[BUG] Duplicate tool result after ask_user causes 400 "each tool_use must have a single result" on Claude

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Dal 19/10/2026.

Valutazione

Difficoltà
3/5
Tempo stimato
1-2 giorni
Idoneità per principianti
40/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Attiva
Stack tecnologico
go
Ambito
backend

Direzione di ricerca

The payload points at the session history replay: GET /api/sessions/<id> returns two functionResponse entries with the same ask_user call ID, and the adk-… confirmation items are skipped. Start by finding where the Go controller converts stored session events into Responses API input items, and check how function_call_output entries are keyed by call_id. Done when the replayed history has one result per call_id, with a test that feeds in a duplicate result for the same call. The root cause is still unconfirmed, so verify it before changing the code.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

📋 Prerequisites
  • I have searched the existing issues to avoid creating a duplicate
  • By submitting this issue, you agree to follow our Code of Conduct
  • I am using the latest version of the software
  • I have tried to clear cache/cookies or used incognito mode (if ui-related)
  • I can consistently reproduce this issue
🎯 Affected Service(s)

Controller Service

🚦 Impact/Severity

Minor inconvenience

🐛 Bug Description

After an agent calls ask_user and the user answers, the next model request fails with 400 Bad Request. Every later request in that session fails the same way, so the session is unusable.

The session history holds two functionResponse entries for the same ask_user call ID. When the history is replayed to the model, both are sent as results for one tool call. Claude on Bedrock rejects that, because each tool_use must have exactly one result.

kagent only shows OpenAI responses request failed: POST ".../responses": 400 Bad Request. The upstream error body is dropped, so the pod logs don't say why.

🔄 Steps To Reproduce
  1. Chat with an agent that has ask_user available, and get it to call ask_user. A vague request that needs clarification, like "what should I do to connect to other clusters?", works.
  2. Answer the question in the UI.
  3. Send another message, or let the agent continue.

The request after the answer fails with 400. It happened in two separate sessions for me.

To see the cause without the agent, fetch the session (GET /api/sessions/) and rebuild the history as Responses API input items: user and assistant text, function_call and function_call_output. Skip the adk-… confirmation items. POST that to the gateway's /responses endpoint with a few function tool definitions.

  • As stored: 400.
  • After keeping only the last function_call_output per call_id: 200.

This is my reconstruction of the replayed history, not a capture of the exact payload the agent sent.

🤔 Expected Behavior

The history sent to the model has exactly one result per tool call ID. For example, the placeholder is replaced by the final result, or dropped when the history is converted for the model.

📱 Actual Behavior

Error from the gateway

400 BAD_REQUEST
{"message":"messages.6.content.1: each tool_use must have a single result.
Found multiple tool_result blocks with id: toolu_bdrk_"}

💻 Environment
  • kagent chart and images 0.10.3 (golang-adk:0.10.3, controller 0.10.3, kagent-tools 0.3.0)
  • ModelConfig: provider OpenAI, apiFormat: responses, pointing at an OpenAI-compatible Responses endpoint on a Databricks AI gateway
  • Model: claude-sonnet-5 (Bedrock behind the gateway), maxTokens: 8192
  • Agent: the default k8s-agent
🔧 CLI Bug Report

No response

🔍 Additional Context

Version 0.10.3 does not fix this. I haven't tested the 1.0 alphas.
Related: #2836 asks for a switch to turn ask_user off, which would work around this.
Suggestion: log the upstream error body for a failed model call, with secrets redacted. Without a manual replay, the bare 400 gave no hint.

📋 Logs
📷 Screenshots
Image
🙋 Are you willing to contribute?
  • I am willing to submit a PR to fix this issue
Lingua principale
Go
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