diff --git a/src/ui/components/messages/user-tool-result-message/FallbackToolResultMessage.tsx b/src/ui/components/messages/user-tool-result-message/FallbackToolResultMessage.tsx
new file mode 100644
index 000000000..9419d6802
--- /dev/null
+++ b/src/ui/components/messages/user-tool-result-message/FallbackToolResultMessage.tsx
@@ -0,0 +1,52 @@
+import { Box, Text } from 'ink'
+import * as React from 'react'
+import { getTheme } from '@utils/theme'
+import type { ToolResultBlockParam } from '@anthropic-ai/sdk/resources/index.mjs'
+
+const MAX_FALLBACK_CONTENT_LINES = 10
+
+function normalizeLineEndings(content: string): string {
+  return content.replace(/\r\n/g, '\n').replace(/\r/g, '\n').trimEnd()
+}
+
+function truncateContent(content: string): string {
+  const lines = normalizeLineEndings(content).split('\n')
+  if (lines.length <= MAX_FALLBACK_CONTENT_LINES) {
+    return lines.join('\n')
+  }
+
+  return [...lines.slice(0, MAX_FALLBACK_CONTENT_LINES - 1), '...'].join('\n')
+}
+
+function indentContent(content: string): string {
+  return content
+    .split('\n')
+    .map(line => `  ${line}`)
+    .join('\n')
+}
+
+type Props = {
+  content: ToolResultBlockParam['content']
+  verbose: boolean
+}
+
+export function FallbackToolResultMessage({
+  content,
+  verbose,
+}: Props): React.ReactNode {
+  const textContent =
+    typeof content === 'string'
+      ? verbose
+        ? normalizeLineEndings(content)
+        : truncateContent(content)
+      : null
+
+  return (
+    <Box flexDirection="column">
+      <Text color={getTheme().secondaryText}> Tool result unavailable</Text>
+      {textContent ? (
+        <Text wrap="wrap">{indentContent(textContent)}</Text>
+      ) : null}
+    </Box>
+  )
+}
diff --git a/src/ui/components/messages/user-tool-result-message/UserToolRejectMessage.tsx b/src/ui/components/messages/user-tool-result-message/UserToolRejectMessage.tsx
index f7644f128..97e95c8f0 100644
--- a/src/ui/components/messages/user-tool-result-message/UserToolRejectMessage.tsx
+++ b/src/ui/components/messages/user-tool-result-message/UserToolRejectMessage.tsx
@@ -21,14 +21,20 @@ export function UserToolRejectMessage({
 }: Props): React.ReactNode {
   const { columns } = useTerminalSize()
   const { conversationKey } = usePermissionContext()
-  const { tool, toolUse } = useGetToolFromMessages(toolUseID, tools, messages)
-  const input = tool.inputSchema.safeParse(toolUse.input)
+  const lookup = useGetToolFromMessages(toolUseID, tools, messages)
+  if (!lookup) {
+    return <FallbackToolUseRejectedMessage />
+  }
+
+  const input = lookup.tool.inputSchema.safeParse(lookup.toolUse.input)
   if (input.success) {
-    return tool.renderToolUseRejectedMessage(input.data, {
-      columns,
-      verbose,
-      conversationKey,
-    })
+    return (
+      lookup.tool.renderToolUseRejectedMessage?.(input.data, {
+        columns,
+        verbose,
+        conversationKey,
+      }) ?? <FallbackToolUseRejectedMessage />
+    )
   }
   return <FallbackToolUseRejectedMessage />
 }
diff --git a/src/ui/components/messages/user-tool-result-message/UserToolSuccessMessage.tsx b/src/ui/components/messages/user-tool-result-message/UserToolSuccessMessage.tsx
index 5f96a6540..8dbe14fe3 100644
--- a/src/ui/components/messages/user-tool-result-message/UserToolSuccessMessage.tsx
+++ b/src/ui/components/messages/user-tool-result-message/UserToolSuccessMessage.tsx
@@ -4,6 +4,7 @@ import * as React from 'react'
 import { Tool } from '@tool'
 import { Message, UserMessage } from '@query'
 import { useGetToolFromMessages } from './utils'
+import { FallbackToolResultMessage } from './FallbackToolResultMessage'
 
 type Props = {
   param: ToolResultBlockParam
@@ -22,13 +23,28 @@ export function UserToolSuccessMessage({
   verbose,
   width,
 }: Props): React.ReactNode {
-  const { tool } = useGetToolFromMessages(param.tool_use_id, tools, messages)
+  const lookup = useGetToolFromMessages(param.tool_use_id, tools, messages)
+
+  if (
+    !lookup ||
+    !lookup.tool.renderToolResultMessage ||
+    !message.toolUseResult
+  ) {
+    return (
+      <Box flexDirection="column" width={width}>
+        <FallbackToolResultMessage content={param.content} verbose={verbose} />
+      </Box>
+    )
+  }
 
   return (
     <Box flexDirection="column" width={width}>
-      {tool.renderToolResultMessage?.(message.toolUseResult!.data as never, {
-        verbose,
-      })}
+      {lookup.tool.renderToolResultMessage(
+        message.toolUseResult.data as never,
+        {
+          verbose,
+        },
+      )}
     </Box>
   )
 }
diff --git a/src/ui/components/messages/user-tool-result-message/utils.tsx b/src/ui/components/messages/user-tool-result-message/utils.tsx
index d0b03e2f9..e33ed0c55 100644
--- a/src/ui/components/messages/user-tool-result-message/utils.tsx
+++ b/src/ui/components/messages/user-tool-result-message/utils.tsx
@@ -35,13 +35,11 @@ export function useGetToolFromMessages(
   toolUseID: string,
   tools: Tool[],
   messages: Message[],
-) {
+): { tool: Tool; toolUse: ToolUseBlockParam } | null {
   return useMemo(() => {
     const toolUse = getToolUseFromMessages(toolUseID, messages)
     if (!toolUse) {
-      throw new ReferenceError(
-        `Tool use not found for tool_use_id ${toolUseID}`,
-      )
+      return null
     }
     const tool = [...tools, GlobTool, GrepTool].find(
       _ => _.name === toolUse.name,
@@ -49,7 +47,7 @@ export function useGetToolFromMessages(
     if (tool === GlobTool || tool === GrepTool) {
     }
     if (!tool) {
-      throw new ReferenceError(`Tool not found for ${toolUse.name}`)
+      return null
     }
     return { tool, toolUse }
   }, [toolUseID, messages, tools])
diff --git a/tests/unit/user-tool-result-message-orphaned.test.tsx b/tests/unit/user-tool-result-message-orphaned.test.tsx
new file mode 100644
index 000000000..c650e5174
--- /dev/null
+++ b/tests/unit/user-tool-result-message-orphaned.test.tsx
@@ -0,0 +1,248 @@
+import { describe, expect, test } from 'bun:test'
+import type { ToolResultBlockParam } from '@anthropic-ai/sdk/resources/index.mjs'
+import { Box, Text, render } from 'ink'
+import React from 'react'
+import { PassThrough } from 'stream'
+import stripAnsi from 'strip-ansi'
+import { z } from 'zod'
+import { PermissionProvider } from '@context/PermissionContext'
+import { UserToolResultMessage } from '@components/messages/user-tool-result-message/UserToolResultMessage'
+import type { Message, UserMessage } from '@query'
+import type { Tool } from '@tool'
+import {
+  createAssistantMessage,
+  createUserMessage,
+  REJECT_MESSAGE,
+} from '@utils/messages'
+
+async function renderToText(element: React.ReactElement): Promise<string> {
+  const stdin = new PassThrough()
+  ;(stdin as any).isTTY = true
+  ;(stdin as any).isRaw = true
+  ;(stdin as any).setRawMode = () => {}
+  stdin.setEncoding('utf8')
+  stdin.resume()
+
+  const stdout = new PassThrough()
+  ;(stdout as any).isTTY = true
+  ;(stdout as any).columns = 100
+  ;(stdout as any).rows = 30
+
+  let rawOutput = ''
+  stdout.on('data', chunk => {
+    rawOutput += chunk.toString('utf8')
+  })
+
+  const instance = render(
+    <PermissionProvider conversationKey="tool-result-test">
+      <Box>{element}</Box>
+    </PermissionProvider>,
+    {
+      stdin: stdin as any,
+      stdout: stdout as any,
+      exitOnCtrlC: false,
+    },
+  )
+
+  await new Promise(resolve => setTimeout(resolve, 0))
+
+  instance.unmount()
+  return stripAnsi(rawOutput)
+}
+
+function makeToolResultParam(
+  toolUseID: string,
+  content: ToolResultBlockParam['content'],
+  isError = false,
+): ToolResultBlockParam {
+  return {
+    type: 'tool_result',
+    tool_use_id: toolUseID,
+    content,
+    is_error: isError,
+  }
+}
+
+function makeToolResultMessage(
+  param: ToolResultBlockParam,
+  data?: unknown,
+): UserMessage {
+  return createUserMessage(
+    [param] as any,
+    data === undefined
+      ? undefined
+      : {
+          data,
+          resultForAssistant: param.content,
+        },
+  )
+}
+
+function makeToolUseMessage(
+  toolUseID: string,
+  name: string,
+  input: unknown = {},
+): Message {
+  const message = createAssistantMessage('ignored') as any
+  message.message.content = [
+    {
+      type: 'tool_use',
+      id: toolUseID,
+      name,
+      input,
+    },
+  ]
+  return message
+}
+
+const inputSchema = z.object({}).passthrough()
+
+function makeTool(overrides: Partial<Tool<typeof inputSchema, unknown>> = {}) {
+  return {
+    name: 'FakeTool',
+    inputSchema,
+    async prompt() {
+      return ''
+    },
+    async isEnabled() {
+      return true
+    },
+    isReadOnly() {
+      return true
+    },
+    isConcurrencySafe() {
+      return true
+    },
+    needsPermissions() {
+      return false
+    },
+    renderResultForAssistant() {
+      return ''
+    },
+    renderToolUseMessage() {
+      return null
+    },
+    async *call() {
+      yield { type: 'result', data: {} }
+    },
+    ...overrides,
+  } satisfies Tool<typeof inputSchema, unknown>
+}
+
+function renderToolResult(args: {
+  param: ToolResultBlockParam
+  message: UserMessage
+  messages: Message[]
+  tools?: Tool[]
+  verbose?: boolean
+}) {
+  return renderToText(
+    <UserToolResultMessage
+      param={args.param}
+      message={args.message}
+      messages={args.messages}
+      tools={args.tools ?? []}
+      verbose={args.verbose ?? false}
+      width={80}
+    />,
+  )
+}
+
+describe('UserToolResultMessage orphaned fallback', () => {
+  test('renders orphaned successful tool_result without throwing', async () => {
+    const param = makeToolResultParam('missing-tool-use', 'first\nsecond')
+    const message = makeToolResultMessage(param)
+
+    const out = await renderToolResult({
+      param,
+      message,
+      messages: [message],
+    })
+
+    expect(out).toContain('Tool result unavailable')
+    expect(out).toContain('first')
+    expect(out).toContain('second')
+    expect(out).not.toContain('Tool use not found')
+  })
+
+  test('renders orphaned rejected tool_result with existing rejection fallback', async () => {
+    const param = makeToolResultParam('missing-tool-use', REJECT_MESSAGE, true)
+    const message = makeToolResultMessage(param)
+
+    const out = await renderToolResult({
+      param,
+      message,
+      messages: [message],
+    })
+
+    expect(out).toContain('No (tell')
+    expect(out).not.toContain('Tool use not found')
+  })
+
+  test('uses the matched tool renderer when the tool_use and tool exist', async () => {
+    const param = makeToolResultParam('tool-use-1', 'assistant content')
+    const message = makeToolResultMessage(param, { value: 'from data' })
+    const toolUse = makeToolUseMessage('tool-use-1', 'FakeTool')
+    let rendered = false
+    const tool = makeTool({
+      renderToolResultMessage(output) {
+        rendered = true
+        return <Text>custom result: {(output as any).value}</Text>
+      },
+    })
+
+    const out = await renderToolResult({
+      param,
+      message,
+      messages: [toolUse, message],
+      tools: [tool],
+    })
+
+    expect(rendered).toBe(true)
+    expect(out).toContain('custom result: from data')
+    expect(out).not.toContain('Tool result unavailable')
+  })
+
+  test('falls back when the tool_use exists but the tool is unavailable', async () => {
+    const param = makeToolResultParam('tool-use-2', 'raw content')
+    const message = makeToolResultMessage(param, { value: 'from data' })
+    const toolUse = makeToolUseMessage('tool-use-2', 'MissingTool')
+
+    const out = await renderToolResult({
+      param,
+      message,
+      messages: [toolUse, message],
+      tools: [],
+    })
+
+    expect(out).toContain('Tool result unavailable')
+    expect(out).toContain('raw content')
+    expect(out).not.toContain('Tool not found')
+  })
+
+  test('truncates fallback string content only outside verbose mode', async () => {
+    const content = Array.from({ length: 12 }, (_, i) => `line ${i + 1}`).join(
+      '\n',
+    )
+    const param = makeToolResultParam('missing-tool-use', content)
+    const message = makeToolResultMessage(param)
+
+    const terse = await renderToolResult({
+      param,
+      message,
+      messages: [message],
+      verbose: false,
+    })
+    const verbose = await renderToolResult({
+      param,
+      message,
+      messages: [message],
+      verbose: true,
+    })
+
+    expect(terse).toContain('line 9')
+    expect(terse).toContain('...')
+    expect(terse).not.toContain('line 10')
+    expect(verbose).toContain('line 12')
+  })
+})