diff --git a/MODULE_SPEC.md b/MODULE_SPEC.md
new file mode 100644
index 0000000..a02cf39
--- /dev/null
+++ b/MODULE_SPEC.md
@@ -0,0 +1,32 @@
+# rStack — Developer Platform
+
+**Module ID:** `rstack`
+**Domain:** `rstack.online`
+**Version:** 0.1.0
+**Framework:** Static HTML/CSS
+**Status:** Landing page only
+
+## Purpose
+
+Developer hub and documentation portal for the r*.online ecosystem. Aggregates API docs, SDK references, and deployment guides. Currently a static landing page.
+
+## Permission Model
+
+No auth needed — public documentation site.
+
+### Future Capabilities (when CLI/API tools added)
+
+| Capability | Required SpaceRole | Description |
+|-----------|-------------------|-------------|
+| `view_docs` | VIEWER | Read documentation |
+| `deploy_space` | PARTICIPANT | Create/deploy new spaces |
+| `manage_infrastructure` | ADMIN | Configure ecosystem settings |
+
+## Canvas Integration
+
+None — standalone site.
+
+## Migration Plan
+
+1. Add EncryptID auth when developer tools are built
+2. Add API key management for inter-module service calls