diff --git a/core/src/agentforge_core/domain/agent.py b/core/src/agentforge_core/domain/agent.py
new file mode 100644
index 0000000..3007b99
--- /dev/null
+++ b/core/src/agentforge_core/domain/agent.py
@@ -0,0 +1,43 @@
+"""Modelos de dominio del agente: definición, configuración LLM y metadata de versión."""
+
+from __future__ import annotations
+
+from datetime import datetime
+from typing import Any, Literal
+
+from pydantic import BaseModel, Field
+
+
+class LLMConfig(BaseModel):
+    """Configuración del proveedor LLM utilizado por un agente."""
+
+    provider: Literal["mock", "azure", "openai"] = "mock"
+    model: str = "gpt-4o"
+    temperature: float = Field(default=0.2, ge=0.0, le=2.0)
+    max_tokens: int = Field(default=2000, ge=1, le=128_000)
+
+
+class AgentVersionMeta(BaseModel):
+    """Metadatos de una versión concreta de un agente (estilo commit Git)."""
+
+    id: str
+    hash: str
+    author: str
+    message: str
+    created_at: datetime
+
+
+class AgentDefinition(BaseModel):
+    """Definición declarativa completa de un agente."""
+
+    name: str
+    version: str
+    owner: str
+    purpose: str
+    state: Literal["draft", "active", "deprecated"]
+    guardrails: list[str]
+    llm: LLMConfig
+    system_prompt: str
+    output_schema: dict[str, Any]
+    risk_threshold_for_hitl: int = Field(default=4, ge=1, le=5)
+    updated_at: datetime
diff --git a/tests/unit/test_domain_agent.py b/tests/unit/test_domain_agent.py
new file mode 100644
index 0000000..203a289
--- /dev/null
+++ b/tests/unit/test_domain_agent.py
@@ -0,0 +1,70 @@
+"""Tests unitarios para los modelos de dominio del agente."""
+
+from datetime import UTC, datetime
+
+import pytest
+from pydantic import ValidationError
+
+from agentforge_core.domain.agent import (
+    AgentDefinition,
+    AgentVersionMeta,
+    LLMConfig,
+)
+
+
+def test_llm_config_default_provider_is_mock() -> None:
+    cfg = LLMConfig()
+    assert cfg.provider == "mock"
+    assert cfg.model == "gpt-4o"
+    assert cfg.temperature == 0.2
+
+
+def test_llm_config_rechaza_provider_invalido() -> None:
+    with pytest.raises(ValidationError):
+        LLMConfig(provider="bedrock")  # type: ignore[arg-type]
+
+
+def test_agent_version_meta_serialize() -> None:
+    meta = AgentVersionMeta(
+        id="v1",
+        hash="abc123",
+        author="Juan",
+        message="inicial",
+        created_at=datetime(2026, 5, 9, tzinfo=UTC),
+    )
+    dumped = meta.model_dump(mode="json")
+    assert dumped["id"] == "v1"
+    assert dumped["created_at"].startswith("2026-05-09")
+
+
+def test_agent_definition_minimo_valido() -> None:
+    agent = AgentDefinition(
+        name="incident_analyzer",
+        version="v1",
+        owner="Juan",
+        purpose="Análisis de incidentes",
+        state="active",
+        guardrails=["default"],
+        llm=LLMConfig(),
+        system_prompt="eres un analista...",
+        output_schema={"type": "object"},
+        updated_at=datetime.now(UTC),
+    )
+    assert agent.risk_threshold_for_hitl == 4  # default
+    assert agent.state == "active"
+
+
+def test_agent_definition_rechaza_state_invalido() -> None:
+    with pytest.raises(ValidationError):
+        AgentDefinition(
+            name="x",
+            version="v1",
+            owner="x",
+            purpose="x",
+            state="archived",  # type: ignore[arg-type]
+            guardrails=[],
+            llm=LLMConfig(),
+            system_prompt="x",
+            output_schema={},
+            updated_at=datetime.now(UTC),
+        )