diff --git a/.changeset/structured-output-finalization-usage.md b/.changeset/structured-output-finalization-usage.md
new file mode 100644
index 000000000..10a8ab58b
--- /dev/null
+++ b/.changeset/structured-output-finalization-usage.md
@@ -0,0 +1,11 @@
+---
+'@tanstack/ai': patch
+'@tanstack/ai-anthropic': patch
+'@tanstack/ai-gemini': patch
+'@tanstack/ai-ollama': patch
+'@tanstack/ai-openrouter': patch
+---
+
+Adapters now report token `usage` from the non-streaming `structuredOutput()` call, and `fallbackStructuredOutputStream` forwards it onto the synthesized `RUN_FINISHED` event. Previously the legacy finalization round-trip was invisible to the chat middleware `onUsage` hook — any cost-tracking middleware silently under-counted by exactly one call whenever an adapter without a native `structuredOutputStream` (Anthropic, Gemini, Ollama, OpenRouter) ran agentic structured output through the legacy path.
+
+`StructuredOutputResult` gains an optional `usage: { promptTokens, completionTokens, totalTokens }` field. Adapters without a token count on the wire (or that fail before usage is known) leave it `undefined`, which the engine treats as "no usage to report" — same as before. No consumer-visible behavior change beyond accurate `onUsage` totals.
diff --git a/packages/typescript/ai-anthropic/src/adapters/text.ts b/packages/typescript/ai-anthropic/src/adapters/text.ts
index f6b5b9d2d..0847e91a0 100644
--- a/packages/typescript/ai-anthropic/src/adapters/text.ts
+++ b/packages/typescript/ai-anthropic/src/adapters/text.ts
@@ -276,9 +276,16 @@ export class AnthropicTextAdapter<
         }
       }
 
+      const inputTokens = response.usage?.input_tokens ?? 0
+      const outputTokens = response.usage?.output_tokens ?? 0
       return {
         data: parsed,
         rawText,
+        usage: {
+          promptTokens: inputTokens,
+          completionTokens: outputTokens,
+          totalTokens: inputTokens + outputTokens,
+        },
       }
     } catch (error: unknown) {
       const err = error as Error
diff --git a/packages/typescript/ai-gemini/src/adapters/text.ts b/packages/typescript/ai-gemini/src/adapters/text.ts
index 8f9ee636a..179ec983b 100644
--- a/packages/typescript/ai-gemini/src/adapters/text.ts
+++ b/packages/typescript/ai-gemini/src/adapters/text.ts
@@ -196,9 +196,17 @@ export class GeminiTextAdapter<
         )
       }
 
+      const usageMetadata = result.usageMetadata
       return {
         data: parsed,
         rawText,
+        ...(usageMetadata && {
+          usage: {
+            promptTokens: usageMetadata.promptTokenCount ?? 0,
+            completionTokens: usageMetadata.candidatesTokenCount ?? 0,
+            totalTokens: usageMetadata.totalTokenCount ?? 0,
+          },
+        }),
       }
     } catch (error) {
       logger.errors('gemini.structuredOutput fatal', {
diff --git a/packages/typescript/ai-ollama/src/adapters/text.ts b/packages/typescript/ai-ollama/src/adapters/text.ts
index 16aa0f1ed..4a9afbb49 100644
--- a/packages/typescript/ai-ollama/src/adapters/text.ts
+++ b/packages/typescript/ai-ollama/src/adapters/text.ts
@@ -201,9 +201,16 @@ export class OllamaTextAdapter<TModel extends string> extends BaseTextAdapter<
         )
       }
 
+      const promptTokens = response.prompt_eval_count ?? 0
+      const completionTokens = response.eval_count ?? 0
       return {
         data: parsed,
         rawText,
+        usage: {
+          promptTokens,
+          completionTokens,
+          totalTokens: promptTokens + completionTokens,
+        },
       }
     } catch (error: unknown) {
       const err = error as Error
diff --git a/packages/typescript/ai-openrouter/src/adapters/text.ts b/packages/typescript/ai-openrouter/src/adapters/text.ts
index c48394953..a98e012ec 100644
--- a/packages/typescript/ai-openrouter/src/adapters/text.ts
+++ b/packages/typescript/ai-openrouter/src/adapters/text.ts
@@ -260,9 +260,17 @@ export class OpenRouterTextAdapter<
       // this).
       const transformed = this.transformStructuredOutput(parsed)
 
+      const usage = response.usage
       return {
         data: transformed,
         rawText,
+        ...(usage && {
+          usage: {
+            promptTokens: usage.promptTokens,
+            completionTokens: usage.completionTokens,
+            totalTokens: usage.totalTokens,
+          },
+        }),
       }
     } catch (error: unknown) {
       // Narrow before logging: raw SDK errors can carry request metadata
diff --git a/packages/typescript/ai/src/activities/chat/adapter.ts b/packages/typescript/ai/src/activities/chat/adapter.ts
index 648e7e6bf..5facc7d43 100644
--- a/packages/typescript/ai/src/activities/chat/adapter.ts
+++ b/packages/typescript/ai/src/activities/chat/adapter.ts
@@ -40,6 +40,17 @@ export interface StructuredOutputResult<T = unknown> {
   data: T
   /** The raw text response from the model before parsing */
   rawText: string
+  /**
+   * Token usage reported by the provider for this call, when available.
+   * Forwarded by `fallbackStructuredOutputStream` onto the synthesized
+   * RUN_FINISHED so middleware `onUsage` hooks can account for the
+   * finalization round-trip.
+   */
+  usage?: {
+    promptTokens: number
+    completionTokens: number
+    totalTokens: number
+  }
 }
 
 /**
diff --git a/packages/typescript/ai/src/activities/chat/index.ts b/packages/typescript/ai/src/activities/chat/index.ts
index 26e3153fc..7d7f670c0 100644
--- a/packages/typescript/ai/src/activities/chat/index.ts
+++ b/packages/typescript/ai/src/activities/chat/index.ts
@@ -2630,7 +2630,15 @@ async function* fallbackStructuredOutputStream(
     timestamp,
   }
 
-  let result: { data: unknown; rawText: string }
+  let result: {
+    data: unknown
+    rawText: string
+    usage?: {
+      promptTokens: number
+      completionTokens: number
+      totalTokens: number
+    }
+  }
   try {
     result = await adapter.structuredOutput(options)
   } catch (error) {
@@ -2686,6 +2694,7 @@ async function* fallbackStructuredOutputStream(
     model,
     timestamp,
     finishReason: 'stop',
+    ...(result.usage ? { usage: result.usage } : {}),
   }
 }