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+# C# Backend Parity Acceptance Criteria (Python Twin)
+
+## Goal
+Create a C# backend that is behaviorally equivalent to the current Python backend for core journaling workflows, with zero data-loss regressions and compatible vault handling.
+
+## Parity Rule
+Behavior parity is required. Internal implementation can differ.
+
+## Source of Truth (Current Python)
+- `journal/core/storage.py`
+- `journal/core/encryption.py`
+- `journal/core/parser.py`
+- `journal/core/models.py`
+- `journal/core/database.py`
+- `journal/cli/main.py`
+- `journal/ai/analysis.py`
+- `journal/ai/chat.py`
+- `journal/core/speech.py`
+
+## Definition of Done (Release Gate)
+1. All `P0` criteria below are marked `Pass`.
+2. Existing Python-created vault files load successfully in C# backend.
+3. Side-by-side output comparison on shared fixture corpus shows no functional mismatch for `P0` flows.
+4. No plaintext journal data remains after graceful shutdown flow.
+
+## Shared Fixture Corpus (Required)
+1. `fixtures/vaults/`
+- Multiple months (`YYYY-MM.vault`) generated by Python app.
+- Includes at least one wrong-password test case.
+2. `fixtures/entries/`
+- Daily, deep, recovery, fragment-heavy entries.
+- Includes multiline fragments, tags, checkboxes, unusual spacing.
+3. `fixtures/search/`
+- Queries for text, section, tag, type, checked, unchecked, date ranges.
+4. `fixtures/ai/`
+- Stubbed LLM/embedding responses for deterministic comparison.
+
+## Acceptance Matrix
+Use status values: `Not Started`, `In Progress`, `Blocked`, `Pass`, `Fail`.
+
+| ID      | Priority | Feature                           | Acceptance Criteria                                                                                                    | Status      | Owner | Evidence |
+| ------- | -------- | --------------------------------- | ---------------------------------------------------------------------------------------------------------------------- | ----------- | ----- | -------- |
+| DOM-001 | P0       | Fragment model parity             | Fragment has `type`, `description`, `time`, `tags`; rejects empty `type`/`description`; trims values.                  | Pass        | Stan44/Codex | `Journal.Core/Models/Fragment.cs`, `Journal.Core/Services/FragmentService.cs`, smoke test `CreateAsync trims fields` + `UpdateAsync rejects whitespace type` |
+| DOM-002 | P0       | Journal entry domain parity       | Entry model supports `date`, `raw_content`, `sections`, `fragments` equivalent to Python semantics.                    | Not Started |       |          |
+| PAR-001 | P0       | Date extraction parity            | Parser reads `**Date:**` or `Date:`; falls back to filename stem when missing.                                         | Not Started |       |          |
+| PAR-002 | P0       | Section parsing parity            | Recognizes canonical section titles and captures section content lines.                                                | Not Started |       |          |
+| PAR-003 | P0       | Checkbox parsing parity           | Parses markdown checkboxes (`- [ ]`, `- [x]`) and preserves checked state by checkbox text.                            | Not Started |       |          |
+| PAR-004 | P0       | Fragment parsing parity           | Parses `!TYPE @time #tags` plus multiline description blocks with same boundary behavior as Python regex parser.       | Not Started |       |          |
+| MRG-001 | P0       | Merge behavior parity             | Saving existing entry merges non-empty section updates and appends only non-duplicate fragments by description.        | Not Started |       |          |
+| MRG-002 | P0       | Markdown reconstruction parity    | Entry serialization writes canonical section order and fragment block formatting equivalent to Python `to_markdown()`. | Not Started |       |          |
+| VLT-001 | P0       | Vault crypto format compatibility | Uses AES-256-GCM with payload layout compatible with Python (`salt + nonce + tag + ciphertext`).                       | Not Started |       |          |
+| VLT-002 | P0       | KDF compatibility                 | Uses PBKDF2-HMAC-SHA256 with matching salt/key sizes and iteration count for Python vault compatibility.               | Not Started |       |          |
+| VLT-003 | P0       | Monthly vault naming parity       | Vault filename format exactly `YYYY-MM.vault`.                                                                         | Not Started |       |          |
+| VLT-004 | P0       | Load workflow parity              | `load all vaults` clears decrypted workspace first, then decrypts/extracts monthly vaults.                             | Not Started |       |          |
+| VLT-005 | P0       | Wrong password behavior           | Wrong password returns explicit failure and does not corrupt existing vault files.                                     | Not Started |       |          |
+| VLT-006 | P1       | Legacy vault handling             | Legacy `_init_vault.vault` handling behavior is preserved or intentionally migrated with backward-compat note.         | Not Started |       |          |
+| VLT-007 | P0       | Current-month optimized save      | Supports current-month save path equivalent to Python optimization.                                                    | Not Started |       |          |
+| VLT-008 | P0       | Full rebuild save                 | Supports full monthly regroup/rebuild save flow from decrypted `.md` files.                                            | Not Started |       |          |
+| DAT-001 | P0       | Decrypted data cleanup            | Graceful shutdown removes decrypted workspace artifacts.                                                               | Not Started |       |          |
+| DB-001  | P1       | SQLCipher compatibility           | Database key derivation and SQLCipher connection behavior are compatible with Python expectations.                     | Not Started |       |          |
+| DB-002  | P1       | Schema parity                     | `entries`, `sections`, `fragments`, `tags`, `fragment_tags` schema exists with compatible constraints.                 | Not Started |       |          |
+| SCH-001 | P0       | Search parity (content)           | Search supports text query over full entry content.                                                                    | Not Started |       |          |
+| SCH-002 | P0       | Search parity (filters)           | Search supports date range, section filter, tag filter, fragment type filter, checked/unchecked filters.               | Not Started |       |          |
+| CLI-001 | P0       | Vault CLI parity                  | CLI supports vault load/save with password prompt semantics matching Python UX.                                        | Not Started |       |          |
+| CLI-002 | P0       | Search CLI parity                 | CLI options match existing Python capabilities sufficiently for drop-in replacement.                                   | Not Started |       |          |
+| API-001 | P0       | Sidecar protocol stability        | Stdin/stdout contract is line-delimited JSON with `{ok,data}` or `{ok:false,error}` and strict action routing.         | In Progress | Stan44/Codex | `Journal.Core/Entry.cs`, smoke tests for unknown action / missing payload / missing id handling |
+| API-002 | P1       | HTTP API parity                   | API exposes endpoints equivalent to supported sidecar actions; no template-only endpoints in parity mode.              | Not Started |       |          |
+| AI-001  | P1       | LLM summarize parity              | Entry/all-entry summarize workflow callable with equivalent behavior and timeout controls.                             | Not Started |       |          |
+| AI-002  | P2       | Embedding parity                  | Embedding endpoint integration available with equivalent request/response contract.                                    | Not Started |       |          |
+| AI-003  | P1       | Cloud chat parity                 | Cloud chat request/response flow available and configurable.                                                           | Not Started |       |          |
+| SPC-001 | P2       | Speech parity                     | Engine-selectable speech flow (whisper/google/sphinx-like modes) retained or intentionally delegated.                  | Not Started |       |          |
+| CFG-001 | P0       | Config parity                     | Equivalent configuration keys exist for paths, vault format, AI endpoints, and speech settings.                        | Not Started |       |          |
+| OBS-001 | P1       | Logging/error parity              | Failures return actionable messages without leaking secrets or plaintext journal data.                                 | In Progress | Stan44/Codex | Error envelope behavior implemented in sidecar; structured logging policy pending |
+
+## Mandatory Gate Tests (P0)
+1. `Vault Compatibility`
+- Given existing Python vault fixtures, C# load succeeds with correct password.
+- Wrong password consistently fails without partial corruption.
+2. `Parser + Merge`
+- Given fixture entries, C# parser output matches Python parser output for sections/fragments/checkboxes.
+- Saving edited entry preserves merge semantics.
+3. `Search`
+- For shared corpus, C# and Python return the same entry set for all P0 search filters.
+4. `Transport`
+- Sidecar commands for core actions produce stable JSON success/error envelopes.
+5. `Cleanup`
+- After graceful shutdown sequence, decrypted workspace is empty.
+
+## Migration Phases (Recommended)
+1. `Phase 1: Fragment Vertical Slice`
+- Complete `DOM-001`, `API-001`, persistence beyond in-memory.
+2. `Phase 2: Entry/Parser/Merge Twin`
+- Complete `DOM-002`, `PAR-*`, `MRG-*`.
+3. `Phase 3: Vault/Crypto Twin`
+- Complete `VLT-*`, `DAT-001`.
+4. `Phase 4: Search + CLI Twin`
+- Complete `SCH-*`, `CLI-*`, `CFG-001`.
+5. `Phase 5: AI/Speech`
+- Complete `AI-*`, `SPC-001`.
+6. `Phase 6: Frontend Cutover`
+- Tauri frontend switches to C# backend only after all P0 criteria pass.
+
+## Rules for Change Requests
+1. Any intentional divergence from Python behavior requires:
+- Written rationale.
+- New acceptance criterion replacing old one.
+- Migration note describing user-visible impact.
+2. No removal of a `P0` criterion without both maintainers approving in writing.
+
+## Status Snapshot (2026-02-22, Phase 1.2 Progress)
+This section is a proposed status/evidence snapshot based on current code in:
+- Python source: `Project_Journal/`
+- C# migration: `Project_Journal/journal-master/journal/`
+
+It does not change release gates or acceptance definitions.
+
+### Phase Summary
+| Phase | Current State | Evidence |
+| ----- | ------------- | -------- |
+| Phase 1: Fragment Vertical Slice | In Progress (near-complete) | Fragment model/service/sidecar + persisted repository + smoke tests: `journal-master/journal/Journal.Core/Models/Fragment.cs`, `journal-master/journal/Journal.Core/Entry.cs`, `journal-master/journal/Journal.Core/Repositories/FileFragmentRepository.cs`, `journal-master/journal/Journal.SmokeTests/Program.cs` |
+| Phase 2: Entry/Parser/Merge Twin | Not Started | No C# entry/parser/merge domain yet. |
+| Phase 3: Vault/Crypto Twin | Not Started | No C# vault/crypto compatibility module yet. |
+| Phase 4: Search + CLI Twin | Not Started | C# search remains fragment-scoped only (not full entry parity). |
+| Phase 5: AI/Speech | Not Started | No C# AI/speech parity services yet. |
+| Phase 6: Frontend Cutover | Not Started | P0 parity not yet achieved. |
+
+### Proposed Acceptance Status Updates
+| ID      | Proposed Status | Evidence | Notes |
+| ------- | --------------- | -------- | ----- |
+| DOM-001 | Pass | `journal-master/journal/Journal.Core/Models/Fragment.cs`, `journal-master/journal/Journal.Core/Services/FragmentService.cs`, `journal-master/journal/Journal.SmokeTests/Program.cs` | Fields/validation/trim behavior implemented and smoke-tested. |
+| DOM-002 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No C# `JournalEntry` parity domain yet. |
+| PAR-001 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No C# parser/date extraction path yet. |
+| PAR-002 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No section parser in C#. |
+| PAR-003 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No checkbox parser in C#. |
+| PAR-004 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No fragment markdown parser in C#. |
+| MRG-001 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No entry merge behavior in C#. |
+| MRG-002 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No markdown reconstruction pipeline in C#. |
+| VLT-001 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No vault encryption/decryption compatibility module yet. |
+| VLT-002 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No PBKDF2 compatibility implementation yet. |
+| VLT-003 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No monthly vault naming/save implementation yet. |
+| VLT-004 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No load-all-vaults workflow in C#. |
+| VLT-005 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | Wrong-password behavior not implemented in C# vault flow. |
+| VLT-006 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | Legacy vault handling not implemented/documented in C#. |
+| VLT-007 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | Current-month optimized save path not implemented in C#. |
+| VLT-008 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | Full rebuild save flow not implemented in C#. |
+| DAT-001 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | Decrypted workspace cleanup flow not implemented in C#. |
+| DB-001  | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No SQLCipher keying/connection behavior in C#. |
+| DB-002  | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No `entries/sections/fragments/tags/fragment_tags` schema in C#. |
+| SCH-001 | Not Started | `journal-master/journal/Journal.Core/Repositories/FileFragmentRepository.cs` | C# search is fragment-centric, not full-entry content search. |
+| SCH-002 | Not Started | `journal-master/journal/Journal.Core/Repositories/FileFragmentRepository.cs` | Date/section/checkbox filters not implemented for full entry search. |
+| CLI-001 | Not Started | `journal-master/journal/Journal.Sidecar/App.cs` | Sidecar exists; vault CLI parity not implemented. |
+| CLI-002 | Not Started | `journal-master/journal/Journal.Sidecar/App.cs` | Search CLI parity not implemented. |
+| API-001 | In Progress | `journal-master/journal/Journal.Core/Entry.cs`, `journal-master/journal/Journal.SmokeTests/Program.cs` | JSON envelope routing implemented and tested; fixture-driven P0 gate tests still pending. |
+| API-002 | Not Started | `journal-master/journal/Journal.Api/Program.cs` | HTTP API still template endpoint, no journal parity endpoints. |
+| AI-001  | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No summarize workflow/service in C#. |
+| AI-002  | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No embeddings integration in C#. |
+| AI-003  | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No cloud chat flow in C#. |
+| SPC-001 | Not Started | `journal-master/journal/Journal.Core/Entry.cs` | No speech module/service in C#. |
+| CFG-001 | Not Started | `journal-master/journal/Journal.Core/ServiceCollectionExtensions.cs` | C# config surface is partial and not parity-complete. |
+| OBS-001 | In Progress | `journal-master/journal/Journal.Core/Entry.cs` | Actionable error envelope exists; structured logging/secret-scrub policy pending. |
+
+### Snapshot Risks/Blockers
+1. Required fixture corpus (`fixtures/vaults`, `fixtures/entries`, `fixtures/search`, `fixtures/ai`) is still missing.
+2. P0 gate test harness for side-by-side Python vs C# parity is not yet implemented.
+3. Phase 1 remaining item is final API-001 hardening + fixture-backed transport stability evidence.