diff --git a/justfile b/justfile
index 8fc5ec3..ac87713 100644
--- a/justfile
+++ b/justfile
@@ -167,8 +167,6 @@ build-substrate MODES="run_tests,exit_code,sentinel":
 # erase/route substrate run, add --v-hack-path explicitly.
 run-substrate INTERV="none" SEED="41" STEPS="60" REFRESH="5" MASK="act":
     {{ TRAIN }} fast --intervention={{ INTERV }} \
-        --teacher-pool-dir=out/pools/substrate \
-        --vhack-pairs-path=out/pairsets/prog_wide.json \
         --vhack-refresh-every={{ REFRESH }} --route2-mask={{ MASK }} \
         --seed={{ SEED }} --steps={{ STEPS }} --out-tag=_sub4_{{ INTERV }}_{{ MASK }}_rf{{ REFRESH }}_s{{ SEED }}
 
diff --git a/src/projected_grpo/train.py b/src/projected_grpo/train.py
index 615d627..3fa11d8 100644
--- a/src/projected_grpo/train.py
+++ b/src/projected_grpo/train.py
@@ -284,6 +284,10 @@ class FastConfig(Config):
     at pp=4 x 20 steps)."""
     model: str = "Qwen/Qwen3-4B"
     steps: int = 60                   # sane new-env default (was 20; 60 lets the gap open at convergence)
+    # current experiment line: 4-mode substrate pool + prog_wide persona pairs are the
+    # default so real runs need only --intervention (+ optional seed/refresh/mask).
+    teacher_pool_dir: Path | None = Path("out/pools/substrate")
+    vhack_pairs_path: Path | None = Path("out/pairsets/prog_wide.json")
     group: int = 8                    # G=8 so the locked-in mix_ratio=0.125 gives 1 teacher / 7 student
     max_new: int = 512
     n_problems: int = 200