Claude Code Usage Analysis: December 2025 - January 2026

Session Date: January 20, 2026 Analysis Period: December 9, 2025 - January 20, 2026 Data Source: ~/.claude/stats-cache.json, git history

Executive Summary

  • Total Cost: $3,674.37 over 42 active days
  • Total Sessions: 306 sessions
  • Total Messages: 110,288 messages
  • Key Finding: 69% reduction in cost-per-message from December to January
  • Implementation: Added context window tracking to session-start hooks

1. January 2026 Daily Activity

Date Messages Sessions Tool Calls Msgs/Session
Jan 3 1,569 3 469 523
Jan 8 100 1 34 100
Jan 10 6,627 31 1,891 214
Jan 11 9,022 22 2,629 410
Jan 12 30 1 10 30
Jan 14 501 3 134 167
Jan 16 7,543 16 1,049 471
Jan 17 22,124 16 1,420 1,383
Jan 18 6,019 11 573 547
Jan 19 19,123 83 2,902 230
Jan 20 8,721 31 1,352 281

January Token Usage by Model

Date Opus 4.5 Haiku 4.5 Sonnet 4.5 Total
Jan 3 67,376 0 0 67,376
Jan 8 20,377 0 0 20,377
Jan 10 590,831 12,023 0 602,854
Jan 11 1,315,439 12,901 47,379 1,375,719
Jan 12 5,207 0 0 5,207
Jan 14 29,742 1,243 0 30,985
Jan 16 149,389 1,598 312 151,299
Jan 17 97,184 211 6,871 104,266
Jan 18 85,665 320 0 85,985
Jan 19 497,342 1,302 49 498,693
Jan 20 180,740 0 0 180,740

January Weekly Comparison

Period Messages Sessions Tokens Avg Tokens/Session
Week 1 (Jan 1-7) 1,569 3 67,376 22,459
Week 2 (Jan 8-14) 16,280 58 2,015,142 34,744
Week 3 (Jan 15-20) 63,530 157 1,020,983 6,503

2. December 2025 Daily Activity

Date Messages Sessions Tool Calls Msgs/Session
Dec 9 1,852 5 651 370
Dec 10 1,714 10 625 171
Dec 11 1,574 2 572 787
Dec 12 127 1 44 127
Dec 14 9,572 27 2,996 355
Dec 16 577 5 159 115
Dec 20 757 1 218 757
Dec 21 115 1 35 115
Dec 24 5,585 14 1,714 399
Dec 25 1,774 7 517 253
Dec 26 200 2 50 100
Dec 27 5,062 13 1,401 389

December Token Usage by Model

Date Opus 4.5 Haiku 4.5 Sonnet 4.5 Total
Dec 9 180,838 7,604 4,390 192,832
Dec 10 142,945 12,550 0 155,495
Dec 11 166,471 9,583 0 176,054
Dec 12 77,116 0 0 77,116
Dec 14 1,055,057 22,840 0 1,077,897
Dec 16 146,036 2,011 0 148,047
Dec 20 107,681 0 0 107,681
Dec 21 8,470 0 0 8,470
Dec 24 823,447 11,348 0 834,795
Dec 25 301,135 7,689 0 308,824
Dec 26 5,466 0 0 5,466
Dec 27 443,140 5,816 0 448,956

3. Monthly Comparison: December vs January

Totals Comparison

Metric December January Change
Messages 28,909 81,379 +181%
Sessions 88 218 +148%
Tool Calls 8,982 12,463 +39%
Total Tokens 3,541,633 3,123,501 -12%
Active Days 12 11 -8%

Averages Comparison

Metric December January Change
Msgs/Day 2,409 7,398 +207%
Sessions/Day 7.3 19.8 +171%
Tools/Day 749 1,133 +51%
Tokens/Day 295,136 283,955 -4%
Tokens/Session 40,246 14,328 -64%
Tokens/Message 122.5 38.4 -69%

Model Distribution

Model December January Change
Opus 4.5 3,457,802 (97.6%) 3,039,292 (97.3%) -12%
Haiku 4.5 79,441 (2.2%) 29,598 (0.9%) -63%
Sonnet 4.5 4,390 (0.1%) 54,611 (1.7%) +1144%

4. Cost Analysis

API Pricing (per million tokens)

Model Input Output Cache Read (0.1x) Cache Write (1.25x)
Opus 4.5 $5.00 $25.00 $0.50 $6.25
Sonnet 4.5 $3.00 $15.00 $0.30 $3.75
Haiku 4.5 $1.00 $5.00 $0.10 $1.25

All-Time Token Usage

Model Input Output Cache Read Cache Write
Opus 4.5 2.76M 3.74M 3,806M 256.2M
Sonnet 4.5 42.7K 16.3K 11.4M 3.2M
Haiku 4.5 32.1K 77.0K 102.9M 29.0M

Cost Breakdown by Model

Claude Opus 4.5

| Category | Tokens | Rate | Cost | |———-|——–|——|——| | Input | 2,755,560 | $5.00/M | $13.78 | | Output | 3,741,534 | $25.00/M | $93.54 | | Cache Read | 3,805,996,551 | $0.50/M | $1,903.00 | | Cache Write | 256,194,956 | $6.25/M | $1,601.22 | | Subtotal | | | $3,611.54 |

Claude Sonnet 4.5

| Category | Tokens | Rate | Cost | |———-|——–|——|——| | Input | 42,689 | $3.00/M | $0.13 | | Output | 16,312 | $15.00/M | $0.24 | | Cache Read | 11,362,461 | $0.30/M | $3.41 | | Cache Write | 3,240,361 | $3.75/M | $12.15 | | Subtotal | | | $15.93 |

Claude Haiku 4.5

| Category | Tokens | Rate | Cost | |———-|——–|——|——| | Input | 32,050 | $1.00/M | $0.03 | | Output | 76,989 | $5.00/M | $0.38 | | Cache Read | 102,914,527 | $0.10/M | $10.29 | | Cache Write | 28,960,773 | $1.25/M | $36.20 | | Subtotal | | | $46.90 |

Total Cost Summary

Model Cost % of Total
Opus 4.5 $3,611.54 98.3%
Haiku 4.5 $46.90 1.3%
Sonnet 4.5 $15.93 0.4%
TOTAL $3,674.37 100%

Cost by Category

Category Cost % of Total
Cache Write $1,649.57 44.9%
Cache Read $1,916.70 52.2%
Output $94.16 2.6%
Input $13.94 0.4%

Monthly Cost Breakdown

Period Token Share Estimated Cost
December 2025 53.1% $1,951.10
January 2026 46.9% $1,723.27
Total 100% $3,674.37

Cost Efficiency Metrics

Metric December January Change
Total Cost $1,951.10 $1,723.27 -12%
Daily Avg Cost $162.59 $156.66 -4%
Cost/Session $22.17 $7.90 -64%
Cost/Message $0.067 $0.021 -69%
Cost/Tool Call $0.217 $0.138 -36%

5. Spike Day Analysis

All Spike Days Comparison

Day Type Sessions Tokens Tokens/Session Commits
Dec 14 Research 27 1.08M 39,922 0
Dec 24 Research 14 835K 59,628 0
Jan 11 Research 22 1.38M 62,533 0
Jan 17 Implementation 16 104K 6,517 13
Jan 19 Rapid iteration 83 499K 6,008 12

December 14 Analysis

The Numbers: | Metric | Dec 14 | Dec Avg | vs Avg | |——–|——–|———|——–| | Tokens | 1,077,897 | 295,136 | 3.7x | | Messages | 9,572 | 2,409 | 4.0x | | Sessions | 27 | 7.3 | 3.7x | | Tool Calls | 2,996 | 749 | 4.0x |

Cause: Research sprint for OpenTelemetry integration (shipped Dec 27)

December 24 Analysis

The Numbers: | Metric | Dec 24 | Dec Avg | vs Avg | |——–|——–|———|——–| | Tokens | 834,795 | 295,136 | 2.8x | | Messages | 5,585 | 2,409 | 2.3x | | Sessions | 14 | 7.3 | 1.9x | | Tool Calls | 1,714 | 749 | 2.3x |

Cause: Final research push before Dec 27 OTel implementation

January 11 Analysis

The Numbers: | Metric | Jan 11 | Average | vs Avg | |——–|——–|———|——–| | Tokens | 1,375,719 | 283,955 | 4.8x | | Messages | 9,022 | 7,398 | 1.2x | | Sessions | 22 | 19.8 | 1.1x | | Tool Calls | 2,629 | 1,133 | 2.3x |

Cause: Research for SigNoz integration (shipped Jan 16)

January 17 Analysis — Anomaly Day

The Numbers: | Metric | Jan 17 | Jan Avg | vs Avg | |——–|——–|———|——–| | Messages | 22,124 | 7,398 | 3.0x (HIGHEST) | | Tokens | 104,266 | 283,955 | 0.37x (LOW) | | Sessions | 16 | 19.8 | 0.8x | | Tool Calls | 1,420 | 1,133 | 1.3x |

Unique Pattern: Highest messages, lowest tokens = Implementation day (not research)

Efficiency: 4.7 tokens/message vs 152.5 on Jan 11 (32x more efficient)

January 19 Analysis — Session Explosion

The Numbers: | Metric | Jan 19 | Jan Avg | vs Avg | |——–|——–|———|——–| | Messages | 19,123 | 7,398 | 2.6x | | Sessions | 83 | 19.8 | 4.2x (RECORD) | | Tool Calls | 2,902 | 1,133 | 2.6x | | Tokens | 498,693 | 283,955 | 1.8x |

Cause: High-velocity shipping day with frequent context resets

6. Research vs Implementation Pattern

Token Efficiency by Activity Type

Type Example Messages Tokens Tokens/Msg
Research Jan 11, Dec 14 Medium Very High 100-150
Implementation Jan 17 Very High Low 4-5

OTel Project Total (Dec 9 - Dec 28)

Phase Dates Tokens % of Project
Sprint 1 Dec 9-16 1,826,321 48%
Break Dec 17-23 116,151 3%
Sprint 2 Dec 24-26 1,149,085 30%
Ship Dec 27-28 723,269 19%
Total   3,814,826 100%

SigNoz Project Total (Jan 10 - Jan 19)

Phase Dates Tokens Commits
Research Jan 10-11 1.98M 0
Quiet Jan 12-14 36K 0
Implementation Jan 16 151K 6
Polish Jan 17-19 689K 25

7. Context Utilization Patterns

Cache Statistics

Model Cache Read Cache Write Read:Write Ratio
Opus 4.5 3,806M 256M 14.9:1
Haiku 4.5 103M 29M 3.6:1
Sonnet 4.5 11M 3.2M 3.5:1

Estimated Context Per Session

Period Sessions Est. Context/Session
December 88 ~1.5M tokens
January 218 ~550K tokens
Change +148% -63%

Context Trend by Day

Day Sessions Tokens Est. Avg Context/Session
Dec 14 27 1.08M 2.7M
Dec 24 14 835K 4.0M
Jan 11 22 1.38M 4.2M
Jan 17 16 104K 437K
Jan 19 83 499K 398K
Jan 20 31 181K 5.8K

8. Implementation: Context Tracking

New Files Created

hooks/lib/context-tracker.ts

  • Estimates tokens from transcript content (~0.25 tokens/char)
  • Records OpenTelemetry metrics
  • Maintains historical data in ~/.claude/context-history.json
  • Tracks daily averages for trend analysis

New Metrics (exported to SigNoz)

Metric Description
session.context.size Estimated tokens at session start
session.context.utilization Context window % used (of 200K)
session.starts Session start counter

New Trace Attributes

Attribute Description
context.estimated_tokens Token estimate
context.utilization_percent % of 200K window
context.transcript_size Raw transcript bytes
context.message_count Conversation turns
context.is_resume Whether session was resumed

Visual Output Format

📊 Context: 45K tokens (22.5%)
   [████░░░░░░░░░░░░░░░░] 🟢

9. Key Insights

Efficiency Gains

  1. 3x more messages in January with fewer tokens = significant efficiency gain
  2. Tokens per message dropped 69%: 122→38 tokens
  3. Tokens per session dropped 64%: 40K→14K
  4. Cost per session dropped 64%: $22.17→$7.90

Usage Patterns

  1. Research days have high tokens, low commits
  2. Implementation days have high messages, low tokens
  3. More sessions = smaller contexts (deliberate management)
  4. Cache hit ratio of 14.9:1 indicates excellent context reuse

Cost Optimization

  1. Cache operations = 97% of cost
  2. Without caching, input would cost ~$19,600 (5.3x more expensive)
  3. Net cache benefit: ~$16,000 saved via cache reads

10. Recommendations

  1. Continue short session strategy — Week 3 showed 81% cost reduction per session
  2. Track context utilization — New hooks will provide visibility
  3. Monitor research spikes — 7x research:implementation token ratio is high
  4. Consider Sonnet for subagents — 11x increase shows good delegation

Report generated: January 20, 2026 Data period: December 9, 2025 - January 20, 2026 Total analysis cost: Included in Jan 20 session metrics