From 2c5e24cbb5132e7848626cc9877e25431b9bd062 Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Sun, 15 Feb 2026 06:11:53 +0000
Subject: [PATCH] refactor(gateway): dedupe session usage file resolution

---
 src/gateway/server-methods/usage.ts | 78 +++++++++++++++--------------
 1 file changed, 41 insertions(+), 37 deletions(-)

diff --git a/src/gateway/server-methods/usage.ts b/src/gateway/server-methods/usage.ts
index b8c55147129..65ce44070c2 100644
--- a/src/gateway/server-methods/usage.ts
+++ b/src/gateway/server-methods/usage.ts
@@ -10,7 +10,7 @@ import type {
   SessionModelUsage,
   SessionToolUsage,
 } from "../../infra/session-cost-usage.js";
-import type { GatewayRequestHandlers } from "./types.js";
+import type { GatewayRequestHandlers, RespondFn } from "./types.js";
 import { loadConfig } from "../../config/config.js";
 import {
   resolveSessionFilePath,
@@ -50,6 +50,40 @@ type CostUsageCacheEntry = {
 
 const costUsageCache = new Map<string, CostUsageCacheEntry>();
 
+function resolveSessionUsageFileOrRespond(
+  key: string,
+  respond: RespondFn,
+): {
+  config: ReturnType<typeof loadConfig>;
+  entry: SessionEntry | undefined;
+  agentId: string | undefined;
+  sessionId: string;
+  sessionFile: string;
+} | null {
+  const config = loadConfig();
+  const { entry, storePath } = loadSessionEntry(key);
+
+  // For discovered sessions (not in store), try using key as sessionId directly
+  const parsed = parseAgentSessionKey(key);
+  const agentId = parsed?.agentId;
+  const rawSessionId = parsed?.rest ?? key;
+  const sessionId = entry?.sessionId ?? rawSessionId;
+  let sessionFile: string;
+  try {
+    const pathOpts = resolveSessionFilePathOptions({ storePath, agentId });
+    sessionFile = resolveSessionFilePath(sessionId, entry, pathOpts);
+  } catch {
+    respond(
+      false,
+      undefined,
+      errorShape(ErrorCodes.INVALID_REQUEST, `Invalid session key: ${key}`),
+    );
+    return null;
+  }
+
+  return { config, entry, agentId, sessionId, sessionFile };
+}
+
 /**
  * Parse a date string (YYYY-MM-DD) to start of day timestamp in UTC.
  * Returns undefined if invalid.
@@ -752,26 +786,11 @@ export const usageHandlers: GatewayRequestHandlers = {
       return;
     }
 
-    const config = loadConfig();
-    const { entry, storePath } = loadSessionEntry(key);
-
-    // For discovered sessions (not in store), try using key as sessionId directly
-    const parsed = parseAgentSessionKey(key);
-    const agentId = parsed?.agentId;
-    const rawSessionId = parsed?.rest ?? key;
-    const sessionId = entry?.sessionId ?? rawSessionId;
-    let sessionFile: string;
-    try {
-      const pathOpts = resolveSessionFilePathOptions({ storePath, agentId });
-      sessionFile = resolveSessionFilePath(sessionId, entry, pathOpts);
-    } catch {
-      respond(
-        false,
-        undefined,
-        errorShape(ErrorCodes.INVALID_REQUEST, `Invalid session key: ${key}`),
-      );
+    const resolved = resolveSessionUsageFileOrRespond(key, respond);
+    if (!resolved) {
       return;
     }
+    const { config, entry, agentId, sessionId, sessionFile } = resolved;
 
     const timeseries = await loadSessionUsageTimeSeries({
       sessionId,
@@ -805,26 +824,11 @@ export const usageHandlers: GatewayRequestHandlers = {
         ? Math.min(params.limit, 1000)
         : 200;
 
-    const config = loadConfig();
-    const { entry, storePath } = loadSessionEntry(key);
-
-    // For discovered sessions (not in store), try using key as sessionId directly
-    const parsed = parseAgentSessionKey(key);
-    const agentId = parsed?.agentId;
-    const rawSessionId = parsed?.rest ?? key;
-    const sessionId = entry?.sessionId ?? rawSessionId;
-    let sessionFile: string;
-    try {
-      const pathOpts = resolveSessionFilePathOptions({ storePath, agentId });
-      sessionFile = resolveSessionFilePath(sessionId, entry, pathOpts);
-    } catch {
-      respond(
-        false,
-        undefined,
-        errorShape(ErrorCodes.INVALID_REQUEST, `Invalid session key: ${key}`),
-      );
+    const resolved = resolveSessionUsageFileOrRespond(key, respond);
+    if (!resolved) {
       return;
     }
+    const { config, entry, agentId, sessionId, sessionFile } = resolved;
 
     const { loadSessionLogs } = await import("../../infra/session-cost-usage.js");
     const logs = await loadSessionLogs({