How do I install the Cost Burn skill?

Run npx skillmds@latest add ruvnet/cost-burn in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Cost Burn safe to use?

This skill has not completed SkillMD's automated safety review yet. Capability flags: makes network calls. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Cost Burn?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Cost Burn free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Cost Burn?

ruvnet (@ruvnet) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Cost Burn by ruvnet — Agent Skill

Name: Cost Burn
Rating: 4.2 (5 reviews)
Author: ruvnet

Cost Burn

Burn-rate trend over time with optional drift-alert exit code. Bins session spend into buckets, surfaces window-over-window delta, and can exit 1 when latest bucket exceeds prior mean by a configurable %. Distinct from `cost-trend` (benchmark drift); this tracks PRODUCTION spend trajectory.

ruvnet 594f738 3.3 KB Updated Sep 9, 2026

File contents

Burn-rate trend observability. The fourth leg of the cost-tracker forward-cost stack:

Question	Skill
"Have we crossed a threshold?" (reactive)	`cost-budget-check`
"When will we cross a threshold?" (predictive)	`cost-projection`
"Could we have spent less?" (comparative)	`cost-counterfactual`
"Is daily burn ACCELERATING?" (trend)	`cost-burn` ← this

Algorithm

Implementation: scripts/burn.mjs.

Read all session-* records from cost-tracking namespace.
Bin into --bucket duration windows (default 1d) over --lookback (default 14d).
For each bucket: {n: sessions, spendUsd: sum(total_cost_usd)}.
Compute delta = latest.spendUsd - mean(prior non-empty buckets).
If --alert-on-acceleration-pct N is set: exit 1 when deltaPct > N.

Smoke transcript (5 days @ $0.10/day, today $0.50 — 400% acceleration)

| Latest bucket spend | $0.500000 (1 sessions) |
| Prior bucket mean | $0.100000 (4 non-empty buckets) |
| **Delta (latest vs prior mean)** | **+$0.400000 (400.00%)** |

# | Window                              | Sessions | Spend
0 | 2026-06-15 14:16 → 2026-06-16 14:16 | 1        | $0.500000
1 | 2026-06-14 14:16 → 2026-06-15 14:16 | 0        | $0.000000
2 | 2026-06-13 14:16 → 2026-06-14 14:16 | 1        | $0.100000
3 | 2026-06-12 14:16 → 2026-06-13 14:16 | 1        | $0.100000
...

Drift alert exit code

$ cost burn --bucket 1d --lookback 7d --alert-on-acceleration-pct 50 ⚠ ALERT: latest bucket $0.500000 is 400.0% above prior mean $0.100000 (threshold +50%) exit 1

$ cost burn --bucket 1d --lookback 7d --alert-on-acceleration-pct 500 ✓ latest bucket within +500% of prior mean (actual delta: 400.0%) — OK exit 0

CI integration

# Fail the build if today's spend accelerated > 100% over the weekly mean
cost burn --bucket 1d --lookback 7d --alert-on-acceleration-pct 100 || alert-oncall

The alert is independent of budget — it triggers on rate ACCELERATION even when total spend is well under budget. Catches "we shipped a hot loop that burns 10× normal" before the budget alarm goes off.

Distinct from `cost-trend`

Skill	Data source	Question
`cost-trend`	`docs/benchmarks/runs/*.json`	"Is the benchmark drifting (win rate, latency)?"
`cost-burn`	`cost-tracking` namespace	"Is production spend accelerating?"

Both useful; they answer different questions on different data.

Edge cases

Sparse history (no prior non-empty buckets): alert is SKIPPED with a reason string, exit 0. Operators don't get spurious alerts on cold-start.
Prior buckets all $0 but latest > $0: delta is Infinity/null in JSON, marked new in the table. No alert fires (no baseline to compare against).
--bucket > --lookback: hard error, exit 2.

Source: ruvnet/ruflo → plugins/ruflo-cost-tracker/skills/cost-burn/SKILL.md

---name: cost-burndescription: Burn-rate trend over time with optional drift-alert exit code. Bins session spend into buckets, surfaces window-over-window delta, and can exit 1 when latest bucket exceeds prior mean by a configurable %. Distinct from `cost-trend` (benchmark drift); this tracks PRODUCTION spend trajectory.--- Burn-rate trend observability. The fourth leg of the cost-tracker forward-cost stack: | Question | Skill | |---|---| | "Have we crossed a threshold?" (reactive) | `cost-budget-check` | | "When will we cross a threshold?" (predictive) | `cost-projection` | | "Could we have spent less?" (comparative) | `cost-counterfactual` | | "Is daily burn ACCELERATING?" (trend) | **`cost-burn`** ← this | ## Algorithm Implementation: [`scripts/burn.mjs`](../../scripts/burn.mjs). 1. Read all `session-*` records from `cost-tracking` namespace. 2. Bin into `--bucket` duration windows (default `1d`) over `--lookback` (default `14d`). 3. For each bucket: `{n: sessions, spendUsd: sum(total_cost_usd)}`. 4. Compute `delta = latest.spendUsd - mean(prior non-empty buckets)`. 5. If `--alert-on-acceleration-pct N` is set: exit 1 when `deltaPct > N`. ## Smoke transcript (5 days @ $0.10/day, today $0.50 — 400% acceleration) ``` | Latest bucket spend | $0.500000 (1 sessions) | | Prior bucket mean | $0.100000 (4 non-empty buckets) | | **Delta (latest vs prior mean)** | **+$0.400000 (400.00%)** | # | Window | Sessions | Spend 0 | 2026-06-15 14:16 → 2026-06-16 14:16 | 1 | $0.500000 1 | 2026-06-14 14:16 → 2026-06-15 14:16 | 0 | $0.000000 2 | 2026-06-13 14:16 → 2026-06-14 14:16 | 1 | $0.100000 3 | 2026-06-12 14:16 → 2026-06-13 14:16 | 1 | $0.100000 ... ``` ## Drift alert exit code $ cost burn --bucket 1d --lookback 7d --alert-on-acceleration-pct 50 ⚠ ALERT: latest bucket $0.500000 is 400.0% above prior mean $0.100000 (threshold +50%) exit 1 $ cost burn --bucket 1d --lookback 7d --alert-on-acceleration-pct 500 ✓ latest bucket within +500% of prior mean (actual delta: 400.0%) — OK exit 0 ## CI integration ```bash # Fail the build if today's spend accelerated > 100% over the weekly mean cost burn --bucket 1d --lookback 7d --alert-on-acceleration-pct 100 || alert-oncall ``` The alert is independent of budget — it triggers on rate ACCELERATION even when total spend is well under budget. Catches "we shipped a hot loop that burns 10× normal" before the budget alarm goes off. ## Distinct from `cost-trend` | Skill | Data source | Question | |---|---|---| | `cost-trend` | `docs/benchmarks/runs/*.json` | "Is the benchmark drifting (win rate, latency)?" | | `cost-burn` | `cost-tracking` namespace | "Is production spend accelerating?" | Both useful; they answer different questions on different data. ## Edge cases - Sparse history (no prior non-empty buckets): alert is SKIPPED with a reason string, exit 0. Operators don't get spurious alerts on cold-start. - Prior buckets all $0 but latest > $0: delta is `Infinity`/`null` in JSON, marked `new` in the table. No alert fires (no baseline to compare against). - `--bucket` > `--lookback`: hard error, exit 2. --- **Source:** [`ruvnet/ruflo`](https://github.com/ruvnet/ruflo) → `plugins/ruflo-cost-tracker/skills/cost-burn/SKILL.md`

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