transcription/docs/mvp/mvp-step1.md

Step 1 Implementation Plan: config.py + models.py + db.py

Purpose

Establish the foundational data layer and configuration system that every subsequent MVP step builds on. At the end of this step, the project has a runnable Python package with a validated schema, typed configuration, and a test suite proving the data layer works — before any UI, worker, or AI provider code exists.

---

1. Prerequisite: Project Structure Scaffolding

Before writing any logic, create the package skeleton so imports work correctly.

Files to create (empty __init__.py stubs)

src/
└── transcription/
    ├── __init__.py
    ├── providers/
    │   └── __init__.py
    ├── services/
    │   └── __init__.py
    └── ui/
        └── __init__.py

Files to create (with logic — the Step 1 deliverables)

src/transcription/config.py
src/transcription/models.py
src/transcription/db.py

Test files to create

tests/
├── __init__.py
├── conftest.py
├── test_config.py
├── test_models.py
└── test_db.py

Update pyproject.toml

Add the dependencies that Step 1 requires and won't change later:

[project]
name = "transcription"
version = "0.1.0"
description = "Historical document transcription system"
readme = "README.md"
requires-python = ">=3.12"
dependencies = [
    "openrouter>=0.7.0",
    "pydantic>=2.13.4",
    "pydantic-settings>=2.9.1",
    "sqlmodel>=0.0.25",
]

[project.optional-dependencies]
dev = [
    "pytest>=8.0",
    "pytest-asyncio>=0.25",
]

[tool.pytest.ini_options]
addopts = "--strict-markers -q"
markers = [
    "unit: pure logic tests with no external dependencies",
    "integration: tests that touch framework or database contracts",
    "external: tests that call external services (slow, requires credentials)",
]

Key additions:

• openrouter — official OpenRouter Python SDK used for model calls
• pydantic-settings — for BaseSettings with env-var loading (this was split out of pydantic core in v2)
• sqlmodel — provides SQLModel (which bundles SQLAlchemy + Pydantic model integration) and the SQLite driver
• pytest + pytest-asyncio — in dev extras for test execution
• [tool.pytest.ini_options] — strict marker checking enabled from the start; markers registered upfront per pytesting skill conventions

Delete hello.py

The placeholder file is no longer needed.

---

2. config.py — Centralized Configuration

Satisfies: REQ-8 (centralized config and logging at startup)

Design Decisions

Decision	Rationale
Use pydantic-settings BaseSettings	Type-safe, validates on construction, loads from env vars and .env files automatically
PROVIDER constrained to openrouter for MVP	Keeps configuration explicit while avoiding premature multi-provider complexity
OPENROUTER_API_KEY required	Matches official SDK docs and avoids ambiguous provider-agnostic naming
PROVIDER_MODEL defaults to None	OpenRouter adapter (Step 3) supplies a sensible default when None
OPENROUTER_HTTP_REFERER and OPENROUTER_APP_TITLE optional	Matches SDK optional app-attribution fields
DATABASE_URL defaults to SQLite	Zero-setup local development; PostgreSQL swap is a single env-var change post-MVP
UPLOAD_DIR and PROMPT_DIR as Path objects	Enables .mkdir(parents=True, exist_ok=True) and path validation at startup
Logging configured via logging.config.dictConfig in setup_logging()	Centralized, explicit formatter/handler/root logger topology; called once at startup with disable_existing_loggers=False

Proposed Implementation

"""Centralized application configuration.

All settings are loaded from environment variables (or a .env file)
once at startup. Provider-specific defaults (model names, base URLs)
are resolved by the provider adapters, not here.
"""

from enum import StrEnum
from functools import lru_cache
from pathlib import Path
import logging
import logging.config

from pydantic_settings import BaseSettings, SettingsConfigDict


class Provider(StrEnum):
    OPENROUTER = "openrouter"


class Settings(BaseSettings):
    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        extra="ignore",
    )

    # --- AI provider ---
    provider: Provider = Provider.OPENROUTER
    openrouter_api_key: str
    provider_model: str | None = None
    openrouter_http_referer: str | None = None
    openrouter_app_title: str | None = None

    # --- persistence ---
    database_url: str = "sqlite:///./transcription.db"

    # --- filesystem paths ---
    upload_dir: Path = Path("./uploads")
    prompt_dir: Path = Path("./prompts")


LOGGING_CONFIG: dict[str, object] = {
    "version": 1,
    "disable_existing_loggers": False,
    "formatters": {
        "standard": {
            "format": "%(asctime)s | %(levelname)-8s | %(name)s | %(message)s",
            "datefmt": "%Y-%m-%d %H:%M:%S",
        }
    },
    "handlers": {
        "console": {
            "class": "logging.StreamHandler",
            "formatter": "standard",
            "stream": "ext://sys.stdout",
        }
    },
    "root": {
        "level": "INFO",
        "handlers": ["console"],
    },
}


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    """Return the singleton Settings instance.

    Cached so the entire application shares one validated config.
    """
    return Settings()


def setup_logging() -> None:
    """Configure root logging once at startup."""
    logging.config.dictConfig(LOGGING_CONFIG)

Key Behaviors

• Startup validation: If OPENROUTER_API_KEY is missing from the environment, Settings() raises a ValidationError immediately — the app won't start with a missing key.
• .env support: Developers can create a .env file in the project root for local keys; it's never committed (already covered by the existing .gitignore pattern or a new entry).
• extra="ignore": Unknown env vars don't cause errors, keeping the config resilient to unrelated environment variables.
• lru_cache: get_settings() is the single access point. All modules import and call this function rather than constructing Settings directly.
• Centralized logging: setup_logging() calls dictConfig exactly once at startup; all modules should use logging.getLogger(__name__) and avoid basicConfig.

.env template (not committed — add to .gitignore)

PROVIDER=openrouter
OPENROUTER_API_KEY=sk-or-...
# PROVIDER_MODEL=          # optional: OpenRouter adapter supplies default
# OPENROUTER_HTTP_REFERER=https://example.com
# OPENROUTER_APP_TITLE=Historical Transcription MVP
# DATABASE_URL=sqlite:///./transcription.db
# UPLOAD_DIR=./uploads
# PROMPT_DIR=./prompts

.gitignore addition

# ... existing entries ...

# Environment secrets
.env

---

3. models.py — SQLModel Domain Models

Satisfies: REQ-3 (persist and expose job states), REQ-4 (persist transcription output and failure details)

Design Decisions

Decision	Rationale
Three models: Document, Job, Transcript	Minimal set from MVP Feature 5. One-to-many from Document→Job and one-to-one from Job→Transcript
JobStatus as a StrEnum	Readable in the database ("queued" not 1), type-safe in Python, trivially serializable to JSON for the UI
Status values: queued, processing, transcribed, failed	Matches MVP Feature 2 lifecycle. REQ-3 also lists upload and completed — these are deferred to post-MVP when revision/review workflows exist
UUIDs for primary keys	Avoids auto-increment collision concerns if we later move to PostgreSQL; safe for distributed ID generation; uuid4 is simple
uploaded_at, created_at, updated_at as UTC datetime	Timezone-naive UTC by convention for MVP. Sufficient for single-user, single-timezone operation
Transcript.text is nullable	A failed job creates a Transcript with text=None and error_detail populated, keeping the query model uniform
Relationships via SQLModel Relationship	Enables document.jobs and job.transcript navigation in service code without manual joins

Proposed Implementation

• resource://skills/fastapi-async-sqlalchemy-modernization/document

"""SQLModel domain models for the transcription system.

Three models capture the MVP lifecycle:
  Document  →  one-to-many  →  Job  →  one-to-one  →  Transcript
"""

from datetime import datetime, timezone
from enum import StrEnum
from uuid import UUID, uuid4

from sqlmodel import Field, Relationship, SQLModel


class JobStatus(StrEnum):
    QUEUED = "queued"
    PROCESSING = "processing"
    TRANSCRIBED = "transcribed"
    FAILED = "failed"


class Document(SQLModel, table=True):
    """An uploaded document image."""

    id: UUID = Field(default_factory=uuid4, primary_key=True)
    filename: str
    file_path: str
    uploaded_at: datetime = Field(
        default_factory=lambda: datetime.now(timezone.utc),
    )

    # --- relationships ---
    jobs: list["Job"] = Relationship(back_populates="document")


class Job(SQLModel, table=True):
    """A transcription job tied to a single document."""

    id: UUID = Field(default_factory=uuid4, primary_key=True)
    document_id: UUID = Field(foreign_key="document.id")
    status: JobStatus = Field(default=JobStatus.QUEUED)
    created_at: datetime = Field(
        default_factory=lambda: datetime.now(timezone.utc),
    )
    updated_at: datetime = Field(
        default_factory=lambda: datetime.now(timezone.utc),
    )

    # --- relationships ---
    document: Document = Relationship(back_populates="jobs")
    transcript: "Transcript | None" = Relationship(back_populates="job")


class Transcript(SQLModel, table=True):
    """The output of a transcription job."""

    id: UUID = Field(default_factory=uuid4, primary_key=True)
    job_id: UUID = Field(foreign_key="job.id", unique=True)
    text: str | None = None
    error_detail: str | None = None
    created_at: datetime = Field(
        default_factory=lambda: datetime.now(timezone.utc),
    )

    # --- relationships ---
    job: Job = Relationship(back_populates="transcript")

Entity-Relationship Summary

┌──────────┐       ┌──────────┐       ┌─────────────┐
│ Document │ 1───* │   Job    │ 1───1 │ Transcript  │
├──────────┤       ├──────────┤       ├─────────────┤
│ id (PK)  │       │ id (PK)  │       │ id (PK)     │
│ filename │       │ doc_id   │──FK──▶│ job_id (FK) │
│ file_path│       │ status   │       │ text        │
│ uploaded │       │ created  │       │ error_detail│
│          │       │ updated  │       │ created     │
└──────────┘       └──────────┘       └─────────────┘

Why Only Four Status Values

REQ-3 lists six states: upload, queued, processing, transcribed, failed, completed. The MVP simplifies this:

REQ-3 State	MVP Treatment
upload	Implicit — the Document record exists before a Job is created. No separate job state needed.
queued	✅ Included — job created, waiting for worker pickup
processing	✅ Included — worker is actively transcribing
transcribed	✅ Included — AI output received and stored
failed	✅ Included — error captured
completed	Deferred — implies human review/acceptance. In MVP, transcribed is the terminal success state.

---

4. db.py — Database Engine and Session Management

Satisfies: MVP Feature 5 (SQLite auto-created on first startup)

Design Decisions

Decision	Rationale
Module-level create_engine + Session factory	REQ-7 (lifespan-owned resources) is deferred. A module-level engine is adequate for MVP's single-process, single-user operation
create_all() as an explicit function	Called at app startup. MVP auto-creates tables (REQ-10 deferred), but the function is isolated so it's easy to gate behind a flag later
get_session() as a generator	Standard FastAPI/SQLModel pattern — yields a session, ensures cleanup. Compatible with Depends() when the API layer arrives in Step 5
echo=False default	Keeps logs clean. Can be toggled for debugging

Proposed Implementation

"""Database engine, session factory, and schema bootstrap.

MVP uses SQLite with auto-create-tables at startup.
PostgreSQL migration is a post-MVP configuration change.
"""
import contextlib
from collections.abc import Generator

from sqlmodel import Session, SQLModel, create_engine

from transcription.config import get_settings


def _build_engine():
    settings = get_settings()
    connect_args = {}
    if settings.database_url.startswith("sqlite"):
        connect_args["check_same_thread"] = False
    return create_engine(
        settings.database_url,
        echo=False,
        connect_args=connect_args,
    )


engine = _build_engine()


def create_all() -> None:
    """Create all tables. Called once at application startup."""
    SQLModel.metadata.create_all(engine)


@contextlib.contextmanager
def get_session() -> Generator[Session]:
    """Yield a database session and ensure cleanup."""
    with Session(engine) as session:
        yield session

SQLite-Specific Note

check_same_thread=False is required for SQLite when the session may be accessed from different threads (e.g., a background worker on a different thread than the request handler). This setting is harmless and ignored for PostgreSQL connection strings.

---

5. Test Plan

Refer to these resources for rules and guidelines about structure:

• resource://skills/pytesting/document
• resource://catalog/prompts/pytest-scaffold
• resource://catalog/prompts/pytest-fill-scaffold

Hierarchy pattern used in this step:

tests/
    conftest.py
    test_config.py
        TestSettingsLoading
            test_loads_from_env
            test_requires_api_key
        TestProviderSettings
            test_defaults_to_openrouter
            test_rejects_invalid_value
            test_optional_fields_default_to_none
        TestPathSettings
            test_path_fields_are_path_objects
    test_models.py
        TestDocumentModel
            test_can_be_persisted
            test_defaults_are_populated
        TestJobModel
            test_can_be_created_for_document
            test_defaults_are_populated
            test_transitions_to_transcribed
            test_transitions_to_failed
        TestTranscriptModel
            test_success_record_persists
            test_failure_record_persists
            test_job_id_is_unique
        TestRelationships
            test_document_exposes_jobs
            test_job_exposes_transcript
    test_db.py
        TestSchemaBootstrap
            test_create_all_creates_expected_tables
        TestSessionFactory
            test_get_session_yields_session
            test_session_is_closed_after_generator_exit

tests/conftest.py — Shared Fixtures

"""Shared test fixtures.

Every test gets a fresh in-memory SQLite database so tests are
isolated, fast, and leave no artifacts on disk.
"""

import pytest
from sqlmodel import Session, SQLModel, create_engine
from sqlmodel.pool import StaticPool


@pytest.fixture
def session():
    """Provide a clean database session for each test."""
    engine = create_engine(
        "sqlite://",
        connect_args={"check_same_thread": False},
        poolclass=StaticPool,
    )
    SQLModel.metadata.create_all(engine)
    with Session(engine) as session:
        yield session

StaticPool ensures a single in-memory SQLite connection is shared across threads, which is required when TestClient (Step 5) spawns threads that would otherwise get separate in-memory databases. Establishing it now keeps the fixture stable across all future steps.

tests/test_config.py — Configuration Hierarchy

Class	Method	What It Verifies
TestSettingsLoading	test_loads_from_env	Settings constructs successfully when OPENROUTER_API_KEY is set via env var
TestSettingsLoading	test_requires_api_key	Settings() raises ValidationError when OPENROUTER_API_KEY is missing
TestProviderSettings	test_defaults_to_openrouter	Default provider is openrouter when not explicitly set
TestProviderSettings	test_rejects_invalid_value	Setting PROVIDER=invalid raises ValidationError
TestProviderSettings	test_optional_fields_default_to_none	provider_model, openrouter_http_referer, and openrouter_app_title are None when unset
TestPathSettings	test_path_fields_are_path_objects	upload_dir and prompt_dir are Path instances

tests/test_models.py — Model & Relationship Hierarchy

Class	Method	What It Verifies
TestDocumentModel	test_can_be_persisted	A Document can be persisted and read back with correct fields
TestDocumentModel	test_defaults_are_populated	id is auto-generated UUID, uploaded_at is populated
TestJobModel	test_can_be_created_for_document	A Job linked to a Document via FK persists correctly
TestJobModel	test_defaults_are_populated	Default status is queued, created_at and updated_at are populated
TestJobModel	test_transitions_to_transcribed	Status can be updated from queued → processing → transcribed
TestJobModel	test_transitions_to_failed	Status can be updated from processing → failed
TestTranscriptModel	test_success_record_persists	A Transcript with text set and error_detail=None persists correctly
TestTranscriptModel	test_failure_record_persists	A Transcript with text=None and error_detail set persists correctly
TestRelationships	test_document_exposes_jobs	document.jobs returns the linked Job list
TestRelationships	test_job_exposes_transcript	job.transcript returns the linked Transcript
TestTranscriptModel	test_job_id_is_unique	Inserting two transcripts with the same job_id raises an integrity error

tests/test_db.py — Database Bootstrap Hierarchy

Class	Method	What It Verifies
TestSchemaBootstrap	test_create_all_creates_expected_tables	After create_all(), the expected tables (document, job, transcript) exist in the database
TestSessionFactory	test_get_session_yields_session	get_session() yields a usable Session object
TestSessionFactory	test_session_is_closed_after_generator_exit	After the generator is exhausted, the session is closed

Marker Strategy (Step 1)

• Markers (unit, integration, external) are registered upfront in pyproject.toml with --strict-markers enabled, per pytesting skill conventions.
• All Step 1 tests are unmarked — they run in the default lane since they are fast, deterministic, and have no external dependencies.
• When slower integration or external tests are introduced in later steps, apply explicit markers and keep test names unchanged.

Test Workflow

Follow the two-phase approach from resource://catalog/prompts/pytest-scaffold and resource://catalog/prompts/pytest-fill-scaffold:

1. Scaffold phase: Create test files with class hierarchy, method names, and one-line docstrings only. Validate collection:
   • uv run pytest --collect-only -q
2. Fill phase: Implement assertions, fixtures, and minimal test data. Treat scaffolded names and docstrings as locked. Validate execution:
   • uv run pytest -q

Scaffolded structure is treated as a stable baseline — do not rename, move, merge, split, or re-nest tests once the scaffold is reviewed.

---

6. Step 1 Completion Checklist

When all of the following are true, Step 1 is done and Step 2 can begin:

#	Criterion	How to Verify
1	src/transcription/ package exists with config.py, models.py, db.py	ls / file inspection
2	Empty __init__.py stubs exist for providers/, services/, ui/	ls / file inspection
3	Settings loads from environment and validates OPENROUTER_API_KEY is present	test_config.py passes
4	Document, Job, Transcript models create tables in SQLite	test_models.py passes
5	JobStatus enum has exactly four values: queued, processing, transcribed, failed	test_models.py passes
6	Foreign key relationships work: Document→Job→Transcript	test_models.py passes
7	create_all() bootstraps the schema; get_session() yields a working session	test_db.py passes
8	All tests pass: uv run pytest -q	CI / local run
9	hello.py is deleted	File inspection
10	pyproject.toml includes openrouter, sqlmodel, pydantic-settings, pytest, pytest-asyncio	File inspection
10a	pyproject.toml has [tool.pytest.ini_options] with --strict-markers and registered markers	File inspection
11	.env.example documents all config vars; .env is in .gitignore	File inspection
12	setup_logging() uses logging.config.dictConfig with centralized formatter/handler/root config	File inspection
13	uv run pytest --collect-only -q shows expected test hierarchy	Local run
14	uv run pytest -q passes all tests	Local run

---

7. What This Step Does NOT Include

Explicitly out of scope to prevent scope creep:

Excluded	Reason
FastAPI / NiceGUI app entrypoint	Step 5
Additional provider adapters beyond OpenRouter	Post-MVP
Upload service logic	Step 4
Worker / background processing	Step 4
Transcription prompt files	Step 2
Alembic or migration tooling	Post-MVP (REQ-10 deferred)
Async session factory	Post-MVP (REQ-7 deferred)

---

This plan produces a fully tested, importable data foundation. Every subsequent step imports from transcription.config, transcription.models, and transcription.db without modification.