Implementation Plan: LLM Table Translation Service

Branch: 028-llm-datasource-supeset | Date: 2026-05-08 | Spec: spec.md Input: Feature specification from /specs/028-llm-datasource-supeset/spec.md (updated 2026-05-14 with multi-language & correction optimization)

Summary

Implement an LLM-powered table translation service as a new backend plugin (TranslationPlugin) with companion API routes, ORM models, Pydantic schemas, and Svelte frontend components. The service reads rows from a Superset datasource (translation column + context columns), auto-detects source language per row via LLM, sends batches to a configured LLM provider for ALL target languages simultaneously (multi-target in single structured JSON response), with optional per-batch filtered multilingual terminology dictionary context (language-pair-aware). Generates safe PostgreSQL INSERT/UPSERT SQL, submits to Superset via /api/v1/sqllab/execute/ with status polling. Supporting capabilities: multilingual terminology dictionaries (source_language + target_language per entry), configurable preview (1-100 rows), inline correction from any run result with dictionary submission, bulk find-and-replace, scheduled execution via APScheduler (new-key-only with baseline_expired fallback), structured event logging with per-language MetricSnapshot persistence, RBAC-gated access control, and 90-day retention with metric continuity.

Total planned modules: 31 contracts across backend (Python/FastAPI) and frontend (Svelte 5/SvelteKit).
Complexity distribution: 2× C5 (orchestrator, event-log), 9× C4 (preview, execute, dictionary, scheduler, SQL-gen, routes, correction), 13× C3 (models, schemas, components, services), 7× C2 (helpers, new models).

Technical Context

Language/Version: Python 3.13+ (backend), JavaScript/TypeScript (frontend Svelte 5)
Primary Dependencies: FastAPI 0.115+, SQLAlchemy 2.0+, APScheduler 3.x, Pydantic v2 (backend); SvelteKit 2.x, Svelte 5.43+, Vite 7.x, Tailwind CSS 3.x (frontend)
Storage: PostgreSQL 16 (shared with existing ss-tools schema)
Testing: pytest 8.x + pytest-asyncio (backend); vitest 4.x + @testing-library/svelte 5.x (frontend)
Target Platform: Linux server (Docker Compose: backend + frontend + PostgreSQL)
Project Type: web application — FastAPI REST + WebSocket backend, SvelteKit SPA frontend
Performance Goals: Preview of 10 rows within 30s (LLM-dependent); INSERT generation <5s for 1000 rows; schedule trigger precision ±60s; event recording <10s after occurrence
Constraints: RBAC enforcement via access-control matrix; dictionary per-batch filtering (case-insensitive, word-boundary-aware); 90-day detailed data retention with MetricSnapshot persistence; plugin lifecycle compatible with PluginBase; dialect-aware SQL generation (PostgreSQL/Greenplum, ClickHouse supported for MVP); snapshot isolation for in-progress runs; structured JSON LLM output required
Scale/Scope: Tens of thousands of rows per run; dictionaries of any size; 50 concurrent users; 5–10 active translation jobs per deployment

Constitution Check

GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.

Principle	Status	Evidence
I. Plugin Architecture	✅ PASS	Feature implemented as a new plugin inheriting from `PluginBase` (`backend/src/plugins/translate/`), consistent with existing `llm_analysis`, `git`, `storage` plugin pattern.
II. API-First Design	✅ PASS	All operations exposed via REST endpoints under `/api/translate/` (jobs, dictionaries, runs, schedules, history) and WebSocket for run progress. Follows existing FastAPI route conventions.
III. Test-First	✅ PASS	Acceptance criteria per user story defined in spec; test strategy in research.md covers unit (pytest), integration (API + DB), and component (vitest + Svelte Testing Library) layers.
IV. RBAC & Security	✅ PASS	Granular permissions (`translate.job.`, `translate.dictionary.`, `translate.schedule.manage`, `translate.history.view`) via existing RBAC model. API keys encrypted via `EncryptionManager`. PII masking for LLM-facing context per existing patterns.
V. Observability & Retention	✅ PASS	Structured Translation Events (FR-046), per-job metrics (FR-047), notification integration (FR-048), 90-day retention with pruning (FR-049). C4+ flows instrumented with `belief_scope`/`reason`/`reflect`/`explore` markers.
Semantic Protocol Compliance	✅ PASS	All planned modules assigned `@COMPLEXITY` 1–5 with appropriate tag density per GRACE complexity scale (C1: anchor only, C2: +BRIEF, C3: +RELATION, C4: +PRE/POST/SIDE_EFFECT, C5: +DATA_CONTRACT/INVARIANT/RATIONALE/REJECTED). `@RATIONALE`/`@REJECTED` reserved for C5 contracts only. Canonical `@RELATION PREDICATE -> TARGET_ID` syntax. Anchor format: `#region`/`#endregion` for Python, `<!-- #region -->`/`<!-- #endregion -->` for Svelte markup.
Fractal Limit (INV_7)	✅ PASS	Planned modules kept under 400 lines each. No planned contract exceeds 150 lines or CC>10. Decomposition strategy documented in contracts/modules.md.

Gate Result: ✅ ALL PASS — no blocking constitutional or semantic conflicts.

Project Structure

Documentation (this feature)

specs/028-llm-datasource-supeset/
├── plan.md              # This file
├── research.md          # Phase 0 output
├── data-model.md        # Phase 1 output
├── quickstart.md        # Phase 1 output
├── contracts/           # Phase 1 output
│   └── modules.md       # Semantic contract design
├── spec.md              # Feature specification
├── ux_reference.md      # Interaction reference
└── checklists/
    └── requirements.md  # Quality validation

Source Code (repository root)

backend/
├── src/
│   ├── api/routes/
│   │   └── translate.py           # New: translation REST endpoints
│   ├── core/
│   │   ├── scheduler.py           # Existing: APScheduler (extend for translation schedules)
│   │   └── superset_client/       # Existing: Superset API client (reuse)
│   ├── models/
│   │   └── translate.py           # New: SQLAlchemy ORM models
│   ├── plugins/
│   │   └── translate/             # New: TranslationPlugin
│   │       ├── __init__.py
│   │       ├── plugin.py          # Plugin entry (inherits PluginBase)
│   │       ├── orchestrator.py    # Run lifecycle orchestration (C5)
│   │       ├── preview.py         # Preview engine (C4)
│   │       ├── executor.py        # Batch execution + INSERT gen (C4)
│   │       ├── dictionary.py      # Dictionary CRUD + filtering (C4)
│   │       ├── sql_generator.py  # INSERT/UPSERT SQL generation (C3)
│   │       ├── scheduler.py       # Schedule management (C4)
│   │       ├── events.py          # Structured event logging (C5)
│   │       ├── metrics.py         # Per-job metrics aggregation (C3)
│   │       └── __tests__/         # Plugin-level tests
│   ├── schemas/
│   │   └── translate.py           # New: Pydantic request/response schemas
│   └── services/
│       ├── llm_provider.py        # Existing: LLM provider management (reuse)
│       └── llm_prompt_templates.py # Existing: prompt rendering (reuse)
└── tests/                         # Integration tests

frontend/
├── src/
│   ├── routes/
│   │   └── translate/             # New: SvelteKit route
│   │       ├── +page.svelte       # Translation job list
│   │       ├── [id]/
│   │       │   └── +page.svelte   # Job config + preview + run
│   │       ├── dictionaries/
│   │       │   ├── +page.svelte   # Dictionary list
│   │       │   └── [id]/
│   │       │       └── +page.svelte # Dictionary editor
│   │       └── history/
│   │           └── +page.svelte   # Run history
│   └── lib/
│       ├── components/
│       │   └── translate/         # New: reusable translation components
│       │       ├── TranslationJobConfig.svelte
│       │       ├── TranslationPreview.svelte
│       │       ├── TranslationRunProgress.svelte
│       │       ├── TranslationRunResult.svelte
│       │       ├── DictionaryEditor.svelte
│       │       ├── TermCorrectionPopup.svelte
│       │       ├── ScheduleConfig.svelte
│       │       └── BulkCorrectionSidebar.svelte
│       ├── stores/
│       │   └── translate.js       # New: Svelte 5 rune stores
│       └── api/
│           └── translate.js       # New: API client module

Semantic Contract Guidance

All planned contracts follow GRACE-Poly v2.6 protocol with #region/#endregion anchors (or [DEF:...]/[/DEF:...] for backward compatibility in docs).
Python backend uses # #region/# #endregion comment-anchor syntax.
Svelte components use / in markup and // #region/// #endregion in script blocks.
Complexity assignments follow strict tag density per GRACE complexity scale (detailed in contracts/modules.md).
C4+ Python modules instrumented with belief_scope() + reason()/reflect()/explore() markers.
C5 contracts carry @RATIONALE and @REJECTED decision memory (C1-C4 MUST NOT have these tags).
@RELATION targets reference existing contracts where applicable (e.g., [LLMProviderService:Module], [SchedulerService:Class], [SupersetClient:Module], [NotificationService:Module]).

Complexity Tracking

No constitutional violations detected. All complexity assignments are justified within the semantic protocol's complexity scale:

Contract	Complexity	Justification
`TranslationOrchestrator`	C5	Stateful lifecycle with PRE/POST, multi-step coordination, decision memory for retry/concurrency policies; updated for multi-target orchestration
`TranslationScheduler`	C4	Stateful schedule CRUD with APScheduler integration, conflict detection
`TranslationEventLog`	C5	Immutable event log with retention enforcement, audit invariants, decision memory for pruning strategy
`TranslationPreview`	C4	Stateful multi-language preview with LLM calls, configurable sample size, approve/edit/reject lifecycle
`TranslationExecutor`	C4	Multi-language batch execution, per-language TranslationLanguage entries, per-language statistics
`DictionaryManager`	C4	Multilingual CRUD with import/export, language-pair-aware batch filtering, conflict resolution
`InlineCorrectionService`	C3	Inline correction with dictionary submission, origin tracking
`BulkFindReplaceService`	C3	Find-and-replace across run results, regex support, multi-language awareness
`TranslationLanguage`	C1	DTO for per-language translation storage
`TranslationRunLanguageStats`	C1	DTO for per-language statistics aggregation
`CorrectionCell` (Svelte)	C3	Inline editable cell with submit-to-dictionary UX state machine
`BulkReplaceModal` (Svelte)	C3	Find-and-replace modal with preview table
`ContextAwarePromptBuilder`	C3	Context-aware dictionary prompt construction with Jaccard similarity, priority flagging, context truncation
`InlineCorrectionService` (extended)	C3	Context capture from source rows, context editing, usage notes, context_source tagging
Other Svelte components	C3	Existing components updated with per-language columns, configurable preview, context display

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