diff --git a/CHANGELOG.md b/CHANGELOG.md
index c4f37a26a4ed..dec778fbc153 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -39,6 +39,7 @@ Docs: https://docs.openclaw.ai
 - Release/CI/E2E: abort stalled Kitchen Sink RPC readiness probes as soon as the gateway exits so proof failures return promptly.
 - Release/CI/E2E: keep Parallels JSON-mode progress on stderr so macOS, Linux, Windows, and aggregate update smoke summaries stay parseable on stdout.
 - Release/CI/E2E: fail Crabbox sparse-sync runs clearly when their temporary full checkout disappears while the child process is running, instead of pretending the child's deleted cwd can be repaired.
+- Release/CI/E2E: fail PTY-backed E2E commands when transcript logs cannot be written instead of letting missing proof capture crash around a live child process.
 
 ## 2026.6.1
 
diff --git a/scripts/e2e/lib/run-with-pty.mjs b/scripts/e2e/lib/run-with-pty.mjs
index 003b57d1d532..14a668f65d84 100644
--- a/scripts/e2e/lib/run-with-pty.mjs
+++ b/scripts/e2e/lib/run-with-pty.mjs
@@ -13,6 +13,16 @@ if (!logPath || !command) {
   process.exit(2);
 }
 
+let exiting = false;
+let forwardedSignal = null;
+let forceKillTimer = null;
+let logFailed = false;
+const outputLimitMarker = `\n[run-with-pty output truncated after ${OUTPUT_MAX_BYTES} bytes]\n`;
+const outputState = {
+  bytes: 0,
+  truncated: false,
+};
+
 const log = fs.createWriteStream(logPath, { flags: "w" });
 const pty = spawn(command, args, {
   name: process.env.TERM || "xterm-256color",
@@ -22,14 +32,23 @@ const pty = spawn(command, args, {
   env: process.env,
 });
 
-let exiting = false;
-let forwardedSignal = null;
-let forceKillTimer = null;
-const outputLimitMarker = `\n[run-with-pty output truncated after ${OUTPUT_MAX_BYTES} bytes]\n`;
-const outputState = {
-  bytes: 0,
-  truncated: false,
-};
+log.on("error", (error) => {
+  if (logFailed) {
+    return;
+  }
+  logFailed = true;
+  console.error(`run-with-pty transcript log failed: ${error.message}`);
+  if (exiting) {
+    process.exit(1);
+  }
+  if (!exiting) {
+    pty.kill("SIGTERM");
+    forceKillTimer ??= setTimeout(() => {
+      pty.kill("SIGKILL");
+    }, FORCE_KILL_MS);
+    forceKillTimer.unref?.();
+  }
+});
 
 function writeCappedOutput(data) {
   if (outputState.truncated) {
@@ -39,18 +58,24 @@ function writeCappedOutput(data) {
   const remainingBytes = OUTPUT_MAX_BYTES - outputState.bytes;
   if (buffer.byteLength <= remainingBytes) {
     outputState.bytes += buffer.byteLength;
-    log.write(buffer);
+    if (!logFailed) {
+      log.write(buffer);
+    }
     process.stdout.write(buffer);
     return;
   }
   if (remainingBytes > 0) {
     const head = buffer.subarray(0, remainingBytes);
-    log.write(head);
+    if (!logFailed) {
+      log.write(head);
+    }
     process.stdout.write(head);
   }
   outputState.bytes = OUTPUT_MAX_BYTES;
   outputState.truncated = true;
-  log.write(outputLimitMarker);
+  if (!logFailed) {
+    log.write(outputLimitMarker);
+  }
   process.stdout.write(outputLimitMarker);
 }
 
@@ -61,6 +86,9 @@ pty.onData((data) => {
 pty.onExit(({ exitCode, signal }) => {
   exiting = true;
   clearTimeout(forceKillTimer);
+  if (logFailed) {
+    process.exit(1);
+  }
   log.end(() => {
     if (forwardedSignal) {
       process.exit(signalExitCode(forwardedSignal));
diff --git a/test/scripts/e2e-run-with-pty.test.ts b/test/scripts/e2e-run-with-pty.test.ts
index 112229cebc3a..2c5e89bc0123 100644
--- a/test/scripts/e2e-run-with-pty.test.ts
+++ b/test/scripts/e2e-run-with-pty.test.ts
@@ -105,6 +105,23 @@ describe("run-with-pty", () => {
     }
   });
 
+  it("fails when the transcript log cannot be written", async () => {
+    const tempRoot = await mkdtemp(path.join(os.tmpdir(), "openclaw-run-with-pty-"));
+    try {
+      const result = await runPtyProbe(
+        tempRoot,
+        {},
+        [process.execPath, "-e", "console.log('ready')"],
+        "",
+      );
+
+      expect(result.code).toBe(1);
+      expect(result.stderr).toContain("run-with-pty transcript log failed:");
+    } finally {
+      await rm(tempRoot, { recursive: true, force: true });
+    }
+  });
+
   posixIt("escalates forwarded termination signals for PTY commands that ignore them", async () => {
     const tempRoot = await mkdtemp(path.join(os.tmpdir(), "openclaw-run-with-pty-"));
     const logPath = path.join(tempRoot, "pty.log");