Spend guard

Spendguard

Will my policy hold when agents share one budget? Spendguard pins a policy to a locked local ledger, lints its rules and replays recorded exposure with exact totals. The existing callback guard checks declared FLOP exposure before spending. Unresolved operations keep their reservation.

Quick start

From the repository root with Node 22 and pnpm. This replays recorded exposure under chosen limits without spending:

pnpm install --frozen-lockfile
pnpm --filter @flop-lab/spendguard build
node packages/spendguard/dist/cli.js replay packages/spendguard/examples/tape-policy.json packages/spendguard/fixtures/settlements.json

Run

From the repository root with Node 22 and pnpm:

pnpm install
pnpm --filter @flop-lab/spendguard run check
pnpm --filter @flop-lab/spendguard run build
node packages/spendguard/dist/cli.js evaluate packages/spendguard/examples/policy.json packages/spendguard/examples/request.json --dry-run

The example is a scripted scenario. Limits, miner labels and prices are chosen inputs. They are not network observations. The CLI signs nothing and reports its file sources and evaluation time. Exit codes: 0 for allow or successful verification, 2 for deny and 1 for invalid input or integrity errors.

Create a ledger in a directory you control:

node packages/spendguard/dist/cli.js init ./spend.jsonl
node packages/spendguard/dist/cli.js verify ./spend.jsonl
node packages/spendguard/dist/cli.js evaluate packages/spendguard/examples/policy.json packages/spendguard/examples/request.json --ledger ./spend.jsonl --dry-run

init refuses existing files. Retain the printed head in a separate trusted location. Verify against it with verify ./spend.jsonl EXPECTED_HEAD. CLI simulation does not authorize a later library spend. The CLI accepts JSON or strict policy YAML. The importable API also provides typed SDK session and wallet guards.

Shared local budgets

import { FileLedger, SharedBudget } from "@flop-lab/spendguard";

const team = new SharedBudget(new FileLedger("./team.jsonl"), policy);
await team.initialize(); // once, by the budget owner
await team.preview("writer", request);
const decision = await team.reserve("writer", request);

Each process opens the same ledger with the same policy. Admission checks the pinned policy, reads the current reservations and appends under one filesystem lock. A policy mismatch fails closed. The legacy callback guard refuses a shared ledger. Request and task IDs are namespaced by agent. Hour, day, total, model and miner caps remain shared. Agent labels are supplied by trusted callers, not authenticated identities.

preview records a content-bound preflight without reserving. reserve ignores a caller's dryRun assertion and requires that preflight when the policy requests it. Preflight expires after 120 seconds. Reusing an admitted ID is refused. Reservations are local holds only: they do not sign, spend or release funds. Shared holds have no release API in this version.

node packages/spendguard/dist/cli.js shared-init packages/spendguard/examples/policy.json ./team.jsonl
node packages/spendguard/dist/cli.js reserve packages/spendguard/examples/policy.json ./team.jsonl writer packages/spendguard/examples/request.json --preview
node packages/spendguard/dist/cli.js reserve packages/spendguard/examples/policy.json ./team.jsonl writer packages/spendguard/examples/request.json

Use regular files on one local filesystem. Stale locks fail closed. This is not a distributed lock. Keep the ledger directory, policy and low-level audit API under trusted control. An owner who can rewrite both the ledger and anchor can bypass local checks.

Policy linter and replay

node packages/spendguard/dist/cli.js lint packages/spendguard/examples/tape-policy.json
node packages/spendguard/dist/cli.js replay packages/spendguard/examples/tape-policy.json packages/spendguard/fixtures/settlements.json
node packages/spendguard/dist/cli.js replay packages/spendguard/examples/policy.json packages/spendguard/fixtures/sdk-estimate.json --estimate demo qwen/qwen2.5-0.5b-instruct demo-miner

lintPolicy and lintPolicyText flag missing ceilings, allow/deny contradictions, zero stop rules, shadowed ceilings, unreachable identity caps and ceilings above the recorded SDK reference. Every finding includes a fix. Lint does not change a policy. Exit codes for lint: 0 for no findings, 2 for findings in a valid policy and 1 for invalid input. Zero ceilings and empty allowlists can be intentional stop policies.

The reference is CALIBRATED_LIMITS in @flop-labs/sdk@0.4.0: per transaction 5 FLOP and daily 50 FLOP. The raw excerpt, source and inspection time are in fixtures/documented-caps.json. These are SDK defaults, not queried runtime ceilings. Proposed limits and circuit-breaker constants are not mapped to these policy fields.

settlementTape, estimateTape and replayTape are browser-safe APIs. The /lint and /replay exports expose them without Node dependencies. The existing flop guard command forwards these CLI commands.

The settlement fixture is a partial page captured at 2026-11-06T04:06:11.831Z from flop_list_settlements. It contains 100 rows while the API reported 356. Replay sorts the supplied page by settlement time and channel ID. Settlement time stands in for unknown admission time. Model hashes remain exact identities. Each recorded agent gets one synthetic task and preflight is assumed. Full escrow remains pending; returned escrow is not treated as a verified refund. Missing model identities and zero escrow rows are skipped with separate totals.

MCP pricePerGflop is fractional raw units per GFLOP. The adapter rounds up to a whole raw unit before converting to FLOP. It checks the escrow split and rejects malformed or duplicate rows. SDK estimates use full channel escrow and explicitly chosen identity bindings. Their architecture, token, calibration and price inputs are synthetic. The SDK estimate is not actual execution cost. Replay signs nothing and never mutates a file ledger.

The sample tape policy uses chosen limits. It admits 7 recorded rows totalling 9.990000000000000164 FLOP and refuses 93 totalling 330.784000000000013554 FLOP. These are counterfactual exposure totals, not observed policy outcomes. Run the replay command to reproduce them.

Policy

See the example and JSON Schema. Quote all FLOP values. Unknown keys fail closed. Decimal strings convert to exact bigint amounts. Exponents, negatives and excess fractional precision are refused.

The YAML example supports two-space mappings, block lists, plain names, quoted strings and JSON inline arrays or maps. Anchors, tags, multiline scalars, tabs and inline comments are refused. Full-line comments are allowed. Use parsePolicyText for the same parser in the browser. This is a deliberate policy subset, not a general YAML parser.

• budgets.task: lifetime net charge for a task ID.
• budgets.hour and budgets.day: rolling windows (now - window, now].
• budgets.total: lifetime net charge for the ledger.
• modelCaps and minerCaps: optional lifetime caps by exact name.
• maxEscrowPerSession: maximum amount at risk for one operation.
• maxPricePerGflop: maximum quoted decimal FLOP per GFLOP.
• allowModels and allowMiners: exact allowlists. Empty lists deny everything.
• denyMiners: takes precedence over the miner allowlist.
• requireDryRun: requires a matching library preflight before execution.
• cooldown: minimum milliseconds between admitted operations across tasks.

Every unresolved reservation counts against rolling windows even after it ages out. A denied request changes no reservation. The audit log records the denial. Evaluation is independent of ledger array order. Admission order can affect which competing request receives a limited budget. Use one ledger for the whole budget boundary. Keep policy files and task naming under trusted control.

Import

import { evaluate, parsePolicy } from "@flop-lab/spendguard/policy";

const policy = parsePolicy(parsedJson);
const decision = evaluate(policy, reservations, request);
console.log(decision.decision, decision.fired);

The /policy export is browser-safe. The main export includes the Node ledger and callback guard.

import { FileLedger, guardedSpend, webhook } from "@flop-lab/spendguard";

const ledger = new FileLedger("./spend.jsonl"); // initialize once
const guard = { policy, ledger, notify: webhook(alertUrl) };
const operation = {
  binding: { destination, amount: request.amount },
  execute: trustedBoundedSpend,
  channelId: () => null,
};
await guardedSpend(guard, request, operation, { dryRun: true });
const result = await guardedSpend(guard, request, operation, { dryRun: false });

The callback is trusted application code. Its maximum spend must equal request.amount. Dry-run authorization binds the policy, task, request ID and operation data. It expires after 120 seconds and cannot be reused after admission. Live calls re-evaluate budgets under the ledger lock. A returned callback value does not establish finality and does not release the reservation.

SDK integration

Spendguard uses an explicitly supplied SDK port. Import your application's installed @flop-labs/sdk@0.4.0 and pass its functions directly. Generic types preserve the SDK's concrete API, signer, estimate and result types. Spendguard itself has no runtime dependency on the SDK.

import { runDirectSession, computeChannel } from "@flop-labs/sdk";
import { guardedSession, reconcileChannel, sdkFinalityPort } from "@flop-lab/spendguard";

const sdkPort = { runDirectSession, estimateSession: computeChannel.estimateSession };
const permit = {
  network: "devnet" as const,
  throwaway: true as const,
  genesisHash: verifiedDevnetGenesis,
  maxFlop: "0.01",
};
// plan.session holds api, signer, miner, model, prompt and maxTokens.
// plan.estimate holds the SDK's architecture, token bound, price and calibration inputs.
// plan.source and plan.measuredAt identify those supplied inputs.
await guardedSession(guard, request, plan, permit, { dryRun: true }, sdkPort);
const result = await guardedSession(guard, request, plan, permit, { dryRun: false }, sdkPort);
// Once the outcome block is known, read finalized state instead of trusting result:
await reconcileChannel(guard, request.id, outcomeBlockHash, rpcSource, sdkFinalityPort(api, channelId));

The guard uses estimateSession, admits exactly one channel and checks that generated tokens cover maxTokens. The full estimated escrow must fit request.amount, the permit's hard ceiling and every policy limit. It passes that exact escrow as maxFlop. It never increases a requested ceiling to make an estimate fit. The dry run invokes the estimator and policy pipeline but does not call runDirectSession.

SDK return values and error messages never release a reservation. Reconciliation requires a matching canonical finalized block, Closed channel state and a matching full-refund event. A finalized settlement ends the pending hold but keeps the full escrow charged. Unknown and partial outcomes remain reserved. RPC reads are fresh. Forced settlement claims are not final settlements.

guardedWalletMove wraps explicit fund, transfer and withdraw calls. Supply the SDK object as its last argument. The request model is wallet:<kind>, miner is the destination and price is "0". Wallet outcomes retain their reservation because wallet finality reconciliation is not implemented. Provisioning wallets, granting session keys and arbitrary nested executeViaSession calls are outside this wrapper.

Read NOTES.md before connecting a signer. Only use a newly generated devnet wallet with a faucet-verified genesis hash. throwaway: true is the owner's assertion, not proof of wallet origin.

Ledger and alerts

Each JSONL record hashes its sequence, previous hash and canonical event. A separate .head anchor detects tail truncation. Writes hold an exclusive local filesystem lock and sync the log before replacing the head. Competing processes evaluate and reserve under the same lock. Spending callbacks run after the lock is released.

An interrupted append or abandoned .lock fails closed. Inspect the owning process and compare a trusted backup or external head before operator recovery. Do not automatically delete lock or head files. Local regular files are supported. Network filesystems and hostile changes by the same OS user are not a supported isolation boundary.

Webhook JSON includes type, measuredAt, source and details. Types are deny, budget80 and tampering. Budget alerts fire when an admitted request crosses the 80 percent threshold. Delivery failure is returned in warnings and never repeats a spend. HTTPS requests time out and retry only 429 or 5xx with bounded backoff. Prompts and callback results are not stored in the ledger.

Evidence and performance

pnpm --filter @flop-lab/spendguard run mutation
pnpm --filter @flop-lab/spendguard run mutation:shared
pnpm --filter @flop-lab/spendguard run measure

The mutation command disables each policy rule separately, requires a failing test and restores the source in finally. Do not interrupt it forcibly. The measurement command reports cold CLI duration and observed socket connections. It signs nothing.

NOTES.md records SDK research and the chain-reconciliation rules. The raw public standing-offer observation in fixtures/offers.json includes source and capture time. Its empty response is not proof that no direct miner endpoint exists. fixtures/sdk-estimate.json records actual SDK output for clearly labelled synthetic inputs. The fixed-profile fake refuses other inputs. The shipped SDK declarations were also type-checked against the generic ports. This CLI is offline. No chain outcome is cached. Library preflight authorization has an explicit 120-second TTL.

What this does not verify

• This is an application guard. A program that has the signer, can edit the policy or supplies an unbounded callback can bypass it.
• The guard budgets declared exposure. Transaction fees, provisioning costs, other wallets and unwrapped calls are outside those budgets.
• Quote authenticity, miner availability and the actual amount moved by an arbitrary callback are not verified.
• A hash chain alone does not detect rewriting both the log and its local anchor. Store an external trusted head to detect that rewrite. Audit metadata is not encrypted.
• The low-level ledger accepts trusted audit events. It is not a finality oracle. The SDK reconciliation adapter trusts the connected RPC node's finalized canonical view. It is not a consensus light client.
• Architecture, token counts, calibration and price provenance are supplied by the integrating application. The guard does not prove those inputs came from a signed miner quote.
• Partial refunds, fraud refunds and wallet finality reconciliation are unsupported. Their reservations stay charged. Successful sessions stay charged until explicit reconciliation.
• Deployed wallet-pallet limits, session-key restrictions, circuit-breaker behavior, miner proofs and hardware attestation were not verified. No wallet was created or funded.
• No real devnet inference round trip was completed. The read-only MCP and a model catalog do not provide the reachable opted-in miner endpoint required by the SDK.
• Shared reservations do not authenticate agents, enforce distributed isolation or support refunds. Trusted low-level ledger access can bypass the shared API.
• Lint does not prove a policy is complete or enforce deployed SDK defaults. Replay does not recover original admission times, task IDs, preflight state or missing history. Its full pending escrow model is conservative.