diff --git a/extensions/codex/src/app-server/run-attempt.context-engine.test.ts b/extensions/codex/src/app-server/run-attempt.context-engine.test.ts
index 88427a9f1549..ae967787d409 100644
--- a/extensions/codex/src/app-server/run-attempt.context-engine.test.ts
+++ b/extensions/codex/src/app-server/run-attempt.context-engine.test.ts
@@ -525,6 +525,7 @@ describe("runCodexAppServerAttempt context-engine lifecycle", () => {
     params.contextEngine = contextEngine;
     params.contextTokenBudget = 300_000;
     params.prompt = "current prompt survives";
+    params.currentInboundContext = { text: "current inbound context survives" };
 
     const run = runCodexAppServerAttempt(params);
     await harness.waitForMethod("turn/start");
@@ -532,6 +533,7 @@ describe("runCodexAppServerAttempt context-engine lifecycle", () => {
     const inputText = getRequestInputText(harness);
     expect(inputText.length).toBeLessThanOrEqual(CODEX_TURN_START_TEXT_INPUT_MAX_CHARS);
     expect(inputText).toContain("recent anchor");
+    expect(inputText).toContain("current inbound context survives");
     expect(inputText).toContain("current prompt survives");
 
     await harness.completeTurn();
diff --git a/extensions/codex/src/app-server/run-attempt.ts b/extensions/codex/src/app-server/run-attempt.ts
index c6ef9bb2824b..dc9b10d136c0 100644
--- a/extensions/codex/src/app-server/run-attempt.ts
+++ b/extensions/codex/src/app-server/run-attempt.ts
@@ -1033,13 +1033,18 @@ export async function runCodexAppServerAttempt(
     promptInputRange: { start: number; end: number } | undefined,
     turnPromptText: string,
   ): CodexProjectedContextRange | undefined => {
+    const promptTextInputOffset = promptInputRange
+      ? promptInputRange.end - promptText.length
+      : undefined;
     if (
       !promptContextRange ||
       !promptInputRange ||
+      promptTextInputOffset === undefined ||
       promptInputRange.start < 0 ||
       promptInputRange.end < promptInputRange.start ||
       promptInputRange.end > prompt.length ||
-      prompt.slice(promptInputRange.start, promptInputRange.end) !== promptText ||
+      promptTextInputOffset < promptInputRange.start ||
+      prompt.slice(promptTextInputOffset, promptInputRange.end) !== promptText ||
       !turnPromptText.endsWith(prompt)
     ) {
       return undefined;
@@ -1049,7 +1054,7 @@ export async function runCodexAppServerAttempt(
     // earlier input span. The exact input range still covers prepend-only hooks.
     const promptTextOffset = prompt.endsWith(promptText)
       ? prompt.length - promptText.length
-      : promptInputRange.end - promptText.length;
+      : promptTextInputOffset;
     if (promptTextOffset < 0) {
       return undefined;
     }