Context you can see
Every agent works inside a context window, and the fuller it gets the worse it works. Sessionboxer shows where you are: a gauge above the prompt box, the tokens and cost of each turn on its divider, and a Context pane that breaks the window down by system prompt, tools, MCP servers, memory files and messages.
Things you can do with it
Know when to start fresh
Past half the window the gauge turns red and says rotting. That is the moment to fork from an earlier snapshot, start a new session or ask for /compact, before the agent starts forgetting.
See what a turn cost
Each turn divider reads like +12.3k context · 3 model calls · in 2 / cached 30.1k / out 610 · $0.04. Expensive turns stand out.
Find out what fills the window
Take a breakdown and see how many tokens your MCP servers' tool schemas or your CLAUDE.md eat before the conversation even starts.
Read what a compaction threw away
Click a compaction marker to see the messages that were summarised next to the summary the agent kept.
How it works
The gauge reads the token counts the agent reports after each reply. The breakdown is taken by asking the agent /context while it is idle; for Claude Code that lists system prompt, built-in tools, each MCP server's tools, memory files, skills, messages and free space; for Devin the system prompt, tools, messages and free space, estimated. Compaction details are read from the agent's own records in the box (Claude Code's transcript file, Devin's session database).
Compared with other products
| Sessionboxer | Devin | Cursor Cloud Agents | Codex cloud | Claude Code on the web | OpenHands | T3 Code | |
|---|---|---|---|---|---|---|---|
| Context gauge and per-turn token cost in the chat | ✓ | — | — | — | — | — | — |
| See the exact model API calls | ✓ | — | — | — | — | — | — |
| Agents | Claude Code, Codex, Cursor, Devin | Devin | Cursor | Codex | Claude Code | own agent, any model | Claude Code, Codex, Cursor, others |
Claude Code's own /context and /cost commands show similar numbers in the terminal on request; Codex has /status. Sessionboxer keeps them on screen for every turn and adds the history and the compaction dialog. The hosted products document usage in credits or requests rather than a live view of the window.
Based on each product's public documentation, September 2026; ✓ = offered, ✗ = not offered, — = not found in the docs. Corrections welcome as an issue.