feat: replace flat context with tuple-keyed store

Context keys are now tuples instead of strings, inspired by
React Query's query keys. This prevents context collisions
when multiple instances of the same source type are registered.

Sources write to structured keys like
["aris.google-calendar", "nextEvent", { account: "work" }]
and consumers can query by prefix via context.find().

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

.claude/skills/gpg-commit-signing/SKILL.md

@@ -0,0 +1,43 @@
+---
+name: gpg-commit-signing
+description: Sign git commits with GPG in non-interactive environments. Use when committing code and the `GPG_PRIVATE_KEY_PASSPHRASE` environment variable is available. Triggers on "commit", "sign commit", "GPG", "git commit -S", or any git operation requiring signed commits.
+---
+
+# GPG Commit Signing
+
+Sign commits in headless/non-interactive environments where `/dev/tty` is unavailable.
+
+## Workflow
+
+1. Check whether `GPG_PRIVATE_KEY_PASSPHRASE` is set:
+
+   ```bash
+   test -n "$GPG_PRIVATE_KEY_PASSPHRASE" && echo "available" || echo "not set"
+   ```
+
+   If not set, skip signing — commit without `-S`.
+
+2. Try a direct signed commit first — the environment may already have loopback pinentry configured:
+
+   ```bash
+   git commit -S -m "message"
+   ```
+
+   If this succeeds, no further steps are needed.
+
+3. If step 2 fails with a `/dev/tty` error, use `--pinentry-mode loopback` via a wrapper script:
+
+   ```bash
+   printf '#!/bin/sh\ngpg --batch --pinentry-mode loopback --passphrase "$GPG_PRIVATE_KEY_PASSPHRASE" "$@"\n' > /tmp/gpg-sign.sh
+   chmod +x /tmp/gpg-sign.sh
+   git -c gpg.program=/tmp/gpg-sign.sh commit -S -m "message"
+   rm /tmp/gpg-sign.sh
+   ```
+
+   This passes the passphrase directly to gpg on each signing invocation, bypassing the need for a configured gpg-agent.
+
+## Anti-patterns
+
+- Do not echo or log `GPG_PRIVATE_KEY_PASSPHRASE`.
+- Do not commit without `-S` when the passphrase is available — the project expects signed commits.
+- Do not leave wrapper scripts on disk after committing.

apps/aris-backend/src/feed/http.test.ts

@@ -1,4 +1,4 @@
-import type { ActionDefinition, Context, FeedItem, FeedSource } from "@aris/core"
+import type { ActionDefinition, ContextEntry, FeedItem, FeedSource } from "@aris/core"
 
 import { describe, expect, test } from "bun:test"
 import { Hono } from "hono"
@@ -27,7 +27,7 @@ function createStubSource(id: string, items: FeedItem[] = []): FeedSource {
 		async executeAction(): Promise<unknown> {
 			return undefined
 		},
-		async fetchContext(): Promise<Partial<Context> | null> {
+		async fetchContext(): Promise<readonly ContextEntry[] | null> {
 			return null
 		},
 		async fetchItems() {

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

@@ -1,4 +1,4 @@
-import type { ActionDefinition, Context, FeedSource } from "@aris/core"
+import type { ActionDefinition, ContextEntry, FeedSource } from "@aris/core"
 
 import { LocationSource } from "@aris/source-location"
 import { describe, expect, test } from "bun:test"
@@ -14,7 +14,7 @@ function createStubSource(id: string): FeedSource {
 		async executeAction(): Promise<unknown> {
 			return undefined
 		},
-		async fetchContext(): Promise<Partial<Context> | null> {
+		async fetchContext(): Promise<readonly ContextEntry[] | null> {
 			return null
 		},
 		async fetchItems() {

bun.lock

@@ -89,6 +89,15 @@
         "arktype": "^2.1.0",
       },
     },
+    "packages/aris-source-caldav": {
+      "name": "@aris/source-caldav",
+      "version": "0.0.0",
+      "dependencies": {
+        "@aris/core": "workspace:*",
+        "ical.js": "^2.1.0",
+        "tsdav": "^2.1.7",
+      },
+    },
     "packages/aris-source-google-calendar": {
       "name": "@aris/source-google-calendar",
       "version": "0.0.0",
@@ -135,6 +144,8 @@
 
     "@aris/data-source-weatherkit": ["@aris/data-source-weatherkit@workspace:packages/aris-data-source-weatherkit"],
 
+    "@aris/source-caldav": ["@aris/source-caldav@workspace:packages/aris-source-caldav"],
+
     "@aris/source-google-calendar": ["@aris/source-google-calendar@workspace:packages/aris-source-google-calendar"],
 
     "@aris/source-location": ["@aris/source-location@workspace:packages/aris-source-location"],
@@ -899,6 +910,8 @@
 
     "bare-events": ["bare-events@2.8.2", "", { "peerDependencies": { "bare-abort-controller": "*" }, "optionalPeers": ["bare-abort-controller"] }, "sha512-riJjyv1/mHLIPX4RwiK+oW9/4c3TEUeORHKefKAKnZ5kyslbN+HXowtbaVEqt4IMUB7OXlfixcs6gsFeo/jhiQ=="],
 
+    "base-64": ["base-64@1.0.0", "", {}, "sha512-kwDPIFCGx0NZHog36dj+tHiwP4QMzsZ3AgMViUBKI0+V5n4U0ufTCUMhnQ04diaRI8EX/QcPfql7zlhZ7j4zgg=="],
+
     "base64-js": ["base64-js@1.5.1", "", {}, "sha512-AKpaYlHn8t4SVbOHCy+b5+KKgvR4vrsD8vbvrbiQJps7fKDTkjkDry6ji0rUJjC0kzbNePLwzxq8iypo41qeWA=="],
 
     "baseline-browser-mapping": ["baseline-browser-mapping@2.9.19", "", { "bin": { "baseline-browser-mapping": "dist/cli.js" } }, "sha512-ipDqC8FrAl/76p2SSWKSI+H9tFwm7vYqXQrItCuiVPt26Km0jS+NzSsBWAaBusvSbQcfJG+JitdMm+wZAgTYqg=="],
@@ -1011,7 +1024,7 @@
 
     "create-require": ["create-require@1.1.1", "", {}, "sha512-dcKFX3jn0MpIaXjisoRvexIJVEKzaq7z2rZKxf+MSr9TkdmHmsU4m2lcLojrj/FHl8mk5VxMmYA+ftRkP/3oKQ=="],
 
-    "cross-fetch": ["cross-fetch@3.2.0", "", { "dependencies": { "node-fetch": "^2.7.0" } }, "sha512-Q+xVJLoGOeIMXZmbUK4HYk+69cQH6LudR0Vu/pRm2YlU/hDV9CiS0gKUMaWY5f2NeUH9C1nV3bsTlCo0FsTV1Q=="],
+    "cross-fetch": ["cross-fetch@4.1.0", "", { "dependencies": { "node-fetch": "^2.7.0" } }, "sha512-uKm5PU+MHTootlWEY+mZ4vvXoCn4fLQxT9dSc1sXVMSFkINTJVN8cAQROpwcKm8bJ/c7rgZVIBWzH5T78sNZZw=="],
 
     "cross-spawn": ["cross-spawn@7.0.6", "", { "dependencies": { "path-key": "^3.1.0", "shebang-command": "^2.0.0", "which": "^2.0.1" } }, "sha512-uV2QOWP2nWzsy2aMp8aRibhi9dlzF5Hgh5SHaB9OiTGEyDTiJJyx0uy51QXdyWbtAHNua4XJzUKca3OzKUd3vA=="],
 
@@ -1389,6 +1402,8 @@
 
     "hyphenate-style-name": ["hyphenate-style-name@1.1.0", "", {}, "sha512-WDC/ui2VVRrz3jOVi+XtjqkDjiVjTtFaAGiW37k6b+ohyQ5wYDOGkvCZa8+H0nx3gyvv0+BST9xuOgIyGQ00gw=="],
 
+    "ical.js": ["ical.js@2.2.1", "", {}, "sha512-yK/UlPbEs316igb/tjRgbFA8ZV75rCsBJp/hWOatpyaPNlgw0dGDmU+FoicOcwX4xXkeXOkYiOmCqNPFpNPkQg=="],
+
     "ieee754": ["ieee754@1.2.1", "", {}, "sha512-dcyqhDvX1C46lXZcVqCpK+FtMRQVdIMN6/Df5js2zouUsqG7I6sFxitIC+7KYK29KdXOLHdu9zL4sFnoVQnqaA=="],
 
     "ignore": ["ignore@5.3.0", "", {}, "sha512-g7dmpshy+gD7mh88OC9NwSGTKoc3kyLAZQRU1mt53Aw/vnvfXnbC+F/7F7QoYVKbV+KNvJx8wArewKy1vXMtlg=="],
@@ -2163,6 +2178,8 @@
 
     "tsconfig-paths": ["tsconfig-paths@3.15.0", "", { "dependencies": { "@types/json5": "^0.0.29", "json5": "^1.0.2", "minimist": "^1.2.6", "strip-bom": "^3.0.0" } }, "sha512-2Ac2RgzDe/cn48GvOe3M+o82pEFewD3UPbyoUHHdKasHwJKjds4fLXWf/Ux5kATBKN20oaFGu+jbElp1pos0mg=="],
 
+    "tsdav": ["tsdav@2.1.8", "", { "dependencies": { "base-64": "1.0.0", "cross-fetch": "4.1.0", "debug": "4.4.3", "xml-js": "1.6.11" } }, "sha512-zvQvhZLzTaEmNNgJbBlUYT/JOq9Xpw/xkxCqs7IT2d2/7o7pss0iZOlZXuHJ5VcvSvTny42Vc6+6GyzZcrCJ1g=="],
+
     "tslib": ["tslib@2.6.2", "", {}, "sha512-AEYxH93jGFPn/a2iVAwW87VuUIkR1FVUKB77NwMF7nBTDkDrrT/Hpt/IrCJ0QXhW27jTBDcf5ZY7w6RiqTMw2Q=="],
 
     "tunnel-agent": ["tunnel-agent@0.6.0", "", { "dependencies": { "safe-buffer": "^5.0.1" } }, "sha512-McnNiV1l8RYeY8tBgEpuodCC1mLUdbSN+CYBL7kJsJNInOP8UjDDEwdk6Mw60vdLLrr5NHKZhMAOSrR2NZuQ+w=="],
@@ -2285,6 +2302,8 @@
 
     "xcode": ["xcode@3.0.1", "", { "dependencies": { "simple-plist": "^1.1.0", "uuid": "^7.0.3" } }, "sha512-kCz5k7J7XbJtjABOvkc5lJmkiDh8VhjVCGNiqdKCscmVpdVUpEAyXv1xmCLkQJ5dsHqx3IPO4XW+NTDhU/fatA=="],
 
+    "xml-js": ["xml-js@1.6.11", "", { "dependencies": { "sax": "^1.2.4" }, "bin": { "xml-js": "./bin/cli.js" } }, "sha512-7rVi2KMfwfWFl+GpPg6m80IVMWXLRjO+PxTq7V2CDhoGak0wzYzFgUY2m4XJ47OGdXd8eLE8EmwfAmdjw7lC1g=="],
+
     "xml2js": ["xml2js@0.6.0", "", { "dependencies": { "sax": ">=0.6.0", "xmlbuilder": "~11.0.0" } }, "sha512-eLTh0kA8uHceqesPqSE+VvO1CDDJWMwlQfB6LuN6T8w6MaDJ8Txm8P7s5cHD0miF0V+GGTZrDQfxPZQVsur33w=="],
 
     "xmlbuilder": ["xmlbuilder@14.0.0", "", {}, "sha512-ts+B2rSe4fIckR6iquDjsKbQFK2NlUk6iG5nf14mDEyldgoc2nEKZ3jZWMPTxGQwVgToSjt6VGIho1H8/fNFTg=="],
@@ -2613,6 +2632,8 @@
 
     "fast-glob/glob-parent": ["glob-parent@5.1.2", "", { "dependencies": { "is-glob": "^4.0.1" } }, "sha512-AOIgSQCepiJYwP3ARnGx+5VnTu2HBYdzbGP45eLw1vr3zB3vZLeyed1sC9hnbcOc9/SrMyM5RPQrkGz4aS9Zow=="],
 
+    "fbjs/cross-fetch": ["cross-fetch@3.2.0", "", { "dependencies": { "node-fetch": "^2.7.0" } }, "sha512-Q+xVJLoGOeIMXZmbUK4HYk+69cQH6LudR0Vu/pRm2YlU/hDV9CiS0gKUMaWY5f2NeUH9C1nV3bsTlCo0FsTV1Q=="],
+
     "fbjs/promise": ["promise@7.3.1", "", { "dependencies": { "asap": "~2.0.3" } }, "sha512-nolQXZ/4L+bP/UGlkfaIujX9BKxGwmQ9OT4mOt5yvy8iK1h3wqTEJCijzGANTCCl9nWjY41juyAn2K3Q1hLLTg=="],
 
     "figures/escape-string-regexp": ["escape-string-regexp@1.0.5", "", {}, "sha512-vbRorB5FUQWvla16U8R/qgaFIya2qGzwDrNmCZuYKrbdSUMG6I1ZCGQRefkRVhuOkIGVne7BQ35DSfo1qvJqFg=="],
@@ -2939,6 +2960,8 @@
 
     "expo/@expo/config-plugins/semver": ["semver@7.7.2", "", { "bin": { "semver": "bin/semver.js" } }, "sha512-RF0Fw+rO5AMf9MAyaRXI4AV0Ulj5lMHqVxxdSgiVbixSCXoEmmX/jk0CuJw4+3SqroYO9VoUh+HcuJivvtJemA=="],
 
+    "fbjs/cross-fetch/node-fetch": ["node-fetch@2.7.0", "", { "dependencies": { "whatwg-url": "^5.0.0" }, "peerDependencies": { "encoding": "^0.1.0" }, "optionalPeers": ["encoding"] }, "sha512-c4FRfUm/dbcWZ7U+1Wq0AwCyFL+3nt2bEw05wfxSz+DWpWsitgmSgYmy2dQdWyKC1694ELPqMs/YzUSNozLt8A=="],
+
     "finalhandler/debug/ms": ["ms@2.0.0", "", {}, "sha512-Tpp60P6IUJDTuOq/5Z8cdskzJujfwqfOTkrwIwj7IRISpnkJnT6SyJ4PCPnGMoFjC9ddhal5KVIYtAt97ix05A=="],
 
     "glob/minimatch/brace-expansion": ["brace-expansion@1.1.12", "", { "dependencies": { "balanced-match": "^1.0.0", "concat-map": "0.0.1" } }, "sha512-9T9UjW3r0UW5c1Q7GTwllptXwhvYmEzFhzMfZ9H7FQWt+uZePjZPjBP/W1ZEyZ1twGWom5/56TF4lPcqjnDHcg=="],

packages/aris-core/src/context-bridge.ts

@@ -1,8 +1,10 @@
-import type { Context } from "./context"
+import type { ContextEntry } from "./context"
 import type { ContextProvider } from "./context-provider"
 
+import { contextKey } from "./context"
+
 interface ContextUpdatable {
-	pushContextUpdate(update: Partial<Context>): void
+	pushContextUpdate(entries: readonly ContextEntry[]): void
 }
 
 export interface ProviderError {
@@ -54,7 +56,7 @@ export class ContextBridge {
 		this.providers.set(provider.key, provider as ContextProvider)
 
 		const cleanup = provider.onUpdate((value) => {
-			this.controller.pushContextUpdate({ [provider.key]: value })
+			this.controller.pushContextUpdate([[contextKey(provider.key), value]])
 		})
 		this.cleanups.push(cleanup)
 
@@ -67,7 +69,7 @@ export class ContextBridge {
 	 * Returns errors from providers that failed to fetch.
 	 */
 	async refresh(): Promise<RefreshResult> {
-		const updates: Partial<Context> = {}
+		const collected: ContextEntry[] = []
 		const errors: ProviderError[] = []
 
 		const entries = Array.from(this.providers.entries())
@@ -78,7 +80,7 @@ export class ContextBridge {
 		entries.forEach(([key], i) => {
 			const result = results[i]
 			if (result?.status === "fulfilled") {
-				updates[key] = result.value
+				collected.push([contextKey(key), result.value])
 			} else if (result?.status === "rejected") {
 				errors.push({
 					key,
@@ -87,7 +89,7 @@ export class ContextBridge {
 			}
 		})
 
-		this.controller.pushContextUpdate(updates)
+		this.controller.pushContextUpdate(collected)
 
 		return { errors }
 	}

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

@@ -0,0 +1,184 @@
+import { describe, expect, test } from "bun:test"
+
+import type { ContextKey } from "./context"
+
+import { Context, contextKey } from "./context"
+
+interface Weather {
+	temperature: number
+}
+
+interface NextEvent {
+	title: string
+}
+
+const WeatherKey: ContextKey<Weather> = contextKey("aris.weather", "current")
+const NextEventKey: ContextKey<NextEvent> = contextKey("aris.google-calendar", "nextEvent")
+
+describe("Context", () => {
+	describe("get", () => {
+		test("returns undefined for missing key", () => {
+			const ctx = new Context()
+			expect(ctx.get(WeatherKey)).toBeUndefined()
+		})
+
+		test("returns value for exact key match", () => {
+			const ctx = new Context()
+			const weather: Weather = { temperature: 20 }
+			ctx.set([[WeatherKey, weather]])
+
+			expect(ctx.get(WeatherKey)).toEqual(weather)
+		})
+
+		test("distinguishes keys with different parts", () => {
+			const ctx = new Context()
+			ctx.set([
+				[WeatherKey, { temperature: 20 }],
+				[NextEventKey, { title: "Standup" }],
+			])
+
+			expect(ctx.get(WeatherKey)).toEqual({ temperature: 20 })
+			expect(ctx.get(NextEventKey)).toEqual({ title: "Standup" })
+		})
+
+		test("last write wins for same key", () => {
+			const ctx = new Context()
+			ctx.set([[WeatherKey, { temperature: 20 }]])
+			ctx.set([[WeatherKey, { temperature: 25 }]])
+
+			expect(ctx.get(WeatherKey)).toEqual({ temperature: 25 })
+		})
+	})
+
+	describe("find", () => {
+		test("returns empty array when no keys match", () => {
+			const ctx = new Context()
+			expect(ctx.find(WeatherKey)).toEqual([])
+		})
+
+		test("returns exact match as single result", () => {
+			const ctx = new Context()
+			ctx.set([[NextEventKey, { title: "Standup" }]])
+
+			const results = ctx.find(NextEventKey)
+			expect(results).toHaveLength(1)
+			expect(results[0]!.value).toEqual({ title: "Standup" })
+		})
+
+		test("prefix match returns multiple instances", () => {
+			const workKey = contextKey<NextEvent>("aris.google-calendar", "nextEvent", {
+				account: "work",
+			})
+			const personalKey = contextKey<NextEvent>("aris.google-calendar", "nextEvent", {
+				account: "personal",
+			})
+
+			const ctx = new Context()
+			ctx.set([
+				[workKey, { title: "Sprint Planning" }],
+				[personalKey, { title: "Dentist" }],
+			])
+
+			const prefix = contextKey<NextEvent>("aris.google-calendar", "nextEvent")
+			const results = ctx.find(prefix)
+
+			expect(results).toHaveLength(2)
+			const titles = results.map((r) => r.value.title).sort()
+			expect(titles).toEqual(["Dentist", "Sprint Planning"])
+		})
+
+		test("prefix match includes exact match and longer keys", () => {
+			const baseKey = contextKey<NextEvent>("aris.google-calendar", "nextEvent")
+			const instanceKey = contextKey<NextEvent>("aris.google-calendar", "nextEvent", {
+				account: "work",
+			})
+
+			const ctx = new Context()
+			ctx.set([
+				[baseKey, { title: "Base" }],
+				[instanceKey, { title: "Instance" }],
+			])
+
+			const results = ctx.find(baseKey)
+			expect(results).toHaveLength(2)
+		})
+
+		test("does not match keys that share a string prefix but differ at segment boundary", () => {
+			const keyA = contextKey<string>("aris.calendar", "next")
+			const keyB = contextKey<string>("aris.calendar", "nextEvent")
+
+			const ctx = new Context()
+			ctx.set([
+				[keyA, "a"],
+				[keyB, "b"],
+			])
+
+			const results = ctx.find(keyA)
+			expect(results).toHaveLength(1)
+			expect(results[0]!.value).toBe("a")
+		})
+
+		test("object key parts with different property order match", () => {
+			const key1 = contextKey<string>("source", "ctx", { b: 2, a: 1 })
+			const key2 = contextKey<string>("source", "ctx", { a: 1, b: 2 })
+
+			const ctx = new Context()
+			ctx.set([[key1, "value"]])
+
+			// Exact match via get should work regardless of property order
+			expect(ctx.get(key2)).toBe("value")
+
+			// find with the reordered key as prefix should also match
+			const prefix = contextKey<string>("source", "ctx")
+			const results = ctx.find(prefix)
+			expect(results).toHaveLength(1)
+		})
+
+		test("single-segment prefix matches all keys starting with that segment", () => {
+			const ctx = new Context()
+			ctx.set([
+				[contextKey("aris.weather", "current"), { temperature: 20 }],
+				[contextKey("aris.weather", "forecast"), { high: 25 }],
+				[contextKey("aris.calendar", "nextEvent"), { title: "Meeting" }],
+			])
+
+			const results = ctx.find(contextKey("aris.weather"))
+			expect(results).toHaveLength(2)
+		})
+
+		test("does not match shorter keys", () => {
+			const ctx = new Context()
+			ctx.set([[contextKey("aris.weather"), "short"]])
+
+			const results = ctx.find(contextKey("aris.weather", "current"))
+			expect(results).toHaveLength(0)
+		})
+
+		test("numeric key parts match correctly", () => {
+			const ctx = new Context()
+			ctx.set([
+				[contextKey("source", 1, "data"), "one"],
+				[contextKey("source", 2, "data"), "two"],
+			])
+
+			const results = ctx.find(contextKey("source", 1))
+			expect(results).toHaveLength(1)
+			expect(results[0]!.value).toBe("one")
+		})
+	})
+
+	describe("size", () => {
+		test("returns 0 for empty context", () => {
+			expect(new Context().size).toBe(0)
+		})
+
+		test("reflects number of entries", () => {
+			const ctx = new Context()
+			ctx.set([
+				[WeatherKey, { temperature: 20 }],
+				[NextEventKey, { title: "Standup" }],
+			])
+			expect(ctx.size).toBe(2)
+		})
+	})
+})

packages/aris-core/src/context.ts

@@ -1,46 +1,131 @@
 /**
- * Branded type for type-safe context keys.
+ * Tuple-keyed context system inspired by React Query's query keys.
  *
- * Each package defines its own keys with associated value types:
- * ```ts
- * const LocationKey: ContextKey<Location> = contextKey("location")
- * ```
+ * Context keys are arrays that form a hierarchy. Sources write to specific
+ * keys (e.g., ["aris.google-calendar", "nextEvent", { account: "work" }])
+ * and consumers can query by exact match or prefix match to get all values
+ * of a given type across source instances.
  */
-export type ContextKey<T> = string & { __contextValue?: T }
 
-/**
- * Creates a typed context key.
- *
- * @example
- * ```ts
- * interface Location { lat: number; lng: number; accuracy: number }
- * const LocationKey: ContextKey<Location> = contextKey("location")
- * ```
- */
-export function contextKey<T>(key: string): ContextKey<T> {
-	return key as ContextKey<T>
+// -- Key types --
+
+/** A single segment of a context key: string, number, or a record of primitives. */
+export type ContextKeyPart = string | number | Record<string, unknown>
+
+/** A context key is a readonly tuple of parts, branded with the value type. */
+export type ContextKey<T> = readonly ContextKeyPart[] & { __contextValue?: T }
+
+/** Creates a typed context key. */
+export function contextKey<T>(...parts: ContextKeyPart[]): ContextKey<T> {
+	return parts as ContextKey<T>
 }
 
-/**
- * Type-safe accessor for context values.
- *
- * @example
- * ```ts
- * const location = contextValue(context, LocationKey)
- * if (location) {
- *   console.log(location.lat, location.lng)
- * }
- * ```
- */
-export function contextValue<T>(context: Context, key: ContextKey<T>): T | undefined {
-	return context[key] as T | undefined
-}
+// -- Serialization --
 
 /**
- * Arbitrary key-value bag representing the current state.
- * Always includes `time`. Other keys are added by context providers.
+ * Deterministic serialization of a context key for use as a Map key.
+ * Object parts have their keys sorted for stable comparison.
  */
-export interface Context {
+export function serializeKey(key: readonly ContextKeyPart[]): string {
+	return JSON.stringify(key, (_key, value) => {
+		if (value !== null && typeof value === "object" && !Array.isArray(value)) {
+			const sorted: Record<string, unknown> = {}
+			for (const k of Object.keys(value).sort()) {
+				sorted[k] = value[k]
+			}
+			return sorted
+		}
+		return value
+	})
+}
+
+// -- Key matching --
+
+/** Returns true if `key` starts with all parts of `prefix`. */
+function keyStartsWith(key: readonly ContextKeyPart[], prefix: readonly ContextKeyPart[]): boolean {
+	if (key.length < prefix.length) return false
+
+	for (let i = 0; i < prefix.length; i++) {
+		if (!partsEqual(key[i]!, prefix[i]!)) return false
+	}
+
+	return true
+}
+
+/** Recursive structural equality, matching React Query's partialMatchKey approach. */
+function partsEqual(a: unknown, b: unknown): boolean {
+	if (a === b) return true
+	if (typeof a !== typeof b) return false
+	if (a && b && typeof a === "object" && typeof b === "object") {
+		const aKeys = Object.keys(a)
+		const bKeys = Object.keys(b)
+		if (aKeys.length !== bKeys.length) return false
+		return aKeys.every((key) =>
+			partsEqual(
+				(a as Record<string, unknown>)[key],
+				(b as Record<string, unknown>)[key],
+			),
+		)
+	}
+	return false
+}
+
+// -- Context store --
+
+/** A single context entry: a key-value pair. */
+export type ContextEntry<T = unknown> = readonly [ContextKey<T>, T]
+
+/**
+ * Mutable context store with tuple keys.
+ *
+ * Supports exact-match lookups and prefix-match queries.
+ * Sources write context in topological order during refresh.
+ */
+export class Context {
 	time: Date
-	[key: string]: unknown
+	private readonly store: Map<string, { key: readonly ContextKeyPart[]; value: unknown }>
+
+	constructor(time: Date = new Date()) {
+		this.time = time
+		this.store = new Map()
+	}
+
+	/** Merges entries into this context. */
+	set(entries: readonly ContextEntry[]): void {
+		for (const [key, value] of entries) {
+			this.store.set(serializeKey(key), { key, value })
+		}
+	}
+
+	/** Exact-match lookup. Returns the value for the given key, or undefined. */
+	get<T>(key: ContextKey<T>): T | undefined {
+		const entry = this.store.get(serializeKey(key))
+		return entry?.value as T | undefined
+	}
+
+	/**
+	 * Prefix-match query. Returns all entries whose key starts with the given prefix.
+	 *
+	 * @example
+	 * ```ts
+	 * // Get all "nextEvent" values across calendar source instances
+	 * const events = context.find(contextKey("nextEvent"))
+	 * ```
+	 */
+	find<T>(prefix: ContextKey<T>): Array<{ key: readonly ContextKeyPart[]; value: T }> {
+		const results: Array<{ key: readonly ContextKeyPart[]; value: T }> = []
+
+		for (const entry of this.store.values()) {
+			if (keyStartsWith(entry.key, prefix)) {
+				results.push({ key: entry.key, value: entry.value as T })
+			}
+		}
+
+		return results
+	}
+
+	/** Returns the number of entries (excluding time). */
+	get size(): number {
+		return this.store.size
+	}
 }

packages/aris-core/src/data-source.ts

@@ -12,7 +12,7 @@ import type { FeedItem } from "./feed"
  *   readonly type = "weather"
  *
  *   async query(context: Context): Promise<WeatherItem[]> {
- *     const location = contextValue(context, LocationKey)
+ *     const location = context.get(LocationKey)
  *     if (!location) return []
  *     const data = await fetchWeather(location)
  *     return [{

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

@@ -1,8 +1,9 @@
-import type { Context } from "./context"
+import type { ContextEntry } from "./context"
 import type { DataSource } from "./data-source"
 import type { FeedItem } from "./feed"
 import type { ReconcileResult } from "./reconciler"
 
+import { Context } from "./context"
 import { Reconciler } from "./reconciler"
 
 export interface FeedControllerConfig {
@@ -40,7 +41,7 @@ const DEFAULT_DEBOUNCE_MS = 100
  * })
  *
  * // Context update triggers debounced reconcile
- * controller.pushContextUpdate({ [LocationKey]: location })
+ * controller.pushContextUpdate([[LocationKey, location]])
  *
  * // Direct reconcile (no debounce)
  * const result = await controller.reconcile()
@@ -59,7 +60,7 @@ export class FeedController<TItems extends FeedItem = never> {
 	private stopped = false
 
 	constructor(config?: FeedControllerConfig) {
-		this.context = config?.initialContext ?? { time: new Date() }
+		this.context = config?.initialContext ?? new Context()
 		this.debounceMs = config?.debounceMs ?? DEFAULT_DEBOUNCE_MS
 		this.timeout = config?.timeout
 	}
@@ -94,9 +95,10 @@ export class FeedController<TItems extends FeedItem = never> {
 		}
 	}
 
-	/** Merges update into context and schedules a debounced reconcile. */
-	pushContextUpdate(update: Partial<Context>): void {
-		this.context = { ...this.context, ...update, time: new Date() }
+	/** Merges entries into context and schedules a debounced reconcile. */
+	pushContextUpdate(entries: readonly ContextEntry[]): void {
+		this.context.time = new Date()
+		this.context.set(entries)
 		this.scheduleReconcile()
 	}
 

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

@@ -1,9 +1,9 @@
 import { describe, expect, test } from "bun:test"
 
-import type { ActionDefinition, Context, ContextKey, FeedItem, FeedSource } from "./index"
+import type { ActionDefinition, ContextEntry, ContextKey, FeedItem, FeedSource } from "./index"
 
 import { FeedEngine } from "./feed-engine"
-import { TimeRelevance, UnknownActionError, contextKey, contextValue } from "./index"
+import { Context, TimeRelevance, UnknownActionError, contextKey } from "./index"
 
 // No-op action methods for test sources
 const noActions = {
@@ -48,7 +48,7 @@ interface SimulatedLocationSource extends FeedSource {
 }
 
 function createLocationSource(): SimulatedLocationSource {
-	let callback: ((update: Partial<Context>) => void) | null = null
+	let callback: ((entries: readonly ContextEntry[]) => void) | null = null
 	let currentLocation: Location = { lat: 0, lng: 0 }
 
 	return {
@@ -63,12 +63,12 @@ function createLocationSource(): SimulatedLocationSource {
 		},
 
 		async fetchContext() {
-			return { [LocationKey]: currentLocation }
+			return [[LocationKey, currentLocation]]
 		},
 
 		simulateUpdate(location: Location) {
 			currentLocation = location
-			callback?.({ [LocationKey]: location })
+			callback?.([[LocationKey, location]])
 		},
 	}
 }
@@ -85,15 +85,15 @@ function createWeatherSource(
 		...noActions,
 
 		async fetchContext(context) {
-			const location = contextValue(context, LocationKey)
+			const location = context.get(LocationKey)
 			if (!location) return null
 
 			const weather = await fetchWeather(location)
-			return { [WeatherKey]: weather }
+			return [[WeatherKey, weather]]
 		},
 
 		async fetchItems(context) {
-			const weather = contextValue(context, WeatherKey)
+			const weather = context.get(WeatherKey)
 			if (!weather) return []
 
 			return [
@@ -123,7 +123,7 @@ function createAlertSource(): FeedSource<AlertFeedItem> {
 		},
 
 		async fetchItems(context) {
-			const weather = contextValue(context, WeatherKey)
+			const weather = context.get(WeatherKey)
 			if (!weather) return []
 
 			if (weather.condition === "storm") {
@@ -265,7 +265,7 @@ describe("FeedEngine", () => {
 				...noActions,
 				async fetchContext() {
 					order.push("location")
-					return { [LocationKey]: { lat: 51.5, lng: -0.1 } }
+					return [[LocationKey, { lat: 51.5, lng: -0.1 }]]
 				},
 			}
 
@@ -275,9 +275,9 @@ describe("FeedEngine", () => {
 				...noActions,
 				async fetchContext(ctx) {
 					order.push("weather")
-					const loc = contextValue(ctx, LocationKey)
+					const loc = ctx.get(LocationKey)
 					expect(loc).toBeDefined()
-					return { [WeatherKey]: { temperature: 20, condition: "sunny" } }
+					return [[WeatherKey, { temperature: 20, condition: "sunny" }]]
 				},
 			}
 
@@ -298,11 +298,11 @@ describe("FeedEngine", () => {
 
 			const { context } = await engine.refresh()
 
-			expect(contextValue(context, LocationKey)).toEqual({
+			expect(context.get(LocationKey)).toEqual({
 				lat: 51.5,
 				lng: -0.1,
 			})
-			expect(contextValue(context, WeatherKey)).toEqual({
+			expect(context.get(WeatherKey)).toEqual({
 				temperature: 20,
 				condition: "sunny",
 			})
@@ -361,7 +361,7 @@ describe("FeedEngine", () => {
 
 			const { context, items } = await engine.refresh()
 
-			expect(contextValue(context, WeatherKey)).toBeUndefined()
+			expect(context.get(WeatherKey)).toBeUndefined()
 			expect(items).toHaveLength(0)
 		})
 
@@ -459,7 +459,7 @@ describe("FeedEngine", () => {
 			await engine.refresh()
 
 			const context = engine.currentContext()
-			expect(contextValue(context, LocationKey)).toEqual({
+			expect(context.get(LocationKey)).toEqual({
 				lat: 51.5,
 				lng: -0.1,
 			})
@@ -734,7 +734,7 @@ describe("FeedEngine", () => {
 		})
 
 		test("reactive item update refreshes cache", async () => {
-			let itemUpdateCallback: (() => void) | null = null
+			let itemUpdateCallback: ((items: FeedItem[]) => void) | null = null
 
 			const source: FeedSource = {
 				id: "reactive-items",
@@ -765,7 +765,7 @@ describe("FeedEngine", () => {
 			engine.start()
 
 			// Trigger item update
-			itemUpdateCallback!()
+			itemUpdateCallback!([])
 
 			// Wait for async refresh
 			await new Promise((resolve) => setTimeout(resolve, 50))
@@ -885,12 +885,12 @@ describe("FeedEngine", () => {
 				...noActions,
 				async fetchContext(ctx) {
 					fetchCount++
-					const loc = contextValue(ctx, LocationKey)
+					const loc = ctx.get(LocationKey)
 					if (!loc) return null
-					return { [WeatherKey]: { temperature: 20, condition: "sunny" } }
+					return [[WeatherKey, { temperature: 20, condition: "sunny" }]]
 				},
 				async fetchItems(ctx) {
-					const weather = contextValue(ctx, WeatherKey)
+					const weather = ctx.get(WeatherKey)
 					if (!weather) return []
 					return [
 						{

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

@@ -1,8 +1,11 @@
 import type { ActionDefinition } from "./action"
-import type { Context } from "./context"
+import type { ContextEntry } from "./context"
 import type { FeedItem } from "./feed"
+import type { FeedPostProcessor, ItemGroup } from "./feed-post-processor"
 import type { FeedSource } from "./feed-source"
 
+import { Context } from "./context"
+
 export interface SourceError {
 	sourceId: string
 	error: Error
@@ -12,6 +15,8 @@ export interface FeedResult<TItem extends FeedItem = FeedItem> {
 	context: Context
 	items: TItem[]
 	errors: SourceError[]
+	/** Item groups produced by post-processors */
+	groupedItems?: ItemGroup[]
 }
 
 export type FeedSubscriber<TItem extends FeedItem = FeedItem> = (result: FeedResult<TItem>) => void
@@ -62,10 +67,11 @@ interface SourceGraph {
 export class FeedEngine<TItems extends FeedItem = FeedItem> {
 	private sources = new Map<string, FeedSource>()
 	private graph: SourceGraph | null = null
-	private context: Context = { time: new Date() }
+	private context: Context = new Context()
 	private subscribers = new Set<FeedSubscriber<TItems>>()
 	private cleanups: Array<() => void> = []
 	private started = false
+	private postProcessors: FeedPostProcessor[] = []
 
 	private readonly cacheTtlMs: number
 	private cachedResult: FeedResult<TItems> | null = null
@@ -108,6 +114,23 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 		return this
 	}
 
+	/**
+	 * Registers a post-processor. Processors run in registration order
+	 * after items are collected, on every update path.
+	 */
+	registerPostProcessor(processor: FeedPostProcessor): this {
+		this.postProcessors.push(processor)
+		return this
+	}
+
+	/**
+	 * Unregisters a post-processor by reference.
+	 */
+	unregisterPostProcessor(processor: FeedPostProcessor): this {
+		this.postProcessors = this.postProcessors.filter((p) => p !== processor)
+		return this
+	}
+
 	/**
 	 * Refreshes the feed by running all sources in dependency order.
 	 * Calls fetchContext() then fetchItems() on each source.
@@ -117,14 +140,14 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 		const errors: SourceError[] = []
 
 		// Reset context with fresh time
-		let context: Context = { time: new Date() }
+		const context = new Context()
 
 		// Run fetchContext in topological order
 		for (const source of graph.sorted) {
 			try {
-				const update = await source.fetchContext(context)
-				if (update) {
-					context = { ...context, ...update }
+				const entries = await source.fetchContext(context)
+				if (entries) {
+					context.set(entries)
 				}
 			} catch (err) {
 				errors.push({
@@ -152,7 +175,18 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 
 		this.context = context
 
-		const result: FeedResult<TItems> = { context, items: items as TItems[], errors }
+		const {
+			items: processedItems,
+			groupedItems,
+			errors: postProcessorErrors,
+		} = await this.applyPostProcessors(items as TItems[], context, errors)
+
+		const result: FeedResult<TItems> = {
+			context,
+			items: processedItems,
+			errors: postProcessorErrors,
+			...(groupedItems.length > 0 ? { groupedItems } : {}),
+		}
 		this.updateCache(result)
 
 		return result
@@ -181,8 +215,8 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 		for (const source of graph.sorted) {
 			if (source.onContextUpdate) {
 				const cleanup = source.onContextUpdate(
-					(update) => {
-						this.handleContextUpdate(source.id, update)
+					(entries) => {
+						this.handleContextUpdate(source.id, entries)
 					},
 					() => this.context,
 				)
@@ -260,6 +294,72 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 		return actions
 	}
 
+	private async applyPostProcessors(
+		items: TItems[],
+		context: Context,
+		errors: SourceError[],
+	): Promise<{ items: TItems[]; groupedItems: ItemGroup[]; errors: SourceError[] }> {
+		let currentItems = items
+		const allGroupedItems: ItemGroup[] = []
+		const allErrors = [...errors]
+		const boostScores = new Map<string, number>()
+
+		for (const processor of this.postProcessors) {
+			const snapshot = currentItems
+			try {
+				const enhancement = await processor(currentItems, context)
+
+				if (enhancement.additionalItems?.length) {
+					// Post-processors operate on FeedItem[] without knowledge of TItems.
+					// Additional items are merged untyped — this is intentional. The
+					// processor contract is "FeedItem in, FeedItem out"; type narrowing
+					// is the caller's responsibility when consuming FeedResult.
+					currentItems = [...currentItems, ...(enhancement.additionalItems as TItems[])]
+				}
+
+				if (enhancement.suppress?.length) {
+					const suppressSet = new Set(enhancement.suppress)
+					currentItems = currentItems.filter((item) => !suppressSet.has(item.id))
+				}
+
+				if (enhancement.groupedItems?.length) {
+					allGroupedItems.push(...enhancement.groupedItems)
+				}
+
+				if (enhancement.boost) {
+					for (const [id, score] of Object.entries(enhancement.boost)) {
+						boostScores.set(id, (boostScores.get(id) ?? 0) + score)
+					}
+				}
+			} catch (err) {
+				const sourceId = processor.name || "anonymous"
+				allErrors.push({
+					sourceId,
+					error: err instanceof Error ? err : new Error(String(err)),
+				})
+				currentItems = snapshot
+			}
+		}
+
+		// Apply boost reordering: positive-boost first (desc), then zero, then negative (desc).
+		// Stable sort within each tier preserves original relative order.
+		if (boostScores.size > 0) {
+			currentItems = applyBoostOrder(currentItems, boostScores)
+		}
+
+		// Remove stale item IDs from groups and drop empty groups
+		const itemIds = new Set(currentItems.map((item) => item.id))
+		const validGroups = allGroupedItems.reduce<ItemGroup[]>((acc, group) => {
+			const ids = group.itemIds.filter((id) => itemIds.has(id))
+			if (ids.length > 0) {
+				acc.push({ ...group, itemIds: ids })
+			}
+			return acc
+		}, [])
+
+		return { items: currentItems, groupedItems: validGroups, errors: allErrors }
+	}
+
 	private ensureGraph(): SourceGraph {
 		if (!this.graph) {
 			this.graph = buildGraph(Array.from(this.sources.values()))
@@ -267,8 +367,9 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 		return this.graph
 	}
 
-	private handleContextUpdate(sourceId: string, update: Partial<Context>): void {
-		this.context = { ...this.context, ...update, time: new Date() }
+	private handleContextUpdate(sourceId: string, entries: readonly ContextEntry[]): void {
+		this.context.time = new Date()
+		this.context.set(entries)
 
 		// Re-run dependents and notify
 		this.refreshDependents(sourceId)
@@ -283,9 +384,9 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 			const source = graph.sources.get(id)
 			if (source) {
 				try {
-					const update = await source.fetchContext(this.context)
-					if (update) {
-						this.context = { ...this.context, ...update }
+					const entries = await source.fetchContext(this.context)
+					if (entries) {
+						this.context.set(entries)
 					}
 				} catch {
 					// Errors during reactive updates are logged but don't stop propagation
@@ -311,10 +412,17 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 			}
 		}
 
+		const {
+			items: processedItems,
+			groupedItems,
+			errors: postProcessorErrors,
+		} = await this.applyPostProcessors(items as TItems[], this.context, errors)
+
 		const result: FeedResult<TItems> = {
 			context: this.context,
-			items: items as TItems[],
-			errors,
+			items: processedItems,
+			errors: postProcessorErrors,
+			...(groupedItems.length > 0 ? { groupedItems } : {}),
 		}
 		this.updateCache(result)
 
@@ -395,6 +503,47 @@ export class FeedEngine<TItems extends FeedItem = FeedItem> {
 	}
 }
 
+function clamp(value: number, min: number, max: number): number {
+	return Math.min(max, Math.max(min, value))
+}
+
+function applyBoostOrder<T extends FeedItem>(items: T[], boostScores: Map<string, number>): T[] {
+	const positive: T[] = []
+	const neutral: T[] = []
+	const negative: T[] = []
+
+	for (const item of items) {
+		const raw = boostScores.get(item.id)
+		if (raw === undefined || raw === 0) {
+			neutral.push(item)
+		} else {
+			const clamped = clamp(raw, -1, 1)
+			if (clamped > 0) {
+				positive.push(item)
+			} else if (clamped < 0) {
+				negative.push(item)
+			} else {
+				neutral.push(item)
+			}
+		}
+	}
+
+	// Sort positive descending by boost, negative descending (least negative first, most negative last)
+	positive.sort((a, b) => {
+		const aScore = clamp(boostScores.get(a.id) ?? 0, -1, 1)
+		const bScore = clamp(boostScores.get(b.id) ?? 0, -1, 1)
+		return bScore - aScore
+	})
+
+	negative.sort((a, b) => {
+		const aScore = clamp(boostScores.get(a.id) ?? 0, -1, 1)
+		const bScore = clamp(boostScores.get(b.id) ?? 0, -1, 1)
+		return bScore - aScore
+	})
+
+	return [...positive, ...neutral, ...negative]
+}
+
 function buildGraph(sources: FeedSource[]): SourceGraph {
 	const byId = new Map<string, FeedSource>()
 	for (const source of sources) {

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

@@ -0,0 +1,602 @@
+import { describe, expect, mock, test } from "bun:test"
+
+import type {
+	ActionDefinition,
+	ContextEntry,
+	FeedItem,
+	FeedPostProcessor,
+	FeedSource,
+} from "./index"
+
+import { FeedEngine } from "./feed-engine"
+import { UnknownActionError } from "./index"
+
+// No-op action methods for test sources
+const noActions = {
+	async listActions(): Promise<Record<string, ActionDefinition>> {
+		return {}
+	},
+	async executeAction(actionId: string): Promise<void> {
+		throw new UnknownActionError(actionId)
+	},
+}
+
+// =============================================================================
+// FEED ITEMS
+// =============================================================================
+
+type WeatherItem = FeedItem<"weather", { temp: number }>
+type CalendarItem = FeedItem<"calendar", { title: string }>
+
+function weatherItem(id: string, temp: number): WeatherItem {
+	return { id, type: "weather", timestamp: new Date(), data: { temp } }
+}
+
+function calendarItem(id: string, title: string): CalendarItem {
+	return { id, type: "calendar", timestamp: new Date(), data: { title } }
+}
+
+// =============================================================================
+// TEST SOURCES
+// =============================================================================
+
+function createWeatherSource(items: WeatherItem[]) {
+	return {
+		id: "aris.weather",
+		...noActions,
+		async fetchContext() {
+			return null
+		},
+		async fetchItems(): Promise<WeatherItem[]> {
+			return items
+		},
+	}
+}
+
+function createCalendarSource(items: CalendarItem[]) {
+	return {
+		id: "aris.calendar",
+		...noActions,
+		async fetchContext() {
+			return null
+		},
+		async fetchItems(): Promise<CalendarItem[]> {
+			return items
+		},
+	}
+}
+
+// =============================================================================
+// REGISTRATION
+// =============================================================================
+
+describe("FeedPostProcessor", () => {
+	describe("registration", () => {
+		test("registerPostProcessor is chainable", () => {
+			const engine = new FeedEngine()
+			const processor: FeedPostProcessor = async () => ({})
+			const result = engine.registerPostProcessor(processor)
+			expect(result).toBe(engine)
+		})
+
+		test("unregisterPostProcessor is chainable", () => {
+			const engine = new FeedEngine()
+			const processor: FeedPostProcessor = async () => ({})
+			const result = engine.unregisterPostProcessor(processor)
+			expect(result).toBe(engine)
+		})
+
+		test("unregistered processor does not run", async () => {
+			const processor = mock(async () => ({}))
+
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(processor)
+				.unregisterPostProcessor(processor)
+
+			await engine.refresh()
+			expect(processor).not.toHaveBeenCalled()
+		})
+	})
+
+	// =============================================================================
+	// ADDITIONAL ITEMS
+	// =============================================================================
+
+	describe("additionalItems", () => {
+		test("injects additional items into the feed", async () => {
+			const extra = calendarItem("c1", "Meeting")
+
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(async () => ({ additionalItems: [extra] }))
+
+			const result = await engine.refresh()
+			expect(result.items).toHaveLength(2)
+			expect(result.items.find((i) => i.id === "c1")).toBeDefined()
+		})
+	})
+
+	// =============================================================================
+	// SUPPRESS
+	// =============================================================================
+
+	describe("suppress", () => {
+		test("removes suppressed items from the feed", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({ suppress: ["w1"] }))
+
+			const result = await engine.refresh()
+			expect(result.items).toHaveLength(1)
+			expect(result.items[0].id).toBe("w2")
+		})
+
+		test("suppressing nonexistent ID is a no-op", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(async () => ({ suppress: ["nonexistent"] }))
+
+			const result = await engine.refresh()
+			expect(result.items).toHaveLength(1)
+		})
+	})
+
+	// =============================================================================
+	// GROUPED ITEMS
+	// =============================================================================
+
+	describe("groupedItems", () => {
+		test("accumulates grouped items on FeedResult", async () => {
+			const engine = new FeedEngine()
+				.register(
+					createCalendarSource([calendarItem("c1", "Meeting A"), calendarItem("c2", "Meeting B")]),
+				)
+				.registerPostProcessor(async () => ({
+					groupedItems: [{ itemIds: ["c1", "c2"], summary: "Busy afternoon" }],
+				}))
+
+			const result = await engine.refresh()
+			expect(result.groupedItems).toEqual([{ itemIds: ["c1", "c2"], summary: "Busy afternoon" }])
+		})
+
+		test("multiple processors accumulate groups", async () => {
+			const engine = new FeedEngine()
+				.register(
+					createCalendarSource([calendarItem("c1", "Meeting A"), calendarItem("c2", "Meeting B")]),
+				)
+				.registerPostProcessor(async () => ({
+					groupedItems: [{ itemIds: ["c1"], summary: "Group A" }],
+				}))
+				.registerPostProcessor(async () => ({
+					groupedItems: [{ itemIds: ["c2"], summary: "Group B" }],
+				}))
+
+			const result = await engine.refresh()
+			expect(result.groupedItems).toEqual([
+				{ itemIds: ["c1"], summary: "Group A" },
+				{ itemIds: ["c2"], summary: "Group B" },
+			])
+		})
+
+		test("stale item IDs are removed from groups after suppression", async () => {
+			const engine = new FeedEngine()
+				.register(
+					createCalendarSource([calendarItem("c1", "Meeting A"), calendarItem("c2", "Meeting B")]),
+				)
+				.registerPostProcessor(async () => ({
+					groupedItems: [{ itemIds: ["c1", "c2"], summary: "Afternoon" }],
+				}))
+				.registerPostProcessor(async () => ({ suppress: ["c1"] }))
+
+			const result = await engine.refresh()
+			expect(result.groupedItems).toEqual([{ itemIds: ["c2"], summary: "Afternoon" }])
+		})
+
+		test("groups with all items suppressed are dropped", async () => {
+			const engine = new FeedEngine()
+				.register(createCalendarSource([calendarItem("c1", "Meeting A")]))
+				.registerPostProcessor(async () => ({
+					groupedItems: [{ itemIds: ["c1"], summary: "Solo" }],
+				}))
+				.registerPostProcessor(async () => ({ suppress: ["c1"] }))
+
+			const result = await engine.refresh()
+			expect(result.groupedItems).toBeUndefined()
+		})
+
+		test("groupedItems is omitted when no processors produce groups", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(async () => ({}))
+
+			const result = await engine.refresh()
+			expect(result.groupedItems).toBeUndefined()
+		})
+	})
+
+	// =============================================================================
+	// BOOST
+	// =============================================================================
+
+	describe("boost", () => {
+		test("positive boost moves item before non-boosted items", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({ boost: { w2: 0.8 } }))
+
+			const result = await engine.refresh()
+			expect(result.items.map((i) => i.id)).toEqual(["w2", "w1"])
+		})
+
+		test("negative boost moves item after non-boosted items", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({ boost: { w1: -0.5 } }))
+
+			const result = await engine.refresh()
+			expect(result.items.map((i) => i.id)).toEqual(["w2", "w1"])
+		})
+
+		test("multiple boosted items are sorted by boost descending", async () => {
+			const engine = new FeedEngine()
+				.register(
+					createWeatherSource([
+						weatherItem("w1", 20),
+						weatherItem("w2", 25),
+						weatherItem("w3", 30),
+					]),
+				)
+				.registerPostProcessor(async () => ({
+					boost: { w3: 0.3, w1: 0.9 },
+				}))
+
+			const result = await engine.refresh()
+			// w1 (0.9) first, w3 (0.3) second, w2 (no boost) last
+			expect(result.items.map((i) => i.id)).toEqual(["w1", "w3", "w2"])
+		})
+
+		test("multiple processors accumulate boost scores", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({ boost: { w1: 0.3 } }))
+				.registerPostProcessor(async () => ({ boost: { w1: 0.4 } }))
+
+			const result = await engine.refresh()
+			// w1 accumulated boost = 0.7, moves before w2
+			expect(result.items.map((i) => i.id)).toEqual(["w1", "w2"])
+		})
+
+		test("accumulated boost is clamped to [-1, 1]", async () => {
+			const engine = new FeedEngine()
+				.register(
+					createWeatherSource([
+						weatherItem("w1", 20),
+						weatherItem("w2", 25),
+						weatherItem("w3", 30),
+					]),
+				)
+				.registerPostProcessor(async () => ({ boost: { w1: 0.8, w2: 0.9 } }))
+				.registerPostProcessor(async () => ({ boost: { w1: 0.8 } }))
+
+			const result = await engine.refresh()
+			// w1 accumulated = 1.6 clamped to 1, w2 = 0.9 — w1 still first
+			expect(result.items.map((i) => i.id)).toEqual(["w1", "w2", "w3"])
+		})
+
+		test("out-of-range boost values are clamped", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({ boost: { w1: 5.0 } }))
+
+			const result = await engine.refresh()
+			// Clamped to 1, still boosted to front
+			expect(result.items.map((i) => i.id)).toEqual(["w1", "w2"])
+		})
+
+		test("boosting a suppressed item is a no-op", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({
+					suppress: ["w1"],
+					boost: { w1: 1.0 },
+				}))
+
+			const result = await engine.refresh()
+			expect(result.items).toHaveLength(1)
+			expect(result.items[0].id).toBe("w2")
+		})
+
+		test("boosting a nonexistent item ID is a no-op", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(async () => ({ boost: { nonexistent: 1.0 } }))
+
+			const result = await engine.refresh()
+			expect(result.items).toHaveLength(1)
+			expect(result.items[0].id).toBe("w1")
+		})
+
+		test("items with equal boost retain original relative order", async () => {
+			const engine = new FeedEngine()
+				.register(
+					createWeatherSource([
+						weatherItem("w1", 20),
+						weatherItem("w2", 25),
+						weatherItem("w3", 30),
+					]),
+				)
+				.registerPostProcessor(async () => ({
+					boost: { w1: 0.5, w3: 0.5 },
+				}))
+
+			const result = await engine.refresh()
+			// w1 and w3 have equal boost — original order preserved: w1 before w3
+			expect(result.items.map((i) => i.id)).toEqual(["w1", "w3", "w2"])
+		})
+
+		test("negative boosts preserve relative order among demoted items", async () => {
+			const engine = new FeedEngine()
+				.register(
+					createWeatherSource([
+						weatherItem("w1", 20),
+						weatherItem("w2", 25),
+						weatherItem("w3", 30),
+					]),
+				)
+				.registerPostProcessor(async () => ({
+					boost: { w1: -0.3, w2: -0.3 },
+				}))
+
+			const result = await engine.refresh()
+			// w3 (neutral) first, then w1 and w2 (equal negative) in original order
+			expect(result.items.map((i) => i.id)).toEqual(["w3", "w1", "w2"])
+		})
+
+		test("boost works alongside additionalItems and groupedItems", async () => {
+			const extra = calendarItem("c1", "Meeting")
+
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({
+					additionalItems: [extra],
+					boost: { c1: 1.0 },
+					groupedItems: [{ itemIds: ["w1", "c1"], summary: "Related" }],
+				}))
+
+			const result = await engine.refresh()
+			// c1 boosted to front
+			expect(result.items[0].id).toBe("c1")
+			expect(result.items).toHaveLength(3)
+			expect(result.groupedItems).toEqual([{ itemIds: ["w1", "c1"], summary: "Related" }])
+		})
+	})
+
+	// =============================================================================
+	// PIPELINE ORDERING
+	// =============================================================================
+
+	describe("pipeline ordering", () => {
+		test("each processor sees items as modified by the previous processor", async () => {
+			const seen: string[] = []
+
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(async () => ({
+					additionalItems: [calendarItem("c1", "Injected")],
+				}))
+				.registerPostProcessor(async (items) => {
+					seen.push(...items.map((i) => i.id))
+					return {}
+				})
+
+			await engine.refresh()
+			expect(seen).toEqual(["w1", "c1"])
+		})
+
+		test("suppression in first processor affects second processor", async () => {
+			const seen: string[] = []
+
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({ suppress: ["w1"] }))
+				.registerPostProcessor(async (items) => {
+					seen.push(...items.map((i) => i.id))
+					return {}
+				})
+
+			await engine.refresh()
+			expect(seen).toEqual(["w2"])
+		})
+	})
+
+	// =============================================================================
+	// ERROR HANDLING
+	// =============================================================================
+
+	describe("error handling", () => {
+		test("throwing processor is recorded in errors and pipeline continues", async () => {
+			const seen: string[] = []
+
+			async function failingProcessor(): Promise<never> {
+				throw new Error("processor failed")
+			}
+
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(failingProcessor)
+				.registerPostProcessor(async (items) => {
+					seen.push(...items.map((i) => i.id))
+					return {}
+				})
+
+			const result = await engine.refresh()
+
+			const ppError = result.errors.find((e) => e.sourceId === "failingProcessor")
+			expect(ppError).toBeDefined()
+			expect(ppError!.error.message).toBe("processor failed")
+
+			// Pipeline continued — observer still saw the original item
+			expect(seen).toEqual(["w1"])
+			expect(result.items).toHaveLength(1)
+		})
+
+		test("anonymous throwing processor uses 'anonymous' as sourceId", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(async () => {
+					throw new Error("anon failed")
+				})
+
+			const result = await engine.refresh()
+			const ppError = result.errors.find((e) => e.sourceId === "anonymous")
+			expect(ppError).toBeDefined()
+		})
+
+		test("non-Error throw is wrapped", async () => {
+			async function failingProcessor(): Promise<never> {
+				throw "string error"
+			}
+
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20)]))
+				.registerPostProcessor(failingProcessor)
+
+			const result = await engine.refresh()
+			const ppError = result.errors.find((e) => e.sourceId === "failingProcessor")
+			expect(ppError).toBeDefined()
+			expect(ppError!.error).toBeInstanceOf(Error)
+		})
+	})
+
+	// =============================================================================
+	// REACTIVE PATHS
+	// =============================================================================
+
+	describe("reactive updates", () => {
+		test("post-processors run during reactive context updates", async () => {
+			let callCount = 0
+
+			let triggerUpdate: ((entries: readonly ContextEntry[]) => void) | null = null
+
+			const source: FeedSource = {
+				id: "aris.reactive",
+				...noActions,
+				async fetchContext() {
+					return null
+				},
+				async fetchItems() {
+					return [weatherItem("w1", 20)]
+				},
+				onContextUpdate(callback, _getContext) {
+					triggerUpdate = callback
+					return () => {
+						triggerUpdate = null
+					}
+				},
+			}
+
+			const engine = new FeedEngine().register(source).registerPostProcessor(async () => {
+				callCount++
+				return {}
+			})
+
+			engine.start()
+
+			// Wait for initial periodic refresh
+			await new Promise((resolve) => setTimeout(resolve, 50))
+			const countAfterStart = callCount
+
+			// Trigger a reactive context update
+			triggerUpdate!([])
+			await new Promise((resolve) => setTimeout(resolve, 50))
+
+			expect(callCount).toBeGreaterThan(countAfterStart)
+
+			engine.stop()
+		})
+
+		test("post-processors run during reactive item updates", async () => {
+			let callCount = 0
+
+			let triggerItemsUpdate: ((items: FeedItem[]) => void) | null = null
+
+			const source: FeedSource = {
+				id: "aris.reactive",
+				...noActions,
+				async fetchContext() {
+					return null
+				},
+				async fetchItems() {
+					return [weatherItem("w1", 20)]
+				},
+				onItemsUpdate(callback, _getContext) {
+					triggerItemsUpdate = callback
+					return () => {
+						triggerItemsUpdate = null
+					}
+				},
+			}
+
+			const engine = new FeedEngine().register(source).registerPostProcessor(async () => {
+				callCount++
+				return {}
+			})
+
+			engine.start()
+
+			await new Promise((resolve) => setTimeout(resolve, 50))
+			const countAfterStart = callCount
+
+			// Trigger a reactive items update
+			triggerItemsUpdate!([weatherItem("w1", 25)])
+			await new Promise((resolve) => setTimeout(resolve, 50))
+
+			expect(callCount).toBeGreaterThan(countAfterStart)
+
+			engine.stop()
+		})
+	})
+
+	// =============================================================================
+	// NO PROCESSORS = NO CHANGE
+	// =============================================================================
+
+	describe("no processors", () => {
+		test("engine without post-processors returns raw items unchanged", async () => {
+			const items = [weatherItem("w1", 20), weatherItem("w2", 25)]
+			const engine = new FeedEngine().register(createWeatherSource(items))
+
+			const result = await engine.refresh()
+			expect(result.items).toHaveLength(2)
+			expect(result.items[0].id).toBe("w1")
+			expect(result.items[1].id).toBe("w2")
+			expect(result.groupedItems).toBeUndefined()
+		})
+	})
+
+	// =============================================================================
+	// COMBINED ENHANCEMENT
+	// =============================================================================
+
+	describe("combined enhancement", () => {
+		test("single processor can use all enhancement fields at once", async () => {
+			const engine = new FeedEngine()
+				.register(createWeatherSource([weatherItem("w1", 20), weatherItem("w2", 25)]))
+				.registerPostProcessor(async () => ({
+					additionalItems: [calendarItem("c1", "Injected")],
+					suppress: ["w2"],
+					groupedItems: [{ itemIds: ["w1", "c1"], summary: "Related" }],
+				}))
+
+			const result = await engine.refresh()
+
+			// w2 suppressed, c1 injected → w1 + c1
+			expect(result.items).toHaveLength(2)
+			expect(result.items.map((i) => i.id)).toEqual(["w1", "c1"])
+
+			// Groups on result
+			expect(result.groupedItems).toEqual([{ itemIds: ["w1", "c1"], summary: "Related" }])
+		})
+	})
+})

packages/aris-core/src/feed-post-processor.ts

@@ -0,0 +1,26 @@
+import type { Context } from "./context"
+import type { FeedItem } from "./feed"
+
+export interface ItemGroup {
+	/** IDs of items to present together */
+	itemIds: string[]
+	/** Summary text for the group */
+	summary: string
+}
+
+export interface FeedEnhancement {
+	/** New items to inject into the feed */
+	additionalItems?: FeedItem[]
+	/** Groups of items to present together with a summary */
+	groupedItems?: ItemGroup[]
+	/** Item IDs to remove from the feed */
+	suppress?: string[]
+	/** Map of item ID to boost score (-1 to 1). Positive promotes, negative demotes. */
+	boost?: Record<string, number>
+}
+
+/**
+ * A function that transforms feed items and produces enhancement directives.
+ * Use named functions for meaningful error attribution.
+ */
+export type FeedPostProcessor = (items: FeedItem[], context: Context) => Promise<FeedEnhancement>

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

@@ -1,8 +1,8 @@
 import { describe, expect, test } from "bun:test"
 
-import type { ActionDefinition, Context, ContextKey, FeedItem, FeedSource } from "./index"
+import type { ActionDefinition, ContextEntry, ContextKey, FeedItem, FeedSource } from "./index"
 
-import { TimeRelevance, UnknownActionError, contextKey, contextValue } from "./index"
+import { Context, TimeRelevance, UnknownActionError, contextKey } from "./index"
 
 // No-op action methods for test sources
 const noActions = {
@@ -47,7 +47,7 @@ interface SimulatedLocationSource extends FeedSource {
 }
 
 function createLocationSource(): SimulatedLocationSource {
-	let callback: ((update: Partial<Context>) => void) | null = null
+	let callback: ((entries: readonly ContextEntry[]) => void) | null = null
 	let currentLocation: Location = { lat: 0, lng: 0 }
 
 	return {
@@ -62,12 +62,12 @@ function createLocationSource(): SimulatedLocationSource {
 		},
 
 		async fetchContext() {
-			return { [LocationKey]: currentLocation }
+			return [[LocationKey, currentLocation]]
 		},
 
 		simulateUpdate(location: Location) {
 			currentLocation = location
-			callback?.({ [LocationKey]: location })
+			callback?.([[LocationKey, location]])
 		},
 	}
 }
@@ -84,15 +84,15 @@ function createWeatherSource(
 		...noActions,
 
 		async fetchContext(context) {
-			const location = contextValue(context, LocationKey)
+			const location = context.get(LocationKey)
 			if (!location) return null
 
 			const weather = await fetchWeather(location)
-			return { [WeatherKey]: weather }
+			return [[WeatherKey, weather]]
 		},
 
 		async fetchItems(context) {
-			const weather = contextValue(context, WeatherKey)
+			const weather = context.get(WeatherKey)
 			if (!weather) return []
 
 			return [
@@ -122,7 +122,7 @@ function createAlertSource(): FeedSource<AlertFeedItem> {
 		},
 
 		async fetchItems(context) {
-			const weather = contextValue(context, WeatherKey)
+			const weather = context.get(WeatherKey)
 			if (!weather) return []
 
 			if (weather.condition === "storm") {
@@ -207,13 +207,13 @@ function buildGraph(sources: FeedSource[]): SourceGraph {
 }
 
 async function refreshGraph(graph: SourceGraph): Promise<{ context: Context; items: FeedItem[] }> {
-	let context: Context = { time: new Date() }
+	const context = new Context()
 
 	// Run fetchContext in topological order
 	for (const source of graph.sorted) {
-		const update = await source.fetchContext(context)
-		if (update) {
-			context = { ...context, ...update }
+		const entries = await source.fetchContext(context)
+		if (entries) {
+			context.set(entries)
 		}
 	}
 
@@ -265,7 +265,7 @@ describe("FeedSource", () => {
 
 		test("source without context returns null from fetchContext", async () => {
 			const source = createAlertSource()
-			const result = await source.fetchContext({ time: new Date() })
+			const result = await source.fetchContext(new Context())
 			expect(result).toBeNull()
 		})
 	})
@@ -369,7 +369,7 @@ describe("FeedSource", () => {
 				...noActions,
 				async fetchContext() {
 					order.push("location")
-					return { [LocationKey]: { lat: 51.5, lng: -0.1 } }
+					return [[LocationKey, { lat: 51.5, lng: -0.1 }]]
 				},
 			}
 
@@ -379,9 +379,9 @@ describe("FeedSource", () => {
 				...noActions,
 				async fetchContext(ctx) {
 					order.push("weather")
-					const loc = contextValue(ctx, LocationKey)
+					const loc = ctx.get(LocationKey)
 					expect(loc).toBeDefined()
-					return { [WeatherKey]: { temperature: 20, condition: "sunny" } }
+					return [[WeatherKey, { temperature: 20, condition: "sunny" }]]
 				},
 			}
 
@@ -400,11 +400,11 @@ describe("FeedSource", () => {
 			const graph = buildGraph([location, weather])
 			const { context } = await refreshGraph(graph)
 
-			expect(contextValue(context, LocationKey)).toEqual({
+			expect(context.get(LocationKey)).toEqual({
 				lat: 51.5,
 				lng: -0.1,
 			})
-			expect(contextValue(context, WeatherKey)).toEqual({
+			expect(context.get(WeatherKey)).toEqual({
 				temperature: 20,
 				condition: "sunny",
 			})
@@ -447,12 +447,10 @@ describe("FeedSource", () => {
 		})
 
 		test("source without location context returns empty items", async () => {
-			// Location source exists but hasn't been updated
 			const location: FeedSource = {
 				id: "location",
 				...noActions,
 				async fetchContext() {
-					// Simulate no location available
 					return null
 				},
 			}
@@ -462,7 +460,7 @@ describe("FeedSource", () => {
 			const graph = buildGraph([location, weather])
 			const { context, items } = await refreshGraph(graph)
 
-			expect(contextValue(context, WeatherKey)).toBeUndefined()
+			expect(context.get(WeatherKey)).toBeUndefined()
 			expect(items).toHaveLength(0)
 		})
 	})
@@ -476,7 +474,7 @@ describe("FeedSource", () => {
 				() => {
 					updateCount++
 				},
-				() => ({ time: new Date() }),
+				() => new Context(),
 			)
 
 			location.simulateUpdate({ lat: 1, lng: 1 })

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

@@ -1,5 +1,5 @@
 import type { ActionDefinition } from "./action"
-import type { Context } from "./context"
+import type { Context, ContextEntry } from "./context"
 import type { FeedItem } from "./feed"
 
 /**
@@ -57,7 +57,7 @@ export interface FeedSource<TItem extends FeedItem = FeedItem> {
 	 * Maps to: source/contextUpdated (notification, source → host)
 	 */
 	onContextUpdate?(
-		callback: (update: Partial<Context>) => void,
+		callback: (entries: readonly ContextEntry[]) => void,
 		getContext: () => Context,
 	): () => void
 
@@ -67,7 +67,7 @@ export interface FeedSource<TItem extends FeedItem = FeedItem> {
 	 * Return null if this source cannot provide context.
 	 * Maps to: source/fetchContext
 	 */
-	fetchContext(context: Context): Promise<Partial<Context> | null>
+	fetchContext(context: Context): Promise<readonly ContextEntry[] | null>
 
 	/**
 	 * Subscribe to reactive feed item updates.

packages/aris-core/src/index.ts

@@ -1,6 +1,6 @@
 // Context
-export type { Context, ContextKey } from "./context"
-export { contextKey, contextValue } from "./context"
+export type { ContextEntry, ContextKey, ContextKeyPart } from "./context"
+export { Context, contextKey, serializeKey } from "./context"
 
 // Actions
 export type { ActionDefinition } from "./action"
@@ -13,6 +13,9 @@ export { TimeRelevance } from "./feed"
 // Feed Source
 export type { FeedSource } from "./feed-source"
 
+// Feed Post-Processor
+export type { FeedEnhancement, FeedPostProcessor, ItemGroup } from "./feed-post-processor"
+
 // Feed Engine
 export type { FeedEngineConfig, FeedResult, FeedSubscriber, SourceError } from "./feed-engine"
 export { FeedEngine } from "./feed-engine"

packages/aris-data-source-weatherkit/src/data-source.test.ts

@@ -1,5 +1,6 @@
-import type { Context } from "@aris/core"
+import type { ContextKey } from "@aris/core"
 
+import { Context, contextKey } from "@aris/core"
 import { describe, expect, test } from "bun:test"
 
 import type { WeatherKitClient, WeatherKitResponse } from "./weatherkit"
@@ -15,14 +16,25 @@ const mockCredentials = {
 	serviceId: "mock",
 }
 
+interface LocationData {
+	lat: number
+	lng: number
+	accuracy: number
+}
+
+const LocationKey: ContextKey<LocationData> = contextKey("aris.location", "location")
+
 const createMockClient = (response: WeatherKitResponse): WeatherKitClient => ({
 	fetch: async () => response,
 })
 
-const createMockContext = (location?: { lat: number; lng: number }): Context => ({
-	time: new Date("2026-01-17T00:00:00Z"),
-	location: location ? { ...location, accuracy: 10 } : undefined,
-})
+function createMockContext(location?: { lat: number; lng: number }): Context {
+	const ctx = new Context(new Date("2026-01-17T00:00:00Z"))
+	if (location) {
+		ctx.set([[LocationKey, { ...location, accuracy: 10 }]])
+	}
+	return ctx
+}
 
 describe("WeatherKitDataSource", () => {
 	test("returns empty array when location is missing", async () => {
@@ -39,7 +51,7 @@ describe("WeatherKitDataSource", () => {
 			credentials: mockCredentials,
 		})
 
-		expect(dataSource.type).toBe(WeatherFeedItemType.current)
+		expect(dataSource.type).toBe(WeatherFeedItemType.Current)
 	})
 
 	test("throws error if neither client nor credentials provided", () => {
@@ -130,9 +142,9 @@ describe("query() with mocked client", () => {
 		const items = await dataSource.query(context)
 
 		expect(items.length).toBeGreaterThan(0)
-		expect(items.some((i) => i.type === WeatherFeedItemType.current)).toBe(true)
-		expect(items.some((i) => i.type === WeatherFeedItemType.hourly)).toBe(true)
-		expect(items.some((i) => i.type === WeatherFeedItemType.daily)).toBe(true)
+		expect(items.some((i) => i.type === WeatherFeedItemType.Current)).toBe(true)
+		expect(items.some((i) => i.type === WeatherFeedItemType.Hourly)).toBe(true)
+		expect(items.some((i) => i.type === WeatherFeedItemType.Daily)).toBe(true)
 	})
 
 	test("applies hourly and daily limits", async () => {
@@ -145,8 +157,8 @@ describe("query() with mocked client", () => {
 
 		const items = await dataSource.query(context)
 
-		const hourlyItems = items.filter((i) => i.type === WeatherFeedItemType.hourly)
-		const dailyItems = items.filter((i) => i.type === WeatherFeedItemType.daily)
+		const hourlyItems = items.filter((i) => i.type === WeatherFeedItemType.Hourly)
+		const dailyItems = items.filter((i) => i.type === WeatherFeedItemType.Daily)
 
 		expect(hourlyItems.length).toBe(3)
 		expect(dailyItems.length).toBe(2)
@@ -176,8 +188,8 @@ describe("query() with mocked client", () => {
 			units: Units.imperial,
 		})
 
-		const metricCurrent = metricItems.find((i) => i.type === WeatherFeedItemType.current)
-		const imperialCurrent = imperialItems.find((i) => i.type === WeatherFeedItemType.current)
+		const metricCurrent = metricItems.find((i) => i.type === WeatherFeedItemType.Current)
+		const imperialCurrent = imperialItems.find((i) => i.type === WeatherFeedItemType.Current)
 
 		expect(metricCurrent).toBeDefined()
 		expect(imperialCurrent).toBeDefined()
@@ -203,7 +215,7 @@ describe("query() with mocked client", () => {
 			expect(item.signals!.timeRelevance).toBeDefined()
 		}
 
-		const currentItem = items.find((i) => i.type === WeatherFeedItemType.current)
+		const currentItem = items.find((i) => i.type === WeatherFeedItemType.Current)
 		expect(currentItem).toBeDefined()
 		expect(currentItem!.signals!.urgency).toBeGreaterThanOrEqual(0.5)
 	})

packages/aris-data-source-weatherkit/src/data-source.ts

@@ -1,6 +1,6 @@
-import type { Context, DataSource, FeedItemSignals } from "@aris/core"
+import type { Context, ContextKey, DataSource, FeedItemSignals } from "@aris/core"
 
-import { TimeRelevance } from "@aris/core"
+import { TimeRelevance, contextKey } from "@aris/core"
 
 import {
 	WeatherFeedItemType,
@@ -40,11 +40,18 @@ export interface WeatherKitQueryConfig {
 	units?: Units
 }
 
+interface LocationData {
+	lat: number
+	lng: number
+}
+
+const LocationKey: ContextKey<LocationData> = contextKey("aris.location", "location")
+
 export class WeatherKitDataSource implements DataSource<WeatherFeedItem, WeatherKitQueryConfig> {
 	private readonly DEFAULT_HOURLY_LIMIT = 12
 	private readonly DEFAULT_DAILY_LIMIT = 7
 
-	readonly type = WeatherFeedItemType.current
+	readonly type = WeatherFeedItemType.Current
 	private readonly client: WeatherKitClient
 	private readonly hourlyLimit: number
 	private readonly dailyLimit: number
@@ -59,7 +66,8 @@ export class WeatherKitDataSource implements DataSource<WeatherFeedItem, Weather
 	}
 
 	async query(context: Context, config: WeatherKitQueryConfig = {}): Promise<WeatherFeedItem[]> {
-		if (!context.location) {
+		const location = context.get(LocationKey)
+		if (!location) {
 			return []
 		}
 
@@ -67,8 +75,8 @@ export class WeatherKitDataSource implements DataSource<WeatherFeedItem, Weather
 		const timestamp = context.time
 
 		const response = await this.client.fetch({
-			lat: context.location.lat,
-			lng: context.location.lng,
+			lat: location.lat,
+			lng: location.lng,
 		})
 
 		const items: WeatherFeedItem[] = []
@@ -228,7 +236,7 @@ function createCurrentWeatherFeedItem(
 
 	return {
 		id: `weather-current-${timestamp.getTime()}`,
-		type: WeatherFeedItemType.current,
+		type: WeatherFeedItemType.Current,
 		timestamp,
 		data: {
 			conditionCode: current.conditionCode,
@@ -262,7 +270,7 @@ function createHourlyWeatherFeedItem(
 
 	return {
 		id: `weather-hourly-${timestamp.getTime()}-${index}`,
-		type: WeatherFeedItemType.hourly,
+		type: WeatherFeedItemType.Hourly,
 		timestamp,
 		data: {
 			forecastTime: new Date(hourly.forecastStart),
@@ -296,7 +304,7 @@ function createDailyWeatherFeedItem(
 
 	return {
 		id: `weather-daily-${timestamp.getTime()}-${index}`,
-		type: WeatherFeedItemType.daily,
+		type: WeatherFeedItemType.Daily,
 		timestamp,
 		data: {
 			forecastDate: new Date(daily.forecastStart),
@@ -323,7 +331,7 @@ function createWeatherAlertFeedItem(alert: WeatherAlert, timestamp: Date): Weath
 
 	return {
 		id: `weather-alert-${alert.id}`,
-		type: WeatherFeedItemType.alert,
+		type: WeatherFeedItemType.Alert,
 		timestamp,
 		data: {
 			alertId: alert.id,

packages/aris-data-source-weatherkit/src/feed-items.ts

@@ -3,10 +3,10 @@ import type { FeedItem } from "@aris/core"
 import type { Certainty, ConditionCode, PrecipitationType, Severity, Urgency } from "./weatherkit"
 
 export const WeatherFeedItemType = {
-	current: "weather-current",
-	hourly: "weather-hourly",
-	daily: "weather-daily",
-	alert: "weather-alert",
+	Current: "weather-current",
+	Hourly: "weather-hourly",
+	Daily: "weather-daily",
+	Alert: "weather-alert",
 } as const
 
 export type WeatherFeedItemType = (typeof WeatherFeedItemType)[keyof typeof WeatherFeedItemType]
@@ -28,7 +28,7 @@ export type CurrentWeatherData = {
 }
 
 export interface CurrentWeatherFeedItem extends FeedItem<
-	typeof WeatherFeedItemType.current,
+	typeof WeatherFeedItemType.Current,
 	CurrentWeatherData
 > {}
 
@@ -49,7 +49,7 @@ export type HourlyWeatherData = {
 }
 
 export interface HourlyWeatherFeedItem extends FeedItem<
-	typeof WeatherFeedItemType.hourly,
+	typeof WeatherFeedItemType.Hourly,
 	HourlyWeatherData
 > {}
 
@@ -68,7 +68,7 @@ export type DailyWeatherData = {
 }
 
 export interface DailyWeatherFeedItem extends FeedItem<
-	typeof WeatherFeedItemType.daily,
+	typeof WeatherFeedItemType.Daily,
 	DailyWeatherData
 > {}
 
@@ -86,7 +86,7 @@ export type WeatherAlertData = {
 }
 
 export interface WeatherAlertFeedItem extends FeedItem<
-	typeof WeatherFeedItemType.alert,
+	typeof WeatherFeedItemType.Alert,
 	WeatherAlertData
 > {}
 

packages/aris-source-caldav/README.md

@@ -0,0 +1,58 @@
+# @aris/source-caldav
+
+A FeedSource that fetches calendar events from any CalDAV server.
+
+## Usage
+
+```ts
+import { CalDavSource } from "@aris/source-caldav"
+
+// Basic auth (Nextcloud, Radicale, Baikal, iCloud, etc.)
+const source = new CalDavSource({
+	serverUrl: "https://caldav.example.com",
+	authMethod: "basic",
+	username: "user",
+	password: "pass",
+	lookAheadDays: 7, // optional, default: 0 (today only)
+	timeZone: "America/New_York", // optional, default: UTC
+})
+
+// OAuth
+const source = new CalDavSource({
+	serverUrl: "https://caldav.provider.com",
+	authMethod: "oauth",
+	accessToken: "...",
+	refreshToken: "...",
+	tokenUrl: "https://provider.com/oauth/token",
+})
+```
+
+### iCloud
+
+Use your Apple ID email as the username and an [app-specific password](https://support.apple.com/en-us/102654):
+
+```ts
+const source = new CalDavSource({
+	serverUrl: "https://caldav.icloud.com",
+	authMethod: "basic",
+	username: "you@icloud.com",
+	password: "<app-specific-password>",
+})
+```
+
+## Testing
+
+```bash
+bun test
+```
+
+### Live test
+
+`bun run test:live` connects to a real CalDAV server and prints all events to the console. It prompts for:
+
+- **CalDAV server URL** — e.g. `https://caldav.icloud.com`
+- **Username** — your account email
+- **Password** — your password (or app-specific password for iCloud)
+- **Look-ahead days** — how many days beyond today to fetch (default: 0)
+
+The script runs both `fetchContext` and `fetchItems`, printing the calendar context (in-progress events, next event, today's count) followed by each event with its title, time, location, signals, and attendees.

packages/aris-source-caldav/fixtures/all-day-event.ics

@@ -0,0 +1,11 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Test//Test//EN
+BEGIN:VEVENT
+UID:all-day-001@test
+DTSTART;VALUE=DATE:20260115
+DTEND;VALUE=DATE:20260116
+SUMMARY:Company Holiday
+STATUS:CONFIRMED
+END:VEVENT
+END:VCALENDAR

packages/aris-source-caldav/fixtures/cancelled-event.ics

@@ -0,0 +1,11 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Test//Test//EN
+BEGIN:VEVENT
+UID:cancelled-001@test
+DTSTART:20260115T120000Z
+DTEND:20260115T130000Z
+SUMMARY:Cancelled Meeting
+STATUS:CANCELLED
+END:VEVENT
+END:VCALENDAR

packages/aris-source-caldav/fixtures/minimal-event.ics

@@ -0,0 +1,10 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Test//Test//EN
+BEGIN:VEVENT
+UID:minimal-001@test
+DTSTART:20260115T180000Z
+DTEND:20260115T190000Z
+SUMMARY:Quick Chat
+END:VEVENT
+END:VCALENDAR

packages/aris-source-caldav/fixtures/recurring-event.ics

@@ -0,0 +1,20 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Test//Test//EN
+BEGIN:VEVENT
+UID:recurring-001@test
+DTSTART:20260115T090000Z
+DTEND:20260115T093000Z
+SUMMARY:Weekly Sync
+RRULE:FREQ=WEEKLY;COUNT=4
+STATUS:CONFIRMED
+END:VEVENT
+BEGIN:VEVENT
+UID:recurring-001@test
+RECURRENCE-ID:20260122T090000Z
+DTSTART:20260122T100000Z
+DTEND:20260122T103000Z
+SUMMARY:Weekly Sync (moved)
+STATUS:CONFIRMED
+END:VEVENT
+END:VCALENDAR

packages/aris-source-caldav/fixtures/single-event.ics

@@ -0,0 +1,26 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Test//Test//EN
+BEGIN:VEVENT
+UID:single-event-001@test
+DTSTART:20260115T140000Z
+DTEND:20260115T150000Z
+SUMMARY:Team Standup
+LOCATION:Conference Room A
+DESCRIPTION:Daily standup meeting
+STATUS:CONFIRMED
+URL:https://example.com/meeting/123
+ORGANIZER;CN=Alice Smith:mailto:alice@example.com
+ATTENDEE;CN=Bob Jones;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED:mailto:bob@example.com
+ATTENDEE;CN=Carol White;ROLE=OPT-PARTICIPANT;PARTSTAT=TENTATIVE:mailto:carol@example.com
+BEGIN:VALARM
+TRIGGER:-PT15M
+ACTION:DISPLAY
+DESCRIPTION:Reminder
+END:VALARM
+BEGIN:VALARM
+TRIGGER:-PT5M
+ACTION:AUDIO
+END:VALARM
+END:VEVENT
+END:VCALENDAR

packages/aris-source-caldav/package.json

@@ -0,0 +1,16 @@
+{
+	"name": "@aris/source-caldav",
+	"version": "0.0.0",
+	"type": "module",
+	"main": "src/index.ts",
+	"types": "src/index.ts",
+	"scripts": {
+		"test": "bun test .",
+		"test:live": "bun run scripts/test-live.ts"
+	},
+	"dependencies": {
+		"@aris/core": "workspace:*",
+		"ical.js": "^2.1.0",
+		"tsdav": "^2.1.7"
+	}
+}

packages/aris-source-caldav/scripts/test-live.ts

@@ -0,0 +1,64 @@
+/**
+ * Live test script for CalDavSource.
+ *
+ * Usage:
+ *   bun run test-live.ts
+ */
+
+import { Context } from "@aris/core"
+
+import { CalDavSource } from "../src/index.ts"
+
+const serverUrl = prompt("CalDAV server URL:")
+const username = prompt("Username:")
+const password = prompt("Password:")
+const lookAheadRaw = prompt("Look-ahead days (default 0):")
+
+if (!serverUrl || !username || !password) {
+	console.error("Server URL, username, and password are required.")
+	process.exit(1)
+}
+
+const lookAheadDays = Number(lookAheadRaw) || 0
+
+const source = new CalDavSource({
+	serverUrl,
+	authMethod: "basic",
+	username,
+	password,
+	lookAheadDays,
+})
+
+const context = new Context()
+
+console.log(`\nFetching from ${serverUrl} as ${username} (lookAheadDays=${lookAheadDays})...\n`)
+
+const contextResult = await source.fetchContext(context)
+const items = await source.fetchItems(context)
+
+console.log("=== Context ===")
+console.log(JSON.stringify(contextResult, null, 2))
+
+console.log(`\n=== Feed Items (${items.length}) ===`)
+for (const item of items) {
+	console.log(`\n--- ${item.data.title} ---`)
+	console.log(`  ID:         ${item.id}`)
+	console.log(`  Calendar:   ${item.data.calendarName ?? "(unknown)"}`)
+	console.log(`  Start:      ${item.data.startDate.toISOString()}`)
+	console.log(`  End:        ${item.data.endDate.toISOString()}`)
+	console.log(`  All-day:    ${item.data.isAllDay}`)
+	console.log(`  Location:   ${item.data.location ?? "(none)"}`)
+	console.log(`  Status:     ${item.data.status ?? "(none)"}`)
+	console.log(`  Urgency:    ${item.signals?.urgency}`)
+	console.log(`  Relevance:  ${item.signals?.timeRelevance}`)
+	if (item.data.attendees.length > 0) {
+		console.log(`  Attendees:  ${item.data.attendees.map((a) => a.name ?? a.email).join(", ")}`)
+	}
+	if (item.data.description) {
+		console.log(`  Desc:       ${item.data.description.slice(0, 100)}`)
+	}
+}
+
+if (items.length === 0) {
+	console.log("(no events found in the time window)")
+}

packages/aris-source-caldav/src/caldav-source.test.ts

@@ -0,0 +1,514 @@
+import type { ContextEntry } from "@aris/core"
+
+import { Context, TimeRelevance } from "@aris/core"
+import { describe, expect, test } from "bun:test"
+import { readFileSync } from "node:fs"
+import { join } from "node:path"
+
+import type {
+	CalDavDAVCalendar,
+	CalDavDAVClient,
+	CalDavDAVObject,
+	CalDavEventData,
+} from "./types.ts"
+
+import { CalDavSource, computeSignals } from "./caldav-source.ts"
+import { CalDavCalendarKey, type CalendarContext } from "./calendar-context.ts"
+
+function loadFixture(name: string): string {
+	return readFileSync(join(import.meta.dir, "..", "fixtures", name), "utf-8")
+}
+
+function createContext(time: Date): Context {
+	return new Context(time)
+}
+
+/** Extract the CalendarContext value from fetchContext entries. */
+function extractCalendar(entries: readonly ContextEntry[] | null): CalendarContext | undefined {
+	if (!entries) return undefined
+	const entry = entries.find(([key]) => key === CalDavCalendarKey)
+	return entry?.[1] as CalendarContext | undefined
+}
+
+class MockDAVClient implements CalDavDAVClient {
+	credentials: Record<string, unknown> = {}
+	fetchCalendarsCallCount = 0
+	lastTimeRange: { start: string; end: string } | null = null
+	private calendars: CalDavDAVCalendar[]
+	private objectsByCalendarUrl: Record<string, CalDavDAVObject[]>
+
+	constructor(
+		calendars: CalDavDAVCalendar[],
+		objectsByCalendarUrl: Record<string, CalDavDAVObject[]>,
+	) {
+		this.calendars = calendars
+		this.objectsByCalendarUrl = objectsByCalendarUrl
+	}
+
+	async login(): Promise<void> {}
+
+	async fetchCalendars(): Promise<CalDavDAVCalendar[]> {
+		this.fetchCalendarsCallCount++
+		return this.calendars
+	}
+
+	async fetchCalendarObjects(params: {
+		calendar: CalDavDAVCalendar
+		timeRange: { start: string; end: string }
+	}): Promise<CalDavDAVObject[]> {
+		this.lastTimeRange = params.timeRange
+		return this.objectsByCalendarUrl[params.calendar.url] ?? []
+	}
+}
+
+function createSource(client: MockDAVClient, lookAheadDays?: number): CalDavSource {
+	return new CalDavSource({
+		serverUrl: "https://caldav.example.com",
+		authMethod: "basic",
+		username: "user",
+		password: "pass",
+		davClient: client,
+		lookAheadDays,
+	})
+}
+
+describe("CalDavSource", () => {
+	test("has correct id", () => {
+		const client = new MockDAVClient([], {})
+		const source = createSource(client)
+		expect(source.id).toBe("aris.caldav")
+	})
+
+	test("returns empty array when no calendars exist", async () => {
+		const client = new MockDAVClient([], {})
+		const source = createSource(client)
+		const items = await source.fetchItems(createContext(new Date("2026-01-15T12:00:00Z")))
+		expect(items).toEqual([])
+	})
+
+	test("returns feed items from a single calendar", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		const items = await source.fetchItems(createContext(new Date("2026-01-15T12:00:00Z")))
+
+		expect(items).toHaveLength(1)
+		expect(items[0]!.type).toBe("caldav-event")
+		expect(items[0]!.id).toBe("caldav-event-single-event-001@test")
+		expect(items[0]!.data.title).toBe("Team Standup")
+		expect(items[0]!.data.location).toBe("Conference Room A")
+		expect(items[0]!.data.calendarName).toBe("Work")
+		expect(items[0]!.data.attendees).toHaveLength(2)
+		expect(items[0]!.data.alarms).toHaveLength(2)
+	})
+
+	test("returns feed items from multiple calendars", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+			"/cal/personal": [
+				{
+					url: "/cal/personal/event2.ics",
+					data: loadFixture("all-day-event.ics"),
+				},
+			],
+		}
+		const client = new MockDAVClient(
+			[
+				{ url: "/cal/work", displayName: "Work" },
+				{ url: "/cal/personal", displayName: "Personal" },
+			],
+			objects,
+		)
+		const source = createSource(client)
+
+		const items = await source.fetchItems(createContext(new Date("2026-01-15T12:00:00Z")))
+
+		expect(items).toHaveLength(2)
+
+		const standup = items.find((i) => i.data.title === "Team Standup")
+		const holiday = items.find((i) => i.data.title === "Company Holiday")
+
+		expect(standup).toBeDefined()
+		expect(standup!.data.calendarName).toBe("Work")
+
+		expect(holiday).toBeDefined()
+		expect(holiday!.data.calendarName).toBe("Personal")
+		expect(holiday!.data.isAllDay).toBe(true)
+	})
+
+	test("skips objects with non-string data", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [
+				{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") },
+				{ url: "/cal/work/bad.ics", data: 12345 },
+				{ url: "/cal/work/empty.ics" },
+			],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		const items = await source.fetchItems(createContext(new Date("2026-01-15T12:00:00Z")))
+		expect(items).toHaveLength(1)
+		expect(items[0]!.data.title).toBe("Team Standup")
+	})
+
+	test("uses context time as feed item timestamp", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		const now = new Date("2026-01-15T12:00:00Z")
+		const items = await source.fetchItems(createContext(now))
+		expect(items[0]!.timestamp).toEqual(now)
+	})
+
+	test("assigns signals based on event proximity", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [
+				{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") },
+				{ url: "/cal/work/allday.ics", data: loadFixture("all-day-event.ics") },
+			],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		// 2 hours before the event at 14:00
+		const items = await source.fetchItems(createContext(new Date("2026-01-15T12:00:00Z")))
+
+		const standup = items.find((i) => i.data.title === "Team Standup")
+		const holiday = items.find((i) => i.data.title === "Company Holiday")
+
+		expect(standup!.signals!.urgency).toBe(0.7) // within 2 hours
+		expect(standup!.signals!.timeRelevance).toBe(TimeRelevance.Upcoming)
+		expect(holiday!.signals!.urgency).toBe(0.3) // all-day
+		expect(holiday!.signals!.timeRelevance).toBe(TimeRelevance.Ambient)
+	})
+
+	test("handles calendar with non-string displayName", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/weird": [
+				{
+					url: "/cal/weird/event1.ics",
+					data: loadFixture("minimal-event.ics"),
+				},
+			],
+		}
+		const client = new MockDAVClient(
+			[{ url: "/cal/weird", displayName: { _cdata: "Weird Calendar" } }],
+			objects,
+		)
+		const source = createSource(client)
+
+		const items = await source.fetchItems(createContext(new Date("2026-01-15T12:00:00Z")))
+		expect(items[0]!.data.calendarName).toBeNull()
+	})
+
+	test("handles recurring events with exceptions", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [
+				{
+					url: "/cal/work/recurring.ics",
+					data: loadFixture("recurring-event.ics"),
+				},
+			],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		const items = await source.fetchItems(createContext(new Date("2026-01-15T08:00:00Z")))
+
+		expect(items).toHaveLength(2)
+
+		const base = items.find((i) => i.data.title === "Weekly Sync")
+		const exception = items.find((i) => i.data.title === "Weekly Sync (moved)")
+
+		expect(base).toBeDefined()
+		expect(base!.data.recurrenceId).toBeNull()
+
+		expect(exception).toBeDefined()
+		expect(exception!.data.recurrenceId).not.toBeNull()
+		expect(exception!.id).toContain("-")
+	})
+
+	test("caches events within the same refresh cycle", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		const context = createContext(new Date("2026-01-15T12:00:00Z"))
+
+		await source.fetchContext(context)
+		await source.fetchItems(context)
+
+		// Same context.time reference — fetchEvents should only hit the client once
+		expect(client.fetchCalendarsCallCount).toBe(1)
+	})
+
+	test("uses timezone for time range when provided", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+
+		// 2026-01-15T22:00:00Z = 2026-01-16T09:00:00 in Australia/Sydney (AEDT, UTC+11)
+		const source = new CalDavSource({
+			serverUrl: "https://caldav.example.com",
+			authMethod: "basic",
+			username: "user",
+			password: "pass",
+			davClient: client,
+			timeZone: "Australia/Sydney",
+		})
+
+		await source.fetchItems(createContext(new Date("2026-01-15T22:00:00Z")))
+
+		// "Today" in Sydney is Jan 16, so start should be Jan 15 13:00 UTC (midnight Jan 16 AEDT)
+		expect(client.lastTimeRange).not.toBeNull()
+		expect(client.lastTimeRange!.start).toBe("2026-01-15T13:00:00.000Z")
+		// End should be Jan 16 13:00 UTC (midnight Jan 17 AEDT) — 1 day window
+		expect(client.lastTimeRange!.end).toBe("2026-01-16T13:00:00.000Z")
+	})
+
+	test("defaults to UTC midnight when no timezone provided", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		await source.fetchItems(createContext(new Date("2026-01-15T22:00:00Z")))
+
+		expect(client.lastTimeRange).not.toBeNull()
+		expect(client.lastTimeRange!.start).toBe("2026-01-15T00:00:00.000Z")
+		expect(client.lastTimeRange!.end).toBe("2026-01-16T00:00:00.000Z")
+	})
+
+	test("refetches events for a different context time", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		await source.fetchItems(createContext(new Date("2026-01-15T12:00:00Z")))
+		await source.fetchItems(createContext(new Date("2026-01-15T13:00:00Z")))
+
+		// Different context.time references — should fetch twice
+		expect(client.fetchCalendarsCallCount).toBe(2)
+	})
+})
+
+describe("CalDavSource.fetchContext", () => {
+	test("returns empty context when no calendars exist", async () => {
+		const client = new MockDAVClient([], {})
+		const source = createSource(client)
+		const entries = await source.fetchContext(createContext(new Date("2026-01-15T12:00:00Z")))
+		const calendar = extractCalendar(entries)
+
+		expect(calendar).toBeDefined()
+		expect(calendar!.inProgress).toEqual([])
+		expect(calendar!.nextEvent).toBeNull()
+		expect(calendar!.hasTodayEvents).toBe(false)
+		expect(calendar!.todayEventCount).toBe(0)
+	})
+
+	test("identifies in-progress events", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		// 14:30 is during the 14:00-15:00 event
+		const entries = await source.fetchContext(createContext(new Date("2026-01-15T14:30:00Z")))
+		const calendar = extractCalendar(entries)
+
+		expect(calendar!.inProgress).toHaveLength(1)
+		expect(calendar!.inProgress[0]!.title).toBe("Team Standup")
+	})
+
+	test("identifies next upcoming event", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		// 12:00 is before the 14:00 event
+		const entries = await source.fetchContext(createContext(new Date("2026-01-15T12:00:00Z")))
+		const calendar = extractCalendar(entries)
+
+		expect(calendar!.inProgress).toHaveLength(0)
+		expect(calendar!.nextEvent).not.toBeNull()
+		expect(calendar!.nextEvent!.title).toBe("Team Standup")
+	})
+
+	test("excludes all-day events from inProgress and nextEvent", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [{ url: "/cal/work/allday.ics", data: loadFixture("all-day-event.ics") }],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		const entries = await source.fetchContext(createContext(new Date("2026-01-15T12:00:00Z")))
+		const calendar = extractCalendar(entries)
+
+		expect(calendar!.inProgress).toHaveLength(0)
+		expect(calendar!.nextEvent).toBeNull()
+		expect(calendar!.hasTodayEvents).toBe(true)
+		expect(calendar!.todayEventCount).toBe(1)
+	})
+
+	test("counts all events including all-day in todayEventCount", async () => {
+		const objects: Record<string, CalDavDAVObject[]> = {
+			"/cal/work": [
+				{ url: "/cal/work/event1.ics", data: loadFixture("single-event.ics") },
+				{ url: "/cal/work/allday.ics", data: loadFixture("all-day-event.ics") },
+			],
+		}
+		const client = new MockDAVClient([{ url: "/cal/work", displayName: "Work" }], objects)
+		const source = createSource(client)
+
+		const entries = await source.fetchContext(createContext(new Date("2026-01-15T12:00:00Z")))
+		const calendar = extractCalendar(entries)
+
+		expect(calendar!.todayEventCount).toBe(2)
+		expect(calendar!.hasTodayEvents).toBe(true)
+	})
+})
+
+describe("computeSignals", () => {
+	const now = new Date("2026-01-15T12:00:00Z")
+
+	function makeEvent(overrides: Partial<CalDavEventData>): CalDavEventData {
+		return {
+			uid: "test-uid",
+			title: "Test",
+			startDate: new Date("2026-01-15T14:00:00Z"),
+			endDate: new Date("2026-01-15T15:00:00Z"),
+			isAllDay: false,
+			location: null,
+			description: null,
+			calendarName: null,
+			status: null,
+			url: null,
+			organizer: null,
+			attendees: [],
+			alarms: [],
+			recurrenceId: null,
+			...overrides,
+		}
+	}
+
+	test("all-day events get urgency 0.3 and ambient relevance", () => {
+		const event = makeEvent({ isAllDay: true })
+		const signals = computeSignals(event, now)
+		expect(signals.urgency).toBe(0.3)
+		expect(signals.timeRelevance).toBe(TimeRelevance.Ambient)
+	})
+
+	test("events starting within 30 minutes get urgency 0.9 and imminent relevance", () => {
+		const event = makeEvent({
+			startDate: new Date("2026-01-15T12:20:00Z"),
+		})
+		const signals = computeSignals(event, now)
+		expect(signals.urgency).toBe(0.9)
+		expect(signals.timeRelevance).toBe(TimeRelevance.Imminent)
+	})
+
+	test("events starting exactly at 30 minutes get urgency 0.9", () => {
+		const event = makeEvent({
+			startDate: new Date("2026-01-15T12:30:00Z"),
+		})
+		expect(computeSignals(event, now).urgency).toBe(0.9)
+	})
+
+	test("events starting within 2 hours get urgency 0.7 and upcoming relevance", () => {
+		const event = makeEvent({
+			startDate: new Date("2026-01-15T13:00:00Z"),
+		})
+		const signals = computeSignals(event, now)
+		expect(signals.urgency).toBe(0.7)
+		expect(signals.timeRelevance).toBe(TimeRelevance.Upcoming)
+	})
+
+	test("events later today get urgency 0.5", () => {
+		const event = makeEvent({
+			startDate: new Date("2026-01-15T20:00:00Z"),
+		})
+		expect(computeSignals(event, now).urgency).toBe(0.5)
+	})
+
+	test("in-progress events get urgency 0.8 and imminent relevance", () => {
+		const event = makeEvent({
+			startDate: new Date("2026-01-15T11:00:00Z"),
+			endDate: new Date("2026-01-15T13:00:00Z"),
+		})
+		const signals = computeSignals(event, now)
+		expect(signals.urgency).toBe(0.8)
+		expect(signals.timeRelevance).toBe(TimeRelevance.Imminent)
+	})
+
+	test("fully past events get urgency 0.2 and ambient relevance", () => {
+		const event = makeEvent({
+			startDate: new Date("2026-01-15T09:00:00Z"),
+			endDate: new Date("2026-01-15T10:00:00Z"),
+		})
+		const signals = computeSignals(event, now)
+		expect(signals.urgency).toBe(0.2)
+		expect(signals.timeRelevance).toBe(TimeRelevance.Ambient)
+	})
+
+	test("events on future days get urgency 0.2", () => {
+		const event = makeEvent({
+			startDate: new Date("2026-01-16T10:00:00Z"),
+		})
+		expect(computeSignals(event, now).urgency).toBe(0.2)
+	})
+
+	test("urgency boundaries are correct", () => {
+		// 31 minutes from now should be 0.7 (within 2 hours, not within 30 min)
+		const event31min = makeEvent({
+			startDate: new Date("2026-01-15T12:31:00Z"),
+		})
+		expect(computeSignals(event31min, now).urgency).toBe(0.7)
+
+		// 2 hours 1 minute from now should be 0.5 (later today, not within 2 hours)
+		const event2h1m = makeEvent({
+			startDate: new Date("2026-01-15T14:01:00Z"),
+		})
+		expect(computeSignals(event2h1m, now).urgency).toBe(0.5)
+	})
+
+	test("cancelled events get urgency 0.1 regardless of timing", () => {
+		const event = makeEvent({
+			status: "cancelled",
+			startDate: new Date("2026-01-15T12:20:00Z"), // would be 0.9 if not cancelled
+		})
+		const signals = computeSignals(event, now)
+		expect(signals.urgency).toBe(0.1)
+		expect(signals.timeRelevance).toBe(TimeRelevance.Ambient)
+	})
+
+	test("uses timezone for 'later today' boundary", () => {
+		// now = 2026-01-15T12:00:00Z = 2026-01-15T21:00:00 JST (UTC+9)
+		// event at 2026-01-15T15:30:00Z = 2026-01-16T00:30:00 JST — next day in JST
+		const event = makeEvent({
+			startDate: new Date("2026-01-15T15:30:00Z"),
+		})
+
+		// Without timezone: UTC day ends at 2026-01-16T00:00:00Z, event is before that → "later today"
+		expect(computeSignals(event, now).urgency).toBe(0.5)
+
+		// With Asia/Tokyo: local day ends at 2026-01-15T15:00:00Z (midnight Jan 16 JST),
+		// event is after that → "future days"
+		expect(computeSignals(event, now, "Asia/Tokyo").urgency).toBe(0.2)
+	})
+})

packages/aris-source-caldav/src/caldav-source.ts

@@ -0,0 +1,351 @@
+import type { ActionDefinition, ContextEntry, FeedItemSignals, FeedSource } from "@aris/core"
+
+import { Context, TimeRelevance, UnknownActionError } from "@aris/core"
+import { DAVClient } from "tsdav"
+
+import type { CalDavDAVClient, CalDavEventData, CalDavFeedItem } from "./types.ts"
+
+import { CalDavCalendarKey, type CalendarContext } from "./calendar-context.ts"
+import { parseICalEvents } from "./ical-parser.ts"
+import { CalDavEventStatus, CalDavFeedItemType } from "./types.ts"
+
+// -- Source options --
+
+interface CalDavSourceBaseOptions {
+	serverUrl: string
+	/** Number of additional days beyond today to fetch. Default: 0 (today only). */
+	lookAheadDays?: number
+	/** IANA timezone for determining "today" (e.g. "America/New_York"). Default: UTC. */
+	timeZone?: string
+	/** Optional DAV client for testing. */
+	davClient?: CalDavDAVClient
+}
+
+interface CalDavSourceBasicAuthOptions extends CalDavSourceBaseOptions {
+	authMethod: "basic"
+	username: string
+	password: string
+}
+
+interface CalDavSourceOAuthOptions extends CalDavSourceBaseOptions {
+	authMethod: "oauth"
+	accessToken: string
+	refreshToken: string
+	tokenUrl: string
+	expiration?: number
+	clientId?: string
+	clientSecret?: string
+}
+
+export type CalDavSourceOptions = CalDavSourceBasicAuthOptions | CalDavSourceOAuthOptions
+
+const DEFAULT_LOOK_AHEAD_DAYS = 0
+
+/**
+ * A FeedSource that fetches calendar events from any CalDAV server.
+ *
+ * Supports Basic auth (username/password) and OAuth (access token + refresh token).
+ * The server URL is provided at construction time.
+ *
+ * @example
+ * ```ts
+ * // Basic auth (self-hosted servers)
+ * const source = new CalDavSource({
+ *   serverUrl: "https://nextcloud.example.com/remote.php/dav",
+ *   authMethod: "basic",
+ *   username: "user",
+ *   password: "pass",
+ * })
+ *
+ * // OAuth (cloud providers)
+ * const source = new CalDavSource({
+ *   serverUrl: "https://caldav.provider.com",
+ *   authMethod: "oauth",
+ *   accessToken: "...",
+ *   refreshToken: "...",
+ *   tokenUrl: "https://provider.com/oauth/token",
+ * })
+ * ```
+ */
+export class CalDavSource implements FeedSource<CalDavFeedItem> {
+	readonly id = "aris.caldav"
+
+	private options: CalDavSourceOptions | null
+	private readonly lookAheadDays: number
+	private readonly timeZone: string | undefined
+	private readonly injectedClient: CalDavDAVClient | null
+	private clientPromise: Promise<CalDavDAVClient> | null = null
+	private cachedEvents: { time: Date; events: CalDavEventData[] } | null = null
+	private pendingFetch: { time: Date; promise: Promise<CalDavEventData[]> } | null = null
+
+	constructor(options: CalDavSourceOptions) {
+		this.options = options
+		this.lookAheadDays = options.lookAheadDays ?? DEFAULT_LOOK_AHEAD_DAYS
+		this.timeZone = options.timeZone
+		this.injectedClient = options.davClient ?? null
+	}
+
+	async listActions(): Promise<Record<string, ActionDefinition>> {
+		return {}
+	}
+
+	async executeAction(actionId: string): Promise<void> {
+		throw new UnknownActionError(actionId)
+	}
+
+	async fetchContext(context: Context): Promise<readonly ContextEntry[] | null> {
+		const events = await this.fetchEvents(context)
+		if (events.length === 0) {
+			return [
+				[
+					CalDavCalendarKey,
+					{
+						inProgress: [],
+						nextEvent: null,
+						hasTodayEvents: false,
+						todayEventCount: 0,
+					},
+				],
+			]
+		}
+
+		const now = context.time
+		const active = events.filter((e) => e.status !== CalDavEventStatus.Cancelled)
+		const inProgress = active.filter((e) => !e.isAllDay && e.startDate <= now && e.endDate > now)
+
+		const upcoming = active
+			.filter((e) => !e.isAllDay && e.startDate > now)
+			.sort((a, b) => a.startDate.getTime() - b.startDate.getTime())
+
+		const calendarContext: CalendarContext = {
+			inProgress,
+			nextEvent: upcoming[0] ?? null,
+			hasTodayEvents: events.length > 0,
+			todayEventCount: events.length,
+		}
+
+		return [[CalDavCalendarKey, calendarContext]]
+	}
+
+	async fetchItems(context: Context): Promise<CalDavFeedItem[]> {
+		const now = context.time
+		const events = await this.fetchEvents(context)
+		return events.map((event) => createFeedItem(event, now, this.timeZone))
+	}
+
+	private fetchEvents(context: Context): Promise<CalDavEventData[]> {
+		if (this.cachedEvents && this.cachedEvents.time === context.time) {
+			return Promise.resolve(this.cachedEvents.events)
+		}
+
+		// Deduplicate concurrent fetches for the same context.time reference
+		if (this.pendingFetch && this.pendingFetch.time === context.time) {
+			return this.pendingFetch.promise
+		}
+
+		const promise = this.doFetchEvents(context).finally(() => {
+			if (this.pendingFetch?.promise === promise) {
+				this.pendingFetch = null
+			}
+		})
+
+		this.pendingFetch = { time: context.time, promise }
+		return promise
+	}
+
+	private async doFetchEvents(context: Context): Promise<CalDavEventData[]> {
+		const client = await this.connectClient()
+		const calendars = await client.fetchCalendars()
+
+		const { start, end } = computeTimeRange(context.time, this.lookAheadDays, this.timeZone)
+
+		const results = await Promise.allSettled(
+			calendars.map(async (calendar) => {
+				const objects = await client.fetchCalendarObjects({
+					calendar,
+					timeRange: {
+						start: start.toISOString(),
+						end: end.toISOString(),
+					},
+				})
+				// tsdav types displayName as string | Record<string, unknown> | undefined
+				const calendarName = typeof calendar.displayName === "string" ? calendar.displayName : null
+				return { objects, calendarName }
+			}),
+		)
+
+		const allEvents: CalDavEventData[] = []
+		for (const result of results) {
+			if (result.status === "rejected") {
+				console.warn("[aris.caldav] Failed to fetch calendar:", result.reason)
+				continue
+			}
+			const { objects, calendarName } = result.value
+			for (const obj of objects) {
+				if (typeof obj.data !== "string") continue
+
+				const events = parseICalEvents(obj.data, calendarName)
+				for (const event of events) {
+					allEvents.push(event)
+				}
+			}
+		}
+
+		this.cachedEvents = { time: context.time, events: allEvents }
+		return allEvents
+	}
+
+	private connectClient(): Promise<CalDavDAVClient> {
+		if (this.injectedClient) {
+			return Promise.resolve(this.injectedClient)
+		}
+
+		if (!this.clientPromise) {
+			this.clientPromise = this.createAndLoginClient().catch((err) => {
+				this.clientPromise = null
+				throw err
+			})
+		}
+
+		return this.clientPromise
+	}
+
+	private async createAndLoginClient(): Promise<CalDavDAVClient> {
+		const opts = this.options
+		if (!opts) {
+			throw new Error("CalDavSource options have already been consumed")
+		}
+
+		let client: CalDavDAVClient
+
+		if (opts.authMethod === "basic") {
+			client = new DAVClient({
+				serverUrl: opts.serverUrl,
+				credentials: {
+					username: opts.username,
+					password: opts.password,
+				},
+				authMethod: "Basic",
+				defaultAccountType: "caldav",
+			})
+		} else {
+			client = new DAVClient({
+				serverUrl: opts.serverUrl,
+				credentials: {
+					tokenUrl: opts.tokenUrl,
+					refreshToken: opts.refreshToken,
+					accessToken: opts.accessToken,
+					expiration: opts.expiration,
+					clientId: opts.clientId,
+					clientSecret: opts.clientSecret,
+				},
+				authMethod: "Oauth",
+				defaultAccountType: "caldav",
+			})
+		}
+
+		await client.login()
+		this.options = null
+		return client
+	}
+}
+
+function computeTimeRange(
+	now: Date,
+	lookAheadDays: number,
+	timeZone?: string,
+): { start: Date; end: Date } {
+	const start = startOfDay(now, timeZone)
+	const end = new Date(start.getTime() + (1 + lookAheadDays) * 24 * 60 * 60 * 1000)
+	return { start, end }
+}
+
+/**
+ * Returns midnight (start of day) as a UTC Date.
+ * When timeZone is provided, "midnight" is local midnight in that timezone
+ * converted to UTC. Otherwise, UTC midnight.
+ */
+function startOfDay(date: Date, timeZone?: string): Date {
+	if (!timeZone) {
+		const d = new Date(date)
+		d.setUTCHours(0, 0, 0, 0)
+		return d
+	}
+
+	// Extract the local year/month/day in the target timezone
+	const parts = new Intl.DateTimeFormat("en-CA", {
+		timeZone,
+		year: "numeric",
+		month: "2-digit",
+		day: "2-digit",
+	}).formatToParts(date)
+
+	const year = Number(parts.find((p) => p.type === "year")!.value)
+	const month = Number(parts.find((p) => p.type === "month")!.value)
+	const day = Number(parts.find((p) => p.type === "day")!.value)
+
+	// Binary-search-free approach: construct a UTC date at the local date's noon,
+	// then use the timezone offset at that moment to find local midnight in UTC.
+	const noonUtc = Date.UTC(year, month - 1, day, 12, 0, 0)
+	const noonLocal = new Date(noonUtc).toLocaleString("sv-SE", { timeZone, hour12: false })
+	// sv-SE locale formats as "YYYY-MM-DD HH:MM:SS" which Date can parse
+	const noonLocalMs = new Date(noonLocal + "Z").getTime()
+	const offsetMs = noonLocalMs - noonUtc
+
+	return new Date(Date.UTC(year, month - 1, day) - offsetMs)
+}
+
+export function computeSignals(
+	event: CalDavEventData,
+	now: Date,
+	timeZone?: string,
+): FeedItemSignals {
+	if (event.status === CalDavEventStatus.Cancelled) {
+		return { urgency: 0.1, timeRelevance: TimeRelevance.Ambient }
+	}
+
+	if (event.isAllDay) {
+		return { urgency: 0.3, timeRelevance: TimeRelevance.Ambient }
+	}
+
+	const msUntilStart = event.startDate.getTime() - now.getTime()
+
+	// Event already started
+	if (msUntilStart < 0) {
+		const isInProgress = now.getTime() < event.endDate.getTime()
+		return isInProgress
+			? { urgency: 0.8, timeRelevance: TimeRelevance.Imminent }
+			: { urgency: 0.2, timeRelevance: TimeRelevance.Ambient }
+	}
+
+	// Starting within 30 minutes
+	if (msUntilStart <= 30 * 60 * 1000) {
+		return { urgency: 0.9, timeRelevance: TimeRelevance.Imminent }
+	}
+
+	// Starting within 2 hours
+	if (msUntilStart <= 2 * 60 * 60 * 1000) {
+		return { urgency: 0.7, timeRelevance: TimeRelevance.Upcoming }
+	}
+
+	// Later today (using local day boundary when timeZone is set)
+	const todayStart = startOfDay(now, timeZone)
+	const endOfDay = new Date(todayStart.getTime() + 24 * 60 * 60 * 1000)
+
+	if (event.startDate.getTime() < endOfDay.getTime()) {
+		return { urgency: 0.5, timeRelevance: TimeRelevance.Upcoming }
+	}
+
+	// Future days
+	return { urgency: 0.2, timeRelevance: TimeRelevance.Ambient }
+}
+
+function createFeedItem(event: CalDavEventData, now: Date, timeZone?: string): CalDavFeedItem {
+	return {
+		id: `caldav-event-${event.uid}${event.recurrenceId ? `-${event.recurrenceId}` : ""}`,
+		type: CalDavFeedItemType.Event,
+		timestamp: now,
+		data: event,
+		signals: computeSignals(event, now, timeZone),
+	}
+}

packages/aris-source-caldav/src/calendar-context.ts

@@ -0,0 +1,24 @@
+import type { ContextKey } from "@aris/core"
+
+import { contextKey } from "@aris/core"
+
+import type { CalDavEventData } from "./types.ts"
+
+/**
+ * Calendar context for downstream sources.
+ *
+ * Provides a snapshot of the user's upcoming CalDAV events so other sources
+ * can adapt (e.g. a commute source checking if there's a meeting soon).
+ */
+export interface CalendarContext {
+	/** Events happening right now */
+	inProgress: CalDavEventData[]
+	/** Next upcoming event, if any */
+	nextEvent: CalDavEventData | null
+	/** Whether the user has any events today */
+	hasTodayEvents: boolean
+	/** Total number of events today */
+	todayEventCount: number
+}
+
+export const CalDavCalendarKey: ContextKey<CalendarContext> = contextKey("aris.caldav", "calendar")

packages/aris-source-caldav/src/ical-parser.test.ts

@@ -0,0 +1,107 @@
+import { describe, expect, test } from "bun:test"
+import { readFileSync } from "node:fs"
+import { join } from "node:path"
+
+import { parseICalEvents } from "./ical-parser.ts"
+
+function loadFixture(name: string): string {
+	return readFileSync(join(import.meta.dir, "..", "fixtures", name), "utf-8")
+}
+
+describe("parseICalEvents", () => {
+	test("parses a full event with all fields", () => {
+		const events = parseICalEvents(loadFixture("single-event.ics"), "Work")
+
+		expect(events).toHaveLength(1)
+		const event = events[0]!
+
+		expect(event.uid).toBe("single-event-001@test")
+		expect(event.title).toBe("Team Standup")
+		expect(event.startDate).toEqual(new Date("2026-01-15T14:00:00Z"))
+		expect(event.endDate).toEqual(new Date("2026-01-15T15:00:00Z"))
+		expect(event.isAllDay).toBe(false)
+		expect(event.location).toBe("Conference Room A")
+		expect(event.description).toBe("Daily standup meeting")
+		expect(event.calendarName).toBe("Work")
+		expect(event.status).toBe("confirmed")
+		expect(event.url).toBe("https://example.com/meeting/123")
+		expect(event.organizer).toBe("Alice Smith")
+		expect(event.recurrenceId).toBeNull()
+
+		expect(event.attendees).toHaveLength(2)
+		expect(event.attendees[0]).toEqual({
+			name: "Bob Jones",
+			email: "bob@example.com",
+			role: "required",
+			status: "accepted",
+		})
+		expect(event.attendees[1]).toEqual({
+			name: "Carol White",
+			email: "carol@example.com",
+			role: "optional",
+			status: "tentative",
+		})
+
+		expect(event.alarms).toHaveLength(2)
+		expect(event.alarms[0]).toEqual({ trigger: "-PT15M", action: "DISPLAY" })
+		expect(event.alarms[1]).toEqual({ trigger: "-PT5M", action: "AUDIO" })
+	})
+
+	test("parses an all-day event with optional fields as null", () => {
+		const events = parseICalEvents(loadFixture("all-day-event.ics"), null)
+
+		expect(events).toHaveLength(1)
+		const event = events[0]!
+
+		expect(event.isAllDay).toBe(true)
+		expect(event.title).toBe("Company Holiday")
+		expect(event.calendarName).toBeNull()
+		expect(event.location).toBeNull()
+		expect(event.description).toBeNull()
+		expect(event.url).toBeNull()
+		expect(event.organizer).toBeNull()
+		expect(event.attendees).toEqual([])
+		expect(event.alarms).toEqual([])
+	})
+
+	test("parses recurring event with exception", () => {
+		const events = parseICalEvents(loadFixture("recurring-event.ics"), "Team")
+
+		expect(events).toHaveLength(2)
+		expect(events[0]!.uid).toBe("recurring-001@test")
+		expect(events[1]!.uid).toBe("recurring-001@test")
+
+		const base = events.find((e) => e.title === "Weekly Sync")
+		expect(base).toBeDefined()
+		expect(base!.recurrenceId).toBeNull()
+
+		const exception = events.find((e) => e.title === "Weekly Sync (moved)")
+		expect(exception).toBeDefined()
+		expect(exception!.recurrenceId).not.toBeNull()
+	})
+
+	test("parses minimal event with defaults", () => {
+		const events = parseICalEvents(loadFixture("minimal-event.ics"), null)
+
+		expect(events).toHaveLength(1)
+		const event = events[0]!
+
+		expect(event.uid).toBe("minimal-001@test")
+		expect(event.title).toBe("Quick Chat")
+		expect(event.startDate).toEqual(new Date("2026-01-15T18:00:00Z"))
+		expect(event.endDate).toEqual(new Date("2026-01-15T19:00:00Z"))
+		expect(event.location).toBeNull()
+		expect(event.description).toBeNull()
+		expect(event.status).toBeNull()
+		expect(event.url).toBeNull()
+		expect(event.organizer).toBeNull()
+		expect(event.attendees).toEqual([])
+		expect(event.alarms).toEqual([])
+		expect(event.recurrenceId).toBeNull()
+	})
+
+	test("parses cancelled status", () => {
+		const events = parseICalEvents(loadFixture("cancelled-event.ics"), null)
+		expect(events[0]!.status).toBe("cancelled")
+	})
+})

packages/aris-source-caldav/src/ical-parser.ts

@@ -0,0 +1,153 @@
+import ICAL from "ical.js"
+
+import {
+	AttendeeRole,
+	AttendeeStatus,
+	CalDavEventStatus,
+	type CalDavAlarm,
+	type CalDavAttendee,
+	type CalDavEventData,
+} from "./types.ts"
+
+/**
+ * Parses a raw iCalendar string and extracts all VEVENT components
+ * into CalDavEventData objects.
+ *
+ * @param icsData - Raw iCalendar string from a CalDAV response
+ * @param calendarName - Display name of the calendar this event belongs to
+ */
+export function parseICalEvents(icsData: string, calendarName: string | null): CalDavEventData[] {
+	const jcal = ICAL.parse(icsData)
+	const comp = new ICAL.Component(jcal)
+	const vevents = comp.getAllSubcomponents("vevent")
+
+	return vevents.map((vevent: InstanceType<typeof ICAL.Component>) =>
+		parseVEvent(vevent, calendarName),
+	)
+}
+
+function parseVEvent(
+	vevent: InstanceType<typeof ICAL.Component>,
+	calendarName: string | null,
+): CalDavEventData {
+	const event = new ICAL.Event(vevent)
+
+	return {
+		uid: event.uid ?? "",
+		title: event.summary ?? "",
+		startDate: event.startDate?.toJSDate() ?? new Date(0),
+		endDate: event.endDate?.toJSDate() ?? new Date(0),
+		isAllDay: event.startDate?.isDate ?? false,
+		location: event.location ?? null,
+		description: event.description ?? null,
+		calendarName,
+		status: parseStatus(asStringOrNull(vevent.getFirstPropertyValue("status"))),
+		url: asStringOrNull(vevent.getFirstPropertyValue("url")),
+		organizer: parseOrganizer(asStringOrNull(event.organizer), vevent),
+		attendees: parseAttendees(Array.isArray(event.attendees) ? event.attendees : []),
+		alarms: parseAlarms(vevent),
+		recurrenceId: event.recurrenceId ? event.recurrenceId.toString() : null,
+	}
+}
+
+function parseStatus(raw: string | null): CalDavEventStatus | null {
+	if (!raw) return null
+	switch (raw.toLowerCase()) {
+		case "confirmed":
+			return CalDavEventStatus.Confirmed
+		case "tentative":
+			return CalDavEventStatus.Tentative
+		case "cancelled":
+			return CalDavEventStatus.Cancelled
+		default:
+			return null
+	}
+}
+
+function parseOrganizer(
+	value: string | null,
+	vevent: InstanceType<typeof ICAL.Component>,
+): string | null {
+	if (!value) return null
+
+	// Try CN parameter first
+	const prop = vevent.getFirstProperty("organizer")
+	if (prop) {
+		const cn = prop.getParameter("cn") as string | undefined
+		if (cn) return cn
+	}
+
+	// Fall back to mailto: value
+	return value.replace(/^mailto:/i, "")
+}
+
+function parseAttendees(properties: unknown[]): CalDavAttendee[] {
+	if (properties.length === 0) return []
+
+	return properties.flatMap((prop) => {
+		if (!prop || typeof prop !== "object" || !("getFirstValue" in prop)) return []
+		const p = prop as InstanceType<typeof ICAL.Property>
+		const value = asStringOrNull(p.getFirstValue())
+		const cn = asStringOrNull(p.getParameter("cn"))
+		const role = asStringOrNull(p.getParameter("role"))
+		const partstat = asStringOrNull(p.getParameter("partstat"))
+
+		return [
+			{
+				name: cn,
+				email: value ? value.replace(/^mailto:/i, "") : null,
+				role: parseAttendeeRole(role),
+				status: parseAttendeeStatus(partstat),
+			},
+		]
+	})
+}
+
+function parseAttendeeRole(raw: string | null): AttendeeRole | null {
+	if (!raw) return null
+	switch (raw.toUpperCase()) {
+		case "CHAIR":
+			return AttendeeRole.Chair
+		case "REQ-PARTICIPANT":
+			return AttendeeRole.Required
+		case "OPT-PARTICIPANT":
+			return AttendeeRole.Optional
+		default:
+			return null
+	}
+}
+
+function parseAttendeeStatus(raw: string | null): AttendeeStatus | null {
+	if (!raw) return null
+	switch (raw.toUpperCase()) {
+		case "ACCEPTED":
+			return AttendeeStatus.Accepted
+		case "DECLINED":
+			return AttendeeStatus.Declined
+		case "TENTATIVE":
+			return AttendeeStatus.Tentative
+		case "NEEDS-ACTION":
+			return AttendeeStatus.NeedsAction
+		default:
+			return null
+	}
+}
+
+function parseAlarms(vevent: InstanceType<typeof ICAL.Component>): CalDavAlarm[] {
+	const valarms = vevent.getAllSubcomponents("valarm")
+	if (!valarms || valarms.length === 0) return []
+
+	return valarms.map((valarm: InstanceType<typeof ICAL.Component>) => {
+		const trigger = valarm.getFirstPropertyValue("trigger")
+		const action = asStringOrNull(valarm.getFirstPropertyValue("action"))
+
+		return {
+			trigger: trigger ? trigger.toString() : "",
+			action: action ?? "DISPLAY",
+		}
+	})
+}
+
+function asStringOrNull(value: unknown): string | null {
+	return typeof value === "string" ? value : null
+}

packages/aris-source-caldav/src/index.ts

@@ -0,0 +1,16 @@
+export { CalDavCalendarKey, type CalendarContext } from "./calendar-context.ts"
+export { CalDavSource, type CalDavSourceOptions } from "./caldav-source.ts"
+export { parseICalEvents } from "./ical-parser.ts"
+export {
+	AttendeeRole,
+	AttendeeStatus,
+	CalDavEventStatus,
+	CalDavFeedItemType,
+	type CalDavAlarm,
+	type CalDavAttendee,
+	type CalDavDAVCalendar,
+	type CalDavDAVClient,
+	type CalDavDAVObject,
+	type CalDavEventData,
+	type CalDavFeedItem,
+} from "./types.ts"

packages/aris-source-caldav/src/types.ts

@@ -0,0 +1,101 @@
+import type { FeedItem } from "@aris/core"
+
+// -- Event status --
+
+export const CalDavEventStatus = {
+	Confirmed: "confirmed",
+	Tentative: "tentative",
+	Cancelled: "cancelled",
+} as const
+
+export type CalDavEventStatus = (typeof CalDavEventStatus)[keyof typeof CalDavEventStatus]
+
+// -- Attendee types --
+
+export const AttendeeRole = {
+	Chair: "chair",
+	Required: "required",
+	Optional: "optional",
+} as const
+
+export type AttendeeRole = (typeof AttendeeRole)[keyof typeof AttendeeRole]
+
+export const AttendeeStatus = {
+	Accepted: "accepted",
+	Declined: "declined",
+	Tentative: "tentative",
+	NeedsAction: "needs-action",
+} as const
+
+export type AttendeeStatus = (typeof AttendeeStatus)[keyof typeof AttendeeStatus]
+
+export interface CalDavAttendee {
+	name: string | null
+	email: string | null
+	role: AttendeeRole | null
+	status: AttendeeStatus | null
+}
+
+// -- Alarm --
+
+export interface CalDavAlarm {
+	/** ISO 8601 duration relative to event start, e.g. "-PT15M" */
+	trigger: string
+	/** e.g. "DISPLAY", "AUDIO" */
+	action: string
+}
+
+// -- Event data --
+
+export interface CalDavEventData extends Record<string, unknown> {
+	uid: string
+	title: string
+	startDate: Date
+	endDate: Date
+	isAllDay: boolean
+	location: string | null
+	description: string | null
+	calendarName: string | null
+	status: CalDavEventStatus | null
+	url: string | null
+	organizer: string | null
+	attendees: CalDavAttendee[]
+	alarms: CalDavAlarm[]
+	recurrenceId: string | null
+}
+
+// -- Feed item type --
+
+export const CalDavFeedItemType = {
+	Event: "caldav-event",
+} as const
+
+export type CalDavFeedItemType = (typeof CalDavFeedItemType)[keyof typeof CalDavFeedItemType]
+
+// -- Feed item --
+
+export type CalDavFeedItem = FeedItem<typeof CalDavFeedItemType.Event, CalDavEventData>
+
+// -- DAV client interface --
+
+export interface CalDavDAVObject {
+	data?: unknown
+	etag?: string
+	url: string
+}
+
+export interface CalDavDAVCalendar {
+	displayName?: string | Record<string, unknown>
+	url: string
+}
+
+/** Subset of tsdav's DAVClient used by CalDavSource. */
+export interface CalDavDAVClient {
+	login(): Promise<void>
+	fetchCalendars(): Promise<CalDavDAVCalendar[]>
+	fetchCalendarObjects(params: {
+		calendar: CalDavDAVCalendar
+		timeRange: { start: string; end: string }
+	}): Promise<CalDavDAVObject[]>
+	credentials: Record<string, unknown>
+}

packages/aris-source-google-calendar/src/calendar-context.ts

@@ -10,4 +10,4 @@ export interface NextEvent {
 	location: string | null
 }
 
-export const NextEventKey: ContextKey<NextEvent> = contextKey("nextEvent")
+export const NextEventKey: ContextKey<NextEvent> = contextKey("aris.google-calendar", "nextEvent")

packages/aris-source-google-calendar/src/feed-items.ts

@@ -3,19 +3,19 @@ import type { FeedItem } from "@aris/core"
 import type { CalendarEventData } from "./types"
 
 export const CalendarFeedItemType = {
-	event: "calendar-event",
-	allDay: "calendar-all-day",
+	Event: "calendar-event",
+	AllDay: "calendar-all-day",
 } as const
 
 export type CalendarFeedItemType = (typeof CalendarFeedItemType)[keyof typeof CalendarFeedItemType]
 
 export interface CalendarEventFeedItem extends FeedItem<
-	typeof CalendarFeedItemType.event,
+	typeof CalendarFeedItemType.Event,
 	CalendarEventData
 > {}
 
 export interface CalendarAllDayFeedItem extends FeedItem<
-	typeof CalendarFeedItemType.allDay,
+	typeof CalendarFeedItemType.AllDay,
 	CalendarEventData
 > {}
 

packages/aris-source-google-calendar/src/google-calendar-source.test.ts

@@ -1,10 +1,10 @@
-import { TimeRelevance, contextValue, type Context } from "@aris/core"
+import { Context, TimeRelevance } from "@aris/core"
 import { describe, expect, test } from "bun:test"
 
 import type { ApiCalendarEvent, GoogleCalendarClient, ListEventsOptions } from "./types"
 
 import fixture from "../fixtures/events.json"
-import { NextEventKey } from "./calendar-context"
+import { NextEventKey, type NextEvent } from "./calendar-context"
 import { CalendarFeedItemType } from "./feed-items"
 import { GoogleCalendarSource } from "./google-calendar-source"
 
@@ -38,7 +38,7 @@ function defaultMockClient(): GoogleCalendarClient {
 }
 
 function createContext(time?: Date): Context {
-	return { time: time ?? NOW }
+	return new Context(time ?? NOW)
 }
 
 describe("GoogleCalendarSource", () => {
@@ -69,7 +69,7 @@ describe("GoogleCalendarSource", () => {
 			const source = new GoogleCalendarSource({ client: defaultMockClient() })
 			const items = await source.fetchItems(createContext())
 
-			const timedItems = items.filter((i) => i.type === CalendarFeedItemType.event)
+			const timedItems = items.filter((i) => i.type === CalendarFeedItemType.Event)
 			expect(timedItems.length).toBe(4)
 		})
 
@@ -77,7 +77,7 @@ describe("GoogleCalendarSource", () => {
 			const source = new GoogleCalendarSource({ client: defaultMockClient() })
 			const items = await source.fetchItems(createContext())
 
-			const allDayItems = items.filter((i) => i.type === CalendarFeedItemType.allDay)
+			const allDayItems = items.filter((i) => i.type === CalendarFeedItemType.AllDay)
 			expect(allDayItems.length).toBe(1)
 		})
 
@@ -229,15 +229,16 @@ describe("GoogleCalendarSource", () => {
 
 		test("returns next upcoming timed event (not ongoing)", async () => {
 			const source = new GoogleCalendarSource({ client: defaultMockClient() })
-			const result = await source.fetchContext(createContext())
+			const entries = await source.fetchContext(createContext())
 
-			expect(result).not.toBeNull()
-			const nextEvent = contextValue(result! as Context, NextEventKey)
-			expect(nextEvent).toBeDefined()
+			expect(entries).not.toBeNull()
+			expect(entries).toHaveLength(1)
+			const [key, nextEvent] = entries![0]! as [typeof NextEventKey, NextEvent]
+			expect(key).toEqual(NextEventKey)
 			// evt-soon starts at 10:10, which is the nearest future timed event
-			expect(nextEvent!.title).toBe("1:1 with Manager")
-			expect(nextEvent!.minutesUntilStart).toBe(10)
-			expect(nextEvent!.location).toBeNull()
+			expect(nextEvent.title).toBe("1:1 with Manager")
+			expect(nextEvent.minutesUntilStart).toBe(10)
+			expect(nextEvent.location).toBeNull()
 		})
 
 		test("includes location when available", async () => {
@@ -255,12 +256,11 @@ describe("GoogleCalendarSource", () => {
 			const source = new GoogleCalendarSource({
 				client: createMockClient({ primary: events }),
 			})
-			const result = await source.fetchContext(createContext())
+			const entries = await source.fetchContext(createContext())
 
-			expect(result).not.toBeNull()
-			const nextEvent = contextValue(result! as Context, NextEventKey)
-			expect(nextEvent).toBeDefined()
-			expect(nextEvent!.location).toBe("123 Main St")
+			expect(entries).not.toBeNull()
+			const [, nextEvent] = entries![0]! as [typeof NextEventKey, NextEvent]
+			expect(nextEvent.location).toBe("123 Main St")
 		})
 
 		test("skips ongoing events for next-event context", async () => {

packages/aris-source-google-calendar/src/google-calendar-source.ts

@@ -1,6 +1,6 @@
-import type { ActionDefinition, Context, FeedItemSignals, FeedSource } from "@aris/core"
+import type { ActionDefinition, ContextEntry, FeedItemSignals, FeedSource } from "@aris/core"
 
-import { TimeRelevance, UnknownActionError } from "@aris/core"
+import { Context, TimeRelevance, UnknownActionError } from "@aris/core"
 
 import type {
 	ApiCalendarEvent,
@@ -58,7 +58,7 @@ const URGENCY_ALL_DAY = 0.4
  *   .register(calendarSource)
  *
  * // Access next-event context in downstream sources
- * const next = contextValue(context, NextEventKey)
+ * const next = context.get(NextEventKey)
  * if (next && next.minutesUntilStart < 15) {
  *   // remind user
  * }
@@ -85,7 +85,7 @@ export class GoogleCalendarSource implements FeedSource<CalendarFeedItem> {
 		throw new UnknownActionError(actionId)
 	}
 
-	async fetchContext(context: Context): Promise<Partial<Context> | null> {
+	async fetchContext(context: Context): Promise<readonly ContextEntry[] | null> {
 		const events = await this.fetchAllEvents(context.time)
 
 		const now = context.time.getTime()
@@ -105,7 +105,7 @@ export class GoogleCalendarSource implements FeedSource<CalendarFeedItem> {
 			location: nextTimedEvent.location,
 		}
 
-		return { [NextEventKey]: nextEvent }
+		return [[NextEventKey, nextEvent]]
 	}
 
 	async fetchItems(context: Context): Promise<CalendarFeedItem[]> {
@@ -209,7 +209,7 @@ function createFeedItem(
 	nowMs: number,
 	lookaheadMs: number,
 ): CalendarFeedItem {
-	const itemType = event.isAllDay ? CalendarFeedItemType.allDay : CalendarFeedItemType.event
+	const itemType = event.isAllDay ? CalendarFeedItemType.AllDay : CalendarFeedItemType.Event
 
 	return {
 		id: `calendar-${event.calendarId}-${event.eventId}`,

packages/aris-source-google-calendar/src/index.ts

@@ -1,7 +1,6 @@
 export { NextEventKey, type NextEvent } from "./calendar-context"
 export {
 	CalendarFeedItemType,
-	type CalendarFeedItemType as CalendarFeedItemTypeType,
 	type CalendarAllDayFeedItem,
 	type CalendarEventFeedItem,
 	type CalendarFeedItem,
@@ -10,7 +9,6 @@ export { DefaultGoogleCalendarClient } from "./google-calendar-api"
 export { GoogleCalendarSource, type GoogleCalendarSourceOptions } from "./google-calendar-source"
 export {
 	EventStatus,
-	type EventStatus as EventStatusType,
 	type ApiCalendarEvent,
 	type ApiEventDateTime,
 	type CalendarEventData,

packages/aris-source-location/src/location-source.test.ts

@@ -1,6 +1,8 @@
 import { describe, expect, mock, test } from "bun:test"
 
-import { LocationKey, LocationSource, type Location } from "./location-source.ts"
+import type { Location } from "./types.ts"
+
+import { LocationKey, LocationSource } from "./location-source.ts"
 
 function createLocation(overrides: Partial<Location> = {}): Location {
 	return {
@@ -39,8 +41,8 @@ describe("LocationSource", () => {
 			const location = createLocation()
 			source.pushLocation(location)
 
-			const context = await source.fetchContext()
-			expect(context).toEqual({ [LocationKey]: location })
+			const entries = await source.fetchContext()
+			expect(entries).toEqual([[LocationKey, location]])
 		})
 	})
 
@@ -65,7 +67,7 @@ describe("LocationSource", () => {
 			source.pushLocation(location)
 
 			expect(listener).toHaveBeenCalledTimes(1)
-			expect(listener).toHaveBeenCalledWith({ [LocationKey]: location })
+			expect(listener).toHaveBeenCalledWith([[LocationKey, location]])
 		})
 	})
 

packages/aris-source-location/src/location-source.ts

@@ -1,11 +1,11 @@
-import type { ActionDefinition, Context, FeedSource } from "@aris/core"
+import type { ActionDefinition, ContextEntry, FeedSource } from "@aris/core"
 
-import { UnknownActionError, contextKey, type ContextKey } from "@aris/core"
+import { Context, UnknownActionError, contextKey, type ContextKey } from "@aris/core"
 import { type } from "arktype"
 
 import { Location, type LocationSourceOptions } from "./types.ts"
 
-export const LocationKey: ContextKey<Location> = contextKey("location")
+export const LocationKey: ContextKey<Location> = contextKey("aris.location", "location")
 
 /**
  * A FeedSource that provides location context.
@@ -20,7 +20,7 @@ export class LocationSource implements FeedSource {
 
 	private readonly historySize: number
 	private locations: Location[] = []
-	private listeners = new Set<(update: Partial<Context>) => void>()
+	private listeners = new Set<(entries: readonly ContextEntry[]) => void>()
 
 	constructor(options: LocationSourceOptions = {}) {
 		this.historySize = options.historySize ?? 1
@@ -59,8 +59,9 @@ export class LocationSource implements FeedSource {
 		if (this.locations.length > this.historySize) {
 			this.locations.shift()
 		}
+		const entries: readonly ContextEntry[] = [[LocationKey, location]]
 		this.listeners.forEach((listener) => {
-			listener({ [LocationKey]: location })
+			listener(entries)
 		})
 	}
 
@@ -78,16 +79,16 @@ export class LocationSource implements FeedSource {
 		return this.locations
 	}
 
-	onContextUpdate(callback: (update: Partial<Context>) => void): () => void {
+	onContextUpdate(callback: (entries: readonly ContextEntry[]) => void): () => void {
 		this.listeners.add(callback)
 		return () => {
 			this.listeners.delete(callback)
 		}
 	}
 
-	async fetchContext(): Promise<Partial<Context> | null> {
+	async fetchContext(): Promise<readonly ContextEntry[] | null> {
 		if (this.lastLocation) {
-			return { [LocationKey]: this.lastLocation }
+			return [[LocationKey, this.lastLocation]]
 		}
 		return null
 	}

packages/aris-source-tfl/src/index.ts

@@ -1,12 +1,13 @@
 export { TflSource } from "./tfl-source.ts"
 export { TflApi } from "./tfl-api.ts"
 export type { TflLineId } from "./tfl-api.ts"
-export type {
-	ITflApi,
-	StationLocation,
-	TflAlertData,
-	TflAlertFeedItem,
-	TflAlertSeverity,
-	TflLineStatus,
-	TflSourceOptions,
+export {
+	TflFeedItemType,
+	type ITflApi,
+	type StationLocation,
+	type TflAlertData,
+	type TflAlertFeedItem,
+	type TflAlertSeverity,
+	type TflLineStatus,
+	type TflSourceOptions,
 } from "./types.ts"

packages/aris-source-tfl/src/tfl-source.test.ts

@@ -1,5 +1,4 @@
-import type { Context } from "@aris/core"
-
+import { Context } from "@aris/core"
 import { LocationKey, type Location } from "@aris/source-location"
 import { describe, expect, test } from "bun:test"
 
@@ -81,9 +80,9 @@ class FixtureTflApi implements ITflApi {
 }
 
 function createContext(location?: Location): Context {
-	const ctx: Context = { time: new Date("2026-01-15T12:00:00Z") }
+	const ctx = new Context(new Date("2026-01-15T12:00:00Z"))
 	if (location) {
-		ctx[LocationKey] = location
+		ctx.set([[LocationKey, location]])
 	}
 	return ctx
 }

packages/aris-source-tfl/src/tfl-source.ts

@@ -1,6 +1,6 @@
-import type { ActionDefinition, Context, FeedItemSignals, FeedSource } from "@aris/core"
+import type { ActionDefinition, ContextEntry, FeedItemSignals, FeedSource } from "@aris/core"
 
-import { TimeRelevance, UnknownActionError, contextValue } from "@aris/core"
+import { Context, TimeRelevance, UnknownActionError } from "@aris/core"
 import { LocationKey } from "@aris/source-location"
 import { type } from "arktype"
 
@@ -15,6 +15,7 @@ import type {
 } from "./types.ts"
 
 import { TflApi, lineId } from "./tfl-api.ts"
+import { TflFeedItemType } from "./types.ts"
 
 const setLinesInput = lineId.array()
 
@@ -111,7 +112,7 @@ export class TflSource implements FeedSource<TflAlertFeedItem> {
 		}
 	}
 
-	async fetchContext(): Promise<null> {
+	async fetchContext(): Promise<readonly ContextEntry[] | null> {
 		return null
 	}
 
@@ -128,7 +129,7 @@ export class TflSource implements FeedSource<TflAlertFeedItem> {
 			this.client.fetchStations(),
 		])
 
-		const location = contextValue(context, LocationKey)
+		const location = context.get(LocationKey)
 
 		const items: TflAlertFeedItem[] = statuses.map((status) => {
 			const closestStationDistance = location
@@ -150,7 +151,7 @@ export class TflSource implements FeedSource<TflAlertFeedItem> {
 
 			return {
 				id: `tfl-alert-${status.lineId}-${status.severity}`,
-				type: "tfl-alert",
+				type: TflFeedItemType.Alert,
 				timestamp: context.time,
 				data,
 				signals,

packages/aris-source-tfl/src/types.ts

@@ -20,7 +20,13 @@ export interface TflAlertData extends Record<string, unknown> {
 	closestStationDistance: number | null
 }
 
-export type TflAlertFeedItem = FeedItem<"tfl-alert", TflAlertData>
+export const TflFeedItemType = {
+	Alert: "tfl-alert",
+} as const
+
+export type TflFeedItemType = (typeof TflFeedItemType)[keyof typeof TflFeedItemType]
+
+export type TflAlertFeedItem = FeedItem<typeof TflFeedItemType.Alert, TflAlertData>
 
 export interface TflSourceOptions {
 	apiKey?: string

packages/aris-source-weatherkit/src/feed-items.ts

@@ -3,10 +3,10 @@ import type { FeedItem } from "@aris/core"
 import type { Certainty, ConditionCode, PrecipitationType, Severity, Urgency } from "./weatherkit"
 
 export const WeatherFeedItemType = {
-	current: "weather-current",
-	hourly: "weather-hourly",
-	daily: "weather-daily",
-	alert: "weather-alert",
+	Current: "weather-current",
+	Hourly: "weather-hourly",
+	Daily: "weather-daily",
+	Alert: "weather-alert",
 } as const
 
 export type WeatherFeedItemType = (typeof WeatherFeedItemType)[keyof typeof WeatherFeedItemType]
@@ -28,7 +28,7 @@ export type CurrentWeatherData = {
 }
 
 export interface CurrentWeatherFeedItem extends FeedItem<
-	typeof WeatherFeedItemType.current,
+	typeof WeatherFeedItemType.Current,
 	CurrentWeatherData
 > {}
 
@@ -49,7 +49,7 @@ export type HourlyWeatherData = {
 }
 
 export interface HourlyWeatherFeedItem extends FeedItem<
-	typeof WeatherFeedItemType.hourly,
+	typeof WeatherFeedItemType.Hourly,
 	HourlyWeatherData
 > {}
 
@@ -68,7 +68,7 @@ export type DailyWeatherData = {
 }
 
 export interface DailyWeatherFeedItem extends FeedItem<
-	typeof WeatherFeedItemType.daily,
+	typeof WeatherFeedItemType.Daily,
 	DailyWeatherData
 > {}
 
@@ -86,7 +86,7 @@ export type WeatherAlertData = {
 }
 
 export interface WeatherAlertFeedItem extends FeedItem<
-	typeof WeatherFeedItemType.alert,
+	typeof WeatherFeedItemType.Alert,
 	WeatherAlertData
 > {}
 

packages/aris-source-weatherkit/src/index.ts

@@ -1,14 +1,8 @@
 export { WeatherKey, type Weather } from "./weather-context"
-export {
-	WeatherSource,
-	Units,
-	type Units as UnitsType,
-	type WeatherSourceOptions,
-} from "./weather-source"
+export { WeatherSource, Units, type WeatherSourceOptions } from "./weather-source"
 
 export {
 	WeatherFeedItemType,
-	type WeatherFeedItemType as WeatherFeedItemTypeType,
 	type WeatherFeedItem,
 	type CurrentWeatherFeedItem,
 	type CurrentWeatherData,
@@ -27,11 +21,6 @@ export {
 	Certainty,
 	PrecipitationType,
 	DefaultWeatherKitClient,
-	type ConditionCode as ConditionCodeType,
-	type Severity as SeverityType,
-	type Urgency as UrgencyType,
-	type Certainty as CertaintyType,
-	type PrecipitationType as PrecipitationTypeType,
 	type WeatherKitClient,
 	type WeatherKitCredentials,
 	type WeatherKitQueryOptions,

packages/aris-source-weatherkit/src/weather-context.ts

@@ -24,4 +24,4 @@ export interface Weather {
 	daylight: boolean
 }
 
-export const WeatherKey: ContextKey<Weather> = contextKey("weather")
+export const WeatherKey: ContextKey<Weather> = contextKey("aris.weather", "weather")

packages/aris-source-weatherkit/src/weather-source.test.ts

@@ -1,4 +1,6 @@
-import { contextValue, type Context } from "@aris/core"
+import type { FeedSource } from "@aris/core"
+
+import { Context } from "@aris/core"
 import { LocationKey } from "@aris/source-location"
 import { describe, expect, test } from "bun:test"
 
@@ -6,7 +8,7 @@ import type { WeatherKitClient, WeatherKitResponse } from "./weatherkit"
 
 import fixture from "../fixtures/san-francisco.json"
 import { WeatherFeedItemType } from "./feed-items"
-import { WeatherKey } from "./weather-context"
+import { WeatherKey, type Weather } from "./weather-context"
 import { WeatherSource, Units } from "./weather-source"
 
 const mockCredentials = {
@@ -23,9 +25,9 @@ function createMockClient(response: WeatherKitResponse): WeatherKitClient {
 }
 
 function createMockContext(location?: { lat: number; lng: number }): Context {
-	const ctx: Context = { time: new Date("2026-01-17T00:00:00Z") }
+	const ctx = new Context(new Date("2026-01-17T00:00:00Z"))
 	if (location) {
-		ctx[LocationKey] = { ...location, accuracy: 10, timestamp: new Date() }
+		ctx.set([[LocationKey, { ...location, accuracy: 10, timestamp: new Date() }]])
 	}
 	return ctx
 }
@@ -63,18 +65,19 @@ describe("WeatherSource", () => {
 			const source = new WeatherSource({ client: mockClient })
 			const context = createMockContext({ lat: 37.7749, lng: -122.4194 })
 
-			const result = await source.fetchContext(context)
-			expect(result).not.toBeNull()
-			const weather = contextValue(result! as Context, WeatherKey)
+			const entries = await source.fetchContext(context)
+			expect(entries).not.toBeNull()
+			expect(entries).toHaveLength(1)
 
-			expect(weather).toBeDefined()
-			expect(typeof weather!.temperature).toBe("number")
-			expect(typeof weather!.temperatureApparent).toBe("number")
-			expect(typeof weather!.condition).toBe("string")
-			expect(typeof weather!.humidity).toBe("number")
-			expect(typeof weather!.uvIndex).toBe("number")
-			expect(typeof weather!.windSpeed).toBe("number")
-			expect(typeof weather!.daylight).toBe("boolean")
+			const [key, weather] = entries![0]! as [typeof WeatherKey, Weather]
+			expect(key).toEqual(WeatherKey)
+			expect(typeof weather.temperature).toBe("number")
+			expect(typeof weather.temperatureApparent).toBe("number")
+			expect(typeof weather.condition).toBe("string")
+			expect(typeof weather.humidity).toBe("number")
+			expect(typeof weather.uvIndex).toBe("number")
+			expect(typeof weather.windSpeed).toBe("number")
+			expect(typeof weather.daylight).toBe("boolean")
 		})
 
 		test("converts temperature to imperial", async () => {
@@ -84,12 +87,12 @@ describe("WeatherSource", () => {
 			})
 			const context = createMockContext({ lat: 37.7749, lng: -122.4194 })
 
-			const result = await source.fetchContext(context)
-			expect(result).not.toBeNull()
-			const weather = contextValue(result! as Context, WeatherKey)
+			const entries = await source.fetchContext(context)
+			expect(entries).not.toBeNull()
 
+			const [, weather] = entries![0]! as [typeof WeatherKey, Weather]
 			// Fixture has temperature around 10°C, imperial should be around 50°F
-			expect(weather!.temperature).toBeGreaterThan(40)
+			expect(weather.temperature).toBeGreaterThan(40)
 		})
 	})
 
@@ -110,9 +113,9 @@ describe("WeatherSource", () => {
 			const items = await source.fetchItems(context)
 
 			expect(items.length).toBeGreaterThan(0)
-			expect(items.some((i) => i.type === WeatherFeedItemType.current)).toBe(true)
-			expect(items.some((i) => i.type === WeatherFeedItemType.hourly)).toBe(true)
-			expect(items.some((i) => i.type === WeatherFeedItemType.daily)).toBe(true)
+			expect(items.some((i) => i.type === WeatherFeedItemType.Current)).toBe(true)
+			expect(items.some((i) => i.type === WeatherFeedItemType.Hourly)).toBe(true)
+			expect(items.some((i) => i.type === WeatherFeedItemType.Daily)).toBe(true)
 		})
 
 		test("applies hourly and daily limits", async () => {
@@ -125,8 +128,8 @@ describe("WeatherSource", () => {
 
 			const items = await source.fetchItems(context)
 
-			const hourlyItems = items.filter((i) => i.type === WeatherFeedItemType.hourly)
-			const dailyItems = items.filter((i) => i.type === WeatherFeedItemType.daily)
+			const hourlyItems = items.filter((i) => i.type === WeatherFeedItemType.Hourly)
+			const dailyItems = items.filter((i) => i.type === WeatherFeedItemType.Daily)
 
 			expect(hourlyItems.length).toBe(3)
 			expect(dailyItems.length).toBe(2)
@@ -158,7 +161,7 @@ describe("WeatherSource", () => {
 				expect(item.signals!.timeRelevance).toBeDefined()
 			}
 
-			const currentItem = items.find((i) => i.type === WeatherFeedItemType.current)
+			const currentItem = items.find((i) => i.type === WeatherFeedItemType.Current)
 			expect(currentItem).toBeDefined()
 			expect(currentItem!.signals!.urgency).toBeGreaterThanOrEqual(0.5)
 		})
@@ -177,12 +180,12 @@ describe("WeatherSource", () => {
 
 	describe("no reactive methods", () => {
 		test("does not implement onContextUpdate", () => {
-			const source = new WeatherSource({ credentials: mockCredentials })
+			const source: FeedSource = new WeatherSource({ credentials: mockCredentials })
 			expect(source.onContextUpdate).toBeUndefined()
 		})
 
 		test("does not implement onItemsUpdate", () => {
-			const source = new WeatherSource({ credentials: mockCredentials })
+			const source: FeedSource = new WeatherSource({ credentials: mockCredentials })
 			expect(source.onItemsUpdate).toBeUndefined()
 		})
 	})

packages/aris-source-weatherkit/src/weather-source.ts

@@ -1,6 +1,6 @@
-import type { ActionDefinition, Context, FeedItemSignals, FeedSource } from "@aris/core"
+import type { ActionDefinition, ContextEntry, FeedItemSignals, FeedSource } from "@aris/core"
 
-import { TimeRelevance, UnknownActionError, contextValue } from "@aris/core"
+import { Context, TimeRelevance, UnknownActionError } from "@aris/core"
 import { LocationKey } from "@aris/source-location"
 
 import { WeatherFeedItemType, type WeatherFeedItem } from "./feed-items"
@@ -86,7 +86,7 @@ const MODERATE_CONDITIONS = new Set<ConditionCode>([
  * })
  *
  * // Access weather context in downstream sources
- * const weather = contextValue(context, WeatherKey)
+ * const weather = context.get(WeatherKey)
  * if (weather?.condition === "Rain") {
  *   // suggest umbrella
  * }
@@ -119,8 +119,8 @@ export class WeatherSource implements FeedSource<WeatherFeedItem> {
 		throw new UnknownActionError(actionId)
 	}
 
-	async fetchContext(context: Context): Promise<Partial<Context> | null> {
-		const location = contextValue(context, LocationKey)
+	async fetchContext(context: Context): Promise<readonly ContextEntry[] | null> {
+		const location = context.get(LocationKey)
 		if (!location) {
 			return null
 		}
@@ -147,11 +147,11 @@ export class WeatherSource implements FeedSource<WeatherFeedItem> {
 			daylight: response.currentWeather.daylight,
 		}
 
-		return { [WeatherKey]: weather }
+		return [[WeatherKey, weather]]
 	}
 
 	async fetchItems(context: Context): Promise<WeatherFeedItem[]> {
-		const location = contextValue(context, LocationKey)
+		const location = context.get(LocationKey)
 		if (!location) {
 			return []
 		}
@@ -291,7 +291,7 @@ function createCurrentWeatherFeedItem(
 
 	return {
 		id: `weather-current-${timestamp.getTime()}`,
-		type: WeatherFeedItemType.current,
+		type: WeatherFeedItemType.Current,
 		timestamp,
 		data: {
 			conditionCode: current.conditionCode,
@@ -325,7 +325,7 @@ function createHourlyWeatherFeedItem(
 
 	return {
 		id: `weather-hourly-${timestamp.getTime()}-${index}`,
-		type: WeatherFeedItemType.hourly,
+		type: WeatherFeedItemType.Hourly,
 		timestamp,
 		data: {
 			forecastTime: new Date(hourly.forecastStart),
@@ -359,7 +359,7 @@ function createDailyWeatherFeedItem(
 
 	return {
 		id: `weather-daily-${timestamp.getTime()}-${index}`,
-		type: WeatherFeedItemType.daily,
+		type: WeatherFeedItemType.Daily,
 		timestamp,
 		data: {
 			forecastDate: new Date(daily.forecastStart),
@@ -386,7 +386,7 @@ function createWeatherAlertFeedItem(alert: WeatherAlert, timestamp: Date): Weath
 
 	return {
 		id: `weather-alert-${alert.id}`,
-		type: WeatherFeedItemType.alert,
+		type: WeatherFeedItemType.Alert,
 		timestamp,
 		data: {
 			alertId: alert.id,