diff --git a/apps/aelis-backend/src/session/user-session-manager.ts b/apps/aelis-backend/src/session/user-session-manager.ts
index 1d8e6a8..f28ee2a 100644
--- a/apps/aelis-backend/src/session/user-session-manager.ts
+++ b/apps/aelis-backend/src/session/user-session-manager.ts
@@ -136,6 +136,52 @@ export class UserSessionManager {
 		}
 	}
 
+	/**
+	 * Validates, persists, and upserts a user's source config, then
+	 * refreshes the cached session. Unlike updateSourceConfig, this
+	 * inserts a new row if one doesn't exist and fully replaces config
+	 * (no merge).
+	 *
+	 * @throws {SourceNotFoundError} if the sourceId has no registered provider
+	 * @throws {InvalidSourceConfigError} if config fails schema validation
+	 */
+	async upsertSourceConfig(
+		userId: string,
+		sourceId: string,
+		data: { enabled: boolean; config: unknown },
+	): Promise<void> {
+		const provider = this.providers.get(sourceId)
+		if (!provider) {
+			throw new SourceNotFoundError(sourceId, userId)
+		}
+
+		if (provider.configSchema) {
+			const validated = provider.configSchema(data.config)
+			if (validated instanceof type.errors) {
+				throw new InvalidSourceConfigError(sourceId, validated.summary)
+			}
+		}
+
+		await sources(this.db, userId).upsertConfig(sourceId, {
+			enabled: data.enabled,
+			config: data.config,
+		})
+
+		const session = this.sessions.get(userId)
+		if (session) {
+			if (!data.enabled) {
+				session.removeSource(sourceId)
+			} else {
+				const source = await provider.feedSourceForUser(userId, data.config)
+				if (session.hasSource(sourceId)) {
+					session.replaceSource(sourceId, source)
+				} else {
+					session.addSource(source)
+				}
+			}
+		}
+	}
+
 	/**
 	 * Replaces a provider and updates all active sessions.
 	 * The new provider must have the same sourceId as an existing one.
diff --git a/apps/aelis-backend/src/session/user-session.ts b/apps/aelis-backend/src/session/user-session.ts
index 6f35a12..aa0d24e 100644
--- a/apps/aelis-backend/src/session/user-session.ts
+++ b/apps/aelis-backend/src/session/user-session.ts
@@ -73,6 +73,32 @@ export class UserSession {
 		return this.sources.has(sourceId)
 	}
 
+	/**
+	 * Registers a new source in the engine and invalidates all caches.
+	 * Stops and restarts the engine to establish reactive subscriptions.
+	 */
+	addSource(source: FeedSource): void {
+		if (this.sources.has(source.id)) {
+			throw new Error(`Cannot add source "${source.id}": already registered`)
+		}
+
+		const wasStarted = this.engine.isStarted()
+
+		if (wasStarted) {
+			this.engine.stop()
+		}
+
+		this.engine.register(source)
+		this.sources.set(source.id, source)
+
+		this.invalidateEnhancement()
+		this.enhancingPromise = null
+
+		if (wasStarted) {
+			this.engine.start()
+		}
+	}
+
 	/**
 	 * Replaces a source in the engine and invalidates all caches.
 	 * Stops and restarts the engine to re-establish reactive subscriptions.
diff --git a/apps/aelis-backend/src/sources/http.test.ts b/apps/aelis-backend/src/sources/http.test.ts
index 08f9078..bbe5103 100644
--- a/apps/aelis-backend/src/sources/http.test.ts
+++ b/apps/aelis-backend/src/sources/http.test.ts
@@ -91,6 +91,20 @@ function createInMemoryStore() {
 						existing.config = update.config as Record<string, unknown>
 					}
 				},
+				async upsertConfig(sourceId: string, data: { enabled: boolean; config: unknown }) {
+					const existing = rows.get(key(userId, sourceId))
+					if (existing) {
+						existing.enabled = data.enabled
+						existing.config = data.config as Record<string, unknown>
+					} else {
+						rows.set(key(userId, sourceId), {
+							userId,
+							sourceId,
+							enabled: data.enabled,
+							config: (data.config ?? {}) as Record<string, unknown>,
+						})
+					}
+				},
 			}
 		},
 	}
@@ -124,6 +138,14 @@ function patch(app: Hono, sourceId: string, body: unknown) {
 	})
 }
 
+function put(app: Hono, sourceId: string, body: unknown) {
+	return app.request(`/api/sources/${sourceId}`, {
+		method: "PUT",
+		headers: { "Content-Type": "application/json" },
+		body: JSON.stringify(body),
+	})
+}
+
 // ---------------------------------------------------------------------------
 // Tests
 // ---------------------------------------------------------------------------
@@ -342,3 +364,195 @@ describe("PATCH /api/sources/:sourceId", () => {
 		expect(row!.enabled).toBe(false)
 	})
 })
+
+// ---------------------------------------------------------------------------
+// PUT /api/sources/:sourceId
+// ---------------------------------------------------------------------------
+
+describe("PUT /api/sources/:sourceId", () => {
+	test("returns 401 without auth", async () => {
+		activeStore = createInMemoryStore()
+		const { app } = createApp([createStubProvider("aelis.weather", weatherConfig)])
+
+		const res = await put(app, "aelis.weather", { enabled: true, config: {} })
+
+		expect(res.status).toBe(401)
+	})
+
+	test("returns 404 for unknown source", async () => {
+		activeStore = createInMemoryStore()
+		const { app } = createApp([createStubProvider("aelis.weather", weatherConfig)], MOCK_USER_ID)
+
+		const res = await put(app, "unknown.source", { enabled: true, config: {} })
+
+		expect(res.status).toBe(404)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("not found")
+	})
+
+	test("returns 400 for invalid JSON", async () => {
+		activeStore = createInMemoryStore()
+		const { app } = createApp([createStubProvider("aelis.weather", weatherConfig)], MOCK_USER_ID)
+
+		const res = await app.request("/api/sources/aelis.weather", {
+			method: "PUT",
+			headers: { "Content-Type": "application/json" },
+			body: "not json",
+		})
+
+		expect(res.status).toBe(400)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("Invalid JSON")
+	})
+
+	test("returns 400 when enabled is missing", async () => {
+		activeStore = createInMemoryStore()
+		const { app } = createApp([createStubProvider("aelis.weather", weatherConfig)], MOCK_USER_ID)
+
+		const res = await put(app, "aelis.weather", { config: {} })
+
+		expect(res.status).toBe(400)
+	})
+
+	test("returns 400 when config is missing", async () => {
+		activeStore = createInMemoryStore()
+		const { app } = createApp([createStubProvider("aelis.weather", weatherConfig)], MOCK_USER_ID)
+
+		const res = await put(app, "aelis.weather", { enabled: true })
+
+		expect(res.status).toBe(400)
+	})
+
+	test("returns 400 when config fails schema validation", async () => {
+		activeStore = createInMemoryStore()
+		const { app } = createApp([createStubProvider("aelis.weather", weatherConfig)], MOCK_USER_ID)
+
+		const res = await put(app, "aelis.weather", {
+			enabled: true,
+			config: { units: "invalid" },
+		})
+
+		expect(res.status).toBe(400)
+	})
+
+	test("returns 204 and inserts when row does not exist", async () => {
+		activeStore = createInMemoryStore()
+		const { app } = createApp([createStubProvider("aelis.weather", weatherConfig)], MOCK_USER_ID)
+
+		const res = await put(app, "aelis.weather", {
+			enabled: true,
+			config: { units: "metric" },
+		})
+
+		expect(res.status).toBe(204)
+		const row = activeStore.rows.get(`${MOCK_USER_ID}:aelis.weather`)
+		expect(row).toBeDefined()
+		expect(row!.enabled).toBe(true)
+		expect(row!.config).toEqual({ units: "metric" })
+	})
+
+	test("returns 204 and fully replaces existing row", async () => {
+		activeStore = createInMemoryStore()
+		activeStore.seed(MOCK_USER_ID, "aelis.weather", {
+			enabled: true,
+			config: { units: "metric", hourlyLimit: 12 },
+		})
+		const { app } = createApp([createStubProvider("aelis.weather", weatherConfig)], MOCK_USER_ID)
+
+		const res = await put(app, "aelis.weather", {
+			enabled: false,
+			config: { units: "imperial" },
+		})
+
+		expect(res.status).toBe(204)
+		const row = activeStore.rows.get(`${MOCK_USER_ID}:aelis.weather`)
+		expect(row!.enabled).toBe(false)
+		// hourlyLimit should be gone — full replace, not merge
+		expect(row!.config).toEqual({ units: "imperial" })
+	})
+
+	test("refreshes source in active session after upsert", async () => {
+		activeStore = createInMemoryStore()
+		activeStore.seed(MOCK_USER_ID, "aelis.weather", {
+			config: { units: "metric" },
+		})
+		const { app, sessionManager } = createApp(
+			[createStubProvider("aelis.weather", weatherConfig)],
+			MOCK_USER_ID,
+		)
+
+		const session = await sessionManager.getOrCreate(MOCK_USER_ID)
+		const replaceSpy = spyOn(session, "replaceSource")
+
+		const res = await put(app, "aelis.weather", {
+			enabled: true,
+			config: { units: "imperial" },
+		})
+
+		expect(res.status).toBe(204)
+		expect(replaceSpy).toHaveBeenCalled()
+		replaceSpy.mockRestore()
+	})
+
+	test("removes source from session when disabled via upsert", async () => {
+		activeStore = createInMemoryStore()
+		activeStore.seed(MOCK_USER_ID, "aelis.weather", {
+			enabled: true,
+			config: { units: "metric" },
+		})
+		const { app, sessionManager } = createApp(
+			[createStubProvider("aelis.weather", weatherConfig)],
+			MOCK_USER_ID,
+		)
+
+		const session = await sessionManager.getOrCreate(MOCK_USER_ID)
+		const removeSpy = spyOn(session, "removeSource")
+
+		const res = await put(app, "aelis.weather", {
+			enabled: false,
+			config: { units: "metric" },
+		})
+
+		expect(res.status).toBe(204)
+		expect(removeSpy).toHaveBeenCalledWith("aelis.weather")
+		removeSpy.mockRestore()
+	})
+
+	test("adds source to active session when inserting a new source", async () => {
+		activeStore = createInMemoryStore()
+		// Seed a different source so the session can be created
+		activeStore.seed(MOCK_USER_ID, "aelis.location", { enabled: true })
+		const { app, sessionManager } = createApp(
+			[createStubProvider("aelis.location"), createStubProvider("aelis.weather", weatherConfig)],
+			MOCK_USER_ID,
+		)
+
+		// Create session — only has aelis.location
+		const session = await sessionManager.getOrCreate(MOCK_USER_ID)
+		expect(session.hasSource("aelis.weather")).toBe(false)
+
+		// PUT a new source that didn't exist before
+		const res = await put(app, "aelis.weather", {
+			enabled: true,
+			config: { units: "metric" },
+		})
+
+		expect(res.status).toBe(204)
+		expect(session.hasSource("aelis.weather")).toBe(true)
+	})
+
+	test("accepts location source with arbitrary config (no schema)", async () => {
+		activeStore = createInMemoryStore()
+		const { app } = createApp([createStubProvider("aelis.location")], MOCK_USER_ID)
+
+		const res = await put(app, "aelis.location", {
+			enabled: true,
+			config: { something: "value" },
+		})
+
+		expect(res.status).toBe(204)
+		const row = activeStore.rows.get(`${MOCK_USER_ID}:aelis.location`)
+		expect(row).toBeDefined()
+		expect(row!.config).toEqual({ something: "value" })
+	})
+})
diff --git a/apps/aelis-backend/src/sources/http.ts b/apps/aelis-backend/src/sources/http.ts
index 8ad7ca7..2d122eb 100644
--- a/apps/aelis-backend/src/sources/http.ts
+++ b/apps/aelis-backend/src/sources/http.ts
@@ -24,6 +24,11 @@ const UpdateSourceConfigRequestBody = type({
 	"config?": "unknown",
 })
 
+const ReplaceSourceConfigRequestBody = type({
+	enabled: "boolean",
+	config: "unknown",
+})
+
 export function registerSourcesHttpHandlers(
 	app: Hono,
 	{ sessionManager, authSessionMiddleware }: SourcesHttpHandlersDeps,
@@ -34,6 +39,7 @@ export function registerSourcesHttpHandlers(
 	})
 
 	app.patch("/api/sources/:sourceId", inject, authSessionMiddleware, handleUpdateSource)
+	app.put("/api/sources/:sourceId", inject, authSessionMiddleware, handleReplaceSource)
 }
 
 async function handleUpdateSource(c: Context<Env>) {
@@ -83,3 +89,49 @@ async function handleUpdateSource(c: Context<Env>) {
 
 	return c.body(null, 204)
 }
+
+async function handleReplaceSource(c: Context<Env>) {
+	const sourceId = c.req.param("sourceId")
+	if (!sourceId) {
+		return c.body(null, 404)
+	}
+
+	const sessionManager = c.get("sessionManager")
+
+	const provider = sessionManager.getProvider(sourceId)
+	if (!provider) {
+		return c.json({ error: `Source "${sourceId}" not found` }, 404)
+	}
+
+	let body: unknown
+	try {
+		body = await c.req.json()
+	} catch {
+		return c.json({ error: "Invalid JSON" }, 400)
+	}
+
+	const parsed = ReplaceSourceConfigRequestBody(body)
+	if (parsed instanceof type.errors) {
+		return c.json({ error: parsed.summary }, 400)
+	}
+
+	const { enabled, config } = parsed
+	const user = c.get("user")!
+
+	try {
+		await sessionManager.upsertSourceConfig(user.id, sourceId, {
+			enabled,
+			config,
+		})
+	} catch (err) {
+		if (err instanceof SourceNotFoundError) {
+			return c.json({ error: err.message }, 404)
+		}
+		if (err instanceof InvalidSourceConfigError) {
+			return c.json({ error: err.message }, 400)
+		}
+		throw err
+	}
+
+	return c.body(null, 204)
+}
diff --git a/apps/aelis-backend/src/sources/user-sources.ts b/apps/aelis-backend/src/sources/user-sources.ts
index 1bfe4f0..8509a65 100644
--- a/apps/aelis-backend/src/sources/user-sources.ts
+++ b/apps/aelis-backend/src/sources/user-sources.ts
@@ -72,6 +72,29 @@ export function sources(db: Database, userId: string) {
 			}
 		},
 
+		/** Inserts a new user source row or fully replaces enabled/config on an existing one. */
+		async upsertConfig(sourceId: string, data: { enabled: boolean; config: unknown }) {
+			const now = new Date()
+			await db
+				.insert(userSources)
+				.values({
+					userId,
+					sourceId,
+					enabled: data.enabled,
+					config: data.config,
+					createdAt: now,
+					updatedAt: now,
+				})
+				.onConflictDoUpdate({
+					target: [userSources.userId, userSources.sourceId],
+					set: {
+						enabled: data.enabled,
+						config: data.config,
+						updatedAt: now,
+					},
+				})
+		},
+
 		/** Updates the encrypted credentials for a source. Throws if the source row doesn't exist. */
 		async updateCredentials(sourceId: string, credentials: Buffer) {
 			const rows = await db