diff --git a/src/process/exec.test.ts b/src/process/exec.test.ts
index e62611112b3..d8d621abc56 100644
--- a/src/process/exec.test.ts
+++ b/src/process/exec.test.ts
@@ -25,7 +25,7 @@ describe("runCommandWithTimeout", () => {
           'process.stdout.write((process.env.OPENCLAW_BASE_ENV ?? "") + "|" + (process.env.OPENCLAW_TEST_ENV ?? ""))',
         ],
         {
-          timeoutMs: 120,
+          timeoutMs: 80,
           env: { OPENCLAW_TEST_ENV: "ok" },
         },
       );
@@ -38,10 +38,10 @@ describe("runCommandWithTimeout", () => {
 
   it("kills command when no output timeout elapses", async () => {
     const result = await runCommandWithTimeout(
-      [process.execPath, "-e", "setTimeout(() => {}, 20)"],
+      [process.execPath, "-e", "setTimeout(() => {}, 10)"],
       {
-        timeoutMs: 80,
-        noOutputTimeoutMs: 8,
+        timeoutMs: 30,
+        noOutputTimeoutMs: 4,
       },
     );
 
@@ -82,9 +82,9 @@ describe("runCommandWithTimeout", () => {
 
   it("reports global timeout termination when overall timeout elapses", async () => {
     const result = await runCommandWithTimeout(
-      [process.execPath, "-e", "setTimeout(() => {}, 12)"],
+      [process.execPath, "-e", "setTimeout(() => {}, 10)"],
       {
-        timeoutMs: 6,
+        timeoutMs: 4,
       },
     );
 
diff --git a/src/process/supervisor/supervisor.test.ts b/src/process/supervisor/supervisor.test.ts
index c2317e8d39f..dec725e1501 100644
--- a/src/process/supervisor/supervisor.test.ts
+++ b/src/process/supervisor/supervisor.test.ts
@@ -4,7 +4,13 @@ import { createProcessSupervisor } from "./supervisor.js";
 type ProcessSupervisor = ReturnType<typeof createProcessSupervisor>;
 type SpawnOptions = Parameters<ProcessSupervisor["spawn"]>[0];
 type ChildSpawnOptions = Omit<Extract<SpawnOptions, { mode: "child" }>, "backendId" | "mode">;
-const OUTPUT_DELAY_MS = 3;
+
+function createWriteStdoutArgv(output: string): string[] {
+  if (process.platform === "win32") {
+    return [process.execPath, "-e", `process.stdout.write(${JSON.stringify(output)})`];
+  }
+  return ["/usr/bin/printf", "%s", output];
+}
 
 async function spawnChild(supervisor: ProcessSupervisor, options: ChildSpawnOptions) {
   return supervisor.spawn({
@@ -19,12 +25,7 @@ describe("process supervisor", () => {
     const supervisor = createProcessSupervisor();
     const run = await spawnChild(supervisor, {
       sessionId: "s1",
-      // Delay stdout slightly so listeners are attached even on heavily loaded runners.
-      argv: [
-        process.execPath,
-        "-e",
-        `setTimeout(() => process.stdout.write("ok"), ${OUTPUT_DELAY_MS})`,
-      ],
+      argv: createWriteStdoutArgv("ok"),
       timeoutMs: 1_000,
       stdinMode: "pipe-closed",
     });
@@ -63,12 +64,7 @@ describe("process supervisor", () => {
       sessionId: "s1",
       scopeKey: "scope:a",
       replaceExistingScope: true,
-      // Small delay makes stdout capture deterministic by giving listeners time to attach.
-      argv: [
-        process.execPath,
-        "-e",
-        `setTimeout(() => process.stdout.write("new"), ${OUTPUT_DELAY_MS})`,
-      ],
+      argv: createWriteStdoutArgv("new"),
       timeoutMs: 1_000,
       stdinMode: "pipe-closed",
     });
@@ -98,12 +94,7 @@ describe("process supervisor", () => {
     let streamed = "";
     const run = await spawnChild(supervisor, {
       sessionId: "s-capture",
-      // Avoid race where child exits before stdout listeners are attached.
-      argv: [
-        process.execPath,
-        "-e",
-        `setTimeout(() => process.stdout.write("streamed"), ${OUTPUT_DELAY_MS})`,
-      ],
+      argv: createWriteStdoutArgv("streamed"),
       timeoutMs: 1_000,
       stdinMode: "pipe-closed",
       captureOutput: false,