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.
npx skills add ChianW/C31 --skill c31-context-engineeringgit clone --depth 1 https://github.com/ChianW/C31Wrote 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.
[](https://agentmods.dev/skills/chianw/c31/c31-context-engineering)<a href="https://agentmods.dev/skills/chianw/c31/c31-context-engineering"><img src="https://agentmods.dev/badge/skills/chianw/c31/c31-context-engineering/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.
<a href="https://agentmods.dev/skills/chianw/c31/c31-context-engineering"><img src="https://agentmods.dev/badge/skills/chianw/c31/c31-context-engineering.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00040 | $0.02109 |
| Opus 5.5 | $0.00016 | $0.00844 |
| Sonnet 5.5 | $0.00008 | $0.00422 |
| Haiku 4.5 | $0.00004 | $0.00211 |
Grade A, and why
C31-context-engineering 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 233 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Multilingual Triggers
| Language | Trigger phrases |
|---|---|
| EN | context, 上下文, 信息组织, 变蠢, context engineering, 信息太多, 你好像忘了, 上下文不够了 |
| ZH | 上下文工程, 管理上下文 |
| JA | コンテキストエンジニアリング, コンテキスト管理 |
Output language: Respond automatically in the user's conversation language.
C31 Context Engineering
The core pain point of the C31 system: a 200K context window, but with poor information organization = effective capacity of only ~30K.
This is not a capacity problem — it is an information structure problem.
Core Principles
- Layered loading — Not all information is worth loading
- On-demand retrieval — GBrain searches only when needed, not on every call
- Active discarding — Expired, completed, or irrelevant information is cleaned up promptly
- Anti-rationalization — Do not retain information "just in case"
Information Layering Architecture (Four-Layer Model)
| Layer | Content | When to Load | Discard Condition |
|---|---|---|---|
| L1 Immediate | Current conversation, task instructions for this turn, active tool calls | Always loaded | Discard when conversation ends |
| L2 Working | Current project files (STATE.md, PLAN.md, CONTEXT.md), active todos | Load at session start | On project switch or completion |
| L3 Rules | AGENTS.md, SKILL.md, SOUL.md, USER.md | Load on-demand at session start | Replace when rules are updated |
| L4 Memory | Historical knowledge, solutions, past projects, long-term memory | Search only when needed | Never proactively loaded |
Hard rule: L4 is never automatically injected into context. It must be explicitly retrieved via GBrain search or memory_search.
Rules Files Management
On-Demand Loading Strategy
AGENTS.md uses modular splits (core.md, decision-boundary.md, communication.md, workflow.md).
Loading rules:
- Every session → load
core.md(always) - Involves decisions/permissions → load
decision-boundary.md - Involves message format/platform → load
communication.md - Involves scheduling/cron/heartbeat → load
workflow.md - Sub-files not relevant to the current task are not loaded
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 1mo ago First seen · 233 lines · 40 tokens per session scan A c2a5fb1dac43
C31-context-engineering is a skill published in the GitHub repository ChianW/C31 (1 stars, last pushed 1mo ago), licensed MIT. It adds 40 tokens to every session and 2,109 once invoked, about $0.0002 per session on Opus 5.5. 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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