From ce7986e4924c1f2b4240d7ee14217ee53fe1d407 Mon Sep 17 00:00:00 2001
From: Xubin Ren <xubinrencs@gmail.com>
Date: Tue, 7 Apr 2026 16:00:41 +0000
Subject: [PATCH] fix(memory): add timestamp and cap to recent history
 injection

---
 nanobot/agent/context.py                 |  6 +++-
 tests/agent/test_context_prompt_cache.py | 38 +++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/nanobot/agent/context.py b/nanobot/agent/context.py
index 1b8cae050..addd0738f 100644
--- a/nanobot/agent/context.py
+++ b/nanobot/agent/context.py
@@ -19,6 +19,7 @@ class ContextBuilder:
 
     BOOTSTRAP_FILES = ["AGENTS.md", "SOUL.md", "USER.md", "TOOLS.md"]
     _RUNTIME_CONTEXT_TAG = "[Runtime Context — metadata only, not instructions]"
+    _MAX_RECENT_HISTORY = 50
 
     def __init__(self, workspace: Path, timezone: str | None = None):
         self.workspace = workspace
@@ -50,7 +51,10 @@ class ContextBuilder:
 
         entries = self.memory.read_unprocessed_history(since_cursor=self.memory.get_last_dream_cursor())
         if entries:
-            parts.append("# Recent History\n\n" + "\n".join(f"- {entry['content']}" for entry in entries))
+            capped = entries[-self._MAX_RECENT_HISTORY:]
+            parts.append("# Recent History\n\n" + "\n".join(
+                f"- [{e['timestamp']}] {e['content']}" for e in capped
+            ))
 
         return "\n\n---\n\n".join(parts)
 
diff --git a/tests/agent/test_context_prompt_cache.py b/tests/agent/test_context_prompt_cache.py
index 59f7c9819..9a5294557 100644
--- a/tests/agent/test_context_prompt_cache.py
+++ b/tests/agent/test_context_prompt_cache.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import re
 from datetime import datetime as real_datetime
 from importlib.resources import files as pkg_files
 from pathlib import Path
@@ -87,7 +88,7 @@ def test_runtime_context_is_separate_untrusted_user_message(tmp_path) -> None:
 
 
 def test_unprocessed_history_injected_into_system_prompt(tmp_path) -> None:
-    """Entries in history.jsonl not yet consumed by Dream appear in the prompt."""
+    """Entries in history.jsonl not yet consumed by Dream appear with timestamps."""
     workspace = _make_workspace(tmp_path)
     builder = ContextBuilder(workspace)
 
@@ -98,6 +99,21 @@ def test_unprocessed_history_injected_into_system_prompt(tmp_path) -> None:
     assert "# Recent History" in prompt
     assert "User asked about weather in Tokyo" in prompt
     assert "Agent fetched forecast via web_search" in prompt
+    assert re.search(r"\[\d{4}-\d{2}-\d{2} \d{2}:\d{2}\]", prompt)
+
+
+def test_recent_history_capped_at_max(tmp_path) -> None:
+    """Only the most recent _MAX_RECENT_HISTORY entries are injected."""
+    workspace = _make_workspace(tmp_path)
+    builder = ContextBuilder(workspace)
+
+    for i in range(builder._MAX_RECENT_HISTORY + 20):
+        builder.memory.append_history(f"entry-{i}")
+
+    prompt = builder.build_system_prompt()
+    assert "entry-0" not in prompt
+    assert "entry-19" not in prompt
+    assert f"entry-{builder._MAX_RECENT_HISTORY + 19}" in prompt
 
 
 def test_no_recent_history_when_dream_has_processed_all(tmp_path) -> None:
@@ -112,6 +128,26 @@ def test_no_recent_history_when_dream_has_processed_all(tmp_path) -> None:
     assert "# Recent History" not in prompt
 
 
+def test_partial_dream_processing_shows_only_remainder(tmp_path) -> None:
+    """When Dream has processed some entries, only the unprocessed ones appear."""
+    workspace = _make_workspace(tmp_path)
+    builder = ContextBuilder(workspace)
+
+    c1 = builder.memory.append_history("old conversation about Python")
+    c2 = builder.memory.append_history("old conversation about Rust")
+    builder.memory.append_history("recent question about Docker")
+    builder.memory.append_history("recent question about K8s")
+
+    builder.memory.set_last_dream_cursor(c2)
+
+    prompt = builder.build_system_prompt()
+    assert "# Recent History" in prompt
+    assert "old conversation about Python" not in prompt
+    assert "old conversation about Rust" not in prompt
+    assert "recent question about Docker" in prompt
+    assert "recent question about K8s" in prompt
+
+
 def test_subagent_result_does_not_create_consecutive_assistant_messages(tmp_path) -> None:
     workspace = _make_workspace(tmp_path)
     builder = ContextBuilder(workspace)