deepseek-ai/deepseek-harness · error

acp: assistant output conversion failed: ${errorChain(error)

Error message

acp: assistant output conversion failed: ${errorChain(error)}

What it means

Error "acp: assistant output conversion failed: ${errorChain(error)}" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/acp/acp/src/index.ts:243

    try {
      if (event.type === 'assistant/message') {
        const inflight = record.inflight?.turn === event.data.turn ? record.inflight : undefined
        const previous = record.outputTail
        const delivery = previous.then(async () => {
          for (const block of event.data.message.content) {
            const content = await assistantBlockToAcp(ctx, block)
            if (content === undefined) continue
            await notify({
              sessionId: record.agent.session.id,
              update: { sessionUpdate: 'agent_message_chunk', content },
            })
          }
        })
        record.outputTail = delivery.catch((error: unknown) => {
          // assistantBlockToAcp owns conversion failures and always throws Error.
          const failure = error as Error
          if (inflight !== undefined) inflight.outputError ??= failure
          logger.warn(`acp: assistant output conversion failed: ${errorChain(error)}`)
        })
      }
    } finally {
      const inflight = record.inflight
      if (inflight !== undefined && event.type === 'turn/end' && inflight.turn === event.data.turn) {
        inflight.endReason = event.data.reason
      }
    }
  })

  ctx.on('agent/inbox/claimed', ({ agent, message, turn }) => {
    const record = ownedRecord(agent)
    const inflight = record?.inflight
    if (inflight !== undefined && inflight.messageId === message.id) inflight.turn = turn
  })

  ctx.on('agent/error', ({ agent, turn, error }) => {
    const record = ownedRecord(agent)

View on GitHub (pinned to b150a551b8)

Solutions

1. Inspect the wrapped error chain and fix the assistant output that failed conversion (unsupported content part).

When it happens

Trigger: Thrown at packages/acp/acp/src/index.ts:243 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/0b0331eb64d6964d. Report an issue: GitHub.