ARC Brain — decisions log

Choices where the master spec said "choose", plus deviations from the letter of the spec to fit ARC.

Date	Decision	Choice	Why
2026-07-29	Primary store	New Prisma models (Note, Folder, Link, …), not ClaudeContext	Spec N1–N4; ClaudeContext is append-only keyed memory
2026-07-29	ClaudeContext	Keep permanently as LLM memory	User: still useful as pure LLM memory; no absorb/delete migration. Spec §18.3 out of scope
2026-07-29	HTTP base	/api/v1/brain via registerVersionedRoute	Match existing ARC API versioning (/api/brain legacy alias also registered)
2026-07-29	Module layout	server/src/modules/brain/* + thin routes/brain*.routes.ts + mcp/brain.tools.ts	Spec module boundary without rewriting all of ARC
2026-07-29	Table naming	@@map("snake_case")	Existing ARC Prisma convention
2026-07-29	Soft delete	Brain models only	Do not retrofit rest of ARC
2026-07-29	Vault root	server/data/vault in dev; /data/vault in Docker; override via BrainSettings.vaultPath / env	Spec default + local-friendly path
2026-07-30	MCP brain tools (core set)	brain_capture, brain_write, brain_read, brain_search, brain_append, brain_resolve, brain_backlinks, brain_daily, folder list/create/move	Enough for agent-first capture; remaining §16 tools in later phase
2026-07-30	Core brain_* always on	requiresPermissionToggle: false for capture/read/search/append/resolve/backlinks/daily/folder_list	Make Brain the default knowledge path without Tool Permissions toggles
2026-07-30	Settings LLM prompts	Recommended + new Brain block + narrowed Context scratch	Steer Claude to Brain for knowledge; context_* for agent prefs only
2026-07-30	In-app coach prompt	SystemPromptBuilder prefers brain_* for knowledge	Same policy as MCP copy-paste prompts
2026-07-30	Vault sync deps	chokidar + p-queue (p-queue reserved for queue polish)	Spec Phase 3; disable via ARC_BRAIN_FILE_SYNC=0
2026-07-30	Note composition	Host notes compose via ![[…]] embeds + arc-* fences; brain_include / brain_split	Notion/Obsidian multi-content: databases/graphs are notes (or views) that can be included or split out
2026-07-30	Vault rename safety	Deferred unlink (2s) + folder hash rename-pair + reattach by frontmatter id	Obsidian folder/file rename must not destroy note ids
2026-07-30	Editor delivery	CM6 + / slash commands + [[ autocomplete + rich preview	Preview renders embeds, mermaid, YouTube/iframe/gif, callouts
2026-07-30	Excalidraw	Excalidraw editor UI on canvas page (autosave + JSON escape hatch)	Scene JSON on Canvas.data
2026-07-30	Public note pages	Per-note isPublished + publicSlug; /brain/p/:slug renders page only	Linked notes / private embeds sealed on public view
2026-07-30	Entity linking UX	API about links + MCP brain_entity_types/brain_notes_about/brain_publish + UI search/slash for all types	Make Person→People (and every type) easy from API/MCP/UI
2026-07-29	Timezone	Europe/Amsterdam at edges; UTC in DB	Spec + existing ARC patterns
2026-07-30	Task due dates	Task.dueDate / priority / completedAt shipped	Was deferred; now on model + API/MCP
2026-07-30	Vault git	gitEnabled + remote + auto-commit after vault writes	Optional; off by default
2026-07-30	Embeddings	Local hash embeddings + hybrid RRF; docker image pgvector/pgvector:pg15	External embedding APIs optional later
2026-07-30	Live editor	Split Live mode (CM6 + rich preview side-by-side)	Full TipTap WYSIWYG not required for vault value
2026-07-30	Interactive views	ArcViewWidget runs /brain/views/run with filter + row links	Replaces static fence dump in preview
2026-07-29	Vector / pgvector	Float[] embeddings + optional pgvector image	App-level cosine when extension absent
2026-07-29	SocialInteraction name	Map to existing Interaction model	ARC schema name differs from spec
2026-07-29	Indexer transport	In-process async queue with backoff (not pg-boss yet)	Non-blocking; failed index must never fail domain writes. May move to pg-boss later — log if changed
2026-07-29	Day ownership	Index via Day.week.userId	Day has no direct userId