diff --git a/.project/tasks/m2b-full-ecosystem/README.md b/.project/tasks/m2b-full-ecosystem/README.md
index 20269688..844aa4ad 100644
--- a/.project/tasks/m2b-full-ecosystem/README.md
+++ b/.project/tasks/m2b-full-ecosystem/README.md
@@ -116,7 +116,7 @@ Tune `biome_trait_weights.json` so each biome generates ecologically appropriate
 
 ### Block 4: Full Sprite Generation
 
-**Agent**: `godot-renderer` | **Blockers**: Block 1 (trait weights defined → species generated → proof_species.json updated)
+**Agent**: `godot-renderer` | **Blockers**: Block 1 (trait weights defined → species generated → proof_species.json updated) + `tools/sprite-generation/IN_DEVELOPMENT_DONT_USE` must not exist (sentinel file — check before any scan/generate/install, poll periodically if blocked)
 
 | # | Task | Description |
 |---|------|-------------|