diff --git a/lyra/poker.py b/lyra/poker.py
index bd17040..dddbbcd 100644
--- a/lyra/poker.py
+++ b/lyra/poker.py
@@ -14,7 +14,7 @@ from __future__ import annotations
 
 import json
 import re
-from datetime import datetime, timezone
+from datetime import datetime, timedelta, timezone
 
 import numpy as np
 
@@ -730,6 +730,13 @@ NOT apply to another — e.g. your hole "ace of spades" is a different card from
 whose suit is unstated (that board ace is "Ax", not "As"). Use null/omit for non-card \
 details not stated. Stay faithful to what's described — do not invent action that isn't implied.
 
+STRADDLES: a straddle is a voluntary blind posted before the deal — always record it as a \
+preflop `post` action by the straddler with its amount, and respect the action order it creates. \
+A BUTTON straddle ("btn straddle", "straddle on the button") means the button posts (usually 2x \
+the BB) and acts LAST preflop, with first preflop action starting in the SB. A UTG straddle posts \
+from UTG and action starts to their left (UTG+1), the straddler acting last preflop. Keep the \
+straddler in players[] at their real seat; never drop the straddle.
+
 POSITIONS: resolve relative seat references ("N seats to my right/left") into real positions. \
 Action moves clockwise, so a player to your RIGHT acts before you (toward the blinds/button) \
 and a player to your LEFT acts after you (toward UTG). Going RIGHT from a player you pass, in \
@@ -905,13 +912,36 @@ def store_hand_history(parsed: dict, session_id: int | None = None,
     return int(cur.lastrowid)
 
 
+def _recent_duplicate_hand(parsed: dict, session_id: int | None, window_sec: int = 180) -> int | None:
+    """Id of an identical hand (same session, hole cards, board) recorded in the last few
+    minutes, else None. The chat turn can execute TWICE — the SSE stream and the blocking
+    fallback both run server-side — which would double-log the same hand; a system-of-record
+    must record an event once. `IS` is NULL-safe so a boardless/cardless hand matches too."""
+    p = normalize_structured(parsed)
+    sid = _resolve(session_id) or _review_session_id()
+    hole = " ".join(p.get("hero_cards") or []) or None
+    board = " ".join(p.get("board") or []) or None
+    cutoff = (datetime.now(timezone.utc) - timedelta(seconds=window_sec)).isoformat()
+    row = _c().execute(
+        "SELECT id FROM poker_hands WHERE session_id = ? AND at >= ? "
+        "AND hole_cards IS ? AND board IS ? ORDER BY id DESC LIMIT 1",
+        (sid, cutoff, hole, board),
+    ).fetchone()
+    return int(row["id"]) if row else None
+
+
 def record_hand(shorthand: str, session_id: int | None = None, stakes: str | None = None,
                 tag: str | None = None, lesson: str | None = None,
                 backend: str | None = None) -> dict:
-    """Parse shorthand -> structured hand -> store. Returns {id, parsed} (id None on parse fail)."""
+    """Parse shorthand -> structured hand -> store. Returns {id, parsed} (id None on parse fail).
+    Idempotent: if this exact hand was just logged for the session (double turn execution),
+    returns the existing one instead of inserting a duplicate."""
     parsed = parse_hand(shorthand, stakes=stakes, backend=backend)
     if not parsed:
         return {"id": None, "parsed": None}
+    dup = _recent_duplicate_hand(parsed, session_id)
+    if dup is not None:
+        return {"id": dup, "parsed": parsed, "linked": 0, "deduped": True}
     hid = store_hand_history(parsed, session_id=session_id, tag=tag, lesson=lesson)
     linked = link_hand_players(hid, parsed, session_id=session_id)  # enrich villain files
     return {"id": hid, "parsed": parsed, "linked": linked}
diff --git a/tests/test_hand_dedup.py b/tests/test_hand_dedup.py
new file mode 100644
index 0000000..3e339bd
--- /dev/null
+++ b/tests/test_hand_dedup.py
@@ -0,0 +1,67 @@
+"""record_hand idempotency + straddle parse coverage.
+
+The chat turn can execute twice — the SSE stream and the blocking fallback both run
+server-side (two 'chat request' lines, 1s apart) — which double-logged the same hand
+once logging became guaranteed. A system-of-record must record an event once."""
+from __future__ import annotations
+
+import importlib
+
+import pytest
+
+
+@pytest.fixture
+def poker(tmp_path, monkeypatch):
+    monkeypatch.setenv("LYRA_DB_PATH", str(tmp_path / "test.db"))
+    from lyra import llm
+    monkeypatch.setattr(llm, "embed", lambda texts: [[0.1, 0.2, 0.3] for _ in texts])
+    import lyra.memory as memory
+    importlib.reload(memory)
+    import lyra.poker as poker
+    importlib.reload(poker)
+    return poker
+
+
+_PARSED = {
+    "game": "NLH", "hero_pos": "SB", "hero_cards": ["Ah", "Kh"],
+    "board": ["Kd", "9d", "4c", "2s"], "players": [], "actions": [],
+    "result": {"hero_net": -200, "pot": 400},
+}
+
+
+def test_record_hand_is_idempotent_across_double_execution(poker, monkeypatch):
+    sid = poker.start_session(venue="Borgata", stakes="1/3", buy_in=400)
+    monkeypatch.setattr(poker, "parse_hand", lambda *a, **k: dict(_PARSED))
+    first = poker.record_hand("i have AhKh in the SB, btn straddle, ...")
+    second = poker.record_hand("i have AhKh in the SB, btn straddle, ...")   # the duplicate turn
+    assert first["id"] == second["id"]
+    assert second.get("deduped") is True
+    assert len(poker.list_hands(sid)) == 1          # ledger holds ONE, not two
+
+
+def test_record_hand_does_not_dedupe_a_genuinely_different_hand(poker, monkeypatch):
+    sid = poker.start_session(venue="Borgata", stakes="1/3", buy_in=400)
+    monkeypatch.setattr(poker, "parse_hand", lambda *a, **k: dict(_PARSED))
+    poker.record_hand("hand one")
+    other = dict(_PARSED, hero_cards=["Qs", "Qd"], board=["Qh", "7c", "2s"])
+    monkeypatch.setattr(poker, "parse_hand", lambda *a, **k: dict(other))
+    poker.record_hand("a different hand entirely")
+    assert len(poker.list_hands(sid)) == 2          # distinct hands both land
+
+
+def test_dedupe_handles_boardless_hand(poker, monkeypatch):
+    # NULL-safe match: a preflop-only hand (no board) still dedupes.
+    sid = poker.start_session(venue="Borgata", buy_in=400)
+    preflop = {"game": "NLH", "hero_pos": "BTN", "hero_cards": ["As", "Ks"],
+               "board": [], "players": [], "actions": [], "result": {"hero_net": 30}}
+    monkeypatch.setattr(poker, "parse_hand", lambda *a, **k: dict(preflop))
+    a = poker.record_hand("AKs btn, i open everyone folds")
+    b = poker.record_hand("AKs btn, i open everyone folds")
+    assert a["id"] == b["id"] and len(poker.list_hands(sid)) == 1
+
+
+def test_parse_prompt_records_straddles():
+    from lyra import poker as pk
+    p = pk._HAND_PARSE_PROMPT.lower()
+    assert "straddle" in p and "button straddle" in p
+    assert "acts last preflop" in p or "act last preflop" in p