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Add configuration for buffer sizes in WASI - #15095
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This commit adds a configuration knob on `WasiCtxBuilder` to control the default and maximum sizes of buffers used throughout wasmtime-wasi where necessary. These sizes have historically been limited in the past to ensure that guest memory usage is capped but this can cause real-world programs to break such as in WebAssembly/wasi-libc#894 where Python expects a `write` with a large size to succeed all in one go and doesn't internally have a retry loop for remaining bytes. The default value of 64KiB is not changed in this commit, but the `wasmtime` CLI now has a default buffer size of 2MiB to work with more programs by default.
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October 30, 2026 19:50
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Nov 3, 2026
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This commit adds a configuration knob on
WasiCtxBuilderto control the default and maximum sizes of buffers used throughout wasmtime-wasi where necessary. These sizes have historically been limited in the past to ensure that guest memory usage is capped but this can cause real-world programs to break such as in WebAssembly/wasi-libc#894 where Python expects awritewith a large size to succeed all in one go and doesn't internally have a retry loop for remaining bytes.The default value of 64KiB is not changed in this commit, but the
wasmtimeCLI now has a default buffer size of 2MiB to work with more programs by default.