Ollama / Ollama

Ollama CUDA Backend Crash on RTX 50-Series (Blackwell) with Q4_K_M Models

Fix Ollama ggml_cuda_cpy crash on RTX 50-series Blackwell GPUs Includes evidence for Ollama troubleshooting demand.

Source-backed Last updated May 12, 2026 1 source Needs local verification

Category: Ollama
Error signature: ggml_cuda_cpy: unsupported type combination (q4_K to q4_K)
Quick fix: Compare the failing environment with a known working setup, then change one configuration value at a time.
Updated: May 12, 2026
Verification status: Source-backed
Evidence: 1 public source URL

Before you change production

This page includes public source URLs in the imported troubleshooting record. Compare those references with your version and environment before applying changes.

Reproduce the smallest failing action and save non-secret logs before changing configuration.
Check versions for Ollama, related SDKs, package managers, CI runners, and hosting providers.
Change one setting or dependency at a time, then rerun the same failing command or request.
Avoid destructive commands, credential rotation, billing changes, or security relaxations without a rollback plan.

What this error means

ggml_cuda_cpy: unsupported type combination (q4_K to q4_K) is a Ollama failure pattern reported for developers trying to fix ollama ggml_cuda_cpy crash on rtx 50-series blackwell gpus. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub issue (updated 2026-05-03). Loading any Q4_K_M GGUF model crashes on RTX 50-series (Blackwell, compute 12.0). ggml_cuda_cpy unsupported type combination. Runner exits with 500. Workaround: force Vulkan backend via OLLAMA_LLM_LIBRARY.

Common causes

Users with RTX 50-series (Blackwell, compute 12.0) GPUs cannot run any Q4_K_M GGUF models in Ollama. The CUDA backend fails immediately with 'unsupported type combination' error. Affects the latest GPU generation with no workaround except forcing Vulkan backend.
GitHub issue (updated 2026-05-03). Loading any Q4_K_M GGUF model crashes on RTX 50-series (Blackwell, compute 12.0). ggml_cuda_cpy unsupported type combination. Runner exits with 500. Workaround: force Vulkan backend via OLLAMA_LLM_LIBRARY.

Quick fixes

Confirm the exact error signature matches ggml_cuda_cpy: unsupported type combination (q4_K to q4_K).
Check the Ollama account, local tool state, and provider configuration involved in the failing workflow.
Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

Verify the command, editor, extension, or API client that produced the error.
Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

Capture the exact error message and the command, editor action, or request that triggered it.
Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
Review the source evidence below and compare it with your environment.
Apply one change at a time and rerun the smallest failing action.
Keep the working fix documented for the team or deployment environment.

How to prevent it

Keep provider/tool configuration documented.
Record non-secret diagnostics such as tool version, provider name, model name, and command path.
Add a lightweight check before CI or production workflows depend on the tool.

Diagnostic flow for this page

Match ggml_cuda_cpy: unsupported type combination (q4_K to q4_K) exactly before applying the quick fix.
Compare the failing environment with Ollama versions, account scope, provider settings, and deployment context.
Check the listed common causes in order, starting with the cause that best matches your logs.
Use the evidence status below to decide whether to confirm against public sources or official documentation.
Apply one reversible change, rerun the smallest failing action, and keep rollback notes.

FAQ

What does ggml_cuda_cpy: unsupported type combination (q4_K to q4_K) mean in Ollama?

ggml_cuda_cpy: unsupported type combination (q4_K to q4_K) indicates the workflow described by "Ollama CUDA Backend Crash on RTX 50-Series (Blackwell) with Q4_K_M Models" failed in a Ollama context. Start by confirming the exact signature and the component that emitted it.

What should I check first for ggml_cuda_cpy: unsupported type combination (q4_K to q4_K)?

Check whether this cause matches your environment: Users with RTX 50-series (Blackwell, compute 12.0) GPUs cannot run any Q4_K_M GGUF models in Ollama. The CUDA backend fails immediately with 'unsupported type combination' error. Affects the latest GPU generation with no workaround except forcing Vulkan backend.

Is the ggml_cuda_cpy: unsupported type combination (q4_K to q4_K) guidance source-backed?

The "Ollama CUDA Backend Crash on RTX 50-Series (Blackwell) with Q4_K_M Models" page is labeled source-backed. It has 1 public source URL from github.com, so use that evidence status when deciding how much additional verification you need.

When should I avoid the quick fix for ggml_cuda_cpy: unsupported type combination (q4_K to q4_K)?

For "Ollama CUDA Backend Crash on RTX 50-Series (Blackwell) with Q4_K_M Models", avoid applying "Compare the failing environment with a known working setup, then change one configuration value at a time." when the error text differs, the affected version or provider is different, or the change would touch credentials, billing, DNS, production deploy settings, or irreversible data.

What should I collect before debugging ggml_cuda_cpy: unsupported type combination (q4_K to q4_K)?

For "Ollama CUDA Backend Crash on RTX 50-Series (Blackwell) with Q4_K_M Models", collect the failing Ollama command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.