Add OpenCode skill waste detectors (closes #54)#160
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willwashburn merged 4 commits intomainfrom Apr 28, 2026
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Two new burn waste --patterns detectors gated to source === 'opencode':
- opencode-skill-recall: flags repeated skill({name}) calls whose content
is not deduplicated by the agent, reporting callCount, turn range, and cost.
- opencode-skill-pruning: tracks skill tool results that ride in the cache
indefinitely (prune-protected by OpenCode's compaction), reporting
ridingTurns, lastCachedTurnIndex, and cost.
Also populates ToolCall.skillName in the OpenCode reader so downstream
detectors can group skill invocations without re-parsing args.
![devin-ai-integration[bot]](https://avatars.githubusercontent.com/in/811515?s=60&v=4){kind=small}
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Estimates the fixed prefix tax (system prompt + skill catalog) on the first turn of an OpenCode session by subtracting the first user message size from cacheCreate. Reports estimatedSystemPromptTokens, ridingTurns, and total cost. Requires userTurnsBySession in DetectPatternsOptions. New pattern kind: opencode-system-prompt. Renders in burn waste --patterns and burn diagnose alongside the other detectors.
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- `burn diagnose` now passes `userTurnsBySession` into `detectPatterns`, so the OpenCode system-prompt-tax detector actually runs (the diagnose call was previously silently emitting `(none)` because the detector bails when user-turn data is absent). - Drop the dead `compactionTurnIndexes` set built but never used in `detectSkillPruningProtectionForSession`; skill tool results are prune-protected, so compaction boundaries don't bound riding-turn counts. The function no longer takes a `compactions` parameter.
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`detectSystemPromptTaxForSession` was iterating over every turn including the first when computing `ridingTurns`. The header comment says "subsequent" — and the sister `detectSkillPruningProtectionForSession` correctly skips its anchor turn. On a resumed OpenCode session the first turn can carry `cacheRead > 0`, which would otherwise inflate both the riding count and totalCost. Added a regression test for the resumed-session shape.
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Summary
burn waste --patternsdetectors gated tosource === 'opencode':opencode-skill-recall— flags repeatedskill({name})calls whose content is not deduplicated by OpenCode, reporting call count, turn range, and cost.opencode-skill-pruning— tracks skill tool results that ride in the cache indefinitely (prune-protected by OpenCode's compaction), reporting riding turns, last cached turn, and cost.ToolCall.skillNamepopulated by the OpenCode reader so downstream detectors can group skill invocations without re-parsing args.burn diagnoserenders the new pattern types;burn waste --patterns --jsonincludes them in output.SessionPatternSummarygainsskillRecallDupCountandskillPruningProtectionCount.Files changed
@relayburn/readerToolCall.skillNamefield; OpenCode reader extracts skill name from tool input@relayburn/analyzeSkillRecallDup+SkillPruningProtectioninterfaces + detectors;detectPatterns,PatternsResult,SessionPatternSummaryextended@relayburn/cliPATTERN_KINDSgainsopencode-skill-recallandopencode-skill-pruning; rendering tables;burn diagnoseupdatedTests
634 tests pass (8 new test cases for the skill detectors).