Prepared: 2026-02-23 Period: October 1 - December 31, 2025 Data sources:
- platform.claude.com cost exports (3 CSV files, full months)
- Langfuse project
cap-llmtoken usage (Nov 22 - Dec 31, 2025)
All Capitol.ai environments and clients shared a single Anthropic API workspace until Feb 20, 2026. EY exclusively uses the agentic-backend service. The agentic-backend's LogFire observability data (which had detailed per-request token usage) was lost, so we are reconstructing EY's share from platform-level billing data.
The Anthropic platform tracks costs by named API key. Our workspace has 5 keys:
| API Key | Used By | Relevant to EY? |
|---|---|---|
capitol |
cap-llm (platform LLM service) + EY agentic-backend | Yes (shared) |
politico |
Politico client services | No |
more coding |
Developer tooling | No |
akshay-code |
Developer tooling | No |
cursor 3 |
Developer tooling | No |
EY's agentic-backend uses the capitol API key. To isolate EY's cost, we subtract known cap-llm usage (tracked via Langfuse) from the capitol key total.
| Month | Total |
|---|---|
| October 2025 | $1,828.27 |
| November 2025 | $1,605.36 |
| December 2025 | $3,459.24 |
| Total | $6,892.87 |
| API Key | Oct | Nov | Dec | Q4 Total | % |
|---|---|---|---|---|---|
politico |
$1,496.49 | $998.06 | $2,917.49 | $5,412.04 | 78.5% |
capitol |
$246.20 | $352.66 | $541.75 | $1,140.61 | 16.5% |
more coding |
$84.80 | $205.98 | $0.00 | $290.78 | 4.2% |
akshay-code |
$0.00 | $48.66 | $0.00 | $48.66 | 0.7% |
cursor 3 |
$0.78 | $0.00 | $0.00 | $0.78 | 0.0% |
The capitol key ($1,140.61) is shared between:
- cap-llm: Capitol's platform LLM service (tracked in Langfuse from Nov 22 onwards)
- EY agentic-backend: EY's dedicated agentic workflow service
Langfuse tracks cap-llm's Anthropic usage by model:
| Model | Input Tokens | Output Tokens |
|---|---|---|
| claude-sonnet-4-20250514 | 74,362,428 | 317,150 |
| claude-sonnet-4-5-20250929 | 51,980,044 | 3,644,540 |
| claude-3-7-sonnet-20250219 | 2,834,786 | 154,195 |
| Total | 129,177,258 | 4,115,885 |
Estimated cap-llm cost (Nov 22 - Dec 31): $449.27
(Calculated from Anthropic's published per-token pricing for each model)
| Period | Capitol Key Cost | Cap-llm (Langfuse) | EY Share |
|---|---|---|---|
| Oct 1 - Nov 21 | $490.91 | No Langfuse data | Unknown |
| Nov 22 - Dec 31 | $649.70 | $449.27 | $200.43 |
| Full Q4 | $1,140.61 | - | - |
For the Nov 22 - Dec 31 period where both data sources overlap:
- Cap-llm: 69.2% of capitol key spend
- EY agentic-backend: 30.8% of capitol key spend
Only count the period where we can definitively split the costs.
| Capitol key (Nov 22 - Dec 31) | $649.70 |
| Less: Langfuse cap-llm | -$449.27 |
| EY cost (Nov 22 - Dec 31) | $200.43 |
Excludes $490.91 of unsplittable Oct 1 - Nov 21 costs. Understates EY's actual usage.
Apply the known Nov 22+ split ratio to the full Q4 period.
| Capitol key (full Q4) | $1,140.61 |
| EY ratio (from Nov 22+ data) | 30.8% |
| EY estimated (full Q4) | $351.87 |
Assumes EY's usage pattern was consistent across the quarter. Most defensible for billing.
Subtract Langfuse total from capitol total (ignores date range mismatch).
| Capitol key (full Q4) | $1,140.61 |
| Less: Langfuse cap-llm | -$449.27 |
| EY estimated | $691.34 |
Overstates EY because it subtracts 40 days of Langfuse data from 92 days of billing. Not recommended.
Method 2 ($351.87) is the most defensible estimate. It uses actual observed data from the overlapping period (Nov 22 - Dec 31) to derive EY's share of the capitol key, then applies that ratio to the full quarter.
| Estimate | Amount |
|---|---|
| Lower bound (Method 1, partial period) | $200.43 |
| Best estimate (Method 2, extrapolated) | $351.87 |
| Upper bound (Method 3, naive subtraction) | $691.34 |
- Langfuse gap: Langfuse tracking for cap-llm only began Nov 22, 2025. There is no per-service breakdown for Oct 1 - Nov 21.
- Usage pattern assumption: Method 2 assumes EY's proportion of
capitolkey usage was roughly constant across Q4. If EY usage ramped up or down significantly, this could be inaccurate. - LogFire data lost: The agentic-backend's LogFire instance (which had per-request token counts) is no longer available. This analysis would be unnecessary if that data existed.
- Shared key retired: As of Feb 20, 2026, EY now has a dedicated Anthropic API key. Future billing will be straightforward.