fix(compact): bound truncated tool result within byte budget#39
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truncateMiddle preserved maxBytes of original content and then added the truncation marker on top, so the returned string exceeded the documented compactToolResultMaxBytes cap. Reserve the marker's footprint inside the budget so head + marker + tail is always <= maxBytes; hard-cap when the budget is too small for the marker. Head/tail preservation is kept for normal budgets and history is still never mutated. Closes #31 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary
truncateMiddlepreservedmaxBytesof original content and appended the truncation marker on top, so the result exceeded the documentedcompactToolResultMaxBytescap by the marker's length.head + marker + tailis always<= maxBytes. When the budget is too small to fit a marker, the output is hard-capped tomaxBytesbytes.Test plan
go test ./internal/agent— 98 passedgo vet ./internal/agentcleanTestTruncateMiddle_NeverExceedsBudgetconfirmed to fail without the fix (maxBytes=1produced 62 bytes) and pass with itTestTruncateMiddle_PreservesHeadTailWithinBudgetlocks marker presence + head/tail preservationTestShrinkHistoryForCompact_TruncatesOversizedToolResultsto require<= maxBytes(was<= 1300for a 1000 budget)Closes #31
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