fix(history_text): preserve recent entries when truncating transcript

mini_coding_agent.py

@@ -58,6 +58,13 @@ def clip(text, limit=MAX_TOOL_OUTPUT):
     return text[:limit] + f"\n...[truncated {len(text) - limit} chars]"
 
 
+def tail_clip(text, limit=MAX_HISTORY):
+    text = str(text)
+    if len(text) <= limit:
+        return text
+    return f"...[truncated {len(text) - limit} chars]\n" + text[-limit:]
+
+
 def middle(text, limit):
     text = str(text).replace("\n", " ")
     if len(text) <= limit:
@@ -414,7 +421,7 @@ def history_text(self):
                 limit = 900 if recent else 220
                 lines.append(f"[{item['role']}] {clip(item['content'], limit)}")
 
-        return clip("\n".join(lines), MAX_HISTORY)
+        return tail_clip("\n".join(lines), MAX_HISTORY)
 
     ########################################################
     #### 2) Prompt Shape And Cache Reuse (Continued) #######

tests/test_mini_coding_agent.py

@@ -397,3 +397,38 @@ def fake_urlopen(request, timeout):
     assert captured["body"]["raw"] is False
     assert captured["body"]["think"] is False
     assert captured["body"]["options"]["num_predict"] == 42
+
+
+def test_history_text_preserves_recent_when_truncating(tmp_path):
+    """When history exceeds MAX_HISTORY, recent items should be preserved."""
+    from mini_coding_agent import MAX_HISTORY
+
+    agent = build_agent(tmp_path, [])
+
+    # Create history that exceeds MAX_HISTORY
+    for i in range(70):
+        agent.record({
+            "role": "tool",
+            "name": "read_file",
+            "args": {"path": f"file{i}.txt"},
+            "content": "x" * 500,  # 500 chars of content
+            "created_at": str(i),
+        })
+
+    history = agent.history_text()
+
+    # Verify truncation message is at the TOP (indicating oldest was cut)
+    assert history.startswith("...[truncated")
+
+    # Verify recent entries are present (last 6 are "recent")
+    assert "file69.txt" in history  # most recent
+    assert "file68.txt" in history
+    assert "file67.txt" in history
+
+    # Verify oldest entries are NOT present
+    assert "file0.txt" not in history
+    assert "file1.txt" not in history
+
+    # Verify the length is strictly controlled
+    # It should be roughly MAX_HISTORY + length of the truncation message
+    assert len(history) <= MAX_HISTORY + 100