Graph Orchestration Architecture¶

Overview¶

DeepCritical implements a graph-based orchestration system for research workflows using Pydantic AI agents as nodes. This enables better parallel execution, conditional routing, and state management compared to simple agent chains.

Graph Patterns¶

Iterative Research Graph¶

The iterative research graph follows this pattern:

[Input] → [Thinking] → [Knowledge Gap] → [Decision: Complete?]
                                              ↓ No          ↓ Yes
                                    [Tool Selector]    [Writer]
                                              ↓
                                    [Execute Tools] → [Loop Back]

Node IDs: thinking → knowledge_gap → continue_decision → tool_selector/writer → execute_tools → (loop back to thinking)

Special Node Handling: - execute_tools: State node that uses search_handler to execute searches and add evidence to workflow state - continue_decision: Decision node that routes based on research_complete flag from KnowledgeGapOutput

Deep Research Graph¶

The deep research graph follows this pattern:

[Input] → [Planner] → [Store Plan] → [Parallel Loops] → [Collect Drafts] → [Synthesizer]
                                        ↓         ↓         ↓
                                     [Loop1]  [Loop2]  [Loop3]

Node IDs: planner → store_plan → parallel_loops → collect_drafts → synthesizer

Special Node Handling: - planner: Agent node that creates ReportPlan with report outline - store_plan: State node that stores ReportPlan in context for parallel loops - parallel_loops: Parallel node that executes IterativeResearchFlow instances for each section - collect_drafts: State node that collects section drafts from parallel loops - synthesizer: Agent node that calls LongWriterAgent.write_report() directly with ReportDraft

Deep Research¶


sequenceDiagram
    actor User
    participant GraphOrchestrator
    participant InputParser
    participant GraphBuilder
    participant GraphExecutor
    participant Agent
    participant BudgetTracker
    participant WorkflowState

    User->>GraphOrchestrator: run(query)
    GraphOrchestrator->>InputParser: detect_research_mode(query)
    InputParser-->>GraphOrchestrator: mode (iterative/deep)
    GraphOrchestrator->>GraphBuilder: build_graph(mode)
    GraphBuilder-->>GraphOrchestrator: ResearchGraph
    GraphOrchestrator->>WorkflowState: init_workflow_state()
    GraphOrchestrator->>BudgetTracker: create_budget()
    GraphOrchestrator->>GraphExecutor: _execute_graph(graph)
    
    loop For each node in graph
        GraphExecutor->>Agent: execute_node(agent_node)
        Agent->>Agent: process_input
        Agent-->>GraphExecutor: result
        GraphExecutor->>WorkflowState: update_state(result)
        GraphExecutor->>BudgetTracker: add_tokens(used)
        GraphExecutor->>BudgetTracker: check_budget()
        alt Budget exceeded
            GraphExecutor->>GraphOrchestrator: emit(error_event)
        else Continue
            GraphExecutor->>GraphOrchestrator: emit(progress_event)
        end
    end
    
    GraphOrchestrator->>User: AsyncGenerator[AgentEvent]

Iterative Research¶

sequenceDiagram
    participant IterativeFlow
    participant ThinkingAgent
    participant KnowledgeGapAgent
    participant ToolSelector
    participant ToolExecutor
    participant JudgeHandler
    participant WriterAgent

    IterativeFlow->>IterativeFlow: run(query)
    
    loop Until complete or max_iterations
        IterativeFlow->>ThinkingAgent: generate_observations()
        ThinkingAgent-->>IterativeFlow: observations
        
        IterativeFlow->>KnowledgeGapAgent: evaluate_gaps()
        KnowledgeGapAgent-->>IterativeFlow: KnowledgeGapOutput
        
        alt Research complete
            IterativeFlow->>WriterAgent: create_final_report()
            WriterAgent-->>IterativeFlow: final_report
        else Gaps remain
            IterativeFlow->>ToolSelector: select_agents(gap)
            ToolSelector-->>IterativeFlow: AgentSelectionPlan
            
            IterativeFlow->>ToolExecutor: execute_tool_tasks()
            ToolExecutor-->>IterativeFlow: ToolAgentOutput[]
            
            IterativeFlow->>JudgeHandler: assess_evidence()
            JudgeHandler-->>IterativeFlow: should_continue
        end
    end

Graph Structure¶

Nodes¶

Graph nodes represent different stages in the research workflow:

Agent Nodes: Execute Pydantic AI agents
Input: Prompt/query
Output: Structured or unstructured response
Examples: KnowledgeGapAgent, ToolSelectorAgent, ThinkingAgent
State Nodes: Update or read workflow state
Input: Current state
Output: Updated state
Examples: Update evidence, update conversation history
Decision Nodes: Make routing decisions based on conditions
Input: Current state/results
Output: Next node ID
Examples: Continue research vs. complete research
Parallel Nodes: Execute multiple nodes concurrently
Input: List of node IDs
Output: Aggregated results
Examples: Parallel iterative research loops

Edges¶

Edges define transitions between nodes:

Sequential Edges: Always traversed (no condition)
From: Source node
To: Target node
Condition: None (always True)
Conditional Edges: Traversed based on condition
From: Source node
To: Target node
Condition: Callable that returns bool
Example: If research complete → go to writer, else → continue loop
Parallel Edges: Used for parallel execution branches
From: Parallel node
To: Multiple target nodes
Execution: All targets run concurrently

State Management¶

State is managed via WorkflowState using ContextVar for thread-safe isolation:

Evidence: Collected evidence from searches
Conversation: Iteration history (gaps, tool calls, findings, thoughts)
Embedding Service: For semantic search

State transitions occur at state nodes, which update the global workflow state.

Execution Flow¶

Graph Construction: Build graph from nodes and edges using create_iterative_graph() or create_deep_graph()
Graph Validation: Ensure graph is valid (no cycles, all nodes reachable) via ResearchGraph.validate_structure()
Graph Execution: Traverse graph from entry node using GraphOrchestrator._execute_graph()
Node Execution: Execute each node based on type:
Agent Nodes: Call agent.run() with transformed input
State Nodes: Update workflow state via state_updater function
Decision Nodes: Evaluate decision_function to get next node ID
Parallel Nodes: Execute all parallel nodes concurrently via asyncio.gather()
Edge Evaluation: Determine next node(s) based on edges and conditions
Parallel Execution: Use asyncio.gather() for parallel nodes
State Updates: Update state at state nodes via GraphExecutionContext.update_state()
Event Streaming: Yield AgentEvent objects during execution for UI

GraphExecutionContext¶

The GraphExecutionContext class manages execution state during graph traversal:

State: Current WorkflowState instance
Budget Tracker: BudgetTracker instance for budget enforcement
Node Results: Dictionary storing results from each node execution
Visited Nodes: Set of node IDs that have been executed
Current Node: ID of the node currently being executed

Methods: - set_node_result(node_id, result): Store result from node execution - get_node_result(node_id): Retrieve stored result - has_visited(node_id): Check if node was visited - mark_visited(node_id): Mark node as visited - update_state(updater, data): Update workflow state

Conditional Routing¶

Decision nodes evaluate conditions and return next node IDs:

Knowledge Gap Decision: If research_complete → writer, else → tool selector
Budget Decision: If budget exceeded → exit, else → continue
Iteration Decision: If max iterations → exit, else → continue

Parallel Execution¶

Parallel nodes execute multiple nodes concurrently:

Each parallel branch runs independently
Results are aggregated after all branches complete
State is synchronized after parallel execution
Errors in one branch don't stop other branches

Budget Enforcement¶

Budget constraints are enforced at decision nodes:

Token Budget: Track LLM token usage
Time Budget: Track elapsed time
Iteration Budget: Track iteration count

If any budget is exceeded, execution routes to exit node.

Error Handling¶

Errors are handled at multiple levels:

Node Level: Catch errors in individual node execution
Graph Level: Handle errors during graph traversal
State Level: Rollback state changes on error

Errors are logged and yield error events for UI.

Backward Compatibility¶

Graph execution is optional via feature flag:

USE_GRAPH_EXECUTION=true: Use graph-based execution
USE_GRAPH_EXECUTION=false: Use agent chain execution (existing)

This allows gradual migration and fallback if needed.