[FEATURE] Context configuration

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I want to be able to customize the guidance and model used for compaction operations (and would prefer the option to do them myself programmatically via plugin) as they are not necessary with my tooling, hooks do not have the desired impact, and I am getting tired of manually compacting.

Proposed Solution

1. onRequestCompaction hook/plugin integration where I can choose to cancel/prevent compaction and stop generation, override the model/provider and/or guidance statement used during compaction, or return the result of a custom compaction solution.
2. compaction.model, compaction.guidance, compaction.targetLength, compaction.maxLength, compaction.truncationMethod (or equivalent) options to allow me to delegate the compaction to a specific model with custom instructions and requirements, a chosen heuristic for fallback.

Alternative Solutions

Manual compaction guidance, slow compaction, wasted context space.

Priority

High - Significant impact on productivity

Feature Category

CLI commands and flags

Use Case Example

Example scenario:

1. I am working with tooling that knows which files I changed and can produce heuristics to very quickly and easily provide higher quality context in a fraction of the time
2. Automatic compaction occurs
3. My plugin intercepts, provides the heuristic solution
4. Context smol, Claude happy
5. AGI achieved internally

Additional Context

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