# Implementation: fix-context-sizing

Implements SPEC.md R1–R6. Files touched:

- `scripts/vram_detect.py` — R1 (double headroom), R2 (fake clamps), R3 (--loop-mode refuse), R4 (JSON fields)
- `config.md` — R5 (`## Loop Role Models` section)
- `prompts/decompose.md` — R6 (4k tier + 16k floor)
- `tests/test_context_sizing.py` — new tests

## Approach

`recommend_context` rewritten so headroom is applied exactly once. `main()` reports honest numbers (no `else 8`/`else 6` fallbacks). New `--loop-mode` CLI flag refuses zero-context-unknown and sub-16k available budget; non-loop callers keep prior behavior. JSON output exposes `available_context_kb` and `loop_mode_eligible`.

`config.md` gets a `## Loop Role Models` section. `decompose.md`'s context-budget table grows a 4k row and an explicit `≤ 16k: refuse` floor statement.