chp-core

The reference local host for the Capability Host Protocol — the open protocol for declaring, governing, and proving what agents, tools, and systems do.

See what your agents and tools actually did — and what governed it.

Try it in two minutes

Your coding agent reads files, runs commands, calls tools. This puts a governed boundary at the point of action — no application code changes:

pip install chp-core
chp hooks install                     # Claude Code
chp hooks install --all-harnesses     # ...or Claude Code + Codex + Gemini CLI

Use your agent normally, then look at what it did:

chp session list
chp session tree <session_id>

Every tool call becomes a typed evidence event, hash-chained and stored locally in ~/.chp/evidence.sqlite. A denial is a first-class event with a reason code — not a swallowed exception — and the chain is tamper-evident, so someone who did not run the agent can still tell whether the record is intact.

Docs: docs.capabilityhostprotocol.com · Source: github.com/capabilityhostprotocol/chp-core

Install

pip install chp-core                 # zero runtime dependencies
pip install 'chp-core[schema]'       # enforce capabilities' declared input_schema
pip install 'chp-core[signing]'      # ed25519 — signed hosts, bundles, mandates

Without [schema], a capability's declared input_schema is not enforced — the host warns at registration and chp host verify reports it rather than letting the gap pass silently. Without [signing], evidence stays at the hash-chain tier rather than the signed tier.

chp host verify     # smoke-tests the host and evidence store in under a second

From a checkout of this repository:

python -m pip install -e packages/python

What this package is

Intentionally small:

register capabilities
discover declarations
invoke through a governed envelope
preserve or generate correlation IDs
emit append-only SQLite evidence
replay evidence by correlation ID
optionally serve discovery, invocation, and replay over local HTTP

Quick Example

from chp_core import LocalCapabilityHost, capability

host = LocalCapabilityHost("example-host")

@capability(
    id="math.add",
    version="1.0.0",
    description="Add two numbers.",
)
def add(a: int, b: int):
    return {"sum": a + b}

host.register(add)

result = host.invoke(
    "math.add",
    {"a": 2, "b": 3},
    correlation_id="demo-correlation",
)

events = host.replay("demo-correlation")

Async handlers are supported. Use await host.ainvoke(...) when already inside an event loop.

By default, invocation payloads are not copied into evidence. Handlers can emit explicit redacted evidence through ctx.emit(...).

Payloads emitted through ctx.emit(...) are redacted by default for common sensitive keys such as token, secret, password, authorization, and api_key.

Adapters

Group related capabilities into an adapter class using BaseAdapter and the @capability decorator. All decorated methods are auto-discovered:

from chp_core import BaseAdapter, capability, LocalCapabilityHost, register_adapter

class MathAdapter(BaseAdapter):
    adapter_id = "math"
    adapter_name = "Math Capabilities"

    @capability(id="math.add", version="1.0.0", description="Add two numbers.")
    async def add(self, ctx, payload):
        return {"sum": payload["a"] + payload["b"]}

    @capability(id="math.mul", version="1.0.0", description="Multiply two numbers.")
    async def multiply(self, ctx, payload):
        return {"product": payload["a"] * payload["b"]}

host = LocalCapabilityHost()
register_adapter(host, MathAdapter())

For standalone functions, use SimpleAdapter:

from chp_core import SimpleAdapter, capability, register_adapter

@capability(id="greet.hello", version="1.0.0", description="Greet someone.")
def hello(name: str):
    return {"message": f"Hello, {name}!"}

register_adapter(host, SimpleAdapter("greet", [hello]))

Shipping an adapter package

Publish your adapter as a standalone package (e.g. chp-linear) and declare it under the chp.adapters entry-point group so hosts can discover it automatically:

# your_adapter/pyproject.toml
[project.entry-points."chp.adapters"]
linear = "chp_linear:LinearAdapter"

Once installed, any host can load all registered adapters:

from chp_core import auto_register_adapters

host = LocalCapabilityHost()
auto_register_adapters(host)  # loads every installed chp.adapters entry point

Or discover them manually:

from chp_core import discover_adapters

for name, adapter_cls in discover_adapters().items():
    print(name, adapter_cls)

chp-core ships a built-in chp-git adapter that exposes Git version-control governance capabilities. It is registered automatically when the package is installed.

HTTP Endpoint

The HTTP helper is transport glue around the same LocalCapabilityHost:

from chp_core import create_http_server

server = create_http_server(host, port=8765)
server.serve_forever()

Routes:

GET /host
GET /capabilities
POST /invoke
POST /replay
GET /replay/{correlation_id}

See examples/capability-host-endpoint-demo/.

The package also installs a small CLI:

chp demo endpoint
chp serve-demo --port 8765
chp host
chp invoke demo.search_information --payload '{"query":"CHP vs MCP"}' --correlation-id corr_demo
chp replay corr_demo

Development Evidence Controls

Use chp work to record local engineering work as CHP evidence:

chp work run \
  --intent "Verify the Python test suite." \
  --correlation-id chp-dev-001 \
  --test-run unit \
  -- python -m unittest discover -s packages/python/tests

chp work summary chp-dev-001
chp work replay chp-dev-001
chp work explain chp-dev-001

Tests

cd packages/python
python -m unittest discover -s tests

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