What is implementation-planner?

A planning tool that turns a requirements document into a phased implementation plan, with separate files for each phase and task. It can also split one large plan into a browsable folder structure.

Use it to plan a feature from a PRD, break work into smaller tasks, or reorganise an existing implementation plan.

It prevents plans from becoming one overwhelming document or a set of empty folders. Each task includes a way to check whether the work is complete.

implementation-planner — Skill for Claude Code and Codex by pantheon-o

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 pantheon-org/tekhne --skill implementation-planner

Clone the repo

git clone --depth 1 https://github.com/pantheon-org/tekhne

Made for: Claude Code, Codex.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/pantheon-org/tekhne/implementation-planner/github.svg)](https://agentmods.dev/skills/pantheon-org/tekhne/implementation-planner)

Your own site

<a href="https://agentmods.dev/skills/pantheon-org/tekhne/implementation-planner"><img src="https://agentmods.dev/badge/skills/pantheon-org/tekhne/implementation-planner/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/pantheon-org/tekhne/implementation-planner"><img src="https://agentmods.dev/badge/skills/pantheon-org/tekhne/implementation-planner.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 138 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 4,344 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 1 finding. 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.

Model	Per session	Once invoked
Fable 5.1	$0.00138	$0.04344
Opus 5	$0.00069	$0.02172
Sonnet 5	$0.00028	$0.00869
Haiku 4.5	$0.00014	$0.00434

Measured 9d ago against content hash f3e782c076e5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade B, and why

implementation-planner scanned grade B with 1 finding 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.

The scan reads SKILL.md. This mod also ships 6 executable files (scripts/generate-structure.sh, scripts/new-phase.sh, scripts/new-plan.sh, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Unrestricted tool accessmediumExcessive agency

A wildcard tool grant or "run any command" leaves no least-privilege boundary at all.

run any scripts, do not create any files. Instead, message the user with the

skills/project-mgmt/planning-toolkit/implementation-planner/SKILL.md · 464 lines

How it starts

The opening of the file, as written. The whole thing — 464 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Implementation Planner

Mental model

An implementation plan is a navigable contract between an agent and a codebase. Each file answers a single question: "What do I need to do next, how do I do it, and how do I prove it is done?"

Two failure modes to avoid:

The monolith — one giant plan.md nobody reads because everything is in one file
The skeleton — directories with empty READMEs that give no useful signal

The sweet spot is a tree where every node either navigates (README) or implements (task file), and every leaf has a runnable verification command.

Quick Start

Mode 1 — Create a new plan from a PRD:

sh scripts/new-plan.sh url-shortener-service
sh scripts/new-phase.sh url-shortener-service 01 workspace-bootstrap
sh scripts/new-task.sh url-shortener-service 01 01 initialise-npm-package
sh scripts/validate-plan.sh url-shortener-service

Mode 2 — Split a monolithic document:

# 1. Create hierarchy manually (steps below) or from JSON:
sh scripts/generate-structure.sh --plan plan.json
# 2. Validate before removing source
sh scripts/validate-structure.sh docs/refactoring/phases

When to use each mode

Signal	Mode
User provides a PRD, spec, or requirements description	Mode 1
User provides a single large planning document to split	Mode 2
User provides flat phase files to reorganise	Mode 2
User says "add a phase" to an existing plan	Mode 1 (additive)
User says "split", "organise", "refactor this plan"	Mode 2

Trigger phrases

Creating a new plan:

"create an implementation plan"
"plan this out in phases"
"break this PRD into tasks"
"generate a phased plan"
"write a detailed implementation plan"
"create tasks from this spec"
"decompose this into phases and tasks"
"create a project plan / roadmap"
"break down tasks" / "task breakdown"
"sprint planning"

Restructuring an existing plan:

"split this plan"
"organize phases"
"break down implementation docs"
"create task hierarchy"
"refactor this planning doc"
"split this into separate files"

Read the full file on GitHub · 464 lines

Files

What ships with it

37 files 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.

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.

9d ago First seen · 464 lines · 138 tokens per session scan B f3e782c076e5

Subscribe to this mod's changes

implementation-planner is a skill published in the GitHub repository pantheon-org/tekhne (10 stars, last pushed yesterday), licensed MIT. It adds 138 tokens to every session and 4,344 once invoked, about $0.0007 per session on Opus 5. A static security scan graded it B with 1 finding (unrestricted tool access). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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