fix(ai): use plain gpt-5 model slug for ChatGPT-account auth

The Codex backend rejects `gpt-5-codex` when authenticated via the
ChatGPT-account OAuth flow with:

  "The 'gpt-5-codex' model is not supported when using Codex with a
   ChatGPT account."

The `-codex` suffix is API-key-auth-only. ChatGPT subscriptions route
through the plain `gpt-5` slug instead. Switch the client default and
expose a `CODEX_MODEL` env override for operators on plan tiers that
prefer a different slug (e.g. `gpt-5-codex-mini` or a future
preview model).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,17 @@
 # Changelog
 
+## [1.4.13] — 2026-05-09
+
+### Fixed — KI Insights via ChatGPT
+
+- **Modell-Slug für ChatGPT-Auth korrigiert.** Der Codex-Backend
+  lehnt `gpt-5-codex` mit ChatGPT-Subscription ab
+  (`The 'gpt-5-codex' model is not supported when using Codex with a
+ChatGPT account.`) — dieses Slug ist nur für API-Key-Auth gültig.
+  Wechsel auf `gpt-5`, das Standard-Modell der ChatGPT-Plus/Pro-Tarife.
+  Operator-Override via `CODEX_MODEL`-Env-Var möglich falls dein
+  Plan einen anderen Default kennt.
+
 ## [1.4.12] — 2026-05-09
 
 ### Fixed — KI Insights via ChatGPT (komplette Codex-Integration)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "healthlog",
-  "version": "1.4.12",
+  "version": "1.4.13",
   "private": true,
   "packageManager": "pnpm@10.31.0",
   "scripts": {

src/lib/ai/codex-client.ts

@@ -21,13 +21,19 @@ import type { AIProvider, CompletionParams, CompletionResult } from "./types";
 const CODEX_ENDPOINT = "https://chatgpt.com/backend-api/codex/responses";
 
 /**
- * `gpt-5.3-codex` is a *test placeholder* in the upstream codebase
- * (`codex-rs/codex-api/src/sse/responses.rs:1374`), not a real model
- * slug. The real CLI default is `gpt-5-codex`. The server safety-routes
- * if needed and reports the actual model in the `OpenAI-Model`
- * response header.
+ * Model slug for the ChatGPT-account auth path.
+ *
+ * Caveat: `gpt-5-codex` is the API-key-auth Codex slug but is rejected
+ * by the chatgpt.com backend with "model is not supported when using
+ * Codex with a ChatGPT account". For ChatGPT-OAuth we send the plain
+ * `gpt-5` slug — that's the Pro/Plus subscription model the backend
+ * routes by default. The server may safety-route to a different slug
+ * and reports the actual model in the `OpenAI-Model` response header.
+ *
+ * Operators can override via `CODEX_MODEL` env var on apps01 if a
+ * different slug works better for their ChatGPT plan tier.
  */
-const CODEX_MODEL = "gpt-5-codex";
+const CODEX_MODEL = process.env.CODEX_MODEL?.trim() || "gpt-5";
 
 const ORIGINATOR = "healthlog";
 const USER_AGENT = "HealthLog/1.0 (+https://healthlog.bombeck.io)";