diff --git a/backend/app/entities.py b/backend/app/entities.py
index 3b1722a..3548f11 100644
--- a/backend/app/entities.py
+++ b/backend/app/entities.py
@@ -96,6 +96,23 @@ def parse_mint_response(text: str) -> dict | None:
     return profile
 
 
+def roll_traits(signature: str) -> dict:
+    """Roll the four hidden truth-traits for an entity, seeded from its
+    signature. These are never derived from — or fed into — the LLM persona
+    prompt (see `mint_prompt`, which never sees this function's output):
+    persona text must stay fully decoupled from ground truth, so a
+    convincing "sweet old lady" persona can pair with any alignment roll.
+    A separate `random.Random` namespace (`"traits:"` vs. `normalize_profile`'s
+    `"norm:"`) keeps this roll independent of the cosmetic-defaults rng."""
+    rng = random.Random(f"traits:{signature}")
+    return {
+        "alignment": rng.uniform(0.0, 1.0),
+        "power": rng.uniform(0.0, 1.0),
+        "volatility": rng.uniform(0.0, 1.0),
+        "deceptiveness": rng.uniform(0.0, 1.0),
+    }
+
+
 def normalize_profile(profile: dict, signature: str) -> dict:
     """Coerce an LLM (or fallback) profile into the exact shape the DB and
     frontend expect, filling gaps with signature-deterministic defaults."""
@@ -138,6 +155,7 @@ def normalize_profile(profile: dict, signature: str) -> dict:
         },
         "quotes": [str(q)[:200] for q in quotes[:4] if isinstance(q, str)]
         or rng.sample(_QUOTE_BANK, 2),
+        "traits": roll_traits(signature),
     }
 
 
diff --git a/backend/app/main.py b/backend/app/main.py
index 5f9a429..887f8e1 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -6,6 +6,7 @@ from pathlib import Path
 from fastapi import FastAPI, HTTPException
 from fastapi.responses import FileResponse
 from fastapi.staticfiles import StaticFiles
+from sqlalchemy import text
 
 import app.models  # noqa: F401 — registers models on Base.metadata before create_all
 from app.config import settings
@@ -45,6 +46,12 @@ async def lifespan(app: FastAPI):
     AUDIO_DIR.mkdir(parents=True, exist_ok=True)
     async with engine.begin() as conn:
         await conn.run_sync(Base.metadata.create_all)
+        # No Alembic in this repo — `create_all` never alters existing
+        # tables, so columns added to live models need a manual, idempotent
+        # migration here. Safe to run on every startup.
+        await conn.execute(text(
+            "ALTER TABLE entities ADD COLUMN IF NOT EXISTS traits JSONB NOT NULL DEFAULT '{}'::jsonb"
+        ))
     cleanup_task = asyncio.create_task(_session_cleanup_loop())
     try:
         yield
diff --git a/backend/app/models/entity.py b/backend/app/models/entity.py
index d5d6042..5a18f61 100644
--- a/backend/app/models/entity.py
+++ b/backend/app/models/entity.py
@@ -24,6 +24,7 @@ class Entity(Base):
     signature: Mapped[str] = mapped_column(String(64), unique=True, index=True)
     voice_profile: Mapped[dict] = mapped_column(JSONB, default=dict)
     visual_profile: Mapped[dict] = mapped_column(JSONB, default=dict)
+    traits: Mapped[dict] = mapped_column(JSONB, default=dict)
     sample_quotes: Mapped[list] = mapped_column(JSONB, default=list)
     contact_count: Mapped[int] = mapped_column(Integer, default=0)
     discovered_by: Mapped[uuid.UUID | None] = mapped_column(
diff --git a/backend/tests/test_entities.py b/backend/tests/test_entities.py
index 212e539..78bfcb2 100644
--- a/backend/tests/test_entities.py
+++ b/backend/tests/test_entities.py
@@ -1,9 +1,15 @@
+import inspect
+
 from app.entities import (
     fallback_profile,
     normalize_profile,
     parse_mint_response,
+    roll_traits,
     signature_from_anomalies,
 )
+from app.llm import prompts as llm_prompts
+
+TRAIT_KEYS = ("alignment", "power", "volatility", "deceptiveness")
 
 
 def _anomaly(freq, mag):
@@ -60,3 +66,88 @@ def test_fallback_profile_is_deterministic_and_valid():
     assert one["name"]
     assert one["rarity"] in ("common", "uncommon", "rare", "mythic")
     assert one["quotes"]
+
+
+# --- hidden traits (Workstream A) -------------------------------------
+
+
+def test_roll_traits_values_are_in_range():
+    traits = roll_traits("some-signature-1")
+    assert set(traits.keys()) == set(TRAIT_KEYS)
+    for key in TRAIT_KEYS:
+        assert isinstance(traits[key], float)
+        assert 0.0 <= traits[key] <= 1.0
+
+
+def test_roll_traits_is_deterministic_for_same_signature():
+    one = roll_traits("repeatable-signature")
+    two = roll_traits("repeatable-signature")
+    assert one == two
+
+
+def test_roll_traits_varies_by_signature():
+    values = {tuple(roll_traits(f"sig-{i}").values()) for i in range(20)}
+    # 20 distinct signatures should not collapse onto a single roll.
+    assert len(values) > 1
+
+
+def test_normalize_profile_includes_traits_in_range():
+    profile = normalize_profile({"name": "Hollow Briar"}, "traits-norm-signature")
+    traits = profile["traits"]
+    assert set(traits.keys()) == set(TRAIT_KEYS)
+    for key in TRAIT_KEYS:
+        assert 0.0 <= traits[key] <= 1.0
+
+
+def test_normalize_profile_traits_match_roll_traits_for_signature():
+    signature = "cross-check-signature"
+    profile = normalize_profile({"name": "X"}, signature)
+    assert profile["traits"] == roll_traits(signature)
+
+
+def test_normalize_profile_traits_are_signature_deterministic():
+    one = normalize_profile({"name": "A"}, "det-signature")
+    two = normalize_profile({"name": "B", "rarity": "rare"}, "det-signature")
+    # Same signature -> same traits every call, regardless of the rest of
+    # the (LLM-supplied or fallback) profile passed in.
+    assert one["traits"] == two["traits"]
+
+
+def test_fallback_profile_includes_traits_in_range():
+    profile = fallback_profile("fallback-traits-signature")
+    traits = profile["traits"]
+    assert set(traits.keys()) == set(TRAIT_KEYS)
+    for key in TRAIT_KEYS:
+        assert 0.0 <= traits[key] <= 1.0
+
+
+def test_fallback_profile_traits_are_signature_deterministic():
+    one = fallback_profile("fallback-det-signature")
+    two = fallback_profile("fallback-det-signature")
+    assert one["traits"] == two["traits"]
+
+
+def test_persona_is_independent_of_rolled_traits():
+    """Persona text must stay fully decoupled from hidden truth: pairing the
+    exact same persona string with many different signatures should surface
+    a spread of alignment rolls, not a single value tied to the persona."""
+    fixed_persona = "A sweet old lady who just wants to chat about her garden."
+    alignments = set()
+    for i in range(40):
+        profile = normalize_profile(
+            {"name": "Nana", "persona": fixed_persona}, f"persona-independence-{i}"
+        )
+        assert profile["persona"] == fixed_persona
+        alignments.add(round(profile["traits"]["alignment"], 3))
+    # A meaningful spread (not clustered on one or two values) shows
+    # alignment isn't derived from — or gated by — the persona text.
+    assert len(alignments) > 20
+
+
+def test_mint_prompt_never_receives_traits():
+    """`mint_prompt` builds the LLM system/user prompt; traits must never be
+    one of its inputs, so hidden ground truth can't leak into persona
+    generation."""
+    params = set(inspect.signature(llm_prompts.mint_prompt).parameters)
+    assert "traits" not in params
+    assert params == {"signature", "channel", "anomaly_summary", "voice_ids"}