---

Contents

• Quickstart
• Unified Cross-runtime Contracts
• Provider Registry and Model Routing
• JavaScript Core
• Media Workflows
• Tool Creation and Evidence Tools
• Wow in 5 Minutes
• Research-only Benchmarks
• Integrations
• Stable API Surface
• Repository Layout
• Development
• Publishing

What It Is

HandoffKit is a lightweight Python framework for building multi-agent AI workflows where agents pass structured state instead of free-text summaries.

Most multi-agent demos do this:

Agent A -> "Here is roughly what happened..." -> Agent B

HandoffKit does this:

Architect
  task: "Build a calculator CLI"
  decisions: ["Use argparse", "Keep operations pure"]
  files: ["calculator.py", "test_calculator.py"]
  next_steps: ["Implement CLI", "Run pytest"]
        |
        v
Coder
  receives HandoffState, not a vague paragraph
        |
        v
Tester
  receives decisions, files, errors, and test evidence

That makes agent workflows easier to inspect, test, replay, and improve.

Unified Cross-runtime Contracts

HandoffKit 1.8.x makes the Python, JavaScript, Rust, and C++ runtimes speak the same wire format. The canonical JSON contracts live in packages/contracts.

• Python uses HandoffState.to_dict() and RunTrace.to_dict().
• JavaScript uses toJSON() / JSON.stringify().
• Rust uses serde structs for the shared contract fixtures.
• C++ uses nlohmann/json adapters for the shared contract fixtures.
• The shared wire format uses snake_case: from_agent, to_agent, important_files, next_steps, run_id, final_output, and tool_results.
• JavaScript still exposes ergonomic camelCase properties in memory, such as state.fromAgent and trace.finalOutput.

from handoffkit import HandoffState

state = HandoffState.from_dict(shared_json)
state.validate()

import { HandoffState } from "@handoffkit/core";

const state = HandoffState.fromJSON(sharedJson);
console.log(state.fromAgent);
console.log(JSON.stringify(state));

The Python, JavaScript, Rust, and C++ test suites read the same fixture files, so contract drift becomes a CI failure instead of a surprise for users.

from handoffkit import build_contract_parity_report

report = build_contract_parity_report(runtime="python", version="1.9.0")
print(report.to_markdown())

Repository Layout

HandoffKit is organized as a clean monorepo. The Python package published to PyPI lives in packages/python:

handoffkit/
  packages/
    contracts/       # Shared JSON schemas and cross-runtime fixtures
    js/
      core/          # JavaScript/TypeScript package: @handoffkit/core
      node/          # Node.js filesystem package: @handoffkit/node
    rust/            # Rust contract package
    cpp/             # C++17 contract package
    python/
      handoffkit/      # Python package published to PyPI
      examples/        # Python examples and demos
      tests/           # Python tests
      docs/            # Python package docs and assets
  apps/
    web/               # Next.js demo and docs app

Use the root pnpm workspace for common commands:

pnpm python:test
pnpm python:build
pnpm web:dev
pnpm web:lint
pnpm web:build

Wow in 5 Minutes

Start with a real coding-agent workflow, not an abstract toy:

pip install handoffkit
handoffkit demos
handoffkit showcase coding-review
handoffkit report runs/latest

Or scaffold the same workflow as a tiny editable project:

handoffkit init coding-review
cd coding-review
python coding_review.py
handoffkit report runs/latest

The demo shows the same handoff as a vague free-text summary and as structured HandoffState: files, decisions, errors, next steps, validation, quality, and replay evidence stay attached to the work.

Bonus educational healthcare workflow:

handoffkit showcase doctor-orchestrator
handoffkit report runs/latest

doctor-orchestrator is a synthetic demo inspired by virtual physician-panel orchestration patterns: Intake -> Hypothesis -> Challenger -> Test Steward -> Checklist -> Final Reviewer. It demonstrates structured uncertainty, missing questions, red-flag tracking, cost-aware test reasoning, and replayable review evidence. It is not medical advice.

Real open-access case benchmark preview:

handoffkit benchmark-doctor --cases 30
handoffkit report runs/latest

benchmark-doctor uses 30 real cases from the public MedCaseReasoning test split, derived from PMC Open Access case reports. It runs in gold_replay mode: it replays clinician-authored diagnoses and reasoning to test HandoffKit contracts, reports, quality scoring, and traceability. It does not claim model diagnostic accuracy and is not medical advice.

MAI/SDBench-style public benchmark preview:

handoffkit benchmark-doctor-mai --cases 30
handoffkit report runs/latest

benchmark-doctor-mai mirrors the public mechanics described for SDBench: opening note, gatekeeper, targeted questions, tests, simulated costs, final diagnosis, trace, and replay. It uses public MedCaseReasoning / PMC Open Access cases, not private NEJM SDBench data.

Fusion-style model panel preview:

handoffkit demo-fusion
python examples/fusion_style_demo.py

demo-fusion is inspired by multi-model deliberation systems: a panel of model roles proposes moves, then a deterministic judge reports consensus, contradictions, coverage gaps, blind spots, and a final next-step strategy. It runs offline by default. Real provider calls are opt-in through the example script with --real.

Media dubbing workflow preview:

handoffkit demo-media
handoffkit media inspect examples/output/media_dubbing_demo/transcript_zh.json
handoffkit media plan input_zh.mp4 --from zh --to es

demo-media shows how a Chinese video translation pipeline can pass structured state through Extract -> Transcribe -> Speaker Map -> Translate -> TTS -> Mux. It writes transcript JSON, Chinese/Spanish SRT subtitles, a reusable report, and a handoff contract for the next audio/video stage. It does not call real transcription, TTS, diarization, or video APIs by default.

Report Gallery

Reports generated by the offline demos:

Demo	Report	Command
Coding agents	reports/coding_review.md	handoffkit showcase coding-review
Support escalation	reports/support_escalation.md	handoffkit showcase support-escalation
Research workflow	reports/research_workflow.md	handoffkit showcase research-workflow
Doctor orchestrator	reports/doctor_orchestrator.md	handoffkit showcase doctor-orchestrator
Doctor benchmark 30	reports/doctor_benchmark_30.md	handoffkit benchmark-doctor --cases 30
MAI-style doctor benchmark 30	reports/mai_style_doctor_benchmark_30.md	handoffkit benchmark-doctor-mai --cases 30
Fusion-style panel	reports/fusion_style_demo.md	handoffkit demo-fusion
Media dubbing workflow	reports/media_dubbing_demo.md	handoffkit demo-media

Technical post: Context Soup vs Contract Handoffs. Launch copy for Hacker News, Reddit, X/LinkedIn, and LangGraph communities: docs/launch/CONTEXT_SOUP_LAUNCH_KIT.md. Full showcase gallery: docs/SHOWCASE_GALLERY.md.

Visual Overview

HandoffKit is built around three ideas:

Layer	API	Why it matters
State transfer	HandoffState, HandoffProtocol, Team	Agents receive explicit task, decisions, files, errors, and next steps.
Quality control	ValidationReport, HandoffQualityReport	Handoffs can be validated, scored, serialized, and reviewed.
Audit trail	RunTrace, FileTraceStore, ReplayRunner	Runs can be stored and replay-inspected without providers, tools, or shell.

What 1.9.0 Adds

HandoffKit 1.9.0 splits the JavaScript/TypeScript layer into browser-safe core and Node-only helpers:

• @handoffkit/core for JS apps that need the same handoff contract shape in browsers, Next.js client components, Vite, Workers, Deno, Bun, or Node,
• @handoffkit/node for local filesystem helpers,
• async Agent.arun() and Team.arun() helpers,
• ToolRegistry, ToolCall, ToolResult, and Agent.runWithTools(),
• ProviderToolAdapter for HandoffKit, OpenAI, and Anthropic-style tool schemas/calls,
• FileTraceStore, writeReportFiles(), loadReportJSON(), and ProjectIndexer live in @handoffkit/node.

The JS core package is dependency-free, browser-safe, and tested offline. Provider SDKs and filesystem features are intentionally left to adapter packages or app code.

pnpm js:check
pnpm js:test

JavaScript Core

Use @handoffkit/core when your Next.js/Node app needs structured agent handoffs without pulling in the Python runtime:

import {
  Agent,
  HandoffProtocol,
  ProviderToolAdapter,
  RunTrace,
  Team,
  defineTool,
} from "@handoffkit/core";

const add = defineTool({
  name: "add",
  description: "Add two numbers.",
  parameters: {
    type: "object",
    properties: { a: { type: "number" }, b: { type: "number" } },
    required: ["a", "b"],
  },
  execute: ({ a, b }) => a + b,
});

const openaiTools = new ProviderToolAdapter().toolsToProviderFormat([add], "openai");

const team = new Team({
  agents: [new Agent({ name: "Architect" }), new Agent({ name: "Coder" })],
  protocol: new HandoffProtocol(),
});

const result = await team.arun("Build a calculator.");
const trace = RunTrace.fromTeamResult(result);

Package source: packages/js/core.

What 1.5.0 Adds

HandoffKit 1.5.0 adds lightweight media workflow contracts and offline demos:

• MediaAsset, TranscriptSegment, SpeakerProfile, DubbingSegment, and MediaWorkflowReport for audiobook, transcription, translation, and dubbing workflows,
• subtitle/transcript helpers: write_srt(), write_transcript_json(), and read_transcript_json(),
• optional ffmpeg wrappers for extracting audio and muxing translated audio back into a video,
• handoffkit demo-media and handoffkit media ... CLI commands.

No media dependency is installed by default. Real transcription, TTS, speaker diarization, source separation, and video processing stay opt-in.

Media Workflows

Use HandoffKit as the contract layer around media agents:

Video -> Audio Extractor -> Transcriber -> Speaker Mapper
      -> Translator -> Voice Generator -> Mixer -> Publisher

The state passed between stages can include:

from handoffkit import TranscriptSegment, SpeakerProfile, build_dubbing_plan, write_srt

segments = [
    TranscriptSegment(1, 0.0, 2.5, "你好", speaker="SPEAKER_01", language="zh"),
]
speakers = [SpeakerProfile("SPEAKER_01", "Narrator", "es-LATAM-calm", "es")]
dubbing = build_dubbing_plan(segments, {1: "Hola."}, speakers)
write_srt(dubbing, "examples/output/media/subtitles_es.srt", translated=True)

Optional ffmpeg helpers are available when an ffmpeg binary is installed:

from handoffkit import extract_audio, mux_audio

extract_audio("input_zh.mp4", "examples/output/media/original.wav")
mux_audio("input_zh.mp4", "dubbed_es.wav", "examples/output/media/output_es.mp4")

Docs: docs/MEDIA_WORKFLOWS.md.

What 1.3.0 Adds

HandoffKit 1.3.0 is focused on stronger tool creation and evidence-aware agent workflows:

• ToolSpec, ToolFactory, DeclarativeTool, and HttpJsonTool for building provider-ready tools without hand-writing wrappers,
• public medical evidence lookup tools for PubMed, ClinicalTrials.gov, and DailyMed,
• clinical MAI-style MiMo benchmark runner with multi-stage handoffs, adversarial challenge, label normalization, and replayable reports.

Medical tools are for research and benchmark workflows only. They do not diagnose, treat, or replace clinical judgment.

from handoffkit.tools import pubmed_search, clinical_trials_search, dailymed_drug_search

pubmed_search.run(query="scleroderma renal crisis case report", max_results=3)
clinical_trials_search.run(condition="systemic sclerosis", max_results=3)
dailymed_drug_search.run(drug_name="ibuprofen", max_results=3)

Tool Creation and Evidence Tools

HandoffKit 1.3.0 makes tool creation explicit and testable. Use declarative tool specs for local workflows, HTTP JSON wrappers for public APIs, and provider-ready schemas when an agent needs tool calls.

from handoffkit import ToolFactory

factory = ToolFactory()
tool = factory.from_function(
    name="summarize_file",
    description="Summarize a project file for the next agent.",
    func=lambda path: f"summary for {path}",
)

print(tool.to_schema())

Research/evidence helpers are opt-in and public-data only:

python examples/medical_tools_demo.py
python examples/opencode_go_agent.py --help
python examples/opencode_zen_agent.py --help

Medical and benchmark tooling is for research workflows only. It is not clinical validation, not patient care, and not a diagnostic system.

What 1.4.5 Adds

HandoffKit 1.4.5 adds native OpenAI-compatible provider entries without adding provider SDK dependencies:

• NVIDIA NIM, including z-ai/glm-5.2 through NVIDIA Build,
• OpenRouter unified routing,
• Groq and xAI Grok,
• Together AI, Fireworks AI, DeepInfra, Perplexity, Mistral AI, Cerebras, SambaNova Cloud, and Z.ai / GLM.

All provider CLI commands stay offline unless --real is passed:

handoffkit providers list
handoffkit providers models --provider nvidia
handoffkit providers select --provider openrouter --models openrouter/auto --json

Real probes use provider-specific env vars:

$env:NVIDIA_API_KEY="..."
handoffkit providers probe --provider nvidia --models z-ai/glm-5.2 --real

$env:OPENROUTER_API_KEY="..."
handoffkit providers probe --provider openrouter --models openrouter/auto --real

What 1.4.0 Adds

HandoffKit 1.4.0 adds experimental provider routing:

• provider registry entries for OpenCode Go, OpenCode Zen, OpenAI-compatible endpoints, and Ollama,
• ProviderSelector for offline model lists and real opt-in probes,
• ProviderRouter for ordered fallback between model candidates,
• retry/backoff for transient OpenCode 429, 5xx, and transport failures,
• handoffkit providers ... CLI commands that never call real APIs unless --real is passed.

handoffkit providers list
handoffkit providers models --provider opencode-go
handoffkit providers select --provider opencode-go --models mimo-v2.5,deepseek-v4-flash --json

Real probes require an explicit flag and a scoped provider key:

$env:OPENCODE_API_KEY="..."
handoffkit providers probe --provider opencode-go --models mimo-v2.5,deepseek-v4-flash --real

Provider Registry and Model Routing

The provider registry is experimental in 1.4.x. It is intended for diagnostics, model selection, and fallback without adding heavy provider SDKs.

from handoffkit.providers import ModelCandidate, ProviderRouter

router = ProviderRouter(
    [
        ModelCandidate("opencode-go", "mimo-v2.5"),
        ModelCandidate("opencode-go", "deepseek-v4-flash"),
    ]
)

print(router.generate("Create a concise release checklist."))

Docs: docs/PROVIDERS.md.

Native providers in 1.4.5:

Provider	Key env var	Default model
nvidia	NVIDIA_API_KEY	z-ai/glm-5.2
openrouter	OPENROUTER_API_KEY	openrouter/auto
groq	GROQ_API_KEY	llama-3.3-70b-versatile
grok	XAI_API_KEY	grok-4.3
together	TOGETHER_API_KEY	meta-llama/Llama-3.3-70B-Instruct-Turbo
fireworks	FIREWORKS_API_KEY	accounts/fireworks/models/deepseek-v3p1
deepinfra	DEEPINFRA_API_KEY	meta-llama/Llama-3.3-70B-Instruct-Turbo
perplexity	PERPLEXITY_API_KEY	sonar-pro
mistral	MISTRAL_API_KEY	mistral-small-latest
cerebras	CEREBRAS_API_KEY	llama3.1-8b
sambanova	SAMBANOVA_API_KEY	Meta-Llama-3.3-70B-Instruct
zai	ZAI_API_KEY	glm-5.2

Fusion-style Model Panels

HandoffKit can also model a Fusion-style workflow without external APIs:

1. assign specialist roles to a panel,
2. collect parallel model answers or deterministic offline stand-ins,
3. compare consensus, contradictions, gaps, and blind spots,
4. write reusable JSON/Markdown reports.

handoffkit demo-fusion
python examples/fusion_style_demo.py --help

For real provider probes, pass --real and configure provider credentials in environment variables. The demo never prints tokens and never calls real APIs unless explicitly requested.

Research-only Benchmarks

HandoffKit includes benchmark tooling to stress-test handoff contracts, traceability, report generation, and model routing. These workflows are educational and research-only.

Run	Model	Cases	Correct	Accuracy	Report
MAI-style clinical panel	mimo-v2.5	400	233	58.25%	clinical_benchmark_400_summary.md

This is not a medical device, not clinical validation, not patient care, and not a diagnostic claim. Full model outputs, partials, logs, and OpenCode live artifacts are intentionally kept out of Git and PyPI.

Integrations

HandoffKit is intentionally small: no heavy runtime integrations are required. Use it as the contract and reporting layer beside orchestration frameworks:

• LangGraph: graph nodes pass HandoffState,
• OpenAI Agents SDK: agent handoffs become auditable contracts,
• Pydantic AI: typed outputs become workflow handoff state,
• OpenCode Go / Zen: provider adapters route OpenCode model families to their matching API endpoint styles.
• Provider Registry: experimental provider listing, probing, model selection, and fallback routing.

Runnable offline examples: examples/langgraph_integration.py, examples/openai_agents_sdk_integration.py, and examples/pydantic_ai_integration.py.

Release Highlights

Older releases built the stable base that 1.3.0 and 1.4.0 sit on:

Release	Highlight
1.2.0	Showcase CLI, report gallery, better onboarding, and integration examples.
1.1.0	Three real-world demos: coding agents, support escalation, and research workflow.
1.0.x	Stable API, Trusted Publishing docs, security docs, async runtime, templates, and evaluator reports.
0.8-0.9	Trace/replay, stable API docs, compatibility tests, and stronger provider validation.
0.6-0.7	Structured outputs, provider tool adapters, contract validators, and quality reports.
0.3-0.5	Tool execution loop, memory/project context, recipes, and extension APIs.

For detailed release notes, see CHANGELOG.md.

Why HandoffKit?

Multi-agent systems break when context handoffs are vague. One agent makes a decision, another agent never sees it. One agent finds an error, the next agent gets only a polished summary. Files, constraints, and validation evidence vanish.

HandoffKit gives you:

• Agent: a small role-based agent abstraction.
• HandoffState: a JSON-friendly contract between agents.
• HandoffProtocol: protocol modes for different transfer styles.
• Team: sequential multi-agent execution.
• tool: typed Python tools with schema metadata.
• EchoProvider: deterministic local provider for tests and demos.
• OllamaProvider: local Ollama integration.
• OpenAIProvider: OpenAI and OpenAI-compatible APIs.
• OpenCodeZenProvider: OpenCode Zen with GPT, Claude, Qwen, DeepSeek, MiniMax, GLM, Kimi, MiMo, Grok, and free model routing.
• OpenCodeGoProvider: OpenCode Go with curated open coding models.

Core Concept

from handoffkit import Agent, HandoffProtocol

architect = Agent("Architect", "Create implementation plans.")
coder = Agent("Coder", "Implement from structured handoff state.")

protocol = HandoffProtocol(mode="hybrid_state")

state = protocol.transfer(
    from_agent=architect,
    to_agent=coder,
    task="Create a small Python CLI calculator with tests.",
    summary="Build a dependency-free CLI with pytest coverage.",
    decisions=["Use argparse.", "Keep calculator operations pure."],
    important_files=["calculator.py", "test_calculator.py"],
    next_steps=["Implement code.", "Run pytest."],
)

state.validate()
print(state.to_json())

Protocols

Mode	What it passes	Best for
natural	Human-readable summary	Simple demos and debugging
compressed	Compact summary	Token-sensitive transfers
hybrid_min	Task, summary, next steps	Lightweight structured chains
hybrid_state	Full state contract	Replayable, testable workflows

Quickstart

from handoffkit import Agent

agent = Agent(
    name="Planner",
    role="Create concise implementation plans.",
)

print(agent.run("Create a plan for a Python CLI app with tests."))

No API key required. By default, HandoffKit uses EchoProvider, so examples and tests run locally and deterministically.

Tool Schema Example

from handoffkit import tool


@tool
def add(a: int, b: int) -> int:
    """Add two numbers."""
    return a + b


print(add.to_schema())
print(add.run(a=2, b=3))

Output:

{
    "name": "add",
    "description": "Add two numbers.",
    "parameters": {
        "type": "object",
        "properties": {
            "a": {"type": "integer"},
            "b": {"type": "integer"},
        },
        "required": ["a", "b"],
    },
}

Tool Execution Loop

Register Python tools, let an agent create structured ToolCall objects, execute them through a ToolRegistry, and receive structured ToolResult objects.

from handoffkit import Agent
from handoffkit.tools.filesystem import list_files, read_file

agent = Agent(
    name="FileAgent",
    role="Use tools to inspect files.",
    tools=[read_file, list_files],
)

result = agent.run_with_tools("read file README.md")
print(result.final_output)
print(result.tool_results)

There are two modes:

• Deterministic/local mode: with EchoProvider, HandoffKit handles simple tasks such as read file README.md, list files ., write file ..., or run command .... This is honest local automation, not hidden AI reasoning.
• Provider JSON mode: if a provider returns JSON with tool_calls, HandoffKit executes those tools and feeds results into the next step until the provider returns {"final": "..."} or max_steps is reached.

Provider tool-call JSON:

{
  "tool_calls": [
    {
      "tool_name": "read_file",
      "arguments": {
        "path": "README.md"
      }
    }
  ],
  "final": null
}

Safety:

• dangerous shell commands such as rm -rf, del /s, format, shutdown, reboot, mkfs, and diskpart are blocked;
• when require_approval=True, write and shell tools return approval_required instead of executing.

Structured Outputs + Provider Tool Adapters

Structured outputs matter because multi-agent workflows need machine-checkable contracts, not only polished prose. HandoffKit can ask a provider for JSON, parse common response shapes, validate the result, and perform small safe repairs such as removing Markdown fences or trailing commas.

from handoffkit import Agent, StructuredOutputSchema

schema = StructuredOutputSchema(
    name="TaskSummary",
    fields={
        "title": str,
        "summary": str,
        "success": bool,
    },
    required=["title", "summary", "success"],
)

agent = Agent(name="Reporter", role="Return structured task summaries.")
result = agent.run_structured("Summarize the task.", schema=schema)

print(result.data)
print(result.to_markdown())

Agent.run_structured() sends schema instructions to the provider, parses the response with JsonOutputParser, validates it with StructuredOutputSchema, and can use OutputRepairer for simple JSON mistakes. It works with fake or local providers, so normal tests do not require API keys.

Provider tool adapters keep tool calling provider-agnostic:

from handoffkit import ProviderToolAdapter, ToolRegistry, tool

@tool
def read_file(path: str) -> str:
    """Read a file."""
    return f"read:{path}"

adapter = ProviderToolAdapter()
provider_tools = adapter.tools_to_provider_format([read_file])
tool_calls = adapter.parse_tool_calls({
    "tool_calls": [
        {
            "function": {
                "name": "read_file",
                "arguments": "{\"path\":\"README.md\"}",
            }
        }
    ]
})

registry = ToolRegistry([read_file])
results = [registry.execute(call) for call in tool_calls]

The internal format stays ToolCall(tool_name="read_file", arguments={...}) whether a provider returns HandoffKit JSON or function-style tool calls. This is provider-neutral by design; HandoffKit does not require any external SDK for normal tests.

Handoff Quality Metrics

Quality checks are deterministic and offline. They help compare handoff states without calling a provider or judging prose with another model.

from handoffkit import HandoffQualityEvaluator, HandoffState

state = HandoffState(
    task="Create a Python CLI calculator.",
    from_agent="Architect",
    to_agent="Coder",
    summary="Build an argparse calculator with pure operations and tests.",
    decisions=["Use argparse.", "Keep operations pure."],
    important_files=["calculator.py", "test_calculator.py"],
    next_steps=["Implement calculator.py", "Run pytest -q"],
    context_refs=["README.md#real-task-demo"],
    metadata={"errors_checked": True},
)

report = HandoffQualityEvaluator().evaluate(state)
print(report.score, report.grade)
print(report.to_markdown())

Metrics:

Metric	Checks
completeness	required fields, summary, decisions, files, context, next steps
clarity	useful summary length and non-empty decisions
actionability	next steps written as concrete actions
traceability	important files and context references
error_awareness	recorded errors or explicit error-check metadata

Contract Validators

Validators return ValidationReport objects that can be serialized, rendered as Markdown, or raised as exceptions. Existing APIs stay compatible: HandoffState.validate() still returns self or raises HandoffValidationError, and StructuredOutputSchema.validate() still returns the input dictionary or raises OutputValidationError.

from handoffkit import (
    HandoffStateValidator,
    StructuredOutputSchema,
    StructuredOutputValidator,
    ToolSchemaValidator,
    tool,
)

@tool
def add(a: int, b: int) -> int:
    """Add two integers."""
    return a + b

schema = StructuredOutputSchema(
    name="Plan",
    fields={"title": str, "ready": bool},
    required=["title", "ready"],
)

print(StructuredOutputValidator().validate(schema, {"title": "Demo", "ready": True}).to_json())
print(ToolSchemaValidator().validate(add).to_markdown())

Provider Tool Formats

ProviderToolAdapter can render tools as HandoffKit, OpenAI function-style, or Anthropic tool_use schemas. It also parses provider-native tool call payloads back into HandoffKit ToolCall objects.

from handoffkit import ProviderToolAdapter, tool

@tool
def read_file(path: str) -> str:
    """Read a file."""
    return f"read:{path}"

openai_adapter = ProviderToolAdapter(provider_format="openai")
anthropic_adapter = ProviderToolAdapter(provider_format="anthropic")

print(openai_adapter.tools_to_provider_format([read_file]))
print(anthropic_adapter.tools_to_provider_format([read_file]))

calls = openai_adapter.parse_tool_calls({
    "tool_calls": [
        {
            "id": "call_123",
            "type": "function",
            "function": {"name": "read_file", "arguments": "{\"path\":\"README.md\"}"},
        }
    ]
})
print(calls[0].tool_name, calls[0].arguments, calls[0].call_id)

Replayable Workflows

Run traces turn team, recipe, and tool execution reports into durable evidence. Replay does not call providers or tools again; it inspects a saved trace.

from handoffkit import Agent, HandoffProtocol, RunTrace, Team

team = Team(
    agents=[Agent("Planner", "Plan."), Agent("Reviewer", "Review.")],
    protocol=HandoffProtocol(mode="hybrid_state"),
)

result = team.run("Prepare a release checklist.")
trace = RunTrace.from_team_result(result)

print(trace.to_json())
print(trace.to_markdown())

Run Traces

RunTrace can be created from TeamRunResult, RecipeRunResult, and ToolExecutionReport.

from handoffkit import FileTraceStore, ReplayRunner, RunTrace

trace = RunTrace.from_team_result(result, name="release-checklist")
path = FileTraceStore("traces").save(trace)
loaded = FileTraceStore("traces").load(path)
summary = ReplayRunner(loaded).summary()

print(summary.to_markdown())

Report Files

Any report object with to_json(), to_markdown(), or to_dict() can be written consistently:

from handoffkit import write_report_files

json_path, markdown_path = write_report_files(trace, "trace_demo")

Evaluation Suite

Use WorkflowEvaluator to check whether workflow artifacts are ready to ship:

from handoffkit import RunTrace, WorkflowEvaluator

trace = RunTrace.from_team_result(team_result)
report = WorkflowEvaluator().evaluate(trace)
print(report.to_markdown())

The evaluator runs offline and checks contracts, handoff quality, replay summaries, trace completeness, and tool result success.

Async Runtime

Synchronous APIs remain the compatibility baseline. Async helpers are additive:

from handoffkit import Agent, Team

team = Team([Agent("Planner", "Plan."), Agent("Reviewer", "Review.")])
result = await team.arun("Prepare a release checklist.")

Providers can implement native agenerate(), or use HandoffKit's default thread-backed async wrapper.

Project Templates

Start small offline projects with built-in templates:

handoffkit init my-agent --template basic-agent --output .
handoffkit init my-team --template team-workflow --output .
handoffkit init coding-review
handoffkit init support-escalation
handoffkit init research-workflow

Templates never overwrite existing files unless --force is passed.

CLI Doctor

handoffkit doctor
handoffkit api
handoffkit demo-async
handoffkit demo-trace
handoffkit demo-replay
handoffkit demo-coding-review
handoffkit demo-support
handoffkit demo-research
handoffkit demo-doctor
handoffkit report runs/latest
handoffkit validate-report reports/trace_demo.json
handoffkit evaluate reports/trace_demo.json

doctor runs local package diagnostics only. It does not make network calls and does not inspect secrets.

Stable API Surface

The following APIs are stable for the 1.x series:

• Agent, Team, HandoffState, HandoffProtocol,
• Tool, ToolCall, ToolResult, ToolRegistry,
• Recipe, RecipeStep, RecipeRunner, RecipeRunResult,
• ValidationReport, HandoffQualityReport,
• WorkflowEvaluator, WorkflowEvaluationReport,
• ProviderToolAdapter,
• RunTrace, ReplayRunner,
• TemplateScaffolder, ProjectTemplate.

See docs/API_STABILITY.md and docs/ROAD_TO_1_0.md.

Road to 1.0

1.0.0 completes the first stable API commitment. The stable surface is documented in docs/PUBLIC_API.md, migration notes live in docs/MIGRATION_1_0.md, and runtime/test/provider support policy lives in docs/COMPATIBILITY.md.

Memory + Project Context

HandoffKit can store durable project decisions, index local files, retrieve relevant context, and hand explicit references from one agent to the next.

from handoffkit import (
    Agent,
    ContextPack,
    ContextRetriever,
    JsonMemoryStore,
    ProjectIndexer,
)

memory = JsonMemoryStore("examples/output/memory.json")
memory.add(
    "Calculator CLI should use argparse and pure functions.",
    kind="decision",
    tags=["calculator", "cli"],
)

documents = ProjectIndexer(".").index()
retriever = ContextRetriever(documents)
matches = retriever.search("calculator argparse tests", limit=3)

context = ContextPack(
    query="Create a calculator CLI implementation plan.",
    documents=matches,
    memories=memory.search("calculator cli", limit=3),
)

agent = Agent("Architect", "Create concise implementation plans.")
result = agent.run_with_context(
    "Create a concise architecture plan for a Python CLI calculator.",
    context=context,
    memory=memory,
)

print(result.final_output)
print(context.to_markdown())

Run the included demos:

python examples/memory_demo.py
python examples/project_context_demo.py
python examples/context_handoff_demo.py

Recipes + Extension API

Recipes make agent workflows reusable. Instead of wiring the same planner, executor, reviewer, tools, context, and memory flow by hand in every script, you can define a Recipe once and run it with RecipeRunner.

from handoffkit import Agent, Recipe, RecipeRunner, RecipeStep

planner = Agent(name="Planner", role="Plan the task.")
executor = Agent(name="Executor", role="Execute the plan.")
reviewer = Agent(name="Reviewer", role="Review the result.")

recipe = Recipe(
    name="plan-execute-review",
    description="A reusable three-step workflow.",
    steps=[
        RecipeStep(name="plan", agent=planner, task="Create a plan."),
        RecipeStep(name="execute", agent=executor, task="Execute the plan."),
        RecipeStep(name="review", agent=reviewer, task="Review the output."),
    ],
)

result = RecipeRunner(recipe).run()
print(result.to_markdown())

Templates create common workflow shapes:

from handoffkit import Agent, WorkflowTemplate

recipe = WorkflowTemplate.sequential(
    name="simple-workflow",
    agents=[
        Agent("Architect", "Plan."),
        Agent("Coder", "Build."),
        Agent("Tester", "Test."),
    ],
    task="Build a small calculator.",
)

Extensions bundle recipes and tools safely:

from handoffkit import Extension, ExtensionRegistry

registry = ExtensionRegistry()
registry.register(
    Extension(
        name="coding",
        description="Local coding workflows.",
        version="0.1.0",
        recipes=[recipe],
        tools=[],
    )
)

print([recipe.name for recipe in registry.recipes()])

HandoffKit does not ship Git/GitHub APIs as core primitives. A repository agent can be built as an extension or recipe using HandoffKit's general tools: structured state, memory, context packs, recipes, and extension registries.

Real Task Demo

HandoffKit includes a reproducible real task demo:

python examples/real_task_calculator.py

It runs this workflow:

Architect -> Coder -> Tester -> Reporter

Task:

Create a tiny Python CLI calculator with add, subtract, multiply and divide
operations, plus tests.

The demo creates a real generated project:

examples/output/calculator_cli/
  calculator.py
  test_calculator.py
  README.md

It also writes reproducibility reports:

reports/real_task_calculator.md
reports/real_task_calculator.json

The generated project is tested with pytest, and the report captures command, cwd, return code, stdout, stderr, files created, provider used, model used, and handoff flow.

Providers

Local deterministic provider

from handoffkit import Agent

agent = Agent("Planner", "Plan work.")
print(agent.run("Prepare a package release."))

Ollama

ollama pull llama3.1
ollama serve
python examples/ollama_agent.py --model llama3.1

OpenAI-compatible APIs

$env:OPENAI_API_KEY="..."
$env:OPENAI_BASE_URL="https://api.freemodel.dev/v1"
$env:OPENAI_MODEL="gpt-4o-mini"
python examples/freemodel_openai_compatible.py

Optional real API tests are skipped unless explicitly enabled:

$env:HANDOFFKIT_RUN_API_TESTS="1"
$env:OPENAI_API_KEY="..."
$env:OPENAI_BASE_URL="https://api.freemodel.dev/v1"
$env:OPENAI_MODEL="gpt-4o-mini"
pytest tests_api -q

Use temporary or scoped provider tokens. Do not commit API keys.

OpenCode Go and OpenCode Zen

HandoffKit can call OpenCode Go and OpenCode Zen without adding provider SDK dependencies. Use one OPENCODE_API_KEY; choose the catalog-specific model with OPENCODE_GO_MODEL or OPENCODE_ZEN_MODEL. For offline model lists, probes, selection, and fallback routing, use the provider registry commands above.

$env:OPENCODE_API_KEY="..."
$env:OPENCODE_GO_MODEL="deepseek-v4-flash"
python examples/opencode_go_agent.py

$env:OPENCODE_API_KEY="..."
$env:OPENCODE_ZEN_MODEL="gpt-5.4"
python examples/opencode_zen_agent.py

Docs: docs/integrations/OPENCODE.md and docs/PROVIDERS.md.

CLI

handoffkit --version
handoffkit demo
handoffkit demo-async
handoffkit demo-recipe
handoffkit demo-extension
handoffkit demo-structured
handoffkit demo-provider-tools
handoffkit demo-quality
handoffkit demo-validators
handoffkit demo-provider-formats
handoffkit doctor
handoffkit api
handoffkit demo-trace
handoffkit demo-replay
handoffkit validate-report reports/trace_demo.json
handoffkit evaluate reports/trace_demo.json
handoffkit providers list
handoffkit providers models --provider opencode-go
handoffkit providers select --provider opencode-go --models mimo-v2.5,deepseek-v4-flash --json
handoffkit init my-agent --template basic-agent --output .

Examples

python examples/simple_agent.py
python examples/coding_review.py
python examples/support_escalation.py
python examples/research_workflow.py
python examples/doctor_orchestrator.py
python examples/handoff_demo.py
python examples/coding_team.py
python examples/tool_schema_demo.py
python examples/tool_execution_demo.py
python examples/fake_provider_tool_call_demo.py
python examples/opencode_go_agent.py
python examples/opencode_zen_agent.py
python examples/structured_output_demo.py
python examples/provider_tool_adapter_demo.py
python examples/handoff_quality_demo.py
python examples/contract_validation_demo.py
python examples/provider_tool_formats_demo.py
python examples/evaluation_demo.py
python examples/async_demo.py
python examples/template_demo.py
python examples/trace_demo.py
python examples/replay_demo.py
python examples/provider_matrix_demo.py
python examples/structured_recipe_demo.py
python examples/recipe_demo.py
python examples/coding_review_recipe.py
python examples/extension_demo.py
python examples/memory_demo.py
python examples/project_context_demo.py
python examples/context_handoff_demo.py
python examples/real_task_calculator.py

Development

git clone https://github.com/DaosPath/handoffkit.git
cd handoffkit
cd packages/python
pip install -e ".[dev]"

Run checks:

ruff check .
pytest -q
python -m build
python -m twine check dist/*

From the repository root, the same checks are available as:

pnpm python:lint
pnpm python:test
pnpm python:build
pnpm python:twine

Publishing

HandoffKit 1.0.0 was uploaded manually with twine. HandoffKit 1.0.1 and later are prepared for PyPI Trusted Publishing through GitHub Actions OIDC.

Trusted Publishing keeps package tokens out of the repository and out of GitHub Secrets. TestPyPI publishing is triggered manually from the Publish workflow; real PyPI publishing is triggered by publishing a GitHub Release after CI is green.

Trusted Publisher settings must be configured on TestPyPI and PyPI before using the workflow:

• owner: DaosPath
• repository: handoffkit
• workflow: publish.yml
• TestPyPI environment: handoffkit
• PyPI environment: pypi

See docs/RELEASE_PROCESS.md for the full release checklist.

Local build validation still uses:

python -m build
python -m twine check dist/*

Inspiration

HandoffKit is inspired by the research and reproducibility repository DaosPath/state-transfer-protocols, especially its comparison of natural, compressed, hybrid_min, and hybrid_state handoff protocols for multi-agent workflows.

HandoffKit is a developer library, not a copy of that repository.

Roadmap

• 1.x compatibility maintenance,
• richer memory persistence adapters after 1.0,
• broader provider-specific integration examples,
• benchmark-inspired quality comparisons,
• more workflow templates and extension examples.

License

MIT.