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.
npx agentmods add skills/kunchenguid/firstmate/firstmate-codexappnpx skills add kunchenguid/firstmate --skill firstmate-codexappgit clone --depth 1 https://github.com/kunchenguid/firstmateWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00071 | $0.01209 |
| Opus 5 | $0.00036 | $0.00605 |
| Sonnet 5 | $0.00014 | $0.00242 |
| Haiku 4.5 | $0.00007 | $0.00121 |
Grade A, and why
firstmate-codexapp 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.
How it starts
The opening of the file, as written. The whole thing — 111 lines — stays where its author put it; the contents beside it link to each section on GitHub.
firstmate-codexapp
Overview
Use this playbook when Firstmate work needs a visible Codex Desktop thread.
The current supported shape is Desktop host-tool choreography plus an explicit status-file return-channel check, not a codex-app value in FM_BACKEND.
Boundary
Codex Desktop visible threads are companion host-tool workflows, not a selectable Firstmate backend.
Read docs/codex-app-backend.md when it exists in this checkout; that document owns the acceptance contract, bridge requirement, status-return requirement, and staged rollout.
If local helper scripts exist for Codex App work, use only helpers explicitly provided by the operator or maintained by Firstmate.
For helpers outside bin/, inspect the source or header before running --help.
Preflight
- Confirm this session is running inside Codex Desktop and that the host tools are exposed.
Search exact names when needed:
create_thread,list_threads,read_thread,send_message_to_thread,archive, andset_thread_archived. - Confirm the target repository is already saved as a Codex Desktop project. No host tool currently creates Codex App projects for an agent, so the human must add the project in Desktop before a created thread can reliably land there.
- Do not create projectless threads for repo work. If the project is absent, stop and ask for the project to be added or use a normal Firstmate backend instead.
- Decide whether this is a real Firstmate-managed task or a visible companion thread.
A real task needs a task id, an isolated worktree or Desktop-owned cwd, a branch plan, and a writable
state/<id>.statuspath.
Create And Send
When creating a visible thread, use the Desktop host tool, not shell imitation. Target the saved project and ask the worker to start by reporting:
pwd
git rev-parse --show-toplevel
git branch --show-current
git log --oneline --max-count=3
For writable repo work, instruct the worker to use the Codex-created current directory.
Do not tell it to cd into the saved project checkout for edits, commits, no-mistakes, pushes, or PR work.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 111 lines · 71 tokens per session scan A f2110451ea8a
firstmate-codexapp is a skill published in the GitHub repository kunchenguid/firstmate (4,623 stars, last pushed today), licensed MIT. It adds 71 tokens to every session and 1,209 once invoked, about $0.0004 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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