diff --git a/.changeset/tolerate-null-swap-approval-fields.md b/.changeset/tolerate-null-swap-approval-fields.md
new file mode 100644
index 0000000..2688206
--- /dev/null
+++ b/.changeset/tolerate-null-swap-approval-fields.md
@@ -0,0 +1,5 @@
+---
+"@across-protocol/app-sdk": patch
+---
+
+Accept `null` (in addition to `undefined`) for optional fields in `swapApprovalResponseSchema`: `approvalTxns`, `steps.originSwap`, `steps.destinationSwap`, and `swapTx`. The `/swap/approval` endpoint now serializes these as explicit `null` for cases where they don't apply (e.g. `bridgeableToBridgeable` routes), which previously caused `getSwapQuote` to throw `Invalid swap approval response`. Consumers already coerce to truthy, so behavior is unchanged.
diff --git a/packages/sdk/src/api/swap-approval.ts b/packages/sdk/src/api/swap-approval.ts
index 37f92ec..2bbef0e 100644
--- a/packages/sdk/src/api/swap-approval.ts
+++ b/packages/sdk/src/api/swap-approval.ts
@@ -201,11 +201,11 @@ export const swapApprovalResponseSchema = z.object({
         data: z.string(),
       }),
     )
-    .optional(),
+    .nullish(),
   steps: z.object({
-    originSwap: swapStepSchema.optional(),
+    originSwap: swapStepSchema.nullish(),
     bridge: bridgeStepSchema,
-    destinationSwap: swapStepSchema.optional(),
+    destinationSwap: swapStepSchema.nullish(),
   }),
   inputToken: z.object({
     address: anyChainAddress,
@@ -280,7 +280,7 @@ export const swapApprovalResponseSchema = z.object({
   expectedOutputAmount: bigNumberString,
   minOutputAmount: bigNumberString,
   expectedFillTime: positiveInteger,
-  swapTx: z.union([swapTxSchema, permitSwapTxSchema]).optional(),
+  swapTx: z.union([swapTxSchema, permitSwapTxSchema]).nullish(),
   id: z.string().optional(),
 });
 
diff --git a/packages/sdk/test/common/sdk.ts b/packages/sdk/test/common/sdk.ts
index 21abac6..c5ddf43 100644
--- a/packages/sdk/test/common/sdk.ts
+++ b/packages/sdk/test/common/sdk.ts
@@ -7,7 +7,6 @@ import {
   polygon,
   linea,
   lisk,
-  scroll,
   zora,
   sepolia,
 } from "viem/chains";
@@ -22,7 +21,6 @@ export const MAINNET_SUPPORTED_CHAINS = [
   polygon,
   linea,
   lisk,
-  scroll,
   zora,
 ] as const;