Code-Exec

Run short code snippets inside a live host process — game engines, editors, any .NET or Python host — with one contract for C# and Python. Built for AI agents: the agent writes only the statements it needs, the result comes back as text, and errors point at the agent's own lines.

using System.Text;                 // optional: own usings, aliases, `using static`
var sb = new StringBuilder("ab");
class Helper { public static int Twice(int v) => v * 2; }   // types and functions are allowed
sb.Append(Helper.Twice(21));
sb.ToString()                      // last expression = the result → "ab42"

import math
x = 21
math.floor(x * 2.5)                # last expression = the result → "52"

The normative contract — request/response fields, snippet semantics, error kinds — is spec/contract.md. Shared golden cases: fixtures/golden/.

Every host already has its own Roslyn constraints (Unity pins 4.8 because of System.Collections.Immutable; Godot and .NET 10 apps can use the latest). So the core library has no dependencies at all, and the Roslyn adapter ships as source: it compiles inside your project, against your Roslyn. CI checks that source against Roslyn 3.8, 4.0, 4.8, 4.14 and 5.x, on .NET Framework 4.8, .NET 8 and .NET 10.

<PackageReference Include="com.IvanMurzak.CodeExec" Version="0.4.0" />
<PackageReference Include="com.IvanMurzak.CodeExec.Roslyn" Version="0.4.0" />
<PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.8.0" />  <!-- your choice, 3.8+ -->

var runner = new CodeRunner(new RoslynCSharpCompiler(), new CodeRunnerOptions
{
    DefaultUsings = new[] { "System", "System.Linq", "UnityEngine" },   // the host's defaults
    IncludeRoot = ".ai-game-dev/snippets",                              // where `include` paths resolve
});
ExecuteResult result = await runner.ExecuteAsync(new ExecuteRequest { Code = "Application.unityVersion" });

• Prepare() compiles and is safe on a background thread; Run() / RunAsync() invoke on the calling (main) thread.
• include takes files and folders (recursive): the agent's helper "micro-projects", compiled with the snippet.
• Unknown simple names are imported automatically when exactly one namespace defines them (autoImported); ambiguous names are reported, never guessed. CoreLib's Internal.* namespaces are never imported.
• ValueConverter turns the result into something that outlives the snippet (Unity: ReflectorNet JSON).
• Execution guards (§3.6): runaway recursion stops with an error before a stack overflow could end the host, and loops stop with Timeout once the time budget is spent, also in synchronous code on the main thread. Budget: TimeoutMs on the request, else DefaultTimeoutMs (120 s), at most MaxTimeoutMs (0 = no cap); stack allowance MaxStackBytes (1 MiB); ExecutionGuards = false turns them off. Threads and tasks the snippet starts (new Thread, ThreadPool, Task.Run, StartNew) stop once its run has ended.
• Agent tools: expose timeoutMs as a timeout argument, default to about 30 s, and cap it below the tool timeout (§1).
• Output is limited before it reaches the agent (§6): a text value, the logs (first and last lines kept, 2k per line) and the error, 20k characters each by default (MaxValueChars, MaxLogChars, MaxLogLineChars, MaxErrorChars on the request; 0 = no limit). Includes stay inside IncludeRoot unless AllowIncludeOutsideRoot.
• Hosts that load assemblies from memory (Godot's game assembly) pass a locationResolver to LoadedAssembliesReferenceProvider, otherwise snippets cannot see those types. On CoreCLR a snippet binds to the copy the process already runs (any load context) before the default context is asked, so a host's AssemblyLoadContext.Default.Resolving handler cannot hand it a second copy.

import code_exec
code_exec.run("x = 21\nx * 2", include=["helpers"], include_root=".ai-game-dev/snippets", imports=["unreal"])
code_exec.run_b64(base64_json_request)   # JSON in, JSON out: one string literal from C++
code_exec.run("print('x')", max_log_chars=0)   # the same limits as C# (JSON: maxLogChars, ...); 0 = no limit
code_exec.run("while True: pass", timeout_ms=5000)   # stopped by a watchdog: errorKind Timeout (JSON: timeoutMs)
code_exec.set_default_timeout_ms(30000)               # the budget of requests without one (default 120000; 0 = none)
code_exec.set_max_timeout_ms(280000)                  # the most a request may ask for (default 0 = no cap)
code_exec.set_max_recursion_limit(3000)               # Python < 3.12: the most a snippet's sys.setrecursionlimit sets (0 = no cap)

scripts/test-all.sh                                  # .NET tests, pack + package consumer, Python tests
ROSLYN_VERSIONS="3.8.0 4.8.0 5.9.0" scripts/test-all.sh
dotnet test dotnet/CodeExec.Tests -p:IncludeNetFx=true -f net48   # Windows: the Mono-like path
scripts/pack.sh                                      # pack + package shape checks, publishes nothing

Releases: .github/workflows/release.yml, dispatch only. See AGENTS.md.

PolyForm Shield 1.0.0. Copyright (c) 2026 Ivan Murzak.