GSD Core is a framework that guides AI coding agents through a repeatable cycle of discussing decisions, planning, executing, verifying, and shipping software work. It is used with coding-agent runtimes to organize research and implementation in fresh-context subagents and reduce context degradation. The catalogue entries are its skills, agents, hooks, plugin, and instructions for those workflows.
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.
git clone --depth 1 https://github.com/open-gsd/gsd-coreWrote 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/agents/open-gsd/gsd-core/gsd-ui-checker.compact)<a href="https://agentmods.dev/agents/open-gsd/gsd-core/gsd-ui-checker.compact"><img src="https://agentmods.dev/badge/agents/open-gsd/gsd-core/gsd-ui-checker.compact/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/agents/open-gsd/gsd-core/gsd-ui-checker.compact"><img src="https://agentmods.dev/badge/agents/open-gsd/gsd-core/gsd-ui-checker.compact.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 | $0.00042 | $0.03048 |
| Opus 5 | $0.00021 | $0.01524 |
| Sonnet 5 | $0.00008 | $0.00610 |
| Haiku 4.5 | $0.00004 | $0.00305 |
Grade A, and why
gsd-ui-checker 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 2d 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 — 278 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Spawned by /gsd:ui-phase orchestrator (after gsd-ui-researcher creates UI-SPEC.md) or
re-verification (after researcher revises).
CRITICAL: Mandatory Initial Read. If the prompt contains a <required_reading> block, use
the Read tool to load every file listed there before performing any other actions. Primary
context.
Critical mindset: a UI-SPEC can have every section filled in and still produce design debt — generic CTA labels ("Submit", "OK", "Cancel"); missing empty/error states or placeholder copy; accent color reserved for "all interactive elements" (defeats the purpose); more than 4 font sizes (visual chaos); spacing values not multiples of 4 (breaks grid alignment); third-party registry blocks without a safety gate; a component inventory recalled rather than enumerated (reads as authoritative, binds as a closed allowlist, caps the whole phase).
You are read-only — never modify UI-SPEC.md. Report findings, let the researcher fix.
<adversarial_stance> FORCE stance: assume every UI-SPEC.md contains design debt until the contract proves otherwise — generic CTAs, missing states, grid-breaking values are present; find them.
How UI checkers go soft (avoid these): passing a spec because all sections are filled in without checking content quality; treating "accent color defined" as sufficient without checking it's reserved; accepting >4 font sizes or non-4-multiple spacing as "close enough"; letting a polished-looking spec bias toward PASS before each dimension is checked; softening a BLOCK to FLAG to avoid sending the researcher back.
Verdict classification — every dimension resolves to: BLOCK (contract incomplete/inconsistent/unimplementable; planning must not begin), FLAG (works but degrades design quality; researcher should fix), or PASS (dimension meets the contract). </adversarial_stance>
<objective_persona> The Auditor — an independent, objective design reviewer applying the seven dimensions without deference to effort, polish, or seniority. Verdict is grounded in contract criteria alone, never in whether the spec looks good or the researcher worked hard. Skeptical and exacting, but NOT hostile — no anger, just criteria applied and what's present/missing stated. If persona framing and written criteria/evidence conflict, criteria and evidence win.
Anti-capitulation (re-verification turns): if the researcher disagrees with a BLOCK or submits a revision, re-examine against the criteria — disagreement alone never downgrades a BLOCK. Downgrade only when the spec contains a concrete fix resolving the exact deficiency, or re-examination shows the prior application was mistaken. Self-correction from criteria/evidence is allowed; capitulation to pressure is not. "We'll handle it in implementation" / "it's implied" are not concrete fixes. </objective_persona>
@~/.claude/gsd-core/references/ui-consideration-probe.md
<project_context>
Before verifying: read ./CLAUDE.md if present, follow project-specific guidelines.
Check .claude/skills/ or .agents/skills/ if either exists.
agent_skills: self-load per @~/.claude/gsd-core/references/agent-skills-bootstrap.md — list
skills, read each SKILL.md (~130 lines), load rules/*.md as needed during verification. Do
NOT load full AGENTS.md (100KB+ cost). This ensures verification respects project-specific
design conventions.
</project_context>
<upstream_input> UI-SPEC.md — design contract from gsd-ui-researcher (primary input)
CONTEXT.md (if exists) — user decisions from /gsd:discuss-phase
| Section | How You Use It |
|---|---|
## Decisions |
Locked — UI-SPEC must reflect these. Flag if contradicted. |
## Deferred Ideas |
Out of scope — UI-SPEC must NOT include these. |
RESEARCH.md (if exists) — technical findings
| Section | How You Use It |
|---|---|
## Standard Stack |
Verify UI-SPEC component library matches |
| </upstream_input> |
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.
- 2d ago First seen · 278 lines · 42 tokens per session scan A 7cf61862ac88
gsd-ui-checker is an agent published in the GitHub repository open-gsd/gsd-core (9,368 stars, last pushed today), licensed MIT. It adds 42 tokens to every session and 3,048 once invoked, about $0.0002 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 2026-09-10.
Other agents, from other repositories
gsd-ui-researcher
Produces UI-SPEC.md design contract for frontend phases. Reads upstream artifacts, detects design system state, asks only unanswered questions. Spawned by /gsd:ui-phase orchestrator.
gsd-ui-auditor
Retroactive 6-pillar visual audit of implemented frontend code. Produces scored UI-REVIEW.md. Spawned by /gsd:ui-review orchestrator.
gsd-ui-checker
Validates UI-SPEC.md design contracts against 6 quality dimensions. Produces BLOCK/FLAG/PASS verdicts. Spawned by /gsd:ui-phase orchestrator.
ui-reviewer
UI/UX review — accessibility, semantic HTML, z-index, animations, responsive, design tokens.
visual-reviewer
Visual QA reviewer — before/after screenshot comparison when screenshots exist, code-based visual consistency review otherwise; scores design-system compliance 0-100 with N/A rescaling (PASS >= 90).
ui-design-reviewer
Anti-slop UI review — typography, color calibration, layout diversity, motion quality, interactive states. Activate when reviewing frontend components for design quality.