diff --git a/scripts/sim_fitness_2x2.py b/scripts/sim_fitness_2x2.py
index 8481ab9..c21aa4f 100644
--- a/scripts/sim_fitness_2x2.py
+++ b/scripts/sim_fitness_2x2.py
@@ -6,8 +6,16 @@
 rng = np.random.default_rng()
 N = 80
 GROUPS = ["ProgramA","ProgramB"]
+DEFAULT_SEED = 7
+
+def simulate(n_per_group=None, seed=DEFAULT_SEED):
+    global rng, N
+    # Allow overriding globals via args, primarily for testing
+    if n_per_group is not None:
+        N = n_per_group * len(GROUPS) # Adjust N based on n_per_group
+    
+    rng = np.random.default_rng(seed)
 
-def simulate():
     os.makedirs("data/synthetic", exist_ok=True)
     subjects = pd.DataFrame({
         "id": np.arange(1, N+1),
@@ -39,7 +47,7 @@ def simulate():
     long.to_csv("data/synthetic/fitness_long.csv", index=False)
 
     meta = dict(
-        seed=int(getattr(rng, "seed_seq", np.random.SeedSequence()).entropy) if hasattr(rng, "seed_seq") else None,
+        seed=seed,
         n=int(N),
         design="2x2 mixed (Group between × Time within)",
         programs=GROUPS,
@@ -50,15 +58,17 @@ def simulate():
         json.dump(meta, f, indent=2)
 
     print("Wrote fitness_subjects.csv, fitness_long.csv, fitness_meta.json")
+    # Return for testing convenience
+    return subjects, long
 
 def main():
     ap = argparse.ArgumentParser()
-    ap.add_argument("--seed", type=int, default=7, help="RNG seed")
-    ap.add_argument("--n-per-group", type=int, default=5, help="(kept for CLI parity; not used here)")
+    ap.add_argument("--seed", type=int, default=DEFAULT_SEED, help="RNG seed")
+    ap.add_argument("--n-per-group", type=int, default=40, help="Number of subjects per group")
     args = ap.parse_args()
-    global rng
-    rng = np.random.default_rng(args.seed)
-    simulate()
+    
+    # Pass CLI args to simulate
+    simulate(n_per_group=args.n_per_group, seed=args.seed)
 
 if __name__ == "__main__":
     main()
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diff --git a/scripts/sim_stroop.py b/scripts/sim_stroop.py
index 6162de9..607b69e 100644
--- a/scripts/sim_stroop.py
+++ b/scripts/sim_stroop.py
@@ -12,7 +12,7 @@
 import pandas as pd
 
 RNG_SEED = 42
-rng = np.random.default_rng(RNG_SEED)
+rng = np.random.default_rng(RNG_SEED) # Will be reset by simulate()
 
 N_SUBJ = 60
 N_TRIALS_PER_COND = 100
@@ -37,7 +37,15 @@
 OUTLIER_RT_LAPSE_SD = 200
 RT_FLOOR = 80
 
-def simulate():
+def simulate(n_subjects=N_SUBJ, n_trials=N_TRIALS_PER_COND, seed=RNG_SEED):
+    global rng, N_SUBJ, N_TRIALS_PER_COND, RNG_SEED
+    
+    # Set globals based on args, primarily for testing
+    N_SUBJ = n_subjects
+    N_TRIALS_PER_COND = n_trials
+    RNG_SEED = seed
+    rng = np.random.default_rng(RNG_SEED)
+    
     os.makedirs("data/synthetic", exist_ok=True)
 
     # subject-level covariates
@@ -93,7 +101,10 @@ def simulate():
     subjects.to_csv("data/synthetic/psych_stroop_subjects.csv", index=False)
     trials.to_csv("data/synthetic/psych_stroop_trials.csv", index=False)
     print("Wrote data/synthetic/psych_stroop_subjects.csv and psych_stroop_trials.csv")
-
+    
+    # Write meta *after* simulation is done
+    write_meta(subjects, trials)
+    
     return subjects, trials
 
 def write_meta(subjects: pd.DataFrame, trials: pd.DataFrame):
@@ -138,17 +149,14 @@ def write_meta(subjects: pd.DataFrame, trials: pd.DataFrame):
 
 def main():
     ap = argparse.ArgumentParser()
-    ap.add_argument("--seed", type=int, default=42)
-    ap.add_argument("--n-subjects", type=int, default=60)
-    ap.add_argument("--n-trials", type=int, default=100)
+    ap.add_argument("--seed", type=int, default=RNG_SEED)
+    ap.add_argument("--n-subjects", type=int, default=N_SUBJ)
+    ap.add_argument("--n-trials", type=int, default=N_TRIALS_PER_COND)
     args = ap.parse_args()
-    global N_SUBJ, N_TRIALS_PER_COND, rng, RNG_SEED
-    N_SUBJ = args.n_subjects
-    N_TRIALS_PER_COND = args.n_trials
-    RNG_SEED = args.seed
-    rng = np.random.default_rng(RNG_SEED)
-    subjects_df, trials_df = simulate()
-    write_meta(subjects_df, trials_df)
+    
+    # Pass CLI args to simulate
+    simulate(n_subjects=args.n_subjects, n_trials=args.n_trials, seed=args.seed)
+
 
 if __name__ == "__main__":
     main()
\ No newline at end of file