diff --git a/src/multi_swarm/genome/mutation.py b/src/multi_swarm/genome/mutation.py
new file mode 100644
index 0000000..4699f94
--- /dev/null
+++ b/src/multi_swarm/genome/mutation.py
@@ -0,0 +1,77 @@
+from __future__ import annotations
+
+import random
+from typing import Any
+
+from .hypothesis import HypothesisAgentGenome
+
+FEATURE_POOL: tuple[str, ...] = ("open", "high", "low", "close", "volume")
+
+COGNITIVE_STYLES: tuple[str, ...] = (
+    "physicist",
+    "biologist",
+    "historian",
+    "meteorologist",
+    "ecologist",
+    "engineer",
+)
+
+
+def _clone_with(g: HypothesisAgentGenome, **overrides: Any) -> HypothesisAgentGenome:
+    payload: dict[str, Any] = g.to_dict()
+    payload.update(overrides)
+    payload.pop("id", None)
+    payload["parent_ids"] = [*g.parent_ids, g.id]
+    payload["generation"] = g.generation + 1
+    return HypothesisAgentGenome.from_dict(payload)
+
+
+def mutate_temperature(g: HypothesisAgentGenome, rng: random.Random) -> HypothesisAgentGenome:
+    delta = rng.choice([-0.1, 0.1])
+    new_t = max(0.6, min(1.3, g.temperature + delta))
+    return _clone_with(g, temperature=round(new_t, 4))
+
+
+def mutate_lookback(g: HypothesisAgentGenome, rng: random.Random) -> HypothesisAgentGenome:
+    delta = rng.choice([-50, 50])
+    new_lb = max(50, min(500, g.lookback_window + delta))
+    return _clone_with(g, lookback_window=new_lb)
+
+
+def mutate_feature_access(g: HypothesisAgentGenome, rng: random.Random) -> HypothesisAgentGenome:
+    current = set(g.feature_access)
+    if len(current) == len(FEATURE_POOL):
+        op = "remove"
+    elif len(current) <= 1:
+        op = "add"
+    else:
+        op = rng.choice(["add", "remove"])
+
+    if op == "add":
+        candidates = [f for f in FEATURE_POOL if f not in current]
+        choice = rng.choice(candidates)
+        new_set = current | {choice}
+    else:
+        choice = rng.choice(sorted(current))
+        new_set = current - {choice}
+
+    return _clone_with(g, feature_access=sorted(new_set))
+
+
+def mutate_cognitive_style(g: HypothesisAgentGenome, rng: random.Random) -> HypothesisAgentGenome:
+    candidates = [s for s in COGNITIVE_STYLES if s != g.cognitive_style]
+    new_style = rng.choice(candidates)
+    return _clone_with(g, cognitive_style=new_style)
+
+
+MUTATION_OPS = (
+    mutate_temperature,
+    mutate_lookback,
+    mutate_feature_access,
+    mutate_cognitive_style,
+)
+
+
+def random_mutate(g: HypothesisAgentGenome, rng: random.Random) -> HypothesisAgentGenome:
+    op = rng.choice(MUTATION_OPS)
+    return op(g, rng)
diff --git a/tests/unit/test_genome_mutation.py b/tests/unit/test_genome_mutation.py
new file mode 100644
index 0000000..41e5159
--- /dev/null
+++ b/tests/unit/test_genome_mutation.py
@@ -0,0 +1,61 @@
+import random
+
+import pytest
+
+from multi_swarm.genome.hypothesis import HypothesisAgentGenome, ModelTier
+from multi_swarm.genome.mutation import (
+    COGNITIVE_STYLES,
+    FEATURE_POOL,
+    mutate_cognitive_style,
+    mutate_feature_access,
+    mutate_lookback,
+    mutate_temperature,
+)
+
+
+@pytest.fixture
+def base_genome() -> HypothesisAgentGenome:
+    return HypothesisAgentGenome(
+        system_prompt="x",
+        feature_access=["close"],
+        temperature=0.9,
+        top_p=0.95,
+        model_tier=ModelTier.C,
+        lookback_window=200,
+        cognitive_style="physicist",
+    )
+
+
+def test_mutate_temperature_within_bounds(base_genome: HypothesisAgentGenome) -> None:
+    rng = random.Random(0)
+    for _ in range(50):
+        new = mutate_temperature(base_genome, rng)
+        assert 0.6 <= new.temperature <= 1.3
+
+
+def test_mutate_lookback_within_bounds(base_genome: HypothesisAgentGenome) -> None:
+    rng = random.Random(0)
+    for _ in range(50):
+        new = mutate_lookback(base_genome, rng)
+        assert 50 <= new.lookback_window <= 500
+
+
+def test_mutate_feature_access_changes_set(base_genome: HypothesisAgentGenome) -> None:
+    rng = random.Random(0)
+    new = mutate_feature_access(base_genome, rng)
+    assert set(new.feature_access) != set(base_genome.feature_access) or len(FEATURE_POOL) == 1
+    assert all(f in FEATURE_POOL for f in new.feature_access)
+    assert len(new.feature_access) >= 1
+
+
+def test_mutate_cognitive_style_uses_pool(base_genome: HypothesisAgentGenome) -> None:
+    rng = random.Random(0)
+    new = mutate_cognitive_style(base_genome, rng)
+    assert new.cognitive_style in COGNITIVE_STYLES
+
+
+def test_mutation_preserves_lineage(base_genome: HypothesisAgentGenome) -> None:
+    rng = random.Random(0)
+    new = mutate_temperature(base_genome, rng)
+    assert base_genome.id in new.parent_ids
+    assert new.id != base_genome.id