diff --git a/projects/keepkey-vault/__tests__/swap-parsing.test.ts b/projects/keepkey-vault/__tests__/swap-parsing.test.ts
index d0b3aa76..4e1fe1bb 100644
--- a/projects/keepkey-vault/__tests__/swap-parsing.test.ts
+++ b/projects/keepkey-vault/__tests__/swap-parsing.test.ts
@@ -7,7 +7,11 @@
  * Run: bun test __tests__/swap-parsing.test.ts
  */
 import { describe, test, expect } from 'bun:test'
-import { parseQuoteResponse, parseAssetsResponse } from '../src/bun/swap-parsing'
+import {
+  assertSwapMemoFitsSource,
+  parseQuoteResponse,
+  parseAssetsResponse,
+} from '../src/bun/swap-parsing'
 
 // ── Fixtures: Real Pioneer SDK response shapes ──────────────────────
 
@@ -325,6 +329,38 @@ describe('parseQuoteResponse', () => {
     expect(parseFloat(result.minimumOutput)).toBeCloseTo(1.239375, 4)
   })
 
+  test('BTC → USDT: skips an overlong full-contract memo for a compact route', () => {
+    const btcCaip = 'bip122:000000000019d6689c085ae165831e93/slip44:0'
+    const usdtCaip = 'eip155:1/erc20:0xdac17f958d2ee523a2206206994597c13d831ec7'
+    const destination = `0x${'a'.repeat(40)}`
+    const fullMemo = `=:ETH.USDT-0XDAC17F958D2EE523A2206206994597C13D831EC7:${destination}:323592379572:keep:30`
+    const compactMemo = `=:ETH.USDT:${destination}:323592379572:keep:30`
+    const quote = (memo: string, buyAmount: string) => ({
+      integration: 'thorchain',
+      quote: {
+        buyAmount,
+        raw: { inbound_address: 'bc1qvaultaddress' },
+        txs: [{ txParams: { memo, vaultAddress: 'bc1qvaultaddress' } }],
+      },
+    })
+
+    expect(Buffer.byteLength(fullMemo, 'utf8')).toBeGreaterThan(80)
+    expect(Buffer.byteLength(compactMemo, 'utf8')).toBeLessThanOrEqual(80)
+    const result = parseQuoteResponse(
+      { data: [quote(fullMemo, '100'), quote(compactMemo, '99')] },
+      { fromCaip: btcCaip, toCaip: usdtCaip, slippageBps: 300 },
+    )
+    expect(result.memo).toBe(compactMemo)
+    expect(result.expectedOutput).toBe('99')
+  })
+
+  test('UTXO memo limit is measured in bytes, not JavaScript characters', () => {
+    const btcCaip = 'bip122:000000000019d6689c085ae165831e93/slip44:0'
+    expect(() => assertSwapMemoFitsSource('a'.repeat(80), btcCaip)).not.toThrow()
+    expect(() => assertSwapMemoFitsSource('é'.repeat(41), btcCaip))
+      .toThrow(/82 bytes; maximum 80/)
+  })
+
   // Minimal response (fields at top-level quote, no raw/txs)
   test('minimal: extracts fields from top-level quote properties', () => {
     const params = { fromCaip: 'eip155:1/slip44:60', toCaip: 'bip122:000000000019d6689c085ae165831e93/slip44:0', slippageBps: 300 }
diff --git a/projects/keepkey-vault/src/bun/swap-parsing.ts b/projects/keepkey-vault/src/bun/swap-parsing.ts
index 513374e3..71bfb530 100644
--- a/projects/keepkey-vault/src/bun/swap-parsing.ts
+++ b/projects/keepkey-vault/src/bun/swap-parsing.ts
@@ -10,6 +10,32 @@ import { COIN_MAP_LONG } from '@pioneer-platform/pioneer-coins'
 
 const TAG = '[swap]'
 
+/** THORChain accepts up to 250 bytes globally, but UTXO deposits encode the
+ * memo in a single OP_RETURN output and the KeepKey signer supports 80 bytes.
+ * Keep this source-aware so an otherwise valid quote cannot survive preview
+ * and then fail only after the user confirms on-device. */
+export const GLOBAL_SWAP_MEMO_MAX_BYTES = 250
+export const UTXO_SWAP_MEMO_MAX_BYTES = 80
+
+export function swapMemoLimitForSource(fromCaip: string): number {
+  return fromCaip.startsWith('bip122:')
+    ? UTXO_SWAP_MEMO_MAX_BYTES
+    : GLOBAL_SWAP_MEMO_MAX_BYTES
+}
+
+export function assertSwapMemoFitsSource(memo: string, fromCaip: string): void {
+  if (!memo) return
+  const byteLength = Buffer.byteLength(memo, 'utf8')
+  const limit = swapMemoLimitForSource(fromCaip)
+  if (byteLength <= limit) return
+
+  const source = fromCaip.startsWith('bip122:') ? 'UTXO source chain' : 'swap protocol'
+  throw new Error(
+    `Swap route memo is too long for this ${source} ` +
+    `(${byteLength} bytes; maximum ${limit}). Refresh the quote or choose another route.`,
+  )
+}
+
 function decodeStrictBase64(value: unknown, field: string, maxBytes: number): string {
   if (typeof value !== 'string' || value.length === 0) {
     throw new Error(`Invalid Solana ClearSign metadata: missing ${field}`)
@@ -175,7 +201,8 @@ export function parseQuoteResponse(
 
 /** Parse ONE Pioneer quote entry into SwapQuote. Throws when the quote is not
  *  buildable (zero/empty output, missing inbound address, EVM inbound for a
- *  UTXO source, or no memo/calldata/deposit instruction). */
+ *  UTXO source, source-chain memo overflow, or no memo/calldata/deposit
+ *  instruction). */
 function parseSingleQuote(
   best: any,
   params: { fromCaip: string; toCaip: string; slippageBps?: number },
@@ -301,6 +328,7 @@ function parseSingleQuote(
   // Memo lives in txParams (Pioneer constructs it), fallback to raw
   // Relay quotes don't use memos — the calldata IS the swap instruction
   const memo = txParams.memo || quote.memo || raw.memo || ''
+  assertSwapMemoFitsSource(memo, params.fromCaip)
   // Router: raw.router or txParams.recipientAddress (Pioneer sets recipient = router for EVM)
   const router = raw.router || quote.router || txParams.recipientAddress
   // Vault/inbound address — check both snake_case and camelCase across all layers
diff --git a/projects/keepkey-vault/src/bun/swap.ts b/projects/keepkey-vault/src/bun/swap.ts
index 98c8beeb..4e76cfe0 100644
--- a/projects/keepkey-vault/src/bun/swap.ts
+++ b/projects/keepkey-vault/src/bun/swap.ts
@@ -22,7 +22,12 @@ import { normalizeBchAddress } from './txbuilder'
 // history rows without CAIP). The swap quote/execute path no longer uses it —
 // vault is CAIP-native end-to-end.
 export { parseAssetsResponse, parseQuoteResponse, assetToCaip } from './swap-parsing'
-import { parseQuoteResponse, parseAssetsResponse, isNativeDepositCaip } from './swap-parsing'
+import {
+  assertSwapMemoFitsSource,
+  parseQuoteResponse,
+  parseAssetsResponse,
+  isNativeDepositCaip,
+} from './swap-parsing'
 
 const TAG = '[swap]'
 
@@ -110,12 +115,6 @@ const DEPOSIT_GAS_LIMITS: Record<string, bigint> = {
   optimism: 200000n,
 }
 
-/** Memo length limits — THORChain global limit is 250 bytes.
- *  THORNode constructs memos optimized for source chain constraints (e.g. short
- *  asset names like AVAX.USDT instead of AVAX.USDT-0x...) so we trust the memo
- *  from Pioneer/THORNode and only enforce the THORChain protocol limit. */
-const MEMO_LIMIT = 250
-
 // Router/inbound-address validation belongs in pioneer-router (which runs
 // each integration's own checks before returning a quote). The vault trusts
 // the router string Pioneer hands back. Kept here as a comment so future
@@ -630,12 +629,7 @@ export async function executeSwap(params: ExecuteSwapParams, ctx: SwapContext):
   const isMemolessTransfer = (fromIsUtxo || fromIsSolana) && !!params.inboundAddress && !params.memo
   if (!params.inboundAddress && !isNativeDeposit && !hasPrebuiltTx) throw new Error('Missing inbound vault address from quote')
   if (!params.memo && !hasPrebuiltTx && !isMemolessTransfer) throw new Error('Missing swap memo from quote')
-  if (params.memo) {
-    const memoByteLength = Buffer.byteLength(params.memo, 'utf8')
-    if (memoByteLength > MEMO_LIMIT) {
-      throw new Error(`Swap memo too long (${memoByteLength} bytes, THORChain max ${MEMO_LIMIT})`)
-    }
-  }
+  assertSwapMemoFitsSource(params.memo, params.fromCaip)
 
   swapLog(`${TAG} Executing: ${params.fromCaip} → ${params.toCaip}, amount=${params.amount}`)
   if (hasPrebuiltTx) {
@@ -1005,6 +999,7 @@ export async function previewSwapBuild(
   const isMemolessTransfer = (fromIsUtxoPreview || fromIsSolanaPreview) && !!params.inboundAddress && !params.memo
   if (!params.inboundAddress && !isNativeDeposit && !hasPrebuiltTx) throw new Error('Missing inbound vault address from quote')
   if (!params.memo && !hasPrebuiltTx && !isMemolessTransfer) throw new Error('Missing swap memo from quote')
+  assertSwapMemoFitsSource(params.memo, params.fromCaip)
 
   const pioneer = await getPioneer()
 
diff --git a/projects/keepkey-vault/src/mainview/components/SwapDialog.tsx b/projects/keepkey-vault/src/mainview/components/SwapDialog.tsx
index f2da72f6..749e60db 100644
--- a/projects/keepkey-vault/src/mainview/components/SwapDialog.tsx
+++ b/projects/keepkey-vault/src/mainview/components/SwapDialog.tsx
@@ -2240,6 +2240,8 @@ export function SwapDialog({ open, onClose, chain, balance, address, resumeSwap,
         friendly = t("approvalReverted", "Approval reverted on-chain — swap aborted to protect funds")
       } else if (/Insufficient.*for gas|insufficient funds/i.test(raw)) {
         friendly = t("insufficientGas", "Not enough gas in the source chain's native asset")
+      } else if (/OP_RETURN.*(?:character count|too .* high)|memo is too long/i.test(raw)) {
+        friendly = t("swapMemoTooLong", "This route returned a memo that is too long for the source chain. Refresh the quote or choose another route.")
       } else if (/nonce|fetch nonce/i.test(raw)) {
         friendly = t("nonceError", "Network error fetching nonce — retry in a moment")
       } else if (/timed out|ETIMEDOUT|fetch failed|network/i.test(raw)) {