refine app foundation

PLAN.md

@@ -18,6 +18,7 @@ sessions, tools, and turn orchestration.
 | Model runtime | Preferences only | Persisted model choice, DFlash toggle, and idle timeout | Downloads, loading, inference, idle unloading, and Metal integration |
 | Local endpoint | Not started | Nothing listening | OpenAI-compatible HTTP and streaming surfaces |
 | Agent | UI shell only | Empty conversation pane and composer placeholder | Messages, generation, tools, approvals, compaction, and cancellation |
+| Dev brain | Not started | No vault access | Obsidian vault selection, durable access, and agent knowledge/memory tools |
 | Release | Not started | Development binary builds and tests | `.app` packaging, signing, entitlements, and notarization |
 
 The application currently manages durable project/session metadata and model
@@ -184,6 +185,7 @@ visual placeholders with no message or agent runtime behind them.
    - file write
    - anchored edit
    - text/file search
+   - opt-in Dev Brain knowledge lookup and memory storage
 4. Stream assistant tokens and partial tool calls into Iced while inference and
    tools run on workers. Preserve cooperative interruption and a valid KV
    prefix at every stop point.
@@ -193,9 +195,33 @@ visual placeholders with no message or agent runtime behind them.
 6. Port context compaction and system-prompt reinjection after ordinary
    multi-turn operation is correct.
 
+### Dev Brain — Obsidian knowledge and memory
+
+- Add an optional Dev Brain setting in Preferences. Use the native macOS folder
+  picker to select an existing Obsidian vault, allow the vault to be changed or
+  disconnected, and persist its canonical path plus a security-scoped bookmark
+  in SQLite so sandboxed builds can regain access after restart.
+- Keep the vault global to the application rather than tied to one project or
+  session. The selected vault remains in its original location; never copy it
+  into Application Support or a project directory.
+- Add one local `dev_brain` agent tool with the minimum useful operations:
+  search Markdown notes, read a selected note, and create or append a memory
+  note. Return vault-relative paths with results so the agent can cite where
+  knowledge came from.
+- Restrict every operation to the explicitly selected vault. Resolve and check
+  paths before access, ignore `.obsidian` and hidden files, and do not provide
+  deletion or arbitrary overwrite operations initially.
+- Let the agent retrieve relevant global knowledge during a turn and record
+  durable conclusions after a turn. Vault access is opt-in, does not preload the
+  model, and must not block sessions when no vault is configured or available.
+- Reuse the existing local file/search implementation underneath the new vault
+  boundary instead of building a second filesystem stack.
+
 Exit criterion: create a project session, ask the model to inspect and edit a
 small fixture repository, review each tool result in the GUI, restart, and
-continue from the persisted session.
+continue from the persisted session. With Dev Brain enabled, store a memory in
+one session and retrieve it with a cited vault-relative note path from a session
+in another project after restarting the app.
 
 ## Verification and packaging
 
@@ -223,3 +249,5 @@ tests, and release packaging remain open.
    chats and HTTP requests cannot load duplicate engines.
 4. Add transcript/KV persistence, then connect the existing conversation UI and
    finally port the agent tools.
+5. Add the opt-in Dev Brain tool after local file/search boundaries and agent
+   approvals are stable.