diff --git a/src/commander_ai_lab/deck_builder/main.py b/src/commander_ai_lab/deck_builder/main.py
index d32cc32..0a23758 100644
--- a/src/commander_ai_lab/deck_builder/main.py
+++ b/src/commander_ai_lab/deck_builder/main.py
@@ -1 +1,139 @@
-# CLI / FastAPI entrypoint — Phase 9
+"""
+FastAPI + CLI entrypoint for the Commander AI Deck Builder.
+
+Run with:
+    uvicorn commander_ai_lab.deck_builder.main:app --reload
+
+Or via CLI:
+    python -m commander_ai_lab.deck_builder.main --commander "Atraxa, Praetors' Voice"
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import logging
+import sys
+
+from fastapi import FastAPI, HTTPException
+from fastapi.middleware.cors import CORSMiddleware
+
+from .core.models import BuildRequest, BuildResult
+from .pipeline.build_deck import build_deck
+
+# ---------------------------------------------------------------------------
+# Logging
+# ---------------------------------------------------------------------------
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
+)
+logger = logging.getLogger(__name__)
+
+# ---------------------------------------------------------------------------
+# FastAPI app
+# ---------------------------------------------------------------------------
+app = FastAPI(
+    title="Commander AI Deck Builder",
+    version="0.1.0",
+    description="Generate optimised 99-card Commander decks using local Ollama AI.",
+)
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+@app.get("/health")
+async def health():
+    """Liveness probe."""
+    return {"status": "ok"}
+
+
+@app.post("/build", response_model=BuildResult)
+async def api_build_deck(request: BuildRequest):
+    """Build a Commander deck from the given request."""
+    try:
+        result = build_deck(request)
+        return result
+    except ValueError as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
+    except Exception as exc:
+        logger.exception("Unhandled error during deck build")
+        raise HTTPException(status_code=500, detail=str(exc)) from exc
+
+
+# ---------------------------------------------------------------------------
+# CLI
+# ---------------------------------------------------------------------------
+def cli() -> None:
+    """Minimal CLI wrapper around build_deck."""
+    parser = argparse.ArgumentParser(description="Commander AI Deck Builder CLI")
+    parser.add_argument("--commander", required=True, help="Commander card name")
+    parser.add_argument(
+        "--collection",
+        default=None,
+        help="Path to collection CSV (optional)",
+    )
+    parser.add_argument(
+        "--collection-only",
+        action="store_true",
+        default=False,
+        help="Only use cards from collection",
+    )
+    parser.add_argument(
+        "--model",
+        default="gpt-oss:20b",
+        help="Ollama model name (default: gpt-oss:20b)",
+    )
+    parser.add_argument(
+        "--output",
+        default=None,
+        help="Output JSON file path (default: stdout)",
+    )
+    args = parser.parse_args()
+
+    # Load collection if provided
+    collection_names: list[str] | None = None
+    if args.collection:
+        import csv
+        from pathlib import Path
+
+        path = Path(args.collection)
+        if not path.exists():
+            print(f"Error: collection file not found: {path}", file=sys.stderr)
+            sys.exit(1)
+        with open(path, newline="", encoding="utf-8") as fh:
+            reader = csv.DictReader(fh)
+            name_col = "Name" if "Name" in (reader.fieldnames or []) else "name"
+            collection_names = [row[name_col] for row in reader if row.get(name_col)]
+
+    request = BuildRequest(
+        commander_name=args.commander,
+        collection_names=collection_names,
+        collection_only=args.collection_only,
+    )
+
+    logger.info("Building deck for %s …", args.commander)
+    result = build_deck(request)
+
+    output = result.model_dump_json(indent=2)
+    if args.output:
+        from pathlib import Path as P
+
+        P(args.output).write_text(output, encoding="utf-8")
+        logger.info("Deck written to %s", args.output)
+    else:
+        print(output)
+
+    if result.warnings:
+        for w in result.warnings:
+            logger.warning("⚠  %s", w)
+
+
+if __name__ == "__main__":
+    cli()