fix(usage): type chat-completions usage details

steipete · steipete · commit b5112714d04a · 2026-05-27T10:35:56.000+01:00
diff --git a/src/agents/usage.ts b/src/agents/usage.ts
@@ -50,6 +50,14 @@ export type NormalizedUsage = {
   total?: number;
 };
 
+export type OpenAiChatCompletionsUsage = {
+  prompt_tokens: number;
+  completion_tokens: number;
+  total_tokens: number;
+  prompt_tokens_details?: { cached_tokens: number };
+  completion_tokens_details?: { reasoning_tokens: number };
+};
+
 export type AssistantUsageSnapshot = {
   input: number;
   output: number;
@@ -201,13 +209,9 @@ export function normalizeUsage(raw?: UsageLike | null): NormalizedUsage | undefi
  * cost. Field name and shape match OpenAI's documented usage breakdown:
  * https://platform.openai.com/docs/guides/prompt-caching
  */
-export function toOpenAiChatCompletionsUsage(usage: NormalizedUsage | undefined): {
-  prompt_tokens: number;
-  completion_tokens: number;
-  total_tokens: number;
-  prompt_tokens_details?: { cached_tokens: number };
-  completion_tokens_details?: { reasoning_tokens: number };
-} {
+export function toOpenAiChatCompletionsUsage(
+  usage: NormalizedUsage | undefined,
+): OpenAiChatCompletionsUsage {
   const input = usage?.input ?? 0;
   const output = usage?.output ?? 0;
   const cacheRead = usage?.cacheRead ?? 0;
diff --git a/src/gateway/openai-http.ts b/src/gateway/openai-http.ts
@@ -9,6 +9,7 @@ import {
   normalizeUsage,
   toOpenAiChatCompletionsUsage,
   type NormalizedUsage,
+  type OpenAiChatCompletionsUsage,
 } from "../agents/usage.js";
 import { createDefaultDeps } from "../cli/deps.js";
 import { agentCommandFromIngress } from "../commands/agent.js";
@@ -348,7 +349,7 @@ function writeUsageChunk(
   params: {
     runId: string;
     model: string;
-    usage: { prompt_tokens: number; completion_tokens: number; total_tokens: number };
+    usage: OpenAiChatCompletionsUsage;
   },
 ) {
   writeSse(res, {
@@ -767,11 +768,7 @@ function resolveStopReasonAndPendingToolCalls(meta: unknown): {
   return { stopReason, pendingToolCalls };
 }
 
-function resolveChatCompletionUsage(result: unknown): {
-  prompt_tokens: number;
-  completion_tokens: number;
-  total_tokens: number;
-} {
+function resolveChatCompletionUsage(result: unknown): OpenAiChatCompletionsUsage {
   return toOpenAiChatCompletionsUsage(resolveAgentRunUsage(result));
 }
 
@@ -1066,13 +1063,7 @@ export async function handleOpenAiHttpRequest(
   let wroteRole = false;
   let wroteStopChunk = false;
   let sawAssistantDelta = false;
-  let finalUsage:
-    | {
-        prompt_tokens: number;
-        completion_tokens: number;
-        total_tokens: number;
-      }
-    | undefined;
+  let finalUsage: OpenAiChatCompletionsUsage | undefined;
   let finalizeRequested = false;
   let finalizeFinishReason: "stop" | "tool_calls" = "stop";
   let resultResolved = false;
