diff --git a/src/agents/anthropic-payload-log.ts b/src/agents/anthropic-payload-log.ts
index 7f4463a6b48..03c2cbc1c1c 100644
--- a/src/agents/anthropic-payload-log.ts
+++ b/src/agents/anthropic-payload-log.ts
@@ -1,5 +1,4 @@
 import crypto from "node:crypto";
-import fs from "node:fs/promises";
 import path from "node:path";
 import type { AgentMessage, StreamFn } from "@mariozechner/pi-agent-core";
 import type { Api, Model } from "@mariozechner/pi-ai";
@@ -8,6 +7,7 @@ import { createSubsystemLogger } from "../logging/subsystem.js";
 import { resolveUserPath } from "../utils.js";
 import { parseBooleanValue } from "../utils/boolean.js";
 import { safeJsonStringify } from "../utils/safe-json.js";
+import { getQueuedFileWriter, type QueuedFileWriter } from "./queued-file-writer.js";
 
 type PayloadLogStage = "request" | "usage";
 
@@ -32,10 +32,7 @@ type PayloadLogConfig = {
   filePath: string;
 };
 
-type PayloadLogWriter = {
-  filePath: string;
-  write: (line: string) => void;
-};
+type PayloadLogWriter = QueuedFileWriter;
 
 const writers = new Map<string, PayloadLogWriter>();
 const log = createSubsystemLogger("agent/anthropic-payload");
@@ -50,27 +47,7 @@ function resolvePayloadLogConfig(env: NodeJS.ProcessEnv): PayloadLogConfig {
 }
 
 function getWriter(filePath: string): PayloadLogWriter {
-  const existing = writers.get(filePath);
-  if (existing) {
-    return existing;
-  }
-
-  const dir = path.dirname(filePath);
-  const ready = fs.mkdir(dir, { recursive: true }).catch(() => undefined);
-  let queue = Promise.resolve();
-
-  const writer: PayloadLogWriter = {
-    filePath,
-    write: (line: string) => {
-      queue = queue
-        .then(() => ready)
-        .then(() => fs.appendFile(filePath, line, "utf8"))
-        .catch(() => undefined);
-    },
-  };
-
-  writers.set(filePath, writer);
-  return writer;
+  return getQueuedFileWriter(writers, filePath);
 }
 
 function formatError(error: unknown): string | undefined {
diff --git a/src/agents/cache-trace.ts b/src/agents/cache-trace.ts
index f8ecd67c3db..0cc770dabe7 100644
--- a/src/agents/cache-trace.ts
+++ b/src/agents/cache-trace.ts
@@ -1,5 +1,4 @@
 import crypto from "node:crypto";
-import fs from "node:fs/promises";
 import path from "node:path";
 import type { AgentMessage, StreamFn } from "@mariozechner/pi-agent-core";
 import type { OpenClawConfig } from "../config/config.js";
@@ -7,6 +6,7 @@ import { resolveStateDir } from "../config/paths.js";
 import { resolveUserPath } from "../utils.js";
 import { parseBooleanValue } from "../utils/boolean.js";
 import { safeJsonStringify } from "../utils/safe-json.js";
+import { getQueuedFileWriter, type QueuedFileWriter } from "./queued-file-writer.js";
 
 export type CacheTraceStage =
   | "session:loaded"
@@ -70,10 +70,7 @@ type CacheTraceConfig = {
   includeSystem: boolean;
 };
 
-type CacheTraceWriter = {
-  filePath: string;
-  write: (line: string) => void;
-};
+type CacheTraceWriter = QueuedFileWriter;
 
 const writers = new Map<string, CacheTraceWriter>();
 
@@ -102,27 +99,7 @@ function resolveCacheTraceConfig(params: CacheTraceInit): CacheTraceConfig {
 }
 
 function getWriter(filePath: string): CacheTraceWriter {
-  const existing = writers.get(filePath);
-  if (existing) {
-    return existing;
-  }
-
-  const dir = path.dirname(filePath);
-  const ready = fs.mkdir(dir, { recursive: true }).catch(() => undefined);
-  let queue = Promise.resolve();
-
-  const writer: CacheTraceWriter = {
-    filePath,
-    write: (line: string) => {
-      queue = queue
-        .then(() => ready)
-        .then(() => fs.appendFile(filePath, line, "utf8"))
-        .catch(() => undefined);
-    },
-  };
-
-  writers.set(filePath, writer);
-  return writer;
+  return getQueuedFileWriter(writers, filePath);
 }
 
 function stableStringify(value: unknown): string {
diff --git a/src/agents/queued-file-writer.ts b/src/agents/queued-file-writer.ts
new file mode 100644
index 00000000000..906ebee6f82
--- /dev/null
+++ b/src/agents/queued-file-writer.ts
@@ -0,0 +1,34 @@
+import fs from "node:fs/promises";
+import path from "node:path";
+
+export type QueuedFileWriter = {
+  filePath: string;
+  write: (line: string) => void;
+};
+
+export function getQueuedFileWriter(
+  writers: Map<string, QueuedFileWriter>,
+  filePath: string,
+): QueuedFileWriter {
+  const existing = writers.get(filePath);
+  if (existing) {
+    return existing;
+  }
+
+  const dir = path.dirname(filePath);
+  const ready = fs.mkdir(dir, { recursive: true }).catch(() => undefined);
+  let queue = Promise.resolve();
+
+  const writer: QueuedFileWriter = {
+    filePath,
+    write: (line: string) => {
+      queue = queue
+        .then(() => ready)
+        .then(() => fs.appendFile(filePath, line, "utf8"))
+        .catch(() => undefined);
+    },
+  };
+
+  writers.set(filePath, writer);
+  return writer;
+}