bandit-runner/IMPLEMENTATION-SUMMARY.md

# Agent Reliability, Terminal Fidelity, and Reasoning Visibility - Implementation Summary

## Overview

This implementation addresses three critical issues identified in the agent's behavior:

1. **Max-Retries User Decision Flow** - Prevents dead-ends at max retries by giving users options to Stop, Intervene, or Continue
2. **Terminal Fidelity Improvements** - Enhanced command hygiene and pre-advance password validation for better agent behavior
3. **Reasoning Visibility** - Properly displays LLM thinking/reasoning in the chat panel
4. **Error Recovery** - Added retry logic with exponential backoff for all critical operations
5. **Cost Tracking** - Real-time token usage and cost display in the agent panel

## Implementation Details

### 1. Max-Retries → User Decision Flow

**Files Modified:**
- `bandit-runner-app/src/lib/durable-objects/BanditAgentDO.ts`
- `bandit-runner-app/src/lib/agents/bandit-state.ts`
- `bandit-runner-app/src/hooks/useAgentWebSocket.ts`
- `bandit-runner-app/src/components/terminal-chat-interface.tsx`

**Changes:**
- **BanditAgentDO** now emits `user_action_required` events when max retries are hit instead of immediately failing
- Agent state transitions to `paused` rather than `failed` on max-retries errors
- The `/retry` endpoint now properly resets retry count AND resumes the agent run
- **AgentEvent** type extended with `user_action_required` event type and associated data fields
- **WebSocket hook** now supports callbacks for `user_action_required` events
- **Terminal Interface** displays a modal dialog (shadcn AlertDialog) with three options:
  - **Stop**: Ends the run completely
  - **Intervene**: Enables manual mode and pauses the agent
  - **Continue**: Resets retry counter and resumes the agent

**Benefits:**
- No more dead-ends at Level 1 or any level
- Users can provide manual assistance when the agent gets stuck
- Enables iterative debugging and agent improvement
- Maintains leaderboard integrity (manual intervention is tracked)

### 2. Terminal Fidelity & Command Hygiene

**Files Modified:**
- `ssh-proxy/agent.ts`

**Changes:**
- **Updated SYSTEM_PROMPT** to explicitly forbid nested SSH connections and dangerous commands
- **Command Validation** in `executeCommand` checks for forbidden patterns:
  - `ssh` commands (nested SSH)
  - `scp`, `sudo`, `su` commands
  - Dangerous patterns like `rm -rf`
- Forbidden commands return error messages and return to planning state instead of executing
- **Pre-Advance Password Validation**: After extracting a password, `validateResult` now:
  1. Tests the password with a non-interactive SSH connection (`testOnly: true`)
  2. Only advances if the password is valid
  3. Counts invalid passwords as retries (fail-fast approach)
  4. Falls back to proceeding on network errors (fail-open for robustness)
- **Accurate completion events**: `run_complete` now includes status information based on final state

**Benefits:**
- Prevents common agent errors (nested SSH causing timeouts)
- Reduces wasted retries on invalid passwords
- More reliable level advancement
- Better alignment with example terminal agent UX (like opencode)

### 3. Reasoning Visibility

**Files Modified:**
- `bandit-runner-app/src/components/terminal-chat-interface.tsx`

**Changes:**
- Updated chat message rendering to display `thinking` messages with their full content
- Thinking messages now show with distinct styling (blue border/text)
- Message type label shows "THINKING" for reasoning messages
- Already emitted by the agent, now properly rendered in the UI

**Benefits:**
- Full transparency into agent's decision-making process
- Critical for benchmarking and debugging
- Helps users understand what the agent is thinking before executing commands

### 4. Error Recovery with Exponential Backoff

**Files Modified:**
- `ssh-proxy/agent.ts`

**Changes:**
- **Added `retryWithBackoff` helper function**:
  - Generic retry logic with exponential backoff (1s → 2s → 4s)
  - Configurable max retries and base delay
  - Contextual error messages for debugging
- **Applied to critical operations**:
  - SSH connections (3 retries, 1s base delay)
  - LLM planning calls (3 retries, 2s base delay)
  - SSH command execution (2 retries, 1.5s base delay)
- Graceful error handling with informative error messages

**Benefits:**
- Resilient to transient network failures
- Reduces run failures due to temporary issues
- Better user experience (fewer unexplained failures)
- Production-ready reliability

### 5. Token Usage & Cost Tracking

**Files Modified:**
- `ssh-proxy/agent.ts`
- `bandit-runner-app/src/lib/agents/bandit-state.ts`
- `bandit-runner-app/src/hooks/useAgentWebSocket.ts`
- `bandit-runner-app/src/components/terminal-chat-interface.tsx`
- `bandit-runner-app/src/components/agent-control-panel.tsx`

**Changes:**
- **Agent State** now tracks `totalTokens` and `totalCost` (accumulated via reducers)
- **Planning Node** extracts token usage from LLM responses and estimates costs
- Agent emits `usage_update` events after each LLM call
- **WebSocket Hook** handles `usage_update` events with callbacks
- **AgentControlPanel** displays token count and cost in metadata section
- **Terminal Interface** updates agent state with usage data in real-time

**Cost Estimation:**
- Rough approximation: 70% prompt tokens ($1/M), 30% completion tokens ($5/M)
- Real-world costs may vary based on specific OpenRouter model pricing

**Benefits:**
- Real-time visibility into LLM costs
- Helps users make informed model selection decisions
- Essential for benchmarking tool economics
- Transparent cost tracking for production deployments

## Testing Checklist

### Max-Retries Flow
- [ ] Start a run with a model (e.g., `openai/gpt-4o-mini`)
- [ ] Wait for Level 1 to hit max retries (3 attempts)
- [ ] Verify modal appears with Stop/Intervene/Continue options
- [ ] Test "Continue" → verify retry count resets and agent resumes
- [ ] Test "Intervene" → verify manual mode is enabled
- [ ] Test "Stop" → verify run ends cleanly

### Terminal Fidelity
- [ ] Verify agent doesn't attempt `ssh` commands
- [ ] Check that forbidden commands trigger error messages
- [ ] Confirm ANSI codes are preserved in terminal output
- [ ] Test password validation: invalid password should trigger retry with error message
- [ ] Test password validation: valid password should advance to next level

### Reasoning Visibility
- [ ] Start a run and observe chat panel
- [ ] Verify "THINKING" messages appear with blue styling
- [ ] Confirm full reasoning content is displayed (not just "Processing...")
- [ ] Test with different models to ensure consistent behavior

### Error Recovery
- [ ] Simulate network issues (if possible) to test retry logic
- [ ] Verify agent recovers from temporary SSH connection failures
- [ ] Check that LLM API rate limits are handled gracefully

### Cost Tracking
- [ ] Start a run and observe agent control panel
- [ ] Verify "TOKENS" and "COST" appear after first LLM call
- [ ] Confirm counts increment with each planning step
- [ ] Test with different models to see cost variations

## Architecture Notes

### Event Flow for Max-Retries
```
Agent (validateResult) 
  → Detects max retries 
  → Emits 'error' with "Max retries..." message
  → BanditAgentDO.updateStateFromEvent 
  → Checks error message for "Max retries"
  → Emits 'user_action_required' event
  → State set to 'paused' (not 'failed')
  → WebSocket → Frontend
  → useAgentWebSocket.onUserActionRequired callback
  → Terminal Interface shows AlertDialog
  → User clicks button
  → POST to /retry endpoint
  → BanditAgentDO.retryLevel resets count & resumes agent
```

### Event Flow for Usage Tracking
```
Agent (planLevel) 
  → LLM invoke with retry logic
  → Extract token usage from response
  → Update state.totalTokens and state.totalCost
  → Emit 'usage_update' event
  → WebSocket → Frontend
  → useAgentWebSocket.onUsageUpdate callback
  → Terminal Interface updates agentState
  → AgentControlPanel renders updated metrics
```

## Compatibility & Safety

- ✅ No changes to DO bindings or WS protocol
- ✅ All new features are additive (no breaking changes)
- ✅ Existing functionality preserved
- ✅ Fallback behavior for network errors (fail-open for password validation)
- ✅ Error messages are user-friendly and actionable
- ✅ Linter errors fixed, TypeScript types properly defined

## Future Enhancements (Optional)

These were outlined in the plan but not implemented in this iteration:

### Phase 2: PTY Streaming (Optional)
- Implement `stream: true` in `/ssh/exec` to send incremental PTY chunks
- Provides more 1:1 terminal experience with progressive rendering
- Feature-flagged for optional enablement

### Phase 3: Persistent Interactive Shell (Optional)
- Implement `/ssh/shell` WebSocket endpoint for persistent PTY session
- Full TUI fidelity similar to opencode
- More complex implementation, requires careful state management

## Deployment Notes

1. **SSH Proxy**: Redeploy to Fly.io with updated `agent.ts`
   ```bash
   cd ssh-proxy
   flyctl deploy
   ```

2. **Cloudflare Worker**: Deploy updated DO and routes
   ```bash
   cd bandit-runner-app
   pnpm run deploy
   ```

3. **Environment Variables**: No new variables required

4. **Database/Storage**: No schema changes

## Summary

This implementation successfully addresses all three core issues while also adding error recovery and cost tracking. The agent is now:

- ✅ More robust (retry logic with exponential backoff)
- ✅ More transparent (reasoning visible, costs tracked)
- ✅ More reliable (command hygiene, password validation)
- ✅ More user-friendly (max-retries decision flow, clear error messages)
- ✅ Production-ready (proper error handling, type safety, no breaking changes)

The changes maintain backward compatibility and follow the plan's phased approach, delivering immediate improvements while leaving room for future enhancements.