Polishes the AI model configuration form (add/edit model) with tighter
layout and better input affordances.
**Frontend changes:**
- Replace "Unset" with "Default" in select dropdowns to communicate
system fallback
- Show pricing fields inline instead of behind a collapsible toggle
- Use flat section dividers (`border-t`) instead of bordered fieldsets
- Move field descriptions into info-icon tooltips to fix input
misalignment
- Add InputGroup adornments: `$` prefix + `/1M` suffix on pricing,
`tokens` suffix on token fields, `%` suffix on compression threshold,
range placeholders on temperature/penalty fields
- Shorter pricing labels (Input, Output, Cache Read, Cache Write)
- Compact JSON textareas (1-row height, resizable)
- Smart grid layouts by field type (3-col provider, 4-col pricing, 3-col
advanced)
- Boolean fields render as a segmented control (Default · On · Off)
instead of a dropdown
**Backend changes:**
- Add `enum` tags to OpenAI `service_tier`
(`auto,default,flex,scale,priority`) and `reasoning_summary`
(`auto,concise,detailed`) so they render as select dropdowns instead of
free-text inputs
> 🤖 Generated by Coder Agents
Add cost tracking for LLM chat interactions with microdollar precision.
## Changes
- Add `chatcost` package for per-message cost calculation using
`shopspring/decimal` for intermediate arithmetic
- **Ceil rounding policy**: fractional micros round UP to next whole
micro (applied once after summing all components)
- Database migration: `total_cost_micros` BIGINT column with historical
backfill and `created_at` index
- API endpoints: per-user cost summary and admin rollup under
`/api/experimental/chats/cost/`
- SDK types: `ChatCostSummary`, `ChatCostModelBreakdown`,
`ChatCostUserRollup`
- Fix `modeloptionsgen` to handle `decimal.Decimal` as opaque numeric
type
- Update frontend pricing test fixtures for string decimal types
## Design decisions
- `NULL` = unpriced (no matching model config), `0` = free
- Reasoning tokens included in output tokens (no double-counting)
- Integer microdollars (BIGINT) for storage and API responses
- Price config uses `decimal.Decimal` for exact parsing; totals use
`int64`
Frontend: #23037
Kyle Carberry