fix: preserve ToolPart structure during pruning to prevent malformed request errors#23
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tuanhung303 merged 1 commit intomasterfrom Feb 13, 2026
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…request errors ACP was replacing pruned ToolParts with TextParts, breaking the tool-call/tool-result pairing that Anthropic's API requires. This caused 'Improperly formed request' errors at high context usage. Now prune only replaces state.output while keeping the ToolPart intact. Also adds empty-parts guard in filterStepMarkers and uses provider-reported token counts for accurate context pressure measurement.
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Summary
ToolParts withTextParts, breaking the tool-call/tool-result pairing that Anthropic's API requires. At high context usage this causedImproperly formed request. (reason: None)errors that locked the session.state.outputon the ToolPart instead of swapping the entire part type. Also adds an empty-parts safety guard infilterStepMarkers.msg.info.tokens) instead of heuristic estimates, closing the ~30-40% undercount gap.Changes
lib/messages/prune.tsstate.output; empty-parts guard infilterStepMarkerslib/strategies/utils.tsgetRealTokenCount()reading real tokens from last assistant messagelib/hooks.tscomputeContextPressurewith heuristic fallbacktests/messages/prune.test.tsfilterStepMarkersteststests/strategies/utils.test.tsgetRealTokenCount()Testing
tscno errors)