Cost tracking dashboard

The Analytics page now ships a // COST BREAKDOWN section below the existing latency / cost / error / volume charts. Three tabs slice the spans table three ways: by LLM model, by agent, and by chain node. Numbers come from the same compute_cost_usd() table that powers the existing per-trace cost column — no double bookkeeping.

Three breakdowns

Tab	What it groups	Useful for
By model	Every LLM span, bucketed by gen_ai.request.model	"Which model is most of my spend on?"
By agent	Root agent spans (run count) plus their LLM children (tokens + cost)	"Which agent is most expensive per run?"
By node	LLM spans bucketed by chain.node_id for one named chain	"Which node in support-flow dominates the bill?"

The By node tab requires a chain name — type it into the input above the table:

Window picker

The same 24h / 7d / 30d window picker at the top of the Analytics page controls the cost-breakdown lookback. The mapping is:

Page choice	Endpoint param
24h	period=1d
7d	period=7d
30d	period=30d

(period=all is also accepted by the endpoint — currently bounded to 90 days for safety.)

Endpoint

GET /api/analytics/costs?group_by=model&period=7d
GET /api/analytics/costs?group_by=agent&period=7d
GET /api/analytics/costs?group_by=node&chain_name=support-flow&period=7d

Response shape (model mode):

{
  "group_by": "model",
  "period": "7d",
  "rows": [
    {"model": "gpt-4o", "calls": 1240, "input_tokens": 2100000,
     "output_tokens": 340000, "cost_usd": 18.42}
  ]
}

For agent mode each row carries runs, avg_tokens, avg_cost_usd, total_cost_usd. For node mode each row carries executions, avg_duration_ms, avg_cost_usd, percent_of_total.

How cost is computed

For every LLM span the endpoint:

1. Reads agent.cost_usd if present (the SDK's preferred field).
2. Falls back to compute_cost_usd(model, input_tokens, output_tokens) from fastaiagent/ui/pricing.py when the explicit cost isn't set.
3. Drops to 0.0 only when both paths fail (unknown model + no reported cost).

This matches the rule the workflows aggregator uses, so per-workflow cost cards and the breakdown tables agree by construction.

Updating prices

The pricing table in fastaiagent/ui/pricing.py is a flat dict keyed by model-name prefix. Longest prefix wins, so adding a new variant is additive:

"gpt-4.1-nano": _Rate(0.10, 0.40),

Bump the rates here whenever a provider changes their per-million pricing — the dashboards re-aggregate from raw token counts on every read, so updates apply retroactively.

Try it from the examples

Any example that runs an LLM through fastaiagent populates the cost breakdowns. For a quick spread across multiple models / agents / chain nodes:

• examples/35_local_ui.py — produces traces, evals, and guardrail events the cost dashboard aggregates.
• examples/39_workflows_demo.py — runs Chain + Swarm + Supervisor in one script, so the By node tab has multiple chain_name values to slice.

After running either, open Analytics in the Local UI and scroll to the // COST BREAKDOWN section.

Where the screenshots come from

Both screenshots are captured by scripts/capture-sprint1-screenshots.sh against the seed in scripts/seed_ui_sprint1.py, which lays down five LLM spans across three models (gpt-4o, gpt-4o-mini, claude-sonnet-4) under three agent names and three chain nodes inside support-flow.