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 jxoesneon/Ciel --skill prompt-and-session-engineeringgit clone --depth 1 https://github.com/jxoesneon/CielWrote 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/jxoesneon/ciel/prompt-and-session-engineering)<a href="https://agentmods.dev/skills/jxoesneon/ciel/prompt-and-session-engineering"><img src="https://agentmods.dev/badge/skills/jxoesneon/ciel/prompt-and-session-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/jxoesneon/ciel/prompt-and-session-engineering"><img src="https://agentmods.dev/badge/skills/jxoesneon/ciel/prompt-and-session-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 | $0.00017 | $0.00482 |
| Opus 5 | $0.00009 | $0.00241 |
| Sonnet 5 | $0.00003 | $0.00096 |
| Haiku 4.5 | $0.00002 | $0.00048 |
Grade A, and why
prompt-and-session-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 9d 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.
What it actually says
CIEL ADAPTATION: Prompt & Session Engineering (The Craft Layer)
This skill manages the internal quality of instructions and the health of long-running sessions.
Prompt Optimization (Advisory)
- Diagnosis: Identify missing context (Tech stack, boundaries, criteria).
- Workflow Matching: Map the intent to CIEL commands (
/plan,/tdd,/verify). - Refinement: Output an optimized prompt that includes explicit scope, tech stack, and verification steps.
- Constraint: Advisory role ONLY. Prohibit executing the task; only provide the optimized text.
Session Hygiene (REPL)
- Task Focus: Keep sessions focused on a single logical unit.
- Branching: Branch the session (
/branch) before performing high-risk or speculative changes. - Compaction: Compact history (
/compact) after major milestones to preserve context for the final integration. - Metrics: Monitor token usage and budget burn per session.
Multi-Prompt Splitting (EPIC)
- Prompt 1: Research + Plan (Architecture).
- Prompt 2-N: Implement one phase per prompt (TDD).
- Final Prompt: Integration + Security Review.
Anti-Patterns
- Execution in Advice: Writing code inside a "Prompt Optimization" turn.
- Amnesiac Resumption: Resuming a session without loading the previous decisions from
context.json. - The Context Cliff: Ignoring history growth until the model starts hallucinating or truncating responses.
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.
- 9d ago First seen · 52 lines · 17 tokens per session scan A 6f1ee1702064
prompt-and-session-engineering is a skill published in the GitHub repository jxoesneon/Ciel (1 stars, last pushed 5d ago), licensed Apache-2.0. It adds 17 tokens to every session and 482 once invoked, about $0.0001 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 2026-09-03.
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