cost-tracking

name	cost-tracking
description	Model-specific pricing tables and cost calculation utilities for Claude API usage tracking and budget management.
user-invocable	false

Cost Tracking — Model Pricing & Calculation

Provides pricing data and calculation methods for API cost estimation.

Model Pricing (per 1M tokens, USD)

Model	Input	Output	Cache Write (5m)	Cache Read
claude-opus-4-6	$5.00	$25.00	$6.25	$0.50
claude-sonnet-4-5	$3.00	$15.00	$3.75	$0.30
claude-haiku-4-5	$1.00	$5.00	$1.25	$0.10

Prices as of 2026-02. Source: platform.claude.com/docs/en/about-claude/pricing. Update when pricing changes.

Cost Calculation

Per-Request Cost

cost = (input_tokens × input_price / 1_000_000) +
       (output_tokens × output_price / 1_000_000) +
       (cache_write_tokens × cache_write_price / 1_000_000) +
       (cache_read_tokens × cache_read_price / 1_000_000)

Session Cost Estimation

When actual API token counts are unavailable, use estimates:

estimated_input_tokens = sum(tool_input_chars) / 4
estimated_output_tokens = sum(tool_result_chars) / 4
estimated_cost = estimated_input_tokens × input_price / 1_000_000 +
                 estimated_output_tokens × output_price / 1_000_000

Accuracy note: chars/4 estimation has ±20% error. Actual API usage data (from api_traces.jsonl) provides exact costs when available.

Budget Thresholds

Level	Threshold	Action
INFO	>$0.50/session	Log to stats
WARNING	>$2.00/session	Alert (MEDIUM severity)
CRITICAL	>$10.00/session	Alert (HIGH severity)

Cost Efficiency Metrics

Metric	Formula	Target
Cost per tool call	session_cost / tool_calls	<$0.03
Cost per productive call	session_cost / productive_calls	<$0.05
Input/Output ratio	input_tokens / output_tokens	3:1 to 6:1 (normal range)

Improvement ROI Scoring

Formula for prioritizing improvement proposals:

ROI_score = (Impact × Confidence) / (Effort × Risk)

Impact (1-10)

token_impact = min(tokens_saved_per_session / 1000, 10)
quality_impact = quality_score_improvement_est × 3
Impact = max(token_impact, quality_impact)

Confidence (0.0-1.0)

base = 0.3 if sessions < 3, 0.6 if sessions 3-7, 0.85 if sessions >= 8
corroboration_bonus = (confirming_agents - 1) × 0.1
Confidence = min(base + corroboration_bonus, 1.0)

Effort (1-5)

Level	Description
1	Single line addition/change
2	Multi-line section modification
3	New section or procedure step
4	Structural change across multiple sections
5	Component rewrite or new component

Risk (1-5)

Level	Description
1	Additive only (no existing behavior changed)
2	Minor behavior modification in non-critical path
3	Critical path modification with clear rollback
4	Cross-component change with interaction risk
5	Core algorithm/flow change

Priority Mapping

ROI >= 2.0 → CRITICAL
ROI >= 1.0 → HIGH
ROI >= 0.5 → MEDIUM
ROI <  0.5 → LOW