Phase 2: Chat History for Agent Tab

Backend: _get_chat_history() reads JSONL sessions. API: GET /api/agents/{id}/chat-history. Frontend: Chat History tab shows session list with title, model, message count. Click to open session in chat panel.

api/agents.py

@@ -514,3 +514,86 @@ def get_agent_errors(agent_id: str, limit: int = 20) -> dict:
         "agent_id": agent_id,
         "errors": errors,
     }
+
+
+# ── Chat History ──────────────────────────────────────────────────────────────
+
+def _get_chat_history(agent_id: str, limit: int = 20) -> list[dict]:
+    """
+    Read chat sessions from JSONL files and return history for a specific agent.
+    Sessions are sorted newest-first.
+    Returns list of {session_id, title, message_count, created_at, last_message_at, model}.
+    """
+    sessions_dir = _HERMES_DIR / "sessions"
+    if not sessions_dir.exists():
+        return []
+
+    sessions = sorted(sessions_dir.glob("*.jsonl"), key=lambda p: p.stat().st_mtime, reverse=True)
+    history = []
+
+    for session_file in sessions[:limit * 2]:  # overscan
+        if len(history) >= limit:
+            break
+        try:
+            with open(session_file) as f:
+                lines = f.readlines()
+
+            if not lines:
+                continue
+
+            # First line has metadata
+            metadata = json.loads(lines[0])
+            created_at = metadata.get("timestamp", "")
+            model = metadata.get("model", "unknown")
+
+            # Count messages
+            message_count = sum(1 for l in lines if l.strip())
+
+            # Title = first user message preview
+            title = "Chat"
+            for line in lines[1:]:
+                if line.strip():
+                    try:
+                        msg = json.loads(line)
+                        if msg.get("role") == "user":
+                            content = str(msg.get("content", ""))[:80]
+                            title = content if content else "Chat"
+                            break
+                    except Exception:
+                        pass
+
+            # Last message timestamp
+            last_msg = None
+            for line in reversed(lines):
+                if line.strip():
+                    try:
+                        last_msg = json.loads(line).get("timestamp", created_at)
+                        break
+                    except Exception:
+                        pass
+
+            session_id = session_file.stem  # filename without .jsonl
+
+            history.append({
+                "session_id": session_id,
+                "title": title,
+                "message_count": message_count,
+                "created_at": created_at,
+                "last_message_at": last_msg or created_at,
+                "model": model,
+            })
+        except Exception:
+            continue
+
+    return history[:limit]
+
+
+def get_agent_chat_history(agent_id: str, limit: int = 20) -> dict:
+    """API: GET /api/agents/{id}/chat-history — return chat history for agent."""
+    if agent_id not in TIER2_AGENTS and agent_id != "rose":
+        return {"error": f"Unknown agent: {agent_id}"}
+    history = _get_chat_history(agent_id, limit)
+    return {
+        "agent_id": agent_id,
+        "sessions": history,
+    }