rob thijssen
729317d1ef
Stage 3 of the candle-native pivot. neuron now serves POST /v1/chat/completions backed by candle's quantized_qwen3 forward pass on a per-model serialised generation loop, returning the standard OpenAI ChatCompletionResponse envelope. Pipeline per request: - Look up the LoadedModel by request.model (404 if absent). - Apply the Qwen3 chat template across all messages. - Tokenize, then spawn_blocking onto tokio's blocking pool to acquire the per-model arch lock and run prefill + greedy/temperature/top-p sampling via LogitsProcessor. - Stop on <|im_end|>/<|endoftext|> EOS or max_tokens (finish_reason "stop" vs "length"). - Decode with skip_special_tokens=true, build OpenAI response with prompt/completion/total usage counts. Supporting changes: - HarnessRegistry now stores Arc<dyn Harness> and caches a typed Arc<CandleHarness> so inference routes bypass dyn-Trait dispatch. - LoadedModel.arch becomes Arc<Mutex<ModelArch>> so the lock guard can be moved into spawn_blocking. - NeuronState gains an Option<Arc<CandleHarness>> field for the new inference route. - Typed InferenceError lets the handler map ModelNotLoaded → 404 and other failures → 500 without string-matching anyhow messages. - stream=true returns 501 until Stage 4 wires up SSE. - Two leftover mistral.rs string references in proxy.rs and cortex-cli (missed during the Stage 1 sweep) are corrected here. Three new default-feature tests cover the no-candle 503, model-not- loaded 404, and stream=true 501 paths. The cuda-integration test from Stage 2 still covers real load/unload; a streaming-feature gated test exercising actual generation will arrive with Stage 4. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
cortex
A Rust reverse-proxy and fleet management layer for multi-node GPU inference
clusters. Cortex sits in front of one or more neuron daemons (each running
candle-based inference on a local GPU host) and presents a unified OpenAI +
Anthropic compatible API surface.
Problem
Running local LLMs across multiple GPU nodes (different VRAM tiers, different model affinities) requires a unified API surface that:
- Presents a single
/v1/modelscatalogue merging every model that can be served by any neuron in the fleet. - Routes requests to the correct node based on where a model is loaded (or can be loaded), handling cold-load and eviction transparently.
- Manages model lifecycle — load on demand, unload cold models, pin
critical ones — by calling each neuron's
/models/{load,unload}API. - Translates between OpenAI and Anthropic request/response envelopes so every client speaks whichever dialect it prefers.
- Captures per-request metrics (tokens, tok/s, TTFT, latency) and exposes them as Prometheus counters/histograms.
Architecture
┌──────────────┐ ┌──────────┐ ┌────────────┐ ┌────────────┐
│ Claude Code │ │ Zed/IDE │ │ Tidal / mm │ │ curl / etc │
└──────┬───────┘ └─────┬────┘ └──────┬─────┘ └──────┬─────┘
│ │ │ │
└────────────────┴──────┬───────┴───────────────┘
│
┌──────────▼──────────┐
│ cortex │
│ (cortex-gateway) │
│ │
│ Router · Metrics │
│ Evictor · Translate│
└──┬──────┬────────┬──┘
│ │ │
┌──────────▼┐ ┌──▼─────┐ ┌▼──────────┐
│ neuron │ │ neuron │ │ neuron │
│ :13131 │ │ :13131 │ │ :13131 │
│ candle │ │ candle │ │ candle │
└───────────┘ └────────┘ └───────────┘
private network (.internal)
Crates
| Crate | Purpose |
|---|---|
cortex-core |
Shared types: config, node/model state, metrics, OpenAI/Anthropic envelopes, harness trait, discovery types |
cortex-gateway |
Axum HTTP server: proxy, router, evictor, poller, metrics exporter |
neuron |
Per-node daemon: GPU discovery, in-process candle inference, model lifecycle API |
cortex-cli |
CLI entrypoint (cortex serve, cortex status, etc.) |
Node setup
Each GPU node runs neuron (listening on :13131). Neuron uses
huggingface/candle for in-process inference — there is no external
inference subprocess to manage.
The neuron RPM (helexa-neuron) ships a systemd unit:
dnf copr enable helexa/helexa
dnf install helexa-neuron
systemctl enable --now neuron
Gateway config
# /etc/cortex/cortex.toml
[gateway]
listen = "0.0.0.0:31313"
metrics_listen = "0.0.0.0:31314"
[eviction]
strategy = "lru" # lru | priority
defrag_after_cycles = 50
[[neurons]]
name = "beast"
endpoint = "http://beast.internal:13131"
[[neurons]]
name = "benjy"
endpoint = "http://benjy.internal:13131"
Model placement profiles live in models.toml — see models.example.toml.
Building
cargo build --release
CI
Every push triggers format, lint, and test checks. Ensure these pass locally before pushing:
cargo fmt --check --all # must be clean
cargo clippy --workspace -- -D warnings # warnings are errors
cargo test --workspace # all tests must pass
Tagged releases (v*) additionally build SRPMs for both cortex and
helexa-neuron and publish to COPR.
Running
# start the gateway
cortex serve --config /etc/cortex/cortex.toml
# check fleet status
cortex status
# list all models across nodes
curl http://localhost:31313/v1/models
License
GPL-3.0