d87a1615ce
- add ACP user and developer docs covering setup, lifecycle, callbacks, permissions, tool rendering, and runtime behavior - add developer guides for agent loop, provider runtime resolution, prompt assembly, context caching/compression, gateway internals, session storage, tools runtime, trajectories, and cron internals - refresh architecture, quickstart, installation, CLI reference, and environments docs to link the new implementation pages and ACP support
183 lines
4.5 KiB
Markdown
183 lines
4.5 KiB
Markdown
---
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sidebar_position: 2
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title: "ACP Internals"
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description: "How the ACP adapter works: lifecycle, sessions, event bridge, approvals, and tool rendering"
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---
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# ACP Internals
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The ACP adapter wraps Hermes' synchronous `AIAgent` in an async JSON-RPC stdio server.
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Key implementation files:
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- `acp_adapter/entry.py`
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- `acp_adapter/server.py`
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- `acp_adapter/session.py`
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- `acp_adapter/events.py`
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- `acp_adapter/permissions.py`
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- `acp_adapter/tools.py`
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- `acp_adapter/auth.py`
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- `acp_registry/agent.json`
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## Boot flow
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```text
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hermes acp / hermes-acp / python -m acp_adapter
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-> acp_adapter.entry.main()
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-> load ~/.hermes/.env
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-> configure stderr logging
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-> construct HermesACPAgent
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-> acp.run_agent(agent)
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```
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Stdout is reserved for ACP JSON-RPC transport. Human-readable logs go to stderr.
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## Major components
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### `HermesACPAgent`
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`acp_adapter/server.py` implements the ACP agent protocol.
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Responsibilities:
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- initialize / authenticate
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- new/load/resume/fork/list/cancel session methods
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- prompt execution
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- session model switching
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- wiring sync AIAgent callbacks into ACP async notifications
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### `SessionManager`
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`acp_adapter/session.py` tracks live ACP sessions.
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Each session stores:
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- `session_id`
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- `agent`
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- `cwd`
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- `model`
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- `history`
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- `cancel_event`
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The manager is thread-safe and supports:
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- create
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- get
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- remove
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- fork
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- list
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- cleanup
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- cwd updates
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### Event bridge
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`acp_adapter/events.py` converts AIAgent callbacks into ACP `session_update` events.
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Bridged callbacks:
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- `tool_progress_callback`
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- `thinking_callback`
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- `step_callback`
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- `message_callback`
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Because `AIAgent` runs in a worker thread while ACP I/O lives on the main event loop, the bridge uses:
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```python
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asyncio.run_coroutine_threadsafe(...)
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```
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### Permission bridge
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`acp_adapter/permissions.py` adapts dangerous terminal approval prompts into ACP permission requests.
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Mapping:
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- `allow_once` -> Hermes `once`
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- `allow_always` -> Hermes `always`
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- reject options -> Hermes `deny`
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Timeouts and bridge failures deny by default.
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### Tool rendering helpers
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`acp_adapter/tools.py` maps Hermes tools to ACP tool kinds and builds editor-facing content.
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Examples:
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- `patch` / `write_file` -> file diffs
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- `terminal` -> shell command text
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- `read_file` / `search_files` -> text previews
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- large results -> truncated text blocks for UI safety
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## Session lifecycle
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```text
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new_session(cwd)
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-> create SessionState
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-> create AIAgent(platform="acp", enabled_toolsets=["hermes-acp"])
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-> bind task_id/session_id to cwd override
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prompt(..., session_id)
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-> extract text from ACP content blocks
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-> reset cancel event
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-> install callbacks + approval bridge
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-> run AIAgent in ThreadPoolExecutor
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-> update session history
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-> emit final agent message chunk
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```
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### Cancelation
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`cancel(session_id)`:
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- sets the session cancel event
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- calls `agent.interrupt()` when available
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- causes the prompt response to return `stop_reason="cancelled"`
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### Forking
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`fork_session()` deep-copies message history into a new live session, preserving conversation state while giving the fork its own session ID and cwd.
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## Provider/auth behavior
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ACP does not implement its own auth store.
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Instead it reuses Hermes' runtime resolver:
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- `acp_adapter/auth.py`
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- `hermes_cli/runtime_provider.py`
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So ACP advertises and uses the currently configured Hermes provider/credentials.
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## Working directory binding
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ACP sessions carry an editor cwd.
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The session manager binds that cwd to the ACP session ID via task-scoped terminal/file overrides, so file and terminal tools operate relative to the editor workspace.
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## Duplicate same-name tool calls
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The event bridge tracks tool IDs FIFO per tool name, not just one ID per name. This is important for:
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- parallel same-name calls
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- repeated same-name calls in one step
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Without FIFO queues, completion events would attach to the wrong tool invocation.
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## Approval callback restoration
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ACP temporarily installs an approval callback on the terminal tool during prompt execution, then restores the previous callback afterward. This avoids leaving ACP session-specific approval handlers installed globally forever.
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## Current limitations
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- ACP sessions are process-local from the ACP server's point of view
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- non-text prompt blocks are currently ignored for request text extraction
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- editor-specific UX varies by ACP client implementation
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## Related files
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- `tests/acp/` — ACP test suite
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- `toolsets.py` — `hermes-acp` toolset definition
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- `hermes_cli/main.py` — `hermes acp` CLI subcommand
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- `pyproject.toml` — `[acp]` optional dependency + `hermes-acp` script
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