fix(runtime): don't truncate the SSE stream on tool results >64 KiB - #3883
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EronWright wants to merge 1 commit into
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fix(runtime): don't truncate the SSE stream on tool results >64 KiB#3883EronWright wants to merge 1 commit into
EronWright wants to merge 1 commit into
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The client SSE reader used bufio.Scanner with the default 64KiB token cap
(bufio.MaxScanTokenSize). Each agent event is delivered as one `data: {json}`
line, and a large tool result (e.g. a big tool_call_response) exceeds that,
so scanner.Scan() trips bufio.ErrTooLong, the loop ends, and the run appears
to stop silently after the preceding event. The scanner error was also
swallowed, leaving no trace.
Raise the reader's buffer ceiling and surface any read error as an Error
event instead of closing the stream without a word.
aheritier
added
area/runtime
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fix(runtime): don't truncate the SSE stream on tool results >64 KiB
Problem
The remote-runtime SSE reader (
pkg/runtime/client.go) usesbufio.NewScannerwith the default 64 KiB token cap (
bufio.MaxScanTokenSize). Each server event isdelivered as one
data: {json}line, so a large tool result — e.g. a bigtool_call_response— overflows it:scanner.Scan()tripsbufio.ErrTooLong, theloop ends, and the run appears to stop silently right after the last event that
fit. The scanner error was discarded, leaving no trace.
Fix
In both SSE readers: raise the buffer ceiling (
maxSSELineBytes, added topkg/runtime/defaults.go) and emit anErrorevent onscanner.Err()instead ofclosing the channel without a word.
Impact
Any agent that returns a tool response larger than 64 KiB over a remote runtime —
today that run vanishes with no error.
Test
go build ./pkg/runtime/ && go test ./pkg/runtime/. Reproduced with a ~78 KBtool_call_responsethat previously cut the stream mid-run; it now streams tocompletion.