Summary

Adds a new plugin hook transform_llm_output that allows plugins to transform the LLM's output text before it's returned to the user.

Motivation

Personalized vocabulary transformation previously required either lots of personality flavor text in the SOUL, a skill that burned inference tokens on every response, or similar systems which burn tokens unnecessarily. A native plugin hook allows zero-cost vocabulary/personality transformation using more "classical" programming methods.

This follows the pattern of existing transform hooks (transform_terminal_output, transform_tool_result):

• Fired once per turn after the tool-calling loop completes
• First non-empty string result wins
• Fail-open: exceptions logged as warnings, don't break agent execution

Changes

hermes_cli/plugins.py  | 4 ++++
run_agent.py           | 21 +++++++++++++++++++++

hermes_cli/plugins.py

Added transform_llm_output to VALID_HOOKS set.

run_agent.py

Added hook invocation after final_response is set, before post_llm_call.

Hook Signature

def transform_llm_output(response_text: str, session_id: str, model: str, platform: str) -> str | None

• Return: Non-empty string to transform, None or empty string to pass through
• Priority: First non-empty string result wins (same as transform_tool_result)
• Error handling: Fail-open, exceptions logged as warnings

Use Case

# ~/.hermes/plugins/spongebob-vocab/handler.py
import os

def transform_llm_output(response_text: str, session_id: str, model: str, platform: str) -> str | None:
    if os.environ.get("SPONGEBOB_MODE") != "on":
        return None  # Pass through unchanged
    
    # Transform exclamations in conversational parts
    # (Preserves code blocks, URLs, paths, commands)
    ...

Testing

Unit test verified:

SPONGEBOB_MODE=on python3 -c "
from hermes_cli.plugins import get_plugin_manager
pm = get_plugin_manager()
pm.discover_and_load()
results = pm.invoke_hook('transform_llm_output', 'Wow!! Amazing!', '', '', '')
print(results[0])  # Output: Tartar sauce!! Holy Krabby Patties!
"

Documentation

This hook will be documented in the plugin hooks reference alongside transform_terminal_output and transform_tool_result.