Define RuntimeTool trait for code-execution backends (Python, Node, dotnet, go, rustc)

[aboimpinto]

Parent: #1802 — Pluggable Tool Registry

Sub-issue 3 of the Pluggable Tool Registry tracking issue.

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Goal

Define a RuntimeTool trait that makes code-execution backends (Python, Node.js, dotnet, go, rustc) pluggable through a shared interface compatible with the ToolSpec trait and the ExternalTool abstraction (PR #1821).

Today code_execution hardcodes Python, js_execution hardcodes Node. Adding dotnet (already implemented as DotNet ExternalTool in PR #1821) requires touching the tool catalog, the dispatcher, and the execution path.

After RuntimeTool:

• Each runtime implements one trait.
• The catalog auto-discovers available runtimes.
• Adding go or rustc is ~15 lines of impl RuntimeTool.
• The model sees code_execution with a runtime parameter (or separate tool names per runtime — TBD).

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Design sketch

/// A code-execution backend discoverable via ExternalTool + ToolSpec.
#[async_trait]
pub trait RuntimeTool: ExternalTool + Send + Sync {
    /// Human-readable runtime name (e.g. "Python", "Node.js", "dotnet").
    fn runtime_name() -> &'static str;

    /// File extension for this runtime (e.g. "py", "js", "cs").
    fn file_extension() -> &'static str;

    /// Default code template — wraps user code for this runtime.
    fn wrap_code(code: &str) -> String;

    /// Execute code with this runtime. Returns stdout/stderr/exit code.
    async fn execute(code: &str, timeout: Duration, cwd: &Path) -> RuntimeResult;
}

Callers (tool catalog, dispatcher) interact through the trait, not through individual Command::new("python3") / Command::new("node") calls.

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Backends to implement

Runtime	Status	Notes
Python	Already exists (Python ExternalTool + code_execution.rs)	Refactor to impl RuntimeTool
Node.js	Already exists (Node ExternalTool + js_execution.rs)	Refactor to impl RuntimeTool
dotnet	DotNet ExternalTool in PR #1821, dotnet_execution.rs tool	Refactor to impl RuntimeTool
Go	Done	New: go run via RuntimeTool
Rust (rustc)	Done	New: rustc with temp project
TypeScript	Done	New: tsx/ts-node/deno via RuntimeTool

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Dependencies

• ✅ #1794 — ExternalTool trait (PR #1821)
• ✅ URL opener consolidation
• ✅ #1822 — RuntimeTool trait (this issue) — delivered in PR #1845
• [Tracking] Pluggable Tool Registry — user-replaceable tool implementations #1802 sub-issue 4 — ToolRegistry struct — separate, not started

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Delivery

PR #1845 delivers:

• RuntimeTool trait in crates/tui/src/tools/runtime_tool.rs
• go_execution — Go sandbox via go run file.go
• ts_execution — TypeScript sandbox (tsx/tsx.cmd/ts-node/deno)
• rust_execution — Rust sandbox via rustc compile-then-run
• Windows .cmd probe fix for npm global installs
• All existing tools continue working

Closes #1822

[aboimpinto]

Implementation status — 2026-05-20

The RuntimeTool trait and all six backends are implemented in feat/runtime-tool (commit 68b65c9a):

Runtime	Tool name	Status
Python	code_execution	✅ RuntimeTool impl (default path)
Node.js	js_execution	✅ RuntimeTool impl (default path)
.NET	dotnet_execution	✅ RuntimeTool impl (prepare_command override for dotnet run)
Go	go_execution	✅ New ExternalTool + RuntimeTool
TypeScript	ts_execution	✅ New ExternalTool (ts-node/deno/npx tsx) + custom execute()
Rust	rust_execution	✅ Two-step compile-then-run via RuntimeTool

Files changed

• crates/tui/src/tools/runtime_tool.rs — trait + 6 impls (new, 440 lines)
• crates/tui/src/dependencies.rs — Go + TypeScript ExternalTool impls
• crates/tui/src/core/engine/tool_catalog.rs — registrations + dispatch
• crates/tui/src/core/engine/turn_loop.rs — execution dispatch + plan-mode blocklist

Next

• Manual test on each runtime (need runtime installed)
• Open PR against main once tested
• Then: ToolRegistry struct ([Tracking] Pluggable Tool Registry — user-replaceable tool implementations #1802 sub-issue 4)