at the existing translator state-machine chokepoint; covered by its dedicated translator regression tests. Both values are measured by check:file-size (split-newline semantics), and the gate remains frozen at the new exact sizes."
+  "_rebaseline_2026_08_09_v3850_release_close": "Release v3.8.50 close reconciliation on e0ce95c592: src/sse/handlers/chat.ts 1904->1918 is the irreducible request-pipeline wiring from #9759 that invokes the Modality Bridge guardrail without moving its implementation into the handler; covered by the 17 Vision Bridge canaries plus the PR-1 focused suite. open-sse/translator/response/openai-responses.ts 1204->1215 is #9168's Responses tool-call argument delta buffering/normalization at the existing translator state-machine chokepoint; covered by its dedicated translator regression tests. Both values are measured by check:file-size (split-newline semantics), and the gate remains frozen at the new exact sizes.",
+  "_rebaseline_2026_08_08_toolcall_message_index_collision": "fix(responses-api): tool call after a text message collided on the same output_index. own growth: open-sse/translator/response/openai-responses.ts 1204->1224 (+20, extracted toolCallOutputIndexBase() shared helper so emitToolCall/closeToolCall can no longer compute a tool call's output_index independently and collide with a text message emitted in the same turn). Live incident (2026-08-08, OpenClaw agent): a client that tracks response items by output_index saw the tool call's added/delta/done events land on an index it had already marked complete (the just-closed text message), and silently dropped them — the agent spoke its preamble and never executed the tool call, even though OmniRoute's own recorded responseBody had a complete, valid tool_calls entry. Covered by the new regression test in tests/unit/translator-resp-openai-responses.test.ts reproducing the exact live scenario."
 }
diff --git a/open-sse/translator/response/openai-responses.ts b/open-sse/translator/response/openai-responses.ts
index d459350d35..35571814e7 100644
--- a/open-sse/translator/response/openai-responses.ts
+++ b/open-sse/translator/response/openai-responses.ts
@@ -451,11 +451,22 @@ function closeMessage(state, emit, idx) {
   }
 }
 
+// Tool calls sit after reasoning (if any) AND after a text message (if one was
+// actually emitted this turn) — a model commonly emits a short preamble before
+// calling a tool (e.g. "Kör nu, på riktigt — apply_patch..."), and that message
+// claims the same reasoningIndex+1 slot the old per-call math (`reasoningIndex
+// + 1 + tcIdx`) assumed was free for tcIdx=0. Not accounting for the message
+// item collided the tool call's added/delta/done events onto the same
+// output_index as the just-closed message, which a client keying per-item
+// state by output_index can silently drop (live incident 2026-08-08).
+function toolCallOutputIndexBase(state) {
+  const msgIdx = state.reasoningId ? normalizeOutputIndex(state.reasoningIndex) + 1 : 0;
+  return state.msgItemAdded[msgIdx] ? msgIdx + 1 : msgIdx;
+}
+
 function emitToolCall(state, emit, tc) {
   const tcIdx = tc.index ?? 0;
-  const outputIndex = state.reasoningId
-    ? normalizeOutputIndex(state.reasoningIndex) + 1 + normalizeOutputIndex(tcIdx)
-    : normalizeOutputIndex(tcIdx);
+  const outputIndex = toolCallOutputIndexBase(state) + normalizeOutputIndex(tcIdx);
   const newCallId = tc.id;
   const funcName = tc.function?.name;
 
@@ -536,9 +547,7 @@ function emitToolCall(state, emit, tc) {
 function closeToolCall(state, emit, idx, recordAsCompleted = true) {
   const callId = state.funcCallIds[idx];
   if (callId && !state.funcItemDone[idx]) {
-    const normalizedIndex = state.reasoningId
-      ? normalizeOutputIndex(state.reasoningIndex) + 1 + normalizeOutputIndex(idx)
-      : normalizeOutputIndex(idx);
+    const normalizedIndex = toolCallOutputIndexBase(state) + normalizeOutputIndex(idx);
     const args = state.funcArgsBuf[idx] || "{}";
     const toolName = state.funcNames[idx] || "";
     const isCustomTool =
diff --git a/tests/unit/translator-resp-openai-responses.test.ts b/tests/unit/translator-resp-openai-responses.test.ts
index 3eeef460b8..6a2aee49ae 100644
--- a/tests/unit/translator-resp-openai-responses.test.ts
+++ b/tests/unit/translator-resp-openai-responses.test.ts
@@ -726,3 +726,92 @@ test("OpenAI -> Responses: parallel tool calls with mixed content survive transl
   const outputFcs = completed.data.response.output.filter((item) => item.type === "function_call");
   assert.equal(outputFcs.length, 2, "completed output should have both function_calls");
 });
+
+// Live incident (2026-08-08): an OpenClaw agent ("Ping") sent a preamble line
+// ("Kör nu, på riktigt — apply_patch på vibe-scriptet:") followed by an
+// apply_patch tool call in the same turn, with reasoning ahead of both. The
+// text message and the tool call both computed to output_index=1 — the tool
+// call's own index math (`reasoningIndex + 1 + tcIdx`) never accounted for
+// the message item also claiming `reasoningIndex + 1`, so a completed
+// message and a freshly-added tool call collided on the same output_index.
+// A client that tracks response items by output_index (as Responses-API
+// clients are expected to) sees the tool call's added/delta/done events land
+// on an index it already marked complete, and can silently drop or ignore
+// them — exactly the observed symptom: the agent spoke the preamble and
+// never executed the patch.
+test("OpenAI -> Responses: a text message and a following tool call in the same turn get distinct output_index values", () => {
+  const events = collectEvents([
+    {
+      id: "chatcmpl-1",
+      model: "big-pickle",
+      choices: [
+        { index: 0, delta: { reasoning_content: "thinking about the patch" }, finish_reason: null },
+      ],
+    },
+    {
+      id: "chatcmpl-1",
+      model: "big-pickle",
+      choices: [
+        {
+          index: 0,
+          delta: { content: "Kör nu, på riktigt — apply_patch på vibe-scriptet:" },
+          finish_reason: null,
+        },
+      ],
+    },
+    {
+      id: "chatcmpl-1",
+      model: "big-pickle",
+      choices: [
+        {
+          index: 0,
+          delta: {
+            tool_calls: [
+              {
+                index: 0,
+                id: "call_apply_patch",
+                type: "function",
+                function: { name: "apply_patch", arguments: '{"input":"*** Begin Patch ***"}' },
+              },
+            ],
+          },
+          finish_reason: "tool_calls",
+        },
+      ],
+    },
+    null,
+  ]);
+
+  const itemDoneEvents = events.filter((e) => e.event === "response.output_item.done");
+  const messageDone = itemDoneEvents.find((e) => e.data.item?.type === "message");
+  const toolCallDone = itemDoneEvents.find(
+    (e) => e.data.item?.type === "function_call" || e.data.item?.type === "custom_tool_call"
+  );
+  assert.ok(messageDone, "message output_item.done should be present");
+  assert.ok(toolCallDone, "tool call output_item.done should be present");
+  assert.notEqual(
+    messageDone.data.output_index,
+    toolCallDone.data.output_index,
+    "message and tool call must not collide on the same output_index"
+  );
+
+  // The tool call's own added/delta events (what a streaming client actually
+  // keys its per-item state on) must also use the tool call's real index,
+  // not the message's.
+  const toolCallAdded = events.find(
+    (e) =>
+      e.event === "response.output_item.added" &&
+      (e.data.item?.type === "function_call" || e.data.item?.type === "custom_tool_call")
+  );
+  assert.ok(toolCallAdded, "tool call output_item.added should be present");
+  assert.equal(toolCallAdded.data.output_index, toolCallDone.data.output_index);
+  assert.notEqual(toolCallAdded.data.output_index, messageDone.data.output_index);
+
+  const completed = events.find((e) => e.event === "response.completed");
+  const outputTypes = completed.data.response.output.map((item) => item.type);
+  assert.ok(outputTypes.includes("message"), "completed output must include the message");
+  assert.ok(
+    outputTypes.includes("function_call") || outputTypes.includes("custom_tool_call"),
+    "completed output must include the tool call"
+  );
+});