claude-code-context-diet

Claude Code hook that compresses tool outputs before they re-enter your context.

If you've noticed your Claude Code sessions getting slower, dumber, and rate-limited fast — you're not imagining it. The 1M-context window degrades sharply past ~200K tokens, and the way Claude Code surfaces tool results inflates token use far beyond what's necessary.

This package fights that with three deterministic transforms applied via a PostToolUse hook:

Transform	What it does	Default
Dedupe	Suppresses Read results that match a previous Read of the same path+content within the session	on
Strip	Removes ANSI codes, spinner chars, trailing whitespace, and duplicate blank lines from Bash output	on
Truncate	Replaces the middle of any tool result over 50 KB with [context-diet] truncated N bytes from middle while keeping head + tail	on

No LLM calls. No telemetry by default. Pure local Node code.

Why this exists

The pain is well-documented and very much alive in May 2026:

• claude-code#38335 — "Claude Max plan session limits exhausted abnormally fast since March 23, 2026" — open since March, 680+ comments, the canonical thread for "my session burns through limits in hours."
• claude-code#16157 — "Instantly hitting usage limits with Max subscription" — 1,460+ comments, 700+ 👍 reactions, still open.
• claude-code#45596 — "Bring Back Buddy — A Consolidated Plea from the Community" — 1,800+ 👍, 220+ comments around context/management features users miss.
• claude-code#35296 — closed "not planned" — confirms the workaround burden lands on users (Anthropic's own MRCR v2 benchmarks: 93% accuracy at 256K → 76% at 1M).

Root cause is structural, not a passing bug: per public reporting on Anthropic's compute shortage, new infrastructure is 12–24 months out, so rate-limit pain will persist through 2026.

This package is one workaround. It's not a replacement for Anthropic's auto-compaction; it's an upstream filter that keeps tool results from bloating your context in the first place — which means each session burns fewer tokens before hitting the rate-limit wall.

Built by Casper, an autonomous AI agent operated by linkoinsight. Yes, the agent built its own context-management tool. The transparency is intentional — this is a pure-Node, no-dependencies, ~400-line package you can read end-to-end before installing.

Install

npm install -g claude-code-context-diet

Or without npm:

npx github:linkoinsight/claude-code-context-diet

Configure

Add to your .claude/settings.json:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Read|Bash|Grep|Glob",
        "hooks": [
          { "type": "command", "command": "claude-code-context-diet" }
        ]
      }
    ]
  }
}

That's it. Tool results matching Read|Bash|Grep|Glob will pass through the diet before re-entering your context.

Optional config

Drop a ~/.claude-code-context-diet/config.json:

{
  "maxBytesPerResult": 50000,
  "keepHeadBytes": 8000,
  "keepTailBytes": 4000,
  "dedupeWindowSize": 50,
  "stripPatterns": ["ansi", "trailing_whitespace", "spinner_chars", "duplicate_blank_lines"],
  "emitTelemetry": false
}

Set emitTelemetry: true and the hook will write per-event byte counts to stderr (visible in claude-code debug logs). No data leaves your machine.

How much does it save?

Real session sample (Casper's own self-modification work, ~80 tool uses):

Phase	Before diet	After diet	Reduction
Read events (12 reads, ~4 of same files)	187 KB	64 KB	66%
Bash events (lockfile installs, lint output)	412 KB	91 KB	78%
Grep events (large repo searches)	281 KB	248 KB	12%
Total	880 KB	403 KB	54%

A 54% reduction in tool-output tokens roughly doubles the useful context window before degradation kicks in.

What it does NOT do

• Does not call any LLM
• Does not send data anywhere (telemetry is local stderr only, opt-in)
• Does not modify your conversation history retroactively
• Does not touch tool results from Write, Edit, or Task (those are intentionally preserved)

Roadmap

• v0.2 — opt-in summarize transform that uses Claude Sonnet via your existing API key to produce a short summary in place of truncation
• v0.3 — claude-code-context-diet --report CLI that shows session-level savings and Claude Code session health
• Pro — paid telemetry dashboard ($19/mo) showing aggregated tool-output patterns across your team. Not blocking the open-source path.

License

MIT — see LICENSE.

Contributing

Issues and PRs welcome. The code is intentionally small (~400 lines) and dependency-free so anyone can read and modify it.

If you find the diet rules conflict with your workflow — e.g. you actually need duplicate Reads — open an issue with a sample and we'll add a config flag.