feat(core): add Slot type and slots field to FeedItem (#53)

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

packages/aris-core/src/feed.test.ts

@@ -0,0 +1,87 @@
+import { describe, expect, test } from "bun:test"
+
+import type { FeedItem, Slot } from "./feed"
+
+describe("FeedItem slots", () => {
+	test("FeedItem without slots is valid", () => {
+		const item: FeedItem<"test", { value: number }> = {
+			id: "test-1",
+			type: "test",
+			timestamp: new Date(),
+			data: { value: 42 },
+		}
+
+		expect(item.slots).toBeUndefined()
+	})
+
+	test("FeedItem with unfilled slots", () => {
+		const item: FeedItem<"weather", { temp: number }> = {
+			id: "weather-1",
+			type: "weather",
+			timestamp: new Date(),
+			data: { temp: 18 },
+			slots: {
+				insight: {
+					description: "A short contextual insight about the current weather",
+					content: null,
+				},
+				"cross-source": {
+					description: "Connection between weather and calendar events",
+					content: null,
+				},
+			},
+		}
+
+		expect(item.slots).toBeDefined()
+		expect(Object.keys(item.slots!)).toEqual(["insight", "cross-source"])
+		expect(item.slots!.insight!.content).toBeNull()
+		expect(item.slots!["cross-source"]!.content).toBeNull()
+	})
+
+	test("FeedItem with filled slots", () => {
+		const item: FeedItem<"weather", { temp: number }> = {
+			id: "weather-1",
+			type: "weather",
+			timestamp: new Date(),
+			data: { temp: 18 },
+			slots: {
+				insight: {
+					description: "A short contextual insight about the current weather",
+					content: "Rain after 3pm — grab a jacket before your walk",
+				},
+			},
+		}
+
+		expect(item.slots!.insight!.content).toBe("Rain after 3pm — grab a jacket before your walk")
+	})
+
+	test("Slot interface enforces required fields", () => {
+		const slot: Slot = {
+			description: "Test slot description",
+			content: null,
+		}
+
+		expect(slot.description).toBe("Test slot description")
+		expect(slot.content).toBeNull()
+
+		const filledSlot: Slot = {
+			description: "Test slot description",
+			content: "Filled content",
+		}
+
+		expect(filledSlot.content).toBe("Filled content")
+	})
+
+	test("FeedItem with empty slots record", () => {
+		const item: FeedItem<"test", { value: number }> = {
+			id: "test-1",
+			type: "test",
+			timestamp: new Date(),
+			data: { value: 1 },
+			slots: {},
+		}
+
+		expect(item.slots).toEqual({})
+		expect(Object.keys(item.slots!)).toHaveLength(0)
+	})
+})

packages/aris-core/src/feed.ts

@@ -23,6 +23,20 @@ export interface FeedItemSignals {
 	timeRelevance?: TimeRelevance
 }
 
+/**
+ * A named slot for LLM-fillable content on a feed item.
+ *
+ * Sources declare slots with a description that tells the LLM what content
+ * to generate. The enhancement harness fills `content` asynchronously;
+ * until then it remains `null`.
+ */
+export interface Slot {
+	/** Tells the LLM what this slot wants — written by the source */
+	description: string
+	/** LLM-filled text content, null until enhanced */
+	content: string | null
+}
+
 /**
  * A single item in the feed.
  *
@@ -36,6 +50,12 @@ export interface FeedItemSignals {
  *   timestamp: new Date(),
  *   data: { temp: 18, condition: "cloudy" },
  *   signals: { urgency: 0.5, timeRelevance: "ambient" },
+ *   slots: {
+ *     insight: {
+ *       description: "A short contextual insight about the current weather",
+ *       content: null,
+ *     },
+ *   },
  * }
  * ```
  */
@@ -53,4 +73,6 @@ export interface FeedItem<
 	data: TData
 	/** Source-provided hints for post-processors. Optional — omit if no signals apply. */
 	signals?: FeedItemSignals
+	/** Named slots for LLM-fillable content. Keys are slot names. */
+	slots?: Record<string, Slot>
 }

packages/aris-core/src/index.ts

@@ -7,7 +7,7 @@ export type { ActionDefinition } from "./action"
 export { UnknownActionError } from "./action"
 
 // Feed
-export type { FeedItem, FeedItemSignals } from "./feed"
+export type { FeedItem, FeedItemSignals, Slot } from "./feed"
 export { TimeRelevance } from "./feed"
 
 // Feed Source