# PR: Arrow 57 / DataFusion 51 / Lance 2 + BlasGraph Algebra + SPO Triple Store

.claude/LANGGRAPH_CRATE_STRUCTURE.md

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+# Recommended Crate Structure
+
+> How the Rust crates should map to Python LangGraph's package structure.
+
+---
+
+## Python LangGraph Package Layout
+
+```
+langgraph (pip install langgraph)
+├── langgraph.graph          # StateGraph, MessageGraph
+├── langgraph.pregel         # Core execution engine (Pregel)
+├── langgraph.channels       # State channels
+├── langgraph.managed        # Managed values
+├── langgraph.func           # Functional API (@task, @entrypoint)
+├── langgraph.types          # Shared types (Command, Send, Interrupt, etc.)
+├── langgraph.constants      # START, END
+├── langgraph.errors         # Error types
+├── langgraph.config         # Config utilities
+├── langgraph.runtime        # Runtime context
+├── langgraph._internal      # Private implementation details
+
+langgraph-prebuilt (pip install langgraph-prebuilt)
+├── langgraph.prebuilt.chat_agent_executor  # create_react_agent
+├── langgraph.prebuilt.tool_node            # ToolNode, tools_condition
+├── langgraph.prebuilt.tool_validator       # ValidationNode
+├── langgraph.prebuilt.interrupt            # HumanInterrupt types
+
+langgraph-checkpoint (pip install langgraph-checkpoint)
+├── langgraph.checkpoint.base     # BaseCheckpointSaver, Checkpoint
+├── langgraph.checkpoint.memory   # MemorySaver
+├── langgraph.checkpoint.serde    # Serialization (jsonplus, msgpack)
+├── langgraph.store.base          # BaseStore, Item
+├── langgraph.store.memory        # InMemoryStore
+├── langgraph.cache               # BaseCache, InMemoryCache
+
+langgraph-checkpoint-postgres
+├── langgraph.checkpoint.postgres   # PostgresSaver
+├── langgraph.store.postgres        # PostgresStore
+
+langgraph-checkpoint-sqlite
+├── langgraph.checkpoint.sqlite     # SqliteSaver
+├── langgraph.store.sqlite          # SqliteStore
+```
+
+---
+
+## Current Rust Crate Layout
+
+```
+rs-graph-llm/
+├── graph-flow/                    # Core framework (≈ langgraph + langgraph-prebuilt)
+│   ├── src/
+│   │   ├── lib.rs                 # Re-exports
+│   │   ├── graph.rs               # Graph, GraphBuilder, edges
+│   │   ├── task.rs                # Task trait, NextAction, TaskResult
+│   │   ├── context.rs             # Context, ChatHistory
+│   │   ├── error.rs               # GraphError
+│   │   ├── storage.rs             # Session, SessionStorage trait, InMemory
+│   │   ├── runner.rs              # FlowRunner
+│   │   ├── streaming.rs           # StreamingRunner, StreamChunk, StreamMode
+│   │   ├── compat.rs              # StateGraph, START/END, Command
+│   │   ├── subgraph.rs            # SubgraphTask
+│   │   ├── fanout.rs              # FanOutTask (≈ Send)
+│   │   ├── typed_context.rs       # TypedContext<S>
+│   │   ├── channels.rs            # Channels, ChannelReducer
+│   │   ├── retry.rs               # RetryPolicy, BackoffStrategy
+│   │   ├── run_config.rs          # RunConfig, BreakpointConfig
+│   │   ├── tool_result.rs         # ToolResult
+│   │   ├── react_agent.rs         # create_react_agent()
+│   │   ├── task_registry.rs       # TaskRegistry
+│   │   ├── thinking.rs            # Thinking graph (custom)
+│   │   ├── mcp_tool.rs            # MCP tool integration (custom)
+│   │   ├── lance_storage.rs       # LanceSessionStorage
+│   │   ├── storage_postgres.rs    # PostgresSessionStorage
+│   │   └── agents/
+│   │       ├── agent_card.rs      # AgentCard YAML
+│   │       └── langgraph_import.rs # JSON import
+│   └── Cargo.toml
+│
+├── graph-flow-server/             # HTTP API (≈ langgraph-api)
+│   ├── src/lib.rs
+│   └── Cargo.toml
+│
+├── examples/                      # Example applications
+├── insurance-claims-service/      # Full example app
+├── recommendation-service/        # Full example app
+└── medical-document-service/      # Full example app
+```
+
+---
+
+## Recommended Rust Crate Layout (Target)
+
+```
+rs-graph-llm/
+├── graph-flow/                        # Core engine (≈ langgraph core)
+│   ├── src/
+│   │   ├── lib.rs
+│   │   │
+│   │   ├── # ─── Graph Construction ───
+│   │   ├── graph.rs                   # Graph, GraphBuilder, Edge, ConditionalEdgeSet
+│   │   ├── compat.rs                  # StateGraph, START/END, Command, RoutingDecision
+│   │   │
+│   │   ├── # ─── Task System ───
+│   │   ├── task.rs                    # Task trait, NextAction, TaskResult
+│   │   ├── subgraph.rs               # SubgraphTask
+│   │   ├── fanout.rs                  # FanOutTask (≈ Send)
+│   │   │
+│   │   ├── # ─── State Management ───
+│   │   ├── context.rs                 # Context, ChatHistory, MessageRole
+│   │   ├── typed_context.rs           # TypedContext<S>, State trait
+│   │   ├── channels.rs               # Channels, ChannelReducer, ChannelConfig
+│   │   │
+│   │   ├── # ─── Execution Engine ───
+│   │   ├── runner.rs                  # FlowRunner (run, run_batch, run_with_config)
+│   │   ├── streaming.rs              # StreamingRunner, StreamChunk, StreamMode
+│   │   ├── run_config.rs             # RunConfig, BreakpointConfig
+│   │   ├── retry.rs                  # RetryPolicy, BackoffStrategy
+│   │   │
+│   │   ├── # ─── Storage / Checkpointing ───
+│   │   ├── storage.rs                # Session, SessionStorage, InMemorySessionStorage
+│   │   ├── storage_postgres.rs       # PostgresSessionStorage
+│   │   ├── lance_storage.rs          # LanceSessionStorage (time-travel)
+│   │   │
+│   │   ├── # ─── Store (NEW — Long-term Memory) ───
+│   │   ├── store/                    # NEW module
+│   │   │   ├── mod.rs               # BaseStore trait, Item, SearchItem
+│   │   │   ├── memory.rs            # InMemoryStore
+│   │   │   └── lance.rs             # LanceStore (backed by lance-graph)
+│   │   │
+│   │   ├── # ─── Errors ───
+│   │   ├── error.rs                  # GraphError, Result
+│   │   │
+│   │   ├── # ─── Prebuilt Components ───
+│   │   ├── prebuilt/                 # NEW submodule (was flat files)
+│   │   │   ├── mod.rs
+│   │   │   ├── react_agent.rs        # create_react_agent() (moved from react_agent.rs)
+│   │   │   ├── tool_node.rs          # ToolNode, tools_condition (NEW)
+│   │   │   ├── interrupt.rs          # HumanInterrupt types (NEW)
+│   │   │   └── validation.rs         # ValidationNode (NEW)
+│   │   │
+│   │   ├── # ─── Tool System ───
+│   │   ├── tool_result.rs            # ToolResult
+│   │   ├── mcp_tool.rs               # McpToolTask, MockMcpToolTask
+│   │   │
+│   │   ├── # ─── Agent Cards ───
+│   │   ├── agents/
+│   │   │   ├── agent_card.rs         # AgentCard, compile_agent_card
+│   │   │   └── langgraph_import.rs   # LangGraph JSON import
+│   │   ├── task_registry.rs          # TaskRegistry
+│   │   │
+│   │   └── # ─── Custom (Our Additions) ───
+│   │       └── thinking.rs           # Thinking graph
+│   │
+│   └── Cargo.toml
+│
+├── graph-flow-server/                 # HTTP API server (≈ langgraph-api)
+│   ├── src/
+│   │   ├── lib.rs                    # Router, endpoints
+│   │   ├── sse.rs                    # SSE streaming endpoint (NEW)
+│   │   └── middleware.rs             # Auth, CORS, logging (NEW)
+│   └── Cargo.toml
+│
+├── graph-flow-macros/                 # Proc macros (NEW — ≈ langgraph.func)
+│   ├── src/lib.rs                    # #[task], #[entrypoint] macros
+│   └── Cargo.toml
+│
+├── examples/
+├── insurance-claims-service/
+├── recommendation-service/
+└── medical-document-service/
+```
+
+---
+
+## Mapping: Python Package → Rust Crate
+
+| Python Package | Rust Crate | Status |
+|---------------|-----------|--------|
+| `langgraph` (core) | `graph-flow` | EXISTS |
+| `langgraph-prebuilt` | `graph-flow` (prebuilt/ submodule) | PARTIAL |
+| `langgraph-checkpoint` (base) | `graph-flow` (storage.rs) | EXISTS |
+| `langgraph-checkpoint-postgres` | `graph-flow` (storage_postgres.rs, feature-gated) | EXISTS |
+| `langgraph-checkpoint-sqlite` | Not planned (Postgres + Lance sufficient) | SKIP |
+| `langgraph.store` | `graph-flow` (store/ submodule) | NEW |
+| `langgraph-api` / `langgraph-cli` | `graph-flow-server` | EXISTS |
+| `langgraph.func` (@task/@entrypoint) | `graph-flow-macros` | NEW |
+
+---
+
+## Mapping: Python Module → Rust Module
+
+| Python Module | Rust Module | File |
+|--------------|------------|------|
+| `langgraph.graph.state.StateGraph` | `compat::StateGraph` | `compat.rs` |
+| `langgraph.graph.state.CompiledStateGraph` | `graph::Graph` | `graph.rs` |
+| `langgraph.graph.message` | `context::ChatHistory` | `context.rs` |
+| `langgraph.graph._branch` | `graph::ConditionalEdgeSet` | `graph.rs` |
+| `langgraph.pregel.main.Pregel` | `graph::Graph` + `runner::FlowRunner` | `graph.rs` + `runner.rs` |
+| `langgraph.pregel.main.NodeBuilder` | `graph::GraphBuilder` | `graph.rs` |
+| `langgraph.pregel.protocol` | `task::Task` trait | `task.rs` |
+| `langgraph.pregel.remote.RemoteGraph` | `graph-flow-server` (server side) | `lib.rs` |
+| `langgraph.channels.*` | `channels::*` | `channels.rs` |
+| `langgraph.types.Command` | `compat::Command` | `compat.rs` |
+| `langgraph.types.Send` | `fanout::FanOutTask` | `fanout.rs` |
+| `langgraph.types.RetryPolicy` | `retry::RetryPolicy` | `retry.rs` |
+| `langgraph.types.StreamMode` | `streaming::StreamMode` | `streaming.rs` |
+| `langgraph.types.Interrupt` | `task::NextAction::WaitForInput` | `task.rs` |
+| `langgraph.errors.*` | `error::GraphError` | `error.rs` |
+| `langgraph.checkpoint.base` | `storage::SessionStorage` | `storage.rs` |
+| `langgraph.checkpoint.memory` | `storage::InMemorySessionStorage` | `storage.rs` |
+| `langgraph.checkpoint.postgres` | `storage_postgres::PostgresSessionStorage` | `storage_postgres.rs` |
+| `langgraph.store.base` | `store::BaseStore` (NEW) | `store/mod.rs` |
+| `langgraph.store.memory` | `store::InMemoryStore` (NEW) | `store/memory.rs` |
+| `langgraph.prebuilt.chat_agent_executor` | `prebuilt::react_agent` | `react_agent.rs` |
+| `langgraph.prebuilt.tool_node` | `prebuilt::tool_node` (NEW) | `prebuilt/tool_node.rs` |
+| `langgraph.prebuilt.interrupt` | `prebuilt::interrupt` (NEW) | `prebuilt/interrupt.rs` |
+| `langgraph.func.task` | `graph-flow-macros` `#[task]` (NEW) | `macros/src/lib.rs` |
+| `langgraph.func.entrypoint` | `graph-flow-macros` `#[entrypoint]` (NEW) | `macros/src/lib.rs` |
+| `langgraph.runtime` | TBD | — |
+
+---
+
+## Feature Flags
+
+```toml
+[features]
+default = ["memory"]
+memory = []                    # InMemorySessionStorage, InMemoryStore
+postgres = ["sqlx"]            # PostgresSessionStorage
+lance = ["lance"]              # LanceSessionStorage, LanceStore
+mcp = ["rmcp"]                 # McpToolTask
+rig = ["rig-core"]             # Rig LLM integration
+macros = ["graph-flow-macros"] # #[task], #[entrypoint] proc macros
+server = ["axum", "tower"]     # HTTP server components
+```
+
+---
+
+## Key Architectural Differences from Python
+
+1. **No Runnable abstraction**: Python LangGraph builds on LangChain's `Runnable` protocol. Rust uses the `Task` trait directly — simpler and more performant.
+
+2. **No channel-per-field model**: Python LangGraph creates one channel per state field. Rust uses `Context` (DashMap) for most cases, with explicit `Channels` for reducer semantics when needed.
+
+3. **No Pregel superstep model**: Python uses a Pregel-inspired superstep execution where all triggered nodes run per step. Rust uses sequential task execution with explicit edges — simpler but less parallel.
+
+4. **Session = Checkpoint**: Python separates Checkpoint (state) from Thread (session). Rust combines them into `Session` with context + position.
+
+5. **Async-native**: Python has sync + async variants for everything. Rust is async-native — no sync wrappers needed (use `tokio::runtime::Runtime::block_on()` for sync callers).
+
+6. **Storage integration**: Python has separate checkpoint + store packages. Rust integrates both into `graph-flow` with feature flags, and lance-graph provides the vector search backend directly.