This file documents the AI gateway subsystem (devplacepy/services/openai_gateway/) - the single point of truth for AI calls, usage metering, and provider/model routing. Claude Code loads it automatically whenever a file under this directory is read or edited.

## Overview

`GatewayService` (`services/openai_gateway/`) is an OpenAI-compatible LLM gateway (the ported `openai5.py`), mounted at `/openai/v1/*` (`routers/openai_gateway.py`, prefix `/openai`). It is a **service that serves an HTTP endpoint** rather than a loop.

- The router is thin: it calls `service_manager.get_service("openai").handle(request, subpath)`. `POST /v1/chat/completions` runs the full gateway (vision augment -> model override -> forward -> optional SSE re-emit via `_fake_stream`); `POST /v1/embeddings` forwards to the configured embeddings upstream (`handle_embeddings`, no vision/streaming); `GET /v1/models` is answered locally from the `gateway_models` chat routes (`_models_response`, publishing the public `molodetz`/`molodetz-pro` names), NOT proxied upstream; `/v1/{path:path}` is a transparent passthrough to the upstream base. **The gateway always forwards NON-streaming upstream** (`payload["stream"] = False`), then re-emits SSE itself when the client asked for `stream`; because `stream_options` is only valid alongside `stream=true`, `handle_chat` strips `stream_options` from the upstream payload (otherwise DeepSeek rejects it with `stream_options should be set along with stream = true`) and, when the client requested `stream_options.include_usage`, `_fake_stream` appends a final `choices: []` usage chunk built from the upstream `usage` before `[DONE]`. Disabled -> 503, unauthorized -> 401, upstream connection failure -> 502.
- `main.py` registers it and exempts `/openai` from the rate-limit middleware and the maintenance gate. No new dependency (`httpx` already required).
- `GatewayService` is `default_enabled=True` so internal callers work out of the box.

## Per-call cost/token response headers

Every gateway response (chat, embeddings, passthrough; success and error) carries `X-Gateway-*` headers describing that single call: `Model`, `Backend`, `Prompt-Tokens`, `Completion-Tokens`, `Total-Tokens`, `Cache-Hit-Tokens`, `Cache-Miss-Tokens`, `Reasoning-Tokens`, `Cost-USD`/`Input-Cost-USD`/`Output-Cost-USD` (dollars), `Cost-Native` (1 if the upstream returned a native cost), `Tokens-Per-Second`, `Upstream-Latency-Ms`, and `Context-Window`/`Context-Utilization` when the model's window is known, plus the timing headers `X-Gateway-Upstream-Latency-Ms`/`X-Gateway-Total-Latency-Ms`. `GatewayUsageLedger.record(...)` RETURNS the computed ledger row (or `None` on failure); each handler's `finalize` closure maps it through `usage.usage_response_headers(row)` and attaches it to the returned `Response` (`resp_headers`). The single denied path with no upstream call (embeddings disabled) carries no headers. This is what lets any caller read its own spend - the AI correction worker reads `X-Gateway-Cost-USD`/token headers off its own correction call to accumulate per-user totals (see "AI content correction" in the root `CLAUDE.md`).

## App-reference header (`X-App-Reference`)

Callers may send an optional `X-App-Reference` header to tag gateway calls by application. The value is validated and stored in the `app_reference` column of `gateway_usage_ledger`, surfaced in analytics and admin reporting.

- **Validation** (`service._validate_app_reference`): trimmed whitespace, then matched against `^[a-zA-Z0-9_.-]{1,30}$`. Any value failing validation (empty, >30 chars, contains spaces or `@`/`/` etc.) silently falls back to `"default"`.
- **Header name:** `X-App-Reference`.
- **All internal callers** (news, bots, Devii, correction, jobs, deepsearch, dbapi, gitea) should pass a `devplace-<component>-v-<major>-<minor>-<patch>` value, e.g. `devplace-devii-v-1-0-0`, `devplace-news-v-1-0-0`.
- The column is indexed (`CREATE INDEX IF NOT EXISTS`) for fast per-app queries.

## Per-worker runtime

**Serves in every worker.** Config/enabled come from `site_settings` (via the service's `get_config()`/`is_enabled()`), so any uvicorn worker answers - not just the supervisor worker. Per-worker runtime (`GatewayRuntime`: `httpx.AsyncClient` pool + `asyncio.Semaphore` sized to `gateway_instances`, plus counters and a `VisionCache`) is created lazily on first request and rebuilt when `instances`/`timeout`/cache size change. `gateway_instances` is the **scaling knob** (concurrency per worker); process scaling is uvicorn workers.

## Auth

`authorize()` reuses `get_current_user` (cookie/X-API-KEY/Bearer/Basic). Allowed if `gateway_require_auth` is off, the presented X-API-KEY/Bearer equals the static `gateway_access_key` **or the auto-generated `gateway_internal_key`**, or the resolved user is an admin (`gateway_allow_admins`) or any user (`gateway_allow_users`).

**Per-user attribution:** the gateway also accepts a real user's `api_key` (Bearer / X-API-KEY / session), gated by `gateway_allow_users` (default **on**); `resolve_owner()` records `(owner_kind, owner_id)` per call, so usage is attributed and limitable per user. With `gateway_allow_users` off, only internal/access/admin keys work and per-user attribution never happens. Devii operating a signed-in user authenticates its LLM calls with that user's own `api_key` (set as the session's `ai_key` in `build_settings(..., owner_kind="user")`), so a user's full gateway spend (Devii and direct API calls) rolls up under their uid - surfaced admin-only on the profile page via `build_user_usage()` / `GET /admin/users/{uid}/ai-usage`. Guests keep the internal key.

## Config fields

All config is `config_fields` (upstream url/model/key, force-model, the Prompt group's `gateway_system_preamble`, timeout, instances, vision url/model/key/cache/toggle, the Embeddings group (`gateway_embed_enabled`/`_url`/`_model`/`_key`), the auth toggles + static key + internal key, plus the Pricing/Reliability/Tracking groups); live metrics (requests/errors/in-flight/vision-calls/embed-calls/latency plus 24h cost/tokens/success rollups) via `collect_metrics`.

## System-message composition (date awareness + operator preamble)

`system_message.py` (`apply_system_directives`) runs in `handle_chat` only (NOT `handle_embeddings`/`handle_passthrough`), after vision augmentation and before the upstream payload is assembled, so it reaches every chat consumer (news, bots, Devii guests, per-user direct API calls). It composes ONE system message in a fixed, cache-friendly order: **operator preamble (`gateway_system_preamble`) -> date line (`Current date: DD/MM/YYYY`) -> the client's original system content**.

Two behaviors:

- **Date awareness (EU, no time).** The current date is injected only when the composed text (preamble + client system content) contains NO date in any common format. Detection lives in `contains_date` via the `_DATE_PATTERNS` regex set: `YYYY-MM-DD` (ISO), `D/M/YYYY` and `DD/MM/YYYY` (also matches `MM/DD/YYYY`), `DD-MM-YYYY`, `DD.MM.YYYY`, and textual months (`14 June 2026`, `June 14, 2026`, `14 Jun 2026`, with abbreviations and optional ordinal/comma). The date is `datetime.now().strftime("%d/%m/%Y")` - **date only, never time**: omitting the time keeps the system message byte-stable for the whole day so upstream prompt/token caching stays effective.
- **Operator preamble.** `gateway_system_preamble` (Prompt group, `type="text"` textarea, default empty) is prepended ahead of the client's system content on every chat call so all calls carry operator preferences. When the client sent NO system message, the composed content (preamble and/or date) becomes a brand-new leading system message; when the client DID send one, its content is replaced in place (preamble + date + original text). A blank/whitespace-only preamble with an already-dated request is a no-op (no empty system message is created). The date detection runs over the preamble too, so an operator preamble that already states a date suppresses the injected date line.

Embeddings/passthrough are untouched by this composition step.

## Usage, cost, latency, and reliability tracking

The gateway records one row per upstream call (chat, vision, passthrough) and surfaces per-hour and 24h analytics. The pieces:

- **`usage.py`** - `GatewayUsageLedger` writes to `gateway_usage_ledger` (one row per call, success and failure) and samples `gateway_concurrency_samples` each 30s tick. `normalize_usage` handles BOTH upstream shapes: DeepSeek (`prompt_cache_hit_tokens`/`prompt_cache_miss_tokens`, `completion_tokens_details.reasoning_tokens`) and OpenRouter (`prompt_tokens_details.cached_tokens`, native `cost`, `cost_details`). `compute_cost` PREFERS the upstream native `cost` (OpenRouter) and FALLS BACK to per-1M pricing for the chat backend (DeepSeek reports no cost); it also returns the input/output split (native cost is split by the modeled-rate share `input_cost / (input_cost + output_cost)` from the configured per-1M prices, not by token volume; a negative native cost is clamped to 0). `record()` is wrapped in try/except so a tracking failure never breaks the proxy.
- **`gateway.py`** - `_send` is the gated/timed/retried path: a `CircuitBreaker` (`reliability.py`) short-circuits when open; `retry_send` retries timeouts/connection errors/5xx with linear backoff; semaphore acquire time is the `queue_wait_ms`; an httpx per-request `trace` extension captures `connect_ms` (0 on pooled reuse). `handle_chat`/`handle_passthrough` record every outcome with timings, tokens, cost, params, and the resolved owner. Vision calls record from `VisionAugmenter._describe_one`.
- **Owner attribution** - `GatewayService.resolve_owner` maps the caller to `(owner_kind, owner_id)`: `internal:devii` (internal key), `key:access` (static key), `user:<uid>`/`admin:<uid>` (session or API key), else `anonymous`.
- **`analytics.py`** - `build_analytics(hours, top_n, pricing)` pulls the bounded window once (clamped to `MAX_WINDOW_HOURS=168`) and computes everything in Python: volume/throughput, tokens (sums + avg + p50/p90/p95/p99 + max via `reliability.percentile`), latency (upstream/overhead/queue/connect/total + tokens/sec), errors by category, cost (per model/caller, input vs output, projected monthly, caching savings), behavior, and an hourly breakdown. `summary_metrics()` runs cheap SQL aggregates for the live service panel. TTFT/inter-token are returned `null` (gateway forwards non-streaming).
- **Admin** - `/admin/ai-usage` (HTML, `templates/ai_usage.html` + `static/js/AiUsageMonitor.js`) and `/admin/ai-usage/data?hours=&top_n=` (JSON) in `routers/admin/` package, admin-gated. Schema `GatewayUsageOut`. Devii action `ai_usage` and docs `admin-ai-usage` expose the same endpoint. The `ai_usage` and `site_analytics` Devii catalog tools are both `requires_admin=True`.
- **Per-user usage** - `analytics.build_user_usage(owner_id, hours=24, pricing)` filters the ledger by `owner_id` (a uid matches both `user:` and `admin:` rows) and returns requests, success/error %, token totals, cost (window / per-hour / per-request / 30-day projection = 24h spend x 30), avg latency + tps, per-model breakdown, and an hourly cost series. Served admin-only at `GET /admin/users/{uid}/ai-usage` (schema `UserAiUsageOut`, docs `admin-user-ai-usage`) and rendered on the profile page by `static/js/UserAiUsage.js` (the `[data-ai-usage]` card, gated `{% if is_admin(user) %}` in `templates/profile.html`). The 24h window is a sound projection basis (unlike a startup burst), so `cost_24h * 30` is honest.
- **Profile visibility split** - `routers/profile/` package `_ai_quota(uid, include_cost=False)` builds the profile quota bar. **The displayed spend is the user's REAL total gateway spend, not the Devii-turn subtotal:** `spent_usd`/`used_pct`/`requests`/`last_used` come from `analytics.user_spend_24h(uid)`, the SAME `gateway_usage_ledger` source (summed by `owner_id`, matching both `user:` and `admin:` rows) that feeds the stat grid's `cost.window_usd`. So the server-rendered `spent_usd` is byte-for-byte the card's "Cost 24h" and the two halves of the card reconcile. `turns` is still the `devii_usage_ledger` `turns_24h` count (Devii conversation turns) and is labeled **"Devii turns"** in the template precisely because it is a *different metric* from the grid's total **API requests** (one Devii turn fans out into several gateway requests; direct API-key calls add requests with no turn, which is why `0 Devii turns` can sit beside `18 API requests`). The `limit`/`turns` still come from the Devii service (`daily_limit_for`/`turns_24h`); an **unlimited** limit (`<= 0`, the admin default) sets `unlimited=True` so the template renders "no cap" / "No daily spend cap" instead of a misleading `/ $0.00`. **This is display-only: the Devii daily-cap ENFORCEMENT and `/devii/usage` still read the Devii-scoped `devii_usage_ledger.spent_24h`** (per-turn, resettable, and the only per-guest spend record since guest Devii calls hit the gateway under the shared internal key, not the guest cookie). The profile page renders three ways: **admin** sees the full gateway stats card *plus* a server-rendered quota bar (with spend/limit/Devii turns); the **owner** (non-admin, `is_self`) sees a quota-**only** card showing just the percentage; everyone else sees nothing AI-related. `_ai_quota` is fail-safe (returns `None` on any error or when the Devii service is unregistered) and the result rides on `ProfileOut.ai_quota`. **Dollar figures (`spent_usd`/`limit_usd`) are included only when `include_cost=viewer_is_admin`** - never for a non-admin owner. This matters because the route serves the same context as JSON via `respond(..., model=ProfileOut)` and `ProfileOut.ai_quota` is a free-form dict, so hiding dollars in the HTML branch alone would still leak them to a member requesting their own profile with `Accept: application/json`; the server-side omission is the real control. Non-admins (HTML and JSON) get only `used_pct`/`turns`/`requests`.
- **Retention** - `run_once` prunes both tables past `gateway_usage_retention_hours` (default 720 = 30 days).

**Financial data is admin-only everywhere.** Any monetary figure (USD cost, pricing, spend, limit) is restricted to administrators; members and guests see only the percentage of quota used - this rule is enforced consistently across the profile card, `ai_correction`/`ai_modifier` usage displays, and the Devii cost tools.

## Image generation

`POST /openai/v1/images/generations` exposes an OpenAI-compatible image-generation endpoint. Clients send the generic model `molodetz-img-small` (`config.INTERNAL_IMAGE_MODEL`), which `handle_images` remaps to `gateway_image_model` exactly like chat remaps `molodetz` -> `gateway_model` (also remapped when `gateway_force_model` is on or the model is empty or `molodetz-img`). It defaults to OpenRouter's `black-forest-labs/flux-1.1-pro` at `https://openrouter.ai/api/v1/images/generations` (`config.IMAGE_*_DEFAULT`, $0.04 per image fallback). `handle_images` mirrors `handle_embeddings`: build the payload, forward via `_send`, and record one ledger row. The config fields are the **Images** group (`gateway_image_enabled` default on, `gateway_image_url`, `gateway_image_model`, `gateway_image_key`) plus the Pricing-group `gateway_image_price_per_call`. `effective_config()` falls the image key back to `gateway_api_key` then `OPENROUTER_API_KEY`. Usage is recorded with **`backend="image"`**; `usage.compute_cost` adds an `image` branch (flat per-call, native OpenRouter `cost` still preferred via `extract_image_usage`). `routing.image_overlay` resolves per-route provider/url/key and uses `price_input_per_m` as the per-image price. `routing.seed_default_image_routes()` (from `migrate_ai_gateway_settings`) idempotently seeds `molodetz-img-small` -> Flux on the `openrouter` provider when `OPENROUTER_API_KEY` is set. When `gateway_image_enabled` is off the endpoint returns 503 with no ledger row.

## Embeddings

`POST /openai/v1/embeddings` exposes an OpenAI-compatible text-embeddings model. Clients send the generic model `molodetz~embed` (`config.INTERNAL_EMBED_MODEL`), which `handle_embeddings` remaps to `gateway_embed_model` exactly like chat remaps `molodetz` -> `gateway_model` (also remapped when `gateway_force_model` is on or the model is empty). It defaults to OpenRouter's `qwen/qwen3-embedding-8b` at `https://openrouter.ai/api/v1/embeddings` (`config.EMBED_*_DEFAULT`, $0.01 per 1M input tokens). `handle_embeddings` mirrors `handle_chat` but is simpler: no vision augmentation and no streaming - build the payload, forward via `_send`, and record one ledger row through the same `finalize(...)` closure. The config fields are the **Embeddings** group (`gateway_embed_enabled` default on, `gateway_embed_url`, `gateway_embed_model`, `gateway_embed_key`) plus the Pricing-group `gateway_embed_price_input_per_m`. `effective_config()` falls the embed key back to `gateway_vision_key` then `OPENROUTER_API_KEY` (NOT `gateway_api_key`: that is the DeepSeek chat upstream key, whereas embeddings target OpenRouter like vision does). Usage is recorded with **`backend="embed"`**; `usage.compute_cost` adds an `embed` branch (input-only, completion always 0, native OpenRouter `cost` still preferred) and `Pricing` gained `embed_input_per_m`. `analytics.py` groups by `backend` generically, so embed rows roll up automatically; `caching_savings` counts only **non-native** chat rows (native-priced rows did not use the configured cache-hit/miss rates, so folding them in would report a fictional saving). When `gateway_embed_enabled` is off the endpoint returns 503 with no ledger row.

## Single point of truth for AI

The gateway is the only place that holds real provider URLs/models/keys. Every other AI consumer (news, bots, Devii guests) points at it by default and never touches a provider key:

- Defaults live in `config.py`: `INTERNAL_GATEWAY_URL` (`http://localhost:10500/openai/v1/chat/completions`, override with `DEVPLACE_INTERNAL_BASE_URL`) and `INTERNAL_MODEL` (`molodetz`). `news_ai_url`, `bot_api_url`, `devii_ai_url` default to `INTERNAL_GATEWAY_URL`; their model defaults to `molodetz`.
- Each consumer's key falls back to `database.internal_gateway_key()` (reads the `gateway_internal_key` setting) when its own key field/env is unset - the provider-key fallbacks (`DEEPSEEK_API_KEY`/`OPENROUTER_API_KEY`) were removed from news and bots.
- `gateway_force_model` (default on) and a `molodetz`/empty alias in `handle_chat` make the upstream always receive `gateway_model`, so `molodetz` is a stable generic alias.
- `database.migrate_ai_gateway_settings()` (called at the end of `init_db()`, under the startup `init_lock`): generates `gateway_internal_key` (uuid4) if missing; migrates `DEEPSEEK_API_KEY`/`OPENROUTER_API_KEY` env into `gateway_api_key`/`gateway_vision_key` when the db value is empty; and rewrites any consumer AI URL still equal to the old `openai.app.molodetz.nl` default to the gateway, plus `bot_model` `deepseek-chat` -> `molodetz` (only uncustomized values).
- The gateway's `gateway_api_key`/`gateway_vision_key`/`gateway_internal_key` fields are **non-secret** so the admin services page shows the value actually in use, editable.
- Bot LLM calls are synchronous `urllib` but already run via `asyncio.to_thread` (`bot/bot.py`), so the local round-trip never blocks the event loop.
- Real provider keys/URLs/models live ONLY in the gateway. The gateway is `default_enabled=True`.

## Provider and model routing (`routing.py`, admin `/admin/gateway`)

Layered ON TOP of the single-provider service config above, which stays THE implicit `default` provider (env migration, internal key, `molodetz`/`molodetz~embed`, vision, embeddings, ledger all unchanged).

**Storage.** Two dataset tables, ensured in `init_db` via `routing.ensure_tables`, cross-worker cache-invalidated under the `"gateway_routing"` cache-version name (module-level `provider_store`/`model_store` over a shared `_ROUTING_CACHE`; writes `bump_cache_version` and clear the cache). They are admin config, NOT in `SOFT_DELETE_TABLES` - hard CRUD, mirroring `site_settings`:

- `gateway_providers` - named upstreams: `name` + `base_url` (chat-completions URL) + `api_key` + `is_active`; the embeddings URL is derived by swapping `/chat/completions` -> `/embeddings`.
- `gateway_models` - source->target routes: `source_model` (unique, what clients request) -> `provider` (blank = default) + `target_model` + `kind` (chat|embed|image) + optional `vision_provider`/`vision_model` for the **text+vision merge** (when set, image content is described by that vision model before forwarding) + `context_window` + its **own economy** (`price_cache_hit_per_m`/`price_cache_miss_per_m`/`price_output_per_m`/`price_input_per_m`, USD per 1M tokens for chat/embed/vision; for image routes `price_input_per_m` is a flat USD per image, plus the tiered/off-peak fields below) + `is_active`.

**Resolution is a per-request overlay, not a fork.** At request time `routing.chat_overlay(requested, cfg)` / `routing.embed_overlay(requested, cfg)` / `routing.image_overlay(requested, cfg)` resolve an active route by the requested model name and return a per-request OVERLAY dict of `gateway_*` cfg keys (`gateway_force_model`+`gateway_model`=target, `gateway_upstream_url`/`gateway_api_key` from the provider, the price keys, an augmented `gateway_model_context_map`, and vision overlay keys); `handle_chat`/`handle_embeddings` merge it onto the base cfg (`cfg = {**cfg, **overlay}`) BEFORE everything else, so the existing model-selection / `pricing_from_cfg` / `parse_context_map` / vision / url+key paths transparently use the route's provider, target model, pricing, vision model and context window. `_ensure` (the httpx pool / semaphore / breaker / vision cache) reads only the non-overlaid pool keys, so the connection pool is never churned per request.

**No matching route = None overlay = model fallback.** When no route matches, the overlay returns `None` and the handler's model selection logic falls back to the default configured model (`gateway_model` for chat, `gateway_embed_model` for embeddings, `gateway_image_model` for images). The unknown model name is discarded, not forwarded upstream. This means an unknown or misspelled model name never causes a 4xx from the upstream - it is gracefully downgraded to the default. The `force_model` guard and the built-in `molodetz`/`molodetz~embed`/`molodetz-img-small` aliases are still respected before the route check: `force_model` or empty/named-alias model -> default directly; known model -> route resolution; unknown model with no route -> default fallback with a log message.

**CRUD.** Admin JSON at `/admin/gateway/{providers,models}` (`routers/admin/gateway_configs.py`, `require_admin`, Pydantic `ProviderIn`/`ModelRouteIn` validation, accepts both JSON from `static/js/GatewayAdmin.js` and form from Devii), audited under `gateway.provider.*`/`gateway.model.*` (category `ai`), included in the admin package with the page at `/admin/gateway` (`templates/admin_gateway.html`, sidebar link, `admin_section="gateway"`).

**Devii tools:** `gateway_providers`/`gateway_models` (read) and `gateway_provider_set`/`gateway_provider_delete`/`gateway_model_set`/`gateway_model_delete` (admin; the two deletes are `CONFIRM_REQUIRED`).

When adding a routed value, overlay it as the matching `gateway_*` cfg key so the runtime needs no new branch.

**Tests:** `tests/unit/services/openai_gateway/routing.py` (overlay/economy/kind isolation), `tests/unit/services/openai_gateway/gateway.py::test_model_route_overrides_upstream` (end-to-end through `handle_chat`), and `tests/api/admin/gateway/` (admin CRUD + validation + role gating).

## Tiered (context-length) and off-peak pricing (model-agnostic variable pricing)

Real providers sometimes charge more than a flat per-1M rate for one component: a rate that jumps once a request crosses a context-length threshold, or a fixed time-of-day discount window. This is layered on top of the cache-hit/cache-miss/output shape (which is already exactly DeepSeek's real billing model - see below), on the SAME `gateway_models` route row, so it stays fully provider-agnostic and opt-in per route.

- **Per-route fields** (each optional/zero by default = feature off, so an unconfigured route is byte-identical to before): `context_tier_threshold_tokens` (0 disables tiering; when the request's input token count exceeds it, `price_*_per_m_tier2` rates apply instead of the tier-1 rates above) and the four nullable `price_cache_hit_per_m_tier2`/`price_cache_miss_per_m_tier2`/`price_output_per_m_tier2`/`price_input_per_m_tier2` (a component left `None` keeps its tier-1 rate even above threshold - so a provider that only re-prices input above a size threshold, keeping output flat, needs just one tier2 field set), plus `off_peak_start_minute`/`off_peak_end_minute` (nullable, UTC minutes-since-midnight, both-or-neither enforced by `ModelRouteIn`'s model validator; a window where start > end wraps past midnight, e.g. DeepSeek's old V3/R1-era 16:30-00:30 UTC window) and `off_peak_discount_pct` (0-100, multiplies whichever tier rate is active). The same fields double for vision (`price_input/output_per_m_tier2`) and embed (`price_input_per_m_tier2`) exactly like their tier-1 counterparts already do.
- **Overlay + computation.** `chat_overlay`/`embed_overlay` propagate all of these into the per-request cfg dict under `gateway_*` keys exactly like the existing price fields (section above); `usage.pricing_from_cfg` reads them generically (defaulting to `None`/`0`/disabled when absent), so **Layer A (the single global flat Pricing config fields) never gains these dimensions** - only a `gateway_models` route can enable them, preserving the "no matching route = byte-identical legacy behavior" guarantee. `usage.compute_cost` selects tier1 vs tier2 per rate component (`_tiered_rate`) based on whether `norm["prompt"]` (billable input tokens) exceeds the threshold, then applies the off-peak discount (`_effective_rate`/`_off_peak_active`, UTC wraparound-aware) to whichever rate was selected. **The response header format and `compute_cost`'s return shape (`total, input_cost, output_cost, native`) are unchanged** - this is purely an internal rate-selection step before the existing input/output split math runs; a native upstream `cost` (OpenRouter) still overrides the modeled total exactly as before.
- **Migration.** New `gateway_models` columns are added via `has_column`/`create_column_by_example` in `routing.ensure_tables()` (the `CREATE TABLE IF NOT EXISTS` DDL string alone would never reach a pre-existing table - see the `database/CLAUDE.md` column-ensure idiom).
- **Admin UI.** `/admin/gateway`'s model-route form has a "Tiered / off-peak pricing (optional)" subsection; off-peak start/end render as `<input type="time">` (converted to/from UTC minutes-of-day by `GatewayAdmin.js`), and the routes table shows `tiered`/`off-peak` badges when a route has either dimension configured.
- **DeepSeek's real pricing is already the tier-1 shape, not a new dimension.** DeepSeek's actual API (verified against `api-docs.deepseek.com/quick_start/pricing`) bills three flat per-1M rates - cache-hit input, cache-miss input, output - with no current context-length tier or off-peak window for the V4 models; that shape was already fully modeled by the pre-existing `chat_cache_hit_per_m`/`chat_cache_miss_per_m`/`chat_output_per_m` fields before this section's tier2/off-peak fields existed. `routing.seed_default_deepseek_routes()` (called once from `database.migrate_ai_gateway_settings()` at the end of `init_db()`) idempotently inserts four ready-made routes - `deepseek-v4-flash` (`$0.0028`/`$0.14`/`$0.28` per 1M, 1M context), `deepseek-v4-pro` (`$0.003625`/`$0.435`/`$0.87` per 1M, 1M context), and the two public `molodetz` aliases `molodetz` -> `deepseek-v4-flash` (flash rates) and `molodetz-pro` -> `deepseek-v4-pro` (pro rates) - only when that `source_model` row does not already exist, so a caller or Devii can request any name explicitly and get correctly-priced, decoupled from whatever the single global `gateway_model` default happens to be set to (switching that global setting between the two real models does NOT retroactively fix the flat Pricing config fields - the seeded routes are the model-agnostic, always-correct way to reference a specific priced model). The `molodetz`/`molodetz-pro` aliases are the public model names; `GET /v1/models` is served locally from these `source_model` rows (not proxied upstream), so it publishes exactly the models the gateway accepts. Neither seeded route sets the tier2/off-peak fields (DeepSeek does not use them today); an admin can add them later on the same row if DeepSeek (or any other provider routed here) introduces such pricing.
