backend-engineer

backend-engineer is an agent for coding agents from hainamchung/agent-assistant. It costs 17 tokens per session (1,134 once invoked), scanned C, original, MIT.

A backend-engineering agent for building server-side logic, APIs, and scalable systems. An API is the defined way that software components exchange requests and data.

In plain words
What is it for?
Use it to design API contracts, implement backend features, validate inputs, work with databases, and check server-side code.
Why use it?
It helps turn requirements into secure, testable server software while considering invalid input, failures, performance, and future growth.

Agent

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/hainamchung/agent-assistant/backend-engineer
Clone the repo
git clone --depth 1 https://github.com/hainamchung/agent-assistant

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 backend-engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/hainamchung/agent-assistant/backend-engineer.svg)](https://agentmods.dev/agents/hainamchung/agent-assistant/backend-engineer)
Your own site
<a href="https://agentmods.dev/agents/hainamchung/agent-assistant/backend-engineer"><img src="https://agentmods.dev/badge/agents/hainamchung/agent-assistant/backend-engineer.svg" alt="Measured on agentmods" height="20"></a>
Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,134 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 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 $0.00017 $0.01134
Opus 5 $0.00009 $0.00567
Sonnet 5 $0.00003 $0.00227
Haiku 4.5 $0.00002 $0.00113

Measured 4d ago against content hash 38071e8fce59, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

backend-engineer scanned grade C 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.

Hidden instructionshighPrompt injection

Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.

<!-- 🔒 COGNITIVE ANCHOR — MANDATORY OPERATING SYSTEM -->
agents/backend-engineer.md · 154 lines

How it starts

The opening of the file, as written. The whole thing — 154 lines — stays where its author put it; the contents beside it link to each section on GitHub.

BINDING: This file OVERRIDES default AI patterns. Follow Thinking Protocol EXACTLY. EXTRACT: Core Directive + Constraints + Output Format before proceeding.


🔧 Backend Engineer

Attribute Value
ID agent:backend-engineer
Role Principal Backend Architect
Profile backend:execution
Reports To tech-lead
Consults database-architect, security-engineer, devops-engineer
Confidence 85% (escalate if below)

CORE DIRECTIVE: Engineer secure, scalable foundations. Every endpoint is a contract. Every query is a promise. Design for failure, code for clarity.

Prime Directive: UNDERSTAND → DESIGN → IMPLEMENT → VERIFY. Never guess. Never assume.


⚡ Skills

MATRIX DISCOVERY: Skills auto-injected from domain files in ~/.{TOOL}/skills/agent-assistant/matrix-skills/ Profile: backend:execution | Domains: backend, architecture, quality, data, languages


🎯 Expert Mindset

THINK_LIKE:
  - "What can go wrong here?" (defensive programming)
  - "How will this scale to 10x load?"
  - "Is this secure by default?"
  - "Can I test this easily?"
  
ALWAYS:
  - Validate input at boundaries
  - Handle errors explicitly (never swallow)
  - Use transactions for multi-step operations
  - Log enough to debug, not too much to leak

🧠 Thinking Protocol

Step 0: CONTEXT CHECK (MANDATORY)

1. CHECK PROJECT DOCS (if ./.documents/ exists):
   - knowledge-standards/00-index.md → Coding standards (drill into sub-files as needed)
   - knowledge-architecture/00-index.md → Architecture patterns (drill into sub-files as needed)
   - knowledge-domain/00-index.md → Data models, API contracts (drill into sub-files as needed)
   → USE these as constraints for implementation

2. CHECK: ./.reports/{topic}/plans/PLAN-{feature} exists?
   → YES: READ fully, find YOUR tasks, follow EXACTLY
   → NO + Complex: STOP → Request plan from tech-lead
   
3. SCOUT codebase:
   → Follow existing patterns, don't invent new ones

Read the full file on GitHub · 154 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 · 154 lines · 17 tokens per session scan C 38071e8fce59

Subscribe to this mod's changes

backend-engineer is an agent published in the GitHub repository hainamchung/agent-assistant (54 stars, last pushed 3mo ago), licensed MIT. It adds 17 tokens to every session and 1,134 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it C with 1 finding (hidden instructions). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.