From d6c07ce66d2e64c58e67edf8868207bc09b591d9 Mon Sep 17 00:00:00 2001
From: Guilhem Lemouel <guilhemlemouel@gmail.com>
Date: Wed, 16 Sep 2026 13:02:35 +0200
Subject: [PATCH] fix(chat-sdk): read a tool's call and a model's thinking off
 the row
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A conversation row carries three things the SDK did not declare and so
never read: what a tool was called with, what it returned, and the
thinking behind an answer. For a tool that runs inside the agent's job
the row is the only copy of the first two, and for a failed tool the
result is what it failed with — so a conversation read back through the
SDK showed a tool call with nothing to expand and a failure with no
reason.

The AI SDK adapter already preferred a tool's result over the row's text
when reporting an error, so it needed only the data.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 chat-sdk/src/ai-sdk.ts | 28 ++++++++++++++++++++++------
 chat-sdk/src/api.ts    |  5 +++++
 chat-sdk/src/chat.ts   | 13 ++++++++++++-
 3 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/chat-sdk/src/ai-sdk.ts b/chat-sdk/src/ai-sdk.ts
index ba500446a3..527ece1e5c 100644
--- a/chat-sdk/src/ai-sdk.ts
+++ b/chat-sdk/src/ai-sdk.ts
@@ -1,5 +1,10 @@
 import type { ChatTransport, UIMessage, UIMessageChunk, UIMessagePart } from 'ai'
-import { WindmillApiError, WindmillChatApi, type WindmillChatApiOptions } from './api'
+import {
+  WindmillApiError,
+  WindmillChatApi,
+  type FlowConversationMessage,
+  type WindmillChatApiOptions
+} from './api'
 import { followJob } from './follow'
 import type { AgentStreamEvent } from './stream'
 import type { ChatMessage, Conversation } from './types'
@@ -101,7 +106,8 @@ export function createWindmillChatTransport<UI_MESSAGE extends UIMessage = UIMes
           stepName: row.step_name ?? undefined,
           pending: false,
           seq: row.created_seq,
-          tool: toolFromRowContent(row.message_type, row.content, row.success ?? true)
+          reasoning: row.reasoning ?? undefined,
+          tool: toolFromRow(row)
         }))
       ) as UI_MESSAGE[]
     },
@@ -123,10 +129,20 @@ export function createWindmillChatTransport<UI_MESSAGE extends UIMessage = UIMes
   }
 }
 
-function toolFromRowContent(role: string, content: string, success: boolean): ChatMessage['tool'] {
-  if (role !== 'tool') return undefined
-  const name = /^Used (.+) tool$/.exec(content)?.[1] ?? /^Error executing (.+)$/.exec(content)?.[1]
-  return name ? { name, status: success ? 'success' : 'error' } : undefined
+/** The call a stored tool row carries: its tool, named by the sentence the worker words
+ *  every tool row from, and the arguments and result the row keeps when its job cannot be
+ *  asked for them — for a failed tool, the result is what it failed with. */
+function toolFromRow(row: FlowConversationMessage): ChatMessage['tool'] {
+  if (row.message_type !== 'tool') return undefined
+  const name =
+    /^Used (.+) tool$/.exec(row.content)?.[1] ?? /^Error executing (.+)$/.exec(row.content)?.[1]
+  if (!name) return undefined
+  return {
+    name,
+    status: (row.success ?? true) ? 'success' : 'error',
+    arguments: row.tool_arguments ?? undefined,
+    result: row.tool_result ?? undefined
+  }
 }
 
 /** Streams a job's answer as AI SDK chunks; resumes from `entry.offset` when the job is already running. */
diff --git a/chat-sdk/src/api.ts b/chat-sdk/src/api.ts
index afc50ff0a1..c86f757247 100644
--- a/chat-sdk/src/api.ts
+++ b/chat-sdk/src/api.ts
@@ -40,6 +40,11 @@ export interface FlowConversationMessage {
   created_seq: number
   step_name?: string | null
   success?: boolean
+  /** The call a tool row carries itself, for a tool whose job cannot be asked for it. */
+  tool_arguments?: string | null
+  tool_result?: string | null
+  /** The thinking behind an answer, which is streamed and stored nowhere else. */
+  reasoning?: string | null
 }
 
 export type JobUpdateEvent =
diff --git a/chat-sdk/src/chat.ts b/chat-sdk/src/chat.ts
index dda8f10d05..3067c2d4f0 100644
--- a/chat-sdk/src/chat.ts
+++ b/chat-sdk/src/chat.ts
@@ -725,7 +725,18 @@ function fromRow(row: FlowConversationMessage): ChatMessage {
     stepName: row.step_name ?? undefined,
     pending: false,
     seq: row.created_seq,
-    tool: toolName ? { name: toolName, status: success ? 'success' : 'error' } : undefined
+    reasoning: row.reasoning ?? undefined,
+    // The call the row carries, which is all there is of it for a tool that ran inside the
+    // agent's job or failed before it had one of its own. For a failed tool the result is
+    // what it failed with, and the row's text names the tool rather than the reason.
+    tool: toolName
+      ? {
+          name: toolName,
+          status: success ? 'success' : 'error',
+          arguments: row.tool_arguments ?? undefined,
+          result: row.tool_result ?? undefined
+        }
+      : undefined
   }
 }