fix: scope a structured answer's claim to its own turn and document the row fields as stored

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

backend/windmill-api/openapi.yaml

@@ -28371,16 +28371,17 @@ components:
           type: string
           nullable: true
           description: >-
-            The call, for a tool that runs inside the agent's job and so has none of its
-            own: an MCP tool, or a provider-native one such as web search. A Windmill tool
-            is a script or flow with its own job, and its call is read from there instead.
+            The arguments of an MCP tool call, which runs inside the agent's job and so has
+            none of its own. Null for a provider-native web search, whose query the provider
+            does not return, and for a Windmill tool, a script or flow whose own job holds
+            its call.
         tool_result:
           type: string
           nullable: true
           description: >-
-            What that same call returned, including the citations of a provider-native web
-            search, and what it failed with when it failed — the row's own text names the
-            tool rather than the reason. Null for a tool whose job holds the answer.
+            An MCP tool's result, a provider-native web search's citations, and for any
+            failed tool what it failed with — the row's own text names the tool rather than
+            the reason. Null for a successful Windmill tool, whose own job holds the result.
         reasoning:
           type: string
           nullable: true

chat-sdk/src/api.ts

@@ -40,10 +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. */
+  /** An MCP tool call's arguments; null for a web search and for a Windmill tool, whose own job holds its call. */
   tool_arguments?: string | null
+  /** An MCP tool's result, a web search's citations, and what any failed tool failed with. */
   tool_result?: string | null
-  /** The thinking behind an answer, which is streamed and stored nowhere else. */
+  /** The thinking of the iteration that produced this row; the agent job keeps the turn's thinking as one string. */
   reasoning?: string | null
 }
 

chat-sdk/src/chat.ts

@@ -622,12 +622,16 @@ class ChatImpl implements Chat {
           (m.content === row.content || (row.tool !== undefined && m.tool?.name === row.tool.name))
       )
       // A structured answer streams as thinking alone, its text arriving as a tool call
-      // the stream never turns into a message, so its row claims the pending message
-      // that holds that thinking and nothing else.
+      // the stream never turns into a message, so its row claims the message that holds
+      // that thinking and nothing else. Only past the newest user message: a turn stopped
+      // before its rows landed leaves such a message behind, and it is not this answer's.
       if (i < 0 && row.role === 'assistant' && row.reasoning !== undefined) {
-        i = messages.findIndex(
-          (m) => m.seq === undefined && m.role === 'assistant' && m.content === '' && m.reasoning !== undefined
-        )
+        let turnStart = messages.length - 1
+        while (turnStart >= 0 && messages[turnStart].role !== 'user') turnStart--
+        const j = messages
+          .slice(turnStart + 1)
+          .findIndex((m) => m.seq === undefined && m.role === 'assistant' && m.content === '' && m.reasoning !== undefined)
+        if (j >= 0) i = turnStart + 1 + j
       }
       if (i >= 0) {
         const m = messages[i]

chat-sdk/test/chat.test.ts

@@ -666,6 +666,49 @@ describe('createChat with server history', () => {
     ])
   })
 
+  test('a structured answer row leaves a stopped earlier turn its thinking', async () => {
+    let jobs = 0
+    const { fetch } = fetchMock(
+      (c) => (c.method === 'POST' && c.url.pathname.includes('/jobs/run/f/') ? text(`job-${++jobs}`) : undefined),
+      (c) =>
+        c.url.pathname.endsWith('/getupdate_sse/job-1')
+          ? sse([{ type: 'update', new_result_stream: ndjson({ type: 'reasoning_token_delta', content: 'first thoughts' }), stream_offset: 1 }])
+          : undefined,
+      (c) =>
+        c.url.pathname.endsWith('/getupdate_sse/job-2')
+          ? sse([
+              {
+                type: 'update',
+                new_result_stream: ndjson({ type: 'reasoning_token_delta', content: 'hmm' }),
+                stream_offset: 1,
+                completed: true,
+                only_result: { output: { n: 1 }, messages: [] }
+              }
+            ])
+          : undefined,
+      (c) => (c.url.pathname.includes('/queue/cancel/') ? text('ok') : undefined),
+      (c) =>
+        c.url.pathname.endsWith('/messages')
+          ? json([messageRow(41, 'user', 'first'), messageRow(42, 'user', 'again'), messageRow(43, 'assistant', '{"n":1}', { job_id: 'step-2', reasoning: 'hmm' })])
+          : undefined,
+      (c) => (c.url.pathname === '/api/w/ws/flow_conversations/list' ? json([]) : undefined)
+    )
+    const chat = createChat(options({}, fetch))
+    const first = chat.sendMessage('first')
+    await new Promise((r) => setTimeout(r, 50))
+    const stopped = chat.stop()
+    await first
+    const second = chat.sendMessage('again')
+    await stopped
+    await second
+    expect(chat.getState().messages.map((m) => [m.role, m.content, m.reasoning])).toEqual([
+      ['user', 'first', undefined],
+      ['assistant', '', 'first thoughts'],
+      ['user', 'again', undefined],
+      ['assistant', '{"n":1}', 'hmm']
+    ])
+  })
+
   test('the stream asks for a server poll interval only when one is set', async () => {
     const answer: Route = (c) =>
       c.url.pathname === streamPath ? sse([{ type: 'update', completed: true, only_result: 'ok' }]) : undefined