agent-top

htop for local coding agents.

You have three Claude Code sessions, a Codex thread in VS Code, and a Gemini CLI you forgot about. Which one is burning tokens right now? Which one is waiting on you? Which MCP server is still alive after the agent that started it died? agent-top answers that in one terminal view, the way htop answers it for processes and btop answers it for the whole machine.

Recorded from a synthetic snapshot (docs/demo-snapshot.json, replayed with --replay) rather than a live machine, because a recording of real sessions would publish real project names, working directories and session ids. Regenerate with vhs docs/demo.tape.

What it shows

The detail pane shows the process tree (agent, subagent, mcp, shell, tool) and the token breakdown. Orphaned MCP processes, servers with no live agent above them, are listed in red. That is the failure mode reported repeatedly against Codex (openai/codex #17574, #25015, #12491, #16256) and it is not specific to Codex.

Supported harnesses

Install

brew install kannandreams/tap/agent-top

Every route ends at the same single binary — no Python, no Node, no daemon, nothing to configure:

--locked builds against the dependency versions the release was tested with; drop it if you would rather cargo picked newer ones. Building from source needs Rust 1.85 or newer (edition 2024).

To upgrade: brew upgrade agent-top, or re-run the cargo install command.

Usage

agent-top                    # interactive, refreshes every second
agent-top --once             # print the table once and exit
agent-top --json             # one snapshot as JSON, for scripts and bug reports
agent-top --interval-ms 500  # faster refresh
agent-top --stopped-window-min 120
agent-top --replay snap.json # render someone else's --json, keys and all

--replay renders a saved snapshot in the full interactive UI without reading anything on the local machine, so a bug report can be inspected exactly as the reporter saw it.

Keys: j/k move, s cycle sort, r reverse, t toggle the detail pane, Tab switch that pane between the process tree and the tool trace, x hide stopped sessions, p pause, ? help, q quit.

Tool trace

Tab turns the detail pane into a waterfall of the selected agent's recent tool calls, on a shared time axis:

 tool trace   5 of 71 calls · window 1m00s
   in tools 58%  slowest Bash 20.0s  1 in flight  1 failed
 Bash             2.5s  ▉▉▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏
 Read             40ms  ▏▏▉▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏
 ↳Grep           12.0s  ▏▏▉▉▉▉▉▉▉▉▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏
 Edit            300ms! ▏▏▏▏▏▏▏▏▏▏▏▏▉▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏
 Bash            20.0s… ▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▏▉▉▉▉▉▉▉▉▉▉▉▉▸

Width is the call's share of the window; colour is how long it took, on a log scale from green under a second, through amber, to red approaching a minute. Those are two channels on purpose: at a typical zoom most calls are one cell wide, so width alone would say nothing about a 40 ms read next to a 30 s test run. ↳ and blue mark a subagent's call, … and amber a call still running, ! and red one the harness reported as failed.

in tools is the share of the window covered by at least one call (overlapping calls merged, not summed) — the rest is the model thinking, which is usually the answer to "why has this agent been busy for eight minutes".

No configuration and no telemetry opt-in: the spans are reconstructed from the transcript the harness already writes, by pairing each call with its result (Claude's tool_use / tool_result on tool_use_id, Codex's function_call / function_call_output on call_id) and reading the timestamps that bracket them. Only the call's name, id and timing are read, never its arguments or output. The spans are in --json as well, so they can be fed to a real tracing tool.

How it works

1. Enumerate processes with sysinfo. Anything whose program is claude, codex, gemini, opencode, aider, copilot or cursor-agent (or a Node script under the corresponding npm package) is an agent root. Harness processes nested under a root are subagents of that root.
2. Attribute a transcript to each root. Claude Code writes ~/.claude/sessions/<pid>.json with the session id, cwd, a derived name and a busy/idle status, so attribution is exact. Codex is matched by working directory and start time.
3. Tail the transcript incrementally (byte offset kept between refreshes) to accumulate usage, tool calls, turns and the last event, which decides running vs idle.
4. Price each message by its model from a static table. Unknown models are counted as unpriced tokens rather than guessed.
5. Any MCP-looking process with no agent ancestor is an orphan.

Everything is read-only. agent-top never signals, writes to, or talks to an agent.

Roadmap

See docs/roadmap.md. Short version: exact Codex attribution, a logical subagent tree from transcripts, trace export to OTLP, user-supplied price tables, and a hook subcommand for harnesses that support it. docs/releasing.md is the release runbook.

Development

cargo test
cargo run -- --once
cargo clippy --all-targets

Two crates, split by dependency rather than by size: crates/agent-top-core is discovery, transcript parsing, pricing and the process model, with no terminal dependency, so all of it is testable without a TTY and it is exactly what --json prints; crates/agent-top is the ratatui front end and the CLI. Both are published, because a crate on crates.io cannot depend on an unpublished one — agent-top-core exists on the registry so that agent-top can. The internal engineering handbook (PRD, RFCs, ADRs, decisions) lives in the sibling agent-top-internal-docs repository.

License

MIT