diff --git a/README.md b/README.md
index e89d6873..1ccc96d0 100644
--- a/README.md
+++ b/README.md
@@ -233,6 +233,19 @@ ANTHROPIC_API_KEY=your-key
 ANTHROPIC_BASE_URL=https://your-gateway.example.com/anthropic
 ```
 
+The `openai` provider likewise supports an alternative, OpenAI-compatible
+endpoint (for example a self-hosted or proxied gateway) via `OPENAI_BASE_URL`,
+set alongside `OPENAI_API_KEY`. This is useful for OpenAI-compatible gateways
+that expose the Responses API, since the `openai` provider routes tool calls
+through the Responses API (`/v1/responses`) rather than chat completions:
+
+```bash
+OPENWIKI_PROVIDER=openai
+OPENAI_API_KEY=your-key
+OPENAI_BASE_URL=https://your-gateway.example.com/v1
+OPENWIKI_MODEL_ID=your-model-name
+```
+
 ### OpenAI-compatible endpoints
 
 The `openai-compatible` provider targets any OpenAI-compatible chat-completions
diff --git a/src/constants.ts b/src/constants.ts
index d6a8b4cb..b9f151e3 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -5,6 +5,7 @@ export const FIREWORKS_API_KEY_ENV_KEY = "FIREWORKS_API_KEY";
 export const NEBIUS_API_KEY_ENV_KEY = "NEBIUS_API_KEY";
 export const NVIDIA_API_KEY_ENV_KEY = "NVIDIA_API_KEY";
 export const OPENAI_API_KEY_ENV_KEY = "OPENAI_API_KEY";
+export const OPENAI_BASE_URL_ENV_KEY = "OPENAI_BASE_URL";
 export const OPENAI_COMPATIBLE_API_KEY_ENV_KEY = "OPENAI_COMPATIBLE_API_KEY";
 export const OPENAI_COMPATIBLE_BASE_URL_ENV_KEY = "OPENAI_COMPATIBLE_BASE_URL";
 export const OPENAI_CHATGPT_ACCESS_TOKEN_ENV_KEY =
@@ -255,6 +256,7 @@ export const PROVIDER_CONFIGS: Record<OpenWikiProvider, ProviderConfig> = {
   },
   openai: {
     apiKeyEnvKey: OPENAI_API_KEY_ENV_KEY,
+    baseUrlEnvKey: OPENAI_BASE_URL_ENV_KEY,
     label: "OpenAI",
     modelOptions: OPENAI_MODEL_OPTIONS,
   },
diff --git a/src/env.ts b/src/env.ts
index 13f6c89c..9a9aa743 100644
--- a/src/env.ts
+++ b/src/env.ts
@@ -19,6 +19,7 @@ import {
   normalizeProvider,
   NVIDIA_API_KEY_ENV_KEY,
   OPENAI_API_KEY_ENV_KEY,
+  OPENAI_BASE_URL_ENV_KEY,
   OPENAI_CHATGPT_ACCESS_TOKEN_ENV_KEY,
   OPENAI_CHATGPT_ACCOUNT_ID_ENV_KEY,
   OPENAI_CHATGPT_EMAIL_ENV_KEY,
@@ -87,6 +88,7 @@ export const MANAGED_ENV_KEYS = [
   NEBIUS_API_KEY_ENV_KEY,
   NVIDIA_API_KEY_ENV_KEY,
   OPENAI_API_KEY_ENV_KEY,
+  OPENAI_BASE_URL_ENV_KEY,
   OPENAI_CHATGPT_ACCESS_TOKEN_ENV_KEY,
   OPENAI_CHATGPT_REFRESH_TOKEN_ENV_KEY,
   OPENAI_CHATGPT_EXPIRES_AT_ENV_KEY,
@@ -381,6 +383,7 @@ function isNonSecretDiagnosticKey(key: string): boolean {
     key === OPENWIKI_PROVIDER_RETRY_ATTEMPTS_ENV_KEY ||
     key === OPENWIKI_OPENROUTER_PROVIDER_ONLY_ENV_KEY ||
     key === ANTHROPIC_BASE_URL_ENV_KEY ||
+    key === OPENAI_BASE_URL_ENV_KEY ||
     key === OPENAI_COMPATIBLE_BASE_URL_ENV_KEY ||
     key === BEDROCK_AWS_REGION_ENV_KEY ||
     key === GOOGLE_CLOUD_PROJECT_ENV_KEY ||