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Epic 6, Story 7, Task 115: Last-modified stamp forensic integrity guardrails

Task ID: E6:S07:T115
Status: IN PROGRESS
Priority: CRITICAL
Estimated Effort: Medium
Created: 2026-04-20
Last updated: 2026-04-20 (ICW planning package created and linked)
Code: E6S07T115

Upstream: UXR-009 – Last-modified stamp forensic integrity and drift protection

Coordinates: E6:S07:T101, E6:S07:T110

Input​

  • User report: row-level Last modified timestamps are being overwritten by board rewrite passes.
  • Observed board state in fbuboard.md / kboard.md showing homogenized timestamps.
  • Existing UKW temporal logic in Story 007 tasks (T101, T110, T108).

Problem statement​

Timestamp churn from non-substantive board rewrites corrupts forensic signal. Operators can no longer infer true recency of work per item, breaking temporal drift triage and stale-work detection.

Deliverable​

  • Deterministic stamp-integrity policy and implementation guardrails where row stamps mutate only with substantive source evidence.
  • Update workflow behavior and validation to suppress synthetic stamp churn.
  • Regression coverage for "rewrite without underlying work" scenarios.

Scope​

  1. Formalize substantive vs non-substantive mutation rules for row timestamps.
  2. Update UKW/RW-related board mutation paths to enforce work-evidence gating.
  3. Add validator/audit reporting for suspicious mass stamp rewrites.
  4. Add test coverage for no-op rewrite, sort/reformat, and real-work update cases.

Acceptance Criteria​

  • AC1: Policy text explicitly states that board rewrite alone does not update Last modified.
  • AC2: UKW/RW row mutation logic updates stamp only on substantive source deltas.
  • AC3: Validation detects synthetic mass updates and emits blocking or high-signal warnings.
  • AC4: Tests cover both allowed stamp updates and prohibited rewrite-only updates.
  • AC5: UXR-009, this task, story checklist, and boards are fully cross-wired.

References​