### Tool System (`packages/harness/deerflow/tools/`)

`get_available_tools(groups, include_mcp, model_name, subagent_enabled)` assembles:
1. **Config-defined tools** - Resolved from `config.yaml` via `resolve_variable()`
2. **MCP tools** - From enabled MCP servers (lazy initialized, cached with resolved-path + content-signature invalidation)
3. **Built-in tools**:
   - `present_files` - Make output files visible to user (only `/mnt/user-data/outputs`); virtual paths use `resolve_runtime_user_id(runtime)` so validation resolves the same user-scoped outputs directory established by `ThreadDataMiddleware`
   - `ask_clarification` - Request clarification (intercepted by ClarificationMiddleware, which preserves text fallback and adds `artifact.human_input` for Web UI Human Input Cards). Beyond free text and single choice, the request-side v2 protocol supports `fields` (structured form card collecting several values at once; field types: text/textarea/number/select/multi_select/checkbox/date, validated and normalized server-side in the middleware — invalid entries are dropped, unknown types degrade to `text`; a standalone multi-select question is a one-field form). Replies stay on the v1 response protocol (`text`/`option`): the form card submits a readable text summary
   - `view_image` - Read image as base64 (added only if model supports vision)
   - `setup_agent` - Bootstrap-only: persist a brand-new custom agent's `SOUL.md` and `config.yaml`. Bound only when `is_bootstrap=True`.
   - `update_agent` - Custom-agent-only: persist self-updates to the current agent's `SOUL.md` / `config.yaml` from inside a normal chat (partial update + atomic write). Bound when `agent_name` is set and `is_bootstrap=False`.
4. **Subagent tool** (if enabled):
   - `task` - Delegate to subagent (description, prompt, subagent_type)

Scheduled-task runtime note:
- Scheduled background runs set `context.non_interactive=true` and therefore exclude `ask_clarification` from the lead-agent tool list. This keeps scheduler-triggered runs from stalling on human confirmation mid-execution. `non_interactive` is an internal-only context key: it is merged from `body.context` only when the request authenticated as the process-internal user (the scheduler path), never from arbitrary HTTP/IM clients.

**Community tools** (`packages/harness/deerflow/community/`): optional integrations, each in its own subpackage and wired through `config.yaml`. Documented examples:
- `tavily/` - Web search (5 results default) and web fetch (4KB limit)
- `jina_ai/` - Web fetch via Jina reader API with readability extraction
- `firecrawl/` - Web scraping via Firecrawl API
- `image_search/` - Image search via DuckDuckGo
- `aio_sandbox/` - Docker-based isolation (`AioSandboxProvider`)
- `browser_automation/` - Agentic browser control (stateful `navigate → observe → click/type` loop) via Playwright, distinct from the read-only `web_fetch`/`web_capture` tools. Tools: `browser_navigate`, `browser_snapshot`, `browser_click`, `browser_type`, `browser_get_text`, `browser_back`, `browser_screenshot`, `browser_close` (config `group: browser`). A process-local `BrowserSessionManager` owns one private, loop-affine Playwright event-loop thread (same pattern as the BoxLite provider) so a per-thread browser session survives across turns regardless of the caller's loop (Gateway / TUI / test). Each action returns a fresh page snapshot whose interactive elements are addressed by a stable numeric `[ref]` index (stamped as `data-df-ref` during snapshot), so the model acts on what it just observed instead of holding stale handles or guessing selectors. URLs are SSRF-screened via the shared `validate_public_http_url` (opt-out `allow_private_addresses` only for intentional internal targets). CDP attachment cannot install the request guard on an existing Chrome context, so `cdp_url` fails closed unless the operator explicitly sets `allow_unguarded_cdp: true` for a trusted local browser. Browser REST/Live access also requires an exact non-NULL thread owner, rather than the general legacy shared-thread policy, because retained pages may contain authenticated state. Session admission is a hard `max_sessions` cap: pinned Live/operation sessions are never evicted, and a new thread is rejected when no unpinned session can be closed; one Live viewer owns a session at a time. Optional dependency: `cd backend && uv sync --extra browser && uv run playwright install chromium`; `scripts/detect_uv_extras.py` preserves the extra when `config.yaml` enables `browser_navigate`, and Gateway startup fails fast if configured browser control cannot import Playwright. Tests: `tests/test_browser_automation.py` (mocked tools + a real-Chromium integration test guarded by `importorskip`); `tests/manual_browser_live_check.py` is a manual DeepSeek-driven end-to-end check (not collected by pytest).
  Live UI input dispatch is kept independent from JPEG capture: non-move actions start a rate-limited background refresh loop, so pointer, wheel, or keyboard input stays responsive while continuous gestures still produce frames throughout the interaction.

Additional providers also live here (`boxlite`, `brave`, `browserless`, `crawl4ai`, `ddg_search`, `e2b_sandbox`, `exa`, `fastcrw`, `groundroute`, `infoquest`, `searxng`, `serper`, `tenki`); see each subpackage for specifics. E2B bootstrap is required. If it fails, the provider kills and closes the unusable remote sandbox. New sandbox creation raises an error. Warm-pool reclaim and remote discovery discard the sandbox and continue acquisition. E2B mounts remain optional.

E2B output sync records remote file versions and actual host file metadata in a thread-local manifest. The manifest binds to the remote sandbox ID. A complete output listing removes entries for deleted files. This avoids repeat downloads when the host filesystem rounds modification times. A single release-time sync pass is bounded by aggregate ceilings (`_MAX_SYNC_TOTAL_BYTES`, `_MAX_SYNC_FILES`, `_SYNC_DEADLINE_SECONDS`) on top of the per-file `_MAX_DOWNLOAD_SIZE` cap, so a pathological outputs tree cannot make release download unboundedly; a truncated pass logs what it dropped and leaves the manifest un-pruned (only entries observed in that pass are reconciled), so files it never reached are retried on the next release rather than being forgotten.

**ACP agent tools**:
- `invoke_acp_agent` - Invokes external ACP-compatible agents from `config.yaml`
- ACP launchers must be real ACP adapters. The standard `codex` CLI is not ACP-compatible by itself; configure a wrapper such as `npx -y @zed-industries/codex-acp` or an installed `codex-acp` binary
- Missing ACP executables now return an actionable error message instead of a raw `[Errno 2]`
- Each ACP agent uses a per-thread workspace at `{base_dir}/users/{user_id}/threads/{thread_id}/acp-workspace/`. The workspace is accessible to the lead agent via the virtual path `/mnt/acp-workspace/` (read-only). In docker sandbox mode, the directory is volume-mounted into the container at `/mnt/acp-workspace` (read-only); in local sandbox mode, path translation is handled by `tools.py`