feat(agent): add tool call cycle detection to prevent infinite loops

[flobo3]

Summary

Adds a CycleDetector class that detects when the agent is stuck in a loop calling the same tools repeatedly. This prevents wasted tokens and time when an LLM gets into a repetitive pattern.

Two detection strategies:

• Same call repetition: identical (tool_name, args) called more than N times (default: 3)
• Pattern repetition: a sequence of 2+ tool calls repeats 2+ times

Changes

• New: nanobot/agent/cycle_detector.py — CycleDetector class with configurable parameters
• New: CycleDetectionConfig in nanobot/config/schema.py with tunable settings:
  • enabled: bool = True
  • window_size: int = 20 — number of recent calls to track
  • max_same_calls: int = 3 — max repetitions before triggering
  • pattern_min_length: int = 2 — minimum pattern length to detect
  • pattern_min_repeats: int = 2 — minimum pattern repetitions
• Modified: nanobot/agent/loop.py — integration into _run_agent_loop()
• Modified: nanobot/agent/subagent.py — integration into subagent execution
• Modified: nanobot/agent/context.py — added "Loop Prevention" hints in system prompt
• Modified: nanobot/cli/commands.py — pass config through CLI

Behavior

When a cycle is detected:

1. Agent logs a warning with the reason
2. Returns an informative message: "I detected I'm stuck in a loop (...). Let me try a different approach or ask for clarification."
3. Breaks out of the tool call loop, allowing the agent to pivot strategies

Example

# Agent keeps calling the same tool:
read_file("config.json")
read_file("config.json")
read_file("config.json")
read_file("config.json")  # <- Cycle detected! Breaks loop.

# Or a repeating pattern:
read_file("a.txt") -> exec("ls") -> read_file("a.txt") -> exec("ls") -> read_file("a.txt") -> exec("ls")
# Pattern of 2 tools repeated 3 times - cycle detected!

Configuration

Users can tune detection via nanobot.yaml:

agents:
  defaults:
    cycle_detection:
      enabled: true
      max_same_calls: 3
      window_size: 20

Test Plan

• Verify basic syntax with python -c "import nanobot.agent.cycle_detector"
• Test cycle detection with repeated calls
• Test pattern detection with alternating tool calls
• Verify reset works between conversation turns

🤖 Generated with Claude Code