Withhold prompt-bearing runner stderr

src/shared/codex-runners.test.ts

@@ -311,6 +311,7 @@ test("runCodex reports opencode exit errors before parsing stdout", async (t) =>
 	const tmp = mkdtempSync(path.join(os.tmpdir(), "needlefish-test-"));
 	const repo = initRepo(tmp);
 	const bin = path.join(tmp, "opencode-bin.js");
+	const stderrMarker = "SECRET_REVIEW_PROMPT_MARKER_7f6a";
 	const previous = {
 		bin: process.env.OPENCODE_BIN,
 		runner: process.env.NEEDLEFISH_RUNNER,
@@ -331,7 +332,7 @@ test("runCodex reports opencode exit errors before parsing stdout", async (t) =>
 		[
 			"#!/usr/bin/env node",
 			"process.stdout.write('not json');",
-			"process.stderr.write('boom');",
+			`process.stderr.write(${JSON.stringify(stderrMarker)});`,
 			"process.exit(2);",
 		].join("\n"),
 	);
@@ -340,15 +341,29 @@ test("runCodex reports opencode exit errors before parsing stdout", async (t) =>
 	process.env.NEEDLEFISH_RUNNER = "opencode";
 	process.env.NEEDLEFISH_ALLOW_OPENCODE_RUNNER = "1";
 
-	await assert.rejects(
-		() =>
-			runCodex("prompt", {
-				repoPath: repo,
-				targetHeadSha: headSha(repo),
-				timeoutMs: 1000,
-			}),
-		/opencode runner exited 2: boom/,
+	let caught: unknown;
+	try {
+		await runCodex("prompt", {
+			repoPath: repo,
+			targetHeadSha: headSha(repo),
+			timeoutMs: 1000,
+		});
+		assert.fail("expected runCodex to reject");
+	} catch (err) {
+		caught = err;
+	}
+	assert.ok(caught instanceof Error);
+	const err = caught as Error & { rawOutput?: string };
+	assert.match(
+		err.message,
+		/opencode runner exited 2; stderr withheld because it may contain the review prompt/,
+	);
+	assert.doesNotMatch(err.message, new RegExp(stderrMarker));
+	assert.match(
+		err.rawOutput ?? "",
+		new RegExp(stderrMarker),
 	);
+	assert.equal(Object.keys(err).includes("rawOutput"), false);
 });
 
 test("runCodex passes grok plan permission mode when unset or set to 0", async () => {

src/shared/codex.ts

@@ -554,24 +554,27 @@ async function runCodexOnce(
 		// sees it — dying is not an escape hatch from detection. All three
 		// surfaces matter: result.out is the resolved model output (codex writes
 		// it to --output-last-message, not stdout), result.res.stdout the raw
-		// stream, and stderr rides UNTRUNCATED (the error message clips it at
-		// 2000 chars — a canary parked past the clip must still reach the scan).
+		// stream, and stderr rides UNTRUNCATED. Keep it non-enumerable so routine
+		// error serialization cannot disclose a review prompt.
 		const withRunnerOutput = (err: Error): Error => {
 			const raw = [
 				...new Set([result.out, result.res.stdout, result.res.stderr]),
 			]
 				.filter(Boolean)
 				.join("\n");
 			if (raw) {
-				(err as Error & { rawOutput?: string }).rawOutput = raw;
+				Object.defineProperty(err, "rawOutput", {
+					value: raw,
+					configurable: true,
+				});
 			}
 			return err;
 		};
 		if (result.res.error) throw withRunnerOutput(result.res.error);
 		if (result.res.status !== 0) {
 			throw withRunnerOutput(
 				new Error(
-					`${runner} runner exited ${result.res.status}: ${(result.res.stderr ?? "").slice(0, 2000)}`,
+					`${runner} runner exited ${result.res.status}; stderr withheld because it may contain the review prompt`,
 				),
 			);
 		}