feat(setup): warm the uv runtime before first server launch - #136
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yjouini
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August 27, 2026 12:19
The host gives up on an MCP server that is still downloading dependencies on its first launch, which is the most common cause of a plugin that never becomes available after install. Warm the runtime during setup instead. Measured on a throwaway UV_CACHE_DIR, time to answer MCP initialize: no warm-up 6.36s after `uv sync --locked --script` 2.80s after one run with stdin closed 0.65s `uv sync --script` caches the downloads but leaves the environment to be created on first launch, so the skill uses a single run-and-exit instead and says explicitly not to substitute sync. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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looks good! i made a slight change to the wording of the run_mcp relative path....codex complained about the previous wording. totally fine if you don't like the new wording. approved either way.
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Summary
Adds a runtime warm-up step to the
dataiku-headless-setupskill added in #129. The host gives up on an MCP server that is still downloading dependencies on its first launch, which is the most common cause of a plugin that appears installed but never becomes available — the "restart Codex / still initializing" reports in #ask-dataiku-headless.The new step 5 runs the server once with stdin closed so it exits immediately, populating the uv cache and the script environment before the host ever launches it. Subsequent steps are renumbered; the frontmatter description now mentions the warm-up.
Why run-and-exit rather than
uv syncuv sync --locked --scriptlooks like the natural fit but only gets partway. Measured on this branch with a throwawayUV_CACHE_DIR(so the real cache was untouched), timing a full MCPinitializeround-trip againstbin/run_mcp.py:uv sync --scriptcaches the downloads but leaves the environment to be created on first launch, so the host still sees a slow first start. The skill therefore uses the run-and-exit form and says explicitly not to substitute sync. A cold cache for this script is ~148 MB, so on a slow or proxied network the 6.36s figure is a floor, not a typical case.