fix(slack): markdown rendering fidelity — fences, entities, bold, links + opt-in markdown blocks

contributors/emails/akitani@akitaninoMac-mini.local

@@ -0,0 +1 @@
+2001Y

contributors/emails/gonzalofrancoceballos@Gonzalos-Mac-mini.local

@@ -0,0 +1 @@
+gonzalofrancoceballos

contributors/emails/mehrzad.karami@gmail.com

@@ -0,0 +1,2 @@
+mzkarami
+# PR #66204 contributor identity

contributors/emails/skywind5487@gmail.com

@@ -0,0 +1 @@
+Skywind5487

contributors/emails/z23@users.noreply.github.com

@@ -0,0 +1 @@
+z23

contributors/emails/zhangk1985@gmail.com

@@ -0,0 +1 @@
+kylezh

gateway/platforms/base.py

@@ -5895,7 +5895,26 @@ def truncate_message(
 
             # Everything remaining fits in one final chunk
             if _len(prefix) + _len(remaining) <= max_length - INDICATOR_RESERVE:
-                chunks.append(prefix + remaining)
+                final_chunk = prefix + remaining
+                # Check fence balance: if carry_lang was set, the chunk
+                # starts with an opening fence.  Walk the remaining text
+                # to see if the code block was closed; if not, close it.
+                _final_in_code = carry_lang is not None
+                _final_lang = carry_lang or ""
+                if _final_in_code:
+                    for _line in remaining.split("\n"):
+                        _stripped = _line.strip()
+                        if _stripped.startswith("```"):
+                            if _final_in_code:
+                                _final_in_code = False
+                                _final_lang = ""
+                            else:
+                                _final_in_code = True
+                                _tag = _stripped[3:].strip()
+                                _final_lang = _tag.split()[0] if _tag else ""
+                    if _final_in_code:
+                        final_chunk += FENCE_CLOSE
+                chunks.append(final_chunk)
                 break
 
             # Find a natural split point (prefer newlines, then spaces).

gateway/run.py

@@ -13634,6 +13634,7 @@ async def _handle_message_with_agent(self, event, source, _quick_key: str, run_g
             if _show_reasoning_effective and response and not _intentional_silence:
                 last_reasoning = agent_result.get("last_reasoning")
                 if last_reasoning:
+                    from gateway.stream_consumer import escape_code_fences_for_display
                     # Collapse long reasoning to keep messages readable
                     lines = last_reasoning.strip().splitlines()
                     if len(lines) > 15:
@@ -13665,6 +13666,9 @@ async def _handle_message_with_agent(self, event, source, _quick_key: str, run_g
                         )
                         response = f"> 💭 **Reasoning:**\n{_quoted}\n\n{response}"
                     else:
+                        # Escape ``` inside reasoning so inner fences don't
+                        # break the outer code block used to render it.
+                        display_reasoning = escape_code_fences_for_display(display_reasoning)
                         response = f"💭 **Reasoning:**\n```\n{display_reasoning}\n```\n\n{response}"
 
             # Runtime-metadata footer — only on the FINAL message of the turn.