fix: render readable text in get_communication_history for all memory…

[Harsh-617]

Fixes #193

Summary

• get_communication_history() in all three memory classes (ShortTermMemory, STLTMemory, EpisodicMemory) was rendering raw Python dicts instead of readable message strings in the LLM prompt
• Added a shared _format_message_entry() helper in memory.py that extracts human-readable text from the nested dict structure produced by speak_to
• Applied the fix across all three memory implementations and added regression tests

Root Cause

The speak_to tool stores messages as a nested dict:

add_to_memory(
    type="message",
    content={"message": "meet me at the north", "sender": 7, "recipients": [1, 2]},
)

This means entry.content["message"] is always a dict, not a string. But get_communication_history() passed it directly into the f-string:

# Before — renders raw dict
f"step {entry.step}: {entry.content['message']}\n\n"
# Output: step 5: {'message': 'meet me at the north', 'sender': 7, 'recipients': [1, 2]}

This garbled output was injected into the ReAct reasoning prompt on every step where agents had exchanged messages, silently corrupting the LLM's view of inter-agent communication.

Changes

mesa_llm/memory/memory.py

• Added _format_message_entry(msg_value) -> str helper that renders {"message": "...", "sender": 42, ...} as "Agent 42 says: ...", with a plain-string passthrough for backward compatibility

mesa_llm/memory/episodic_memory.py, st_lt_memory.py, st_memory.py

• Updated get_communication_history() in all three to use _format_message_entry() instead of raw f-string interpolation

Tests

• TestFormatMessageEntry (5 tests) in test_memory_parent.py — unit tests for the helper covering: nested dict with sender, without sender, plain string passthrough, missing message key fallback, and EpisodicMemory's importance-augmented payload
• test_get_communication_history_nested_dict added to all three memory test files — reproduces the real speak_to payload structure and asserts readable output
• test_get_communication_history_skips_non_message_entries added to all three — asserts non-message entries are correctly excluded
• test_get_communication_history_returns_empty_string_when_no_messages added to STLTMemory and ShortTermMemory

Before / After

# Before
step 5: {'message': 'meet me at the north', 'sender': 7, 'recipients': [1, 2]}

# After
step 5: Agent 7 says: meet me at the north

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.69%. Comparing base (27f0f50) to head (1bbd86f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #194      +/-   ##
==========================================
+ Coverage   90.64%   90.69%   +0.04%     
==========================================
  Files          19       19              
  Lines        1540     1548       +8     
==========================================
+ Hits         1396     1404       +8     
  Misses        144      144              

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