diff --git a/web/src/app/api/v1/chat/completions/__tests__/completions.test.ts b/web/src/app/api/v1/chat/completions/__tests__/completions.test.ts
index 99c1e559a..a5a91dee0 100644
--- a/web/src/app/api/v1/chat/completions/__tests__/completions.test.ts
+++ b/web/src/app/api/v1/chat/completions/__tests__/completions.test.ts
@@ -779,6 +779,10 @@ describe('/api/v1/chat/completions POST endpoint', () => {
         const fetchedUrls: string[] = []
         const fetchViaDeepSeek = mock(
           async (url: string | URL | Request, init?: RequestInit) => {
+            if (String(url).startsWith('https://api.ipinfo.io/lookup/')) {
+              return Response.json({})
+            }
+
             fetchedUrls.push(String(url))
             fetchedBodies.push(JSON.parse(init?.body as string))
             return new Response(
diff --git a/web/src/llm-api/__tests__/deepseek-image-compat.integration.test.ts b/web/src/llm-api/__tests__/deepseek-image-compat.integration.test.ts
new file mode 100644
index 000000000..35ba1957b
--- /dev/null
+++ b/web/src/llm-api/__tests__/deepseek-image-compat.integration.test.ts
@@ -0,0 +1,113 @@
+import { describe, expect, it } from 'bun:test'
+
+import {
+  buildDeepSeekRequestBody,
+  normalizeDeepSeekRequestBody,
+} from '../deepseek-request-body'
+
+import type { ChatCompletionRequestBody } from '../types'
+
+describe('normalizeDeepSeekRequestBody', () => {
+  it('converts multimodal user content into DeepSeek text content without mutating input', () => {
+    const body: ChatCompletionRequestBody = {
+      model: 'deepseek/deepseek-v4-pro',
+      messages: [
+        {
+          role: 'user',
+          content: [
+            { type: 'text', text: 'What is in this image?' },
+            {
+              type: 'image_url',
+              image_url: { url: 'data:image/png;base64,AAECAw==' },
+            },
+          ],
+        },
+      ],
+    }
+
+    const normalized = normalizeDeepSeekRequestBody(body)
+
+    expect(normalized.messages[0].content).toBe(
+      'What is in this image?\n\n[1 image was omitted because the DeepSeek API does not support image input.]',
+    )
+    expect(body.messages[0].content).toEqual([
+      { type: 'text', text: 'What is in this image?' },
+      {
+        type: 'image_url',
+        image_url: { url: 'data:image/png;base64,AAECAw==' },
+      },
+    ])
+  })
+
+  it('keeps text-only messages unchanged', () => {
+    const body: ChatCompletionRequestBody = {
+      model: 'deepseek/deepseek-v4-pro',
+      messages: [{ role: 'user', content: 'Hello' }],
+    }
+
+    expect(normalizeDeepSeekRequestBody(body)).toEqual({
+      ...body,
+      model: 'deepseek-v4-pro',
+    })
+  })
+
+  it('does not throw on minimal provider-path bodies without messages', () => {
+    const body = {
+      model: 'deepseek/deepseek-v4-pro',
+      stream: false,
+    } as ChatCompletionRequestBody
+
+    expect(normalizeDeepSeekRequestBody(body)).toEqual({
+      ...body,
+      model: 'deepseek-v4-pro',
+    })
+  })
+})
+
+describe('buildDeepSeekRequestBody', () => {
+  it('builds DeepSeek-compatible JSON when the request contains an image attachment', () => {
+    const body: ChatCompletionRequestBody = {
+      model: 'deepseek/deepseek-v4-pro',
+      messages: [
+        { role: 'system', content: 'You are a coding assistant.' },
+        {
+          role: 'user',
+          content: [
+            { type: 'text', text: 'Please inspect this screenshot.' },
+            {
+              type: 'image_url',
+              image_url: { url: 'data:image/jpeg;base64,/9j/4AAQSkZJRg==' },
+            },
+          ],
+        },
+      ],
+      stream: true,
+      reasoning: { enabled: true, effort: 'medium' },
+      provider: { order: ['DeepSeek'] },
+      transforms: ['middle-out'],
+      codebuff_metadata: { run_id: 'run-1', cost_mode: 'free' },
+      usage: { include: true },
+    }
+
+    const sentBody = buildDeepSeekRequestBody(body, body.model)
+
+    expect(sentBody).toMatchObject({
+      model: 'deepseek-v4-pro',
+      stream: true,
+      stream_options: { include_usage: true },
+      thinking: { type: 'enabled', reasoning_effort: 'high' },
+    })
+    expect(sentBody).not.toHaveProperty('reasoning')
+    expect(sentBody).not.toHaveProperty('provider')
+    expect(sentBody).not.toHaveProperty('transforms')
+    expect(sentBody).not.toHaveProperty('codebuff_metadata')
+    expect(sentBody).not.toHaveProperty('usage')
+
+    const messages = sentBody.messages as Array<{ content: string }>
+    expect(messages[1].content).toBe(
+      'Please inspect this screenshot.\n\n[1 image was omitted because the DeepSeek API does not support image input.]',
+    )
+    expect(JSON.stringify(sentBody)).not.toContain('image_url')
+    expect(JSON.stringify(body)).toContain('image_url')
+  })
+})
diff --git a/web/src/llm-api/deepseek-request-body.ts b/web/src/llm-api/deepseek-request-body.ts
new file mode 100644
index 000000000..582e690ef
--- /dev/null
+++ b/web/src/llm-api/deepseek-request-body.ts
@@ -0,0 +1,139 @@
+import { deepseekModels } from '@codebuff/common/constants/model-config'
+
+import type { ChatCompletionRequestBody } from './types'
+
+export const DEEPSEEK_MODEL_IDS: Record<string, string> = {
+  [deepseekModels.deepseekV4ProDirect]: deepseekModels.deepseekV4ProDirect,
+  [deepseekModels.deepseekV4Pro]: deepseekModels.deepseekV4ProDirect,
+}
+
+export function getDeepSeekModelId(openrouterModel: string): string {
+  return DEEPSEEK_MODEL_IDS[openrouterModel] ?? openrouterModel
+}
+
+function toDeepSeekReasoningEffort(effort: unknown): 'high' | 'max' {
+  return effort === 'max' || effort === 'xhigh' ? 'max' : 'high'
+}
+
+function unsupportedAttachmentNotice(kind: string, count: number): string {
+  const noun = count === 1 ? kind : `${kind}s`
+  const verb = count === 1 ? 'was' : 'were'
+  return `[${count} ${noun} ${verb} omitted because the DeepSeek API does not support ${kind} input.]`
+}
+
+function contentPartsToDeepSeekText(
+  content: NonNullable<
+    ChatCompletionRequestBody['messages'][number]['content']
+  >,
+): string {
+  if (!Array.isArray(content)) {
+    return content
+  }
+
+  const textParts: string[] = []
+  let imageCount = 0
+  let fileCount = 0
+  let unsupportedCount = 0
+
+  for (const part of content) {
+    switch (part.type) {
+      case 'text': {
+        if (typeof part.text === 'string' && part.text.length > 0) {
+          textParts.push(part.text)
+        }
+        break
+      }
+      case 'image_url': {
+        imageCount += 1
+        break
+      }
+      case 'file': {
+        fileCount += 1
+        break
+      }
+      default: {
+        unsupportedCount += 1
+        break
+      }
+    }
+  }
+
+  if (imageCount > 0) {
+    textParts.push(unsupportedAttachmentNotice('image', imageCount))
+  }
+  if (fileCount > 0) {
+    textParts.push(unsupportedAttachmentNotice('file', fileCount))
+  }
+  if (unsupportedCount > 0) {
+    textParts.push(
+      unsupportedAttachmentNotice('unsupported content part', unsupportedCount),
+    )
+  }
+
+  return textParts.join('\n\n')
+}
+
+export function normalizeDeepSeekRequestBody(
+  body: ChatCompletionRequestBody,
+  originalModel: string = body.model,
+): ChatCompletionRequestBody {
+  const messages = Array.isArray(body.messages)
+    ? body.messages.map((message) => ({
+        ...message,
+        content:
+          message.content === undefined || message.content === null
+            ? message.content
+            : contentPartsToDeepSeekText(message.content),
+      }))
+    : body.messages
+
+  return {
+    ...body,
+    model: getDeepSeekModelId(originalModel),
+    messages,
+  }
+}
+
+export function buildDeepSeekRequestBody(
+  body: ChatCompletionRequestBody,
+  originalModel: string = body.model,
+): Record<string, unknown> {
+  const deepseekBody = normalizeDeepSeekRequestBody(
+    body,
+    originalModel,
+  ) as unknown as Record<string, unknown>
+
+  // DeepSeek uses `thinking` instead of OpenRouter's `reasoning`.
+  if (deepseekBody.reasoning && typeof deepseekBody.reasoning === 'object') {
+    const reasoning = deepseekBody.reasoning as {
+      enabled?: boolean
+      effort?: 'high' | 'medium' | 'low'
+    }
+    deepseekBody.thinking = {
+      type: reasoning.enabled === false ? 'disabled' : 'enabled',
+      reasoning_effort: toDeepSeekReasoningEffort(reasoning.effort),
+    }
+  } else if (deepseekBody.reasoning_effort) {
+    deepseekBody.thinking = {
+      type: 'enabled',
+      reasoning_effort: toDeepSeekReasoningEffort(
+        deepseekBody.reasoning_effort,
+      ),
+    }
+  }
+  delete deepseekBody.reasoning
+  delete deepseekBody.reasoning_effort
+
+  // Strip OpenRouter-specific / internal fields.
+  delete deepseekBody.provider
+  delete deepseekBody.transforms
+  delete deepseekBody.codebuff_metadata
+  delete deepseekBody.usage
+
+  // For streaming, request usage in the final chunk.
+  if (deepseekBody.stream) {
+    deepseekBody.stream_options = { include_usage: true }
+  }
+
+  return deepseekBody
+}
diff --git a/web/src/llm-api/deepseek.ts b/web/src/llm-api/deepseek.ts
index 12ac66265..037851410 100644
--- a/web/src/llm-api/deepseek.ts
+++ b/web/src/llm-api/deepseek.ts
@@ -1,6 +1,5 @@
 import { Agent } from 'undici'
 
-import { deepseekModels } from '@codebuff/common/constants/model-config'
 import { PROFIT_MARGIN } from '@codebuff/common/constants/limits'
 import { getErrorObject } from '@codebuff/common/util/error'
 import { env } from '@codebuff/internal/env'
@@ -10,6 +9,10 @@ import {
   extractRequestMetadata,
   insertMessageToBigQuery,
 } from './helpers'
+import {
+  buildDeepSeekRequestBody,
+  DEEPSEEK_MODEL_IDS,
+} from './deepseek-request-body'
 
 import type { UsageData } from './helpers'
 import type { InsertMessageBigqueryFn } from '@codebuff/common/types/contracts/bigquery'
@@ -40,21 +43,18 @@ const DEEPSEEK_V4_PRO_PRICING: DeepSeekPricing = {
   outputCostPerToken: 0.87 / 1_000_000,
 }
 
-/** Single source of truth for DeepSeek model metadata and pricing.
- *  Kept as one map so adding a model can't drift between routing and billing. */
 const DEEPSEEK_MODELS: Record<
   string,
   { deepseekId: string; pricing: DeepSeekPricing }
-> = {
-  [deepseekModels.deepseekV4ProDirect]: {
-    deepseekId: deepseekModels.deepseekV4ProDirect,
-    pricing: DEEPSEEK_V4_PRO_PRICING,
-  },
-  [deepseekModels.deepseekV4Pro]: {
-    deepseekId: deepseekModels.deepseekV4ProDirect,
-    pricing: DEEPSEEK_V4_PRO_PRICING,
-  },
-}
+> = Object.fromEntries(
+  Object.entries(DEEPSEEK_MODEL_IDS).map(([model, deepseekId]) => [
+    model,
+    {
+      deepseekId,
+      pricing: DEEPSEEK_V4_PRO_PRICING,
+    },
+  ]),
+)
 
 const DEEPSEEK_ROUTED_MODELS = new Set<string>(Object.keys(DEEPSEEK_MODELS))
 
@@ -62,10 +62,6 @@ export function isDeepSeekModel(model: string): boolean {
   return DEEPSEEK_ROUTED_MODELS.has(model)
 }
 
-function getDeepSeekModelId(openrouterModel: string): string {
-  return DEEPSEEK_MODELS[openrouterModel]?.deepseekId ?? openrouterModel
-}
-
 function getDeepSeekPricing(model: string): DeepSeekPricing {
   const entry = DEEPSEEK_MODELS[model]
   if (!entry) {
@@ -87,52 +83,13 @@ type LineResult = {
   patchedLine: string
 }
 
-function toDeepSeekReasoningEffort(effort: unknown): 'high' | 'max' {
-  return effort === 'max' || effort === 'xhigh' ? 'max' : 'high'
-}
-
-function createDeepSeekRequest(params: {
+export function createDeepSeekRequest(params: {
   body: ChatCompletionRequestBody
   originalModel: string
   fetch: typeof globalThis.fetch
 }) {
   const { body, originalModel, fetch } = params
-  const deepseekBody: Record<string, unknown> = {
-    ...body,
-    model: getDeepSeekModelId(originalModel),
-  }
-
-  // DeepSeek uses `thinking` instead of OpenRouter's `reasoning`.
-  if (deepseekBody.reasoning && typeof deepseekBody.reasoning === 'object') {
-    const reasoning = deepseekBody.reasoning as {
-      enabled?: boolean
-      effort?: 'high' | 'medium' | 'low'
-    }
-    deepseekBody.thinking = {
-      type: reasoning.enabled === false ? 'disabled' : 'enabled',
-      reasoning_effort: toDeepSeekReasoningEffort(reasoning.effort),
-    }
-  } else if (deepseekBody.reasoning_effort) {
-    deepseekBody.thinking = {
-      type: 'enabled',
-      reasoning_effort: toDeepSeekReasoningEffort(
-        deepseekBody.reasoning_effort,
-      ),
-    }
-  }
-  delete deepseekBody.reasoning
-  delete deepseekBody.reasoning_effort
-
-  // Strip OpenRouter-specific / internal fields
-  delete deepseekBody.provider
-  delete deepseekBody.transforms
-  delete deepseekBody.codebuff_metadata
-  delete deepseekBody.usage
-
-  // For streaming, request usage in the final chunk
-  if (deepseekBody.stream) {
-    deepseekBody.stream_options = { include_usage: true }
-  }
+  const deepseekBody = buildDeepSeekRequestBody(body, originalModel)
 
   if (!env.DEEPSEEK_API_KEY) {
     throw new Error('DEEPSEEK_API_KEY is not configured')
diff --git a/web/src/llm-api/types.ts b/web/src/llm-api/types.ts
index 66a3425a5..3c8500bdb 100644
--- a/web/src/llm-api/types.ts
+++ b/web/src/llm-api/types.ts
@@ -15,7 +15,7 @@ export interface CodebuffMetadata {
 
 export interface ChatMessage {
   role: 'system' | 'user' | 'assistant' | 'tool'
-  content?: string | null
+  content?: string | ChatCompletionContentPart[] | null
   name?: string
   tool_calls?: Array<{
     id: string
@@ -28,6 +28,27 @@ export interface ChatMessage {
   tool_call_id?: string
 }
 
+export type ChatCompletionContentPart =
+  | {
+      type: 'text'
+      text?: string
+    }
+  | {
+      type: 'image_url'
+      image_url?: string | { url?: string }
+    }
+  | {
+      type: 'file'
+      file?: {
+        filename?: string
+        file_data?: string
+      }
+    }
+  | {
+      type: string
+      [key: string]: unknown
+    }
+
 export interface ChatCompletionTool {
   id?: string
   type: string