Ideation workflow: §5.2 trigger list vs §6.1 blast-class table read as one axis

Context

Live empirical anchor, 2026-07-16 (the D#15249 graduation): the Discussion author declared Scope: low-blast per §6.1's class table (feature-implementation/documentation wave — a correct §6.1 reading), the design authority confirmed the classification, and both independently concluded the §5.2 Architectural Step-Back was voluntary. Both were wrong: §5.2's own trigger list makes "Epic-bound (decomposes to ≥3 sub-tickets)" a standalone Step-Back trigger, independent of the §6.1 consensus axis. The miss surfaced only at PR review (PR #15255 cycle 1, cross-family), cost a [GRADUATION_DEFERRED] cycle, and was resolved by conservative reclassification. Two maintainers misreading the same seam the same way in one pass is a substrate defect, not a reader defect.

The Problem

.agents/skills/ideation-sandbox/references/ideation-sandbox-workflow.md carries two classification surfaces that read as one axis but govern different gates:

• §5.2 "Trigger — high-blast-radius (any ONE qualifies)" — six conditions (durable-content layout, CI coupling, migration, skill/rule substrate, cross-substrate, epic-bound ≥3 subs) gating the mandatory Step-Back sweep. Its "Out of scope" paragraph exempts "low-blast-radius proposals (single-PR-worth, bounded artifact, no cross-substrate coupling)".
• §6.1's blast-class table — high-blast (substrate evolution, rule changes, architectural primitives, cross-cutting policies) vs low-blast (bug fix, feature implementation, documentation, tests) gating the §6 Consensus Mandate (Signal Ledger, family-keyed quorum).

The trap: an epic-bound feature/documentation wave is low-blast under the §6.1 table yet Step-Back-mandatory under §5.2's trigger list — and §5.2's own "Out of scope" wording ("low-blast-radius proposals … do NOT require §5.2") invites reading a §6.1 low-blast declaration as a §5.2 exemption. Nothing states the axes are independent.

The Architectural Reality

• .agents/skills/ideation-sandbox/references/ideation-sandbox-workflow.md — §5.2 trigger list (~lines 91–97), §5.2 "Out of scope" (~line 114), §6.1 classification paragraph + table (~lines 124–133).
• The §5.2 out-of-scope wording defines its own exemption ("single-PR-worth, bounded artifact, no cross-substrate coupling") — which is NARROWER than §6.1 low-blast, but shares the "low-blast-radius" name with it. The name collision is the defect.

The Fix

Two clarifying sentences, trigger-scoped (no new rules):

1. In §6.1's classification paragraph: "Blast-class governs the §6 Consensus Mandate only; §5.2's Step-Back triggers fire independently — an epic-bound (≥3 subs) wave is Step-Back-mandatory even when its consensus class is low-blast."
2. In §5.2's "Out of scope" paragraph, replace the bare "low-blast-radius proposals" phrase with its own definition to break the name collision: "proposals outside every trigger above (single-PR-worth, bounded artifact, no cross-substrate coupling) — note this is narrower than §6.1's low-blast consensus class."

Substrate Accretion Defense: net +2 sentences; decay-mitigation rationale — a demonstrated same-day two-maintainer misread with a full deferral-cycle cost; the sentences are cross-reference clarifications, not new gates; sunset condition — if the two classification axes are ever merged into one (a legitimate future MX-loop outcome), these sentences retire with the merge.

Acceptance Criteria

• Both sentences landed at the named seams; no other workflow semantics changed.
• The §5.2/§6.1 independence is stated at BOTH reading entry points (an author reading §6.1 first, a reviewer reading §5.2 first).
• PR body carries the §1.1 substrate-mutation slot-rationale.

Out of Scope

• Merging the two classification axes (a real design question — belongs in a future ideation pass if the friction recurs post-clarification, not in this fix).
• Any change to the trigger conditions or the consensus quorum rules themselves.

Related

• D#15249 (the live misread + conservative resolution), PR #15255 cycles 1–2 (the catch + acceptance), #15254.

Decision Record impact: none (clarifies existing authority; changes no decision).

Origin Session ID: 75ed6708-c66b-4989-862d-2286e87abbf1 Retrieval Hint: "step-back trigger blast-class two axes epic-bound low-blast misread" Live latest-open sweep: latest 20 open checked 2026-07-16 ~14:35Z — no equivalent (#15257/#15258 are review-culture/escalation substrate, disjoint). A2A claim window scanned same minute — no competing claim.