fix(agent): prevent silent tool result loss during context compression#1993
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_align_boundary_backward only checked messages[idx-1] to decide if the compress-end boundary splits a tool_call/result group. When an assistant issues 3+ parallel tool calls, their results span multiple consecutive messages. If the boundary fell in the middle of that group, the parent assistant was summarized away and orphaned tool results were silently deleted by _sanitize_tool_pairs. Now walks backward through all consecutive tool results to find the parent assistant, then pulls the boundary before the entire group. 6 regression tests added in tests/test_compression_boundary.py. Co-authored-by: Gutslabs <Gutslabs@users.noreply.github.com>
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angelburgosrosado
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Apr 27, 2026
NousResearch#1993) _align_boundary_backward only checked messages[idx-1] to decide if the compress-end boundary splits a tool_call/result group. When an assistant issues 3+ parallel tool calls, their results span multiple consecutive messages. If the boundary fell in the middle of that group, the parent assistant was summarized away and orphaned tool results were silently deleted by _sanitize_tool_pairs. Now walks backward through all consecutive tool results to find the parent assistant, then pulls the boundary before the entire group. 6 regression tests added in tests/test_compression_boundary.py. Co-authored-by: Guts <Gutslabs@users.noreply.github.com>
02356abc
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May 14, 2026
NousResearch#1993) _align_boundary_backward only checked messages[idx-1] to decide if the compress-end boundary splits a tool_call/result group. When an assistant issues 3+ parallel tool calls, their results span multiple consecutive messages. If the boundary fell in the middle of that group, the parent assistant was summarized away and orphaned tool results were silently deleted by _sanitize_tool_pairs. Now walks backward through all consecutive tool results to find the parent assistant, then pulls the boundary before the entire group. 6 regression tests added in tests/test_compression_boundary.py. Co-authored-by: Guts <Gutslabs@users.noreply.github.com>
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May 16, 2026
NousResearch#1993) _align_boundary_backward only checked messages[idx-1] to decide if the compress-end boundary splits a tool_call/result group. When an assistant issues 3+ parallel tool calls, their results span multiple consecutive messages. If the boundary fell in the middle of that group, the parent assistant was summarized away and orphaned tool results were silently deleted by _sanitize_tool_pairs. Now walks backward through all consecutive tool results to find the parent assistant, then pulls the boundary before the entire group. 6 regression tests added in tests/test_compression_boundary.py. Co-authored-by: Guts <Gutslabs@users.noreply.github.com>
gweeteve
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Jun 2, 2026
NousResearch#1993) _align_boundary_backward only checked messages[idx-1] to decide if the compress-end boundary splits a tool_call/result group. When an assistant issues 3+ parallel tool calls, their results span multiple consecutive messages. If the boundary fell in the middle of that group, the parent assistant was summarized away and orphaned tool results were silently deleted by _sanitize_tool_pairs. Now walks backward through all consecutive tool results to find the parent assistant, then pulls the boundary before the entire group. 6 regression tests added in tests/test_compression_boundary.py. Co-authored-by: Guts <Gutslabs@users.noreply.github.com>
Egavasyug
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Jun 10, 2026
NousResearch#1993) _align_boundary_backward only checked messages[idx-1] to decide if the compress-end boundary splits a tool_call/result group. When an assistant issues 3+ parallel tool calls, their results span multiple consecutive messages. If the boundary fell in the middle of that group, the parent assistant was summarized away and orphaned tool results were silently deleted by _sanitize_tool_pairs. Now walks backward through all consecutive tool results to find the parent assistant, then pulls the boundary before the entire group. 6 regression tests added in tests/test_compression_boundary.py. Co-authored-by: Guts <Gutslabs@users.noreply.github.com>
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Summary
Salvage of #1976 by @Gutslabs — cherry-picked the core fix onto current main.
The bug:
_align_boundary_backwardonly checkedmessages[idx-1]to decide if the compress-end boundary splits a tool_call/result group. When an assistant issues 3+ parallel tool calls, their results span multiple consecutive messages. If the boundary fell in the middle of that group, the parent assistant was summarized away and orphaned tool results were silently deleted by_sanitize_tool_pairs. No error, no warning — data just vanished.The fix: Walk backward through all consecutive tool results to find the parent assistant, then pull the boundary before the entire group so it gets summarized together.
What changed vs the original PR:
api_keyconstructor addition andprint→loggercleanup from fix(agent): prevent silent tool result loss during context compression #1976 were already independently merged to main, so only the core boundary fix and tests were needed.Test Plan
6 regression tests in
tests/test_compression_boundary.py:compress()with 7 parallel tool calls — verifies no orphans and no stub resultsAll 72 compression-related tests pass.