opencode-ide-plugin/packages/opencode/src/plugin/codex.ts

import type { Hooks, PluginInput } from "@opencode-ai/plugin"
import { Log } from "../util/log"
import { Installation } from "../installation"
import { Auth, OAUTH_DUMMY_KEY } from "../auth"
import os from "os"

const log = Log.create({ service: "plugin.codex" })

const CLIENT_ID = "app_EMoamEEZ73f0CkXaXp7hrann"
const ISSUER = "https://auth.openai.com"
const CODEX_API_ENDPOINT = "https://chatgpt.com/backend-api/codex/responses"
const OAUTH_PORT = 1455

interface PkceCodes {
  verifier: string
  challenge: string
}

async function generatePKCE(): Promise<PkceCodes> {
  const verifier = generateRandomString(43)
  const encoder = new TextEncoder()
  const data = encoder.encode(verifier)
  const hash = await crypto.subtle.digest("SHA-256", data)
  const challenge = base64UrlEncode(hash)
  return { verifier, challenge }
}

function generateRandomString(length: number): string {
  const chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~"
  const bytes = crypto.getRandomValues(new Uint8Array(length))
  return Array.from(bytes)
    .map((b) => chars[b % chars.length])
    .join("")
}

function base64UrlEncode(buffer: ArrayBuffer): string {
  const bytes = new Uint8Array(buffer)
  const binary = String.fromCharCode(...bytes)
  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "")
}

function generateState(): string {
  return base64UrlEncode(crypto.getRandomValues(new Uint8Array(32)).buffer)
}

export interface IdTokenClaims {
  chatgpt_account_id?: string
  organizations?: Array<{ id: string }>
  email?: string
  "https://api.openai.com/auth"?: {
    chatgpt_account_id?: string
  }
}

export function parseJwtClaims(token: string): IdTokenClaims | undefined {
  const parts = token.split(".")
  if (parts.length !== 3) return undefined
  try {
    return JSON.parse(Buffer.from(parts[1], "base64url").toString())
  } catch {
    return undefined
  }
}

export function extractAccountIdFromClaims(claims: IdTokenClaims): string | undefined {
  return (
    claims.chatgpt_account_id ||
    claims["https://api.openai.com/auth"]?.chatgpt_account_id ||
    claims.organizations?.[0]?.id
  )
}

export function extractAccountId(tokens: TokenResponse): string | undefined {
  if (tokens.id_token) {
    const claims = parseJwtClaims(tokens.id_token)
    const accountId = claims && extractAccountIdFromClaims(claims)
    if (accountId) return accountId
  }
  if (tokens.access_token) {
    const claims = parseJwtClaims(tokens.access_token)
    return claims ? extractAccountIdFromClaims(claims) : undefined
  }
  return undefined
}

function buildAuthorizeUrl(redirectUri: string, pkce: PkceCodes, state: string): string {
  const params = new URLSearchParams({
    response_type: "code",
    client_id: CLIENT_ID,
    redirect_uri: redirectUri,
    scope: "openid profile email offline_access",
    code_challenge: pkce.challenge,
    code_challenge_method: "S256",
    id_token_add_organizations: "true",
    codex_cli_simplified_flow: "true",
    state,
    originator: "opencode",
  })
  return `${ISSUER}/oauth/authorize?${params.toString()}`
}

interface TokenResponse {
  id_token: string
  access_token: string
  refresh_token: string
  expires_in?: number
}

async function exchangeCodeForTokens(code: string, redirectUri: string, pkce: PkceCodes): Promise<TokenResponse> {
  const response = await fetch(`${ISSUER}/oauth/token`, {
    method: "POST",
    headers: { "Content-Type": "application/x-www-form-urlencoded" },
    body: new URLSearchParams({
      grant_type: "authorization_code",
      code,
      redirect_uri: redirectUri,
      client_id: CLIENT_ID,
      code_verifier: pkce.verifier,
    }).toString(),
  })
  if (!response.ok) {
    throw new Error(`Token exchange failed: ${response.status}`)
  }
  return response.json()
}

async function refreshAccessToken(refreshToken: string): Promise<TokenResponse> {
  const response = await fetch(`${ISSUER}/oauth/token`, {
    method: "POST",
    headers: { "Content-Type": "application/x-www-form-urlencoded" },
    body: new URLSearchParams({
      grant_type: "refresh_token",
      refresh_token: refreshToken,
      client_id: CLIENT_ID,
    }).toString(),
  })
  if (!response.ok) {
    throw new Error(`Token refresh failed: ${response.status}`)
  }
  return response.json()
}

const HTML_SUCCESS = `<!doctype html>
<html>
  <head>
    <title>OpenCode - Codex Authorization Successful</title>
    <style>
      body {
        font-family:
          system-ui,
          -apple-system,
          sans-serif;
        display: flex;
        justify-content: center;
        align-items: center;
        height: 100vh;
        margin: 0;
        background: #131010;
        color: #f1ecec;
      }
      .container {
        text-align: center;
        padding: 2rem;
      }
      h1 {
        color: #f1ecec;
        margin-bottom: 1rem;
      }
      p {
        color: #b7b1b1;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <h1>Authorization Successful</h1>
      <p>You can close this window and return to OpenCode.</p>
    </div>
    <script>
      setTimeout(() => window.close(), 2000)
    </script>
  </body>
</html>`

const HTML_ERROR = (error: string) => `<!doctype html>
<html>
  <head>
    <title>OpenCode - Codex Authorization Failed</title>
    <style>
      body {
        font-family:
          system-ui,
          -apple-system,
          sans-serif;
        display: flex;
        justify-content: center;
        align-items: center;
        height: 100vh;
        margin: 0;
        background: #131010;
        color: #f1ecec;
      }
      .container {
        text-align: center;
        padding: 2rem;
      }
      h1 {
        color: #fc533a;
        margin-bottom: 1rem;
      }
      p {
        color: #b7b1b1;
      }
      .error {
        color: #ff917b;
        font-family: monospace;
        margin-top: 1rem;
        padding: 1rem;
        background: #3c140d;
        border-radius: 0.5rem;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <h1>Authorization Failed</h1>
      <p>An error occurred during authorization.</p>
      <div class="error">${error}</div>
    </div>
  </body>
</html>`

interface PendingOAuth {
  pkce: PkceCodes
  state: string
  resolve: (tokens: TokenResponse) => void
  reject: (error: Error) => void
}

let oauthServer: ReturnType<typeof Bun.serve> | undefined
let pendingOAuth: PendingOAuth | undefined

async function startOAuthServer(): Promise<{ port: number; redirectUri: string }> {
  if (oauthServer) {
    return { port: OAUTH_PORT, redirectUri: `http://localhost:${OAUTH_PORT}/auth/callback` }
  }

  oauthServer = Bun.serve({
    port: OAUTH_PORT,
    fetch(req) {
      const url = new URL(req.url)

      if (url.pathname === "/auth/callback") {
        const code = url.searchParams.get("code")
        const state = url.searchParams.get("state")
        const error = url.searchParams.get("error")
        const errorDescription = url.searchParams.get("error_description")

        if (error) {
          const errorMsg = errorDescription || error
          pendingOAuth?.reject(new Error(errorMsg))
          pendingOAuth = undefined
          return new Response(HTML_ERROR(errorMsg), {
            headers: { "Content-Type": "text/html" },
          })
        }

        if (!code) {
          const errorMsg = "Missing authorization code"
          pendingOAuth?.reject(new Error(errorMsg))
          pendingOAuth = undefined
          return new Response(HTML_ERROR(errorMsg), {
            status: 400,
            headers: { "Content-Type": "text/html" },
          })
        }

        if (!pendingOAuth || state !== pendingOAuth.state) {
          const errorMsg = "Invalid state - potential CSRF attack"
          pendingOAuth?.reject(new Error(errorMsg))
          pendingOAuth = undefined
          return new Response(HTML_ERROR(errorMsg), {
            status: 400,
            headers: { "Content-Type": "text/html" },
          })
        }

        const current = pendingOAuth
        pendingOAuth = undefined

        exchangeCodeForTokens(code, `http://localhost:${OAUTH_PORT}/auth/callback`, current.pkce)
          .then((tokens) => current.resolve(tokens))
          .catch((err) => current.reject(err))

        return new Response(HTML_SUCCESS, {
          headers: { "Content-Type": "text/html" },
        })
      }

      if (url.pathname === "/cancel") {
        pendingOAuth?.reject(new Error("Login cancelled"))
        pendingOAuth = undefined
        return new Response("Login cancelled", { status: 200 })
      }

      return new Response("Not found", { status: 404 })
    },
  })

  log.info("codex oauth server started", { port: OAUTH_PORT })
  return { port: OAUTH_PORT, redirectUri: `http://localhost:${OAUTH_PORT}/auth/callback` }
}

function stopOAuthServer() {
  if (oauthServer) {
    oauthServer.stop()
    oauthServer = undefined
    log.info("codex oauth server stopped")
  }
}

function waitForOAuthCallback(pkce: PkceCodes, state: string): Promise<TokenResponse> {
  return new Promise((resolve, reject) => {
    const timeout = setTimeout(
      () => {
        if (pendingOAuth) {
          pendingOAuth = undefined
          reject(new Error("OAuth callback timeout - authorization took too long"))
        }
      },
      5 * 60 * 1000,
    ) // 5 minute timeout

    pendingOAuth = {
      pkce,
      state,
      resolve: (tokens) => {
        clearTimeout(timeout)
        resolve(tokens)
      },
      reject: (error) => {
        clearTimeout(timeout)
        reject(error)
      },
    }
  })
}

export async function CodexAuthPlugin(input: PluginInput): Promise<Hooks> {
  return {
    auth: {
      provider: "openai",
      async loader(getAuth, provider) {
        const auth = await getAuth()
        if (auth.type !== "oauth") return {}

        // Filter models to only allowed Codex models for OAuth
        const allowedModels = new Set([
          "gpt-5.1-codex-max",
          "gpt-5.1-codex-mini",
          "gpt-5.2",
          "gpt-5.2-codex",
          "gpt-5.1-codex",
        ])
        for (const modelId of Object.keys(provider.models)) {
          if (!allowedModels.has(modelId)) {
            delete provider.models[modelId]
          }
        }

        // Zero out costs for Codex (included with ChatGPT subscription)
        for (const model of Object.values(provider.models)) {
          model.cost = {
            input: 0,
            output: 0,
            cache: { read: 0, write: 0 },
          }
        }

        return {
          apiKey: OAUTH_DUMMY_KEY,
          async fetch(requestInput: RequestInfo | URL, init?: RequestInit) {
            // Remove dummy API key authorization header
            if (init?.headers) {
              if (init.headers instanceof Headers) {
                init.headers.delete("authorization")
                init.headers.delete("Authorization")
              } else if (Array.isArray(init.headers)) {
                init.headers = init.headers.filter(([key]) => key.toLowerCase() !== "authorization")
              } else {
                delete init.headers["authorization"]
                delete init.headers["Authorization"]
              }
            }

            const currentAuth = await getAuth()
            if (currentAuth.type !== "oauth") return fetch(requestInput, init)

            // Cast to include accountId field
            const authWithAccount = currentAuth as typeof currentAuth & { accountId?: string }

            // Check if token needs refresh
            if (!currentAuth.access || currentAuth.expires < Date.now()) {
              log.info("refreshing codex access token")
              const tokens = await refreshAccessToken(currentAuth.refresh)
              const newAccountId = extractAccountId(tokens) || authWithAccount.accountId
              await input.client.auth.set({
                path: { id: "openai" },
                body: {
                  type: "oauth",
                  refresh: tokens.refresh_token,
                  access: tokens.access_token,
                  expires: Date.now() + (tokens.expires_in ?? 3600) * 1000,
                  ...(newAccountId && { accountId: newAccountId }),
                },
              })
              currentAuth.access = tokens.access_token
              authWithAccount.accountId = newAccountId
            }

            // Build headers
            const headers = new Headers()
            if (init?.headers) {
              if (init.headers instanceof Headers) {
                init.headers.forEach((value, key) => headers.set(key, value))
              } else if (Array.isArray(init.headers)) {
                for (const [key, value] of init.headers) {
                  if (value !== undefined) headers.set(key, String(value))
                }
              } else {
                for (const [key, value] of Object.entries(init.headers)) {
                  if (value !== undefined) headers.set(key, String(value))
                }
              }
            }

            // Set authorization header with access token
            headers.set("authorization", `Bearer ${currentAuth.access}`)

            // Set ChatGPT-Account-Id header for organization subscriptions
            if (authWithAccount.accountId) {
              headers.set("ChatGPT-Account-Id", authWithAccount.accountId)
            }

            // Rewrite URL to Codex endpoint
            const parsed =
              requestInput instanceof URL
                ? requestInput
                : new URL(typeof requestInput === "string" ? requestInput : requestInput.url)
            const url =
              parsed.pathname.includes("/v1/responses") || parsed.pathname.includes("/chat/completions")
                ? new URL(CODEX_API_ENDPOINT)
                : parsed

            return fetch(url, {
              ...init,
              headers,
            })
          },
        }
      },
      methods: [
        {
          label: "ChatGPT Pro/Plus",
          type: "oauth",
          authorize: async () => {
            const { redirectUri } = await startOAuthServer()
            const pkce = await generatePKCE()
            const state = generateState()
            const authUrl = buildAuthorizeUrl(redirectUri, pkce, state)

            const callbackPromise = waitForOAuthCallback(pkce, state)

            return {
              url: authUrl,
              instructions: "Complete authorization in your browser. This window will close automatically.",
              method: "auto" as const,
              callback: async () => {
                const tokens = await callbackPromise
                stopOAuthServer()
                const accountId = extractAccountId(tokens)
                return {
                  type: "success" as const,
                  refresh: tokens.refresh_token,
                  access: tokens.access_token,
                  expires: Date.now() + (tokens.expires_in ?? 3600) * 1000,
                  accountId,
                }
              },
            }
          },
        },
        {
          label: "Manually enter API Key",
          type: "api",
        },
      ],
    },
    "chat.headers": async (input, output) => {
      if (input.model.providerID !== "openai") return
      output.headers.originator = "opencode"
      output.headers["User-Agent"] = `opencode/${Installation.VERSION} (${os.platform()} ${os.release()}; ${os.arch()})`
      output.headers.session_id = input.sessionID
    },
  }
}