fix: replace SAC with SEP-41 terminology

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- Replace generic SAC terminology with SEP-41 across docs, comments, and error messages ([#39](https://github.com/stellar/stellar-mpp-sdk/pull/39))
+
 ### Fixed
 
 - Fix CHANGELOG entries for v0.3.0 ([#36](https://github.com/stellar/stellar-mpp-sdk/pull/36))
@@ -38,7 +40,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Initial release of `@stellar/mpp` — a TypeScript SDK for Stellar blockchain payment methods in the Machine Payments Protocol (MPP)
-- **Charge module**: one-time on-chain SAC token transfers with pull (transaction credential) and push (hash credential) modes, following the [draft-stellar-charge-00](https://paymentauth.org/draft-stellar-charge-00) specification
+- **Charge module**: one-time on-chain SEP-41 token transfers with pull (transaction credential) and push (hash credential) modes, following the [draft-stellar-charge-00](https://paymentauth.org/draft-stellar-charge-00) specification
 - **Channel module**: off-chain payment commitments via one-way payment channel contracts with batch settlement on close (session spec in progress)
 - Subpath exports for selective imports (`@stellar/mpp/charge/client`, `@stellar/mpp/charge/server`, `@stellar/mpp/channel/client`, `@stellar/mpp/channel/server`, `@stellar/mpp/env`)
 - Env parsing primitives for Stellar-aware configuration

CLAUDE.md

@@ -6,7 +6,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 Stellar MPP SDK — a TypeScript SDK implementing Stellar blockchain payment methods for the Machine Payments Protocol (MPP). Provides two payment modes:
 
-- **Charge**: One-time on-chain SAC (Stellar Asset Contract) token transfers with pull/push credential modes
+- **Charge**: One-time on-chain SEP-41 token transfers with pull/push credential modes
 - **Channel**: Off-chain payment commitments via one-way payment channel contracts (batch settlement on close)
 
 Built on the `mppx` framework. Peer dependencies: `@stellar/stellar-sdk` (^14.6.1) and `mppx` (^0.4.11).
@@ -110,8 +110,8 @@ Methods.ts (Zod schema) → client/ (create credentials) + server/ (verify crede
 | Path                                | Role                                                                                                                               |
 | ----------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------- |
 | `sdk/src/charge/Methods.ts`         | Charge method schema (Zod discriminated union: `transaction` vs `hash` credentials)                                                |
-| `sdk/src/charge/client/Charge.ts`   | Creates SAC `transfer` invocations; handles pull (send XDR) and push (broadcast + send hash) flows                                 |
-| `sdk/src/charge/server/Charge.ts`   | Verifies and broadcasts SAC transfers; supports fee sponsorship via FeeBumpTransaction                                             |
+| `sdk/src/charge/client/Charge.ts`   | Creates SEP-41 `transfer` invocations; handles pull (send XDR) and push (broadcast + send hash) flows                              |
+| `sdk/src/charge/server/Charge.ts`   | Verifies and broadcasts SEP-41 transfers; supports fee sponsorship via FeeBumpTransaction                                          |
 | `sdk/src/channel/Methods.ts`        | Channel method schema (discriminated union: `open` / `voucher` / `close` actions)                                                  |
 | `sdk/src/channel/client/Channel.ts` | Signs cumulative commitment amounts off-chain via ed25519; handles `open` action (sends signed deploy tx XDR + initial commitment) |
 | `sdk/src/channel/server/Channel.ts` | Verifies commitment signatures via contract simulation; `open` action broadcasts the deploy tx and initialises cumulative store    |
@@ -158,7 +158,7 @@ All other `shared/` modules are strictly internal and consumed only by `charge/`
 
 - **mppx integration**: Methods defined via `Method.from()`, adapted with `.toClient()` / `.toServer()`. Namespaced as `stellar.charge()` and `stellar.channel()`.
 - **Serialization locks**: Both Charge and Channel servers use Promise-based locks (`let verifyLock: Promise<unknown> = Promise.resolve()`) to serialize verification and prevent race conditions on store get/put.
-- **Contract simulation**: Uses Soroban RPC `simulateTransaction` for read-only verification — SAC transfer validation, `prepare_commitment` for commitment bytes, and channel state queries.
+- **Contract simulation**: Uses Soroban RPC `simulateTransaction` for read-only verification — SEP-41 transfer validation, `prepare_commitment` for commitment bytes, and channel state queries.
 - **Zod validation**: All method schemas use Zod v4 with discriminated unions for credential/action types.
 - **Shared utility extraction**: Common logic (polling, fee bumps, simulation, keypair resolution, validation, error types, logging) lives in `shared/` and is imported by both `charge/` and `channel/`.
 - **Configurable defaults**: Server and client functions accept optional parameters (`pollMaxAttempts`, `pollDelayMs`, `pollTimeoutMs`, `simulationTimeoutMs`, `maxFeeBumpStroops`, `logger`) with defaults from `shared/defaults.ts`, applied via parameter destructuring.

README.md

@@ -1,6 +1,6 @@
 # @stellar/mpp
 
-Stellar blockchain payment method for the [Machine Payments Protocol (MPP)](https://mpp.dev). Enables machine-to-machine payments using Soroban SAC token transfers on the Stellar network, with optional support for [one-way payment channels](https://github.com/stellar-experimental/one-way-channel) for high-frequency off-chain payments.
+Stellar blockchain payment method for the [Machine Payments Protocol (MPP)](https://mpp.dev). Enables machine-to-machine payments using Soroban SEP-41 token transfers on the Stellar network, with optional support for [one-way payment channels](https://github.com/stellar-experimental/one-way-channel) for high-frequency off-chain payments.
 
 ## Specification
 
@@ -10,7 +10,7 @@ The charge payment mode implements the [draft-stellar-charge-00](https://payment
 
 ### Charge (one-time transfers)
 
-Each payment is a Soroban SAC `transfer` settled on-chain individually.
+Each payment is a Soroban SEP-41 `transfer` settled on-chain individually.
 
 ```
 Client                          Server                         Stellar
@@ -23,7 +23,7 @@ Client                          Server                         Stellar
   |<------------------------------|                               |
   |                               |                               |
   |  prepareTransaction ----------------- (simulate) ------------>|
-  |  Sign SAC transfer            |                               |
+  |  Sign SEP-41 transfer          |                               |
   |  Send credential (XDR)        |                               |
   |------------------------------>|                               |
   |                               |  sendTransaction ------------>|
@@ -232,7 +232,7 @@ const data = await response.json()
 ```ts
 stellar.charge({
   recipient: string,              // Stellar public key (G...) or contract (C...)
-  currency: string,               // SAC contract address
+  currency: string,               // SEP-41 token contract address
   network?: 'stellar:testnet' | 'stellar:pubnet', // default: 'stellar:testnet'
   decimals?: number,              // default: 7
   rpcUrl?: string,                // custom Soroban RPC URL

demo/README.md

@@ -4,7 +4,7 @@ Interactive playground for testing the Stellar MPP payment flow — via browser
 
 Two demo modes are available:
 
-- **Charge** — one-time on-chain SAC token transfers (default)
+- **Charge** — one-time on-chain SEP-41 token transfers (default)
 - **Channel** — off-chain payment channel commitments (no on-chain tx per payment)
 
 ## Prerequisites
@@ -82,7 +82,7 @@ Client                          Server
   |   currency, recipient)        |
   |<------------------------------|
   |                               |
-  |  Sign Soroban SAC transfer    |
+  |  Sign Soroban SEP-41 transfer |
   |  Send credential (XDR/hash)   |
   |------------------------------>|
   |                               |

diagrams/charge-flow.md

@@ -1,4 +1,4 @@
-# Charge Payment Flow — On-Chain SAC Transfer
+# Charge Payment Flow — On-Chain SEP-41 Transfer
 
 > Implements [draft-stellar-charge-00](https://paymentauth.org/draft-stellar-charge-00)
 
@@ -18,7 +18,7 @@ sequenceDiagram
     SC-->>App: 402 + Challenge JSON<br/>{amount, currency, recipient, methodDetails}
 
     App->>CC: createCredential(challenge)
-    CC->>CC: Resolve network, build SAC transfer(from, to, amount)
+    CC->>CC: Resolve network, build SEP-41 transfer(from, to, amount)
 
     alt Pull Mode — Sponsored (feePayer: true, default when server has feePayer)
         Note over CC: Uses all-zeros source account (GAAA...WHF)<br/>so server can substitute its own account
@@ -29,7 +29,7 @@ sequenceDiagram
         CC->>CC: Sign only sorobanCredentialsAddress<br/>auth entries (not the envelope)
         CC-->>App: Credential {type:'transaction', transaction: xdr}
         App->>SC: Credential with auth-entry-signed XDR
-        SC->>SC: verifySacInvocation(tx) — validate structure
+        SC->>SC: verifyTokenInvocation(tx) — validate structure
         SC->>SC: Detect all-zeros source → spec rebuild path
         SC->>RPC: getAccount(feePayerKey)
         RPC-->>SC: Server account with current sequence
@@ -51,7 +51,7 @@ sequenceDiagram
         CC->>CC: keypair.sign(preparedTx)
         CC-->>App: Credential {type:'transaction', transaction: xdr}
         App->>SC: Credential with fully-signed XDR
-        SC->>SC: verifySacInvocation(tx) — validate structure
+        SC->>SC: verifyTokenInvocation(tx) — validate structure
         SC->>RPC: simulateTransaction(signedTx)
         RPC-->>SC: Verify transfer events match challenge
         SC->>RPC: sendTransaction(signedTx as-is)
@@ -71,7 +71,7 @@ sequenceDiagram
         App->>SC: Credential with tx hash
         SC->>RPC: getTransaction(hash)
         RPC-->>SC: TX result
-        SC->>SC: verifySacTransfer(result) — verify on-chain
+        SC->>SC: verifyTokenTransfer(result) — verify on-chain
         SC-->>App: Receipt {status:'success', reference:hash}
     end
 ```

diagrams/mindmap.md

@@ -40,8 +40,8 @@ mindmap
         defaults hook: currency + recipient
         request hook: toBaseUnits, UUID, methodDetails
         verify hook
-          Pull: verifySacInvocation → broadcast → poll
-          Push: fetch tx → verifySacTransfer
+          Pull: verifyTokenInvocation → broadcast → poll
+          Push: fetch tx → verifyTokenTransfer
           Fee-bump wrapping
           Replay protection via Store
       Channel — channel/server/Channel.ts

examples/charge-client.ts

@@ -2,7 +2,7 @@
  * Example: Stellar MPP Client
  *
  * Automatically handles 402 Payment Required responses by paying
- * via Soroban SAC transfer on Stellar testnet.
+ * via Soroban SEP-41 transfer on Stellar testnet.
  *
  * Usage:
  *   STELLAR_SECRET=SYOUR_SECRET_KEY npx tsx examples/charge-client.ts

examples/charge-server.ts

@@ -1,7 +1,7 @@
 /**
  * Example: Stellar MPP Server
  *
- * Charges 0.01 USDC per request via Soroban SAC transfer.
+ * Charges 0.01 USDC per request via Soroban SEP-41 transfer.
  * Uses Express with security headers (helmet, rate limiting).
  *
  * Usage:

sdk/src/charge/Methods.ts

@@ -2,11 +2,11 @@ import { Method } from 'mppx'
 import { z } from 'zod/mini'
 
 /**
- * Stellar charge intent for one-time SAC token transfers.
+ * Stellar charge intent for one-time SEP-41 token transfers.
  *
  * Supports two credential flows:
  * - `type: "transaction"` — **server-broadcast** (pull mode):
- *   Client signs a Soroban SAC `transfer` invocation and sends the
+ *   Client signs a Soroban SEP-41 `transfer` invocation and sends the
  *   serialised XDR as `payload.transaction`. The server broadcasts it.
  * - `type: "hash"` — **client-broadcast** (push mode):
  *   Client broadcasts itself and sends the transaction hash.
@@ -29,7 +29,7 @@ export const charge = Method.from({
     request: z.object({
       /** Payment amount in base units (stroops). */
       amount: z.string(),
-      /** SAC contract address (C...) for the token to transfer. */
+      /** SEP-41 token contract address (C...) for the token to transfer. */
       currency: z.string(),
       /** Recipient Stellar public key (G...) or contract address (C...). */
       recipient: z.string(),

sdk/src/charge/client/Charge.ts

@@ -36,7 +36,7 @@ import {
 /**
  * Creates a Stellar charge method for use on the **client**.
  *
- * Builds a Soroban SAC `transfer` invocation, signs it, and either:
+ * Builds a Soroban SEP-41 `transfer` invocation, signs it, and either:
  * - **pull** (default): sends the signed XDR to the server to broadcast
  * - **push**: broadcasts itself and sends the tx hash
  *
@@ -101,7 +101,7 @@ export function charge(parameters: charge.Parameters) {
       const networkPassphrase = NETWORK_PASSPHRASE[network]
       const server = new rpc.Server(resolvedRpcUrl)
 
-      // Build SAC `transfer(from, to, amount)` invocation
+      // Build SEP-41 `transfer(from, to, amount)` invocation
       const contract = new Contract(currency)
       const stellarAmount = BigInt(amount)
 

sdk/src/charge/server/Charge.test.ts

@@ -371,7 +371,7 @@ describe('charge transaction verification', () => {
 
     await expect(
       method.verify({ credential: cred as any, request: cred.challenge.request }),
-    ).rejects.toThrow('matching SAC transfer invocation')
+    ).rejects.toThrow('matching SEP-41 transfer invocation')
   })
 
   it('rejects transaction with wrong amount', async () => {
@@ -395,7 +395,7 @@ describe('charge transaction verification', () => {
 
     await expect(
       method.verify({ credential: cred as any, request: cred.challenge.request }),
-    ).rejects.toThrow('matching SAC transfer invocation')
+    ).rejects.toThrow('matching SEP-41 transfer invocation')
   })
 
   it('rejects transaction with wrong currency', async () => {
@@ -420,7 +420,7 @@ describe('charge transaction verification', () => {
 
     await expect(
       method.verify({ credential: cred as any, request: cred.challenge.request }),
-    ).rejects.toThrow('matching SAC transfer invocation')
+    ).rejects.toThrow('matching SEP-41 transfer invocation')
   })
 
   it('rejects sponsored source without feePayer configured', async () => {

sdk/src/charge/server/Charge.ts

@@ -41,7 +41,7 @@
 /**
  * Creates a Stellar charge method for use on the **server**.
  *
- * Verifies and settles Soroban SAC `transfer` invocations received as
+ * Verifies and settles Soroban SEP-41 `transfer` invocations received as
  * pull-mode (signed XDR) or push-mode (on-chain tx hash) credentials.
  *
  * @see https://paymentauth.org/draft-stellar-charge-00
@@ -93,7 +93,7 @@
     },
     async verify({ credential }) {
       // Serialize through the lock to prevent concurrent race conditions
       const result = await new Promise<any>((resolve, reject) => {
         verifyLock = verifyLock.then(
           () => doVerify(credential).then(resolve, reject),
           () => doVerify(credential).then(resolve, reject),
@@ -103,7 +103,7 @@
     },
   })
 
   async function doVerify(credential: any) {
     const { challenge } = credential
     const { request: challengeRequest } = challenge
 
@@ -161,7 +161,7 @@
           timeoutMs: pollTimeoutMs,
         })
 
-        verifySacTransfer(
+        verifyTokenTransfer(
           txResult,
           {
             amount: expectedAmount,
@@ -195,7 +195,7 @@
 
         verifyExactlyOneInvokeOp(tx)
 
-        verifySacInvocation(tx, {
+        verifyTokenInvocation(tx, {
           amount: expectedAmount,
           currency: expectedCurrency,
           recipient: expectedRecipient,
@@ -485,7 +485,7 @@
   }
 }
 
-function verifySacInvocation(
+function verifyTokenInvocation(
   tx: Transaction,
   expected: { amount: bigint; currency: string; recipient: string },
 ) {
@@ -534,7 +534,7 @@
 
   if (!found) {
     throw new PaymentVerificationError(
-      `${LOG_PREFIX} Transaction does not contain a matching SAC transfer invocation.`,
+      `${LOG_PREFIX} Transaction does not contain a matching SEP-41 transfer invocation.`,
       {
         currency: expected.currency,
         recipient: expected.recipient,
@@ -544,7 +544,7 @@
   }
 }
 
-function verifySacTransfer(
+function verifyTokenTransfer(
   txResult: rpc.Api.GetSuccessfulTransactionResponse,
   expected: { amount: bigint; currency: string; recipient: string },
   networkPassphrase: string,

sdk/src/constants.ts

@@ -32,22 +32,22 @@ export const HORIZON_URLS: Record<NetworkId, string> = {
 }
 
 // ---------------------------------------------------------------------------
-// USDC Stellar Asset Contract (SAC) addresses
+// USDC SEP-41 token contract addresses (SAC)
 // ---------------------------------------------------------------------------
 
-/** USDC SAC contract address on Stellar mainnet. */
+/** USDC SEP-41 token contract address on Stellar mainnet (SAC). */
 export const USDC_SAC_MAINNET = 'CCW67TSZV3SSS2HXMBQ5JFGCKJNXKZM7UQUWUZPUTHXSTZLEO7SJMI'
 
-/** USDC SAC contract address on Stellar testnet. */
+/** USDC SEP-41 token contract address on Stellar testnet (SAC). */
 export const USDC_SAC_TESTNET = 'CBIELTK6YBZJU5UP2WWQEUCYKLPU6AUNZ2BQ4WWFEIE3USCIHMXQDAMA'
 
-/** Native XLM SAC contract address on mainnet. */
+/** Native XLM SEP-41 token contract address on mainnet (SAC). */
 export const XLM_SAC_MAINNET = 'CAS3J7GYLGVE45MR3HPSFG352DAANEV5GGMFTO3IZIE4JMCDALQO57Y'
 
-/** Native XLM SAC contract address on testnet. */
+/** Native XLM SEP-41 token contract address on testnet (SAC). */
 export const XLM_SAC_TESTNET = 'CDLZFC3SYJYDZT7K67VZ75HPJVIEUVNIXF47ZG2FB2RMQQVU2HHGCYSC'
 
-/** Map from network to well-known SAC addresses. */
+/** Map from network to well-known SEP-41 token addresses. */
 export const SAC_ADDRESSES = {
   [STELLAR_PUBNET]: {
     USDC: USDC_SAC_MAINNET,