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Run npx skillmds@latest add gabrielmoreira/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.

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Is Cost Burn free to use?

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Who published Cost Burn?

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

Cost Burn by gabrielmoreira — Agent Skill

Name: Cost Burn
Rating: 4.5 (4 reviews)
Author: gabrielmoreira

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.

gabrielmoreira Updated Sep 9, 2026 17 repo stars

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.

---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.

Frequently asked questions