Preserve in-progress message history when agent run errors

packages/agent-runtime/src/__tests__/main-prompt.test.ts

@@ -375,6 +375,7 @@ describe('mainPrompt', () => {
   it('should update consecutiveAssistantMessages when new prompt is received', async () => {
     const sessionState = getInitialSessionState(mockFileContext)
     sessionState.mainAgentState.stepsRemaining = 12
+    const initialStepsRemaining = sessionState.mainAgentState.stepsRemaining
 
     const action = {
       type: 'prompt' as const,
@@ -394,7 +395,7 @@ describe('mainPrompt', () => {
 
     // When there's a new prompt, consecutiveAssistantMessages should be set to 1
     expect(newSessionState.mainAgentState.stepsRemaining).toBe(
-      sessionState.mainAgentState.stepsRemaining - 1,
+      initialStepsRemaining - 1,
     )
   })
 

packages/agent-runtime/src/run-agent-step.ts

@@ -536,6 +536,17 @@ export const runAgentStep = async (
   }
 }
 
+/**
+ * Runs the agent loop.
+ *
+ * IMPORTANT: This function mutates `params.agentState` in place throughout the
+ * run (not just at return time). Fields like `messageHistory`, `systemPrompt`,
+ * `toolDefinitions`, `creditsUsed`, and `output` are updated as work progresses
+ * so that callers holding a reference to the same object (e.g. the SDK's
+ * `sessionState.mainAgentState`) see in-progress work immediately — which
+ * matters when an error is thrown mid-run and the normal return path is
+ * skipped.
+ */
 export async function loopAgentSteps(
   params: {
     addAgentStep: AddAgentStepFn
@@ -800,12 +811,13 @@ export async function loopAgentSteps(
     return cachedAdditionalToolDefinitions
   }
 
-  let currentAgentState: AgentState = {
-    ...initialAgentState,
-    messageHistory: initialMessages,
-    systemPrompt: system,
-    toolDefinitions,
-  }
+  // Mutate initialAgentState so that in-progress work propagates back to the
+  // caller's shared reference (e.g. SDK's sessionState.mainAgentState) even if
+  // an error is thrown before we return.
+  initialAgentState.messageHistory = initialMessages
+  initialAgentState.systemPrompt = system
+  initialAgentState.toolDefinitions = toolDefinitions
+  let currentAgentState: AgentState = initialAgentState
 
   // Convert tool definitions to Anthropic format for accurate token counting
   // Tool definitions are stored as { [name]: { description, inputSchema } }
@@ -908,7 +920,8 @@ export async function loopAgentSteps(
         } = programmaticResult
         n = generateN
 
-        currentAgentState = programmaticAgentState
+        Object.assign(initialAgentState, programmaticAgentState)
+        currentAgentState = initialAgentState
         totalSteps = stepNumber
 
         shouldEndTurn = endTurn
@@ -989,7 +1002,8 @@ export async function loopAgentSteps(
         logger.error('No runId found for agent state after finishing agent run')
       }
 
-      currentAgentState = newAgentState
+      Object.assign(initialAgentState, newAgentState)
+      currentAgentState = initialAgentState
       shouldEndTurn = llmShouldEndTurn
       nResponses = generatedResponses
 

sdk/src/__tests__/run-error-preserves-history.test.ts

@@ -0,0 +1,315 @@
+import * as mainPromptModule from '@codebuff/agent-runtime/main-prompt'
+import { getInitialSessionState } from '@codebuff/common/types/session-state'
+import { getStubProjectFileContext } from '@codebuff/common/util/file'
+import { assistantMessage, userMessage } from '@codebuff/common/util/messages'
+import { afterEach, describe, expect, it, mock, spyOn } from 'bun:test'
+
+import { CodebuffClient } from '../client'
+import * as databaseModule from '../impl/database'
+
+interface ToolCallContentBlock {
+  type: 'tool-call'
+  toolCallId: string
+  toolName: string
+  input: Record<string, unknown>
+}
+
+const setupDatabaseMocks = () => {
+  spyOn(databaseModule, 'getUserInfoFromApiKey').mockResolvedValue({
+    id: 'user-123',
+    email: 'test@example.com',
+    discord_id: null,
+    referral_code: null,
+    stripe_customer_id: null,
+    banned: false,
+    created_at: new Date('2024-01-01T00:00:00Z'),
+  })
+  spyOn(databaseModule, 'fetchAgentFromDatabase').mockResolvedValue(null)
+  spyOn(databaseModule, 'startAgentRun').mockResolvedValue('run-1')
+  spyOn(databaseModule, 'finishAgentRun').mockResolvedValue(undefined)
+  spyOn(databaseModule, 'addAgentStep').mockResolvedValue('step-1')
+}
+
+describe('Error preserves in-progress message history', () => {
+  afterEach(() => {
+    mock.restore()
+  })
+
+  it('preserves in-progress assistant work on error (simulated via shared state mutation)', async () => {
+    setupDatabaseMocks()
+
+    // Simulate the agent runtime:
+    // 1. Mutates the shared session state with the user message and partial work
+    // 2. Then throws due to a downstream timeout/service error
+    spyOn(mainPromptModule, 'callMainPrompt').mockImplementation(
+      async (params: Parameters<typeof mainPromptModule.callMainPrompt>[0]) => {
+        const mainAgentState = params.action.sessionState.mainAgentState
+
+        // Match the real runtime's behavior: replace messageHistory with a new
+        // array that includes the user prompt as its first entry. The SDK
+        // detects runtime progress via reference inequality, so we must
+        // reassign the array rather than pushing into it.
+        mainAgentState.messageHistory = [
+          ...mainAgentState.messageHistory,
+          {
+            role: 'user',
+            content: [{ type: 'text', text: 'Fix the bug in auth.ts' }],
+            tags: ['USER_PROMPT'],
+          },
+          {
+            role: 'assistant',
+            content: [
+              { type: 'text', text: 'Let me read the auth file first.' },
+              {
+                type: 'tool-call',
+                toolCallId: 'read-1',
+                toolName: 'read_files',
+                input: { paths: ['auth.ts'] },
+              } as ToolCallContentBlock,
+            ],
+          },
+          {
+            role: 'tool',
+            toolCallId: 'read-1',
+            toolName: 'read_files',
+            content: [
+              {
+                type: 'json',
+                value: [{ path: 'auth.ts', content: 'const auth = ...' }],
+              },
+            ],
+          },
+          {
+            role: 'assistant',
+            content: [
+              { type: 'text', text: 'Found the issue, writing the fix now.' },
+              {
+                type: 'tool-call',
+                toolCallId: 'write-1',
+                toolName: 'write_file',
+                input: { path: 'auth.ts', content: 'const auth = fixed' },
+              } as ToolCallContentBlock,
+            ],
+          },
+          {
+            role: 'tool',
+            toolCallId: 'write-1',
+            toolName: 'write_file',
+            content: [{ type: 'json', value: { file: 'auth.ts', message: 'File written' } }],
+          },
+        ]
+
+        // Now simulate a server timeout on the next LLM call
+        const timeoutError = new Error('Service Unavailable') as Error & {
+          statusCode: number
+          responseBody: string
+        }
+        timeoutError.statusCode = 503
+        timeoutError.responseBody = JSON.stringify({
+          message: 'Request timeout after 30s',
+        })
+        throw timeoutError
+      },
+    )
+
+    const client = new CodebuffClient({ apiKey: 'test-key' })
+    const result = await client.run({
+      agent: 'base2',
+      prompt: 'Fix the bug in auth.ts',
+    })
+
+    // Error output with correct status code
+    expect(result.output.type).toBe('error')
+    const errorOutput = result.output as {
+      type: 'error'
+      message: string
+      statusCode?: number
+    }
+    expect(errorOutput.statusCode).toBe(503)
+
+    const history = result.sessionState!.mainAgentState.messageHistory
+
+    // The user's prompt should appear exactly once
+    const userPromptMessages = history.filter(
+      (m) =>
+        m.role === 'user' &&
+        (m.content as Array<{ type: string; text?: string }>).some(
+          (c) => c.type === 'text' && c.text?.includes('Fix the bug'),
+        ),
+    )
+    expect(userPromptMessages.length).toBe(1)
+
+    // Assistant text messages from both steps should be preserved
+    const firstAssistantText = history.find(
+      (m) =>
+        m.role === 'assistant' &&
+        (m.content as Array<{ type: string; text?: string }>).some(
+          (c) => c.type === 'text' && c.text?.includes('read the auth file'),
+        ),
+    )
+    expect(firstAssistantText).toBeDefined()
+
+    const secondAssistantText = history.find(
+      (m) =>
+        m.role === 'assistant' &&
+        (m.content as Array<{ type: string; text?: string }>).some(
+          (c) => c.type === 'text' && c.text?.includes('writing the fix'),
+        ),
+    )
+    expect(secondAssistantText).toBeDefined()
+
+    // Both tool calls and both tool results should be preserved
+    const readToolCall = history.find(
+      (m) =>
+        m.role === 'assistant' &&
+        (m.content as Array<{ type: string; toolCallId?: string }>).some(
+          (c) => c.type === 'tool-call' && c.toolCallId === 'read-1',
+        ),
+    )
+    expect(readToolCall).toBeDefined()
+
+    const writeToolCall = history.find(
+      (m) =>
+        m.role === 'assistant' &&
+        (m.content as Array<{ type: string; toolCallId?: string }>).some(
+          (c) => c.type === 'tool-call' && c.toolCallId === 'write-1',
+        ),
+    )
+    expect(writeToolCall).toBeDefined()
+
+    const readToolResult = history.find(
+      (m) => m.role === 'tool' && m.toolCallId === 'read-1',
+    )
+    expect(readToolResult).toBeDefined()
+
+    const writeToolResult = history.find(
+      (m) => m.role === 'tool' && m.toolCallId === 'write-1',
+    )
+    expect(writeToolResult).toBeDefined()
+  })
+
+  it('a subsequent run after error includes the preserved in-progress history', async () => {
+    setupDatabaseMocks()
+
+    // Run 1: agent does some work then hits an error
+    spyOn(mainPromptModule, 'callMainPrompt').mockImplementation(
+      async (params: Parameters<typeof mainPromptModule.callMainPrompt>[0]) => {
+        const mainAgentState = params.action.sessionState.mainAgentState
+
+        mainAgentState.messageHistory = [
+          ...mainAgentState.messageHistory,
+          {
+            role: 'user',
+            content: [{ type: 'text', text: 'Investigate the login bug' }],
+            tags: ['USER_PROMPT'],
+          },
+          assistantMessage('I found the problem in auth.ts on line 42.'),
+          {
+            role: 'assistant',
+            content: [
+              {
+                type: 'tool-call',
+                toolCallId: 'read-login',
+                toolName: 'read_files',
+                input: { paths: ['login.ts'] },
+              } as ToolCallContentBlock,
+            ],
+          },
+          {
+            role: 'tool',
+            toolCallId: 'read-login',
+            toolName: 'read_files',
+            content: [{ type: 'json', value: [{ path: 'login.ts', content: 'login code' }] }],
+          },
+        ]
+
+        const error = new Error('Service Unavailable') as Error & {
+          statusCode: number
+        }
+        error.statusCode = 503
+        throw error
+      },
+    )
+
+    const client = new CodebuffClient({ apiKey: 'test-key' })
+    const firstResult = await client.run({
+      agent: 'base2',
+      prompt: 'Investigate the login bug',
+    })
+
+    expect(firstResult.output.type).toBe('error')
+
+    // Run 2: use the failed run as previousRun
+    mock.restore()
+    setupDatabaseMocks()
+
+    let historyReceivedByRuntime: unknown[] | undefined
+    spyOn(mainPromptModule, 'callMainPrompt').mockImplementation(
+      async (params: Parameters<typeof mainPromptModule.callMainPrompt>[0]) => {
+        const { sendAction, promptId } = params
+        historyReceivedByRuntime = [
+          ...params.action.sessionState.mainAgentState.messageHistory,
+        ]
+
+        const responseSessionState = getInitialSessionState(
+          getStubProjectFileContext(),
+        )
+        responseSessionState.mainAgentState.messageHistory = [
+          ...params.action.sessionState.mainAgentState.messageHistory,
+          userMessage('Now try again'),
+          assistantMessage('Continuing with the fix.'),
+        ]
+
+        await sendAction({
+          action: {
+            type: 'prompt-response',
+            promptId,
+            sessionState: responseSessionState,
+            output: { type: 'lastMessage', value: [] },
+          },
+        })
+
+        return {
+          sessionState: responseSessionState,
+          output: { type: 'lastMessage' as const, value: [] },
+        }
+      },
+    )
+
+    const secondResult = await client.run({
+      agent: 'base2',
+      prompt: 'Now try again',
+      previousRun: firstResult,
+    })
+
+    // The runtime should have received history containing the work from the first run
+    expect(historyReceivedByRuntime).toBeDefined()
+    const receivedReadCall = historyReceivedByRuntime!.find(
+      (m) =>
+        (m as { role: string }).role === 'assistant' &&
+        ((m as { content: Array<{ type: string; toolCallId?: string }> })
+          .content ?? []).some(
+          (c) => c.type === 'tool-call' && c.toolCallId === 'read-login',
+        ),
+    )
+    expect(receivedReadCall).toBeDefined()
+
+    const receivedToolResult = historyReceivedByRuntime!.find(
+      (m) =>
+        (m as { role: string }).role === 'tool' &&
+        (m as { toolCallId: string }).toolCallId === 'read-login',
+    )
+    expect(receivedToolResult).toBeDefined()
+
+    // Final result should preserve history
+    const finalHistory = secondResult.sessionState!.mainAgentState.messageHistory
+    const finalReadCall = finalHistory.find(
+      (m) =>
+        m.role === 'assistant' &&
+        (m.content as Array<{ type: string; toolCallId?: string }>).some(
+          (c) => c.type === 'tool-call' && c.toolCallId === 'read-login',
+        ),
+    )
+    expect(finalReadCall).toBeDefined()
+  })
+})