Phase 3: extract EvidenceService and rewrite the service ownership rule

Decompose SourceService along the aggregate boundary and then correct the
instruction file that caused it to grow, in that order. The refactor is the
empirical test of the rule.

services/evidence.py (new)
  EvidenceService owns ExecutionAttempt: read_latest_execution_attempt,
  list_execution_attempts, promote_machine_attempt, build_evidence_export,
  plus the LatestExecutionAttempt projection. Moved verbatim from sources.py.

services/errors.py (new)
  The five-class error hierarchy (PromptLoadError, TranscriptionError,
  TranscriptionNotFoundError, SourceDeleteBlockedError,
  CandidatePromotionError) moved out of sources.py. evidence.py needs
  TranscriptionNotFoundError, and test_service_boundaries.py correctly
  rejected the sibling import. errors.py defines no *Service class, so it is
  a legal shared home. This was the boundary test doing its job, not an
  obstacle to route around.

sources.py 1,389 -> 885 lines (1,063 after Phase 2).

services/__init__.py
  ServiceBundle and from_session_factory register evidence. Note that
  field-by-field ServiceBundle construction silently binds services to the
  process-global session factory via default_factory; from_session_factory is
  the only safe constructor. Two test bundles were fixed for this.

.github/instructions/services.instructions.md
  Rewritten to describe the boundaries the decomposition actually produced,
  per plan Phase 3 task 7 and review log [59].

  - "1 service class per data model" -> one service class per aggregate.
    The table-shaped rule is the measured cause of sources.py reaching
    1,389 lines; DocumentType has no lifecycle without Document.
  - New Model Ownership section. Junctions are owned by their lifecycle
    owner, the service that creates and deletes the rows: document_person
    to PeopleService (sole writer, measured), job_source to SourceService.
    Two carve-outs are stated rather than left as silent violations:
    cascade deletion when a service deletes its own aggregate root, and
    status transitions that create and delete nothing (cancel_job,
    resubmit_failed_sources), which are Job lifecycle events on the work
    queue. EvidenceService.promote_machine_attempt's two-field write to
    Source is named and scoped.
  - Mandatory CRUD softened to intent. It was already false: five modules
    define no service class, EvidenceService has no create/delete because
    ExecutionAttempt is append-only, RegistryService uses <op>_entry.
  - Separated reading across models via eager loads from the owning root,
    which is allowed, from importing another service, which is not. The old
    line 13 and lines 75-77 read as contradictory.
  - Typo: picutre.

  No code was moved to satisfy the rule.

tests/test_service_boundaries.py
  Docstring no longer cites the instruction file by line number; that anchor
  would desynchronise silently. errors.py added to the neutral-module list.

Verified: 292 passed, 4 skipped, 0 ruff, 0 ty. All 25 /ui/* routes walked
against the live app; 24x 200. /ui/documents/{id}/sources 404s via a 307 that
drops the /ui prefix, confirmed pre-existing (last touched in 6a3ee26) and
left alone as out of scope.

Co-authored-by: Copilot App <[email protected]>

.github/instructions/services.instructions.md

@@ -7,29 +7,89 @@ applyTo: 'src/transcription/services/*.py'
 
 ## Structure
 
-- Project core data models defined in [models](../../src/transcription/db/models.py)
-- 1 service class per data model
-- Only services directly interact with the database, and only through async methods
-- Services are completely independent of one another. Any operation that needs to use more than a single service, which is most of them, needs to have a separate orchestration function.
+- Project core data models are defined in [models](../../src/transcription/db/models.py)
+- One service class per **aggregate**, not per table. An aggregate is a root model plus
+  the models that have no independent lifecycle of their own. `DocumentType` has no
+  meaning without `Document`, so it belongs to `DocumentService`; it does not get its
+  own service. Splitting per table produces services that must reach across each other
+  for every real operation, which is what line 13 forbids.
+- Only services interact with the database, and only through async methods.
+- **A service module must not import another service module.** This is enforced by
+  [test_service_boundaries](../../tests/test_service_boundaries.py). Shared types go in a
+  neutral module that defines no service class (see [errors](../../src/transcription/services/errors.py)).
+- Not every module in this package is a service. Helper modules that define no `*Service`
+  class (`base`, `errors`, `normalization`, `prompts`, `quality`, `media_storage`,
+  `source_media`) are free-function modules and are exempt from the service rules below.
+
+## Model Ownership
+
+Every model has exactly one owning service. The owner defines that model's invariants and
+is the only service that may **create or delete** its rows.
+
+| Model | Owner |
+| --- | --- |
+| `Document`, `DocumentType` | `DocumentService` |
+| `Source`, `JobSource` | `SourceService` |
+| `Job` | `JobService` |
+| `Person`, `PersonRole`, `DocumentPerson` | `PeopleService` |
+| `ExecutionAttempt` | `EvidenceService` |
+
+### Junction tables
+
+A junction table is owned by the service that **creates and deletes its rows** — its
+lifecycle owner. The service on the other side may read through the junction (via
+`selectinload`) but must not create rows in it.
+
+- `document_person` -> `PeopleService`. Every write is there; `DocumentService` only
+  eager-loads through it.
+- `job_source` -> `SourceService`, which creates the row, records each page's outcome,
+  and deletes it.
+
+Two consequences follow, and both are deliberate:
+
+- **Cascade deletion is not a violation.** A service deleting the aggregate root it owns
+  may delete junction rows referencing that root, because they cannot outlive it
+  (`JobService.delete_job_with_guardrails`).
+- **Ownership governs creation and deletion, not every state transition.** `job_source` is
+  both a link and the transcription work queue. `JobService.cancel_job` and
+  `resubmit_failed_sources` transition `job_source.status` across a whole job, because that
+  transition is a Job lifecycle event, not a per-page outcome. They create and delete
+  nothing.
+
+`EvidenceService.promote_machine_attempt` writes two fields on `Source`
+(`preferred_execution_attempt_id`, `raw_transcription`). This is allowed on the same
+principle: selecting which attempt a Source presents is an evidence decision that happens
+to land on `Source`. It is scoped to those two projection fields.
+
+If a new operation cannot be expressed within one owner, it belongs in an orchestration
+module, not in a cross-service import.
 
 ## Error Handling
 
-- Service-specific errors defined at the top of the respective module and inherit from `AppError`
-- Use a context manager for large `try/except` blocks like `handle_transcription_errors` in [sources](../../src/transcription/services/sources.py)
+- Errors used by a single service are defined at the top of that module and inherit from `AppError`.
+- Errors shared by more than one service go in [errors](../../src/transcription/services/errors.py),
+  which defines no service class and is therefore importable by any of them.
+- Use a context manager for large `try/except` blocks, like `handle_transcription_errors` in
+  [sources](../../src/transcription/services/sources.py).
 
 ## Checklist
 
 - [ ] Uses `ServiceBase` for common logic
-- [ ] CRUD methods created at the top
-- [ ] Session kwarg for `AsyncSession` to pass in a session object to each method
-- [ ] Services use `self._session_scope` in their methods to pass the session thru.
-    - Multiple operations on the same object(s) require sharing a session between all the methods used.
+- [ ] Session kwarg for `AsyncSession` to pass a session object into each method
+- [ ] Services use `self._session_scope` in their methods to pass the session through
+    - Multiple operations on the same object(s) require sharing a session between all the methods used
+- [ ] Every model the module touches is either owned by it or reached read-only
 
 ## CRUD Methods
 
-- Create, read, update, and delete, created in that order
-- Name format `<operation>_<model >`, for example `create_document` or `update_job`
-- All services must define these 4 methods first, and in that order
+- Name format `<operation>_<model>`, for example `create_document` or `update_job`.
+- Where a service exposes create/read/update/delete for its root model, define them at the
+  top of the class in that order, before derived reads and workflow helpers.
+- Not every aggregate needs all four. `ExecutionAttempt` is append-only evidence written by
+  `workflows.py`, so `EvidenceService` deliberately exposes reads and no create or delete.
+  Do not add unused CRUD methods to satisfy symmetry.
+- `RegistryService` is generic across small lookup models and uses `<operation>_entry`
+  naming instead.
 
 ## Transaction Finalization
 
@@ -74,4 +134,11 @@ Separation of concerns:
 
 # Service Composition
 
-Some operations, like uploading a picutre, require modifications to multiple tables, which can be done by composing methods from the service object into a separate function.
+A service method may read across models it does not own, using eager loads from its own
+aggregate root. What it may not do is import another service.
+
+Operations that must **write** models owned by more than one service — uploading a picture,
+for example — are composed in an orchestration module
+([store](../../src/transcription/services/store.py),
+[workflows](../../src/transcription/services/workflows.py)). Orchestration modules define no
+service class, may import any service, and own the commit boundary.

src/transcription/services/__init__.py

@@ -9,12 +9,21 @@ from sqlmodel.ext.asyncio.session import AsyncSession
 
 from ..config import Settings
 from .documents import DocumentService
+from .evidence import EvidenceService
 from .jobs import JobService
 from .people import PeopleService
 from .prompts import PromptStore
 from .sources import SourceService
 
-__all__ = ["DocumentService", "JobService", "PeopleService", "PromptStore", "ServiceBundle", "SourceService"]
+__all__ = [
+    "DocumentService",
+    "EvidenceService",
+    "JobService",
+    "PeopleService",
+    "PromptStore",
+    "ServiceBundle",
+    "SourceService",
+]
 
 
 @dataclass(frozen=True, slots=True)
@@ -25,6 +34,7 @@ class ServiceBundle:
     sources: SourceService = field(default_factory=SourceService)
     jobs: JobService = field(default_factory=JobService)
     people: PeopleService = field(default_factory=PeopleService)
+    evidence: EvidenceService = field(default_factory=EvidenceService)
 
     @classmethod
     def from_session_factory(
@@ -41,6 +51,7 @@ class ServiceBundle:
             sources=SourceService(session_factory=session_factory, settings=settings),
             jobs=JobService(session_factory=session_factory, settings=settings),
             people=PeopleService(session_factory=session_factory, settings=settings),
+            evidence=EvidenceService(session_factory=session_factory, settings=settings),
         )
 
     async def aclose(self) -> None:

src/transcription/services/errors.py

@@ -0,0 +1,32 @@
+"""Error vocabulary shared across the source, evidence, and prompt services.
+
+These live in a neutral module rather than in the service that raises them
+because more than one service raises them, and ``services.instructions.md``
+forbids a service module from importing a sibling. Orchestration modules and
+the UI import from here, so the exception a caller catches does not change when
+an operation moves between services.
+"""
+
+from __future__ import annotations
+
+from transcription.errors import AppError
+
+
+class PromptLoadError(AppError):
+    """Raised when prompt artifacts cannot be loaded safely."""
+
+
+class TranscriptionError(AppError):
+    """Raised when transcription execution fails."""
+
+
+class TranscriptionNotFoundError(TranscriptionError):
+    """Raised when a transcription-related resource is not found."""
+
+
+class SourceDeleteBlockedError(TranscriptionError):
+    """Raised when source deletion is blocked by dependency policy."""
+
+
+class CandidatePromotionError(TranscriptionError):
+    """Raised when a machine attempt cannot be selected for its Source."""

src/transcription/services/evidence.py

@@ -0,0 +1,210 @@
+"""Read and export the immutable execution evidence trail.
+
+``ExecutionAttempt`` is append-only: one row per provider call, written once by
+the transcription workflow and never updated. Everything here is therefore a
+read, a projection, or an export, with one exception - ``promote_machine_attempt``
+selects which attempt a ``Source`` presents, which is an evidence decision even
+though the write lands on ``Source``.
+"""
+
+from __future__ import annotations
+
+import base64
+import hashlib
+from collections.abc import Sequence
+from dataclasses import dataclass
+from uuid import UUID
+
+from pydantic import JsonValue
+from sqlalchemy import inspect as sqlalchemy_inspect
+from sqlmodel import col
+from sqlmodel import select
+from sqlmodel.ext.asyncio.session import AsyncSession
+
+from transcription.db.models import ExecutionAttempt
+from transcription.db.models import JobSourceStatus
+from transcription.db.models import Source
+from transcription.errors import ErrorCategory
+
+from ..db.loading import defer
+from .base import ServiceBase
+from .errors import CandidatePromotionError
+from .errors import TranscriptionNotFoundError
+
+
+@dataclass(frozen=True, slots=True)
+class LatestExecutionAttempt:
+    """One execution attempt plus the loader facts a caller needs to render it."""
+
+    attempt: ExecutionAttempt
+    transport_body_deferred: bool
+
+
+class EvidenceService(ServiceBase):
+    """Read, project, and export execution attempt evidence."""
+
+    async def read_latest_execution_attempt(
+        self,
+        *,
+        job_source_id: UUID,
+        session: AsyncSession | None = None,
+    ) -> LatestExecutionAttempt | None:
+        """Read only the latest immutable attempt for one compatibility projection.
+
+        The transport body is deferred because it can be arbitrarily large; the
+        returned read model reports that as a plain flag so callers never have to
+        inspect ORM loader state.
+        """
+        async with self._session_scope(session) as _session:
+            query = (
+                select(ExecutionAttempt)
+                .options(defer(ExecutionAttempt.transport_body))
+                .where(ExecutionAttempt.job_source_id == job_source_id)
+                .order_by(
+                    col(ExecutionAttempt.attempt_number).desc(),
+                    col(ExecutionAttempt.id).desc(),
+                )
+                .limit(1)
+            )
+            attempt = (await _session.exec(query)).first()
+            if attempt is None:
+                return None
+            deferred = "transport_body" in sqlalchemy_inspect(attempt).unloaded
+            return LatestExecutionAttempt(attempt=attempt, transport_body_deferred=deferred)
+
+    async def list_execution_attempts(
+        self,
+        *,
+        source_id: UUID | None = None,
+        job_id: UUID | None = None,
+        session: AsyncSession | None = None,
+    ) -> Sequence[ExecutionAttempt]:
+        """List immutable execution evidence in stable attempt order."""
+        async with self._session_scope(session) as _session:
+            query = select(ExecutionAttempt)
+            if source_id is not None:
+                query = query.where(ExecutionAttempt.source_id == source_id)
+            if job_id is not None:
+                query = query.where(ExecutionAttempt.job_id == job_id)
+            query = query.order_by(
+                col(ExecutionAttempt.job_id),
+                col(ExecutionAttempt.source_id),
+                col(ExecutionAttempt.attempt_number),
+                col(ExecutionAttempt.id),
+            )
+            return (await _session.exec(query)).all()
+
+    async def promote_machine_attempt(
+        self,
+        *,
+        source_id: UUID,
+        execution_attempt_id: UUID,
+        session: AsyncSession | None = None,
+    ) -> Source:
+        """Atomically select one successful machine attempt as the Source projection."""
+        async with self._session_scope(session) as _session:
+            source = await self._read_source(
+                session=_session,
+                source_id=source_id,
+                suggestion="Refresh Source Detail and retry.",
+            )
+            attempt = await _session.get(ExecutionAttempt, execution_attempt_id)
+            if (
+                attempt is None
+                or attempt.source_id != source_id
+                or attempt.status != JobSourceStatus.TRANSCRIBED
+                or not attempt.raw_transcription
+            ):
+                raise CandidatePromotionError(
+                    "Only a successful transcription attempt belonging to this Source can be selected",
+                    category=ErrorCategory.VALIDATION,
+                    suggestion="Select an available successful candidate from Source Detail.",
+                )
+            source.preferred_execution_attempt_id = attempt.id
+            source.raw_transcription = attempt.raw_transcription
+            await self._finalize(session=_session, caller_session=session, refresh=(source,))
+            return source
+
+    async def build_evidence_export(
+        self,
+        *,
+        source_id: UUID,
+        session: AsyncSession | None = None,
+    ) -> dict[str, JsonValue]:
+        """Build a versioned, source-reference-only evidence export."""
+        async with self._session_scope(session) as _session:
+            source = await self._read_source(session=_session, source_id=source_id)
+            attempts = list(await self.list_execution_attempts(source_id=source_id, session=_session))
+
+        attempt_payloads = [
+            {
+                "id": str(attempt.id),
+                "job_id": str(attempt.job_id),
+                "source_id": str(attempt.source_id),
+                "attempt_number": attempt.attempt_number,
+                "status": attempt.status.value,
+                "provider": attempt.provider,
+                "model": attempt.model,
+                "request_manifest": attempt.request_manifest,
+                "request_manifest_sha256": attempt.request_manifest_sha256,
+                "request_manifest_schema_version": attempt.request_manifest_schema_version,
+                "transport": {
+                    "response_received": attempt.response_received,
+                    "status_code": attempt.transport_status_code,
+                    "body_base64": (
+                        base64.b64encode(attempt.transport_body).decode("ascii")
+                        if attempt.transport_body is not None
+                        else None
+                    ),
+                    "body_sha256": (
+                        hashlib.sha256(attempt.transport_body).hexdigest()
+                        if attempt.transport_body is not None
+                        else None
+                    ),
+                    "content_type": attempt.transport_content_type,
+                    "content_encoding": attempt.transport_content_encoding,
+                    "safe_headers": attempt.transport_safe_headers,
+                    "request_id": attempt.router_request_id,
+                    "generation_id": attempt.router_generation_id,
+                },
+                "sdk_response_snapshot": attempt.sdk_response_snapshot,
+                "normalized_metadata": attempt.normalized_metadata,
+                "software_context": attempt.software_context,
+                "raw_transcription": attempt.raw_transcription,
+                "error_category": attempt.error_category,
+                "error_detail": attempt.error_detail,
+                "failure_phase": attempt.failure_phase,
+                "started_at": attempt.started_at.isoformat(),
+                "finished_at": attempt.finished_at.isoformat(),
+                "duration_ms": attempt.duration_ms,
+            }
+            for attempt in attempts
+        ]
+        return {
+            "schema_name": "transcription.evidence-export",
+            "schema_version": "1",
+            "source": {
+                "id": str(source.id),
+                "digest_sha256": source.file_hash,
+                "byte_size": source.file_size_bytes,
+                "page_number": source.page_number,
+                "upload_name": source.upload_name,
+            },
+            "attempts": attempt_payloads,
+        }
+
+    async def _read_source(
+        self,
+        *,
+        session: AsyncSession,
+        source_id: UUID,
+        suggestion: str = "Verify the source id and retry.",
+    ) -> Source:
+        return await self._get_or_raise(
+            Source,
+            source_id,
+            session=session,
+            error=TranscriptionNotFoundError,
+            noun="Source",
+            suggestion=suggestion,
+        )

src/transcription/services/sources.py

@@ -3,7 +3,6 @@
 from __future__ import annotations
 
 import asyncio
-import base64
 import hashlib
 import logging
 from collections.abc import Sequence
@@ -22,7 +21,6 @@ from pydantic import JsonValue
 from pydantic import TypeAdapter
 from pydantic import ValidationError
 from sqlalchemy import func
-from sqlalchemy import inspect as sqlalchemy_inspect
 from sqlalchemy import literal
 from sqlalchemy import tuple_
 from sqlalchemy.ext.asyncio import async_sessionmaker
@@ -37,7 +35,6 @@ from transcription.db.models import Job
 from transcription.db.models import JobSource
 from transcription.db.models import JobSourceStatus
 from transcription.db.models import Source
-from transcription.errors import AppError
 from transcription.errors import ErrorCategory
 from transcription.providers import ProviderAuthError
 from transcription.providers import ProviderError
@@ -50,10 +47,13 @@ from transcription.providers import TranscriptionResult
 from transcription.providers import TransportEvidence
 from transcription.providers import get_transcription_provider
 
-from ..db.loading import defer
 from ..db.loading import orm_attribute
 from ..db.loading import selectinload
 from .base import ServiceBase
+from .errors import PromptLoadError
+from .errors import SourceDeleteBlockedError
+from .errors import TranscriptionError
+from .errors import TranscriptionNotFoundError
 from .source_media import lookup_source_mime_type
 from .source_media import supported_source_formats
 
@@ -76,26 +76,6 @@ class PromptExecution(BaseModel):
     top_p: float | None = Field(ge=0.0, le=1.0)
 
 
-class PromptLoadError(AppError):
-    """Raised when prompt artifacts cannot be loaded safely."""
-
-
-class TranscriptionError(AppError):
-    """Raised when transcription execution fails."""
-
-
-class TranscriptionNotFoundError(TranscriptionError):
-    """Raised when a transcription-related resource is not found."""
-
-
-class SourceDeleteBlockedError(TranscriptionError):
-    """Raised when source deletion is blocked by dependency policy."""
-
-
-class CandidatePromotionError(TranscriptionError):
-    """Raised when a machine attempt cannot be selected for its Source."""
-
-
 @dataclass(frozen=True, slots=True)
 class SourceNavigation:
     """Adjacent Source identifiers within one ordered Document."""
@@ -128,14 +108,6 @@ def build_provider_input(source: Source) -> ProviderInput:
     )
 
 
-@dataclass(frozen=True, slots=True)
-class LatestExecutionAttempt:
-    """One execution attempt plus the loader facts a caller needs to render it."""
-
-    attempt: ExecutionAttempt
-    transport_body_deferred: bool
-
-
 class SourceService(ServiceBase):
     """Manage source records, media payloads, revisions, and page execution output."""
 
@@ -214,35 +186,6 @@ class SourceService(ServiceBase):
             )
         return source
 
-    async def read_latest_execution_attempt(
-        self,
-        *,
-        job_source_id: UUID,
-        session: AsyncSession | None = None,
-    ) -> LatestExecutionAttempt | None:
-        """Read only the latest immutable attempt for one compatibility projection.
-
-        The transport body is deferred because it can be arbitrarily large; the
-        returned read model reports that as a plain flag so callers never have to
-        inspect ORM loader state.
-        """
-        async with self._session_scope(session) as _session:
-            query = (
-                select(ExecutionAttempt)
-                .options(defer(ExecutionAttempt.transport_body))
-                .where(ExecutionAttempt.job_source_id == job_source_id)
-                .order_by(
-                    col(ExecutionAttempt.attempt_number).desc(),
-                    col(ExecutionAttempt.id).desc(),
-                )
-                .limit(1)
-            )
-            attempt = (await _session.exec(query)).first()
-            if attempt is None:
-                return None
-            deferred = "transport_body" in sqlalchemy_inspect(attempt).unloaded
-            return LatestExecutionAttempt(attempt=attempt, transport_body_deferred=deferred)
-
     async def read_source_navigation(
         self,
         source_id: UUID,
@@ -640,127 +583,6 @@ class SourceService(ServiceBase):
             await self._finalize(session=_session, caller_session=session, refresh=(job, source, job_source, attempt))
             return job_source
 
-    async def promote_machine_attempt(
-        self,
-        *,
-        source_id: UUID,
-        execution_attempt_id: UUID,
-        session: AsyncSession | None = None,
-    ) -> Source:
-        """Atomically select one successful machine attempt as the Source projection."""
-        async with self._session_scope(session) as _session:
-            source = await self._read_source(
-                session=_session,
-                source_id=source_id,
-                suggestion="Refresh Source Detail and retry.",
-            )
-            attempt = await _session.get(ExecutionAttempt, execution_attempt_id)
-            if (
-                attempt is None
-                or attempt.source_id != source_id
-                or attempt.status != JobSourceStatus.TRANSCRIBED
-                or not attempt.raw_transcription
-            ):
-                raise CandidatePromotionError(
-                    "Only a successful transcription attempt belonging to this Source can be selected",
-                    category=ErrorCategory.VALIDATION,
-                    suggestion="Select an available successful candidate from Source Detail.",
-                )
-            source.preferred_execution_attempt_id = attempt.id
-            source.raw_transcription = attempt.raw_transcription
-            await self._finalize(session=_session, caller_session=session, refresh=(source,))
-            return source
-
-    async def list_execution_attempts(
-        self,
-        *,
-        source_id: UUID | None = None,
-        job_id: UUID | None = None,
-        session: AsyncSession | None = None,
-    ) -> Sequence[ExecutionAttempt]:
-        """List immutable execution evidence in stable attempt order."""
-        async with self._session_scope(session) as _session:
-            query = select(ExecutionAttempt)
-            if source_id is not None:
-                query = query.where(ExecutionAttempt.source_id == source_id)
-            if job_id is not None:
-                query = query.where(ExecutionAttempt.job_id == job_id)
-            query = query.order_by(
-                col(ExecutionAttempt.job_id),
-                col(ExecutionAttempt.source_id),
-                col(ExecutionAttempt.attempt_number),
-                col(ExecutionAttempt.id),
-            )
-            return (await _session.exec(query)).all()
-
-    async def build_evidence_export(
-        self,
-        *,
-        source_id: UUID,
-        session: AsyncSession | None = None,
-    ) -> dict[str, JsonValue]:
-        """Build a versioned, source-reference-only evidence export."""
-        async with self._session_scope(session) as _session:
-            source = await self._read_source(session=_session, source_id=source_id)
-            attempts = list(await self.list_execution_attempts(source_id=source_id, session=_session))
-
-        attempt_payloads = [
-            {
-                "id": str(attempt.id),
-                "job_id": str(attempt.job_id),
-                "source_id": str(attempt.source_id),
-                "attempt_number": attempt.attempt_number,
-                "status": attempt.status.value,
-                "provider": attempt.provider,
-                "model": attempt.model,
-                "request_manifest": attempt.request_manifest,
-                "request_manifest_sha256": attempt.request_manifest_sha256,
-                "request_manifest_schema_version": attempt.request_manifest_schema_version,
-                "transport": {
-                    "response_received": attempt.response_received,
-                    "status_code": attempt.transport_status_code,
-                    "body_base64": (
-                        base64.b64encode(attempt.transport_body).decode("ascii")
-                        if attempt.transport_body is not None
-                        else None
-                    ),
-                    "body_sha256": (
-                        hashlib.sha256(attempt.transport_body).hexdigest()
-                        if attempt.transport_body is not None
-                        else None
-                    ),
-                    "content_type": attempt.transport_content_type,
-                    "content_encoding": attempt.transport_content_encoding,
-                    "safe_headers": attempt.transport_safe_headers,
-                    "request_id": attempt.router_request_id,
-                    "generation_id": attempt.router_generation_id,
-                },
-                "sdk_response_snapshot": attempt.sdk_response_snapshot,
-                "normalized_metadata": attempt.normalized_metadata,
-                "software_context": attempt.software_context,
-                "raw_transcription": attempt.raw_transcription,
-                "error_category": attempt.error_category,
-                "error_detail": attempt.error_detail,
-                "failure_phase": attempt.failure_phase,
-                "started_at": attempt.started_at.isoformat(),
-                "finished_at": attempt.finished_at.isoformat(),
-                "duration_ms": attempt.duration_ms,
-            }
-            for attempt in attempts
-        ]
-        return {
-            "schema_name": "transcription.evidence-export",
-            "schema_version": "1",
-            "source": {
-                "id": str(source.id),
-                "digest_sha256": source.file_hash,
-                "byte_size": source.file_size_bytes,
-                "page_number": source.page_number,
-                "upload_name": source.upload_name,
-            },
-            "attempts": attempt_payloads,
-        }
-
     async def upsert_revision_for_source(
         self,
         *,

src/transcription/services/store.py

@@ -23,10 +23,10 @@ from ..db.models import JobSourceStatus
 from ..db.models import Source
 from ..db.session import SessionFactory
 from ..db.session import session_scope
+from .errors import TranscriptionError
 from .media_storage import build_stored_filename
 from .media_storage import write_media_bytes
 from .normalization import normalize_orientation_async
-from .sources import TranscriptionError
 from .sources import build_prompt_execution
 from .sources import source_mime_type
 from .sources import validate_source_content

src/transcription/ui/pages/sources_page.py

@@ -14,10 +14,11 @@ from transcription.db.models import ExecutionAttempt
 from transcription.db.models import JobSource
 from transcription.db.models import JobSourceStatus
 from transcription.db.models import Source
-from transcription.services.sources import LatestExecutionAttempt
-from transcription.services.sources import SourceDeleteBlockedError
+from transcription.services.errors import SourceDeleteBlockedError
+from transcription.services.errors import TranscriptionNotFoundError
+from transcription.services.evidence import EvidenceService
+from transcription.services.evidence import LatestExecutionAttempt
 from transcription.services.sources import SourceService
-from transcription.services.sources import TranscriptionNotFoundError
 from transcription.ui.components.app_shell import render_navigation_header
 from transcription.ui.components.cards import archival_card
 from transcription.ui.components.confirm_delete import render_delete_actions
@@ -112,6 +113,7 @@ def register_page() -> None:  # noqa: PLR0915
     @ui.page("/sources/{source_id}")
     async def source_detail_page(source_id: str, request: Request, session_factory: SessionFactoryDep) -> None:
         sources_service = SourceService(session_factory=session_factory)
+        evidence_service = EvidenceService(session_factory=session_factory)
         render_navigation_header(current_path="/sources")
 
         parsed_source_id = parsed_record_id(source_id, noun="Source")
@@ -123,11 +125,11 @@ def register_page() -> None:  # noqa: PLR0915
             navigation = await sources_service.read_source_navigation(parsed_source_id)
             latest_job_source = source.latest_job_source
             latest_attempt = (
-                await sources_service.read_latest_execution_attempt(job_source_id=latest_job_source.id)
+                await evidence_service.read_latest_execution_attempt(job_source_id=latest_job_source.id)
                 if latest_job_source is not None
                 else None
             )
-            attempts = list(await sources_service.list_execution_attempts(source_id=parsed_source_id))
+            attempts = list(await evidence_service.list_execution_attempts(source_id=parsed_source_id))
         except TranscriptionNotFoundError:
             render_record_not_found("Source")
             return
@@ -158,7 +160,7 @@ def register_page() -> None:  # noqa: PLR0915
                         "Export Evidence",
                         on_click=lambda: _download_evidence(
                             source_id=source.id,
-                            sources_service=sources_service,
+                            evidence_service=evidence_service,
                         ),
                         icon="download",
                     ).props("flat")
@@ -185,7 +187,7 @@ def register_page() -> None:  # noqa: PLR0915
                 _render_machine_candidates(
                     source=source,
                     attempts=attempts,
-                    sources_service=sources_service,
+                    evidence_service=evidence_service,
                 )
                 _render_source_metadata_column(
                     source=source,
@@ -409,9 +411,9 @@ def _transport_display(latest_attempt: LatestExecutionAttempt) -> dict[str, obje
     }
 
 
-async def _download_evidence(*, source_id: UUID, sources_service: SourceService) -> None:
+async def _download_evidence(*, source_id: UUID, evidence_service: EvidenceService) -> None:
     try:
-        payload = await sources_service.build_evidence_export(source_id=source_id)
+        payload = await evidence_service.build_evidence_export(source_id=source_id)
     except Exception as exc:  # noqa: BLE001
         show_error(exc, title="Export failed", operation="sources.evidence_export")
         return
@@ -521,7 +523,7 @@ def _render_machine_candidates(
     *,
     source: Source,
     attempts: list[ExecutionAttempt],
-    sources_service: SourceService,
+    evidence_service: EvidenceService,
 ) -> None:
     successful = [
         attempt
@@ -581,7 +583,7 @@ def _render_machine_candidates(
 
                     async def promote(candidate_id: UUID = attempt.id) -> None:
                         try:
-                            await sources_service.promote_machine_attempt(
+                            await evidence_service.promote_machine_attempt(
                                 source_id=source.id,
                                 execution_attempt_id=candidate_id,
                             )

tests/services/test_job_service.py

@@ -13,6 +13,7 @@ from transcription.db.models import JobSourceStatus
 from transcription.db.models import JobStatus
 from transcription.db.models import Source
 from transcription.services.documents import DocumentService
+from transcription.services.evidence import EvidenceService
 from transcription.services.jobs import JobCancelBlockedError
 from transcription.services.jobs import JobDeleteBlockedError
 from transcription.services.jobs import JobNotFoundError
@@ -274,6 +275,7 @@ class TestJobService:
         document_service: DocumentService,
     ):
         source_service = SourceService(session_factory=job_service.session_factory)
+        evidence_service = EvidenceService(session_factory=job_service.session_factory)
         document = await document_service.create_document(Document(name="evidence-delete-doc"))
         job = await job_service.create_job(Job(document_id=document.id, status=JobStatus.FAILED))
         source = await source_service.create_source(
@@ -299,7 +301,7 @@ class TestJobService:
 
         with pytest.raises(JobNotFoundError):
             await job_service.read_job(job_id=job.id)
-        assert await source_service.list_execution_attempts(job_id=job.id) == []
+        assert await evidence_service.list_execution_attempts(job_id=job.id) == []
         assert (await source_service.read_source(source.id)).id == source.id
 
     @pytest.mark.asyncio

tests/services/test_transcription_service.py

@@ -13,10 +13,10 @@ from transcription.db.models import JobSourceStatus
 from transcription.db.models import JobStatus
 from transcription.db.models import Source
 from transcription.services.documents import DocumentService
+from transcription.services.errors import SourceDeleteBlockedError
+from transcription.services.errors import TranscriptionNotFoundError
 from transcription.services.jobs import JobService
-from transcription.services.sources import SourceDeleteBlockedError
 from transcription.services.sources import SourceService
-from transcription.services.sources import TranscriptionNotFoundError
 
 
 @pytest.mark.integration

tests/services/test_v2_crud.py

@@ -13,10 +13,11 @@ from transcription.db.models import Source
 from transcription.errors import ErrorCategory
 from transcription.services.documents import DocumentDeleteBlockedError
 from transcription.services.documents import DocumentService
+from transcription.services.errors import SourceDeleteBlockedError
+from transcription.services.evidence import EvidenceService
 from transcription.services.jobs import JobService
 from transcription.services.people import PeopleError
 from transcription.services.people import PeopleService
-from transcription.services.sources import SourceDeleteBlockedError
 from transcription.services.sources import SourceService
 
 
@@ -324,7 +325,8 @@ async def test_update_job_source_transcription_persists_provider_json_payloads(d
     assert len(stored_rows) == 1
     assert stored_rows[0].status == JobSourceStatus.TRANSCRIBED
 
-    attempt = await transcriptions.read_latest_execution_attempt(job_source_id=stored_rows[0].id)
+    evidence = EvidenceService(session_factory=transcriptions.session_factory)
+    attempt = await evidence.read_latest_execution_attempt(job_source_id=stored_rows[0].id)
     assert attempt is not None
     assert attempt.attempt.raw_transcription == "provider transcript"
     assert attempt.attempt.normalized_metadata == metadata

tests/services/test_v45_candidates.py

@@ -11,19 +11,12 @@ from transcription.db.models import JobPurpose
 from transcription.db.models import JobSource
 from transcription.db.models import Source
 from transcription.services import ServiceBundle
-from transcription.services.documents import DocumentService
-from transcription.services.jobs import JobService
-from transcription.services.sources import CandidatePromotionError
-from transcription.services.sources import SourceService
+from transcription.services.errors import CandidatePromotionError
 from transcription.services.workflows import create_source_retranscription_job
 
 
 def _services(default_session_factory, settings: Settings) -> ServiceBundle:
-    return ServiceBundle(
-        documents=DocumentService(session_factory=default_session_factory, settings=settings),
-        jobs=JobService(session_factory=default_session_factory, settings=settings),
-        sources=SourceService(session_factory=default_session_factory, settings=settings),
-    )
+    return ServiceBundle.from_session_factory(default_session_factory, settings=settings)
 
 
 async def _seed_source(services: ServiceBundle) -> Source:
@@ -71,14 +64,14 @@ async def test_first_success_is_preferred_and_later_success_remains_candidate(de
         model="model-b",
     )
     unchanged = await services.sources.read_source(source.id)
-    attempts = await services.sources.list_execution_attempts(source_id=source.id)
+    attempts = await services.evidence.list_execution_attempts(source_id=source.id)
 
     assert unchanged.raw_transcription == "first result"
     assert unchanged.preferred_execution_attempt_id == first_attempt_id
     assert {attempt.raw_transcription for attempt in attempts} == {"first result", "candidate result"}
 
     candidate = next(attempt for attempt in attempts if attempt.raw_transcription == "candidate result")
-    promoted = await services.sources.promote_machine_attempt(
+    promoted = await services.evidence.promote_machine_attempt(
         source_id=source.id,
         execution_attempt_id=candidate.id,
     )
@@ -95,7 +88,7 @@ async def test_promotion_rejects_unrelated_attempt(default_session_factory):
     source = await _seed_source(services)
 
     with pytest.raises(CandidatePromotionError):
-        await services.sources.promote_machine_attempt(
+        await services.evidence.promote_machine_attempt(
             source_id=source.id,
             execution_attempt_id=uuid4(),
         )

tests/services/test_workflows_reliability.py

@@ -109,12 +109,7 @@ class TestWorkflowReliability:
         default_session_factory,
         monkeypatch,
     ):
-        services = ServiceBundle(
-            documents=ServiceBundle().documents.__class__(session_factory=default_session_factory),
-            jobs=ServiceBundle().jobs.__class__(session_factory=default_session_factory),
-            sources=ServiceBundle().sources.__class__(session_factory=default_session_factory),
-            people=ServiceBundle().people.__class__(session_factory=default_session_factory),
-        )
+        services = ServiceBundle.from_session_factory(default_session_factory)
         async with services.jobs._session_scope() as session:
             document = Document(id=uuid4(), name="durability-doc")
             session.add(document)
@@ -155,7 +150,7 @@ class TestWorkflowReliability:
         task = asyncio.create_task(process_queued_job(job=loaded, services=services))
         await asyncio.wait_for(second_started.wait(), timeout=2)
 
-        attempts = await services.sources.list_execution_attempts(job_id=job.id)
+        attempts = await services.evidence.list_execution_attempts(job_id=job.id)
         assert len(attempts) == 1
         assert attempts[0].raw_transcription == "page 1"
 

tests/test_prompts.py

@@ -7,8 +7,8 @@ import pytest
 from pydantic import ValidationError
 
 from transcription.config import Settings
+from transcription.services.errors import PromptLoadError
 from transcription.services.sources import PromptExecution
-from transcription.services.sources import PromptLoadError
 from transcription.services.sources import build_prompt_execution
 from transcription.services.sources import load_prompt_text
 

tests/test_service_boundaries.py

@@ -1,9 +1,10 @@
 """Structural rules for the services package.
 
-`.github/instructions/services.instructions.md:13` requires that service classes
-stay independent of one another. Shared behavior belongs in a neutral module
-(`base.py`, `registry.py`, `source_media.py`, `media_storage.py`), and any
-operation spanning two services belongs in an orchestration module.
+The "Structure" section of `.github/instructions/services.instructions.md` requires
+that service modules stay independent of one another. Shared behavior belongs in a
+neutral module that defines no service class (`base.py`, `errors.py`, `registry.py`,
+`source_media.py`, `media_storage.py`), and any operation that writes models owned by
+two services belongs in an orchestration module.
 """
 
 from __future__ import annotations
@@ -13,7 +14,7 @@ from pathlib import Path
 
 SERVICES_DIR = Path(__file__).resolve().parents[1] / "src" / "transcription" / "services"
 
-# Modules that intentionally compose several services rather than owning one table.
+# Modules that intentionally compose several services rather than owning one aggregate.
 ORCHESTRATION_MODULES = frozenset({"store", "workflows", "__init__"})
 
 

tests/test_v42_evidence.py

@@ -25,6 +25,7 @@ from transcription.providers.base import TranscriptionResult
 from transcription.providers.evidence import SourceEvidenceReference
 from transcription.providers.openrouter import OpenRouterTranscriptionProvider
 from transcription.services.documents import DocumentService
+from transcription.services.evidence import EvidenceService
 from transcription.services.jobs import JobDeleteBlockedError
 from transcription.services.jobs import JobService
 from transcription.services.sources import SourceService
@@ -203,6 +204,7 @@ async def test_attempts_are_append_only_and_exported_with_integrity(default_sess
     documents = DocumentService(session_factory=default_session_factory)
     jobs = JobService(session_factory=default_session_factory)
     sources = SourceService(session_factory=default_session_factory)
+    evidence = EvidenceService(session_factory=default_session_factory)
     document = await documents.create_document(Document(name="Evidence"))
     job = await jobs.create_job(Job(document_id=document.id))
     source = await sources.create_source(
@@ -239,14 +241,14 @@ async def test_attempts_are_append_only_and_exported_with_integrity(default_sess
         finished_at=now,
     )
 
-    attempts = await sources.list_execution_attempts(source_id=source.id)
+    attempts = await evidence.list_execution_attempts(source_id=source.id)
     assert [attempt.attempt_number for attempt in attempts] == [1, 2]
     assert attempts[0].status == JobSourceStatus.FAILED
     assert attempts[0].error_detail == "first failed"
     assert attempts[1].status == JobSourceStatus.TRANSCRIBED
     assert attempts[1].raw_transcription == "second succeeded"
 
-    export = await sources.build_evidence_export(source_id=source.id)
+    export = await evidence.build_evidence_export(source_id=source.id)
     assert _json_object(export["source"])["digest_sha256"] == "a" * 64
     assert [_json_object(item)["attempt_number"] for item in _json_array(export["attempts"])] == [1, 2]
     assert "file_path" not in json.dumps(export)
@@ -257,7 +259,7 @@ async def test_attempts_are_append_only_and_exported_with_integrity(default_sess
     latest_job_source = detail.latest_job_source
     assert latest_job_source is not None
     assert latest_job_source.execution_attempts == []
-    latest_attempt = await sources.read_latest_execution_attempt(job_source_id=latest_job_source.id)
+    latest_attempt = await evidence.read_latest_execution_attempt(job_source_id=latest_job_source.id)
     assert latest_attempt is not None
     assert latest_attempt.attempt.attempt_number == 2