fix: tweaks to transform logic for anthropic and bedrock (#26276)

packages/opencode/src/provider/transform.ts

@@ -135,9 +135,16 @@ function normalizeMessages(
         }
         if (!Array.isArray(msg.content)) return msg
         const filtered = msg.content.filter((part) => {
-          if (part.type === "text" || part.type === "reasoning") {
+          if (part.type === "text") {
             return part.text !== ""
           }
+          if (part.type === "reasoning") {
+            return (
+              part.text.trim().length > 0 ||
+              part.providerOptions?.anthropic?.signature != null ||
+              part.providerOptions?.anthropic?.redactedData != null
+            )
+          }
           return true
         })
         if (filtered.length === 0) return undefined
@@ -156,9 +163,16 @@ function normalizeMessages(
         }
         if (!Array.isArray(msg.content)) return msg
         const filtered = msg.content.filter((part) => {
-          if (part.type === "text" || part.type === "reasoning") {
+          if (part.type === "text") {
             return part.text !== ""
           }
+          if (part.type === "reasoning") {
+            return (
+              part.text.trim().length > 0 ||
+              part.providerOptions?.bedrock?.signature != null ||
+              part.providerOptions?.bedrock?.redactedData != null
+            )
+          }
           return true
         })
         if (filtered.length === 0) return undefined

packages/opencode/src/session/message-v2.ts

@@ -35,7 +35,7 @@ interface FetchDecompressionError extends Error {
   path: string
 }
 
-export const SYNTHETIC_ATTACHMENT_PROMPT = "Attached image(s) from tool result:"
+export const SYNTHETIC_ATTACHMENT_PROMPT = "Attached media from tool result:"
 export { isMedia }
 
 export const OutputLengthError = namedSchemaError("MessageOutputLengthError", {})
@@ -734,25 +734,25 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
   const result: UIMessage[] = []
   const toolNames = new Set<string>()
   // Track media from tool results that need to be injected as user messages
-  // for providers that don't support media in tool results.
+  // for providers that don't support that media type in tool results.
   //
   // OpenAI-compatible APIs only support string content in tool results, so we need
-  // to extract media and inject as user messages. Other SDKs (anthropic, google,
-  // bedrock) handle type: "content" with media parts natively.
+  // to extract media and inject as user messages. Some SDKs only support a subset
+  // of media in tool results; e.g. Bedrock supports images but not PDFs there.
   //
-  // Only apply this workaround if the model actually supports image input -
-  // otherwise there's no point extracting images.
-  const supportsMediaInToolResults = (() => {
+  // Only apply this workaround if the model actually supports that media input -
+  // otherwise unsupportedParts() will turn it into a user-visible error.
+  const supportsMediaInToolResult = (attachment: { mime: string }) => {
     if (model.api.npm === "@ai-sdk/anthropic") return true
     if (model.api.npm === "@ai-sdk/openai") return true
-    if (model.api.npm === "@ai-sdk/amazon-bedrock") return true
+    if (model.api.npm === "@ai-sdk/amazon-bedrock") return attachment.mime.startsWith("image/")
     if (model.api.npm === "@ai-sdk/google-vertex/anthropic") return true
     if (model.api.npm === "@ai-sdk/google") {
       const id = model.api.id.toLowerCase()
       return id.includes("gemini-3") && !id.includes("gemini-2")
     }
     return false
-  })()
+  }
 
   const toModelOutput = (options: { toolCallId: string; input: unknown; output: unknown }) => {
     const output = options.output
@@ -797,9 +797,9 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
         role: "user",
         parts: [],
       }
-      result.push(userMessage)
       for (const part of msg.parts) {
-        if (part.type === "text" && !part.ignored)
+        // User message parts should never be empty
+        if (part.type === "text" && !part.ignored && part.text !== "")
           userMessage.parts.push({
             type: "text",
             text: part.text,
@@ -834,11 +834,12 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
           })
         }
       }
+      if (userMessage.parts.length > 0) result.push(userMessage)
     }
 
     if (msg.info.role === "assistant") {
       const differentModel = `${model.providerID}/${model.id}` !== `${msg.info.providerID}/${msg.info.modelID}`
-      const media: Array<{ mime: string; url: string }> = []
+      const media: Array<{ mime: string; url: string; filename?: string }> = []
 
       if (
         msg.info.error &&
@@ -864,11 +865,10 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
       // a proxy, or a lower-level library, but preserving a non-empty separator
       // here is the only safe replay point we have.
       // Use a single space so the separator survives replay without changing
-      // the neighboring signed reasoning blocks. Bedrock-hosted Claude stores
-      // the same signature under the bedrock metadata namespace.
+      // the neighboring signed reasoning blocks.
       const hasSignedReasoning = msg.parts.some((part) => {
         if (part.type !== "reasoning") return false
-        return part.metadata?.anthropic?.signature != null || part.metadata?.bedrock?.signature != null
+        return part.metadata?.anthropic?.signature != null
       })
       for (const part of msg.parts) {
         if (part.type === "text") {
@@ -894,11 +894,11 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
             // For providers that don't support media in tool results, extract media files
             // (images, PDFs) to be sent as a separate user message
             const mediaAttachments = attachments.filter((a) => isMedia(a.mime))
-            const nonMediaAttachments = attachments.filter((a) => !isMedia(a.mime))
-            if (!supportsMediaInToolResults && mediaAttachments.length > 0) {
-              media.push(...mediaAttachments)
+            const extractedMedia = mediaAttachments.filter((a) => !supportsMediaInToolResult(a))
+            if (extractedMedia.length > 0) {
+              media.push(...extractedMedia)
             }
-            const finalAttachments = supportsMediaInToolResults ? attachments : nonMediaAttachments
+            const finalAttachments = attachments.filter((a) => !isMedia(a.mime) || supportsMediaInToolResult(a))
 
             const output =
               finalAttachments.length > 0
@@ -988,6 +988,7 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
                 type: "file" as const,
                 url: attachment.url,
                 mediaType: attachment.mime,
+                filename: attachment.filename,
               })),
             ],
           })

packages/opencode/test/session/message-v2.test.ts

@@ -155,6 +155,54 @@ describe("session.message-v2.toModelMessage", () => {
     expect(await MessageV2.toModelMessages(input, model)).toStrictEqual([])
   })
 
+  test("filters out user messages with only empty text parts", async () => {
+    const messageID = "m-user"
+
+    const input: MessageV2.WithParts[] = [
+      {
+        info: userInfo(messageID),
+        parts: [
+          {
+            ...basePart(messageID, "p1"),
+            type: "text",
+            text: "",
+          },
+        ] as MessageV2.Part[],
+      },
+    ]
+
+    expect(await MessageV2.toModelMessages(input, model)).toStrictEqual([])
+  })
+
+  test("filters empty user text parts while keeping non-empty parts", async () => {
+    const messageID = "m-user"
+
+    const input: MessageV2.WithParts[] = [
+      {
+        info: userInfo(messageID),
+        parts: [
+          {
+            ...basePart(messageID, "p1"),
+            type: "text",
+            text: "",
+          },
+          {
+            ...basePart(messageID, "p2"),
+            type: "text",
+            text: "hello",
+          },
+        ] as MessageV2.Part[],
+      },
+    ]
+
+    expect(await MessageV2.toModelMessages(input, model)).toStrictEqual([
+      {
+        role: "user",
+        content: [{ type: "text", text: "hello" }],
+      },
+    ])
+  })
+
   test("includes synthetic text parts", async () => {
     const messageID = "m-user"
 
@@ -443,6 +491,108 @@ describe("session.message-v2.toModelMessage", () => {
     })
   })
 
+  test("moves bedrock pdf tool-result media into a separate user message", async () => {
+    const bedrockModel: Provider.Model = {
+      ...model,
+      id: ModelID.make("amazon-bedrock/anthropic.claude-sonnet-4-6"),
+      providerID: ProviderID.make("amazon-bedrock"),
+      api: {
+        id: "anthropic.claude-sonnet-4-6",
+        url: "https://bedrock-runtime.us-east-1.amazonaws.com",
+        npm: "@ai-sdk/amazon-bedrock",
+      },
+      capabilities: {
+        ...model.capabilities,
+        attachment: true,
+        input: {
+          ...model.capabilities.input,
+          image: true,
+          pdf: true,
+        },
+      },
+    }
+    const pdf = Buffer.from("%PDF-1.4\n").toString("base64")
+    const userID = "m-user-bedrock-pdf"
+    const assistantID = "m-assistant-bedrock-pdf"
+    const input: MessageV2.WithParts[] = [
+      {
+        info: userInfo(userID),
+        parts: [
+          {
+            ...basePart(userID, "u1-bedrock-pdf"),
+            type: "text",
+            text: "run tool",
+          },
+        ] as MessageV2.Part[],
+      },
+      {
+        info: assistantInfo(assistantID, userID),
+        parts: [
+          {
+            ...basePart(assistantID, "a1-bedrock-pdf"),
+            type: "tool",
+            callID: "call-bedrock-pdf-1",
+            tool: "read",
+            state: {
+              status: "completed",
+              input: { filePath: "/tmp/example.pdf" },
+              output: "PDF read successfully",
+              title: "Read",
+              metadata: {},
+              time: { start: 0, end: 1 },
+              attachments: [
+                {
+                  ...basePart(assistantID, "file-bedrock-pdf-1"),
+                  type: "file",
+                  mime: "application/pdf",
+                  filename: "example.pdf",
+                  url: `data:application/pdf;base64,${pdf}`,
+                },
+              ],
+            },
+          },
+        ] as MessageV2.Part[],
+      },
+    ]
+
+    expect(await MessageV2.toModelMessages(input, bedrockModel)).toStrictEqual([
+      {
+        role: "user",
+        content: [{ type: "text", text: "run tool" }],
+      },
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "tool-call",
+            toolCallId: "call-bedrock-pdf-1",
+            toolName: "read",
+            input: { filePath: "/tmp/example.pdf" },
+            providerExecuted: undefined,
+          },
+        ],
+      },
+      {
+        role: "tool",
+        content: [
+          {
+            type: "tool-result",
+            toolCallId: "call-bedrock-pdf-1",
+            toolName: "read",
+            output: { type: "text", value: "PDF read successfully" },
+          },
+        ],
+      },
+      {
+        role: "user",
+        content: [
+          { type: "text", text: "Attached media from tool result:" },
+          { type: "file", mediaType: "application/pdf", filename: "example.pdf", data: `data:application/pdf;base64,${pdf}` },
+        ],
+      },
+    ])
+  })
+
   test("omits provider metadata when assistant model differs", async () => {
     const userID = "m-user"
     const assistantID = "m-assistant"
@@ -1134,8 +1284,9 @@ describe("session.message-v2.toModelMessage", () => {
     expect((result[1].content as any[]).find((p) => p.type === "text").text).toBe("the answer")
   })
 
-  test("substitutes space for empty text when reasoning signature is under 'bedrock' namespace", async () => {
-    // AWS Bedrock hosts Anthropic Claude but stores signatures under metadata.bedrock
+  test("leaves empty text alone when reasoning signature is under 'bedrock' namespace", async () => {
+    // Bedrock signed reasoning is preserved as reasoning metadata, but unlike the
+    // direct Anthropic path we do not preserve empty text separators for Bedrock.
     const assistantID = "m-assistant-bedrock"
     const input: MessageV2.WithParts[] = [
       {
@@ -1157,7 +1308,7 @@ describe("session.message-v2.toModelMessage", () => {
 
     expect(result).toHaveLength(1)
     const texts = (result[0].content as any[]).filter((p) => p.type === "text")
-    expect(texts.map((t) => t.text)).toStrictEqual([" ", "answer"])
+    expect(texts.map((t) => t.text)).toStrictEqual(["", "answer"])
   })
 
   test("leaves empty text alone when reasoning has no Anthropic signature", async () => {