NeoGraph

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NeoGraph is a C++20 runtime for stateful workflows described as graphs. A graph defines executable nodes, named state channels, rules for merging writes, and edges that determine what runs next. Nodes can perform ordinary computation, call tools, or request model output. The runtime schedules those nodes, applies their writes, and, when configured with a checkpoint store, saves progress for interruption and resumption. Python bindings expose the same C++ engine.

Consider a research workflow: retrieve documents, extract findings from several documents, combine the findings, and ask a reviewer whether another retrieval round is needed. The documents and findings belong in state channels; retrieval, extraction, and review are nodes; edges select the next stage or return to retrieval. A graph makes those transitions explicit instead of hiding them in a sequence of model prompts. See the examples for research, tool use, human review, and multi-agent workflows.

How a graph changes state

Suppose a channel named count holds 2. An increment node reads 2 and returns a write proposing 3. The runtime applies that write through the channel's reducer after the scheduled node batch finishes. A downstream node in the next batch reads 3.

Committed state       Node computation          Reduced state
count = 2       ->    read 2; propose 3     ->    count = 3
                                                  |
                                            next node reads 3

The terms in that trace describe the execution model:

During a normal batch, ready nodes read the pre-batch channel state. Returning a ChannelWrite does not immediately change what a sibling node reads. After successful completion, the executor applies the results, and later steps see the updated state. In a multi-branch Send batch, each branch receives its input in an isolated state copy and merges its output afterward. This is a Pregel-style organization of work; NeoGraph's channel/reducer rules are its own contract, not a claim that it implements every Pregel feature.

Concurrent execution does not make every reducer order-independent. If two nodes append text or overwrite the same channel, write order affects the result. Use independent channels or an order-independent reducer when the workflow requires that property. Channel retention also differs from combination: an append channel can keep only a bounded suffix. See concepts and concurrency for scheduling, reducers, barriers, and cancellation.

A worked Core example

The complete C++ quickstart registers an uppercase node and compiles this topology:

__start__ -> upper -> __end__

Input channel:   text = "hello"
Node reads:      "hello"
Node returns:    ChannelWrite{"text", "HELLO"}
Reducer:         overwrite
Output channel:  text = "HELLO"

The node's computation is ordinary C++:

class UpperNode final : public neograph::graph::GraphNode {
public:
    asio::awaitable<neograph::graph::NodeOutput> run(
        neograph::graph::NodeInput input) override {
        auto text = input.state.get(neograph::graph::ChannelKey<std::string>{"text"});
        for (auto& character : text)
            character = static_cast<char>(
                std::toupper(static_cast<unsigned char>(character)));
        co_return neograph::graph::NodeOutput{{
            neograph::graph::ChannelWrite{"text", neograph::json(std::move(text))}}};
    }
    std::string get_name() const override { return "upper"; }
};

The complete source includes the headers, node registration with declared reads/writes, topology, GraphEngine::build_strict, run input, and typed output access. No model call or API key is needed. The expected output is HELLO.

Build and run

SchemaProvider is a required external SDK even when NEOGRAPH_BUILD_LLM=OFF, because Core exports its typed provider contracts. The commands below use an installed SchemaProvider runtime package: set SCHEMAPROVIDER_PREFIX to its install prefix. An explicit checkout supplied with -DNEOGRAPH_SCHEMAPROVIDER_SOURCE_DIR=../SchemaProvider takes precedence; otherwise CMake prefers an installed package and, if none is found, fetches the pinned public SDK archive. Set NEOGRAPH_FETCH_SCHEMAPROVIDER=OFF for an offline build with an installed package or explicit checkout. CMake does not guess a sibling checkout or use the removed bundled interpreter.

Prerequisites include a C++20 compiler, CMake 3.20 or newer, and the SDK's runtime dependencies, including OpenSSL and libcurl 7.88 or newer. Full builds with NeoGraph's HTTPS components require OpenSSL 3. The default build also enables SQLite and PostgreSQL integrations; the command below disables unnecessary NeoGraph components without removing SDK dependencies. Recorded SDK interface 4 checks cover Linux x86_64 and local protocol/state peers; the SDK conformance record gives their exact scope. They do not establish new Windows, macOS, ARM64, HTTP/3, hosted-vendor or WASM qualification. See troubleshooting for platform and build constraints.

git clone https://github.com/fox1245/NeoGraph.git
cd NeoGraph
cmake -S . -B build-core \
  -DCMAKE_PREFIX_PATH="$SCHEMAPROVIDER_PREFIX" \
  -DCMAKE_BUILD_TYPE=Release \
  -DNEOGRAPH_BUILD_EXAMPLES=ON \
  -DNEOGRAPH_BUILD_PROGRAM=OFF \
  -DNEOGRAPH_BUILD_LLM=OFF \
  -DNEOGRAPH_BUILD_ASYNC=OFF \
  -DNEOGRAPH_BUILD_MCP=OFF \
  -DNEOGRAPH_BUILD_A2A=OFF \
  -DNEOGRAPH_BUILD_ACP=OFF \
  -DNEOGRAPH_BUILD_POSTGRES=OFF \
  -DNEOGRAPH_BUILD_SQLITE=OFF
cmake --build build-core --parallel --target example_core_quickstart
./build-core/example_core_quickstart

Core and ProgramRuntime

GraphEngine executes a compiled graph. It owns node scheduling, state updates, routing, retries, streaming, cancellation, and graph checkpoint/resume. A compiled topology is immutable; supported generation migration occurs at controlled safe points rather than through arbitrary mutation while nodes run.

ProgramRuntime coordinates admitted Programs that can call Core graphs and manage child Programs. It adds immutable Program versions, catalogs and policy snapshots, command journals, child lineage, budgets, replay, and admitted replacement or migration. The host registers executable capabilities, compiles and admits a Program, and starts an invocation. Core remains the graph node executor.

For the research workflow, one Core graph can perform retrieval and review. A Program can call that graph, start child Programs for separate tasks, await their results, and record lifecycle transitions. Durable recovery requires the configured stores and the relevant custody contracts; an in-memory store does not survive process exit, and a journal does not by itself make an external tool effect exactly-once.

QuickJS is an optional Program authoring surface. Programs use bounded JavaScript computation and generator commands such as callCore, spawn, await, all, parallel, race, quorum, emit, checkpoint, and cancelScope. The host admits capabilities and validates generated source before publication. A model-generated proposal does not receive compiler, credential, catalog, or authority-granting access.

cmake -S . -B build-program \
  -DCMAKE_PREFIX_PATH="$SCHEMAPROVIDER_PREFIX" \
  -DCMAKE_BUILD_TYPE=Release \
  -DNEOGRAPH_BUILD_PROGRAM=ON \
  -DNEOGRAPH_BUILD_QUICKJS_CONTROL=ON \
  -DNEOGRAPH_BUILD_EXAMPLES=ON
cmake --build build-program --parallel --target example_program_quickstart
./build-program/example_program_quickstart

The Program quickstart compiles and admits a Program that calls an increment graph; its expected output is 1. It uses in-memory stores and the C++ Program builder. For JavaScript authoring and durable execution, start with the authoring boundary, recursive Programs, and strict runtime contracts.

Typed provider calls

Model calls use a validated descriptor, runtime options, and a typed request. Descriptor admission accepts closed, versioned data; it does not execute a request/response interpreter. Credentials belong in runtime options, not public descriptor files. SchemaProvider::Defaults contains typed OpenRouter routing and Responses retention controls. Images, Veo, and Decisions use separate typed clients and authorization.

#include <neograph/llm/schema_provider.h>
#include <neograph/types.h>

sp::runtime::Result first_call(
    sp::descriptor::ValidatedDescriptor descriptor,
    sp::runtime::Options options, std::string model) {
    neograph::llm::SchemaProvider provider(
        std::move(descriptor), std::move(options), {});
    std::vector<sp::Message> history{
        {.role = sp::Role::User, .parts = {sp::Text{"hi"}}}};
    auto request = neograph::make_provider_request(
        provider, std::move(model), std::move(history));
    auto prepared = provider.prepare(std::move(request));
    return provider.dispatch(std::move(prepared));
}

A prepared request is consumed once. sp::runtime::Result owns an immutable sp::Outcome containing a Completion or Failure. Keep that outcome when you need ordered messages and parts, native continuation, raw observations, stop evidence, attempt metadata, or failure partials. Usage counters are nullable: missing means unknown, while an observed zero remains zero. A usage report and a budget charge are separate records; a portable report cannot grant spending authority.

After first_call returns, use std::get_if<sp::Completion>(result.get()) to inspect a completion's messages, stop, and usage. Otherwise, std::get<sp::Failure>(*result) provides error.kind, error.safe_message, retry evidence, and the partial messages and usage in partial. For example, an absent completion.usage.output_total means the output-token count is unknown; a present counter whose value is 0 reports zero. Display text is only one view of the retained outcome.

ChatMessage, ChatTool, and JSON are portable projections. Authentic native history can stay in memory with its native checkpoint sidecar; durable native history requires a real sp::NativeArchive and protected owner-private custody. Portable JSON cannot recreate that authority. The archive authenticates custody with an independent key; it is neither encryption nor vendor-issuer authentication. Do not publish archive bodies, keys, native blobs, or raw wire observations. See the provider reference and migration guide for persistence failures, observers, managed budget banks, and replay boundaries.

The typed cutover removes CompletionParams, ChatCompletion, CompletionProvider, OpenAIProvider, RateLimitedProvider, SchemaPrimitiveRegistry, the descriptor interpreter, and the Responses WebSocket path. Recompile C++ consumers and migrate custom providers; there are no compatibility aliases. The SDK package is 0.1.0 with an alpha interface, interface revision 4, and shared ABI 4; matching revisions are required, and these numbers do not declare a stable SDK interface.

Python

pip install neograph-engine

The typed-provider API described here targets NeoGraph 0.13.0; historical wheels expose the older interface. The Python binding guide documents the source API and build prerequisites.

This graph needs no API key:

import neograph_engine as ng

@ng.node("greet")
def greet(state):
    return [ng.ChannelWrite(
        "messages",
        [{"role": "assistant", "content": f"Hello, {state.get('name')}!"}],
    )]

definition = {
    "schema_version": ng.TOPOLOGY_SCHEMA_VERSION,
    "name": "demo",
    "channels": {
        "name": {"reducer": "overwrite"},
        "messages": {"reducer": "append"},
    },
    "nodes": {"greet": {"type": "greet"}},
    "edges": [
        {"from": ng.START_NODE, "to": "greet"},
        {"from": "greet", "to": ng.END_NODE},
    ],
}

engine = ng.GraphEngine.compile(definition, ng.NodeContext())
result = engine.run(ng.RunConfig(thread_id="t1", input={"name": "NeoGraph"}))
print(result.output["channels"]["messages"]["value"])

The expected message content is Hello, NeoGraph!. Python also exposes Program compilation and execution, Hooks, runtime-context requirements, strict profiles, SQLite durability, and exact checkpoint resume. Typed providers use ProviderMessage and make_provider_request, then prepare/dispatch or invoke; outcomes retain native-owned completion or failure evidence. These messages differ from graph convenience ChatMessage values. Blocking provider calls release the GIL; asyncio.to_thread can move them off an event-loop thread. See the Python examples for complete provider and Program inputs.

Workloads and limits

NeoGraph fits workflows with explicit state transitions, branches or loops, parallel tasks, checkpoints, and human review. It can also embed small fixed graphs in a C++ application. Node computation remains the application's responsibility: the graph runtime does not train a model or replace a numerical-computing library, and a model call still has the provider's latency, availability, and cost.

The runtime supports graph-wide and per-node retry policies, bounded reusable node caching, Send fan-out, Command routing, subgraphs, state history, forks, HITL, and NodeInterrupt. MCP, A2A, ACP, gRPC, and observability integrations are optional components. Runtime context and Hooks can require particular dispatch inputs and record delivery evidence; those checks do not prove a model attended to every token. Durable native recovery and bounded forks need their original shared accounting authority; copying a snapshot cannot renew a budget.

Measure a workload with its actual nodes, provider, stores, concurrency, and build profile. Benchmarks and the performance guide describe measured configurations and limitations, not universal speed claims. Single-config builds should specify CMAKE_BUILD_TYPE=Release when measuring optimized execution. NEOGRAPH_ENABLE_NATIVE_OPTIMIZATION=ON adds host-specific tuning on supported compilers; keep it off for distributable binaries.

Build configuration and further reading

Installed consumers link only the enabled components they need:

find_package(SchemaProvider 0.1.0 CONFIG REQUIRED COMPONENTS runtime)
find_package(NeoGraph CONFIG REQUIRED)
target_link_libraries(app PRIVATE neograph::core neograph::llm SchemaProvider::runtime)

Local CI verification (Windows and WSL)

Run from the source root with Python 3.10+, CMake/CTest, and the profile's native toolchain and dependencies already provisioned. Use a VS2022 x64 developer PowerShell for Windows; provide the vcpkg transport toolchain through CMAKE_TOOLCHAIN_FILE, its private VCPKG_INSTALLED_DIR, and OpenSSL/curl runtime tools on PATH. In WSL, provision a C++20 compiler, pkg-config, libpq, SQLite, OpenSSL and HTTP/2 curl development packages. Linux native-linux and asan also require psql and NEOGRAPH_TEST_POSTGRES_URL pointing to a reachable destructive-test-only database. Provision Python pytest/pydantic/certifi; native-linux additionally needs a2a-sdk[http-server]>=1.1,<2, agent-client-protocol==0.12.1, uvicorn and httpx in the selected interpreter.

# Windows: choose a new output path for each invocation.
python scripts/verify_ci.py native-windows --work-dir build/local-windows-01 --jobs 4
python scripts/verify_ci.py install --work-dir build/local-install-01 --jobs 4 --shared --program

# WSL/Linux: provision the test database and dependencies before running.
python scripts/verify_ci.py native-linux --work-dir build/local-linux-01 --jobs 4
python scripts/verify_ci.py quickjs-performance --work-dir build/local-quickjs-01 --jobs 4

--work-dir must be a fresh, nonexistent output path you own, not the source root or its ancestor; --jobs must be positive. Existing outputs are refused and retained, never automatically cleaned. The runner does not install dependencies or change host policy; existing pinned dependency fetches and cibuildwheel's declared bootstrap/repair still apply.

Local Windows/WSL results do not replace native ARM/macOS or VS2026 sanitizer rows. CI retains all ten installed-consumer rows, four native wheel/archive platforms, CPython 3.9–3.13, glibc 2.34/macOS 14 floors, full installed-wheel tests, cold-loader/LGPL replacement gates, and protected tag/OIDC publication dependencies. Source review or CLI help is not execution or release proof.

• Concepts and graph semantics
• C++ reference and Python binding guide
• Async guide and concurrency/cancellation
• Runtime context and strict interposition
• Harness MCP and QuickJS authoring
• Migration guide and troubleshooting
• C++ examples, Python examples, and benchmark methodology

License

MIT; see LICENSE. Third-party notices are in THIRD_PARTY_LICENSES.md.