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helexa/neuron.example.toml
rob thijssen 4f05a87449
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feat(neuron): self-derived context-limit core — physics + policy (#67 phase 1)
Refs #67. The correct limit{context,input,output} for a deployment is a
computed function of model architecture + live free VRAM + a
coherence/throughput trade-off, not an operator-declared static fact that
goes stale on model swap. This lands the arch-agnostic derivation core;
later phases capture per-model physics at load, measure throughput, and
advertise/enforce the computed limit.

- crates/neuron/src/harness/context_limit.rs (new):
  - kv_bytes_per_token(): shared per-card KV cost (counts only
    full-attention layers; sharded by TP world size). The TP load paths'
    inline math folds onto this in phase 2.
  - ContextProfile: per-model physics snapshot (max_position_embeddings,
    kv_bytes_per_token_per_card, world_size).
  - derive_limit(): context = min(max_pos, vram_ceiling,
    throughput_ceiling) clamped by an optional backstop; input = context −
    output; rounded to 1024. 6 unit tests.
- config.rs: [harness.candle.context_limit] block (mirrors prefix_cache):
  target_prefill_latency_secs, bootstrap_prefill_tok_per_sec,
  activation_headroom_mb, min_free_floor_mb, output_reserve_tokens.
- neuron.example.toml: documented the new block.

No runtime behaviour change yet. fmt/clippy/test green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-17 13:00:52 +03:00

113 lines
4.9 KiB
TOML

# neuron.example.toml — example configuration
#
# Copy to /etc/neuron/neuron.toml and adjust for your environment.
#
# Environment variable overrides use NEURON_ prefix with __ separators:
# NEURON_PORT=13131
port = 13131
# -- Harnesses ---------------------------------------------------------------
# Each [[harnesses]] entry enables an inference engine. Currently only
# "candle" is supported — it runs in-process and uses huggingface/candle
# for inference on local CUDA devices (or CPU when CUDA is unavailable).
[[harnesses]]
name = "candle"
# -- Candle harness settings -------------------------------------------------
# Optional tuning for the candle harness.
[harness.candle]
# HuggingFace cache directory for model weights.
#
# Resolution order (first hit wins):
# 1. `hf_cache` here in this file (applies to the synth `huggingface`
# source only — see [harness.candle.sources.*] below for explicit
# per-source paths).
# 2. `HF_HUB_CACHE` env var — same convention as the Python
# `huggingface_hub` library, so an existing cache directory shared
# with other tooling can be reused without per-tool config.
# 3. `HF_HOME` env var (cache appended as `$HF_HOME/hub`).
# 4. hf-hub's default (`~/.cache/huggingface/hub`).
#
# For per-host overrides (e.g. one neuron has an SSD with prefetched
# weights), prefer a systemd drop-in over editing this file:
# /etc/systemd/system/neuron.service.d/local.conf:
# [Service]
# Environment=HF_HUB_CACHE=/archive/hf-cache
# hf_cache = "/var/lib/neuron/hf-cache"
# Default scheme applied to bare `org/name` model ids (those without a
# `scheme:` prefix). Defaults to "huggingface" when unset. Set to
# "helexa" to make `default_models = [{ model_id = "Helexa/Foo" }]`
# resolve via the helexa registry without prefixing every entry.
# default_source = "huggingface"
# Per-scheme source endpoints. Each scheme maps to an HF-compatible
# registry. The `huggingface` source is auto-synthesised pointing at
# `https://huggingface.co` when omitted; declare it explicitly here to
# override the endpoint, auth env, or cache dir.
#
# [harness.candle.sources.huggingface]
# endpoint = "https://huggingface.co"
# auth_env = "HF_TOKEN" # optional bearer token via env var
# cache_dir = "/archive3/llm-cache/huggingface"
#
# Add helexa (or any operator-run mirror speaking the HF-compatible
# wire format) by adding another sources entry. Caches are
# disambiguated per scheme so a mirror serving the same `org/name` as
# HF cannot collide on disk.
#
# [harness.candle.sources.helexa]
# endpoint = "https://registry.helexa.ai"
# auth_env = "HELEXA_TOKEN"
# cache_dir = "/archive3/llm-cache/helexa"
# -- Prefix KV cache ----------------------------------------------------------
# Reuse cache state across requests when a new prompt starts with the
# exact token sequence of a previous one (chat/agent workloads), so
# prefill only runs on the new suffix. Applies per loaded model, on
# architectures that expose their cache state (qwen3_5). Snapshots
# live in device memory: budget_mb is per loaded model and comes out
# of the same VRAM that serves inference.
#
# [harness.candle.prefix_cache]
# enabled = true
# budget_mb = 1024
# max_entries = 8
# -- Self-derived context limits (#67) ---------------------------------------
# neuron computes the most-efficient limit{context,input,output} that still
# allows coherent agentic performance, from model architecture + live free
# VRAM + a self-measured prefill throughput ceiling, advertises it on
# /models, and enforces it. The advertised limit tracks the resident model
# and rises automatically as efficiency work (e.g. prefix caching, #11)
# frees headroom or speeds prefill — no operator action. These defaults
# rarely need changing; raise target_prefill_latency_secs once prefix
# caching makes long-context re-prefill cheap.
#
# [harness.candle.context_limit]
# enabled = true
# target_prefill_latency_secs = 120.0 # coherence wall (longest prefill/turn)
# bootstrap_prefill_tok_per_sec = 800.0 # cold-start estimate until measured
# activation_headroom_mb = 2048 # per-card prefill activation reserve
# min_free_floor_mb = 1500 # per-card free-VRAM floor to keep
# output_reserve_tokens = 8192 # generation reserve below the wall
# -- Default models ----------------------------------------------------------
# Models listed here are loaded automatically when the neuron service
# activates. Loading is sequential — a slow or failing entry doesn't
# block the rest of the fleet, but it does push out the time before
# neuron starts serving HTTP, so keep the list short. Operators can
# load additional models on demand via POST /models/load.
#
# Make sure data/neuron.service's TimeoutStartSec is generous enough to
# cover the slowest entry's first-time download + materialisation.
# [[default_models]]
# model_id = "Qwen/Qwen3-0.6B-GGUF"
# harness = "candle"
# quant = "Q4_K_M"
# devices = [0]