---
phase: 04-folders-sharing-quotas-document-ux
plan: "05"
subsystem: backend-api
tags: [streaming-proxy, content-delivery, preferences, pdf, range-requests, doc-02, doc-01]
dependency_graph:
  requires:
    - 04-02  # pdf_open_mode migration 0004 adds users.pdf_open_mode column
    - 04-04  # Share model with recipient_id for access control
  provides:
    - "GET /api/documents/{id}/content — streaming proxy from MinIO"
    - "GET /api/auth/me/preferences — read pdf_open_mode"
    - "PATCH /api/auth/me/preferences — update pdf_open_mode"
  affects:
    - 04-09  # frontend uses content URL + preferences PATCH for PDF display
tech_stack:
  added: []
  patterns:
    - "StreamingResponse with iter([bytes]) for zero-copy streaming"
    - "_parse_range() module-level helper for RFC 7233 byte range parsing"
    - "Literal['in_app', 'new_tab'] Pydantic field for allowlist enforcement (T-04-05-05)"
    - "get_regular_user dep blocks admin access to content proxy (T-04-05-01)"
key_files:
  created: []
  modified:
    - path: backend/api/documents.py
      role: "Added _parse_range() + stream_document_content endpoint"
    - path: backend/api/auth.py
      role: "Added PreferencesUpdate model + GET/PATCH /me/preferences endpoints"
    - path: backend/db/models.py
      role: "Added pdf_open_mode column to User ORM model"
    - path: backend/tests/test_documents.py
      role: "Replaced xfail stubs with 8 real streaming proxy tests"
    - path: backend/tests/test_auth_api.py
      role: "Added 7 preferences endpoint tests"
decisions:
  - "Use get_regular_user (not get_current_user) for content proxy: admin role blocked at dep level (T-04-05-01)"
  - "Fetch bytes via get_object() directly — presigned_get_url() forbidden in proxy handler (T-04-05-02)"
  - "Access check inline in handler body (not helper function) for test mocking simplicity"
  - "HTTP_416_RANGE_NOT_SATISFIABLE used instead of deprecated HTTP_416_REQUESTED_RANGE_NOT_SATISFIABLE"
  - "pdf_open_mode added to User ORM model (migration 0004 already added the DB column)"
  - "GET /me/preferences uses AttributeError guard for env without migration run"
metrics:
  duration: "~15 minutes"
  completed: "2026-05-25"
  tasks_completed: 2
  tasks_total: 2
  files_modified: 5
---

# Phase 04 Plan 05: Document Streaming Proxy + PDF Preferences Summary

**One-liner:** MinIO streaming proxy for document content with Range header support (DOC-02) and pdf_open_mode user preference endpoint (DOC-01) backed by Literal validation.

## What Was Built

### Task 1: GET /api/documents/{id}/content (DOC-02)

Added a streaming proxy endpoint to `backend/api/documents.py`:

- **`_parse_range(range_header, file_size)`** module-level helper that parses RFC 7233 `bytes=X-Y` syntax, handles open-ended ranges (`bytes=X-` and `bytes=-Y`), and raises HTTP 416 on any invalid or out-of-bounds range
- **`stream_document_content`** endpoint at `GET /api/documents/{id}/content`:
  - Uses `get_regular_user` dep — admin role → 403 (T-04-05-01, CRITICAL)
  - Parses doc_id as UUID → 404 on ValueError
  - Loads Document via session.get → 404 if None
  - Access: `doc.user_id == current_user.id` OR `Share.recipient_id == current_user.id`; neither → 404 (T-04-05-04)
  - Fetches bytes via `get_storage_backend().get_object(doc.object_key)` — no presigned URL (T-04-05-02)
  - Returns `StreamingResponse` with `content-type`, `content-disposition: inline`, `accept-ranges: bytes`, `content-length`
  - Range header present → 206 with `content-range: bytes {start}-{end}/{total}` (T-04-05-03)
  - No Range → 200

Also added `pdf_open_mode` column to `User` ORM model (migration 0004 already added the DB column).

### Task 2: Preferences Endpoints (DOC-01)

Added to `backend/api/auth.py`:

- **`PreferencesUpdate`** Pydantic model with `pdf_open_mode: Literal["in_app", "new_tab"]`
- **`GET /api/auth/me/preferences`** — returns `{"pdf_open_mode": ...}` using `get_current_user` (both roles)
- **`PATCH /api/auth/me/preferences`** — validates via Literal, updates `current_user.pdf_open_mode`, commits, returns updated value

## Commits

| Hash | Message |
|------|---------|
| `8e6cb6e` | test(phase-4-05): add failing tests for document streaming proxy (DOC-02) — RED phase |
| `f868a4e` | feat(phase-4-05): document streaming proxy GET /api/documents/{id}/content (DOC-02) — GREEN phase |
| `2a0df32` | feat(phase-4-05): PATCH /api/auth/me/preferences for pdf_open_mode (DOC-01) |

## Test Results

**Before this plan:** 85 passed, 10 xfailed (document tests only had xfail stubs)
**After this plan:** 137 passed, 35 xfailed — all new tests green

| Test | Result |
|------|--------|
| test_content_stream_200 | PASSED |
| test_content_stream_206_range | PASSED |
| test_content_stream_admin_403 | PASSED |
| test_content_stream_no_presigned_url | PASSED |
| test_content_stream_share_recipient_200 | PASSED |
| test_content_stream_not_found | PASSED |
| test_content_stream_invalid_id | PASSED |
| test_parse_range_416 | PASSED |
| test_get_preferences_default | PASSED |
| test_patch_preferences_in_app | PASSED |
| test_patch_preferences_new_tab | PASSED |
| test_patch_preferences_invalid_value | PASSED |
| test_patch_preferences_persists | PASSED |
| test_preferences_requires_auth | PASSED |
| test_patch_preferences_requires_auth | PASSED |

Pre-existing failure: `test_extract_docx` (missing `python-docx` module in local env — not introduced by this plan).

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Deprecated HTTP_416 status constant**
- **Found during:** Task 1 implementation
- **Issue:** `HTTP_416_REQUESTED_RANGE_NOT_SATISFIABLE` is deprecated in the installed FastAPI version; `HTTP_416_RANGE_NOT_SATISFIABLE` is the current constant
- **Fix:** Used `HTTP_416_RANGE_NOT_SATISFIABLE` throughout
- **Files modified:** `backend/api/documents.py`
- **Commit:** f868a4e

**2. [Rule 2 - Missing functionality] pdf_open_mode absent from User ORM model**
- **Found during:** Task 2 — plan noted "migration 0004 adds column" but the ORM `User` class in `models.py` did not declare `pdf_open_mode`
- **Fix:** Added `pdf_open_mode: Mapped[str]` with `server_default="in_app"` to the User class
- **Files modified:** `backend/db/models.py`
- **Commit:** f868a4e

## Security Invariants Verified

| Threat ID | Status |
|-----------|--------|
| T-04-05-01: Admin blocked at content proxy | VERIFIED — `get_regular_user` dep; `test_content_stream_admin_403` passes |
| T-04-05-02: No presigned URL in proxy | VERIFIED — `presigned_mock.assert_not_called()` in `test_content_stream_no_presigned_url` |
| T-04-05-03: Range validation bounds | VERIFIED — `test_parse_range_416` confirms 416 on out-of-bounds |
| T-04-05-04: Non-recipient 404 | VERIFIED — unshared doc returns 404; share recipient gets 200 |
| T-04-05-05: pdf_open_mode Literal | VERIFIED — `test_patch_preferences_invalid_value` confirms 422 on invalid value |

## Known Stubs

None — all behavior is fully implemented and wired.

## Threat Flags

None — no new network endpoints, auth paths, or file access patterns beyond what was planned in the threat model.

## Self-Check: PASSED

- [x] `backend/api/documents.py` — stream_document_content endpoint exists
- [x] `backend/api/auth.py` — /me/preferences routes registered (GET + PATCH)
- [x] `backend/db/models.py` — pdf_open_mode column on User model
- [x] `backend/tests/test_documents.py` — 8 streaming proxy tests pass
- [x] `backend/tests/test_auth_api.py` — 7 preferences tests pass
- [x] Commits: 8e6cb6e (RED), f868a4e (GREEN Task 1), 2a0df32 (Task 2)
- [x] Full suite: 137 passed, 1 pre-existing failure (test_extract_docx — missing docx module)
