# Bug Report: fix-context-sizing

## Status: NO_BUGS_FOUND

## Method
Static re-read of `vram_detect.py` changes against the SPEC and against pre-existing behaviors. Focused on:
1. **Backward compatibility**: non-loop callers must keep prior behavior.
2. **Override authority**: `_parse_config_model`'s override flow must still be authoritative in loop mode.
3. **Negative-budget propagation**: `max_peak_kb` can now be negative when overhead exceeds budget — does any consumer read it without wrapping in `max(0, ...)`?
4. **Exit codes**: `--loop-mode` refuse paths must exit `2`, not `0`.

## Findings

### F1. Non-loop behavior preserved — CONFIRMED SAFE
Pre-existing CLI callers (`vram_detect.py` without `--loop-mode`) and dashboard invocations are unaffected. Warning lines are emitted on degraded conditions but exit code stays `0`. Verified by `test_non_loop_mode_does_not_refuse_unknown_model`.

### F2. Override authority — CONFIRMED SAFE
In `detect_model_context`, the `if override_context and override_context != "auto"` branch (line 343-345) returns the override *before* reaching the fallback-return-zero path. So when a user has set `Override context window` in `config.md`, `detect_model_context` returns a positive value and the `--loop-mode` unknown-model refuse never fires. Matches D13 spec.

### F3. Negative `max_peak_kb` propagation — LOW RISK, OUT OF SCOPE
`recommend_context` now returns a negative `max_peak_kb` when `overhead_tokens > recommended_kb`. No current consumer reads it without arithmetic. The dashboard (`automaton/dashboard/__main__.py`) computes its own derived numbers and does not display this value directly. The loop runner (task `add-loop-runner`) must `max(0, available_context_kb)` before scheduling; that's the runner's obligation, not this task's. Acceptable.

### F4. Exit code correctness — CONFIRMED
`--loop-mode` refuse paths call `return 2`. Verified directly: `python3 vram_detect.py --model zzz --loop-mode; echo $?` returns `2`. Support: `test_loop_mode_refuses_unknown_model` writes a regression guard.

## Bugs Found
None.

## Out of Scope (for downstream tasks)
- Loop runner's `max(0, available_context_kb)` wrap (task 3 `add-loop-runner`)
- Dashboard showing the new `loop_mode_eligible` field (v1.1 dashboard panel)
- Tier 2 cleanup: `last-read-sha` drift detection, etc.