fix(ai): drop blank text from Bedrock error tool results

packages/ai/src/protocols/anthropic-messages.ts

@@ -814,7 +814,10 @@ const lowerMedia = Effect.fnUntraced(function* (part: MediaPart, request: LLMReq
 // Tool results may carry structured text, images, and documents. Keep media as provider-native
 // content instead of JSON-stringifying base64 into a prompt string.
 const lowerToolResultContentItem = Effect.fnUntraced(function* (item: Tool.Content, request: LLMRequest) {
-  if (item.type === "text") return { type: "text" as const, text: item.text } satisfies AnthropicTextBlock
+  if (item.type === "text") {
+    if (item.text.trim() === "") return
+    return { type: "text" as const, text: item.text } satisfies AnthropicTextBlock
+  }
   return yield* lowerMedia(ProviderShared.toolFileMedia(item), request)
 })
 
@@ -825,7 +828,8 @@ const lowerToolResultContent = Effect.fnUntraced(function* (part: ToolResultPart
   if (part.result.type === "error") return lowerToolErrorContent(part, rich ?? [])
   // Text and json results stay as a string for backward compatibility with existing cassettes.
   if (part.result.type !== "content") return ProviderShared.toolResultText(part)
-  return yield* Effect.forEach(part.result.value, (item) => lowerToolResultContentItem(item, request))
+  const blocks = yield* Effect.forEach(part.result.value, (item) => lowerToolResultContentItem(item, request))
+  return blocks.flatMap((block) => (block === undefined ? [] : [block]))
 })
 
 const lowerToolErrorContent = (part: ToolResultPart, content: ReadonlyArray<Tool.Content>) => {

packages/ai/src/protocols/bedrock-converse.ts

@@ -317,30 +317,45 @@ const lowerToolCall = (part: ToolCallPart, normalizeID: (id: string) => string):
   },
 })
 
+const omittedToolErrorNote = (mime: string) => {
+  if (mime.startsWith("image/")) return "[image omitted]"
+  if (mime === "application/pdf") return "[document omitted]"
+  return "[file omitted]"
+}
+
 const lowerToolResultContent = Effect.fnUntraced(function* (
   part: ToolResultPart,
   documentNames: Set<string>,
+  omitErrorMedia: boolean,
 ) {
   if (part.result.type === "text") return [{ text: ProviderShared.toolResultText(part) }]
   if (part.result.type === "error") {
     const rich = ProviderShared.toolErrorContent(part)
     const text = { text: ProviderShared.toolResultText(part) }
     if (rich === undefined) return [text]
-    const blocks: Array<Schema.Schema.Type<typeof BedrockToolResultContentItem>> = [text]
+    const blocks: Array<Schema.Schema.Type<typeof BedrockToolResultContentItem>> = []
     for (const item of rich) {
       if (item.type === "text") {
+        if (item.text.trim() === "") continue
         blocks.push({ text: item.text })
         continue
       }
+      // Claude and Nova reject image and document blocks inside an error tool result.
+      if (omitErrorMedia) {
+        blocks.push({ text: omittedToolErrorNote(item.mime) })
+        continue
+      }
       blocks.push(...(yield* BedrockMedia.lower(ProviderShared.toolFileMedia(item), documentNames)))
     }
+    if (blocks.length === 0 || part.result.empty !== true) blocks.unshift(text)
     return blocks
   }
   if (part.result.type === "json") return [{ json: part.result.value }]
 
   const content: Array<Schema.Schema.Type<typeof BedrockToolResultContentItem>> = []
   for (const item of part.result.value) {
     if (item.type === "text") {
+      if (item.text.trim() === "") continue
       content.push({ text: item.text })
       continue
     }
@@ -354,11 +369,12 @@ const lowerToolResult = Effect.fnUntraced(function* (
   part: ToolResultPart,
   documentNames: Set<string>,
   normalizeID: (id: string) => string,
+  omitErrorMedia: boolean,
 ) {
   return {
     toolResult: {
       toolUseId: normalizeID(part.id),
-      content: yield* lowerToolResultContent(part, documentNames),
+      content: yield* lowerToolResultContent(part, documentNames, omitErrorMedia),
       status: part.result.type === "error" ? "error" : "success",
     },
   } satisfies BedrockToolResultBlock
@@ -462,7 +478,7 @@ const lowerMessages = Effect.fnUntraced(function* (
     for (const part of message.content) {
       if (!ProviderShared.supportsContent(part, ["tool-result"]))
         return yield* ProviderShared.unsupportedContent("Bedrock Converse", "tool", ["tool-result"])
-      const result = yield* lowerToolResult(part, documentNames, normalizeID)
+      const result = yield* lowerToolResult(part, documentNames, normalizeID, keepToolImagesInline(request.model.id))
       const images: BedrockMedia.ImageBlock[] = hoistImages
         ? result.toolResult.content.filter((item) => "image" in item)
         : []

packages/ai/src/schema/messages.ts

@@ -70,6 +70,9 @@ const toolResultValueSchema = Schema.Union([
     type: Schema.Literal("error"),
     value: Schema.Unknown,
     content: Schema.optional(Schema.Array(Tool.Content)),
+    // Set when history replaced a blank error value. Providers can tell that apart from a real
+    // error whose text is the same placeholder.
+    empty: Schema.optional(Schema.Boolean),
   }),
   Schema.Struct({
     type: Schema.Literal("content"),

packages/ai/src/tool-history.ts

@@ -2,6 +2,7 @@ import { Message, ToolResultPart, type ToolCallPart } from "./schema/messages.js
 
 const EMPTY_TOOL_OUTPUT = "(no tool output)"
 const MISSING_TOOL_RESULT = "Tool result missing"
+const blankText = (value: unknown) => typeof value === "string" && value.trim() === ""
 
 export function normalizeToolHistory(messages: ReadonlyArray<Message>) {
   const normalized: Message[] = []
@@ -86,13 +87,17 @@ function normalizeToolResult(part: ToolResultPart, call: ToolCallPart | undefine
     call === undefined || (part.name === call.name && part.namespace === call.namespace)
       ? part
       : { ...part, name: call.name, namespace: call.namespace }
-  if (named.result.type === "text" && named.result.value === "")
+  if (named.result.type === "text" && blankText(named.result.value))
     return { ...named, result: { type: "text", value: EMPTY_TOOL_OUTPUT } }
-  if (named.result.type === "error" && named.result.value === "")
-    return { ...named, result: { ...named.result, value: EMPTY_TOOL_OUTPUT } }
+  if (named.result.type === "error" && blankText(named.result.value))
+    return { ...named, result: { ...named.result, value: EMPTY_TOOL_OUTPUT, empty: true } }
   if (named.result.type !== "content") return named
+  // Exact "" is not a separator. Drop it, then replace the array only when every remaining
+  // item is blank and there is no media. Whitespace such as "\n" stays: Mistral joins text
+  // with "", so ["foo", "\n", "bar"] must remain "foo\nbar".
   const value = named.result.value.filter((item) => item.type !== "text" || item.text !== "")
-  if (value.length === 0) return { ...named, result: { type: "text", value: EMPTY_TOOL_OUTPUT } }
+  if (value.every((item) => item.type === "text" && blankText(item.text)))
+    return { ...named, result: { type: "text", value: EMPTY_TOOL_OUTPUT } }
   if (value.length === named.result.value.length) return named
   return { ...named, result: { type: "content", value } }
 }

packages/ai/test/provider/anthropic-messages.test.ts

@@ -823,6 +823,47 @@ describe("Anthropic Messages route", () => {
     }),
   )
 
+  it.effect("drops whitespace-only tool-result text and keeps non-blank text", () =>
+    Effect.gen(function* () {
+      const spaced = "  Keep this spacing.  "
+      const prepared = yield* compileRequest(
+        LLM.request({
+          model,
+          cache: "none",
+          messages: [
+            Message.assistant([ToolCallPart.make({ id: "call_1", name: "read", input: {} })]),
+            Message.tool({
+              id: "call_1",
+              name: "read",
+              resultType: "content",
+              result: [
+                { type: "text", text: " \n\t" },
+                { type: "text", text: spaced },
+                { type: "file", uri: "data:image/png;base64,AAECAw==", mime: "image/png" },
+              ],
+            }),
+          ],
+        }),
+      )
+      const blank = yield* compileRequest(
+        LLM.request({
+          model,
+          cache: "none",
+          messages: [
+            Message.assistant([ToolCallPart.make({ id: "call_1", name: "read", input: {} })]),
+            Message.tool({ id: "call_1", name: "read", resultType: "text", result: " \n\t" }),
+          ],
+        }),
+      )
+
+      expect(expectToolResult(prepared.body).content).toEqual([
+        { type: "text", text: spaced },
+        { type: "image", source: { type: "base64", media_type: "image/png", data: "AAECAw==" } },
+      ])
+      expect(expectToolResult(blank.body).content).toBe("(no tool output)")
+    }),
+  )
+
   it.effect("lowers single-image tool-result content as a structured image block", () =>
     Effect.gen(function* () {
       const prepared = yield* compileRequest(
@@ -1036,7 +1077,7 @@ describe("Anthropic Messages route", () => {
       const prepared = yield* compileErrorToolResult("  \n", [{ type: "text", text: "\t " }])
       const result = expectToolResult(prepared.body)
       expect(result.is_error).toBe(true)
-      expect(result.content).toEqual([{ type: "text", text: "[tool error]" }])
+      expect(result.content).toEqual([{ type: "text", text: "(no tool output)" }])
       expectNoEmptyText(result.content)
     }),
   )

packages/ai/test/provider/bedrock-converse.test.ts

@@ -648,6 +648,53 @@ describe("Bedrock Converse route", () => {
     }),
   )
 
+  it.effect("drops blank tool-result text and keeps the image", () =>
+    Effect.gen(function* () {
+      const prepared = yield* compileRequest(
+        LLM.request({
+          id: "req_tool_blank_text",
+          model,
+          messages: [
+            Message.user("Capture the screen."),
+            Message.assistant([ToolCallPart.make({ id: "tool_1", name: "screenshot", input: {} })]),
+            Message.tool({
+              id: "tool_1",
+              name: "screenshot",
+              result: {
+                type: "content",
+                value: [
+                  { type: "text", text: " " },
+                  { type: "file", uri: "data:image/png;base64,AAAA", mime: "image/png" },
+                ],
+              },
+            }),
+          ],
+          cache: "none",
+        }),
+      )
+
+      expect(prepared.body.messages).toEqual([
+        { role: "user", content: [{ text: "Capture the screen." }] },
+        {
+          role: "assistant",
+          content: [{ toolUse: { toolUseId: "tool_1", name: "screenshot", input: {} } }],
+        },
+        {
+          role: "user",
+          content: [
+            {
+              toolResult: {
+                toolUseId: "tool_1",
+                content: [{ image: { format: "png", source: { bytes: "AAAA" } } }],
+                status: "success",
+              },
+            },
+          ],
+        },
+      ])
+    }),
+  )
+
   it.effect("hoists tool-result images beside the result for Bedrock GPT models", () =>
     Effect.gen(function* () {
       const prepared = yield* compileRequest(
@@ -819,7 +866,7 @@ describe("Bedrock Converse route", () => {
     }),
   )
 
-  it.effect("lowers rich tool failures with status error and an image", () =>
+  it.effect("lowers rich Claude tool failures as text notes", () =>
     Effect.gen(function* () {
       const prepared = yield* compileRequest(
         LLM.request({
@@ -853,7 +900,7 @@ describe("Bedrock Converse route", () => {
                 text: JSON.stringify({ error: { type: "tool.execution", message: "snapshot failed" }, content: [] }),
               },
               { text: "could not capture" },
-              { image: { format: "png", source: { bytes: "AAAA" } } },
+              { text: "[image omitted]" },
             ],
           },
         },
@@ -865,6 +912,132 @@ describe("Bedrock Converse route", () => {
     }),
   )
 
+  it.effect("drops blank rich text from a Claude or Nova error and sends an omission note", () =>
+    Effect.gen(function* () {
+      for (const id of [model.id, "us.amazon.nova-pro-v1:0"]) {
+        const prepared = yield* compileRequest(
+          LLM.request({
+            model: AmazonBedrock.configure({ baseURL: "https://bedrock-runtime.test", apiKey: "test-bearer" }).model(
+              id,
+            ),
+            cache: "none",
+            messages: [
+              Message.assistant([ToolCallPart.make({ id: "tool_1", name: "snapshot", input: {} })]),
+              Message.tool({
+                id: "tool_1",
+                name: "snapshot",
+                result: {
+                  type: "error",
+                  value: "\n",
+                  content: [
+                    { type: "text", text: "\n" },
+                    { type: "file", uri: "data:image/png;base64,AAAA", mime: "image/png" },
+                    { type: "file", uri: "data:application/pdf;base64,QkI=", mime: "application/pdf" },
+                    { type: "file", uri: "data:text/plain;base64,Zg==", mime: "text/plain" },
+                  ],
+                },
+              }),
+            ],
+          }),
+        )
+
+        expect(prepared.body.messages).toEqual([
+          {
+            role: "assistant",
+            content: [{ toolUse: { toolUseId: "tool_1", name: "snapshot", input: {} } }],
+          },
+          {
+            role: "user",
+            content: [
+              {
+                toolResult: {
+                  toolUseId: "tool_1",
+                  status: "error",
+                  content: [{ text: "[image omitted]" }, { text: "[document omitted]" }, { text: "[file omitted]" }],
+                },
+              },
+            ],
+          },
+        ])
+      }
+    }),
+  )
+
+  it.effect("keeps an error whose text is the empty-output placeholder when media is present", () =>
+    Effect.gen(function* () {
+      const prepared = yield* compileRequest(
+        LLM.request({
+          model,
+          cache: "none",
+          messages: [
+            Message.assistant([ToolCallPart.make({ id: "tool_1", name: "snapshot", input: {} })]),
+            Message.tool({
+              id: "tool_1",
+              name: "snapshot",
+              result: {
+                type: "error",
+                value: "(no tool output)",
+                content: [{ type: "file", uri: "data:image/png;base64,AAAA", mime: "image/png" }],
+              },
+            }),
+          ],
+        }),
+      )
+
+      expect(prepared.body.messages[1]?.content).toEqual([
+        {
+          toolResult: {
+            toolUseId: "tool_1",
+            status: "error",
+            content: [{ text: "(no tool output)" }, { text: "[image omitted]" }],
+          },
+        },
+      ])
+    }),
+  )
+
+  it.effect("hoists an image from a blank error for models that do not keep tool images inline", () =>
+    Effect.gen(function* () {
+      const prepared = yield* compileRequest(
+        LLM.request({
+          model: AmazonBedrock.configure({ baseURL: "https://bedrock-runtime.test", apiKey: "test-bearer" }).model(
+            "global.openai.gpt-6-sol",
+          ),
+          cache: "none",
+          messages: [
+            Message.assistant([ToolCallPart.make({ id: "tool_1", name: "snapshot", input: {} })]),
+            Message.tool({
+              id: "tool_1",
+              name: "snapshot",
+              result: {
+                type: "error",
+                value: "\n",
+                content: [
+                  { type: "text", text: "\n" },
+                  { type: "file", uri: "data:image/png;base64,AAAA", mime: "image/png" },
+                ],
+              },
+            }),
+          ],
+        }),
+      )
+
+      expect(prepared.body.messages[1]).toEqual({
+        role: "user",
+        content: [
+          {
+            toolResult: {
+              toolUseId: "tool_1",
+              status: "error",
+              content: [{ text: "See attached image." }],
+            },
+          },
+          { image: { format: "png", source: { bytes: "AAAA" } } },
+        ],
+      })
+    }),
+  )
+
   it.effect("decodes text-delta + messageStop + metadata usage from binary event stream", () =>
     Effect.gen(function* () {
       const body = eventStreamBody(