weaver-contracts 0.4.0

Minimal Python contracts for the Weaver Stack (contextweaver, agent-kernel, ChainWeaver)

weaver_contracts Python Package

Minimal Python contracts for the Weaver Stack.

This package provides dataclasses and type definitions for all Core Weaver contracts. It has no runtime dependencies beyond the Python standard library (Python 3.9+).

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Installation

pip install weaver_contracts

For development (includes pytest and jsonschema):

pip install "weaver_contracts[dev]"

Verifying SLSA build provenance

Starting with version 0.3.0, releases ship with a PEP 740 Sigstore-signed SLSA build provenance attestation. Earlier releases (0.2.0 and below) do not carry an attestation. Verify a downloaded wheel before installing in production:

pip install sigstore
pip download "weaver_contracts==<VERSION>" --no-deps -d ./dist
sigstore verify identity \
  --cert-identity-regexp '^https://github.com/dgenio/weaver-spec/' \
  --cert-oidc-issuer 'https://token.actions.githubusercontent.com' \
  ./dist/weaver_contracts-*.whl

See SECURITY.md for the full adopter security guidance.

---

Usage

from weaver_contracts import (
    SelectableItem,
    ChoiceCard,
    RoutingDecision,
    Capability,
    CapabilityToken,
    PolicyDecision,
    Frame,
    Handle,
    TraceEvent,
)
from weaver_contracts.version import CONTRACT_VERSION, is_compatible
from datetime import datetime, timezone

# Routing
item = SelectableItem(id="search-1", label="Search docs", description="Search documentation")
card = ChoiceCard(id="card-1", items=[item], context_hint="Select a retrieval action")
rd = RoutingDecision(
    id="rd-abc",
    choice_cards=[card],
    timestamp=datetime.now(timezone.utc),
    selected_item_id="search-1",
)

# Authorization
token = CapabilityToken(
    token_id="tok-xyz",
    principal="my-agent",
    scope=["org.myapp.search_docs"],
    issued_at=datetime.now(timezone.utc),
    expires_at=datetime(2099, 1, 1, tzinfo=timezone.utc),
)

# Frame (safe output)
frame = Frame(
    frame_id="frame-001",
    capability_id="org.myapp.search_docs",
    summary="Found 3 documents matching 'query'.",
    created_at=datetime.now(timezone.utc),
    handle_refs=["handle-abc"],  # reference to raw artifact
)

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Contract Tiers

Module	Contents	Stability
weaver_contracts.core	Core contracts (all 9 types)	Stable within major version
weaver_contracts.extended	Optional metadata types	May evolve in minor versions
weaver_contracts.version	Version constants + is_compatible()	Stable

---

Running Tests

cd contracts/python
pip install -e ".[dev]"
pytest

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Schema Alignment

The JSON Schemas in contracts/json/ are the language-agnostic source of truth. The Python types mirror the schemas exactly. If a schema changes, the corresponding Python type and tests should be updated in the same PR.