fix(core): correct Codex OAuth context limit

packages/core/src/plugin/provider/openai-codex.ts

@@ -12,6 +12,22 @@ export * as OpenAICodex from "./openai-codex"
 /** ChatGPT-plan requests must target the codex backend instead of the public API. */
 export const baseURL = "https://chatgpt.com/backend-api/codex"
 
+// ChatGPT Codex OAuth exposes a smaller window than the public Responses API.
+// Cap instead of replacing so models with smaller windows retain their limit.
+const contextWindow = 272_000
+
+type Limits = {
+  readonly context: number
+  readonly input?: number
+  readonly output: number
+}
+
+export const limits = (value: Limits): Limits => ({
+  context: Math.min(value.context, contextWindow),
+  ...(value.input === undefined ? {} : { input: Math.min(value.input, contextWindow) }),
+  output: value.output,
+})
+
 const methodIDs: readonly string[] = ["chatgpt-browser", "chatgpt-headless"]
 
 /** Structural credential shape so both core and plugin-facing credential types fit. */

packages/core/src/plugin/provider/openai.ts

@@ -206,6 +206,7 @@ export const OpenAIPlugin = define({
             return
           }
           draft.cost = []
+          draft.limit = OpenAICodex.limits(draft.limit)
         })
       }
     })

packages/core/src/session/runner/model.ts

@@ -295,14 +295,17 @@ const codexModel = (
   key: ReturnType<typeof Auth.value> | undefined,
 ) => {
   const account = OpenAICodex.accountID(credential)
-  return withDefaults(model, OpenAIResponses.route)
+  const runtime = produce(model, (draft) => {
+    draft.limit = OpenAICodex.limits(draft.limit)
+  })
+  return withDefaults(runtime, OpenAIResponses.route)
     .with({
       endpoint: { baseURL: OpenAICodex.baseURL },
       auth: (key === undefined ? Auth.none : Auth.bearer(key)).andThen(
         account === undefined ? Auth.none : Auth.headers({ "chatgpt-account-id": account }),
       ),
     })
-    .model({ id: model.modelID ?? model.id })
+    .model({ id: runtime.modelID ?? runtime.id })
 }
 
 const unsupported = (model: ModelV2.Info) =>

packages/core/test/plugin/provider-openai.test.ts

@@ -184,12 +184,17 @@ describe("OpenAIPlugin", () => {
           ]
         })
         catalog.model.update(item.id, ModelV2.ID.make("gpt-5.5-pro"), () => {})
+        catalog.model.update(item.id, ModelV2.ID.make("gpt-5.3-codex-spark"), (model) => {
+          model.limit = { context: 128_000, input: 100_000, output: 16_000 }
+        })
         catalog.model.update(item.id, ModelV2.ID.make("gpt-5.4-pro"), (model) => {
           model.modelID = ModelV2.ID.make("gpt-5.4")
           model.body = { reasoning: { mode: "pro" } }
         })
         catalog.model.update(item.id, ModelV2.ID.make("gpt-5.6"), () => {})
-        catalog.model.update(item.id, ModelV2.ID.make("gpt-5.6-sol"), () => {})
+        catalog.model.update(item.id, ModelV2.ID.make("gpt-5.6-sol"), (model) => {
+          model.limit = { context: 1_050_000, input: 922_000, output: 128_000 }
+        })
         catalog.model.update(item.id, ModelV2.ID.make("gpt-4.1"), () => {})
       })
       yield* credentials.create({
@@ -215,9 +220,12 @@ describe("OpenAIPlugin", () => {
         false,
       )
       expect(required(yield* catalog.model.get(ProviderV2.ID.openai, ModelV2.ID.make("gpt-5.6"))).enabled).toBe(false)
-      expect(required(yield* catalog.model.get(ProviderV2.ID.openai, ModelV2.ID.make("gpt-5.6-sol"))).enabled).toBe(
-        true,
-      )
+      const sol = required(yield* catalog.model.get(ProviderV2.ID.openai, ModelV2.ID.make("gpt-5.6-sol")))
+      expect(sol.enabled).toBe(true)
+      expect(sol.limit).toEqual({ context: 272_000, input: 272_000, output: 128_000 })
+      expect(
+        required(yield* catalog.model.get(ProviderV2.ID.openai, ModelV2.ID.make("gpt-5.3-codex-spark"))).limit,
+      ).toEqual({ context: 128_000, input: 100_000, output: 16_000 })
       expect(required(yield* catalog.model.get(ProviderV2.ID.openai, ModelV2.ID.make("gpt-4.1"))).enabled).toBe(false)
     }),
   )
@@ -234,7 +242,9 @@ describe("OpenAIPlugin", () => {
         catalog.provider.update(item.id, (draft) => {
           draft.package = item.package
         })
-        catalog.model.update(item.id, ModelV2.ID.make("gpt-5.5"), () => {})
+        catalog.model.update(item.id, ModelV2.ID.make("gpt-5.5"), (model) => {
+          model.limit = { context: 1_050_000, input: 922_000, output: 128_000 }
+        })
         catalog.model.update(item.id, ModelV2.ID.make("gpt-4.1"), () => {})
       })
       yield* credentials.create({
@@ -243,7 +253,9 @@ describe("OpenAIPlugin", () => {
       })
       yield* addPlugin()
 
-      expect(required(yield* catalog.model.get(ProviderV2.ID.openai, ModelV2.ID.make("gpt-5.5"))).enabled).toBe(true)
+      const gpt = required(yield* catalog.model.get(ProviderV2.ID.openai, ModelV2.ID.make("gpt-5.5")))
+      expect(gpt.enabled).toBe(true)
+      expect(gpt.limit).toEqual({ context: 1_050_000, input: 922_000, output: 128_000 })
       expect(required(yield* catalog.model.get(ProviderV2.ID.openai, ModelV2.ID.make("gpt-4.1"))).enabled).toBe(true)
     }),
   )

packages/core/test/session-runner-model.test.ts

@@ -16,6 +16,7 @@ import { it } from "./lib/effect"
 
 interface ModelOptions {
   readonly modelID?: string
+  readonly limit?: ModelV2.Info["limit"]
   readonly settings?: ModelV2.Info["settings"]
   readonly headers?: ModelV2.Info["headers"]
   readonly body?: ModelV2.Info["body"]
@@ -38,7 +39,7 @@ const model = (packageName: string | undefined, options: ModelOptions = {}) =>
     cost: [],
     status: "active",
     enabled: true,
-    limit: { context: 100, output: 20 },
+    limit: options.limit ?? { context: 100, output: 20 },
   })
 
 describe("SessionRunnerModel", () => {
@@ -297,6 +298,7 @@ describe("SessionRunnerModel", () => {
           settings: { baseURL: "https://openai.example/v1" },
           headers: {},
           body: {},
+          limit: { context: 1_050_000, input: 922_000, output: 128_000 },
         }),
         Credential.Key.make({ type: "key", key: "secret" }),
       )
@@ -310,6 +312,7 @@ describe("SessionRunnerModel", () => {
       })
 
       expect(headers.authorization).toBe("Bearer secret")
+      expect(resolved.route.defaults.limits).toEqual({ context: 1_050_000, output: 128_000 })
     }),
   )
 
@@ -366,6 +369,7 @@ describe("SessionRunnerModel", () => {
           settings: { baseURL: "https://openai.example/v1" },
           headers: {},
           body: {},
+          limit: { context: 1_050_000, input: 922_000, output: 128_000 },
         }),
         Credential.OAuth.make({
           type: "oauth",
@@ -388,6 +392,7 @@ describe("SessionRunnerModel", () => {
       expect(resolved.route).toMatchObject({
         id: "openai-responses",
         endpoint: { baseURL: "https://chatgpt.com/backend-api/codex" },
+        defaults: { limits: { context: 272_000, output: 128_000 } },
       })
       expect(headers.authorization).toBe("Bearer chatgpt-token")
       expect(headers["chatgpt-account-id"]).toBe("acct_123")