diff --git a/.changeset/fix-openrouter-callmodel-metrics.md b/.changeset/fix-openrouter-callmodel-metrics.md
new file mode 100644
index 000000000..0cf6abd79
--- /dev/null
+++ b/.changeset/fix-openrouter-callmodel-metrics.md
@@ -0,0 +1,5 @@
+---
+"braintrust": patch
+---
+
+fix(openrouter): avoid double-counting callModel token and cost metrics
diff --git a/e2e/scenarios/openrouter-instrumentation/__snapshots__/openrouter-v0123.span-events.json b/e2e/scenarios/openrouter-instrumentation/__snapshots__/openrouter-v0123.span-events.json
index ddf193a91..4533e3b10 100644
--- a/e2e/scenarios/openrouter-instrumentation/__snapshots__/openrouter-v0123.span-events.json
+++ b/e2e/scenarios/openrouter-instrumentation/__snapshots__/openrouter-v0123.span-events.json
@@ -282,17 +282,7 @@
       "model": "gemini-2.5-flash-lite",
       "provider": "google"
     },
-    "metric_keys": [
-      "completion_reasoning_tokens",
-      "completion_tokens",
-      "cost",
-      "cost_upstream_inference_cost",
-      "cost_upstream_inference_input_cost",
-      "cost_upstream_inference_output_cost",
-      "prompt_cached_tokens",
-      "prompt_tokens",
-      "tokens"
-    ],
+    "metric_keys": [],
     "name": "openrouter.callModel",
     "root_span_id": "<span:1>",
     "span_id": "<span:15>",
diff --git a/e2e/scenarios/openrouter-instrumentation/__snapshots__/openrouter-v0911.span-events.json b/e2e/scenarios/openrouter-instrumentation/__snapshots__/openrouter-v0911.span-events.json
index b3a7cc45a..35bccc17a 100644
--- a/e2e/scenarios/openrouter-instrumentation/__snapshots__/openrouter-v0911.span-events.json
+++ b/e2e/scenarios/openrouter-instrumentation/__snapshots__/openrouter-v0911.span-events.json
@@ -238,17 +238,7 @@
       "model": "gemini-2.5-flash-lite",
       "provider": "google"
     },
-    "metric_keys": [
-      "completion_reasoning_tokens",
-      "completion_tokens",
-      "cost",
-      "cost_upstream_inference_cost",
-      "cost_upstream_inference_input_cost",
-      "cost_upstream_inference_output_cost",
-      "prompt_cached_tokens",
-      "prompt_tokens",
-      "tokens"
-    ],
+    "metric_keys": [],
     "name": "openrouter.callModel",
     "root_span_id": "<span:1>",
     "span_id": "<span:13>",
diff --git a/js/src/instrumentation/plugins/openrouter-agent-plugin.test.ts b/js/src/instrumentation/plugins/openrouter-agent-plugin.test.ts
index 137232d6a..b531ca4ab 100644
--- a/js/src/instrumentation/plugins/openrouter-agent-plugin.test.ts
+++ b/js/src/instrumentation/plugins/openrouter-agent-plugin.test.ts
@@ -430,6 +430,7 @@ describe("OpenRouter Agent Plugin", () => {
           inputTokens: 10,
           outputTokens: 4,
           totalTokens: 14,
+          cost: 0.01,
         },
       };
       const finalResponse = {
@@ -447,6 +448,7 @@ describe("OpenRouter Agent Plugin", () => {
           inputTokens: 12,
           outputTokens: 3,
           totalTokens: 15,
+          cost: 0.02,
         },
       };
       const request = {
@@ -544,11 +546,10 @@ describe("OpenRouter Agent Plugin", () => {
         turn_count: 2,
       });
       expect(callModelSpan?.output).toMatchObject(finalResponse.output);
-      expect(callModelSpan?.metrics).toMatchObject({
-        prompt_tokens: 22,
-        completion_tokens: 7,
-        tokens: 29,
-      });
+      expect(callModelSpan?.metrics?.prompt_tokens).toBeUndefined();
+      expect(callModelSpan?.metrics?.completion_tokens).toBeUndefined();
+      expect(callModelSpan?.metrics?.tokens).toBeUndefined();
+      expect(callModelSpan?.metrics?.cost).toBeUndefined();
 
       expect(turnSpans).toHaveLength(2);
       expect(turnSpans[0]?.metadata).toMatchObject({
@@ -559,6 +560,12 @@ describe("OpenRouter Agent Plugin", () => {
         step: 1,
         step_type: "initial",
       });
+      expect(turnSpans[0]?.metrics).toMatchObject({
+        prompt_tokens: 10,
+        completion_tokens: 4,
+        tokens: 14,
+        cost: 0.01,
+      });
       expect(turnSpans[1]?.metadata).toMatchObject({
         provider: TEST_PROVIDER,
         model: TEST_MODEL,
@@ -567,6 +574,24 @@ describe("OpenRouter Agent Plugin", () => {
         step: 2,
         step_type: "continue",
       });
+      expect(turnSpans[1]?.metrics).toMatchObject({
+        prompt_tokens: 12,
+        completion_tokens: 3,
+        tokens: 15,
+        cost: 0.02,
+      });
+      expect(
+        spans.reduce(
+          (sum: number, span: any) => sum + (span.metrics?.prompt_tokens ?? 0),
+          0,
+        ),
+      ).toBe(22);
+      expect(
+        spans.reduce(
+          (sum: number, span: any) => sum + (span.metrics?.cost ?? 0),
+          0,
+        ),
+      ).toBeCloseTo(0.03);
 
       expect(toolSpan?.span_attributes).toMatchObject({
         name: "lookup_weather",
diff --git a/js/src/instrumentation/plugins/openrouter-agent-plugin.ts b/js/src/instrumentation/plugins/openrouter-agent-plugin.ts
index 414d110a5..f95336371 100644
--- a/js/src/instrumentation/plugins/openrouter-agent-plugin.ts
+++ b/js/src/instrumentation/plugins/openrouter-agent-plugin.ts
@@ -920,10 +920,16 @@ function patchOpenRouterCallModelResult(args: {
         finalResponse,
         rounds.length + 1,
       );
+      const metrics =
+        tracedTurnCount === 0
+          ? aggregateOpenRouterCallModelMetrics(rounds, finalResponse)
+          : undefined;
       span.log({
         output: extractOpenRouterResponseOutput(finalResponse, fallbackOutput),
         ...(metadata ? { metadata } : {}),
-        metrics: aggregateOpenRouterCallModelMetrics(rounds, finalResponse),
+        // Child turn spans already carry per-response usage. Duplicating those
+        // metrics on the parent makes trace-level token/cost totals double count.
+        ...(metrics && Object.keys(metrics).length > 0 ? { metrics } : {}),
       });
       span.end();
       return;
diff --git a/js/src/instrumentation/plugins/openrouter-plugin.test.ts b/js/src/instrumentation/plugins/openrouter-plugin.test.ts
index bc67af92a..27933d9cc 100644
--- a/js/src/instrumentation/plugins/openrouter-plugin.test.ts
+++ b/js/src/instrumentation/plugins/openrouter-plugin.test.ts
@@ -432,6 +432,7 @@ describe("OpenRouter Plugin", () => {
           inputTokens: 10,
           outputTokens: 4,
           totalTokens: 14,
+          cost: 0.01,
         },
       };
       const finalResponse = {
@@ -449,6 +450,7 @@ describe("OpenRouter Plugin", () => {
           inputTokens: 12,
           outputTokens: 3,
           totalTokens: 15,
+          cost: 0.02,
         },
       };
       const request = {
@@ -543,11 +545,10 @@ describe("OpenRouter Plugin", () => {
         turn_count: 2,
       });
       expect(callModelSpan?.output).toMatchObject(finalResponse.output);
-      expect(callModelSpan?.metrics).toMatchObject({
-        prompt_tokens: 22,
-        completion_tokens: 7,
-        tokens: 29,
-      });
+      expect(callModelSpan?.metrics?.prompt_tokens).toBeUndefined();
+      expect(callModelSpan?.metrics?.completion_tokens).toBeUndefined();
+      expect(callModelSpan?.metrics?.tokens).toBeUndefined();
+      expect(callModelSpan?.metrics?.cost).toBeUndefined();
 
       expect(turnSpans).toHaveLength(2);
       expect(turnSpans[0]?.metadata).toMatchObject({
@@ -558,6 +559,12 @@ describe("OpenRouter Plugin", () => {
         step: 1,
         step_type: "initial",
       });
+      expect(turnSpans[0]?.metrics).toMatchObject({
+        prompt_tokens: 10,
+        completion_tokens: 4,
+        tokens: 14,
+        cost: 0.01,
+      });
       expect(turnSpans[1]?.metadata).toMatchObject({
         provider: TEST_PROVIDER,
         model: TEST_MODEL,
@@ -566,6 +573,24 @@ describe("OpenRouter Plugin", () => {
         step: 2,
         step_type: "continue",
       });
+      expect(turnSpans[1]?.metrics).toMatchObject({
+        prompt_tokens: 12,
+        completion_tokens: 3,
+        tokens: 15,
+        cost: 0.02,
+      });
+      expect(
+        spans.reduce(
+          (sum: number, span: any) => sum + (span.metrics?.prompt_tokens ?? 0),
+          0,
+        ),
+      ).toBe(22);
+      expect(
+        spans.reduce(
+          (sum: number, span: any) => sum + (span.metrics?.cost ?? 0),
+          0,
+        ),
+      ).toBeCloseTo(0.03);
 
       expect(toolSpan?.span_attributes).toMatchObject({
         name: "lookup_weather",
diff --git a/js/src/instrumentation/plugins/openrouter-plugin.ts b/js/src/instrumentation/plugins/openrouter-plugin.ts
index 2edf46d3c..ec022b43f 100644
--- a/js/src/instrumentation/plugins/openrouter-plugin.ts
+++ b/js/src/instrumentation/plugins/openrouter-plugin.ts
@@ -1102,10 +1102,16 @@ function patchOpenRouterCallModelResult(args: {
         finalResponse,
         rounds.length + 1,
       );
+      const metrics =
+        tracedTurnCount === 0
+          ? aggregateOpenRouterCallModelMetrics(rounds, finalResponse)
+          : undefined;
       span.log({
         output: extractOpenRouterResponseOutput(finalResponse, fallbackOutput),
         ...(metadata ? { metadata } : {}),
-        metrics: aggregateOpenRouterCallModelMetrics(rounds, finalResponse),
+        // Child turn spans already carry per-response usage. Duplicating those
+        // metrics on the parent makes trace-level token/cost totals double count.
+        ...(metrics && Object.keys(metrics).length > 0 ? { metrics } : {}),
       });
       span.end();
       return;