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/lucasduys/forge/backpropagationnpx skills add LucasDuys/forge --skill backpropagationgit clone --depth 1 https://github.com/LucasDuys/forgeWrote 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/lucasduys/forge/backpropagation)<a href="https://agentmods.dev/skills/lucasduys/forge/backpropagation"><img src="https://agentmods.dev/badge/skills/lucasduys/forge/backpropagation.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00027 | $0.02400 |
| Opus 5 | $0.00014 | $0.01200 |
| Sonnet 5 | $0.00005 | $0.00480 |
| Haiku 4.5 | $0.00003 | $0.00240 |
Grade A, and why
backpropagation 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 4d 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 — 223 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Backpropagation Skill
You are running the Forge backpropagation workflow. Your job is to trace a runtime bug back to a specification gap, update the spec to close that gap, generate a regression test, and log the correction for systemic pattern detection.
Inputs
You will receive:
- Bug description: Natural-language description of the bug, or test failure output + test source code (from
--from-testmode) - Test file path (optional): Path to the failing test, if
--from-testwas used - Test source code (optional): Contents of the failing test file
- Spec files: List of spec files in
.forge/specs/
Workflow
Step 1: TRACE — Which spec?
Find the spec and requirement that should have prevented this bug.
-
Read all spec files in
.forge/specs/. For each spec, extract:- Domain name (from frontmatter)
- All R-numbered requirements and their acceptance criteria
- The
linked_reposfield (to know which repos are involved)
-
Analyze the bug description (and test failure output if available) to determine:
- What component or feature is affected?
- What behavior went wrong?
- What was the expected behavior?
-
Match the bug to the most relevant spec and requirement:
- Use keyword matching between the bug description and requirement names/descriptions
- Use code context: if the bug mentions specific files, endpoints, or functions, grep the spec for those references
- If
--from-testwas used: read the test source code to understand which feature it tests, cross-reference with spec requirements
-
If no spec appears to cover this area at all, note this as a potential "missing requirement" gap and pick the closest spec by domain.
-
Present your finding to the user:
Traced to:
spec-{domain}.md> R{NNN}: {requirement name} Reasoning: {why this requirement is the match}
Step 2: ANALYZE — What was missed?
Determine exactly what the spec's acceptance criteria failed to cover.
- Read the identified requirement's acceptance criteria in full.
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.
- 4d ago First seen · 223 lines · 27 tokens per session scan A f61d3498eda0
backpropagation is a skill published in the GitHub repository LucasDuys/forge (55 stars, last pushed 1mo ago), licensed MIT. It adds 27 tokens to every session and 2,400 once invoked, about $0.0001 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.
Other skills, from other repositories
coding-agent-standards
Defines practical standards for implementation-focused coding agents. Use when creating or editing code, especially when reliability, clarity, and low-risk delivery are required.
prompt-architect
Designs clear, testable prompts for agent workflows. Use when creating new prompts, refining weak prompts, or establishing reusable prompting patterns.
verification-agent
Provides a structured verification workflow for code and prompt outputs. Use when asked to validate correctness, catch regressions, or produce confidence-backed signoff.
opencli-sitemap-author
Use when creating or maintaining OpenCLI site sitemaps: agent-facing navigation, page-state, action, workflow, API-reference, pitfall, and fallback knowledge for a website. Use after browser exploration discovers durable site context, when a sitemap is stale, or when promoting local site knowledge into the repo.
golden-rss
Use when testing the rss golden build.
agent-memory
../../../engineering/agent-memory/skills/agent-memory/SKILL.md.