AI agents fail. Understanding why is hard.
Black Box Execution
Most agent frameworks expose logs, not reasoning. You see what happened, not why it happened.
Missing Context
Tool calls, MCP requests, prompts, and file changes are scattered across systems. No single source of truth.
No Reproducibility
Failures are difficult to replay and investigate later. Context is lost the moment the process exits.
How Halfhand Works
Three simple steps to full agent observability.
Record
Wrap any agent execution with a single command.
- Wraps any CLI agent transparently
- Zero configuration required
- Captures full execution context
Replay
Navigate execution timelines step-by-step.
- Chronological step navigation
- Jump to any timestamp
- Keyboard-driven interface
Understand
Inspect every detail of agent behavior.
- Prompt history with full context
- Tool outputs and MCP traffic
- Unified diff for file changes
Everything you need to debug agents
Purpose-built observability for autonomous systems.
Deterministic Replay
Replay historical executions with full context. Every prompt, tool call, and state change is preserved so you can step through failures exactly as they happened.
Execution Timeline
View agent decisions chronologically. Navigate through events with millisecond precision to understand the exact sequence of actions.
MCP Visibility
Inspect Model Context Protocol requests and responses. See exactly what data was exchanged between your agent and external systems.
File Diff Inspection
See exactly what changed. Unified diffs show every file modification your agent made, with before and after context.
Agent Audit Trail
Maintain historical execution records. Build trust in autonomous systems with complete, queryable logs of every decision.
Local-First
Data remains under your control. All execution history is stored locally, never uploaded to external servers.
SQLite Storage
Portable, queryable execution history. Use SQL to analyze agent behavior patterns across thousands of runs.
Terminal Native
Built for developers who live in the terminal. Keyboard shortcuts, vim-like navigation, and zero GUI overhead.
CLI-first interface
Three core commands. Zero learning curve.
hh runRecord any agent
hh replayStep through history
hh inspectAnalyze sessions
Halfhand vs. Traditional Logs
Observability designed for agents, not applications.
| Feature | Halfhand | Traditional Logs |
|---|---|---|
| Replay execution | ||
| Inspect tool calls | Partial | |
| Track file changes | ||
| MCP visibility | ||
| Deterministic replay | ||
| Agent audit trail |
The flight recorder for AI agents.
As AI systems become responsible for more production work, debugging and observability become critical. Halfhand records prompts, tool calls, MCP traffic, file modifications, terminal commands, and execution history so developers can replay failures, audit behavior, and understand exactly what happened.
Your data stays on your machine
Query with SQL, backup with tools you know
Exact reproduction of every execution
Built for developers
Start locally. Integrate with existing workflows. Keep ownership of your execution history.
Start locally
Install via cargo, run on your machine. No cloud account, no tokens, no API keys required.
Integrates with CI/CD
Export sessions as artifacts. Replay failures in CI pipelines. Generate reports for PRs.
Keep ownership
Your execution data never leaves your machine. Full privacy and compliance from day one.
What developers are saying
“This is super cool! It's like a VCR for LLMs.”
Stop guessing why your agents failed.
Replay every action. Inspect every decision. Built for the engineers shipping AI systems.
Requires Rust 1.75+ · macOS, Linux, Windows · Other install methods