Context Control

by T&N Control

A VSCode / Cursor / Windsurf extension that monitors AI coding context usage of your local AI assistant conversations (Claude Code, Codex, Cline) and warns you before the context window fills up — then generates a portable handoff markdown you can paste into another AI session.

Everything runs 100% locally. No conversation ever leaves your machine.

What it does

Reads conversation history from local storage (no API keys, no network).
Tracks token usage against the model's real context window.
Shows a live status bar item ($(pulse) CC: 45% 116k/258k).
Warns at a configurable threshold, alerts when critical.
Predicts how many messages remain until critical, and estimates cost.
A Dashboard lists every session across tools, sorted by usage.
Generates a structured handoff (.md) with goal, progress, decisions, pending TODOs, referenced files, and a suggested next prompt.

Token counting

Claude Code exposes real token counts in each message's usage field, and Codex reports its real model_context_window — Context Control uses those directly (most accurate).
For sources without usage data, it falls back to a tiktoken (cl100k_base) estimate. This is approximate for Claude/Gemini, which use different tokenizers.

Install

VS Code — open the Extensions panel (Ctrl+Shift+X), search “T&N Context Control”, and click Install. Or run:

code --install-extension tn-control.tn-context-control

Windsurf / Cursor — install the packaged file: Extensions panel → … → Install from VSIX… → pick tn-context-control-<version>.vsix. (An Open VSX listing for in-app search is planned.)

Getting started

Install the extension and reload the window.
Open a folder where you use an AI coding assistant (Claude Code / Codex / Cline).
A status bar item appears bottom-right, e.g. $(pulse) CC: 45% 116k/258k — that's your current context usage. Hover it for tokens/message, an estimate of how many messages remain until critical, and cost.
It turns yellow at the warning threshold and red when critical.
Run a command (Ctrl+Shift+P → type “Context Control”):
- Open Dashboard — every session across tools, sorted by usage.
- Generate Handoff — writes a portable summary .md to .ai-memory/ so you can continue the work in a fresh AI session before you run out of context.

Develop from source

npm install
npm run bundle   # production bundle (or: npm run compile)
npm test         # run the unit tests

Press F5 to launch an Extension Development Host.

Commands

Command	Description
`Context Control: Scan Conversations`	Scan local storage and analyze the newest session
`Context Control: Show Context Status`	Show current token usage, ETA, and cost
`Context Control: Open Dashboard`	List all sessions sorted by usage
`Context Control: Generate Handoff`	Build a handoff and write it to `.md`
`Context Control: Export Handoff to .md`	Alias of Generate Handoff

Settings

Setting	Default	Description
`contextControl.warningThreshold`	`75`	% usage that triggers a warning
`contextControl.criticalThreshold`	`90`	% usage that triggers a critical alert
`contextControl.outputDir`	`.ai-memory`	Where handoff files are written (relative to workspace)
`contextControl.adapters`	`["claude-code", "cline", "codex"]`	Which adapters to enable

Supported adapters

Adapter	Status
Claude Code	✅ Verified against real storage (`~/.claude/projects/*.jsonl`)
Codex CLI	✅ Verified against real storage (`~/.codex/sessions/*/rollout-.jsonl`). Uses the provider-reported `model_context_window`. Cost is not estimated (no GPT pricing table).
Cline	⚠️ Implemented from public docs, not yet verified. See `// TODO:` markers in `src/adapters/cline.ts`.

Known limitations

tiktoken counts are estimates for non-OpenAI models.
The Cline adapter is unverified — field names/paths may differ per version.
The handoff generator is rule-based (regex/keyword), not LLM-powered, so its summaries are best-effort.
Context window is inferred per model (Opus/Sonnet 4.5+ → 1M, Haiku/older → 200k) unless the provider reports it (Codex). If usage exceeds the inferred window, the limit is escalated so usage never reports a nonsensical >100%.
Cost is estimated from published Claude prices (Opus $5/$25, Sonnet $3/$15, Haiku $1/$5 per 1M; cache read ×0.1, write ×1.25–2.0). GPT/other providers are not priced.

Privacy

Context Control reads local files only and never transmits conversation content. docs/research/findings.md and the .ai-memory/ output folder are gitignored.

T&N Context Control

T&N Control