wasmtime "unknown import" / import not found at instantiation in CI

A wasm module lists the imports it needs (functions, memory, globals). At instantiation the host must supply every one. wasmtime fails with "unknown import" when the module asks for something the embedder did not define.

What this error means

Instantiation fails with "unknown import: env::log has not been defined" or "import ... not found", naming a function the host did not provide.

error: failed to instantiate "app.wasm"

Caused by:
    unknown import: `env::log` has not been defined

Common causes

The host did not provide a declared import

The module imports a function from a namespace (often env) that the embedding code or CLI never defines, so linking the imports fails.

A name or module mismatch in the import

The host defines an import under a different module or field name than the module expects, so the lookup misses.

How to fix it

Define every import the module declares

1. List the module imports to see exactly what it needs.
2. Provide each one in the host with the exact module and field name.
3. Re-instantiate.

wasmtime explore app.wasm   # or: wasm-objdump -j Import -x app.wasm

Match the import namespace and name

Ensure the host links the function under the same module/field the wasm declares, since env::log and host::log are different imports.

How to prevent it

• Inspect a module's imports and provide each before instantiation.
• Keep host-provided import names identical to what the module declares.
• Validate instantiation in CI so missing imports fail before deploy.

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