engineering-mode

engineering-mode is a skill for Claude Code, Codex from olddonkey/olddonkey-skills. It costs 101 tokens per session (1,614 once invoked), scanned A, a copy of cursor-engineering-mode, MIT.

An engineering workflow for taking a coding goal from investigation through planning, implementation, and verification. It focuses on finding the underlying cause before changes are made.

In plain words
What is it for?
Use it to fix bugs, build features, investigate failures, or make an existing system work from start to finish.
Why use it?
It helps prevent quick fixes that address symptoms instead of the real problem. It also provides a structured way to coordinate implementation and check the result.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to fix bugs, build features, investigate failures, or make an existing system work from start to finish.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/olddonkey/olddonkey-skills/engineering-mode
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 olddonkey/olddonkey-skills --skill engineering-mode
Clone the repo
git clone --depth 1 https://github.com/olddonkey/olddonkey-skills

Made for: Claude Code, Codex.

Its marketplace also offers this one on its own, as the plugin engineering-mode — /plugin install engineering-mode after adding the marketplace above.

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 engineering-mode

README.md
[![agentmods](https://agentmods.dev/badge/skills/olddonkey/olddonkey-skills/engineering-mode/github.svg)](https://agentmods.dev/skills/olddonkey/olddonkey-skills/engineering-mode)
Your own site
<a href="https://agentmods.dev/skills/olddonkey/olddonkey-skills/engineering-mode"><img src="https://agentmods.dev/badge/skills/olddonkey/olddonkey-skills/engineering-mode/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 engineering-mode

Your own site · 80×15
<a href="https://agentmods.dev/skills/olddonkey/olddonkey-skills/engineering-mode"><img src="https://agentmods.dev/badge/skills/olddonkey/olddonkey-skills/engineering-mode.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 101 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,614 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.
Origin 94% copy Near-identical to another mod 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 $0.00101 $0.01614
Opus 5.5 $0.00040 $0.00646
Sonnet 5.5 $0.00020 $0.00323
Haiku 4.5 $0.00010 $0.00161

Measured 2mo ago against content hash ea1ac6966271, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

engineering-mode 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 2mo ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/tree-oid-selftest.sh, scripts/tree-oid.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Origin

This is a copy

94% identical to cursor-engineering-mode — 10 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/engineering-mode/SKILL.md · 74 lines

How it starts

The opening of the file, as written. The whole thing — 74 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Engineering mode

Own the outcome; delegate every code change. Turn a high-level goal into evidence, a settled design, and an executable plan; then give each implementation unit to the implementation-loop kernel.

Routing precedence

Evaluate these rules strictly in order. Stop at the first decisive route.

  1. Explicit invocation wins, always. An explicitly invoked skill owns the request. Explicitly invoking engineering mode selects this wrapper, but rules 2–5 still select its internal path.
  2. Plan-only or no-implementation instructions stop implementation. Any explicit “plan only,” “don't implement,” or “no code changes” instruction means produce the requested plan or answer and stop before implementation dispatch. Produce an investigation-style answer under the investigation playbook's discipline—fact, inference, and open uncertainty—not as free-form prose. A direct prohibition on code changes dominates every shortcut below.
  3. Fast-path only an explicitly requested code change. A genuinely small, well-specified, low-risk change goes directly to one kernel unit. Merely mentioning code is not a change request: fall through to rule 5. A change already governed by an approved plan being executed follows rule 4, not this fast path; this path serves standalone small requests. Check it before playbook selection, so smallness trumps category. Record verification under the verification contract. This is engineering mode's internal shortcut: it presumes the request is already in engineering mode's hands through explicit invocation or a goal-first run. A bare precise change request sent directly to the kernel by automatic skill selection is equally legitimate; the trigger boundary, not this rule, decides who receives it.
  4. Pass approved plans through without redesign. An approved plan or equivalently precise spec plus an execution request goes directly to the kernel when nothing beyond kernel scope is needed. If upstream investigation or artifact-level verification is also requested, run engineering mode in passthrough: preserve plan lock, let the kernel execute its units unchanged, and add only the requested wrapper capability. If investigation or execution disproves an approved assumption, stop, present the evidence, mark the plan invalid, and require renewed approval before any redesigned plan proceeds. Plan lock forbids silent drift, not honest invalidation.
  5. Choose a playbook by evidence. Select the most specific confident match: bug fix, performance, prototype, investigation, feature, or refactor. Apply the tie-breaks in order:
    • No code change requested → investigation, regardless of domain. A performance question is investigation.
    • Measured improvement is the deliverable → performance.
    • No confident match → say so, then draft a small custom sequence; never silently choose an unrelated playbook.

Read the full file on GitHub · 74 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. 2mo ago First seen · 74 lines · 101 tokens per session scan A ea1ac6966271

Subscribe to this mod's changes

engineering-mode is a skill published in the GitHub repository olddonkey/olddonkey-skills (17 stars, last pushed 14d ago), licensed MIT. It adds 101 tokens to every session and 1,614 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 94% identical to cursor-engineering-mode, differing in 10 lines, and is treated as a copy.

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