OpenAI tool calling for GLM-5.2: gated tool declaration + parse_tool_calls, non-tool path preserved, opt-in salvage (#96)

* openai_server: parse GLM-5.2 tool calls into OpenAI tool_calls

Fills the 'tools not supported yet' stub. Upstream declared nothing and
rejected tools/functions; this makes them real end to end:

  render_chat:  emit a tools-declaration <|system|> block; replay assistant
                tool_calls as <tool_call>NAME<arg_key>K</arg_key><arg_value>V
                </arg_value></tool_call>; render tool-result messages as
                <|observation|><tool_response>...</tool_response> (one
                observation per consecutive tool run).
  parse_tool_calls: turn the model's <tool_call> markers back into OpenAI
                tool_calls; strip <think> from surfaced content.
  generation:   non-stream returns message.tool_calls + finish_reason
                'tool_calls'; stream suppresses the markers from content
                deltas (marker-length hold-back so a split <tool_call> is
                caught) and emits tool_calls deltas after generation.

Default-safe: with no tools in the request, render and streaming take the
exact upstream path (byte-identical); tool handling is gated on tools present.
Marker format is authoritative (GLM-5.2 chat_template.jinja).

Optional de-mangler (COLI_TOOL_SALVAGE=1, default OFF) recovers malformed
calls from heavily-quantized models by mapping a lone payload onto the tool's
primary parameter; never rewrites well-formed output, never on by default.
A [api] tool-calls telemetry line reports strict vs de-mangled.

Pure stdlib; no new deps.

* openai_server: COLI_THINK global thinking default (opt-in)

COLI_THINK=1 makes thinking the default when a request sends neither
reasoning_effort nor enable_thinking (a launch-time global switch equivalent
to the old server's --think, useful because reasoningEffort propagation from
openai-compatible front-ends is unreliable). An explicit client value always
wins. Default off => exact OpenAI-standard behavior, so this is inert unless
enabled.

* openai_server: keepalive during long prefill (SSE reasoning pings)

engine.generate() blocks silently through the cold prefill (minutes for a
large prompt), and OpenCode/undici drop the socket after their idle timeout
-> the stream is 'terminated' before the first token. Upstream's SSE path
emits nothing until generation produces text, so it has no heartbeat.

A background pump emits a reasoning_content '.' delta whenever no event has
been written for KA_GAP (10s): the channel that reliably resets the client
timer and lands in the thinking panel, so answer content stays clean. All
wfile writes share a lock so the pump and event() never interleave; a
last-write timestamp gates the pump so it's silent while real tokens flow
(decode). The pump stops as soon as generation returns.

Inert for fast responses (nothing sent if events flow within 10s). No new
deps.

* openai_server: COLI_DEBUG echoes decoded tokens to stderr

Upstream sends decoded tokens only to the client (stdout->SSE), so the
console shows no generation text -- painful when the client has disconnected
or for local debugging. COLI_DEBUG=1 tees each decoded chunk to stderr at the
engine-callback boundary (both the plain and tool-call streaming paths).
Default off; no effect unless enabled.

* openai_server: use GLM-5.2 authoritative tool-declaration block

The tools were declared with a hand-written preamble; GLM-5.2 was trained on
the '# Tools' + <tools></tools> XML structure from chat_template.jinja. With
the wrong preamble the model doesn't recognize the tools as native and
hallucinates other frameworks' syntax (observed: repetitive 'end_action' and
key+value concatenated into one arg). Switch render_chat to the byte-exact
trained format so the model emits well-formed <tool_call> blocks.

c/openai_server.py

@@ -151,7 +151,87 @@ def content_text(content, param):
     return "".join(parts)
 
 
-def render_chat(messages, enable_thinking=False, reasoning_effort=None):
+# ---- GLM-5.2 tool calling -----------------------------------------------------------------
+# The model expresses tool calls as ordinary text (from chat_template.jinja):
+#   <tool_call>{name}<arg_key>{k}</arg_key><arg_value>{v}</arg_value>...</tool_call>
+# and tool results come back as <|observation|><tool_response>{content}</tool_response>.
+# We render those markers into the prompt and parse them back into OpenAI `tool_calls`.
+import re
+
+BOX_START, BOX_END = "<tool_call>", "</tool_call>"
+TR_OPEN,  TR_CLOSE = "<tool_response>", "</tool_response>"
+THINK_OPEN, THINK_CLOSE = "<think>", "</think>"
+
+_BOX_RE  = re.compile(re.escape(BOX_START) + r"(.*?)" + re.escape(BOX_END), re.DOTALL)
+_ARG_RE  = re.compile(r"<arg_key>([^<]*)</arg_key><arg_value>(.*?)</arg_value>", re.DOTALL)
+_NAME_RE = re.compile(r"\s*([A-Za-z0-9_.\-]+)")
+_TAG_RE  = re.compile(r"</?arg_key>|</?arg_value>")
+
+# De-mangler: opt-in recovery for heavily-quantized models that drop the
+# <arg_key>K</arg_key><arg_value> structure. Default OFF (never rewrites well-formed output).
+_SALVAGE = os.environ.get("COLI_TOOL_SALVAGE", "0") == "1"
+
+
+def _tool_param_order(tools):
+    """name -> ordered param names (required first) from the request schema, for de-mangling."""
+    out = {}
+    for tool in (tools or []):
+        fn = tool.get("function", tool) if isinstance(tool, dict) else {}
+        name = fn.get("name")
+        if not name:
+            continue
+        params = ((fn.get("parameters") or {}).get("properties") or {})
+        required = list((fn.get("parameters") or {}).get("required") or [])
+        out[name] = required + [p for p in params if p not in required]
+    return out
+
+
+def parse_tool_calls(reply, tools=None):
+    """Return (content, tool_calls). Strict GLM parse; optional de-mangler (COLI_TOOL_SALVAGE=1)
+    rescues malformed int4 output by mapping a lone payload onto the tool's primary parameter."""
+    param_order = _tool_param_order(tools)
+    calls, salvaged = [], []
+    for match in _BOX_RE.finditer(reply):
+        inner = match.group(1)
+        name_match = _NAME_RE.match(inner)
+        name = name_match.group(1) if name_match else inner.strip()
+        args = {}
+        for arg in _ARG_RE.finditer(inner):
+            key, value = arg.group(1), arg.group(2)
+            try:
+                value = json.loads(value)
+            except (json.JSONDecodeError, TypeError):
+                pass
+            args[key] = value
+        if not args and _SALVAGE:
+            rest = inner[name_match.end():] if name_match else ""
+            payload = _TAG_RE.sub("", rest).strip()
+            if payload.startswith("(") and payload.endswith(")"):
+                payload = payload[1:-1].strip()
+            if payload:
+                key = (param_order.get(name) or ["input"])[0]
+                try:
+                    payload = json.loads(payload)
+                except (json.JSONDecodeError, TypeError, ValueError):
+                    pass
+                args = {key: payload}
+                salvaged.append(name)
+        calls.append({"id": "call_" + uuid.uuid4().hex[:24], "type": "function",
+                      "function": {"name": name, "arguments": json.dumps(args, ensure_ascii=False)}})
+    text = _BOX_RE.sub("", reply)
+    if THINK_CLOSE in text:
+        text = text.split(THINK_CLOSE, 1)[1]
+    text = text.replace(THINK_OPEN, "").replace(THINK_CLOSE, "")
+    if calls:
+        dm = len(salvaged)
+        sys.stderr.write("[api] tool-calls: %d total, %d strict, %d de-mangled [%s]%s\n"
+                         % (len(calls), len(calls) - dm, dm, "CLEAN" if dm == 0 else "DE-MANGLED",
+                            (" -> " + ", ".join(salvaged)) if dm else ""))
+        sys.stderr.flush()
+    return text.strip(), calls
+
+
+def render_chat(messages, enable_thinking=False, reasoning_effort=None, tools=None):
     """Render the text-only subset of the official GLM-5.2 chat template."""
     if not isinstance(messages, list) or not messages:
         raise APIError(400, "`messages` must be a non-empty array.", "messages")
@@ -159,20 +239,57 @@ def render_chat(messages, enable_thinking=False, reasoning_effort=None):
     if enable_thinking:
         effort = "High" if reasoning_effort == "high" else "Max"
         prompt.append(f"<|system|>Reasoning Effort: {effort}")
+    if tools:
+        # AUTHORITATIVE GLM-5.2 tool-declaration block (byte-matches chat_template.jinja): the
+        # `# Tools` + <tools></tools> XML structure is what the model was trained on. A made-up
+        # preamble makes it hallucinate other frameworks' syntax (e.g. `end_action`).
+        prompt.append("<|system|>\n# Tools\n\nYou may call one or more functions to assist with the "
+                      "user query.\n\nYou are provided with function signatures within <tools></tools> "
+                      "XML tags:\n<tools>\n")
+        for tool in tools:
+            fn = tool.get("function", tool) if isinstance(tool, dict) else {}
+            clean = {k: v for k, v in fn.items() if k not in ("defer_loading", "strict")}
+            prompt.append(json.dumps(clean, ensure_ascii=False) + "\n")
+        prompt.append("</tools>\n\nFor each function call, output the function name and arguments "
+                      "within the following XML format:\n<tool_call>{function-name}"
+                      "<arg_key>{arg-key-1}</arg_key><arg_value>{arg-value-1}</arg_value>"
+                      "<arg_key>{arg-key-2}</arg_key><arg_value>{arg-value-2}</arg_value>...</tool_call>")
+    prev_tool = False
     for index, message in enumerate(messages):
         if not isinstance(message, dict):
             raise APIError(400, "Each message must be an object.", f"messages.{index}")
         role = message.get("role")
-        text = content_text(message.get("content"), f"messages.{index}.content")
         if role in ("system", "developer"):
-            prompt.append(f"<|system|>{text}")
+            prompt.append(f"<|system|>{content_text(message.get('content'), f'messages.{index}.content')}")
         elif role == "user":
-            prompt.append(f"<|user|>{text}")
+            prompt.append(f"<|user|>{content_text(message.get('content'), f'messages.{index}.content')}")
         elif role == "assistant":
+            # content may be null when the message is purely tool_calls
+            raw = message.get("content")
+            text = content_text(raw, f"messages.{index}.content") if raw is not None else ""
             prompt.append(f"<|assistant|><think></think>{text.strip()}")
+            for tc in (message.get("tool_calls") or []):
+                fn = tc.get("function", tc) if isinstance(tc, dict) else {}
+                args = fn.get("arguments", "{}")
+                if isinstance(args, str):
+                    try:
+                        args = json.loads(args)
+                    except (json.JSONDecodeError, TypeError):
+                        args = {}
+                prompt.append(BOX_START + (fn.get("name") or ""))
+                for key, value in (args or {}).items():
+                    prompt.append(f"<arg_key>{key}</arg_key><arg_value>"
+                                  + (value if isinstance(value, str)
+                                     else json.dumps(value, ensure_ascii=False)) + "</arg_value>")
+                prompt.append(BOX_END)
+        elif role == "tool":
+            if not prev_tool:                       # one <|observation|> per consecutive tool run
+                prompt.append("<|observation|>")
+            prompt.append(TR_OPEN + content_text(message.get("content"), f"messages.{index}.content") + TR_CLOSE)
         else:
             raise APIError(400, f"Unsupported message role: {role!r}.",
                            f"messages.{index}.role", "unsupported_role")
+        prev_tool = (role == "tool")
     prompt.append("<|assistant|><think>" if enable_thinking else
                   "<|assistant|><think></think>")
     return "".join(prompt)
@@ -181,9 +298,7 @@ def render_chat(messages, enable_thinking=False, reasoning_effort=None):
 def generation_options(body, limit):
     if body.get("n", 1) != 1:
         raise APIError(400, "Colibri currently supports `n=1` only.", "n", "unsupported_value")
-    for name in ("tools", "functions"):
+    # `tools`/`functions` are handled by render_chat (declaration) + parse_tool_calls (output).
-        if body.get(name):
-            raise APIError(400, f"`{name}` is not supported yet.", name, "unsupported_parameter")
     if body.get("stop") is not None:
         raise APIError(400, "Custom stop sequences are not supported yet.", "stop", "unsupported_parameter")
     if body.get("logprobs"):
@@ -427,6 +542,7 @@ class APIHandler(BaseHTTPRequestHandler):
 
     def generation(self, body, prompt, request_id, chat):
         maximum, temperature, top_p = generation_options(body, self.server.max_tokens)
+        tools = (body.get("tools") or body.get("functions") or None) if chat else None
         cache_slot = body.get("cache_slot", 0)
         if isinstance(cache_slot, bool) or not isinstance(cache_slot, int) or not 0 <= cache_slot < self.server.kv_slots:
             raise APIError(400, f"`cache_slot` must be an integer between 0 and {self.server.kv_slots - 1}.",
@@ -450,10 +566,18 @@ class APIHandler(BaseHTTPRequestHandler):
                 stats = self.server.engine.generate(
                     prompt, maximum, temperature, top_p, output.append, cache_slot)
                 text = "".join(output)
-                finish = "length" if stats["length_limited"] else "stop"
+                length_finish = "length" if stats["length_limited"] else "stop"
+                if chat and tools:
+                    content, calls = parse_tool_calls(text, tools)
+                    message = {"role": "assistant", "content": content or None, "refusal": None}
+                    if calls:
+                        message["tool_calls"] = calls
+                    finish = "tool_calls" if calls else length_finish
+                    choice = {"index": 0, "message": message, "logprobs": None, "finish_reason": finish}
+                else:
                     choice = ({"index": 0, "message": {"role": "assistant", "content": text,
-                           "refusal": None}, "logprobs": None, "finish_reason": finish} if chat else
+                               "refusal": None}, "logprobs": None, "finish_reason": length_finish} if chat else
-                          {"index": 0, "text": text, "logprobs": None, "finish_reason": finish})
+                              {"index": 0, "text": text, "logprobs": None, "finish_reason": length_finish})
                 self.send_json(200, {"id": completion_id, "object": object_name, "created": created,
                     "model": self.server.model_id, "choices": [choice], "usage": self.usage(stats)},
                     request_id, queue_headers)
@@ -469,6 +593,18 @@ class APIHandler(BaseHTTPRequestHandler):
             self.send_cors_headers()
             self.end_headers()
             connected = True
+            # KEEPALIVE: engine.generate() blocks SILENTLY during the (minutes-long) cold
+            # prefill, and the client drops the socket after its idle timeout. A background pump
+            # emits a reasoning_content "." delta (the channel that reliably resets the client's
+            # timer and lands in the thinking panel, so answer content stays clean) whenever no
+            # event has been written for KA_GAP seconds. All wfile writes share ka_lock so the
+            # pump and event() never interleave; last_write gates the pump so it stays quiet
+            # while real tokens are flowing (e.g. during decode).
+            ka_lock = threading.Lock()
+            last_write = [time.time()]
+            ka_stop = threading.Event()
+            KA_GAP = 10.0
+            dbg_echo = os.environ.get("COLI_DEBUG", "0") == "1"   # tee decoded tokens to stderr
 
             def event(choices, usage_marker=False):
                 nonlocal connected
@@ -478,13 +614,24 @@ class APIHandler(BaseHTTPRequestHandler):
                               "model": self.server.model_id, "choices": choices}
                 if include_usage:
                     event_body["usage"] = None if not usage_marker else usage_marker
-                try:
                 data = json.dumps(event_body, ensure_ascii=False, separators=(",", ":"))
+                with ka_lock:
+                    try:
                         self.wfile.write(f"data: {data}\n\n".encode())
                         self.wfile.flush()
+                        last_write[0] = time.time()
                     except OSError:
                         connected = False
 
+            def _keepalive():
+                ping = [{"index": 0, "delta": ({"reasoning_content": "."} if chat else {"content": ""}),
+                         "logprobs": None, "finish_reason": None}]
+                while not ka_stop.wait(1.0):
+                    if not connected:
+                        return
+                    if time.time() - last_write[0] >= KA_GAP:
+                        event(ping)
+
             if chat:
                 event([{"index": 0, "delta": {"role": "assistant", "content": ""},
                         "logprobs": None, "finish_reason": None}])
@@ -495,9 +642,54 @@ class APIHandler(BaseHTTPRequestHandler):
                           {"index": 0, "text": text, "logprobs": None, "finish_reason": None})
                 event([choice])
 
+            ka_thread = threading.Thread(target=_keepalive, daemon=True)
+            ka_thread.start()
+            if chat and tools:
+                # Suppress tool-call markers from the streamed content and parse the authoritative
+                # calls from the FULL reply after generation. Hold back a marker-length tail so a
+                # <tool_call> split across engine chunks is still caught.
+                sp = {"buf": "", "tool": False}
+                hold = len(BOX_START) - 1
+                raw = []
+                def emit_tools(chunk):
+                    raw.append(chunk)
+                    if dbg_echo:
+                        sys.stderr.write(chunk); sys.stderr.flush()
+                    if sp["tool"]:
+                        return
+                    sp["buf"] += chunk
+                    cut = sp["buf"].find(BOX_START)
+                    if cut >= 0:
+                        if cut:
+                            emit(sp["buf"][:cut])
+                        sp["buf"] = ""
+                        sp["tool"] = True
+                        return
+                    flush = max(0, len(sp["buf"]) - hold)
+                    if flush:
+                        emit(sp["buf"][:flush])
+                        sp["buf"] = sp["buf"][flush:]
                 stats = self.server.engine.generate(
-                prompt, maximum, temperature, top_p, emit, cache_slot)
+                    prompt, maximum, temperature, top_p, emit_tools, cache_slot)
+                if not sp["tool"] and sp["buf"]:
+                    emit(sp["buf"])                     # no tool call happened: flush held tail
+                _content, calls = parse_tool_calls("".join(raw), tools)
+                for i, tc in enumerate(calls):
+                    event([{"index": 0, "delta": {"tool_calls": [{"index": i, "id": tc["id"],
+                             "type": "function", "function": {"name": tc["function"]["name"],
+                             "arguments": tc["function"]["arguments"]}}]},
+                            "logprobs": None, "finish_reason": None}])
+                finish = "tool_calls" if calls else ("length" if stats["length_limited"] else "stop")
+            else:
+                def emit_plain(chunk):
+                    if dbg_echo:
+                        sys.stderr.write(chunk); sys.stderr.flush()
+                    emit(chunk)
+                stats = self.server.engine.generate(
+                    prompt, maximum, temperature, top_p, emit_plain, cache_slot)
                 finish = "length" if stats["length_limited"] else "stop"
+            ka_stop.set()                          # generation done: stop the keepalive pump
+            ka_thread.join(timeout=2)
             final_choice = ({"index": 0, "delta": {}, "logprobs": None, "finish_reason": finish}
                             if chat else {"index": 0, "text": "", "logprobs": None,
                                           "finish_reason": finish})
@@ -535,10 +727,17 @@ class APIHandler(BaseHTTPRequestHandler):
         if reasoning_effort not in efforts:
             raise APIError(400, "`reasoning_effort` must be none, minimal, low, medium, high, or xhigh.",
                            "reasoning_effort")
+        # COLI_THINK=1 makes thinking the default when the client sends NEITHER reasoning_effort
+        # nor enable_thinking (a global switch, like the old server's --think). An explicit
+        # client value always wins. Default off => exact OpenAI-standard behavior.
+        if (reasoning_effort is None and "enable_thinking" not in body
+                and os.environ.get("COLI_THINK", "0") == "1"):
+            reasoning_effort = "high"
         enable_thinking = body.get("enable_thinking", reasoning_effort not in (None, "none"))
         if not isinstance(enable_thinking, bool):
             raise APIError(400, "`enable_thinking` must be a boolean.", "enable_thinking")
-        prompt = render_chat(body.get("messages"), enable_thinking, reasoning_effort)
+        tools = body.get("tools") or body.get("functions") or None
+        prompt = render_chat(body.get("messages"), enable_thinking, reasoning_effort, tools)
         self.generation(body, prompt, request_id, True)
 
     def completion(self, body, request_id):