diff --git a/packages/protocol/src/crypto/receive-envelope.ts b/packages/protocol/src/crypto/receive-envelope.ts
index c40dad8..f875db8 100644
--- a/packages/protocol/src/crypto/receive-envelope.ts
+++ b/packages/protocol/src/crypto/receive-envelope.ts
@@ -75,17 +75,17 @@ export async function receiveEnvelope(
   selfId: string,
   deps: ReceiveEnvelopeDeps,
 ): Promise<ReceiveEnvelopeResult> {
-  // Step 0: known wire version
+  // Step 1 (§4.3): pre-decode wire size cap — before any JSON.parse
+  if (utf8ToBytes(wire).length > MAX_ENVELOPE_WIRE_BYTES) {
+    return { ok: false, error: "envelope_too_large" };
+  }
+
+  // §4.1 wire version gate (between §4.3 steps 1 and 2)
   const outerVersion = parseOuterVersion(wire);
   if (outerVersion !== null && outerVersion !== 1) {
     return { ok: false, error: "unsupported_version" };
   }
 
-  // Step 1: pre-decode wire size cap
-  if (utf8ToBytes(wire).length > MAX_ENVELOPE_WIRE_BYTES) {
-    return { ok: false, error: "envelope_too_large" };
-  }
-
   // Step 2: strict-decode outer + parse body JSON
   let outer: OuterEnvelope;
   try {
diff --git a/packages/protocol/src/receive-envelope.test.ts b/packages/protocol/src/receive-envelope.test.ts
index 38bf5f4..d368fc3 100644
--- a/packages/protocol/src/receive-envelope.test.ts
+++ b/packages/protocol/src/receive-envelope.test.ts
@@ -110,8 +110,8 @@ function tamperBody(wire: string, patch: (body: EnvelopeBody) => void): string {
   return serializeOuterEnvelope(tampered);
 }
 
-describe("receiveEnvelope steps 0–6 (§4.3)", () => {
-  it("step 0: unknown wire version → unsupported_version, dispatch not called", async () => {
+describe("receiveEnvelope steps 1–6 (§4.3)", () => {
+  it("§4.1 wire version: unknown version at valid size → unsupported_version, dispatch not called", async () => {
     const { wire, bob, bobId } = makeValidWire();
     const deps = makeDeps(bob);
     const badWire = tamperOuter(wire, (outer) => {
@@ -137,6 +137,24 @@ describe("receiveEnvelope steps 0–6 (§4.3)", () => {
     expect(deps.seqStore.commitAccepted).not.toHaveBeenCalled();
   });
 
+  it("step 1: oversized wire with v:2 → envelope_too_large (not unsupported_version)", async () => {
+    const { wire, bob, bobId } = makeValidWire();
+    const deps = makeDeps(bob);
+    const badWire = padWireToSize(
+      tamperOuter(wire, (outer) => {
+        outer.v = 2;
+      }),
+      MAX_ENVELOPE_WIRE_BYTES + 1,
+    );
+    expect(wireUtf8Length(badWire)).toBeGreaterThan(MAX_ENVELOPE_WIRE_BYTES);
+
+    const result = await receiveEnvelope(badWire, bobId, deps);
+
+    expect(result).toEqual({ ok: false, error: "envelope_too_large" });
+    expect(deps.dispatch).not.toHaveBeenCalled();
+    expect(deps.seqStore.commitAccepted).not.toHaveBeenCalled();
+  });
+
   it("step 1: wire === 65536 bytes passes size check", async () => {
     const { wire, bob, bobId } = makeValidWire();
     const deps = makeDeps(bob);
@@ -286,7 +304,7 @@ describe("receiveEnvelope steps 0–6 (§4.3)", () => {
     expect(deps.seqStore.commitAccepted).not.toHaveBeenCalled();
   });
 
-  it("valid wire passing steps 0–6 continues to step 7+ (not rejected early)", async () => {
+  it("valid wire passing steps 1–6 continues to step 7+ (not rejected early)", async () => {
     const { wire, bob, bobId } = makeValidWire();
     const deps = makeDeps(bob);