Fix validate_tool hang: pass stdin=DEVNULL to the validation subprocess#218
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lilly-luo merged 3 commits intoJul 17, 2026
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`validate_tool` runs each tool's smoke test (e.g. `pi --print "say hi in 5 words or less"`) via `subprocess.run(..., timeout=60)` without setting `stdin`, so the child inherits ucode's own stdin. In print/headless mode some agent CLIs (pi among them) still open stdin and block waiting for input/EOF. When ucode is launched from a non-interactive parent whose stdin is an open pipe with no EOF — e.g. an agent harness spawning `ucode <tool>` as a subprocess — the validation command never sees EOF, blocks for the full 60s, and `validate_tool` returns `(False, "timed out")`. The caller (`_auto_configure_tool` / configure) then reverts the config and aborts with "<tool> validation failed — config reverted", even though the tool is correctly configured and the gateway is reachable. The validation smoke test is one-shot and never needs interactive input, so pass `stdin=subprocess.DEVNULL`. This is benign for every tool (an interactive prompt in a validation run would itself be a bug) and makes validation robust regardless of how ucode was launched. Verified on a managed sandbox: `pi --print "say hi"` returns instantly with `stdin=DEVNULL` but hangs to the timeout when it inherits an open stdin pipe. Signed-off-by: Edwin He <edwin.he@databricks.com>
Edwinhe03
marked this pull request as draft
July 16, 2026 19:32
Edwinhe03
marked this pull request as ready for review
July 16, 2026 21:17
Edwinhe03
marked this pull request as draft
July 16, 2026 21:30
lilly-luo
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Jul 17, 2026
lilly-luo
previously approved these changes
Jul 17, 2026
Per review: the kwarg is self-explanatory; drop the comment block.
Edwinhe03
marked this pull request as ready for review
July 17, 2026 18:38
lilly-luo
approved these changes
Jul 17, 2026
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What
validate_toolruns each tool's smoke test (pi --print …,codex exec …) viasubprocess.run(..., timeout=60)without settingstdin, so the child inherits ucode's stdin. pi and codex open stdin in print/exec mode and block on it. When ucode is launched from a non-interactive parent whose stdin is an open pipe with no EOF (e.g. an agent harness spawningucode <tool>), validation hangs the full 60s and returns a spurioustimed out→<tool> validation failed — config reverted, even though the tool is configured correctly.Fix
Pass
stdin=subprocess.DEVNULL— the smoke test is one-shot and never needs input. Benign for every tool.Verified
Open-stdin-pipe condition, before (
main) vs after:validate_tool)timed out, 60svalidate_tool)timed out, 60spi --printon sandboxcodex execon sandboxAdded
TestValidateTool(assertsstdin=DEVNULL;TimeoutExpired→timed out). Full suite: 875 passed, ruff clean.