diff --git a/Makefile b/Makefile
index cb854c2..2782a03 100644
--- a/Makefile
+++ b/Makefile
@@ -76,7 +76,7 @@ api-diff: ## Compare API snapshots
 	$(BIN)/proxmox-api-contract diff $(ARGS)
 
 seed: ## Seed simulation data
-	@echo "Database seed is scheduled for milestone D2" >&2; exit 2
+	$(BIN)/python -m app.simulation.seed_cli
 
 clean: ## Remove generated local artifacts
 	rm -rf $(VENV) .coverage coverage.xml htmlcov .mypy_cache .pytest_cache .ruff_cache
diff --git a/README.md b/README.md
index 7349905..2d93694 100644
--- a/README.md
+++ b/README.md
@@ -25,11 +25,14 @@ make docker-up
 curl http://localhost:8006/health/live
 curl http://localhost:8006/health/ready
 make db-migrate
+make seed
 ```
 
 Database migrations are ordered SQL files applied transactionally and recorded
 with SHA-256 checksums. Re-running `make db-migrate` is safe; changing an already
 applied migration is rejected instead of silently drifting the schema.
+The initial `small` seed is deterministic and idempotent: it creates two nodes,
+one stopped QEMU guest, and local storage with stable UUIDv5 identifiers.
 
 Contract artifacts can be validated and imported into immutable local revisions:
 
diff --git a/app/simulation/__init__.py b/app/simulation/__init__.py
new file mode 100644
index 0000000..8026428
--- /dev/null
+++ b/app/simulation/__init__.py
@@ -0,0 +1 @@
+"""Persistent deterministic simulation services."""
diff --git a/app/simulation/seed.py b/app/simulation/seed.py
new file mode 100644
index 0000000..991505a
--- /dev/null
+++ b/app/simulation/seed.py
@@ -0,0 +1,101 @@
+"""Deterministic idempotent simulation seed profiles."""
+
+from __future__ import annotations
+
+import json
+import uuid
+from dataclasses import dataclass
+
+import asyncpg  # type: ignore[import-untyped]
+from asyncpg import Connection
+
+NAMESPACE = uuid.UUID("c9040a72-b391-4a7e-9864-3ae46291a531")
+
+
+@dataclass(frozen=True, slots=True)
+class SeedNode:
+    id: uuid.UUID
+    name: str
+    status: str
+
+
+@dataclass(frozen=True, slots=True)
+class SeedResource:
+    id: uuid.UUID
+    node_id: uuid.UUID
+    kind: str
+    external_id: str
+    state: dict[str, object]
+
+
+@dataclass(frozen=True, slots=True)
+class SeedProfile:
+    name: str
+    nodes: tuple[SeedNode, ...]
+    resources: tuple[SeedResource, ...]
+
+    def logical_state(self) -> dict[str, object]:
+        nodes = [{"name": node.name, "status": node.status} for node in self.nodes]
+        resources = [
+            {
+                "kind": resource.kind,
+                "external_id": resource.external_id,
+                "node": next(node.name for node in self.nodes if node.id == resource.node_id),
+                "state": resource.state,
+            }
+            for resource in self.resources
+        ]
+        return {"profile": self.name, "nodes": nodes, "resources": resources}
+
+
+def stable_id(name: str) -> uuid.UUID:
+    return uuid.uuid5(NAMESPACE, name)
+
+
+def small_profile() -> SeedProfile:
+    first = SeedNode(stable_id("node:pve1"), "pve1", "online")
+    second = SeedNode(stable_id("node:pve2"), "pve2", "online")
+    resources = (
+        SeedResource(
+            stable_id("qemu:100"), first.id, "qemu", "100", {"name": "demo", "status": "stopped"}
+        ),
+        SeedResource(
+            stable_id("storage:local"), first.id, "storage", "local", {"content": ["iso", "backup"]}
+        ),
+    )
+    return SeedProfile("small", (first, second), resources)
+
+
+async def apply_seed(connection: Connection, profile: SeedProfile) -> None:
+    async with connection.transaction():
+        await connection.executemany(
+            """INSERT INTO nodes(id, name, status) VALUES($1, $2, $3)
+            ON CONFLICT (id) DO UPDATE SET name=EXCLUDED.name, status=EXCLUDED.status""",
+            [(node.id, node.name, node.status) for node in profile.nodes],
+        )
+        await connection.executemany(
+            """INSERT INTO resources(id, node_id, kind, external_id, state)
+            VALUES($1, $2, $3, $4, $5::jsonb)
+            ON CONFLICT (id) DO UPDATE SET node_id=EXCLUDED.node_id,
+            kind=EXCLUDED.kind, external_id=EXCLUDED.external_id, state=EXCLUDED.state""",
+            [
+                (
+                    resource.id,
+                    resource.node_id,
+                    resource.kind,
+                    resource.external_id,
+                    json.dumps(resource.state, sort_keys=True),
+                )
+                for resource in profile.resources
+            ],
+        )
+
+
+async def seed_url(database_url: str) -> dict[str, object]:
+    connection = await asyncpg.connect(database_url)
+    try:
+        profile = small_profile()
+        await apply_seed(connection, profile)
+        return profile.logical_state()
+    finally:
+        await connection.close()
diff --git a/app/simulation/seed_cli.py b/app/simulation/seed_cli.py
new file mode 100644
index 0000000..b85797c
--- /dev/null
+++ b/app/simulation/seed_cli.py
@@ -0,0 +1,16 @@
+"""Apply a deterministic simulation seed."""
+
+import asyncio
+import json
+
+from app.config import get_settings
+from app.simulation.seed import seed_url
+
+
+async def run() -> None:
+    state = await seed_url(get_settings().database_url.get_secret_value())
+    print(json.dumps(state, sort_keys=True))
+
+
+if __name__ == "__main__":
+    asyncio.run(run())
diff --git a/tests/integration/test_migrations.py b/tests/integration/test_migrations.py
index 02aaffd..7e1f472 100644
--- a/tests/integration/test_migrations.py
+++ b/tests/integration/test_migrations.py
@@ -7,6 +7,7 @@ import asyncpg  # type: ignore[import-untyped]
 import pytest
 
 from app.db.migrations import migrate
+from app.simulation.seed import apply_seed, small_profile
 
 pytestmark = [
     pytest.mark.integration,
@@ -34,3 +35,23 @@ async def test_migration_is_repeatable_and_constraints_hold() -> None:
                 )
     finally:
         await connection.close()
+
+
+async def test_small_seed_is_idempotent() -> None:
+    connection = await asyncpg.connect(os.environ["TEST_DATABASE_URL"])
+    try:
+        await migrate(connection)
+        await apply_seed(connection, small_profile())
+        await apply_seed(connection, small_profile())
+        assert (
+            await connection.fetchval("SELECT count(*) FROM nodes WHERE name IN ('pve1', 'pve2')")
+            == 2
+        )
+        assert (
+            await connection.fetchval(
+                "SELECT count(*) FROM resources WHERE external_id IN ('100', 'local')"
+            )
+            == 2
+        )
+    finally:
+        await connection.close()
diff --git a/tests/unit/test_seed.py b/tests/unit/test_seed.py
new file mode 100644
index 0000000..055018f
--- /dev/null
+++ b/tests/unit/test_seed.py
@@ -0,0 +1,36 @@
+"""Deterministic seed profile tests."""
+
+from app.simulation.seed import small_profile, stable_id
+
+
+def test_small_profile_has_stable_logical_state() -> None:
+    first = small_profile()
+    second = small_profile()
+
+    assert first == second
+    assert first.logical_state() == {
+        "profile": "small",
+        "nodes": [
+            {"name": "pve1", "status": "online"},
+            {"name": "pve2", "status": "online"},
+        ],
+        "resources": [
+            {
+                "kind": "qemu",
+                "external_id": "100",
+                "node": "pve1",
+                "state": {"name": "demo", "status": "stopped"},
+            },
+            {
+                "kind": "storage",
+                "external_id": "local",
+                "node": "pve1",
+                "state": {"content": ["iso", "backup"]},
+            },
+        ],
+    }
+
+
+def test_stable_ids_are_namespaced_and_repeatable() -> None:
+    assert stable_id("qemu:100") == stable_id("qemu:100")
+    assert stable_id("qemu:100") != stable_id("qemu:101")