Velt Approval Engine Best Practices

Velt Approval Engine Best Practices

Implementation guide for the Velt Approval Engine — a declarative workflow runtime for multi-step agent + human approval processes. Covers the workflow model (definitions = nodes + edges + groups), the 14 REST endpoints under /v2/workflow/* (definitions, executions, steps), webhook delivery with HMAC signature verification, and idempotency/recovery patterns.

When to Apply

Reference these guidelines when:

• Authoring approval workflow definitions — nodes (agent, human), edges (with optional when gating expressions), groups (parallel quorum)
• Dispatching executions — always with an idempotencyKey; configuring webhookUrl + webhookSecret together
• Recording decisions — human reviewer approvals/rejections (/steps/recordReviewerDecision) or external blocking-agent resolutions (/steps/recordAgentResolution)
• Building webhook receivers — HMAC-SHA256 signature verification on raw bytes, idempotency on (executionId, seq), retry schedule, missed-event recovery
• Using quorum groups with waitAll / cancelOnQuorum / joinOnQuorum policies
• Configuring SLAs (slaMs on a node) and the required breach-routed outgoing edge
• Admin-scoped operations (/steps/cancel, /steps/resolve)
• Debugging INVALID_ARGUMENT linter rejections (cycle, dangling-edge, unreachable-node, missing-breach-edge, group-joinonquorum-members-must-share-successors)

For general Velt REST API patterns (Comments, Notifications, Activity, etc.), see velt-rest-apis-best-practices — only the Approval Engine domain is covered here.

Rule Categories by Priority

Quick Reference

Concepts (HIGH)

• concepts-workflow-model — definitions = nodes + edges + groups + loops; node shapes (agent / human); reviewerEmails (0–50, surfaces in step output); commentBody (stored on output — engine does NOT auto-create annotations); onReject shorthand (Form A: routeToNodeId; Form B: loopBack); strict-mode: every human node needs onReject or loop membership; top-level loops[] (loopId, entryNodeId, bodyNodeIds 1–50, maxIterations 1–20, previousAttempts threading); default loop predicate decision == 'reject' && rejectorMandatory == true does NOT fire when step resolved via /steps/resolve reject actions (use recordReviewerDecision instead); edge when expressions; group quorum policies (waitAll / cancelOnQuorum / joinOnQuorum)

REST Endpoints (HIGH)

• rest-foundations — auth headers, request/response envelope, canonical error codes (including DEADLINE_EXCEEDED), schema-level validation message reference
• rest-definitions — 5 endpoints: create / update (with ifVersion optimistic lock) / get / list / delete; full 25-rule linter reference (16 graph+group rules + 9 new loop rules); scope per-level required fields (organizationId for organization scope; both organizationId + documentId for document scope); server-namespaced ID caveat; triggers shape ({ triggerId, eventName?, filters? }) — descriptive metadata only in v1, engine does NOT auto-dispatch
• rest-executions — 5 endpoints: dispatch (idempotencyKey + webhook config) / get / list / cancel / getEvents (sinceSeq recovery + externally-visible event enumeration cross-referenced to webhooks-delivery, including loop events); v1 list limitation: no organizationId/documentId filter support
• rest-steps — 4 endpoints: recordReviewerDecision (unknown reviewer silently accepted as unknown responder — no INVALID_ARGUMENT) / recordAgentResolution / cancel (admin, actorId REQUIRED 1–256 chars, error matrix: INVALID_ARGUMENT/FAILED_PRECONDITION/NOT_FOUND) / resolve (action-discriminated: force-approve, force-reject, force-complete, force-fail, reviewer-approve, reviewer-reject; actorId REQUIRED 1–256 chars; reason ≤ 2000 chars; reject actions do NOT populate rejectorMandatory — loop predicates won't fire; response shape { resolved, executionId, stepId, action })
• rest-object-views — TypeScript shapes for ExecutionView, StepView, DefinitionView, ApprovalEventView, the human step output aggregator rollup, and the joinOnQuorum successor input

Webhooks (HIGH)

• webhooks-delivery — HMAC-SHA256 signature verification on raw bytes, delivery headers, retry schedule, event-type catalog (now includes loop.iteration-started and loop.exhausted), at-least-once idempotency
• webhooks-inbound-handler — inbound HTTP endpoint that external systems POST raw JSON to (no {data: ...} envelope), bearer-token auth, signed callback tokens, per-source rate limiting, body-size limits, SSRF URL guard; distinct from outbound delivery and from the deferred node.type === "webhook"

How to Use

Read individual rule files for detailed explanations and code examples:

rules/shared/concepts/concepts-workflow-model.md
rules/shared/rest/rest-foundations.md
rules/shared/rest/rest-definitions.md
rules/shared/rest/rest-executions.md
rules/shared/rest/rest-steps.md
rules/shared/rest/rest-object-views.md
rules/shared/webhooks/webhooks-delivery.md
rules/shared/webhooks/webhooks-inbound-handler.md

Each rule file contains:

• Brief explanation of why it matters
• Concrete request/response examples
• Common pitfalls and what NOT to do
• Verification checklist
• Source pointers to official docs

Compiled Documents

• AGENTS.md — Compressed index of all rules with file paths (start here)
• AGENTS.full.md — Full verbose guide with all rules expanded inline