ModelEntry and CortexModelEntry gain a `capabilities: Vec<String>`
field (serde-default for back-compat). The poller copies it verbatim
from each neuron's ModelInfo.capabilities; list_models computes the
union across every node where a model is loaded so a checkpoint loaded
text-only on one neuron and text+vision on another reports both to the
fleet. Catalogue-only and mid-prewarm entries default to empty until
the catalogue gains a capabilities declaration.
Aliases inherit their target's capability union. New gateway test mocks
two nodes with differing capability arrays and asserts the unioned
/v1/models response.
Closes part of #16 (Stage C3).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Operators can now define tier aliases in models.toml:
[aliases]
"helexa/small" = "Qwen/Qwen3-1.7B"
"helexa/balanced" = "Qwen/Qwen3-8B"
"helexa/large" = "Qwen/Qwen3.6-27B"
A client request for `model: "helexa/small"` is resolved to the concrete
model id at routing time. The gateway also rewrites the proxied body's
`model` field to the concrete id so neuron sees a name that matches its
loaded handle (otherwise the harness rejects the request).
Motivated by the finger-in-the-wind benchmark: same "what's the capital
of Georgia" probe runs in 2.5s on the 1.7B vs 6.7s on the 27B with
identical correctness. Aliases let clients pick a latency tier without
hardcoding model ids, and let operators swap targets without changing
client code.
Changes:
* cortex-core: `ModelCatalogue` gains `aliases: HashMap<String, String>`
+ `resolve_alias(&str) -> &str`. Unit tests cover the basic
resolution + TOML round-trip.
* cortex-gateway:
* `RouteDecision` gains `resolved_model_id: String`. `router::resolve`
consumes aliases at entry and threads the concrete id through.
* Handlers (chat_completions, completions, anthropic_messages
streaming + non-streaming) rewrite the body's `model` field with
`rewrite_model_in_body` before proxying, using the resolved id
for metrics labels, LRU touch, and the body itself.
* `/v1/models` (Pass 4) emits each alias as its own entry mirroring
the target's `loaded` flag, feasible_on, and locations — clients
browsing the endpoint see both names and can pick either.
* `models.toml` declares the three tier aliases; `models.example.toml`
documents the section as opt-in.
* Integration tests verify: end-to-end alias→concrete request flow,
alias surfacing in /v1/models, and no-op fall-through for
non-alias model ids.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
