diff --git a/pySEQTarget/SEQopts.py b/pySEQTarget/SEQopts.py
index c4fc496..6a6ae88 100644
--- a/pySEQTarget/SEQopts.py
+++ b/pySEQTarget/SEQopts.py
@@ -15,7 +15,7 @@ class SEQopts:
     :type bootstrap_sample: float
     :param bootstrap_CI: If bootstrapped, confidence interval level
     :type bootstrap_CI: float
-    :param bootstrap_CI_method: If bootstrapped, confidence method generation method ['SE' or 'percentile']
+    :param bootstrap_CI_method: If bootstrapped, confidence interval method ['SE' or 'percentile']
     :type bootstrap_CI_method: str
     :param cense_colname: Column name for censoring effect (LTFU, etc.)
     :type cense_colname: str
@@ -109,6 +109,8 @@ class SEQopts:
     :type weight_p99: bool
     :param weight_preexpansion: Boolean to fit weights on preexpanded data
     :type weight_preexpansion: bool
+    :param verbose: Boolean to print dataset size summaries and bootstrap information
+    :type verbose: bool
     :param weighted: Boolean to weight analysis
     :type weighted: bool
     """
@@ -163,6 +165,7 @@ class SEQopts:
     weight_lag_condition: bool = True
     weight_p99: bool = False
     weight_preexpansion: bool = True
+    verbose: bool = False
     weighted: bool = False
 
     def _validate_bools(self):
@@ -178,6 +181,7 @@ def _validate_bools(self):
             "selection_first_trial",
             "selection_random",
             "trial_include",
+            "verbose",
             "weight_lag_condition",
             "weight_p99",
             "weight_preexpansion",
diff --git a/pySEQTarget/SEQoutput.py b/pySEQTarget/SEQoutput.py
index cdc11eb..0bff491 100644
--- a/pySEQTarget/SEQoutput.py
+++ b/pySEQTarget/SEQoutput.py
@@ -62,7 +62,7 @@ class SEQoutput:
 
     def plot(self) -> None:
         """
-        Displays the kaplan-meier graph
+        Displays the Kaplan-Meier graph
         """
         if self.km_graph is None:
             raise ValueError(
diff --git a/pySEQTarget/SEQuential.py b/pySEQTarget/SEQuential.py
index a6ebaf7..c46cb61 100644
--- a/pySEQTarget/SEQuential.py
+++ b/pySEQTarget/SEQuential.py
@@ -114,6 +114,13 @@ def expand(self):
         :class:`polars.DataFrame` and skips all subsequent analysis steps.
         """
         start = time.perf_counter()
+
+        if self.verbose:
+            n, m = self.data.shape
+            print(f"Full dataset: {n:,} observations, {m} variables")
+            n_elig = self.data.filter(pl.col(self.eligible_col) == 1).shape[0]
+            print(f"Eligible observations: {n_elig:,}")
+
         kept = [
             self.cense_colname,
             self.cense_eligible_colname,
@@ -162,14 +169,25 @@ def expand(self):
             pl.col(self.id_col).cast(pl.Utf8).alias(self.id_col)
         )
 
+        if self.verbose:
+            n, m = self.DT.shape
+            print(f"Expanded dataset: {n:,} observations, {m} variables")
+
         if self.method == "dose-response" or (
             self.method == "censoring" and not self.expand_only
         ):
             _dynamic(self)
         if self.selection_random:
             _random_selection(self)
+            if self.verbose:
+                n, m = self.DT.shape
+                print(f"Sampled expanded dataset: {n:,} observations, {m} variables")
         _diagnostics(self)
 
+        if self.verbose:
+            n, m = self.DT.shape
+            print(f"Final analysis dataset: {n:,} observations, {m} variables")
+
         end = time.perf_counter()
         self._expansion_time = _format_time(start, end)
 
@@ -200,6 +218,16 @@ def bootstrap(self, **kwargs) -> None:
         )
         NIDs = len(UIDs)
 
+        if self.verbose:
+            n_sample = round(self.bootstrap_sample * NIDs)
+            n_obs_sample = round(self.bootstrap_sample * len(self.DT))
+            print(
+                f"Bootstrapping with {self.bootstrap_sample * 100:.4g}% of "
+                f"{NIDs:,} subjects "
+                f"({n_sample:,} subjects, ~{n_obs_sample:,} observations per resample) "
+                f"{self.bootstrap_nboot} times"
+            )
+
         self._boot_samples = []
         for _ in range(self.bootstrap_nboot):
             sampled_IDs = self._rng.choice(
@@ -244,8 +272,23 @@ def fit(self) -> None:
             _weight_bind(self, WDT)
             self.weight_stats = _weight_stats(self)
 
+        is_boot = boot_idx is not None
+        start = getattr(self, "_outcome_start_params", None) if is_boot else None
+
         if self.subgroup_colname is not None:
-            return _subgroup_fit(self)
+            models_list = _subgroup_fit(self, start_params=start)
+            if not is_boot:
+                self._outcome_start_params = {
+                    val: {
+                        key: (m.params.values, list(m.model.exog_names))
+                        for key, m in sg.items()
+                    }
+                    for val, sg in zip(self._unique_subgroups, models_list)
+                }
+            return models_list
+
+        start_outcome = (start or {}).get("outcome")
+        start_compevent = (start or {}).get("compevent")
 
         models = {
             "outcome": _outcome_fit(
@@ -255,6 +298,7 @@ def fit(self) -> None:
                 self.covariates,
                 self.weighted,
                 "weight",
+                start_params=start_outcome,
             )
         }
         if self.compevent_colname is not None:
@@ -265,7 +309,15 @@ def fit(self) -> None:
                 self.covariates,
                 self.weighted,
                 "weight",
+                start_params=start_compevent,
             )
+
+        if not is_boot:
+            self._outcome_start_params = {
+                k: (m.params.values, list(m.model.exog_names))
+                for k, m in models.items()
+            }
+
         if self.offload:
             offloaded_models = {}
             for key, model in models.items():
@@ -332,7 +384,7 @@ def plot(self, **kwargs) -> None:
 
     def collect(self) -> SEQoutput:
         """
-        Collects all results current created into ``SEQoutput`` class
+        Collects all results currently created into ``SEQoutput`` class
         """
         self._time_collected = datetime.datetime.now()
 
diff --git a/pySEQTarget/analysis/_hazard.py b/pySEQTarget/analysis/_hazard.py
index 0062fc8..64613fd 100644
--- a/pySEQTarget/analysis/_hazard.py
+++ b/pySEQTarget/analysis/_hazard.py
@@ -182,7 +182,7 @@ def _hazard_handler(self, data, idx, boot_idx, rng):
     sim_data_pd = sim_data.to_pandas()
 
     try:
-        # COXPHFITER CURRENTLY HAS DEPRECATED datetime.datetime.utcnow()
+        # COXPHFITTER CURRENTLY HAS DEPRECATED datetime.datetime.utcnow()
         warnings.filterwarnings("ignore", message=".*datetime.datetime.utcnow.*")
         if ce_model is not None:
             cox_data = sim_data_pd[sim_data_pd["event"].isin([0, 1])].copy()
diff --git a/pySEQTarget/analysis/_outcome_fit.py b/pySEQTarget/analysis/_outcome_fit.py
index a0fdda6..ed049a4 100644
--- a/pySEQTarget/analysis/_outcome_fit.py
+++ b/pySEQTarget/analysis/_outcome_fit.py
@@ -68,6 +68,7 @@ def _outcome_fit(
     formula: str,
     weighted: bool = False,
     weight_col: str = "weight",
+    start_params=None,
 ):
     if weighted:
         df = df.with_columns(
@@ -102,5 +103,23 @@ def _outcome_fit(
         glm_kwargs["var_weights"] = df_pd[weight_col]
 
     model = smf.glm(**glm_kwargs)
-    model_fit = model.fit()
+
+    # Drop warm-start coefs unless the design matrix columns match exactly
+    # by name — bootstrap resamples can shift categorical reference levels or
+    # column ordering, in which case the cached coefs are meaningless and
+    # IRLS can diverge into NaN/Inf and crash LAPACK.
+    if start_params is not None:
+        sp_values, sp_names = start_params
+        if list(model.exog_names) != list(sp_names):
+            start_params = None
+        else:
+            start_params = sp_values
+
+    try:
+        model_fit = model.fit(start_params=start_params)
+    except Exception:
+        if start_params is not None:
+            model_fit = model.fit()
+        else:
+            raise
     return model_fit
diff --git a/pySEQTarget/analysis/_subgroup_fit.py b/pySEQTarget/analysis/_subgroup_fit.py
index fd481cf..e78e19d 100644
--- a/pySEQTarget/analysis/_subgroup_fit.py
+++ b/pySEQTarget/analysis/_subgroup_fit.py
@@ -3,17 +3,24 @@
 from ._outcome_fit import _outcome_fit
 
 
-def _subgroup_fit(self):
+def _subgroup_fit(self, start_params=None):
     subgroups = sorted(self.DT[self.subgroup_colname].unique().to_list())
     self._unique_subgroups = subgroups
 
     models_list = []
     for val in subgroups:
         subDT = self.DT.filter(pl.col(self.subgroup_colname) == val)
+        sg_start = (start_params or {}).get(val, {}) or {}
 
         models = {
             "outcome": _outcome_fit(
-                self, subDT, self.outcome_col, self.covariates, self.weighted, "weight"
+                self,
+                subDT,
+                self.outcome_col,
+                self.covariates,
+                self.weighted,
+                "weight",
+                start_params=sg_start.get("outcome"),
             )
         }
 
@@ -25,6 +32,7 @@ def _subgroup_fit(self):
                 self.covariates,
                 self.weighted,
                 "weight",
+                start_params=sg_start.get("compevent"),
             )
         models_list.append(models)
     return models_list
diff --git a/pySEQTarget/analysis/_survival_pred.py b/pySEQTarget/analysis/_survival_pred.py
index 48b7e56..ac9a4ef 100644
--- a/pySEQTarget/analysis/_survival_pred.py
+++ b/pySEQTarget/analysis/_survival_pred.py
@@ -1,5 +1,8 @@
+import numpy as np
 import polars as pl
+from patsy import PatsyError, dmatrix
 
+from ..helpers._fix_categories import _fix_categories_for_predict
 from ..helpers._predict_model import _safe_predict
 from ._outcome_fit import _cast_categories
 
@@ -25,20 +28,79 @@ def _store_boot_risks(obj, treatment_val, TxDT, boot_cols, is_survival=False):
     )
 
 
+def _build_design_matrix(design_info, data):
+    """
+    Build a design matrix from a cached design_info, applying the same
+    category-alignment fallback that _safe_predict uses on mismatch.
+    """
+    try:
+        return np.asarray(dmatrix(design_info, data))
+    except PatsyError as e:
+        if "mismatching levels" not in str(e):
+            raise
+
+        # Reuse the existing fix by wrapping design_info in a stub object
+        class _Stub:
+            class model:
+                class data:
+                    pass
+
+        stub = _Stub()
+        stub.model.data.design_info = design_info
+        fixed = _fix_categories_for_predict(stub, data.copy())
+        return np.asarray(dmatrix(design_info, fixed))
+
+
+def _cached_predict(model, X_cached, ref_column_names, data):
+    """
+    Predict using a pre-built design matrix when the model's design_info
+    column structure matches the reference, falling back to patsy via
+    _safe_predict on mismatch (e.g. a bootstrap resample that dropped a
+    categorical level).
+    """
+    dinfo = model.model.data.design_info
+    if list(dinfo.column_names) == ref_column_names:
+        probs = np.asarray(model.predict(X_cached, transform=False))
+        if not np.any(np.isnan(probs)):
+            return np.clip(probs, 0, 1)
+    return _safe_predict(model, data)
+
+
 def _get_outcome_predictions(self, TxDT, idx=None):
     data = _cast_categories(self, TxDT.to_pandas())
     predictions = {"outcome": []}
     if self.compevent_colname is not None:
         predictions["compevent"] = []
 
+    # Pre-build the design matrix once using the main fit's design_info.
+    # Each bootstrap model that shares the same column structure can then
+    # reuse it, skipping patsy entirely on the predict path.
+    main = self.outcome_model[0]
+    main_dict = main[idx] if idx is not None else main
+    main_outcome = self._offloader.load_model(main_dict["outcome"])
+    outcome_dinfo = main_outcome.model.data.design_info
+    X_outcome = _build_design_matrix(outcome_dinfo, data)
+    outcome_cols = list(outcome_dinfo.column_names)
+
+    X_compevent = compevent_cols = None
+    if self.compevent_colname is not None:
+        main_compevent = self._offloader.load_model(main_dict["compevent"])
+        compevent_dinfo = main_compevent.model.data.design_info
+        X_compevent = _build_design_matrix(compevent_dinfo, data)
+        compevent_cols = list(compevent_dinfo.column_names)
+
     for boot_model in self.outcome_model:
         model_dict = boot_model[idx] if idx is not None else boot_model
         outcome_model = self._offloader.load_model(model_dict["outcome"])
-        predictions["outcome"].append(_safe_predict(outcome_model, data))
+        predictions["outcome"].append(
+            _cached_predict(outcome_model, X_outcome, outcome_cols, data)
+        )
 
         if self.compevent_colname is not None:
             compevent_model = self._offloader.load_model(model_dict["compevent"])
-            predictions["compevent"].append(_safe_predict(compevent_model, data))
+            predictions["compevent"].append(
+                _cached_predict(compevent_model, X_compevent, compevent_cols, data)
+            )
 
     return predictions
 
diff --git a/pySEQTarget/error/_data_checker.py b/pySEQTarget/error/_data_checker.py
index 15c0817..217be1c 100644
--- a/pySEQTarget/error/_data_checker.py
+++ b/pySEQTarget/error/_data_checker.py
@@ -31,8 +31,8 @@ def _data_checker(self):
     invalid = check.filter(pl.col("row_count") != pl.col("max_time") + 1)
     if len(invalid) > 0:
         raise ValueError(
-            f"Data validation failed: {len(invalid)} ID(s) have mismatched "
-            f"This suggests invalid times"
+            f"Data validation failed: {len(invalid)} ID(s) have mismatched row counts. "
+            f"This suggests invalid times. "
             f"Invalid IDs:\n{invalid}"
         )
 
diff --git a/pySEQTarget/error/_param_checker.py b/pySEQTarget/error/_param_checker.py
index 66492cb..fcacad4 100644
--- a/pySEQTarget/error/_param_checker.py
+++ b/pySEQTarget/error/_param_checker.py
@@ -1,3 +1,5 @@
+import warnings
+
 from ..helpers import _pad
 
 
@@ -26,13 +28,13 @@ def _param_checker(self):
 
     if len(self.excused_colnames) == 0 and self.excused:
         self.excused = False
-        raise Warning(
+        warnings.warn(
             "Excused column names not provided but excused is set to True. Automatically set excused to False"
         )
 
     if len(self.excused_colnames) > 0 and not self.excused:
         self.excused = True
-        raise Warning(
+        warnings.warn(
             "Excused column names provided but excused is set to False. Automatically set excused to True"
         )
 
diff --git a/pySEQTarget/expansion/_binder.py b/pySEQTarget/expansion/_binder.py
index 3b5a723..4e10271 100644
--- a/pySEQTarget/expansion/_binder.py
+++ b/pySEQTarget/expansion/_binder.py
@@ -5,7 +5,7 @@
 
 def _binder(self, kept_cols):
     """
-    Internal function to bind data to the map created by __mapper
+    Internal function to bind data to the map created by _mapper
     """
     excluded = {
         "dose",
diff --git a/pySEQTarget/expansion/_dynamic.py b/pySEQTarget/expansion/_dynamic.py
index 8d1918f..52060a8 100644
--- a/pySEQTarget/expansion/_dynamic.py
+++ b/pySEQTarget/expansion/_dynamic.py
@@ -3,7 +3,7 @@
 
 def _dynamic(self):
     """
-    Handles special cases for the data from the __mapper -> __binder pipeline
+    Handles special cases for the data from the _mapper -> _binder pipeline
     """
     if self.method == "dose-response":
         DT = self.DT.with_columns(
diff --git a/pyproject.toml b/pyproject.toml
index 73035e1..0eb1343 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pySEQTarget"
-version = "0.13.3"
+version = "0.13.4"
 description = "Sequentially Nested Target Trial Emulation"
 readme = "README.md"
 license = {text = "MIT"}
diff --git a/tests/test_expansion.py b/tests/test_expansion.py
index eac5b39..1a27261 100644
--- a/tests/test_expansion.py
+++ b/tests/test_expansion.py
@@ -2,6 +2,7 @@
 from polars.testing import assert_frame_equal
 
 from pySEQTarget import SEQopts, SEQuential
+from pySEQTarget.data import load_data
 
 
 def _make_model(data):
@@ -126,3 +127,59 @@ def test_expand_only_returns_expanded_dataframe():
     model_full.expand()
 
     assert_frame_equal(result, model_full.DT)
+
+
+def _make_verbose_model(verbose, **extra_opts):
+    data = load_data("SEQdata")
+    return SEQuential(
+        data,
+        id_col="ID",
+        time_col="time",
+        eligible_col="eligible",
+        treatment_col="tx_init",
+        outcome_col="outcome",
+        time_varying_cols=["N", "L", "P"],
+        fixed_cols=["sex"],
+        method="ITT",
+        parameters=SEQopts(verbose=verbose, **extra_opts),
+    )
+
+
+def test_verbose_expand(capsys):
+    s = _make_verbose_model(verbose=True)
+    s.expand()
+    out = capsys.readouterr().out
+    assert "Full dataset:" in out
+    assert "Eligible observations:" in out
+    assert "Expanded dataset:" in out
+    assert "Final analysis dataset:" in out
+    assert "Sampled expanded dataset:" not in out
+    assert "observations" in out
+    assert "variables" in out
+
+
+def test_verbose_expand_with_sampling(capsys):
+    s = _make_verbose_model(verbose=True, selection_random=True, selection_sample=0.5)
+    s.expand()
+    out = capsys.readouterr().out
+    assert "Sampled expanded dataset:" in out
+
+
+def test_verbose_bootstrap(capsys):
+    s = _make_verbose_model(verbose=True, bootstrap_nboot=10)
+    s.expand()
+    capsys.readouterr()
+    s.bootstrap()
+    out = capsys.readouterr().out
+    assert "Bootstrapping" in out
+    assert "subjects" in out
+    assert "observations per resample" in out
+    assert "10 times" in out
+
+
+def test_verbose_false_no_output(capsys):
+    s = _make_verbose_model(verbose=False, bootstrap_nboot=5)
+    s.expand()
+    s.bootstrap()
+    out = capsys.readouterr().out
+    assert out == ""