Proposal: Refactoring - Split large monolithic files into submodules

[krisclarkdev]

Hey! As the project has grown, a few of the core structural files have become quite large and difficult to navigate. I noticed that crates/tui/src/tui/app.rs is sitting at over 5,000 lines and crates/tui/src/compaction.rs is over 2,600 lines.

To help pay down some technical debt and make the codebase easier to approach for new contributors, I'd like to propose splitting these monoliths into smaller, isolated submodules (without changing any underlying logic or behavior).

Here is the structure I'd like to implement:

1. tui/app.rs -> tui/app/

• state.rs: Struct/enum definitions (App, SessionState, etc.)
• mutators.rs: State mutation functions / impl App.
• actions.rs: UI action enums and standalone helpers.
• mod.rs: Facade re-exporting the APIs so external callers don't break.

2. compaction.rs -> compaction/

• estimation.rs: Token estimation and budget logic.
• summary.rs: Summarization request execution.
• rules.rs: Heuristics (should_compact, limits).
• planning.rs: Compaction planning and pinning logic.
• extraction.rs / pruning.rs: Path extraction and truncation utilities.

I actually have this working locally on a branch right now and everything compiles cleanly with all tests passing.

Before I open a PR with a 7,000+ line diff, I wanted to check in to see if you'd be open to this structure? I don't want to create massive merge conflicts if you have active development going on in these files. If this looks good to you, I can open the PR whenever you are ready!

[Hmbown]

This is exactly the kind of structural cleanup we need — splitting app.rs (5000+ lines) and compaction.rs (2600+ lines) into focused submodules will make the codebase much more approachable for contributors.

The proposed structure looks solid:

• app/{state, mutators, actions, mod}.rs — clean separation of data, mutations, and UI actions
• compaction/{estimation, summary, rules, planning, extraction}.rs — each module has a single responsibility

Since you have this working locally with all tests passing, please open the PR whenever you're ready. We'll review and get it merged. The crate consolidation work in v0.8.48 (merging hooks → core, agent → config) is orthogonal and won't conflict.

A few review notes when you open:

• Make sure pub use re-exports in mod.rs cover everything external callers need — we don't want to break the public API
• If you moved any use statements or changed import paths, verify cargo check --workspace passes
• The diff will be large, so a summary comment in the PR describing what went where would help reviewers

Looking forward to it — this is high-value technical debt reduction.

[Hmbown]

Closing with a pointer — the monolith split is happening through the staged command-boundary refactor: EPIC #2870 / #2791, with aboimpinto's layered series (#2871 → #2878 → #2888) already landing. Thanks for the early call; follow along there.