99 lines
6.4 KiB
Markdown
99 lines
6.4 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 or generic OIDC. `tht` is the only operator CLI.
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For sessions, roles, groups, diagnostics, and recovery, see the [authentication documentation](authentication.md).
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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 --> 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 independent projects
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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 with installation-local database
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configurations stored in PostgreSQL through Kysely.
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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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Application settings remain in `backend/data/settings.json`; session state remains in harness phase
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documents. PostgreSQL stores only the administrative database catalog, bindings, observed tables,
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and curated descriptions. Connector secrets remain write-only in the encrypted workspace secret
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store. Catalog SSH support is limited to connection tests and table synchronization; it does not
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change the 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. The shared Qdrant
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collection keeps the unnamed dense vector used by Schema and Memory. Evidence preprocessing may
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add only the sparse `bm25` vector with `idf`, without deleting, renaming, or recreating the collection.
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`workspace preprocess evidence` and the Evidence part of `workspace preprocess run` are the only public
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operations that perform this upgrade.
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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 are in English. Document *content* stays in the workspace language because it is the actual data; only chrome and labels are in English.
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- Each workspace defines its DWH target and working directories. Secrets remain in protected installation files, not in the workspace repository.
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- Settings are global (`backend/data/settings.json`: workspace/provider/model/thinking); the new-session form asks only for the question.
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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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## Starting the stack
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Start the local stack with `./scripts/run-stack.sh` after creating
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`deploy/env/local.env` from `deploy/env/local.env.example`. The Compose core includes Pi; DWH,
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the vector database, embeddings, and the LLM are external endpoints configured in the local file.
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