fix(memory): add timestamp and cap to recent history injection

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)