feat: direct tool invocation via /tool_name(arg=val) + wire Curry as real tools

Adds synapse/slash_commands.py: a chat message that's nothing but
/tool_name(arg=val, arg=val) dispatches straight through tools.dispatch(),
skipping model selection, RAG/playbook context assembly, and the ask-policy
approval round-trip entirely. A human typing this IS the approval - there's
no one else to ask - so it's a deliberate, reviewed bypass of the approval
step specifically, not of anything a tool validates internally (path
boundaries, size caps, Curry's own sandbox checks all still run). Argument
values parse via ast.literal_eval only: strings/numbers/bools/None/literal
containers, no names, no calls, no attribute access - a malformed or
hostile-looking argument fails to parse rather than executing anything.

Wired into chat_stream_endpoint (main.py) as an early short-circuit, before
any of the RAG/model-selection work that a slash-command doesn't need. Web
needed no changes (it already forwards raw text unchanged); the TUI
previously swallowed every leading "/" locally and never reached the backend
with it, so tui_app.py's _handle_slash now falls through to _start_chat for
anything shaped like a tool call while still handling its own local
meta-commands (/help, /model, /new, ...) exactly as before.

Also finally wires Curry in as ten real tools (curry_declare_constant,
curry_get_constant/_latest, curry_list_constants, curry_retire_constant,
curry_declare_function, curry_get_function, curry_list_functions,
curry_call_function, curry_retire_function) - deferred from the vendoring
pass. The five write/execute ones are ACTION tools in the same
always-ask-regardless-of-global-policy floor as edit_source
(ALWAYS_ASK_ACTION_TOOLS, generalized in tools.py from the old
self_edit-only ALWAYS_ASK_TOOLS so future tool families share one place to
register into). curry_call_function is gated as an action for the same
reason run_snippet is: it executes code, even sandboxed.

Fixed a real bug surfaced while wiring this up: curry_db is a long-lived
singleton holding one sqlite3 connection (unlike NexusOS's own memory store,
which opens/closes a fresh connection per call specifically to dodge this),
and sqlite3 forbids using a connection from a different thread than created
it. That's a non-issue in production (uvicorn's single event-loop thread),
but Starlette's TestClient runs the ASGI app through an anyio portal thread,
so it broke immediately under test. Fixed at the source (curry_core.py,
Curry.__init__) with check_same_thread=False, documented as a second
deliberate vendoring deviation alongside the PR #4 sandbox fix - there was
never real concurrent access here, just an overly strict same-thread
assertion tripping on a thread-identity change with only one logical caller.

Verified: 244 backend tests pass (18 new for the parser + endpoint wiring +
curry tool registration, 4 new for the TUI passthrough); the 12 pre-existing
C/C++/Rust toolchain failures are unrelated and unchanged. Confirmed by hand
over the real HTTP endpoint: successful dispatch, zero tool_request events
(approval bypass working as designed), a format()-dunder exploit attempt
still rejected by the vendored sandbox fix even through the new tool
registration, malformed arguments rejected before ever reaching dispatch,
and an unknown tool name rejected cleanly. Wheel rebuilt and content-checked
(bin/check.sh's gate now also asserts slash_commands.py ships).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

synapse/main.py

@@ -209,6 +209,7 @@ from .memory.store import store, MemoryItem
 from .playbooks.store import playbook_store
 from .curry_store import curry_db  # noqa: F401 - import triggers Curry's own preload at startup
 from .search import needs_web_search, web_search
+from . import slash_commands as _slash_commands
 
 MEMORY_SERVICE = settings.memory_url
 
@@ -335,6 +336,47 @@ async def root():
 
 # -------------------------
 # Chat (streaming)
+async def _slash_command_stream(
+    slash: "_slash_commands.SlashCommand | _slash_commands.SlashCommandError",
+    conversation_id: str,
+) -> AsyncGenerator[str, None]:
+    """Dispatch a parsed slash-command and stream its result the same shape a
+    normal reply streams in — a single content chunk, `event: done`, nothing
+    else. No model call, no tool-loop, no approval round-trip: see
+    slash_commands.py for why that's the deliberate design here."""
+    if isinstance(slash, _slash_commands.SlashCommandError):
+        yield f"event: error\ndata: {_json.dumps({'detail': slash.text})}\n\n"
+        return
+
+    if slash.tool not in _tools.REGISTRY:
+        yield (
+            "event: error\ndata: "
+            f"{_json.dumps({'detail': f'unknown tool: {slash.tool}'})}\n\n"
+        )
+        return
+
+    yield f"event: status\ndata: {_json.dumps({'tool': slash.tool})}\n\n"
+    raw_result = await _tools.dispatch(slash.tool, slash.args)
+
+    # Tools that emit a fence (curry_*, edit_*, run_snippet) carry it as
+    # `"fence"` in their JSON result — reuse it verbatim so the existing
+    # nexus-run/nexus-edit renderers pick it up with no new frontend code.
+    # Anything else is shown as pretty-printed JSON.
+    content = raw_result
+    try:
+        parsed = _json.loads(raw_result)
+        if isinstance(parsed, dict) and isinstance(parsed.get("fence"), str):
+            content = parsed["fence"]
+        else:
+            content = _json.dumps(parsed, indent=2, ensure_ascii=False)
+    except (TypeError, ValueError):
+        pass
+
+    store.add_message(conversation_id, "assistant", content)
+    yield f"data: {_json.dumps(content)}\n\n"
+    yield "event: done\ndata: {}\n\n"
+
+
 # -------------------------
 @app.post("/chat/stream")
 async def chat_stream_endpoint(payload: Dict[str, Any]):
@@ -345,13 +387,37 @@ async def chat_stream_endpoint(payload: Dict[str, Any]):
     _chat_slot_held = True
     try:
         message = payload.get("message", "")
+        conversation_id = payload.get("conversation_id") or str(_uuid.uuid4())
+
+        if not message:
+            raise HTTPException(status_code=400, detail="Missing 'message'")
+
+        # Direct tool invocation: /tool_name(arg=val, ...). A human typing this
+        # IS the approval, so it skips model selection, RAG/playbook context
+        # assembly, and the ask-policy round-trip entirely — see
+        # slash_commands.py for what it does and does not bypass.
+        _slash = _slash_commands.parse_slash_command(message)
+        if _slash is not None:
+            store.create_conversation(conversation_id, "")
+            store.add_message(conversation_id, "user", message)
+            _slash_inner = _slash_command_stream(_slash, conversation_id)
+
+            async def _slash_guarded() -> AsyncGenerator[str, None]:
+                try:
+                    async for _chunk in _slash_inner:
+                        yield _chunk
+                finally:
+                    _CHAT_INFLIGHT.release()
+
+            _chat_slot_held = False
+            return StreamingResponse(_slash_guarded(), media_type="text/event-stream")
+
         app_settings = store.get_settings()
         # Model precedence: explicit request > active playbook's pinned model > auto-select.
         _active_pb = playbooks.get_main_playbook()
         _pb_model = _active_pb.model if (_active_pb and _active_pb.model) else ""
         model = payload.get("model") or _pb_model or await _auto_select_model(message)
         context = payload.get("context", {})
-        conversation_id = payload.get("conversation_id") or str(_uuid.uuid4())
         history = payload.get("history", [])
         temperature = payload.get("temperature", app_settings.get("temperature"))
         num_ctx = payload.get("num_ctx", app_settings.get("num_ctx", 0))
@@ -359,9 +425,6 @@ async def chat_stream_endpoint(payload: Dict[str, Any]):
         gpu_offload = payload.get("gpu_offload", app_settings.get("gpu_offload", -1))
         num_gpu = await get_ollama_manager().resolve_num_gpu(gpu_offload, model)
 
-        if not message:
-            raise HTTPException(status_code=400, detail="Missing 'message'")
-
         rendered_message = message  # chat has no template vars; render_prompt is for the playbook path
         system_prompt = playbooks.get_system_prompt() or app_settings.get("system_prompt", "")