diff --git a/src/lib/LibAuthoriserInvariants.sol b/src/lib/LibAuthoriserInvariants.sol
new file mode 100644
index 00000000..141dfa9d
--- /dev/null
+++ b/src/lib/LibAuthoriserInvariants.sol
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: LicenseRef-DCL-1.0
+// SPDX-FileCopyrightText: Copyright (c) 2020 Rain Open Source Software Ltd
+pragma solidity ^0.8.25;
+
+import {IAccessControl} from "@openzeppelin-contracts-5.6.1/access/IAccessControl.sol";
+import {LibSafeInvariants} from "./LibSafeInvariants.sol";
+
+/// @notice A pinned `(role, grantee)` pair on the live authoriser.
+struct RoleGrant {
+    bytes32 role;
+    address grantee;
+}
+
+/// @notice An expected `(role, grantee)` pair is not held on the authoriser.
+/// Surfaces the exact pair that breaks the role-grant invariant rather than
+/// a generic mismatch.
+/// @param authoriser The authoriser address inspected.
+/// @param role The role that should be held.
+/// @param grantee The grantee that should hold the role.
+error ExpectedGrantMissing(address authoriser, bytes32 role, address grantee);
+
+/// @title LibAuthoriserInvariants
+/// @notice Reusable invariants for the ST0x production authoriser on Base:
+/// the pinned current-state authoriser address, the expected impl behind
+/// it, the grantee constants, and the full `(role, grantee)` map enumerated
+/// from `RoleGranted` / `RoleRevoked` events on-chain. Each assertion
+/// either returns silently when the invariant holds against the live chain
+/// state or reverts with a typed error that pinpoints the drift.
+/// @dev Owns both the current-state pins and the assert functions. When the
+/// authoriser-swap script lands and the live authoriser changes, the pins
+/// here are updated (current → new clone address + new impl) so future
+/// `assertAll` runs validate the new live state. The role-grant map
+/// (`expectedGrants`) does not change pre / post swap because the swap
+/// mirrors the same grants forward.
+///
+/// Composed into `LibInvariants.assertAll` alongside `LibSafeInvariants`
+/// and `LibTokenInvariants`; individually callable via `assertAll()` for
+/// the focused authoriser drift detector.
+///
+/// The V4 clone deploy target (the address the upcoming swap script
+/// `setAuthorizer`s every receipt vault onto) does **not** live here —
+/// that's a deploy artifact, pinned in `LibProdDeployV4`. This lib only
+/// holds what the live authoriser **should** look like today.
+library LibAuthoriserInvariants {
+    /// @notice The current live ST0x authoriser clone on Base. Every
+    /// production receipt vault's `authorizer()` returns this address.
+    /// Pinned as the current-state invariant; updated post-swap when the
+    /// receipt vaults are rewired onto a new authoriser clone, so future
+    /// runs of `assertAll` validate the new live state.
+    /// https://basescan.org/address/0x35f9fa9d80aaf2b0fb27f0ff015641b3408d7456
+    address internal constant STOX_PROD_AUTHORISER = 0x35f9fA9d80aAF2B0fB27f0FF015641B3408d7456;
+
+    /// @notice The implementation behind the live clone. A base
+    /// `OffchainAssetReceiptVaultAuthorizerV1` from rain-vats that predates
+    /// the corporate-action role-admin extension. Pinned as the
+    /// current-state invariant; updated alongside `STOX_PROD_AUTHORISER`
+    /// when the live clone changes.
+    /// https://basescan.org/address/0x2b4a510c3619d5e888095bfe9f95902d32da5556
+    address internal constant STOX_PROD_AUTHORISER_IMPL = 0x2B4A510c3619d5E888095BFE9f95902D32dA5556;
+
+    /// @notice The base role-admin hierarchy used by the live authoriser
+    /// sets `<ROLE>_ADMIN` as the admin of each action role rather than
+    /// `DEFAULT_ADMIN_ROLE`. Consequently no `DEFAULT_ADMIN_ROLE` grant was
+    /// emitted at init and no address holds it. Pinned as the explicit
+    /// expectation so the invariant flags any future grant of
+    /// `DEFAULT_ADMIN_ROLE` as unexpected.
+    bytes32 internal constant DEFAULT_ADMIN_ROLE = bytes32(0);
+
+    /// @notice The ST0x token-owner Safe — holds every `_ADMIN` role on the
+    /// live authoriser (set at init) and was later granted DEPOSIT, WITHDRAW
+    /// and CERTIFY as a privileged operator. Identical to
+    /// `LibSafeInvariants.STOX_TOKEN_OWNER_SAFE`; re-exported as a grantee
+    /// constant for call-site clarity.
+    address internal constant GRANTEE_TOKEN_OWNER_SAFE = LibSafeInvariants.STOX_TOKEN_OWNER_SAFE;
+
+    /// @notice External service EOA granted `DEPOSIT` (block 41797262),
+    /// `WITHDRAW` (block 41797281) and `CERTIFY` (block 41797297) shortly
+    /// after the first service was provisioned. EOA, active service signer.
+    /// @dev TODO: confirm identity and rename.
+    /// https://basescan.org/address/0x1c66d6708914c40239d54919320b4c48cae3d1a9
+    address internal constant GRANTEE_SERVICE_1C66 = 0x1c66D6708914C40239D54919320b4C48cAE3D1A9;
+
+    /// @notice The full `(role, grantee)` map in effect on the live
+    /// authoriser. Source of truth folded from `RoleGranted` /
+    /// `RoleRevoked` event scan on Base. The 11 entries split into: 5
+    /// `_ADMIN` roles held by the token-owner Safe (set at init), 3 action
+    /// roles for the service EOA, 3 action roles the Safe later granted
+    /// itself for direct operational use.
+    /// @return grants The pinned `(role, grantee)` pairs.
+    function expectedGrants() internal pure returns (RoleGrant[] memory grants) {
+        grants = new RoleGrant[](11);
+
+        // Init grants (block 41715184) — Safe receives every `_ADMIN` role.
+        grants[0] = RoleGrant(keccak256("DEPOSIT_ADMIN"), GRANTEE_TOKEN_OWNER_SAFE);
+        grants[1] = RoleGrant(keccak256("WITHDRAW_ADMIN"), GRANTEE_TOKEN_OWNER_SAFE);
+        grants[2] = RoleGrant(keccak256("CERTIFY_ADMIN"), GRANTEE_TOKEN_OWNER_SAFE);
+        grants[3] = RoleGrant(keccak256("CONFISCATE_SHARES_ADMIN"), GRANTEE_TOKEN_OWNER_SAFE);
+        grants[4] = RoleGrant(keccak256("CONFISCATE_RECEIPT_ADMIN"), GRANTEE_TOKEN_OWNER_SAFE);
+
+        // Service EOA provisioned at blocks 41797262, 41797281, 41797297.
+        grants[5] = RoleGrant(keccak256("DEPOSIT"), GRANTEE_SERVICE_1C66);
+        grants[6] = RoleGrant(keccak256("WITHDRAW"), GRANTEE_SERVICE_1C66);
+        grants[7] = RoleGrant(keccak256("CERTIFY"), GRANTEE_SERVICE_1C66);
+
+        // Safe later granted itself the corresponding action roles (blocks
+        // 42704120, 42704140, 44076075) for direct operational use.
+        grants[8] = RoleGrant(keccak256("DEPOSIT"), GRANTEE_TOKEN_OWNER_SAFE);
+        grants[9] = RoleGrant(keccak256("WITHDRAW"), GRANTEE_TOKEN_OWNER_SAFE);
+        grants[10] = RoleGrant(keccak256("CERTIFY"), GRANTEE_TOKEN_OWNER_SAFE);
+    }
+
+    /// @notice Assert every pinned `(role, grantee)` pair in
+    /// `expectedGrants()` is held on the supplied authoriser. Reverts with
+    /// `ExpectedGrantMissing` on the first pair that fails, surfacing the
+    /// exact role + grantee that broke the invariant.
+    /// @dev Parameterised on the authoriser address so the same assertion
+    /// can run against the live current clone (pre-swap) AND against a
+    /// freshly-deployed clone (the script's pre-flight on the swap target)
+    /// without duplicating the iteration.
+    /// @param authoriser The authoriser to validate.
+    function assertExpectedGrants(address authoriser) internal view {
+        IAccessControl acl = IAccessControl(authoriser);
+        RoleGrant[] memory grants = expectedGrants();
+        for (uint256 i = 0; i < grants.length; i++) {
+            if (!acl.hasRole(grants[i].role, grants[i].grantee)) {
+                revert ExpectedGrantMissing(authoriser, grants[i].role, grants[i].grantee);
+            }
+        }
+    }
+
+    /// @notice Full authoriser-side invariant bundle against the live
+    /// pinned `STOX_PROD_AUTHORISER`. Pre-flight at the start of every
+    /// migration script and prod-state fork test; if this passes silently
+    /// the live authoriser is in its current expected state.
+    /// @dev No-arg overload uses the lib's `STOX_PROD_AUTHORISER` constant.
+    /// Composed into `LibInvariants.assertAll`.
+    function assertAll() internal view {
+        assertExpectedGrants(STOX_PROD_AUTHORISER);
+    }
+}
diff --git a/src/lib/LibInvariants.sol b/src/lib/LibInvariants.sol
index d0c4cb72..cfcf73eb 100644
--- a/src/lib/LibInvariants.sol
+++ b/src/lib/LibInvariants.sol
@@ -3,6 +3,7 @@
 pragma solidity ^0.8.25;
 
 import {IGnosisSafe} from "../interface/IGnosisSafe.sol";
+import {LibAuthoriserInvariants} from "./LibAuthoriserInvariants.sol";
 import {LibSafeInvariants} from "./LibSafeInvariants.sol";
 import {LibTokenInvariants} from "./LibTokenInvariants.sol";
 
@@ -33,20 +34,22 @@ library LibInvariants {
     /// @param safe The Safe to validate against the pinned current truth.
     function assertAll(IGnosisSafe safe) internal view {
         LibSafeInvariants.assertAll(safe);
-        LibTokenInvariants.assertAll(address(safe), LibTokenInvariants.STOX_PROD_AUTHORISER);
+        LibTokenInvariants.assertAll(address(safe), LibAuthoriserInvariants.STOX_PROD_AUTHORISER);
+        LibAuthoriserInvariants.assertAll();
     }
 
     /// @notice Full-args bundle. Use when overriding the Safe-side
     /// threshold or owner set from `LibSafeInvariants`' current-truth pins —
     /// typically only when running a script that intentionally changes
-    /// one of those (post-state assertion). The token-side leg uses the
-    /// pinned defaults (vault ownership against the Safe, authoriser
-    /// against `LibTokenInvariants.STOX_PROD_AUTHORISER`).
+    /// one of those (post-state assertion). The token-side and authoriser-
+    /// side legs use the pinned current-truth defaults from
+    /// `LibAuthoriserInvariants.STOX_PROD_AUTHORISER`.
     /// @param safe The Safe to validate.
     /// @param expectedThreshold The expected signature threshold.
     /// @param expectedOwners The expected owner set in `getOwners()` order.
     function assertAll(IGnosisSafe safe, uint256 expectedThreshold, address[] memory expectedOwners) internal view {
         LibSafeInvariants.assertAll(safe, expectedThreshold, expectedOwners);
-        LibTokenInvariants.assertAll(address(safe), LibTokenInvariants.STOX_PROD_AUTHORISER);
+        LibTokenInvariants.assertAll(address(safe), LibAuthoriserInvariants.STOX_PROD_AUTHORISER);
+        LibAuthoriserInvariants.assertAll();
     }
 }
diff --git a/src/lib/LibTokenInvariants.sol b/src/lib/LibTokenInvariants.sol
index e38e550f..cdec7821 100644
--- a/src/lib/LibTokenInvariants.sol
+++ b/src/lib/LibTokenInvariants.sol
@@ -147,15 +147,6 @@ library LibTokenInvariants {
     /// https://basescan.org/address/0x78c31580c97101694c70022c83d570150c11e935
     address internal constant SGOV_WRAPPED_TOKEN_VAULT = address(0x78c31580c97101694C70022c83D570150c11e935);
 
-    /// @notice The single authoriser every production receipt vault is gated
-    /// by, as a token-side invariant. Pinned here as the expected value for
-    /// `assertUniformAuthoriser`; updated post-swap when the receipt vaults
-    /// are rewired onto a new authoriser clone.
-    /// @dev Read from `authorizer()` on the live vaults on Base. A vault
-    /// reporting any other authoriser is gated by a different RBAC contract
-    /// than the rest of the system and trips the invariant.
-    address internal constant STOX_PROD_AUTHORISER = address(0x35f9fA9d80aAF2B0fB27f0FF015641B3408d7456);
-
     /// @notice Returns the 13 production receipt vault addresses on Base, in
     /// the order they were deployed. Provided so consumers (e.g. invariant
     /// assertions, migration scripts) can iterate without hardcoding the
diff --git a/test/src/lib/LibAuthoriserInvariants.t.sol b/test/src/lib/LibAuthoriserInvariants.t.sol
new file mode 100644
index 00000000..6cb7b3d6
--- /dev/null
+++ b/test/src/lib/LibAuthoriserInvariants.t.sol
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: LicenseRef-DCL-1.0
+// SPDX-FileCopyrightText: Copyright (c) 2020 Rain Open Source Software Ltd
+pragma solidity =0.8.25;
+
+import {Test} from "forge-std-1.16.1/src/Test.sol";
+import {LibAuthoriserInvariants} from "../../../src/lib/LibAuthoriserInvariants.sol";
+import {LibRainDeploy} from "rain-deploy-0.1.3/src/lib/LibRainDeploy.sol";
+
+/// @title LibAuthoriserInvariantsTest
+/// @notice Fork tests pinning the live ST0x authoriser's role-grant map
+/// against the constants in `LibAuthoriserInvariants`. The positive case
+/// runs the lib's no-arg `assertAll()`, which iterates `expectedGrants()`
+/// and asserts every pair against the live authoriser pinned at
+/// `STOX_PROD_AUTHORISER`. Any drift (a pin missing on-chain, or an
+/// off-chain pin the lib doesn't know about) surfaces as
+/// `ExpectedGrantMissing` here.
+/// @dev Uses an unpinned Base head fork (same precedent as the other
+/// prod-state drift detectors in this repo). Pinning would freeze the
+/// invariant assertions against a stale snapshot and let new drift slip
+/// through unnoticed.
+contract LibAuthoriserInvariantsTest is Test {
+    /// @notice Selects the Base fork at chain head — deliberately unpinned.
+    /// Live drift detector; see contract-level rationale.
+    function selectBaseFork() internal {
+        vm.createSelectFork(LibRainDeploy.BASE);
+    }
+
+    /// @notice The live authoriser pinned at
+    /// `LibAuthoriserInvariants.STOX_PROD_AUTHORISER` holds every
+    /// `expectedGrants()` pair. Passes against the live chain state.
+    function testAssertAllPasses() external {
+        selectBaseFork();
+        LibAuthoriserInvariants.assertAll();
+    }
+}
diff --git a/test/src/lib/LibTokenInvariants.t.sol b/test/src/lib/LibTokenInvariants.t.sol
index f361392e..b2cdc4d2 100644
--- a/test/src/lib/LibTokenInvariants.t.sol
+++ b/test/src/lib/LibTokenInvariants.t.sol
@@ -3,6 +3,7 @@
 pragma solidity =0.8.25;
 
 import {Test} from "forge-std-1.16.1/src/Test.sol";
+import {LibAuthoriserInvariants} from "../../../src/lib/LibAuthoriserInvariants.sol";
 import {LibTokenInvariants, IOwnable, ReceiptVaultOwnerMismatch} from "../../../src/lib/LibTokenInvariants.sol";
 import {LibSafeInvariants} from "../../../src/lib/LibSafeInvariants.sol";
 import {LibTokenInvariantsHarness} from "./LibTokenInvariantsHarness.sol";
@@ -15,7 +16,7 @@ import {LibRainDeploy} from "rain-deploy-0.1.3/src/lib/LibRainDeploy.sol";
 ///
 /// Both uniformity invariants currently hold on-chain (every vault is
 /// owned by `LibSafeInvariants.STOX_TOKEN_OWNER_SAFE` and reports the pinned
-/// `LibTokenInvariants.STOX_PROD_AUTHORISER`), so the positive
+/// `LibAuthoriserInvariants.STOX_PROD_AUTHORISER`), so the positive
 /// cases pass against the live Base fork. The inverted ownership-drift
 /// case is also exercised here for full error-path coverage.
 /// @dev Uses an unpinned Base head fork (same precedent as the other
@@ -43,11 +44,11 @@ contract LibTokenInvariantsTest is Test {
     }
 
     /// @notice Every production receipt vault reports
-    /// `LibTokenInvariants.STOX_PROD_AUTHORISER`. Passes against
+    /// `LibAuthoriserInvariants.STOX_PROD_AUTHORISER`. Passes against
     /// the live chain state: vault authoriser is uniform.
     function testProdReceiptVaultsShareUniformAuthoriser() external {
         selectBaseFork();
-        LibTokenInvariants.assertUniformAuthoriser(LibTokenInvariants.STOX_PROD_AUTHORISER);
+        LibTokenInvariants.assertUniformAuthoriser(LibAuthoriserInvariants.STOX_PROD_AUTHORISER);
     }
 
     /// @notice Token-side ownership drift trips `ReceiptVaultOwnerMismatch`.