diff --git a/cloudflare/src/index.ts b/cloudflare/src/index.ts
index 29858b0..f04a28c 100644
--- a/cloudflare/src/index.ts
+++ b/cloudflare/src/index.ts
@@ -35,6 +35,12 @@ import {
   parsePublicSigningKeysDocument,
   publicSigningKeysKvKey,
 } from "./signing_keys.js";
+import {
+  SyncPushConflictError,
+  SyncPushPersistenceError,
+  SyncPushRequestError,
+  syncPushDocument,
+} from "./sync_push.js";
 import { SyncRequestError, SyncSchemaError, syncPullDocument } from "./sync_pull.js";
 import { jsonResponse } from "./responses.js";
 
@@ -205,6 +211,40 @@ export async function handleRequest(request: Request, env: Env): Promise<Respons
       },
     );
   }
+  if (url.pathname === "/api/sync/push") {
+    return withApprovedDeviceApiControls(
+      request,
+      env,
+      "sync.push",
+      ["POST"],
+      async (context) => {
+        try {
+          return jsonResponse(await syncPushDocument(request, env, context), 201, {
+            "Cache-Control": "no-store",
+          });
+        } catch (error) {
+          if (error instanceof SyncPushRequestError) {
+            return jsonResponse(
+              { error: "invalid_sync_push" },
+              400,
+              { "Cache-Control": "no-store" },
+            );
+          }
+          if (error instanceof SyncPushConflictError) {
+            return jsonResponse({ error: "sync_conflict" }, 409, { "Cache-Control": "no-store" });
+          }
+          if (error instanceof SyncPushPersistenceError) {
+            return jsonResponse(
+              { error: "sync_push_failed" },
+              500,
+              { "Cache-Control": "no-store" },
+            );
+          }
+          throw error;
+        }
+      },
+    );
+  }
   if (url.pathname === "/api/plugins/signing-keys") {
     return withPublicApiControls(request, env, "plugins.signing_keys", ["GET"], () =>
       handlePublicSigningKeys(env),
diff --git a/cloudflare/src/storage.ts b/cloudflare/src/storage.ts
index 63ee986..dfeb1d5 100644
--- a/cloudflare/src/storage.ts
+++ b/cloudflare/src/storage.ts
@@ -195,7 +195,7 @@ function assertSegment(value: string, name: string): void {
   }
 }
 
-function assertSyncObjectType(value: string): void {
+export function assertSyncObjectType(value: string): void {
   if (!SYNC_OBJECT_TYPES.has(value)) {
     throw new StorageObjectError("object_type_invalid");
   }
diff --git a/cloudflare/src/sync_push.ts b/cloudflare/src/sync_push.ts
new file mode 100644
index 0000000..4bc0169
--- /dev/null
+++ b/cloudflare/src/sync_push.ts
@@ -0,0 +1,255 @@
+import type { AuthContext } from "./auth.js";
+import type { Env } from "./bindings.js";
+import type { ElyD1PreparedStatement } from "./bindings.js";
+import { StorageObjectError, putVerifiedObject } from "./storage.js";
+import {
+  type SyncObjectRow,
+  SyncPushConflictError,
+  type SyncPushDocument,
+  SyncPushPersistenceError,
+  type SyncPushRequest,
+  SyncPushRequestError,
+  type SyncPushedObjectDocument,
+  currentDeviceId,
+  syncObjectDocument,
+  syncPushRequest,
+} from "./sync_push_schema.js";
+
+export {
+  SyncPushConflictError,
+  SyncPushPersistenceError,
+  SyncPushRequestError,
+} from "./sync_push_schema.js";
+
+const SYNC_OBJECT_BY_ID_QUERY = `
+  SELECT
+    object_id,
+    object_type,
+    payload_r2_key,
+    payload_hash,
+    schema_rev,
+    logical_clock,
+    device_id,
+    created_at,
+    updated_at,
+    deleted_at
+  FROM sync_objects
+  WHERE user_id = ? AND object_id = ?
+`;
+const SYNC_OBJECT_UPSERT_QUERY = `
+  INSERT INTO sync_objects (
+    user_id,
+    object_id,
+    object_type,
+    payload_inline,
+    payload_r2_key,
+    payload_hash,
+    schema_rev,
+    logical_clock,
+    device_id,
+    created_at,
+    updated_at,
+    deleted_at
+  ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+  ON CONFLICT(user_id, object_id) DO UPDATE SET
+    object_type = excluded.object_type,
+    payload_inline = excluded.payload_inline,
+    payload_r2_key = excluded.payload_r2_key,
+    payload_hash = excluded.payload_hash,
+    schema_rev = excluded.schema_rev,
+    logical_clock = excluded.logical_clock,
+    device_id = excluded.device_id,
+    updated_at = excluded.updated_at,
+    deleted_at = excluded.deleted_at
+  WHERE excluded.logical_clock >= sync_objects.logical_clock
+`;
+const SYNC_CHANGE_INSERT_QUERY = `
+  INSERT INTO sync_change_log (
+    user_id,
+    object_id,
+    object_type,
+    operation,
+    payload_hash,
+    logical_clock,
+    device_id,
+    created_at
+  )
+  SELECT ?, ?, ?, ?, ?, ?, ?, ?
+  WHERE EXISTS (
+    SELECT 1
+    FROM sync_objects
+    WHERE user_id = ?
+      AND object_id = ?
+      AND object_type = ?
+      AND payload_hash = ?
+      AND logical_clock = ?
+      AND device_id = ?
+      AND ((? = 1 AND deleted_at IS NOT NULL) OR (? = 0 AND deleted_at IS NULL))
+  )
+  ON CONFLICT(user_id, object_id, logical_clock, device_id, operation) DO NOTHING
+`;
+const SYNC_TOMBSTONE_UPSERT_QUERY = `
+  INSERT INTO sync_tombstones (
+    user_id,
+    object_id,
+    object_type,
+    logical_clock,
+    device_id,
+    deleted_at
+  )
+  SELECT user_id, object_id, object_type, logical_clock, device_id, deleted_at
+  FROM sync_objects
+  WHERE user_id = ? AND object_id = ? AND logical_clock = ? AND deleted_at IS NOT NULL
+  ON CONFLICT(user_id, object_id) DO UPDATE SET
+    object_type = excluded.object_type,
+    logical_clock = excluded.logical_clock,
+    device_id = excluded.device_id,
+    deleted_at = excluded.deleted_at
+  WHERE excluded.logical_clock >= sync_tombstones.logical_clock
+`;
+
+export async function syncPushDocument(
+  request: Request,
+  env: Env,
+  context: AuthContext,
+  nowSeconds = Math.floor(Date.now() / 1000),
+): Promise<SyncPushDocument> {
+  const deviceId = currentDeviceId(context);
+  const push = await syncPushRequest(request, context.userId);
+  const existingRow = await env.ELY_DB.prepare(SYNC_OBJECT_BY_ID_QUERY)
+    .bind(context.userId, push.objectId)
+    .first<SyncObjectRow>();
+  if (existingRow !== null) {
+    assertPushCanReplaceExisting(push, deviceId, syncObjectDocument(existingRow));
+  }
+
+  await persistR2PayloadIfNeeded(env, push);
+  await env.ELY_DB.batch(syncPushStatements(env, context.userId, deviceId, push, nowSeconds));
+
+  const savedRow = await env.ELY_DB.prepare(SYNC_OBJECT_BY_ID_QUERY)
+    .bind(context.userId, push.objectId)
+    .first<SyncObjectRow>();
+  if (savedRow === null) {
+    throw new SyncPushPersistenceError("sync_object_missing");
+  }
+  const object = syncObjectDocument(savedRow);
+  assertSavedObjectMatchesPush(push, deviceId, object);
+
+  return { version: 1, user_id: context.userId, device_id: deviceId, object };
+}
+
+async function persistR2PayloadIfNeeded(env: Env, push: SyncPushRequest): Promise<void> {
+  if (push.payload.kind !== "r2") {
+    return;
+  }
+  try {
+    await putVerifiedObject(
+      env.ELY_STORAGE,
+      push.payload.r2Key,
+      push.payload.bytes,
+      push.payloadHash,
+      "application/octet-stream",
+    );
+  } catch (error) {
+    if (error instanceof StorageObjectError) {
+      throw new SyncPushRequestError(error.message);
+    }
+    throw error;
+  }
+}
+
+function syncPushStatements(
+  env: Env,
+  userId: string,
+  deviceId: string,
+  push: SyncPushRequest,
+  nowSeconds: number,
+): ElyD1PreparedStatement[] {
+  const deletedAt = push.operation === "delete" ? nowSeconds : null;
+  const isDelete = push.operation === "delete" ? 1 : 0;
+  const statements = [
+    env.ELY_DB.prepare(SYNC_OBJECT_UPSERT_QUERY).bind(
+      userId,
+      push.objectId,
+      push.objectType,
+      push.payload.kind === "inline" ? push.payload.bytes : null,
+      push.payload.r2Key,
+      push.payloadHash,
+      push.schemaRev,
+      push.logicalClock,
+      deviceId,
+      nowSeconds,
+      nowSeconds,
+      deletedAt,
+    ),
+    env.ELY_DB.prepare(SYNC_CHANGE_INSERT_QUERY).bind(
+      userId,
+      push.objectId,
+      push.objectType,
+      push.operation,
+      push.payloadHash,
+      push.logicalClock,
+      deviceId,
+      nowSeconds,
+      userId,
+      push.objectId,
+      push.objectType,
+      push.payloadHash,
+      push.logicalClock,
+      deviceId,
+      isDelete,
+      isDelete,
+    ),
+  ];
+  if (push.operation === "delete") {
+    statements.push(
+      env.ELY_DB.prepare(SYNC_TOMBSTONE_UPSERT_QUERY).bind(
+        userId,
+        push.objectId,
+        push.logicalClock,
+      ),
+    );
+  }
+  return statements;
+}
+
+function assertPushCanReplaceExisting(
+  push: SyncPushRequest,
+  deviceId: string,
+  existing: SyncPushedObjectDocument,
+): void {
+  if (existing.logical_clock > push.logicalClock) {
+    throw new SyncPushConflictError("logical_clock_stale");
+  }
+  if (existing.logical_clock < push.logicalClock) {
+    return;
+  }
+  if (
+    existing.operation !== push.operation ||
+    existing.payload_hash !== push.payloadHash ||
+    existing.device_id !== deviceId
+  ) {
+    throw new SyncPushConflictError("logical_clock_conflict");
+  }
+}
+
+function assertSavedObjectMatchesPush(
+  push: SyncPushRequest,
+  deviceId: string,
+  object: SyncPushedObjectDocument,
+): void {
+  if (object.logical_clock > push.logicalClock) {
+    throw new SyncPushConflictError("logical_clock_stale");
+  }
+  if (
+    object.object_id !== push.objectId ||
+    object.object_type !== push.objectType ||
+    object.operation !== push.operation ||
+    object.payload_hash !== push.payloadHash ||
+    object.schema_rev !== push.schemaRev ||
+    object.logical_clock !== push.logicalClock ||
+    object.device_id !== deviceId
+  ) {
+    throw new SyncPushPersistenceError("sync_object_mismatch");
+  }
+}
diff --git a/cloudflare/src/sync_push_schema.ts b/cloudflare/src/sync_push_schema.ts
new file mode 100644
index 0000000..4413091
--- /dev/null
+++ b/cloudflare/src/sync_push_schema.ts
@@ -0,0 +1,348 @@
+import type { AuthContext } from "./auth.js";
+import {
+  StorageObjectError,
+  assertSyncObjectType,
+  syncPayloadKey,
+} from "./storage.js";
+
+const MAX_INLINE_PAYLOAD_BYTES = 64 * 1024;
+const MAX_R2_PAYLOAD_BYTES = 10 * 1024 * 1024;
+const SYNC_OBJECT_ID_PATTERN = /^[a-zA-Z0-9._:-]{1,128}$/;
+const SYNC_OBJECT_TYPE_PATTERN = /^[a-z0-9][a-z0-9._:-]{0,127}$/;
+const SHA256_HEX = /^[a-f0-9]{64}$/;
+const BASE64 = /^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$/;
+const REGION = /^[a-z0-9][a-z0-9-]{1,31}$/;
+
+export interface SyncPushDocument {
+  version: 1;
+  user_id: string;
+  device_id: string;
+  object: SyncPushedObjectDocument;
+}
+
+export interface SyncPushedObjectDocument {
+  object_id: string;
+  object_type: string;
+  operation: "upsert" | "delete";
+  payload_hash: string;
+  schema_rev: number;
+  logical_clock: number;
+  device_id: string;
+  created_at: number;
+  updated_at: number;
+  deleted_at: number | null;
+  payload_storage: "inline" | "r2" | "tombstone";
+  payload_r2_key: string | null;
+}
+
+export interface SyncPushRequest {
+  objectId: string;
+  objectType: string;
+  operation: "upsert" | "delete";
+  payloadHash: string;
+  schemaRev: number;
+  logicalClock: number;
+  payload: SyncPushPayload;
+}
+
+export type SyncPushPayload =
+  | { kind: "inline"; bytes: ArrayBuffer; r2Key: null }
+  | { kind: "r2"; bytes: ArrayBuffer; region: string; r2Key: string }
+  | { kind: "tombstone"; bytes: null; r2Key: null };
+
+export interface SyncObjectRow {
+  object_id: unknown;
+  object_type: unknown;
+  payload_r2_key: unknown;
+  payload_hash: unknown;
+  schema_rev: unknown;
+  logical_clock: unknown;
+  device_id: unknown;
+  created_at: unknown;
+  updated_at: unknown;
+  deleted_at: unknown;
+}
+
+type RequestBody = Record<string, unknown>;
+
+export class SyncPushRequestError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = "SyncPushRequestError";
+  }
+}
+
+export class SyncPushConflictError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = "SyncPushConflictError";
+  }
+}
+
+export class SyncPushPersistenceError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = "SyncPushPersistenceError";
+  }
+}
+
+export function currentDeviceId(context: AuthContext): string {
+  if (context.deviceId === undefined) {
+    throw new SyncPushRequestError("device_context_required");
+  }
+  return context.deviceId;
+}
+
+export async function syncPushRequest(
+  request: Request,
+  userId: string,
+): Promise<SyncPushRequest> {
+  const body = await requestBody(request);
+  assertOnlyFields(body, [
+    "version",
+    "object_id",
+    "object_type",
+    "operation",
+    "payload_hash",
+    "schema_rev",
+    "logical_clock",
+    "payload",
+  ]);
+  if (body.version !== 1) {
+    throw new SyncPushRequestError("version_invalid");
+  }
+
+  const objectId = syncObjectId(body.object_id);
+  const operation = syncOperation(body.operation);
+  const objectType = syncObjectType(body.object_type);
+  const payloadHash = sha256HexValue(body.payload_hash, "payload_hash");
+  const payload =
+    operation === "delete"
+      ? tombstonePayload(body.payload)
+      : await upsertPayload(body.payload, userId, objectType, objectId, payloadHash);
+
+  return {
+    objectId,
+    objectType,
+    operation,
+    payloadHash,
+    schemaRev: integer(body.schema_rev, "schema_rev", 1, Number.MAX_SAFE_INTEGER),
+    logicalClock: integer(body.logical_clock, "logical_clock", 0, Number.MAX_SAFE_INTEGER),
+    payload,
+  };
+}
+
+export function syncObjectDocument(row: SyncObjectRow): SyncPushedObjectDocument {
+  const deletedAt = nullableInteger(row.deleted_at, "deleted_at", 0, Number.MAX_SAFE_INTEGER);
+  const payloadR2Key = nullableText(row.payload_r2_key, "payload_r2_key");
+  return {
+    object_id: syncObjectId(row.object_id),
+    object_type: syncObjectType(row.object_type),
+    operation: deletedAt === null ? "upsert" : "delete",
+    payload_hash: sha256HexValue(row.payload_hash, "payload_hash"),
+    schema_rev: integer(row.schema_rev, "schema_rev", 1, Number.MAX_SAFE_INTEGER),
+    logical_clock: integer(row.logical_clock, "logical_clock", 0, Number.MAX_SAFE_INTEGER),
+    device_id: syncObjectId(row.device_id),
+    created_at: integer(row.created_at, "created_at", 0, Number.MAX_SAFE_INTEGER),
+    updated_at: integer(row.updated_at, "updated_at", 0, Number.MAX_SAFE_INTEGER),
+    deleted_at: deletedAt,
+    payload_storage: deletedAt !== null ? "tombstone" : payloadR2Key === null ? "inline" : "r2",
+    payload_r2_key: payloadR2Key,
+  };
+}
+
+async function upsertPayload(
+  value: unknown,
+  userId: string,
+  objectType: string,
+  objectId: string,
+  payloadHash: string,
+): Promise<SyncPushPayload> {
+  const payload = record(value, "payload");
+  const kind = text(payload.kind, "payload.kind");
+  if (kind === "inline") {
+    assertOnlyFields(payload, ["kind", "data_base64"]);
+    const bytes = payloadBytes(payload.data_base64, "payload.data_base64", MAX_INLINE_PAYLOAD_BYTES);
+    await assertPayloadHash(bytes, payloadHash);
+    return { kind, bytes, r2Key: null };
+  }
+  if (kind === "r2") {
+    assertOnlyFields(payload, ["kind", "region", "data_base64"]);
+    const region = regionValue(payload.region);
+    const bytes = payloadBytes(payload.data_base64, "payload.data_base64", MAX_R2_PAYLOAD_BYTES);
+    await assertPayloadHash(bytes, payloadHash);
+    return {
+      kind,
+      bytes,
+      region,
+      r2Key: await syncPayloadStorageKey(region, userId, objectType, objectId, payloadHash),
+    };
+  }
+  throw new SyncPushRequestError("payload.kind_invalid");
+}
+
+async function syncPayloadStorageKey(
+  region: string,
+  userId: string,
+  objectType: string,
+  objectId: string,
+  payloadHash: string,
+): Promise<string> {
+  try {
+    return syncPayloadKey({
+      region,
+      userHash: await sha256Hex(arrayBufferFromBytes(new TextEncoder().encode(userId))),
+      objectType,
+      objectId,
+      payloadHash,
+    });
+  } catch (error) {
+    if (error instanceof StorageObjectError) {
+      throw new SyncPushRequestError(error.message);
+    }
+    throw error;
+  }
+}
+
+function tombstonePayload(value: unknown): SyncPushPayload {
+  if (value !== undefined) {
+    throw new SyncPushRequestError("payload_forbidden");
+  }
+  return { kind: "tombstone", bytes: null, r2Key: null };
+}
+
+async function requestBody(request: Request): Promise<RequestBody> {
+  let value: unknown;
+  try {
+    value = await request.json();
+  } catch {
+    throw new SyncPushRequestError("json_invalid");
+  }
+  return record(value, "body");
+}
+
+function record(value: unknown, label: string): RequestBody {
+  if (typeof value !== "object" || value === null || Array.isArray(value)) {
+    throw new SyncPushRequestError(`${label}_invalid`);
+  }
+  return value as RequestBody;
+}
+
+function assertOnlyFields(value: RequestBody, fields: string[]): void {
+  const allowed = new Set(fields);
+  for (const field of Object.keys(value)) {
+    if (!allowed.has(field)) {
+      throw new SyncPushRequestError(`unexpected_field:${field}`);
+    }
+  }
+}
+
+function syncOperation(value: unknown): SyncPushRequest["operation"] {
+  if (value !== "upsert" && value !== "delete") {
+    throw new SyncPushRequestError("operation_invalid");
+  }
+  return value;
+}
+
+function syncObjectId(value: unknown): string {
+  if (typeof value !== "string" || !SYNC_OBJECT_ID_PATTERN.test(value)) {
+    throw new SyncPushRequestError("object_id_invalid");
+  }
+  return value;
+}
+
+function syncObjectType(value: unknown): string {
+  if (typeof value !== "string" || !SYNC_OBJECT_TYPE_PATTERN.test(value)) {
+    throw new SyncPushRequestError("object_type_invalid");
+  }
+  try {
+    assertSyncObjectType(value);
+  } catch (error) {
+    if (error instanceof StorageObjectError) {
+      throw new SyncPushRequestError(error.message);
+    }
+    throw error;
+  }
+  return value;
+}
+
+function sha256HexValue(value: unknown, label: string): string {
+  if (typeof value !== "string" || !SHA256_HEX.test(value)) {
+    throw new SyncPushRequestError(`${label}_invalid`);
+  }
+  return value;
+}
+
+function integer(value: unknown, label: string, min: number, max: number): number {
+  if (typeof value !== "number" || !Number.isSafeInteger(value) || value < min || value > max) {
+    throw new SyncPushRequestError(`${label}_invalid`);
+  }
+  return value;
+}
+
+function nullableInteger(value: unknown, label: string, min: number, max: number): number | null {
+  if (value === null) {
+    return null;
+  }
+  return integer(value, label, min, max);
+}
+
+function text(value: unknown, label: string): string {
+  if (typeof value !== "string" || value.length === 0) {
+    throw new SyncPushRequestError(`${label}_invalid`);
+  }
+  return value;
+}
+
+function nullableText(value: unknown, label: string): string | null {
+  if (value === null) {
+    return null;
+  }
+  return text(value, label);
+}
+
+function regionValue(value: unknown): string {
+  if (typeof value !== "string" || !REGION.test(value)) {
+    throw new SyncPushRequestError("payload.region_invalid");
+  }
+  return value;
+}
+
+function payloadBytes(value: unknown, label: string, maxBytes: number): ArrayBuffer {
+  const encoded = text(value, label);
+  if (!BASE64.test(encoded)) {
+    throw new SyncPushRequestError(`${label}_invalid`);
+  }
+  const bytes = bytesFromBase64(encoded);
+  if (bytes.byteLength === 0 || bytes.byteLength > maxBytes) {
+    throw new SyncPushRequestError(`${label}_size_invalid`);
+  }
+  return bytes;
+}
+
+function bytesFromBase64(value: string): ArrayBuffer {
+  const binary = atob(value);
+  const bytes = new Uint8Array(binary.length);
+  for (let index = 0; index < binary.length; index += 1) {
+    bytes[index] = binary.charCodeAt(index);
+  }
+  return bytes.buffer;
+}
+
+function arrayBufferFromBytes(bytes: Uint8Array): ArrayBuffer {
+  const copy = new Uint8Array(bytes.byteLength);
+  copy.set(bytes);
+  return copy.buffer;
+}
+
+async function assertPayloadHash(payload: ArrayBuffer, expectedHash: string): Promise<void> {
+  const actualHash = await sha256Hex(payload);
+  if (actualHash !== expectedHash) {
+    throw new SyncPushRequestError("payload_hash_mismatch");
+  }
+}
+
+async function sha256Hex(payload: ArrayBuffer): Promise<string> {
+  const digest = await crypto.subtle.digest("SHA-256", payload);
+  return [...new Uint8Array(digest)].map((byte) => byte.toString(16).padStart(2, "0")).join("");
+}
diff --git a/cloudflare/tests/devices_test_support.ts b/cloudflare/tests/devices_test_support.ts
index 6822f45..29c3ad8 100644
--- a/cloudflare/tests/devices_test_support.ts
+++ b/cloudflare/tests/devices_test_support.ts
@@ -14,6 +14,7 @@ export interface TestEnvOptions {
   d1?: RecordedD1Database;
   kvEntries?: [string, string][];
   kvReads?: string[];
+  r2Puts?: RecordedR2Put[];
 }
 
 export interface RecordedD1Database extends ElyD1Database {
@@ -22,6 +23,12 @@ export interface RecordedD1Database extends ElyD1Database {
   queries: string[];
 }
 
+export interface RecordedR2Put {
+  key: string;
+  payload: ArrayBuffer;
+  options: ElyR2PutOptions;
+}
+
 interface TestD1DatabaseOptions {
   allRows?: unknown[];
   firstRows?: unknown[];
@@ -38,7 +45,7 @@ export function testEnv(options: TestEnvOptions): Env {
         return Promise.resolve(values.get(key) ?? null);
       },
     },
-    ELY_STORAGE: testR2Bucket(),
+    ELY_STORAGE: testR2Bucket(options.r2Puts),
     ELY_RATE_LIMITER: {
       limit(): Promise<{ success: boolean }> {
         return Promise.resolve({ success: true });
@@ -112,12 +119,13 @@ function testD1PreparedStatement(
   };
 }
 
-function testR2Bucket(): Env["ELY_STORAGE"] {
+function testR2Bucket(puts: RecordedR2Put[] = []): Env["ELY_STORAGE"] {
   return {
     get() {
       return Promise.resolve(null);
     },
-    put(_key: string, value: ArrayBuffer, _options?: ElyR2PutOptions) {
+    put(key: string, value: ArrayBuffer, options: ElyR2PutOptions = {}) {
+      puts.push({ key, payload: value, options });
       return Promise.resolve({
         arrayBuffer() {
           return Promise.resolve(value);
diff --git a/cloudflare/tests/sync_push_routes.test.ts b/cloudflare/tests/sync_push_routes.test.ts
new file mode 100644
index 0000000..55b275c
--- /dev/null
+++ b/cloudflare/tests/sync_push_routes.test.ts
@@ -0,0 +1,313 @@
+import assert from "node:assert/strict";
+import { createHash } from "node:crypto";
+import { describe, it } from "node:test";
+
+import { authSessionCacheKvKey, authTokenHash } from "../src/auth.js";
+import { handleRequest } from "../src/index.js";
+import {
+  ACCESS_TOKEN,
+  type RecordedR2Put,
+  sessionDocument,
+  testD1Database,
+  testEnv,
+} from "./devices_test_support.js";
+
+const USER_ID = "user-01";
+const DEVICE_ID = "device-01";
+const OBJECT_ID = "tab-01";
+const OBJECT_TYPE = "tabs";
+
+describe("sync push routes", () => {
+  it("pushes an inline encrypted sync object from an approved current device", async () => {
+    const payload = bytes("encrypted tab payload");
+    const payloadHash = sha256(payload);
+    const tokenHash = await authTokenHash(ACCESS_TOKEN);
+    const d1 = testD1Database({
+      firstRows: [
+        { device_id: DEVICE_ID },
+        null,
+        syncObjectRow({ payload_hash: payloadHash }),
+      ],
+    });
+
+    const response = await handleRequest(
+      syncPushRequest(syncPushBody({ payload_hash: payloadHash, payload: inlinePayload(payload) })),
+      testEnv({
+        d1,
+        kvEntries: [[authSessionCacheKvKey("local", tokenHash), sessionDocument(DEVICE_ID)]],
+      }),
+    );
+
+    assert.equal(response.status, 201);
+    assert.equal(response.headers.get("cache-control"), "no-store");
+    assert.deepEqual(await response.json(), {
+      version: 1,
+      user_id: USER_ID,
+      device_id: DEVICE_ID,
+      object: syncObjectDocument({ payload_hash: payloadHash }),
+    });
+    assert.equal(d1.batches[0], 2);
+    assert.ok(d1.queries[0]?.includes("approval_status = 'approved'"));
+    assert.ok(d1.queries[1]?.includes("FROM sync_objects"));
+    assert.ok(d1.queries[2]?.includes("INSERT INTO sync_objects"));
+    assert.ok(d1.queries[3]?.includes("INSERT INTO sync_change_log"));
+    assert.deepEqual(d1.binds[0], [USER_ID, DEVICE_ID]);
+    assert.deepEqual(d1.binds[1], [USER_ID, OBJECT_ID]);
+    assert.deepEqual(d1.binds[2]?.slice(0, 3), [USER_ID, OBJECT_ID, OBJECT_TYPE]);
+    assert.deepEqual(new Uint8Array(d1.binds[2]?.[3] as ArrayBuffer), new Uint8Array(payload));
+    assert.equal(d1.binds[2]?.[4], null);
+    assert.equal(d1.binds[3]?.[3], "upsert");
+  });
+
+  it("pushes an R2 encrypted sync object after checksum verification", async () => {
+    const payload = bytes("large encrypted tab payload");
+    const payloadHash = sha256(payload);
+    const userHash = sha256(bytes(USER_ID));
+    const r2Puts: RecordedR2Put[] = [];
+    const tokenHash = await authTokenHash(ACCESS_TOKEN);
+    const d1 = testD1Database({
+      firstRows: [
+        { device_id: DEVICE_ID },
+        null,
+        syncObjectRow({
+          payload_hash: payloadHash,
+          payload_r2_key: `sync-payloads/us-east/${userHash}/tabs/${OBJECT_ID}/${payloadHash}.bin`,
+        }),
+      ],
+    });
+
+    const response = await handleRequest(
+      syncPushRequest(
+        syncPushBody({ payload_hash: payloadHash, payload: r2Payload("us-east", payload) }),
+      ),
+      testEnv({
+        d1,
+        r2Puts,
+        kvEntries: [[authSessionCacheKvKey("local", tokenHash), sessionDocument(DEVICE_ID)]],
+      }),
+    );
+
+    assert.equal(response.status, 201);
+    assert.equal(r2Puts.length, 1);
+    assert.equal(
+      r2Puts[0]?.key,
+      `sync-payloads/us-east/${userHash}/tabs/${OBJECT_ID}/${payloadHash}.bin`,
+    );
+    assert.equal(r2Puts[0]?.options.customMetadata?.sha256, payloadHash);
+    const body = (await response.json()) as { object: { payload_storage: string } };
+    assert.equal(body.object.payload_storage, "r2");
+    assert.equal(d1.binds[2]?.[3], null);
+    assert.equal(d1.binds[2]?.[4], r2Puts[0]?.key);
+  });
+
+  it("pushes a delete tombstone and writes the change log", async () => {
+    const payloadHash = "b".repeat(64);
+    const tokenHash = await authTokenHash(ACCESS_TOKEN);
+    const d1 = testD1Database({
+      firstRows: [
+        { device_id: DEVICE_ID },
+        syncObjectRow({ payload_hash: "a".repeat(64), logical_clock: 41 }),
+        syncObjectRow({ payload_hash: payloadHash, logical_clock: 42, deleted_at: 1_780_000_800 }),
+      ],
+    });
+
+    const response = await handleRequest(
+      syncPushRequest(
+        syncPushBody({ operation: "delete", payload_hash: payloadHash, payload: undefined }),
+      ),
+      testEnv({
+        d1,
+        kvEntries: [[authSessionCacheKvKey("local", tokenHash), sessionDocument(DEVICE_ID)]],
+      }),
+    );
+
+    assert.equal(response.status, 201);
+    assert.equal(d1.batches[0], 3);
+    assert.ok(d1.queries[4]?.includes("INSERT INTO sync_tombstones"));
+    assert.equal(d1.binds[2]?.[3], null);
+    assert.equal(d1.binds[2]?.[4], null);
+    assert.equal(d1.binds[3]?.[3], "delete");
+    const body = (await response.json()) as { object: { payload_storage: string } };
+    assert.equal(body.object.payload_storage, "tombstone");
+  });
+
+  it("rejects payload checksum mismatches before D1 writes", async () => {
+    const tokenHash = await authTokenHash(ACCESS_TOKEN);
+    const d1 = testD1Database({ firstRows: [{ device_id: DEVICE_ID }] });
+    const response = await handleRequest(
+      syncPushRequest(
+        syncPushBody({
+          payload_hash: "c".repeat(64),
+          payload: inlinePayload(bytes("encrypted tab payload")),
+        }),
+      ),
+      testEnv({
+        d1,
+        kvEntries: [[authSessionCacheKvKey("local", tokenHash), sessionDocument(DEVICE_ID)]],
+      }),
+    );
+
+    assert.equal(response.status, 400);
+    assert.deepEqual(await response.json(), { error: "invalid_sync_push" });
+    assert.equal(d1.queries.length, 1);
+    assert.deepEqual(d1.batches, []);
+  });
+
+  it("rejects R2 object ids that cannot form storage keys before D1 writes", async () => {
+    const payload = bytes("large encrypted tab payload");
+    const payloadHash = sha256(payload);
+    const r2Puts: RecordedR2Put[] = [];
+    const tokenHash = await authTokenHash(ACCESS_TOKEN);
+    const d1 = testD1Database({ firstRows: [{ device_id: DEVICE_ID }] });
+
+    const response = await handleRequest(
+      syncPushRequest(
+        syncPushBody({
+          object_id: "Tab:01",
+          payload_hash: payloadHash,
+          payload: r2Payload("us-east", payload),
+        }),
+      ),
+      testEnv({
+        d1,
+        r2Puts,
+        kvEntries: [[authSessionCacheKvKey("local", tokenHash), sessionDocument(DEVICE_ID)]],
+      }),
+    );
+
+    assert.equal(response.status, 400);
+    assert.deepEqual(await response.json(), { error: "invalid_sync_push" });
+    assert.equal(r2Puts.length, 0);
+    assert.equal(d1.queries.length, 1);
+    assert.deepEqual(d1.batches, []);
+  });
+
+  it("rejects stale logical clocks before persistence writes", async () => {
+    const payload = bytes("encrypted tab payload");
+    const payloadHash = sha256(payload);
+    const tokenHash = await authTokenHash(ACCESS_TOKEN);
+    const d1 = testD1Database({
+      firstRows: [
+        { device_id: DEVICE_ID },
+        syncObjectRow({ payload_hash: "d".repeat(64), logical_clock: 43 }),
+      ],
+    });
+
+    const response = await handleRequest(
+      syncPushRequest(
+        syncPushBody({
+          payload_hash: payloadHash,
+          logical_clock: 42,
+          payload: inlinePayload(payload),
+        }),
+      ),
+      testEnv({
+        d1,
+        kvEntries: [[authSessionCacheKvKey("local", tokenHash), sessionDocument(DEVICE_ID)]],
+      }),
+    );
+
+    assert.equal(response.status, 409);
+    assert.deepEqual(await response.json(), { error: "sync_conflict" });
+    assert.deepEqual(d1.batches, []);
+  });
+
+  it("rejects revoked devices before reading the sync push body", async () => {
+    const tokenHash = await authTokenHash(ACCESS_TOKEN);
+    const d1 = testD1Database({ firstRows: [null] });
+    const response = await handleRequest(
+      syncPushRequest(syncPushBody()),
+      testEnv({
+        d1,
+        kvEntries: [[authSessionCacheKvKey("local", tokenHash), sessionDocument(DEVICE_ID)]],
+      }),
+    );
+
+    assert.equal(response.status, 403);
+    assert.deepEqual(await response.json(), { error: "device_not_approved" });
+    assert.equal(d1.queries.length, 1);
+    assert.deepEqual(d1.batches, []);
+  });
+});
+
+function syncPushRequest(body: Record<string, unknown>): Request {
+  return new Request("https://elydora.test/api/sync/push", {
+    method: "POST",
+    headers: {
+      authorization: `Bearer ${ACCESS_TOKEN}`,
+      "content-type": "application/json",
+    },
+    body: JSON.stringify(body),
+  });
+}
+
+function syncPushBody(overrides: Record<string, unknown> = {}): Record<string, unknown> {
+  const payload = bytes("encrypted tab payload");
+  const payloadHash = sha256(payload);
+  return {
+    version: 1,
+    object_id: OBJECT_ID,
+    object_type: OBJECT_TYPE,
+    operation: "upsert",
+    payload_hash: payloadHash,
+    schema_rev: 1,
+    logical_clock: 42,
+    payload: inlinePayload(payload),
+    ...overrides,
+  };
+}
+
+function inlinePayload(payload: ArrayBuffer): Record<string, unknown> {
+  return { kind: "inline", data_base64: base64(payload) };
+}
+
+function r2Payload(region: string, payload: ArrayBuffer): Record<string, unknown> {
+  return { kind: "r2", region, data_base64: base64(payload) };
+}
+
+function syncObjectRow(overrides: Record<string, unknown> = {}): Record<string, unknown> {
+  return {
+    object_id: OBJECT_ID,
+    object_type: OBJECT_TYPE,
+    payload_r2_key: null,
+    payload_hash: "a".repeat(64),
+    schema_rev: 1,
+    logical_clock: 42,
+    device_id: DEVICE_ID,
+    created_at: 1_780_000_700,
+    updated_at: 1_780_000_700,
+    deleted_at: null,
+    ...overrides,
+  };
+}
+
+function syncObjectDocument(overrides: Record<string, unknown> = {}): Record<string, unknown> {
+  const row = syncObjectRow(overrides);
+  return {
+    object_id: row.object_id,
+    object_type: row.object_type,
+    operation: row.deleted_at === null ? "upsert" : "delete",
+    payload_hash: row.payload_hash,
+    schema_rev: row.schema_rev,
+    logical_clock: row.logical_clock,
+    device_id: row.device_id,
+    created_at: row.created_at,
+    updated_at: row.updated_at,
+    deleted_at: row.deleted_at,
+    payload_storage:
+      row.deleted_at !== null ? "tombstone" : row.payload_r2_key === null ? "inline" : "r2",
+    payload_r2_key: row.payload_r2_key,
+  };
+}
+
+function bytes(value: string): ArrayBuffer {
+  return new TextEncoder().encode(value).buffer;
+}
+
+function base64(payload: ArrayBuffer): string {
+  return Buffer.from(payload).toString("base64");
+}
+
+function sha256(payload: ArrayBuffer): string {
+  return createHash("sha256").update(new Uint8Array(payload)).digest("hex");
+}