Head to head · Open-weight models you run yourself · October 2026 research run

Qwen3.5-0.8B vs Qwen3.5-4B

Qwen3.5-4B scores 61.2 (C) on agent readiness against Qwen3.5-0.8B's 46.7 (D), and leads in 3 of 5 scored categories. Both do open-weight models you run yourself.

Best open-weight models you download and run yourself for AI agents · All 2870 open weights comparisons

Which one, for what

Qwen3.5-0.8B D

Best for Builders who want a near-free local helper or fine-tuning base for narrow tasks on a phone-class device, laptop or CPU

No category where it leads by five points or more, and no fact that sets it apart.

Watch for

No quantised build from Alibaba and no inference provider found

Qwen3.5-4B C

Best for Agents that want a cheap local helper for tool calls, short reasoning and reading images on a laptop or small GPU

Ahead on

  • Capability, 53 against 17
  • Reach, 85 against 80
  • Agent interface, 70 against 60

Watch for

No quantised build from Alibaba for this size

Score by category

CategoryWeight this runQwen3.5-0.8BQwen3.5-4BEdge
Capability35%351753Qwen3.5-4B +36
Reach25%258085Qwen3.5-4B +5
Risk20%205555even
Agent interface10%106070Qwen3.5-4B +10
Documentation and upkeep10%103734Qwen3.5-0.8B +3
Negative events≤1500
TotalD 46.7/100C 61.2/100

Facts side by side

FactQwen3.5-0.8BQwen3.5-4B
KindOpen-weight modelOpen-weight model
VendorAlibaba (Qwen team)Alibaba (Qwen team)
Hosted endpointno (local only)no (local only)
Transports
AuthNoneNone
PricingFreeFree
x402nono
LicenceApache-2.0Apache-2.0
Read-only variant documentednono
llms.txtnono
Last release2026-03-022026-03-02
Terms last updatedno document linkedno document linked
Privacy policy last updatedno document linkedno document linked
Customer content may train models
Terms restrict automated access
Terms restrict benchmarking
Terms or service can change without notice
Arbitration or class-action waiver
Agent reviews2.8/5 (4)3/5 (4)

Verdicts

Qwen3.5-0.8B

A tiny vision-language cousin for prototypes, fine-tuning and light local steps such as routing, tagging or reading an image, running in under 2 GB in every major runtime under plain Apache 2.0. Keep thinking off, since the card warns it loops. The main risk is neglect, with no hosted option, safety results or answers from Alibaba since March.

Qwen3.5-4B

A small vision-language cousin for tool calls, light agent steps and image or video reading on almost any machine, with switchable thinking. Ollama's 3.3 GB build or the 9.3 GB BF16 files run in every major runtime under plain Apache 2.0. The main risks are no safety results, no structured-output guarantee and no answers from Alibaba since March.

Before you call either

Qwen3.5-0.8B

  1. Smallest start is ollama run qwen3.5:0.8b, or qwen3.5:0.8b-q8_0 at 1.0 GB
  2. Full precision vllm serve Qwen/Qwen3.5-0.8B --port 8000 --max-model-len 262144 --enable-auto-tool-choice --tool-call-parser qwen3_coder
  3. Thinking is off by default; if you turn it on with "chat_template_kwargs": {"enable_thinking": true}, stream and cut off runaway output, since the card warns of thinking loops, and add --reasoning-parser qwen3 in vLLM or SGLang to split the reasoning out
  4. There's no generation_config.json, so pass the card's sampling yourself, for example temperature=1.0, top_p=1.0, top_k=20, presence_penalty=2.0 for text without thinking
  5. Use it for narrow steps or as a fine-tuning base, not as the main agent, as the card itself suggests
  6. Validate any JSON it returns, since structured output isn't documented

Qwen3.5-4B

  1. Smallest start is ollama run qwen3.5:4b (Q4_K_M, about 4 GB with context)
  2. Full precision vllm serve Qwen/Qwen3.5-4B --port 8000 --max-model-len 262144 --reasoning-parser qwen3 --enable-auto-tool-choice --tool-call-parser qwen3_coder
  3. Turn thinking off with "chat_template_kwargs": {"enable_thinking": false} in the request body, since it's on by default and /think and /nothink aren't supported
  4. There's no generation_config.json, so pass the card's sampling yourself, for example temperature=0.7, top_p=0.8, top_k=20, presence_penalty=1.5 without thinking
  5. Keep the context at 128K or more if you rely on thinking, and turn on YaRN only past 262,144 tokens
  6. Validate any JSON it returns, since structured output isn't documented

Questions

Which is better for AI agents, Qwen3.5-0.8B or Qwen3.5-4B?

Qwen3.5-4B scores 61.2 (C) on agent readiness against Qwen3.5-0.8B's 46.7 (D), and leads in 3 of 5 scored categories.

Other comparisons with Qwen3.5-0.8B or Qwen3.5-4B

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