diff --git a/CHANGELOG.md b/CHANGELOG.md
index 257b78b..74ecf5e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- `SerializedSignedOrder` type and `serializeOrder`/`deserializeOrder` now flatten `owner` and `signature` to the top level, matching Rust's `#[serde(flatten)]` on `Permit2Batch`
+
+### Changed
+
+- Added JSDoc comments to all exported functions, types, interfaces, and constants
+- Added JSDoc requirement to CLAUDE.md code style guidelines
+
 ### Added
 
 - `deadline_expired` check in `checkOrderFeasibility` — detects orders with expired permit deadlines
diff --git a/CLAUDE.md b/CLAUDE.md
index 3a5b7a4..bf7d988 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -27,6 +27,8 @@
 - Keep functions small and focused
 - Write tests that fail fast - use direct assertions, no Result returns
 - Avoid unnecessary nesting and closures
+- ALWAYS write JSDoc comments for all exported functions, types, interfaces, and constants
+- JSDoc should explain the purpose and any non-obvious design decisions (e.g. why a structure is shaped a certain way)
 
 ## Project Structure
 
diff --git a/package.json b/package.json
index 08cbcb6..e1a39c9 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@signet-sh/sdk",
-  "version": "0.4.4",
+  "version": "0.4.5",
   "description": "TypeScript SDK for Signet Orders - create, sign, and verify orders compatible with signet-types",
   "type": "module",
   "main": "./dist/index.js",
diff --git a/src/abi/bundleHelper.ts b/src/abi/bundleHelper.ts
index a8f3498..1ac22a3 100644
--- a/src/abi/bundleHelper.ts
+++ b/src/abi/bundleHelper.ts
@@ -1,4 +1,4 @@
-// Generated from crates/zenith/abi/BundleHelper.json
+/** BundleHelper contract ABI. Generated from crates/zenith/abi/BundleHelper.json. */
 export const bundleHelperAbi = [
   {
     type: "constructor",
diff --git a/src/abi/hostOrders.ts b/src/abi/hostOrders.ts
index aa178ae..d67629b 100644
--- a/src/abi/hostOrders.ts
+++ b/src/abi/hostOrders.ts
@@ -1,4 +1,4 @@
-// Generated from crates/zenith/abi/HostOrders.json
+/** HostOrders contract ABI. Generated from crates/zenith/abi/HostOrders.json. */
 export const hostOrdersAbi = [
   {
     type: "constructor",
diff --git a/src/abi/passage.ts b/src/abi/passage.ts
index 82b8e0d..12bf7d2 100644
--- a/src/abi/passage.ts
+++ b/src/abi/passage.ts
@@ -1,4 +1,4 @@
-// Generated from crates/zenith/abi/Passage.json
+/** Passage contract ABI. Generated from crates/zenith/abi/Passage.json. */
 export const passageAbi = [
   {
     type: "constructor",
diff --git a/src/abi/rollupPassage.ts b/src/abi/rollupPassage.ts
index 3bf3258..0c799a1 100644
--- a/src/abi/rollupPassage.ts
+++ b/src/abi/rollupPassage.ts
@@ -1,4 +1,4 @@
-// Generated from crates/zenith/abi/RollupPassage.json
+/** RollupPassage contract ABI. Generated from crates/zenith/abi/RollupPassage.json. */
 export const rollupPassageAbi = [
   {
     type: "constructor",
diff --git a/src/abi/transactor.ts b/src/abi/transactor.ts
index f6f7453..6537bb4 100644
--- a/src/abi/transactor.ts
+++ b/src/abi/transactor.ts
@@ -1,4 +1,4 @@
-// Generated from crates/zenith/abi/Transactor.json
+/** Transactor contract ABI. Generated from crates/zenith/abi/Transactor.json. */
 export const transactorAbi = [
   {
     type: "constructor",
diff --git a/src/abi/zenith.ts b/src/abi/zenith.ts
index c7de4d0..6bdd5c0 100644
--- a/src/abi/zenith.ts
+++ b/src/abi/zenith.ts
@@ -1,4 +1,4 @@
-// Generated from crates/zenith/abi/Zenith.json
+/** Zenith contract ABI. Generated from crates/zenith/abi/Zenith.json. */
 export const zenithAbi = [
   {
     type: "constructor",
diff --git a/src/client/txCache.ts b/src/client/txCache.ts
index e5723f6..8899b0b 100644
--- a/src/client/txCache.ts
+++ b/src/client/txCache.ts
@@ -1,13 +1,18 @@
+/**
+ * Client for the Signet transaction cache service.
+ */
 import type { SignetEthBundle } from "../types/bundle.js";
 import type { SignedOrder } from "../types/order.js";
 import { serializeEthBundle } from "../types/bundleSerialization.js";
 import { serializeOrder } from "../types/serialization.js";
 
+/** Client interface for submitting orders and bundles to the transaction cache. */
 export interface TxCacheClient {
   submitOrder(order: SignedOrder): Promise<{ id: string }>;
   submitBundle(bundle: SignetEthBundle): Promise<{ id: string }>;
 }
 
+/** Create a {@link TxCacheClient} that posts to the given base URL. */
 export function createTxCacheClient(baseUrl: string): TxCacheClient {
   async function post(path: string, body: unknown): Promise<{ id: string }> {
     const response = await fetch(`${baseUrl}${path}`, {
diff --git a/src/constants/chains.ts b/src/constants/chains.ts
index ab0af09..78f87ae 100644
--- a/src/constants/chains.ts
+++ b/src/constants/chains.ts
@@ -1,6 +1,10 @@
+/**
+ * Chain configuration constants for Signet networks.
+ */
 import type { Address } from "viem";
 import type { TokenSymbol } from "../tokens/constants.js";
 
+/** System-wide contract addresses and chain IDs for a Signet deployment. */
 export interface SignetSystemConstants {
   readonly hostChainId: bigint;
   readonly rollupChainId: bigint;
@@ -15,6 +19,7 @@ export interface SignetSystemConstants {
   readonly tokenDecimals?: Partial<Record<TokenSymbol, number>>;
 }
 
+/** Signet mainnet (host chain 1, rollup chain 519) constants. */
 export const MAINNET: SignetSystemConstants = {
   hostChainId: 1n,
   rollupChainId: 519n,
@@ -28,6 +33,7 @@ export const MAINNET: SignetSystemConstants = {
   slotTime: 12n,
 } as const;
 
+/** Parmigiana testnet (host chain 3151908, rollup chain 88888) constants. */
 export const PARMIGIANA: SignetSystemConstants = {
   hostChainId: 3151908n,
   rollupChainId: 88888n,
@@ -44,6 +50,7 @@ export const PARMIGIANA: SignetSystemConstants = {
   },
 } as const;
 
+/** Look up the orders contract address for a given chain ID within a deployment. */
 export function getOrdersContract(
   constants: SignetSystemConstants,
   chainId: bigint
diff --git a/src/constants/viemChains.ts b/src/constants/viemChains.ts
index 431246d..83d00ce 100644
--- a/src/constants/viemChains.ts
+++ b/src/constants/viemChains.ts
@@ -1,5 +1,9 @@
+/**
+ * Viem chain definitions for Signet networks.
+ */
 import { defineChain } from "viem";
 
+/** Viem chain definition for the Signet mainnet rollup (chain 519). */
 export const signetRollup = defineChain({
   id: 519,
   name: "Signet",
@@ -9,6 +13,7 @@ export const signetRollup = defineChain({
   },
 });
 
+/** Viem chain definition for the Parmigiana testnet rollup (chain 88888). */
 export const parmigianaRollup = defineChain({
   id: 88888,
   name: "Parmigiana",
@@ -24,6 +29,7 @@ export const parmigianaRollup = defineChain({
   },
 });
 
+/** Viem chain definition for the Parmigiana testnet host chain (chain 3151908). */
 export const parmigianaHost = defineChain({
   id: 3151908,
   name: "Parmigiana Host",
diff --git a/src/signing/encode.ts b/src/signing/encode.ts
index be6cdd3..2e5abe6 100644
--- a/src/signing/encode.ts
+++ b/src/signing/encode.ts
@@ -1,9 +1,13 @@
+/**
+ * ABI encoding helpers for order and fill contract calls.
+ */
 import { encodeFunctionData, type Address, type Hex } from "viem";
 import type { SignedOrder } from "../types/order.js";
 import type { SignedFill } from "../types/fill.js";
 import { rollupOrdersAbi } from "../abi/rollupOrders.js";
 import { hostOrdersAbi } from "../abi/hostOrders.js";
 
+/** Encode calldata for `RollupOrders.initiatePermit2`. */
 export function encodeInitiatePermit2(
   order: SignedOrder,
   tokenRecipient: Address
@@ -15,6 +19,7 @@ export function encodeInitiatePermit2(
   });
 }
 
+/** Encode calldata for `HostOrders.fillPermit2`. */
 export function encodeFillPermit2(fill: SignedFill): Hex {
   return encodeFunctionData({
     abi: hostOrdersAbi,
diff --git a/src/signing/validate.ts b/src/signing/validate.ts
index 3471c26..4638606 100644
--- a/src/signing/validate.ts
+++ b/src/signing/validate.ts
@@ -1,8 +1,12 @@
+/**
+ * Runtime validation for signed orders and fills.
+ */
 import { isAddressEqual } from "viem";
 import type { SignedFill } from "../types/fill.js";
 import type { SignedOrder } from "../types/order.js";
 import { nowSeconds } from "../utils/time.js";
 
+/** Validate that a signed order has not expired. Throws on failure. */
 export function validateOrder(order: SignedOrder): void {
   const now = nowSeconds();
   if (order.permit.permit.deadline < now) {
@@ -12,6 +16,7 @@ export function validateOrder(order: SignedOrder): void {
   }
 }
 
+/** Validate that a signed fill has not expired and its outputs match permitted tokens. Throws on failure. */
 export function validateFill(fill: SignedFill): void {
   const now = nowSeconds();
   if (fill.permit.permit.deadline < now) {
diff --git a/src/tokens/addresses.ts b/src/tokens/addresses.ts
index 1008a4c..1f44afd 100644
--- a/src/tokens/addresses.ts
+++ b/src/tokens/addresses.ts
@@ -1,3 +1,6 @@
+/**
+ * Token address lookups for Signet networks.
+ */
 import { isAddressEqual, type Address } from "viem";
 import type { SignetSystemConstants } from "../constants/chains.js";
 import type { TokenSymbol } from "./constants.js";
@@ -59,6 +62,7 @@ function getSide(
   return undefined;
 }
 
+/** Get the on-chain address for a token symbol on a specific chain. */
 export function getTokenAddress(
   symbol: TokenSymbol,
   chainId: bigint,
@@ -69,6 +73,7 @@ export function getTokenAddress(
   return getSide(network, chainId, constants)?.[symbol];
 }
 
+/** Resolve a token address back to its symbol on a specific chain. */
 export function resolveTokenSymbol(
   address: Address,
   chainId: bigint,
@@ -84,6 +89,7 @@ export function resolveTokenSymbol(
   return entry?.[0] as TokenSymbol | undefined;
 }
 
+/** List all token symbols available on a specific chain. */
 export function getAvailableTokens(
   chainId: bigint,
   constants: SignetSystemConstants
diff --git a/src/tokens/constants.ts b/src/tokens/constants.ts
index 83638eb..c2c64b7 100644
--- a/src/tokens/constants.ts
+++ b/src/tokens/constants.ts
@@ -1,11 +1,16 @@
+/**
+ * Token metadata and decimal lookups.
+ */
 import type { SignetSystemConstants } from "../constants/chains.js";
 
+/** Metadata for a known token. */
 export interface TokenMeta {
   readonly symbol: string;
   readonly name: string;
   readonly decimals: number;
 }
 
+/** Registry of known tokens and their metadata. */
 export const TOKENS = {
   ETH: { symbol: "ETH", name: "Ether", decimals: 18 },
   WETH: { symbol: "WETH", name: "Wrapped Ether", decimals: 18 },
@@ -16,6 +21,7 @@ export const TOKENS = {
   USD: { symbol: "USD", name: "USD", decimals: 18 },
 } as const satisfies Record<string, TokenMeta>;
 
+/** Union of known token symbol strings. */
 export type TokenSymbol = keyof typeof TOKENS;
 
 /**
diff --git a/src/tokens/mapping.ts b/src/tokens/mapping.ts
index afa80db..f0e4b92 100644
--- a/src/tokens/mapping.ts
+++ b/src/tokens/mapping.ts
@@ -19,6 +19,7 @@ const BRIDGEABLE_TOKENS = new Set<TokenSymbol>([
   "USDT",
 ]);
 
+/** Map a token symbol across chains. Returns the symbol if bridgeable, undefined otherwise. */
 export function mapTokenCrossChain(
   symbol: TokenSymbol
 ): TokenSymbol | undefined {
diff --git a/src/types/order.ts b/src/types/order.ts
index 648eddc..3968ad4 100644
--- a/src/types/order.ts
+++ b/src/types/order.ts
@@ -46,20 +46,22 @@ export interface UnsignedOrderParams {
 /**
  * Serialized form of a signed order for JSON transport.
  * Amounts are hex-encoded strings.
+ *
+ * The `owner` and `signature` fields are flattened to the top level to match
+ * Rust's `#[serde(flatten)]` on `Permit2Batch`. The `permit` field contains
+ * only the inner `PermitBatchTransferFrom` data.
  */
 export interface SerializedSignedOrder {
+  readonly owner: Address;
   readonly permit: {
-    readonly permit: {
-      readonly permitted: readonly {
-        readonly token: Address;
-        readonly amount: Hex;
-      }[];
-      readonly nonce: Hex;
-      readonly deadline: Hex;
-    };
-    readonly owner: Address;
-    readonly signature: Hex;
+    readonly permitted: readonly {
+      readonly token: Address;
+      readonly amount: Hex;
+    }[];
+    readonly nonce: Hex;
+    readonly deadline: Hex;
   };
+  readonly signature: Hex;
   readonly outputs: readonly {
     readonly token: Address;
     readonly amount: Hex;
diff --git a/src/types/serialization.ts b/src/types/serialization.ts
index d0e02d7..e3e4eef 100644
--- a/src/types/serialization.ts
+++ b/src/types/serialization.ts
@@ -1,21 +1,23 @@
+/**
+ * Serialization and deserialization for signed orders.
+ */
 import { fromHex, toHex } from "viem";
 import type { SignedOrder, SerializedSignedOrder } from "./order.js";
 
+/** Serialize a {@link SignedOrder} to its JSON-transport representation. */
 export function serializeOrder(order: SignedOrder): SerializedSignedOrder {
   const { permit, outputs } = order;
   return {
+    owner: permit.owner,
     permit: {
-      permit: {
-        permitted: permit.permit.permitted.map((p) => ({
-          token: p.token,
-          amount: toHex(p.amount),
-        })),
-        nonce: toHex(permit.permit.nonce),
-        deadline: toHex(permit.permit.deadline),
-      },
-      owner: permit.owner,
-      signature: permit.signature,
+      permitted: permit.permit.permitted.map((p) => ({
+        token: p.token,
+        amount: toHex(p.amount),
+      })),
+      nonce: toHex(permit.permit.nonce),
+      deadline: toHex(permit.permit.deadline),
     },
+    signature: permit.signature,
     outputs: outputs.map((o) => ({
       token: o.token,
       amount: toHex(o.amount),
@@ -25,19 +27,20 @@ export function serializeOrder(order: SignedOrder): SerializedSignedOrder {
   };
 }
 
+/** Deserialize a {@link SerializedSignedOrder} back into a {@link SignedOrder}. */
 export function deserializeOrder(raw: SerializedSignedOrder): SignedOrder {
   return {
     permit: {
       permit: {
-        permitted: raw.permit.permit.permitted.map((p) => ({
+        permitted: raw.permit.permitted.map((p) => ({
           token: p.token,
           amount: fromHex(p.amount, "bigint"),
         })),
-        nonce: fromHex(raw.permit.permit.nonce, "bigint"),
-        deadline: fromHex(raw.permit.permit.deadline, "bigint"),
+        nonce: fromHex(raw.permit.nonce, "bigint"),
+        deadline: fromHex(raw.permit.deadline, "bigint"),
       },
-      owner: raw.permit.owner,
-      signature: raw.permit.signature,
+      owner: raw.owner,
+      signature: raw.signature,
     },
     outputs: raw.outputs.map((o) => ({
       token: o.token,
diff --git a/tests/serialization.test.ts b/tests/serialization.test.ts
index cda18d1..8e8f558 100644
--- a/tests/serialization.test.ts
+++ b/tests/serialization.test.ts
@@ -59,5 +59,11 @@ describe("serialization round-trip", () => {
       const deserialized = deserializeOrder(serialized);
       expect(deserialized).toEqual(order);
     });
+
+    it(`serializes ${v.name} to match Rust vector shape`, () => {
+      const order = parseVector(v);
+      const serialized = serializeOrder(order);
+      expect(serialized).toEqual(v.signedOrder);
+    });
   }
 });