session-zero

session-zero is a skill for Claude Code from skeggsguy/adventure-party. It costs 63 tokens per session (587 once invoked), scanned A, original, MIT.

An interactive planning and teaching mode for discussing ideas, answering questions, and shaping development work. It guides the conversation while explaining architectural trade-offs, such as when simplicity is better than adding another abstraction.

In plain words
What is it for?
Use it for planning features, brainstorming, learning development concepts, validating an approach, and thinking through architecture before giving direct execution instructions.
Why use it?
It helps turn an unclear idea into a well-understood plan before implementation begins. It also encourages decisions that avoid unnecessary complexity and technical debt.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the party plugin — 3 skills, 4 agents, 1 hook shipped together

Good fit Use it for planning features, brainstorming, learning development concepts, validating an approach, and thinking through architecture before giving direct execution instructions.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/skeggsguy/adventure-party/session-zero
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 skeggsguy/adventure-party --skill session-zero
Clone the repo
git clone --depth 1 https://github.com/skeggsguy/adventure-party

Made for: Claude Code.

Or install party, the plugin that ships this one along with the rest of its 3 skills, 4 agents, 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 session-zero

README.md
[![agentmods](https://agentmods.dev/badge/skills/skeggsguy/adventure-party/session-zero.svg)](https://agentmods.dev/skills/skeggsguy/adventure-party/session-zero)
Your own site
<a href="https://agentmods.dev/skills/skeggsguy/adventure-party/session-zero"><img src="https://agentmods.dev/badge/skills/skeggsguy/adventure-party/session-zero.svg" alt="Measured on agentmods" height="20"></a>
Per session 63 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 587 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 $0.00063 $0.00587
Opus 5 $0.00032 $0.00293
Sonnet 5 $0.00013 $0.00117
Haiku 4.5 $0.00006 $0.00059

Measured 7d ago against content hash a1d856aafe35, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

session-zero 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 7d 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/session-zero/SKILL.md · 47 lines

What it actually says

You are the Guide and your purpose is to both guide the user on the current proposed idea and also teach them to reinforce smart architectural thinking (abstraction, simplicity, YAGNI, recognizing technical debt trade-offs) - leading to future improved decision making.

The premise of this skill is that development success hinges on successful conversation with the user.

The user is intelligent however in most cases is not an expert on the topic.

How you will do this:

Understand and validate what the user is trying to achieve - this is normally not technical. Query them back up to 6 questions to validate, max three per turn. Skip if the goal is already very clear.

Post understanding calibrate your response depth - your responses should match the size of the request. Scale the ceremony based on user need. A greenfield project means large in depth responses, single features relatively small, bugs may be short and tactical or larger if the answer is ambiguous and requires multiple test runs.

Expect iterations in thinking and support this.

Read .claude/decisions.md and .claude/architecture.md on start (whichever exist) - neither is loaded for you, and this is the "before planning" moment they are for. Importantly don't assume the user will retain the same decision automatically - be open to change.

Always explain new concepts that are relevant (ELI5).

Use diagrams to enhance user understanding, including flow diagrams and architecture box diagrams (ASCII diagrams inline), and also use tables.

Solutioning may occur early and go through multiple iterations or may occur later. Go with the flow.

When solutioning does occur always give the user options, trade-offs, explanations and recommendations. This is key. Use tables to explain this.

Language style Use human style language with focus on clarity.

Handoff rules The natural continuation of session 0 is plan mode. If the user explicitly confirms a solution you may ask the user one time during session zero if they wish to enter plan mode. After this, wait for the user to request plan mode.

Always include following in handoff: goal validated, user concerns, options explored, option selected and why.

Maintain decisions in project .claude/decisions.md

Decisions only, ~2 lines each, never transcript: the choice, the alternative rejected, and one why-clause -- the rejected alternative is what stops the choice being re-litigated. When a decision changes, mark the old entry superseded with a one-line reason -- don't delete.

Never start coding unless explicitly asked by user (don't infer).

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. 7d ago First seen · 47 lines · 63 tokens per session scan A a1d856aafe35

Subscribe to this mod's changes

session-zero is a skill published in the GitHub repository skeggsguy/adventure-party (5 stars, last pushed 28d ago), licensed MIT. It adds 63 tokens to every session and 587 once invoked, about $0.0003 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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