feat: Implement initial Langflow Assistant API with streaming support by Cristhianzl · Pull Request #11374 · langflow-ai/langflow (original) (raw)

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Walkthrough

This PR introduces a new Langflow Agentic Module backend with API endpoints to execute named flows, check assistant configuration, and validate generated component code. It includes flow execution services with validation and retry logic, provider and model management, helper utilities for code extraction and error handling, and comprehensive test coverage.

Changes

Sequence Diagram(s)

sequenceDiagram participant Client participant APIRouter as API Router
(assist endpoint) participant ProviderSvc as Provider
Service participant AssistSvc as Assistant
Service participant FlowExec as Flow
Executor participant Validation as Code
Validation

Client->>APIRouter: POST /agentic/assist<br/>(flow_id, input_value)
APIRouter->>ProviderSvc: get_enabled_providers_for_user()
ProviderSvc-->>APIRouter: enabled providers list
APIRouter->>ProviderSvc: get_default_provider()
ProviderSvc-->>APIRouter: provider name
APIRouter->>ProviderSvc: check_api_key(provider)
ProviderSvc-->>APIRouter: API key
APIRouter->>AssistSvc: execute_flow_with_validation()
Note over AssistSvc: Attempt 1 (max_retries=3)
AssistSvc->>FlowExec: execute_flow_file()
FlowExec-->>AssistSvc: response text
AssistSvc->>Validation: extract_python_code()
Validation-->>AssistSvc: code block
AssistSvc->>Validation: validate_component_code()
alt Code is valid
    Validation-->>AssistSvc: ValidationResult(is_valid=True)
    AssistSvc-->>APIRouter: result with validation
else Code is invalid
    Validation-->>AssistSvc: ValidationResult(is_valid=False, error)
    Note over AssistSvc: Attempt 2+ with error context
    AssistSvc->>FlowExec: execute_flow_file()<br/>(retry prompt with error)
    FlowExec-->>AssistSvc: corrected response
    AssistSvc->>Validation: validate_component_code()
    Validation-->>AssistSvc: ValidationResult(is_valid=True)
    AssistSvc-->>APIRouter: result with validation
end
APIRouter-->>Client: 200 OK<br/>{validated, class_name, code}

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sequenceDiagram participant Client participant APIRouter as API Router
(assist_stream) participant ProviderSvc as Provider
Service participant AssistSvc as Assistant
Service participant FlowExec as Flow
Executor participant SSEHelper as SSE
Formatter

Client->>APIRouter: POST /agentic/assist_stream
APIRouter->>ProviderSvc: get_enabled_providers_for_user()
ProviderSvc-->>APIRouter: enabled providers
APIRouter->>AssistSvc: execute_flow_with_validation_streaming()
AssistSvc->>SSEHelper: format_progress_event(generating)
SSEHelper-->>AssistSvc: SSE data line
AssistSvc-->>APIRouter: progress event
APIRouter-->>Client: SSE event
AssistSvc->>FlowExec: execute_flow_file_streaming()
loop Token streaming
    FlowExec-->>AssistSvc: token chunks
    AssistSvc-->>APIRouter: token events
    APIRouter-->>Client: SSE token data
end
AssistSvc->>SSEHelper: format_progress_event(extracting_code)
AssistSvc-->>APIRouter: progress event
APIRouter-->>Client: SSE event
AssistSvc->>SSEHelper: format_progress_event(validating)
AssistSvc-->>APIRouter: progress event
APIRouter-->>Client: SSE event
alt Validation passes
    AssistSvc->>SSEHelper: format_complete_event(validated)
    SSEHelper-->>AssistSvc: complete event
    AssistSvc-->>APIRouter: complete event
    APIRouter-->>Client: SSE complete
else Validation fails (retry < max)
    AssistSvc->>SSEHelper: format_progress_event(retrying)
    AssistSvc-->>APIRouter: retry event
    APIRouter-->>Client: SSE event
    AssistSvc->>FlowExec: execute_flow_file_streaming()<br/>(error context)
    loop Retry token streaming
        FlowExec-->>AssistSvc: tokens
        AssistSvc-->>APIRouter: token events
        APIRouter-->>Client: SSE tokens
    end
    AssistSvc->>SSEHelper: format_complete_event(validated)
    AssistSvc-->>APIRouter: complete event
    APIRouter-->>Client: SSE complete
else Max retries exhausted
    AssistSvc->>SSEHelper: format_complete_event(validated=False, error)
    SSEHelper-->>AssistSvc: complete event
    AssistSvc-->>APIRouter: complete event
    APIRouter-->>Client: SSE complete with error
end

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Estimated code review effort

🎯 4 (Complex) | ⏱️ ~55 minutes

🚥 Pre-merge checks | ✅ 6 | ❌ 1 ❌ Failed checks (1 warning)

✅ Passed checks (6 passed)

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✨ Finishing touches 🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch cz/agentic-api

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