Post to bsky from the CLI.md

http \
  POST \
  https://bsky.social/xrpc/com.atproto.server.createSession \
  identifier=USERNAME.bsky.social \
  password=APP_SPECIFIC_PASSWORD

http \
  POST \
  https://bsky.social/xrpc/com.atproto.repo.createRecord \
  Authorization:"Bearer ACCESS_JWT" \
  repo=DID \
  collection=app.bsky.feed.post \
  record\[\$type\]=app.bsky.feed.post \
  record\[text\]="Test post please ignore" \
  record\[createdAt\]="$(date -Iseconds)"

Copy the ACCESS_JWT and DID from the response of the createSession call (in real code, you'd store the response in a variable).

These resources helped me put this together:

• https://docs.bsky.app/docs/api/com-atproto-server-create-session
• https://docs.bsky.app/docs/advanced-guides/api-directory
• https://atproto.com/specs/xrpc
• https://docs.bsky.app/docs/advanced-guides/posts

using System.Net.Http.Headers;
using System.Net.Http.Json;
using System.Text.Json.Serialization;

var client = new HttpClient { BaseAddress = new Uri("https://bsky.social/xrpc/") };
var resp = await client.PostAsJsonAsync("com.atproto.server.createSession", new CreateSessionRequest("julia.cool", "5u2w-awce-e4z6-tknq"));
resp.EnsureSuccessStatusCode();

var creds = await resp.Content.ReadFromJsonAsync<CreateSessionResponse>();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", creds.AccessJwt);

resp = await client.PostAsJsonAsync("com.atproto.repo.createRecord", new CreateRecordRequest(
    creds.Did,
    new Post("👋")));
resp.EnsureSuccessStatusCode();

Console.WriteLine(await resp.Content.ReadAsStringAsync());

internal record CreateSessionRequest(
    [property: JsonPropertyName("identifier")] string Identifier,
    [property: JsonPropertyName("password")] string Password);

internal record CreateSessionResponse(
    [property: JsonPropertyName("did")] string Did,
    [property: JsonPropertyName("accessJwt")] string AccessJwt);

internal record CreateRecordRequest(
    [property: JsonPropertyName("repo")] string Repo,
    [property: JsonPropertyName("record")] Post Record)
{
    [JsonPropertyName("collection")]
    internal static string Collection => "app.bsky.feed.post";
}

internal record Post
{
    [JsonPropertyName("$type")]
    internal static string Type => "app.bsky.feed.post";

    [JsonPropertyName("text")]
    internal string Text { get; }

    [JsonPropertyName("createdAt")]
    internal static DateTime CreatedAt => DateTime.UtcNow;

    internal Post(string text)
    {
        Text = text ?? throw new ArgumentNullException(nameof(text));
    }
}