diff --git a/src/config/index.mjs b/src/config/index.mjs
index abd174a67..5941704c7 100644
--- a/src/config/index.mjs
+++ b/src/config/index.mjs
@@ -91,6 +91,8 @@ export const customApiModelKeys = ['customModel']
 export const ollamaApiModelKeys = ['ollamaModel']
 export const azureOpenAiApiModelKeys = ['azureOpenAi']
 export const claudeApiModelKeys = [
+  'claudeFable51Api',
+  'claudeFable5Api',
   'claudeOpus41Api',
   'claudeOpus45Api',
   'claudeOpus46Api',
@@ -338,6 +340,14 @@ export const Models = {
   chatgptApi4_1_nano: { value: 'gpt-4.1-nano', desc: 'OpenAI (GPT-4.1 nano)' },
 
   claude2WebFree: { value: '', desc: 'Claude.ai (Web)' },
+  claudeFable51Api: {
+    value: 'claude-fable-5-1',
+    desc: 'Anthropic (Claude Fable 5.1)',
+  },
+  claudeFable5Api: {
+    value: 'claude-fable-5',
+    desc: 'Anthropic (Claude Fable 5)',
+  },
   claudeOpus41Api: {
     value: 'claude-opus-4-1-20250805',
     desc: 'Anthropic (Claude Opus 4.1)',
@@ -751,6 +761,7 @@ export const defaultApiModeIds = [
   'chatgptApi5_6Luna',
   'xaiGrok4_6',
   'xaiGrok4_5',
+  'claudeFable51Api',
   'claudeOpus5Api',
   'claudeSonnet5Api',
   'claudeHaiku45Api',
diff --git a/src/services/apis/temperature-params.mjs b/src/services/apis/temperature-params.mjs
index fb9693e7e..69d7f96e7 100644
--- a/src/services/apis/temperature-params.mjs
+++ b/src/services/apis/temperature-params.mjs
@@ -3,6 +3,8 @@ const MODELS_WITHOUT_CUSTOM_TEMPERATURE = new Set([
   'claude-opus-4-8',
   'claude-sonnet-5',
   'claude-opus-5',
+  'claude-fable-5',
+  'claude-fable-5-1',
 ])
 
 function normalizeModelId(model) {
diff --git a/tests/unit/services/apis/claude-fable-api.test.mjs b/tests/unit/services/apis/claude-fable-api.test.mjs
new file mode 100644
index 000000000..1daedfd61
--- /dev/null
+++ b/tests/unit/services/apis/claude-fable-api.test.mjs
@@ -0,0 +1,59 @@
+import assert from 'node:assert/strict'
+import { beforeEach, test } from 'node:test'
+import { generateAnswersWithClaudeApi } from '../../../../src/services/apis/claude-api.mjs'
+import { createFakePort } from '../../helpers/port.mjs'
+import { createMockSseResponse } from '../../helpers/sse-response.mjs'
+
+const setStorage = (values) => {
+  globalThis.__TEST_BROWSER_SHIM__.replaceStorage(values)
+}
+
+beforeEach(() => {
+  globalThis.__TEST_BROWSER_SHIM__.clearStorage()
+})
+
+test('claude-api: supports Fable models with adaptive thinking defaults', async (t) => {
+  t.mock.method(console, 'debug', () => {})
+
+  for (const [modelName, model] of [
+    ['claudeFable5Api', 'claude-fable-5'],
+    ['claudeFable51Api', 'claude-fable-5-1'],
+  ]) {
+    await t.test(modelName, async (t) => {
+      setStorage({
+        customClaudeApiUrl: 'https://api.anthropic.com',
+        claudeApiKey: 'sk-ant-test',
+        maxConversationContextLength: 3,
+        maxResponseTokenLength: 1024,
+        temperatureOverrideEnabled: true,
+        temperature: 0.9,
+      })
+
+      const session = {
+        modelName,
+        conversationRecords: [],
+        isRetry: false,
+      }
+      const port = createFakePort()
+
+      let capturedInit
+      t.mock.method(globalThis, 'fetch', async (_input, init) => {
+        capturedInit = init
+        return createMockSseResponse([
+          'data: {"type":"content_block_delta","delta":{"type":"text_delta","text":"OK"}}\n\n',
+          'data: {"type":"message_delta","delta":{"stop_reason":"end_turn"}}\n\n',
+          'data: {"type":"message_stop"}\n\n',
+        ])
+      })
+
+      await generateAnswersWithClaudeApi(port, 'Q', session)
+
+      const body = JSON.parse(capturedInit.body)
+      assert.equal(body.model, model)
+      assert.equal(body.max_tokens, 1024)
+      assert.equal(body.stream, true)
+      assert.equal(Object.hasOwn(body, 'temperature'), false)
+      assert.equal(Object.hasOwn(body, 'thinking'), false)
+    })
+  }
+})
diff --git a/tests/unit/services/apis/temperature-params.test.mjs b/tests/unit/services/apis/temperature-params.test.mjs
index 9358611e8..444552a61 100644
--- a/tests/unit/services/apis/temperature-params.test.mjs
+++ b/tests/unit/services/apis/temperature-params.test.mjs
@@ -35,6 +35,9 @@ test('temperature overrides omit known Anthropic models across provider ID forma
     'claude-opus-4-8-20260801',
     'claude-sonnet-5',
     'claude-opus-5',
+    'claude-fable-5',
+    'claude-fable-5-1',
+    'anthropic/claude-fable-5.1',
   ]) {
     assert.equal(canApplyTemperatureOverride(model), false, model)
     assert.deepEqual(