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 hoangsonww/Claude-Code-Agent-Monitor --skill error-propagationgit clone --depth 1 https://github.com/hoangsonww/Claude-Code-Agent-MonitorWrote 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/hoangsonww/claude-code-agent-monitor/error-propagation)<a href="https://agentmods.dev/skills/hoangsonww/claude-code-agent-monitor/error-propagation"><img src="https://agentmods.dev/badge/skills/hoangsonww/claude-code-agent-monitor/error-propagation/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/hoangsonww/claude-code-agent-monitor/error-propagation"><img src="https://agentmods.dev/badge/skills/hoangsonww/claude-code-agent-monitor/error-propagation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00072 | $0.00617 |
| Opus 5 | $0.00036 | $0.00309 |
| Sonnet 5 | $0.00014 | $0.00123 |
| Haiku 4.5 | $0.00007 | $0.00062 |
Grade A, and why
error-propagation 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 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.
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 — 57 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Error Propagation
Trace where a multi-agent session's failures started and how far they spread.
Input
The user provides: $ARGUMENTS
A session ID. If empty, fetch GET /api/sessions?limit=1, but prefer the most recent session whose status is error or abandoned; state which one you picked.
Data Sources
| Endpoint | Returns |
|---|---|
GET /api/workflows/{sessionId} |
The errorPropagation dataset: failures grouped by agent depth, with originating depth and cascade paths to parents |
GET /api/events?session_id={sessionId} |
The event stream — corroborate with APIError, SubagentStop, and failing PostToolUse events (event_type, tool_name, summary, timestamp) |
Report Sections
1. Failure Summary
From errorPropagation: total errors, the depth where the first error originated, and how many distinct agents were affected.
Origin depth: d · Errors: N · Agents affected: M
2. Errors by Depth
| Depth | Errors originated | Errors inherited from children | Net failing agents |
|---|---|---|---|
| Show whether failures concentrate deep in the tree (leaf subagents) or shallow (orchestrator). |
3. Cascade Paths
For each originating failure, the path it propagated along:
debugger (depth 2, tool failure) → code-review (depth 1, marked error) → root (depth 0, aborted)
Tie each step to a concrete event from /api/events (event_type + tool_name + timestamp) where available.
4. Error Taxonomy
Break errors down by type from the event stream: APIError vs failing tool calls vs SubagentStop with error status. Note the most frequent tool involved in failures.
5. Containment Assessment
Whether failures were contained at the depth where they originated or leaked to parents. Name any parent that aborted solely because a child failed — a candidate for better error handling / isolation.
Output
- Markdown tables for the depth breakdown; a fenced list for cascade paths.
- Timestamps for the first and last error.
- Cite only errors present in
errorPropagationand the event stream; never invent failures or causes. - If the session has no errors, say so plainly and stop.
- If the dashboard is unreachable, tell the user to start it with
npm startfrom the repo root.
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.
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 · 57 lines · 72 tokens per session scan A 2b55594c9868
error-propagation is a skill published in the GitHub repository hoangsonww/Claude-Code-Agent-Monitor (989 stars, last pushed 3d ago), licensed MIT. It adds 72 tokens to every session and 617 once invoked, about $0.0004 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 2026-09-03.
Other skills, from other repositories
code-remediate
Apply selected review fixes; bare PR targets use current online items, while PR +review adds the latest matching artifact.
php-quality-tooling
Use when setting up PHPStan, Rector, or PHP-CS-Fixer on a non-Laravel PHP project, incl. CI wiring. Do NOT use for Laravel (Pint/Larastan), tests, or syntax.
breaking-changes
Use when checking whether a Claude Code update breaks our plugin ecosystem — hooks, agent frontmatter, manifest schema, or skill format.
radin-doctor
Check that radin's own install under /.claude is complete and its optional companion tools are reachable. Use for /radin-doctor, "check my radin install", "is radin installed correctly", "radin doctor", "verify radin install".
systematic-debugging
Guides root cause investigation before proposing fixes. Use when debugging, diagnosing failures, investigating test errors, or tracing unexpected behaviour.
qa-check
Auto-detects the project's tech stack, then audits for Accessibility, Performance, and Code Quality. Works across WordPress/PHP, Python, Node/JS, and static web projects.