csharp.md

codexcw — C# examples

The .NET library lives in dotnet/Codexcw and is published to NuGet as C3OSS.Codexcw (namespace C3OSS.Codexcw) by the dotnet-v* release train.

dotnet add package C3OSS.Codexcw

To build against the repository directly, reference the project instead:

dotnet add reference path/to/codexcw/dotnet/Codexcw/Codexcw.csproj

Runners drive Codex (the default agent) or Claude Code; the selected agent's executable must be on PATH and authenticated — codex new enough to support codex exec --json, claude new enough to support --output-format stream-json (see the Claude agent section below). Codex defaults are automation-friendly: read-only sandbox, approval never, ephemeral sessions, color off, git-check skipped.

Two ways to run

Every recipe works in either mode:

• Blocking — runner.RunAsync(request) starts the process, drains its events, and returns the final RunResult.
• Streaming — runner.Start(request) returns immediately with a Session; consume session.Events() with await foreach and call session.WaitAsync() for the result.

using C3OSS.Codexcw;

var runner = new Runner();

// Blocking.
var result = await runner.RunAsync(new Request { Prompt = "diga oi" });
Console.WriteLine(result.FinalMessage);

// Streaming: consume events live, then collect the result.
using var session = runner.Start(new Request { Prompt = "resuma este repo" });

await foreach (var evt in session.Events())
{
    if (evt.ItemCompleted?.Item is { Kind: ItemKind.AgentMessage } item)
    {
        Console.WriteLine(item.Text);
    }
}

var result = await session.WaitAsync();
Console.WriteLine($"usage: {result.Usage.TotalTokens}");

The event stream is single-consumer, and waiting never depends on it: calling WaitAsync without reading Events() is safe. Session and Group are disposable: Dispose cancels anything still active and releases the run's resources, and await using (DisposeAsync) additionally waits for the internal tasks to finish. The recipes below use RunAsync for brevity; swap in the Start pattern above to consume events live.

Per-event callback

A RunOptions.Handler runs for every decoded event. Throwing cancels the run.

var result = await runner.RunAsync(new Request { Prompt = "trabalhe" }, new RunOptions
{
    Handler = (evt, _) =>
    {
        switch (evt.Kind)
        {
            case EventKind.ItemCompleted when evt.ItemCompleted!.Item.Kind == ItemKind.CommandExecution:
                Console.WriteLine($"$ {evt.ItemCompleted.Item.Command}");
                break;
            case EventKind.TurnCompleted:
                Console.WriteLine($"tokens: {evt.TurnCompleted!.Usage.TotalTokens}");
                break;
        }
        return ValueTask.CompletedTask;
    },
});

// A handler that aborts the run on the first command execution.
try
{
    await runner.RunAsync(new Request { Prompt = "..." }, new RunOptions
    {
        Handler = (evt, _) =>
            evt.ItemStarted?.Item.Kind == ItemKind.CommandExecution
                ? throw new InvalidOperationException("stop")
                : ValueTask.CompletedTask,
    });
}
catch (HandlerException ex)
{
    Console.WriteLine($"cancelled by handler: {ex.InnerException?.Message}");
}

Resume a session

Codex sessions are resumable by thread id, but only persisted ones: runs are ephemeral by default (--ephemeral), so both the original run and the resume need Persistent = true. Run once, capture result.ThreadId, then continue the same thread with ResumeId.

var first = await runner.RunAsync(new Request
{
    Prompt = "crie um arquivo TODO.md",
    Persistent = true,
});
var threadId = first.ThreadId;

var second = await runner.RunAsync(new Request
{
    Prompt = "agora adicione 3 itens ao TODO.md",
    ResumeId = threadId,
    Persistent = true,
});
Console.WriteLine(second.FinalMessage);

// Resume the most recent persisted thread instead of tracking ids yourself.
await runner.RunAsync(new Request { Prompt = "continue", ResumeLast = true, Persistent = true });

// ResumeAll disables Codex's cwd filtering while resuming.
await runner.RunAsync(new Request
{
    Prompt = "continue",
    ResumeId = threadId,
    ResumeAll = true,
    Persistent = true,
});

Resume runs do not accept Dir, AddDirs, or Profile — setting them throws InvalidRequestException.

Sandbox modes

// Read-only is the default. Let Codex write inside the workspace:
await runner.RunAsync(new Request
{
    Prompt = "refatore o pacote foo",
    Sandbox = SandboxMode.WorkspaceWrite,
});

// Remove sandbox filesystem restrictions entirely:
await runner.RunAsync(new Request
{
    Prompt = "...",
    Sandbox = SandboxMode.DangerFullAccess,
});

Approval policies

// Defaults to ApprovalPolicy.Never (no prompts). The safer interactive middle ground:
await runner.RunAsync(new Request
{
    Prompt = "...",
    Sandbox = SandboxMode.WorkspaceWrite,
    Approval = ApprovalPolicy.OnRequest,
});

⚠️ Bypass sandbox and approvals

Danger. DangerouslyBypassSandbox runs Codex with --dangerously-bypass-approvals-and-sandbox: no sandbox, no approval prompts. Only use this in a disposable, fully-trusted environment.

await runner.RunAsync(new Request
{
    Prompt = "...",
    DangerouslyBypassSandbox = true,
});

// Run enabled hooks without persisted trust:
await runner.RunAsync(new Request
{
    Prompt = "...",
    DangerouslyBypassHooks = true,
});

Run many with bounded concurrency

using var group = runner.RunMany(
    [
        new Request { Prompt = "review package A" },
        new Request { Prompt = "review package B" },
        new Request { Prompt = "review package C" },
    ],
    new GroupOptions { MaxConcurrent = 2 });

// Multiplexed events across all runs.
await foreach (var runEvent in group.Events())
{
    Console.WriteLine($"[{runEvent.Index}] {runEvent.Event.Type}");
}

try
{
    var results = await group.WaitAsync();
    foreach (var result in results)
    {
        Console.WriteLine($"[{result.Index}] {result.Result!.FinalMessage}");
    }
}
catch (GroupException ex) // thrown when any run failed; all results ride along
{
    foreach (var result in ex.Results)
    {
        Console.WriteLine(result.Error is null
            ? $"[{result.Index}] {result.Result!.FinalMessage}"
            : $"[{result.Index}] failed: {result.Error.Message}");
    }
}

Config overrides

Each ConfigOverride becomes a -c key=value argument.

await runner.RunAsync(new Request
{
    Prompt = "...",
    Config =
    [
        new ConfigOverride("model_reasoning_effort", "\"high\""),
        new ConfigOverride("tools.web_search", "true"),
    ],
});

Fast mode (/fast)

Codex Fast mode uses the priority service tier.

await runner.RunAsync(new Request
{
    Prompt = "...",
    Config = [new ConfigOverride("service_tier", "\"priority\"")],
});

Structured output

Ask Codex to conform its final message to a JSON Schema, and write it to a file.

const string schema = """{"type":"object","properties":{"summary":{"type":"string"}},"required":["summary"]}""";

var result = await runner.RunAsync(new Request
{
    Prompt = "resuma o repo como JSON",
    OutputSchema = schema, // written to a temp file and passed as --output-schema
    OutputLastMessagePath = "out.json",
});
Console.WriteLine(result.FinalMessage); // conforms to the schema

Working directory and extra dirs

await runner.RunAsync(new Request
{
    Prompt = "...",
    Dir = "/work/project",
    AddDirs = ["/work/shared", "/work/vendor"],
});

Model and profile

Model availability depends on how the codex CLI is authenticated (a ChatGPT account exposes a different set than an API key); a request for an unavailable model fails the run with a Codex error event.

await runner.RunAsync(new Request
{
    Prompt = "...",
    Model = "gpt-5.4-mini",
    Profile = "work",
});

Claude Code agent

The runner also wraps Claude Code's non-interactive mode (claude -p --output-format stream-json). Select it with RunnerOptions.Agent; the claude executable must be on PATH and authenticated. Events are normalized into the same Event model — thread.started carries the Claude session id, tool calls become item.started/item.completed pairs, and the final result maps to turn.completed — with Raw always keeping the original Claude JSON line.

var runner = new Runner(new RunnerOptions { Agent = Agent.Claude });

var result = await runner.RunAsync(new Request
{
    Prompt = "crie um arquivo TODO.md",
    Model = ClaudeModels.Haiku, // "haiku", "sonnet", or "opus"
    PermissionMode = PermissionMode.AcceptEdits,
});

Console.WriteLine($"tokens: {result.Usage.TotalTokens}");
Console.WriteLine($"cost USD: {result.Usage.TotalCostUsd}");

// Tool filters, structured output, and resume work per request:
await runner.RunAsync(new Request
{
    Prompt = "rode os testes",
    Model = ClaudeModels.Sonnet,
    AllowedTools = ["Bash(dotnet test *)", "Read"],
    DisallowedTools = ["WebSearch"],
});

var first = await runner.RunAsync(new Request { Prompt = "lembre disto", Persistent = true });
await runner.RunAsync(new Request
{
    Prompt = "continue",
    ResumeId = first.ThreadId, // or ResumeLast = true
    Persistent = true,
});

Claude runs support Dir (applied as the process working directory), AddDirs, OutputSchema/OutputSchemaPath (passed as --json-schema), and DangerouslyBypassSandbox (passed as --dangerously-skip-permissions). PermissionMode, AllowedTools, and DisallowedTools are claude-only; codex-only fields (Sandbox, Approval, Profile, Config, Images, feature flags) throw InvalidRequestException on a claude runner. The permission modes are AcceptEdits, Auto, BypassPermissions, Manual, DontAsk, and Plan. Claude usage includes cache creation, total cost, and per-model details in Usage.ModelUsage.

Claude account limits are available through the CLI's /usage report:

var accountUsage = await ClaudeAccount.GetClaudeAccountUsageAsync();
foreach (var window in accountUsage.Windows)
{
    Console.WriteLine($"{window.Label}: {window.UsedPercent:0.#}% used, resets {window.ResetsAt}");
}

ClaudeAccountUsage.Raw preserves the complete JSON result and Report preserves Claude Code's human-readable response.

Stdin input

using System.Text;

// Prompt via stdin only:
await runner.RunAsync(new Request
{
    Stdin = new MemoryStream(Encoding.UTF8.GetBytes("diga oi")),
});

// Prompt plus extra stdin context (wrapped in <stdin> markers):
await runner.RunAsync(new Request
{
    Prompt = "resuma o diff abaixo",
    Stdin = File.OpenRead("large.diff"),
});

Custom executable and environment

var runner = new Runner(new RunnerOptions
{
    Executable = "/opt/codex/bin/codex",
    Env = ["CODEX_HOME=/tmp/codex-home"],
});

Account usage and limits

CodexAccount.GetAccountUsageAsync reads account limits and credits through codex app-server. It accepts the same executable/env shape used by runners. CODEX_HOME defaults to ~/.codex when it is not set. Timeout bounds each JSON-RPC request; non-positive values use the 10-second default.

var usage = await CodexAccount.GetAccountUsageAsync(new AccountUsageRequest
{
    Env = new Dictionary<string, string> { ["CODEX_HOME"] = "/tmp/codex-home" },
    Timeout = TimeSpan.FromSeconds(5),
});

if (usage.Account is { } account)
{
    Console.WriteLine($"account: {account.Email}");
}
if (usage.RateLimits.Primary is { } primary)
{
    Console.WriteLine($"primary used: {primary.UsedPercent}");
}
if (usage.TokenUsage is { } tokens)
{
    Console.WriteLine($"lifetime tokens: {tokens.Summary.LifetimeTokens}");
}

Account and TokenUsage are null when codex answers those reads with a JSON-RPC error; transport errors and timeouts fail the whole call.

Error handling

Failures are typed exceptions rooted at CodexcwException, and every run failure carries the partial report in Result. The one exception is cancellation: RunCanceledException derives from OperationCanceledException — so idiomatic cancellation handling keeps working — and exposes the same Result property.

try
{
    var result = await runner.RunAsync(new Request { Prompt = "..." });
}
catch (ExitException ex)
{
    Console.WriteLine($"agent exited {ex.ExitCode}: {ex.Stderr}");
}
catch (CodexErrorException ex)
{
    Console.WriteLine($"codex reported an error: {ex.Message}");
}
catch (ClaudeErrorException ex)
{
    Console.WriteLine($"claude reported an error: {ex.Message}");
}
catch (DecodeException ex)
{
    Console.WriteLine($"bad JSONL on line {ex.Line}");
}
catch (PromptRequiredException)
{
    Console.WriteLine("prompt or stdin is required");
}
catch (CodexcwException ex)
{
    Console.WriteLine($"error: {ex.Message} (events so far: {ex.Result?.Events.Count})");
}

Cancellation

// Cancel a streaming session explicitly:
using var session = runner.Start(new Request { Prompt = "..." });
_ = Task.Delay(TimeSpan.FromSeconds(5)).ContinueWith(_ => session.Cancel());
await foreach (var _ in session.Events())
{
}
try
{
    await session.WaitAsync();
}
catch (RunCanceledException ex) // derives OperationCanceledException
{
    Console.WriteLine($"cancelled; events so far: {ex.Result?.Events.Count}");
}

// Or cancel through a CancellationToken:
using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(30));
await runner.RunAsync(new Request { Prompt = "..." }, cancellationToken: cts.Token);

---

See the README for the cross-language overview and AGENTS.md for the project guide.