objectstack-automation

Automation Design — ObjectStack Automation Protocol

Expert instructions for designing business automation using the ObjectStack specification. This skill covers Flows (visual logic orchestration), state machines & approvals, Triggers (event-driven automation), and ETL pipelines.

When to Use This Skill

• You are building a visual flow (auto-launched, screen, or scheduled).
• You need a state machine or approval process for a business object.
• You are setting up event-driven triggers (record create/update/delete).
• You need scheduled automation (daily reports, data cleanup).
• You are designing an ETL pipeline for data synchronisation.

Predicates and conditions are CEL. Every condition / guard / entryCondition / filter value in this skill is an Expression envelope evaluated by @objectstack/formula. Use the P\...`andcel`...`tagged templates from@objectstack/spec. See the **objectstack-formula** skill for the full CEL contract, stdlib (now(), today(), daysFromNow(n), daysBetween(a, b), isBlank(v), coalesce(v, fb)`), and the legacy → CEL translation table.

Flows — Visual Logic Orchestration

A Flow is a directed graph of nodes that execute sequentially or in parallel. Flows are the primary automation building block in ObjectStack.

Flow Types

Flow Node Types

Flows are built from 20 built-in node types (the FlowNodeAction seed set — plugins register more via registerNodeExecutor, e.g. approval below):

Control Flow

Data Operations

External Integration

Human Decision

Flow Variables

Every flow defines input/output variables. variables is an array of { name, type, isInput, isOutput } entries — not a name-keyed map, and there is no label property on a variable:

variables: [
  {
    name: 'case_id',
    type: 'text',
    isInput: true,    // passed in when flow is invoked
    isOutput: false,
  },
  {
    name: 'approval_result',
    type: 'boolean',
    isInput: false,
    isOutput: true,   // returned when flow completes
  },
],

Flow Example — Auto-Escalate Overdue Cases

Nodes connect via edges, not a next property. The engine traverses flow.edges ({ source, target }); a bare next: on a node is ignored. update_record selects rows with filter — an ObjectQL where map of field → value / field → { $operator: value }, NOT the UI view-filter [{ field, operator, value }] triples — and writes with fields (a single call updates every matching row — no per-row loop needed). label is required on the flow and on every node.

Handling a failed node: a fault edge. { source, target, type: 'fault' } routes a failed node to a handler instead of ending the run. type: 'fault' is what routes — a label: 'error' alone does nothing: the edge stays ordinary, and every unconditional out-edge traverses on SUCCESS, so the handler would run when the node succeeds and never when it fails (objectstack validate reports flow-error-label-not-fault). A handled failure does NOT consume a flow-level errorHandling.retry, which replays the flow from the start — prefer a fault edge when the failure is local. The handler reads {<nodeId>.error} (or run-wide {$error}). The run then reports success, and the failed step stays in the trace.

It is not a way past a guardrail. Only runtime failures route — a 404, a rate-limit, a rejected write, a subflow that failed on its own. A guard refusal stays fatal with or without a fault edge. A failure is a guard when re-running unchanged could never succeed and the fix is to edit metadata: a missing required config key (objectName, url, flowName, connectorId/actionId), a filter token that resolved to nothing so the condition was dropped, a graph that recurses past the nesting ceiling, or a run that would execute unscoped.

Never add a fault edge to silence such an error: a dropped filter condition widens the query, so routing it would let a delete_record empty the object while the run reported success. Fix the metadata — objectstack validate names the offending template.

Writing a readonly field? Set runAs: 'system'. readonly: true governs the end-user surface: under the default runAs: 'user', the engine silently strips a readonly field from an update_record payload — the step reports success but the value never lands. A flow that maintains a readonly field (approval stamps, conversion flags, SLA markers, rollups) must run runAs: 'system', the trusted-writer channel. os validate / os build fail a runAs:'user' update_record that writes a readonly field, so the mismatch surfaces at build time, not as wrong data days later. (readonlyWhen fields are the same story, per record state — flagged as a warning.) Do not work around this by removing readonly; that loses the field's edit protection.

{
  name: 'escalate_overdue_cases',
  label: 'Escalate Overdue Cases',
  type: 'schedule',
  runAs: 'system',   // a scheduled run has no trigger user — elevate explicitly
  nodes: [
    {
      id: 'start',
      type: 'start',
      label: 'Daily at 09:00',
      // The cadence lives HERE, on the start node's config — FlowSchema has NO
      // top-level `schedule` key (one there is silently stripped and the flow
      // never binds). A bare cron string also works: schedule: '0 9 * * *'.
      // Do NOT use the cron`…` tagged template — its envelope is not a
      // recognized schedule shape.
      config: { schedule: { type: 'cron', expression: '0 9 * * *' } },
    },
    {
      id: 'escalate_overdue',
      type: 'update_record',
      label: 'Escalate Overdue Cases',
      config: {
        objectName: 'support_case',
        // which rows to update — `filter` is a `where` map, not filter triples
        filter: {
          status: { $in: ['new', 'open'] },
          due_date: { $lt: '{TODAY()}' },   // template token → today's date at run time
        },
        // what to write — `fields`, not `values`
        fields: { status: 'escalated' },
      },
    },
    {
      id: 'notify_manager',
      type: 'http',
      label: 'Notify Manager',
      config: {
        url: 'https://hooks.slack.com/services/...',
        method: 'POST',
        body: { text: 'Escalated overdue support cases.' },
        timeoutMs: 10000,   // unset = NO timeout at all — always set one
      },
    },
    { id: 'end', type: 'end', label: 'End' },
  ],
  edges: [
    { id: 'e1', source: 'start',            target: 'escalate_overdue' },
    { id: 'e2', source: 'escalate_overdue', target: 'notify_manager' },
    { id: 'e3', source: 'notify_manager',   target: 'end' },
  ],
}

State Machines & Approvals

A record's state machine locks the legal transitions of its status field so that automation — increasingly AI-generated — cannot drive a record into an illegal state.

State Machine — a state_machine validation rule (ADR-0020)

Since ADR-0020 there is no workflow metadata type and no object.stateMachines map. A record state machine is one state_machine validation rule in the object's validations array: a flat field + { from: [allowedTo] } transition table. It is enforced on the write path — an update whose field moves to a state not listed for the current state is rejected with the rule's message. A from state mapped to [] is a declared dead-end.

{
  type: 'state_machine',
  name: 'case_lifecycle',
  label: 'Case Lifecycle',
  field: 'status',                 // the field that holds the state
  message: 'Invalid status transition.',
  initialStates: ['new'],          // states a record may be CREATED in
  transitions: {
    new:       ['open'],
    open:      ['escalated', 'resolved'],
    escalated: ['open', 'resolved'],
    resolved:  ['open', 'closed'],
    closed:    [],                 // final — no outgoing transitions
  },
}

Notes:

• One rule per field. Parallel lifecycles (e.g. status + payment_status) are N separate state_machine rules, one per field.
• initialStates (optional) gates INSERT: a record created with its state field outside this list is rejected. transitions only governs updates, so without it a record can be born mid-flow (e.g. created already resolved). Omit to keep the legacy no-check-on-insert behavior.
• Conditional transitions / side effects are NOT part of the machine. A guard is expressed as a sibling script / conditional validation rule; "do something when the state changes" is a record-triggered Flow (ADR-0019) — a record_change flow whose start-node condition gates on the transition, e.g. previous.status != 'escalated' && record.status == 'escalated'.
• Introspection: GET /api/v1/meta/object/:name/state/:field?from=:state returns the legal next states so UIs/agents can read the transition table instead of hard-coding it (next: null = no FSM governs the field, or ?from= was omitted — always pass from).
• Predicate conditions in sibling rules evaluate against the merged record in the record.<field> CEL scope (bare field names do not resolve).

Approvals (Flow Nodes)

Since ADR-0019 there is no standalone approval-process type. An approval is authored as an Approval node (type: 'approval') on an ordinary flow — the run suspends when it reaches the node and resumes down the node's approve / reject out-edge once a decision is recorded. Multi-step review is just successive Approval nodes wired together on the canvas, so the whole review is one diagram a reviewer (or AI) can read end-to-end.

The old process-level concepts re-home onto the flow graph + node config — see the re-home table below. The approval state (sys_approval_request / sys_approval_action, the record lock, the status mirror, approver resolution) is unchanged and still owned by plugin-approvals.

// A record-triggered flow: high-value opportunities need manager sign-off,
// and director sign-off too when the amount clears 500k.
{
  name: 'opportunity_discount_approval',
  label: 'Opportunity Discount Approval',
  type: 'record_change',
  nodes: [
    // Record-change flows bind via the START NODE's config — there is no
    // separate top-level `trigger`. `triggerType` is one of
    // `record-(before|after)-(create|update|delete)`; `condition` (bare CEL)
    // gates whether the flow launches.
    {
      id: 'start',
      type: 'start',
      label: 'On Opportunity Update',
      config: {
        objectName: 'opportunity',
        triggerType: 'record-after-update',
        condition: cel`record.amount > 100000`,
      },
    },
    {
      id: 'manager_review',
      type: 'approval',
      label: 'Sales Manager Review',
      config: {
        approvers: [{ type: 'position', value: 'sales_manager' }],
        behavior: 'first_response',            // or 'unanimous' / 'quorum' / 'per_group'
        lockRecord: true,                      // lock the record while pending
        approvalStatusField: 'approval_status', // mirror pending|approved|rejected|recalled onto the row
      },
    },
    // Decision routing lives on the OUT-EDGES, not in node config: the engine
    // evaluates each out-edge's `condition` and follows every match — and an
    // out-edge with NO condition ALWAYS runs (all such edges execute in
    // PARALLEL). Guard every branch with a condition — see e4/e5 below.
    { id: 'needs_director', type: 'decision', label: 'Needs Director?' },
    {
      id: 'director_signoff',
      type: 'approval',
      label: 'Sales Director Sign-off',
      config: {
        approvers: [{ type: 'position', value: 'sales_director' }],
        behavior: 'unanimous',
        approvalStatusField: 'approval_status',
      },
    },
    { id: 'mark_won', type: 'update_record', label: 'Mark Won',
      config: { objectName: 'opportunity', filter: { id: '{record.id}' }, fields: { stage: 'closed_won' } } },
    { id: 'approved', type: 'end', label: 'Approved' },
    { id: 'rejected', type: 'end', label: 'Rejected' },
  ],
  edges: [
    { id: 'e1', source: 'start',          target: 'manager_review',
      // entry criteria re-homes onto the edge entering the approval node:
      condition: cel`record.amount > 100000` },
    { id: 'e2', source: 'manager_review',  target: 'needs_director',   label: 'approve' },
    { id: 'e3', source: 'manager_review',  target: 'rejected',         label: 'reject'  },
    // Decision branches: mutually-exclusive edge `condition` predicates.
    // Without them BOTH branches would execute (unguarded edges run in parallel).
    { id: 'e4', source: 'needs_director',  target: 'director_signoff', label: 'true',
      condition: cel`record.amount > 500000` },
    { id: 'e5', source: 'needs_director',  target: 'mark_won',         label: 'false',
      condition: cel`record.amount <= 500000` },
    { id: 'e6', source: 'director_signoff', target: 'mark_won',        label: 'approve' },
    { id: 'e7', source: 'director_signoff', target: 'rejected',        label: 'reject'  },
    { id: 'e8', source: 'mark_won',         target: 'approved' },
  ],
}

Send-back for revision (ADR-0044)

Approval centers also model send back for revision (退回修改) — distinct from reject (terminate) and from a comment thread (which keeps the request pending). Send-back is a flow movement: the request finalizes as returned, the run walks a revise out-edge to an approval_revise node (the revise window) where the record unlocks and the submitter reworks it, and an explicit resubmit re-enters the approval node over a declared back-edge, opening round N+1 with a fresh approver slate.

approval ──approve──▶ …
         ──reject───▶ …
         ──revise───▶ approval_revise (record unlocked, submitter edits)
                        └──resubmit──[type:'back']──▶ approval   (round N+1)

Three pieces author it:

1. revise out-edge — a third branch label alongside approve / reject, targeting an approval_revise node. It must be that node type: the window is a service-owned pause (resumeAuthority: 'service'), so only POST /api/v1/approvals/requests/:id/resubmit can end it. ADR-0044 D3 first prescribed an ordinary wait here and its 2026-07-28 amendment reversed that — a wait is resumeAuthority: 'any', so a raw POST /api/v1/automation/:name/runs/:runId/resume walked the back-edge with no submitter check and no audit row, and could destroy the run outright. The approval_revise node takes no config — there is no signal to wait on.
2. type: 'back' resubmit edge — the edge from the revise window back into the approval node MUST be typed 'back'. This is the only thing that legalizes the cycle: registerFlow validates the graph minus back edges as a DAG, so an unmarked cycle is rejected — you opt in, edge by edge. At run time a back-edge traverses normally (it just re-enters the node).
3. maxRevisions on the approval config (default 3) — the budget of send-backs per run; exceeding it auto-rejects (resumes down the reject edge). maxRevisions: 0 disables send-back, so never pair 0 with a revise edge.

{
  id: 'manager_review', type: 'approval', label: 'Manager Review',
  config: { approvers: [{ type: 'position', value: 'manager' }], lockRecord: true, maxRevisions: 2 },
},
// No config and no `waitEventConfig`: the window ends on the submitter's
// explicit resubmit, not on a signal or a timer.
{ id: 'wait_revision', type: 'approval_revise', label: 'Awaiting Revision' },
// …among the approval's edges…
{ id: 'rev',  source: 'manager_review', target: 'wait_revision',  label: 'revise' },
{ id: 'back', source: 'wait_revision',  target: 'manager_review', label: 'resubmit', type: 'back' },

Three mistakes the compile-time flow lint flags: a revise edge into anything but an approval_revise node (an error — sendBack refuses that metadata, so the branch cannot run; flow-approval-revise-target-not-service-owned), a revise edge whose window never loops back (a dead end registerFlow accepts but that leaves the submitter nowhere to resubmit), and a resubmit edge left without type: 'back' (an unmarked cycle registerFlow rejects). Resubmit is an explicit verb (POST /api/v1/approvals/requests/:id/resubmit), never a record-save. See the showcase_budget_approval flow in the showcase app in the framework repo for the canonical shape.

Re-homing the old process model

If you've seen the pre-ADR-0019 ApprovalProcess.create({...}) shape, every concept maps onto the flow:

There is no approvals: [...] stack collection anymore — approval flows live in your normal flows: [...].

Recording a decision

A decision is recorded through ApprovalService.decide() (or the REST routes POST /api/v1/approvals/requests/:id/approve | /reject). That finalizes the sys_approval_request and resumes the suspended run down the matching branch — you never resume the flow by hand, and you cannot: the approval node declares resumeAuthority: 'service', so POST /api/v1/automation/:name/runs/:runId/resume answers 403 for a run parked on one (including via a subflow pause) and changes nothing.

A decision may also carry structured outputs ({ outputs: { … } } in the decide body) when the node declares the keys in decisionOutputs — the author declares keys, approvers only fill values. Accepted outputs resume the run as <nodeId>.<key> flow variables, so a LATER node reads them as vars.<nodeId>.<key> — this is how "the previous approver picks the next step's approvers" works without writing to a record field (see Dynamic approvers below). A decision carrying an undeclared key is rejected; decision / requestId are reserved. A declaration marked required: true must carry a non-blank value to approve (never to reject) — enforced before any write, with no elevation bypass, so the run cannot resume past the node with the key a later expression approver reads still missing.

Approver Types

Dynamic approvers (type: 'expression')

An expression approver computes WHO approves at the moment the node is entered. Its CEL source sees exactly three roots — nothing else:

record and bare field names are NOT available and fail the node loudly. Everywhere else on this platform record means "the record at event time" (flow conditions: the trigger snapshot; hook conditions: the stored record overlaid with the write's payload) — at an approval node that phrase is ambiguous between two different times, so you must say which one: current.x or trigger.x. Do not carry the record.x habit over from conditions.

Result contract: a user-id string, a CSV string, or an array of ids. An empty result (present-but-empty field/variable) triggers onEmptyApprovers. A missing key (vars.never_written) is a loud error, never a silent empty slate — guard genuinely-optional inputs explicitly, e.g. has(vars.picked) ? vars.picked : [].

// ① Route on a field an EARLIER approver filled in mid-flow (live value):
{ type: 'expression', value: cel`current.co_review_departments`, resolveAs: 'department' }

// ② The previous approval node's decision outputs pick this node's approvers:
{ type: 'expression', value: cel`vars.lead_review.next_reviewers` }

// ③ Dynamic co-sign (会签): expression yields department ids; resolveAs expands
//    each into its members, and with behavior: 'per_group' EACH department is
//    its own sign-off group:
{
  approvers: [{ type: 'expression', value: cel`current.picked_departments`, resolveAs: 'department' }],
  behavior: 'per_group',
  onEmptyApprovers: 'fail',
}

The full "previous approver picks the next step's approvers" loop, end to end (the shipped showcase_dynamic_approval flow in the showcase app is this shape):

import { defineFlow } from '@objectstack/spec';

export const DynamicApprovalFlow = defineFlow({
  name: 'dynamic_approval',
  label: 'Dynamic Approval',
  type: 'autolaunched',
  status: 'active',
  nodes: [
    {
      id: 'start', type: 'start', label: 'On Submit',
      config: { objectName: 'expense', triggerType: 'record-after-update', condition: "status == 'submitted'" },
    },
    {
      // Node A declares what a decision may hand to the flow. The TYPED
      // declaration renders a multi-select sys_user picker in the decision
      // dialog; the lead approves with outputs:
      //   POST …/approve { outputs: { next_reviewers: ['u2', 'u3'] } }
      // `required: true` is enforced by the runtime on APPROVE (never on
      // reject) — node B below has nobody to route to without it.
      id: 'lead_review', type: 'approval', label: 'Lead Review',
      config: {
        approvers: [{ type: 'org_membership_level', value: 'owner' }],
        decisionOutputs: [{ key: 'next_reviewers', label: 'Next Reviewers', type: 'user', multiple: true, required: true }],
      },
    },
    {
      // Node B resolves them at entry from the lead's decision outputs.
      id: 'co_sign', type: 'approval', label: 'Co-sign',
      config: {
        approvers: [{ type: 'expression', value: 'vars.lead_review.next_reviewers' }],
        behavior: 'unanimous',
        onEmptyApprovers: 'fail',
      },
    },
    { id: 'approved', type: 'end', label: 'Approved' },
    { id: 'rejected', type: 'end', label: 'Rejected' },
  ],
  edges: [
    { id: 'e1', source: 'start', target: 'lead_review' },
    { id: 'e2', source: 'lead_review', target: 'co_sign', label: 'approve' },
    { id: 'e3', source: 'lead_review', target: 'rejected', label: 'reject' },
    { id: 'e4', source: 'co_sign', target: 'approved', label: 'approve' },
    { id: 'e5', source: 'co_sign', target: 'rejected', label: 'reject' },
  ],
});

Time-word cheat sheet across surfaces (do not mix them up):

There is no ctx.record. HookContext declares input / result / previous / session / ql (plus object / event) — a handler reads the write payload as ctx.input. The bare record / previous roots are the condition's CEL scope, not the handler's context object: record is the stored row overlaid with this write's payload and previous is the pre-write row, both made total over the object's declared fields. See objectstack-formula §5 for where previous is bound and where it is not.

Node Config (ApprovalNodeConfigSchema)

Branching, side-effects & rejection

These are wired on the graph, not in node config:

• Conditional step — put a decision node before the Approval node, or a condition on the edge entering it (the old per-step entryCriteria).
• On approve / on reject — wire downstream nodes (update_record, http, a notify node, …) to the approve / reject out-edge.
• Roll back on reject — route the reject edge as a back-edge to an earlier node so the submitter can revise (the old back_to_previous).
• Send back for revision (ADR-0044) — distinct from a plain reject: an Approval node can emit a third decision revise on a revise-labeled out-edge that routes to an approval_revise rework window (not a plain wait). The submitter edits and resubmits, re-entering the node via an edge type: 'back' (a declared back-edge — traversed at run time but excluded from DAG cycle validation). maxRevisions (node config, default 3) caps the loop before auto-reject.
• Hard reject — route the reject edge to an end node (the old reject_process).

Approval Best Practices

1. Gate entry on the edge (condition into the Approval node) so the flow only pauses for records that actually need sign-off.
2. Set approvalStatusField to mirror status onto the row — views and formulas can then filter on it without joining sys_approval_request.
3. Keep lockRecord: true unless you have a strong reason to allow edits while pending — otherwise approvers chase a moving target.
4. Model rejection as a visible branch — a back-edge to revise, or an end node to terminate. The path is on the diagram, not hidden in config.
5. Notify from downstream nodes wired to the approve / reject edges rather than expecting the node to send mail itself.

Triggers — Event-Driven Automation

A record_change flow fires automatically on a data event. There is no standalone trigger object and no top-level trigger / event key — the binding lives entirely in the flow's start node config, which the automation engine parses (resolveTriggerBinding) and wires to the matching ObjectQL lifecycle hook.

Prerequisite — enable the triggers capability

Record-change, schedule, and inbound-webhook (api) triggers ship behind the triggers capability. Without it the flows register but never fire. Add it to the package config:

defineStack({
  // …
  requires: ['automation', 'triggers'],
  //   + 'job'   for scheduled (cron) flows
  //   + 'queue' for inbound-webhook ('api') flows — the trigger-api plugin
  //             depends on the queue service; without it every inbound POST
  //             returns 503 queue_unavailable.
});

Inbound webhook (api) triggers (ADR-0041 Tier 1)

An api flow can be bound to an inbound HTTP endpoint: POST /api/v1/automation/hooks/:flowName/:hookId. Configure it on the start node config (the start config is a free-form record, so these keys are read at runtime, not Zod-validated):

• Signature: sender sends x-objectstack-signature: sha256=<hex> (GitHub/Stripe style).
• Idempotency: x-idempotency-key dedupes retries — author the flow to be idempotent (delivery is at-least-once).
• Queue-backed: the endpoint ACKs 202 and enqueues; the flow runs on the consumer, never in-band. Requires the queue service (see prerequisite).
• The JSON body surfaces to the flow as the trigger record (record.* / bare fields) plus params.

Trigger Types (start-node config.triggerType)

Trigger Configuration — on the start node

{
  name: 'notify_on_escalation',
  label: 'Notify on Escalation',
  type: 'record_change',
  nodes: [
    {
      id: 'start',
      type: 'start',
      label: 'On Case Escalated',
      config: {
        objectName: 'support_case',
        triggerType: 'record-after-update',
        // bare CEL; gates whether the flow launches on the event
        condition: cel`previous.status != 'escalated' && record.status == 'escalated'`,
      },
    },
    // …downstream nodes, connected via `edges`
  ],
}

previous and record are the CEL variables available in update triggers — previous.x is the value before the change, record.x is the value after. (Salesforce-flavor OLD / NEW were removed in M9.5 and now evaluate to null.) See objectstack-formula.

Time-relative triggers — scheduled per-record date sweep

Don't express "act N days before/after a date" (renewal reminders, "expiring soon", overdue sweeps) as a record_change flow gated on date-equality (end_date == daysFromNow(60)) — that predicate is only evaluated when the record happens to change, so unattended it almost never fires. Use a declarative time-relative trigger: a schedule-type flow whose start node carries a timeRelative descriptor is swept on a schedule (daily by default) and launched once per record whose date field falls in the window. The record is on the context, so the start condition and {record.*} interpolation work exactly as for a record-change flow — and because the window is evaluated every day, a threshold is never missed.

{
  name: 'renewal_alert',
  label: 'Renewal Alert',
  type: 'schedule',
  runAs: 'system',              // a sweep has no trigger user — elevate explicitly
  nodes: [
    {
      id: 'start', type: 'start', label: 'Daily Sweep',
      config: {
        timeRelative: {
          object: 'contracts',
          dateField: 'end_date',
          offsetDays: [60, 30, 7],   // fire exactly at T-60 / T-30 / T-7
          // — or — withinDays: 30    // "expiring within 30 days" (negative = overdue lookback)
          filter: { status: 'active' },  // optional, ANDed with the date window
          // maxRecords: 1000            // optional per-sweep cap (default 1000)
        },
        // Optional sweep cadence; omit for daily 08:00 UTC. Plain shape only:
        // schedule: { type: 'cron', expression: '0 8 * * *' }
      },
    },
    // …downstream nodes (notify, update_record, …)
  ],
  edges: [ /* start → downstream */ ],
}

Exactly one of offsetDays (discrete T-minus days) or withinDays (a range; negative = overdue) is required. Ships in @objectstack/trigger-schedule — needs requires: ['automation', 'triggers'] plus 'job' (the sweep cadence runs on the job service). Full descriptor schema: node_modules/@objectstack/spec/src/automation/time-relative-trigger.zod.ts.

Best Practices

Flow Design

1. Keep flows small and composable. Use subflow nodes to break complex logic into reusable parts.
2. Always handle errors. Add boundary_event nodes for timeout and error scenarios.
3. Use variables for all dynamic values. Never hard-code record IDs or API keys in node config.
4. Prefer get_record over multiple http calls when the data lives in ObjectStack.
5. Always set timeoutMs on http nodes. Unset means no timeout at all — a hung endpoint stalls the run indefinitely.

State Machine Design (ADR-0020)

1. Author it as a state_machine validation rule on the object, not a workflow metadata type (retired) — one rule per state field.
2. Define explicit transitions — { from: [allowedTo] }. A state mapped to [] is a final/dead-end state.
3. Don't rely on implicit "any → any" — an update to a from state not listed as a key is treated leniently (no lock), so list every state you want guarded.
4. Put guards in a sibling script / conditional rule, not in the transition table (the machine stays a flat table).
5. Put side-effects (emails, notifications, task creation) in a record-triggered Flow (ADR-0019), not on the transition.

Trigger Design

1. Prefer record-after-* triggers unless you need to modify/reject the record.
2. Avoid infinite loops: Do not update the same object in a record-after-update trigger without a guard condition.
3. Use the start-node condition to narrow when the trigger fires — avoid running expensive logic on every save.

Common Pitfalls

1. Circular flow references. Flow A calls Flow B which calls Flow A. Use a depth counter or visited set to detect cycles.
2. Unmatched parallel_gateway / join_gateway. Every fork must have a corresponding join.
3. Missing end node. Every path through the flow must terminate.
4. record-before-* trigger throwing unhandled errors. This silently prevents the record operation — always provide a user-friendly error message.
5. Scheduled flows without idempotency. If the flow runs twice accidentally, the result should be the same.

Valid-but-silently-wrong (passes build, fails at runtime)

These are legal metadata that authors — AI especially — get wrong. Most are now caught by objectstack build (a hard error, or an advisory warning), but write them right the first time:

6. Flow node VALUE interpolation uses SINGLE braces. Value fields on a node's config (fields, inputs, notify message/title, …) interpolate {token}:

   • {var} / {record.title} — variable / record field
   • {record.tags.0} — array index (e.g. a multiple: true lookup, stored as an array)
   • {$User.Id} / {NOW()} / {TODAY() + 30} — current user / date macros
   • anything without {…} is a literal

   ❌ body: '{{ai_reply}}' — double-brace is the formula / template-field dialect, not flow values ❌ ticket: '$source.id' — a bare $ref is a literal string, not interpolated ✅ body: '{ai_reply}', ticket: '{source.id}'

7. create_record's outputVariable holds the created RECORD, not its id. Reference a field explicitly. ❌ update_record … fields: { ref: '{newRec}' } → yields the whole record object ✅ fields: { ref: '{newRec.id}' }

8. Time-relative rules ("alert N days before a date") are SCHEDULE flows, not record-change date-equality. record.end_date == daysFromNow(60) on a record-* trigger only fires if the record happens to be written on that exact day — unattended rules never run. And date EQUALITY never matches anyway: a date field carries a time component, so field == daysFromNow(N) (or { $in: [daysFromNow(N), …] }) compares two differently-timed timestamps and silently returns nothing (build warns flow-date-equality-filter). ✅ A daily schedule flow whose get_record filters each tier as a one-day window ($gte/$lt), never an equality:

   filter: { status: 'active', $or: [
     { end_date: { $gte: '{TODAY() + 7}',  $lt: '{TODAY() + 8}'  } },
     { end_date: { $gte: '{TODAY() + 30}', $lt: '{TODAY() + 31}' } },
     { end_date: { $gte: '{TODAY() + 60}', $lt: '{TODAY() + 61}' } },
   ] }
   

   (Use {TODAY() + N} template tokens in CRUD-node filter values — a cel\…`envelope is not evaluated there and would be compared as a literal object.) Abutting windows tile the timeline so each record matches exactly one tier — fires once, idempotent, no guard field. For "days remaining" in the message,daysBetween(today(), record.end_date)`.

9. script nodes call a registered function — that is all they do. Set config.function to a function registered via defineStack({ functions: { my_fn: (ctx) => … } }). It is required: an empty script node refuses at execute, and one pointing at an unregistered function fails loudly.

   The other dispatch forms were retired in spec 17 because none of them ran: config.actionType: 'email' | 'slack' were logger-backed stubs that delivered nothing (with config.template / .recipients / .variables feeding a message no channel sent), and inline config.script JS was never executed (no server-side sandbox). Use a notify node for real notification delivery, a connector_action (Slack connector) or http webhook for Slack, and a registered function for logic. Stored flows convert with os migrate meta --from 16.

   A flow function is a PURE compute step — it does NOT read/write the database. It receives ctx.input and returns a value; config.outputVariable exposes that value as a flow variable, and a later declarative node persists it. Keep data effects on the flow graph (visible, governed, build-checkable):

   // ❌ DON'T: expect the function to update the record itself (it has no data API)
   // ✅ DO: function returns values → outputVariable → update_record persists
   { id: 'ai', type: 'script', config: {
       function: 'helpdesk.aiTriageStub',     // returns { ai_category, ai_sentiment, … }
       inputs: { ticketId: '{record.id}' },   // inputs are interpolated
       outputVariable: 'ai',
   } },
   { id: 'apply', type: 'update_record', config: {
       objectName: 'helpdesk_ticket',
       filter: { id: '{record.id}' },
       fields: { ai_category: '{ai.ai_category}', ai_sentiment: '{ai.ai_sentiment}' },
   } },
   

   defineStack({ functions: { 'helpdesk.aiTriageStub': (ctx) => ({ ai_category: 'other', … }) } }). If you genuinely need data-lifecycle side effects (read/write other records), that's an L2 hook (objectstack-data) — hooks get ctx.api; flow functions don't.

   The rule is load-bearing: a script step reports no record metrics in the run summary because every write a pure function causes is a downstream node that counts itself. A function that writes anyway makes its run report acted: 0 — indistinguishable from a sweep that silently did nothing. When a function must write somewhere the platform cannot see (an upstream billing API), declare it so the run stays honest — its step is then counted as an effect that cannot be measured, never as zero:

   defineStack({ functions: {
     'helpdesk.aiTriageStub': (ctx) => ({ ai_category: 'other' }),  // pure — the default
     'billing.sync': { handler: syncBilling, effect: 'writes' },    // declared writer
   } });
   

10. Conditions are bare CEL — only the stdlib is callable. now(), today(), daysFromNow(n), daysAgo(n), daysBetween(a, b), isBlank(v), coalesce(a, b), abs/round/min/max, upper/lower/contains/matches, plus CEL built-ins (has, size, int, string, …) — see objectstack-formula for the full table. An UNKNOWN function (PRIOR(), a typo'd name) fails the build. And never wrap a field reference in {…} inside a condition — that's a template brace and fails as CEL: write record.x, not {record.x}.

CRM Automation Blueprint

For enterprise automation design, align with this CRM-style structure:

Default approach for metadata apps: model business lifecycle in Flow/Approval metadata first; reserve custom code for edge-case integrations.

Verify your work

Flow predicates fail silently at runtime when malformed: a typo'd field name, an unknown function, or a {…}-wrapped reference in a condition evaluates to null/false, so the flow "fires" but does nothing — and nothing errors at edit time. (Bare field refs like status == 'open' DO resolve in start/decision/edge conditions — the engine flattens the trigger record's fields into scope — but record.status == 'open' remains the canonical style.) Catch it at author time before reporting a flow done:

os validate     # CEL/predicate validation (record.<field> existence) + schema
# or: os build  # the same gates, plus emits dist/

This runs the ADR-0032 expression gate over every flow condition, edge guard, validation rule and sharing rule, exiting non-zero with a located, corrective message. Remember conditions are bare CEL (record.status == 'x'); only string node fields use {…} templates — see objectstack-formula. In a scaffolded project this is npm run validate.

References

See references/_index.md for the full list of Zod schemas (with one-line descriptions) — pointers into node_modules/@objectstack/spec/src/. Always Read the source for exact field shapes; do not rely on memory of property names.