Kamiwaza-MLX 📦

A simple openai (chat.completions) compatible mlx server that:

• Supports both vision models (via flag or config/model-name detection) and text-only models
• Supports streaming boolean flag
• Has a --strip-thinking which will remove tag (in both streaming and not) - good for backwards compat
• Supports usage to the client in openai style
• Prints usage on the server side output
• Appears to deliver reasonably good performance across all paths (streaming/not, vision/not)
• Has a terminal client that works with the server, which also support syntax like image:/path/to/image.png Describe this image in detail
• Experimental direct multi-node bootstrap via mlx.distributed when PAIRED_HOST is provided; the current Kamiwaza TP=2 launcher/proxy flow is documented in MLX_TWO_NODE_README.md

Tested largely with Qwen2.5-VL and Qwen3 models.

Current MLX Stack

The current dependency floor tracks the latest MLX packages validated for the two-node work:

• mlx>=0.31.2,<0.32.0
• mlx-lm>=0.31.3,<0.32.0
• mlx-metal>=0.31.2,<0.32.0
• mlx-vlm>=0.4.4,<0.5.0
• mlx-audio>=0.4.3,<0.5.0

Nemotron 3 Nano Omni currently needs mlx-vlm 0.4.5 code from upstream GitHub for the MLX-community conversions. PyPI only has mlx-vlm 0.4.4 at the time of this validation, so requirements.txt and the redeploy helpers pin:

git+https://github.com/Blaizzy/mlx-vlm.git@15dbf7265c02e4bb5deee580030e13ee8659b643

mlx-community/Nemotron-3-Nano-Omni-30B-A3B-Reasoning-4bit works locally via mlx_vlm generate for combined text, image, and audio inputs. Native video is not yet functional in this MLX path; the current upstream Nemotron MLX model code raises NotImplementedError: Efficient video sampling is not implemented for Nemotron Omni yet.

Experimental DFlash speculative decoding

DFlash is available as an opt-in text-only generation path. Configure a draft model and the server will use a DFlash speculative loop instead of the normal mlx_lm.generate.stream_generate loop. The default backend is auto: it uses the standalone dflash-mlx implementation when installed, otherwise it falls back to ZLab's dflash.model_mlx.

The DFlash backends install from git (PyPI does not allow direct-URL dependencies in package metadata). These are the tested pins:

# ZLab backend
pip install "dflash[mlx] @ git+https://github.com/z-lab/dflash.git@6d6229eaddce58fcd7e4cc91945da632f5544c86"

# Standalone dflash-mlx backend
pip install "dflash-mlx @ git+https://github.com/bstnxbt/dflash-mlx.git@fada1eb2b75cd1c875ca6547b6518783fd3d2956"

python -m kamiwaza_mlx.server \
  -m mlx-community/Qwen3.5-27B-5bit \
  --dflash-draft-model z-lab/Qwen3.5-27B-DFlash \
  --dflash-backend auto \
  --dflash-block-size 16 \
  --dflash-default-max-tokens 2048 \
  --dflash-max-context -1

Equivalent environment variables:

export KAMIWAZA_MLX_DFLASH_DRAFT_MODEL=z-lab/Qwen3.5-27B-DFlash
export KAMIWAZA_MLX_DFLASH_BACKEND=auto
export KAMIWAZA_MLX_DFLASH_BLOCK_SIZE=16
export KAMIWAZA_MLX_DFLASH_DEFAULT_MAX_TOKENS=2048
export KAMIWAZA_MLX_DFLASH_MAX_CONTEXT=-1
export KAMIWAZA_MLX_DFLASH_VERIFY_MODE=auto
export KAMIWAZA_MLX_DFLASH_VERIFY_QMM=true
export KAMIWAZA_MLX_DFLASH_STREAM_SYNC_EVERY=0

Notes:

• DFlash is only enabled when --dflash-draft-model is non-empty, and that forces a text-only mlx-lm target load even for Qwen3.5 conversions that retain a vision_config.
• The Qwen3.5-27B drafter is trained for target Qwen/Qwen3.5-27B; MLX quantized conversions such as mlx-community/Qwen3.5-27B-5bit and mlx-community/Qwen3.5-27B-6bit are structurally compatible targets to try, but acceptance and quality need measurement per quant.
• The z-lab/Qwen3.5-27B-DFlash draft config uses five full_attention layers. The dflash-mlx runtime has draft sink/window machinery for other draft shapes, but those knobs do not change this Qwen3.5 speculative model's draft attention.
• Server KV and prefix caches are disabled while DFlash is enabled because DFlash allocates its own per-request target/draft prompt caches and mutates target model hooks during generation.
• --dflash-backend auto picks dflash-mlx when the standalone dflash_mlx package is installed (see the tested git pin above); otherwise it falls back to the ZLab backend. The inline dflash-mlx adapter runs without that package's own prefix snapshot cache, so it is meant for local kernel/runtime experiments, not as a replacement for that package's full OpenAI-compatible server. It also installs a Qwen target-op compatibility patch that skips the full-vocabulary lm-head projection for large prompt-prefill chunks whose logits are discarded by the DFlash loop, and disables unused prefix-snapshot work because the inline adapter does not provide a dflash-mlx prefix cache.
• For eligible 4-bit or 8-bit MLX target linears, the dflash-mlx adapter also installs that package's verifier-linear wrappers. Use --dflash-verify-mode off to disable the swap, or --no-dflash-verify-qmm to keep the wrappers while disabling the custom qmm kernels.
• --dflash-max-context is a degradation guard: prompts at or above that token count bypass DFlash and use the normal MLX generation path. Omit it, or set it to -1, to use the conservative auto cap of 4000 prompt tokens. Set it to 0 only when you intentionally want to route every prompt through DFlash. Because DFlash mode disables the server-level shared KV/prefix caches, bypassed requests do not use shared prefix-cache optimizations, but they still allocate the normal bounded per-request generation cache.
• DFlash generation is serialized with an internal lock. That protects the target model hidden-state hooks and Qwen3.5 gated-delta rollback patch.
• Extra mx.synchronize() calls in the DFlash streaming loop are disabled by default. Set --dflash-stream-sync-every N only when diagnosing stream timing or device scheduling.

Note: Not specific to Kamiwaza (that is, you can use on any Mac, Kamiwaza not required)

pip install kamiwaza-mlx

# start the server
a) python -m kamiwaza_mlx.server -m ./path/to/model --port 18000
# or, if you enabled the optional entry-points during install
b) kamiwaza-mlx-server -m ./path/to/model --port 18000

# chat from another terminal (note: specify --host to match server port)
python -m kamiwaza_mlx.infer --host localhost:18000 -p "Say hello"

The remainder of this README documents the original features in more detail.

MLX-LM 🦙 — Drop-in OpenAI-style API for any local MLX model

A FastAPI micro-server (server.py) that speaks the OpenAI /v1/chat/completions dialect, plus a tiny CLI client (infer.py) for quick experiments. Ideal for poking at huge models like Dracarys-72B on an M4-Max/Studio, hacking on prompts, or piping the output straight into other tools that already understand the OpenAI schema.

✨ Highlight reel

🚀 Running the server

# minimal
python server.py -m /var/tmp/models/mlx-community/Dracarys2-72B-Instruct-4bit

# custom port / host
python server.py -m ./Qwen2.5-VL-72B-Instruct-6bit --host 0.0.0.0 --port 12345

Default host/port: 0.0.0.0:18000

Most useful flags:

KV cache flags (all KV-related CLI knobs)

System-prefix cache (system-only)

Conversation cache (simple global prefix-match)

Simple mode uses a single global prefix-match KV cache. If the incoming prompt shares the previous prompt as a prefix, we skip prefill for the cached portion; otherwise the cache is reset. Conversation IDs are used for logging/metadata only (they do not create separate caches).

Experimental multi-node via mlx.distributed

This section documents the direct server.py distributed bootstrap path.

It is distinct from the current Kamiwaza-managed two-node serving flow, which uses kamiwaza-mlx-distributed plus upstream mlx_lm.server and is documented in MLX_TWO_NODE_README.md.

The server can bootstrap a two-node mesh using mlx.distributed. Set a rendezvous host via PAIRED_HOST (optionally in a .env file) and launch each node with matching ranks/world-size. The helper will automatically read .env files passed via --distributed-env-file or located beside the server script.

# shared settings (either export or place in .env)
PAIRED_HOST=10.0.0.2
PAIRED_PORT=17863
WORLD_SIZE=2

# leader node (rank 0 hosts FastAPI)
RANK=0 python -m kamiwaza_mlx.server --distributed-env-file .env -m ./model

# worker node (rank 1 participates in mlx.distributed but does not bind HTTP)
RANK=1 python -m kamiwaza_mlx.server --distributed-env-file .env -m ./model

Useful knobs:

• --distributed – force-enable/disable distributed mode (auto when PAIRED_HOST or WORLD_SIZE>1).
• --distributed-rank / --distributed-world-size – override RANK/WORLD_SIZE env vars.
• --distributed-host / --distributed-port – override PAIRED_HOST / PAIRED_PORT.
• --distributed-server-rank – choose which rank should host the HTTP server (defaults to 0).

In this direct path, non-leader ranks simply keep the MLX runtime alive for collective ops once the model weights are synchronized. Treat it as a bootstrap/experimentation path, not as the primary Kamiwaza-managed TP=2 serving mode.

💬 Talking to it with the CLI

python kamiwaza_mlx/infer.py --host localhost:18000 --max_new_tokens 2048

Interactive keys

• Ctrl-N: reset conversation
• Ctrl-C: quit

🌐 HTTP API

GET /v1/models

Returns a list with the currently loaded model:

{
  "object": "list",
  "data": [
    {
      "id": "Dracarys2-72B-Instruct-4bit",
      "object": "model",
      "created": 1727389042,
      "owned_by": "kamiwaza"
    }
  ]
}

The created field is set when the server starts and mirrors the OpenAI API's timestamp.

POST /v1/chat/completions

{
  "model": "Dracarys2-72B-Instruct-4bit",
  "messages": [
    { "role": "user",
      "content": [
        { "type": "text", "text": "Describe this image." },
        { "type": "image_url",
          "image_url": { "url": "data:image/jpeg;base64,..." } }
      ]
    }
  ],
  "max_tokens": 512,
  "stream": false
}

Response (truncated):

{
  "id": "chatcmpl-d4c5…",
  "object": "chat.completion",
  "created": 1715242800,
  "model": "Dracarys2-72B-Instruct-4bit",
  "choices": [
    {
      "index": 0,
      "message": { "role": "assistant", "content": "The image shows…" },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 143,
    "completion_tokens": 87,
    "total_tokens": 230,
    "tokens_per_second": 32.1
  }
}

Add "stream": true and you'll get Server-Sent Events chunks followed by data: [DONE].

System Prefix Caching (Text-Only Models):

• Purpose: Dramatically speed up repeated queries that share the same system context (e.g., large document in role: system). The server caches only the system message(s), not the whole prompt, so subsequent turns process only new user tokens.
• Flags:
  • --enable-prefix-caching (default True)
  • --prompt-cache-dir (default ./.cache/mlx_prompt_caches/)
  • --system-cache-max-tokens (default 2048, 0 disables the cap)
  • --prefix-cache-headroom (default 64)
• How it works (high‑level):
  1. On first request with a system message, the server builds a KV cache for just the system portion and saves three files under --prompt-cache-dir:
     • <model>.safetensors (KV), <model>.safetensors.len (token count), <model>.safetensors.hash (SHA256 over token IDs)
  2. On subsequent requests with the same system text (hash matches), the server deep‑copies the cached KV and processes only new user/assistant tokens.
  3. If the system message changes, the old cache is discarded and replaced automatically.
  4. If the system prompt exceeds --system-cache-max-tokens, system caching is skipped and the full prompt is prefetched normally.
• Example: A 10,000‑token system document is processed once; later questions only process the user tokens.
• Notes: text‑only models; fully transparent to clients (no special fields needed).

Conversation KV Caching (Long chats, fast follow‑ups):

• Rationale: Reuse KV across turns so only the tail of the prompt is prefetched.
• Behavior:
  • Provide conversation or conversation_id (or X-Conversation-Id) if you want IDs reflected in logs/metadata. If omitted, the server uses default.
  • The server returns headers for every request (JSON & SSE):
    • X-Conv-Id (resolved ID), X-Conv-KV (fresh|hit|reset|none|busy|disabled), X-Conv-Cached-Tokens, X-Conv-Processing-Tokens.
  • Non‑stream JSON also includes usage.input_tokens_details.cached_tokens and metadata.conversation_id.
  • The global cache is capped at min(model context, 128k) unless overridden by --kv-cache-max-tokens.
  • Concurrency: only one request at a time uses KV caches. When the cache is in use, other concurrent requests run with caching disabled (X-Conv-KV: busy).
• Breaking change: the legacy /v1/conv_kv/* endpoints were removed in this branch.

🛠️ Internals (two-sentence tour)

• server.py – loads the model with mlx-vlm, converts incoming OpenAI vision messages to the model's chat-template, handles images / video frames, and streams tokens back. For text-only models, if enabled via server flags, it automatically manages a system message cache to speed up processing when multiple queries reference the same system context.
• infer.py – lightweight REPL that keeps conversation context and shows latency / TPS stats.

That's it – drop it in front of any MLX model and start chatting!