Ln 21 System Design Baseline Builder

System Design Baseline Builder

Goal: Create or update one durable source of truth for the project's architecture-driving requirements and constraints. Change only the approved architecture document; do not design the solution, review a plan, audit implementation, edit product code, or invent missing targets.

Execution contract: The checklist defines completion. Track each item internally as PENDING, PROVEN with evidence, CLEARED with evidence its condition is absent, or UNPROVEN with a gap; reading, delegation, tool failure, a zero exit status, or a self-reported success is not proof; only the observed outcome is. Reconcile after each section. Before returning, resolve all PENDING, count only PROVEN and CLEARED, and apply verdict and approval rules to every gap. Preserve intent, scope, and existing authorization. Continue authorized work; ask only for consequential unresolved choices or required external approval. When no one can answer during the run, state the exact question and apply the skill's verdict for the remaining gap instead of waiting or guessing. Scale depth to material risk without skipping checks. Preserve dependency and safety order; otherwise choose an appropriate verification method. Accept equivalent user or repository evidence; no other skill, named artifact, or complete lifecycle is required. Preserve source requirement and decision IDs. Bind reused evidence to relevant source versions, dirty changes, configuration, and environment; invalidate only affected claims. On continuation, reconcile task, authorization, current state, and unresolved evidence. For long work, return a compact continuation record or update an already authorized artifact; read-only skills do not persist it. Distinguish artifact readiness, verified behavior, and external-action authority. Prepare authorized work before required approval. If blocked by an instruction, cite its exact source and unresolved boundary; do not invent approval gates from caution.

Tool Routing

Use external research only when a time-sensitive fact changes a constraint. Do not browse for values that must come from product owners, operators, the repository, or measured workload.

Artifact Rules

• Prefer an existing unambiguous architecture-requirements document.
• Otherwise use docs/architecture/system-design-baseline.md.
• Read before writing, preserve unrelated content, and update facts in place instead of creating parallel truth.
• Classify applicability separately as APPLICABLE or NOT_APPLICABLE, with evidence for exclusions.
• Rank each applicable item as DRIVER, SUPPORTING, or INFORMATIONAL.
• Classify evidence separately as CONFIRMED, ASSUMED, or UNKNOWN.
• Separate observed current values, required targets, hard limits, and future evolution triggers.
• Express quality attributes through observable scenarios and response measures; record undecided targets as missing decisions rather than inventing numbers.
• Treat the baseline as versioned project knowledge, not an immutable promise.

Checklist

1. Establish Scope and Destination

• Resolve the project, business outcome, intended readers, approved documentation scope, and language.
• Read applicable repository instructions and inspect Git state so unrelated changes remain untouched.
• Search for existing requirement, architecture, SLO, recovery, security, cost, and ownership documents.
• Select one canonical artifact: reuse a clear equivalent or choose the default path; explain why no duplicate will be created.
• Return BLOCKED if the destination is ambiguous and choosing one could split project truth.

2. Build the Evidence Ledger

• Collect business goals, actors, journeys, scope, non-goals, and decision horizon with their sources and confidence for the driver analysis; do not create a second context inventory.
• Record sources for current workload, data volume, service behavior, platform limits, and existing commitments.
• Separate repository facts from stakeholder choices and estimates.
• Detect contradictions between documents, code, configuration, and stated requirements; preserve both claims until resolved.
• Ask only for choices whose absence materially changes architecture; mark all other gaps UNKNOWN.

3. Define and Prioritize Architecture Drivers

• Business and scope: Record actors, critical journeys, business horizon, scope, non-goals, and externally committed outcomes.
• Demand and data scale: Record current and target users, rates, concurrency, payloads, growth, retention, and forecast horizon where relevant.
• User-observable service quality: Define SLIs and SLOs for availability, latency, throughput, error rate, correctness, or freshness with measurement windows.
• Data semantics and recovery: Define consistency, ordering, idempotency, reconciliation, durability, backup, RTO, RPO, and acceptable data loss at affected boundaries.
• Security, privacy, and compliance: Define trust boundaries, data classification, residency, access, audit, and destructive-action constraints.
• Operations and economics: Define ownership, operational capacity, cost envelope, supported regions, delivery cadence, and platform or vendor constraints.
• Evolution: Record thresholds, business events, or evidence that justify revisiting an assumption, target, or deferred capability.
• Separate applicability, criticality, and evidence status; do not use UNKNOWN to mean unimportant or NOT_APPLICABLE.
• Prioritize the few scenarios most likely to shape architecture and express each as source/stimulus/environment/artifact/response/measure.