diff --git a/.env.example b/.env.example
index faf9c85..f424cda 100644
--- a/.env.example
+++ b/.env.example
@@ -14,8 +14,12 @@ export AZURE_OPENAI_API_KEY=
 # export AZURE_OPENAI_AUTH_MODE=managed_identity
 # export AZURE_OPENAI_MANAGED_IDENTITY_CLIENT_ID=your-client-id
 
-# ── OpenAI (alternative to Azure) ────────────────────────────────────
-# export OPENAI_API_KEY=sk-...
+# ── OpenAI-compatible endpoints ──────────────────────────────────────
+# Set AUTH_MODE to openai_compatible and reuse AZURE_OPENAI_ENDPOINT / _API_KEY.
+# The plain OpenAI client is used; no Azure auth, no api-version header.
+# export AZURE_OPENAI_ENDPOINT=https://api.openai.com/v1
+# export AZURE_OPENAI_API_KEY=sk-...
+# export AZURE_OPENAI_AUTH_MODE=openai_compatible
 
 # ── Anthropic / Claude (for claude_chat backend) ─────────────────────
 # export ANTHROPIC_API_KEY=sk-ant-...
diff --git a/README.md b/README.md
index 6342cff..f81c37b 100644
--- a/README.md
+++ b/README.md
@@ -45,13 +45,22 @@ export AZURE_OPENAI_API_KEY="your-key"
 export AZURE_OPENAI_AUTH_MODE="azure_cli"
 ```
 
-> **Note:** `AZURE_OPENAI_ENDPOINT` is always required. Without it, all LLM calls will fail.
+> **Note:** `AZURE_OPENAI_ENDPOINT` is required for all three modes (`api_key`, `azure_cli`,
+> `openai_compatible`). Without it, all LLM calls will fail.
 
-**OpenAI** directly:
+**OpenAI-compatible endpoints**:
 ```bash
-export OPENAI_API_KEY="sk-..."
+export AZURE_OPENAI_ENDPOINT="https://api.openai.com/v1"
+export AZURE_OPENAI_API_KEY="sk-..."
+export AZURE_OPENAI_AUTH_MODE="openai_compatible"
 ```
 
+This routes all calls through the plain OpenAI Python client (no Azure auth, no `api-version`
+header).
+
+> **Note:** SkillOpt reuses the `AZURE_OPENAI_*` env var names even in this mode — there is no
+> separate `OPENAI_API_KEY` knob.
+
 **Anthropic Claude**:
 ```bash
 export ANTHROPIC_API_KEY="sk-ant-..."
diff --git a/configs/_base_/default.yaml b/configs/_base_/default.yaml
index 9ec2270..ed8f61d 100644
--- a/configs/_base_/default.yaml
+++ b/configs/_base_/default.yaml
@@ -28,19 +28,19 @@ model:
   azure_openai_endpoint: ""           # e.g. "https://your-resource.openai.azure.com/"
   azure_openai_api_version: "2024-12-01-preview"
   azure_openai_api_key: ""       # Fill locally if you do not export AZURE_OPENAI_API_KEY
-  azure_openai_auth_mode: azure_cli
+  azure_openai_auth_mode: ""           # empty → fall back to AZURE_OPENAI_AUTH_MODE env (default "azure_cli")
   azure_openai_ad_scope: "https://cognitiveservices.azure.com/.default"
   azure_openai_managed_identity_client_id: ""
   optimizer_azure_openai_endpoint: ""   # e.g. "https://your-resource.openai.azure.com/"
   optimizer_azure_openai_api_version: "2024-12-01-preview"
   optimizer_azure_openai_api_key: ""
-  optimizer_azure_openai_auth_mode: azure_cli
+  optimizer_azure_openai_auth_mode: ""           # empty → fall back to OPTIMIZER_AZURE_OPENAI_AUTH_MODE env, then shared
   optimizer_azure_openai_ad_scope: "https://cognitiveservices.azure.com/.default"
   optimizer_azure_openai_managed_identity_client_id: ""
   target_azure_openai_endpoint: ""   # e.g. "https://your-resource.openai.azure.com/"
   target_azure_openai_api_version: "2024-12-01-preview"
   target_azure_openai_api_key: ""
-  target_azure_openai_auth_mode: azure_cli
+  target_azure_openai_auth_mode: ""           # empty → fall back to TARGET_AZURE_OPENAI_AUTH_MODE env, then shared
   target_azure_openai_ad_scope: "https://cognitiveservices.azure.com/.default"
   target_azure_openai_managed_identity_client_id: ""