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+# Dual-Project Selective Synchronization Design
+
+Date: 2026-07-16
+
+## Scope
+
+Two repositories remain independently deployable and independently releasable.
+
+| Repository | Role | Primary success measure |
+| --- | --- | --- |
+| `732642856/yinduzhanxing` | Backup/research implementation | Calculation correctness, evidence closure, reproducible regressions |
+| `jesse-ux/Jyotisha` | Commercial product | Safe user experience, authenticated delivery, deployable operations |
+
+No repository becomes a submodule, package dependency, or required runtime peer of
+the other. Cross-project work is a reviewed copy with an auditable provenance
+record, not automatic mirroring.
+
+## Directional Adoption
+
+### Research to commercial
+
+Port only a passing, self-contained change plus its focused tests:
+
+- effective calculation parameters and result hashes;
+- runtime-truth evidence manifests and honest external-oracle status;
+- Prashna server-authoritative context and blocked approximate verdicts;
+- precision-timing output gate;
+- privacy, report-renderer isolation, Origin/capability-token/TTL controls;
+- external parity diagnostics and Western evidence packet contracts.
+
+### Commercial to research
+
+Port only configuration-free product patterns plus tests:
+
+- mobile consultation flow and accessibility improvements;
+- authenticated account/session and credit contracts using local test doubles;
+- Docker, health checks, CI workflow structure and deployment documentation;
+- user-facing error, timeout and degradation presentation.
+
+Never copy production secrets, server addresses, SSH material, Supabase project
+identifiers, live user records, payment credentials, or production `.env` files.
+
+## Shared Contract
+
+Each project will contain the same versioned fixture manifest. For every fixture it
+must record birth input, effective parameters, local result hash, evidence packet
+schema version, external-oracle state and required test IDs.
+
+The acceptance command compares only public, synthetic fixtures. A mismatch blocks
+the port; it never overwrites either project automatically. External parity fields
+must use `local_operational`, `externally_verified`, and `prediction_validated` as
+separate states.
+
+## Sync Ledger
+
+Each port gets one ledger row:
+
+| Field | Requirement |
+| --- | --- |
+| source repository and commit | immutable source reference |
+| target repository and commit | immutable landing reference |
+| change class | calculation, evidence, security, UX, deployment, or docs |
+| copied files and dependency delta | explicit allow-list |
+| secret/privacy review | pass required |
+| focused tests | command and result |
+| hash-contract result | pass, mismatch, or not applicable |
+| rollback | source and target commit references |
+
+## Delivery Order
+
+1. Add the identical public cross-project fixture manifest, comparator and sync
+   ledger schema to both repositories.
+2. Port research safety/correctness gates into Jyotisha, preserving its production
+   deployment constraints.
+3. Port Jyotisha product patterns into the backup repository using local-only
+   configuration and test doubles.
+4. Add CI acceptance in each repository that validates its own copy of the shared
+   fixture manifest.
+5. Only after two successful directional ports, evaluate reusable extraction. No
+   repository merge is in scope.
+
+## Failure Policy
+
+- A missing external raw artifact is `blocked`, never `verified`.
+- A missing local scratch file cannot fail a public release truth gate.
+- Any copied calculation path that changes a public fixture result hash requires
+  manual review and fresh external-oracle comparison.
+- Any commercial-origin file containing a production identifier or secret is
+  rejected before staging.