diff --git a/examples/00_template.py b/examples/00_template.py
index d786280..cc48a23 100644
--- a/examples/00_template.py
+++ b/examples/00_template.py
@@ -72,4 +72,4 @@ if __name__ == "__main__":
     print(result.summary())
     print(f"\nElapsed: {perf_counter() - t0:.2f}s")
 
-    mbt.plot.tearsheet(result, show=True)
+    mbt.plot.tearsheet(result)
diff --git a/examples/01_trend_following.py b/examples/01_trend_following.py
index d72ba8f..5a87d9c 100644
--- a/examples/01_trend_following.py
+++ b/examples/01_trend_following.py
@@ -75,4 +75,4 @@ if __name__ == "__main__":
     print(f"\nElapsed: {elapsed:.3f}s")
 
     # Plot
-    mbt.plot.summary(result, show=True)
+    mbt.plot.summary(result)
diff --git a/examples/02_mean_reversion.py b/examples/02_mean_reversion.py
index 88f6c2b..602ed29 100644
--- a/examples/02_mean_reversion.py
+++ b/examples/02_mean_reversion.py
@@ -63,4 +63,4 @@ if __name__ == "__main__":
 
     print(result.summary())
     print(f"\nElapsed: {elapsed:.3f}s")
-    mbt.plot.summary(result, show=True)
+    mbt.plot.summary(result)
diff --git a/examples/03_multi_asset_momentum.py b/examples/03_multi_asset_momentum.py
index 7fe0be7..ba49b1f 100644
--- a/examples/03_multi_asset_momentum.py
+++ b/examples/03_multi_asset_momentum.py
@@ -70,4 +70,4 @@ if __name__ == "__main__":
 
     print(result.summary())
     print(f"\nElapsed: {elapsed:.3f}s")
-    mbt.plot.summary(result, show=True)
+    mbt.plot.summary(result)
diff --git a/examples/04_linear_regression.py b/examples/04_linear_regression.py
index 7dcd099..34a4292 100644
--- a/examples/04_linear_regression.py
+++ b/examples/04_linear_regression.py
@@ -101,4 +101,4 @@ if __name__ == "__main__":
 
     print(result.summary())
     print(f"\nElapsed: {elapsed:.3f}s")
-    mbt.plot.summary(result, show=True)
+    mbt.plot.summary(result)
diff --git a/examples/05_stat_arb.py b/examples/05_stat_arb.py
index fcd7c05..2f3f381 100644
--- a/examples/05_stat_arb.py
+++ b/examples/05_stat_arb.py
@@ -71,4 +71,4 @@ if __name__ == "__main__":
 
     print(result.summary())
     print(f"\nElapsed: {elapsed:.3f}s")
-    mbt.plot.summary(result, show=True)
+    mbt.plot.summary(result)
diff --git a/examples/06_full_visualization.py b/examples/06_full_visualization.py
index ba75b81..c533739 100644
--- a/examples/06_full_visualization.py
+++ b/examples/06_full_visualization.py
@@ -92,7 +92,7 @@ if __name__ == "__main__":
     )
 
     # -- 3. Summary 3-panel ---------------------------------------------------
-    mbt.plot.summary(result, show=True)
+    mbt.plot.summary(result)
 
     # -- 4. Candlestick chart (first symbol in universe) --------------------
     mbt.plot.chart(
@@ -101,18 +101,17 @@ if __name__ == "__main__":
         smas=[50],
         n_bars=120,
         interactive=False,
-        show=True,
     )
 
     # -- 5. Individual charts -------------------------------------------------
-    mbt.plot.equity(result, show=True)
-    mbt.plot.drawdown(result, show=True)
-    mbt.plot.monthly_returns(result, show=True)
-    mbt.plot.annual_returns(result, show=True)
-    mbt.plot.returns_histogram(result, show=True)
-    mbt.plot.var_chart(result, show=True)
-    mbt.plot.rolling_sharpe(result, show=True)
-    mbt.plot.rolling_volatility(result, show=True)
+    mbt.plot.equity(result)
+    mbt.plot.drawdown(result)
+    mbt.plot.monthly_returns(result)
+    mbt.plot.annual_returns(result)
+    mbt.plot.returns_histogram(result)
+    mbt.plot.var_chart(result)
+    mbt.plot.rolling_sharpe(result)
+    mbt.plot.rolling_volatility(result)
 
     # -- 6. Sweep heatmap 2D -------------------------------------------------
     # Sweep over RSI period and oversold threshold
@@ -160,7 +159,7 @@ if __name__ == "__main__":
         "metric_grid": metric_grid,
     }
     print(f"Sweep done in {time.perf_counter() - t0:.1f}s")
-    mbt.plot.heatmap_2d(sweep_result, show=True)
+    mbt.plot.heatmap_2d(sweep_result)
 
     # -- 7. Walk-forward validation -------------------------------------------
     print("\nRunning walk-forward (manual folds)...")
@@ -201,11 +200,11 @@ if __name__ == "__main__":
         "folds": wf_folds,
     }
     print(f"Walk-forward done in {time.perf_counter() - t0:.1f}s")
-    mbt.plot.walk_forward(wf_result, show=True)
+    mbt.plot.walk_forward(wf_result)
 
     # -- 8. Monte Carlo -------------------------------------------------------
     print("\nRunning Monte Carlo (1000 paths)...")
-    mbt.plot.monte_carlo(result, n_simulations=1000, seed=42, show=True)
+    mbt.plot.monte_carlo(result, n_simulations=1000, seed=42)
 
     # -- 9. Parameter stability -----------------------------------------------
     print("\nRunning stability analysis (RSI period)...")
@@ -241,7 +240,7 @@ if __name__ == "__main__":
         "stability_score": 1.0 - (std_m / abs(mean_m)) if mean_m != 0 else 0.0,
     }
     print(f"Stability done in {time.perf_counter() - t0:.1f}s")
-    mbt.plot.stability(stab_result, show=True)
+    mbt.plot.stability(stab_result)
 
     # -- 10. Research report (composite) --------------------------------------
     print("\nGenerating research report...")
diff --git a/examples/07_walk_forward.py b/examples/07_walk_forward.py
index 3369ef0..5b788d1 100644
--- a/examples/07_walk_forward.py
+++ b/examples/07_walk_forward.py
@@ -93,4 +93,4 @@ if __name__ == "__main__":
     print(f"\n{len(folds)} folds in {elapsed:.2f}s")
 
     if folds:
-        mbt.plot.walk_forward({"optimize_metric": metric, "folds": folds}, show=True)
+        mbt.plot.walk_forward({"optimize_metric": metric, "folds": folds})
diff --git a/examples/08_sweep_2d_heatmap.py b/examples/08_sweep_2d_heatmap.py
index 3385f5f..ed41a8e 100644
--- a/examples/08_sweep_2d_heatmap.py
+++ b/examples/08_sweep_2d_heatmap.py
@@ -87,4 +87,4 @@ if __name__ == "__main__":
         "y_values": slow_values,
         "metric": "t-stat(alpha)",
         "metric_grid": metric_grid,
-    }, show=True)
+    })
diff --git a/examples/09_surface_3d.py b/examples/09_surface_3d.py
index f52254e..4a73c29 100644
--- a/examples/09_surface_3d.py
+++ b/examples/09_surface_3d.py
@@ -84,4 +84,4 @@ if __name__ == "__main__":
         "y_values": slow_values,
         "metric": "t-stat(alpha)",
         "metric_grid": metric_grid,
-    }, show=True)
+    })
diff --git a/examples/10_monte_carlo.py b/examples/10_monte_carlo.py
index 3da0d8c..f6566c4 100644
--- a/examples/10_monte_carlo.py
+++ b/examples/10_monte_carlo.py
@@ -66,4 +66,4 @@ if __name__ == "__main__":
     print(f"Elapsed: {time.perf_counter() - t0:.3f}s\n")
 
     # 2. Monte Carlo fan chart
-    mbt.plot.monte_carlo(result, n_simulations=10000, seed=42, show=True)
+    mbt.plot.monte_carlo(result, n_simulations=10000, seed=42)
diff --git a/examples/11_portfolio.py b/examples/11_portfolio.py
index 120faa7..26f5103 100644
--- a/examples/11_portfolio.py
+++ b/examples/11_portfolio.py
@@ -72,4 +72,4 @@ if __name__ == "__main__":
     print(result.summary())
     print(f"\nElapsed: {elapsed:.3f}s")
 
-    mbt.plot.tearsheet(result, show=True)
+    mbt.plot.tearsheet(result)
diff --git a/examples/13_stochastic_simulation.py b/examples/13_stochastic_simulation.py
index 157b38d..68ca03c 100644
--- a/examples/13_stochastic_simulation.py
+++ b/examples/13_stochastic_simulation.py
@@ -141,5 +141,4 @@ if __name__ == "__main__":
     mbt.plot.stochastic_paths(
         result,
         title=f"Mean-reverting model (S0=80, target=100, {N_PLOT:,} paths)",
-        show=True,
     )
diff --git a/examples/14_multi_timeframe.py b/examples/14_multi_timeframe.py
index e6668a4..3036143 100644
--- a/examples/14_multi_timeframe.py
+++ b/examples/14_multi_timeframe.py
@@ -83,4 +83,4 @@ if __name__ == "__main__":
     print(result.summary())
     print(f"\nElapsed: {elapsed:.3f}s")
 
-    mbt.plot.equity(result, show=True)
+    mbt.plot.equity(result)
diff --git a/examples/15_cross_exchange.py b/examples/15_cross_exchange.py
index 8db4e6d..58310fb 100644
--- a/examples/15_cross_exchange.py
+++ b/examples/15_cross_exchange.py
@@ -105,4 +105,4 @@ if __name__ == "__main__":
 
     print(result.summary())
     print(f"\nElapsed: {elapsed:.3f}s")
-    result.plot_equity(show=True)
+    result.plot_equity()
diff --git a/examples/16_hashrate_exogene.py b/examples/16_hashrate_exogene.py
index 1a21820..231c614 100644
--- a/examples/16_hashrate_exogene.py
+++ b/examples/16_hashrate_exogene.py
@@ -211,4 +211,4 @@ if __name__ == "__main__":
 
     print(result.summary())
     print(f"\nElapsed: {elapsed:.3f}s")
-    result.plot_equity(show=True)
+    result.plot_equity()
diff --git a/pyproject.toml b/pyproject.toml
index 98a6803..5b8c313 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "manifoldbt"
-version = "0.13.2"
+version = "0.14.0"
 description = "Rust-powered backtesting engine for quantitative research"
 requires-python = ">=3.9"
 license = { file = "LICENSE" }
diff --git a/python/manifoldbt/__init__.py b/python/manifoldbt/__init__.py
index 250a4de..44729f4 100644
--- a/python/manifoldbt/__init__.py
+++ b/python/manifoldbt/__init__.py
@@ -29,6 +29,7 @@ from manifoldbt._native import (
     run_portfolio as _run_portfolio_native,
     py_ingest as _ingest_native,
     py_import_csv as _import_csv_native,
+    py_import_dataframe as _import_dataframe_native,
 )
 from manifoldbt._serde import scalar_value_to_json
 from manifoldbt.config import (
@@ -183,6 +184,32 @@ def _require_pro_over_combos(n_combos: int, what: str) -> None:
     )
 
 
+def _validate_swept_params(strategy: "Strategy", names, what: str) -> None:
+    """Reject swept parameter names the strategy never declares.
+
+    Sweeping a name the strategy does not use is a silent no-op: the value is
+    merged into a parameter map nothing reads, so every combo runs the same
+    backtest and the sweep returns N identical results with no warning. That
+    is worse than an error, because an "optimisation" over thousands of combos
+    looks like it worked and its best result is meaningless.
+
+    A parameter counts as declared whether it came from ``mbt.param()`` inside
+    an expression or from an explicit ``.param()`` call: ``to_json_dict()``
+    merges both into ``parameters`` (and is memoised, so this costs nothing).
+    """
+    declared = set(strategy.to_json_dict().get("parameters") or {})
+    unknown = [n for n in names if n not in declared]
+    if not unknown:
+        return
+    known = ", ".join(sorted(declared)) if declared else "none"
+    raise StrategyError(
+        f"{what}: parameter(s) {unknown} are not declared by strategy "
+        f"'{strategy.name}' (declared: {known}). Sweeping them would run the "
+        f"same backtest for every combination. Use mbt.param(\"name\") where "
+        f"the value is consumed, e.g. ema(close, mbt.param(\"fast\"))."
+    )
+
+
 def _classify_error(exc: Exception) -> Exception:
     """Wrap a Rust ValueError/RuntimeError in a more specific exception."""
     msg = str(exc)
@@ -682,6 +709,128 @@ def import_csv(
     )
 
 
+_BARS_REQUIRED_COLUMNS = ("timestamp", "open", "high", "low", "close", "volume")
+
+
+def _df_to_bars_batch(data):
+    """Normalise a pandas/polars DataFrame (or dict) to a pyarrow RecordBatch.
+
+    Output contract (what the native import expects): columns
+    ``timestamp`` (timestamp[ns, UTC]), ``open/high/low/close/volume`` (f64).
+    Naive timestamps are assumed UTC. A pandas DatetimeIndex is promoted to
+    the ``timestamp`` column when the column is absent.
+    """
+    import pyarrow as pa
+
+    # --- to Arrow Table (same dispatch as register_exo) ---
+    if hasattr(data, "to_arrow"):
+        # Polars DataFrame
+        table = data.to_arrow()
+    elif hasattr(data, "columns"):
+        # Pandas DataFrame
+        import pandas as pd
+        if "timestamp" not in data.columns and isinstance(data.index, pd.DatetimeIndex):
+            data = data.reset_index(names="timestamp")
+        table = pa.Table.from_pandas(data, preserve_index=False)
+    elif isinstance(data, dict):
+        table = pa.table(data)
+    else:
+        raise TypeError(
+            f"Unsupported data type: {type(data)}. Use a pandas/polars DataFrame or dict."
+        )
+
+    missing = [c for c in _BARS_REQUIRED_COLUMNS if c not in table.column_names]
+    if missing:
+        raise DataError(
+            f"DataFrame is missing required column(s): {', '.join(missing)}. "
+            f"Expected: {', '.join(_BARS_REQUIRED_COLUMNS)}"
+        )
+    table = table.select(list(_BARS_REQUIRED_COLUMNS))
+
+    # --- timestamp → timestamp[ns, UTC] ---
+    ts_type = table.schema.field("timestamp").type
+    if not pa.types.is_timestamp(ts_type):
+        raise DataError(
+            f"'timestamp' column must be a datetime type, got {ts_type}. "
+            "For epoch integers, convert first: pd.to_datetime(ts, unit='ms', utc=True)"
+        )
+    target_ts = pa.timestamp("ns", tz="UTC")
+    if ts_type != target_ts:
+        table = table.set_column(
+            0, pa.field("timestamp", target_ts), table.column(0).cast(target_ts)
+        )
+
+    # --- value columns → float64 ---
+    for i, name in enumerate(_BARS_REQUIRED_COLUMNS[1:], start=1):
+        if table.schema.field(i).type != pa.float64():
+            table = table.set_column(
+                i, pa.field(name, pa.float64()), table.column(i).cast(pa.float64())
+            )
+
+    if table.num_rows == 0:
+        raise DataError("DataFrame contains no data rows")
+
+    # Single contiguous batch for the zero-copy FFI crossing.
+    return table.combine_chunks().to_batches()[0]
+
+
+def import_dataframe(
+    data,
+    symbol: str,
+    symbol_id: int,
+    *,
+    interval: str = "1m",
+    data_root: str = "data",
+    metadata_db: str = "metadata/metadata.sqlite",
+    exchange: str = "DATAFRAME",
+    asset_class: str = "crypto_spot",
+) -> DataStore:
+    """Import bars from an in-memory DataFrame into the Arrow IPC store. Free on all tiers.
+
+    The in-memory twin of :func:`import_csv`: edit your data as a DataFrame,
+    then import it directly — no intermediate CSV. Returns a :class:`DataStore`
+    ready for :func:`run` (same store, metadata and versioning as ``bt.ingest``).
+
+    Accepts a pandas DataFrame, polars DataFrame, or dict of columns with
+    ``timestamp`` (datetime; naive values are assumed UTC), ``open``, ``high``,
+    ``low``, ``close``, ``volume``. A pandas DatetimeIndex is used as
+    ``timestamp`` if that column is absent. Rows must be sorted by timestamp.
+
+    Example::
+
+        df = pd.read_parquet("EURUSD_1m.parquet")
+        df["close"] = df["close"].clip(upper=1.5)   # edit in memory
+        store = bt.import_dataframe(df, symbol="EURUSD", symbol_id=1,
+                                    interval="1m", asset_class="forex")
+        result = bt.run(strategy, config, store)
+
+    Args:
+        data: pandas/polars DataFrame or dict of columns.
+        symbol: Ticker name (e.g. ``"EURUSD"``, ``"BTCUSDT"``).
+        symbol_id: Unique integer ID for this symbol in the store.
+        interval: Bar interval of the rows (``"1m"``, ``"5m"``, ``"1h"``, ``"1d"``, ...).
+        data_root: Store directory (default ``"data"``).
+        metadata_db: Metadata SQLite path.
+        exchange: Exchange label for metadata (default ``"DATAFRAME"``).
+        asset_class: ``crypto_spot``, ``crypto_perp``, ``equity``, ``future``,
+            ``option``, ``forex``, or ``index``.
+    """
+    batch = _df_to_bars_batch(data)
+    try:
+        return _import_dataframe_native(
+            batch,
+            symbol=symbol,
+            symbol_id=symbol_id,
+            interval=interval,
+            data_root=data_root,
+            metadata_db=metadata_db,
+            exchange=exchange,
+            asset_class=asset_class,
+        )
+    except (ValueError, RuntimeError) as exc:
+        raise _classify_error(exc) from exc
+
+
 def _ingest_single(
     *, provider, symbol, symbol_id, start, end, interval, dataset,
     data_root, metadata_db, exchange, asset_class, progress,
@@ -759,6 +908,7 @@ def run_sweep(
         A :class:`SweepResult` with ``.to_df()``, ``.best()``, ``.plot_metric()``.
     """
     _require_pro_over_combos(_grid_combos(param_grid), "Parameter sweep")
+    _validate_swept_params(strategy, param_grid.keys(), "Parameter sweep")
     try:
         config = _cap_output_resolution(config)
         store = _resolve_store(config, store)
@@ -930,6 +1080,7 @@ def run_sweep_lite(
         One :class:`BatchResultLite` per combo (Cartesian product order).
     """
     _require_pro_over_combos(_grid_combos(param_grid), "Parameter sweep")
+    _validate_swept_params(strategy, param_grid.keys(), "Parameter sweep")
     _require_pro_for_gpu(device, "GPU sweep")
     try:
         config = _cap_output_resolution(config)
@@ -939,7 +1090,11 @@ def run_sweep_lite(
             name: [scalar_value_to_json(v) for v in values]
             for name, values in param_grid.items()
         })
-        return _run_sweep_lite_native(
+        # Wrapped in a list subclass: echoing a sweep in a notebook cell
+        # printed one BatchResultLite line per combo. Indexing, iteration and
+        # len() are unchanged.
+        from manifoldbt._reprs import wrap_sweep_lite
+        return wrap_sweep_lite(_run_sweep_lite_native(
             strategy.to_json(),
             grid_json,
             cfg_json,
@@ -947,7 +1102,7 @@ def run_sweep_lite(
             max_parallelism,
             device,
             precision,
-        )
+        ))
     except (ValueError, RuntimeError) as exc:
         raise _classify_error(exc) from exc
 
@@ -1029,9 +1184,15 @@ def run_walk_forward(
     # in `py_run_walk_forward` (check_feature("walk_forward")), so this cannot be
     # bypassed by calling the native function directly.
     _require_pro("Walk-forward optimization")
+    _validate_swept_params(strategy, (wf_config.get("param_grid") or {}).keys(),
+                           "Walk-forward")
     config = _prepare_config(config, strategy, store)
     wf_json = json.dumps(_convert_param_grid_in_config(wf_config))
-    return _run_walk_forward_native(strategy.to_json(), wf_json, config.to_json(), store)
+    raw = _run_walk_forward_native(strategy.to_json(), wf_json, config.to_json(), store)
+    # Wrapped in a dict subclass: the raw dict holds a full equity curve per
+    # fold, so echoing it in a cell printed tens of thousands of floats.
+    from manifoldbt._reprs import wrap_walk_forward
+    return wrap_walk_forward(raw)
 
 
 def run_sweep_2d(
@@ -1061,6 +1222,10 @@ def run_sweep_2d(
         len(sweep_config.get("x_values", [])) * len(sweep_config.get("y_values", [])),
         "2D parameter sweep",
     )
+    _validate_swept_params(
+        strategy,
+        [n for n in (sweep_config.get("x_param"), sweep_config.get("y_param")) if n],
+        "2D parameter sweep")
     config = _prepare_config(config, strategy, store)
     sweep_json = json.dumps(_convert_scalar_values_in_sweep(sweep_config))
     return _run_sweep_2d_native(strategy.to_json(), sweep_json, config.to_json(), store)
@@ -1088,6 +1253,10 @@ def run_stability(
         Dict with ``stability_score``, ``metric_values``, ``mean_metric``, ``std_metric``.
     """
     _require_pro_over_combos(len(stability_config.get("values", [])), "Parameter stability analysis")
+    _validate_swept_params(
+        strategy,
+        [n for n in (stability_config.get("param_name"),) if n],
+        "Parameter stability analysis")
     config = _prepare_config(config, strategy, store)
     stab_json = json.dumps(_convert_scalar_values_in_stability(stability_config))
     return _run_stability_native(strategy.to_json(), stab_json, config.to_json(), store)
@@ -1404,6 +1573,7 @@ __all__ = [
     # Data ingestion
     "ingest",
     "import_csv",
+    "import_dataframe",
     # Run functions
     "run",
     "run_sweep",
diff --git a/python/manifoldbt/_reprs.py b/python/manifoldbt/_reprs.py
new file mode 100644
index 0000000..0d7cf7c
--- /dev/null
+++ b/python/manifoldbt/_reprs.py
@@ -0,0 +1,107 @@
+"""Compact reprs for the big containers returned to notebooks.
+
+A sweep returns one object per combo and a walk-forward carries a full
+equity curve per fold, so echoing either in a Jupyter cell used to print
+thousands of lines. These wrappers subclass ``list``/``dict`` so every
+existing access keeps working (indexing, iteration, ``.keys()``, JSON
+round-trips); only the repr changes.
+"""
+from __future__ import annotations
+
+from typing import Any, Dict, List
+
+_MAX_SCAN = 100_000  # cap the repr's own cost on million-combo sweeps
+
+
+def _fmt(v: float) -> str:
+    """Compact number: 3 significant-ish digits, thousands as k."""
+    if v is None:
+        return "?"
+    a = abs(v)
+    if a >= 1_000_000:
+        return f"{v / 1_000_000:.2f}M"
+    if a >= 1_000:
+        return f"{v / 1_000:.2f}k"
+    if a >= 1:
+        return f"{v:.2f}"
+    return f"{v:.4g}"
+
+
+def _span(values) -> str:
+    vals = [v for v in values if v is not None]
+    if not vals:
+        return "n/a"
+    lo, hi = min(vals), max(vals)
+    return _fmt(lo) if lo == hi else f"{_fmt(lo)}..{_fmt(hi)}"
+
+
+class SweepLiteResults(list):
+    """``run_sweep_lite`` output: a list, with a one-line repr.
+
+    Printing 400 combos used to emit 400 lines of ``BatchResultLite(...)``.
+    """
+
+    def __repr__(self) -> str:
+        n = len(self)
+        if n == 0:
+            return "SweepLiteResults(empty)"
+        head = self[:_MAX_SCAN]
+        eq = _span([getattr(r, "final_equity", None) for r in head])
+        sharpes = []
+        for r in head:
+            m = getattr(r, "metrics", None)
+            if isinstance(m, dict):
+                sharpes.append(m.get("sharpe"))
+        name = getattr(self[0], "strategy_name", "?")
+        parts = [f"{n:,} combos", f"strategy {name!r}", f"final_equity {eq}"]
+        if any(s is not None for s in sharpes):
+            parts.append(f"sharpe {_span(sharpes)}")
+        if n > _MAX_SCAN:
+            parts.append(f"(range over first {_MAX_SCAN:,})")
+        return ("<SweepLiteResults: " + " | ".join(parts) +
+                "\n  r[i] for one combo, mbt.sweep_columns(r, 'sharpe') for arrays>")
+
+
+class WalkForwardResult(dict):
+    """``run_walk_forward`` output: a dict, with a one-line repr.
+
+    The raw dict carries a full IS and OOS equity curve per fold, so echoing
+    it in a cell used to print tens of thousands of floats.
+    """
+
+    def __repr__(self) -> str:
+        folds = self.get("folds") or []
+        if not folds:
+            return "<WalkForwardResult: no folds>"
+        metric = self.get("optimize_metric", "sharpe")
+
+        def _m(fold, key):
+            v = fold.get(key)
+            return v.get(metric) if isinstance(v, dict) else v
+
+        is_v = [_m(f, "is_metrics") for f in folds]
+        oos_v = [_m(f, "oos_metrics") for f in folds]
+        lines = [
+            f"<WalkForwardResult: {len(folds)} folds | metric {metric!r} | "
+            f"IS {_span(is_v)} | OOS {_span(oos_v)}"
+        ]
+        for f in folds:
+            best = f.get("best_params") or {}
+            flat = {k: (list(v.values())[0] if isinstance(v, dict) else v)
+                    for k, v in best.items()}
+            i, o = _m(f, "is_metrics"), _m(f, "oos_metrics")
+            lines.append(
+                f"  fold {f.get('fold_index', '?')}: "
+                f"IS {_fmt(i) if i is not None else '?':>8}  "
+                f"OOS {_fmt(o) if o is not None else '?':>8}  {flat}"
+            )
+        lines.append("  keys: " + ", ".join(sorted(self.keys())) + ">")
+        return "\n".join(lines)
+
+
+def wrap_sweep_lite(results: List[Any]) -> "SweepLiteResults":
+    return SweepLiteResults(results)
+
+
+def wrap_walk_forward(result: Dict[str, Any]) -> "WalkForwardResult":
+    return WalkForwardResult(result) if isinstance(result, dict) else result
diff --git a/python/manifoldbt/plot/__init__.py b/python/manifoldbt/plot/__init__.py
index 86c68ce..e61a6c8 100644
--- a/python/manifoldbt/plot/__init__.py
+++ b/python/manifoldbt/plot/__init__.py
@@ -10,11 +10,24 @@ Quick start::
 
     result = bt.run(strategy, config, store)
     bt.plot.tearsheet(result)              # full-page dashboard
-    bt.plot.equity(result, show=True)      # single chart
+    bt.plot.equity(result)                 # single chart, opens on its own
 
-Every chart is interactive (crosshair, hover, zoom). ``show=True`` opens it
-in a native window (``pip install manifoldbt[window]``; falls back to a
+Every chart is interactive (crosshair, hover, zoom) and **shows itself by
+default**: plotting is what you asked for, so no ``show=`` is needed. Charts
+open in a native window (``pip install manifoldbt[window]``; falls back to a
 browser tab, which you can also force with ``show="browser"``).
+
+Three cases opt out of showing automatically, because showing would be
+wrong: passing ``save=`` (you asked for a file, not a window), running
+under pytest/CI (a window there blocks the run), and running inside a
+notebook, where the cell already renders the returned Figure and showing
+would print a second copy of the same chart.
+
+Pass an explicit ``show=True`` to override any of them, or ``show=False``
+to get the Figure back silently and compose it yourself. To place a chart
+in the middle of a notebook cell, where there is no trailing expression for
+Jupyter to display, call IPython's ``display(fig)`` on the returned figure.
+
 ``save=".html"`` writes a responsive interactive page. Static ``save=".png"``
 is optional and needs ``pip install manifoldbt[png]`` (pulls a headless Chromium).
 """
diff --git a/python/manifoldbt/plot/_utils.py b/python/manifoldbt/plot/_utils.py
index 27354da..6122717 100644
--- a/python/manifoldbt/plot/_utils.py
+++ b/python/manifoldbt/plot/_utils.py
@@ -29,6 +29,57 @@ def new_figure(
     return fig
 
 
+def _in_notebook() -> bool:
+    """True inside a Jupyter/IPython kernel (not a plain terminal REPL)."""
+    try:
+        from IPython import get_ipython  # type: ignore
+    except ImportError:
+        return False
+    try:
+        ip = get_ipython()
+    except Exception:
+        return False
+    return ip is not None and hasattr(ip, "kernel")
+
+
+def _in_test_or_ci() -> bool:
+    """True under pytest or on a CI runner.
+
+    A test that builds a figure must not queue a window: show() runs from
+    the atexit hook and blocks on the window process, so one bare plot call
+    in a test suite hangs the whole run until a human closes it.
+    """
+    import os
+    return bool(os.environ.get("PYTEST_CURRENT_TEST") or os.environ.get("CI"))
+
+
+def resolve_show(show: "bool | str | None",
+                 save: Optional[Union[str, Path]]) -> "bool | str":
+    """Resolve the ``show=None`` auto default.
+
+    A chart you asked for is a chart you want to see, so the default shows
+    it. Three cases opt out, because showing there would be wrong:
+
+    - ``save`` was given: you asked for a file, not a window.
+    - pytest/CI: show() runs from atexit and blocks on the window process.
+    - a notebook: the cell already renders the returned Figure. Calling
+      show() here too would emit a SECOND copy of the same chart, so the
+      notebook path stays silent and lets the cell do the rendering.
+
+    Explicit ``True``/``False``/``"browser"`` always wins. There is no
+    "render it inline" value to pass, because that is what the notebook
+    already does with the returned Figure; to place a chart mid-cell, call
+    IPython's ``display(fig)``.
+    """
+    if show is not None:
+        return show
+    if save is not None:
+        return False
+    if _in_test_or_ci():
+        return False
+    return False if _in_notebook() else True
+
+
 def format_pct(value: float, decimals: int = 1) -> str:
     """Format a decimal fraction as a percentage string."""
     return f"{value * 100:+.{decimals}f}%"
@@ -43,7 +94,7 @@ def format_currency(value: float, currency: str = "USD") -> str:
 def finalize(
     fig,
     *,
-    show: "bool | str" = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
     dpi: int = 150,
     window_size: Optional[Tuple[int, int]] = None,
@@ -52,10 +103,20 @@ def finalize(
 
     ``save`` routes on extension: ``.html`` writes a responsive interactive
     page; image extensions (.png/.svg/.pdf/...) go through kaleido.
-    ``show``: ``True`` (or ``"window"``) opens a native window (needs pywebview,
-    else falls back to a browser tab); ``"browser"`` forces a browser tab.
+    ``show``: ``None`` (default) shows the chart unless ``save`` was given or
+    we are in a notebook (see :func:`resolve_show`); ``True`` (or ``"window"``)
+    opens a native window (needs pywebview, else falls back to a browser tab);
+    ``"browser"`` forces a browser tab; ``False`` returns the figure silently.
     ``dpi`` is kept for backward compatibility and maps to an export scale.
     """
+    show = resolve_show(show, save)
+    if _in_notebook():
+        # new_figure() sets a pixel width sized for a window (1120px by
+        # default). A notebook cell is narrower than that, so the chart
+        # overflowed its output area: the right edge and the modebar were
+        # pushed out of view. Drop the fixed width and let it track the cell,
+        # keeping the height so the cell still has a definite size.
+        fig.update_layout(width=None, autosize=True)
     if save is not None:
         path = Path(save)
         ext = path.suffix.lower()
@@ -71,7 +132,13 @@ def finalize(
                 ) from exc
         else:
             write_responsive_html(fig, path)
-    if show == "browser":
+    if show == "inline" and _in_notebook():
+        # No-op on purpose. Rendering in the cell IS the notebook default, so
+        # calling show() here would emit a second copy of the chart the cell
+        # is already going to render. To place a chart mid-cell, where there
+        # is no trailing expression, use IPython's display(fig).
+        pass
+    elif show in ("browser", "inline"):
         fig.show()
     elif show:  # True or "window" -> native window (browser tab fallback)
         from manifoldbt.plot._window import open_in_window
diff --git a/python/manifoldbt/plot/backtest.py b/python/manifoldbt/plot/backtest.py
index 052c55f..4a06a6c 100644
--- a/python/manifoldbt/plot/backtest.py
+++ b/python/manifoldbt/plot/backtest.py
@@ -71,7 +71,7 @@ def summary(
     result,
     *,
     figsize: Tuple[float, float] = (14, 8),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """The essential chart: TWR equity + buy-and-hold benchmark, trade activity.
@@ -264,7 +264,7 @@ def equity(
     color: str = ACCENT,
     title: str = "Equity Curve",
     figsize: Tuple[float, float] = (14, 5),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Plot the portfolio equity curve over time.
@@ -298,7 +298,7 @@ def benchmark_equity(
     labels: Tuple[str, str] = ("Strategy", "Buy & Hold"),
     title: str = "Strategy vs Benchmark",
     figsize: Tuple[float, float] = (14, 5),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Overlay strategy equity and a benchmark, both normalized to 100."""
@@ -339,7 +339,7 @@ def drawdown(
     color: str = RED,
     title: str = "Drawdown",
     figsize: Tuple[float, float] = (14, 3),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Plot the drawdown as a filled area chart."""
@@ -373,7 +373,7 @@ def monthly_returns(
     annotate: bool = True,
     title: str = "Monthly Returns (%)",
     figsize: Tuple[float, float] = (12, 5),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Monthly returns heatmap (year rows x month columns + annual)."""
@@ -439,7 +439,7 @@ def annual_returns(
     ax=None,
     title: str = "Annual Returns",
     figsize: Tuple[float, float] = (10, 4),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Annual returns bar chart with green/red conditional coloring."""
@@ -479,7 +479,7 @@ def returns_histogram(
     bins: int = 100,
     title: str = "Returns Distribution",
     figsize: Tuple[float, float] = (12, 5),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Histogram of daily returns with green/red coloring by sign."""
@@ -541,7 +541,7 @@ def var_chart(
     bins: int = 120,
     title: str = "Value at Risk",
     figsize: Tuple[float, float] = (12, 5),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Returns histogram with VaR and CVaR lines at 5% and 1% levels."""
@@ -610,7 +610,7 @@ def rolling_sharpe(
     title: str = "Rolling Sharpe",
     trading_days_per_year: float = 365.25,
     figsize: Tuple[float, float] = (14, 4),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Rolling annualized Sharpe ratio."""
@@ -652,7 +652,7 @@ def rolling_volatility(
     title: str = "Rolling Volatility",
     trading_days_per_year: float = 365.25,
     figsize: Tuple[float, float] = (14, 4),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Rolling annualized volatility."""
diff --git a/python/manifoldbt/plot/chart.py b/python/manifoldbt/plot/chart.py
index 290eec3..4314a34 100644
--- a/python/manifoldbt/plot/chart.py
+++ b/python/manifoldbt/plot/chart.py
@@ -212,7 +212,7 @@ def chart(
     n_bars: int = 120,
     interactive: bool = True,
     figsize: Tuple[float, float] = (14, 7),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ):
     """Plot candlestick chart with indicators and trade markers.
diff --git a/python/manifoldbt/plot/research.py b/python/manifoldbt/plot/research.py
index 3d98131..ab77d71 100644
--- a/python/manifoldbt/plot/research.py
+++ b/python/manifoldbt/plot/research.py
@@ -112,14 +112,29 @@ def heatmap_2d(
     annotate: bool = True,
     fmt: str = ".3f",
     highlight_best: bool = True,
+    zones: "bool | List[float] | None" = None,
+    drift: int = 2,
     title: Optional[str] = None,
     figsize: Tuple[float, float] = (10, 8),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """2D parameter sweep heatmap from ``run_sweep_2d()`` result.
 
     Expected keys: metric_grid, x_values, y_values, x_param, y_param, metric.
+
+    Args:
+        zones: Colour cells by discrete robustness zone instead of by the
+            metric. A zone is what the area still guarantees when the
+            parameters drift by ``drift`` cells, so a lucky spike is shown in
+            a low zone despite scoring well on its own cell. ``True`` picks
+            the bands (conventional 0/0.5/1.0/1.5 for risk-adjusted ratios,
+            an even split of the observed range otherwise); pass a list of
+            thresholds to set them yourself. The metric value stays on hover
+            and in the cell labels. Same option as ``surface_3d``.
+        drift: Neighbourhood radius in grid cells for the worst case. Cells,
+            not parameter units: with an x step of 1 and a y step of 5,
+            ``drift=2`` means +/-2 on x but +/-10 on y.
     """
     with theme_context():
         grid = np.array(sweep_result["metric_grid"], dtype=np.float64)
@@ -135,22 +150,50 @@ def heatmap_2d(
             text = np.vectorize(lambda v: "" if np.isnan(v) else f"{v:{fmt}}")(grid)
 
         fig = new_figure(figsize)
-        fig.add_trace(go.Heatmap(
-            z=grid, x=x_vals, y=y_vals,
-            colorscale=CS_SEQUENTIAL,
-            text=text, texttemplate="%{text}" if text is not None else None,
-            textfont=dict(size=9),
-            hovertemplate=(
-                f"{x_param} %{{x}}<br>{y_param} %{{y}}<br>"
-                f"{metric} %{{z:{fmt}}}<extra></extra>"
-            ),
-            colorbar=dict(outlinewidth=0, thickness=12),
-            hoverongaps=False,
-        ))
+        if zones:
+            worst = _worst_case(grid, drift)
+            band, scale, labels, edges, n_bands = _zone_bands(worst, zones, metric)
+            # z carries the band so colour is discrete; the metric and what it
+            # holds ride along in customdata so the cell still reports both.
+            fig.add_trace(go.Heatmap(
+                z=band, x=x_vals, y=y_vals,
+                colorscale=scale, zmin=-0.5, zmax=n_bands - 0.5,
+                customdata=np.dstack((grid, worst)),
+                text=text, texttemplate="%{text}" if text is not None else None,
+                textfont=dict(size=9),
+                hovertemplate=(
+                    f"{x_param} %{{x}}<br>{y_param} %{{y}}<br>"
+                    f"{metric} %{{customdata[0]:{fmt}}}<br>"
+                    f"held %{{customdata[1]:{fmt}}}<extra></extra>"
+                ),
+                colorbar=dict(
+                    title=dict(text=f"{metric}<br>held under drift", side="right"),
+                    outlinewidth=0, thickness=12,
+                    tickmode="array", tickvals=list(range(n_bands)),
+                    ticktext=labels),
+                hoverongaps=False,
+            ))
+        else:
+            fig.add_trace(go.Heatmap(
+                z=grid, x=x_vals, y=y_vals,
+                colorscale=CS_SEQUENTIAL,
+                text=text, texttemplate="%{text}" if text is not None else None,
+                textfont=dict(size=9),
+                hovertemplate=(
+                    f"{x_param} %{{x}}<br>{y_param} %{{y}}<br>"
+                    f"{metric} %{{z:{fmt}}}<extra></extra>"
+                ),
+                colorbar=dict(outlinewidth=0, thickness=12),
+                hoverongaps=False,
+            ))
 
         best_label = None
         if highlight_best:
-            best_idx = _plateau_best(grid)
+            if zones:
+                # Match the colouring: best = what holds up, not the spike.
+                best_idx = np.unravel_index(np.argmax(worst), worst.shape)
+            else:
+                best_idx = _plateau_best(grid)
             best_val = grid[best_idx]
             best_x = x_vals[best_idx[1]]
             best_y = y_vals[best_idx[0]]
@@ -163,7 +206,12 @@ def heatmap_2d(
                 x0=best_x - dx, x1=best_x + dx, y0=best_y - dy, y1=best_y + dy,
                 line=dict(color="white", width=2.5),
             )
-            best_label = f"best: {best_val:{fmt}} ({x_param}={best_x:.0f}, {y_param}={best_y:.0f})"
+            kind = "most robust" if zones else "plateau centre"
+            best_label = (f"{kind}: {best_val:{fmt}} "
+                          f"({x_param}={best_x:.0f}, {y_param}={best_y:.0f})")
+            if zones:
+                best_label += (f", holds {worst[best_idx]:{fmt}} "
+                               f"under +/-{drift} cells")
 
         combos = nx * ny
         main_title = title or f"{metric} · Parameter Sweep ({combos:,} combos)"
@@ -188,21 +236,162 @@ def heatmap_2d(
 # ── 3D Surface Plot ─────────────────────────────────────────────────────────
 
 
+def _worst_case(grid: np.ndarray, radius: int) -> np.ndarray:
+    """Lowest value reachable within +/-``radius`` cells of each cell.
+
+    This is what a combo still returns if the parameters drift, as opposed
+    to what its own cell scored. Lucky spikes collapse to their surroundings;
+    plateaus keep their value. Edges are replicated so the border is not
+    flattered by having fewer neighbours.
+    """
+    if radius < 1:
+        return grid
+    filled = np.nan_to_num(grid, nan=np.nanmin(grid))
+    padded = np.pad(filled, radius, mode="edge")
+    n, m = filled.shape
+    stack = np.stack([padded[i:i + n, j:j + m]
+                      for i in range(2 * radius + 1)
+                      for j in range(2 * radius + 1)])
+    return stack.min(axis=0)
+
+
+# Metrics where 0 separates losing from winning, so 0 is worth keeping as a
+# band edge even when the data would not have put one there.
+_RATIO_METRICS = ("sharpe", "sortino", "calmar", "tstat_alpha", "information")
+_ZONE_COLORS = ["#3f1d1d", "#7c3a1d", "#8a7a1e", "#2f6b3a", ACCENT]
+
+
+def _nice_step(span: float, n_bands: int) -> float:
+    """A 1/2/2.5/5 x 10^k step covering ``span`` in about ``n_bands`` steps.
+
+    Rounded steps keep the legend readable: "0.8 - 1.2" rather than
+    "0.7834 - 1.2017".
+    """
+    if not np.isfinite(span) or span <= 0:
+        return 1.0
+    raw = span / n_bands
+    mag = 10.0 ** np.floor(np.log10(raw))
+    for m in (1.0, 2.0, 2.5, 5.0):
+        if raw <= m * mag:
+            return m * mag
+    return 10.0 * mag
+
+
+def _auto_edges(worst: np.ndarray, metric: str, n_bands: int = 5):
+    """Band edges fitted to the data, snapped to round numbers.
+
+    Fixed conventional thresholds (0/0.5/1.0/1.5 for a Sharpe) collapse to a
+    single flat band whenever the sweep happens to live inside one of them,
+    which is common: a grid whose guaranteed Sharpe runs 1.5-2.0 came out
+    entirely one colour.
+
+    Edges sit at -1.5 to +1.5 standard deviations around the sweep's mean, so
+    the zones say how exceptional a region is *within this sweep*. That is a
+    relative statement, not a quality certificate: a sweep where every combo
+    loses money still has a top zone, it is just the least bad. Read the
+    colourbar, which prints the real thresholds, and pass explicit
+    ``zones=[...]`` whenever the bands must mean something absolute.
+    """
+    finite = worst[np.isfinite(worst)]
+    if finite.size == 0:
+        return [0.0]
+    lo, hi = float(finite.min()), float(finite.max())
+    if hi <= lo:                       # a flat grid has nothing to band
+        return [lo]
+
+    # Quantiles, not an even split of the range. Taking a minimum over the
+    # drift window skews the distribution hard toward its low tail, so even
+    # edges dumped 93% of the cells into one band and the map came out flat.
+    # Quantiles balance the bands by construction; the snap keeps the numbers
+    # readable and the colourbar prints them.
+    # Bands in standard deviations around the mean of the sweep.
+    #
+    # Quantiles were the other candidate and they are worse here: they force
+    # ~20% of cells into every band, so a grid that is genuinely uniform
+    # after erosion still comes out looking structured. Sigma bands scale
+    # with the actual dispersion, so a flat sweep reads flat and a sweep with
+    # a real standout region shows it. They also carry a meaning a reader can
+    # use: "+1 sigma" is how exceptional the region is for THIS sweep.
+    mu, sd = float(np.mean(finite)), float(np.std(finite))
+    if sd <= 0:
+        return [lo]
+    sigmas = np.linspace(-1.5, 1.5, n_bands - 1)   # 5 bands -> -1.5..+1.5
+    raw_edges = mu + sigmas * sd
+    step = _nice_step(float(raw_edges[-1] - raw_edges[0]),
+                      max(len(raw_edges) - 1, 1))
+    edges = sorted({round(float(np.round(e / step) * step), 10)
+                    for e in raw_edges})
+    edges = [e for e in edges if lo < e < hi]
+    if len(edges) < len(raw_edges):
+        # Rounding merged edges (a very tight spread): keep them unsnapped.
+        edges = sorted({float(f"{e:.4g}") for e in raw_edges if lo < e < hi})
+
+    # 0 is a real boundary for a ratio: above it you make money, below you
+    # lose it. Keep it even if the rounding would have skipped it.
+    if any(k in metric.lower() for k in _RATIO_METRICS) and lo < 0.0 < hi:
+        edges = sorted(set(edges + [0.0]))
+        if len(edges) > n_bands - 1:   # drop the edge nearest 0, not 0 itself
+            nonzero = [e for e in edges if e != 0.0]
+            drop = min(nonzero, key=lambda e: abs(e))
+            edges.remove(drop)
+    return edges or [(lo + hi) / 2.0]
+
+
+def _zone_bands(worst: np.ndarray, zones, metric: str):
+    """Resolve ``zones`` into thresholds, then bucket ``worst`` into bands."""
+    if zones is True:
+        edges = _auto_edges(worst, metric)
+    else:
+        edges = sorted(float(z) for z in zones)
+
+    band = np.digitize(worst, edges).astype(float)
+    n_bands = len(edges) + 1
+    labels = [f"< {edges[0]:g}"]
+    labels += [f"{edges[i]:g} - {edges[i + 1]:g}" for i in range(len(edges) - 1)]
+    labels.append(f">= {edges[-1]:g}")
+
+    colors = _ZONE_COLORS
+    if n_bands != len(colors):  # stretch or trim the ramp to the band count
+        idx = np.linspace(0, len(colors) - 1, n_bands).round().astype(int)
+        colors = [colors[i] for i in idx]
+
+    scale = []
+    for i, c in enumerate(colors):   # duplicated stops = hard borders
+        scale.append([i / n_bands, c])
+        scale.append([(i + 1) / n_bands, c])
+    return band, scale, labels, edges, n_bands
+
+
 def surface_3d(
     sweep_result: Dict[str, Any],
     *,
     highlight_best: bool = True,
+    zones: "bool | List[float] | None" = None,
+    drift: int = 2,
     title: Optional[str] = None,
     figsize: Tuple[float, float] = (12, 8),
     elev: float = 30,
     azim: float = -45,
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """3D surface plot from a 2D parameter sweep result.
 
     Same input format as ``heatmap_2d``. ``elev``/``azim`` are kept for
     backward compatibility and mapped to the plotly camera.
+
+    Args:
+        zones: Colour the surface by discrete robustness zones instead of by
+            height. Height still shows the metric; colour shows what each
+            area still guarantees when the parameters drift by ``drift``
+            cells, so a lucky spike lands in a low zone despite standing
+            tall. ``True`` picks the bands (conventional 0/0.5/1.0/1.5 for
+            risk-adjusted ratios, an even split of the observed range
+            otherwise); pass a list of thresholds to set them yourself,
+            which is what you want whenever the bands carry meaning.
+        drift: Neighbourhood radius in grid cells used for the worst case.
+            Note this is cells, not parameter units: with an x step of 1 and
+            a y step of 5, ``drift=2`` means +/-2 on x but +/-10 on y.
     """
     with theme_context():
         grid = np.array(sweep_result["metric_grid"], dtype=np.float64)
@@ -213,34 +402,94 @@ def surface_3d(
         metric = sweep_result.get("metric", "metric")
 
         fig = new_figure(figsize)
-        fig.add_trace(go.Surface(
-            x=x_vals, y=y_vals, z=grid,
-            colorscale=CS_SEQUENTIAL, opacity=0.98,
-            colorbar=dict(title=dict(text=metric, side="right"),
-                          outlinewidth=0, thickness=13, len=0.6),
-            lighting=dict(ambient=0.75, diffuse=0.5, roughness=0.9, specular=0.1),
-            contours=dict(z=dict(show=True, usecolormap=True, project_z=True,
-                                 width=1)),
-            hovertemplate=(
-                f"{x_param} %{{x:.2f}}<br>{y_param} %{{y:.2f}}<br>"
-                f"{metric} %{{z:.3f}}<extra></extra>"
-            ),
-        ))
+        lighting = dict(ambient=0.75, diffuse=0.5, roughness=0.9, specular=0.1)
+
+        if zones:
+            worst = _worst_case(grid, drift)
+            band, scale, labels, edges, n_bands = _zone_bands(worst, zones, metric)
+            fig.add_trace(go.Surface(
+                x=x_vals, y=y_vals, z=grid,
+                surfacecolor=band, colorscale=scale,
+                cmin=-0.5, cmax=n_bands - 0.5, opacity=0.98,
+                colorbar=dict(
+                    title=dict(text=f"{metric}<br>held under drift", side="right"),
+                    outlinewidth=0, thickness=13, len=0.62,
+                    tickmode="array", tickvals=list(range(n_bands)),
+                    ticktext=labels),
+                lighting=lighting,
+                contours=dict(z=dict(show=True, color="rgba(255,255,255,0.13)",
+                                     width=1)),
+                customdata=worst,
+                hovertemplate=(
+                    f"{x_param} %{{x:.2f}}<br>{y_param} %{{y:.2f}}<br>"
+                    f"{metric} %{{z:.3f}}<br>held %{{customdata:.3f}}"
+                    f"<extra></extra>"
+                ),
+            ))
+        else:
+            fig.add_trace(go.Surface(
+                x=x_vals, y=y_vals, z=grid,
+                colorscale=CS_SEQUENTIAL, opacity=0.98,
+                colorbar=dict(title=dict(text=metric, side="right"),
+                              outlinewidth=0, thickness=13, len=0.6),
+                lighting=lighting,
+                contours=dict(z=dict(show=True, usecolormap=True, project_z=True,
+                                     width=1)),
+                hovertemplate=(
+                    f"{x_param} %{{x:.2f}}<br>{y_param} %{{y:.2f}}<br>"
+                    f"{metric} %{{z:.3f}}<extra></extra>"
+                ),
+            ))
 
         best_label = None
         if highlight_best:
-            best_idx = _plateau_best(grid)
+            if zones:
+                # With zones on, "best" means the combo that holds up best
+                # under drift, not the tallest cell. Reporting the spike here
+                # would contradict the colouring right next to it.
+                best_idx = np.unravel_index(np.argmax(worst), worst.shape)
+                held = worst[best_idx]
+            else:
+                best_idx = _plateau_best(grid)
+                held = None
             best_val = grid[best_idx]
             bx = x_vals[best_idx[1]]
             by = y_vals[best_idx[0]]
+
+            # A dot sitting exactly at best_val is half-buried in the surface
+            # it marks, and a stem dropped to the floor runs underneath that
+            # surface, hidden by it. So the marker is a pin standing ABOVE
+            # the peak: the stalk clears the geometry and stays readable from
+            # any camera angle and over any colour.
+            span = float(np.nanmax(grid) - np.nanmin(grid)) or 1.0
+            tip = best_val + span * 0.10
             fig.add_trace(go.Scatter3d(
-                x=[bx], y=[by], z=[best_val], mode="markers",
-                marker=dict(color="white", size=6,
-                            line=dict(color="black", width=2)),
-                name="best", showlegend=False,
-                hovertemplate=f"best {metric} %{{z:.3f}}<extra></extra>",
+                x=[bx, bx], y=[by, by], z=[best_val, tip], mode="lines",
+                line=dict(color=WHITE, width=5),
+                name="best", showlegend=False, hoverinfo="skip",
             ))
-            best_label = f"best: {best_val:.3f} ({x_param}={bx:.0f}, {y_param}={by:.0f})"
+            # Name the criterion. Calling this "best <metric>" was a lie
+            # whenever zones were on: it is not the highest cell, it is the
+            # one that survives drift, and the highest cell is elsewhere and
+            # visibly taller.
+            if zones:
+                pin_text = (f"most robust<br>{metric} {best_val:.3f}"
+                            f"<br>holds {worst[best_idx]:.3f} "
+                            f"under +/-{drift} cells")
+            else:
+                pin_text = f"plateau centre<br>{metric} {best_val:.3f}"
+            fig.add_trace(go.Scatter3d(
+                x=[bx], y=[by], z=[tip], mode="markers",
+                marker=dict(color=WHITE, size=9, symbol="diamond",
+                            line=dict(color="black", width=3)),
+                name="best", showlegend=False,
+                hovertemplate=pin_text + "<extra></extra>",
+            ))
+            kind = "most robust" if zones else "plateau centre"
+            best_label = (f"{kind}: {best_val:.3f} "
+                          f"({x_param}={bx:.0f}, {y_param}={by:.0f})")
+            if held is not None:
+                best_label += f", holds {held:.3f} under +/-{drift} cells"
 
         # Map matplotlib elev/azim to a plotly camera eye position
         r = 1.9
@@ -283,7 +532,7 @@ def walk_forward(
     oos_color: str = ORANGE,
     title: Optional[str] = None,
     figsize: Tuple[float, float] = (10, 5),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Walk-forward analysis chart.
@@ -507,7 +756,7 @@ def stability(
     band_alpha: float = 0.15,
     title: Optional[str] = None,
     figsize: Tuple[float, float] = (10, 5),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Parameter stability chart with mean +/- std shaded bands.
@@ -572,7 +821,7 @@ def correlation_matrix(
     annotate: bool = True,
     title: str = "Correlation Matrix",
     figsize: Tuple[float, float] = (8, 7),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Symbol correlation matrix heatmap."""
@@ -652,7 +901,7 @@ def monte_carlo(
     title: Optional[str] = None,
     figsize: Tuple[float, float] = (12, 5),
     seed: Optional[int] = None,
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Monte Carlo fan chart with percentile bands, sample paths, and risk stats.
@@ -805,7 +1054,7 @@ def stochastic_paths(
     band_color: str = ACCENT,
     title: Optional[str] = None,
     figsize: Tuple[float, float] = (12, 5),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
 ) -> go.Figure:
     """Fan chart for stochastic simulation paths with percentile bands.
diff --git a/python/manifoldbt/plot/tearsheet.py b/python/manifoldbt/plot/tearsheet.py
index 5128859..ffbc4a8 100644
--- a/python/manifoldbt/plot/tearsheet.py
+++ b/python/manifoldbt/plot/tearsheet.py
@@ -16,7 +16,7 @@ from manifoldbt.plot._theme import (
     theme_context,
 )
 from manifoldbt.plot._convert import equity_with_dates
-from manifoldbt.plot._utils import auto_title, chart_div, format_pct
+from manifoldbt.plot._utils import auto_title, chart_div, format_pct, resolve_show
 from manifoldbt.plot.backtest import (
     annual_returns,
     drawdown,
@@ -139,7 +139,7 @@ def tearsheet(
     *,
     benchmark=None,
     title: Optional[str] = None,
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
     dpi: int = 150,
     plotlyjs: str = "cdn",
@@ -165,14 +165,16 @@ def tearsheet(
 
     # ── Generate interactive chart divs ────────────────────────────
     with theme_context():
-        div_summary = _div(summary(result), height=520)
-        div_dd = _div(drawdown(result), height=210)
-        div_annual = _div(annual_returns(result), height=330)
-        div_monthly = _div(monthly_returns(result), height=340)
-        div_hist = _div(returns_histogram(result), height=340)
-        div_sharpe = _div(rolling_sharpe(result), height=300)
-        div_vol = _div(rolling_volatility(result), height=300)
-        div_var = _div(var_chart(result), height=340)
+        # show=False on every panel: these are embedded as divs in the page
+        # below, so the auto-show default would open 8 stray windows.
+        div_summary = _div(summary(result, show=False), height=520)
+        div_dd = _div(drawdown(result, show=False), height=210)
+        div_annual = _div(annual_returns(result, show=False), height=330)
+        div_monthly = _div(monthly_returns(result, show=False), height=340)
+        div_hist = _div(returns_histogram(result, show=False), height=340)
+        div_sharpe = _div(rolling_sharpe(result, show=False), height=300)
+        div_vol = _div(rolling_volatility(result, show=False), height=300)
+        div_var = _div(var_chart(result, show=False), height=340)
 
     # ── Metrics ───────────────────────────────────────────────────
     ret = metrics.get("total_return", 0)
@@ -273,7 +275,9 @@ def tearsheet(
     if save is not None:
         Path(save).write_text(html, encoding="utf-8")
 
-    if show:
+    # A report is an HTML page, not a Figure: it always opens in a browser
+    # tab, so "inline" resolves to the same thing here.
+    if resolve_show(show, save):
         if save is not None:
             report_path = Path(save).resolve()
         else:
@@ -295,7 +299,7 @@ def research_report(
     *,
     title: str = "Research Report",
     figsize: tuple = (14, 6),
-    show: bool = False,
+    show: "bool | str | None" = None,
     save: Optional[Union[str, Path]] = None,
     dpi: int = 150,
 ) -> List[Any]:
@@ -309,12 +313,13 @@ def research_report(
     _ = title
     figs = []
     with theme_context():
+        # show=False: this function does its own showing at the end.
         if sweep_result is not None:
-            figs.append(heatmap_2d(sweep_result, figsize=figsize))
+            figs.append(heatmap_2d(sweep_result, figsize=figsize, show=False))
         if wf_result is not None:
-            figs.append(walk_forward(wf_result, figsize=figsize))
+            figs.append(walk_forward(wf_result, figsize=figsize, show=False))
         if stability_result is not None:
-            figs.append(stability(stability_result, figsize=figsize))
+            figs.append(stability(stability_result, figsize=figsize, show=False))
 
     if not figs:
         raise ValueError("At least one result (sweep, wf, or stability) required.")
@@ -330,7 +335,7 @@ def research_report(
             else:
                 scale = max(1.0, dpi / 96.0)
                 f.write_image(str(out), scale=scale)
-    if show:
+    if resolve_show(show, save):
         for f in figs:
             f.show()
 
diff --git a/python/manifoldbt/sweep.py b/python/manifoldbt/sweep.py
index e4a51f1..1f4ffce 100644
--- a/python/manifoldbt/sweep.py
+++ b/python/manifoldbt/sweep.py
@@ -107,7 +107,9 @@ class SweepResult:
 
         df = self.to_df(backend="pandas")
         param_cols = [c for c in df.columns if c.startswith("param_")]
-        show = kwargs.pop("show", True)
+        # None = the auto default (show, unless save= or a notebook); both
+        # branches below hand it to finalize(), which resolves it.
+        show = kwargs.pop("show", None)
         save = kwargs.pop("save", None)
 
         if len(param_cols) == 2:
diff --git a/python/tests/test_golden_buy_and_hold.py b/python/tests/test_golden_buy_and_hold.py
index 0f012d8..cc47a8d 100644
--- a/python/tests/test_golden_buy_and_hold.py
+++ b/python/tests/test_golden_buy_and_hold.py
@@ -11,13 +11,13 @@ import pytest
 import manifoldbt as bt
 from manifoldbt import run_with_parquet
 
-# The golden fixtures were generated at full (Pro) resolution; the Community
-# resolution cap changes the equity-point count and the comparison is
-# meaningless. CI unlocks via BT_UNLOCKED=1 (debug builds); locally this needs
-# an activated Pro license.
+# The golden fixtures assert on 1-second output resolution, below even the Pro
+# floor (60s) — exactly like the Rust golden test, which sets BT_UNLOCKED=1.
+# The override is only honored by debug builds (cargo test / maturin develop),
+# so this needs BOTH: a dev build and BT_UNLOCKED=1 in the environment.
 pytestmark = pytest.mark.skipif(
-    bt.license_info()[0] != "Pro",
-    reason="requires Pro (fixtures generated at sub-daily resolution); activate a license or use a BT_UNLOCKED dev build",
+    os.environ.get("BT_UNLOCKED") != "1",
+    reason="requires BT_UNLOCKED=1 on a dev (debug) build: fixtures assert 1s output, below the Pro 60s floor",
 )
 
 
@@ -38,9 +38,14 @@ def test_golden_buy_and_hold_matches_fixtures(golden_buy_hold_dir):
         universe=[1],
         time_range_start=0,
         time_range_end=4_000_000_000,
-        bar_interval={"Days": 1},
+        # The fixture is 4 bars at 1-second spacing; the Rust golden test runs
+        # them at Seconds(1) with per-bar output. Days(1) would resample the
+        # whole range into a single bar and the comparison would be meaningless.
+        bar_interval={"Seconds": 1},
+        output_resolution={"Seconds": 1},
         initial_capital=1000.0,
         currency="USD",
+        risk_free_rate=0.025,
         execution=bt.ExecutionConfig(
             signal_delay=1,
             execution_price="AtClose",
@@ -92,8 +97,11 @@ def test_golden_buy_and_hold_matches_fixtures(golden_buy_hold_dir):
     with open(os.path.join(golden_buy_hold_dir, "expected_metrics.json")) as f:
         expected_metrics = json.load(f)
 
+    # Mirror the Rust golden test: annualized metrics (CAGR, volatility,
+    # sharpe, sortino, calmar) are not compared because the fixture uses 4
+    # synthetic 1-second bars, making annualization numerically extreme.
     metrics = result.metrics
-    for key in expected_metrics:
+    for key in ("total_return", "max_drawdown"):
         assert abs(metrics[key] - expected_metrics[key]) <= 1e-12, (
             f"Metric {key}: {metrics[key]} != {expected_metrics[key]}"
         )
@@ -102,7 +110,11 @@ def test_golden_buy_and_hold_matches_fixtures(golden_buy_hold_dir):
     with open(os.path.join(golden_buy_hold_dir, "expected_manifest_snapshot.json")) as f:
         expected_manifest = json.load(f)
 
+    # Mirror the Rust golden test: engine_version is excluded from the snapshot
+    # (it tracks the crate version and would break on every release bump);
+    # assert only that it is populated.
     manifest = result.manifest
     assert manifest["strategy_name"] == expected_manifest["strategy_name"]
-    assert manifest["engine_version"] == expected_manifest["engine_version"]
+    assert manifest["engine_version"], "engine_version should be populated"
+    assert manifest["data_versions"].get("bars_1m", "") == expected_manifest["data_version"]
     assert manifest["config"] == expected_manifest["config"]
diff --git a/python/tests/test_import_dataframe.py b/python/tests/test_import_dataframe.py
new file mode 100644
index 0000000..17f0dcc
--- /dev/null
+++ b/python/tests/test_import_dataframe.py
@@ -0,0 +1,164 @@
+"""Tests for bt.import_dataframe — in-memory DataFrame → Arrow IPC store.
+
+The contract under test: import_dataframe is the in-memory twin of
+import_csv. Same data through either path must produce an identical store
+(same backtest results), and the normalisation layer must give clear errors
+for bad inputs instead of a Rust panic.
+"""
+import os
+
+import pytest
+
+import manifoldbt as bt
+
+pd = pytest.importorskip("pandas")
+
+N_BARS = 120
+START_MS = 1_577_836_800_000  # 2020-01-01T00:00:00Z
+
+
+def _bars_df(n=N_BARS, tz="UTC"):
+    """Synthetic 1m bars as a pandas DataFrame."""
+    ts = pd.date_range("2020-01-01", periods=n, freq="1min", tz=tz)
+    close = [100.0 + i * 0.5 for i in range(n)]
+    return pd.DataFrame(
+        {
+            "timestamp": ts,
+            "open": close,
+            "high": [c + 1.0 for c in close],
+            "low": [c - 1.0 for c in close],
+            "close": close,
+            "volume": [10.0] * n,
+        }
+    )
+
+
+def _store_paths(tmp_path, name):
+    root = tmp_path / name
+    return str(root / "data"), str(root / "metadata.sqlite")
+
+
+def _import_df(df, tmp_path, name="df", **kw):
+    data_root, metadata_db = _store_paths(tmp_path, name)
+    os.makedirs(os.path.dirname(metadata_db), exist_ok=True)
+    return bt.import_dataframe(
+        df, symbol="BTCUSDT", symbol_id=1,
+        data_root=data_root, metadata_db=metadata_db, **kw
+    )
+
+
+def _run_buy_and_hold(store):
+    strategy = bt.Strategy(
+        name="bh",
+        signals={"signal": bt.lit(1.0)},
+        position_sizing=bt.col("signal"),
+    )
+    config = bt.BacktestConfig(
+        universe=[1],
+        time_range_start=0,
+        time_range_end=START_MS * 1_000_000 + N_BARS * 60_000_000_000,
+        bar_interval={"Minutes": 1},
+        initial_capital=1000.0,
+        currency="USD",
+        execution=bt.ExecutionConfig(
+            signal_delay=1,
+            execution_price="AtClose",
+            max_position_pct=1.0,
+            allow_short=False,
+            allow_fractional=True,
+            skip_gap_bars=False,
+            position_sizing_mode="Units",
+        ),
+        fees=bt.FeeConfig(),
+        slippage={"FixedBps": {"bps": 0.0}},
+        rng_seed=7,
+    )
+    return bt.run(strategy, config, store)
+
+
+def test_import_dataframe_roundtrip(tmp_path):
+    """DataFrame → store → run produces a usable backtest."""
+    store = _import_df(_bars_df(), tmp_path)
+    assert store.resolve_symbol("BTCUSDT") == 1
+
+    result = _run_buy_and_hold(store)
+    equity = result.equity_curve.to_pylist()
+    assert len(equity) > 0
+    # Price rises monotonically → buy & hold ends above initial capital.
+    assert equity[-1] > 1000.0
+
+
+def test_import_dataframe_matches_import_csv(tmp_path):
+    """Same bars through import_csv and import_dataframe → identical results."""
+    df = _bars_df()
+
+    # CSV path (standard format: epoch-ms timestamp).
+    #
+    # Built from START_MS rather than derived from the datetime column:
+    # `.astype("int64")` returns the underlying integer in the COLUMN's
+    # resolution, which pandas picks for itself. Locally that was ns (so
+    # //1e6 gave ms), on CI it was us (so //1e6 gave seconds) and the import
+    # rejected the row. The bars are 1 minute apart by construction here, so
+    # spelling the epoch out keeps the CSV identical on every pandas.
+    csv_df = df.copy()
+    csv_df["timestamp"] = [START_MS + i * 60_000 for i in range(len(csv_df))]
+    csv_path = tmp_path / "bars.csv"
+    csv_df.to_csv(csv_path, index=False)
+    csv_root, csv_meta = _store_paths(tmp_path, "csv")
+    os.makedirs(os.path.dirname(csv_meta), exist_ok=True)
+    store_csv = bt.import_csv(
+        str(csv_path), symbol="BTCUSDT", symbol_id=1,
+        data_root=csv_root, metadata_db=csv_meta,
+    )
+
+    store_df = _import_df(df, tmp_path)
+
+    res_csv = _run_buy_and_hold(store_csv)
+    res_df = _run_buy_and_hold(store_df)
+    assert res_df.equity_curve.to_pylist() == res_csv.equity_curve.to_pylist()
+    assert res_df.metrics == res_csv.metrics
+
+
+def test_import_dataframe_naive_timestamps_assumed_utc(tmp_path):
+    """tz-naive datetimes are accepted and treated as UTC."""
+    naive = _bars_df(tz=None)
+    aware = _bars_df(tz="UTC")
+    store_naive = _import_df(naive, tmp_path, name="naive")
+    store_aware = _import_df(aware, tmp_path, name="aware")
+    assert _run_buy_and_hold(store_naive).equity_curve.to_pylist() == \
+        _run_buy_and_hold(store_aware).equity_curve.to_pylist()
+
+
+def test_import_dataframe_datetime_index_promoted(tmp_path):
+    """A pandas DatetimeIndex is used as the timestamp column."""
+    df = _bars_df().set_index("timestamp")
+    assert "timestamp" not in df.columns
+    store = _import_df(df, tmp_path)
+    assert store.resolve_symbol("BTCUSDT") == 1
+
+
+def test_import_dataframe_polars(tmp_path):
+    """Polars DataFrames go through the zero-copy to_arrow path."""
+    pl = pytest.importorskip("polars")
+    df = pl.from_pandas(_bars_df())
+    store = _import_df(df, tmp_path)
+    assert store.resolve_symbol("BTCUSDT") == 1
+
+
+def test_import_dataframe_missing_column_raises(tmp_path):
+    df = _bars_df().drop(columns=["volume"])
+    with pytest.raises(bt.DataError, match="volume"):
+        _import_df(df, tmp_path)
+
+
+def test_import_dataframe_integer_timestamp_raises(tmp_path):
+    """Epoch integers are ambiguous (ms? ns?) — require datetimes."""
+    df = _bars_df()
+    df["timestamp"] = df["timestamp"].astype("int64")
+    with pytest.raises(bt.DataError, match="datetime"):
+        _import_df(df, tmp_path)
+
+
+def test_import_dataframe_empty_raises(tmp_path):
+    with pytest.raises(bt.DataError, match="no data rows"):
+        _import_df(_bars_df(0), tmp_path)
diff --git a/python/tests/test_sweep.py b/python/tests/test_sweep.py
index b5023b0..1d3733b 100644
--- a/python/tests/test_sweep.py
+++ b/python/tests/test_sweep.py
@@ -31,7 +31,9 @@ def test_sweep_returns_one_result_per_combo(golden_buy_hold_dir):
         universe=[1],
         time_range_start=0,
         time_range_end=4_000_000_000,
-        bar_interval={"Days": 1},
+        # Fixture bars are 1-second spaced; Days(1) collapses them into a
+        # single bar and signal_delay=1 then never fills → zero trades.
+        bar_interval={"Seconds": 1},
         execution=bt.ExecutionConfig(
             signal_delay=1,
             execution_price="AtClose",
@@ -89,7 +91,7 @@ def test_sweep_golden_grid_deterministic_order(golden_buy_hold_dir):
         universe=[1],
         time_range_start=0,
         time_range_end=4_000_000_000,
-        bar_interval={"Days": 1},
+        bar_interval={"Seconds": 1},
         execution=bt.ExecutionConfig(
             signal_delay=1,
             execution_price="AtClose",
diff --git a/python/tests/test_sweep_validation.py b/python/tests/test_sweep_validation.py
new file mode 100644
index 0000000..18dc56e
--- /dev/null
+++ b/python/tests/test_sweep_validation.py
@@ -0,0 +1,109 @@
+"""Sweeping a parameter the strategy never declares must fail loudly.
+
+It used to be a silent no-op: the unknown name landed in a parameter map
+nothing reads, so every combination ran the same backtest and the sweep
+returned N identical results with no warning. An "optimisation" over
+thousands of combos looked like it had worked.
+
+These tests only exercise the Python-side guard, so they need no data store:
+validation happens before any native call.
+"""
+import pytest
+
+import manifoldbt as bt
+from manifoldbt.exceptions import StrategyError
+from manifoldbt.indicators import close, ema
+
+
+def _declared():
+    """Strategy whose 'fast' comes from mbt.param() inside an indicator."""
+    fast = ema(close, bt.param("fast"))
+    return (
+        bt.Strategy.create("declared")
+        .signal("fast", fast)
+        .size(bt.when(close > fast, 1.0, 0.0))
+    )
+
+
+def _hardcoded():
+    """The shape that caused the bug: the period is a literal, not a param."""
+    fast = ema(close, 12)
+    return (
+        bt.Strategy.create("hardcoded")
+        .signal("fast", fast)
+        .size(bt.when(close > fast, 1.0, 0.0))
+    )
+
+
+def _cfg():
+    # Never reaches the engine: the guard raises before config is used.
+    return bt.BacktestConfig(universe={"binance": ["BTC-USDT:perp"]})
+
+
+def test_sweep_lite_rejects_undeclared_param():
+    with pytest.raises(StrategyError) as exc:
+        bt.run_sweep_lite(_hardcoded(), {"fast": [10, 20, 30]}, _cfg(), None)
+    msg = str(exc.value)
+    assert "fast" in msg
+    # The message must say what to do, not just that it failed.
+    assert "mbt.param" in msg
+
+
+def test_sweep_rejects_undeclared_param():
+    with pytest.raises(StrategyError):
+        bt.run_sweep(_hardcoded(), {"fast": [10, 20]}, _cfg(), None)
+
+
+def test_walk_forward_rejects_undeclared_param():
+    wf = {
+        "method": "Rolling", "n_splits": 2, "train_ratio": 0.7,
+        "optimize_metric": "sharpe", "param_grid": {"fast": [10, 20]},
+    }
+    with pytest.raises((StrategyError, bt.LicenseError)) as exc:
+        bt.run_walk_forward(_hardcoded(), wf, _cfg(), None)
+    # Walk-forward is Pro-gated first; only assert our message when we got past it.
+    if isinstance(exc.value, StrategyError):
+        assert "fast" in str(exc.value)
+
+
+def test_sweep_2d_rejects_undeclared_params():
+    sweep = {
+        "x_param": "fast", "y_param": "slow",
+        "x_values": [5, 10], "y_values": [20, 40], "metric": "sharpe",
+    }
+    with pytest.raises(StrategyError) as exc:
+        bt.run_sweep_2d(_hardcoded(), sweep, _cfg(), None)
+    assert "fast" in str(exc.value) and "slow" in str(exc.value)
+
+
+def test_stability_rejects_undeclared_param():
+    stab = {"param_name": "fast", "values": [5, 10, 15], "metric": "sharpe"}
+    with pytest.raises(StrategyError) as exc:
+        bt.run_stability(_hardcoded(), stab, _cfg(), None)
+    assert "fast" in str(exc.value)
+
+
+def test_declared_param_passes_validation():
+    """A declared param must get past the guard (it then fails on the store)."""
+    with pytest.raises(Exception) as exc:
+        bt.run_sweep_lite(_declared(), {"fast": [10, 20]}, _cfg(), None)
+    # Whatever stops it next, it must not be our guard.
+    assert "not declared" not in str(exc.value)
+
+
+def test_explicit_param_call_counts_as_declared():
+    """.param() declares a name even when no expression references it."""
+    strat = _hardcoded().param("fast", default=12)
+    with pytest.raises(Exception) as exc:
+        bt.run_sweep_lite(strat, {"fast": [10, 20]}, _cfg(), None)
+    assert "not declared" not in str(exc.value)
+
+
+def test_message_lists_only_the_unknown_names():
+    """A mixed grid must blame the unknown name, not the good one."""
+    with pytest.raises(StrategyError) as exc:
+        bt.run_sweep_lite(_declared(), {"fast": [10], "slow": [50]}, _cfg(), None)
+    msg = str(exc.value)
+    assert "slow" in msg
+    # 'fast' is declared, so it must appear as available, never as unknown.
+    assert "['slow']" in msg