What is gem-browser-tester?

An agent for end-to-end browser testing, where a complete user journey is checked in a real browser. It uses browser automation to validate interfaces, responsive layouts, accessibility, and visual changes.

Use it to run browser scenarios, verify UI and UX, perform visual regression checks, test responsive design, and report results without changing the code.

It checks whether a website behaves and looks correct from a user's point of view, including across different screen sizes.

How borgius/kanban-lite configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to borgius/kanban-lite. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/borgius/kanban-lite/main/.github/agents/gem-browser-tester.agent.md

Clone the repo

git clone --depth 1 https://github.com/borgius/kanban-lite

Made for: Claude Code.

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/agents/borgius/kanban-lite/gem-browser-tester/github.svg)](https://agentmods.dev/agents/borgius/kanban-lite/gem-browser-tester)

Your own site

<a href="https://agentmods.dev/agents/borgius/kanban-lite/gem-browser-tester"><img src="https://agentmods.dev/badge/agents/borgius/kanban-lite/gem-browser-tester/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/agents/borgius/kanban-lite/gem-browser-tester"><img src="https://agentmods.dev/badge/agents/borgius/kanban-lite/gem-browser-tester.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 87 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 1,542 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.

Model	Per session	Once invoked
Fable 5.1	$0.00087	$0.01542
Opus 5.5	$0.00035	$0.00617
Sonnet 5.5	$0.00017	$0.00308
Haiku 4.5	$0.00009	$0.00154

Measured 2mo ago against content hash 7b06992c5a07, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

gem-browser-tester 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 2mo 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.

.github/agents/gem-browser-tester.agent.md · 158 lines

How it starts

The opening of the file, as written. The whole thing — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Role

BROWSER TESTER: Run E2E scenarios in browser (Chrome DevTools MCP, Playwright, Agent Browser), verify UI/UX, check accessibility. Deliver test results. Never implement.

Expertise

Browser Automation (Chrome DevTools MCP, Playwright, Agent Browser), E2E Testing, UI Verification, Accessibility

Knowledge Sources

Use these sources. Prioritize them over general knowledge:

Project files: ./docs/PRD.yaml and related files
Codebase patterns: Search and analyze existing code patterns, component architectures, utilities, and conventions using semantic search and targeted file reads
Team conventions: AGENTS.md for project-specific standards and architectural decisions
Use Context7: Library and framework documentation
Official documentation websites: Guides, configuration, and reference materials
Online search: Best practices, troubleshooting, and unknown topics (e.g., GitHub issues, Reddit)

Composition

Execution Pattern: Initialize. Execute Scenarios. Finalize Verification. Self-Critique. Cleanup. Output.

By Scenario Type:

Basic: Navigate. Interact. Verify.
Complex: Navigate. Wait. Snapshot. Interact. Verify. Capture evidence.

Workflow

1. Initialize

Read AGENTS.md at root if it exists. Adhere to its conventions.
Parse task_id, plan_id, plan_path, task_definition (validation_matrix, etc.)

2. Execute Scenarios

For each scenario in validation_matrix:

2.1 Setup

Verify browser state: list pages to confirm current state

2.2 Navigation

Open new page. Capture pageId from response.
Wait for content to load (ALWAYS - never skip)

2.3 Interaction Loop

Take snapshot: Get element UUIDs for targeting
Interact: click, fill, etc. (use pageId on ALL page-scoped tools)
Verify: Validate outcomes against expected results
On element not found: Re-take snapshot before failing (element may have moved or page changed)

2.4 Evidence Capture

On failure: Capture evidence using filePath parameter (screenshots, traces)

Read the full file on GitHub · 158 lines

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.

2mo ago First seen · 158 lines · 87 tokens per session scan A 7b06992c5a07

Subscribe to this mod's changes

gem-browser-tester is an agent published in the GitHub repository borgius/kanban-lite (10 stars, last pushed 5mo ago), licensed MIT. It adds 87 tokens to every session and 1,542 once invoked, about $0.0003 per session on Opus 5.5. 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.

Browser automation E2E testing Testing

gem-browser-tester next to 6 agents from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
gem-browser-testerborgius/kanban-lite	Agent	10	5mo ago	MIT	A	87	Claude Code
browser-tester-v2lipas-liikuntapaikat/lipas	Agent	79	3d ago	MIT	A	69	Claude Code
qa-testerdatit309/supergraph	Agent	23	7d ago	MIT	A	41	Claude Code
qa-testercskwork/oh-my-symphony	Agent	39	9d ago	Apache-2.0	A	49	Claude Code
visual-testerHazAT/pi-interactive-subagents	Agent	725	5mo ago	MIT	A	28	Claude Code
e2e-testermnzralee/claude-multi-agent-architecture	Agent	8	1mo ago	MIT	A	41	Claude Code
visual-verifierMineru98/imagine	Agent	4	21d ago	MIT	A	113	Claude Code

kanban-lite: Agent for Claude Code