Models and inference: what AI runs on
04
Key concepts
8 min read · Chapter 4 of 10
01
Entity and identity
What is the unit of record, and how do we know it is the same one?
"The model" has at least three parts: a family (Sonnet, gpt-6.1-sol), a snapshot ID (the exact version), and the host or deployment that serves it. On Azure you call a deployment name you created, and on Bedrock the same Claude model has its own ID and its own retirement date. Open-weight models add the precision and serving stack, which is why OpenRouter lets you filter hosts by quantization. The billing identity is a tree of organization, workspace or project, and API key, and rate limits attach to the organization (Anthropic, OpenAI) or the project (Google), per model, so teams in one organization share its headroom.
The law names its own entities. Under the EU AI Act the "provider" places a model on the market and the "deployer" uses it, and a company that fine-tunes with more than a third of the original training compute becomes the provider of the result. An IP indemnity keys on plan, service and model together, so one API key can be covered for one model and not another. US export rules now follow a company's ultimate parent, wherever its subsidiary is registered (guidance of May 31, 2026).
02
State and lifecycle
What states exist, and what moves an entity between them?
A request goes from admitted to queued, prefilling, decoding and streaming, and ends complete, incomplete or failed. A model goes from preview to generally available, legacy, deprecated (still works, retirement date set) and retired. A prompt cache is written, stays warm while used, and dies when it expires or when the prefix, tools or reasoning settings change. An account climbs tiers with spend history and pauses at its spend cap until the next month. Capacity goes from contracted to built, energized and allocated.
Retirement clocks differ by vendor and are getting shorter at some:
| Vendor | Typical notice before retirement | Notes |
|---|---|---|
| Anthropic | At least 60 days; 60-62 days for every 2026 notice | Down from 181-189 days in 2025; Opus 4.1 lived exactly 12 months |
| OpenAI | At least 6 months for generally available models, 3 for specialized ones, about 2 weeks for previews | A restricted cyber model got 20 days in September 2026 |
| Google (Gemini API) | Dates are "earliest possible"; previews retire 2-4 months after release | Some previews run in production for months |
| Microsoft Foundry | 18-month lifecycle for most generally available models, at least 60 days' notice | Standard deployments auto-upgrade; "retirement dates aren't extendable" |
| AWS Bedrock | "End of life no sooner than" a stated date; Legacy for 6 months or 45 days | Legacy blocks new customers and provisioned throughput |
| Mistral | No formal policy; about 24 days observed for one model | |
| Self-hosted open weights | None | Hosted versions at clouds still retire |
The same model can retire on different dates at the lab and at each cloud. Products retire too: OpenAI ends its Assistants API, hosted evals and self-serve fine-tuning jobs between August 2026 and January 2027.
03
System of record and ledger
Who owns the truth, and how do systems reconcile?
| Fact | System of record |
|---|---|
| What one call used | The provider's usage record per request: input, cache write, cache read, output, tier, region |
| What the company spent | The provider's usage and cost API, the gateway's log and the cloud invoice, which rarely agree |
| How much headroom is left | Rate-limit headers on every response |
| Whether the provider was up | Its status page, which the provider writes and which can lag |
| What a lab has contracted to buy | Backlog at the clouds; take-or-pay schedules in filings |
On cloud marketplaces Anthropic converts usage into consumption units of $0.01 and reports them to AWS or Azure, so a discount shows up as fewer units. A private lab's "run-rate" is a recent month times twelve. Your own gateway log is the only record of errors from your side, and it's the evidence an SLA claim needs.
04
Rules and policy
What logic decides outcomes, and who can change it?
Access is rationed by rules the provider writes and can change:
Anthropic
- Tiers
- Evaluation, Start, Build, Scale, Custom
- Monthly spend cap
- $500 / $1,000 / $200,000
- Example limit at the top self-serve tier
- Opus 5.5: 10,000 requests and 10 million input tokens a minute; Fable 5.x: 4,000 and 4 million
OpenAI
- Tiers
- Free, Build, Launch, Grow (after $5, $100 and $500 of purchases)
- Monthly spend cap
- $100 / $500 / $5,000 / $200,000
- Example limit at the top self-serve tier
- gpt-6 Astra, Sol and Terra: 15,000 requests and 40 million tokens a minute
Google (Gemini API)
- Tiers
- Free, Tiers 1-3 (by spend and account age)
- Monthly spend cap
- $250 to $100,000 or more, plus a 10-minute spend limit
- Example limit at the top self-serve tier
- Per project, per model
The top model gets the tightest limit, and Anthropic calls its limits "maximum allowed usage, not guaranteed minimums". New organizations start lower "to prevent fraud and abuse", and fast ramps hit acceleration limits. Gateways add the customer's own policy (route by price or speed, cap the price per token, use only zero-retention hosts, set budgets per team), and the labs' usage policies restrict high-stakes uses without human review.
05
Effective dating
Which version of the rule applied at that moment?
Dates I'd keep on a calendar as of October 2026:
| Change | Effective | Status (Oct 2026) |
|---|---|---|
| EU AI Act duties for general-purpose model providers | August 2, 2025 | In force |
| California SB 53 for frontier developers | January 1, 2026 | In force |
| H200-class chips to China move to case-by-case review | January 13, 2026 | In force; China limits imports |
| EU AI Office enforcement powers, including fines | August 2, 2026 | In force; first requests September 1 |
| Claude Sonnet 4.5 retires | November 30, 2026 | Upcoming |
| EU Product Liability Directive covers software | December 9, 2026 | Upcoming |
| OpenAI GPT-5 and o3 snapshots retire | December 11, 2026 | Upcoming |
| Gemini 3.6-3.8 Flash prices double | January 1, 2027 | Upcoming |
| New York RAISE Act | January 1, 2027 (some sources say July 1) | Upcoming |
| Older general-purpose models must comply with the AI Act | August 2, 2027 | Upcoming |
Some dates float. Retirement dates are "not sooner than" (Anthropic, AWS) or "earliest possible" (Google), and introductory prices can end or be made permanent: Anthropic kept Sonnet 5's and cancelled a rise planned for September 1, 2026. DeepSeek even prices by time of day.
06
Interfaces and standards
What format and protocol do counterparties speak?
OpenAI's Chat Completions and Responses formats are the de facto interface: Bedrock exposes them ("change the base URL and API key"), most inference providers do, and Anthropic runs an OpenAI-compatible endpoint next to its own Messages API. That makes switching mechanically cheap. Everything around the call is unstandardized: usage fields, rate-limit headers, deprecation metadata and reasoning controls differ per provider. Tokenizers differ too, so the same text can be about 30-35% more tokens on Anthropic's newest models than on its older ones.
Measurement is its own layer. Artificial Analysis measures time to the first token and output speed from one server over 72 hours, MLPerf audits hardware results that vendors submit, and SemiAnalysis's InferenceX turns benchmarks into cost per million tokens. Model makers have started checking hosts: Moonshot publishes a Kimi Vendor Verifier and OpenAI added a compatibility test for gpt-oss. Below the token the units change again: GPU-hours for renting chips, gigawatts of power capacity for compute deals, and megawatt-days in power markets.
07
Networks and counterparties
Who sits between us and the outcome, and what do they want?
| Party | What they control | What they earn |
|---|---|---|
| Lab | Quality, prices, limits, retention, retirements | Tokens, subscriptions, enterprise deals |
| Cloud platform | Procurement, regions, its own SLA and dates | Resold tokens; commitments drawn down |
| Inference provider | Speed and price for open models | Tokens, dedicated endpoints, GPU rental |
| GPU cloud | Energized capacity | Multi-year take-or-pay contracts |
| Chip maker | Allocation of new chips | Hardware at about 74% gross margin (Nvidia) |
| Gateway | Routing and budgets | A small fee, or nothing (open source) |
| Grid operator and utility | Power and connection dates | Capacity payments, set by auction |
Money flows down the chain and equity flows back up it: Nvidia invests in OpenAI and in GPU clouds and providers, Amazon and Google in Anthropic, Microsoft owns about 27% of OpenAI and has invested in Anthropic, and AMD gave OpenAI warrants for up to 160 million of its shares. Amazon sells Claude on Bedrock, holds Anthropic notes, supplies it Trainium and sells its own Nova models, all at once.
08
Regulatory layering
Jurisdiction × activity × entity type: is it a license or a certification?
Model makers
- US
- California SB 53 (frontier developers above 10^26 operations); New York RAISE from 2027
- EU
- AI Act duties for general-purpose models; Code of Practice
- China and elsewhere
- Chinese labs mostly outside the EU Code
Chips and weights
- US
- Export controls: case-by-case H200 licences for China, approved entities in the UAE
- EU
- China and elsewhere
- Beijing approves or blocks imports
Data
- US
- Sector rules; court preservation orders
- EU
- GDPR; residency demands
- China and elsewhere
- Data stays in-country in many sovereign deals
Products
- US
- Deployer liability (case law)
- EU
- Product Liability Directive from December 9, 2026
- China and elsewhere
The same model reached through the lab, Bedrock or Vertex can come with different retention, residency, SLA and indemnity terms, so the route is a legal choice too. For most builders the law arrives through vendor terms and procurement questionnaires.
09
Exceptions and reversals
What goes wrong, and how is it undone?
Rate limit or spend cap hit
- Who starts it
- The provider's limiter
- Clock
- Seconds, or until the 1st of next month
- The way back
- Back off with jitter; fail over; ask for a tier increase
Model retired
- Who starts it
- The lab or cloud
- Clock
- 60 days to 6 months; 20 days seen
- The way back
- Re-test on the replacement; pin the next snapshot
Bad serving change
- Who starts it
- The provider
- Clock
- Hours to weeks to detect
- The way back
- Provider rollback (GPT-4o's sycophantic update came out about four days after release); your own evals
Price step-up
- Who starts it
- The provider
- Clock
- A dated announcement, or a promotion ending
- The way back
- Route elsewhere; renegotiate
Capacity product withdrawn
- Who starts it
- The provider
- Clock
- Immediate for new buyers
- The way back
- Existing contracts honoured; buy elsewhere
Compute deal cancelled or reshaped
- Who starts it
- Either party
- Clock
- 90 days for xAI's capacity to Anthropic; years for take-or-pay
- The way back
- Other sites, other chips
Rule reversed
- Who starts it
- A government
- Clock
- Months
- The way back
- Switchable architecture; exit rights in contracts
Reversals run both ways. OpenAI's "$1.4 trillion" of compute ambitions became about $600 billion through 2030 in reporting by February 2026, and the expansion of the Abilene site beyond 1.2 GW was dropped. Export rules went from ban to unban to a revenue share that was never codified, all within 2025.
10
Liability allocation
When it fails, who pays?
| Failure | Who absorbs it | Mechanism |
|---|---|---|
| Outage | The builder, minus a small credit where an SLA exists | Bedrock: 99.9% per region, credits of 10-100% of that region's charges as future credit; lab standard tiers: best effort, no credit |
| Silent quality drop | The builder | No SLA found that counts wrong answers as downtime |
| Retirement and migration | The builder | Notice periods; no compensation |
| Copyright claim on an output | The vendor, if the indemnity's conditions are met | Paid plan, covered model, output unmodified, filters on; usually outside the liability cap |
| Copyright claim over training data | The lab | Bartz, the New York Times case; reaches builders only through prices |
| Harm from an answer | The deployer by default | Air Canada's chatbot case; consumer cases against model makers are pending or settled |
| Unused compute | The lab, then its investors | Take-or-pay contracts: about 80% of Anthropic's commitments, as reported |
| GPU cloud failure | Lenders, then customers mid-contract | Debt against contracts |
Builders carry price and capacity risk, labs carry volume risk, GPU clouds carry financing and obsolescence risk, and household electricity customers carry part of the grid cost. Liability caps in the labs' and clouds' terms are typically 12 months of fees.