diff --git a/src/selfhost/ai.ts b/src/selfhost/ai.ts
index cf5b9f1f92..203c1b5e90 100644
--- a/src/selfhost/ai.ts
+++ b/src/selfhost/ai.ts
@@ -75,7 +75,7 @@ function toCliPrompt(options: AiRunOptions, systemAppend: string | undefined): s
     .join("\n\n");
 }
 
-function prependCodexSystemAppend(prompt: string, systemAppend: string | undefined): string {
+function prependCliSystemAppend(prompt: string, systemAppend: string | undefined): string {
   return systemAppend
     ? `ADDITIONAL SYSTEM INSTRUCTIONS:\n${systemAppend}\n\n${prompt}`
     : prompt;
@@ -736,10 +736,9 @@ export function createClaudeCodeAi(parentEnv: Record<string, string | undefined>
           OTEL_METRIC_EXPORT_INTERVAL: parentEnv.OTEL_METRIC_EXPORT_INTERVAL,
         });
         const systemAppend = normalizedSystemAppend(options);
-        const prompt = toCliPrompt(options, systemAppend);
+        const prompt = prependCliSystemAppend(toCliPrompt(options, systemAppend), systemAppend);
         const spawn = spawnImpl ?? (await defaultSpawn());
         const args = ["--print", "--output-format", "json", "--model", claudeModel, "--permission-mode", "plan", "--effort", effort, "--disallowedTools", "Bash,Edit,Write,WebFetch,WebSearch"];
-        if (systemAppend) args.push("--append-system-prompt", systemAppend);
         attempted = true;
         const { stdout, code, stderr, timedOut } = await spawn(
           "claude",
@@ -808,7 +807,7 @@ export function createCodexAi(
         await authCheckImpl(parentEnv);
         const env = codexCliEnv(parentEnv);
         const systemAppend = normalizedSystemAppend(options);
-        const prompt = prependCodexSystemAppend(toCliPrompt(options, systemAppend), systemAppend);
+        const prompt = prependCliSystemAppend(toCliPrompt(options, systemAppend), systemAppend);
         const spawn = spawnImpl ?? (await defaultSpawn());
         const args = ["exec", "--json", "--skip-git-repo-check", "--sandbox", "read-only"];
         if (codexModel) args.push("--model", codexModel);
diff --git a/test/unit/selfhost-ai.test.ts b/test/unit/selfhost-ai.test.ts
index c1486d261e..ddda1b71a3 100644
--- a/test/unit/selfhost-ai.test.ts
+++ b/test/unit/selfhost-ai.test.ts
@@ -979,7 +979,7 @@ describe("subscription CLI helpers + fail-safe", () => {
     expect(seen[seen.indexOf("--effort") + 1]).toBe("medium");
   });
 
-  it("Claude Code passes systemAppend through --append-system-prompt and strips the duplicate stdin copy (#1471)", async () => {
+  it("Claude Code keeps systemAppend out of argv and supplies it through stdin once (#1471)", async () => {
     const systemAppend = "REPOSITORY REVIEW INSTRUCTIONS: Follow async-error conventions.";
     let seen: string[] = [];
     let capturedInput = "";
@@ -995,10 +995,11 @@ describe("subscription CLI helpers + fail-safe", () => {
       ],
       systemAppend,
     });
-    expect(seen[seen.indexOf("--append-system-prompt") + 1]).toBe(systemAppend);
+    expect(seen).not.toContain("--append-system-prompt");
+    expect(seen).not.toContain(systemAppend);
     expect(capturedInput).toContain("Base system.");
     expect(capturedInput).toContain("Review this diff.");
-    expect(capturedInput).not.toContain(systemAppend);
+    expect(countOccurrences(capturedInput, systemAppend)).toBe(1);
 
     await createClaudeCodeAi({ CLAUDE_CODE_OAUTH_TOKEN: "t" }, cap).run("", {
       prompt: "Review this diff.",