feat: map interchange's neutral effort to codex reasoning.effort

AGENTS.md

@@ -39,7 +39,7 @@ than reimplementing OAuth or the Responses wire protocol.
   build-time rewrite script to paper over an extensionless import.
 - Tests exist only for load-bearing risk: the exact Codex request shape,
   `accountIdFromIdToken` on hostile input, the bridge-message tag structure,
-  and the content-type repair's conditions.
+  the neutral-effort mapping, and the content-type repair's conditions.
 
 ## Local development
 

README.md

@@ -107,7 +107,7 @@ process.stdout.write("\n");
 | `CODEX_DEFAULT_MODELS`                                     | The models the Codex CLI's bundled catalog lists in its picker.                                                      |
 | `CODEX_ACCOUNT_ID_OPTION`                                  | `providerOptions` key sent as the `chatgpt-account-id` header.                                                       |
 | `CODEX_SESSION_ID_OPTION`                                  | `providerOptions` key sent as `prompt_cache_key` and the `session_id` header.                                        |
-| `CODEX_REASONING_EFFORT_OPTION`                            | `providerOptions` key sent as `reasoning.effort`; `"none"` omits it.                                                 |
+| `CODEX_REASONING_EFFORT_OPTION`                            | `providerOptions` key sent as `reasoning.effort`; `"none"` omits it. Wins over the neutral `effort`.                 |
 | `CODEX_REFRESH_SKEW_MS`                                    | Refresh this long before expiry.                                                                                     |
 
 The OAuth constants behind `codexOAuthConfig` (`CODEX_CLIENT_ID`, `CODEX_AUTHORIZE_URL`, `CODEX_TOKEN_URL`, `CODEX_REDIRECT_URI`, `CODEX_SCOPES`, `CODEX_AUTHORIZE_EXTRA_PARAMS`, `CODEX_ORIGINATOR`, `CODEX_TOKEN_TIMEOUT_MS`) are exported too.
@@ -161,6 +161,8 @@ export const deps = {
 
 Each Codex source points at `CODEX_BASE_URL`, uses the OAuth access token as its credential, and carries `quirks: { productName, environmentTagName }` naming the host. Put the credential's `accountId` metadata in the source's quirks as `accountId`; it is sent as `chatgpt-account-id`, and a per-call `providerOptions[CODEX_ACCOUNT_ID_OPTION]` overrides it. The quirk binds the source to one ChatGPT account, so each account's credential needs its own source, and the quirk is re-set when the credential is signed in to another account.
 
+Interchange's neutral `effort` is sent as `reasoning.effort`: `low`, `medium` and `high` as given, and `max` as the highest level up to `max` that the model lists in the Codex CLI catalog (`max`, or `xhigh` on `gpt-5.5`), or `high` for a model the catalog does not list.
+
 ## License
 
 [LGPL-2.1-only](https://github.com/corbitsdev/corbits-codex-provider/blob/main/LICENSE)

src/responses-adapter.test.ts

@@ -129,3 +129,39 @@ describe("Codex responses adapter — request shape", () => {
     });
   });
 });
+
+describe("Codex responses adapter — neutral effort", () => {
+  const adapter = createCodexResponsesAdapter(source, quirks);
+  const effortOf = (
+    model: string,
+    options: Parameters<typeof adapter.buildRequest>[2],
+  ) =>
+    parseCodexBody(adapter.buildRequest(turns, model, options).body).reasoning;
+
+  test("max is the model's highest listed level, else high", () => {
+    expect(effortOf("gpt-6-sol", { effort: "max" })).toEqual({ effort: "max" });
+    expect(effortOf("gpt-5.5", { effort: "max" })).toEqual({ effort: "xhigh" });
+    expect(effortOf("unlisted", { effort: "max" })).toEqual({ effort: "high" });
+  });
+
+  test("a non-empty explicit effort option wins", () => {
+    expect(
+      effortOf("gpt-5.5", {
+        effort: "high",
+        providerOptions: { codexReasoningEffort: "low" },
+      }),
+    ).toEqual({ effort: "low" });
+    expect(
+      effortOf("gpt-5.5", {
+        effort: "high",
+        providerOptions: { codexReasoningEffort: "none" },
+      }),
+    ).toBeUndefined();
+    expect(
+      effortOf("gpt-5.5", {
+        effort: "high",
+        providerOptions: { codexReasoningEffort: "" },
+      }),
+    ).toEqual({ effort: "high" });
+  });
+});

src/responses-adapter.ts

@@ -4,6 +4,7 @@ import {
   type ResponsesQuirks,
 } from "@corbits/openai-responses";
 import type { AdapterFactory } from "@intx/inference";
+import type { InferenceEffort, InferenceOptions } from "@intx/types/runtime";
 import {
   CODEX_ACCOUNT_ID_OPTION,
   CODEX_ORIGINATOR,
@@ -55,6 +56,50 @@ function codexResponsesHooks(quirks: CodexQuirks): ResponsesHooks {
   };
 }
 
+// The highest reasoning level each model lists, from the same catalog as
+// `CODEX_DEFAULT_MODELS` (`supported_reasoning_levels`). `ultra` sits above
+// `max` on some models but is not the neutral `max`. A model missing here,
+// including `gpt-6.1`, which that catalog does not list, sends `high`.
+const CODEX_MAX_EFFORT: Readonly<Record<string, "max" | "xhigh">> = {
+  "gpt-6.1-sol": "max",
+  "gpt-6-astra": "max",
+  "gpt-6-sol": "max",
+  "gpt-6-luna": "max",
+  "gpt-5.6-sol": "max",
+  "gpt-5.6-terra": "max",
+  "gpt-5.6-luna": "max",
+  "gpt-5.5": "xhigh",
+};
+
+function codexEffort(
+  model: string,
+  effort: InferenceEffort,
+): InferenceEffort | "xhigh" {
+  return effort === "max" ? (CODEX_MAX_EFFORT[model] ?? "high") : effort;
+}
+
+// Interchange's neutral `effort` becomes the effort option the request
+// builder reads, unless the caller already set that option to a non-empty
+// string, which is the only value the builder sends.
+function withNeutralEffort(
+  model: string,
+  options: InferenceOptions,
+): InferenceOptions {
+  const explicit = options.providerOptions?.[CODEX_REASONING_EFFORT_OPTION];
+  if (
+    options.effort === undefined ||
+    (typeof explicit === "string" && explicit.length > 0)
+  )
+    return options;
+  return {
+    ...options,
+    providerOptions: {
+      ...options.providerOptions,
+      [CODEX_REASONING_EFFORT_OPTION]: codexEffort(model, options.effort),
+    },
+  };
+}
+
 /**
  * `AdapterFactory` for Codex's Responses-speaking ChatGPT backend. `quirks`
  * is this package's own {@link CodexQuirks} (an `InferenceSource.quirks`
@@ -67,8 +112,13 @@ function codexResponsesHooks(quirks: CodexQuirks): ResponsesHooks {
  */
 export const createCodexResponsesAdapter: AdapterFactory = (source, quirks) => {
   const parsed = parseCodexQuirks(quirks);
-  return responsesAdapterFactory(
+  const adapter = responsesAdapterFactory(
     codexResponsesQuirks(parsed),
     codexResponsesHooks(parsed),
   )(source);
+  return {
+    ...adapter,
+    buildRequest: (messages, model, options) =>
+      adapter.buildRequest(messages, model, withNeutralEffort(model, options)),
+  };
 };