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schema_version: 1 status: stable last_revised: 2026-04-28 sprint: W4

Workflow DAG Schema — version 1.0

This document is the formal contract for workflow.json files consumed by boruna workflow validate, boruna workflow run, the coordinator/worker HTTP protocol, and any downstream reader. It freezes the on-disk shape at sprint W4 of the 0.5.0 spec-freeze track.

Versioning

The schema follows a simple-semver rule:

The schema_version field is a single integer representing the current major version. Today: 1.
Minor revisions (“1.y”) add optional, additive fields. Readers built against any 1.x MUST accept any 1.y document (y >= x) and silently ignore fields they do not know.
Major revisions (“2.x”) signal a breaking change. Readers built for 1.x MUST refuse a schema_version: 2 document — they cannot guarantee correctness against a format they have not been taught.

This implies a forward-compatibility promise within a major and explicit operator action across a major.

Reader gate

The reference Rust reader is boruna_orchestrator::workflow::definition::WorkflowDef. It enforces the gate at parse time, per project conventions §1 (reject at parse, not later):

Condition	Result
`schema_version` field absent	`WorkflowParseError::MissingSchemaVersion`
`schema_version > 1`	`WorkflowParseError::UnsupportedSchemaVersion { found, supported_max }`
`schema_version` not an integer	`WorkflowParseError::InvalidJson`
`schema_version: 1` + valid body	`Ok(WorkflowDef)`

Stable surface strings (project conventions §2):

workflow.missing_schema_version
workflow.unsupported_schema_version
workflow.invalid_json

The constant boruna_orchestrator::WORKFLOW_DAG_SCHEMA_VERSION = 1 is the authoritative max-supported version for this build.

JSON Schema

Authoritative JSON Schema (Draft 2020-12) for a workflow.json document conforming to schema_version 1:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://boruna.dev/spec/workflow-dag/1.0.json",
  "title": "Boruna Workflow DAG (schema_version 1)",
  "type": "object",
  "required": ["schema_version", "name", "version", "steps", "edges"],
  "properties": {
    "schema_version": {
      "description": "Major schema version. MUST be 1 for this spec.",
      "type": "integer",
      "minimum": 1,
      "maximum": 1
    },
    "name": {
      "description": "Human-readable workflow identifier.",
      "type": "string",
      "minLength": 1
    },
    "version": {
      "description": "Operator-controlled workflow version (semver string).",
      "type": "string",
      "minLength": 1
    },
    "description": {
      "description": "Optional free-form description.",
      "type": "string"
    },
    "steps": {
      "description": "Map of step id -> step definition. Order is canonicalized via BTreeMap on read.",
      "type": "object",
      "minProperties": 1,
      "additionalProperties": { "$ref": "#/$defs/Step" }
    },
    "edges": {
      "description": "Explicit DAG edges as [from_step_id, to_step_id] pairs. Edges may also be implied via a step's `depends_on`. Cycles are rejected by the validator.",
      "type": "array",
      "items": {
        "type": "array",
        "minItems": 2,
        "maxItems": 2,
        "items": { "type": "string" }
      }
    }
  },
  "$defs": {
    "Step": {
      "type": "object",
      "required": ["kind"],
      "properties": {
        "kind": {
          "description": "One of: \"source\", \"approval_gate\", \"external_trigger\".",
          "type": "string",
          "enum": ["source", "approval_gate", "external_trigger"]
        },
        "source": {
          "description": "Path (relative to workflow dir) to the .ax file. Required for kind=\"source\".",
          "type": "string"
        },
        "required_role": {
          "description": "Required reviewer role. Required for kind=\"approval_gate\".",
          "type": "string"
        },
        "condition": {
          "description": "Optional gate condition expression (kind=\"approval_gate\"). Informational; not currently enforced by the runner.",
          "type": ["string", "null"]
        },
        "confidence_gate": {
          "description": "Optional calibrated auto-approval (kind=\"approval_gate\"). Additive in 1.x. When the score clears the threshold the gate completes without a human; otherwise it pauses as usual. See docs/design-conformal-gating.md.",
          "type": "object",
          "required": ["source_step", "calibration", "alpha_permille"],
          "properties": {
            "source_step": {
              "description": "A source step in the gate's depends_on (or with an edge into the gate). Its `result` must be an Int in 0..=1000 (permille); anything else escalates to a human.",
              "type": "string"
            },
            "calibration": {
              "description": "Calibration file, relative to the workflow directory, no `..`. JSON: {\"version\":1,\"examples\":[{\"score\":0..1000,\"correct\":bool}]}.",
              "type": "string"
            },
            "alpha_permille": {
              "description": "Largest allowed chance that a wrong answer skips a human, in permille.",
              "type": "integer",
              "minimum": 1,
              "maximum": 999
            }
          }
        },
        "description": {
          "description": "Optional human-readable description (kind=\"external_trigger\").",
          "type": ["string", "null"]
        },
        "capabilities": {
          "description": "Capabilities this step is allowed to invoke. Subset of the workflow policy's allow-list.",
          "type": "array",
          "items": { "type": "string" },
          "default": []
        },
        "inputs": {
          "description": "Map of local input name -> upstream reference of the form \"<step_id>.<output_name>\". Cross-step data flow.",
          "type": "object",
          "additionalProperties": { "type": "string" },
          "default": {}
        },
        "outputs": {
          "description": "Map of output name -> declared type label (informational). The runner stores the actual step value under the key \"result\".",
          "type": "object",
          "additionalProperties": { "type": "string" },
          "default": {}
        },
        "depends_on": {
          "description": "Implicit edges: this step runs only after every listed step has completed. Combined with `edges` to form the full DAG.",
          "type": "array",
          "items": { "type": "string" },
          "default": []
        },
        "timeout_ms": {
          "description": "Wall-clock budget per attempt. Exceeding fails the attempt with `wall_time_exceeded`.",
          "type": ["integer", "null"],
          "minimum": 0
        },
        "retry": { "$ref": "#/$defs/RetryPolicy" },
        "budget": { "$ref": "#/$defs/StepBudget" }
      }
    },
    "RetryPolicy": {
      "type": ["object", "null"],
      "required": ["max_attempts"],
      "properties": {
        "max_attempts": {
          "description": "Upper bound on attempts. <= 1 means single-attempt always.",
          "type": "integer",
          "minimum": 1
        },
        "on_transient": {
          "description": "Legacy gate (used when `retry_on` is empty): true retries on any failure, false is single-attempt.",
          "type": "boolean",
          "default": false
        },
        "retry_on": {
          "description": "Allowlist of error classes that should trigger a retry. Unknown class strings are silently ignored (typo-safe; conservative-by-default).",
          "type": "array",
          "items": { "type": "string" },
          "default": []
        }
      }
    },
    "StepBudget": {
      "type": ["object", "null"],
      "properties": {
        "max_tokens": { "type": ["integer", "null"], "minimum": 0 },
        "max_calls":  { "type": ["integer", "null"], "minimum": 0 }
      }
    }
  }
}

Notes:

The schema does NOT use "additionalProperties": false. Forward- compatibility (§Versioning above) requires that 1.x readers accept additive fields introduced in 1.y minors.
The schema does NOT require description, capabilities, inputs, outputs, depends_on, timeout_ms, retry, budget. The reference reader applies serde defaults.
The schema does NOT enforce DAG acyclicity, edge endpoint existence, or input reference well-formedness — these are enforced by the validator (WorkflowValidator::validate), one layer above structural parsing.

Field-level documentation

Top-level

schema_version (required, integer = 1) — major schema version. See §Versioning and §Reader gate above.
name (required, non-empty string) — workflow identifier surfaced in CLI output, logs, and evidence bundles.
version (required, non-empty string) — operator-controlled workflow version (typically semver). Independent of schema_version; this versions the workflow, not the schema.
description (optional string) — free-form prose.
steps (required, non-empty map) — step_id -> step body. Step ids are unique within a workflow.
edges (required array) — [from_step_id, to_step_id] pairs. Combined with each step’s depends_on to form the DAG.

Step body

A step’s kind discriminates which fields are required:

kind: "source" — compile and run an .ax file. Requires source (path relative to the workflow directory). The step’s return value is stored as the canonical result output and is available to downstream steps via <step_id>.result.
kind: "approval_gate" — pause the run until an operator records an approval/rejection via boruna workflow approve. Requires required_role. Optional condition is informational. Optional confidence_gate lets the gate complete without a human when a calibrated confidence score is high enough (see docs/design-conformal-gating.md). It is not supported with --submit-only or the coordinator, which reject it at submit time.
kind: "external_trigger" — pause the run until an external event arrives via boruna workflow trigger <run-id> <step-id>. Optional description is operator-facing only.

Common optional fields (all kinds):

capabilities, inputs, outputs, depends_on, timeout_ms, retry, budget — see the JSON Schema §$defs above for shape and defaults. Detailed runner semantics: see docs/architecture-coordinator-worker-http.md and docs/architecture-output-blob-refs.md.

Backwards-compatibility commitment

For any reader built against schema_version 1.x:

Within a major (1.x → 1.y, y > x): the reader MUST accept the document. Future minors only ADD fields; they MUST NOT change the meaning of existing fields, MUST NOT introduce new required fields, and MUST NOT tighten existing field types.
Across a major (1.x → 2.0): the reader MUST refuse with a typed UnsupportedSchemaVersion error. The operator must upgrade Boruna or downgrade the workflow.

This commitment is exercised in unit tests at orchestrator/tests/workflow_integration.rs (sprint W4):

workflow_def_loads_with_schema_version_1
workflow_def_rejects_missing_schema_version
workflow_def_rejects_future_major_version
workflow_def_accepts_unknown_optional_fields (forward-compat)
example_workflows_all_validate

Replay invariant (§15)

schema_version is part of the canonical-JSON serialization that feeds WorkflowRunner::workflow_hash_from_def. Two workflows that differ only in schema_version produce different workflow_hash values, so evidence bundles correctly bind the schema generation under which a run was executed. Replay verification fails closed if the on-disk schema_version no longer matches the recorded hash.

Post-1.0 additive notes (no version bump)

These behaviors are additive extensions of the 1.0 spec — they are visible only to operators who opt in, do not change the on-disk shape of any 1.0 workflow, and do not change the schema_version: 1 constant.

Versioned worker capability advertisements (post1-T-1.3). RegisterRequest.advertised_capabilities (the wire shape used at worker registration, not part of the workflow def) now accepts {name, version} objects in addition to bare strings. The coord normalizes legacy strings to the coord’s current Capability::version() for that name. Routing and the new coord.capability_version_mismatch claim error are documented in docs/reference/error-kinds.md. No workflow JSON change.

Cross-references

docs/architecture-coordinator-worker-http.md — the wire protocol that ships WorkflowDef between coordinator and worker.
docs/architecture-claim-lease-persistence.md — how the persisted run metadata embeds WorkflowDef for resume.
docs/architecture-output-blob-refs.md — how step outputs (the result slot) reference large blobs.
docs/ORCHESTRATOR_SPEC.md — broader orchestrator design rationale.

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