# SeaShell vs Aider: terminal AI coding tools compared (2026)

> SeaShell and Aider are both terminal AI coding tools you run on your own keys; SeaShell adds a full TUI, permission-gated tools, plugins, and Model Context Protocol support.

SeaShell and Aider are both terminal-based AI coding tools you run with your own model keys. In 2026 the difference is depth of interface and extensibility: SeaShell is a full TUI with permission-gated tools, a plan agent, plugins, and Model Context Protocol support, while Aider is a lean, git-centric command-line tool. Aider is open source; SeaShell is proprietary with a free core.

## Key takeaways

- Both are terminal-based and bring-your-own-keys; Aider is open source, SeaShell is proprietary with a free core.
- Aider is lean and git-centric; SeaShell is a full keyboard-first TUI.
- SeaShell adds a plan agent, permission-gated tools, plugins, and MCP.
- SeaShell indexes code with hybrid semantic + keyword search and can embed locally.

## Comparison

| Capability | SeaShell | Aider |
| --- | --- | --- |
| Interface | Full SolidJS TUI | Lean CLI |
| Planning | Read-only plan agent | Direct git-commit loop |
| Tool safety | Permission-gated (allow/ask/deny) | Git-centric |
| Extensibility | Plugins + Model Context Protocol | Focused core |
| Code search | Hybrid semantic + keyword (RRF) | Repo map |
| Source | Proprietary, free core | Open source |

## Pick SeaShell if

- You want a full TUI with a plan agent and permission-gated tools
- You want plugins and Model Context Protocol support
- You want hybrid semantic code search with optional local embeddings

## Pick the other tool if

- You want the smallest possible git-centric CLI
- You prefer a commit-as-you-go loop over a separate plan step
- You do not need a plugin system

## Interface and interaction

Aider is a minimal command-line tool driven by git, which keeps it fast and scriptable. SeaShell is a full terminal UI rendered with SolidJS, with a command palette, themes, and interactive review built in.

If you want the smallest possible surface, Aider's lean CLI is appealing. SeaShell invests in the TUI: a charcoal-and-blue theme system, model and provider switching from a picker, and an interactive diff-and-approve loop. Both stay in the terminal, but SeaShell offers a richer, more discoverable interface.

## Review model and safety

SeaShell gates every tool call against allow, ask, and deny rules and drafts a plan in a read-only plan agent before implementing. Aider centers a tight git-commit loop where changes are committed as you go.

SeaShell computes a unified diff for each edit and can roll back via git-patch snapshots, giving explicit approval points. Aider's git-first model is simple and effective for many workflows. Teams that want permission-gated tools and a separate planning step will prefer SeaShell; developers who want a minimal commit loop may prefer Aider.

## Extensibility

SeaShell is extensible through plugins and Model Context Protocol servers and can index code with local Ollama embeddings. Aider focuses on a focused core without a plugin system.

SeaShell's plugin system contributes tools and hooks into agent lifecycle events, and MCP support lets you bring your own tools and surfaces. Its codebase index uses hybrid semantic and keyword retrieval fused by reciprocal rank fusion. Aider keeps a smaller, sharper scope, which some developers prefer for simplicity.

## FAQ

### Are SeaShell and Aider free to run?

Aider is open source and free. The SeaShell core is free to run with your own model keys, with paid Pro and Company tiers on top.

### What does SeaShell add over Aider?

A full TUI, a read-only plan agent, permission-gated tools, plugins, Model Context Protocol support, and hybrid semantic code search.

### Is Aider simpler than SeaShell?

Aider has a leaner, git-centric command-line surface; SeaShell offers a richer interactive TUI with more built-in capabilities.

### Can SeaShell keep my code local?

Yes. SeaShell can build its code index with local Ollama embeddings, keeping code off third-party servers.

### Do both work with any model?

Both are bring-your-own-keys; SeaShell adds an in-TUI picker to switch active model and provider.

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Canonical HTML: https://seashell.sh/resources/compare/seashell-vs-aider
Source of truth: aeo_pages row `/resources/compare/seashell-vs-aider` (segment: Compare) (this file is generated from it, never hand-edited).
Licence: SeaShell is proprietary with a free core. It is not open source and there is no public source repository.