codegen-sync

A check that keeps TypeScript client types synchronized with protocol definitions written in Elixir. Code generation automatically creates the TypeScript files from those Elixir definitions.

In plain words
What is it for?
Regenerating and checking SDK types after changing Elixir structs, protocol messages, RPC types, or tool schemas, then reviewing the generated changes.
Why use it?
It prevents the TypeScript client and the Elixir side from describing different message or data shapes, which can cause build or CI failures.

Skill for Claude CodeCodex

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 skills/matteing/opal/codegen-sync
Any agent
npx skills add matteing/opal --skill codegen-sync
Clone the repo
git clone --depth 1 https://github.com/matteing/opal

Made for: Claude Code, Codex.

Per session 50 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 360 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 $0.00050 $0.00360
Opus 5 $0.00025 $0.00180
Sonnet 5 $0.00010 $0.00072
Haiku 4.5 $0.00005 $0.00036

Measured 2d ago against content hash ee5b36c253df, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

codegen-sync 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.

.claude/skills/codegen-sync/SKILL.md · 39 lines

What it actually says

Codegen Sync Skill

This project uses code generation to keep TypeScript SDK types in sync with Elixir protocol definitions. When Elixir types change, the TypeScript side must be regenerated.

When to act

  • After modifying any Elixir structs, message types, or RPC definitions in lib/opal/.
  • After adding or changing tool schemas in lib/opal/tool/.
  • When CI fails with a codegen drift error.
  • When the user asks to sync or regenerate types.

Commands

# Run codegen (Elixir -> TypeScript)
mix run scripts/codegen_ts.exs

# Verify codegen is up to date (what CI runs)
mix run scripts/codegen_ts.exs --check

Workflow

  1. After modifying Elixir protocol types, run mix run scripts/codegen_ts.exs.
  2. Review the generated diff in cli/src/sdk/ to verify correctness.
  3. Include the regenerated files in the same commit as the Elixir changes.

Rules

  1. Never hand-edit generated files. Always regenerate from the Elixir source.
  2. If codegen output looks wrong, fix the Elixir definitions or the codegen script (scripts/codegen_ts.exs), not the output.
  3. Always commit codegen output alongside the source changes — never in a separate commit.
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 · 39 lines · 50 tokens per session scan A ee5b36c253df

Subscribe to this mod's changes

codegen-sync is a skill published in the GitHub repository matteing/opal (58 stars, last pushed 20d ago), licensed MIT. It adds 50 tokens to every session and 360 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 2026-08-30.

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