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 julianobarbosa/claude-code-skills --skill premortemgit clone --depth 1 https://github.com/julianobarbosa/claude-code-skillsWrote 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/julianobarbosa/claude-code-skills/premortem)<a href="https://agentmods.dev/skills/julianobarbosa/claude-code-skills/premortem"><img src="https://agentmods.dev/badge/skills/julianobarbosa/claude-code-skills/premortem/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/julianobarbosa/claude-code-skills/premortem"><img src="https://agentmods.dev/badge/skills/julianobarbosa/claude-code-skills/premortem.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to medium
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 →
- medium Data Exfiltration · line 95 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
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 | $0.00207 | $0.01959 |
| Opus 5 | $0.00103 | $0.00979 |
| Sonnet 5 | $0.00041 | $0.00392 |
| Haiku 4.5 | $0.00021 | $0.00196 |
Grade A, and why
premortem scanned grade A 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 8d 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -s -X POST http://localhost:31337/notify \ How it starts
The opening of the file, as written. The whole thing — 138 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Premortem
Imagine the plan already failed, then explain why. This "prospective hindsight" tense-shift (Klein, HBR 2007) generates ~30% more failure causes than asking "what could go wrong?" — and the causes are more specific. The skill turns that mechanism into a repeatable run that ends in a revised plan, not just a list of worries.
Workflow Routing
| Trigger | Workflow |
|---|---|
| "premortem this", "run a premortem", "what could kill this", high-stakes plan | Workflows/RunPremortem.md (full: parallel deep-dive agents) |
| "quick premortem", small/personal decision, fast gut-check, thin context | Workflows/QuickPremortem.md (solo single-pass, no fan-out) |
| "update the premortem skill", add/fix a workflow | Workflows/Update.md |
Default to RunPremortem for anything with real stakes. Drop to QuickPremortem only when
the decision is small or the user explicitly wants speed.
The Mechanism (don't skip the framing)
The entire technique is one move: state that failure has already happened, with certainty, and
ask what caused it. Everything else is delivery. If a step doesn't help the user inhabit
"it already failed," cut it. Full evidence and citations: References/Methodology.md.
Quick Reference
- Frame in past tense. "It's [horizon]. [The plan] has failed. Here's why." Not "could fail."
- Generate causes independently first. In
RunPremortem, parallel agents must NOT see each other's output — this is the anti-anchoring safeguard, and it is load-bearing. - Demand plan-specific causes. Reject generic risks ("timeline slips"). Ground every cause in actual plan details.
- Always land on action. Each retained risk → a mitigation + an early-warning signal. End with a revised plan and a pre-launch checklist. A premortem with no follow-through is theater.
- Markdown is canonical. The transcript (
.md) is the record. HTML is an optional visual artifact viaTools/GenerateReport.ts --html, never the primary output.
What ships with it
7 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.
- 8d ago First seen · 138 lines · 207 tokens per session scan A 12b4397a4ec1
premortem is a skill published in the GitHub repository julianobarbosa/claude-code-skills (10 stars, last pushed 16d ago), licensed MIT. It adds 207 tokens to every session and 1,959 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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