diff --git a/pyproject.toml b/pyproject.toml
index dcb945b..c5e34da 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,6 +4,7 @@ version = "0.1.0"
 description = "Open Memory Benchmark"
 requires-python = ">=3.11"
 dependencies = [
+    "anthropic>=0.84.0",
     "datasets>=2.0",
     "typer>=0.12",
     "rich>=13",
diff --git a/src/memory_bench/cli.py b/src/memory_bench/cli.py
index c3ea8e4..506ffe2 100644
--- a/src/memory_bench/cli.py
+++ b/src/memory_bench/cli.py
@@ -12,7 +12,7 @@
 load_dotenv(dotenv_path=Path(__file__).parents[2] / ".env", override=True)
 
 from .dataset import REGISTRY as DATASET_REGISTRY, get_dataset
-from .llm import REGISTRY as LLM_REGISTRY, get_llm, get_answer_llm
+from .llm import REGISTRY as LLM_REGISTRY, get_answer_llm
 from .memory import REGISTRY as MEMORY_REGISTRY, get_memory_provider
 from .modes import REGISTRY as MODE_REGISTRY, get_mode
 from .runner import EvalRunner
@@ -22,12 +22,63 @@
 console = Console()
 
 
-def _resolve_gemini_key() -> None:
-    key = os.environ.get("GEMINI_API_KEY") or os.environ.get("GOOGLE_API_KEY")
-    if not key:
-        typer.echo("Error: GEMINI_API_KEY environment variable is not set.", err=True)
+def _ensure_provider_env(provider: str, role: str) -> None:
+    if provider not in LLM_REGISTRY:
+        typer.echo(
+            f"Error: unknown {role.lower()} LLM provider '{provider}'. Available: {', '.join(LLM_REGISTRY)}.",
+            err=True,
+        )
         raise typer.Exit(1)
-    os.environ["GOOGLE_API_KEY"] = key
+
+    if provider == "anthropic":
+        if not os.environ.get("ANTHROPIC_API_KEY"):
+            typer.echo(f"Error: {role} LLM provider '{provider}' requires ANTHROPIC_API_KEY.", err=True)
+            raise typer.Exit(1)
+        return
+
+    if provider == "gemini":
+        key = os.environ.get("GEMINI_API_KEY") or os.environ.get("GOOGLE_API_KEY")
+        if not key:
+            typer.echo(f"Error: {role} LLM provider '{provider}' requires GEMINI_API_KEY.", err=True)
+            raise typer.Exit(1)
+        os.environ["GOOGLE_API_KEY"] = key
+        return
+
+    if provider == "groq":
+        if not os.environ.get("GROQ_API_KEY"):
+            typer.echo(f"Error: {role} LLM provider '{provider}' requires GROQ_API_KEY.", err=True)
+            raise typer.Exit(1)
+        return
+
+    if provider == "openai":
+        if not os.environ.get("OPENAI_API_KEY"):
+            typer.echo(f"Error: {role} LLM provider '{provider}' requires OPENAI_API_KEY.", err=True)
+            raise typer.Exit(1)
+        return
+
+
+def _validate_run_env(memory: str, mode: str, answer_provider: str | None = None) -> None:
+    if answer_provider is not None:
+        os.environ["OMB_ANSWER_LLM"] = answer_provider
+
+    answer_provider = os.environ.get("OMB_ANSWER_LLM", "groq")
+    judge_provider = os.environ.get("OMB_JUDGE_LLM", "gemini")
+    _ensure_provider_env(answer_provider, "Answer")
+    _ensure_provider_env(judge_provider, "Judge")
+
+    if mode == "agentic-rag" and answer_provider != "gemini":
+        typer.echo(
+            f"Error: response mode 'agentic-rag' requires a tool-capable LLM provider; '{answer_provider}' is not supported.",
+            err=True,
+        )
+        raise typer.Exit(1)
+
+    if memory == "hindsight":
+        key = os.environ.get("GEMINI_API_KEY") or os.environ.get("GOOGLE_API_KEY")
+        if not key:
+            typer.echo("Error: memory provider 'hindsight' requires GEMINI_API_KEY for embedded extraction.", err=True)
+            raise typer.Exit(1)
+        os.environ["GOOGLE_API_KEY"] = key
 
 
 @app.command()
@@ -36,7 +87,7 @@ def run(
     dataset: str = typer.Option("tempo", "--dataset", help=f"Dataset. Available: {', '.join(DATASET_REGISTRY)}"),
     memory: str = typer.Option("bm25", "--memory", "-m", help=f"Memory provider. Available: {', '.join(MEMORY_REGISTRY)}"),
     mode: str = typer.Option("rag", "--mode", help=f"Response mode. Available: {', '.join(MODE_REGISTRY)}"),
-    llm: str = typer.Option("gemini", "--llm", help=f"LLM for answer generation. Available: {', '.join(LLM_REGISTRY)}"),
+    llm: str | None = typer.Option(None, "--llm", help=f"LLM provider for answer generation. Overrides OMB_ANSWER_LLM. Available: {', '.join(LLM_REGISTRY)}"),
     category: str = typer.Option(None, "--category", "-c", help="Category filter(s), comma-separated (e.g. 'a,b,c'). With --query-limit, runs N queries per category."),
     query_limit: int = typer.Option(None, "--query-limit", "-q", help="Max queries to evaluate. When combined with multiple --category values, applies per category."),
     query_id: str = typer.Option(None, "--query-id", help="Run a single specific query by ID"),
@@ -53,7 +104,7 @@ def run(
     description: str = typer.Option(None, "--description", "-d", help="Optional description for this run (stored in the result JSON)"),
 ) -> None:
     """Run an evaluation on a single split (optionally filtered to a category)."""
-    _resolve_gemini_key()
+    _validate_run_env(memory, mode, llm)
 
     ds = get_dataset(dataset)
 
diff --git a/src/memory_bench/llm/__init__.py b/src/memory_bench/llm/__init__.py
index 99be8ec..49b2134 100644
--- a/src/memory_bench/llm/__init__.py
+++ b/src/memory_bench/llm/__init__.py
@@ -1,11 +1,13 @@
 import os
 
+from .anthropic import AnthropicLLM
 from .base import LLM, Schema
 from .gemini import GeminiLLM
 from .groq import GroqLLM
 from .openai import OpenAILLM
 
 REGISTRY: dict[str, type[LLM]] = {
+    "anthropic": AnthropicLLM,
     "gemini": GeminiLLM,
     "groq": GroqLLM,
     "openai": OpenAILLM,
diff --git a/src/memory_bench/llm/anthropic.py b/src/memory_bench/llm/anthropic.py
new file mode 100644
index 0000000..b5228a1
--- /dev/null
+++ b/src/memory_bench/llm/anthropic.py
@@ -0,0 +1,183 @@
+import json
+import os
+import re
+import time
+
+from .base import LLM, Schema
+
+_MAX_RETRIES = 6
+_RETRY_BASE_DELAY = 5
+
+
+class _StructuredOutputError(ValueError):
+    """Raised when the model response does not match the requested schema."""
+
+
+def _parse_json_payload(text: str) -> dict:
+    text = text.strip()
+
+    try:
+        payload = json.loads(text)
+    except json.JSONDecodeError:
+        pass
+    else:
+        if not isinstance(payload, dict):
+            raise _StructuredOutputError("Model response must be a JSON object")
+        return payload
+
+    fenced = re.search(r"```(?:json)?\s*(\{.*\})\s*```", text, flags=re.DOTALL | re.IGNORECASE)
+    if fenced:
+        payload = json.loads(fenced.group(1))
+        if not isinstance(payload, dict):
+            raise _StructuredOutputError("Model response must be a JSON object")
+        return payload
+
+    start = text.find("{")
+    end = text.rfind("}")
+    if start != -1 and end != -1 and end > start:
+        payload = json.loads(text[start : end + 1])
+        if not isinstance(payload, dict):
+            raise _StructuredOutputError("Model response must be a JSON object")
+        return payload
+
+    raise json.JSONDecodeError("Could not find JSON object in model response", text, 0)
+
+
+def _coerce_text_payload(text: str, schema: Schema) -> dict | None:
+    text = text.strip()
+    if not text:
+        return None
+    if len(schema.required) != 1:
+        return None
+
+    field = schema.required[0]
+    spec = schema.properties.get(field, {})
+    field_type = spec.get("type", "string")
+
+    if field_type == "string":
+        return {field: text}
+
+    if field_type == "boolean":
+        lowered = text.lower()
+        if lowered == "true":
+            return {field: True}
+        if lowered == "false":
+            return {field: False}
+
+    return None
+
+
+def _validate_schema_payload(payload: dict, schema: Schema) -> dict:
+    extra = sorted(set(payload) - set(schema.properties))
+    if extra:
+        raise _StructuredOutputError(f"Model response included unsupported field(s): {', '.join(extra)}")
+
+    missing = [field for field in schema.required if field not in payload]
+    if missing:
+        raise _StructuredOutputError(f"Model response omitted required field(s): {', '.join(missing)}")
+
+    for field, value in payload.items():
+        spec = schema.properties.get(field, {})
+        expected_type = spec.get("type", "string")
+        if expected_type == "string":
+            valid = isinstance(value, str)
+        elif expected_type == "boolean":
+            valid = isinstance(value, bool)
+        elif expected_type == "integer":
+            valid = isinstance(value, int) and not isinstance(value, bool)
+        elif expected_type == "number":
+            valid = isinstance(value, (int, float)) and not isinstance(value, bool)
+        elif expected_type == "array":
+            valid = isinstance(value, list)
+        elif expected_type == "object":
+            valid = isinstance(value, dict)
+        else:
+            valid = True
+
+        if not valid:
+            raise _StructuredOutputError(
+                f"Model response field '{field}' must be {expected_type}, got {type(value).__name__}"
+            )
+
+    return payload
+
+
+class AnthropicLLM(LLM):
+    def __init__(self, model: str | None = None):
+        from anthropic import Anthropic
+
+        api_key = os.environ.get("ANTHROPIC_API_KEY")
+        if not api_key:
+            raise RuntimeError("Anthropic provider requires ANTHROPIC_API_KEY")
+
+        base_url = os.environ.get("ANTHROPIC_BASE_URL")
+        self._client = Anthropic(
+            api_key=api_key,
+            base_url=base_url or None,
+            max_retries=0,
+        )
+        self._model = (
+            model
+            or os.environ.get("ANTHROPIC_MODEL")
+            or "claude-sonnet-4-5"
+        )
+
+    @property
+    def model_id(self) -> str:
+        return f"anthropic:{self._model}"
+
+    def generate(self, prompt: str, schema: Schema) -> dict:
+        from anthropic import APIConnectionError, APIStatusError, RateLimitError
+
+        schema_json = {
+            "type": "object",
+            "properties": schema.properties,
+            "required": schema.required,
+            "additionalProperties": False,
+        }
+        system_prompt = (
+            "Return only a valid JSON object matching this schema. "
+            "Do not wrap JSON in markdown fences.\n\n"
+            f"{json.dumps(schema_json, ensure_ascii=False)}"
+        )
+
+        delay = _RETRY_BASE_DELAY
+        last_exc = None
+
+        for attempt in range(_MAX_RETRIES):
+            try:
+                response = self._client.messages.create(
+                    model=self._model,
+                    max_tokens=4096,
+                    temperature=0.0,
+                    system=system_prompt,
+                    messages=[{"role": "user", "content": prompt}],
+                )
+                text = "".join(block.text for block in response.content if getattr(block, "type", None) == "text")
+                try:
+                    payload = _parse_json_payload(text)
+                except json.JSONDecodeError:
+                    coerced = _coerce_text_payload(text, schema)
+                    if coerced is None:
+                        raise _StructuredOutputError("Model response was not valid JSON") from None
+                    payload = coerced
+                return _validate_schema_payload(payload, schema)
+            except (RateLimitError, APIConnectionError) as e:
+                last_exc = e
+            except APIStatusError as e:
+                last_exc = e
+                if e.status_code not in (429, 500, 502, 503, 504):
+                    raise
+            except _StructuredOutputError as e:
+                last_exc = e
+            except Exception as e:
+                last_exc = e
+                msg = str(e)
+                if "429" not in msg and "rate" not in msg.lower():
+                    raise
+
+            if attempt < _MAX_RETRIES - 1:
+                time.sleep(delay)
+                delay *= 2
+
+        raise RuntimeError(f"Anthropic request failed after {_MAX_RETRIES} retries: {last_exc}")
diff --git a/src/memory_bench/modes/agentic_rag.py b/src/memory_bench/modes/agentic_rag.py
index 3eaf508..4b94af2 100644
--- a/src/memory_bench/modes/agentic_rag.py
+++ b/src/memory_bench/modes/agentic_rag.py
@@ -4,7 +4,7 @@
 from .base import ResponseMode
 from .rag import RAGMode, _OPEN_SCHEMA, _MCQ_SCHEMA
 from ..dataset.base import _DEFAULT_OPEN_PROMPT as _OPEN_PROMPT, _DEFAULT_MCQ_PROMPT as _MCQ_PROMPT
-from ..llm.base import ToolDef
+from ..llm.base import LLM, ToolDef
 from ..llm.gemini import GeminiLLM
 from ..memory.base import MemoryProvider
 from ..models import AnswerResult
@@ -23,8 +23,10 @@ class AgenticRAGMode(ResponseMode):
     name = "agentic-rag"
     description = "The LLM acts as an agent with a recall tool and can make multiple retrieval calls with different queries before finalising its answer."
 
-    def __init__(self, llm: GeminiLLM | None = None, k: int = 10):
+    def __init__(self, llm: LLM | None = None, k: int = 10):
         self._llm = llm or GeminiLLM()
+        if type(self._llm).tool_loop is LLM.tool_loop:
+            raise ValueError(f"{self._llm.model_id} does not support agentic-rag tool calling")
         self._rag = RAGMode(llm=self._llm, k=k)
         self.k = k
 
diff --git a/uv.lock b/uv.lock
index bab77d3..d87b8fc 100644
--- a/uv.lock
+++ b/uv.lock
@@ -3634,6 +3634,7 @@ name = "omb"
 version = "0.1.0"
 source = { editable = "." }
 dependencies = [
+    { name = "anthropic" },
     { name = "cognee" },
     { name = "datasets" },
     { name = "fastapi", extra = ["standard"] },
@@ -3646,6 +3647,7 @@ dependencies = [
     { name = "qdrant-client" },
     { name = "rank-bm25" },
     { name = "rich" },
+    { name = "scipy" },
     { name = "sentence-transformers" },
     { name = "supermemory" },
     { name = "tiktoken" },
@@ -3655,6 +3657,7 @@ dependencies = [
 
 [package.metadata]
 requires-dist = [
+    { name = "anthropic", specifier = ">=0.84.0" },
     { name = "cognee", specifier = ">=0.5.4" },
     { name = "datasets", specifier = ">=2.0" },
     { name = "fastapi", extras = ["standard"], specifier = ">=0.135.1" },
@@ -3667,6 +3670,7 @@ requires-dist = [
     { name = "qdrant-client", specifier = ">=1.13" },
     { name = "rank-bm25", specifier = ">=0.2" },
     { name = "rich", specifier = ">=13" },
+    { name = "scipy", specifier = ">=1.11" },
     { name = "sentence-transformers", specifier = ">=3.0" },
     { name = "supermemory", specifier = ">=0.1" },
     { name = "tiktoken", specifier = ">=0.12.0" },