diff --git a/README.md b/README.md
index e390eed..565bf86 100644
--- a/README.md
+++ b/README.md
@@ -38,11 +38,13 @@ instance when you are done.
 ## Global Options
 
 When creating a `GTPScript` instance, you can pass the following global options. These options are also available as
-run `Options`. Anything specified as a run option will take precedence over the global option.
+run `Options`. Except `Env`, anything specified as a run option will take precedence over the global
+option. Any `env` provided in the run options are appended.
 
 - `APIKey`: Specify an OpenAI API key for authenticating requests
 - `BaseURL`: A base URL for an OpenAI compatible API (the default is `https://api.openai.com/v1`)
 - `DefaultModel`: The default model to use for OpenAI requests
+- `Env`: Replace the system's environment variables with these in the for `KEY=VAL`
 
 ## Run Options
 
diff --git a/src/gptscript.ts b/src/gptscript.ts
index acd92d4..a83b64b 100644
--- a/src/gptscript.ts
+++ b/src/gptscript.ts
@@ -8,25 +8,23 @@ export interface GlobalOpts {
 	APIKey?: string
 	BaseURL?: string
 	DefaultModel?: string
+	Env?: string[]
 }
 
-function globalOptsToArgs(opts?: GlobalOpts): string[] {
-	const args: string[] = []
+function globalOptsToEnv(env: NodeJS.ProcessEnv, opts?: GlobalOpts) {
 	if (!opts) {
-		return args
+		return
 	}
 
 	if (opts.APIKey) {
-		args.push("--openai-api-key", opts.APIKey)
+		env["OPENAI_API_KEY"] = opts.APIKey
 	}
 	if (opts.BaseURL) {
-		args.push("--openai-base-url", opts.BaseURL)
+		env["OPENAI_BASE_URL"] = opts.BaseURL
 	}
 	if (opts.DefaultModel) {
-		args.push("--default-model", opts.DefaultModel)
+		env["GPTSCRIPT_DEFAULT_MODEL"] = opts.DefaultModel
 	}
-
-	return args
 }
 
 export interface RunOpts {
@@ -83,10 +81,23 @@ export class GPTScript {
 					GPTScript.serverURL = "http://" + u.hostname + ":" + String((s.address() as net.AddressInfo).port)
 					srv.close()
 
-					const args = globalOptsToArgs(opts)
-					args.push("--listen-address", GPTScript.serverURL.replace("http://", ""), "sdkserver")
-					GPTScript.serverProcess = child_process.spawn(getCmdPath(), args, {
-						env: process.env,
+					let env = process.env
+					if (opts && opts.Env) {
+						env = {}
+						for (const v of opts.Env) {
+							const equalIndex = v.indexOf("=")
+							if (equalIndex === -1) {
+								env[v] = ""
+							} else {
+								env[v.substring(0, equalIndex)] = v.substring(equalIndex + 1)
+							}
+						}
+					}
+
+					globalOptsToEnv(env, opts)
+
+					GPTScript.serverProcess = child_process.spawn(getCmdPath(), ["--listen-address", GPTScript.serverURL.replace("http://", ""), "sdkserver"], {
+						env: env,
 						stdio: ["pipe"]
 					})
 
diff --git a/tests/gptscript.test.ts b/tests/gptscript.test.ts
index 702e32c..e061a82 100644
--- a/tests/gptscript.test.ts
+++ b/tests/gptscript.test.ts
@@ -12,7 +12,7 @@ describe("gptscript module", () => {
 			throw new Error("neither OPENAI_API_KEY nor GPTSCRIPT_URL is set")
 		}
 
-		g = new gptscript.GPTScript({APIKey: process.env.GPTSCRIPT_API_KEY!})
+		g = new gptscript.GPTScript({APIKey: process.env.OPENAI_API_KEY})
 	})
 	afterAll(() => {
 		g.close()