Architecture Signals & Invalidated Assumptions — Retrospective

Scope:

• Derived from Weekly Learnings published between 2026-02-21 and 2026-03-01

Architecture signals (emergent)

• Pattern: Observability as architectural contract (event emission + taxonomy + test-backed enforcement).
• Pattern: Deterministic-first design before introducing generative layers.
• Pattern: Mode awareness centralized at system boundary (orchestrator-owned configuration).
• Pattern: Canonical builder ownership to eliminate duplication (SnapshotBuilder as single source of truth).
• Anti-pattern: Service-layer infrastructure leakage (UI imports, logging, file I/O inside domain-facing services).
• Anti-pattern: Inferred LLM usage telemetry instead of execution-based tracking.
• Heuristic: LLM should decorate insights, not decide core system positioning.
• Heuristic: If span lifecycle cannot be reasoned about deterministically, observability is incomplete.
• Heuristic: Remove duplication early to prevent silent metric drift.

Assumptions invalidated

• Assumption: Observability would be sufficient without strict taxonomy enforcement.
• Assumption: LLM usage inference was adequate for cost governance.
• Assumption: Roadmap clarity could be maintained without consolidation into a single decision surface.
• Assumption: Boundary discipline could be relaxed temporarily without architectural consequences.

Notes on confidence

• High confidence: Observability-as-contract and deterministic-first signals (repeated across multiple audit iterations).
• High confidence: Boundary discipline and mode-centralization principles (validated through refactors).
• Medium confidence: Orchestrator breadth as future risk (signal emerging but not yet critical).
• Tentative: Need for earlier architectural checklists before feature implementation (requires repetition across more cycles).