The pytest for Mixture-of-Experts models. Catch expert collapse, routing entropy collapse, and load imbalance — before they silently wreck your training run.

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MoEWatch is a lightweight diagnostic and audit library for MoE models in HuggingFace Transformers. Drop it into any training loop — it instruments router modules with zero-weight-modification PyTorch hooks, aggregates routing statistics, and surfaces structured alerts the moment something goes wrong.

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Features

• Expert collapse detection — tracks dead and cold experts per layer across the full training run
• Routing entropy analysis — catches distribution collapse relative to theoretical maximum entropy
• Load imbalance alerts — fires when any single expert dominates token dispatch (max/mean ratio)
• Auto-detection — recognises Mixtral, OLMoE, DeepSeek-MoE, Qwen-MoE, Phi-MoE, Switch Transformer, and more out of the box; falls back to heuristic scan for unknown architectures
• Two integration modes — one-shot audit() for offline diagnostics, or MoEWatch for live training-time monitoring
• HuggingFace Trainer support — attach as a TrainerCallback with one line
• Structured output — console (coloured ASCII), JSON (for log pipelines), or silent (results only via AuditReport)
• Configurable overhead — sample_every=10 keeps instrumentation below 2 % in production; sample_every=1 for maximum fidelity during debugging
• Fixed memory footprint — ring buffer with configurable capacity; no unbounded growth over long runs

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Supported Architectures

Auto-detected via registry (no configuration needed):

Family	Models
Mixtral	mistralai/Mixtral-*
OLMoE	allenai/OLMoE-*
DeepSeek-MoE	deepseek-ai/DeepSeek-V2, DeepSeek-V3
Qwen-MoE	Qwen/Qwen2-MoE-*, Qwen3-MoE-*
Phi-MoE	microsoft/Phi-*-MoE
Switch Transformer	Google's HuggingFace port
NLLB-MoE	facebook/nllb-moe-*
Arctic	Snowflake/snowflake-arctic-*
Jamba	ai21labs/Jamba-*

Any custom architecture can be targeted via WatchConfig(router_modules=[...]).

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Installation

pip install moewatch

Requires Python ≥ 3.8, PyTorch ≥ 1.10, and Transformers (optional — required only for MoEWatch.attach(trainer)).

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Quick Start

Offline audit (one-shot)

Run a diagnostic against a model and dataloader without modifying your training loop:

import moewatch

report = moewatch.audit(model, dataloader, steps=200)
print(report.summary())

Live monitoring (HuggingFace Trainer)

from moewatch import MoEWatch, WatchConfig

watcher = MoEWatch(model, config=WatchConfig())
watcher.attach(trainer)          # injects as a TrainerCallback
trainer.train()
watcher.detach()

Live monitoring (custom loop)

from moewatch import MoEWatch

watcher = MoEWatch(model)
watcher.start()

for step, batch in enumerate(dataloader):
    loss = model(**batch).loss
    loss.backward()
    optimizer.step()
    alerts = watcher.step(step)   # returns List[Alert]; empty when healthy

watcher.stop()

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Configuration

All thresholds and options live in WatchConfig. Three presets cover most use cases:

from moewatch import WatchConfig

WatchConfig.default()      # balanced — recommended starting point
WatchConfig.aggressive()   # tighter thresholds, every-step sampling — for debugging
WatchConfig.lightweight()  # minimal overhead — for large-scale production runs

Common overrides:

config = WatchConfig(
    dead_threshold=0.001,        # < 0.1 % token share → expert is DEAD
    entropy_warn=0.60,           # < 60 % of H_max → WARN
    entropy_critical=0.40,       # < 40 % of H_max → ERROR
    load_imbalance_error=5.0,    # max/mean > 5× → ERROR
    sample_every=10,             # instrument every 10th forward pass
    output="json",               # "console" | "json" | "silent"
)

See the Configuration reference → for all fields and their defaults.

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Alert Levels

Level	Meaning
INFO	Routine routing statistics — everything healthy
WARN	Degraded routing — investigate soon
ERROR	Severe collapse or imbalance — likely harming training

MoEWatch never stops your training run. It diagnoses; you decide.

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Output Modes

# Human-readable console output (default)
WatchConfig(output="console")

# Newline-delimited JSON — pipe to Grafana, Splunk, or a custom pipeline
WatchConfig(output="json")

# No real-time output — results available only via AuditReport
WatchConfig(output="silent")

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Documentation

• Getting started
• Configuration reference
• API reference
• Adding a custom architecture
• Contributing

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Contributing

Issues and pull requests are welcome. To add a new architecture to the auto-detection registry, open an issue or add the router class name(s) to _ARCHITECTURE_REGISTRY in hooks/detection.py and submit a PR.

For full contribution guidelines, see CONTRIBUTING.md.

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License

Apache 2.0 — see LICENSE.

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Built by Abinesh.