feat: Base Sepolia internal funding and controlled test USDC

Cargo.toml

@@ -13,6 +13,7 @@ axum = "0.7.9"
 seismic-alloy-network = { git = "https://github.com/SeismicSystems/seismic-alloy.git", rev = "c8fad0b93da53f2b423d2f6720abdb4a6cbb9082" }
 seismic-alloy-provider = { git = "https://github.com/SeismicSystems/seismic-alloy.git", rev = "c8fad0b93da53f2b423d2f6720abdb4a6cbb9082" }
 seismic-alloy-rpc-types = { git = "https://github.com/SeismicSystems/seismic-alloy.git", rev = "c8fad0b93da53f2b423d2f6720abdb4a6cbb9082" }
+alloy-consensus = "=1.1.0"
 alloy-contract = "=1.1.0"
 alloy-chains = "=0.2.17"
 alloy-eips = "=1.1.0"

contracts/script/DeployBaseTestnetUSDC.s.sol

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+pragma solidity ^0.8.30;
+
+import {Script, console} from "forge-std/Script.sol";
+import {TestnetUSDC} from "../src/TestnetUSDC.sol";
+
+/// @notice Deploys the controlled six-decimal test USDC on Base Sepolia and
+/// mints the initial supply into the machine-funding reserve. There is no
+/// faucet contract on Base: the reserve key transfers directly, so the
+/// reserve holds the tokens and the deployer keeps mint authority.
+contract DeployBaseTestnetUSDCScript is Script {
+    uint256 internal constant DEFAULT_INITIAL_RESERVE_SUPPLY = 1_000_000e6;
+
+    function run() external {
+        uint256 deployerPrivateKey = vm.envUint("BASE_DEPLOYER_PRIVATE_KEY");
+        address reserveAccount = vm.envAddress("INTERNAL_FUNDING_BASE_ADDRESS");
+        uint256 initialSupply = vm.envOr("BASE_ERC20_USDC_INITIAL_RESERVE_SUPPLY", DEFAULT_INITIAL_RESERVE_SUPPLY);
+
+        address deployer = vm.addr(deployerPrivateKey);
+        require(reserveAccount != address(0), "Invalid reserve account");
+        require(initialSupply > 0, "Invalid initial supply");
+        vm.startBroadcast(deployerPrivateKey);
+
+        TestnetUSDC usdc = new TestnetUSDC(deployer);
+        usdc.mint(reserveAccount, initialSupply);
+
+        vm.stopBroadcast();
+
+        console.log("=== Base Testnet USDC Deployment ===");
+        console.log("USDC token:", address(usdc));
+        console.log("Chain ID:", block.chainid);
+        console.log("Token owner / minter:", deployer);
+        console.log("Machine funding reserve:", reserveAccount);
+        console.log("Initial reserve supply (USDC, 6d):", initialSupply);
+    }
+}

deploy/bash_aliases

@@ -152,6 +152,12 @@ deploy_machine_faucet_server() (
             http://127.0.0.1:3002/api/internal/erc20-usdc/readiness
         echo
     fi
+    if [ "${INTERNAL_FUNDING_BASE_ENABLED:-false}" = true ]; then
+        curl --fail --silent --show-error \
+            -H "Authorization: Bearer $INTERNAL_FUNDING_TOKEN" \
+            http://127.0.0.1:3002/api/internal/base/readiness
+        echo
+    fi
 )
 
 deploy_contracts() (
@@ -282,3 +288,76 @@ deploy_erc20_usdc_contracts() (
     echo "ERC20 USDC preflight passed and configuration is enabled in $machine_env"
     echo "activate it with: deploy_machine_faucet_server"
 )
+
+# Base Sepolia test USDC: a plain six-decimal ERC20 minted into the dedicated
+# Base reserve. No faucet contract is deployed on Base — the reserve key
+# transfers directly — so only the token address is recorded. The human must
+# have funded INTERNAL_FUNDING_BASE_ADDRESS with Base Sepolia ETH first; the
+# deployer key pays for the deployment itself. Uses stock foundry (forge/cast)
+# because Base is a standard EVM network.
+deploy_base_erc20_usdc_contract() (
+    set -e
+    _faucet_lock_acquire deploy_base_erc20_usdc_contract
+    machine_env=$_faucet_repo/.env.machine-funding
+
+    _faucet_require_file "$machine_env"
+    _faucet_require_command jq
+    _faucet_require_command cast
+    _faucet_require_command forge
+
+    set -a
+    source "$machine_env"
+    set +a
+    _faucet_require_env BASE_RPC_URL
+    _faucet_require_env BASE_CHAIN_ID
+    _faucet_require_env BASE_DEPLOYER_PRIVATE_KEY
+    _faucet_require_env INTERNAL_FUNDING_BASE_ADDRESS
+    _faucet_require_env INTERNAL_FUNDING_BASE_PRIVATE_KEY
+    _faucet_require_env INTERNAL_FUNDING_BASE_GAS_ETH_AMOUNT
+    _faucet_require_env INTERNAL_FUNDING_MAX_BASE_ERC20_USDC_AMOUNT
+    _faucet_require_env INTERNAL_FUNDING_GLOBAL_BASE_GAS_ETH_BUDGET
+    _faucet_require_env INTERNAL_FUNDING_GLOBAL_BASE_ERC20_USDC_BUDGET
+
+    chain_id=$(cast chain-id --rpc-url "$BASE_RPC_URL")
+    [ "$chain_id" = "$BASE_CHAIN_ID" ] || {
+        echo "BASE_RPC_URL reports chain id $chain_id, expected BASE_CHAIN_ID=$BASE_CHAIN_ID" >&2
+        exit 1
+    }
+
+    _faucet_set_env_value "$machine_env" INTERNAL_FUNDING_BASE_ENABLED false
+
+    cd "$_faucet_repo/contracts"
+    forge script script/DeployBaseTestnetUSDC.s.sol \
+        --rpc-url "$BASE_RPC_URL" \
+        --broadcast \
+        --private-key "$BASE_DEPLOYER_PRIVATE_KEY"
+
+    broadcast=$_faucet_repo/contracts/broadcast/DeployBaseTestnetUSDC.s.sol/$chain_id/run-latest.json
+    _faucet_require_file "$broadcast"
+    usdc_address=$(jq -er '
+        [.transactions[]
+            | select(.contractName == "TestnetUSDC")
+            | .contractAddress
+            | select(. != null)]
+        | last
+    ' "$broadcast")
+    [[ "$usdc_address" =~ ^0x[0-9a-fA-F]{40}$ ]] || {
+        echo "invalid Base ERC20 USDC address in $broadcast: $usdc_address" >&2
+        exit 1
+    }
+
+    _faucet_set_env_value "$machine_env" BASE_ERC20_USDC_TOKEN_ADDRESS "$usdc_address"
+
+    cd "$_faucet_repo"
+    cargo build --release --locked -p faucet-machine-funding
+    INTERNAL_FUNDING_BASE_ENABLED=true \
+        BASE_ERC20_USDC_TOKEN_ADDRESS="$usdc_address" \
+        target/release/faucet-machine-funding --check-base
+
+    _faucet_set_env_value "$machine_env" INTERNAL_FUNDING_BASE_ENABLED true
+
+    echo "deployed Base Sepolia test USDC: $usdc_address"
+    echo "Base preflight passed and configuration is enabled in $machine_env"
+    echo "record BASE_ERC20_USDC_ADDRESS=$usdc_address on the sandbox machine; integrations must read it from there, never hardcode it"
+    echo "activate it with: deploy_machine_faucet_server"
+)

machine-funding-server/Cargo.toml

@@ -38,6 +38,7 @@ uuid.workspace = true
 url.workspace = true
 
 [dev-dependencies]
+alloy-consensus = { workspace = true, features = ["k256"] }
 http-body-util.workspace = true
 tempfile = "3.21.0"
 tower = { workspace = true, features = ["util"] }

machine-funding-server/RISK_REGISTER.md

@@ -241,6 +241,35 @@ actor can consume it before other testers. Likewise, a poisoned queue can keep
 legitimate work behind low-value requests. Per-principal quotas and a bounded or
 fair queue are separate future controls.
 
+## Base Sepolia Funding
+
+The Base Sepolia routes (`/api/internal/base/gas`, `/api/internal/base/erc20-usdc/transfers`,
+`/api/internal/base/readiness`) reuse every existing control: the same nginx
+source-IP gate and bearer token, the same Redis reservation, idempotency, and
+operator serialization, and per-asset budgets and rate windows. What differs:
+
+- **The signer is the reserve.** There is no faucet contract on Base, so the
+  reserve key holds both the native ETH gas reserve and the ERC20 USDC supply
+  and transfers them directly. A stolen Base key drains both balances outright;
+  the containment is the small, explicitly funded reserve and the dedicated key.
+  `INTERNAL_FUNDING_BASE_PRIVATE_KEY` is refused when it matches a Seismic
+  funding key unless `INTERNAL_FUNDING_BASE_ALLOW_SHARED_KEY=true` is set with
+  explicit approval.
+- **Native gas is real value on other networks.** Base Sepolia ETH has no
+  real-world value, but the same key format on Base mainnet would. The chain id
+  is verified at connect time and on every readiness probe, and every Base
+  ledger key is scoped to `chain id + token + reserve`, so a mispointed RPC
+  fails closed rather than replaying a testnet ledger against another network.
+- **Reserve depletion is a diagnostic, not a surprise.** Startup preflight and
+  `/api/internal/base/readiness` compare both balances to configured floors
+  (`INTERNAL_FUNDING_BASE_ETH_RESERVE_FLOOR`,
+  `INTERNAL_FUNDING_BASE_ERC20_USDC_RESERVE_FLOOR`); readiness answers
+  `503 reserve_low` below either floor so an alert fires before a drip fails
+  on-chain with `insufficient funds`, which is otherwise a terminal `422`.
+- **EIP-1559 fees are estimated, not capped.** The estimate is doubled for
+  headroom without a configured ceiling, the same deferred control as the
+  Seismic gas price.
+
 ## Deferred Hardening
 
 ### Staging Hardening