Added the exact token count for Anthropic and OpenAI (#1004)

app/MindWork AI Studio/Provider/Anthropic/AnthropicUsage.cs

@@ -0,0 +1,49 @@
+// ReSharper disable ClassNeverInstantiated.Global
+namespace AIStudio.Provider.Anthropic;
+
+/// <summary>
+/// What Anthropic reports a messages call carried, as it opens the stream.
+/// </summary>
+/// <remarks>
+/// The input arrives in up to three parts, and only their sum is what the request carried: the
+/// input tokens are just those after the last cache breakpoint, the other two are what was written
+/// to and read from the cache before it. Read on 2026-09-24 at
+/// https://platform.claude.com/docs/en/build-with-claude/prompt-caching.
+///
+/// A missing cache part means that nothing was cached, not that its size is unknown: the API
+/// caches only for a request which asks for it with cache_control, which AI Studio never does on
+/// its own -- somebody could, though, through the additional API parameters. A missing input part
+/// is different, and without it the block states nothing.
+///
+/// The output tokens are left unread on purpose, for the reason given at TokenUsage: they include
+/// the model's thinking, which no later request carries.
+/// </remarks>
+public sealed record AnthropicUsage
+{
+    /// <summary>
+    /// What the request carried after its last cache breakpoint, which is all of it without caching.
+    /// </summary>
+    public int? InputTokens { get; init; }
+
+    /// <summary>
+    /// What the request wrote to the cache.
+    /// </summary>
+    public int? CacheCreationInputTokens { get; init; }
+
+    /// <summary>
+    /// What the request read from the cache.
+    /// </summary>
+    public int? CacheReadInputTokens { get; init; }
+
+    /// <summary>
+    /// States what this block reports, as far as it can be believed.
+    /// </summary>
+    /// <remarks>
+    /// The one way from the wire to a usage, shared by the plain text path and the tool calling
+    /// path, so that what counts as believable is decided in a single place.
+    /// </remarks>
+    /// <returns>The usage, or TokenUsage.UNKNOWN when the block states nothing usable.</returns>
+    public TokenUsage ToTokenUsage() => this.InputTokens is { } inputTokens
+        ? TokenUsage.OfReported(inputTokens + (this.CacheCreationInputTokens ?? 0) + (this.CacheReadInputTokens ?? 0))
+        : TokenUsage.UNKNOWN;
+}