diff --git a/packages/app/src/runtime/server/global-sync/utils.test.ts b/packages/app/src/runtime/server/global-sync/utils.test.ts
index 2a39fce84f0c..ec8ee8dc0168 100644
--- a/packages/app/src/runtime/server/global-sync/utils.test.ts
+++ b/packages/app/src/runtime/server/global-sync/utils.test.ts
@@ -48,7 +48,7 @@ describe("normalizeProviderList", () => {
           modelID: "gpt-5",
           providerID: "openai",
           name: "GPT-5",
-          capabilities: { tools: true, input: ["text", "image"], output: ["text"] },
+          capabilities: { tools: true, reasoning: true, input: ["text", "image"], output: ["text"] },
           variants: [{ id: "high" }],
           time: { released: 1 },
           cost: [{ input: 1, output: 2, cache: { read: 0.1, write: 0.2 } }],
@@ -69,6 +69,19 @@ describe("normalizeProviderList", () => {
           enabled: true,
           limit: { context: 1, output: 1 },
         },
+        {
+          id: "gpt-classic",
+          modelID: "gpt-classic",
+          providerID: "openai",
+          name: "GPT Classic",
+          capabilities: { tools: true, input: ["text"], output: ["text"] },
+          variants: [],
+          time: { released: 0 },
+          cost: [],
+          status: "active",
+          enabled: true,
+          limit: { context: 1, output: 1 },
+        },
       ] as ModelListOutput["data"],
     )
 
@@ -78,10 +91,12 @@ describe("normalizeProviderList", () => {
     expect(result.all.get("openai")?.models["gpt-5"]).toMatchObject({
       id: "gpt-5",
       providerID: "openai",
-      capabilities: { toolcall: true, attachment: true },
+      capabilities: { toolcall: true, attachment: true, reasoning: true },
       cost: { input: 1, output: 2 },
       variants: { high: {} },
     })
+    // Models without a catalog reasoning flag map to false instead of being hardcoded
+    expect(result.all.get("openai")?.models["gpt-classic"]?.capabilities.reasoning).toBe(false)
   })
 })
 
diff --git a/packages/app/src/runtime/server/global-sync/utils.ts b/packages/app/src/runtime/server/global-sync/utils.ts
index af36458c609d..652693aa6c62 100644
--- a/packages/app/src/runtime/server/global-sync/utils.ts
+++ b/packages/app/src/runtime/server/global-sync/utils.ts
@@ -79,7 +79,7 @@ export function normalizeProviderList(
       family: model.family,
       capabilities: {
         temperature: false,
-        reasoning: false,
+        reasoning: model.capabilities.reasoning ?? false,
         attachment: model.capabilities.input.some((item) => item !== "text"),
         toolcall: model.capabilities.tools,
         input: {
diff --git a/packages/client/src/promise/generated/types.ts b/packages/client/src/promise/generated/types.ts
index f5db7ce7e535..0c59a085f52e 100644
--- a/packages/client/src/promise/generated/types.ts
+++ b/packages/client/src/promise/generated/types.ts
@@ -186,7 +186,13 @@ export type ModelCacheFormat = "anthropic" | "alibaba"
 
 export type ModelMediaInput = "assets" | "state" | "root"
 
-export type ModelCapabilities = { tools: boolean; input: Array<string>; output: Array<string>; temperature?: boolean }
+export type ModelCapabilities = {
+  tools: boolean
+  reasoning?: boolean
+  input: Array<string>
+  output: Array<string>
+  temperature?: boolean
+}
 
 export type MoneyUSDPerMillionTokens = number
 
diff --git a/packages/core/src/model.ts b/packages/core/src/model.ts
index 0640ba8a01b4..e597d0a19c32 100644
--- a/packages/core/src/model.ts
+++ b/packages/core/src/model.ts
@@ -29,13 +29,19 @@ export const Capabilities = Model.Capabilities
 export type Capabilities = Model.Capabilities
 
 /** Merges partial config capabilities onto a base model's capabilities, defaulting unset fields. */
-export const mergeCapabilities = (config: Partial<Capabilities>, base: Capabilities | undefined) => {
-  const fallback = base ?? Capabilities.default()
+export const mergeCapabilities = (
+  config: Partial<Omit<Capabilities, "reasoning">> & { reasoning?: boolean | { readonly supported: boolean } },
+  base: Capabilities | undefined,
+) => {
+  const fallback: Capabilities = base ?? Capabilities.default()
+  // Config may carry the rich reasoning object; the runtime capability flag is its `supported` boolean.
+  const reasoning = typeof config.reasoning === "object" ? config.reasoning.supported : config.reasoning
   return {
     tools: config.tools ?? fallback.tools,
     input: [...(config.input ?? fallback.input)],
     output: [...(config.output ?? fallback.output)],
     temperature: config.temperature ?? base?.temperature,
+    reasoning: reasoning ?? fallback.reasoning,
   }
 }
 
diff --git a/packages/core/src/models-dev.ts b/packages/core/src/models-dev.ts
index 79d85807a953..bf18885b807e 100644
--- a/packages/core/src/models-dev.ts
+++ b/packages/core/src/models-dev.ts
@@ -441,6 +441,7 @@ function modelInfo(
     settings: Object.keys(settings).length === 0 ? undefined : settings,
     capabilities: {
       tools: model.capabilities.tools.supported,
+      reasoning: model.capabilities.reasoning.supported,
       input: modalities(model.modalities.input),
       output: modalities(model.modalities.output),
       temperature: model.capabilities.temperature,
diff --git a/packages/core/src/v1/config/migrate.ts b/packages/core/src/v1/config/migrate.ts
index b64cbea4758c..c7f9a87c811f 100644
--- a/packages/core/src/v1/config/migrate.ts
+++ b/packages/core/src/v1/config/migrate.ts
@@ -225,9 +225,13 @@ function migrateModel(info: typeof ConfigProviderV1.Model.Type, npm: string | un
   ]
   const defaults = Model.Capabilities.default()
   const capabilities =
-    info.tool_call !== undefined || info.modalities?.input !== undefined || info.modalities?.output !== undefined
+    info.tool_call !== undefined ||
+    info.modalities?.input !== undefined ||
+    info.modalities?.output !== undefined ||
+    info.reasoning !== undefined
       ? {
           tools: info.tool_call ?? defaults.tools,
+          ...(info.reasoning === undefined ? {} : { reasoning: { supported: info.reasoning } }),
           input: info.modalities?.input ?? defaults.input,
           output: info.modalities?.output ?? defaults.output,
         }
diff --git a/packages/core/test/config/config.test.ts b/packages/core/test/config/config.test.ts
index e28cce00d3a5..cdee953c954f 100644
--- a/packages/core/test/config/config.test.ts
+++ b/packages/core/test/config/config.test.ts
@@ -1229,6 +1229,34 @@ describe("Config", () => {
     })
   })
 
+  test("preserves a model's declared reasoning through the v1 provider migration", () => {
+    const migrated = migrateV1({
+      provider: {
+        localtest: {
+          npm: "@ai-sdk/openai-compatible",
+          models: {
+            "glm-flash": { name: "GLM Flash", reasoning: true },
+            "plain-model": { name: "Plain Model", tool_call: true },
+            silent: { name: "Silent" },
+          },
+        },
+      },
+    })
+
+    expect(migrated.providers?.localtest?.models?.["glm-flash"]?.capabilities).toEqual({
+      tools: true,
+      reasoning: { supported: true },
+      input: ["text", "image"],
+      output: ["text"],
+    })
+    expect(migrated.providers?.localtest?.models?.["plain-model"]?.capabilities).toEqual({
+      tools: true,
+      input: ["text", "image"],
+      output: ["text"],
+    })
+    expect(migrated.providers?.localtest?.models?.silent?.capabilities).toBeUndefined()
+  })
+
   test("renames old provider IDs while migrating v1 configuration", () => {
     const migrated = migrateV1({
       model: "azure-cognitive-services/deployment",
diff --git a/packages/core/test/config/provider.test.ts b/packages/core/test/config/provider.test.ts
index 2acd4a9e3c88..ef4ea642bffd 100644
--- a/packages/core/test/config/provider.test.ts
+++ b/packages/core/test/config/provider.test.ts
@@ -543,6 +543,42 @@ describe("ConfigProviderPlugin.Plugin", () => {
     }),
   )
 
+  it.effect("keeps a config-declared reasoning capability", () =>
+    Effect.gen(function* () {
+      const providers = yield* Provider.Service
+      const models = yield* Model.Service
+      const providerID = Provider.ID.make("custom")
+      const modelID = Model.ID.make("reasoning")
+      yield* providers.transform((editor) => {
+        editor.models.update(providerID, modelID, (model) => {
+          model.capabilities = { tools: false, input: ["text"], output: ["text"] }
+        })
+      })
+      const entries = [
+        new Document({
+          type: "document",
+          info: decode({
+            providers: {
+              custom: {
+                package: "aisdk:@ai-sdk/openai-compatible",
+                models: { reasoning: { capabilities: { reasoning: { supported: true } } } },
+              },
+            },
+          }),
+        }),
+      ]
+
+      yield* addPlugin(entries)
+
+      expect((yield* models.get(providerID, modelID))?.capabilities).toEqual({
+        tools: false,
+        reasoning: true,
+        input: ["text"],
+        output: ["text"],
+      })
+    }),
+  )
+
   it.effect("resolves a config model with only input/output capabilities using default tools", () =>
     Effect.gen(function* () {
       const models = yield* Model.Service
diff --git a/packages/core/test/models.test.ts b/packages/core/test/models.test.ts
index b9a3801a2f5e..9952e5021aca 100644
--- a/packages/core/test/models.test.ts
+++ b/packages/core/test/models.test.ts
@@ -92,7 +92,7 @@ const fixtureSnapshot = [
         family: undefined,
         package: undefined,
         settings: { provider: "acme" },
-        capabilities: { tools: true, input: ["text"], output: ["text"], temperature: true },
+        capabilities: { tools: true, reasoning: false, input: ["text"], output: ["text"], temperature: true },
         variants: [],
         time: { released: Date.parse("2026-01-01") },
         cost: zeroCost,
@@ -143,7 +143,7 @@ const fixture2Snapshot = [
         family: undefined,
         package: undefined,
         settings: { provider: "beta" },
-        capabilities: { tools: false, input: ["text"], output: ["text"], temperature: false },
+        capabilities: { tools: false, reasoning: false, input: ["text"], output: ["text"], temperature: false },
         variants: [],
         time: { released: Date.parse("2026-02-01") },
         cost: zeroCost,
diff --git a/packages/protocol/openapi.json b/packages/protocol/openapi.json
index 1789c459277b..05c944da129a 100644
--- a/packages/protocol/openapi.json
+++ b/packages/protocol/openapi.json
@@ -18952,6 +18952,9 @@
           "tools": {
             "type": "boolean"
           },
+          "reasoning": {
+            "type": "boolean"
+          },
           "input": {
             "type": "array",
             "items": {
diff --git a/packages/schema/src/model.ts b/packages/schema/src/model.ts
index 8d198338b1f4..d43da3c3c10d 100644
--- a/packages/schema/src/model.ts
+++ b/packages/schema/src/model.ts
@@ -77,6 +77,7 @@ export const Overlays = {
 export interface Capabilities extends Schema.Schema.Type<typeof Capabilities> {}
 export const Capabilities = Schema.Struct({
   tools: Schema.Boolean,
+  reasoning: optional(Schema.Boolean),
   input: Schema.Array(Schema.String),
   output: Schema.Array(Schema.String),
   /** Whether the model accepts a sampling temperature. Unknown when unset. */