context-monitor

context-monitor is a skill for Claude Code from sliday/harn. It costs 40 tokens per session (879 once invoked), scanned A, original, MIT.

A monitoring hook that counts an agent's tool calls and warns when a long session may be using too much working context. Working context is the information the agent can keep active while solving a task.

In plain words
What is it for?
Use it to monitor the agent trace log, warn at high tool-call counts, and exit safely when the log or the jq command-line data tool is unavailable.
Why use it?
Long sessions can make earlier details harder for the agent to use accurately. The warnings prompt a progress summary or context compaction before quality declines.

Skill for Claude Code

Written for Claude Code: PostToolUse hook event. Also seen: reads .claude/ paths; mentions subagents; mentions AGENTS.md.

Part of the harn plugin — 10 skills, 10 commands, 1 agent, 1 hook shipped together

Good fit Use it to monitor the agent trace log, warn at high tool-call counts, and exit safely when the log or the jq command-line data tool is unavailable.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/sliday/harn/context-monitor
View source ↗ sliday/harn
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add sliday/harn --skill context-monitor
Clone the repo
git clone --depth 1 https://github.com/sliday/harn

Made for: Claude Code.

Or install harn, the plugin that ships this one along with the rest of its 10 skills, 10 commands, 1 agent, 1 hook.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for context-monitor

README.md
[![agentmods](https://agentmods.dev/badge/skills/sliday/harn/context-monitor/github.svg)](https://agentmods.dev/skills/sliday/harn/context-monitor)
Your own site
<a href="https://agentmods.dev/skills/sliday/harn/context-monitor"><img src="https://agentmods.dev/badge/skills/sliday/harn/context-monitor/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for context-monitor

Your own site · 80×15
<a href="https://agentmods.dev/skills/sliday/harn/context-monitor"><img src="https://agentmods.dev/badge/skills/sliday/harn/context-monitor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 40 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 879 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00040 $0.00879
Opus 5 $0.00020 $0.00439
Sonnet 5 $0.00008 $0.00176
Haiku 4.5 $0.00004 $0.00088

Measured 11d ago against content hash 2267d175df2f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

context-monitor scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/context-monitor/SKILL.md · 115 lines

How it starts

The opening of the file, as written. The whole thing — 115 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Context Monitor Skill

Generate a context backpressure system that monitors tool call volume and warns the agent before context rot degrades session quality.

Step 1: Generate scripts/harness/context_backpressure.sh

Create the file scripts/harness/context_backpressure.sh with the following content:

#!/usr/bin/env bash
# Harn context monitor — prevents context rot in long sessions
# Why: https://harn.app/kb/context.html — "Context as finite resource with diminishing returns"
# Pattern: https://harn.app/kb/context.html — "Context-Efficient Backpressure"

set -euo pipefail

TRACE_LOG=".claude/agent-trace.jsonl"

# Dependency check
if ! command -v jq &>/dev/null; then
  echo "Harn: context_backpressure.sh requires jq (not installed, skipping)" >&2
  exit 0
fi

# Graceful fallback if trace log doesn't exist
if [[ ! -f "$TRACE_LOG" ]]; then
  exit 0
fi

# Count tool calls in current session
TOOL_CALLS=$(wc -l < "$TRACE_LOG" | tr -d ' ')

if [[ "$TOOL_CALLS" -ge 75 ]]; then
  echo "Harn: 75 tool calls — high context usage. Summarize progress before continuing." >&2
elif [[ "$TOOL_CALLS" -ge 50 ]]; then
  echo "Harn: 50 tool calls — recommend compacting: update CHECKPOINT.json, then compact" >&2
elif [[ "$TOOL_CALLS" -ge 30 ]]; then
  echo "Harn: 30 tool calls — consider delegating research to sub-agents" >&2
fi

exit 0

Make sure scripts/harness/ directory exists before writing the file.

Step 2: Add context management section to AGENTS.md

Append the following section to the project's AGENTS.md file. If AGENTS.md does not exist, create it with this content. If it already exists, add this section at the end:

## Context Management
- Delegate research and grep tasks to sub-agents — only summaries return
- After 30+ tool calls, consider compacting: summarize progress, update CHECKPOINT.json
- Use LEARNED.md for discoveries that must survive compaction
- Prefer just-in-time retrieval (read files when needed) over pre-loading everything

Read the full file on GitHub · 115 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 11d ago First seen · 115 lines · 40 tokens per session scan A 2267d175df2f

Subscribe to this mod's changes

context-monitor is a skill published in the GitHub repository sliday/harn (5 stars, last pushed 10d ago), licensed MIT. It adds 40 tokens to every session and 879 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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