diff --git a/.github/instructions/services.instructions.md b/.github/instructions/services.instructions.md
index ba7c956..bd29d76 100644
--- a/.github/instructions/services.instructions.md
+++ b/.github/instructions/services.instructions.md
@@ -134,7 +134,7 @@ Separation of concerns:
 ## V4 Contract Alignment
 
 - Treat `docs/ver4/` as the active architecture and requirements baseline.
-- `Job.status` success path is `TRANSCRIBED`; `COMPLETED` is legacy-compatible and must not be used for new success transitions.
+- `Job.status` success path is `TRANSCRIBED`.
 - `JobSource.status` is queue/projection state only (`PENDING`, `TRANSCRIBED`, `FAILED`, `CANCELLED`).
 - Source ingest may normalize media before persistence; persisted bytes/hash are canonical for processing and provenance.
 
diff --git a/docs/ver4/architecture_v4.md b/docs/ver4/architecture_v4.md
index 063f434..cf611b1 100644
--- a/docs/ver4/architecture_v4.md
+++ b/docs/ver4/architecture_v4.md
@@ -103,9 +103,8 @@ Responsibilities:
 
 ## Status Semantics
 
-- **Job statuses:** `queued`, `processing`, `transcribed`, `completed`, `partial_success`, `failed`
-  - Operational success path currently resolves to `transcribed`.
-  - `completed` remains a recognized legacy-compatible status value.
+- **Job statuses:** `queued`, `processing`, `transcribed`, `partial_success`, `failed`
+  - Operational success path resolves to `transcribed`.
 - **JobSource statuses:** `pending`, `transcribed`, `failed`, `cancelled`
 
 ## Security and Path Handling Boundaries
@@ -123,6 +122,45 @@ Responsibilities:
 - Non-retriable worker-loop faults are surfaced and stop loop spin.
 - Per-page outcomes are durably persisted before processing next page.
 
+## Design Decisions and Rationale
+
+### Why `transcribed` is the success terminal state
+
+- The worker and job orchestration resolve successful completion to `JobStatus.TRANSCRIBED`, with mixed and failure outcomes represented by `partial_success` and `failed`.
+- This keeps terminal status vocabulary aligned with what the pipeline actually produces: transcribed page content and evidence, not a generic completion marker.
+
+### Why evidence history is append-only while page text is a projection
+
+- `ExecutionAttempt` stores immutable per-call evidence and preserves full attempt history across retries.
+- `Source.raw_transcription` is intentionally a mutable projection so UI and exports can show a selected current machine text without mutating historical evidence.
+- This split keeps auditability and UX both first-class: history is durable, presentation is editable.
+
+### Why orchestration modules own cross-service workflows
+
+- Service modules do not import each other; aggregate ownership remains local to each service.
+- Multi-aggregate writes are coordinated in orchestration modules (`store.py`, `workflows.py`) so transaction boundaries are explicit and testable.
+- This avoids circular dependencies and keeps cross-cutting workflow logic centralized.
+
+### Why explicit eager loading is required
+
+- ORM relationships are configured with `lazy="raise"` in key paths, so code must request needed relationships up front.
+- This prevents hidden query behavior in UI/service code and makes read shape deterministic and reviewable.
+
+### Why canonical source bytes may be ingest-normalized
+
+- Ingest normalization can correct orientation before persistence so provider calls, evidence hashes, and rendered processing source are consistent.
+- The canonical stored bytes, digest, and size become the durable processing identity for that source.
+
+### Why media access uses controlled routes/helpers
+
+- Print/export media uses record-validated API endpoints to avoid direct filesystem path exposure.
+- General UI media URLs are generated through shared resolver helpers to keep path handling consistent and centralized.
+
+## Historical Context Boundary
+
+Superseded V4.x scope/plan/review documents were intentionally removed from the active tree and archived at git tag `docs-v4x-archive`.  
+Current architecture rules live only in `docs/ver4/*`; historical files are reference material only.
+
 ## Related References
 
 - [System Requirements](requirements_v4.md)
diff --git a/docs/ver4/error_handling_v4.md b/docs/ver4/error_handling_v4.md
index 182978f..f4b9621 100644
--- a/docs/ver4/error_handling_v4.md
+++ b/docs/ver4/error_handling_v4.md
@@ -19,6 +19,25 @@ This policy defines active V4 error taxonomy, translation boundaries, and retry
 - **Service layer:** map raw exceptions into domain-aware categories and preserve causal chain.
 - **UI/API layer:** convert category to user-safe message with contextual action guidance.
 
+## Decision Context
+
+### Why taxonomy is category-based (not exception-class-based)
+
+- Categories encode operator-facing recovery semantics (fix input, retry later, investigate internal failure) independent of low-level exception type.
+- This keeps retry and messaging behavior consistent even when provider/client libraries change.
+
+### Why page-level failure is isolated
+
+- Multi-page archival documents often contain a mix of readable and degraded pages.
+- Isolating failures to page scope preserves successful results and avoids all-or-nothing loss when one page fails.
+- Aggregate job status then communicates overall outcome (`transcribed`, `partial_success`, `failed`) without hiding page detail.
+
+### Why retries append evidence instead of mutating rows
+
+- Retry operations are new observations, not corrections of history.
+- Appending attempts preserves forensic traceability, timing history, and provider variability analysis.
+- Projection updates remain explicit user/workflow decisions, separate from immutable evidence.
+
 ## Job and Page Failure Semantics
 
 ### Page-Level (`JobSource`)
@@ -45,6 +64,12 @@ This policy defines active V4 error taxonomy, translation boundaries, and retry
 2. Avoid leaking stack traces or local paths into user-facing message envelopes.
 3. Preserve causal exception chains for internal diagnostics.
 
+## Operator Recovery Guidance
+
+- **validation/conflict:** correct input or state and retry manually.
+- **external/timeout:** allow bounded retries and keep prior attempt evidence visible.
+- **internal:** stop automatic retries, surface a safe message, and inspect diagnostics with correlation context.
+
 ## UI Messaging Contract
 
 - User-visible errors must be actionable, bounded, and category-consistent.
diff --git a/docs/ver4/requirements_v4.md b/docs/ver4/requirements_v4.md
index c35e601..508fdde 100644
--- a/docs/ver4/requirements_v4.md
+++ b/docs/ver4/requirements_v4.md
@@ -16,7 +16,7 @@ These requirements define the active V4 contract and align to current implementa
 - **REQ-4-010 Job Creation:** The system must create `Job` records from uploaded sources and from retranscription of existing sources.
 - **REQ-4-011 Prompt Snapshotting:** Job creation must persist effective prompt and runtime settings as immutable per-job snapshots.
 - **REQ-4-012 Queue Membership:** Each `(job, source)` pair must be represented by one `JobSource` row.
-- **REQ-4-013 Job Status Lifecycle:** `Job.status` must use one of `queued`, `processing`, `transcribed`, `completed`, `partial_success`, `failed`.
+- **REQ-4-013 Job Status Lifecycle:** `Job.status` must use one of `queued`, `processing`, `transcribed`, `partial_success`, `failed`.
 - **REQ-4-014 JobSource Status Lifecycle:** `JobSource.status` must use one of `pending`, `transcribed`, `failed`, `cancelled`.
 - **REQ-4-015 Terminal Job Resolution:** Job terminal status must derive from page outcomes as `transcribed`, `partial_success`, or `failed`.
 - **REQ-4-016 Cancellation Semantics:** Job cancellation must set remaining `pending` page entries to `cancelled`.
@@ -50,6 +50,30 @@ These requirements define the active V4 contract and align to current implementa
 - **REQ-4-104 Evidence Durability:** Attempt evidence must survive process restart once the transaction commits.
 - **REQ-4-105 Test Guardrails:** Architecture boundary tests must remain in place for services and UI boundaries.
 
+## Requirement Interpretation Notes
+
+### Status and lifecycle semantics
+
+- `REQ-4-013` and `REQ-4-015` intentionally bind success to `transcribed`, not a generic `completed`, so docs, tests, and runtime transitions stay consistent.
+- `REQ-4-016` and `REQ-4-042` distinguish cancellation from failure at page level (`cancelled` vs `failed`) while still allowing targeted retranscription.
+
+### Evidence semantics
+
+- `REQ-4-020` through `REQ-4-024` separate authoritative history (`ExecutionAttempt`) from operational projection (`Source.raw_transcription`).
+- This supports immutable provenance while allowing explicit candidate promotion for operator workflows.
+
+### Boundary and loading semantics
+
+- `REQ-4-100` and `REQ-4-101` codify aggregate/service ownership and keep UI out of persistence concerns.
+- `REQ-4-102` exists to enforce deterministic query shape under `lazy="raise"` and avoid hidden data access in rendering callbacks.
+
+## Verification Anchors
+
+- Service boundary enforcement: `tests/test_service_boundaries.py`
+- UI boundary enforcement: `tests/test_ui_boundaries.py`
+- Job lifecycle reliability and terminal status behavior: `tests/services/test_workflows_reliability.py`
+- Evidence append-only and projection behavior: `tests/services/test_store.py`, `tests/services/test_transcription_service.py`
+
 ## Traceability Notes
 
 - Source of truth for status enums:
diff --git a/docs/ver4/schema_v4.md b/docs/ver4/schema_v4.md
index ee148e2..72f9c06 100644
--- a/docs/ver4/schema_v4.md
+++ b/docs/ver4/schema_v4.md
@@ -87,7 +87,6 @@ erDiagram
 - `queued`
 - `processing`
 - `transcribed`
-- `completed` (legacy-compatible)
 - `partial_success`
 - `failed`
 
@@ -112,6 +111,31 @@ erDiagram
 4. `Job` terminal status is derived from `JobSource` outcomes.
 5. Registry semantic keys, when present, are immutable once created.
 
+## Schema Design Rationale
+
+### Why `ExecutionAttempt` exists alongside `JobSource`
+
+- `JobSource` is the mutable queue/projection row for workflow control and current-facing page outcome state.
+- `ExecutionAttempt` is the durable, append-only evidence timeline for each provider call.
+- Keeping both avoids overloading one table with competing concerns (queue state vs immutable audit history).
+
+### Why `Source.raw_transcription` remains on `Source`
+
+- `Source` needs a stable, current projection for UI and print behavior.
+- Projection reads are fast and direct, while deep historical inspection remains available through attempts.
+- Explicit candidate promotion updates the projection pointer without rewriting history.
+
+### Why semantic registries use UUID identity plus optional semantic keys
+
+- UUIDs are durable relationship identifiers for public/domain links.
+- Optional immutable semantic keys support protected built-ins without exposing internal meaning as external API identity.
+- Labels can evolve without breaking relationships.
+
+### Why status enums are narrow
+
+- Restricting `JobStatus` and `JobSourceStatus` keeps lifecycle transitions explicit and testable.
+- Queue/state transitions and terminal derivation logic remain deterministic across worker and UI flows.
+
 ## Media Storage Semantics
 
 1. `Source.storage_path` references canonical stored bytes used by processing.
@@ -123,6 +147,12 @@ erDiagram
 - Relationship access from service/UI layers must use explicit eager loading patterns compatible with `lazy="raise"`.
 - Candidate-attempt views should select latest/selected attempts explicitly; do not rely on implicit lazy traversal.
 
+## Evolution and Migration Policy
+
+- Additive schema evolution is preferred for evidence-bearing records.
+- Deprecated semantics should be removed only when model enums, service logic, tests, and docs are updated together.
+- Historical V4.x schema discussions are archived under tag `docs-v4x-archive`; this file is the active contract.
+
 ## Cross-Reference
 
 - [System Architecture](architecture_v4.md)
diff --git a/src/transcription/db/models.py b/src/transcription/db/models.py
index 77dab18..744873e 100644
--- a/src/transcription/db/models.py
+++ b/src/transcription/db/models.py
@@ -61,7 +61,6 @@ class JobStatus(StrEnum):
     QUEUED = "queued"
     PROCESSING = "processing"
     TRANSCRIBED = "transcribed"
-    COMPLETED = "completed"
     PARTIAL_SUCCESS = "partial_success"
     FAILED = "failed"
 
diff --git a/src/transcription/services/jobs.py b/src/transcription/services/jobs.py
index 425d94b..cfc8433 100644
--- a/src/transcription/services/jobs.py
+++ b/src/transcription/services/jobs.py
@@ -324,9 +324,9 @@ class JobService(ServiceBase):
             if job is None:
                 raise self._not_found(job_id)
 
-            if job.status in {JobStatus.TRANSCRIBED, JobStatus.COMPLETED}:
+            if job.status == JobStatus.TRANSCRIBED:
                 raise JobCancelBlockedError(
-                    "Job cancel is not allowed for transcribed/completed jobs",
+                    "Job cancel is not allowed for transcribed jobs",
                     category=ErrorCategory.VALIDATION,
                     suggestion="Use resubmit for reprocessing needs, or leave the terminal job unchanged.",
                 )
diff --git a/src/transcription/ui/static/theme.css b/src/transcription/ui/static/theme.css
index 72e3e79..99f0b8b 100644
--- a/src/transcription/ui/static/theme.css
+++ b/src/transcription/ui/static/theme.css
@@ -298,7 +298,6 @@ input:focus-visible,
   background: var(--theme-surface-muted);
 }
 
-.ui-status--completed,
 .ui-status--partial_success,
 .ui-status--transcribed {
   color: var(--theme-text);
diff --git a/tests/services/test_v44_workflows.py b/tests/services/test_v44_workflows.py
index 67381e2..af71bc9 100644
--- a/tests/services/test_v44_workflows.py
+++ b/tests/services/test_v44_workflows.py
@@ -152,7 +152,7 @@ async def test_document_print_projection_uses_semantic_author_and_current_text(d
     await jobs.create_job(
         Job(
             document_id=document.id,
-            status=JobStatus.COMPLETED,
+            status=JobStatus.TRANSCRIBED,
             provider="openrouter",
             model="model-a",
             prompt_name="transcribe_document.md",
@@ -167,4 +167,4 @@ async def test_document_print_projection_uses_semantic_author_and_current_text(d
     assert [source.page_number for source in projection.sources] == [1, 2]
     assert [source.current_text for source in projection.sources] == ["raw first", "revised second"]
     assert [source.media_type for source in projection.sources] == ["image/png", "image/png"]
-    assert projection.jobs[0].status == "completed"
+    assert projection.jobs[0].status == "transcribed"
diff --git a/tests/services/test_workflows_reliability.py b/tests/services/test_workflows_reliability.py
index abac4cc..852238a 100644
--- a/tests/services/test_workflows_reliability.py
+++ b/tests/services/test_workflows_reliability.py
@@ -95,12 +95,15 @@ class TestWorkflowReliability:
 
         async with services.jobs._session_scope() as session:
             attempts = (
-                await session.execute(
-                    select(ExecutionAttempt).where(
-                        col(ExecutionAttempt.job_source_id).in_([js.id for js in result.job_sources])
+                (
+                    await session.exec(
+                        select(ExecutionAttempt).where(
+                            col(ExecutionAttempt.job_source_id).in_([js.id for js in result.job_sources])
+                        )
                     )
                 )
-            ).scalars().all()
+                .all()
+            )
         error_detail = next(attempt.error_detail for attempt in attempts if attempt.error_detail is not None)
         assert "timed out" in error_detail.lower()
         assert "20.0s" in error_detail
diff --git a/tests/test_models.py b/tests/test_models.py
index 544f355..3308432 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -141,7 +141,7 @@ class TestJobModel:
         assert job.date_created is not None
         assert job.date_updated is not None
 
-    def test_transitions_to_completed(self, session):
+    def test_transitions_to_transcribed(self, session):
         document = _persist_document(session)
         job = _persist_job(session, document)
 
@@ -150,12 +150,12 @@ class TestJobModel:
         session.commit()
         session.refresh(job)
 
-        job.status = JobStatus.COMPLETED
+        job.status = JobStatus.TRANSCRIBED
         session.add(job)
         session.commit()
         session.refresh(job)
 
-        assert job.status == JobStatus.COMPLETED
+        assert job.status == JobStatus.TRANSCRIBED
 
 
 class TestSourceModel:
diff --git a/tests/ui/test_jobs_page.py b/tests/ui/test_jobs_page.py
index 77f2c92..91fa01d 100644
--- a/tests/ui/test_jobs_page.py
+++ b/tests/ui/test_jobs_page.py
@@ -148,7 +148,7 @@ class TestJobsPageRendering:
         assert "Delete is blocked while the job is processing." in response.text
 
     @pytest.mark.asyncio
-    async def test_job_delete_page_allows_deletion_for_queued_or_completed_job(
+    async def test_job_delete_page_allows_deletion_for_queued_job(
         self, app_client, seed_document_with_unlinked_job
     ):
         _, client = app_client