diff --git a/README.md b/README.md
index bfc2855..d4b8a09 100644
--- a/README.md
+++ b/README.md
@@ -219,8 +219,13 @@ with `tool_start`/`tool_result` events as each tool runs — so a UI can type th
 answer out live and show tool activity as it happens.
 
 ```bash
-# Run the agent API (default model: kimi via NVIDIA build)
+# Run the agent API (default provider: nvidia or openrouter)
 export FLOW_NVIDIA_API_KEY="nvapi-..."
+# Or use OpenRouter:
+# export OPENROUTER_API_KEY="sk-or-v1-..."
+# export FLOW_AGENT_PROVIDER="openrouter"
+# export FLOW_AGENT_MODEL="moonshotai/kimi-k2.6"
+
 flow agent                       # POST /agent/chat (SSE), GET /agent/models, POST /agent/undo
 
 # Or expose the same tools to external coding agents over MCP
diff --git a/config/config.example.toml b/config/config.example.toml
index 4b209ee..79984bd 100644
--- a/config/config.example.toml
+++ b/config/config.example.toml
@@ -81,10 +81,11 @@ auto_generate_topics = true
 
 [agent]
 # The in-app video agent — an LLM that operates the project through 41 tools.
-# Served by the NVIDIA build API (OpenAI-compatible). Run with: `flow agent`
+# Supported providers: "nvidia" (NVIDIA Build API) or "openrouter" (OpenRouter.ai API)
+# Can also be overridden via FLOW_AGENT_PROVIDER, FLOW_AGENT_MODEL, FLOW_AGENT_BASE_URL, FLOW_AGENT_API_KEY env vars.
 provider = "nvidia"
 base_url = "https://integrate.api.nvidia.com/v1"
-api_key = ""  # or set FLOW_NVIDIA_API_KEY
+api_key = ""  # or set FLOW_NVIDIA_API_KEY / OPENROUTER_API_KEY
 model = "kimi"  # alias -> moonshotai/kimi-k2.6; see all via GET /agent/models
 max_iterations = 12  # safety cap on the tool-calling loop
 
diff --git a/src/flow/agent/nvidia.py b/src/flow/agent/nvidia.py
index deb40bb..25d43e4 100644
--- a/src/flow/agent/nvidia.py
+++ b/src/flow/agent/nvidia.py
@@ -11,21 +11,38 @@
 
 import httpx
 
+OPENROUTER_BASE = "https://openrouter.ai/api/v1"
 NVIDIA_BASE = "https://integrate.api.nvidia.com/v1"
 MODEL_ALIASES = {"kimi": "moonshotai/kimi-k2.6"}
 
 
 class NvidiaClient:
     def __init__(self, api_key: str | None = None, base_url: str = NVIDIA_BASE,
-                 model: str = "kimi", timeout: float = 120.0) -> None:
-        self.api_key = api_key or os.environ.get("FLOW_NVIDIA_API_KEY", "")
+                 model: str = "kimi", timeout: float = 120.0,
+                 extra_headers: dict | None = None) -> None:
         self.base_url = base_url.rstrip("/")
+        if not api_key:
+            is_or = ("openrouter" in self.base_url or os.environ.get("OPENROUTER_API_KEY")
+                     or os.environ.get("FLOW_OPENROUTER_API_KEY"))
+            if is_or:
+                api_key = (os.environ.get("OPENROUTER_API_KEY")
+                           or os.environ.get("FLOW_OPENROUTER_API_KEY")
+                           or os.environ.get("FLOW_NVIDIA_API_KEY", ""))
+            else:
+                api_key = os.environ.get("FLOW_NVIDIA_API_KEY", "")
+        self.api_key = api_key
         self.model = MODEL_ALIASES.get(model, model)
         self.timeout = timeout
+        self.extra_headers = extra_headers or {}
+        if "openrouter" in self.base_url:
+            self.extra_headers.setdefault("HTTP-Referer", "https://openx-flow.stanl.ink")
+            self.extra_headers.setdefault("X-Title", "OpenX Flow")
 
     def _headers(self) -> dict:
-        return {"Authorization": f"Bearer {self.api_key}",
-                "Content-Type": "application/json"}
+        headers = {"Authorization": f"Bearer {self.api_key}",
+                   "Content-Type": "application/json"}
+        headers.update(self.extra_headers)
+        return headers
 
     def list_models(self) -> list[str]:
         with httpx.Client(timeout=30) as c:
diff --git a/src/flow/api/app.py b/src/flow/api/app.py
index 50e8c3a..2a98274 100644
--- a/src/flow/api/app.py
+++ b/src/flow/api/app.py
@@ -12,7 +12,7 @@
 from sse_starlette.sse import EventSourceResponse
 
 from flow.agent.loop import Agent
-from flow.agent.nvidia import NvidiaClient
+from flow.agent.nvidia import NVIDIA_BASE, OPENROUTER_BASE, NvidiaClient
 from flow.config import Config, load_config
 from flow.store.store import ProjectStore
 from flow.tools.context import ToolContext, dispatch
@@ -39,7 +39,10 @@ def get_config() -> Config:
 
 def _client() -> NvidiaClient:
     cfg = get_config().agent
-    return NvidiaClient(api_key=cfg.api_key or None, base_url=cfg.base_url, model=cfg.model)
+    base_url = cfg.base_url
+    if cfg.provider == "openrouter" and base_url == NVIDIA_BASE:
+        base_url = OPENROUTER_BASE
+    return NvidiaClient(api_key=cfg.api_key or None, base_url=base_url, model=cfg.model)
 
 
 def _make_agent(project_id: str) -> Agent:
diff --git a/src/flow/config.py b/src/flow/config.py
index 27754bd..fbba613 100644
--- a/src/flow/config.py
+++ b/src/flow/config.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import os
 import tomllib
 from pathlib import Path
 from typing import Any
@@ -108,9 +109,19 @@ class Config(BaseModel):
 
 
 def load_config(path: str | Path = "config/config.toml") -> Config:
-    """Load configuration from TOML file."""
+    """Load configuration from TOML file with environment variable overrides."""
     config_path = Path(path)
-    if not config_path.exists():
-        return Config()
-    data: dict[str, Any] = tomllib.loads(config_path.read_text())
-    return Config(**data)
+    data: dict[str, Any] = tomllib.loads(config_path.read_text()) if config_path.exists() else {}
+    cfg = Config(**data)
+
+    # Environment variable overrides for AgentConfig
+    if os.environ.get("FLOW_AGENT_PROVIDER"):
+        cfg.agent.provider = os.environ["FLOW_AGENT_PROVIDER"]
+    if os.environ.get("FLOW_AGENT_BASE_URL"):
+        cfg.agent.base_url = os.environ["FLOW_AGENT_BASE_URL"]
+    if os.environ.get("FLOW_AGENT_API_KEY"):
+        cfg.agent.api_key = os.environ["FLOW_AGENT_API_KEY"]
+    if os.environ.get("FLOW_AGENT_MODEL"):
+        cfg.agent.model = os.environ["FLOW_AGENT_MODEL"]
+
+    return cfg
diff --git a/tests/test_agent.py b/tests/test_agent.py
index e40003d..dbaf95e 100644
--- a/tests/test_agent.py
+++ b/tests/test_agent.py
@@ -112,3 +112,18 @@ def test_run_collects_stream():
     assert out["reply"] == "all set"
     assert len(out["tool_calls"]) == 1
     assert out["tool_calls"][0]["tool"] == "create_character"
+
+
+# --- OpenRouter client tests ---
+
+def test_nvidia_client_openrouter_defaults(monkeypatch):
+    monkeypatch.setenv("OPENROUTER_API_KEY", "sk-or-v1-test")
+    from flow.agent.nvidia import OPENROUTER_BASE, NvidiaClient
+
+    client = NvidiaClient(base_url=OPENROUTER_BASE)
+    assert client.api_key == "sk-or-v1-test"
+    headers = client._headers()
+    assert headers["Authorization"] == "Bearer sk-or-v1-test"
+    assert headers["HTTP-Referer"] == "https://openx-flow.stanl.ink"
+    assert headers["X-Title"] == "OpenX Flow"
+
diff --git a/tests/test_config.py b/tests/test_config.py
index 7e6484a..b040a04 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -16,3 +16,17 @@ def test_load_missing_config():
     """Loading a nonexistent config returns defaults."""
     config = load_config("/nonexistent/path.toml")
     assert config.llm.provider == "openai"
+
+
+def test_agent_config_env_overrides(monkeypatch):
+    monkeypatch.setenv("FLOW_AGENT_PROVIDER", "openrouter")
+    monkeypatch.setenv("FLOW_AGENT_MODEL", "moonshotai/kimi-k2.6")
+    monkeypatch.setenv("FLOW_AGENT_BASE_URL", "https://openrouter.ai/api/v1")
+    monkeypatch.setenv("FLOW_AGENT_API_KEY", "sk-or-v1-test")
+
+    cfg = load_config("/nonexistent/path.toml")
+    assert cfg.agent.provider == "openrouter"
+    assert cfg.agent.model == "moonshotai/kimi-k2.6"
+    assert cfg.agent.base_url == "https://openrouter.ai/api/v1"
+    assert cfg.agent.api_key == "sk-or-v1-test"
+
diff --git a/uv.lock b/uv.lock
index c76627b..cd9baea 100644
--- a/uv.lock
+++ b/uv.lock
@@ -538,7 +538,7 @@ wheels = [
 
 [[package]]
 name = "flow"
-version = "0.9.0"
+version = "0.9.1"
 source = { editable = "." }
 dependencies = [
     { name = "edge-tts" },