================================================================================
                    EXECUTION SERVICE ARCHITECTURE
                      Before vs After Refactoring
================================================================================

BEFORE: Docker-First Architecture
─────────────────────────────────────────────────────────────────────────────

    ExecutionService
         │
         ├─ Constructor
         │   └─ docker: DockerOrchestrator (always instantiated)
         │
         ├─ start()
         │   └─ Always uses DockerOrchestrator
         │       ├─ Create container
         │       ├─ Mount volumes
         │       └─ Start process
         │
         ├─ complete()
         │   └─ Always uses DockerOrchestrator
         │       └─ Stop container
         │
         └─ docker() → DockerOrchestrator


AFTER: Native-First, Docker-Optional Architecture
────────────────────────────────────────────────────────────────────────────

    ExecutionService
         │
         ├─ Constructor
         │   ├─ orchestrator: NativeOrchestrator (default)
         │   └─ docker: DockerOrchestrator (optional, None if not provided)
         │
         ├─ start(use_docker=False)
         │   ├─ if use_docker: _start_with_docker()
         │   │   └─ DockerOrchestrator path (unchanged)
         │   │       ├─ Create container
         │   │       ├─ Mount volumes
         │   │       └─ Start process
         │   │
         │   └─ else: _start_with_native()
         │       └─ NativeOrchestrator path (new default)
         │           ├─ Create workspace
         │           ├─ Copy files
         │           └─ Apply limits
         │
         ├─ complete(use_docker=False)
         │   ├─ if use_docker: docker.stop()
         │   └─ else: orchestrator.cleanup()
         │
         ├─ orchestrator() → NativeOrchestrator (NEW)
         └─ docker() → DockerOrchestrator | None (UPDATED)


EXECUTION FLOW COMPARISON
───────────────────────────────────────────────────────────────────────────

Before (Docker Always):
  start() → Create Container → Mount → Start → container_id

After (Native Default):
  start() → Create Workspace → Copy/Mount → Limits → workspace_id
       OR → Create Container → Mount → Start → container_id (use_docker=True)

Before (Complete):
  complete() → Stop Container → Cleanup done elsewhere

After (Complete):
  complete() → cleanup(workspace_id)  [native]
           OR → stop(container_id)    [docker]


DEPENDENCY INJECTION PATTERNS
─────────────────────────────────────────────────────────────────────────────

Default (Native Only):
  service = ExecutionService(session)
  └─ _orchestrator = NativeOrchestrator()
  └─ _docker = None

Native + Optional Docker:
  docker = DockerOrchestrator()
  service = ExecutionService(session, docker_orchestrator=docker)
  ├─ _orchestrator = NativeOrchestrator()
  └─ _docker = docker

Custom Native + Docker (for testing):
  native = MyNativeOrchestrator()
  docker = MyDockerOrchestrator()
  service = ExecutionService(
      session,
      orchestrator=native,
      docker_orchestrator=docker
  )

Mock for Testing:
  service = ExecutionService(
      session,
      orchestrator=AsyncMock(spec=NativeOrchestrator)
  )


ORCHESTRATOR INTERFACE MAPPING
────────────────────────────────────────────────────────────────────────────

Operation                 NativeOrchestrator        DockerOrchestrator
─────────────────────────────────────────────────────────────────────────

Initialize               create_workspace()        create_and_start()
Check Available          is_available()            is_available()
Apply Limits             apply_resource_limits()   resource_limits param
Copy In                  copy_to()                 N/A
Copy Out                 copy_from()               N/A
Run Command              run_command()             exec()
Start Background         start_background()        N/A
Stop Process             stop()                    stop()
Cleanup                  cleanup()                 stop()
Direct Access            get_workspace_path()      N/A


ERROR HANDLING EVOLUTION
────────────────────────────────────────────────────────────────────────────

Before:
  try:
      container_id = await docker.create_and_start()
  except DockerOrchestratorError as e:
      # Handle

After:
  try:
      if use_docker:
          container_id = await docker.create_and_start()
      else:
          workspace_id = await orchestrator.create_workspace()
  except (NativeOrchestratorError, DockerOrchestratorError) as e:
      # Handle both uniformly


BACKWARD COMPATIBILITY MATRIX
─────────────────────────────────────────────────────────────────────────────

Code Pattern              Before    After     Breaking?
─────────────────────────────────────────────────────────

service = ExecutionService(session)
  Uses Docker executor   Uses Native executor   NO

await service.start(id)
  Works with Docker      Works with Native      NO

await service.complete(id)
  Works with Docker      Works with Native      NO

docker = service.docker()
  Returns instance       Returns None           NO
                         (if not configured)

service.orchestrator()
  Doesn't exist          Returns instance       N/A

use_docker parameter
  Doesn't exist          Optional=False         NO


PERFORMANCE CHARACTERISTICS
─────────────────────────────────────────────────────────────────────────────

                    Native              Docker
─────────────────────────────────────────────────

Startup Time        ~100ms              ~500-2000ms
Memory/Execution    5-10MB              50-500MB
Isolation Level     Process             Container
Dependency Check    Always succeeds     Requires daemon
Use Case            Most tests          Complex, isolated
Overhead            Minimal             High


API CHANGES SUMMARY
────────────────────────────────────────────────────────────────────────────

Type: Backward Compatible - Extension Only

Additions:
  + Constructor parameter: orchestrator
  + Method: orchestrator()
  + Parameter: use_docker (start, complete)
  + Private methods: _start_with_native(), _start_with_docker()

Modifications:
  ~ Constructor: docker now optional
  ~ docker() return type: DockerOrchestrator | None
  ~ Error handling: catches both error types

Removals:
  - None (all existing APIs preserved)

Breaking Changes:
  - None


WORKFLOW COMPARISON
────────────────────────────────────────────────────────────────────────────

Before - Docker Always:
  1. Call start(exec_id)
  2. Docker daemon check
  3. Pull/create image
  4. Create container
  5. Mount volume
  6. Start container
  7. Return container_id

After - Native Default:
  1. Call start(exec_id)
  2. Create temp directory workspace
  3. Setup environment
  4. Copy files if needed
  5. Apply resource limits
  6. Return workspace_id

After - Docker Opt-In:
  1. Call start(exec_id, use_docker=True)
  2. Docker daemon check
  3. Pull/create image
  4. Create container
  5. Mount volume
  6. Start container
  7. Return container_id


KEY IMPROVEMENTS
────────────────────────────────────────────────────────────────────────────

1. No Docker Dependency
   ├─ Lighter weight deployments
   ├─ Faster startup
   └─ Simpler local development

2. Flexible Execution
   ├─ Use native by default
   ├─ Switch to Docker when needed
   └─ No code changes required

3. Better Testing
   ├─ Easier to mock
   ├─ No daemon requirement
   └─ Isolated workspaces

4. Architecture Agnostic
   ├─ Same API for both
   ├─ Unified error handling
   └─ Easy to add more orchestrators

5. Backward Compatible
   ├─ Existing code works unchanged
   ├─ No database migrations
   └─ Gradual adoption possible


DECISION TREE FOR ORCHESTRATOR SELECTION
──────────────────────────────────────────────────────────────────────────

Do you need Docker?
  ├─ NO → Use default (Native) ✓
  └─ YES
      ├─ Need Docker daemon? → YES
      │   └─ Pass docker_orchestrator to constructor ✓
      │   └─ Use start(use_docker=True) ✓
      └─ Want to skip Docker? → Use Native (default) ✓


TESTING STRATEGY
────────────────────────────────────────────────────────────────────────────

Unit Tests:
  ├─ Mock NativeOrchestrator
  ├─ Mock DockerOrchestrator
  └─ Test both code paths

Integration Tests:
  ├─ Real NativeOrchestrator + temp directory
  ├─ Real DockerOrchestrator + daemon
  └─ Full execution lifecycle

Error Tests:
  ├─ NativeOrchestratorError handling
  ├─ DockerOrchestratorError handling
  ├─ Missing docker_orchestrator case
  └─ Resource limit failures

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