execute-spec-in-fork

execute-spec-in-fork is a skill for Claude Code, Codex from tt-a1i/matt-skills-with-to-goal. It costs 117 tokens per session (1,709 once invoked), scanned A, original, MIT.

A process for handing an approved software specification to a separate coding-agent task for implementation. A fork here means a temporary child task that carries out the work while the planning task keeps the product decisions.

In plain words
What is it for?
Use it to launch implementation from a finalized specification, route questions between the planning and execution tasks, validate the returned completion record, and archive the finished child task.
Why use it?
It keeps planning decisions and implementation details separate, while sending evidence back to the original task. It also checks that the specification is complete enough to execute before starting.

Skill for Claude CodeCodex

Written for Claude Code and Codex: shipped in a Claude Code plugin, but also agents/openai.yaml present. Also seen: mentions Codex.

Part of the matt-skills-with-to-goal plugin — 40 skills shipped together

Good fit Use it to launch implementation from a finalized specification, route questions between the planning and execution tasks, validate the returned completion record, and archive the finished child task.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/tt-a1i/matt-skills-with-to-goal/execute-spec-in-fork
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.

Any agent
npx skills add tt-a1i/matt-skills-with-to-goal --skill execute-spec-in-fork
Clone the repo
git clone --depth 1 https://github.com/tt-a1i/matt-skills-with-to-goal

Made for: Claude Code, Codex.

Or install matt-skills-with-to-goal, the plugin that ships this one along with the rest of its 40 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for execute-spec-in-fork

README.md
[![agentmods](https://agentmods.dev/badge/skills/tt-a1i/matt-skills-with-to-goal/execute-spec-in-fork/github.svg)](https://agentmods.dev/skills/tt-a1i/matt-skills-with-to-goal/execute-spec-in-fork)
Your own site
<a href="https://agentmods.dev/skills/tt-a1i/matt-skills-with-to-goal/execute-spec-in-fork"><img src="https://agentmods.dev/badge/skills/tt-a1i/matt-skills-with-to-goal/execute-spec-in-fork/github.svg" alt="Measured on agentmods" height="20"></a>

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.

agentmods 80×15 button for execute-spec-in-fork

Your own site · 80×15
<a href="https://agentmods.dev/skills/tt-a1i/matt-skills-with-to-goal/execute-spec-in-fork"><img src="https://agentmods.dev/badge/skills/tt-a1i/matt-skills-with-to-goal/execute-spec-in-fork.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 117 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,709 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. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 2 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Privilege Escalation · line 45
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Memory Poisoning · line 85
    Skill manipulates agent memory, state, or stored context. Memory corruption can alter personality, override safety rules, or cause unpredictable behavior.
    Fix: Protect agent memory and state from modification by untrusted content. Use read-only memory for critical instructions and validate all state changes.
How audits are shown
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 $0.00117 $0.01709
Opus 5 $0.00059 $0.00855
Sonnet 5 $0.00023 $0.00342
Haiku 4.5 $0.00012 $0.00171

Measured 12d ago against content hash a03e50faea18, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

execute-spec-in-fork 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 12d 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.

skills/engineering/execute-spec-in-fork/SKILL.md · 106 lines

How it starts

The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Execute Spec in Fork

Turn one approved SPEC READY into a disposable Codex execution task. Keep product decisions in the planning task, keep implementation logs in the fork, and return evidence to the planning task automatically.

Require a launchable contract

Before creating anything:

  1. Find the latest completed SPEC READY block and apply later user corrections.
  2. Require it to route to forked execution, fit one reliable implementation session, and contain no unresolved product decisions. Use /to-tickets or /to-goal when it does not.
  3. Require the current harness to expose native Codex App task tools for forking, messaging, reading, naming, pinning, and archiving.
  4. Require /codex-task-messenger to be installed with its Ask, Reply, and Resume card protocol (v2 or later) available.

If a prerequisite is missing, do not create a plain new task or simulate the transport. Explain the missing capability and give the manual fallback: fork from the final SPEC READY, run /spec-executor there, and paste its receipt back. After the receipt is pasted, ask once for Goal / spec quality; a skipped answer does not block using the receipt.

Harness capability map

This workflow is a Codex App adapter, so it depends on that harness's task tools by name. The names live here and nowhere else; everything below this section is written in capabilities. When a tool is renamed or reshaped, change this table only. The decision and its consequences live in ADR 0003.

Capability Codex App tool (harness-specific)
Fork the calling task into a same-directory child fork_thread
Read a child task's current state read_thread
Block until a child finishes — not used by default wait_threads
Archive a validated child task set_thread_archived
Identify the source task behind an inbound card the App-supplied source_thread_id

Titling and pinning use the App's native task controls and are referred to by what they do.

Read the full file on GitHub · 106 lines

Files

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.

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. 12d ago First seen · 106 lines · 117 tokens per session scan A a03e50faea18

Subscribe to this mod's changes

execute-spec-in-fork is a skill published in the GitHub repository tt-a1i/matt-skills-with-to-goal (160 stars, last pushed 15d ago), licensed MIT. It adds 117 tokens to every session and 1,709 once invoked, about $0.0006 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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