diff --git a/src/blockstore/fp-envelope.ts b/src/blockstore/fp-envelope.ts
new file mode 100644
index 00000000..2efb3882
--- /dev/null
+++ b/src/blockstore/fp-envelope.ts
@@ -0,0 +1,116 @@
+import { CID } from "multiformats";
+import { encode, decode } from "cborg";
+import { Result } from "@adviser/cement"
+
+export interface FPEnvelope<T> {
+    readonly type: string; // "car" | "file" | "meta" | "wal"
+    readonly payload: T
+}
+
+export interface FPEnvelopeCar extends FPEnvelope<Uint8Array> {
+    readonly type: "car";
+}
+
+export interface FPEnvelopeFile extends FPEnvelope<Uint8Array> {
+    readonly type: "file";
+}
+
+export interface FPMeta {
+    readonly cid: string;
+    readonly data: Uint8Array;
+    readonly parents: string[];
+}
+
+export interface FPEnvelopeMeta extends FPEnvelope<FPMeta> {
+    readonly type: "meta";
+}
+
+export interface FPWALCarsOps {
+    readonly cars: CID[];
+}
+export interface FPWAL {
+    // fileOperations: any[]; will be added with connector-fixes
+    // noLoaderOps: any[]; will be added with connector-fixes
+    readonly operations: FPWALCarsOps[];
+}
+export interface FPEnvelopeWAL extends FPEnvelope<FPWAL> {
+    readonly type: "wal";
+}
+
+export function WAL2FPMsg(fpwal: FPWAL): Uint8Array {
+    return encode({ type: "wal", payload: JSON.parse(JSON.stringify(fpwal)) } as FPEnvelopeWAL);
+}
+
+export function FPMsg2WAL(fpmsg: Uint8Array): Result<FPWAL> {
+    const renv = FPMsgMatch2Envelope(fpmsg, "wal");
+    if (renv.isErr()) {
+        return Result.Err(renv.Err());
+    }
+    const convertCids = renv.Ok().payload as FPWAL;
+    for (const op of convertCids.operations) {
+        const cars = []
+        for (const strCid of op.cars) {
+            for (const cidVal of Object.values(strCid)) {
+                cars.push(CID.parse(cidVal));
+            }
+        }
+        (op as {cars: CID[]}).cars = cars;
+    }
+    return Result.Ok(renv.Ok().payload as FPWAL);
+}
+
+export function Meta2FPMsg(fpmeta: FPMeta): Uint8Array {
+    return encode({ type: "meta", payload: fpmeta } as FPEnvelopeMeta);
+}
+
+export function FPMsg2Meta(fpmsg: Uint8Array): Result<FPMeta> {
+    const renv = FPMsgMatch2Envelope(fpmsg, "meta");
+    if (renv.isErr()) {
+        return Result.Err(renv.Err());
+    }
+    return Result.Ok(renv.Ok().payload as FPMeta);
+}
+
+export function Car2FPMsg(fpcar: Uint8Array): Uint8Array {
+    return encode({ type: "car", payload: fpcar } as FPEnvelopeCar);
+}
+
+export function FPMsg2Car(fpmsg: Uint8Array): Result<Uint8Array> {
+    const renv = FPMsgMatch2Envelope(fpmsg, "car");
+    if (renv.isErr()) {
+        return Result.Err(renv.Err());
+    }
+    return Result.Ok(renv.Ok().payload as Uint8Array);
+}
+
+export function File2FPMsg(fpfile: Uint8Array): Uint8Array {
+    return encode({ type: "file", payload: fpfile } as FPEnvelopeFile);
+}
+
+export function FPMsg2File(fpmsg: Uint8Array): Result<Uint8Array> {
+    const renv = FPMsgMatch2Envelope(fpmsg, "file");
+    if (renv.isErr()) {
+        return Result.Err(renv.Err());
+    }
+    return Result.Ok(renv.Ok().payload as Uint8Array);
+}
+
+export function FPMsgMatch2Envelope(fpmsg: Uint8Array, ...types: string[]): Result<FPEnvelope<unknown>> {
+    let env: FPEnvelope<unknown>;
+    try {
+        env = decode(fpmsg);
+    } catch (e) {
+        return Result.Err(`failed to decode envelope: ${e}`);
+    }
+    if (typeof env !== "object") {
+        return Result.Err(`expected envelope to be an object`);
+    }
+    if (typeof env.type !== "string") {
+        return Result.Err(`expected type to be a string`);
+    }
+    if (types.length > 0 && !types.includes(env.type)) {
+        return Result.Err(`expected type to be ${types}`);
+    }
+    // need to check if the payload is a valid WAL
+    return Result.Ok(env);
+}
\ No newline at end of file
diff --git a/src/blockstore/index.ts b/src/blockstore/index.ts
index 41179748..02c56621 100644
--- a/src/blockstore/index.ts
+++ b/src/blockstore/index.ts
@@ -4,6 +4,8 @@ export * from "./store-factory.js";
 export * from "./gateway.js";
 export * from "./fragment-gateway.js";
 
+export * from "./fp-envelope.js"
+
 import { type Connectable } from "./connection-base.js";
 export { Connectable };
 
diff --git a/src/blockstore/store.ts b/src/blockstore/store.ts
index 99e30eaf..fb1b3535 100644
--- a/src/blockstore/store.ts
+++ b/src/blockstore/store.ts
@@ -30,6 +30,7 @@ import { keyedCryptoFactory } from "../runtime/keyed-crypto.js";
 import { KeyBag } from "../runtime/key-bag.js";
 import { FragmentGateway } from "./fragment-gateway.js";
 import { Link } from "multiformats";
+import { FPEnvelopeCar, FPEnvelopeFile, FPMsg2Car, FPMsgMatch2Envelope } from "./fp-envelope.js";
 
 function guardVersion(url: URI): Result<URI> {
   if (!url.hasParam("version")) {
@@ -287,7 +288,19 @@ export class DataStoreImpl extends BaseStoreImpl implements DataStore {
     if (res.isErr()) {
       throw res.Err();
     }
-    return { cid, bytes: res.Ok() };
+    const rfpenv = FPMsgMatch2Envelope(res.Ok(), "car", "file");
+    if (rfpenv.isErr()) {
+      throw this.logger.Error().Err(rfpenv.Err()).Msg("got error from FPMsgMatch2Envelope").AsError();
+    }
+    const fpenv = rfpenv.Ok() as FPEnvelopeFile|FPEnvelopeCar
+    switch (fpenv.type) {
+      case "car":
+        return { cid, bytes: fpenv.payload };
+      case "file":
+        return { cid, bytes: fpenv.payload };
+      default:
+        throw this.logger.Error().Msg("unexpected type").AsError();
+    }
   }
 
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
@@ -297,7 +310,13 @@ export class DataStoreImpl extends BaseStoreImpl implements DataStore {
     if (url.isErr()) {
       throw this.logger.Error().Err(url.Err()).Ref("cid", car.cid).Msg("got error from gateway.buildUrl").AsError();
     }
-    const res = await this.gateway.put(url.Ok(), car.bytes);
+    // without URL changes in super-this branch we
+    // can distinguish between car and file
+    const rfpenv = FPMsg2Car(car.bytes);
+    if (rfpenv.isErr()) {
+      throw this.logger.Error().Err(rfpenv.Err()).Msg("got error from FPMsg2Car").AsError();
+    }
+    const res = await this.gateway.put(url.Ok(), rfpenv.Ok());
     if (res.isErr()) {
       throw this.logger.Error().Err(res.Err()).Msg("got error from gateway.put").AsError();
     }
diff --git a/src/runtime/gateways/file/gateway.ts b/src/runtime/gateways/file/gateway.ts
index 972489a7..d0b7d339 100644
--- a/src/runtime/gateways/file/gateway.ts
+++ b/src/runtime/gateways/file/gateway.ts
@@ -4,6 +4,7 @@ import { ensureLogger, exceptionWrapper, isNotFoundError, NotFoundError } from "
 import { Gateway, GetResult, TestGateway } from "../../../blockstore/gateway.js";
 import { getFileName, getFileSystem, getPath } from "./utils.js";
 import { SuperThis, SysFileSystem } from "../../../types.js";
+import { FPEnvelopeCar, FPEnvelopeFile, FPMsg2Car, FPMsgMatch2Envelope } from "../../../blockstore/fp-envelope.js";
 
 const versionFiles = new KeyedResolvOnce<string>();
 
@@ -77,10 +78,18 @@ export class FileGateway implements Gateway {
   }
 
   async put(url: URI, body: Uint8Array): Promise<Result<void>> {
+    const rbuf = FPMsgMatch2Envelope(body) as Result<FPEnvelopeCar | FPEnvelopeFile>;
+    if (rbuf.isErr()) {
+      return Result.Err(rbuf.Err());
+    }
+    let payload = body
+    if (["car", "file"].includes(rbuf.Ok().type)) {
+      payload = rbuf.Ok().payload
+    }
     return exception2Result(async () => {
       const file = await this.getFilePath(url);
       this.logger.Debug().Str("url", url.toString()).Str("file", file).Msg("put");
-      await this.fs.writefile(file, body);
+      await this.fs.writefile(file, payload);
     });
   }
 
@@ -90,6 +99,9 @@ export class FileGateway implements Gateway {
       try {
         const res = await this.fs.readfile(file);
         this.logger.Debug().Url(url.asURL()).Str("file", file).Msg("get");
+        if (url.getParam("store") === "data") {
+          return FPMsg2Car(res);
+        }
         return Result.Ok(new Uint8Array(res));
       } catch (e: unknown) {
         // this.logger.Error().Err(e).Str("file", file).Msg("get");
diff --git a/tests/blockstore/fp-envelope.test.ts b/tests/blockstore/fp-envelope.test.ts
new file mode 100644
index 00000000..ef4fc1d1
--- /dev/null
+++ b/tests/blockstore/fp-envelope.test.ts
@@ -0,0 +1,56 @@
+import { encode } from "cborg";
+import { bs, Result } from '@fireproof/core'
+import { CID } from "multiformats";
+
+it("unknown bytes", () => {
+    expect(bs.FPMsgMatch2Envelope(Uint8Array.from([1, 2, 3]), "bla").Err().message).toStrictEqual(
+        "failed to decode envelope: Error: CBOR decode error: too many terminals, data makes no sense"
+    );
+});
+
+it("unknown type", () => {
+    expect(bs.FPMsgMatch2Envelope(encode({ type: "blax", payload: 4 }), "bla"))
+    .toStrictEqual(Result.Err("expected type to be bla"));
+})
+
+it("no type", () => {
+    expect(bs.FPMsgMatch2Envelope(encode({ type: "blax", payload: 4 })))
+    .toStrictEqual(Result.Ok({ type: "blax", payload: 4 }));
+})
+
+it("car type", () => {
+    expect(bs.FPMsg2Car(bs.Car2FPMsg(Uint8Array.from([1, 2, 3]))).Ok()).toStrictEqual(Uint8Array.from([1, 2, 3]));
+})
+
+it("file type", () => {
+    expect(bs.FPMsg2File(bs.File2FPMsg(Uint8Array.from([1, 2, 3]))).Ok()).toStrictEqual(Uint8Array.from([1, 2, 3]));
+})
+
+it("meta type", () => {
+    const ref = {
+        cid: "CID",
+        data: Uint8Array.from([1, 2, 3]),
+        parents: ["C1", "C2"]
+    };
+    expect(bs.FPMsg2Meta(bs.Meta2FPMsg(ref)).Ok()).toStrictEqual(ref);
+})
+
+it("wal type", () => {
+    const ref: bs.FPWAL = {
+        operations: [
+            {
+                cars: [
+                    CID.parse("bag4yvqabciqdzvfxrxfi6feubspyz666zegmp3z5w556mr4ykya2kkdm22r7pyy")
+                ]
+            },
+            {
+                cars: [
+                    CID.parse("bag4yvqabciqd2ul2tw4mdcpvfq2pdqhvnqp2ktuyrtcl3j3gwhxbjzjt62xzeaq")
+                ]
+            }
+        ]
+    };
+    const res = bs.FPMsg2WAL(bs.WAL2FPMsg(ref)).Ok();
+    expect(res).toStrictEqual(ref);
+    expect(res.operations[0].cars[0].version).toStrictEqual(1);
+})
\ No newline at end of file