D12-F03-A04 / Complete engineering topic

Cancel-on-Disconnect

A production-minded guide to Cancel-on-Disconnect.

D12 · MATCHING ENGINES AND VENUE LO…
D12-F03-A04Canonical / Tested / Open
D12 / D12-F03

Turn a disconnect event and explicit retention policy into a deterministic purge ledger.

The decision this tutorial makes visible

Disconnect controls limit orphaned-order risk, but trigger types, auction exceptions, GTC handling, and ownership scope differ materially.

The precise question is: Which orders owned by a disconnected session must be canceled or retained under the effective port policy?

An operator needs a deterministic accept, reject, prevent, purge, or trigger decision with its exact reason. A builder needs the same point-in-time policy and order state to reproduce that decision in code, audit data, visuals, and the browser lab.

Intuition before notation

A connection loss is not enough information by itself. The engine needs the trigger class, owning session, and exact retention policy.

The result depends on instrument and venue scope, effective policy identity, session ownership, decision-time reference state, equality rules, and exact units. Changing any one of them creates a different control decision even when the output field name is unchanged.

Scope and nearby methods

The canonical control scopes orders by session and applies cancel-all, cancel-continuous, or keep-GTC only when the observed disconnect type is configured to trigger.

VariantDefinitionBest useMain limitation
Cancel allCancel all session-owned open ordersStrong orphan-risk reductionCan remove auction/GTC intent
Cancel continuousRetain auction ordersVenue policy with auction carve-outAuction cutoffs may add exceptions
Keep GTCRetain good-till-canceled ordersPersistent intentCan preserve unwanted risk

What is sourced, selected, synthetic, and derived

RoleMaterial claimEvidenceBoundary
Sourced factNasdaq and Cboe documentation show that cancel-on-disconnect behavior is configurable by trigger and retention policy, with session, auction, and persistent-order qualifications.S1, S2The historical Nasdaq alert and current Cboe specification do not establish another venue's settings or the state of any private session.
Implementation choiceThe canonical control scopes orders by session and applies cancel-all, cancel-continuous, or keep-GTC only when the observed disconnect type is configured to trigger.Frozen package definitionProduction control hierarchies, exemptions, overrides, and account/venue rules remain outside scope unless explicitly named.
Synthetic teaching inputCanonical orders, prices, thresholds, sessions, and identifiers are repository-authored.datasets/canonical-input.json and scenario-results.jsonThey are not observed participant or venue records.
Author-derived calculationA hard disconnect for S-1 under cancel-continuous selects O-1 and O-2, retains auction order O-3, and leaves S-2 order O-4 untouched.Formula, canonical fixture, Python/TypeScript parity, and independent arithmeticCorrect arithmetic does not establish compliance, latency, or trading value.

The primary sources support only the named regulatory or venue behavior. They do not certify the synthetic policy IDs, orders, thresholds, sessions, or outputs. Those values are repository-authored, and every displayed result is an author-derived calculation under the selected control contract.

Formula, symbols, and numerical policy

Plain text
cancel(order) = owns_session ∧ trigger_enabled ∧ policy_selects(order)
SymbolMeaningUnitPolicy
S_ddisconnected sessionidentifierstable
T_ddisconnect classenumobserved
Pretention policyenumeffective configuration
  • Treat identifiers and classifications exactly.
  • Do not infer a graceful logout from a timeout.
  • Keep purge selection separate from cancellation acknowledgement/finality.

Read the formula in the same order as the algorithm. Validate identity, ordering, units, and supported state first. Apply the selected equality and window rules second. Calculate with unrounded numeric values. Round only at the declared presentation boundary, and preserve null as a diagnostic rather than coercing it to zero.

Build the algorithm

  1. Validate session, trigger list, policy, and orders
  2. Test whether the disconnect class triggers
  3. Filter orders by owning session
  4. Apply book/TIF retention policy
  5. Return canceled IDs and retention reasons

Production-minded operational checklist

  1. Identify owning session and disconnect class
  2. Load effective port policy
  3. Snapshot open orders consistently
  4. Issue cancels and retain reasons
  5. Reconcile acknowledgements before declaring the book clean

The checklist is intentionally strict: an explicit rejection is safer than a plausible output built from stale, malformed, or unsupported state.

Worked synthetic example

The canonical fixture is synthetic teaching data, not an observed control event, customer order, or broker execution. Its primary author-derived output, canceled_order_ids, is orders O-1 and O-2 are selected for cancellation, while the auction order and the other session remain retained. The complete input and output are in datasets/canonical-input.json and datasets/expected-output.json.

A hard disconnect for S-1 under cancel-continuous selects O-1 and O-2, retains auction order O-3, and leaves S-2 order O-4 untouched.

Counterfactual checkpoint

Trigger is not configured. Observe a timeout while the trigger whitelist contains only hard, graceful, and server disconnects. The output changes because Ownership and retention are evaluated only after the disconnect class activates the control.

The structured result retains state and diagnostics in addition to the primary number. That makes the calculation independently reviewable and prevents a partial, null, rejected, or venue-bounded outcome from being mistaken for an unqualified value.

Boundary and counterexample workbook

The playground computes every scenario at 61 deterministic parameter states. The table uses the declared focus step and states whether that focus reproduces the canonical fixture. The full state ledger and compressed transition segments are in datasets/scenario-results.json.

ScenarioReview focusPurposeStatePrimary outputDiagnosticDecision segments
Hard disconnect, continuous onlyStep 30 · canonical fixtureCancel session-owned continuous orders while retaining auction and other-session orders. Synthetic data; the effective policy remains explicit.purge-applied2 orders canceledpurge-applied; 2 retained with reasons1
Hard disconnect, cancel allStep 30 · comparison focusSelect every cancellable order owned by the disconnected session. Synthetic data; the effective policy remains explicit.purge-applied3 orders canceledpurge-applied; 1 retained with reasons1
Keep-GTC retentionStep 30 · comparison focusRetain GTC orders while canceling eligible non-GTC session-owned orders. Synthetic data; the effective policy remains explicit.purge-applied2 orders canceledpurge-applied; 2 retained with reasons1
Graceful logout triggerStep 30 · comparison focusApply the configured continuous-only policy to a graceful logout. Synthetic data; the effective policy remains explicit.purge-applied2 orders canceledpurge-applied; 2 retained with reasons1
Server failure, cancel allStep 30 · comparison focusApply cancel-all after a configured server-side failure. Synthetic data; the effective policy remains explicit.purge-applied3 orders canceledpurge-applied; 1 retained with reasons1
Triggered session with no ordersStep 30 · comparison focusActivate the control for a session that owns no open orders. Synthetic data; the effective policy remains explicit.purge-applied0 orders canceledpurge-applied; 4 retained with reasons1
Unconfigured timeoutStep 30 · comparison focusObserve a timeout excluded from the trigger whitelist and retain every order with reasons. Synthetic data; the effective policy remains explicit.no-purge0 orders canceledno-purge; 4 retained with reasons1

These rows are not backtest observations. They are controlled counterexamples that expose how one driver changes the state, output, or reason code while the rest of the contract stays fixed.

Visualize the boundary

Cancel-on-Disconnect annotated teaching map

Open this SVG at full size, or use the guided playground to compare the seven topic-specific canonical, boundary, policy, and failure scenarios.

The Mermaid flow answers where the selected calculation sits in the processing sequence. The SVG keeps the formula, output, decision boundary, and invariant visible together. The lab lets the reader step through the same structured states without changing the underlying definition.

Implementation walkthrough

The Python and TypeScript references validate policy identity, price/quantity units, session or remembered state, and the supported mode before applying the control. Both return the decision together with distances, violations, cancellation/prevention events, or trigger state so an operator can reconstruct why the gate acted.

The main implementation branches are:

  • disconnect type not configured — No purge, because Trigger condition absent.
  • order belongs to another session — Retain, because Ownership boundary.
  • policy selects owned order — Cancel, because Orphan-risk control.

Neither reference silently fetches data, mutates caller-owned inputs outside the declared engine behavior, guesses hidden state, or substitutes a provider default. Shared JSON fixtures make value, null, state, and reason-code drift visible across languages.

Testing and validation

Definition tests compare every canonical field, reject malformed state, and exercise the material boundary. Family validation recomputes every playground state from the reference function. Independent arithmetic is recorded beside the fixture rather than inferred only from implementation output.

The audit must preserve these invariants:

  • Orders from another session are never canceled.
  • Every input order is either canceled or retained exactly once.
  • No purge occurs for an unconfigured disconnect type.
  • The structured output retains canceled_order_ids, state, policy context, and reason fields.

Passing these checks proves that the deterministic reference matches the selected control contract. It does not certify exchange conformance, regulatory compliance, latency, operational resilience, or the safety of an override.

Failure modes and misuse

  • Passing one control does not imply an order passes every venue, broker, regulatory, credit, position, or market-access check.
  • Reference prices, bands, thresholds, group identifiers, and disconnect ownership must be point-in-time inputs; later values cannot repair an earlier decision.
  • A definition-correct control does not certify production latency, legal compliance, operational resilience, or trading profitability.

Debugging order

When a result looks surprising, inspect the state in this order:

  1. Confirm instrument, venue/product, session, order type, side, and policy ID.
  2. Confirm integer price scale, quantity units, reference or band as-of time, and trigger clock.
  3. Confirm identity/ownership scope, mode, equality rule, threshold ordering, and remembered state.
  4. Recalculate the invariant and the declared scenario focus before changing code.

Evidence and historical boundary

Historical decision: deferred. A named production-control event would require complete point-in-time order, policy-version, reference-data, session, override, acknowledgement, and venue evidence plus redistribution permission. A labeled synthetic fixture is more reproducible and avoids implying a public record proves private control behavior.

The primary sources are Nasdaq cancel-on-disconnect alert, Cboe U.S. Equities FIX. They support the source roles listed in the research ledger, not a redistributable historical observation, a private participant decision, current configuration at an unnamed venue, compliance certification, trading outcome, profitability claim, or prediction claim.

Summary and next topic

You can now select and audit a deterministic disconnect purge. The learning flow is: Self-Trade Prevention → Cancel-on-Disconnect → Fat-Finger Limit. Carry the result forward only with its scope, clock, state, and evidence label.

Cancel-on-Disconnect calculation flow

This flow identifies the selected calculation stages and the structured output.

Rendering system map…

Takeaway: Disconnect type activates the control; session ownership and retention policy determine its exact scope.

ReferencesPrimary sources and evidence notes

Expand the source trail, evidence role, and limitations behind the engineering choices.

S1 — Nasdaq Introduces Changes to Cancel on Disconnect Functionality

  • Organization or authors: Nasdaq
  • Source type: Official exchange technical alert
  • Publication or effective date: 2016-12-19
  • Version: ETA2016-129
  • URL or DOI: https://www.nasdaqtrader.com/TraderNews.aspx?id=ETA2016-129
  • Accessed: 2026-07-30
  • Jurisdiction: Nasdaq U.S. equities
  • Supports: Hard disconnect, graceful logout, server-failure triggers and configurable cancel-all versus retained cross-order behavior.
  • Limitations: Historical alert; current production settings must be verified from current port configuration and specifications.

S2 — Cboe Titanium U.S. Equities FIX Specification

  • Organization or authors: Cboe Global Markets
  • Source type: Official exchange technical specification
  • Publication or effective date: Current specification accessed 2026-07-30
  • Version: Current online specification
  • URL or DOI: https://www.cboe.com/document/tech-spec/document/technical-specifications/cboe-titanium-u.s.-equities-fix-specification
  • Accessed: 2026-07-30
  • Jurisdiction: Cboe U.S. equities venues
  • Supports: Configurable match-trade-prevention, cancel-on-disconnect variants, purge filters, and fat-finger port attributes.
  • Limitations: Exact availability and behavior depend on venue, port, protocol, capacity, order type, and the current configuration.

Evidence boundary

The sources establish only the current or historical rule and protocol facts named in each source record. They do not verify the repository-authored orders, policy identifiers, reference values, thresholds, session state, override authority, or output.

order-controls.ts
/* Deterministic reference algorithms for D12-F03 Order Controls. */

type Inputs = Record<string, any>;

function integer(name: string, value: unknown, positive = false, nonnegative = false): number {
  if (typeof value !== "number" || !Number.isInteger(value)) throw new Error(`${name} must be an integer`);
  if (positive && value <= 0) throw new Error(`${name} must be positive`);
  if (nonnegative && value < 0) throw new Error(`${name} must be nonnegative`);
  return value;
}

function text(name: string, value: unknown): string {
  if (typeof value !== "string" || !value.trim()) throw new Error(`${name} must be a nonempty string`);
  return value.trim();
}

function booleanValue(name: string, value: unknown): boolean {
  if (typeof value !== "boolean") throw new Error(`${name} must be boolean`);
  return value;
}

export function tickSizeValidation(
  price_atoms: unknown,
  tick_size_atoms: unknown,
  price_scale: unknown,
  effective_policy_id: unknown,
): Record<string, unknown> {
  const price = integer("price_atoms", price_atoms, true);
  const tick = integer("tick_size_atoms", tick_size_atoms, true);
  const scale = integer("price_scale", price_scale, true);
  const policyId = text("effective_policy_id", effective_policy_id);
  if (tick > price) throw new Error("tick_size_atoms cannot exceed price_atoms");
  const quotient = Math.floor(price / tick);
  const remainder = price % tick;
  const lower = quotient * tick;
  const upper = remainder === 0 ? lower : lower + tick;
  const valid = remainder === 0;
  return {
    effective_policy_id: policyId,
    price_atoms: price,
    tick_size_atoms: tick,
    price_scale: scale,
    valid,
    remainder_atoms: remainder,
    lower_valid_price_atoms: lower,
    upper_valid_price_atoms: upper,
    distance_to_lower_atoms: price - lower,
    distance_to_upper_atoms: upper - price,
    reason: valid ? "on-grid" : "off-grid",
    state: valid ? "accepted" : "rejected",
  };
}

export function priceBandValidation(
  side: unknown,
  limit_price_atoms: unknown,
  lower_band_atoms: unknown,
  upper_band_atoms: unknown,
  band_as_of_ns: unknown,
  inclusive: unknown = true,
): Record<string, unknown> {
  const orderSide = text("side", side).toLowerCase();
  if (!["buy", "sell"].includes(orderSide)) throw new Error("side must be buy or sell");
  const price = integer("limit_price_atoms", limit_price_atoms, true);
  const lower = integer("lower_band_atoms", lower_band_atoms, true);
  const upper = integer("upper_band_atoms", upper_band_atoms, true);
  const asOf = integer("band_as_of_ns", band_as_of_ns, false, true);
  const includeEdges = booleanValue("inclusive", inclusive);
  if (lower >= upper) throw new Error("lower_band_atoms must be less than upper_band_atoms");
  const valid = includeEdges ? lower <= price && price <= upper : lower < price && price < upper;
  let reason = "inside-band";
  let violation = 0;
  if (price < lower || (price === lower && !includeEdges)) {
    reason = "below-lower-band"; violation = lower - price;
  } else if (price > upper || (price === upper && !includeEdges)) {
    reason = "above-upper-band"; violation = price - upper;
  }
  return {
    side: orderSide, limit_price_atoms: price, lower_band_atoms: lower, upper_band_atoms: upper,
    band_as_of_ns: asOf, inclusive: includeEdges, valid,
    distance_from_lower_atoms: price - lower, distance_to_upper_atoms: upper - price,
    violation_atoms: violation, reason, state: valid ? "accepted" : "rejected",
  };
}

export function selfTradePrevention(incoming_order: unknown, resting_orders: unknown, mode: unknown): Record<string, unknown> {
  if (!incoming_order || typeof incoming_order !== "object" || Array.isArray(incoming_order)) throw new Error("incoming_order must be an object");
  if (!Array.isArray(resting_orders)) throw new Error("resting_orders must be an array");
  const incoming = incoming_order as Inputs;
  const selectedMode = text("mode", mode).toLowerCase();
  if (!["cancel_newest", "cancel_oldest", "decrement_both"].includes(selectedMode)) throw new Error("unsupported self-trade-prevention mode");
  const incomingId = text("incoming_order.order_id", incoming.order_id);
  const side = text("incoming_order.side", incoming.side).toLowerCase();
  if (!["buy", "sell"].includes(side)) throw new Error("incoming_order.side must be buy or sell");
  const price = integer("incoming_order.price_atoms", incoming.price_atoms, true);
  const quantity = integer("incoming_order.quantity", incoming.quantity, true);
  const participant = text("incoming_order.participant_id", incoming.participant_id);
  const group = text("incoming_order.stp_group", incoming.stp_group);
  const seen = new Set<string>([incomingId]);
  const parsed = resting_orders.map((raw: any, index: number) => {
    if (!raw || typeof raw !== "object" || Array.isArray(raw)) throw new Error(`resting_orders[${index}] must be an object`);
    const orderId = text(`resting_orders[${index}].order_id`, raw.order_id);
    if (seen.has(orderId)) throw new Error("order identifiers must be unique");
    seen.add(orderId);
    const restingSide = text(`resting_orders[${index}].side`, raw.side).toLowerCase();
    if (!["buy", "sell"].includes(restingSide) || restingSide === side) throw new Error("resting orders must be on the contra side");
    return {
      order_id: orderId, side: restingSide,
      price_atoms: integer(`resting_orders[${index}].price_atoms`, raw.price_atoms, true),
      quantity: integer(`resting_orders[${index}].quantity`, raw.quantity, true),
      participant_id: text(`resting_orders[${index}].participant_id`, raw.participant_id),
      stp_group: text(`resting_orders[${index}].stp_group`, raw.stp_group),
      sequence: integer(`resting_orders[${index}].sequence`, raw.sequence, false, true),
    };
  });
  parsed.sort((a, b) => side === "buy" ? a.price_atoms - b.price_atoms || a.sequence - b.sequence : b.price_atoms - a.price_atoms || a.sequence - b.sequence);
  let remaining = quantity;
  let externalExecuted = 0, prevented = 0, canceledIncoming = 0, canceledResting = 0;
  let stopped = false;
  const events: any[] = [], finalBook: any[] = [];
  for (const original of parsed) {
    const resting = { ...original };
    const marketable = side === "buy" ? resting.price_atoms <= price : resting.price_atoms >= price;
    if (stopped || remaining === 0 || !marketable) { finalBook.push(resting); continue; }
    const sameGroup = resting.participant_id === participant && resting.stp_group === group;
    const matchQty = Math.min(remaining, resting.quantity);
    if (sameGroup) {
      if (selectedMode === "cancel_newest") {
        canceledIncoming = remaining; prevented += matchQty;
        events.push({ action: "cancel-incoming", incoming_order_id: incomingId, resting_order_id: resting.order_id, prevented_quantity: matchQty });
        remaining = 0; stopped = true; finalBook.push(resting);
      } else if (selectedMode === "cancel_oldest") {
        canceledResting += resting.quantity; prevented += matchQty;
        events.push({ action: "cancel-resting", incoming_order_id: incomingId, resting_order_id: resting.order_id, prevented_quantity: matchQty });
      } else {
        resting.quantity -= matchQty; remaining -= matchQty; prevented += matchQty;
        events.push({ action: "decrement-both", incoming_order_id: incomingId, resting_order_id: resting.order_id, prevented_quantity: matchQty });
        if (resting.quantity > 0) finalBook.push(resting);
      }
    } else {
      resting.quantity -= matchQty; remaining -= matchQty; externalExecuted += matchQty;
      events.push({ action: "execute-external", incoming_order_id: incomingId, resting_order_id: resting.order_id, quantity: matchQty, price_atoms: resting.price_atoms });
      if (resting.quantity > 0) finalBook.push(resting);
    }
  }
  const state = prevented ? "self-trade-prevented" : remaining === 0 ? "externally-filled" : "resting-or-residual";
  return {
    mode: selectedMode, incoming_order_id: incomingId, original_incoming_quantity: quantity,
    external_executed_quantity: externalExecuted, prevented_self_quantity: prevented,
    canceled_incoming_quantity: canceledIncoming, canceled_resting_quantity: canceledResting,
    remaining_incoming_quantity: remaining, events, resting_orders: finalBook, state,
  };
}

export function cancelOnDisconnect(
  disconnected_session_id: unknown,
  disconnect_type: unknown,
  trigger_disconnect_types: unknown,
  policy: unknown,
  orders: unknown,
): Record<string, unknown> {
  const session = text("disconnected_session_id", disconnected_session_id);
  const eventType = text("disconnect_type", disconnect_type).toLowerCase();
  if (!Array.isArray(trigger_disconnect_types) || !trigger_disconnect_types.length) throw new Error("trigger_disconnect_types must be a nonempty array");
  const triggers = trigger_disconnect_types.map((item) => text("trigger_disconnect_type", item).toLowerCase());
  const selectedPolicy = text("policy", policy).toLowerCase();
  if (!["cancel_all", "cancel_continuous", "keep_gtc"].includes(selectedPolicy)) throw new Error("unsupported cancel-on-disconnect policy");
  if (!Array.isArray(orders)) throw new Error("orders must be an array");
  const seen = new Set<string>();
  const parsed = orders.map((raw: any, index: number) => {
    if (!raw || typeof raw !== "object" || Array.isArray(raw)) throw new Error(`orders[${index}] must be an object`);
    const orderId = text(`orders[${index}].order_id`, raw.order_id);
    if (seen.has(orderId)) throw new Error("order identifiers must be unique");
    seen.add(orderId);
    const book = text(`orders[${index}].book`, raw.book).toLowerCase();
    if (!["continuous", "auction"].includes(book)) throw new Error("book must be continuous or auction");
    return {
      order_id: orderId, session_id: text(`orders[${index}].session_id`, raw.session_id), book,
      time_in_force: text(`orders[${index}].time_in_force`, raw.time_in_force).toUpperCase(),
      quantity: integer(`orders[${index}].quantity`, raw.quantity, true),
    };
  });
  const triggered = triggers.includes(eventType);
  const canceled: string[] = [], retained: Array<{ order_id: string; reason: string }> = [];
  for (const order of parsed) {
    if (order.session_id !== session) { retained.push({ order_id: order.order_id, reason: "different-session" }); continue; }
    if (!triggered) { retained.push({ order_id: order.order_id, reason: "disconnect-type-not-configured" }); continue; }
    const shouldCancel = selectedPolicy === "cancel_all"
      || (selectedPolicy === "cancel_continuous" && order.book === "continuous")
      || (selectedPolicy === "keep_gtc" && order.time_in_force !== "GTC");
    if (shouldCancel) canceled.push(order.order_id);
    else retained.push({ order_id: order.order_id, reason: order.book === "auction" ? "auction-order-retained" : "gtc-retained" });
  }
  return {
    disconnected_session_id: session, disconnect_type: eventType, triggered, policy: selectedPolicy,
    canceled_order_ids: canceled, retained_orders: retained, canceled_count: canceled.length,
    retained_count: retained.length, state: triggered ? "purge-applied" : "no-purge",
  };
}

export function fatFingerLimit(
  side: unknown,
  limit_price_atoms: unknown,
  reference_price_atoms: unknown,
  quantity: unknown,
  max_quantity: unknown,
  max_notional_atoms: unknown,
  max_aggressive_deviation_bps: unknown,
): Record<string, unknown> {
  const orderSide = text("side", side).toLowerCase();
  if (!["buy", "sell"].includes(orderSide)) throw new Error("side must be buy or sell");
  const price = integer("limit_price_atoms", limit_price_atoms, true);
  const reference = integer("reference_price_atoms", reference_price_atoms, true);
  const qty = integer("quantity", quantity, true);
  const maxQty = integer("max_quantity", max_quantity, true);
  const maxNotional = integer("max_notional_atoms", max_notional_atoms, true);
  const maxDeviation = integer("max_aggressive_deviation_bps", max_aggressive_deviation_bps, false, true);
  const notional = price * qty;
  const signed = orderSide === "buy" ? price - reference : reference - price;
  const aggressiveDeviationBps = Math.max(0, Math.round((signed * 10000 / reference) * 1e6) / 1e6);
  const checks = {
    quantity: { value: qty, limit: maxQty, passed: qty <= maxQty },
    notional: { value: notional, limit: maxNotional, passed: notional <= maxNotional },
    aggressive_deviation_bps: { value: aggressiveDeviationBps, limit: maxDeviation, passed: aggressiveDeviationBps <= maxDeviation },
  };
  const violations = Object.entries(checks).filter(([, check]) => !check.passed).map(([name]) => name);
  return {
    side: orderSide, limit_price_atoms: price, reference_price_atoms: reference, quantity: qty,
    order_notional_atoms: notional, aggressive_deviation_bps: aggressiveDeviationBps,
    checks, violations, valid: violations.length === 0,
    reason: violations.length ? `limit-breached:${violations.join(",")}` : "within-configured-limits",
    state: violations.length ? "rejected" : "accepted",
  };
}

export function circuitBreakerTrigger(
  reference_close_atoms: unknown,
  current_index_atoms: unknown,
  level_thresholds_bps: unknown,
  previously_triggered_level: unknown = 0,
): Record<string, unknown> {
  const reference = integer("reference_close_atoms", reference_close_atoms, true);
  const current = integer("current_index_atoms", current_index_atoms, true);
  const previous = integer("previously_triggered_level", previously_triggered_level, false, true);
  if (previous > 3) throw new Error("previously_triggered_level cannot exceed 3");
  if (!Array.isArray(level_thresholds_bps) || level_thresholds_bps.length !== 3) throw new Error("level_thresholds_bps must contain exactly three thresholds");
  const thresholds = level_thresholds_bps.map((value) => integer("threshold_bps", value, true));
  if (new Set(thresholds).size !== 3 || thresholds.some((value, index) => index > 0 && value <= thresholds[index - 1])) throw new Error("thresholds must be strictly increasing");
  const declineBps = Math.max(0, Math.round(((reference - current) * 10000 / reference) * 1e6) / 1e6);
  let reached = 0;
  thresholds.forEach((threshold, index) => { if (declineBps >= threshold) reached = index + 1; });
  const newlyTriggered = reached > previous;
  const triggerLevel = newlyTriggered ? reached : 0;
  const actions = ["continue", "level-1-halt", "level-2-halt", "level-3-close"];
  const nextThreshold = reached < thresholds.length ? thresholds[reached] : null;
  const distance = nextThreshold === null ? null : Math.max(0, Math.round((nextThreshold - declineBps) * 1e6) / 1e6);
  return {
    reference_close_atoms: reference, current_index_atoms: current, decline_bps: declineBps,
    level_thresholds_bps: thresholds, previously_triggered_level: previous,
    reached_level: reached, newly_triggered_level: triggerLevel, newly_triggered: newlyTriggered,
    action: actions[triggerLevel], next_threshold_bps: nextThreshold,
    distance_to_next_threshold_bps: distance,
    state: newlyTriggered ? "triggered" : reached ? "already-triggered" : "normal",
  };
}

export function calculate(topicId: string, inputs: Inputs): Record<string, unknown> {
  if (!inputs || typeof inputs !== "object" || Array.isArray(inputs)) throw new Error("inputs must be an object");
  if (topicId === "D12-F03-A01") return tickSizeValidation(inputs.price_atoms, inputs.tick_size_atoms, inputs.price_scale, inputs.effective_policy_id);
  if (topicId === "D12-F03-A02") return priceBandValidation(inputs.side, inputs.limit_price_atoms, inputs.lower_band_atoms, inputs.upper_band_atoms, inputs.band_as_of_ns, inputs.inclusive);
  if (topicId === "D12-F03-A03") return selfTradePrevention(inputs.incoming_order, inputs.resting_orders, inputs.mode);
  if (topicId === "D12-F03-A04") return cancelOnDisconnect(inputs.disconnected_session_id, inputs.disconnect_type, inputs.trigger_disconnect_types, inputs.policy, inputs.orders);
  if (topicId === "D12-F03-A05") return fatFingerLimit(inputs.side, inputs.limit_price_atoms, inputs.reference_price_atoms, inputs.quantity, inputs.max_quantity, inputs.max_notional_atoms, inputs.max_aggressive_deviation_bps);
  if (topicId === "D12-F03-A06") return circuitBreakerTrigger(inputs.reference_close_atoms, inputs.current_index_atoms, inputs.level_thresholds_bps, inputs.previously_triggered_level);
  throw new Error(`unsupported topic_id: ${topicId}`);
}
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