From 7902c769dabe5fdd45c7bd2edef2eb823e9d5dd4 Mon Sep 17 00:00:00 2001
From: Vincent Koc <vincentkoc@ieee.org>
Date: Sun, 26 Apr 2026 16:24:02 -0700
Subject: [PATCH] fix(codex): normalize cached harness input tokens

---
 .../src/app-server/event-projector.test.ts    | 16 +++++-----
 .../codex/src/app-server/event-projector.ts   | 32 +++++++++++++------
 2 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/extensions/codex/src/app-server/event-projector.test.ts b/extensions/codex/src/app-server/event-projector.test.ts
index c6997ea0a31..3ceaa739b4f 100644
--- a/extensions/codex/src/app-server/event-projector.test.ts
+++ b/extensions/codex/src/app-server/event-projector.test.ts
@@ -167,7 +167,7 @@ describe("CodexAppServerEventProjector", () => {
             outputTokens: 100_000,
           },
           last: {
-            totalTokens: 14,
+            totalTokens: 12,
             inputTokens: 5,
             cachedInputTokens: 2,
             outputTokens: 7,
@@ -186,12 +186,12 @@ describe("CodexAppServerEventProjector", () => {
     expect(result.assistantTexts).toEqual(["hello"]);
     expect(result.messagesSnapshot.map((message) => message.role)).toEqual(["user", "assistant"]);
     expect(result.lastAssistant?.content).toEqual([{ type: "text", text: "hello" }]);
-    expect(result.attemptUsage).toMatchObject({ input: 5, output: 7, cacheRead: 2, total: 14 });
+    expect(result.attemptUsage).toMatchObject({ input: 3, output: 7, cacheRead: 2, total: 12 });
     expect(result.lastAssistant?.usage).toMatchObject({
-      input: 5,
+      input: 3,
       output: 7,
       cacheRead: 2,
-      totalTokens: 14,
+      totalTokens: 12,
     });
     expect(result.replayMetadata.replaySafe).toBe(true);
   });
@@ -289,7 +289,7 @@ describe("CodexAppServerEventProjector", () => {
         tokenUsage: {
           total: { total_tokens: 1_000_000 },
           last_token_usage: {
-            total_tokens: 20,
+            total_tokens: 17,
             input_tokens: 8,
             cached_input_tokens: 3,
             output_tokens: 9,
@@ -300,12 +300,12 @@ describe("CodexAppServerEventProjector", () => {
 
     const result = projector.buildResult(buildEmptyToolTelemetry());
 
-    expect(result.attemptUsage).toMatchObject({ input: 8, output: 9, cacheRead: 3, total: 20 });
+    expect(result.attemptUsage).toMatchObject({ input: 5, output: 9, cacheRead: 3, total: 17 });
     expect(result.lastAssistant?.usage).toMatchObject({
-      input: 8,
+      input: 5,
       output: 9,
       cacheRead: 3,
-      totalTokens: 20,
+      totalTokens: 17,
     });
   });
 
diff --git a/extensions/codex/src/app-server/event-projector.ts b/extensions/codex/src/app-server/event-projector.ts
index 6b5d4805d57..dc40dc6260b 100644
--- a/extensions/codex/src/app-server/event-projector.ts
+++ b/extensions/codex/src/app-server/event-projector.ts
@@ -61,6 +61,13 @@ const CURRENT_TOKEN_USAGE_KEYS = [
   "last_token_usage",
 ] as const;
 
+const CODEX_PROMPT_TOTAL_INPUT_KEYS = [
+  "inputTokens",
+  "input_tokens",
+  "promptTokens",
+  "prompt_tokens",
+] as const;
+
 const MAX_TOOL_OUTPUT_DELTA_MESSAGES_PER_ITEM = 20;
 
 export class CodexAppServerEventProjector {
@@ -910,17 +917,24 @@ function readNumberAlias(record: JsonObject, keys: readonly string[]): number |
 }
 
 function normalizeCodexTokenUsage(record: JsonObject): ReturnType<typeof normalizeUsage> {
+  const promptTotalInput = readNumberAlias(record, CODEX_PROMPT_TOTAL_INPUT_KEYS);
+  const cacheRead = readNumberAlias(record, [
+    "cachedInputTokens",
+    "cached_input_tokens",
+    "cacheRead",
+    "cache_read",
+    "cache_read_input_tokens",
+    "cached_tokens",
+  ]);
+  const input =
+    promptTotalInput !== undefined && cacheRead !== undefined
+      ? Math.max(0, promptTotalInput - cacheRead)
+      : (promptTotalInput ?? readNumber(record, "input"));
+
   return normalizeUsage({
-    input: readNumberAlias(record, ["inputTokens", "input_tokens", "input", "promptTokens"]),
+    input,
     output: readNumberAlias(record, ["outputTokens", "output_tokens", "output"]),
-    cacheRead: readNumberAlias(record, [
-      "cachedInputTokens",
-      "cached_input_tokens",
-      "cacheRead",
-      "cache_read",
-      "cache_read_input_tokens",
-      "cached_tokens",
-    ]),
+    cacheRead,
     cacheWrite: readNumberAlias(record, [
       "cacheWrite",
       "cache_write",