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junjo: Skill for Claude Code

.agents/skills/studio-backend-rust/SKILL.md

studio-backend-rust is a skill for Claude Code, Codex from mdrideout/junjo. It costs 49 tokens per session (767 once invoked), scanned A, original, Apache-2.0.

A project-specific guide for changing and reviewing the Rust backend of Junjo AI Studio, including its web routes, database files, queries, evidence logic, and tests.

In plain words
What is it for?
Use it when modifying backend APIs, request or response types, SQL, schemas, metadata indexing, DataFusion queries, evidence assembly, backend tests, or code organization.
Why use it?
It helps an agent find the right source files and read the relevant project rules before changing backend behavior. It also clarifies when another guide should be used instead, such as for frontend or authentication work.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents); mentions AGENTS.md.

This is mdrideout/junjo's own configuration. It tells Claude Code and Codex how to work on junjo itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything junjo configures →

not rated 20repo 17d ago A scan 49 tokens original Apache-2.0
View source ↗ mdrideout/junjo python-api.junjo.ai
Reuse

Borrowing it

Nothing to install: this file belongs to mdrideout/junjo. 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/mdrideout/junjo/master/.agents/skills/studio-backend-rust/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/mdrideout/junjo

Made for: Claude Code, Codex.

Wrote this? Show the measurements

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README.md
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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.

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Your own site · 80×15
<a href="https://agentmods.dev/skills/mdrideout/junjo/studio-backend-rust"><img src="https://agentmods.dev/badge/skills/mdrideout/junjo/studio-backend-rust.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 49 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 767 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00049 $0.00767
Opus 5.5 $0.00020 $0.00307
Sonnet 5.5 $0.00010 $0.00153
Haiku 4.5 $0.00005 $0.00077

Measured 17d ago against content hash b9010230afe0, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

studio-backend-rust 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 17d 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.

.agents/skills/studio-backend-rust/SKILL.md · 70 lines

How it starts

The opening of the file, as written. The whole thing — 70 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Studio Backend Rust

Use This Skill When

  • The task touches apps/studio/backend/server/, apps/studio/backend/evidence/, or apps/studio/backend/schema/.
  • The task changes HTTP routes, request or response types, feature SQL, the schema files, the metadata indexer, DataFusion queries, evidence assembly, or backend-visible ingestion query behavior.
  • The task changes backend tests, scripts, or organization.

Do Not Use This Skill When

  • The task is primarily ingestion runtime flow work.
  • The task is primarily frontend UI or state work.
  • The task is primarily an authentication review better handled by studio-security-auth.

Workflow

  1. Read apps/studio/AGENTS.md, then start from the touched code and nearest tests.
  2. Use owner docs only where they constrain the work:
    • apps/studio/docs/adr/011-rust-backend-and-single-origin-studio.md for the runtime, SQLite and schema ownership, the error body, and one-origin routing
    • apps/studio/backend/README.md for layout, commands, and database guidance
    • apps/studio/TESTING.md
    • apps/studio/ingestion/adr/002-sqlite-metadata-index.md for indexing and recent-cold bridge invariants
    • apps/studio/ingestion/adr/001-segmented-wal-architecture.md for hot snapshot or WAL semantics
    • apps/studio/docs/adr/004-events-json-contract.md for events_json
  3. Keep backend code explicit and single-purpose. Each feature under server/src/features owns its routes, its SQL statements, and its tests. Evidence logic stays in the evidence crate, which performs no I/O.
  4. Follow the scoped runtime rules: no legacy fallbacks and no hand-written migrations. A schema file is the desired state of its database.
  5. Pair with studio-ingestion-flow when changing query bridging, proto contracts, or hot-snapshot behavior. Its performance section also applies to any change to a DataFusion query, the metadata indexer, or the work a request does: measure it with the real-world test before proposing it.
  6. Pair with studio-security-auth when changing an authentication trust boundary, layer order, session policy, or API-key validation.
  7. Keep ADRs strategic and update the owning document only.
  8. Never access a running backend container's bind-mounted SQLite database or WAL from a host process. apps/studio/TESTING.md owns the stopped-stack reset procedure.

Read the full file on GitHub · 70 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. 17d ago First seen · 70 lines · 49 tokens per session scan A b9010230afe0

Subscribe to this mod's changes

studio-backend-rust is a skill published in the GitHub repository mdrideout/junjo (20 stars, last pushed 17d ago), licensed Apache-2.0. It adds 49 tokens to every session and 767 once invoked, about $0.0002 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 2026-10-08.

Backend and APIsLLMLanguagesRustagentsaiai-workflowsdagdirected-graph
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