fix(agent): bound compaction summary and mechanically fold on failure#4138
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A manual /compact (or auto-compaction) could show "compacting…" then hang forever: the call passed context.Background() with no deadline and summarize ranged over the provider channel without watching ctx, so a stalled stream pinned the placeholder with no card and no error. Fast failures already surfaced; an unbounded wait did not. Bound each summary call to 90s, select on ctx.Done so a stalled stream unblocks, retry one transient failure, and — when the summarizer is genuinely unreachable — fold mechanically (the region is already archived) to a deterministic marker so /compact always frees context instead of aborting on a still-full window. Verbatim user turns stay untouched and the fold/keep algorithm is unchanged, so cache behavior matches a normal compaction.
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Problem
A user reported that
/compactshowed "compacting conversation…" and then nothing — no card, no error, indefinitely.Root cause (traced through the code): after the
CompactionStartedevent, every fast failure already surfaces (compact failed: …for archive/stream/empty-output errors). The one gap was an unbounded wait:ctrl.Compact(context.Background(), …)— no deadline anywhere down the chain.summarizedidfor chunk := range ch, which only unblocks when the provider closes the channel — it never watchedctx.So a stalled summarizer stream (open but never delivering/closing — a hung connection, or a reasoning model streaming thinking with no final text) pinned the "compacting…" placeholder forever: no
CompactionDone, no error, no resolution.Fix
All in
internal/agent/compact.go; the fold/keep algorithm is unchanged.summaryTimeout).selectonctx.Done()in the stream loop, so a stalled stream unblocks even if the provider never closes the channel./compactthen always frees context instead of aborting on a still-full window (and auto-compaction can't loop on one). Verbatim user turns are untouched.Cache safety
The fold/keep logic is unchanged; the fallback produces a digest with the same structure as a normal compaction (head + kept-verbatim + digest + tail), just with deterministic content. No new prompt-history cache hazard beyond what compaction already does.
Tests
TestCompactFallsBackToMechanicalFoldWhenSummaryFails— summarizer errors → session still compacts,CompactionDonecarries a mechanical-fold summary.TestSummarizeRespectsContextCancel— a stalled (never-closing) stream returns on cancellation rather than hanging.internal/agentsuite green.Deferred
Live progress streaming ("thinking…" during a slow summary) touches the CLI + desktop renderers and is a separate change; the 90s bound + always-resolving fallback already removes the "infinite nothing" symptom.