fix(backend): handle remove() during in-flight session creation

Cancel pending getOrCreate when remove() is called mid-flight.
Destroy the resulting session to prevent it from leaking.

Co-authored-by: Ona <no-reply@ona.com>

.github/workflows/build-waitlist-website.yml

@@ -0,0 +1,42 @@
+name: Build waitlist website
+
+on:
+  push:
+    branches: [master]
+    paths:
+      - apps/waitlist-website/**
+      - .github/workflows/build-waitlist-website.yml
+
+  workflow_dispatch:
+
+env:
+  REGISTRY: cr.nym.sh
+  IMAGE_NAME: aelis-waitlist-website
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Log in to container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_PASSWORD }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: apps/waitlist-website
+          push: true
+          tags: |
+            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
+            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max

.github/workflows/test.yml

@@ -21,4 +21,4 @@ jobs:
         run: bun install --frozen-lockfile
 
       - name: Run tests
-        run: bun test
+        run: bun run test

.ona/automations.yaml

@@ -1,8 +1,8 @@
 services:
   expo:
     name: Expo Dev Server
-    description: Expo development server for aris-client
+    description: Expo development server for aelis-client
     triggeredBy:
       - postDevcontainerStart
     commands:
-      start: cd apps/aris-client && ./scripts/run-dev-server.sh
+      start: cd apps/aelis-client && ./scripts/run-dev-server.sh

AGENTS.md

@@ -2,7 +2,7 @@
 
 ## Project
 
-ARIS is an AI-powered personal assistant that aggregates data from various sources into a contextual feed. Monorepo with `packages/` (shared libraries) and `apps/` (applications).
+AELIS is an AI-powered personal assistant that aggregates data from various sources into a contextual feed. Monorepo with `packages/` (shared libraries) and `apps/` (applications).
 
 ## Commands
 

README.md

@@ -1,4 +1,4 @@
-# aris
+# aelis
 
 To install dependencies:
 
@@ -8,14 +8,14 @@ bun install
 
 ## Packages
 
-### @aris/source-tfl
+### @aelis/source-tfl
 
 TfL (Transport for London) feed source for tube, overground, and Elizabeth line alerts.
 
 #### Testing
 
 ```bash
-cd packages/aris-source-tfl
+cd packages/aelis-source-tfl
 bun run test
 ```
 

apps/aelis-backend/.env.example

@@ -7,6 +7,11 @@ BETTER_AUTH_SECRET=
 # Base URL of the backend
 BETTER_AUTH_URL=http://localhost:3000
 
+# OpenRouter (LLM feed enhancement)
+OPENROUTER_API_KEY=
+# Optional: override the default model (default: openai/gpt-4.1-mini)
+# OPENROUTER_MODEL=openai/gpt-4.1-mini
+
 # Apple WeatherKit credentials
 WEATHERKIT_PRIVATE_KEY=
 WEATHERKIT_KEY_ID=

apps/aelis-backend/package.json

@@ -1,5 +1,5 @@
 {
-	"name": "@aris/backend",
+	"name": "@aelis/backend",
 	"version": "0.0.0",
 	"type": "module",
 	"main": "src/server.ts",
@@ -9,10 +9,13 @@
 		"test": "bun test src/"
 	},
 	"dependencies": {
-		"@aris/core": "workspace:*",
-		"@aris/source-location": "workspace:*",
-		"@aris/source-tfl": "workspace:*",
-		"@aris/source-weatherkit": "workspace:*",
+		"@aelis/core": "workspace:*",
+		"@aelis/source-caldav": "workspace:*",
+		"@aelis/source-google-calendar": "workspace:*",
+		"@aelis/source-location": "workspace:*",
+		"@aelis/source-tfl": "workspace:*",
+		"@aelis/source-weatherkit": "workspace:*",
+		"@openrouter/sdk": "^0.9.11",
 		"arktype": "^2.1.29",
 		"better-auth": "^1",
 		"hono": "^4",

apps/aelis-backend/src/auth/session-middleware.ts

@@ -61,7 +61,7 @@ export async function getSessionFromHeaders(
 }
 
 /**
- * Test-only middleware that injects a fake user and session.
+ * Dev/test middleware that injects a fake user and session.
  * Pass userId to simulate an authenticated request, or omit to get 401.
  */
 export function mockAuthSessionMiddleware(userId?: string): AuthSessionMiddleware {
@@ -69,8 +69,34 @@ export function mockAuthSessionMiddleware(userId?: string): AuthSessionMiddlewar
 		if (!userId) {
 			return c.json({ error: "Unauthorized" }, 401)
 		}
-		c.set("user", { id: userId } as AuthUser)
-		c.set("session", { id: "mock-session" } as AuthSession)
+
+		const now = new Date()
+		const expiresAt = new Date(now.getTime() + 7 * 24 * 60 * 60 * 1000)
+
+		const user: AuthUser = {
+			id: "k7Gx2mPqRvNwYs9TdLfA4bHcJeUo1iZn",
+			name: "Dev User",
+			email: "dev@aelis.local",
+			emailVerified: true,
+			image: null,
+			createdAt: now,
+			updatedAt: now,
+		}
+
+		const session: AuthSession = {
+			id: "Wt3FvBpXaQrMhD8sKjE6LcYn0gUz5iRo",
+			userId: "k7Gx2mPqRvNwYs9TdLfA4bHcJeUo1iZn",
+			token: "Vb9CxNfRm2KwQs7TjPeA5dLhYg0UoZi4",
+			expiresAt,
+			ipAddress: "127.0.0.1",
+			userAgent: "aelis-dev",
+			createdAt: now,
+			updatedAt: now,
+		}
+
+		c.set("user", user)
+		c.set("session", session)
+
 		await next()
 	}
 }

apps/aelis-backend/src/engine/http.test.ts

@@ -0,0 +1,336 @@
+import type { ActionDefinition, ContextEntry, FeedItem, FeedSource } from "@aelis/core"
+
+import { contextKey } from "@aelis/core"
+import { describe, expect, spyOn, test } from "bun:test"
+import { Hono } from "hono"
+
+import { mockAuthSessionMiddleware } from "../auth/session-middleware.ts"
+import { UserSessionManager } from "../session/index.ts"
+import { registerFeedHttpHandlers } from "./http.ts"
+
+interface FeedResponse {
+	items: Array<{
+		id: string
+		type: string
+		priority: number
+		timestamp: string
+		data: Record<string, unknown>
+	}>
+	errors: Array<{ sourceId: string; error: string }>
+}
+
+function createStubSource(
+	id: string,
+	items: FeedItem[] = [],
+	contextEntries: readonly ContextEntry[] | null = null,
+): FeedSource {
+	return {
+		id,
+		async listActions(): Promise<Record<string, ActionDefinition>> {
+			return {}
+		},
+		async executeAction(): Promise<unknown> {
+			return undefined
+		},
+		async fetchContext(): Promise<readonly ContextEntry[] | null> {
+			return contextEntries
+		},
+		async fetchItems() {
+			return items
+		},
+	}
+}
+
+function buildTestApp(sessionManager: UserSessionManager, userId?: string) {
+	const app = new Hono()
+	registerFeedHttpHandlers(app, {
+		sessionManager,
+		authSessionMiddleware: mockAuthSessionMiddleware(userId),
+	})
+	return app
+}
+
+describe("GET /api/feed", () => {
+	test("returns 401 without auth", async () => {
+		const manager = new UserSessionManager({ providers: [] })
+		const app = buildTestApp(manager)
+
+		const res = await app.request("/api/feed")
+
+		expect(res.status).toBe(401)
+	})
+
+	test("returns cached feed when available", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "test",
+				type: "test",
+				priority: 0.8,
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: 42 },
+			},
+		]
+		const manager = new UserSessionManager({
+			providers: [async () => createStubSource("test", items)],
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		// Prime the cache
+		const session = await manager.getOrCreate("user-1")
+		await session.engine.refresh()
+		expect(session.engine.lastFeed()).not.toBeNull()
+
+		const res = await app.request("/api/feed")
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as FeedResponse
+		expect(body.items).toHaveLength(1)
+		expect(body.items[0]!.id).toBe("item-1")
+		expect(body.items[0]!.type).toBe("test")
+		expect(body.items[0]!.priority).toBe(0.8)
+		expect(body.items[0]!.timestamp).toBe("2025-01-01T00:00:00.000Z")
+		expect(body.errors).toHaveLength(0)
+	})
+
+	test("forces refresh when no cached feed", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "fresh-1",
+				sourceId: "test",
+				type: "test",
+				priority: 0.5,
+				timestamp: new Date("2025-06-01T12:00:00.000Z"),
+				data: { fresh: true },
+			},
+		]
+		const manager = new UserSessionManager({
+			providers: [async () => createStubSource("test", items)],
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		// No prior refresh — lastFeed() returns null, handler should call refresh()
+		const res = await app.request("/api/feed")
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as FeedResponse
+		expect(body.items).toHaveLength(1)
+		expect(body.items[0]!.id).toBe("fresh-1")
+		expect(body.items[0]!.data.fresh).toBe(true)
+		expect(body.errors).toHaveLength(0)
+	})
+
+	test("serializes source errors as message strings", async () => {
+		const failingSource: FeedSource = {
+			id: "failing",
+			async listActions() {
+				return {}
+			},
+			async executeAction() {
+				return undefined
+			},
+			async fetchContext() {
+				return null
+			},
+			async fetchItems() {
+				throw new Error("connection timeout")
+			},
+		}
+		const manager = new UserSessionManager({ providers: [async () => failingSource] })
+		const app = buildTestApp(manager, "user-1")
+
+		const res = await app.request("/api/feed")
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as FeedResponse
+		expect(body.items).toHaveLength(0)
+		expect(body.errors).toHaveLength(1)
+		expect(body.errors[0]!.sourceId).toBe("failing")
+		expect(body.errors[0]!.error).toBe("connection timeout")
+	})
+
+	test("returns 503 when all providers fail", async () => {
+		const manager = new UserSessionManager({
+			providers: [
+				async () => {
+					throw new Error("provider down")
+				},
+			],
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		const spy = spyOn(console, "error").mockImplementation(() => {})
+
+		const res = await app.request("/api/feed")
+
+		expect(res.status).toBe(503)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toBe("Service unavailable")
+
+		spy.mockRestore()
+	})
+})
+
+describe("GET /api/context", () => {
+	const weatherKey = contextKey("aelis.weather", "weather")
+	const weatherData = { temperature: 20, condition: "Clear" }
+	const contextEntries: readonly ContextEntry[] = [[weatherKey, weatherData]]
+
+	// The mock auth middleware always injects this hardcoded user ID
+	const mockUserId = "k7Gx2mPqRvNwYs9TdLfA4bHcJeUo1iZn"
+
+	async function buildContextApp(userId?: string) {
+		const manager = new UserSessionManager({
+			providers: [async () => createStubSource("weather", [], contextEntries)],
+		})
+		const app = buildTestApp(manager, userId)
+		const session = await manager.getOrCreate(mockUserId)
+		return { app, session }
+	}
+
+	test("returns 401 without auth", async () => {
+		const manager = new UserSessionManager({ providers: [] })
+		const app = buildTestApp(manager)
+
+		const res = await app.request('/api/context?key=["aelis.weather","weather"]')
+
+		expect(res.status).toBe(401)
+	})
+
+	test("returns 400 when key param is missing", async () => {
+		const { app } = await buildContextApp("user-1")
+
+		const res = await app.request("/api/context")
+
+		expect(res.status).toBe(400)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("key")
+	})
+
+	test("returns 400 when key is invalid JSON", async () => {
+		const { app } = await buildContextApp("user-1")
+
+		const res = await app.request("/api/context?key=notjson")
+
+		expect(res.status).toBe(400)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("key")
+	})
+
+	test("returns 400 when key is not an array", async () => {
+		const { app } = await buildContextApp("user-1")
+
+		const res = await app.request('/api/context?key="string"')
+
+		expect(res.status).toBe(400)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("key")
+	})
+
+	test("returns 400 when key contains invalid element types", async () => {
+		const { app } = await buildContextApp("user-1")
+
+		const res = await app.request("/api/context?key=[true,null,[1,2]]")
+
+		expect(res.status).toBe(400)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("key")
+	})
+
+	test("returns 400 when key is an empty array", async () => {
+		const { app } = await buildContextApp("user-1")
+
+		const res = await app.request("/api/context?key=[]")
+
+		expect(res.status).toBe(400)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("key")
+	})
+
+	test("returns 400 when match param is invalid", async () => {
+		const { app } = await buildContextApp("user-1")
+
+		const res = await app.request('/api/context?key=["aelis.weather"]&match=invalid')
+
+		expect(res.status).toBe(400)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("match")
+	})
+
+	test("returns exact match with match=exact", async () => {
+		const { app, session } = await buildContextApp("user-1")
+		await session.engine.refresh()
+
+		const res = await app.request('/api/context?key=["aelis.weather","weather"]&match=exact')
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as { match: string; value: unknown }
+		expect(body.match).toBe("exact")
+		expect(body.value).toEqual(weatherData)
+	})
+
+	test("returns 404 with match=exact when only prefix would match", async () => {
+		const { app, session } = await buildContextApp("user-1")
+		await session.engine.refresh()
+
+		const res = await app.request('/api/context?key=["aelis.weather"]&match=exact')
+
+		expect(res.status).toBe(404)
+	})
+
+	test("returns prefix match with match=prefix", async () => {
+		const { app, session } = await buildContextApp("user-1")
+		await session.engine.refresh()
+
+		const res = await app.request('/api/context?key=["aelis.weather"]&match=prefix')
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as {
+			match: string
+			entries: Array<{ key: unknown[]; value: unknown }>
+		}
+		expect(body.match).toBe("prefix")
+		expect(body.entries).toHaveLength(1)
+		expect(body.entries[0]!.key).toEqual(["aelis.weather", "weather"])
+		expect(body.entries[0]!.value).toEqual(weatherData)
+	})
+
+	test("default mode returns exact match when available", async () => {
+		const { app, session } = await buildContextApp("user-1")
+		await session.engine.refresh()
+
+		const res = await app.request('/api/context?key=["aelis.weather","weather"]')
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as { match: string; value: unknown }
+		expect(body.match).toBe("exact")
+		expect(body.value).toEqual(weatherData)
+	})
+
+	test("default mode falls back to prefix when no exact match", async () => {
+		const { app, session } = await buildContextApp("user-1")
+		await session.engine.refresh()
+
+		const res = await app.request('/api/context?key=["aelis.weather"]')
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as {
+			match: string
+			entries: Array<{ key: unknown[]; value: unknown }>
+		}
+		expect(body.match).toBe("prefix")
+		expect(body.entries).toHaveLength(1)
+		expect(body.entries[0]!.value).toEqual(weatherData)
+	})
+
+	test("returns 404 when neither exact nor prefix matches", async () => {
+		const { app, session } = await buildContextApp("user-1")
+		await session.engine.refresh()
+
+		const res = await app.request('/api/context?key=["nonexistent"]')
+
+		expect(res.status).toBe(404)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toBe("Context key not found")
+	})
+})

apps/aelis-backend/src/engine/http.ts

@@ -0,0 +1,133 @@
+import type { Context, Hono } from "hono"
+
+import { contextKey } from "@aelis/core"
+import { createMiddleware } from "hono/factory"
+
+import type { AuthSessionMiddleware } from "../auth/session-middleware.ts"
+import type { UserSessionManager } from "../session/index.ts"
+
+type Env = {
+	Variables: {
+		sessionManager: UserSessionManager
+	}
+}
+
+interface FeedHttpHandlersDeps {
+	sessionManager: UserSessionManager
+	authSessionMiddleware: AuthSessionMiddleware
+}
+
+export function registerFeedHttpHandlers(
+	app: Hono,
+	{ sessionManager, authSessionMiddleware }: FeedHttpHandlersDeps,
+) {
+	const inject = createMiddleware<Env>(async (c, next) => {
+		c.set("sessionManager", sessionManager)
+		await next()
+	})
+
+	app.get("/api/feed", inject, authSessionMiddleware, handleGetFeed)
+	app.get("/api/context", inject, authSessionMiddleware, handleGetContext)
+}
+
+async function handleGetFeed(c: Context<Env>) {
+	const user = c.get("user")!
+	const sessionManager = c.get("sessionManager")
+
+	let session
+	try {
+		session = await sessionManager.getOrCreate(user.id)
+	} catch (err) {
+		console.error("[handleGetFeed] Failed to create session:", err)
+		return c.json({ error: "Service unavailable" }, 503)
+	}
+
+	const feed = await session.feed()
+
+	return c.json({
+		items: feed.items,
+		errors: feed.errors.map((e) => ({
+			sourceId: e.sourceId,
+			error: e.error.message,
+		})),
+	})
+}
+
+async function handleGetContext(c: Context<Env>) {
+	const keyParam = c.req.query("key")
+	if (!keyParam) {
+		return c.json({ error: 'Invalid or missing "key" parameter: must be a JSON array' }, 400)
+	}
+
+	let parsed: unknown
+	try {
+		parsed = JSON.parse(keyParam)
+	} catch {
+		return c.json({ error: 'Invalid or missing "key" parameter: must be a JSON array' }, 400)
+	}
+
+	if (!Array.isArray(parsed) || parsed.length === 0 || !parsed.every(isContextKeyPart)) {
+		return c.json({ error: 'Invalid or missing "key" parameter: must be a JSON array' }, 400)
+	}
+
+	const matchParam = c.req.query("match")
+	if (matchParam !== undefined && matchParam !== "exact" && matchParam !== "prefix") {
+		return c.json({ error: 'Invalid "match" parameter: must be "exact" or "prefix"' }, 400)
+	}
+
+	const user = c.get("user")!
+	const sessionManager = c.get("sessionManager")
+
+	let session
+	try {
+		session = await sessionManager.getOrCreate(user.id)
+	} catch (err) {
+		console.error("[handleGetContext] Failed to create session:", err)
+		return c.json({ error: "Service unavailable" }, 503)
+	}
+
+	const context = session.engine.currentContext()
+	const key = contextKey(...parsed)
+
+	if (matchParam === "exact") {
+		const value = context.get(key)
+		if (value === undefined) {
+			return c.json({ error: "Context key not found" }, 404)
+		}
+		return c.json({ match: "exact", value })
+	}
+
+	if (matchParam === "prefix") {
+		const entries = context.find(key)
+		if (entries.length === 0) {
+			return c.json({ error: "Context key not found" }, 404)
+		}
+		return c.json({ match: "prefix", entries })
+	}
+
+	// Default: single find() covers both exact and prefix matches
+	const entries = context.find(key)
+	if (entries.length === 0) {
+		return c.json({ error: "Context key not found" }, 404)
+	}
+
+	// If exactly one result with the same key length, treat as exact match
+	if (entries.length === 1 && entries[0]!.key.length === parsed.length) {
+		return c.json({ match: "exact", value: entries[0]!.value })
+	}
+
+	return c.json({ match: "prefix", entries })
+}
+
+/** Validates that a value is a valid ContextKeyPart (string, number, or plain object of primitives). */
+function isContextKeyPart(value: unknown): boolean {
+	if (typeof value === "string" || typeof value === "number") {
+		return true
+	}
+	if (typeof value === "object" && value !== null && !Array.isArray(value)) {
+		return Object.values(value).every(
+			(v) => typeof v === "string" || typeof v === "number" || typeof v === "boolean",
+		)
+	}
+	return false
+}

apps/aelis-backend/src/enhancement/enhance-feed.ts

@@ -0,0 +1,51 @@
+import type { FeedItem } from "@aelis/core"
+
+import type { LlmClient } from "./llm-client.ts"
+
+import { mergeEnhancement } from "./merge.ts"
+import { buildPrompt, hasUnfilledSlots } from "./prompt-builder.ts"
+
+/** Takes feed items, returns enhanced feed items. */
+export type FeedEnhancer = (items: FeedItem[]) => Promise<FeedItem[]>
+
+export interface FeedEnhancerConfig {
+	client: LlmClient
+	/** Defaults to Date.now — override for testing */
+	clock?: () => Date
+}
+
+/**
+ * Creates a FeedEnhancer that uses the provided LlmClient.
+ *
+ * Skips the LLM call when no items have unfilled slots.
+ * Returns items unchanged on LLM failure.
+ */
+export function createFeedEnhancer(config: FeedEnhancerConfig): FeedEnhancer {
+	const { client } = config
+	const clock = config.clock ?? (() => new Date())
+
+	return async function enhanceFeed(items) {
+		if (!hasUnfilledSlots(items)) {
+			return items
+		}
+
+		const currentTime = clock()
+		const { systemPrompt, userMessage } = buildPrompt(items, currentTime)
+
+		let result
+		try {
+			result = await client.enhance({ systemPrompt, userMessage })
+		} catch (err) {
+			console.error("[enhancement] LLM call failed:", err)
+			result = null
+		}
+
+		if (!result) {
+			return items
+		}
+
+		return mergeEnhancement(items, result, currentTime)
+	}
+}
+
+

apps/aelis-backend/src/enhancement/llm-client.ts

@@ -0,0 +1,71 @@
+import { OpenRouter } from "@openrouter/sdk"
+
+import type { EnhancementResult } from "./schema.ts"
+
+import { enhancementResultJsonSchema, parseEnhancementResult } from "./schema.ts"
+
+const DEFAULT_MODEL = "openai/gpt-4.1-mini"
+const DEFAULT_TIMEOUT_MS = 30_000
+
+export interface LlmClientConfig {
+	apiKey: string
+	model?: string
+	timeoutMs?: number
+}
+
+export interface LlmClientRequest {
+	systemPrompt: string
+	userMessage: string
+}
+
+export interface LlmClient {
+	enhance(request: LlmClientRequest): Promise<EnhancementResult | null>
+}
+
+/**
+ * Creates a reusable LLM client backed by OpenRouter.
+ * The OpenRouter SDK instance is created once and reused across calls.
+ */
+export function createLlmClient(config: LlmClientConfig): LlmClient {
+	const client = new OpenRouter({
+		apiKey: config.apiKey,
+		timeoutMs: config.timeoutMs ?? DEFAULT_TIMEOUT_MS,
+	})
+	const model = config.model ?? DEFAULT_MODEL
+
+	return {
+		async enhance(request) {
+			const response = await client.chat.send({
+				chatGenerationParams: {
+					model,
+					messages: [
+						{ role: "system" as const, content: request.systemPrompt },
+						{ role: "user" as const, content: request.userMessage },
+					],
+					responseFormat: {
+						type: "json_schema" as const,
+						jsonSchema: {
+							name: "enhancement_result",
+							strict: true,
+							schema: enhancementResultJsonSchema,
+						},
+					},
+					stream: false,
+				},
+			})
+
+			const content = response.choices?.[0]?.message?.content
+			if (typeof content !== "string") {
+				console.warn("[enhancement] LLM returned no content in response")
+				return null
+			}
+
+			const result = parseEnhancementResult(content)
+			if (!result) {
+				console.warn("[enhancement] Failed to parse LLM response:", content)
+			}
+
+			return result
+		},
+	}
+}

apps/aelis-backend/src/enhancement/merge.test.ts

@@ -0,0 +1,151 @@
+import type { FeedItem } from "@aelis/core"
+
+import { describe, expect, test } from "bun:test"
+
+import type { EnhancementResult } from "./schema.ts"
+
+import { mergeEnhancement } from "./merge.ts"
+
+function makeItem(overrides: Partial<FeedItem> = {}): FeedItem {
+	return {
+		id: "item-1",
+		sourceId: "test",
+		type: "test",
+		timestamp: new Date("2025-01-01T00:00:00Z"),
+		data: { value: 42 },
+		...overrides,
+	}
+}
+
+const now = new Date("2025-06-01T12:00:00Z")
+
+describe("mergeEnhancement", () => {
+	test("fills matching slots", () => {
+		const item = makeItem({
+			slots: {
+				insight: { description: "Weather insight", content: null },
+			},
+		})
+		const result: EnhancementResult = {
+			slotFills: {
+				"item-1": { insight: "Rain after 3pm" },
+			},
+			syntheticItems: [],
+		}
+
+		const merged = mergeEnhancement([item], result, now)
+
+		expect(merged).toHaveLength(1)
+		expect(merged[0]!.slots!.insight!.content).toBe("Rain after 3pm")
+		// Description preserved
+		expect(merged[0]!.slots!.insight!.description).toBe("Weather insight")
+	})
+
+	test("does not mutate original items", () => {
+		const item = makeItem({
+			slots: {
+				insight: { description: "test", content: null },
+			},
+		})
+		const result: EnhancementResult = {
+			slotFills: { "item-1": { insight: "filled" } },
+			syntheticItems: [],
+		}
+
+		mergeEnhancement([item], result, now)
+
+		expect(item.slots!.insight!.content).toBeNull()
+	})
+
+	test("ignores fills for non-existent items", () => {
+		const item = makeItem()
+		const result: EnhancementResult = {
+			slotFills: { "non-existent": { insight: "text" } },
+			syntheticItems: [],
+		}
+
+		const merged = mergeEnhancement([item], result, now)
+
+		expect(merged).toHaveLength(1)
+		expect(merged[0]!.id).toBe("item-1")
+	})
+
+	test("ignores fills for non-existent slots", () => {
+		const item = makeItem({
+			slots: {
+				insight: { description: "test", content: null },
+			},
+		})
+		const result: EnhancementResult = {
+			slotFills: { "item-1": { "non-existent-slot": "text" } },
+			syntheticItems: [],
+		}
+
+		const merged = mergeEnhancement([item], result, now)
+
+		expect(merged[0]!.slots!.insight!.content).toBeNull()
+	})
+
+	test("skips null fills", () => {
+		const item = makeItem({
+			slots: {
+				insight: { description: "test", content: null },
+			},
+		})
+		const result: EnhancementResult = {
+			slotFills: { "item-1": { insight: null } },
+			syntheticItems: [],
+		}
+
+		const merged = mergeEnhancement([item], result, now)
+
+		expect(merged[0]!.slots!.insight!.content).toBeNull()
+	})
+
+	test("passes through items without slots unchanged", () => {
+		const item = makeItem()
+		const result: EnhancementResult = {
+			slotFills: {},
+			syntheticItems: [],
+		}
+
+		const merged = mergeEnhancement([item], result, now)
+
+		expect(merged[0]).toBe(item)
+	})
+
+	test("appends synthetic items with backfilled fields", () => {
+		const item = makeItem()
+		const result: EnhancementResult = {
+			slotFills: {},
+			syntheticItems: [
+				{
+					id: "briefing-morning",
+					type: "briefing",
+					text: "Light afternoon ahead.",
+				},
+			],
+		}
+
+		const merged = mergeEnhancement([item], result, now)
+
+		expect(merged).toHaveLength(2)
+		expect(merged[1]!.id).toBe("briefing-morning")
+		expect(merged[1]!.type).toBe("briefing")
+		expect(merged[1]!.timestamp).toEqual(now)
+		expect(merged[1]!.data).toEqual({ text: "Light afternoon ahead." })
+	})
+
+	test("handles empty enhancement result", () => {
+		const item = makeItem()
+		const result: EnhancementResult = {
+			slotFills: {},
+			syntheticItems: [],
+		}
+
+		const merged = mergeEnhancement([item], result, now)
+
+		expect(merged).toHaveLength(1)
+		expect(merged[0]).toBe(item)
+	})
+})

apps/aelis-backend/src/enhancement/merge.ts

@@ -0,0 +1,48 @@
+import type { FeedItem } from "@aelis/core"
+
+import type { EnhancementResult } from "./schema.ts"
+
+const ENHANCEMENT_SOURCE_ID = "aelis.enhancement"
+
+/**
+ * Merges an EnhancementResult into feed items.
+ *
+ * - Writes slot content from slotFills into matching items
+ * - Appends synthetic items to the list
+ * - Returns a new array (no mutation)
+ * - Ignores fills for items/slots that don't exist
+ */
+export function mergeEnhancement(
+	items: FeedItem[],
+	result: EnhancementResult,
+	currentTime: Date,
+): FeedItem[] {
+	const merged = items.map((item) => {
+		const fills = result.slotFills[item.id]
+		if (!fills || !item.slots) return item
+
+		const mergedSlots = { ...item.slots }
+		let changed = false
+
+		for (const [slotName, content] of Object.entries(fills)) {
+			if (slotName in mergedSlots && content !== null) {
+				mergedSlots[slotName] = { ...mergedSlots[slotName]!, content }
+				changed = true
+			}
+		}
+
+		return changed ? { ...item, slots: mergedSlots } : item
+	})
+
+	for (const synthetic of result.syntheticItems) {
+		merged.push({
+			id: synthetic.id,
+			sourceId: ENHANCEMENT_SOURCE_ID,
+			type: synthetic.type,
+			timestamp: currentTime,
+			data: { text: synthetic.text },
+		})
+	}
+
+	return merged
+}

apps/aelis-backend/src/enhancement/prompt-builder.test.ts

@@ -0,0 +1,170 @@
+import type { FeedItem } from "@aelis/core"
+
+import { describe, expect, test } from "bun:test"
+
+import { buildPrompt, hasUnfilledSlots } from "./prompt-builder.ts"
+
+function makeItem(overrides: Partial<FeedItem> = {}): FeedItem {
+	return {
+		id: "item-1",
+		sourceId: "test",
+		type: "test",
+		timestamp: new Date("2025-01-01T00:00:00Z"),
+		data: { value: 42 },
+		...overrides,
+	}
+}
+
+function parseUserMessage(userMessage: string): Record<string, unknown> {
+	return JSON.parse(userMessage)
+}
+
+describe("hasUnfilledSlots", () => {
+	test("returns false for items without slots", () => {
+		expect(hasUnfilledSlots([makeItem()])).toBe(false)
+	})
+
+	test("returns false for items with all slots filled", () => {
+		const item = makeItem({
+			slots: {
+				insight: { description: "test", content: "filled" },
+			},
+		})
+		expect(hasUnfilledSlots([item])).toBe(false)
+	})
+
+	test("returns true when at least one slot is unfilled", () => {
+		const item = makeItem({
+			slots: {
+				insight: { description: "test", content: null },
+			},
+		})
+		expect(hasUnfilledSlots([item])).toBe(true)
+	})
+
+	test("returns false for empty array", () => {
+		expect(hasUnfilledSlots([])).toBe(false)
+	})
+})
+
+describe("buildPrompt", () => {
+	test("puts items with unfilled slots in items", () => {
+		const item = makeItem({
+			slots: {
+				insight: { description: "Weather insight", content: null },
+				filled: { description: "Already done", content: "done" },
+			},
+		})
+
+		const { userMessage } = buildPrompt([item], new Date("2025-06-01T12:00:00Z"))
+		const parsed = parseUserMessage(userMessage)
+
+		expect(parsed.items).toHaveLength(1)
+		expect((parsed.items as Array<Record<string, unknown>>)[0]!.id).toBe("item-1")
+		expect((parsed.items as Array<Record<string, unknown>>)[0]!.slots).toEqual({
+			insight: "Weather insight",
+		})
+		expect((parsed.items as Array<Record<string, unknown>>)[0]!.type).toBeUndefined()
+		expect(parsed.context).toHaveLength(0)
+	})
+
+	test("puts slotless items in context", () => {
+		const withSlots = makeItem({
+			id: "with-slots",
+			slots: { insight: { description: "test", content: null } },
+		})
+		const withoutSlots = makeItem({ id: "no-slots" })
+
+		const { userMessage } = buildPrompt([withSlots, withoutSlots], new Date("2025-06-01T12:00:00Z"))
+		const parsed = parseUserMessage(userMessage)
+
+		expect(parsed.items).toHaveLength(1)
+		expect((parsed.items as Array<Record<string, unknown>>)[0]!.id).toBe("with-slots")
+		expect(parsed.context).toHaveLength(1)
+		expect((parsed.context as Array<Record<string, unknown>>)[0]!.id).toBe("no-slots")
+	})
+
+	test("includes time in ISO format", () => {
+		const { userMessage } = buildPrompt([], new Date("2025-06-01T12:00:00Z"))
+		const parsed = parseUserMessage(userMessage)
+
+		expect(parsed.time).toBe("2025-06-01T12:00:00.000Z")
+	})
+
+	test("system prompt is non-empty", () => {
+		const { systemPrompt } = buildPrompt([], new Date())
+		expect(systemPrompt.length).toBeGreaterThan(0)
+	})
+
+	test("includes schedule in system prompt", () => {
+		const calEvent = makeItem({
+			id: "cal-1",
+			type: "caldav-event",
+			data: {
+				title: "Team standup",
+				startDate: "2025-06-01T10:00:00Z",
+				endDate: "2025-06-01T10:30:00Z",
+				isAllDay: false,
+				location: null,
+			},
+			slots: {
+				insight: { description: "test", content: null },
+			},
+		})
+
+		const { systemPrompt } = buildPrompt([calEvent], new Date("2025-06-01T12:00:00Z"))
+
+		expect(systemPrompt).toContain("Schedule:\n")
+		expect(systemPrompt).toContain("Team standup")
+		expect(systemPrompt).toContain("10:00")
+	})
+
+	test("includes location in schedule", () => {
+		const calEvent = makeItem({
+			id: "cal-1",
+			type: "caldav-event",
+			data: {
+				title: "Therapy",
+				startDate: "2025-06-02T18:00:00Z",
+				endDate: "2025-06-02T19:00:00Z",
+				isAllDay: false,
+				location: "92 Tooley Street, London",
+			},
+		})
+
+		const { systemPrompt } = buildPrompt([calEvent], new Date("2025-06-01T12:00:00Z"))
+
+		expect(systemPrompt).toContain("Therapy @ 92 Tooley Street, London")
+	})
+
+	test("includes week calendar but omits schedule when no calendar items", () => {
+		const weatherItem = makeItem({
+			type: "weather-current",
+			data: { temperature: 14 },
+		})
+
+		const { systemPrompt } = buildPrompt([weatherItem], new Date("2025-06-01T12:00:00Z"))
+
+		expect(systemPrompt).toContain("Week:")
+		expect(systemPrompt).not.toContain("Schedule:")
+	})
+
+	test("user message is pure JSON", () => {
+		const calEvent = makeItem({
+			id: "cal-1",
+			type: "caldav-event",
+			data: {
+				title: "Budget Review",
+				startTime: "2025-06-01T14:00:00Z",
+				endTime: "2025-06-01T15:00:00Z",
+				isAllDay: false,
+				location: "https://meet.google.com/abc",
+			},
+		})
+
+		const { userMessage } = buildPrompt([calEvent], new Date("2025-06-01T12:00:00Z"))
+
+		expect(userMessage.startsWith("{")).toBe(true)
+		expect(() => JSON.parse(userMessage)).not.toThrow()
+	})
+})

apps/aelis-backend/src/enhancement/prompt-builder.ts

@@ -0,0 +1,218 @@
+import type { FeedItem } from "@aelis/core"
+
+import { CalDavFeedItemType } from "@aelis/source-caldav"
+import { CalendarFeedItemType } from "@aelis/source-google-calendar"
+
+import systemPromptBase from "./prompts/system.txt"
+
+const CALENDAR_ITEM_TYPES = new Set<string>([
+	CalDavFeedItemType.Event,
+	CalendarFeedItemType.Event,
+	CalendarFeedItemType.AllDay,
+])
+
+/**
+ * Builds the system prompt and user message for the enhancement harness.
+ *
+ * Includes a pre-computed mini calendar so the LLM doesn't have to
+ * parse timestamps to understand the user's schedule.
+ */
+export function buildPrompt(
+	items: FeedItem[],
+	currentTime: Date,
+): { systemPrompt: string; userMessage: string } {
+	const schedule = buildSchedule(items, currentTime)
+
+	const enhanceItems: Array<{
+		id: string
+		data: Record<string, unknown>
+		slots: Record<string, string>
+	}> = []
+	const contextItems: Array<{
+		id: string
+		type: string
+		data: Record<string, unknown>
+	}> = []
+
+	for (const item of items) {
+		const hasUnfilledSlots =
+			item.slots &&
+			Object.values(item.slots).some((slot) => slot.content === null)
+
+		if (hasUnfilledSlots) {
+			enhanceItems.push({
+				id: item.id,
+				data: item.data,
+				slots: Object.fromEntries(
+					Object.entries(item.slots!)
+						.filter(([, slot]) => slot.content === null)
+						.map(([name, slot]) => [name, slot.description]),
+				),
+			})
+		} else {
+			contextItems.push({
+				id: item.id,
+				type: item.type,
+				data: item.data,
+			})
+		}
+	}
+
+	const userMessage = JSON.stringify({
+		time: currentTime.toISOString(),
+		items: enhanceItems,
+		context: contextItems,
+	})
+
+	const weekCalendar = buildWeekCalendar(currentTime)
+	let systemPrompt = systemPromptBase
+	systemPrompt += `\n\nWeek:\n${weekCalendar}`
+	if (schedule) {
+		systemPrompt += `\n\nSchedule:\n${schedule}`
+	}
+
+	return { systemPrompt, userMessage }
+}
+
+/**
+ * Returns true if any item has at least one unfilled slot.
+ */
+export function hasUnfilledSlots(items: FeedItem[]): boolean {
+	return items.some(
+		(item) =>
+			item.slots &&
+			Object.values(item.slots).some((slot) => slot.content === null),
+	)
+}
+
+// -- Helpers --
+
+interface CalendarEntry {
+	date: Date
+	title: string
+	location: string | null
+	isAllDay: boolean
+	startTime: Date
+	endTime: Date
+}
+
+function toValidDate(value: unknown): Date | null {
+	if (value instanceof Date) return Number.isNaN(value.getTime()) ? null : value
+	if (typeof value === "string" || typeof value === "number") {
+		const date = new Date(value)
+		return Number.isNaN(date.getTime()) ? null : date
+	}
+	return null
+}
+
+function extractCalendarEntry(item: FeedItem): CalendarEntry | null {
+	if (!CALENDAR_ITEM_TYPES.has(item.type)) return null
+
+	const d = item.data
+	const title = d.title
+	if (typeof title !== "string" || !title) return null
+
+	// CalDAV uses startDate/endDate, Google Calendar uses startTime/endTime
+	const startTime = toValidDate(d.startDate ?? d.startTime)
+	if (!startTime) return null
+
+	const endTime = toValidDate(d.endDate ?? d.endTime) ?? startTime
+
+	return {
+		date: startTime,
+		title,
+		location: typeof d.location === "string" ? d.location : null,
+		isAllDay: typeof d.isAllDay === "boolean" ? d.isAllDay : false,
+		startTime,
+		endTime,
+	}
+}
+
+const DAYS = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"] as const
+const MONTHS = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"] as const
+
+function pad2(n: number): string {
+	return n.toString().padStart(2, "0")
+}
+
+function formatTime(date: Date): string {
+	return `${pad2(date.getUTCHours())}:${pad2(date.getUTCMinutes())}`
+}
+
+function formatDayShort(date: Date): string {
+	return `${DAYS[date.getUTCDay()]}, ${date.getUTCDate()} ${MONTHS[date.getUTCMonth()]}`
+}
+
+function formatDayLabel(date: Date, currentTime: Date): string {
+	const currentDay = Date.UTC(currentTime.getUTCFullYear(), currentTime.getUTCMonth(), currentTime.getUTCDate())
+	const targetDay = Date.UTC(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate())
+	const diffDays = Math.round((targetDay - currentDay) / (1000 * 60 * 60 * 24))
+
+	const dayName = formatDayShort(date)
+
+	if (diffDays === 0) return `Today: ${dayName}`
+	if (diffDays === 1) return `Tomorrow: ${dayName}`
+	return dayName
+}
+
+/**
+ * Builds a week overview mapping day names to dates,
+ * so the LLM can easily match ISO timestamps to days.
+ */
+function buildWeekCalendar(currentTime: Date): string {
+	const lines: string[] = []
+	for (let i = 0; i < 7; i++) {
+		const date = new Date(currentTime)
+		date.setUTCDate(date.getUTCDate() + i)
+		const label = i === 0 ? "Today" : i === 1 ? "Tomorrow" : ""
+		const dayStr = formatDayShort(date)
+		const iso = date.toISOString().slice(0, 10)
+		const prefix = label ? `${label}: ` : ""
+		lines.push(`${prefix}${dayStr} = ${iso}`)
+	}
+	return lines.join("\n")
+}
+
+/**
+ * Builds a compact text calendar from all calendar-type items.
+ * Groups events by day relative to currentTime.
+ */
+function buildSchedule(items: FeedItem[], currentTime: Date): string {
+	const entries: CalendarEntry[] = []
+	for (const item of items) {
+		const entry = extractCalendarEntry(item)
+		if (entry) entries.push(entry)
+	}
+
+	if (entries.length === 0) return ""
+
+	entries.sort((a, b) => a.startTime.getTime() - b.startTime.getTime())
+
+	const byDay = new Map<string, CalendarEntry[]>()
+	for (const entry of entries) {
+		const key = entry.date.toISOString().slice(0, 10)
+		const group = byDay.get(key)
+		if (group) {
+			group.push(entry)
+		} else {
+			byDay.set(key, [entry])
+		}
+	}
+
+	const lines: string[] = []
+	for (const [, dayEntries] of byDay) {
+		lines.push(formatDayLabel(dayEntries[0]!.startTime, currentTime))
+		for (const entry of dayEntries) {
+			if (entry.isAllDay) {
+				const loc = entry.location ? ` @ ${entry.location}` : ""
+				lines.push(`  all day  ${entry.title}${loc}`)
+			} else {
+				const timeRange = `${formatTime(entry.startTime)}–${formatTime(entry.endTime)}`
+				const loc = entry.location ? ` @ ${entry.location}` : ""
+				lines.push(`  ${timeRange}  ${entry.title}${loc}`)
+			}
+		}
+	}
+
+	return lines.join("\n")
+}

apps/aelis-backend/src/enhancement/prompts/system.txt

@@ -0,0 +1,21 @@
+You are AELIS, a personal assistant. You enhance a user's feed by filling slots and optionally generating synthetic items.
+
+The user message is a JSON object with:
+- "items": feed items with data and named slots to fill. Each slot has a description of what to write.
+- "context": other feed items (no slots) for cross-source reasoning.
+- "time": current ISO timestamp.
+
+Your output has two fields:
+- "slotFills": map of item ID → slot name → short text (or null if you can't fill it or cannot provide answer). Each item ID appears ONCE with ALL its slots in a single object.
+- "syntheticItems": array of { id, type, text } for new items (briefings, nudges, insights). Only when genuinely useful and when not redundant.
+
+Rules:
+- DO NOT USE EMDASH OR DASH OR ATTEMPT TO USE SYMBOLS TO CIRCUMVENT THIS RULE.
+- One sentence per slot. Two max if absolutely necessary. Be direct.
+- Say "I" not "we."
+- Hedge when inferring. Don't state guesses as facts.
+- Use the week and schedule below to understand when events happen. Match weather data to the correct date.
+- Look for connections across items.
+- Don't pad — return null for slots you can't meaningfully fill, and skip synthetic items if there's nothing useful to add.
+- Never fabricate information not present in the feed. If you don't have data to support a fill, return null.
+- Read each slot's description carefully — it defines when to return null.

apps/aelis-backend/src/enhancement/schema.test.ts

@@ -0,0 +1,176 @@
+import { describe, expect, test } from "bun:test"
+
+import {
+	emptyEnhancementResult,
+	enhancementResultJsonSchema,
+	parseEnhancementResult,
+} from "./schema.ts"
+
+describe("parseEnhancementResult", () => {
+	test("parses valid result", () => {
+		const input = JSON.stringify({
+			slotFills: {
+				"weather-1": {
+					insight: "Rain after 3pm",
+					"cross-source": null,
+				},
+			},
+			syntheticItems: [
+				{
+					id: "briefing-morning",
+					type: "briefing",
+					text: "Light afternoon ahead.",
+				},
+			],
+		})
+
+		const result = parseEnhancementResult(input)
+
+		expect(result).not.toBeNull()
+		expect(result!.slotFills["weather-1"]!.insight).toBe("Rain after 3pm")
+		expect(result!.slotFills["weather-1"]!["cross-source"]).toBeNull()
+		expect(result!.syntheticItems).toHaveLength(1)
+		expect(result!.syntheticItems[0]!.id).toBe("briefing-morning")
+		expect(result!.syntheticItems[0]!.text).toBe("Light afternoon ahead.")
+	})
+
+	test("parses empty result", () => {
+		const input = JSON.stringify({
+			slotFills: {},
+			syntheticItems: [],
+		})
+
+		const result = parseEnhancementResult(input)
+
+		expect(result).not.toBeNull()
+		expect(Object.keys(result!.slotFills)).toHaveLength(0)
+		expect(result!.syntheticItems).toHaveLength(0)
+	})
+
+	test("returns null for invalid JSON", () => {
+		expect(parseEnhancementResult("not json")).toBeNull()
+	})
+
+	test("returns null for non-object", () => {
+		expect(parseEnhancementResult('"hello"')).toBeNull()
+		expect(parseEnhancementResult("42")).toBeNull()
+		expect(parseEnhancementResult("null")).toBeNull()
+	})
+
+	test("returns null when slotFills is missing", () => {
+		const input = JSON.stringify({ syntheticItems: [] })
+		expect(parseEnhancementResult(input)).toBeNull()
+	})
+
+	test("returns null when syntheticItems is missing", () => {
+		const input = JSON.stringify({ slotFills: {} })
+		expect(parseEnhancementResult(input)).toBeNull()
+	})
+
+	test("returns null when slotFills has non-string values", () => {
+		const input = JSON.stringify({
+			slotFills: { "item-1": { slot: 42 } },
+			syntheticItems: [],
+		})
+		expect(parseEnhancementResult(input)).toBeNull()
+	})
+
+	test("returns null when syntheticItem is missing required fields", () => {
+		const input = JSON.stringify({
+			slotFills: {},
+			syntheticItems: [{ id: "x" }],
+		})
+		expect(parseEnhancementResult(input)).toBeNull()
+	})
+})
+
+describe("emptyEnhancementResult", () => {
+	test("returns empty slotFills and syntheticItems", () => {
+		const result = emptyEnhancementResult()
+		expect(result.slotFills).toEqual({})
+		expect(result.syntheticItems).toEqual([])
+	})
+})
+
+describe("schema sync", () => {
+	const referencePayloads = [
+		{
+			name: "full payload with null slot fill",
+			payload: {
+				slotFills: {
+					"weather-1": { insight: "Rain after 3pm", crossSource: null },
+					"cal-2": { summary: "Busy morning" },
+				},
+				syntheticItems: [
+					{ id: "briefing-morning", type: "briefing", text: "Light day ahead." },
+					{ id: "nudge-umbrella", type: "nudge", text: "Bring an umbrella." },
+				],
+			},
+		},
+		{
+			name: "empty collections",
+			payload: { slotFills: {}, syntheticItems: [] },
+		},
+		{
+			name: "slot fills only",
+			payload: {
+				slotFills: { "item-1": { slot: "filled" } },
+				syntheticItems: [],
+			},
+		},
+		{
+			name: "synthetic items only",
+			payload: {
+				slotFills: {},
+				syntheticItems: [{ id: "insight-1", type: "insight", text: "Something." }],
+			},
+		},
+	]
+
+	for (const { name, payload } of referencePayloads) {
+		test(`arktype and JSON Schema agree on: ${name}`, () => {
+			// arktype accepts it
+			const parsed = parseEnhancementResult(JSON.stringify(payload))
+			expect(parsed).not.toBeNull()
+
+			// JSON Schema structure matches
+			const jsonSchema = enhancementResultJsonSchema
+			expect(Object.keys(jsonSchema.properties).sort()).toEqual(
+				Object.keys(payload).sort(),
+			)
+			expect([...jsonSchema.required].sort()).toEqual(Object.keys(payload).sort())
+
+			// syntheticItems item schema has the right required fields
+			const itemSchema = jsonSchema.properties.syntheticItems.items
+			expect([...itemSchema.required].sort()).toEqual(["id", "text", "type"])
+
+			// Verify each synthetic item has exactly the fields the JSON Schema expects
+			for (const item of payload.syntheticItems) {
+				expect(Object.keys(item).sort()).toEqual([...itemSchema.required].sort())
+			}
+		})
+	}
+
+	test("JSON Schema rejects what arktype rejects: missing required field", () => {
+		// Missing syntheticItems
+		expect(parseEnhancementResult(JSON.stringify({ slotFills: {} }))).toBeNull()
+
+		// JSON Schema also requires it
+		expect(enhancementResultJsonSchema.required).toContain("syntheticItems")
+	})
+
+	test("JSON Schema rejects what arktype rejects: wrong slot fill value type", () => {
+		const bad = { slotFills: { "item-1": { slot: 42 } }, syntheticItems: [] }
+
+		// arktype rejects it
+		expect(parseEnhancementResult(JSON.stringify(bad))).toBeNull()
+
+		// JSON Schema only allows string or null for slot values
+		const slotValueTypes =
+			enhancementResultJsonSchema.properties.slotFills.additionalProperties
+				.additionalProperties.type
+		expect(slotValueTypes).toContain("string")
+		expect(slotValueTypes).toContain("null")
+		expect(slotValueTypes).not.toContain("number")
+	})
+})

apps/aelis-backend/src/enhancement/schema.ts

@@ -0,0 +1,89 @@
+import { type } from "arktype"
+
+const SyntheticItem = type({
+	id: "string",
+	type: "string",
+	text: "string",
+})
+
+const EnhancementResult = type({
+	slotFills: "Record<string, Record<string, string | null>>",
+	syntheticItems: SyntheticItem.array(),
+})
+
+export type SyntheticItem = typeof SyntheticItem.infer
+export type EnhancementResult = typeof EnhancementResult.infer
+
+/**
+ * JSON Schema passed to OpenRouter's structured output.
+ * OpenRouter doesn't support arktype, so this is maintained separately.
+ *
+ * ⚠️  Must stay in sync with EnhancementResult above.
+ * If you add/remove fields, update both schemas.
+ */
+export const enhancementResultJsonSchema = {
+	type: "object",
+	properties: {
+		slotFills: {
+			type: "object",
+			description:
+				"Map of feed item ID to an object of slot name to filled text content. Use null for slots that cannot be meaningfully filled.",
+			additionalProperties: {
+				type: "object",
+				additionalProperties: {
+					type: ["string", "null"],
+				},
+			},
+		},
+		syntheticItems: {
+			type: "array",
+			description:
+				"New feed items to inject (briefings, nudges, cross-source insights). Keep these short and actionable.",
+			items: {
+				type: "object",
+				properties: {
+					id: {
+						type: "string",
+						description: "Unique ID, e.g. 'briefing-morning'",
+					},
+					type: {
+						type: "string",
+						description: "One of: 'briefing', 'nudge', 'insight'",
+					},
+					text: {
+						type: "string",
+						description: "Display text, 1-3 sentences",
+					},
+				},
+				required: ["id", "type", "text"],
+				additionalProperties: false,
+			},
+		},
+	},
+	required: ["slotFills", "syntheticItems"],
+	additionalProperties: false,
+} as const
+
+/**
+ * Parses a JSON string into an EnhancementResult.
+ * Returns null if the input is malformed.
+ */
+export function parseEnhancementResult(json: string): EnhancementResult | null {
+	let parsed: unknown
+	try {
+		parsed = JSON.parse(json)
+	} catch {
+		return null
+	}
+
+	const result = EnhancementResult(parsed)
+	if (result instanceof type.errors) {
+		return null
+	}
+
+	return result
+}
+
+export function emptyEnhancementResult(): EnhancementResult {
+	return { slotFills: {}, syntheticItems: [] }
+}

apps/aelis-backend/src/location/http.ts

@@ -44,8 +44,16 @@ async function handleUpdateLocation(c: Context<Env>) {
 
 	const user = c.get("user")!
 	const sessionManager = c.get("sessionManager")
-	const session = sessionManager.getOrCreate(user.id)
-	await session.engine.executeAction("aris.location", "update-location", {
+
+	let session
+	try {
+		session = await sessionManager.getOrCreate(user.id)
+	} catch (err) {
+		console.error("[handleUpdateLocation] Failed to create session:", err)
+		return c.json({ error: "Service unavailable" }, 503)
+	}
+
+	await session.engine.executeAction("aelis.location", "update-location", {
 		lat: result.lat,
 		lng: result.lng,
 		accuracy: result.accuracy,

apps/aelis-backend/src/server.ts

@@ -0,0 +1,67 @@
+import { LocationSource } from "@aelis/source-location"
+import { Hono } from "hono"
+
+import { registerAuthHandlers } from "./auth/http.ts"
+import { mockAuthSessionMiddleware, requireSession } from "./auth/session-middleware.ts"
+import { registerFeedHttpHandlers } from "./engine/http.ts"
+import { createFeedEnhancer } from "./enhancement/enhance-feed.ts"
+import { createLlmClient } from "./enhancement/llm-client.ts"
+import { registerLocationHttpHandlers } from "./location/http.ts"
+import { UserSessionManager } from "./session/index.ts"
+import { WeatherSourceProvider } from "./weather/provider.ts"
+
+function main() {
+	const openrouterApiKey = process.env.OPENROUTER_API_KEY
+	const feedEnhancer = openrouterApiKey
+		? createFeedEnhancer({
+				client: createLlmClient({
+					apiKey: openrouterApiKey,
+					model: process.env.OPENROUTER_MODEL || undefined,
+				}),
+			})
+		: null
+	if (!feedEnhancer) {
+		console.warn("[enhancement] OPENROUTER_API_KEY not set — feed enhancement disabled")
+	}
+
+	const sessionManager = new UserSessionManager({
+		providers: [
+			async () => new LocationSource(),
+			new WeatherSourceProvider({
+				credentials: {
+					privateKey: process.env.WEATHERKIT_PRIVATE_KEY!,
+					keyId: process.env.WEATHERKIT_KEY_ID!,
+					teamId: process.env.WEATHERKIT_TEAM_ID!,
+					serviceId: process.env.WEATHERKIT_SERVICE_ID!,
+				},
+			}),
+		],
+		feedEnhancer,
+	})
+
+	const app = new Hono()
+
+	app.get("/health", (c) => c.json({ status: "ok" }))
+
+	const isDev = process.env.NODE_ENV !== "production"
+	const authSessionMiddleware = isDev ? mockAuthSessionMiddleware("dev-user") : requireSession
+
+	if (!isDev) {
+		registerAuthHandlers(app)
+	}
+
+	registerFeedHttpHandlers(app, {
+		sessionManager,
+		authSessionMiddleware,
+	})
+	registerLocationHttpHandlers(app, { sessionManager })
+
+	return app
+}
+
+const app = main()
+
+export default {
+	port: 3000,
+	fetch: app.fetch,
+}

apps/aelis-backend/src/session/feed-source-provider.ts

@@ -0,0 +1,9 @@
+import type { FeedSource } from "@aelis/core"
+
+export interface FeedSourceProvider {
+	feedSourceForUser(userId: string): Promise<FeedSource>
+}
+
+export type FeedSourceProviderFn = (userId: string) => Promise<FeedSource>
+
+export type FeedSourceProviderInput = FeedSourceProvider | FeedSourceProviderFn

apps/aelis-backend/src/session/user-session-manager.test.ts

@@ -0,0 +1,259 @@
+import type { WeatherKitClient, WeatherKitResponse } from "@aelis/source-weatherkit"
+
+import { LocationSource } from "@aelis/source-location"
+import { describe, expect, mock, spyOn, test } from "bun:test"
+
+import { WeatherSourceProvider } from "../weather/provider.ts"
+import { UserSessionManager } from "./user-session-manager.ts"
+
+const mockWeatherClient: WeatherKitClient = {
+	fetch: async () => ({}) as WeatherKitResponse,
+}
+
+describe("UserSessionManager", () => {
+	test("getOrCreate creates session on first call", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		const session = await manager.getOrCreate("user-1")
+
+		expect(session).toBeDefined()
+		expect(session.engine).toBeDefined()
+	})
+
+	test("getOrCreate returns same session for same user", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		const session1 = await manager.getOrCreate("user-1")
+		const session2 = await manager.getOrCreate("user-1")
+
+		expect(session1).toBe(session2)
+	})
+
+	test("getOrCreate returns different sessions for different users", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		const session1 = await manager.getOrCreate("user-1")
+		const session2 = await manager.getOrCreate("user-2")
+
+		expect(session1).not.toBe(session2)
+	})
+
+	test("each user gets independent source instances", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		const session1 = await manager.getOrCreate("user-1")
+		const session2 = await manager.getOrCreate("user-2")
+
+		const source1 = session1.getSource<LocationSource>("aelis.location")
+		const source2 = session2.getSource<LocationSource>("aelis.location")
+
+		expect(source1).not.toBe(source2)
+	})
+
+	test("remove destroys session and allows re-creation", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		const session1 = await manager.getOrCreate("user-1")
+		manager.remove("user-1")
+		const session2 = await manager.getOrCreate("user-1")
+
+		expect(session1).not.toBe(session2)
+	})
+
+	test("remove is no-op for unknown user", () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		expect(() => manager.remove("unknown")).not.toThrow()
+	})
+
+	test("accepts function providers", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		const session = await manager.getOrCreate("user-1")
+		const result = await session.engine.refresh()
+
+		expect(result.errors).toHaveLength(0)
+	})
+
+	test("accepts object providers", async () => {
+		const provider = new WeatherSourceProvider({ client: mockWeatherClient })
+		const manager = new UserSessionManager({
+			providers: [async () => new LocationSource(), provider],
+		})
+
+		const session = await manager.getOrCreate("user-1")
+
+		expect(session.getSource("aelis.weather")).toBeDefined()
+	})
+
+	test("accepts mixed providers", async () => {
+		const provider = new WeatherSourceProvider({ client: mockWeatherClient })
+		const manager = new UserSessionManager({
+			providers: [async () => new LocationSource(), provider],
+		})
+
+		const session = await manager.getOrCreate("user-1")
+
+		expect(session.getSource("aelis.location")).toBeDefined()
+		expect(session.getSource("aelis.weather")).toBeDefined()
+	})
+
+	test("refresh returns feed result through session", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		const session = await manager.getOrCreate("user-1")
+		const result = await session.engine.refresh()
+
+		expect(result).toHaveProperty("context")
+		expect(result).toHaveProperty("items")
+		expect(result).toHaveProperty("errors")
+		expect(result.context.time).toBeInstanceOf(Date)
+	})
+
+	test("location update via executeAction works", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+
+		const session = await manager.getOrCreate("user-1")
+		await session.engine.executeAction("aelis.location", "update-location", {
+			lat: 51.5074,
+			lng: -0.1278,
+			accuracy: 10,
+			timestamp: new Date(),
+		})
+
+		const source = session.getSource<LocationSource>("aelis.location")
+		expect(source?.lastLocation?.lat).toBe(51.5074)
+	})
+
+	test("subscribe receives updates after location push", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+		const callback = mock()
+
+		const session = await manager.getOrCreate("user-1")
+		session.engine.subscribe(callback)
+
+		await session.engine.executeAction("aelis.location", "update-location", {
+			lat: 51.5074,
+			lng: -0.1278,
+			accuracy: 10,
+			timestamp: new Date(),
+		})
+
+		// Wait for async update propagation
+		await new Promise((resolve) => setTimeout(resolve, 10))
+
+		expect(callback).toHaveBeenCalled()
+	})
+
+	test("remove stops reactive updates", async () => {
+		const manager = new UserSessionManager({ providers: [async () => new LocationSource()] })
+		const callback = mock()
+
+		const session = await manager.getOrCreate("user-1")
+		session.engine.subscribe(callback)
+
+		manager.remove("user-1")
+
+		// Create new session and push location — old callback should not fire
+		const session2 = await manager.getOrCreate("user-1")
+		await session2.engine.executeAction("aelis.location", "update-location", {
+			lat: 51.5074,
+			lng: -0.1278,
+			accuracy: 10,
+			timestamp: new Date(),
+		})
+
+		await new Promise((resolve) => setTimeout(resolve, 10))
+
+		expect(callback).not.toHaveBeenCalled()
+	})
+
+	test("creates session with successful providers when some fail", async () => {
+		const manager = new UserSessionManager({
+			providers: [
+				async () => new LocationSource(),
+				async () => {
+					throw new Error("provider failed")
+				},
+			],
+		})
+
+		const spy = spyOn(console, "error").mockImplementation(() => {})
+
+		const session = await manager.getOrCreate("user-1")
+
+		expect(session).toBeDefined()
+		expect(session.getSource("aelis.location")).toBeDefined()
+		expect(spy).toHaveBeenCalled()
+
+		spy.mockRestore()
+	})
+
+	test("throws AggregateError when all providers fail", async () => {
+		const manager = new UserSessionManager({
+			providers: [
+				async () => {
+					throw new Error("first failed")
+				},
+				async () => {
+					throw new Error("second failed")
+				},
+			],
+		})
+
+		await expect(manager.getOrCreate("user-1")).rejects.toBeInstanceOf(AggregateError)
+	})
+
+	test("concurrent getOrCreate for same user returns same session", async () => {
+		let callCount = 0
+		const manager = new UserSessionManager({
+			providers: [
+				async () => {
+					callCount++
+					// Simulate async work to widen the race window
+					await new Promise((resolve) => setTimeout(resolve, 10))
+					return new LocationSource()
+				},
+			],
+		})
+
+		const [session1, session2] = await Promise.all([
+			manager.getOrCreate("user-1"),
+			manager.getOrCreate("user-1"),
+		])
+
+		expect(session1).toBe(session2)
+		expect(callCount).toBe(1)
+	})
+
+	test("remove during in-flight getOrCreate prevents session from being stored", async () => {
+		let resolveProvider: () => void
+		const providerGate = new Promise<void>((r) => {
+			resolveProvider = r
+		})
+
+		const manager = new UserSessionManager({
+			providers: [
+				async () => {
+					await providerGate
+					return new LocationSource()
+				},
+			],
+		})
+
+		const sessionPromise = manager.getOrCreate("user-1")
+
+		// remove() while provider is still resolving
+		manager.remove("user-1")
+
+		// Let the provider finish
+		resolveProvider!()
+
+		await expect(sessionPromise).rejects.toThrow("removed during creation")
+
+		// A fresh getOrCreate should produce a new session, not the cancelled one
+		const freshSession = await manager.getOrCreate("user-1")
+		expect(freshSession).toBeDefined()
+		expect(freshSession.engine).toBeDefined()
+	})
+})

apps/aelis-backend/src/session/user-session-manager.ts

@@ -0,0 +1,86 @@
+import type { FeedSource } from "@aelis/core"
+
+import type { FeedEnhancer } from "../enhancement/enhance-feed.ts"
+import type { FeedSourceProviderInput } from "./feed-source-provider.ts"
+
+import { UserSession } from "./user-session.ts"
+
+export interface UserSessionManagerConfig {
+	providers: FeedSourceProviderInput[]
+	feedEnhancer?: FeedEnhancer | null
+}
+
+export class UserSessionManager {
+	private sessions = new Map<string, UserSession>()
+	private pending = new Map<string, Promise<UserSession>>()
+	private readonly providers: FeedSourceProviderInput[]
+	private readonly feedEnhancer: FeedEnhancer | null
+
+	constructor(config: UserSessionManagerConfig) {
+		this.providers = config.providers
+		this.feedEnhancer = config.feedEnhancer ?? null
+	}
+
+	async getOrCreate(userId: string): Promise<UserSession> {
+		const existing = this.sessions.get(userId)
+		if (existing) return existing
+
+		const inflight = this.pending.get(userId)
+		if (inflight) return inflight
+
+		const promise = this.createSession(userId)
+		this.pending.set(userId, promise)
+		try {
+			const session = await promise
+			// If remove() was called while we were awaiting, it clears the
+			// pending entry. Detect that and destroy the session immediately.
+			if (!this.pending.has(userId)) {
+				session.destroy()
+				throw new Error(`Session for user ${userId} was removed during creation`)
+			}
+			this.sessions.set(userId, session)
+			return session
+		} finally {
+			this.pending.delete(userId)
+		}
+	}
+
+	remove(userId: string): void {
+		const session = this.sessions.get(userId)
+		if (session) {
+			session.destroy()
+			this.sessions.delete(userId)
+		}
+		// Cancel any in-flight creation so getOrCreate won't store the session
+		this.pending.delete(userId)
+	}
+
+	private async createSession(userId: string): Promise<UserSession> {
+		const results = await Promise.allSettled(
+			this.providers.map((p) =>
+				typeof p === "function" ? p(userId) : p.feedSourceForUser(userId),
+			),
+		)
+
+		const sources: FeedSource[] = []
+		const errors: unknown[] = []
+
+		for (const result of results) {
+			if (result.status === "fulfilled") {
+				sources.push(result.value)
+			} else {
+				errors.push(result.reason)
+			}
+		}
+
+		if (sources.length === 0 && errors.length > 0) {
+			throw new AggregateError(errors, "All feed source providers failed")
+		}
+
+		for (const error of errors) {
+			console.error("[UserSessionManager] Feed source provider failed:", error)
+		}
+
+		return new UserSession(sources, this.feedEnhancer)
+	}
+}

apps/aelis-backend/src/session/user-session.test.ts

@@ -0,0 +1,216 @@
+import type { ActionDefinition, ContextEntry, FeedItem, FeedSource } from "@aelis/core"
+
+import { LocationSource } from "@aelis/source-location"
+import { describe, expect, test } from "bun:test"
+
+import { UserSession } from "./user-session.ts"
+
+function createStubSource(id: string, items: FeedItem[] = []): FeedSource {
+	return {
+		id,
+		async listActions(): Promise<Record<string, ActionDefinition>> {
+			return {}
+		},
+		async executeAction(): Promise<unknown> {
+			return undefined
+		},
+		async fetchContext(): Promise<readonly ContextEntry[] | null> {
+			return null
+		},
+		async fetchItems() {
+			return items
+		},
+	}
+}
+
+describe("UserSession", () => {
+	test("registers sources and starts engine", async () => {
+		const session = new UserSession([createStubSource("test-a"), createStubSource("test-b")])
+
+		const result = await session.engine.refresh()
+
+		expect(result.errors).toHaveLength(0)
+	})
+
+	test("getSource returns registered source", () => {
+		const location = new LocationSource()
+		const session = new UserSession([location])
+
+		const result = session.getSource<LocationSource>("aelis.location")
+
+		expect(result).toBe(location)
+	})
+
+	test("getSource returns undefined for unknown source", () => {
+		const session = new UserSession([createStubSource("test")])
+
+		expect(session.getSource("unknown")).toBeUndefined()
+	})
+
+	test("destroy stops engine and clears sources", () => {
+		const session = new UserSession([createStubSource("test")])
+
+		session.destroy()
+
+		expect(session.getSource("test")).toBeUndefined()
+	})
+
+	test("engine.executeAction routes to correct source", async () => {
+		const location = new LocationSource()
+		const session = new UserSession([location])
+
+		await session.engine.executeAction("aelis.location", "update-location", {
+			lat: 51.5,
+			lng: -0.1,
+			accuracy: 10,
+			timestamp: new Date(),
+		})
+
+		expect(location.lastLocation).toBeDefined()
+		expect(location.lastLocation!.lat).toBe(51.5)
+	})
+})
+
+describe("UserSession.feed", () => {
+	test("returns feed items without enhancer", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "test",
+				type: "test",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: 42 },
+			},
+		]
+		const session = new UserSession([createStubSource("test", items)])
+
+		const result = await session.feed()
+
+		expect(result.items).toHaveLength(1)
+		expect(result.items[0]!.id).toBe("item-1")
+	})
+
+	test("returns enhanced items when enhancer is provided", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "test",
+				type: "test",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: 42 },
+			},
+		]
+		const enhancer = async (feedItems: FeedItem[]) =>
+			feedItems.map((item) => ({ ...item, data: { ...item.data, enhanced: true } }))
+
+		const session = new UserSession([createStubSource("test", items)], enhancer)
+
+		const result = await session.feed()
+
+		expect(result.items).toHaveLength(1)
+		expect(result.items[0]!.data.enhanced).toBe(true)
+	})
+
+	test("caches enhanced items on subsequent calls", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "test",
+				type: "test",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: 42 },
+			},
+		]
+		let enhancerCallCount = 0
+		const enhancer = async (feedItems: FeedItem[]) => {
+			enhancerCallCount++
+			return feedItems.map((item) => ({ ...item, data: { ...item.data, enhanced: true } }))
+		}
+
+		const session = new UserSession([createStubSource("test", items)], enhancer)
+
+		const result1 = await session.feed()
+		expect(result1.items[0]!.data.enhanced).toBe(true)
+		expect(enhancerCallCount).toBe(1)
+
+		const result2 = await session.feed()
+		expect(result2.items[0]!.data.enhanced).toBe(true)
+		expect(enhancerCallCount).toBe(1)
+	})
+
+	test("re-enhances after engine refresh with new data", async () => {
+		let currentItems: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "test",
+				type: "test",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { version: 1 },
+			},
+		]
+		const source = createStubSource("test", currentItems)
+		// Make fetchItems dynamic so refresh returns new data
+		source.fetchItems = async () => currentItems
+
+		const enhancedVersions: number[] = []
+		const enhancer = async (feedItems: FeedItem[]) => {
+			const version = feedItems[0]!.data.version as number
+			enhancedVersions.push(version)
+			return feedItems.map((item) => ({
+				...item,
+				data: { ...item.data, enhanced: true },
+			}))
+		}
+
+		const session = new UserSession([source], enhancer)
+
+		// First feed triggers refresh + enhancement
+		const result1 = await session.feed()
+		expect(result1.items[0]!.data.version).toBe(1)
+		expect(result1.items[0]!.data.enhanced).toBe(true)
+
+		// Update source data and trigger engine refresh
+		currentItems = [
+			{
+				id: "item-1",
+				sourceId: "test",
+				type: "test",
+				timestamp: new Date("2025-01-02T00:00:00.000Z"),
+				data: { version: 2 },
+			},
+		]
+		await session.engine.refresh()
+
+		// Wait for subscriber-triggered background enhancement
+		await new Promise((resolve) => setTimeout(resolve, 10))
+
+		// feed() should now serve re-enhanced items with version 2
+		const result2 = await session.feed()
+		expect(result2.items[0]!.data.version).toBe(2)
+		expect(result2.items[0]!.data.enhanced).toBe(true)
+		expect(enhancedVersions).toEqual([1, 2])
+	})
+
+	test("falls back to unenhanced items when enhancer throws", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "test",
+				type: "test",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: 42 },
+			},
+		]
+		const enhancer = async () => {
+			throw new Error("enhancement exploded")
+		}
+
+		const session = new UserSession([createStubSource("test", items)], enhancer)
+
+		const result = await session.feed()
+
+		expect(result.items).toHaveLength(1)
+		expect(result.items[0]!.id).toBe("item-1")
+		expect(result.items[0]!.data.value).toBe(42)
+	})
+})

apps/aelis-backend/src/session/user-session.ts

@@ -0,0 +1,104 @@
+import { FeedEngine, type FeedItem, type FeedResult, type FeedSource } from "@aelis/core"
+
+import type { FeedEnhancer } from "../enhancement/enhance-feed.ts"
+
+export class UserSession {
+	readonly engine: FeedEngine
+	private sources = new Map<string, FeedSource>()
+	private readonly enhancer: FeedEnhancer | null
+	private enhancedItems: FeedItem[] | null = null
+	/** The FeedResult that enhancedItems was derived from. */
+	private enhancedSource: FeedResult | null = null
+	private enhancingPromise: Promise<void> | null = null
+	private unsubscribe: (() => void) | null = null
+
+	constructor(sources: FeedSource[], enhancer?: FeedEnhancer | null) {
+		this.engine = new FeedEngine()
+		this.enhancer = enhancer ?? null
+		for (const source of sources) {
+			this.sources.set(source.id, source)
+			this.engine.register(source)
+		}
+
+		if (this.enhancer) {
+			this.unsubscribe = this.engine.subscribe((result) => {
+				this.invalidateEnhancement()
+				this.runEnhancement(result)
+			})
+		}
+
+		this.engine.start()
+	}
+
+	/**
+	 * Returns the current feed, refreshing if the engine cache expired.
+	 * Enhancement runs eagerly on engine updates; this method awaits
+	 * any in-flight enhancement or triggers one if needed.
+	 */
+	async feed(): Promise<FeedResult> {
+		const cached = this.engine.lastFeed()
+		const result = cached ?? (await this.engine.refresh())
+
+		if (!this.enhancer) {
+			return result
+		}
+
+		// Wait for any in-flight background enhancement to finish
+		if (this.enhancingPromise) {
+			await this.enhancingPromise
+		}
+
+		// Serve cached enhancement only if it matches the current engine result
+		if (this.enhancedItems && this.enhancedSource === result) {
+			return { ...result, items: this.enhancedItems }
+		}
+
+		// Stale or missing — re-enhance
+		await this.runEnhancement(result)
+
+		if (this.enhancedItems) {
+			return { ...result, items: this.enhancedItems }
+		}
+
+		return result
+	}
+
+	getSource<T extends FeedSource>(sourceId: string): T | undefined {
+		return this.sources.get(sourceId) as T | undefined
+	}
+
+	destroy(): void {
+		this.unsubscribe?.()
+		this.unsubscribe = null
+		this.engine.stop()
+		this.sources.clear()
+		this.invalidateEnhancement()
+		this.enhancingPromise = null
+	}
+
+	private invalidateEnhancement(): void {
+		this.enhancedItems = null
+		this.enhancedSource = null
+	}
+
+	private runEnhancement(result: FeedResult): Promise<void> {
+		const promise = this.enhance(result)
+		this.enhancingPromise = promise
+		promise.finally(() => {
+			if (this.enhancingPromise === promise) {
+				this.enhancingPromise = null
+			}
+		})
+		return promise
+	}
+
+	private async enhance(result: FeedResult): Promise<void> {
+		try {
+			this.enhancedItems = await this.enhancer!(result.items)
+			this.enhancedSource = result
+		} catch (err) {
+			console.error("[enhancement] Unexpected error:", err)
+			this.invalidateEnhancement()
+		}
+	}
+}

apps/aelis-backend/src/tfl/provider.ts

@@ -1,4 +1,4 @@
-import { TflSource, type ITflApi } from "@aris/source-tfl"
+import { TflSource, type ITflApi } from "@aelis/source-tfl"
 
 import type { FeedSourceProvider } from "../session/feed-source-provider.ts"
 
@@ -13,7 +13,7 @@ export class TflSourceProvider implements FeedSourceProvider {
 		this.options = options
 	}
 
-	feedSourceForUser(_userId: string): TflSource {
+	async feedSourceForUser(_userId: string): Promise<TflSource> {
 		return new TflSource(this.options)
 	}
 }

apps/aelis-backend/src/weather/provider.ts

@@ -1,4 +1,4 @@
-import { WeatherSource, type WeatherSourceOptions } from "@aris/source-weatherkit"
+import { WeatherSource, type WeatherSourceOptions } from "@aelis/source-weatherkit"
 
 import type { FeedSourceProvider } from "../session/feed-source-provider.ts"
 
@@ -9,7 +9,7 @@ export class WeatherSourceProvider implements FeedSourceProvider {
 		this.options = options
 	}
 
-	feedSourceForUser(_userId: string): WeatherSource {
+	async feedSourceForUser(_userId: string): Promise<WeatherSource> {
 		return new WeatherSource(this.options)
 	}
 }

apps/aelis-client/app.json

@@ -1,11 +1,11 @@
 {
 	"expo": {
-		"name": "Aris",
-		"slug": "aris-client",
+		"name": "Aelis",
+		"slug": "aelis-client",
 		"version": "1.0.0",
 		"orientation": "portrait",
 		"icon": "./assets/images/icon.png",
-		"scheme": "aris",
+		"scheme": "aelis",
 		"userInterfaceStyle": "automatic",
 		"newArchEnabled": true,
 		"ios": {
@@ -15,7 +15,7 @@
 				},
 				"ITSAppUsesNonExemptEncryption": false
 			},
-			"bundleIdentifier": "sh.nym.aris"
+			"bundleIdentifier": "sh.nym.aelis"
 		},
 		"android": {
 			"adaptiveIcon": {
@@ -26,7 +26,7 @@
 			},
 			"edgeToEdgeEnabled": true,
 			"predictiveBackGestureEnabled": false,
-			"package": "sh.nym.aris"
+			"package": "sh.nym.aelis"
 		},
 		"web": {
 			"output": "static",

apps/aelis-client/package.json

@@ -1,5 +1,5 @@
 {
-	"name": "aris-client",
+	"name": "aelis-client",
 	"version": "1.0.0",
 	"private": true,
 	"main": "expo-router/entry",
@@ -18,9 +18,11 @@
 		"@expo-google-fonts/inter": "^0.4.2",
 		"@expo-google-fonts/source-serif-4": "^0.4.1",
 		"@expo/vector-icons": "^15.0.3",
+		"@json-render/react-native": "^0.13.0",
 		"@react-navigation/bottom-tabs": "^7.4.0",
 		"@react-navigation/elements": "^2.6.3",
 		"@react-navigation/native": "^7.1.8",
+		"@tanstack/react-query": "^5.90.21",
 		"expo": "~54.0.33",
 		"expo-constants": "~18.0.13",
 		"expo-dev-client": "~6.0.20",
@@ -45,7 +47,8 @@
 		"react-native-svg": "15.12.1",
 		"react-native-web": "~0.21.0",
 		"react-native-worklets": "0.5.1",
-		"twrnc": "^4.16.0"
+		"twrnc": "^4.16.0",
+		"zod": "^4.3.6"
 	},
 	"devDependencies": {
 		"@types/react": "~19.1.0",

apps/aelis-client/src/api/auth-middleware.ts

@@ -0,0 +1,6 @@
+import { ApiRequestMiddleware } from "./client"
+
+export const authMiddleware: ApiRequestMiddleware = (_url, init) => {
+	// TODO: placeholder auth middleware
+	return init
+}

apps/aelis-client/src/api/client.ts

@@ -0,0 +1,39 @@
+import { createContext, useContext } from "react"
+
+export type ApiRequestMiddleware = (
+	url: Parameters<typeof fetch>[0],
+	init: RequestInit,
+) => RequestInit
+
+export class ApiClient {
+	private readonly baseUrl: string
+	private readonly middlewares: readonly ApiRequestMiddleware[]
+
+	static noop = new ApiClient({ baseUrl: "" })
+
+	constructor({
+		baseUrl,
+		middlewares = [],
+	}: {
+		baseUrl: string
+		middlewares?: ApiRequestMiddleware[]
+	}) {
+		this.baseUrl = baseUrl
+		this.middlewares = middlewares
+	}
+
+	async request<T>(...[url, init = {}]: Parameters<typeof fetch>): Promise<[Response, T]> {
+		const finalInit = this.middlewares.reduce(
+			(prevInit, middleware) => middleware(url, prevInit),
+			init,
+		)
+		return fetch(this.baseUrl ? new URL(url.toString(), this.baseUrl) : url, finalInit).then((res) =>
+			Promise.all([Promise.resolve(res), res.json()]),
+		)
+	}
+}
+
+export const ApiClientContext = createContext(ApiClient.noop)
+export function useApiClient() {
+	return useContext(ApiClientContext)
+}

apps/aelis-client/src/app/_layout.tsx

@@ -0,0 +1,65 @@
+import "react-native-reanimated"
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query"
+import { Stack } from "expo-router"
+import { StatusBar } from "expo-status-bar"
+import React from "react"
+import { useColorScheme } from "react-native"
+import tw, { useDeviceContext } from "twrnc"
+
+import { authMiddleware } from "@/api/auth-middleware"
+import { ApiClient, ApiClientContext } from "@/api/client"
+
+const queryClient = new QueryClient()
+const apiClient = new ApiClient({
+	baseUrl: process.env.EXPO_PUBLIC_API_BASE_URL ?? "",
+	middlewares: [authMiddleware],
+})
+
+export default function RootLayout() {
+	useDeviceContext(tw)
+
+	const colorScheme = useColorScheme()
+	const headerBg = colorScheme === "dark" ? "#1c1917" : "#f5f5f4"
+	const headerTint = colorScheme === "dark" ? "#e7e5e4" : "#1c1917"
+
+	return (
+		<ContextProvider>
+			<Stack
+				screenOptions={{
+					headerShown: false,
+					contentStyle: { backgroundColor: headerBg },
+				}}
+			>
+				<Stack.Screen
+					name="components/index"
+					options={{
+						headerShown: true,
+						title: "Components",
+						headerStyle: { backgroundColor: headerBg },
+						headerTintColor: headerTint,
+						headerShadowVisible: false,
+					}}
+				/>
+				<Stack.Screen
+					name="components/[name]"
+					options={{
+						headerShown: true,
+						title: "",
+						headerStyle: { backgroundColor: headerBg },
+						headerTintColor: headerTint,
+						headerShadowVisible: false,
+					}}
+				/>
+			</Stack>
+			<StatusBar style="auto" />
+		</ContextProvider>
+	)
+}
+
+function ContextProvider({ children }: React.PropsWithChildren) {
+	return (
+		<QueryClientProvider client={queryClient}>
+			<ApiClientContext value={apiClient}>{children}</ApiClientContext>
+		</QueryClientProvider>
+	)
+}

apps/aelis-client/src/app/components/[name].tsx

@@ -0,0 +1,48 @@
+import { useLocalSearchParams, useNavigation } from "expo-router"
+import { useEffect } from "react"
+import { ScrollView, View } from "react-native"
+import tw from "twrnc"
+
+import { buttonShowcase } from "@/components/ui/button.showcase"
+import { feedCardShowcase } from "@/components/ui/feed-card.showcase"
+import { monospaceTextShowcase } from "@/components/ui/monospace-text.showcase"
+import { sansSerifTextShowcase } from "@/components/ui/sans-serif-text.showcase"
+import { serifTextShowcase } from "@/components/ui/serif-text.showcase"
+import { type Showcase } from "@/components/showcase"
+import { SansSerifText } from "@/components/ui/sans-serif-text"
+
+const showcases: Record<string, Showcase> = {
+	button: buttonShowcase,
+	"feed-card": feedCardShowcase,
+	"serif-text": serifTextShowcase,
+	"sans-serif-text": sansSerifTextShowcase,
+	"monospace-text": monospaceTextShowcase,
+}
+
+export default function ComponentDetailScreen() {
+	const { name } = useLocalSearchParams<{ name: string }>()
+	const navigation = useNavigation()
+	const showcase = showcases[name]
+
+	useEffect(() => {
+		if (showcase) {
+			navigation.setOptions({ title: showcase.title })
+		}
+	}, [navigation, showcase])
+
+	if (!showcase) {
+		return (
+			<View style={tw`bg-stone-100 dark:bg-stone-900 flex-1 items-center justify-center`}>
+				<SansSerifText>Component not found</SansSerifText>
+			</View>
+		)
+	}
+
+	const ShowcaseComponent = showcase.component
+
+	return (
+		<ScrollView style={tw`bg-stone-100 dark:bg-stone-900 flex-1`} contentContainerStyle={tw`px-5 pb-10 pt-4 gap-6`}>
+			<ShowcaseComponent />
+		</ScrollView>
+	)
+}

apps/aelis-client/src/app/components/index.tsx

@@ -0,0 +1,37 @@
+import { Link } from "expo-router"
+import { FlatList, Pressable, View } from "react-native"
+import tw from "twrnc"
+
+import { SansSerifText } from "@/components/ui/sans-serif-text"
+
+const components = [
+	{ name: "button", label: "Button" },
+	{ name: "feed-card", label: "FeedCard" },
+	{ name: "serif-text", label: "SerifText" },
+	{ name: "sans-serif-text", label: "SansSerifText" },
+	{ name: "monospace-text", label: "MonospaceText" },
+] as const
+
+export default function ComponentsScreen() {
+	return (
+		<View style={tw`flex-1`}>
+			<View style={tw`mx-4 mt-4 rounded-xl border border-stone-200 dark:border-stone-800 overflow-hidden`}>
+				<FlatList
+					data={components}
+					keyExtractor={(item) => item.name}
+					scrollEnabled={false}
+					ItemSeparatorComponent={() => (
+						<View style={tw`border-b border-stone-200 dark:border-stone-800`} />
+					)}
+					renderItem={({ item }) => (
+						<Link href={`/components/${item.name}`} asChild>
+							<Pressable style={tw`px-4 py-3`}>
+								<SansSerifText style={tw`text-base`}>{item.label}</SansSerifText>
+							</Pressable>
+						</Link>
+					)}
+				/>
+			</View>
+		</View>
+	)
+}

apps/aelis-client/src/app/index.tsx

@@ -0,0 +1,28 @@
+import { Link } from "expo-router"
+import { Pressable } from "react-native"
+import { SafeAreaView } from "react-native-safe-area-context"
+import tw from "twrnc"
+
+import { Button } from "@/components/ui/button"
+import { FeedCard } from "@/components/ui/feed-card"
+import { MonospaceText } from "@/components/ui/monospace-text"
+import { SansSerifText } from "@/components/ui/sans-serif-text"
+import { SerifText } from "@/components/ui/serif-text"
+
+export default function HomeScreen() {
+	return (
+		<SafeAreaView style={tw`bg-stone-100 dark:bg-stone-900 flex-1 px-5 pt-6 gap-4`}>
+			<FeedCard>
+				<SerifText style={tw`text-4xl`}>Hello world asdsadsa</SerifText>
+				<SansSerifText style={tw`text-4xl font-bold`}>Hello world</SansSerifText>
+				<MonospaceText style={tw`text-4xl`}>asdjsakljdl</MonospaceText>
+				<Button style={tw`self-start`} label="Test" />
+			</FeedCard>
+			<Link href="/components" asChild>
+				<Pressable>
+					<SansSerifText style={tw`text-teal-600`}>View component library</SansSerifText>
+				</Pressable>
+			</Link>
+		</SafeAreaView>
+	)
+}

apps/aelis-client/src/components/showcase.tsx

@@ -0,0 +1,18 @@
+import { View } from "react-native"
+import tw from "twrnc"
+
+import { SansSerifText } from "./ui/sans-serif-text"
+
+export type Showcase = {
+	title: string
+	component: React.ComponentType
+}
+
+export function Section({ title, children }: { title: string; children: React.ReactNode }) {
+	return (
+		<View style={tw`gap-3`}>
+			<SansSerifText style={tw`text-sm text-stone-500 dark:text-stone-400`}>{title}</SansSerifText>
+			{children}
+		</View>
+	)
+}

apps/aelis-client/src/components/ui/button.showcase.tsx

@@ -0,0 +1,42 @@
+import { View } from "react-native"
+import tw from "twrnc"
+
+import { Button } from "./button"
+import { type Showcase, Section } from "../showcase"
+
+function ButtonShowcase() {
+	return (
+		<View style={tw`gap-6`}>
+			<Section title="Default">
+				<Button style={tw`self-start`} label="Press me" />
+			</Section>
+			<Section title="Leading icon">
+				<Button
+					style={tw`self-start`}
+					label="Add item"
+					leadingIcon={<Button.Icon name="plus" />}
+				/>
+			</Section>
+			<Section title="Trailing icon">
+				<Button
+					style={tw`self-start`}
+					label="Next"
+					trailingIcon={<Button.Icon name="arrow-right" />}
+				/>
+			</Section>
+			<Section title="Both icons">
+				<Button
+					style={tw`self-start`}
+					label="Download"
+					leadingIcon={<Button.Icon name="download" />}
+					trailingIcon={<Button.Icon name="chevron-down" />}
+				/>
+			</Section>
+		</View>
+	)
+}
+
+export const buttonShowcase: Showcase = {
+	title: "Button",
+	component: ButtonShowcase,
+}

apps/aelis-client/src/components/ui/button.tsx

@@ -0,0 +1,43 @@
+import Feather from "@expo/vector-icons/Feather"
+import { type PressableProps, Pressable, View } from "react-native"
+import tw from "twrnc"
+
+import { SansSerifText } from "./sans-serif-text"
+
+type FeatherIconName = React.ComponentProps<typeof Feather>["name"]
+
+type ButtonIconProps = {
+	name: FeatherIconName
+}
+
+function ButtonIcon({ name }: ButtonIconProps) {
+	return <Feather name={name} size={18} color={tw.color("text-stone-100 dark:text-stone-200")} />
+}
+
+type ButtonProps = Omit<PressableProps, "children"> & {
+	label: string
+	leadingIcon?: React.ReactNode
+	trailingIcon?: React.ReactNode
+}
+
+export function Button({ style, label, leadingIcon, trailingIcon, ...props }: ButtonProps) {
+	const hasIcons = leadingIcon != null || trailingIcon != null
+
+	const textElement = <SansSerifText style={tw`text-stone-100 dark:text-stone-200 font-medium`}>{label}</SansSerifText>
+
+	return (
+		<Pressable style={[tw`rounded-full bg-teal-600 px-4 py-3 w-fit`, style]} {...props}>
+			{hasIcons ? (
+				<View style={tw`flex-row items-center gap-1.5`}>
+					{leadingIcon}
+					{textElement}
+					{trailingIcon}
+				</View>
+			) : (
+				textElement
+			)}
+		</Pressable>
+	)
+}
+
+Button.Icon = ButtonIcon