feat: add openai model info configuration (#551)

In reference to [Issue 548](https://github.com/openai/codex/issues/548)
- part 1.

codex-cli/src/utils/model-info.ts

@@ -0,0 +1,198 @@
+export type ModelInfo = {
+  /** The human-readable label for this model */
+  label: string;
+  /** The max context window size for this model */
+  maxContextLength: number;
+};
+
+export type SupportedModelId = keyof typeof openAiModelInfo;
+export const openAiModelInfo = {
+  "o1-pro-2025-03-19": {
+    label: "o1 Pro (2025-03-19)",
+    maxContextLength: 200000,
+  },
+  "o3": {
+    label: "o3",
+    maxContextLength: 200000,
+  },
+  "o3-2025-04-16": {
+    label: "o3 (2025-04-16)",
+    maxContextLength: 200000,
+  },
+  "o4-mini": {
+    label: "o4 Mini",
+    maxContextLength: 200000,
+  },
+  "gpt-4.1-nano": {
+    label: "GPT-4.1 Nano",
+    maxContextLength: 1000000,
+  },
+  "gpt-4.1-nano-2025-04-14": {
+    label: "GPT-4.1 Nano (2025-04-14)",
+    maxContextLength: 1000000,
+  },
+  "o4-mini-2025-04-16": {
+    label: "o4 Mini (2025-04-16)",
+    maxContextLength: 200000,
+  },
+  "gpt-4": {
+    label: "GPT-4",
+    maxContextLength: 8192,
+  },
+  "o1-preview-2024-09-12": {
+    label: "o1 Preview (2024-09-12)",
+    maxContextLength: 128000,
+  },
+  "gpt-4.1-mini": {
+    label: "GPT-4.1 Mini",
+    maxContextLength: 1000000,
+  },
+  "gpt-3.5-turbo-instruct-0914": {
+    label: "GPT-3.5 Turbo Instruct (0914)",
+    maxContextLength: 4096,
+  },
+  "gpt-4o-mini-search-preview": {
+    label: "GPT-4o Mini Search Preview",
+    maxContextLength: 128000,
+  },
+  "gpt-4.1-mini-2025-04-14": {
+    label: "GPT-4.1 Mini (2025-04-14)",
+    maxContextLength: 1000000,
+  },
+  "chatgpt-4o-latest": {
+    label: "ChatGPT-4o Latest",
+    maxContextLength: 128000,
+  },
+  "gpt-3.5-turbo-1106": {
+    label: "GPT-3.5 Turbo (1106)",
+    maxContextLength: 16385,
+  },
+  "gpt-4o-search-preview": {
+    label: "GPT-4o Search Preview",
+    maxContextLength: 128000,
+  },
+  "gpt-4-turbo": {
+    label: "GPT-4 Turbo",
+    maxContextLength: 128000,
+  },
+  "gpt-4o-realtime-preview-2024-12-17": {
+    label: "GPT-4o Realtime Preview (2024-12-17)",
+    maxContextLength: 128000,
+  },
+  "gpt-3.5-turbo-instruct": {
+    label: "GPT-3.5 Turbo Instruct",
+    maxContextLength: 4096,
+  },
+  "gpt-3.5-turbo": {
+    label: "GPT-3.5 Turbo",
+    maxContextLength: 16385,
+  },
+  "gpt-4-turbo-preview": {
+    label: "GPT-4 Turbo Preview",
+    maxContextLength: 128000,
+  },
+  "gpt-4o-mini-search-preview-2025-03-11": {
+    label: "GPT-4o Mini Search Preview (2025-03-11)",
+    maxContextLength: 128000,
+  },
+  "gpt-4-0125-preview": {
+    label: "GPT-4 (0125) Preview",
+    maxContextLength: 128000,
+  },
+  "gpt-4o-2024-11-20": {
+    label: "GPT-4o (2024-11-20)",
+    maxContextLength: 128000,
+  },
+  "o3-mini": {
+    label: "o3 Mini",
+    maxContextLength: 200000,
+  },
+  "gpt-4o-2024-05-13": {
+    label: "GPT-4o (2024-05-13)",
+    maxContextLength: 128000,
+  },
+  "gpt-4-turbo-2024-04-09": {
+    label: "GPT-4 Turbo (2024-04-09)",
+    maxContextLength: 128000,
+  },
+  "gpt-3.5-turbo-16k": {
+    label: "GPT-3.5 Turbo 16k",
+    maxContextLength: 16385,
+  },
+  "o3-mini-2025-01-31": {
+    label: "o3 Mini (2025-01-31)",
+    maxContextLength: 200000,
+  },
+  "o1-preview": {
+    label: "o1 Preview",
+    maxContextLength: 128000,
+  },
+  "o1-2024-12-17": {
+    label: "o1 (2024-12-17)",
+    maxContextLength: 128000,
+  },
+  "gpt-4-0613": {
+    label: "GPT-4 (0613)",
+    maxContextLength: 8192,
+  },
+  "o1": {
+    label: "o1",
+    maxContextLength: 128000,
+  },
+  "o1-pro": {
+    label: "o1 Pro",
+    maxContextLength: 200000,
+  },
+  "gpt-4.5-preview": {
+    label: "GPT-4.5 Preview",
+    maxContextLength: 128000,
+  },
+  "gpt-4.5-preview-2025-02-27": {
+    label: "GPT-4.5 Preview (2025-02-27)",
+    maxContextLength: 128000,
+  },
+  "gpt-4o-search-preview-2025-03-11": {
+    label: "GPT-4o Search Preview (2025-03-11)",
+    maxContextLength: 128000,
+  },
+  "gpt-4o": {
+    label: "GPT-4o",
+    maxContextLength: 128000,
+  },
+  "gpt-4o-mini": {
+    label: "GPT-4o Mini",
+    maxContextLength: 128000,
+  },
+  "gpt-4o-2024-08-06": {
+    label: "GPT-4o (2024-08-06)",
+    maxContextLength: 128000,
+  },
+  "gpt-4.1": {
+    label: "GPT-4.1",
+    maxContextLength: 1000000,
+  },
+  "gpt-4.1-2025-04-14": {
+    label: "GPT-4.1 (2025-04-14)",
+    maxContextLength: 1000000,
+  },
+  "gpt-4o-mini-2024-07-18": {
+    label: "GPT-4o Mini (2024-07-18)",
+    maxContextLength: 128000,
+  },
+  "o1-mini": {
+    label: "o1 Mini",
+    maxContextLength: 128000,
+  },
+  "gpt-3.5-turbo-0125": {
+    label: "GPT-3.5 Turbo (0125)",
+    maxContextLength: 16385,
+  },
+  "o1-mini-2024-09-12": {
+    label: "o1 Mini (2024-09-12)",
+    maxContextLength: 128000,
+  },
+  "gpt-4-1106-preview": {
+    label: "GPT-4 (1106) Preview",
+    maxContextLength: 128000,
+  },
+} as const satisfies Record<string, ModelInfo>;

codex-cli/src/utils/model-utils.ts

@@ -2,6 +2,7 @@ import type { ResponseItem } from "openai/resources/responses/responses.mjs";
 
 import { approximateTokensUsed } from "./approximate-tokens-used.js";
 import { getBaseUrl, getApiKey } from "./config";
+import { type SupportedModelId, openAiModelInfo } from "./model-info.js";
 import OpenAI from "openai";
 
 const MODEL_LIST_TIMEOUT_MS = 2_000; // 2 seconds
@@ -89,10 +90,12 @@ export async function isModelSupportedForResponses(
 }
 
 /** Returns the maximum context length (in tokens) for a given model. */
-function maxTokensForModel(model: string): number {
-  // TODO: These numbers are best‑effort guesses and provide a basis for UI percentages. They
-  // should be provider & model specific instead of being wild guesses.
+export function maxTokensForModel(model: string): number {
+  if (model in openAiModelInfo) {
+    return openAiModelInfo[model as SupportedModelId].maxContextLength;
+  }
 
+  // fallback to heuristics for models not in the registry
   const lower = model.toLowerCase();
   if (lower.includes("32k")) {
     return 32000;

codex-cli/tests/model-info.test.ts

@@ -0,0 +1,19 @@
+import { describe, expect, test } from "vitest";
+import { openAiModelInfo } from "../src/utils/model-info";
+
+describe("Model Info", () => {
+  test("supportedModelInfo contains expected models", () => {
+    expect(openAiModelInfo).toHaveProperty("gpt-4o");
+    expect(openAiModelInfo).toHaveProperty("gpt-4.1");
+    expect(openAiModelInfo).toHaveProperty("o3");
+  });
+
+  test("model info entries have required properties", () => {
+    Object.entries(openAiModelInfo).forEach(([_, info]) => {
+      expect(info).toHaveProperty("label");
+      expect(info).toHaveProperty("maxContextLength");
+      expect(typeof info.label).toBe("string");
+      expect(typeof info.maxContextLength).toBe("number");
+    });
+  });
+});

codex-cli/tests/model-utils.test.ts

@@ -0,0 +1,78 @@
+import { describe, test, expect } from "vitest";
+import {
+  calculateContextPercentRemaining,
+  maxTokensForModel,
+} from "../src/utils/model-utils";
+import { openAiModelInfo } from "../src/utils/model-info";
+import type { ResponseItem } from "openai/resources/responses/responses.mjs";
+
+describe("Model Utils", () => {
+  describe("openAiModelInfo", () => {
+    test("model info entries have required properties", () => {
+      Object.entries(openAiModelInfo).forEach(([_, info]) => {
+        expect(info).toHaveProperty("label");
+        expect(info).toHaveProperty("maxContextLength");
+        expect(typeof info.label).toBe("string");
+        expect(typeof info.maxContextLength).toBe("number");
+      });
+    });
+  });
+
+  describe("maxTokensForModel", () => {
+    test("returns correct token limit for known models", () => {
+      const knownModel = "gpt-4o";
+      const expectedTokens = openAiModelInfo[knownModel].maxContextLength;
+      expect(maxTokensForModel(knownModel)).toBe(expectedTokens);
+    });
+
+    test("handles models with size indicators in their names", () => {
+      expect(maxTokensForModel("some-model-32k")).toBe(32000);
+      expect(maxTokensForModel("some-model-16k")).toBe(16000);
+      expect(maxTokensForModel("some-model-8k")).toBe(8000);
+      expect(maxTokensForModel("some-model-4k")).toBe(4000);
+    });
+
+    test("defaults to 128k for unknown models not in the registry", () => {
+      expect(maxTokensForModel("completely-unknown-model")).toBe(128000);
+    });
+  });
+
+  describe("calculateContextPercentRemaining", () => {
+    test("returns 100% for empty items", () => {
+      const result = calculateContextPercentRemaining([], "gpt-4o");
+      expect(result).toBe(100);
+    });
+
+    test("calculates percentage correctly for non-empty items", () => {
+      const mockItems: Array<ResponseItem> = [
+        {
+          id: "test-id",
+          type: "message",
+          role: "user",
+          status: "completed",
+          content: [
+            {
+              type: "input_text",
+              text: "A".repeat(
+                openAiModelInfo["gpt-4o"].maxContextLength * 0.25 * 4,
+              ),
+            },
+          ],
+        } as ResponseItem,
+      ];
+
+      const result = calculateContextPercentRemaining(mockItems, "gpt-4o");
+      expect(result).toBeCloseTo(75, 0);
+    });
+
+    test("handles models that are not in the registry", () => {
+      const mockItems: Array<ResponseItem> = [];
+
+      const result = calculateContextPercentRemaining(
+        mockItems,
+        "unknown-model",
+      );
+      expect(result).toBe(100);
+    });
+  });
+});