diff --git a/REPORT.md b/REPORT.md
new file mode 100644
index 0000000..89439ed
--- /dev/null
+++ b/REPORT.md
@@ -0,0 +1,138 @@
+# Security Audit Report
+
+Date: 2026-02-21
+Repository: /Users/bedas/Developer/GitHub/dcm
+Audit type: Static, read-only code and configuration review
+
+## Scope
+- Backend API, worker, extraction and routing pipeline, settings handling, and storage interactions.
+- Frontend dependency posture.
+- Docker runtime and service exposure.
+
+## Method
+- File-level inspection with targeted code tracing for authn/authz, input validation, upload and archive processing, outbound network behavior, secret handling, logging, and deployment hardening.
+- No runtime penetration testing was performed.
+
+## Findings
+
+### 1) Critical - Missing authentication and authorization on privileged API routes
+- Impact: Any reachable client can access document, settings, and log-management functionality.
+- Evidence:
+  - `backend/app/main.py:29`
+  - `backend/app/api/router.py:14`
+  - `backend/app/api/routes_documents.py:464`
+  - `backend/app/api/routes_documents.py:666`
+  - `backend/app/api/routes_settings.py:148`
+  - `backend/app/api/routes_processing_logs.py:22`
+- Recommendation:
+  - Enforce authentication globally for non-health routes.
+  - Add per-endpoint authorization checks for read/update/delete/admin actions.
+
+### 2) Critical - SSRF and data exfiltration risk via configurable model provider base URL
+- Impact: An attacker can redirect model calls to attacker-controlled or internal hosts and exfiltrate document-derived content.
+- Evidence:
+  - `backend/app/api/routes_settings.py:148`
+  - `backend/app/schemas/settings.py:24`
+  - `backend/app/services/app_settings.py:249`
+  - `backend/app/services/model_runtime.py:144`
+  - `backend/app/services/model_runtime.py:170`
+  - `backend/app/worker/tasks.py:505`
+  - `backend/app/services/routing_pipeline.py:803`
+- Recommendation:
+  - Restrict provider endpoints to an allowlist.
+  - Validate URL scheme and block private/link-local destinations.
+  - Protect settings updates behind strict admin authorization.
+  - Enforce outbound egress controls at runtime.
+
+### 3) High - Unbounded upload and archive extraction can cause memory/disk denial of service
+- Impact: Oversized files or compressed archive bombs can exhaust API/worker resources.
+- Evidence:
+  - `backend/app/api/routes_documents.py:486`
+  - `backend/app/services/extractor.py:309`
+  - `backend/app/services/extractor.py:312`
+  - `backend/app/worker/tasks.py:122`
+  - `backend/app/core/config.py:20`
+- Recommendation:
+  - Enforce request and file size limits.
+  - Stream uploads and extraction where possible.
+  - Cap total uncompressed archive size and per-entry size.
+
+### 4) High - Sensitive data logging exposed through unsecured log endpoints
+- Impact: Extracted text, prompts, and model outputs may be retrievable by unauthorized callers.
+- Evidence:
+  - `backend/app/models/processing_log.py:31`
+  - `backend/app/models/processing_log.py:32`
+  - `backend/app/services/routing_pipeline.py:803`
+  - `backend/app/services/routing_pipeline.py:814`
+  - `backend/app/worker/tasks.py:479`
+  - `backend/app/schemas/processing_logs.py:21`
+  - `backend/app/api/routes_processing_logs.py:22`
+- Recommendation:
+  - Require admin authorization for log endpoints.
+  - Remove or redact sensitive payloads from logs.
+  - Reduce retention for operational logs that may include sensitive context.
+
+### 5) High - Internal services exposed with weak default posture in docker compose
+- Impact: Exposed Redis/Postgres/Typesense can enable data compromise and queue abuse.
+- Evidence:
+  - `docker-compose.yml:5`
+  - `docker-compose.yml:6`
+  - `docker-compose.yml:9`
+  - `docker-compose.yml:21`
+  - `docker-compose.yml:29`
+  - `docker-compose.yml:32`
+  - `docker-compose.yml:68`
+  - `backend/app/worker/queue.py:15`
+  - `backend/app/core/config.py:34`
+- Recommendation:
+  - Remove unnecessary host port exposure for internal services.
+  - Use strong credentials and network ACL segmentation.
+  - Enable authentication and transport protections for stateful services.
+
+### 6) Medium - Plaintext secrets and weak defaults in configuration paths
+- Impact: Credentials and API keys can be exposed from source or storage.
+- Evidence:
+  - `backend/app/services/app_settings.py:129`
+  - `backend/app/services/app_settings.py:257`
+  - `backend/app/services/app_settings.py:667`
+  - `backend/app/core/config.py:17`
+  - `backend/app/core/config.py:34`
+  - `backend/.env.example:15`
+- Recommendation:
+  - Use managed secrets storage and encryption at rest.
+  - Remove default credentials.
+  - Rotate exposed and default keys/credentials.
+
+### 7) Low - Minimal HTTP hardening headers and broad CORS shape
+- Impact: Increased browser-side attack surface, especially once authentication is introduced.
+- Evidence:
+  - `backend/app/main.py:23`
+  - `backend/app/main.py:25`
+  - `backend/app/main.py:26`
+  - `backend/app/main.py:27`
+- Recommendation:
+  - Add standard security headers middleware.
+  - Constrain allowed methods and headers to actual application needs.
+
+### 8) Low - Containers appear to run as root by default
+- Impact: In-container compromise has higher blast radius.
+- Evidence:
+  - `backend/Dockerfile:1`
+  - `backend/Dockerfile:17`
+  - `frontend/Dockerfile:1`
+  - `frontend/Dockerfile:16`
+- Recommendation:
+  - Run containers as non-root users.
+  - Drop unnecessary Linux capabilities.
+
+## Residual Risk and Assumptions
+- This audit assumes services may be reachable beyond a strictly isolated localhost-only environment.
+- If an external auth proxy is enforced upstream, risk severity of unauthenticated routes is reduced but not eliminated unless backend also enforces trust boundaries.
+- Dependency CVE posture was not exhaustively enumerated in this static pass.
+
+## Priority Remediation Order
+1. Enforce authentication and authorization across API routes.
+2. Lock down settings mutation paths, especially model provider endpoint configuration.
+3. Add strict upload/extraction resource limits.
+4. Remove sensitive logging and protect log APIs.
+5. Harden Docker/network exposure and secrets management.
diff --git a/backend/.env.example b/backend/.env.example
index c2ba58d..d67fc6a 100644
--- a/backend/.env.example
+++ b/backend/.env.example
@@ -2,6 +2,17 @@ APP_ENV=development
 DATABASE_URL=postgresql+psycopg://dcm:dcm@db:5432/dcm
 REDIS_URL=redis://redis:6379/0
 STORAGE_ROOT=/data/storage
+ADMIN_API_TOKEN=replace-with-random-admin-token
+USER_API_TOKEN=replace-with-random-user-token
+MAX_UPLOAD_FILES_PER_REQUEST=50
+MAX_UPLOAD_FILE_SIZE_BYTES=26214400
+MAX_UPLOAD_REQUEST_SIZE_BYTES=104857600
+MAX_ZIP_MEMBER_UNCOMPRESSED_BYTES=26214400
+MAX_ZIP_TOTAL_UNCOMPRESSED_BYTES=157286400
+MAX_ZIP_COMPRESSION_RATIO=120
+PROVIDER_BASE_URL_ALLOWLIST=["api.openai.com"]
+PROVIDER_BASE_URL_ALLOW_HTTP=false
+PROVIDER_BASE_URL_ALLOW_PRIVATE_NETWORK=false
 DEFAULT_OPENAI_BASE_URL=https://api.openai.com/v1
 DEFAULT_OPENAI_MODEL=gpt-4.1-mini
 DEFAULT_OPENAI_TIMEOUT_SECONDS=45
diff --git a/backend/Dockerfile b/backend/Dockerfile
index 955d1a6..4464217 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -12,6 +12,11 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY requirements.txt /app/requirements.txt
 RUN pip install --no-cache-dir -r /app/requirements.txt
 
-COPY app /app/app
+RUN addgroup --system appgroup && adduser --system --ingroup appgroup --uid 10001 appuser
+RUN mkdir -p /data/storage && chown -R appuser:appgroup /app /data
+
+COPY --chown=appuser:appgroup app /app/app
+
+USER appuser
 
 CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]
diff --git a/backend/app/api/auth.py b/backend/app/api/auth.py
new file mode 100644
index 0000000..a06ef06
--- /dev/null
+++ b/backend/app/api/auth.py
@@ -0,0 +1,87 @@
+"""Token-based authentication and authorization dependencies for privileged API routes."""
+
+import hmac
+from typing import Annotated
+
+from fastapi import Depends, HTTPException, status
+from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
+
+from app.core.config import Settings, get_settings
+
+
+bearer_auth = HTTPBearer(auto_error=False)
+
+
+class AuthRole:
+    """Declares supported authorization roles for privileged API operations."""
+
+    ADMIN = "admin"
+    USER = "user"
+
+
+def _raise_unauthorized() -> None:
+    """Raises an HTTP 401 response with bearer authentication challenge headers."""
+
+    raise HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Invalid or missing API token",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+
+
+def _configured_admin_token(settings: Settings) -> str:
+    """Returns required admin token or raises configuration error when unset."""
+
+    token = settings.admin_api_token.strip()
+    if token:
+        return token
+    raise HTTPException(
+        status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+        detail="Admin API token is not configured",
+    )
+
+
+def _resolve_token_role(token: str, settings: Settings) -> str:
+    """Resolves role from a bearer token using constant-time comparisons."""
+
+    admin_token = _configured_admin_token(settings)
+    if hmac.compare_digest(token, admin_token):
+        return AuthRole.ADMIN
+
+    user_token = settings.user_api_token.strip()
+    if user_token and hmac.compare_digest(token, user_token):
+        return AuthRole.USER
+
+    _raise_unauthorized()
+
+
+def get_request_role(
+    credentials: Annotated[HTTPAuthorizationCredentials | None, Depends(bearer_auth)],
+    settings: Annotated[Settings, Depends(get_settings)],
+) -> str:
+    """Authenticates request token and returns its authorization role."""
+
+    if credentials is None:
+        _raise_unauthorized()
+
+    token = credentials.credentials.strip()
+    if not token:
+        _raise_unauthorized()
+    return _resolve_token_role(token=token, settings=settings)
+
+
+def require_user_or_admin(role: Annotated[str, Depends(get_request_role)]) -> str:
+    """Requires a valid user or admin token and returns resolved role."""
+
+    return role
+
+
+def require_admin(role: Annotated[str, Depends(get_request_role)]) -> str:
+    """Requires admin role and rejects requests authenticated as regular users."""
+
+    if role != AuthRole.ADMIN:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Admin token required",
+        )
+    return role
diff --git a/backend/app/api/router.py b/backend/app/api/router.py
index 8c02398..845e27d 100644
--- a/backend/app/api/router.py
+++ b/backend/app/api/router.py
@@ -1,7 +1,8 @@
 """API router registration for all HTTP route modules."""
 
-from fastapi import APIRouter
+from fastapi import APIRouter, Depends
 
+from app.api.auth import require_admin, require_user_or_admin
 from app.api.routes_documents import router as documents_router
 from app.api.routes_health import router as health_router
 from app.api.routes_processing_logs import router as processing_logs_router
@@ -11,7 +12,27 @@ from app.api.routes_settings import router as settings_router
 
 api_router = APIRouter()
 api_router.include_router(health_router)
-api_router.include_router(documents_router, prefix="/documents", tags=["documents"])
-api_router.include_router(processing_logs_router, prefix="/processing/logs", tags=["processing-logs"])
-api_router.include_router(search_router, prefix="/search", tags=["search"])
-api_router.include_router(settings_router, prefix="/settings", tags=["settings"])
+api_router.include_router(
+    documents_router,
+    prefix="/documents",
+    tags=["documents"],
+    dependencies=[Depends(require_user_or_admin)],
+)
+api_router.include_router(
+    processing_logs_router,
+    prefix="/processing/logs",
+    tags=["processing-logs"],
+    dependencies=[Depends(require_admin)],
+)
+api_router.include_router(
+    search_router,
+    prefix="/search",
+    tags=["search"],
+    dependencies=[Depends(require_user_or_admin)],
+)
+api_router.include_router(
+    settings_router,
+    prefix="/settings",
+    tags=["settings"],
+    dependencies=[Depends(require_admin)],
+)
diff --git a/backend/app/api/routes_documents.py b/backend/app/api/routes_documents.py
index b8d8a7d..0b52d17 100644
--- a/backend/app/api/routes_documents.py
+++ b/backend/app/api/routes_documents.py
@@ -1,4 +1,4 @@
-"""Document CRUD, lifecycle, metadata, file access, and content export endpoints."""
+"""Authenticated document CRUD, lifecycle, metadata, file access, and content export endpoints."""
 
 import io
 import re
@@ -14,7 +14,7 @@ from fastapi.responses import FileResponse, Response, StreamingResponse
 from sqlalchemy import or_, func, select
 from sqlalchemy.orm import Session
 
-from app.services.app_settings import read_predefined_paths_settings, read_predefined_tags_settings
+from app.core.config import get_settings
 from app.db.base import get_session
 from app.models.document import Document, DocumentStatus
 from app.schemas.documents import (
@@ -26,6 +26,7 @@ from app.schemas.documents import (
     UploadConflict,
     UploadResponse,
 )
+from app.services.app_settings import read_predefined_paths_settings, read_predefined_tags_settings
 from app.services.extractor import sniff_mime
 from app.services.handwriting_style import delete_many_handwriting_style_documents
 from app.services.processing_logs import log_processing_event, set_processing_log_autocommit
@@ -35,6 +36,7 @@ from app.worker.queue import get_processing_queue
 
 
 router = APIRouter()
+settings = get_settings()
 
 
 def _parse_csv(value: str | None) -> list[str]:
@@ -227,6 +229,33 @@ def _build_document_list_statement(
     return statement
 
 
+def _enforce_upload_shape(files: list[UploadFile]) -> None:
+    """Validates upload request shape against configured file-count bounds."""
+
+    if not files:
+        raise HTTPException(status_code=400, detail="Upload request must include at least one file")
+    if len(files) > settings.max_upload_files_per_request:
+        raise HTTPException(
+            status_code=413,
+            detail=(
+                "Upload request exceeds file count limit "
+                f"({len(files)} > {settings.max_upload_files_per_request})"
+            ),
+        )
+
+
+async def _read_upload_bytes(file: UploadFile, max_bytes: int) -> bytes:
+    """Reads one upload file while enforcing per-file byte limits."""
+
+    data = await file.read(max_bytes + 1)
+    if len(data) > max_bytes:
+        raise HTTPException(
+            status_code=413,
+            detail=f"File '{file.filename or 'upload'}' exceeds per-file limit of {max_bytes} bytes",
+        )
+    return data
+
+
 def _collect_document_tree(session: Session, root_document_id: UUID) -> list[tuple[int, Document]]:
     """Collects a document and all descendants for recursive permanent deletion."""
 
@@ -472,18 +501,29 @@ async def upload_documents(
 ) -> UploadResponse:
     """Uploads files, records metadata, and enqueues asynchronous extraction tasks."""
 
+    _enforce_upload_shape(files)
     set_processing_log_autocommit(session, True)
     normalized_tags = _normalize_tags(tags)
     queue = get_processing_queue()
     uploaded: list[DocumentResponse] = []
     conflicts: list[UploadConflict] = []
+    total_request_bytes = 0
 
     indexed_relative_paths = relative_paths or []
     prepared_uploads: list[dict[str, object]] = []
 
     for idx, file in enumerate(files):
         filename = file.filename or f"uploaded_{idx}"
-        data = await file.read()
+        data = await _read_upload_bytes(file, settings.max_upload_file_size_bytes)
+        total_request_bytes += len(data)
+        if total_request_bytes > settings.max_upload_request_size_bytes:
+            raise HTTPException(
+                status_code=413,
+                detail=(
+                    "Upload request exceeds total size limit "
+                    f"({total_request_bytes} > {settings.max_upload_request_size_bytes} bytes)"
+                ),
+            )
         sha256 = compute_sha256(data)
         source_relative_path = indexed_relative_paths[idx] if idx < len(indexed_relative_paths) else filename
         extension = Path(filename).suffix.lower()
diff --git a/backend/app/api/routes_processing_logs.py b/backend/app/api/routes_processing_logs.py
index fcbd051..dd19906 100644
--- a/backend/app/api/routes_processing_logs.py
+++ b/backend/app/api/routes_processing_logs.py
@@ -1,10 +1,11 @@
-"""Read-only API endpoints for processing pipeline event logs."""
+"""Admin-only API endpoints for processing pipeline event logs."""
 
 from uuid import UUID
 
 from fastapi import APIRouter, Depends, Query
 from sqlalchemy.orm import Session
 
+from app.core.config import get_settings
 from app.db.base import get_session
 from app.schemas.processing_logs import ProcessingLogEntryResponse, ProcessingLogListResponse
 from app.services.app_settings import read_processing_log_retention_settings
@@ -17,12 +18,13 @@ from app.services.processing_logs import (
 
 
 router = APIRouter()
+settings = get_settings()
 
 
 @router.get("", response_model=ProcessingLogListResponse)
 def get_processing_logs(
     offset: int = Query(default=0, ge=0),
-    limit: int = Query(default=120, ge=1, le=400),
+    limit: int = Query(default=120, ge=1, le=settings.processing_log_max_unbound_entries),
     document_id: UUID | None = Query(default=None),
     session: Session = Depends(get_session),
 ) -> ProcessingLogListResponse:
@@ -43,8 +45,8 @@ def get_processing_logs(
 
 @router.post("/trim")
 def trim_processing_logs(
-    keep_document_sessions: int | None = Query(default=None, ge=0, le=20),
-    keep_unbound_entries: int | None = Query(default=None, ge=0, le=400),
+    keep_document_sessions: int | None = Query(default=None, ge=0, le=settings.processing_log_max_document_sessions),
+    keep_unbound_entries: int | None = Query(default=None, ge=0, le=settings.processing_log_max_unbound_entries),
     session: Session = Depends(get_session),
 ) -> dict[str, int]:
     """Deletes old processing logs using query values or persisted retention defaults."""
@@ -61,10 +63,19 @@ def trim_processing_logs(
         else int(retention_defaults.get("keep_unbound_entries", 80))
     )
 
+    capped_keep_document_sessions = min(
+        settings.processing_log_max_document_sessions,
+        max(0, int(resolved_keep_document_sessions)),
+    )
+    capped_keep_unbound_entries = min(
+        settings.processing_log_max_unbound_entries,
+        max(0, int(resolved_keep_unbound_entries)),
+    )
+
     result = cleanup_processing_logs(
         session=session,
-        keep_document_sessions=resolved_keep_document_sessions,
-        keep_unbound_entries=resolved_keep_unbound_entries,
+        keep_document_sessions=capped_keep_document_sessions,
+        keep_unbound_entries=capped_keep_unbound_entries,
     )
     session.commit()
     return result
diff --git a/backend/app/api/routes_settings.py b/backend/app/api/routes_settings.py
index 865eb71..8ecf493 100644
--- a/backend/app/api/routes_settings.py
+++ b/backend/app/api/routes_settings.py
@@ -1,6 +1,6 @@
-"""API routes for managing persistent single-user application settings."""
+"""Admin-only API routes for managing persistent single-user application settings."""
 
-from fastapi import APIRouter
+from fastapi import APIRouter, HTTPException
 
 from app.schemas.settings import (
     AppSettingsUpdateRequest,
@@ -18,6 +18,7 @@ from app.schemas.settings import (
     UploadDefaultsResponse,
 )
 from app.services.app_settings import (
+    AppSettingsValidationError,
     TASK_OCR_HANDWRITING,
     TASK_ROUTING_CLASSIFICATION,
     TASK_SUMMARY_GENERATION,
@@ -179,16 +180,19 @@ def set_app_settings(payload: AppSettingsUpdateRequest) -> AppSettingsResponse:
     if payload.predefined_tags is not None:
         predefined_tags_payload = [item.model_dump(exclude_none=True) for item in payload.predefined_tags]
 
-    updated = update_app_settings(
-        providers=providers_payload,
-        tasks=tasks_payload,
-        upload_defaults=upload_defaults_payload,
-        display=display_payload,
-        processing_log_retention=processing_log_retention_payload,
-        handwriting_style=handwriting_style_payload,
-        predefined_paths=predefined_paths_payload,
-        predefined_tags=predefined_tags_payload,
-    )
+    try:
+        updated = update_app_settings(
+            providers=providers_payload,
+            tasks=tasks_payload,
+            upload_defaults=upload_defaults_payload,
+            display=display_payload,
+            processing_log_retention=processing_log_retention_payload,
+            handwriting_style=handwriting_style_payload,
+            predefined_paths=predefined_paths_payload,
+            predefined_tags=predefined_tags_payload,
+        )
+    except AppSettingsValidationError as error:
+        raise HTTPException(status_code=400, detail=str(error)) from error
     return _build_response(updated)
 
 
@@ -203,14 +207,17 @@ def reset_settings_to_defaults() -> AppSettingsResponse:
 def set_handwriting_settings(payload: HandwritingSettingsUpdateRequest) -> AppSettingsResponse:
     """Updates handwriting transcription settings and returns the resulting configuration."""
 
-    updated = update_handwriting_settings(
-        enabled=payload.enabled,
-        openai_base_url=payload.openai_base_url,
-        openai_model=payload.openai_model,
-        openai_timeout_seconds=payload.openai_timeout_seconds,
-        openai_api_key=payload.openai_api_key,
-        clear_openai_api_key=payload.clear_openai_api_key,
-    )
+    try:
+        updated = update_handwriting_settings(
+            enabled=payload.enabled,
+            openai_base_url=payload.openai_base_url,
+            openai_model=payload.openai_model,
+            openai_timeout_seconds=payload.openai_timeout_seconds,
+            openai_api_key=payload.openai_api_key,
+            clear_openai_api_key=payload.clear_openai_api_key,
+        )
+    except AppSettingsValidationError as error:
+        raise HTTPException(status_code=400, detail=str(error)) from error
     return _build_response(updated)
 
 
diff --git a/backend/app/core/config.py b/backend/app/core/config.py
index 38d7158..0362c4d 100644
--- a/backend/app/core/config.py
+++ b/backend/app/core/config.py
@@ -1,7 +1,10 @@
 """Application settings and environment configuration."""
 
 from functools import lru_cache
+import ipaddress
 from pathlib import Path
+import socket
+from urllib.parse import urlparse, urlunparse
 
 from pydantic import Field
 from pydantic_settings import BaseSettings, SettingsConfigDict
@@ -18,9 +21,24 @@ class Settings(BaseSettings):
     redis_url: str = "redis://redis:6379/0"
     storage_root: Path = Path("/data/storage")
     upload_chunk_size: int = 4 * 1024 * 1024
+    max_upload_files_per_request: int = 50
+    max_upload_file_size_bytes: int = 25 * 1024 * 1024
+    max_upload_request_size_bytes: int = 100 * 1024 * 1024
     max_zip_members: int = 250
     max_zip_depth: int = 2
+    max_zip_member_uncompressed_bytes: int = 25 * 1024 * 1024
+    max_zip_total_uncompressed_bytes: int = 150 * 1024 * 1024
+    max_zip_compression_ratio: float = 120.0
     max_text_length: int = 500_000
+    admin_api_token: str = ""
+    user_api_token: str = ""
+    provider_base_url_allowlist: list[str] = Field(default_factory=lambda: ["api.openai.com"])
+    provider_base_url_allow_http: bool = False
+    provider_base_url_allow_private_network: bool = False
+    processing_log_max_document_sessions: int = 20
+    processing_log_max_unbound_entries: int = 400
+    processing_log_max_payload_chars: int = 4096
+    processing_log_max_text_chars: int = 12000
     default_openai_base_url: str = "https://api.openai.com/v1"
     default_openai_model: str = "gpt-4.1-mini"
     default_openai_timeout_seconds: int = 45
@@ -39,6 +57,187 @@ class Settings(BaseSettings):
     cors_origins: list[str] = Field(default_factory=lambda: ["http://localhost:5173", "http://localhost:3000"])
 
 
+LOCAL_HOSTNAME_SUFFIXES = (".local", ".internal", ".home.arpa")
+
+
+def _normalize_allowlist(allowlist: object) -> tuple[str, ...]:
+    """Normalizes host allowlist entries to lowercase DNS labels."""
+
+    if not isinstance(allowlist, (list, tuple, set)):
+        return ()
+    normalized = {
+        candidate.strip().lower().rstrip(".")
+        for candidate in allowlist
+        if isinstance(candidate, str) and candidate.strip()
+    }
+    return tuple(sorted(normalized))
+
+
+def _host_matches_allowlist(hostname: str, allowlist: tuple[str, ...]) -> bool:
+    """Returns whether a hostname is included by an exact or subdomain allowlist rule."""
+
+    if not allowlist:
+        return False
+    candidate = hostname.lower().rstrip(".")
+    for allowed_host in allowlist:
+        if candidate == allowed_host or candidate.endswith(f".{allowed_host}"):
+            return True
+    return False
+
+
+def _is_private_or_special_ip(value: ipaddress.IPv4Address | ipaddress.IPv6Address) -> bool:
+    """Returns whether an IP belongs to private, loopback, link-local, or reserved ranges."""
+
+    return (
+        value.is_private
+        or value.is_loopback
+        or value.is_link_local
+        or value.is_multicast
+        or value.is_reserved
+        or value.is_unspecified
+    )
+
+
+def _validate_resolved_host_ips(hostname: str, port: int, allow_private_network: bool) -> None:
+    """Resolves hostnames and rejects private or special addresses when private network access is disabled."""
+
+    try:
+        addresses = socket.getaddrinfo(hostname, port, type=socket.SOCK_STREAM)
+    except socket.gaierror as error:
+        raise ValueError(f"Provider base URL host cannot be resolved: {hostname}") from error
+
+    resolved_ips: set[ipaddress.IPv4Address | ipaddress.IPv6Address] = set()
+    for entry in addresses:
+        sockaddr = entry[4]
+        if not sockaddr:
+            continue
+        ip_text = sockaddr[0]
+        try:
+            resolved_ips.add(ipaddress.ip_address(ip_text))
+        except ValueError:
+            continue
+
+    if not resolved_ips:
+        raise ValueError(f"Provider base URL host resolved without usable IP addresses: {hostname}")
+
+    if allow_private_network:
+        return
+
+    blocked = [ip for ip in resolved_ips if _is_private_or_special_ip(ip)]
+    if blocked:
+        blocked_text = ", ".join(str(ip) for ip in blocked)
+        raise ValueError(f"Provider base URL resolves to private or special IP addresses: {blocked_text}")
+
+
+def _normalize_and_validate_provider_base_url(
+    raw_value: str,
+    allowlist: tuple[str, ...],
+    allow_http: bool,
+    allow_private_network: bool,
+    resolve_dns: bool,
+) -> str:
+    """Normalizes and validates provider base URLs with SSRF-safe scheme and host checks."""
+
+    trimmed = raw_value.strip().rstrip("/")
+    if not trimmed:
+        raise ValueError("Provider base URL must not be empty")
+
+    parsed = urlparse(trimmed)
+    scheme = parsed.scheme.lower()
+    if scheme not in {"http", "https"}:
+        raise ValueError("Provider base URL must use http or https")
+    if scheme == "http" and not allow_http:
+        raise ValueError("Provider base URL must use https")
+    if parsed.query or parsed.fragment:
+        raise ValueError("Provider base URL must not include query strings or fragments")
+    if parsed.username or parsed.password:
+        raise ValueError("Provider base URL must not include embedded credentials")
+
+    hostname = (parsed.hostname or "").lower().rstrip(".")
+    if not hostname:
+        raise ValueError("Provider base URL must include a hostname")
+    if allowlist and not _host_matches_allowlist(hostname, allowlist):
+        allowed_hosts = ", ".join(allowlist)
+        raise ValueError(f"Provider base URL host is not in allowlist: {hostname}. Allowed hosts: {allowed_hosts}")
+
+    if hostname == "localhost" or hostname.endswith(LOCAL_HOSTNAME_SUFFIXES):
+        if not allow_private_network:
+            raise ValueError("Provider base URL must not target local or internal hostnames")
+
+    try:
+        ip_host = ipaddress.ip_address(hostname)
+    except ValueError:
+        ip_host = None
+
+    if ip_host is not None:
+        if not allow_private_network and _is_private_or_special_ip(ip_host):
+            raise ValueError("Provider base URL must not target private or special IP addresses")
+    elif resolve_dns:
+        resolved_port = parsed.port
+        if resolved_port is None:
+            resolved_port = 443 if scheme == "https" else 80
+        _validate_resolved_host_ips(
+            hostname=hostname,
+            port=resolved_port,
+            allow_private_network=allow_private_network,
+        )
+
+    path = (parsed.path or "").rstrip("/")
+    if not path.endswith("/v1"):
+        path = f"{path}/v1" if path else "/v1"
+
+    normalized_hostname = hostname
+    if ":" in normalized_hostname and not normalized_hostname.startswith("["):
+        normalized_hostname = f"[{normalized_hostname}]"
+    netloc = f"{normalized_hostname}:{parsed.port}" if parsed.port is not None else normalized_hostname
+    return urlunparse((scheme, netloc, path, "", "", ""))
+
+
+@lru_cache(maxsize=256)
+def _normalize_and_validate_provider_base_url_cached(
+    raw_value: str,
+    allowlist: tuple[str, ...],
+    allow_http: bool,
+    allow_private_network: bool,
+) -> str:
+    """Caches provider URL validation results for non-DNS-resolved checks."""
+
+    return _normalize_and_validate_provider_base_url(
+        raw_value=raw_value,
+        allowlist=allowlist,
+        allow_http=allow_http,
+        allow_private_network=allow_private_network,
+        resolve_dns=False,
+    )
+
+
+def normalize_and_validate_provider_base_url(raw_value: str, *, resolve_dns: bool = False) -> str:
+    """Validates and normalizes provider base URL values using configured SSRF protections."""
+
+    settings = get_settings()
+    allowlist = _normalize_allowlist(settings.provider_base_url_allowlist)
+    allow_http = settings.provider_base_url_allow_http if isinstance(settings.provider_base_url_allow_http, bool) else False
+    allow_private_network = (
+        settings.provider_base_url_allow_private_network
+        if isinstance(settings.provider_base_url_allow_private_network, bool)
+        else False
+    )
+    if resolve_dns:
+        return _normalize_and_validate_provider_base_url(
+            raw_value=raw_value,
+            allowlist=allowlist,
+            allow_http=allow_http,
+            allow_private_network=allow_private_network,
+            resolve_dns=True,
+        )
+    return _normalize_and_validate_provider_base_url_cached(
+        raw_value=raw_value,
+        allowlist=allowlist,
+        allow_http=allow_http,
+        allow_private_network=allow_private_network,
+    )
+
+
 @lru_cache(maxsize=1)
 def get_settings() -> Settings:
     """Returns a cached settings object for dependency injection and service access."""
diff --git a/backend/app/main.py b/backend/app/main.py
index 5d26f9a..364bd70 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -1,7 +1,8 @@
 """FastAPI entrypoint for the DMS backend service."""
 
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import JSONResponse
 
 from app.api.router import api_router
 from app.core.config import get_settings
@@ -28,6 +29,35 @@ def create_app() -> FastAPI:
     )
     app.include_router(api_router, prefix="/api/v1")
 
+    @app.middleware("http")
+    async def enforce_upload_request_size(request: Request, call_next):
+        """Rejects upload requests without deterministic length or exceeding configured limits."""
+
+        if request.url.path.endswith("/api/v1/documents/upload"):
+            content_length = request.headers.get("content-length", "").strip()
+            if not content_length:
+                return JSONResponse(
+                    status_code=411,
+                    content={"detail": "Content-Length header is required for document uploads"},
+                )
+            try:
+                content_length_value = int(content_length)
+            except ValueError:
+                return JSONResponse(status_code=400, content={"detail": "Invalid Content-Length header"})
+            if content_length_value <= 0:
+                return JSONResponse(status_code=400, content={"detail": "Content-Length must be a positive integer"})
+            if content_length_value > settings.max_upload_request_size_bytes:
+                return JSONResponse(
+                    status_code=413,
+                    content={
+                        "detail": (
+                            "Upload request exceeds total size limit "
+                            f"({content_length_value} > {settings.max_upload_request_size_bytes} bytes)"
+                        )
+                    },
+                )
+        return await call_next(request)
+
     @app.on_event("startup")
     def startup_event() -> None:
         """Initializes storage directories and database schema on service startup."""
diff --git a/backend/app/models/processing_log.py b/backend/app/models/processing_log.py
index 15988ed..25b17dc 100644
--- a/backend/app/models/processing_log.py
+++ b/backend/app/models/processing_log.py
@@ -2,14 +2,118 @@
 
 import uuid
 from datetime import UTC, datetime
+import re
+from typing import Any
 
 from sqlalchemy import BigInteger, DateTime, ForeignKey, String, Text
 from sqlalchemy.dialects.postgresql import JSONB, UUID
-from sqlalchemy.orm import Mapped, mapped_column
+from sqlalchemy.orm import Mapped, mapped_column, validates
 
+from app.core.config import get_settings
 from app.db.base import Base
 
 
+settings = get_settings()
+
+
+SENSITIVE_KEY_MARKERS = (
+    "api_key",
+    "apikey",
+    "authorization",
+    "bearer",
+    "token",
+    "secret",
+    "password",
+    "credential",
+    "cookie",
+)
+SENSITIVE_TEXT_PATTERNS = (
+    re.compile(r"(?i)\bauthorization\b\s*[:=]\s*bearer\s+[a-z0-9._~+/\-]+=*"),
+    re.compile(r"(?i)\bbearer\s+[a-z0-9._~+/\-]+=*"),
+    re.compile(r"\b[a-z0-9_-]{8,}\.[a-z0-9_-]{8,}\.[a-z0-9_-]{8,}\b", flags=re.IGNORECASE),
+    re.compile(r"(?i)\bsk-[a-z0-9]{16,}\b"),
+    re.compile(r"(?i)\b(api[_-]?key|token|secret|password)\b\s*[:=]\s*['\"]?[^\s,'\";]+['\"]?"),
+)
+REDACTED_TEXT = "[REDACTED]"
+MAX_PAYLOAD_KEYS = 80
+MAX_PAYLOAD_LIST_ITEMS = 80
+
+
+def _truncate(value: str, limit: int) -> str:
+    """Truncates long log fields to configured bounds with stable suffix marker."""
+
+    normalized = value.strip()
+    if len(normalized) <= limit:
+        return normalized
+    return normalized[: max(0, limit - 3)] + "..."
+
+
+def _is_sensitive_key(key: str) -> bool:
+    """Returns whether a payload key likely contains sensitive credential data."""
+
+    normalized = key.strip().lower()
+    return any(marker in normalized for marker in SENSITIVE_KEY_MARKERS)
+
+
+def _redact_sensitive_text(value: str) -> str:
+    """Redacts token-like segments from log text while retaining non-sensitive context."""
+
+    redacted = value
+    for pattern in SENSITIVE_TEXT_PATTERNS:
+        redacted = pattern.sub(lambda _: REDACTED_TEXT, redacted)
+    return redacted
+
+
+def sanitize_processing_log_payload_value(value: Any, *, parent_key: str | None = None) -> Any:
+    """Sanitizes payload structures by redacting sensitive fields and bounding size."""
+
+    if parent_key and _is_sensitive_key(parent_key):
+        return REDACTED_TEXT
+
+    if isinstance(value, dict):
+        sanitized: dict[str, Any] = {}
+        for index, (raw_key, raw_value) in enumerate(value.items()):
+            if index >= MAX_PAYLOAD_KEYS:
+                break
+            key = str(raw_key)
+            sanitized[key] = sanitize_processing_log_payload_value(raw_value, parent_key=key)
+        return sanitized
+
+    if isinstance(value, list):
+        return [
+            sanitize_processing_log_payload_value(item, parent_key=parent_key)
+            for item in value[:MAX_PAYLOAD_LIST_ITEMS]
+        ]
+
+    if isinstance(value, tuple):
+        return [
+            sanitize_processing_log_payload_value(item, parent_key=parent_key)
+            for item in list(value)[:MAX_PAYLOAD_LIST_ITEMS]
+        ]
+
+    if isinstance(value, str):
+        redacted = _redact_sensitive_text(value)
+        return _truncate(redacted, settings.processing_log_max_payload_chars)
+
+    if isinstance(value, (int, float, bool)) or value is None:
+        return value
+
+    as_text = _truncate(str(value), settings.processing_log_max_payload_chars)
+    return _redact_sensitive_text(as_text)
+
+
+def sanitize_processing_log_text(value: str | None) -> str | None:
+    """Sanitizes prompt and response fields by redacting credentials and clamping length."""
+
+    if value is None:
+        return None
+    normalized = value.strip()
+    if not normalized:
+        return None
+    redacted = _redact_sensitive_text(normalized)
+    return _truncate(redacted, settings.processing_log_max_text_chars)
+
+
 class ProcessingLogEntry(Base):
     """Stores a timestamped processing event with optional model prompt and response text."""
 
@@ -31,3 +135,17 @@ class ProcessingLogEntry(Base):
     prompt_text: Mapped[str | None] = mapped_column(Text, nullable=True)
     response_text: Mapped[str | None] = mapped_column(Text, nullable=True)
     payload_json: Mapped[dict] = mapped_column(JSONB, nullable=False, default=dict)
+
+    @validates("prompt_text", "response_text")
+    def _validate_text_fields(self, key: str, value: str | None) -> str | None:
+        """Redacts and bounds free-text log fields before persistence."""
+
+        return sanitize_processing_log_text(value)
+
+    @validates("payload_json")
+    def _validate_payload_json(self, key: str, value: dict[str, Any] | None) -> dict[str, Any]:
+        """Redacts and bounds structured payload fields before persistence."""
+
+        if not isinstance(value, dict):
+            return {}
+        return sanitize_processing_log_payload_value(value)
diff --git a/backend/app/schemas/processing_logs.py b/backend/app/schemas/processing_logs.py
index ed5b994..e5862ff 100644
--- a/backend/app/schemas/processing_logs.py
+++ b/backend/app/schemas/processing_logs.py
@@ -1,13 +1,16 @@
 """Pydantic schemas for processing pipeline log API payloads."""
 
 from datetime import datetime
+from typing import Any
 from uuid import UUID
 
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, field_validator
+
+from app.models.processing_log import sanitize_processing_log_payload_value, sanitize_processing_log_text
 
 
 class ProcessingLogEntryResponse(BaseModel):
-    """Represents one persisted processing log event returned by API endpoints."""
+    """Represents one persisted processing log event with already-redacted sensitive fields."""
 
     id: int
     created_at: datetime
@@ -20,7 +23,26 @@ class ProcessingLogEntryResponse(BaseModel):
     model_name: str | None
     prompt_text: str | None
     response_text: str | None
-    payload_json: dict
+    payload_json: dict[str, Any]
+
+    @field_validator("prompt_text", "response_text", mode="before")
+    @classmethod
+    def _sanitize_text_fields(cls, value: Any) -> str | None:
+        """Ensures log text fields are redacted in API responses."""
+
+        if value is None:
+            return None
+        return sanitize_processing_log_text(str(value))
+
+    @field_validator("payload_json", mode="before")
+    @classmethod
+    def _sanitize_payload_field(cls, value: Any) -> dict[str, Any]:
+        """Ensures payload fields are redacted in API responses."""
+
+        if not isinstance(value, dict):
+            return {}
+        sanitized = sanitize_processing_log_payload_value(value)
+        return sanitized if isinstance(sanitized, dict) else {}
 
     class Config:
         """Enables ORM object parsing for SQLAlchemy model instances."""
diff --git a/backend/app/services/app_settings.py b/backend/app/services/app_settings.py
index c3d6117..8294db4 100644
--- a/backend/app/services/app_settings.py
+++ b/backend/app/services/app_settings.py
@@ -5,12 +5,16 @@ import re
 from pathlib import Path
 from typing import Any
 
-from app.core.config import get_settings
+from app.core.config import get_settings, normalize_and_validate_provider_base_url
 
 
 settings = get_settings()
 
 
+class AppSettingsValidationError(ValueError):
+    """Raised when user-provided settings values fail security or contract validation."""
+
+
 TASK_OCR_HANDWRITING = "ocr_handwriting"
 TASK_SUMMARY_GENERATION = "summary_generation"
 TASK_ROUTING_CLASSIFICATION = "routing_classification"
@@ -156,13 +160,13 @@ def _clamp_cards_per_page(value: int) -> int:
 def _clamp_processing_log_document_sessions(value: int) -> int:
     """Clamps the number of recent document log sessions kept during cleanup."""
 
-    return max(0, min(20, value))
+    return max(0, min(settings.processing_log_max_document_sessions, value))
 
 
 def _clamp_processing_log_unbound_entries(value: int) -> int:
     """Clamps retained unbound processing log events kept during cleanup."""
 
-    return max(0, min(400, value))
+    return max(0, min(settings.processing_log_max_unbound_entries, value))
 
 
 def _clamp_predefined_entries_limit(value: int) -> int:
@@ -242,12 +246,19 @@ def _normalize_provider(
     api_key_value = payload.get("api_key", fallback_values.get("api_key", defaults["api_key"]))
     api_key = str(api_key_value).strip() if api_key_value is not None else ""
 
+    raw_base_url = str(payload.get("base_url", fallback_values.get("base_url", defaults["base_url"]))).strip()
+    if not raw_base_url:
+        raw_base_url = str(defaults["base_url"]).strip()
+    try:
+        normalized_base_url = normalize_and_validate_provider_base_url(raw_base_url)
+    except ValueError as error:
+        raise AppSettingsValidationError(str(error)) from error
+
     return {
         "id": provider_id,
         "label": str(payload.get("label", fallback_values.get("label", provider_id))).strip() or provider_id,
         "provider_type": provider_type,
-        "base_url": str(payload.get("base_url", fallback_values.get("base_url", defaults["base_url"]))).strip()
-        or defaults["base_url"],
+        "base_url": normalized_base_url,
         "timeout_seconds": _clamp_timeout(
             _safe_int(
                 payload.get("timeout_seconds", fallback_values.get("timeout_seconds", defaults["timeout_seconds"])),
diff --git a/backend/app/services/extractor.py b/backend/app/services/extractor.py
index 421b618..cf73e89 100644
--- a/backend/app/services/extractor.py
+++ b/backend/app/services/extractor.py
@@ -300,16 +300,39 @@ def extract_text_content(filename: str, data: bytes, mime_type: str) -> Extracti
 
 
 def extract_archive_members(data: bytes, depth: int = 0) -> list[ArchiveMember]:
-    """Extracts processable members from zip archives with configurable depth limits."""
+    """Extracts processable ZIP members within configured decompression safety budgets."""
 
     members: list[ArchiveMember] = []
     if depth > settings.max_zip_depth:
         return members
 
-    with zipfile.ZipFile(io.BytesIO(data)) as archive:
-        infos = [info for info in archive.infolist() if not info.is_dir()][: settings.max_zip_members]
-        for info in infos:
-            member_data = archive.read(info.filename)
-            members.append(ArchiveMember(name=info.filename, data=member_data))
+    total_uncompressed_bytes = 0
+    try:
+        with zipfile.ZipFile(io.BytesIO(data)) as archive:
+            infos = [info for info in archive.infolist() if not info.is_dir()][: settings.max_zip_members]
+            for info in infos:
+                if info.file_size <= 0:
+                    continue
+                if info.file_size > settings.max_zip_member_uncompressed_bytes:
+                    continue
+                if total_uncompressed_bytes + info.file_size > settings.max_zip_total_uncompressed_bytes:
+                    continue
+
+                compressed_size = max(1, int(info.compress_size))
+                compression_ratio = float(info.file_size) / float(compressed_size)
+                if compression_ratio > settings.max_zip_compression_ratio:
+                    continue
+
+                with archive.open(info, mode="r") as archive_member:
+                    member_data = archive_member.read(settings.max_zip_member_uncompressed_bytes + 1)
+                if len(member_data) > settings.max_zip_member_uncompressed_bytes:
+                    continue
+                if total_uncompressed_bytes + len(member_data) > settings.max_zip_total_uncompressed_bytes:
+                    continue
+
+                total_uncompressed_bytes += len(member_data)
+                members.append(ArchiveMember(name=info.filename, data=member_data))
+    except zipfile.BadZipFile:
+        return []
 
     return members
diff --git a/backend/app/services/model_runtime.py b/backend/app/services/model_runtime.py
index eea609e..b18916e 100644
--- a/backend/app/services/model_runtime.py
+++ b/backend/app/services/model_runtime.py
@@ -2,10 +2,10 @@
 
 from dataclasses import dataclass
 from typing import Any
-from urllib.parse import urlparse, urlunparse
 
 from openai import APIConnectionError, APIError, APITimeoutError, OpenAI
 
+from app.core.config import normalize_and_validate_provider_base_url
 from app.services.app_settings import read_task_runtime_settings
 
 
@@ -36,18 +36,9 @@ class ModelTaskRuntime:
 
 
 def _normalize_base_url(raw_value: str) -> str:
-    """Normalizes provider base URL and appends /v1 for OpenAI-compatible servers."""
+    """Normalizes provider base URL and enforces SSRF protections before outbound calls."""
 
-    trimmed = raw_value.strip().rstrip("/")
-    if not trimmed:
-        return "https://api.openai.com/v1"
-
-    parsed = urlparse(trimmed)
-    path = parsed.path or ""
-    if not path.endswith("/v1"):
-        path = f"{path}/v1" if path else "/v1"
-
-    return urlunparse(parsed._replace(path=path))
+    return normalize_and_validate_provider_base_url(raw_value, resolve_dns=True)
 
 
 def _should_fallback_to_chat(error: Exception) -> bool:
@@ -137,11 +128,16 @@ def resolve_task_runtime(task_name: str) -> ModelTaskRuntime:
     if provider_type != "openai_compatible":
         raise ModelTaskError(f"unsupported_provider_type:{provider_type}")
 
+    try:
+        normalized_base_url = _normalize_base_url(str(provider_payload.get("base_url", "https://api.openai.com/v1")))
+    except ValueError as error:
+        raise ModelTaskError(f"invalid_provider_base_url:{error}") from error
+
     return ModelTaskRuntime(
         task_name=task_name,
         provider_id=str(provider_payload.get("id", "")),
         provider_type=provider_type,
-        base_url=_normalize_base_url(str(provider_payload.get("base_url", "https://api.openai.com/v1"))),
+        base_url=normalized_base_url,
         timeout_seconds=int(provider_payload.get("timeout_seconds", 45)),
         api_key=str(provider_payload.get("api_key", "")).strip() or "no-key-required",
         model=str(task_payload.get("model", "")).strip(),
diff --git a/backend/tests/test_security_controls.py b/backend/tests/test_security_controls.py
new file mode 100644
index 0000000..29092b4
--- /dev/null
+++ b/backend/tests/test_security_controls.py
@@ -0,0 +1,273 @@
+"""Unit coverage for API auth, SSRF validation, and processing-log redaction controls."""
+
+from __future__ import annotations
+
+from datetime import UTC, datetime
+import socket
+import sys
+from pathlib import Path
+from types import ModuleType, SimpleNamespace
+import unittest
+from unittest.mock import patch
+
+
+BACKEND_ROOT = Path(__file__).resolve().parents[1]
+if str(BACKEND_ROOT) not in sys.path:
+    sys.path.insert(0, str(BACKEND_ROOT))
+
+if "pydantic_settings" not in sys.modules:
+    pydantic_settings_stub = ModuleType("pydantic_settings")
+
+    class _BaseSettings:
+        """Minimal BaseSettings replacement for dependency-light unit test execution."""
+
+        def __init__(self, **kwargs: object) -> None:
+            for key, value in kwargs.items():
+                setattr(self, key, value)
+
+    def _settings_config_dict(**kwargs: object) -> dict[str, object]:
+        """Returns configuration values using dict semantics expected by settings module."""
+
+        return kwargs
+
+    pydantic_settings_stub.BaseSettings = _BaseSettings
+    pydantic_settings_stub.SettingsConfigDict = _settings_config_dict
+    sys.modules["pydantic_settings"] = pydantic_settings_stub
+
+if "fastapi" not in sys.modules:
+    fastapi_stub = ModuleType("fastapi")
+
+    class _HTTPException(Exception):
+        """Minimal HTTPException compatible with route dependency tests."""
+
+        def __init__(self, status_code: int, detail: str, headers: dict[str, str] | None = None) -> None:
+            super().__init__(detail)
+            self.status_code = status_code
+            self.detail = detail
+            self.headers = headers or {}
+
+    class _Status:
+        """Minimal status namespace for auth unit tests."""
+
+        HTTP_401_UNAUTHORIZED = 401
+        HTTP_403_FORBIDDEN = 403
+        HTTP_503_SERVICE_UNAVAILABLE = 503
+
+    def _depends(dependency):  # type: ignore[no-untyped-def]
+        """Returns provided dependency unchanged for unit testing."""
+
+        return dependency
+
+    fastapi_stub.Depends = _depends
+    fastapi_stub.HTTPException = _HTTPException
+    fastapi_stub.status = _Status()
+    sys.modules["fastapi"] = fastapi_stub
+
+if "fastapi.security" not in sys.modules:
+    fastapi_security_stub = ModuleType("fastapi.security")
+
+    class _HTTPAuthorizationCredentials:
+        """Minimal bearer credential object used by auth dependency tests."""
+
+        def __init__(self, *, scheme: str, credentials: str) -> None:
+            self.scheme = scheme
+            self.credentials = credentials
+
+    class _HTTPBearer:
+        """Minimal HTTPBearer stand-in for dependency construction."""
+
+        def __init__(self, auto_error: bool = True) -> None:
+            self.auto_error = auto_error
+
+    fastapi_security_stub.HTTPAuthorizationCredentials = _HTTPAuthorizationCredentials
+    fastapi_security_stub.HTTPBearer = _HTTPBearer
+    sys.modules["fastapi.security"] = fastapi_security_stub
+
+from fastapi import HTTPException
+from fastapi.security import HTTPAuthorizationCredentials
+
+from app.api.auth import AuthRole, get_request_role, require_admin
+from app.core import config as config_module
+from app.models.processing_log import sanitize_processing_log_payload_value, sanitize_processing_log_text
+from app.schemas.processing_logs import ProcessingLogEntryResponse
+
+
+def _security_settings(
+    *,
+    allowlist: list[str] | None = None,
+    allow_http: bool = False,
+    allow_private_network: bool = False,
+) -> SimpleNamespace:
+    """Builds lightweight settings object for provider URL validation tests."""
+
+    return SimpleNamespace(
+        provider_base_url_allowlist=allowlist if allowlist is not None else ["api.openai.com"],
+        provider_base_url_allow_http=allow_http,
+        provider_base_url_allow_private_network=allow_private_network,
+    )
+
+
+class AuthDependencyTests(unittest.TestCase):
+    """Verifies token authentication and admin authorization behavior."""
+
+    def test_get_request_role_accepts_admin_token(self) -> None:
+        """Admin token resolves admin role."""
+
+        settings = SimpleNamespace(admin_api_token="admin-token", user_api_token="user-token")
+        credentials = HTTPAuthorizationCredentials(scheme="Bearer", credentials="admin-token")
+        role = get_request_role(credentials=credentials, settings=settings)
+        self.assertEqual(role, AuthRole.ADMIN)
+
+    def test_get_request_role_rejects_missing_credentials(self) -> None:
+        """Missing bearer credentials return 401."""
+
+        settings = SimpleNamespace(admin_api_token="admin-token", user_api_token="user-token")
+        with self.assertRaises(HTTPException) as context:
+            get_request_role(credentials=None, settings=settings)
+        self.assertEqual(context.exception.status_code, 401)
+
+    def test_require_admin_rejects_user_role(self) -> None:
+        """User role cannot access admin-only endpoints."""
+
+        with self.assertRaises(HTTPException) as context:
+            require_admin(role=AuthRole.USER)
+        self.assertEqual(context.exception.status_code, 403)
+
+
+class ProviderBaseUrlValidationTests(unittest.TestCase):
+    """Verifies allowlist, scheme, and private-network SSRF protections."""
+
+    def setUp(self) -> None:
+        """Clears URL validation cache to keep tests independent."""
+
+        config_module._normalize_and_validate_provider_base_url_cached.cache_clear()
+
+    def test_validation_accepts_allowlisted_https_url(self) -> None:
+        """Allowlisted HTTPS URLs are normalized with /v1 suffix."""
+
+        with patch.object(config_module, "get_settings", return_value=_security_settings(allowlist=["api.openai.com"])):
+            normalized = config_module.normalize_and_validate_provider_base_url("https://api.openai.com")
+        self.assertEqual(normalized, "https://api.openai.com/v1")
+
+    def test_validation_rejects_non_allowlisted_host(self) -> None:
+        """Hosts outside configured allowlist are rejected."""
+
+        with patch.object(config_module, "get_settings", return_value=_security_settings(allowlist=["api.openai.com"])):
+            with self.assertRaises(ValueError):
+                config_module.normalize_and_validate_provider_base_url("https://example.org/v1")
+
+    def test_validation_rejects_private_ip_literal(self) -> None:
+        """Private and loopback IP literals are blocked."""
+
+        with patch.object(config_module, "get_settings", return_value=_security_settings(allowlist=[])):
+            with self.assertRaises(ValueError):
+                config_module.normalize_and_validate_provider_base_url("https://127.0.0.1/v1")
+
+    def test_validation_rejects_private_ip_after_dns_resolution(self) -> None:
+        """DNS rebind protection blocks public hostnames resolving to private addresses."""
+
+        mocked_dns_response = [
+            (socket.AF_INET, socket.SOCK_STREAM, socket.IPPROTO_TCP, "", ("127.0.0.1", 443)),
+        ]
+        with (
+            patch.object(config_module, "get_settings", return_value=_security_settings(allowlist=["api.openai.com"])),
+            patch.object(config_module.socket, "getaddrinfo", return_value=mocked_dns_response),
+        ):
+            with self.assertRaises(ValueError):
+                config_module.normalize_and_validate_provider_base_url(
+                    "https://api.openai.com/v1",
+                    resolve_dns=True,
+                )
+
+    def test_resolve_dns_validation_revalidates_each_call(self) -> None:
+        """DNS-resolved validation is not cached and re-checks host resolution each call."""
+
+        mocked_dns_response = [
+            (socket.AF_INET, socket.SOCK_STREAM, socket.IPPROTO_TCP, "", ("8.8.8.8", 443)),
+        ]
+        with (
+            patch.object(config_module, "get_settings", return_value=_security_settings(allowlist=["api.openai.com"])),
+            patch.object(config_module.socket, "getaddrinfo", return_value=mocked_dns_response) as getaddrinfo_mock,
+        ):
+            first = config_module.normalize_and_validate_provider_base_url(
+                "https://api.openai.com/v1",
+                resolve_dns=True,
+            )
+            second = config_module.normalize_and_validate_provider_base_url(
+                "https://api.openai.com/v1",
+                resolve_dns=True,
+            )
+        self.assertEqual(first, "https://api.openai.com/v1")
+        self.assertEqual(second, "https://api.openai.com/v1")
+        self.assertEqual(getaddrinfo_mock.call_count, 2)
+
+
+class ProcessingLogRedactionTests(unittest.TestCase):
+    """Verifies sensitive processing-log values are redacted for persistence and responses."""
+
+    def test_payload_redacts_sensitive_keys(self) -> None:
+        """Sensitive payload keys are replaced with redaction marker."""
+
+        sanitized = sanitize_processing_log_payload_value(
+            {
+                "api_key": "secret-value",
+                "nested": {
+                    "authorization": "Bearer sample-token",
+                },
+            }
+        )
+        self.assertEqual(sanitized["api_key"], "[REDACTED]")
+        self.assertEqual(sanitized["nested"]["authorization"], "[REDACTED]")
+
+    def test_text_redaction_removes_bearer_and_jwt_values(self) -> None:
+        """Bearer and JWT token substrings are fully removed from log text."""
+
+        bearer_token = "super-secret-token-123"
+        jwt_token = (
+            "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9."
+            "eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4ifQ."
+            "signaturevalue123456789"
+        )
+        sanitized = sanitize_processing_log_text(
+            f"Authorization: Bearer {bearer_token}\nraw_jwt={jwt_token}"
+        )
+        self.assertIsNotNone(sanitized)
+        sanitized_text = sanitized or ""
+        self.assertIn("[REDACTED]", sanitized_text)
+        self.assertNotIn(bearer_token, sanitized_text)
+        self.assertNotIn(jwt_token, sanitized_text)
+
+    def test_response_schema_applies_redaction_to_existing_entries(self) -> None:
+        """API schema validators redact sensitive fields from legacy stored rows."""
+
+        bearer_token = "abc123token"
+        jwt_token = (
+            "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9."
+            "eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4ifQ."
+            "signaturevalue123456789"
+        )
+        response = ProcessingLogEntryResponse.model_validate(
+            {
+                "id": 1,
+                "created_at": datetime.now(UTC),
+                "level": "info",
+                "stage": "summary",
+                "event": "response",
+                "document_id": None,
+                "document_filename": "sample.txt",
+                "provider_id": "provider",
+                "model_name": "model",
+                "prompt_text": f"Authorization: Bearer {bearer_token}",
+                "response_text": f"token={jwt_token}",
+                "payload_json": {"password": "secret", "trace_id": "trace-1"},
+            }
+        )
+        self.assertEqual(response.payload_json["password"], "[REDACTED]")
+        self.assertIn("[REDACTED]", response.prompt_text or "")
+        self.assertIn("[REDACTED]", response.response_text or "")
+        self.assertNotIn(bearer_token, response.prompt_text or "")
+        self.assertNotIn(jwt_token, response.response_text or "")
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/doc/README.md b/doc/README.md
index 1065d48..5aaa36c 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -6,7 +6,7 @@ This directory contains technical documentation for DMS.
 
 - `../README.md` - project overview, setup, and quick operations
 - `architecture-overview.md` - backend, frontend, and infrastructure architecture
-- `api-contract.md` - API endpoint contract grouped by route module, including settings and processing-log trim defaults
+- `api-contract.md` - API endpoint contract grouped by route module, including token auth roles, upload limits, and settings or processing-log security constraints
 - `data-model-reference.md` - database entity definitions and lifecycle states
-- `operations-and-configuration.md` - runtime operations, ports, volumes, and persisted settings configuration
+- `operations-and-configuration.md` - runtime operations, hardened compose defaults, security environment variables, and persisted settings configuration
 - `frontend-design-foundation.md` - frontend visual system, tokens, UI implementation rules, processing-log timeline behavior, and settings helper-copy guidance
diff --git a/doc/api-contract.md b/doc/api-contract.md
index d37b888..94aa60b 100644
--- a/doc/api-contract.md
+++ b/doc/api-contract.md
@@ -10,6 +10,17 @@ Primary implementation modules:
 - `backend/app/api/routes_processing_logs.py`
 - `backend/app/api/routes_settings.py`
 
+## Authentication And Authorization
+
+- Protected endpoints require `Authorization: Bearer <token>`.
+- `ADMIN_API_TOKEN` is required for all privileged access and acts as fail-closed root credential.
+- `USER_API_TOKEN` is optional and, when configured, grants access to document endpoints only.
+- Authorization matrix:
+  - `documents/*`: `admin` or `user`
+  - `search/*`: `admin` or `user`
+  - `settings/*`: `admin` only
+  - `processing/logs/*`: `admin` only
+
 ## Health
 
 - `GET /health`
@@ -18,6 +29,8 @@ Primary implementation modules:
 
 ## Documents
 
+- Access: admin or user token required
+
 ### Collection and metadata helpers
 
 - `GET /documents`
@@ -76,9 +89,13 @@ Primary implementation modules:
   - `ask`: returns `conflicts` if duplicate checksum is detected
   - `replace`: creates new document linked to replaced document id
   - `duplicate`: creates additional document record
+  - request rejected with `411` when `Content-Length` is missing
+  - request rejected with `413` when file count, per-file size, or total request size exceeds configured limits
 
 ## Search
 
+- Access: admin or user token required
+
 - `GET /search`
 - Query: `query` (min length 2), `offset`, `limit`, `include_trashed`, `only_trashed`, `path_filter`, `tag_filter`, `type_filter`, `processed_from`, `processed_to`
 - Response model: `SearchResponse`
@@ -86,23 +103,31 @@ Primary implementation modules:
 
 ## Processing Logs
 
+- Access: admin token required
+
 - `GET /processing/logs`
   - Query: `offset`, `limit`, `document_id`
   - Response model: `ProcessingLogListResponse`
+  - `limit` is capped by runtime configuration
+  - sensitive fields are redacted in API responses
 - `POST /processing/logs/trim`
   - Query: optional `keep_document_sessions`, `keep_unbound_entries`
   - Behavior: omitted query values fall back to persisted `/settings.processing_log_retention`
+  - query values are capped by runtime retention limits
   - Response: trim counters
 - `POST /processing/logs/clear`
   - Response: clear counters
 
 ## Settings
 
+- Access: admin token required
+
 - `GET /settings`
   - Response model: `AppSettingsResponse`
 - `PATCH /settings`
   - Body model: `AppSettingsUpdateRequest`
   - Response model: `AppSettingsResponse`
+  - rejects invalid provider base URLs with `400` when scheme, allowlist, or network safety checks fail
 - `POST /settings/reset`
   - Response model: `AppSettingsResponse`
 - `PATCH /settings/handwriting`
diff --git a/doc/operations-and-configuration.md b/doc/operations-and-configuration.md
index 483aace..928fde3 100644
--- a/doc/operations-and-configuration.md
+++ b/doc/operations-and-configuration.md
@@ -3,12 +3,12 @@
 ## Runtime Services
 
 `docker-compose.yml` defines the runtime stack:
-- `db` (Postgres 16, port `5432`)
-- `redis` (Redis 7, port `6379`)
-- `typesense` (Typesense 29, port `8108`)
-- `api` (FastAPI backend, port `8000`)
+- `db` (Postgres 16, localhost-bound port `5432`)
+- `redis` (Redis 7, localhost-bound port `6379`)
+- `typesense` (Typesense 29, localhost-bound port `8108`)
+- `api` (FastAPI backend, localhost-bound port `8000`)
 - `worker` (RQ background worker)
-- `frontend` (Vite UI, port `5173`)
+- `frontend` (Vite UI, localhost-bound port `5173`)
 
 ## Named Volumes
 
@@ -44,6 +44,15 @@ Tail logs:
 docker compose logs -f
 ```
 
+Before running compose, provide explicit API tokens in your shell or project `.env` file:
+
+```bash
+export ADMIN_API_TOKEN="<random-admin-token>"
+export USER_API_TOKEN="<random-user-token>"
+```
+
+Compose now fails fast if either token variable is missing.
+
 ## Backend Configuration
 
 Settings source:
@@ -55,8 +64,13 @@ Key environment variables used by `api` and `worker` in compose:
 - `DATABASE_URL`
 - `REDIS_URL`
 - `STORAGE_ROOT`
+- `ADMIN_API_TOKEN`
+- `USER_API_TOKEN`
 - `PUBLIC_BASE_URL`
 - `CORS_ORIGINS` (API service)
+- `PROVIDER_BASE_URL_ALLOWLIST`
+- `PROVIDER_BASE_URL_ALLOW_HTTP`
+- `PROVIDER_BASE_URL_ALLOW_PRIVATE_NETWORK`
 - `TYPESENSE_PROTOCOL`
 - `TYPESENSE_HOST`
 - `TYPESENSE_PORT`
@@ -65,9 +79,17 @@ Key environment variables used by `api` and `worker` in compose:
 
 Selected defaults from `Settings` (`backend/app/core/config.py`):
 - `upload_chunk_size = 4194304`
+- `max_upload_files_per_request = 50`
+- `max_upload_file_size_bytes = 26214400`
+- `max_upload_request_size_bytes = 104857600`
 - `max_zip_members = 250`
 - `max_zip_depth = 2`
+- `max_zip_member_uncompressed_bytes = 26214400`
+- `max_zip_total_uncompressed_bytes = 157286400`
+- `max_zip_compression_ratio = 120.0`
 - `max_text_length = 500000`
+- `processing_log_max_document_sessions = 20`
+- `processing_log_max_unbound_entries = 400`
 - `default_openai_model = "gpt-4.1-mini"`
 - `default_openai_timeout_seconds = 45`
 - `default_summary_model = "gpt-4.1-mini"`
@@ -105,6 +127,25 @@ Settings include:
 
 Retention settings are used by worker cleanup and by `POST /api/v1/processing/logs/trim` when trim query values are not provided.
 
+## Security Controls
+
+- Privileged APIs are token-gated with bearer auth:
+  - `documents` endpoints: user token or admin token
+  - `settings` and `processing/logs` endpoints: admin token only
+- Authentication fails closed when `ADMIN_API_TOKEN` is not configured.
+- Provider base URLs are validated on settings updates and before outbound model calls:
+  - allowlist enforcement (`PROVIDER_BASE_URL_ALLOWLIST`)
+  - scheme restrictions (`https` by default)
+  - local/private-network blocking and per-request DNS revalidation checks for outbound runtime calls
+- Upload and archive safety guards are enforced:
+  - multipart upload requires `Content-Length` and enforces file-count, per-file size, and total request size limits
+  - ZIP member count, per-member uncompressed size, total decompressed size, and compression-ratio guards
+- Processing logs redact sensitive payload and text fields, and trim endpoints enforce retention caps from runtime config.
+- Compose hardening defaults:
+  - host ports bind to `127.0.0.1` unless `HOST_BIND_IP` override is set
+  - `api`, `worker`, and `frontend` drop all Linux capabilities and set `no-new-privileges`
+  - backend and frontend containers run as non-root users by default
+
 ## Validation Checklist
 
 After operational or configuration changes, verify:
diff --git a/docker-compose.yml b/docker-compose.yml
index 523ebcf..57bb3a2 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -6,7 +6,7 @@ services:
       POSTGRES_PASSWORD: dcm
       POSTGRES_DB: dcm
     ports:
-      - "5432:5432"
+      - "${HOST_BIND_IP:-127.0.0.1}:5432:5432"
     volumes:
       - db-data:/var/lib/postgresql/data
     healthcheck:
@@ -18,7 +18,7 @@ services:
   redis:
     image: redis:7-alpine
     ports:
-      - "6379:6379"
+      - "${HOST_BIND_IP:-127.0.0.1}:6379:6379"
     volumes:
       - redis-data:/data
 
@@ -29,7 +29,7 @@ services:
       - "--api-key=dcm-typesense-key"
       - "--enable-cors"
     ports:
-      - "8108:8108"
+      - "${HOST_BIND_IP:-127.0.0.1}:8108:8108"
     volumes:
       - typesense-data:/data
 
@@ -41,16 +41,25 @@ services:
       DATABASE_URL: postgresql+psycopg://dcm:dcm@db:5432/dcm
       REDIS_URL: redis://redis:6379/0
       STORAGE_ROOT: /data/storage
+      ADMIN_API_TOKEN: ${ADMIN_API_TOKEN:?ADMIN_API_TOKEN must be set}
+      USER_API_TOKEN: ${USER_API_TOKEN:?USER_API_TOKEN must be set}
+      PROVIDER_BASE_URL_ALLOWLIST: '${PROVIDER_BASE_URL_ALLOWLIST:-["api.openai.com"]}'
+      PROVIDER_BASE_URL_ALLOW_HTTP: ${PROVIDER_BASE_URL_ALLOW_HTTP:-false}
+      PROVIDER_BASE_URL_ALLOW_PRIVATE_NETWORK: ${PROVIDER_BASE_URL_ALLOW_PRIVATE_NETWORK:-false}
       OCR_LANGUAGES: eng,deu
-      PUBLIC_BASE_URL: http://192.168.2.5:8000
-      CORS_ORIGINS: '["http://localhost:5173","http://localhost:3000","http://192.168.2.5:5173"]'
+      PUBLIC_BASE_URL: ${PUBLIC_BASE_URL:-http://localhost:8000}
+      CORS_ORIGINS: '${CORS_ORIGINS:-["http://localhost:5173","http://localhost:3000"]}'
       TYPESENSE_PROTOCOL: http
       TYPESENSE_HOST: typesense
       TYPESENSE_PORT: 8108
       TYPESENSE_API_KEY: dcm-typesense-key
       TYPESENSE_COLLECTION_NAME: documents
     ports:
-      - "8000:8000"
+      - "${HOST_BIND_IP:-127.0.0.1}:8000:8000"
+    security_opt:
+      - no-new-privileges:true
+    cap_drop:
+      - ALL
     volumes:
       - ./backend/app:/app/app
       - dcm-storage:/data
@@ -71,6 +80,11 @@ services:
       DATABASE_URL: postgresql+psycopg://dcm:dcm@db:5432/dcm
       REDIS_URL: redis://redis:6379/0
       STORAGE_ROOT: /data/storage
+      ADMIN_API_TOKEN: ${ADMIN_API_TOKEN:?ADMIN_API_TOKEN must be set}
+      USER_API_TOKEN: ${USER_API_TOKEN:?USER_API_TOKEN must be set}
+      PROVIDER_BASE_URL_ALLOWLIST: '${PROVIDER_BASE_URL_ALLOWLIST:-["api.openai.com"]}'
+      PROVIDER_BASE_URL_ALLOW_HTTP: ${PROVIDER_BASE_URL_ALLOW_HTTP:-false}
+      PROVIDER_BASE_URL_ALLOW_PRIVATE_NETWORK: ${PROVIDER_BASE_URL_ALLOW_PRIVATE_NETWORK:-false}
       OCR_LANGUAGES: eng,deu
       PUBLIC_BASE_URL: http://localhost:8000
       TYPESENSE_PROTOCOL: http
@@ -81,6 +95,10 @@ services:
     volumes:
       - ./backend/app:/app/app
       - dcm-storage:/data
+    security_opt:
+      - no-new-privileges:true
+    cap_drop:
+      - ALL
     depends_on:
       db:
         condition: service_healthy
@@ -93,9 +111,9 @@ services:
     build:
       context: ./frontend
     environment:
-      VITE_API_BASE: http://192.168.2.5:8000/api/v1
+      VITE_API_BASE: ${VITE_API_BASE:-http://localhost:8000/api/v1}
     ports:
-      - "5173:5173"
+      - "${HOST_BIND_IP:-127.0.0.1}:5173:5173"
     volumes:
       - ./frontend/src:/app/src
       - ./frontend/index.html:/app/index.html
@@ -103,6 +121,10 @@ services:
     depends_on:
       api:
         condition: service_started
+    security_opt:
+      - no-new-privileges:true
+    cap_drop:
+      - ALL
 
 volumes:
   db-data:
diff --git a/frontend/Dockerfile b/frontend/Dockerfile
index b6a9a31..859380d 100644
--- a/frontend/Dockerfile
+++ b/frontend/Dockerfile
@@ -3,14 +3,17 @@ FROM node:22-alpine
 WORKDIR /app
 
 COPY package.json /app/package.json
-RUN npm install
+COPY package-lock.json /app/package-lock.json
+RUN npm ci
 
-COPY tsconfig.json /app/tsconfig.json
-COPY tsconfig.node.json /app/tsconfig.node.json
-COPY vite.config.ts /app/vite.config.ts
-COPY index.html /app/index.html
-COPY src /app/src
+COPY --chown=node:node tsconfig.json /app/tsconfig.json
+COPY --chown=node:node tsconfig.node.json /app/tsconfig.node.json
+COPY --chown=node:node vite.config.ts /app/vite.config.ts
+COPY --chown=node:node index.html /app/index.html
+COPY --chown=node:node src /app/src
 
 EXPOSE 5173
 
+USER node
+
 CMD ["npm", "run", "dev", "--", "--host", "0.0.0.0", "--port", "5173"]