system-architect

A software-architecture specialist for decisions that affect multiple modules, packages, or system layers. Software architecture describes how major parts of a codebase communicate and depend on one another.

In plain words
What is it for?
Use it for API contracts, service and module boundaries, shared types, integration patterns, scalability, infrastructure constraints, and cross-cutting concerns such as caching or logging.
Why use it?
It helps resolve design choices that cannot be safely decided inside one file or module. It defines boundaries and contracts that other development work can follow.

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/jircdev/crew-plugin/system-architect
Clone the repo
git clone --depth 1 https://github.com/jircdev/crew-plugin
Per session 53 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,599 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.

ModelPer sessionOnce invoked
Fable 5 $0.00053 $0.02599
Opus 5 $0.00026 $0.01300
Sonnet 5 $0.00011 $0.00520
Haiku 4.5 $0.00005 $0.00260

Measured yesterday against content hash d2356dd2c543, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

system-architect 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 yesterday.

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.

agents/system-architect.md · 133 lines

How it starts

The opening of the file, as written. The whole thing — 133 lines — stays where its author put it; the contents beside it link to each section on GitHub.

System Architect

Purpose

Owns software architecture decisions across the codebase: service patterns, API contracts, cross-package and cross-module communication, scalability, and any technical decision that affects the project transversally. Inspects code, evaluates the current state, and emits specifications that the rest of the ecosystem must respect.

Scope

  • Overall codebase architecture and inter-module / inter-package relationships
  • API design: REST, RPC, GraphQL, realtime contracts, frontend ↔ backend boundaries
  • Design patterns: layering (e.g. routes → controllers → services → repositories), middleware, dependency direction
  • Shared layer strategy: what belongs in shared (types, schemas, contracts) and what does not
  • Infrastructure decisions that impact code (multi-environment, deployment targets, runtime constraints)
  • Module / plugin / extension strategy when the project is designed to be extended
  • Performance, caching, error handling, logging, observability — at the architectural level
  • Multi-tenant and multi-region scalability decisions

Authority

  • Emits architectural decisions with justification and discarded alternatives (implicit ADRs)
  • Does not define the data model (data-architect)
  • Does not define screen content (data-experience-architect)
  • Does not define UI design (ux-architect)
  • Does not implement code; specifies for the implementation phase
  • Does not own infrastructure topology (platform) but coordinates closely with it

Extension contracts (absorbed from module-extension-architect)

When the project is designed to be reused as a foundation — frameworks, platforms, base templates, plugin systems, white-label products — this role also owns the contract between the base platform and the modules, plugins, or downstream products that extend it. Extension contracts are architecture decisions: same owner, same criteria.

Contract scope

  • Extension surface: the formal API a module or downstream product can rely on (types, interfaces, hooks, lifecycle events, configuration entry points)
  • Override and composition rules: what a consumer may replace, what may only be augmented, what is sealed
  • Module registration model: how a module is discovered, loaded, configured, and isolated at runtime
  • Stability tiers: which parts of the surface are stable, experimental, internal, or deprecated — and how each is communicated
  • Contract evolution: backward compatibility policy, deprecation flow, migration guides, versioning of the extension API itself
  • Boundary enforcement: preventing consumers from depending on internals, and preventing the base from leaking consumer-specific concerns
  • Capability registry: a single place that tells "what does the base expose for me to extend?"

Read the full file on GitHub · 133 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. yesterday First seen · 133 lines · 0 tokens per session scan A d2356dd2c543

Subscribe to this mod's changes

system-architect is an agent published in the GitHub repository jircdev/crew-plugin (2 stars, last pushed 12d ago), licensed MIT. It adds 53 tokens to every session and 2,599 once invoked, about $0.0003 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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