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 skills add jszmajda/lid --skill bidirectional-differentialgit clone --depth 1 https://github.com/jszmajda/lidWrote 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.
[](https://agentmods.dev/skills/jszmajda/lid/bidirectional-differential)<a href="https://agentmods.dev/skills/jszmajda/lid/bidirectional-differential"><img src="https://agentmods.dev/badge/skills/jszmajda/lid/bidirectional-differential/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.
<a href="https://agentmods.dev/skills/jszmajda/lid/bidirectional-differential"><img src="https://agentmods.dev/badge/skills/jszmajda/lid/bidirectional-differential.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
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 Tool Misuse · line 66 Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
- high Excessive Agency · line 115 Skill selects an external model or provider that may use a different account or billing plan than the operator expects. Undisclosed model switches can cause unexpected cost or quota consumption.Fix: Remove the model/provider override or disclose it prominently and require explicit operator approval before invoking an external coding CLI or billed model.
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00172 | $0.02571 |
| Opus 5.5 | $0.00069 | $0.01028 |
| Sonnet 5.5 | $0.00034 | $0.00514 |
| Haiku 4.5 | $0.00017 | $0.00257 |
Grade B, and why
bidirectional-differential scanned grade B with 1 finding 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 1mo 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.
Recursive force deletemediumDestructive command
rm -rf with a variable or a broad path is one typo away from removing the wrong tree.
**Do not mutate existing per-arrow overlay files** (`docs/arrows/{segment}.md`, `docs/arrows/index.yaml`). Experiment artifacts stay in the reserved subtree so arrow-maintenance's audit loop can ignore them. Retirement o Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
How it starts
The opening of the file, as written. The whole thing — 130 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Bidirectional Differential
This skill runs a bidirectional differential audit on EARS↔code pairs. The audit is advisory — findings concentrate human review on specific cases, and acting on findings is always user-judged. When the audit surfaces drift, the recommended repair path walks the whole arrow: validate intent with the user, then cascade EARS → Tests → Code.
When to act
Command mode — user invokes /differential-audit:
- No arguments → open the scoping conversation (see §Scoping).
- One or more EARS IDs as arguments → audit them directly with configured defaults; skip the scoping conversation.
Ambient mode — at linked-intent-dev's Phase 6 boundary (code is complete for a change) in a project where arrow-maintenance's overlay exists and ambient triggering is not disabled. Emit one batched prompt listing every EARS the change touched, offering all, none, a comma-separated subset, or skip-arrow. If ambient is disabled in the project's CLAUDE.md (see §Configuration), do not fire.
Ambient mode is advisory: declining, skipping, or any classification outcome MUST NOT block Phase 6 completion.
Hard precondition — arrow-maintenance overlay
Before spawning any blind sessions in either mode, verify the arrow-maintenance overlay exists:
docs/arrows/index.yamlpresent, and- at least one per-arrow overlay file under
docs/arrows/.
If absent, abort with:
Bidirectional differential audits attach to the arrow-maintenance overlay. Run /update-lid and then /arrow-maintenance first to establish the arrow surface this skill extends.
Do not spawn any claude -p sessions and do not write any files when the overlay is absent. This skill is heavier maintenance than arrow-maintenance; a project without the lighter layer in place will not act on this skill's findings either.
Scoping
The scoping conversation is the first user-facing moment. The audit itself runs without further input once scope is fixed. Full script in references/scoping-conversation.md.
What ships with it
5 files 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.
- 1mo ago First seen · 130 lines · 172 tokens per session scan B 8d10cbc26d21
bidirectional-differential is a skill published in the GitHub repository jszmajda/lid (114 stars, last pushed 9d ago), licensed MIT. It adds 172 tokens to every session and 2,571 once invoked, about $0.0007 per session on Opus 5.5. A static security scan graded it B with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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