A spec-first software development workflow called SAGE: Spec, Assert, Generate, Export. It moves from a feature specification to behavior scenarios, implementation, and generated pull-request or documentation files, using SDD, BDD, and Harness Engineering.

Writing or updating specs, creating behavior scenarios, generating implementation code, initializing a project harness, and producing pull-request or documentation drafts.

It puts decisions and expected behavior in writing before code generation. This makes requirements, tests, updates, project rules, and final documentation easier to keep aligned.

sage — Skill for Claude Code and Codex by gustavobarbosab: A spec-first software development workflow called SAGE: Spec, Assert…

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.

agentmods

npx agentmods add skills/gustavobarbosab/sage/skill

Any agent

npx skills add gustavobarbosab/sage --skill skill

Clone the repo

git clone --depth 1 https://github.com/gustavobarbosab/sage

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/gustavobarbosab/sage/skill.svg)](https://agentmods.dev/skills/gustavobarbosab/sage/skill)

Your own site

<a href="https://agentmods.dev/skills/gustavobarbosab/sage/skill"><img src="https://agentmods.dev/badge/skills/gustavobarbosab/sage/skill.svg" alt="Measured on agentmods" height="20"></a>

Per session 122 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,111 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

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	$0.00122	$0.01111
Opus 5	$0.00061	$0.00556
Sonnet 5	$0.00024	$0.00222
Haiku 4.5	$0.00012	$0.00111

Measured 4d ago against content hash c31ab0352a62, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

sage 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 4d 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

sage — 100% identical, 0 lines differ

skill/SKILL.md · 93 lines

How it starts

The opening of the file, as written. The whole thing — 93 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SAGE

Spec · Assert · Generate · Export

A spec-first workflow that combines SDD, BDD, and Harness Engineering to front-load thinking and back-load generation.

spec.md  →  behavior.md  →  code       →  pr.md + doc.md
 (you)      (you + AI)      (you + AI)     (AI + you)

Commands

The user interacts with SAGE using /sage <command> [argument].

Command	Argument	Reference file	Output
`/sage spec <description>`	Feature description, ticket text, or idea	`references/spec.md`	Interview → spec.md + behavior.md
`/sage behavior`	(none — reads spec.md)	`references/behavior.md`	behavior.md (standalone regeneration)
`/sage code`	(none — reads spec.md + behavior.md)	`references/code.md`	Implementation files
`/sage update <feedback>`	Precise feedback tied to spec or behavior	`references/update.md`	Updated files
`/sage pr`	(none — reads full context)	`references/pr.md`	pr.md
`/sage doc`	(none — reads full context)	`references/doc.md`	doc.md
`/sage harness init`	(none — interactive wizard)	`references/harness-init.md`	.sage/harness.md
`/sage harness generate`	(none — reads codebase files)	`references/harness-generate.md`	.sage/harness.md
`/sage harness review`	(none — reads harness.md)	`references/harness-review.md`	Review report

How to handle each command

When the user types a /sage command:

Identify the sub-command from the table above
Read the corresponding reference file — it contains the full prompt and instructions for that step
Extract the inline argument if provided (e.g. /sage spec "Login screen with email and password" → argument is "Login screen with email and password")
Execute the step following the reference file instructions

If the user types /sage with no sub-command, show the command table above and ask which step they want to run.

Special flow for `/sage spec`

Read the full file on GitHub · 93 lines

Files

What ships with it

60 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.

4d ago First seen · 93 lines · 122 tokens per session scan A c31ab0352a62

Subscribe to this mod's changes

sage is a skill published in the GitHub repository gustavobarbosab/sage (2 stars, last pushed 2mo ago), licensed MIT. It adds 122 tokens to every session and 1,111 once invoked, about $0.0006 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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