This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Anchor AppView is a location-based social feed generator built on AT Protocol. The system uses a PDS-only architecture where all checkin data is read directly from users' Personal Data Servers, with minimal local storage used only for OAuth session management.

Critical architectural constraint: This system does NOT store checkin data locally. All checkins are:

1. Created directly in users' PDS via AT Protocol com.atproto.repo.createRecord
2. Read on-demand from PDS via com.atproto.repo.getRecord and com.atproto.repo.listRecords
3. Never cached or persisted in local database

Exception for Likes and Comments: While checkins remain PDS-only, likes and comments use a hybrid architecture with local indexing for performance:

• Like/comment records are stored in users' PDS (fully decentralized)
• A local index (checkin_interactions and checkin_counts tables) tracks interactions for efficient discovery and counting
• Index is updated when likes/comments are created/deleted through this AppView
• Trade-off: External likes/comments (created directly via PDS) won't appear until indexed
• Future: Background sync process could crawl for external interactions

Local database storage:

• iron_session_storage: OAuth session management
• checkin_interactions: Index of likes/comments for efficient queries
• checkin_counts: Aggregated counts per checkin for performance

• Main file: main.tsx (deployed to Val Town with // @val-town anchordashboard comment)
• Base URL: https://dropanchor.app (configurable via ANCHOR_BASE_URL)
• Framework: Hono web server serving unified API, OAuth, and React frontend
• Runtime: Deno on Val Town platform

OAuth Authentication (backend/routes/oauth.ts, backend/oauth/):

• Uses custom package jsr:@tijs/atproto-oauth-hono@^0.3.0
• Provides web and mobile (iOS) authentication flows
• Mobile: Custom URL scheme anchor-app://auth-callback
• Session storage via Drizzle ORM with SQLite
• Automatic token refresh and DPoP handling built into OAuth sessions

Checkin API (backend/api/checkins.ts):

• Creates checkins via AT Protocol createRecord with immediate PDS writes
• Two-record pattern: address record + checkin record with StrongRef
• Optional image attachments uploaded as blobs to user's PDS
• Image validation via magic numbers, EXIF stripping for privacy
• Address enhancement via Overpass API (OpenStreetMap)
• Authentication via Bearer tokens (mobile) or cookies (web)
• Supports both JSON and multipart/form-data (for images)

Feed API (backend/api/anchor-api.ts):

• Reads checkins directly from users' PDS
• Spatial queries, user feeds, following feeds
• No local database reads for checkin data

Likes and Comments API (backend/api/likes.ts, backend/api/comments.ts):

• Creates likes/comments via AT Protocol createRecord in user's PDS
• Updates local index for efficient discovery
• Authentication via OAuth session with automatic token refresh
• Uses OAuth session's makeRequest() for all PDS communication
• REST endpoints: /api/checkins/:did/:rkey/likes and /api/checkins/:did/:rkey/comments

Database Layer (backend/database/):

• Drizzle ORM with sqlite-proxy adapter
• Schema: backend/database/schema.ts (OAuth sessions + interaction indexes)
• Migrations: backend/database/migrations.ts

# Run all tests (unit + integration)
deno task test
# or
./scripts/test.sh

# Run only unit tests
deno task test:unit

# Run only integration tests
deno task test:integration

# Watch mode for TDD
deno task test:watch

# Format, lint, type check, and test
deno task quality

# Quality check without type checking (faster)
deno task quality-no-check

# Individual checks
deno fmt              # Format code
deno lint             # Lint code
deno check --allow-import   # Type check

# Deploy to Val Town (runs quality checks first)
deno task deploy

# Manual deployment
vt push

CRITICAL: Always use sqlite2, not the deprecated sqlite module.

// ✅ CORRECT
import { sqlite } from "https://esm.town/v/std/sqlite2";

const result = await sqlite.execute({
  sql: "SELECT * FROM users WHERE id = ?",
  args: [userId],
});

// ❌ WRONG - old deprecated module
import { sqlite } from "https://esm.town/v/std/sqlite";
await sqlite.execute("SELECT * FROM users", [userId]);

This project uses Drizzle ORM with the sqlite-proxy adapter to wrap Val Town's sqlite2:

// See backend/database/db.ts for the adapter implementation
export const db = drizzle(
  async (sql, params) => {
    const result = await sqlite.execute({ sql, args: params || [] });
    return { rows: result.rows };
  },
  { schema },
);

When adding new tables:

1. Define schema in backend/database/schema.ts using Drizzle syntax
2. Create migration SQL in backend/database/migrations.ts
3. Tables auto-create on startup via initializeTables() in main.tsx

Never hardcode secrets:

const secret = Deno.env.get("COOKIE_SECRET");
const baseUrl = Deno.env.get("ANCHOR_BASE_URL") || "https://dropanchor.app";

• Use https://esm.sh for npm packages
• Use jsr: for JSR packages (Hono, atproto-oauth-hono)
• Use https://esm.town/v/std/ for Val Town utilities

The OAuth system uses a custom package that handles:

• PKCE flow with automatic PDS discovery
• DPoP (Demonstrating Proof of Possession) tokens
• Token refresh logic
• Mobile and web authentication modes
• Session storage via Drizzle adapter

import { createATProtoOAuth } from "jsr:@tijs/atproto-oauth-hono@^0.3.0";

const oauth = createATProtoOAuth({
  baseUrl: BASE_URL,
  cookieSecret: COOKIE_SECRET,
  mobileScheme: "anchor-app://auth-callback",
  sessionTtl: 60 * 60 * 24 * 30, // 30 days
  storage, // DrizzleStorage instance
});

// Export for use in other modules
export const oauthRoutes = oauth.routes; // Hono routes
export const sessions = oauth.sessions; // Session management API

OAuth sessions provide automatic token refresh and DPoP handling:

const oauthSession = await sessions.getOAuthSession(did);
if (!oauthSession) {
  return { error: "No session" };
}

// makeRequest handles token refresh and DPoP automatically
const response = await oauthSession.makeRequest(
  "POST",
  `${oauthSession.pdsUrl}/xrpc/com.atproto.repo.createRecord`,
  {
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ repo: did, collection: "...", record: {...} })
  }
);

Never manually construct Authorization headers - always use oauthSession.makeRequest().

Checkin record (app.dropanchor.checkin):

{
  $type: "app.dropanchor.checkin",
  text: string,
  createdAt: string,  // ISO8601
  addressRef: StrongRef,  // Reference to address record
  coordinates: { latitude: number, longitude: number },
  category?: string,
  categoryGroup?: string,
  categoryIcon?: string
}

Address record (community.lexicon.location.address):

{
  $type: "community.lexicon.location.address",
  name?: string,
  street?: string,
  locality?: string,
  region?: string,
  country?: string,
  postalCode?: string
}

Like record (app.dropanchor.like):

{
  $type: "app.dropanchor.like",
  createdAt: string,  // ISO8601
  checkinRef: StrongRef  // Reference to the liked checkin
}

Comment record (app.dropanchor.comment):

{
  $type: "app.dropanchor.comment",
  text: string,  // Max 1000 characters
  createdAt: string,  // ISO8601
  checkinRef: StrongRef  // Reference to the commented checkin
}

Checkins reference addresses via StrongRefs (CID + URI):

addressRef: {
  uri: "at://did:plc:abc123/community.lexicon.location.address/3k2...",
  cid: "bafyreicv3pecq6fuua22xcoguxep76otivb33nlaofzl76fpagczo5t5jm"
}

This ensures data integrity via content-addressing.

POST   /api/checkins                    Create checkin
GET    /api/checkins/:did                Get all checkins for user
GET    /api/checkins/:did/:rkey          Get specific checkin
DELETE /api/checkins/:did/:rkey          Delete checkin

GET    /api/checkins/:did/:rkey/likes       Get likes for checkin
POST   /api/checkins/:did/:rkey/likes       Like a checkin (requires auth)
DELETE /api/checkins/:did/:rkey/likes       Unlike a checkin (requires auth)

GET    /api/checkins/:did/:rkey/comments    Get comments for checkin
POST   /api/checkins/:did/:rkey/comments    Comment on checkin (requires auth)
DELETE /api/checkins/:did/:rkey/comments    Delete comment (requires auth)

GET /api/nearby?lat=52.0&lng=4.3&radius=5&limit=50     Spatial query
GET /api/user?did=did:plc:abc123&limit=50              User's checkins
GET /api/following?user=did:plc:abc123&limit=50        Following feed

GET  /login                         Initiate OAuth (web)
GET  /oauth/callback                OAuth redirect handler
POST /api/checkins                  Create checkin (requires auth)
GET  /api/auth/session              Session validation
POST /api/auth/logout               Session cleanup

GET /api/stats                      System health metrics
GET /api/places/nearby              OpenStreetMap POI search via Overpass
GET /api/places/categories          Category system for mobile apps

The project has comprehensive test coverage with two categories:

Unit tests (tests/unit/):

• Test individual functions in isolation
• Mock external dependencies (AT Protocol, Overpass API, OAuth)
• Focus on business logic correctness

Integration tests (tests/integration/):

• Test full request/response cycles
• Mock Val Town services (sqlite, blob storage) but test real code paths
• Validate API contract and error handling

Key testing patterns:

• Use assertAlmostEquals for floating-point coordinate calculations
• Mock OAuth sessions for authenticated endpoint tests
• Test both success and error cases
• Validate TypeScript types with proper inference

1. Add route to main.tsx:

app.get("/api/newfeature", async (c) => {
  return await anchorApiHandler(c.req.raw);
});

2. Handle in backend/api/anchor-api.ts or create new handler file

3. Add integration test in tests/integration/api.test.ts

OAuth is configured in backend/routes/oauth.ts:

const oauth = createATProtoOAuth({
  baseUrl: BASE_URL, // Public base URL
  cookieSecret: COOKIE_SECRET, // Session encryption
  mobileScheme: "anchor-app://auth-callback",
  sessionTtl: 60 * 60 * 24 * 30, // 30 days
  storage, // Drizzle storage adapter
});

Never modify the package's internal logic - all customization via config.

Always use OAuth sessions for PDS requests:

// ✅ CORRECT - automatic token refresh and DPoP
const oauthSession = await sessions.getOAuthSession(did);
const response = await oauthSession.makeRequest(
  "POST",
  `${oauthSession.pdsUrl}/xrpc/com.atproto.repo.createRecord`,
  { headers: {...}, body: JSON.stringify({...}) }
);

// ❌ WRONG - manual token handling breaks DPoP and refresh logic
const response = await fetch(`${pdsUrl}/xrpc/...`, {
  headers: { "Authorization": `Bearer ${accessToken}` }
});

The system supports iOS app integration via WebView OAuth flow:

1. iOS app opens WebView to https://dropanchor.app/login?handle=user.bsky.social
2. User completes OAuth in WebView
3. Success page triggers anchor-app://auth-callback with session data
4. iOS app extracts session and closes WebView

anchor-app://auth-callback?
  access_token=...
  &refresh_token=...
  &did=...
  &handle=...
  &session_id=...
  &pds_url=...
  &avatar=...
  &display_name=...

• Register anchor-app URL scheme in Info.plist
• Set WebView User-Agent to "AnchorApp" for detection
• Use Bearer token authentication: Authorization: Bearer {session_id}
• Store tokens securely in iOS Keychain

# Run debug script to inspect OAuth sessions
deno run --allow-net scripts/debug-oauth-sessions.ts

Or check via API endpoint:

GET https://dropanchor.app/api/debug/oauth-sessions

All PDS requests go through OAuth session's makeRequest(). Enable logging:

console.log("PDS request:", {
  method,
  url,
  pdsUrl: oauthSession.pdsUrl,
  did: oauthSession.did,
});

If deployment fails:

1. Check Val Town CLI is authenticated: vt whoami
2. Verify deno.json tasks work locally: deno task quality
3. Check Val Town dashboard for runtime errors
4. Verify environment variables are set correctly

DO NOT create local database tables for checkin data. The PDS-only architecture is intentional:

• Checkins live in users' PDS (decentralized, user-controlled)
• AppView reads on-demand (no sync lag, no stale data)
• Only OAuth sessions stored locally (for authentication)

If you need to cache data, use Val Town blob storage with TTL, not SQLite.

Always follow AT Protocol patterns:

• Use com.atproto.repo.* XRPC methods for record operations
• Respect StrongRef pattern for references between records
• Include proper $type fields in all records
• Use ISO8601 timestamps with Z suffix

• No API keys or secrets in code - only Deno.env.get()
• OAuth sessions are encrypted with Iron Session
• Mobile sessions use sealed tokens (not raw JWTs)
• CORS headers on all public API endpoints

Originally designed as a traditional AppView with background ingestion and local database caching. Now migrated to PDS-only architecture where:

• No background crawlers or ingestion workers
• No local checkin tables (checkins_v1, address_cache_v1, etc. removed)
• Direct PDS reads provide fresh data with user control

Comments and variable names may reference old architecture - these are safe to update.