# Context Strategies

apfel manages the 4096-token context window automatically so chat sessions and long prompts do not crash. Choose a strategy with `--context-strategy` based on what you want apfel to keep when history approaches the limit.

```bash
apfel --chat --context-strategy newest-first     # default: keep recent turns
apfel --chat --context-strategy oldest-first     # keep earliest turns
apfel --chat --context-strategy sliding-window --context-max-turns 6
apfel --chat --context-strategy summarize        # compress old turns via on-device model
apfel --chat --context-strategy strict           # error on overflow, no trimming
apfel --chat --context-output-reserve 256        # custom output token reserve
```

## Strategies

| Strategy | What it keeps | When to use |
|---|---|---|
| `newest-first` (default) | Most recent turns. Old turns are dropped when the window fills. | Normal chat. You want the model to remember what you just said. |
| `oldest-first` | Earliest turns. New turns are dropped when the window fills. | Instructions or context at the start of a session that must never fall out. |
| `sliding-window` | A rolling window of the last N turns (`--context-max-turns N`). | Predictable memory usage, simple last-N-turns semantics. |
| `summarize` | Old turns compressed into a short summary by the on-device model, then appended as context. | Long sessions where you want continuity without losing old content entirely. Costs one extra on-device inference per rotation. |
| `strict` | Everything. Errors with `contextOverflow` when the window fills. | CI, scripts, batch pipelines - fail loud instead of silently dropping content. |

## Output token reserve

`--context-output-reserve N` (default `512`) reserves `N` tokens of the window for the model's response. The remaining `4096 - N` tokens are available for input + history. Lower the reserve if your prompts are long and your answers are short, raise it if answers get cut off.

## Environment variables

All four settings have env var equivalents:

- `APFEL_CONTEXT_STRATEGY` - one of `newest-first`, `oldest-first`, `sliding-window`, `summarize`, `strict`
- `APFEL_CONTEXT_MAX_TURNS` - positive integer for sliding-window
- `APFEL_CONTEXT_OUTPUT_RESERVE` - positive integer, tokens reserved for output

CLI flags always override env vars.