Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add bdfinst/agentic-dev-team/plugin install dev-teamWrote 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/bdfinst/agentic-dev-team/mutation-testing)<a href="https://agentmods.dev/skills/bdfinst/agentic-dev-team/mutation-testing"><img src="https://agentmods.dev/badge/skills/bdfinst/agentic-dev-team/mutation-testing/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/bdfinst/agentic-dev-team/mutation-testing"><img src="https://agentmods.dev/badge/skills/bdfinst/agentic-dev-team/mutation-testing.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00069 | $0.08980 |
| Opus 5.5 | $0.00028 | $0.03592 |
| Sonnet 5.5 | $0.00014 | $0.01796 |
| Haiku 4.5 | $0.00007 | $0.00898 |
Grade A, and why
mutation-testing 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 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.
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 — 390 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mutation Testing
Role: worker. This command runs the mutation tool and triages survivors directly — it does not generate or estimate mutations, and it does not replace the tests it validates.
Wraps a real mutation tool (Stryker, pitest, mutmut, Stryker.NET, go-mutesting) and adds AI triage of survivors. The tool generates mutations and reports survivors; the AI classifies survivors and writes fix tests. Never estimate or guess mutation outcomes — if no tool is available, help set one up; do not substitute reasoning for execution.
This file describes the language-agnostic workflow and the data contract. Per-language detail — install, run commands, timeout flag names, native-report mapping — lives in references/languages/. Detect the language first via references/tool-detection.md, then load the matching language file.
Unattended, LLM-free overnight measurement. scripts/mutation_nightwatch.py (detection/repair/measurement mechanics split into scripts/mutation_nightwatch_stacks.py) is a third, report-only mode alongside mutation-kill's interactive and --headless fixing modes — no generation, no LLM, no commits, so it can run overnight unattended. See the companion mutation-night-watch skill for launch/detach/schedule guidance.
Committed, human-approved exclude-policy bootstrap. When no mutation-exclude-policy.json exists at the repo root yet, a night-watch run drafts one via scripts/mutation_exclude_policy.py — the same two-signal judgment (score < 15%, NoCoverage > 50%, filename hint promotes to a stronger tier) mutation-kill's own Infrastructure exclusion detection applies, but persisted as a source-controlled file instead of a build-output-only convergence log. The night-watch run only ever drafts a proposal alongside its other reports; mutation_exclude_policy.py --approve is the only code path that writes the committed file, and it is never called unattended.
What ships with it
30 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.
- references/languages/csharp-stryker-net.md 45 KB
- references/languages/go-go-mutesting.md 3.9 KB
- references/languages/java-pitest.md 2.9 KB
- references/languages/javascript-stryker.md 10.0 KB
- references/languages/python-mutmut.md 4.9 KB
- references/time-estimation.md 1.7 KB
- references/tool-detection.md 1.7 KB
- references/workflow-callers.md 3.1 KB
- scripts/csharp_stryker_net_slice_runner.py 25 KB runs code
- scripts/csharp_stryker_net_status_loop.py 19 KB runs code
- scripts/csharp_stryker_net_wrapper.py 29 KB runs code
- scripts/mutation_baseline_reuse.py 12 KB runs code
- scripts/mutation_exclude_policy.py 11 KB runs code
- scripts/mutation_feasibility_gate.py 19 KB runs code
- scripts/mutation_kill_headless.py 14 KB runs code
- scripts/mutation_kill_insert_python.py 6.8 KB runs code
- scripts/mutation_kill_insert.py 8.9 KB runs code
- scripts/mutation_kill_loop_python.py 41 KB runs code
- scripts/mutation_kill_loop.py 38 KB runs code
- scripts/mutation_kill_retry.py 29 KB runs code
- scripts/mutation_kill_shared.py 28 KB runs code
- scripts/mutation_nightwatch_stacks.py 15 KB runs code
- scripts/mutation_nightwatch.py 18 KB runs code
- scripts/mutation_report_cli.py 6.9 KB runs code
- scripts/mutation_report.py 31 KB runs code
- scripts/mutation_safety_gate.py 3.2 KB runs code
- scripts/stryker_shard_pipeline.py 33 KB runs code
- scripts/stryker_shard_setup.py 17 KB runs code
- scripts/stryker_timeout_retry.py 5.4 KB runs code
- scripts/xunit_v3_feature_detector.py 14 KB runs code
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 Changed 38d3fc0b7cbc
- 1mo ago First seen · 390 lines · 69 tokens per session scan A 3af0b4bc4fb8
mutation-testing is a skill published in the GitHub repository bdfinst/agentic-dev-team (295 stars, last pushed 4d ago), licensed MIT. It adds 69 tokens to every session and 8,980 once invoked, about $0.0003 per session on Opus 5.5. 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.
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