hakmem/docs/analysis/SAFE_TO_DELETE_ENV_VARS.md

# ENV Variables Safe to Delete (Docs-Only, Already Off the Code Path)

## Summary

- **21 ENV variables** live only in documentation; **0 getenv() hits** across `core/`, `include/`, `src/`, and `tools/`.
- These toggles were proposal placeholders; none of them ever crossed the runtime boundary.
- Status: treated as **removed from the supported surface**; only lingering mentions remain in docs archives and can be dropped when touched.

## Docs-Only Variables (21)

- HAKMEM_ALLOC_LEARN
- HAKMEM_ALLOC_LEARN_RATE
- HAKMEM_ALLOC_LEARN_WINDOW
- HAKMEM_BUILD_3LAYER
- HAKMEM_BUILD_ROUTE
- HAKMEM_DEBUG
- HAKMEM_DEBUG_LEVEL
- HAKMEM_DEBUG_TINY
- HAKMEM_EXPERIMENTAL_ADAPTIVE_DRAIN
- HAKMEM_EXPERIMENTAL_CACHE_TUNING
- HAKMEM_FORCE_LIBC
- HAKMEM_INTEGRITY_CHECKS
- HAKMEM_LEARN_ADVANCED
- HAKMEM_LEARN_DECAY
- HAKMEM_MEM_LEARN
- HAKMEM_MEM_LEARN_THRESHOLD
- HAKMEM_MEM_LEARN_WINDOW
- HAKMEM_PROFILE_SYSCALLS
- HAKMEM_STATS_ENABLE      (docs/archive のみ・現行コードでは未使用、備考コメントに変更済み)
- HAKMEM_STATS_INTERVAL_SEC (同上)
- HAKMEM_STATS_VERBOSE

## How We Verified

1) `rg 'getenv\\(\"HAKMEM_' core include src tools -n --sort path` → **0 matches** for all 21 names.  
2) `comm -23 docs_env code_env` diff to isolate documentation-only names.  
3) Spot-checked `docs/specs/ENV_VARS*.md` and related papers to ensure these are proposal artifacts, not active flags.

## Recommended Cleanup

- Remove these names from `docs/specs/ENV_VARS.md`, `docs/specs/ENV_VARS_COMPLETE.md`, and any status reports when you next touch them (no code changes needed).
- Keep a single sentence in change logs noting that these toggles never existed in runtime code (A/B rollback not needed).

## Notes

- These were planning placeholders (adaptive tuning knobs, generic debug toggles, and early build-time experiments) that never materialized.
- Keeping them in docs increases cognitive load; deleting them is a zero-risk, reversible documentation-only change.