[folathecoder]

Summary

Builds the protocol contract (aldwin.protocol), the in-process transport and turn runner (aldwin.host), the per-step session store (aldwin.host.sessions), and the async client (aldwin.client). Doors can now stream turns, answer approval prompts, stop active turns within a second, switch models, and resume saved conversations without importing aldwin.core or agentling.

Ticket

• Closes ENG-379
• Dev plan: ENG-387
• Test plan: ENG-391

Changes

• Protocol (src/aldwin/protocol/messages.py, docs/protocol.md): Added the v1 envelope, 6 request models (hello, turn, stop, approve, history, set_model), 7 event models (text, tool_call, tool_result, approval, history, done, error), discriminated unions (Request, Event, Message), ConfigDict(extra="ignore"), and JSON parsers.
• Transport (src/aldwin/host/in_process.py): Added ClientTransport and InProcessTransport using inbound and outbound asyncio.Queues with JSON wire validation and clean close sentinels.
• Sessions (src/aldwin/host/sessions.py): Added SessionStore, StoredSession, and SessionMeta for atomic 0600 per-step saves in sessions/<YYYY-MM-DD>_<shortid>.json, latest-session resume, 60-character title derivation, /new session creation, and render_history(limit=20) with one-line tool summaries.
• Host runner (src/aldwin/host/runner.py): Added RequestScope (enforcing one terminal event per request), ApprovalBroker (ask, resolve, cancel_all), classify_turn_error, and AldwinHost (handshake check, streaming event mapping, mid-stream and mid-approval stop, set_model, and new_conversation).
• Client (src/aldwin/client/client.py): Added AldwinClient (connect, turn, stop, approve, history, set_model, new_conversation, close) with re-keyed event demultiplexing.
• Tests (tests/): Added FakeModel and FakeTurn in tests/fakes/model.py, plus tests/test_protocol.py, tests/test_sessions.py, tests/test_host_runner.py, and tests/test_client.py covering TC-01 through TC-30.

How it was tested

• Automated:
  • uv run pytest -v --cov=aldwin (91 passed in 0.61s, 94% total coverage; 100% on protocol/, 100% on host/in_process.py, 95% on host/sessions.py, 93% on host/runner.py, 93% on client/client.py)
  • uv run ruff check src tests and uv run ruff format --check src tests (all passed)
  • uv run mypy --strict src tests (0 issues across 28 files)
• Manual:
  • Verified all test cases TC-01 through TC-30 and manual checks M-01 through M-03 in ENG-391.