backstage-fullstack-developer

backstage-fullstack-developer is an agent for coding agents from bendaamerahmed/backstage-idp-plugin. It costs 93 tokens per session (13,801 once invoked), scanned A, original, MIT.

A senior engineering agent specialized in Spotify Backstage developer portals. It covers the portal's frontend, backend, software catalogue, templates, documentation, search, identity, access control, integrations, and maintenance.

In plain words
What is it for?
Use it to design or build Backstage plugins, configure the Software Catalog or Scaffolder, work with TechDocs and Search, add authentication or authorization, integrate services, test changes, troubleshoot problems, and plan upgrades.
Why use it?
Backstage changes depend on its evolving architecture and many connected systems. This agent provides one place for specialized implementation, debugging, testing, security, and upgrade work.

Agent

Part of the backstage-idp plugin — 15 skills, 1 agent shipped together

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 agents/bendaamerahmed/backstage-idp-plugin/backstage-fullstack-developer
Clone the repo
git clone --depth 1 https://github.com/bendaamerahmed/backstage-idp-plugin

Or install backstage-idp, the plugin that ships this one along with the rest of its 15 skills, 1 agent.

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 backstage-fullstack-developer

README.md
[![agentmods](https://agentmods.dev/badge/agents/bendaamerahmed/backstage-idp-plugin/backstage-fullstack-developer.svg)](https://agentmods.dev/agents/bendaamerahmed/backstage-idp-plugin/backstage-fullstack-developer)
Your own site
<a href="https://agentmods.dev/agents/bendaamerahmed/backstage-idp-plugin/backstage-fullstack-developer"><img src="https://agentmods.dev/badge/agents/bendaamerahmed/backstage-idp-plugin/backstage-fullstack-developer.svg" alt="Measured on agentmods" height="20"></a>
Per session 93 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 13,801 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. 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.

ModelPer sessionOnce invoked
Fable 5 $0.00093 $0.13801
Opus 5 $0.00046 $0.06901
Sonnet 5 $0.00019 $0.02760
Haiku 4.5 $0.00009 $0.01380

Measured 4d ago against content hash 342a6a7ed211, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

backstage-fullstack-developer scanned grade A 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 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.

Enumerates other installed skillslowAgent snooping

Other skills' SKILL.md files reveal prompts, capabilities and secrets that should be invisible to peers.

Before inventing a workflow, inspect available skills. Prefer a maintained skill for repeated procedures.

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

plugins/backstage-idp/agents/backstage-fullstack-developer.md · 2,091 lines

How it starts

The opening of the file, as written. The whole thing — 2,091 lines — stays where its author put it; the contents beside it link to each section on GitHub.


0. Version Baseline

This definition was verified against Backstage as of August 2026. Treat the facts below as a starting hypothesis with a shelf life, never as settled truth: Backstage ships a mainline release every month, so this section goes stale fast.

Fact Value as verified (Aug 2026)
Current stable release line v1.53.x
Release cadence Mainline monthly, on the Tuesday before the third Wednesday; next line weekly on Tuesdays
Supported Node.js Exactly two adjacent even majors — 22 and 24 (policy since v1.46.0)
Frontend system New Frontend System is the default for newly created apps since v1.49.0; create-app --next was replaced by create-app --legacy
Backend system New Backend System is the established default; legacy backend composition is migration-only
UI library @backstage/ui ("BUI", formerly Canon) — core components and entity cards are migrating off Material UI
Deprecation policy A deprecation must ship in at least one mainline release before removal
Community plugins Live in the separate backstage/community-plugins repo under @backstage-community/plugin-*

Rule: before implementing anything version-sensitive, verify the repository's actual installed versions first (§5.1, §5.2), and re-check official documentation when the repository's release line differs from the table above. If the repository is on a release line older than this table, the table is wrong for that repository and the repository wins.

Read the full file on GitHub · 2,091 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.

  1. 4d ago First seen · 2,091 lines · 93 tokens per session scan A 342a6a7ed211

Subscribe to this mod's changes

backstage-fullstack-developer is an agent published in the GitHub repository bendaamerahmed/backstage-idp-plugin (1 stars, last pushed 24d ago), licensed MIT. It adds 93 tokens to every session and 13,801 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (enumerates other installed skills). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.