diff --git a/packages/core/src/schema.ts b/packages/core/src/schema.ts
index 55b118451..5185c9481 100644
--- a/packages/core/src/schema.ts
+++ b/packages/core/src/schema.ts
@@ -2,6 +2,19 @@ import { z } from "zod";
 
 import { ModelFamily } from "./family";
 
+const BodyValue: z.ZodType<
+  string | number | boolean | null | Array<unknown> | Record<string, unknown>
+> = z.lazy(() =>
+  z.union([
+    z.string(),
+    z.number(),
+    z.boolean(),
+    z.null(),
+    z.array(BodyValue),
+    z.record(BodyValue),
+  ]),
+);
+
 const Cost = z.object({
   input: z.number().min(0, "Input price cannot be negative"),
   output: z.number().min(0, "Output price cannot be negative"),
@@ -74,6 +87,7 @@ export const Model = z
         npm: z.string().optional(),
         api: z.string().optional(),
         shape: z.enum(["responses", "completions"]).optional(),
+        body: z.record(BodyValue).optional(),
       })
       .optional(),
   })
diff --git a/providers/anthropic/models/claude-opus-4-6-fast.toml b/providers/anthropic/models/claude-opus-4-6-fast.toml
new file mode 100644
index 000000000..a758629c6
--- /dev/null
+++ b/providers/anthropic/models/claude-opus-4-6-fast.toml
@@ -0,0 +1,28 @@
+name = "Claude Opus 4.6 Fast"
+family = "claude-opus"
+release_date = "2026-02-05"
+last_updated = "2026-03-16"
+attachment = true
+reasoning = true
+temperature = true
+tool_call = true
+knowledge = "2025-05"
+open_weights = false
+status = "beta"
+
+[cost]
+input = 30.00
+output = 150.00
+cache_read = 3.00
+cache_write = 37.50
+
+[limit]
+context = 1_000_000
+output = 128_000
+
+[modalities]
+input = ["text", "image", "pdf"]
+output = ["text"]
+
+[provider.body]
+speed = "fast"
diff --git a/providers/openai/models/gpt-5.4-fast.toml b/providers/openai/models/gpt-5.4-fast.toml
new file mode 100644
index 000000000..a9ff18a4f
--- /dev/null
+++ b/providers/openai/models/gpt-5.4-fast.toml
@@ -0,0 +1,28 @@
+name = "GPT-5.4 Fast"
+family = "gpt"
+release_date = "2026-03-05"
+last_updated = "2026-03-16"
+attachment = true
+reasoning = true
+temperature = false
+knowledge = "2025-08-31"
+tool_call = true
+structured_output = true
+open_weights = false
+
+[cost]
+input = 5.00
+output = 30.00
+cache_read = 0.50
+
+[limit]
+context = 1_050_000
+input = 922_000
+output = 128_000
+
+[modalities]
+input = ["text", "image", "pdf"]
+output = ["text"]
+
+[provider.body]
+service_tier = "priority"
diff --git a/providers/opencode/models/claude-opus-4-6-fast.toml b/providers/opencode/models/claude-opus-4-6-fast.toml
new file mode 100644
index 000000000..201603515
--- /dev/null
+++ b/providers/opencode/models/claude-opus-4-6-fast.toml
@@ -0,0 +1,31 @@
+name = "Claude Opus 4.6 Fast"
+family = "claude-opus"
+release_date = "2026-02-05"
+last_updated = "2026-03-16"
+attachment = true
+reasoning = true
+temperature = true
+tool_call = true
+knowledge = "2025-08-31"
+open_weights = false
+status = "beta"
+
+[cost]
+input = 30.00
+output = 150.00
+cache_read = 3.00
+cache_write = 37.50
+
+[limit]
+context = 1_000_000
+output = 128_000
+
+[modalities]
+input = ["text", "image", "pdf"]
+output = ["text"]
+
+[provider]
+npm = "@ai-sdk/anthropic"
+
+[provider.body]
+speed = "fast"
diff --git a/providers/opencode/models/gpt-5.4-fast.toml b/providers/opencode/models/gpt-5.4-fast.toml
new file mode 100644
index 000000000..f5b9ea7b3
--- /dev/null
+++ b/providers/opencode/models/gpt-5.4-fast.toml
@@ -0,0 +1,31 @@
+name = "GPT-5.4 Fast"
+family = "gpt"
+release_date = "2026-03-05"
+last_updated = "2026-03-16"
+attachment = true
+reasoning = true
+temperature = false
+knowledge = "2025-08-31"
+tool_call = true
+structured_output = true
+open_weights = false
+
+[cost]
+input = 5.00
+output = 30.00
+cache_read = 0.50
+
+[limit]
+context = 1_050_000
+input = 922_000
+output = 128_000
+
+[modalities]
+input = ["text", "image", "pdf"]
+output = ["text"]
+
+[provider]
+npm = "@ai-sdk/openai"
+
+[provider.body]
+service_tier = "priority"