12-EFT.WP.Methods.Repro v1.0 | Chapter 13 Change Management and Version Strategy

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Chapter 13 Change Management and Version Strategy

I. Scope and Objectives

• Establish an end-to-end strategy—from change identification, impact assessment, dual-run comparison, cutover and rollback, to archival—so that any version evolution is measurable, reversible, and forensically verifiable under a fixed EnvLock, data fingerprint, time-base mapping ts = alpha + beta * tau_mono, and the benchmark-suite gauges.
• Expected outputs: MigPlan, DiffMatrix, CutoverReport, RollbackReport, CHANGELOG, and the set of compatibility flags; all linked to Chapter 8 scoring and Chapter 12 acceptance gates to keep the risks on delta_rep, delta_psd, r_tb, and eps_mass within budget.

II. Terms and Symbols

• version = MAJOR.MINOR.PATCH: semantic versioning; channel ∈ {canary, stable, LTS}.
• compat flag: a set of compatibility toggles, e.g., flag.strict_nan, flag.psd_window_v2, flag.timebase_v2.
• W_mig: migration window; T_dep: deprecation effective time; T_grace: grace period.
• budget = { b_rep , b_psd , b_tb , b_mass }: change-differential budgets limiting delta_rep, delta_psd, r_tb, eps_mass.
• anchor: rollback anchor, defined as anchor = hash( EnvLock || PipelineCard || ParamCard || fingerprint ).
• DiffMatrix: per-case dual-run matrix with delta_rep_i, delta_psd_i, r_tb_i, R_coef_i, and perf_norm_i.

III. Postulates and Minimal Equations

1. P31-50 Compatibility corridor postulate
   With compatibility flags enabled and an agreed budget, the observable behavioral differences between the old and new implementations satisfy
   Pr( delta_rep <= b_rep ∧ delta_psd <= b_psd ∧ r_tb <= b_tb ∧ eps_mass <= b_mass ) → 1 as samples and windows become sufficient.
2. P31-51 Rollback reachability postulate
   Any stable/LTS release must define an anchor and a rollback playbook such that rollback_to( anchor ) returns to an in-gate state in a finite number of steps.
3. S32-60 Change-class criterion
   • class(change) = MAJOR iff schema_break ∨ api_break ∨ require_new_data ∨ require_new_EnvLock
   • class(change) = MINOR iff default_param_change ∨ perf_shift ∨ feature_add with no breaking semantics
   • else class(change) = PATCH.
4. S32-61 Dual-run aggregate deltas
   • Delta_agg = ( Σ ( w_i * delta_rep_i ) ) / ( Σ w_i )
   • PSD_agg = ( Σ ( w_i * delta_psd_i ) ) / ( Σ w_i )
   • TB_agg = ( Σ ( w_i * r_tb_i ) ) / ( Σ w_i )
   • Pass condition: Delta_agg <= b_rep ∧ PSD_agg <= b_psd ∧ TB_agg <= b_tb.
5. S32-62 Upgrade conservation & regression tolerance
   score_new - score_old >= -tau_reg and lower( CI_score_new ) >= tau_score; tau_reg per Chapter 12.
6. S32-63 Deprecation-plan consistency
   For any deprecated item d, require ( T_dep - now ) >= T_grace and provide a flag-based transition compat flag(d) within W_mig.

IV. Data and Manifest Gauges

• Minimum change-entry fields
  version, channel, change_type ∈ {MAJOR, MINOR, PATCH}, compat flags, W_mig, T_dep / T_grace, budget, impact surface (EnvLock, PipelineCard/ParamCard, data schema, time-base gauge alpha,beta, window U_w/ENBW), and risk assessment.
• Dual-run evidence bundle
  Raw DiffMatrix, case weights w_i, dual T_arr values and delta_form, ScoreSummary(old,new), and audit-chain H_k with sig_k.
• Archival and forensics
  For every cutover, produce CutoverReport and RollbackPlan; harden both with hash(•) and fingerprint, with cross-channel references.

V. Algorithms and Implementation Bindings

• I30-25 plan_migration(change:dict, baseline:any, constraints:dict) -> MigPlan
  Produce the budget, W_mig, compat flags, affected inventory, and TS.* observation points.
• I30-26 run_dual_track(plan:dict) -> DiffMatrix
  Under fixed EnvLock, seed, alpha, beta, run old/new implementations in parallel; emit per-case deltas and performance measures.
• I30-27 evaluate_compat(diff:any, thresholds:dict) -> { pass:bool, report:any }
  Implement S32-61/62; return decision and delta decomposition.
• I30-28 execute_cutover(plan:dict, mode:str) -> CutoverReport
  mode ∈ {shadow, canary, blue-green, all-at-once}; coordinate alerts and register the rollback anchor.
• I30-29 rollback_to(anchor:any) -> RollbackReport
  Execute rollback and verify recovery to gates gate.rep, tau_psd, tau_tb.

VI. Metrology Flows and Run Graph

1. Mx-35 classify-and-scope
   • Label change_type and impact surface (environment, data, algorithm, gauges).
   • Set budget and compat flags.
   • Emit MigPlan and the observation matrix (aligned to TS.*).
2. Mx-36 dual-run-and-compare
   • Call I30-26 to obtain DiffMatrix.
   • Compute Delta_agg / PSD_agg / TB_agg and delta_form.
   • Trigger I30-27 for pass/fail and remediation guidance.
3. Mx-37 decide-and-cutover
   • If evaluate_compat.pass = true and score_new meets gates, execute I30-28 with the chosen mode.
   • If some cases exceed budget but can be shielded via flags, enter shadow or canary to expand samples.
   • On failure, enter rollback and fix-iterate (I30-29).
4. Mx-38 deprecate-and-archive
   • Publish T_dep / T_grace with migration guidance.
   • Register H_k on the Chapter 9 audit trail; archive CutoverReport, RollbackPlan, and CHANGELOG.
   • Update baselines and benchmark-suite mappings.

VII. Verification and Test Matrix

1. Tiered verification
   • MAJOR: mandatory full dual-run; conservative budgets; must pass S32-61/62, with delta_form contribution within cap.
   • MINOR: sampled dual-run with full coverage of critical cases; allow positive perf_norm shifts backed by CI_score.
   • PATCH: minimal regression set plus audit-trail integrity checks.
2. Boundary scenarios
   • Data-schema evolution: apply reversible operator Migrate(schema_v_old -> schema_v_new); verify idempotence and rollback.
   • Time-base gauge change: refit alpha, beta; report r_tb and its marginal impact on score.
   • Window & spectral-gauge switch: analyze sensitivity of delta_psd to changes in U_w / ENBW.
3. Alerts and gate coupling
   • Hard gates: Delta_agg <= b_rep, PSD_agg <= b_psd, TB_agg <= b_tb, eps_mass <= b_mass.
   • Soft gates: lower( CI_score_new ) >= tau_score, score_new - score_old >= -tau_reg.

VIII. Cross-References and Dependencies

IX. Risks, Limits, and Open Questions

• Risks
  Long-lived compatibility flags create gauge fragmentation; partial EnvLock relaxation induces latent E_ENV_DRIFT; poor aggregation weights trigger Simpson-type bias; vendor driver updates introduce E_NONDETERMINISM.
• Limits
  Linear budgets are insensitive to strong nonlinearities; CI_score approximations degrade with small migrations; cross-domain c_ref, n_eff disparities may inflate delta_form.
• Open questions
  Adaptive budget scheduling and risk weighting; cross-site joint dual-run distributional equivalence tests; optimal deprecation strategy and allocation of W_mig.

X. Deliverables and Version Policy

1. Deliverables
   • MigPlan (budget / W_mig / T_dep / T_grace / compat flags / anchor).
   • DiffMatrix and ScoreSummary(old,new).
   • CutoverReport, RollbackReport, and audit chain H_k / sig_k.
   • CHANGELOG (per-version deltas, impact surface, flags, window and gate updates).
   • Migration guide and rollback playbook.
2. Version strategy
   • Events triggering MAJOR require a new LTS branch and freezing the prior LTS to security fixes only.
   • MINOR rides the canary → stable release train, keeping dual-run active within W_mig.
   • PATCH may go directly to stable, but must update CHANGELOG and anchor.
   • Every version is hardened with hash(•) and fingerprint, supporting long-term forensics and one-click rollback.