feat(gateway): render terminal commands as bare fenced code blocks in chat (#42576)

Terminal tool progress on markdown-capable gateways (Telegram, Slack,
Discord, WhatsApp, Matrix, Weixin, Feishu) renders the full command in a
fenced code block again, in all/new AND verbose modes — gated on the
adapter's supports_code_blocks capability. Plain-text platforms keep the
short truncated preview.

No language tag is emitted: Slack mrkdwn renders a '```bash' fence with
'bash' as a literal first code line, so a bare '```' fence is used, which
renders correctly on every platform that supports blocks.

This restores the #41215 feature (removed in #41950 due to the command
showing in group chats) as the default. For a personal assistant the
command display is desired; the group-chat concern is a preference, not a
vulnerability.

gateway/platforms/base.py

@@ -1797,9 +1797,10 @@ class BasePlatformAdapter(ABC):
     # ``format_message`` translates/preserves markdown fences into a real code
     # block).  Capability flag for markdown-aware presentation choices.
     # Default False (plain-text platforms); markdown-rendering adapters set True.
-    # Note: tool-progress deliberately does NOT use this to render a terminal
-    # command as a ```bash block — that exposed full commands in chat. Progress
-    # shows a short truncated preview only (see gateway/run.py progress_callback).
+    # Tool-progress uses this to render a terminal command as a bare fenced code
+    # block (no language tag — Slack mrkdwn would print the tag as a literal
+    # first code line).  Plain-text platforms fall back to the short truncated
+    # preview (see gateway/run.py progress_callback).
     supports_code_blocks: bool = False
 
     def __init__(self, config: PlatformConfig, platform: Platform):

gateway/run.py

@@ -12971,9 +12971,33 @@ class GatewayRunner(GatewayAuthorizationMixin, GatewayKanbanWatchersMixin, Gatew
             # Build progress message with primary argument preview
             from agent.display import get_tool_emoji
             emoji = get_tool_emoji(tool_name, default="⚙️")
-            
+
+            # Markdown-capable platforms render a terminal command as a fenced
+            # code block (full command, no truncation) instead of the compact
+            # `terminal: "cmd…"` preview.  Gated on the adapter's
+            # ``supports_code_blocks`` capability so plain-text platforms keep
+            # the short line.  No language tag is emitted — Slack mrkdwn renders
+            # the tag as a literal first code line ("bash"), and a bare fence
+            # renders correctly everywhere that supports blocks.
+            _code_block = None
+            try:
+                _progress_adapter = self.adapters.get(source.platform)
+            except Exception:
+                _progress_adapter = None
+            if (
+                getattr(_progress_adapter, "supports_code_blocks", False)
+                and tool_name == "terminal"
+                and isinstance(args, dict)
+                and isinstance(args.get("command"), str)
+                and args["command"].strip()
+            ):
+                _code_block = f"{emoji} {tool_name}\n```\n{args['command'].rstrip()}\n```"
+
             # Verbose mode: show detailed arguments, respects tool_preview_length
             if progress_mode == "verbose":
+                if _code_block is not None:
+                    progress_queue.put(_code_block)
+                    return
                 if args:
                     from agent.display import get_tool_preview_max_len
                     _pl = get_tool_preview_max_len()
@@ -12994,7 +13018,11 @@ class GatewayRunner(GatewayAuthorizationMixin, GatewayKanbanWatchersMixin, Gatew
             # "all" / "new" modes: short preview, respects tool_preview_length
             # config (defaults to 40 chars when unset to keep gateway messages
             # compact — unlike CLI spinners, these persist as permanent messages).
-            if preview:
+            # Terminal commands on markdown platforms get the full fenced block
+            # built above instead of the truncated preview.
+            if _code_block is not None:
+                msg = _code_block
+            elif preview:
                 from agent.display import get_tool_preview_max_len
                 _pl = get_tool_preview_max_len()
                 _cap = _pl if _pl > 0 else 40

tests/gateway/test_run_progress_topics.py

@@ -1295,10 +1295,10 @@ class TerminalCommandAgent:
 
 
 @pytest.mark.asyncio
-async def test_terminal_progress_is_truncated_preview_not_bash_block(monkeypatch, tmp_path):
-    """Regression for #41215: terminal progress must render as a short truncated
-    preview, never the full command in a fenced ```bash block, even on a
-    markdown-capable (supports_code_blocks) gateway."""
+async def test_terminal_progress_renders_fenced_code_block(monkeypatch, tmp_path):
+    """Terminal progress on a markdown-capable (supports_code_blocks) gateway
+    renders the full command in a bare fenced code block — no language tag
+    (Slack mrkdwn would print 'bash' as a literal first code line)."""
     monkeypatch.setenv("HERMES_TOOL_PROGRESS_MODE", "all")
 
     fake_dotenv = types.ModuleType("dotenv")
@@ -1328,18 +1328,20 @@ async def test_terminal_progress_is_truncated_preview_not_bash_block(monkeypatch
         context_prompt="",
         history=[],
         source=source,
-        session_id="sess-terminal-no-bash-block",
+        session_id="sess-terminal-code-block",
         session_key="agent:main:telegram:dm:12345",
     )
 
     assert result["final_response"] == "done"
     all_content = " ".join(call["content"] for call in adapter.sent)
     all_content += " ".join(call["content"] for call in adapter.edits)
-    # Compact truncated preview, not a fenced bash block.
+    # Bare fenced block, no language tag (no '```bash').
+    assert "```" in all_content
     assert "```bash" not in all_content
-    assert 'terminal: "' in all_content
-    # The full multi-line command body must not reach the chat.
-    assert "npm install -g hyperframes@latest" not in all_content
+    # The full multi-line command body IS present in the block.
+    assert "npm install -g hyperframes@latest" in all_content
+    # No truncated quoted preview for the terminal command.
+    assert 'terminal: "' not in all_content
 
 
 @pytest.mark.asyncio