diff --git a/README.md b/README.md
index 1dc4d7d..e206a72 100644
--- a/README.md
+++ b/README.md
@@ -31,6 +31,15 @@ pip install -e .
 In order to use the framework, you need to have access to an LLM.
 Please follow the instructions in the [Controller README](graph_of_thoughts/controller/README.md) to configure the LLM of your choice.
 
+### OpenRouter and OpenAI-compatible HTTP API
+
+1. Install API extras: `pip install "graph_of_thoughts[api]"` (or `pip install -e ".[api]"` from a source checkout).
+2. Copy [`graph_of_thoughts/language_models/config.openrouter.example.yaml`](graph_of_thoughts/language_models/config.openrouter.example.yaml) to `config.openrouter.yaml`, add your [OpenRouter](https://openrouter.ai/) keys and model ids, and either place it in `graph_of_thoughts/language_models/` or point `OPENROUTER_CONFIG` at your file.
+3. Run the server: `got-openrouter-api` (or `python -m graph_of_thoughts.api`).
+4. Call `POST /v1/chat/completions` with a standard OpenAI-style JSON body (`messages`, optional `model`, `temperature`, `max_tokens`). The server runs a small Graph of Operations (generate multiple candidates, score, keep the best) via OpenRouter.
+
+Details: [Language models README](graph_of_thoughts/language_models/README.md).
+
 ## Quick Start
 
 The following code snippet shows how to use the framework to solve the sorting problem for a list of 32 numbers using a CoT-like approach.  
diff --git a/graph_of_thoughts/api/__init__.py b/graph_of_thoughts/api/__init__.py
new file mode 100644
index 0000000..39ad245
--- /dev/null
+++ b/graph_of_thoughts/api/__init__.py
@@ -0,0 +1 @@
+"""HTTP API helpers (FastAPI) for running Graph of Thoughts with OpenRouter."""
diff --git a/graph_of_thoughts/api/__main__.py b/graph_of_thoughts/api/__main__.py
new file mode 100644
index 0000000..8bee279
--- /dev/null
+++ b/graph_of_thoughts/api/__main__.py
@@ -0,0 +1,4 @@
+from graph_of_thoughts.api.app import run
+
+if __name__ == "__main__":
+    run()
diff --git a/graph_of_thoughts/api/app.py b/graph_of_thoughts/api/app.py
new file mode 100644
index 0000000..1c91697
--- /dev/null
+++ b/graph_of_thoughts/api/app.py
@@ -0,0 +1,192 @@
+# Copyright (c) 2023 ETH Zurich.
+#                    All rights reserved.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from __future__ import annotations
+
+import logging
+import os
+import time
+import uuid
+from typing import Any, Dict, List, Optional
+
+from graph_of_thoughts.api.got_openai_pipeline import (
+    ChatCompletionParser,
+    ChatCompletionPrompter,
+    build_default_chat_graph,
+    extract_assistant_text,
+    format_chat_messages,
+)
+from graph_of_thoughts.controller import Controller
+from graph_of_thoughts.language_models.openrouter import (
+    OpenRouter,
+    OpenRouterBadRequestError,
+    OpenRouterRateLimitError,
+)
+
+try:
+    from fastapi import FastAPI, HTTPException
+    from fastapi.responses import JSONResponse
+    from pydantic import BaseModel, Field
+except ImportError as e:
+    raise ImportError(
+        "FastAPI and Pydantic are required for the HTTP API. "
+        'Install with: pip install "graph_of_thoughts[api]"'
+    ) from e
+
+
+class ChatMessage(BaseModel):
+    role: str
+    content: str
+
+
+class ChatCompletionRequest(BaseModel):
+    model: Optional[str] = None
+    messages: List[ChatMessage]
+    temperature: Optional[float] = None
+    max_tokens: Optional[int] = None
+    stream: Optional[bool] = False
+    n: Optional[int] = Field(default=1, ge=1, le=1)
+
+
+def _get_config_path() -> str:
+    return os.environ.get(
+        "OPENROUTER_CONFIG",
+        os.path.join(
+            os.path.dirname(os.path.dirname(os.path.abspath(__file__))),
+            "language_models",
+            "config.openrouter.yaml",
+        ),
+    )
+
+
+def _run_controller(lm: OpenRouter, user_text: str) -> str:
+    graph = build_default_chat_graph(num_candidates=3)
+    ctrl = Controller(
+        lm,
+        graph,
+        ChatCompletionPrompter(),
+        ChatCompletionParser(),
+        {"input": user_text},
+    )
+    ctrl.run()
+    return extract_assistant_text(ctrl.get_final_thoughts())
+
+
+app = FastAPI(
+    title="Graph of Thoughts (OpenRouter)",
+    version="0.1.0",
+    description="OpenAI-compatible chat completions backed by Graph of Operations + OpenRouter.",
+)
+
+
+@app.on_event("startup")
+def _startup() -> None:
+    logging.basicConfig(level=os.environ.get("LOG_LEVEL", "INFO"))
+
+
+@app.get("/v1/models")
+def list_models() -> Dict[str, Any]:
+    path = _get_config_path()
+    if not os.path.isfile(path):
+        return {"object": "list", "data": []}
+    from graph_of_thoughts.language_models.openrouter import load_openrouter_config
+
+    cfg = load_openrouter_config(path)
+    models = cfg.get("models") or []
+    if isinstance(models, str):
+        models = [models]
+    data = [
+        {
+            "id": m,
+            "object": "model",
+            "created": int(time.time()),
+            "owned_by": "openrouter",
+        }
+        for m in models
+    ]
+    return {"object": "list", "data": data}
+
+
+@app.post("/v1/chat/completions")
+def chat_completions(body: ChatCompletionRequest) -> JSONResponse:
+    if body.stream:
+        raise HTTPException(
+            status_code=400,
+            detail="stream=true is not supported; use stream=false.",
+        )
+    if body.n != 1:
+        raise HTTPException(status_code=400, detail="Only n=1 is supported.")
+
+    path = _get_config_path()
+    if not os.path.isfile(path):
+        raise HTTPException(
+            status_code=500,
+            detail=f"OpenRouter config not found at {path}. Set OPENROUTER_CONFIG.",
+        )
+
+    lm = OpenRouter(config_path=path)
+    user_text = format_chat_messages(
+        [{"role": m.role, "content": m.content} for m in body.messages]
+    )
+    try:
+        lm.set_request_overrides(
+            model=body.model,
+            temperature=body.temperature,
+            max_tokens=body.max_tokens,
+        )
+        try:
+            answer = _run_controller(lm, user_text)
+        finally:
+            lm.clear_request_overrides()
+    except OpenRouterRateLimitError as e:
+        raise HTTPException(status_code=429, detail=str(e)) from e
+    except OpenRouterBadRequestError as e:
+        raise HTTPException(status_code=400, detail=str(e)) from e
+
+    model_id = (
+        body.model
+        or lm.generation_model_id
+        or lm.last_model_id
+        or (lm.models[0] if lm.models else "openrouter")
+    )
+    resp_id = f"chatcmpl-{uuid.uuid4().hex}"
+    now = int(time.time())
+    payload = {
+        "id": resp_id,
+        "object": "chat.completion",
+        "created": now,
+        "model": model_id,
+        "choices": [
+            {
+                "index": 0,
+                "message": {"role": "assistant", "content": answer},
+                "finish_reason": "stop",
+            }
+        ],
+        "usage": {
+            "prompt_tokens": lm.prompt_tokens,
+            "completion_tokens": lm.completion_tokens,
+            "total_tokens": lm.prompt_tokens + lm.completion_tokens,
+        },
+    }
+    return JSONResponse(content=payload)
+
+
+def run() -> None:
+    import uvicorn
+
+    host = os.environ.get("HOST", "0.0.0.0")
+    port = int(os.environ.get("PORT", "8000"))
+    uvicorn.run(
+        "graph_of_thoughts.api.app:app",
+        host=host,
+        port=port,
+        reload=os.environ.get("RELOAD", "").lower() in ("1", "true", "yes"),
+    )
+
+
+if __name__ == "__main__":
+    run()
diff --git a/graph_of_thoughts/api/got_openai_pipeline.py b/graph_of_thoughts/api/got_openai_pipeline.py
new file mode 100644
index 0000000..b3ddc8e
--- /dev/null
+++ b/graph_of_thoughts/api/got_openai_pipeline.py
@@ -0,0 +1,123 @@
+# Copyright (c) 2023 ETH Zurich.
+#                    All rights reserved.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from __future__ import annotations
+
+import json
+import re
+from typing import Any, Dict, List, Union
+
+from graph_of_thoughts.operations import GraphOfOperations, operations
+from graph_of_thoughts.operations.thought import Thought
+from graph_of_thoughts.parser import Parser
+from graph_of_thoughts.prompter import Prompter
+
+
+def format_chat_messages(messages: List[Dict[str, str]]) -> str:
+    parts: List[str] = []
+    for m in messages:
+        role = m.get("role", "user")
+        content = m.get("content", "")
+        if not isinstance(content, str):
+            content = str(content)
+        parts.append(f"{role.upper()}:\n{content}")
+    return "\n\n".join(parts)
+
+
+class ChatCompletionPrompter(Prompter):
+    """Prompter for a small generate → score → keep-best Graph of Operations."""
+
+    def generate_prompt(self, num_branches: int, **kwargs: Any) -> str:
+        problem = kwargs.get("input", "")
+        return (
+            "You are a careful assistant. Read the conversation below and produce "
+            "one candidate answer for the USER's latest needs.\n\n"
+            f"{problem}\n\n"
+            "Reply with your answer only, no preamble."
+        )
+
+    def score_prompt(self, state_dicts: List[Dict], **kwargs: Any) -> str:
+        lines = [
+            "You evaluate candidate answers for the same problem. "
+            "Score each candidate from 0 (worst) to 10 (best) on correctness, "
+            "completeness, and relevance.",
+            "",
+            "Return ONLY a JSON array of numbers, one score per candidate in order, e.g. [7, 5, 9].",
+            "",
+        ]
+        for i, st in enumerate(state_dicts):
+            cand = st.get("candidate", "")
+            lines.append(f"Candidate {i}:\n{cand}\n")
+        return "\n".join(lines)
+
+    def aggregation_prompt(self, state_dicts: List[Dict], **kwargs: Any) -> str:
+        raise RuntimeError("aggregation_prompt is not used by the chat completion pipeline")
+
+    def improve_prompt(self, **kwargs: Any) -> str:
+        raise RuntimeError("improve_prompt is not used by the chat completion pipeline")
+
+    def validation_prompt(self, **kwargs: Any) -> str:
+        raise RuntimeError("validation_prompt is not used by the chat completion pipeline")
+
+
+class ChatCompletionParser(Parser):
+    def parse_generate_answer(self, state: Dict, texts: List[str]) -> List[Dict]:
+        out: List[Dict] = []
+        for i, t in enumerate(texts):
+            out.append({"candidate": (t or "").strip(), "branch_index": i})
+        return out
+
+    def parse_score_answer(self, states: List[Dict], texts: List[str]) -> List[float]:
+        raw = texts[0] if texts else ""
+        scores = self._scores_from_text(raw, len(states))
+        if len(scores) < len(states):
+            scores.extend([0.0] * (len(states) - len(scores)))
+        return scores[: len(states)]
+
+    def _scores_from_text(self, raw: str, n: int) -> List[float]:
+        raw = raw.strip()
+        try:
+            data = json.loads(raw)
+            if isinstance(data, list):
+                return [float(x) for x in data]
+        except (json.JSONDecodeError, ValueError, TypeError):
+            pass
+        nums = re.findall(r"-?\d+(?:\.\d+)?", raw)
+        return [float(x) for x in nums[:n]]
+
+    def parse_aggregation_answer(
+        self, states: List[Dict], texts: List[str]
+    ) -> Union[Dict, List[Dict]]:
+        raise RuntimeError("parse_aggregation_answer is not used")
+
+    def parse_improve_answer(self, state: Dict, texts: List[str]) -> Dict:
+        raise RuntimeError("parse_improve_answer is not used")
+
+    def parse_validation_answer(self, state: Dict, texts: List[str]) -> bool:
+        raise RuntimeError("parse_validation_answer is not used")
+
+
+def build_default_chat_graph(num_candidates: int = 3) -> GraphOfOperations:
+    g = GraphOfOperations()
+    g.append_operation(
+        operations.Generate(
+            num_branches_prompt=1, num_branches_response=num_candidates
+        )
+    )
+    g.append_operation(operations.Score(combined_scoring=True))
+    g.append_operation(operations.KeepBestN(1))
+    return g
+
+
+def extract_assistant_text(final_thoughts_list: List[List[Thought]]) -> str:
+    """``get_final_thoughts`` returns one list per leaf operation; we take the first leaf's first thought."""
+    if not final_thoughts_list:
+        return ""
+    thoughts = final_thoughts_list[0]
+    if not thoughts:
+        return ""
+    state = thoughts[0].state or {}
+    return str(state.get("candidate", ""))
diff --git a/graph_of_thoughts/language_models/README.md b/graph_of_thoughts/language_models/README.md
index 9ca6d8f..cce7051 100644
--- a/graph_of_thoughts/language_models/README.md
+++ b/graph_of_thoughts/language_models/README.md
@@ -4,6 +4,7 @@ The Language Models module is responsible for managing the large language models
 
 Currently, the framework supports the following LLMs:
 - GPT-4 / GPT-3.5 (Remote - OpenAI API)
+- OpenRouter (Remote - [OpenRouter](https://openrouter.ai/) OpenAI-compatible API, multi-key / multi-model rotation)
 - LLaMA-2 (Local - HuggingFace Transformers)
 
 The following sections describe how to instantiate individual LLMs and how to add new LLMs to the framework.
@@ -28,12 +29,26 @@ The following sections describe how to instantiate individual LLMs and how to ad
 
 - Instantiate the language model based on the selected configuration key (predefined / custom).
 ```python
-lm = controller.ChatGPT(
-    "path/to/config.json", 
+from graph_of_thoughts.language_models import ChatGPT
+
+lm = ChatGPT(
+    "path/to/config.json",
     model_name=<configuration key>
 )
 ```
 
+### OpenRouter
+- Copy `config.openrouter.example.yaml` (or `.json`) to `config.openrouter.yaml` next to this module, or pass an explicit path.
+- Set `api_keys` (list) and `models` (list). Each request picks a **random** key and a **random** model (uniform over the lists). If the HTTP API passes a `model` field, that model id is used for that request instead of a random one.
+- Optional: `http_referer` and `x_title` for OpenRouter attribution headers (see [OpenRouter docs](https://openrouter.ai/docs)).
+- HTTP **429** responses trigger exponential backoff and further rotation; **400** responses are retried a limited number of times with a new key/model pair, then surfaced as an error.
+
+```python
+from graph_of_thoughts.language_models import OpenRouter
+
+lm = OpenRouter("/path/to/config.openrouter.yaml")
+```
+
 ### LLaMA-2
 - Requires local hardware to run inference and a HuggingFace account.
 - Adjust the predefined `llama7b-hf`, `llama13b-hf` or `llama70b-hf` configurations or create a new configuration with an unique key.
@@ -50,8 +65,10 @@ lm = controller.ChatGPT(
 
 - Instantiate the language model based on the selected configuration key (predefined / custom).
 ```python
-lm = controller.Llama2HF(
-    "path/to/config.json", 
+from graph_of_thoughts.language_models import Llama2HF
+
+lm = Llama2HF(
+    "path/to/config.json",
     model_name=<configuration key>
 )
 ```
diff --git a/graph_of_thoughts/language_models/__init__.py b/graph_of_thoughts/language_models/__init__.py
index 076d62e..a39251d 100644
--- a/graph_of_thoughts/language_models/__init__.py
+++ b/graph_of_thoughts/language_models/__init__.py
@@ -1,3 +1,10 @@
 from .abstract_language_model import AbstractLanguageModel
 from .chatgpt import ChatGPT
 from .llamachat_hf import Llama2HF
+from .openrouter import (
+    OpenRouter,
+    OpenRouterBadRequestError,
+    OpenRouterError,
+    OpenRouterRateLimitError,
+    load_openrouter_config,
+)
diff --git a/graph_of_thoughts/language_models/config.openrouter.example.json b/graph_of_thoughts/language_models/config.openrouter.example.json
new file mode 100644
index 0000000..8c6f4ad
--- /dev/null
+++ b/graph_of_thoughts/language_models/config.openrouter.example.json
@@ -0,0 +1,21 @@
+{
+  "base_url": "https://openrouter.ai/api/v1",
+  "api_keys": [
+    "sk-or-v1-replace-me-1",
+    "sk-or-v1-replace-me-2"
+  ],
+  "models": [
+    "openai/gpt-4o-mini",
+    "anthropic/claude-3.5-haiku"
+  ],
+  "temperature": 0.7,
+  "max_tokens": 4096,
+  "stop": null,
+  "prompt_token_cost": 0.0,
+  "response_token_cost": 0.0,
+  "max_retries_429": 8,
+  "max_retries_400": 3,
+  "base_backoff_seconds": 1.0,
+  "http_referer": "",
+  "x_title": ""
+}
diff --git a/graph_of_thoughts/language_models/config.openrouter.example.yaml b/graph_of_thoughts/language_models/config.openrouter.example.yaml
new file mode 100644
index 0000000..75d7f8a
--- /dev/null
+++ b/graph_of_thoughts/language_models/config.openrouter.example.yaml
@@ -0,0 +1,29 @@
+# Copy to config.openrouter.yaml (or set path explicitly) and fill in keys.
+# Per chat request, an API key and model are chosen at random (uniform) from the lists.
+
+base_url: https://openrouter.ai/api/v1
+
+api_keys:
+  - sk-or-v1-replace-me-1
+  - sk-or-v1-replace-me-2
+
+models:
+  - openai/gpt-4o-mini
+  - anthropic/claude-3.5-haiku
+
+temperature: 0.7
+max_tokens: 4096
+stop: null
+
+# Optional cost accounting (set to 0 if unknown)
+prompt_token_cost: 0.0
+response_token_cost: 0.0
+
+# Retries after HTTP 429 / 400 (each retry uses a fresh random key + model)
+max_retries_429: 8
+max_retries_400: 3
+base_backoff_seconds: 1.0
+
+# Optional OpenRouter attribution headers (recommended by OpenRouter)
+http_referer: ""
+x_title: ""
diff --git a/graph_of_thoughts/language_models/openrouter.py b/graph_of_thoughts/language_models/openrouter.py
new file mode 100644
index 0000000..d9b53ff
--- /dev/null
+++ b/graph_of_thoughts/language_models/openrouter.py
@@ -0,0 +1,287 @@
+# Copyright (c) 2023 ETH Zurich.
+#                    All rights reserved.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from __future__ import annotations
+
+import json
+import logging
+import os
+import random
+import time
+from typing import Any, Dict, List, Optional, Union
+
+import yaml
+from openai import APIStatusError, OpenAI
+from openai.types.chat.chat_completion import ChatCompletion
+
+from .abstract_language_model import AbstractLanguageModel
+
+
+class OpenRouterError(Exception):
+    """Base error for OpenRouter integration."""
+
+
+class OpenRouterBadRequestError(OpenRouterError):
+    """Raised when OpenRouter returns HTTP 400 after retries."""
+
+
+class OpenRouterRateLimitError(OpenRouterError):
+    """Raised when OpenRouter returns HTTP 429 after retries."""
+
+
+def load_openrouter_config(path: str) -> Dict[str, Any]:
+    """Load a YAML or JSON OpenRouter configuration file."""
+    return _load_config_file(path)
+
+
+def _load_config_file(path: str) -> Dict[str, Any]:
+    ext = os.path.splitext(path)[1].lower()
+    with open(path, "r", encoding="utf-8") as f:
+        if ext in (".yaml", ".yml"):
+            data = yaml.safe_load(f)
+        else:
+            data = json.load(f)
+    if not isinstance(data, dict):
+        raise ValueError(f"Config at {path} must be a JSON/YAML object")
+    return data
+
+
+class OpenRouter(AbstractLanguageModel):
+    """
+    OpenRouter-backed language model with per-request rotation of API keys and models.
+
+    Configuration is loaded from YAML or JSON (see ``config.openrouter.example.yaml``).
+    """
+
+    def __init__(
+        self,
+        config_path: str = "",
+        model_name: str = "openrouter",
+        cache: bool = False,
+    ) -> None:
+        self._rotation_model_name = model_name
+        self._request_overrides: Dict[str, Any] = {}
+        super().__init__(config_path, model_name, cache)
+        self._apply_openrouter_config()
+
+    def load_config(self, path: str) -> None:
+        if path == "":
+            path = os.path.join(
+                os.path.dirname(os.path.abspath(__file__)),
+                "config.openrouter.yaml",
+            )
+        self.config_path = path
+        self.config = _load_config_file(path)
+        self.logger.debug("Loaded OpenRouter config from %s", path)
+
+    def _apply_openrouter_config(self) -> None:
+        cfg = self.config
+        self.base_url: str = cfg.get("base_url", "https://openrouter.ai/api/v1")
+        keys = cfg.get("api_keys") or []
+        if isinstance(keys, str):
+            keys = [keys]
+        self.api_keys: List[str] = [k for k in keys if k]
+        if not self.api_keys:
+            raise ValueError("OpenRouter config must define non-empty 'api_keys'")
+
+        models = cfg.get("models") or []
+        if isinstance(models, str):
+            models = [models]
+        self.models: List[str] = [m for m in models if m]
+        if not self.models:
+            raise ValueError("OpenRouter config must define non-empty 'models'")
+
+        self.temperature: float = float(cfg.get("temperature", 1.0))
+        self.max_tokens: int = int(cfg.get("max_tokens", 4096))
+        self.stop: Union[str, List[str], None] = cfg.get("stop")
+        self.prompt_token_cost: float = float(cfg.get("prompt_token_cost", 0.0))
+        self.response_token_cost: float = float(cfg.get("response_token_cost", 0.0))
+
+        self.max_retries_429: int = int(cfg.get("max_retries_429", 8))
+        self.max_retries_400: int = int(cfg.get("max_retries_400", 3))
+        self.base_backoff_seconds: float = float(cfg.get("base_backoff_seconds", 1.0))
+
+        self.http_referer: str = cfg.get("http_referer", "") or os.getenv(
+            "OPENROUTER_HTTP_REFERER", ""
+        )
+        self.x_title: str = cfg.get("x_title", "") or os.getenv("OPENROUTER_X_TITLE", "")
+
+        self.model_name = self._rotation_model_name
+        self.last_model_id: Optional[str] = None
+        self.generation_model_id: Optional[str] = None
+
+    def set_request_overrides(self, **kwargs: Any) -> None:
+        """Optional per-request parameters (used by the HTTP API). Cleared with :meth:`clear_request_overrides`."""
+        self._request_overrides = {k: v for k, v in kwargs.items() if v is not None}
+
+    def clear_request_overrides(self) -> None:
+        self._request_overrides = {}
+
+    def _pick_key(self) -> str:
+        return random.choice(self.api_keys)
+
+    def _pick_model(self, override: Optional[str]) -> str:
+        if override:
+            return override
+        o = self._request_overrides.get("model")
+        if o:
+            return str(o)
+        return random.choice(self.models)
+
+    def _effective_temperature(self) -> float:
+        t = self._request_overrides.get("temperature")
+        return float(t) if t is not None else self.temperature
+
+    def _effective_max_tokens(self) -> int:
+        m = self._request_overrides.get("max_tokens")
+        return int(m) if m is not None else self.max_tokens
+
+    def _client_for_key(self, api_key: str) -> OpenAI:
+        headers: Dict[str, str] = {}
+        if self.http_referer:
+            headers["HTTP-Referer"] = self.http_referer
+        if self.x_title:
+            headers["X-Title"] = self.x_title
+        return OpenAI(
+            base_url=self.base_url,
+            api_key=api_key,
+            default_headers=headers or None,
+        )
+
+    def _sleep_backoff(self, attempt: int) -> None:
+        cap = 60.0
+        delay = min(
+            self.base_backoff_seconds * (2**attempt) + random.random(),
+            cap,
+        )
+        self.logger.warning("Backing off %.2fs (attempt %d)", delay, attempt + 1)
+        time.sleep(delay)
+
+    def chat(
+        self,
+        messages: List[Dict[str, str]],
+        num_responses: int = 1,
+        model_override: Optional[str] = None,
+    ) -> ChatCompletion:
+        """
+        Call OpenRouter chat completions with rotation and retries for 429/400.
+        """
+        attempts_429 = 0
+        attempts_400 = 0
+        attempt = 0
+        last_exc: Optional[Exception] = None
+
+        while True:
+            api_key = self._pick_key()
+            model_id = self._pick_model(model_override)
+            client = self._client_for_key(api_key)
+            try:
+                response = client.chat.completions.create(
+                    model=model_id,
+                    messages=messages,
+                    temperature=self._effective_temperature(),
+                    max_tokens=self._effective_max_tokens(),
+                    n=num_responses,
+                    stop=self.stop,
+                )
+                if response.usage is not None:
+                    self.prompt_tokens += response.usage.prompt_tokens or 0
+                    self.completion_tokens += response.usage.completion_tokens or 0
+                    pt_k = float(self.prompt_tokens) / 1000.0
+                    ct_k = float(self.completion_tokens) / 1000.0
+                    self.cost = (
+                        self.prompt_token_cost * pt_k
+                        + self.response_token_cost * ct_k
+                    )
+                self.last_model_id = model_id
+                if self.generation_model_id is None:
+                    self.generation_model_id = model_id
+                self.logger.info(
+                    "OpenRouter response model=%s id=%s", model_id, response.id
+                )
+                return response
+            except APIStatusError as e:
+                last_exc = e
+                code = e.status_code
+                if code == 429:
+                    if attempts_429 >= self.max_retries_429:
+                        raise OpenRouterRateLimitError(
+                            f"OpenRouter rate limited after {attempts_429} retries: {e.message}"
+                        ) from e
+                    attempts_429 += 1
+                    self._sleep_backoff(attempt)
+                    attempt += 1
+                    continue
+                if code == 400:
+                    self.logger.warning(
+                        "OpenRouter HTTP 400 (will retry with rotated key/model if allowed): %s body=%s",
+                        e.message,
+                        e.body,
+                    )
+                    if attempts_400 >= self.max_retries_400:
+                        raise OpenRouterBadRequestError(
+                            f"OpenRouter bad request after {attempts_400} retries: {e.message}"
+                        ) from e
+                    attempts_400 += 1
+                    attempt += 1
+                    time.sleep(random.uniform(0.2, 0.8))
+                    continue
+                raise
+            except Exception:
+                self.logger.exception("Unexpected error calling OpenRouter")
+                raise
+
+    def query(
+        self, query: str, num_responses: int = 1
+    ) -> Union[List[ChatCompletion], ChatCompletion]:
+        if self.cache and query in self.response_cache:
+            return self.response_cache[query]
+
+        messages = [{"role": "user", "content": query}]
+        model_ov = self._request_overrides.get("model")
+        model_override = str(model_ov) if model_ov else None
+
+        if num_responses == 1:
+            response = self.chat(messages, 1, model_override=model_override)
+        else:
+            response = []
+            next_try = num_responses
+            total_num_attempts = num_responses
+            remaining = num_responses
+            while remaining > 0 and total_num_attempts > 0:
+                try:
+                    assert next_try > 0
+                    res = self.chat(
+                        messages, next_try, model_override=model_override
+                    )
+                    response.append(res)
+                    remaining -= next_try
+                    next_try = min(remaining, next_try)
+                except Exception as e:
+                    next_try = max(1, (next_try + 1) // 2)
+                    self.logger.warning(
+                        "Error in OpenRouter query: %s, retrying with n=%s",
+                        e,
+                        next_try,
+                    )
+                    time.sleep(random.uniform(0.5, 2.0))
+                    total_num_attempts -= 1
+
+        if self.cache:
+            self.response_cache[query] = response
+        return response
+
+    def get_response_texts(
+        self, query_response: Union[List[ChatCompletion], ChatCompletion]
+    ) -> List[str]:
+        if not isinstance(query_response, list):
+            query_response = [query_response]
+        texts: List[str] = []
+        for response in query_response:
+            for choice in response.choices:
+                c = choice.message.content
+                texts.append(c if c is not None else "")
+        return texts
diff --git a/pyproject.toml b/pyproject.toml
index ecbf97c..827ad7b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -22,6 +22,7 @@ classifiers = [
 dependencies = [
   "backoff>=2.2.1,<3.0.0",
   "openai>=1.0.0,<2.0.0",
+  "pyyaml>=6.0.1,<7.0.0",
   "matplotlib>=3.7.1,<4.0.0",
   "numpy>=1.24.3,<2.0.0",
   "pandas>=2.0.3,<3.0.0",
@@ -33,7 +34,14 @@ dependencies = [
   "scipy>=1.10.1,<2.0.0",
 ]
 
+[project.optional-dependencies]
+api = [
+  "fastapi>=0.109.0,<1.0.0",
+  "uvicorn[standard]>=0.27.0,<1.0.0",
+]
+
 [project.urls]
 Homepage = "https://github.com/spcl/graph-of-thoughts"
 
 [project.scripts]
+got-openrouter-api = "graph_of_thoughts.api.app:run"