Every term in this reference carries exactly one sense, fixed here. Terms are linked on first use and never synonymized. Where vocabulary and engine behavior appear to disagree, the Evidence Ledger is authoritative and the documentation is treated as defective.
Core concepts
Execution plane
The runtime category Escepine occupies: the layer between declarative workflow definitions and the agents and tools that execute them, owning dispatch, state, checkpointing, policy enforcement, verification, compensation, and audit. Guarantees specified in the architecture overview.
SOP (Standard Operating Procedure)
The declarative workflow definition — a JSON artifact stating what must happen, in what order, under which policies, against which verification criteria. The entire authoring surface of the platform: no second configuration language, no imperative escape hatch. Contract: SOP reference; worked example: annotated SOP.
Engine pipeline
The ordered phases run for every step: hydration, strategist, gatekeeping, planner, policy evaluation, schema validation, executor, verifier — and compensation on terminal failure. Each phase has a defined input, output, and failure behavior; none improvises. Specified in the execution engine.
Evidence Ledger
The append-only, checksum-chained record of every event and artifact a workflow produces — the audit surface and the source of truth. The Control Plane renders views of it; nothing feeds it. Specified in evidence ledger and ledger and artifact formats.
Saga compensations
The rollback discipline for partial execution: halt, reverse-iterate completed steps, compensate each, reset state to the last valid checkpoint, record the full sequence in the Evidence Ledger. Exists because retry cannot undo committed side effects. Specified in saga compensations.
Regeneration
The bounded retry mechanism for failed sub-workflows: re-instantiation as a new generation — new identity, new checkpoint trail — never a re-run in place. Escalation counters persist across generations; the circuit breaker halts repeat deterministic failures. Specified in sub-SOP orchestration and retry and recovery.
Zero-case rule
The authoring rule that verification criteria must be satisfiable by every valid outcome, including an empty one. Under honest scarcity the correct output is a self-attesting empty result, and verification must treat it as success — criteria that cannot pass on empty are an authoring defect no retry fixes. Specified in verification blocks.
HITL gate
The point at which the engine parks a workflow and waits for an explicit human signal before proceeding. An escalation ladder precedes the park; a response is consumed exactly once and triggers a fresh planning iteration with the answer injected — not a blind re-run. Specified in HITL gates and HITL blocks.
Reference vocabulary
| Term | Definition |
|---|---|
| Action type | Execution class of a step: HUMAN, REASONING, EXECUTION, SUB_SOP. See step types. |
| Artifact | Immutable, checksummed output record, referenced by identifier during hydration. |
| Budget hierarchy | Nested limits bounding every workflow: iterations, step retries, escalations, regeneration cap, global timeout. |
| Checkpoint | Persisted state at a safe boundary; the unit of resume-from and the reset target of compensation. |
| Circuit breaker | Halts regeneration when successive generations fail with the same deterministic signature. |
| Control Plane | Operator surface: live canvas, signal channel, per-step inspection. A view over the Evidence Ledger. |
| Dependency | Explicit ordering constraint between steps; what makes a state machine a DAG. |
| Deterministic failure | Recurs identically on re-execution with no state change. Not retryable by definition. |
| Escalation | Tiered human signal — 1 of N, 2 of N — preceding a park; carries diagnosis and consumed inputs. |
| Fan-out | Concurrent dispatch of steps whose dependencies are satisfied; artifacts merge at the join. |
| Fresh-iteration resume | On a human response: execution state cleared, planning rerun with the response in context. |
| Gatekeeping | Pipeline phase deciding whether a step requires human participation, and at what tier. |
| Generation | The nth instantiation of a sub-workflow within one parent run; the _rN suffix in identifiers. |
| Global timeout | Wall-clock ceiling on a workflow, max_global_workflow_timeout_ms. |
| Honest scarcity | Input contains no items meeting a step's selection criteria. A valid outcome, not a failure. |
| Hydration | Pipeline phase assembling a step's input context from artifacts, state, and prior outputs. |
| Intent matching | Mapping a natural-language request to a candidate SOP, ahead of execution. |
| Iteration | One planner-to-verifier cycle within a step attempt; a failed verdict's critique feeds the next. |
| MCP tool | Executable capability exposed through the sandbox orchestrator, declared with a JSON schema. |
| Park | Paused state awaiting human resolution. Consumes no compute. Resolution: data provision, instruction, gap acceptance. |
| Phase | One stage of the engine pipeline. |
| Planner | Pipeline phase producing a step's structured output proposal. |
| Policy evaluation | Pre-execution decision: ALLOW proceeds; DENY halts and parks. See policy gateway. |
| Policy Gateway | The Cedar evaluation service; embedded engine-side in the current baseline. |
| Resume-from | Checkpoint-based restart with the completed prefix seeded and the failed step re-entered. |
| Sandbox | Ephemeral, restricted container in which MCP tools execute; destroyed after each execution. |
| Schema validation | Two structural gates: tool input before execution, output before commit. Deviation is failure, never pass-through. |
| Step | Atomic unit of a state machine: identity, action type, dependencies, policy attachment, verification contract. |
| Strategist | Pipeline phase routing the step on each entry: planning, verifier back-edge, or human intake. |
| Strict mode | Global SOP flag tightening validation and failure semantics. Behavior matrix in the SOP reference. |
| Sub-SOP | A step whose action invokes another SOP as a nested workflow. |
| Sub-workflow | Running child instance of a sub-SOP: own identity, checkpoint trail, budget envelope. |
| Verification | Post-completion, pre-commit check of output against criteria, with step input in scope. |
| Verifier | Pipeline phase rendering the verdict: pass, or fail with a critique routed back to planning. |
| White-glove deployment | Staging pilot in your environment, then production in your VPC. No self-serve tier. |
| Workflow | Running instance of an SOP: one identifier, one ledger trail, one budget envelope. |
Identifier notation
Formats are contractual; values are per-run.
| Notation | Meaning | Specified in |
|---|---|---|
art_… |
Artifact identifier; content-checksum-addressed. | Evidence Ledger |
_rN |
Generation suffix on a sub-workflow instance. | Sub-SOP orchestration |
sop_id |
SOP identity, as in competitor_deep_dive. |
SOP reference |
step_id |
Step identity within an SOP. | SOP reference |
workflow_id |
Running instance identity. | Ledger and artifact formats |
| Event types | Closed event vocabulary: step_start, policy_eval, hitl_park, compensation, and the rest. |
Evidence Ledger |
DD01–DD12 |
Step identifiers of the annotated example SOP. | Annotated SOP |
Terminology discipline
Informal terms surface in stack traces and engine output during evaluation. The mapping connects them to the canonical terms every document uses.
| Term you may encounter | Canonical term |
|---|---|
| node | phase |
| respawn, re-run | regeneration |
| child flow, sub-flow | sub-workflow |
| flow config, DAG file | SOP |
| waiting queue | park |
| cached output | artifact |
| retry storm | unbounded regeneration — the defect class the circuit breaker prevents |