docs: add base64 payload finding to SESSION-LOG and CLAUDE.md rules

CLAUDE.md

@@ -204,6 +204,10 @@ git push origin main
 - **ALWAYS** use `storage.exportAll()` (namespaced) or `storage.export(namespace)` (service-level) to batch-load
 - Filter items client-side after a single fetch: `for (const [key, value] of Object.entries(all)) { ... }`
 - After mutations (add/update), either do optimistic local state update or a single `refresh()` — never both
+- **NEVER store large binary data (base64 files) inside entity JSON** — this makes list loading transfer tens of MB
+- For modules with attachments: use `exportAll({ lightweight: true })` for listing, `storage.get()` for single-entry full load
+- The API `?lightweight=true` parameter strips `data`/`fileData` strings >1KB from JSON values server-side
+- Future: move file data to MinIO; only store metadata (name, size, type, url) in the entity JSON
 
 ### Module Development Pattern
 

SESSION-LOG.md

@@ -56,6 +56,24 @@ With 6 registry entries + ~10 contacts + ~20 tags, the Registratura page fired *
 ### Commits
 
 - `c45a30e` perf: fix N+1 query pattern across all modules + rack numbering
+- `c22848b` perf(registratura): lightweight API mode strips base64 attachments from list
+
+### Second Root Cause — Base64 Attachment Payloads (found after first fix)
+
+After deploying the N+1 fix, Registratura STILL loaded in 2+ minutes. Deeper investigation revealed:
+
+**Root cause:** `RegistryAttachment.data` stores full base64-encoded files directly in JSON. A 5MB PDF = ~6.7MB base64. With 6 entries having attachments, `/api/storage?namespace=registratura` returned **30-60MB of JSON** on every page load.
+
+**Fix:** Added `?lightweight=true` parameter to the API route. Server-side `stripHeavyFields()` recursively strips large `data` and `fileData` string fields (>1KB) from JSON, replacing with `"__stripped__"`. List loading now transfers ~100KB. Full entry data loaded on-demand only when editing (single entry = manageable).
+
+**Additional files:**
+
+- `src/app/api/storage/route.ts` — `stripHeavyFields()` + lightweight param
+- `src/core/storage/types.ts` — `export()` accepts `{ lightweight?: boolean }`
+- `src/core/storage/adapters/database-adapter.ts` — passes flag to API
+- `src/modules/registratura/services/registry-service.ts` — `getAllEntries()` uses `lightweight: true`, new `getFullEntry()`
+- `src/modules/registratura/hooks/use-registry.ts` — exports `loadFullEntry()`
+- `src/modules/registratura/components/registratura-module.tsx` — `handleEdit` loads full entry on demand
 
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