fix(ai-chat): capture reasoning content during streaming for DeepSeek V4, resolving 400 errors

subediparas5 · subediparas5 · commit 65c63d0fb7f2 · 2026-05-15T08:56:21.000+05:45
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- AI Chat: DeepSeek V4 thinking content (`reasoning_content`) is now captured during streaming and passed back in subsequent turns, fixing 400 errors when using deepseek-v4-pro or deepseek-v4-flash.
 - MongoDB: the connection form now shows a Username field. It was hidden for databases where authentication is optional, so connections to auth-enabled servers saved with no credentials and every query failed with "requires authentication" even though the connection looked healthy.
 - SQL import dropped statements when the database executed them slower than the file was parsed, so a re-imported export could fail with errors like "relation does not exist". The parser now waits for each statement to be consumed before reading more. (#1264)
 - SQL import ignored the database dialect, so PostgreSQL dumps with dollar-quoted function bodies were split at semicolons inside the body. (#1264)
diff --git a/TablePro/Core/AI/OpenAICompatibleProvider.swift b/TablePro/Core/AI/OpenAICompatibleProvider.swift
@@ -71,6 +71,9 @@ final class OpenAICompatibleProvider: ChatTransport {
                         for event in result.events { continuation.yield(event) }
                         if result.shouldBreak { break }
                     }
+                    if let reasoningEnd = state.flushReasoningEnd() {
+                        continuation.yield(reasoningEnd)
+                    }
                     if let usage = state.finalUsageEvent() {
                         continuation.yield(usage)
                     }
@@ -113,6 +116,19 @@ final class OpenAICompatibleProvider: ChatTransport {
         let firstChoice = choices?.first
         let delta = firstChoice?["delta"] as? [String: Any]
 
+        if let delta, let reasoningContent = delta["reasoning_content"] as? String, !reasoningContent.isEmpty {
+            let reasoningID: String
+            if let existing = state.reasoningBlockID {
+                reasoningID = existing
+            } else {
+                let newID = "reasoning_\(UUID().uuidString.prefix(8))"
+                state.reasoningBlockID = newID
+                events.append(.reasoningStart(id: newID))
+                reasoningID = newID
+            }
+            events.append(.reasoningDelta(id: reasoningID, text: reasoningContent))
+        }
+
         if let delta, let content = delta["content"] as? String, !content.isEmpty {
             events.append(.textDelta(content))
         } else if let message = json["message"] as? [String: Any],
@@ -128,9 +144,13 @@ final class OpenAICompatibleProvider: ChatTransport {
             events.append(contentsOf: handleOllamaToolCalls(toolCalls, state: &state))
         }
 
-        if let finishReason = firstChoice?["finish_reason"] as? String,
-           finishReason == "tool_calls" {
-            events.append(contentsOf: state.flushToolUseEnds())
+        if let finishReason = firstChoice?["finish_reason"] as? String, !finishReason.isEmpty {
+            if let event = state.flushReasoningEnd() {
+                events.append(event)
+            }
+            if finishReason == "tool_calls" {
+                events.append(contentsOf: state.flushToolUseEnds())
+            }
         }
 
         if let usage = json["usage"] as? [String: Any],
@@ -373,6 +393,10 @@ final class OpenAICompatibleProvider: ChatTransport {
                     ]
                 ]
             }
+            let reasoningText = Self.plainReasoningText(from: turn)
+            if !reasoningText.isEmpty {
+                message["reasoning_content"] = reasoningText
+            }
             return [message]
         }
 
@@ -411,10 +435,26 @@ final class OpenAICompatibleProvider: ChatTransport {
         }
 
         guard !textContent.isEmpty else { return [] }
-        return [[
+        var message: [String: Any] = [
             "role": turn.role.rawValue,
             "content": textContent
-        ]]
+        ]
+        if turn.role == .assistant {
+            let reasoningText = Self.plainReasoningText(from: turn)
+            if !reasoningText.isEmpty {
+                message["reasoning_content"] = reasoningText
+            }
+        }
+        return [message]
+    }
+
+    private static func plainReasoningText(from turn: ChatTurnWire) -> String {
+        turn.blocks.compactMap { block -> String? in
+            guard case .reasoning(let rb) = block.kind,
+                  rb.opaque == nil,
+                  let text = rb.text else { return nil }
+            return text
+        }.joined()
     }
 
     private func chatCompletionsImagePart(_ input: ChatImageInput) -> [String: Any]? {
@@ -523,6 +563,13 @@ struct OpenAIStreamState {
     var outputTokens: Int = 0
     var toolCallIndexToId: [Int: String] = [:]
     var toolCallOrder: [Int] = []
+    var reasoningBlockID: String?
+
+    mutating func flushReasoningEnd() -> ChatStreamEvent? {
+        guard let id = reasoningBlockID else { return nil }
+        reasoningBlockID = nil
+        return .reasoningEnd(id: id, opaque: nil)
+    }
 
     /// Yield `.toolUseEnd` for every tracked tool call and clear the map.
     /// Called when the provider signals tool-call completion (`finish_reason`
diff --git a/TableProTests/Core/AI/OpenAICompatibleProviderEncodingTests.swift b/TableProTests/Core/AI/OpenAICompatibleProviderEncodingTests.swift
@@ -92,6 +92,59 @@ struct OpenAICompatibleProviderEncodingTests {
         #expect(messages[1]["tool_call_id"] as? String == "call_2")
     }
 
+    @Test("Assistant turn with plain reasoning block includes reasoning_content field")
+    func assistantWithPlainReasoning() {
+        let reasoning = ReasoningBlock(text: "I think about this step by step", opaque: nil)
+        let turn = ChatTurnWire(role: .assistant, blocks: [
+            .reasoning(reasoning),
+            .text("Here is my answer")
+        ])
+        let messages = makeProvider().encodeTurn(turn)
+        #expect(messages.count == 1)
+        #expect(messages[0]["role"] as? String == "assistant")
+        #expect(messages[0]["content"] as? String == "Here is my answer")
+        #expect(messages[0]["reasoning_content"] as? String == "I think about this step by step")
+    }
+
+    @Test("Assistant turn with Anthropic-signed reasoning does not include reasoning_content")
+    func assistantWithAnthropicReasoningOmitsField() {
+        let opaque = ReasoningOpaque(kind: .anthropicSignature, itemID: "blk_1", value: "sig123", blockType: "thinking")
+        let reasoning = ReasoningBlock(text: "hidden thinking", opaque: opaque)
+        let turn = ChatTurnWire(role: .assistant, blocks: [
+            .reasoning(reasoning),
+            .text("My answer")
+        ])
+        let messages = makeProvider().encodeTurn(turn)
+        #expect(messages.count == 1)
+        #expect(messages[0]["reasoning_content"] == nil)
+    }
+
+    @Test("Assistant turn with tool calls and plain reasoning includes reasoning_content")
+    func assistantWithToolCallsAndReasoning() {
+        let reasoning = ReasoningBlock(text: "need to check tables", opaque: nil)
+        let toolUse = ToolUseBlock(id: "call_1", name: "list_tables", input: .object([:]))
+        let turn = ChatTurnWire(role: .assistant, blocks: [
+            .reasoning(reasoning),
+            .toolUse(toolUse)
+        ])
+        let messages = makeProvider().encodeTurn(turn)
+        #expect(messages.count == 1)
+        #expect(messages[0]["tool_calls"] != nil)
+        #expect(messages[0]["reasoning_content"] as? String == "need to check tables")
+    }
+
+    @Test("User turn never includes reasoning_content even with reasoning blocks")
+    func userTurnWithReasoningOmitsField() {
+        let reasoning = ReasoningBlock(text: "user reasoning", opaque: nil)
+        let turn = ChatTurnWire(role: .user, blocks: [
+            .reasoning(reasoning),
+            .text("my question")
+        ])
+        let messages = makeProvider().encodeTurn(turn)
+        #expect(messages.count == 1)
+        #expect(messages[0]["reasoning_content"] == nil)
+    }
+
     @Test("Empty text turn returns no messages")
     func emptyTurnYieldsNothing() {
         let turn = ChatTurnWire(role: .user, blocks: [.text("")])
diff --git a/TableProTests/Core/AI/OpenAICompatibleProviderParserTests.swift b/TableProTests/Core/AI/OpenAICompatibleProviderParserTests.swift
@@ -4,8 +4,8 @@
 //
 
 import Foundation
-import TableProPluginKit
 @testable import TablePro
+import TableProPluginKit
 import Testing
 
 @Suite("OpenAICompatibleProvider stream parser")
@@ -175,6 +175,112 @@ struct OpenAICompatibleProviderParserTests {
         #expect(text == "hi")
     }
 
+    @Test("delta.reasoning_content on first chunk emits reasoningStart then reasoningDelta")
+    func reasoningContentFirstChunk() {
+        var state = OpenAIStreamState()
+        let result = OpenAICompatibleProvider.parseChunk([
+            "choices": [[
+                "delta": ["reasoning_content": "Let me think..."]
+            ]]
+        ], state: &state)
+        #expect(result.events.count == 2)
+        guard case .reasoningStart(let id) = result.events[0] else {
+            Issue.record("expected reasoningStart; got \(result.events[0])")
+            return
+        }
+        guard case .reasoningDelta(let deltaID, let text) = result.events[1] else {
+            Issue.record("expected reasoningDelta; got \(result.events[1])")
+            return
+        }
+        #expect(deltaID == id)
+        #expect(text == "Let me think...")
+        #expect(state.reasoningBlockID == id)
+    }
+
+    @Test("Subsequent delta.reasoning_content chunks emit only reasoningDelta (no duplicate start)")
+    func reasoningContentSubsequentChunk() {
+        var state = OpenAIStreamState()
+        state.reasoningBlockID = "reasoning_abc"
+        let result = OpenAICompatibleProvider.parseChunk([
+            "choices": [[
+                "delta": ["reasoning_content": " more thinking"]
+            ]]
+        ], state: &state)
+        #expect(result.events.count == 1)
+        guard case .reasoningDelta(let id, let text) = result.events[0] else {
+            Issue.record("expected reasoningDelta; got \(result.events)")
+            return
+        }
+        #expect(id == "reasoning_abc")
+        #expect(text == " more thinking")
+    }
+
+    @Test("finish_reason: stop flushes open reasoning block as reasoningEnd with nil opaque")
+    func finishReasonStopClosesReasoningBlock() {
+        var state = OpenAIStreamState()
+        state.reasoningBlockID = "reasoning_xyz"
+        let result = OpenAICompatibleProvider.parseChunk([
+            "choices": [["finish_reason": "stop"]]
+        ], state: &state)
+        #expect(result.events.count == 1)
+        guard case .reasoningEnd(let id, let opaque) = result.events[0] else {
+            Issue.record("expected reasoningEnd; got \(result.events)")
+            return
+        }
+        #expect(id == "reasoning_xyz")
+        #expect(opaque == nil)
+        #expect(state.reasoningBlockID == nil)
+    }
+
+    @Test("reasoning_content followed by finish_reason in same chunk emits start, delta, end")
+    func reasoningContentWithFinishReason() {
+        var state = OpenAIStreamState()
+        let result = OpenAICompatibleProvider.parseChunk([
+            "choices": [[
+                "delta": ["reasoning_content": "final thought"],
+                "finish_reason": "stop"
+            ]]
+        ], state: &state)
+        let kinds = result.events.map { event -> String in
+            switch event {
+            case .reasoningStart: return "start"
+            case .reasoningDelta: return "delta"
+            case .reasoningEnd: return "end"
+            default: return "other"
+            }
+        }
+        #expect(kinds == ["start", "delta", "end"])
+        #expect(state.reasoningBlockID == nil)
+    }
+
+    @Test("delta.reasoning_content: null is ignored and does not emit reasoningStart")
+    func reasoningContentNullIgnored() {
+        var state = OpenAIStreamState()
+        let result = OpenAICompatibleProvider.parseChunk([
+            "choices": [[
+                "delta": ["content": "hello", "reasoning_content": NSNull()]
+            ]]
+        ], state: &state)
+        #expect(state.reasoningBlockID == nil)
+        #expect(result.events.count == 1)
+        guard case .textDelta = result.events[0] else {
+            Issue.record("expected only textDelta; got \(result.events)")
+            return
+        }
+    }
+
+    @Test("finish_reason: stop does not flush pending tool calls")
+    func finishReasonStopLeavesToolCallsIntact() {
+        var state = OpenAIStreamState()
+        state.toolCallIndexToId = [0: "call_a"]
+        state.toolCallOrder = [0]
+        let result = OpenAICompatibleProvider.parseChunk([
+            "choices": [["finish_reason": "stop"]]
+        ], state: &state)
+        #expect(result.events.isEmpty)
+        #expect(state.toolCallIndexToId[0] == "call_a")
+    }
+
     @Test("Empty chunk yields no events and doesn't break")
     func emptyChunk() {
         var state = OpenAIStreamState()
