feat reasoning

chatbot.py

@@ -16,7 +16,7 @@ if _cuda_path:
 from ddgs import DDGS  # noqa: E402
 from llama_cpp import Llama  # noqa: E402
 
-MODEL_PATH = Path(__file__).parent / "Qwen2.5-Coder-14B-Instruct-Q5_K_M.gguf"
+MODEL_PATH = Path(__file__).parent / "Qwen3.5-27B-IQ4_XS.gguf"
 
 SYSTEM_PROMPT = (
     "You are a knowledgeable developer assistant. Answer questions about "
@@ -56,9 +56,20 @@ WEB_SEARCH_TOOL = {
     },
 }
 
-# Matches the <tool_call>{...}</tool_call> blocks Qwen's chat template trains
-# it to emit when it wants to invoke a tool.
-TOOL_CALL_RE = re.compile(r"<tool_call>\s*(\{.*?\})\s*</tool_call>", re.DOTALL)
+# Matches the <tool_call><function=name>...</function></tool_call> blocks
+# Qwen3.5's chat template trains it to emit when it wants to invoke a tool -
+# an XML-style syntax, not Qwen2.5's JSON-in-<tool_call> format.
+TOOL_CALL_RE = re.compile(
+    r"<tool_call>\s*<function=([^>]+)>(.*?)</function>\s*</tool_call>", re.DOTALL
+)
+# Matches each <parameter=name>value</parameter> inside a tool call's body.
+PARAMETER_RE = re.compile(r"<parameter=([^>]+)>\n?(.*?)\n?</parameter>", re.DOTALL)
+
+# Qwen3.5 thinks by default, wrapping its reasoning trace in these tags
+# before the actual answer (or tool call). _route_stream_piece splits a
+# streamed response between the two so a caller can render them separately.
+THINK_OPEN = "<think>"
+THINK_CLOSE = "</think>"
 
 
 def web_search(query: str, max_results: int = 5) -> str:
@@ -82,42 +93,15 @@ def web_search(query: str, max_results: int = 5) -> str:
 TOOLS = {"web_search": web_search}
 
 
-def _iter_balanced_braces(text: str):
-    """Yield each top-level {...} substring of text, respecting nesting."""
-    depth = 0
-    start = None
-    for i, ch in enumerate(text):
-        if ch == "{":
-            if depth == 0:
-                start = i
-            depth += 1
-        elif ch == "}" and depth > 0:
-            depth -= 1
-            if depth == 0 and start is not None:
-                yield text[start : i + 1]
-
-
 def extract_tool_calls(text: str) -> list[dict]:
     calls = []
-    for match in TOOL_CALL_RE.finditer(text):
-        try:
-            calls.append(json.loads(match.group(1)))
-        except json.JSONDecodeError:
-            continue
-    if calls:
-        return calls
-
-    # This model often skips the <tool_call> wrapper it's instructed to use
-    # and just emits a bare JSON object instead - sometimes with leading
-    # prose alongside it (e.g. "Let's try again. {...}") - so scan for any
-    # JSON object in the text rather than requiring the whole message to be one.
-    for candidate in _iter_balanced_braces(text):
-        try:
-            call = json.loads(candidate)
-        except json.JSONDecodeError:
-            continue
-        if isinstance(call, dict) and call.get("name") in TOOLS:
-            calls.append(call)
+    for call_match in TOOL_CALL_RE.finditer(text):
+        name = call_match.group(1).strip()
+        arguments = {
+            param_match.group(1).strip(): param_match.group(2)
+            for param_match in PARAMETER_RE.finditer(call_match.group(2))
+        }
+        calls.append({"name": name, "arguments": arguments})
     return calls
 
 
@@ -133,9 +117,11 @@ def build_messages(history: list[tuple[str, str]], question: str) -> list[dict[s
 def load_model() -> Llama:
     return Llama(
         model_path=str(MODEL_PATH),
-        # the model supports up to 32k context natively; give plenty of room
-        # for chat history plus a long generated response
-        n_ctx=24000,
+        # Qwen3.5-27B's hybrid attention keeps KV cache small (most layers
+        # carry a fixed-size state rather than one that grows with context),
+        # so this fits alongside the IQ4_XS weights on a 16GB card with room
+        # to spare - unlike a same-sized dense-attention model.
+        n_ctx=32768,
         # -1 offloads every layer to the GPU
         n_gpu_layers=-1,
         # number of tokens in the prompt that are fed into the model at a time
@@ -144,14 +130,55 @@ def load_model() -> Llama:
     )
 
 
+def _route_stream_piece(
+    piece: str,
+    state: dict,
+    on_token: Callable[[str], None] | None,
+    on_thinking_token: Callable[[str], None] | None,
+) -> None:
+    """Forward piece to on_thinking_token while inside a <think>...</think>
+    block and to on_token otherwise, using state (a per-call {"in_think",
+    "buffer"} dict) to track which side of a tag boundary we're on and to
+    hold back text that might be the start of a tag split across pieces."""
+    buffer = state["buffer"] + piece
+    while True:
+        tag = THINK_CLOSE if state["in_think"] else THINK_OPEN
+        idx = buffer.find(tag)
+        if idx == -1:
+            break
+        before, buffer = buffer[:idx], buffer[idx + len(tag) :]
+        callback = on_thinking_token if state["in_think"] else on_token
+        if before and callback is not None:
+            callback(before)
+        state["in_think"] = not state["in_think"]
+
+    # The buffer may end with a prefix of the tag we're now watching for
+    # (e.g. a chunk boundary landing mid-"</think>"), so hold that part back
+    # rather than misrouting it as ordinary content.
+    tag = THINK_CLOSE if state["in_think"] else THINK_OPEN
+    keep = 0
+    for length in range(min(len(tag), len(buffer)), 0, -1):
+        if tag.startswith(buffer[-length:]):
+            keep = length
+            break
+    emit, state["buffer"] = buffer[: len(buffer) - keep], buffer[len(buffer) - keep :]
+    callback = on_thinking_token if state["in_think"] else on_token
+    if emit and callback is not None:
+        callback(emit)
+
+
 def _stream_content(
     llm: Llama,
     messages: list[dict],
     tools: list[dict] | None,
     on_token: Callable[[str], None] | None,
+    on_thinking_token: Callable[[str], None] | None = None,
 ) -> str:
     """Run one streaming create_chat_completion call, forwarding each piece
-    of generated text to on_token as it arrives, and return the full text."""
+    of generated text to on_token (or on_thinking_token, while inside a
+    <think> block) as it arrives, and return the full raw text, thinking
+    tags included, so the caller's message history matches what the model
+    actually produced."""
     kwargs = {}
     if tools is not None:
         kwargs["tools"] = tools
@@ -165,21 +192,40 @@ def _stream_content(
         **kwargs,
     )
     content = ""
+    # Qwen3.5's chat template appends "<think>\n" to the prompt itself before
+    # generation starts (see its tokenizer.chat_template's add_generation_prompt
+    # block), so the model's own streamed output never contains that opening
+    # tag - it starts already "inside" one, and only emits "</think>" once
+    # reasoning is done.
+    route_state = {"in_think": True, "buffer": ""}
     for chunk in stream:
         piece = chunk["choices"][0]["delta"].get("content")
         if piece:
             content += piece
-            if on_token is not None:
-                on_token(piece)
+            _route_stream_piece(piece, route_state, on_token, on_thinking_token)
+    if route_state["buffer"]:
+        callback = on_thinking_token if route_state["in_think"] else on_token
+        if callback is not None:
+            callback(route_state["buffer"])
     return content
 
 
+def _strip_thinking(text: str) -> str:
+    """Drop a leading reasoning trace from raw model output, the same way
+    the chat template splits it back out when re-rendering a past turn:
+    everything before the first </think> is reasoning (there's no opening
+    tag to look for - see _stream_content), everything after is the answer."""
+    before, sep, after = text.partition(THINK_CLOSE)
+    return after.lstrip("\n") if sep else before
+
+
 def ask(
     llm: Llama,
     messages: list[dict],
     on_tool_call: Callable[[str], None] | None = None,
     on_usage: Callable[[dict], None] | None = None,
     on_token: Callable[[str], None] | None = None,
+    on_thinking_token: Callable[[str], None] | None = None,
 ) -> str:
     """Run the chat loop for one question, letting the model call web_search
     up to MAX_TOOL_ROUNDS times before returning its final answer text.
@@ -189,14 +235,16 @@ def ask(
     model call, so a caller can track how much of the context window is
     filled. If given, on_token is invoked with each piece of generated text
     as it streams from the model, so a caller can render the answer live
-    instead of waiting for it to finish."""
+    instead of waiting for it to finish. If given, on_thinking_token is
+    invoked the same way but for text inside the model's <think> block,
+    letting a caller render its reasoning trace separately from the answer."""
     for _ in range(MAX_TOOL_ROUNDS):
-        content = _stream_content(llm, messages, [WEB_SEARCH_TOOL], on_token)
+        content = _stream_content(llm, messages, [WEB_SEARCH_TOOL], on_token, on_thinking_token)
         if on_usage is not None:
             on_usage({"total_tokens": llm.n_tokens})
         calls = extract_tool_calls(content)
         if not calls:
-            return content
+            return _strip_thinking(content)
 
         messages.append({"role": "assistant", "content": content})
         for call in calls:
@@ -216,7 +264,7 @@ def ask(
     # Ran out of tool-call rounds without a plain answer; ask one more time
     # without offering the tool, forcing it to answer from what it has
     # instead of returning a leftover tool-call as if it were the answer.
-    content = _stream_content(llm, messages, None, on_token)
+    content = _stream_content(llm, messages, None, on_token, on_thinking_token)
     if on_usage is not None:
         on_usage({"total_tokens": llm.n_tokens})
-    return content
+    return _strip_thinking(content)

gui.py

@@ -6,9 +6,10 @@ from pygments import highlight
 from pygments.formatters import HtmlFormatter
 from pygments.lexers import TextLexer, get_lexer_by_name, guess_lexer
 from pygments.util import ClassNotFound
-from PyQt6.QtCore import Qt, QThread, QTimer, pyqtSignal
+from PyQt6.QtCore import Qt, QThread, QTimer, QUrl, pyqtSignal
 from PyQt6.QtGui import (
     QColor,
+    QDesktopServices,
     QFont,
     QIcon,
     QLinearGradient,
@@ -87,8 +88,14 @@ ROLE_STYLES = {
     "user": (CORAL_GLOW, "#3a2c26"),
     "assistant": (SILVER, "#2f3342"),
     "system": (BLUE_SLATE, "#262a36"),
+    "thinking": (TEXT_SECONDARY, "#282b38"),
 }
 
+# Prefix for the fake anchor href used to make a thinking block's header
+# clickable (e.g. "think:think-3"), intercepted in _on_chat_anchor_clicked
+# rather than let QTextBrowser try to navigate to it.
+_THINK_ANCHOR_PREFIX = "think:"
+
 _STYLESHEET = f"""
 QMainWindow {{
     background-color: {BG_APP};
@@ -376,6 +383,7 @@ class AskThread(QThread):
     tool_call = pyqtSignal(str)
     usage = pyqtSignal(dict)
     token = pyqtSignal(str)
+    thinking_token = pyqtSignal(str)
     finished_ok = pyqtSignal(str)
     failed = pyqtSignal(str)
 
@@ -392,6 +400,7 @@ class AskThread(QThread):
                 on_tool_call=self.tool_call.emit,
                 on_usage=self.usage.emit,
                 on_token=self.token.emit,
+                on_thinking_token=self.thinking_token.emit,
             )
         except Exception as e:
             self.failed.emit(str(e))
@@ -414,6 +423,22 @@ class ChatWindow(QMainWindow):
         # incoming tokens; both None when no answer is currently streaming.
         self._stream_start_pos: int | None = None
         self._stream_body_cursor: QTextCursor | None = None
+        # Whether a real (non-newline) answer character has been inserted
+        # yet for the in-progress card - the model's text after </think>
+        # typically opens with a blank line or two, which _on_token trims
+        # rather than showing as a gap at the top of the answer bubble.
+        self._answer_started = False
+
+        # Thinking blocks (one per model reasoning round), keyed by an id
+        # referenced from the clickable "think:<id>" anchor in their header.
+        # Each holds the full reasoning text, whether it's currently shown
+        # expanded, a fixed cursor marking where its content region starts,
+        # and a live cursor tracking where that region currently ends - see
+        # _render_thinking(). self._stream_thinking_id names whichever block
+        # (if any) is still actively streaming in the current round.
+        self._thinking_blocks: dict[str, dict] = {}
+        self._thinking_seq = 0
+        self._stream_thinking_id: str | None = None
 
         central = QWidget()
         self.setCentralWidget(central)
@@ -448,7 +473,12 @@ class ChatWindow(QMainWindow):
 
         self.chat_view = QTextBrowser()
         self.chat_view.setObjectName("chatView")
-        self.chat_view.setOpenExternalLinks(True)
+        # Links are handled by hand in _on_chat_anchor_clicked (real URLs get
+        # opened externally there too) rather than left to QTextBrowser,
+        # since its own link handling doesn't know about the fake
+        # "think:<id>" anchors used to toggle a thinking block.
+        self.chat_view.setOpenLinks(False)
+        self.chat_view.anchorClicked.connect(self._on_chat_anchor_clicked)
         self.chat_view.setFont(QFont("Segoe UI Variable Text", 10))
         layout.addWidget(self.chat_view)
 
@@ -551,6 +581,8 @@ class ChatWindow(QMainWindow):
         self.statusBar().showMessage("Thinking...")
         self._stream_start_pos = None
         self._stream_body_cursor = None
+        self._answer_started = False
+        self._stream_thinking_id = None
 
         messages = chatbot.build_messages(self._history, question)
         self._pending_question = question
@@ -559,12 +591,14 @@ class ChatWindow(QMainWindow):
         self._ask_thread.tool_call.connect(self._on_tool_call)
         self._ask_thread.usage.connect(self._on_usage)
         self._ask_thread.token.connect(self._on_token)
+        self._ask_thread.thinking_token.connect(self._on_thinking_token)
         self._ask_thread.finished_ok.connect(self._on_answer)
         self._ask_thread.failed.connect(self._on_ask_failed)
         self._ask_thread.start()
 
     def _on_token(self, piece: str) -> None:
         if self._stream_body_cursor is None:
+            self._collapse_open_thinking()
             self.statusBar().showMessage("Generating...")
             cursor = self.chat_view.textCursor()
             cursor.movePosition(QTextCursor.MoveOperation.End)
@@ -574,6 +608,13 @@ class ChatWindow(QMainWindow):
             body.insertHtml(f'<span style="color:{accent}; font-weight:600; font-size:8.5pt;">ASSISTANT</span>')
             body.insertBlock(QTextBlockFormat(), QTextCharFormat())
             self._stream_body_cursor = body
+            self._answer_started = False
+
+        if not self._answer_started:
+            piece = piece.lstrip("\n")
+            if not piece:
+                return
+            self._answer_started = True
 
         char_format = QTextCharFormat()
         char_format.setForeground(QColor(TEXT_PRIMARY))
@@ -593,7 +634,95 @@ class ChatWindow(QMainWindow):
         self._stream_start_pos = None
         self._stream_body_cursor = None
 
+    def _on_thinking_token(self, piece: str) -> None:
+        if self._stream_thinking_id is None:
+            cursor = self.chat_view.textCursor()
+            cursor.movePosition(QTextCursor.MoveOperation.End)
+            accent, bg = ROLE_STYLES["thinking"]
+            body = _insert_message_card(cursor, accent, bg)
+            body.insertHtml(f'<span style="color:{accent}; font-weight:600; font-size:8.5pt;">THINKING</span>')
+            body.insertBlock(QTextBlockFormat(), QTextCharFormat())
+
+            self._thinking_seq += 1
+            block_id = f"think-{self._thinking_seq}"
+            content_start = QTextCursor(body)
+            # Without this, inserting the header right at content_start's own
+            # position (both here and on every later toggle) would drag it
+            # forward along with that insertion, per QTextCursor's default -
+            # it needs to stay pinned at the true start of the region instead.
+            content_start.setKeepPositionOnInsert(True)
+            self._thinking_blocks[block_id] = {
+                "text": "",
+                "expanded": True,
+                "content_start": content_start,
+                "cursor": body,
+            }
+            self._insert_thinking_header(body, block_id, expanded=True)
+            body.insertBlock(QTextBlockFormat(), QTextCharFormat())
+            self._stream_thinking_id = block_id
+
+        block = self._thinking_blocks[self._stream_thinking_id]
+        block["text"] += piece
+        italic_format = QTextCharFormat()
+        italic_format.setForeground(QColor(TEXT_SECONDARY))
+        italic_format.setFontItalic(True)
+        block["cursor"].insertText(piece, italic_format)
+        self.chat_view.moveCursor(QTextCursor.MoveOperation.End)
+
+    def _insert_thinking_header(self, cursor: QTextCursor, block_id: str, expanded: bool) -> None:
+        arrow = "▼" if expanded else "▶"
+        cursor.insertHtml(
+            f'<a href="{_THINK_ANCHOR_PREFIX}{block_id}" '
+            f'style="color:{TEXT_SECONDARY}; text-decoration:none;">{arrow} Thinking</a>'
+        )
+
+    def _render_thinking(self, block_id: str, expanded: bool) -> None:
+        """Rewrite a thinking block's header and body to match expanded,
+        replacing everything from its fixed content_start cursor through
+        wherever its content currently ends (tracked by its own cursor,
+        which - like any QTextCursor - keeps up with edits made elsewhere in
+        the document, so this stays correct even if other messages have
+        since been appended below it)."""
+        block = self._thinking_blocks[block_id]
+        cursor = block["cursor"]
+        old_end = cursor.position()
+        cursor.setPosition(block["content_start"].position())
+        cursor.setPosition(old_end, QTextCursor.MoveMode.KeepAnchor)
+        cursor.removeSelectedText()
+
+        self._insert_thinking_header(cursor, block_id, expanded)
+        if expanded:
+            cursor.insertBlock(QTextBlockFormat(), QTextCharFormat())
+            italic_format = QTextCharFormat()
+            italic_format.setForeground(QColor(TEXT_SECONDARY))
+            italic_format.setFontItalic(True)
+            cursor.insertText(block["text"], italic_format)
+        block["expanded"] = expanded
+        self.chat_view.moveCursor(QTextCursor.MoveOperation.End)
+
+    def _collapse_open_thinking(self) -> None:
+        if self._stream_thinking_id is not None:
+            self._render_thinking(self._stream_thinking_id, expanded=False)
+            self._stream_thinking_id = None
+
+    def _on_chat_anchor_clicked(self, url: QUrl) -> None:
+        href = url.toString()
+        if not href.startswith(_THINK_ANCHOR_PREFIX):
+            QDesktopServices.openUrl(url)
+            return
+        # A generation currently in flight may be inserting content through
+        # this same block's cursor further down; leave the block alone
+        # rather than risk racing that live cursor.
+        if self._ask_thread is not None:
+            return
+        block_id = href[len(_THINK_ANCHOR_PREFIX) :]
+        block = self._thinking_blocks.get(block_id)
+        if block is None:
+            return
+        self._render_thinking(block_id, expanded=not block["expanded"])
+
     def _on_tool_call(self, query: str) -> None:
+        self._collapse_open_thinking()
         self._discard_stream_card()
         self.statusBar().showMessage(f"Searching: {query}")
         self._append_system(f"Searching the web for: {query}")
@@ -604,6 +733,10 @@ class ChatWindow(QMainWindow):
         self.context_status_label.setText(f"Context: {total} / {self._n_ctx} ({pct:.0f}%)")
 
     def _on_answer(self, answer: str) -> None:
+        # Normally already collapsed by the first answer token (_on_token),
+        # but a response that hit max_tokens mid-<think> would leave this
+        # block open with nothing to trigger the collapse - catch that here.
+        self._collapse_open_thinking()
         # The streamed card holds the raw, plain-text answer; swap it out for
         # a fully markdown-rendered and syntax-highlighted one now that the
         # complete text is available.
@@ -615,6 +748,7 @@ class ChatWindow(QMainWindow):
         self._set_input_enabled(True)
 
     def _on_ask_failed(self, message: str) -> None:
+        self._collapse_open_thinking()
         self._discard_stream_card()
         self._append_system(f"Error: {message}")
         self.statusBar().showMessage("Ready.")