Sentinel

Programmable compliance for Token-2022 tokenized assets — built on Transfer Hooks.

Sentinel attaches compliance rules to a Token-2022 mint so every transfer is checked on-chain: an allowlist, a blocklist (sender, recipient, and a delegate moving someone else's tokens), and a per-transfer limit — all toggled by a per-mint policy the issuer controls. Regulated and real-world-asset (RWA) tokens can enforce who may hold and move them, without giving up composability.

Confidential transfers. Token-2022 hides the amount of a confidential transfer from the hook, which means an amount limit cannot be enforced on one — it is unenforceable, not satisfied. So a mint that sets maxTransferAmount refuses confidential transfers unless its policy also sets allowConfidential, which is the issuer accepting in the open that the limit does not reach them. The allowlist and blocklist work on addresses, which stay public, so they apply to confidential transfers exactly as they do to public ones.

Status: v2.0.2 — stable API, self-audited, deployed on Solana devnet (not independently audited). Built by Softseco.

Devnet program: 5fH1jj6XeZC96jPCxKiSb2onAXcs7f4rMeqMmSsP6puD

Why

Token-2022's Transfer Hook extension runs a program on every transfer. Sentinel turns that hook into a reusable, configurable compliance engine, so issuers don't have to write and audit their own transfer-gating program. Set a policy once; Sentinel enforces it on every move of the asset.

What's here

• On-chain program (Rust / Anchor) — the transfer hook + policy, allowlist, blocklist, limit; a two-step handover of the policy authority (to a multisig, for example); an event for every policy change and every refused transfer. 44 integration tests on a local validator, 11 of them with real Token-2022 confidential transfers, where Token-2022 itself calls the hook. CI runs all of them on every push.
• Threat model — docs/threat-model.md: what Sentinel protects, who is trusted, the invariants it keeps, and its known limits.
• TypeScript SDK — @softseco/sentinel: create a compliant mint, manage the policy and entries, hook-aware transfers, and reads.
• Runnable demo — sdk/examples/compliant-asset-demo.ts.

Quickstart (SDK)

npm install @softseco/sentinel

import { SentinelClient } from "@softseco/sentinel";

const sentinel = new SentinelClient(provider); // AnchorProvider

await sentinel.createCompliantMint({ mint, decimals: 0 });
await sentinel.initializePolicy({ mint: mint.publicKey, allowlist: true, blocklist: true, maxTransferAmount: 1000n });
await sentinel.initializeExtraAccountMetaList(mint.publicKey);
await sentinel.addToAllowlist(mint.publicKey, investor);
await sentinel.transfer({ mint: mint.publicKey, destinationOwner: investor, amount: 100n, decimals: 0 });

Demo

A compliant "ACME" security token, gated live:

Terminal 1:  anchor localnet          # validator + deployed program
Terminal 2:  cd sdk && npm install && npm run demo

✅ Issuer → Alice    500   (allowlisted, within limit)
⛔ Issuer → Carol    500   → recipient not allowlisted
⛔ Issuer → Alice   2000   → exceeds transfer limit
⛔ Issuer → Mallory  100   → recipient sanctioned
✅ Issuer → Alice   2000   (now within the new limit, after a policy update)

Repository layout

programs/sentinel/   on-chain Anchor program
sdk/                 @softseco/sentinel TypeScript SDK (+ examples/)
tests/               integration tests (anchor test)

Status

v2.1.0 — program + SDK + demo, 44 integration tests, self-audited before release (see CHANGELOG.md · SECURITY.md · threat model). Not independently audited. The devnet program runs 2.1.0 since 12 October 2026; mints set up before 2.1 call update_extra_account_meta_list once to get the delegate check. Breaking since 1.0.0: PolicyConfig gained allow_confidential and existing policy accounts must be recreated. A confidential transfer through a Sentinel mint, with the blocklist enforced on the same transfer, runs end-to-end on devnet in paper-devnet.

Local development

anchor build -- --tools-version v1.57                                   # program
anchor idl build -o sdk/src/idl/sentinel.json -t sdk/src/idl/sentinel.ts  # IDL
anchor test --skip-build                                                # 44 integration tests
cd sdk && npm install && npm run build                                  # SDK

Requires the Anchor toolchain (0.31.0), Solana CLI, and Node ≥ 20. The --tools-version flag is needed because the default platform-tools build cannot parse Rust edition-2024 dependencies, and the IDL step is run separately because that flag is not valid there — see CONTRIBUTING.md.

License

Apache-2.0. See LICENSE.