diff --git a/src/commander_ai_lab/deck_builder/core/models.py b/src/commander_ai_lab/deck_builder/core/models.py
index afea282..f56a19e 100644
--- a/src/commander_ai_lab/deck_builder/core/models.py
+++ b/src/commander_ai_lab/deck_builder/core/models.py
@@ -1 +1,145 @@
-# Pydantic models (CardEntry, CommanderDeck) — Phase 2
+"""
+Pydantic models for the Commander AI Deck Builder.
+
+Defines CardEntry, DeckCategory, CommanderDeck, and BuildRequest
+with full color identity validation and 99-card singleton enforcement.
+"""
+
+from __future__ import annotations
+
+from enum import Enum
+from typing import List, Optional, Set
+
+from pydantic import BaseModel, Field, field_validator, model_validator
+
+
+# ── colour identity ──────────────────────────────────────────────
+class Color(str, Enum):
+    WHITE = "W"
+    BLUE = "U"
+    BLACK = "B"
+    RED = "R"
+    GREEN = "G"
+
+
+WUBRG: Set[str] = {c.value for c in Color}
+
+
+# ── card entry ───────────────────────────────────────────────────
+class CardEntry(BaseModel):
+    """A single card in a deck list."""
+
+    name: str
+    quantity: int = Field(default=1, ge=1)
+    category: str = Field(
+        default="uncategorized",
+        description="ramp | removal | card_draw | lands | synergy | protection | wincon | uncategorized",
+    )
+    color_identity: Set[str] = Field(default_factory=set)
+    mana_cost: Optional[str] = None
+    cmc: float = 0.0
+    type_line: Optional[str] = None
+    scryfall_id: Optional[str] = None
+    edhrec_rank: Optional[int] = None
+    source: Optional[str] = None  # edhrec | scryfall | moxfield | archidekt | reddit | ollama
+
+    @field_validator("color_identity", mode="before")
+    @classmethod
+    def normalize_colors(cls, v):
+        if isinstance(v, str):
+            return {c.upper() for c in v if c.upper() in WUBRG}
+        if isinstance(v, (list, set)):
+            return {c.upper() for c in v if c.upper() in WUBRG}
+        return set()
+
+
+# ── deck category targets ────────────────────────────────────────
+class DeckRatios(BaseModel):
+    """Target card counts per category (must sum to 99)."""
+
+    lands: int = Field(default=36, ge=30, le=42)
+    ramp: int = Field(default=10, ge=6, le=15)
+    card_draw: int = Field(default=10, ge=6, le=15)
+    removal: int = Field(default=8, ge=4, le=14)
+    protection: int = Field(default=5, ge=2, le=10)
+    synergy: int = Field(default=25, ge=15, le=35)
+    wincon: int = Field(default=3, ge=1, le=8)
+    uncategorized: int = Field(default=2, ge=0, le=10)
+
+    @model_validator(mode="after")
+    def check_total(self) -> "DeckRatios":
+        total = (
+            self.lands
+            + self.ramp
+            + self.card_draw
+            + self.removal
+            + self.protection
+            + self.synergy
+            + self.wincon
+            + self.uncategorized
+        )
+        if total != 99:
+            raise ValueError(f"Card type targets must sum to 99, got {total}")
+        return self
+
+
+# ── commander deck ───────────────────────────────────────────────
+class CommanderDeck(BaseModel):
+    """Full 99-card Commander deck plus the commander card."""
+
+    commander: CardEntry
+    companion: Optional[CardEntry] = None
+    cards: List[CardEntry] = Field(default_factory=list)
+    ratios: DeckRatios = Field(default_factory=DeckRatios)
+
+    @model_validator(mode="after")
+    def validate_deck(self) -> "CommanderDeck":
+        # ── singleton check (basic lands exempt) ──
+        basic_lands = {
+            "Plains", "Island", "Swamp", "Mountain", "Forest",
+            "Wastes", "Snow-Covered Plains", "Snow-Covered Island",
+            "Snow-Covered Swamp", "Snow-Covered Mountain", "Snow-Covered Forest",
+        }
+        seen: dict[str, int] = {}
+        for card in self.cards:
+            if card.name not in basic_lands:
+                seen[card.name] = seen.get(card.name, 0) + card.quantity
+                if seen[card.name] > 1:
+                    raise ValueError(f"Singleton violation: '{card.name}' appears {seen[card.name]} times")
+
+        # ── 99-card check ──
+        total = sum(c.quantity for c in self.cards)
+        if total != 99:
+            raise ValueError(f"Deck must contain exactly 99 cards, got {total}")
+
+        # ── color identity check ──
+        commander_ci = self.commander.color_identity
+        for card in self.cards:
+            if card.color_identity and not card.color_identity.issubset(commander_ci):
+                violation = card.color_identity - commander_ci
+                raise ValueError(
+                    f"'{card.name}' has colors {violation} outside commander identity {commander_ci}"
+                )
+        return self
+
+
+# ── build request (API input) ────────────────────────────────────
+class BuildRequest(BaseModel):
+    """Input payload for the deck build pipeline."""
+
+    commander_name: str
+    collection_only: bool = False
+    collection_path: Optional[str] = None  # path to CSV
+    budget_limit: Optional[float] = None
+    ratios: DeckRatios = Field(default_factory=DeckRatios)
+    strategy_notes: Optional[str] = None  # free-text guidance for Ollama
+
+
+# ── build result (API output) ────────────────────────────────────
+class BuildResult(BaseModel):
+    """Output payload from the deck build pipeline."""
+
+    deck: CommanderDeck
+    warnings: List[str] = Field(default_factory=list)
+    sources_consulted: List[str] = Field(default_factory=list)
+    build_time_seconds: float = 0.0