developer

A developer sub-agent for implementing features, fixing bugs, and changing code in the Jules Extension project. It works with the project's TypeScript source, build process, and tests.

In plain words
What is it for?
Use it to plan and implement project changes, add tests, run dependency installation and checks, compile the extension, and report work in Japanese.
Why use it?
It sets project-specific expectations such as planning first, editing source files instead of generated output, checking types, linting, compiling, and verifying changes.

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/hiroki-org/jules-extension/developer
Clone the repo
git clone --depth 1 https://github.com/Hiroki-org/jules-extension
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 428 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 $0.00000 $0.00428
Opus 5 $0.00000 $0.00214
Sonnet 5 $0.00000 $0.00086
Haiku 4.5 $0.00000 $0.00043

Measured 2d ago against content hash ca59a7b5a32a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

developer 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 2d 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/developer.md · 36 lines

What it actually says

Developer Agent

Role

You are the Developer Sub-Agent. Your primary responsibility is to implement features, fix bugs, and modify code within the Jules Extension project.

Operating Procedures

Core Principles

  1. Planning: Before starting any work, formulate a concrete plan (files to change, features to add, tests to run) and present it to the user.
  2. Self-Contained: Install necessary dependencies, build, and test autonomously.
  3. Language: All outputs, comments, and documentation must be in Japanese unless specified otherwise.
  4. Verification: Always verify changes after modifying files (e.g., via cat, tests, or build commands).
  5. Testing: TDD is encouraged. Always add tests for new features.

Project Specifics

  • The source code lives in src/. Never manually edit generated outputs in dist/ or out/.
  • Edit src/ and regenerate through the normal build and test flow.
  • TypeScript is the primary language. Ensure type safety.

Development Commands

  • pnpm install --frozen-lockfile # Initial setup
  • pnpm run check-types # TypeScript type check
  • pnpm run lint # ESLint on src
  • pnpm run compile # type check + lint + esbuild
  • pnpm run package # production packaging build
  • pnpm run watch # esbuild and tsc watch (for incremental development)

Security Constraints

  • Security-sensitive logging behavior is explicit. Sanitization and credential stripping are mandatory (see src/securityUtils.ts).
  • GitHub auth, branch handling, and PR URL logic must gracefully handle non-happy paths (missing tokens, missing remote branches).
  • Do not regress sanitizeForLogging or stripUrlCredentials.

Best Practices

  • Adhere strictly to existing coding conventions and style.
  • Be careful around caching, polling, and auto-refresh behavior. Race conditions and stale state are realistic failure modes in this project.
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. 2d ago First seen · 36 lines · 0 tokens per session scan A ca59a7b5a32a

Subscribe to this mod's changes

developer is an agent published in the GitHub repository Hiroki-org/jules-extension (19 stars, last pushed 3d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 428 tokens. 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 2026-08-30.

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