test-codex-runtime

A procedure for running the Codex runtime against an isolated test server. The Codex runtime is the service that executes coding-agent tasks, and the procedure specifies the supported model and SDK version.

In plain words
What is it for?
Use it to launch Codex against a test server, verify that the required runtime package is installed, and check that the configured model can run with the available account and SDK.
Why use it?
It provides a repeatable way to check runtime behavior without using a production server. It also documents compatibility limits that can otherwise cause a test run to fail before starting.

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/nick-pape/grackle/test-codex-runtime
Any agent
npx skills add nick-pape/grackle --skill test-codex-runtime
Clone the repo
git clone --depth 1 https://github.com/nick-pape/grackle

Made for: Claude Code, Codex.

Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 791 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 $0.00058 $0.00791
Opus 5 $0.00029 $0.00396
Sonnet 5 $0.00012 $0.00158
Haiku 4.5 $0.00006 $0.00079

Measured 3d ago against content hash 8ff22df44282, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

test-codex-runtime 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 3d 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/test-codex-runtime/SKILL.md · 45 lines

How it starts

The opening of the file, as written. The whole thing — 45 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test the Codex runtime

How to spawn the codex runtime against an isolated test server. Assumes a server from /launch-grackle (with GRACKLE_URL + GRACKLE_API_KEY exported).

Allowed model names ✅ / ❌ (ChatGPT-account auth)

Model Works? Notes
gpt-5.5 confirmed live Needs Codex SDK >= 0.135.0 (the catalog pin). On the old 0.111.0 it errored "requires a newer version of Codex."
o3, o3-mini, gpt-5-codex, gpt-5, gpt-5.1, gpt-5-mini "not supported when using Codex with a ChatGPT account" — these are account-gated (likely need OpenAI API-key auth or a higher tier), independent of SDK version

The catalog (packages/common/src/runtime-catalog.ts) advertises gpt-5.5 and pins @openai/codex-sdk ^0.135.0. If grackle runtimes still shows o3, the catalog hasn't been rebuilt/installed.

History: the SDK was bumped ^0.111.0 → ^0.135.0 precisely to unlock gpt-5.5 (validated 2026-05-29). The runtime installer (runtime-installer.ts) auto-reinstalls when the catalog spec changes (it compares the persisted package spec), so the global ~/.grackle/runtimes/codex/ upgrades on the next codex spawn.

Spawn it

grackle persona create "Codex Tester" --runtime codex --model gpt-5.5 --prompt "You are a test agent."
grackle spawn local "Run exactly this one shell command and nothing else, then stop: cat /nonexistent_file_xyz" --persona codex-tester

Read the full file on GitHub · 45 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. 3d ago First seen · 45 lines · 58 tokens per session scan A 8ff22df44282

Subscribe to this mod's changes

test-codex-runtime is a skill published in the GitHub repository nick-pape/grackle (21 stars, last pushed 2mo ago), licensed MIT. It adds 58 tokens to every session and 791 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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