Cost Health

The four CI-gate skills (budget / burn / anomaly / projection) each answer a different question. This skill composes them — runs all four IN PARALLEL, returns max(exit_codes), prints a one-line summary per check.

Subcheck	Question	Default threshold
budget	"Have we crossed the configured budget?"	HARD_STOP at 100%
burn	"Is daily burn accelerating?"	+100% vs prior-week mean
anomaly	"Is any specific session a >3.5σ outlier?"	≥1 outlier
projection	"When will we hit 100% of budget?"	<14 days

Algorithm

Implementation: scripts/health.mjs.

1. Spawn all four subcheck scripts in parallel (Promise.all over child_process.spawn).
2. Each subcheck emits --format json; parse and capture exit code.
3. Projection has no built-in exit code — synthesize one from daysUntilReached[100%] < --alert-days-to-exhaust.
4. Final exit code = max(subcheck exits). Any single failure fails the gate.
5. Print one-line summary per check + overall HEALTHY/UNHEALTHY badge.

CI integration

- name: Cost health gate
  run: cost health --alert-acceleration 100 --alert-outliers 1

A single step covers four alert ladders. Before this skill you'd wire four separate gates that each duplicated the npx + memory-list overhead; now it's one shell-out (and the four subcheck npx calls run in parallel internally).

Customizing thresholds

# Quarterly review — stricter thresholds
cost health --alert-acceleration 50 --alert-outliers 1 --alert-days-to-exhaust 30

# Production drift gate — only fire on egregious changes
cost health --alert-acceleration 200 --alert-outliers 3 --alert-days-to-exhaust 7

# Skip the slow burn check during a smoke run
cost health --skip burn

Smoke transcript (5 healthy sessions, then add 1 outlier)

# Healthy
Overall: ✓ HEALTHY (max exit code 0)
| Check | Status | Detail |
| budget | ✓ | unknown — no budget configured |
| burn | ✓ | delta within ±100% |
| anomaly | ✓ | 0 outliers — under threshold ≥1 |
| projection | ✓ | no budget configured — skipping |

# After adding $5 outlier (vs $0.10 baseline)
Overall: ⚠ UNHEALTHY (max exit code 1)
| burn | ⚠ | ALERT 5163.2% acceleration: latest bucket $5.00 is 5163.2% above prior mean $0.095 |
| anomaly | ⚠ | ALERT 1 outlier (|z|>3.5) |

Skipping subchecks

cost health --skip burn,projection   # only budget + anomaly

Useful when:

• A subcheck doesn't apply (no budget set → skip projection)
• A subcheck is too slow for fast-feedback contexts (smoke runs)
• A subcheck is being independently CI-gated already

Exit code semantics

Exit	Meaning
0	All subchecks OK
1	At least one subcheck fired an alert (budget HARD_STOP, burn drift, anomaly outlier, projection imminent-exhaust)
2	A subcheck had a config/usage error (e.g. invalid CLI args propagated to a subscript)
127	A subcheck failed to launch (script missing, etc.)

max() means the worst signal wins — exit 2 (config error) always dominates exit 1 (alert), so you spot misconfigured pipelines before they masquerade as healthy.