fix: recover OpenAI text-only image rejections

OpenAI-compatible chat proxies serialize user images as image_url parts. Text-only upstreams such as DeepSeek-compatible endpoints can reject that schema before the model can respond, so classify the schema rejection as the existing unsupported-image condition and let the media recovery path strip the offending image on later turns.

Constraint: OpenAI-compatible providers vary in whether content parts accept image_url; text-only endpoints can fail during request deserialization.

Rejected: Strip images before every OpenAI-compatible request | would break vision-capable OpenAI-compatible models and silently remove user input.

Confidence: high

Scope-risk: narrow

Directive: Do not broaden this to strip OpenAI image parts preflight unless provider/model vision capability is explicitly modeled.

Tested: bun test src/services/api/errors.test.ts

Tested: bun test tests/mediaRecoveryAndEstimation.test.ts

Tested: bun test src/server/__tests__/proxy-transform.test.ts

Tested: bun run check:server

Not-tested: Live DeepSeek proxy request with real image credentials.

src/services/api/errors.test.ts

@@ -17,6 +17,11 @@ describe('image unsupported API errors', () => {
         'unsupported modality: image input is not available',
       ),
     ).toBe(true)
+    expect(
+      isUnsupportedImageInputErrorMessage(
+        'Failed to deserialize the JSON body into the target type: messages[1]: unknown variant `image_url`, expected `text` at line 1 column 394097',
+      ),
+    ).toBe(true)
     expect(isUnsupportedImageInputErrorMessage('image exceeds maximum')).toBe(false)
   })
 

src/services/api/errors.ts

@@ -430,6 +430,9 @@ export function extractUnknownErrorFormat(value: unknown): string | undefined {
 export function isUnsupportedImageInputErrorMessage(message: string): boolean {
   const raw = message.toLowerCase()
   if (!raw.includes('image')) return false
+  if (raw.includes('image_url') && raw.includes('expected') && raw.includes('text')) {
+    return true
+  }
   return (
     raw.includes('not support') ||
     raw.includes('not supported') ||