126 lines
8.1 KiB
Markdown
126 lines
8.1 KiB
Markdown
# Architecture overview
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> For details about modules and flows, see [Components, modules, and flows](components.md).
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ThothII is a **human-in-the-loop datamart builder**. It turns a natural-language question into validated SQL, and optionally a dbt datamart, through a **deterministic eight-phase NL-to-SQL workflow** in which the model *proposes* and a human reviewer *decides* at gates.
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Production authentication uses local authentication, generic OIDC, or the
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trusted-proxy upstream path used by Omics. `tht` is the operator CLI for the
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installation and local/OIDC configuration. For roles and recovery, see
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[authentication](authentication.md). One React build supports full and embedded;
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[rendering architecture](application-shell.md) separates presentation from identity.
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```mermaid
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flowchart LR
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USER["Reviewer"] --> FE["Frontend\nReact and SSE"]
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FE --> BE["Backend\nFastify"]
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BE --> CATALOG["Metadata catalog\nPostgreSQL"]
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BE --> MODEL["Configured AI model\nvia short-lived LiteLLM helper"]
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BE -->|bounded read-only samples| DWH
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BE --> PI["Pi\nRPC per sessione"]
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PI --> THT["tht and harness\nworkflow and persistence"]
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THT --> DWH["DWH\nread only"]
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THT --> EVIDENCE["Evidence\ncurated corpus"]
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EVIDENCE --> THT
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THT --> FE
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```
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## The three independently built layers
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```
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frontend (React/SSE) → backend (Fastify) → pi --mode rpc → tht/harness → DWH (read-only)
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```
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| Layer | Stack | Ruolo |
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|---|---|---|
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| **harness/** | Python (`tht` CLI) + Pi gate extension (JS) | Owns the workflow and all session persistence |
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| **backend/** | Fastify + TypeScript + Kysely | Session bridge plus the isolated administrative metadata catalog |
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| **frontend/** | React 18 + Vite | UI that renders gate widgets and rebuilds the live transcript from the SSE stream |
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## The harness owns the workflow
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`tht` (Python) is a deterministic CLI. `harness/.pi/extensions/tht-gate.js` is a Pi extension that guides the eight-phase workflow. `harness/workflow.yaml` is the single source of workflow truth, and `harness/.pi/skills/tht-sessione/SKILL.md` contains the orchestration rules the model must follow. The "current phase" is **not stored**. It is computed by folding the decision ledger (`harness/tht/phase.py`), which must be read before reasoning about phase logic.
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## Persistence means phase documents, not chat
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A session is a directory under `sessions/` (the workspace defines the path): `session_manifest.yaml`, phase artifacts (`question.md`, `schema_linking.json`, `sql_final.sql`, and others), and `review_decisions.jsonl`. The contract says: *"persisted state is the truth; what is not recorded did not happen"*. There is no verbatim transcript store. A resumed Pi process rebuilds context from `tht session show <id>` and the artifacts on disk.
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## The backend bridges sessions and owns the metadata catalog
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- `ThtRunner` runs `tht` subcommands in a shell.
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- `PiProcessManager` runs one Pi child process per session and bridges its RPC stream.
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- `SessionBridge` maps Pi RPC events to client events (`ui_request` / `text_delta` / `info`).
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- `SseHub` distributes these events to the browser over SSE.
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- `CatalogService` joins authoritative YAML workspace identities and Evidence settings with the
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sole database authority: installation-local PostgreSQL Metadata Catalog records.
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- `CatalogTableService` reconciles persisted Catalog Tables with a successful external schema scan;
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`ConcreteCatalogTableIntrospector` isolates direct PostgreSQL, typed REST, and SSH-tunnel access.
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- `DescriptionGenerationWorker` admits one installation-wide run and processes its table or column
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targets sequentially.
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- `PostgresDescriptionSourceSampler` reads bounded real rows and five representative examples from
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the configured DWH connection; `ProcessModelCompleter` invokes the short-lived Python LiteLLM
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helper with the installation-selected model.
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Application settings keep only workspace and thinking preferences in `backend/data/settings.json`;
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provider/model defaults come from the generated Installation Model Catalog. Session state remains in
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harness phase documents. PostgreSQL stores the administrative database catalog, bindings, observed tables,
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curated and generated descriptions, description-generation runs, sanitized run events, and the
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authoritative preprocessing state/revisions.
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Connector secrets remain write-only in the encrypted workspace secret store; model credentials
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remain in the protected installation secret bundle. Catalog SSH support is limited to connection
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tests, table synchronization, and bounded description-generation sampling; it does not change the
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session runtime binding contract.
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## Human-in-the-loop gate contract
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The model proposes; a human reviewer decides at gates through widgets:
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- **`reviewer_select`**: single choice. An option with a `decision` payload confirms and persists directly; an option without a payload only asks.
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- **`reviewer_decide`**: multiselect. Each choice is a decision.
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- **`reviewer_confirm`**: artifact or phase gate.
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The frontend renders these widget descriptors (registry in `src/widgets/`). It rebuilds the live transcript in memory from the SSE stream (`src/store/sessionStore.ts`); it is **not persisted**.
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## Curated and immutable Evidence
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The workspace repository is the publication boundary. The curator prepares `evidence/source/`,
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reviews units in `evidence/curated/`, validates them, and merges them. With `evidence.schema_version: 2`,
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the runtime materializes the full `evidence/` tree from the exact Git commit, but the renderer passes
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only `curated/**/*.md` from the immutable revision root to preprocessing. Sources, manifests, and
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evaluation data remain available for traceability. The runtime never modifies, stages, commits, or
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publishes the authoring repository.
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Before indexing, the curated corpus from the pinned revision is validated. Each workspace has two
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physical Qdrant collections with different lifecycles. `reference` contains Schema, relationships,
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and Evidence and may be replaced or cleared by preprocessing; `memory` contains `memory` and
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`solved_question` records and is never preprocessing output. Only the `reference` collection has the
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sparse `bm25` vector with `idf`, and only the Evidence stage writes sparse values.
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The Administration control can clear the replaceable reference collection, LSH, corpus, and derived
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checkpoints. The operation preserves the memory collection and makes preprocessing required before
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the core can admit a new session.
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## Recurring points of attention
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- `tht -c`/`--config` is a **per-command** option. It must follow the subcommand, never precede it (`ThtRunner.buildArgv` enforces this).
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- `--json` output must be plain JSON on stdout. It is a machine-readable contract.
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- UI strings support English and Italian, with English fallback. Session interaction language
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is pinned at creation; document content remains in the workspace language. See
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[shell and localization](../operations/shell-and-localization.md).
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- Each workspace defines identity and optional Evidence only. The PostgreSQL Metadata Catalog defines
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its DWH target and binding; secrets remain in the protected workspace secret store.
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- Settings are global (`backend/data/settings.json`: workspace/thinking); provider/model choices are
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canonical catalog references selected per session.
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- **Resume**: a resumable session returns to its last incomplete phase. The backend rejects resume with 409 when `finalized` or `archived`; `PiProcessManager.spawnFor` must send `/riprendi-sessione <id>` for resume and `/nuova-domanda` for a new session. The wrong prompt silently turns a resume into a new question.
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## Runtime composition
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The local stack is started by `./scripts/run-stack.sh` after the installation descriptor and
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`deploy/env/local.env` exist. `core` includes Pi. `catalog-db`, Qdrant, and the Ollama embedding
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service are internal Compose services; only the DWH and model-provider endpoint remain external.
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The launcher runs the explicit `catalog-migrate` one-shot service before application startup.
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For the operator sequence, see [Install and first start](../install/first-start.md). For the
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two user-facing paths, see [User guide](../guida-utente.md) and
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[Database management](../operations/database-management.md).
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