diff --git a/src/backend/drivers/ai-chat/providers/claude/ClaudeProvider.test.ts b/src/backend/drivers/ai-chat/providers/claude/ClaudeProvider.test.ts
index 3e928fcbc..89dfd8aa7 100644
--- a/src/backend/drivers/ai-chat/providers/claude/ClaudeProvider.test.ts
+++ b/src/backend/drivers/ai-chat/providers/claude/ClaudeProvider.test.ts
@@ -790,7 +790,12 @@ describe('ClaudeProvider.complete request shape', () => {
         });
     });
 
-    it.each(['claude-fable-5-1', 'claude-opus-5-5', 'claude-sonnet-5'])(
+    it.each([
+        'claude-fable-5-1',
+        'claude-opus-5-5',
+        'claude-sonnet-5-5',
+        'claude-sonnet-5',
+    ])(
         'omits temperature for %s',
         async (model) => {
             const { provider } = makeProvider();
@@ -809,7 +814,12 @@ describe('ClaudeProvider.complete request shape', () => {
         },
     );
 
-    it.each(['claude-fable-5-1', 'claude-opus-5-5', 'claude-sonnet-5'])(
+    it.each([
+        'claude-fable-5-1',
+        'claude-opus-5-5',
+        'claude-sonnet-5-5',
+        'claude-sonnet-5',
+    ])(
         'uses adaptive thinking and output effort on %s',
         async (model) => {
             const { provider } = makeProvider();
@@ -941,7 +951,23 @@ describe('ClaudeProvider model resolution', () => {
         );
     });
 
-    it('falls back to the default model when given an unknown id', async () => {
+    it('routes the bare claude-sonnet alias to sonnet 5.5 rather than sonnet 5', async () => {
+        const { provider } = makeProvider();
+        messagesCreateMock.mockResolvedValueOnce(baseResponse);
+
+        await withTestActor(() =>
+            provider.complete({
+                model: 'claude-sonnet',
+                messages: [{ role: 'user', content: 'hi' }],
+            }),
+        );
+
+        expect(messagesCreateMock.mock.calls[0]![0].model).toBe(
+            'claude-sonnet-5-5',
+        );
+    });
+
+        it('falls back to the default model when given an unknown id', async () => {
         const { provider } = makeProvider();
         messagesCreateMock.mockResolvedValueOnce(baseResponse);
 
@@ -975,6 +1001,9 @@ describe('ClaudeProvider.complete non-stream output', () => {
         ['claude-opus', 'claude-opus-5-5', 400, 500, 800, 20, 2000],
         ['claude-opus-latest', 'claude-opus-5-5', 400, 500, 800, 20, 2000],
         ['claude-opus-5-latest', 'claude-opus-5', 500, 625, 1000, 50, 2500],
+        ['claude-sonnet-5-5', 'claude-sonnet-5-5', 200, 250, 400, 20, 1000],
+        ['claude-sonnet', 'claude-sonnet-5-5', 200, 250, 400, 20, 1000],
+        ['claude-sonnet-latest', 'claude-sonnet-5-5', 200, 250, 400, 20, 1000],
         ['claude-sonnet-5', 'claude-sonnet-5', 200, 250, 400, 20, 1000],
     ])(
         'resolves and meters %s at its current rates',
diff --git a/src/backend/drivers/ai-chat/providers/claude/ClaudeProvider.ts b/src/backend/drivers/ai-chat/providers/claude/ClaudeProvider.ts
index e6e9adcec..ff88f533c 100644
--- a/src/backend/drivers/ai-chat/providers/claude/ClaudeProvider.ts
+++ b/src/backend/drivers/ai-chat/providers/claude/ClaudeProvider.ts
@@ -358,11 +358,12 @@ export class ClaudeProvider implements IChatProvider {
             reasoningEffort: requestedReasoningEffort,
             maxTokens: max_tokens,
         });
-        // Fable 5/5.1, Sonnet 5, and Opus 4.7+ reject non-default sampling; omit temperature entirely.
+        // Fable 5/5.1, Sonnet 5/5.5, and Opus 4.7+ reject non-default sampling; omit temperature entirely.
         // Other models require temperature=1 when thinking is enabled.
         const omitsTemperature = [
             'claude-fable-5-1',
             'claude-fable-5',
+            'claude-sonnet-5-5',
             'claude-sonnet-5',
             'claude-opus-4-7',
             'claude-opus-4-8',
@@ -377,6 +378,7 @@ export class ClaudeProvider implements IChatProvider {
         const supportsEffort = [
             'claude-fable-5-1',
             'claude-fable-5',
+            'claude-sonnet-5-5',
             'claude-sonnet-5',
             'claude-opus-5-5',
             'claude-opus-5',
@@ -811,6 +813,7 @@ export class ClaudeProvider implements IChatProvider {
         if (
             modelId === 'claude-fable-5-1' ||
             modelId === 'claude-fable-5' ||
+            modelId === 'claude-sonnet-5-5' ||
             modelId === 'claude-sonnet-5' ||
             modelId === 'claude-opus-5-5' ||
             modelId === 'claude-opus-5' ||
diff --git a/src/backend/drivers/ai-chat/providers/claude/models.ts b/src/backend/drivers/ai-chat/providers/claude/models.ts
index 79a146c67..ff6bceef0 100644
--- a/src/backend/drivers/ai-chat/providers/claude/models.ts
+++ b/src/backend/drivers/ai-chat/providers/claude/models.ts
@@ -74,6 +74,36 @@ export const CLAUDE_MODELS: IChatModel[] = [
         context: 1000000,
         max_tokens: 128000,
     },
+    {
+        puterId: 'anthropic:anthropic/claude-sonnet-5-5',
+        id: 'claude-sonnet-5-5',
+        modalities: { input: ['text', 'image', 'pdf'], output: ['text'] },
+        open_weights: false,
+        tool_call: true,
+        knowledge: '2026-06',
+        release_date: '2026-09-28',
+        aliases: [
+            'claude-sonnet',
+            'claude-sonnet-latest',
+            'claude-sonnet-5-5-latest',
+            'claude-sonnet-5.5',
+            'anthropic/claude-sonnet-5-5',
+        ],
+        name: 'Claude Sonnet 5.5',
+        costs_currency: 'usd-cents',
+        input_cost_key: 'input_tokens',
+        output_cost_key: 'output_tokens',
+        costs: {
+            tokens: 1_000_000,
+            input_tokens: 200,
+            ephemeral_5m_input_tokens: 200 * 1.25,
+            ephemeral_1h_input_tokens: 200 * 2,
+            cache_read_input_tokens: 200 * 0.1,
+            output_tokens: 1000,
+        },
+        context: 1000000,
+        max_tokens: 128000,
+    },
     {
         puterId: 'anthropic:anthropic/claude-sonnet-5',
         id: 'claude-sonnet-5',
@@ -82,12 +112,7 @@ export const CLAUDE_MODELS: IChatModel[] = [
         tool_call: true,
         knowledge: '2026-01',
         release_date: '2026-06-30',
-        aliases: [
-            'claude-sonnet',
-            'claude-sonnet-latest',
-            'claude-sonnet-5-latest',
-            'anthropic/claude-sonnet-5',
-        ],
+        aliases: ['claude-sonnet-5-latest', 'anthropic/claude-sonnet-5'],
         name: 'Claude Sonnet 5',
         costs_currency: 'usd-cents',
         input_cost_key: 'input_tokens',