fix: convert media content to provider format before recording

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 Notable additions, fixes, or breaking changes to the Freeplay SDK.
 
+## [0.6.2] - 2026-03-13
+
+### Fixed
+
+- Media content in recorded messages now uses provider-formatted objects instead of internal content_part_type objects, fixing validation errors when recording prompts with media inputs.
+
 ## [0.6.1] - 2026-03-10
 
 ### Fixed

package.json

@@ -1,6 +1,6 @@
 {
   "name": "freeplay",
-  "version": "0.6.1",
+  "version": "0.6.2",
   "description": "Node.js/Typescript SDK for Freeplay AI",
   "type": "module",
   "typesVersions": {

src/resources/prompts.ts

@@ -477,12 +477,34 @@ export class BoundPrompt {
           provider: llmAdapter.provider(),
         }
       : this.promptInfo;
-    const prepared = prepareMessages(
+    let prepared = prepareMessages(
       this.messages,
       llmAdapter.roleSupport,
       finalFlavor,
     );
     const llmFormat = llmAdapter.toLLMSyntax(prepared);
+
+    // Kind of a hack: bound messages may contain internal content objects
+    // (content_part_type: "text", "media_base64", etc.) that aren't in any
+    // provider format. Ideally bind() wouldn't produce these internal objects.
+    // For now, re-run each media message through the adapter individually to
+    // get provider-formatted content while preserving messages the adapter
+    // would otherwise drop (e.g. system for Responses API).
+    prepared = prepared.map((msg) => {
+      if (
+        Array.isArray(msg.content) &&
+        msg.content.some(
+          (part: Record<string, any>) => "content_part_type" in part,
+        )
+      ) {
+        const formatted = llmAdapter.toLLMSyntax([msg]);
+        if (Array.isArray(formatted) && formatted.length > 0) {
+          return formatted[0];
+        }
+        return msg;
+      }
+      return msg;
+    });
     const llmFormatText = typeof llmFormat === "string" ? llmFormat : undefined;
     const formattedToolSchema = this.toolSchema
       ? this.formatToolSchema(this.toolSchema, finalFlavor)

test/resources/prompts.test.ts

@@ -123,6 +123,77 @@ describe("prompts", () => {
     expect(formattedPrompt.outputSchema).toEqual(outputSchema);
   });
 
+  test("media messages in allMessages have provider format, not internal content_part_type", () => {
+    const promptInfo: PromptInfo = {
+      promptTemplateId: "test-id",
+      promptTemplateVersionId: "test-version-id",
+      templateName: "test-template",
+      modelParameters: {},
+      provider: "openai",
+      model: "gpt-4o",
+      flavorName: "openai_responses",
+    };
+
+    const messages: TemplateMessage[] = [
+      { role: "system", content: "You are a helpful assistant." },
+      {
+        role: "user",
+        content: "Describe this image: {{description}}",
+        media_slots: [{ type: "image", placeholder_name: "photo" }],
+      },
+    ];
+
+    const media: MediaInputMap = {
+      photo: {
+        type: "base64",
+        content_type: "image/png",
+        data: "iVBORw0KGgoAAAANSUhEUg==",
+      },
+    };
+
+    const templatePrompt = new TemplatePrompt(promptInfo, messages);
+    const boundPrompt = templatePrompt.bind(
+      { description: "a sunset" },
+      undefined,
+      media,
+    );
+    const formattedPrompt = boundPrompt.format("openai_responses");
+
+    const completionOutput = {
+      role: "assistant",
+      content: "It shows a beautiful sunset.",
+    };
+    const allMsgs = formattedPrompt.allMessages(completionOutput);
+
+    // allMessages should be JSON-serializable (JS objects always are, but verify no cycles etc.)
+    expect(() => JSON.stringify(allMsgs)).not.toThrow();
+
+    // No content block should have the internal `content_part_type` field
+    for (const msg of allMsgs) {
+      if (Array.isArray(msg.content)) {
+        for (const block of msg.content) {
+          expect(block).not.toHaveProperty("content_part_type");
+          expect(block).not.toHaveProperty("slot_name");
+          expect(block).not.toHaveProperty("slot_type");
+        }
+      }
+    }
+
+    // System message should be preserved in allMessages
+    const systemMsg = allMsgs.find((m) => m.role === "system");
+    expect(systemMsg).toBeDefined();
+    expect(systemMsg!.content).toBe("You are a helpful assistant.");
+
+    // The user message should have provider-formatted content blocks with `type`, not `content_part_type`
+    const userMsg = allMsgs.find(
+      (m) => m.role === "user" && Array.isArray(m.content),
+    );
+    expect(userMsg).toBeDefined();
+    for (const block of userMsg!.content as Array<Record<string, any>>) {
+      expect(block).toHaveProperty("type");
+    }
+  });
+
   test("output schema with unsupported provider throws error", () => {
     const outputSchema = {
       type: "object",

test/sdk.test.ts

@@ -1634,21 +1634,18 @@ describe("Chat Completions", function () {
           role: "user",
           content: [
             {
-              content_part_type: "text",
+              type: "text",
               text: "Answer this question: How do these images look?",
             },
             {
-              content_part_type: "media_url",
-              url: "http://localhost/bird.png",
-              slot_name: "image-1",
-              slot_type: "image",
+              type: "image_url",
+              image_url: { url: "http://localhost/bird.png" },
             },
             {
-              content_part_type: "media_base64",
-              content_type: "image/png",
-              data: onePixelPng,
-              slot_name: "image-2",
-              slot_type: "image",
+              type: "image_url",
+              image_url: {
+                url: `data:image/png;base64,${onePixelPng}`,
+              },
             },
           ],
         },