ADR-013: Cross-phase informs edges are valid when declared on the downstream artifact

Source identity (from 02-design/adr/ADR-013-cross-phase-informs-edges.md):

ddx:
  id: ADR-013
  depends_on:
    - helix.prd

ADR-013: Cross-phase informs edges are valid when declared on the downstream artifact

Date	Status	Deciders	Related	Confidence
2026-05-30	Accepted	HELIX maintainers	artifact dependencies, schema validator	High

Context

Aspect	Description
Problem	The audit flagged the Deploy artifact `monitoring-setup` declaring `informs: metrics-dashboard`, an Iterate artifact in a later phase. It is unclear whether HELIX permits an artifact to declare an `informs` edge that crosses a phase boundary into a downstream phase, and whether the back-edge must also be declared on the consumer.
Current State	`workflows/activities/05-deploy/artifacts/monitoring-setup/meta.yml` declares `informs: metrics-dashboard`. `workflows/activities/06-iterate/artifacts/metrics-dashboard/meta.yml` declares both `informed_by` and `informs` lists but does not currently encode every back-edge for every upstream `informs`. The schema validator does not enforce edge symmetry across artifacts.
Requirements	The methodology must not forbid real evidence-flow edges that cross phases (production telemetry feeding dashboards is a real flow). At the same time, cross-phase edges must be explicit on both ends so that walking from either side reveals the relationship.

Decision

An artifact may declare informs an artifact in a later phase. The cross-phase edge is valid when:

The source artifact’s purpose produces evidence the target consumes (the edge encodes a real evidence flow, not a speculative association), and
The edge is declared on both sides — informs on the source artifact and informed_by on the target artifact — or in a single canonical place chosen by the consumer when only one direction can be authoritative.

The monitoring-setup → metrics-dashboard edge is the canonical example: production telemetry configured in Deploy feeds the dashboards consumed in Iterate. The methodology accepts this as a valid cross-phase informs edge.

Key Points: cross-phase informs allowed | edge must be real evidence flow | declared on both ends (or canonical single place) | symmetry check is a follow-up validator concern, not required by this ADR

Alternatives

Option	Pros	Cons	Evaluation
Forbid cross-phase informs edges entirely; restrict `informs` to same-phase artifacts	Simpler validator; clear phase boundary	Erases real evidence flows (Deploy telemetry → Iterate dashboards); forces artifacts to invent intermediate hops or drop the edge	Rejected: phase boundary is not a methodology firewall against evidence flow
Allow cross-phase informs but only when declared on the upstream side	Single source of truth	Walking from the consumer no longer reveals the upstream; reviewers must scan all earlier phases to find inbound edges	Rejected: breaks bidirectional discoverability
Allow cross-phase informs; require declaration on both ends (or a canonical single place); leave symmetry enforcement as a follow-up validator concern	Preserves real evidence flows; keeps edges discoverable from both ends; does not block this ADR on validator work	Phase 3 walk must check both sides; some artifacts will need back-edges added	Selected: accepts the real flow without overcommitting the validator

Consequences

Type	Impact
Positive	Real cross-phase evidence flows (e.g., Deploy telemetry → Iterate dashboards) are recognized as first-class edges.
Positive	Both-end declaration keeps the dependency graph walkable from either direction.
Positive	Phase 3 has a clear rule: walk all artifacts for `informs` edges and ensure the back-edge is declared.
Negative	Phase 3 must check edge symmetry across the full artifact set and add missing back-edges where the upstream declares `informs` but the downstream does not declare `informed_by`.
Neutral	The schema validator is unchanged in this ADR. Symmetry enforcement is a follow-up Phase 1B validator concern.

Risks

Risk	Prob	Impact	Mitigation
Authors declare speculative cross-phase edges that are not real evidence flows	M	M	Phase 3 walk and reviewers reject edges that do not match the source artifact’s stated purpose
Back-edges drift out of sync as artifacts evolve	M	M	Follow-up Phase 1B validator extension checks edge symmetry; until then, the Phase 3 walk establishes the baseline
Confusion about whether to declare on one end or both	L	L	This ADR states the rule: both ends, or a single canonical place chosen by the consumer when only one direction can be authoritative

Validation

Success Metric	Review Trigger
Every `informs` edge declared on an upstream artifact has a matching `informed_by` entry on the downstream artifact (or a documented canonical-single-place choice)	A Phase 3 walk finds an upstream `informs` with no corresponding downstream `informed_by`
`monitoring-setup` → `metrics-dashboard` is preserved as a valid cross-phase informs edge	A review flags the edge as invalid because it crosses a phase boundary
Schema validator extension for edge symmetry is filed as a follow-up Phase 1B concern	Edge symmetry drift recurs and is not surfaced mechanically

References

PRD
Plan: 2026-05-30 Artifact Types and Concerns Audit
ADR-004: Dependencies Encoding