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fix: signature + correct field for streaming reasoning thinking blocks #17

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fix: signature + correct field for streaming reasoning thinking blocks #17

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49 changes: 38 additions & 11 deletions internal/server/handlers.go
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Original file line number Diff line number Diff line change
Expand Up @@ -278,7 +278,35 @@ func streamOpenAIToClaude(w *bufio.Writer, reader io.Reader, providerModel strin
thinkingBlockIndex := 0 // Thinking block is always index 0
thinkingBlockStarted := false
thinkingBlockHasContent := false
textBlockStarted := false // Track if we've sent text block_start
thinkingBlockClosed := false // Track if thinking block was closed (with signature)
textBlockStarted := false // Track if we've sent text block_start

// closeThinkingBlock finalizes an open thinking block by emitting a
// signature_delta followed by content_block_stop. Claude Code discards
// thinking blocks that arrive without a signature, so reasoning models
// (LM Studio / OpenAI reasoning_content) would otherwise yield an empty
// response. The signature value is opaque for local/OpenAI-compatible
// providers (never validated against Anthropic), so a constant is safe.
// Idempotent: safe to call before every text/tool block and at stream end.
closeThinkingBlock := func() {
if !thinkingBlockStarted || !thinkingBlockHasContent || thinkingBlockClosed {
return
}
writeSSEEvent(w, "content_block_delta", map[string]interface{}{
"type": "content_block_delta",
"index": thinkingBlockIndex,
"delta": map[string]interface{}{
"type": "signature_delta",
"signature": "Y2MtcHJveHktbG9jYWwtcmVhc29uaW5n",
},
})
writeSSEEvent(w, "content_block_stop", map[string]interface{}{
"type": "content_block_stop",
"index": thinkingBlockIndex,
})
thinkingBlockClosed = true
_ = w.Flush()
}

// Send initial SSE events
writeSSEEvent(w, "message_start", map[string]interface{}{
Expand Down Expand Up @@ -412,8 +440,8 @@ func streamOpenAIToClaude(w *bufio.Writer, reader io.Reader, providerModel strin
"type": "content_block_delta",
"index": thinkingBlockIndex,
"delta": map[string]interface{}{
"type": "thinking_delta",
"text": reasoningContent,
"type": "thinking_delta",
"thinking": reasoningContent,
},
})
}
Expand Down Expand Up @@ -505,6 +533,8 @@ func streamOpenAIToClaude(w *bufio.Writer, reader io.Reader, providerModel strin

// Handle text delta
if content, ok := delta["content"].(string); ok && content != "" {
// Finalize any open thinking block (with signature) before text
closeThinkingBlock()
// Send content_block_start for text block on first text delta
if !textBlockStarted {
writeSSEEvent(w, "content_block_start", map[string]interface{}{
Expand Down Expand Up @@ -532,6 +562,8 @@ func streamOpenAIToClaude(w *bufio.Writer, reader io.Reader, providerModel strin

// Handle tool call deltas
if toolCallsRaw, ok := delta["tool_calls"]; ok {
// Finalize any open thinking block (with signature) before tool_use
closeThinkingBlock()
// Debug: Log raw tool_calls from provider
if cfg.Debug {
toolCallsJSON, _ := json.Marshal(toolCallsRaw)
Expand Down Expand Up @@ -671,14 +703,9 @@ func streamOpenAIToClaude(w *bufio.Writer, reader io.Reader, providerModel strin
}
}

// Send content_block_stop for thinking block if it had content
if thinkingBlockStarted && thinkingBlockHasContent {
writeSSEEvent(w, "content_block_stop", map[string]interface{}{
"type": "content_block_stop",
"index": thinkingBlockIndex,
})
_ = w.Flush()
}
// Finalize thinking block if still open (e.g. reasoning-only response with
// no text/tool content). Emits signature_delta + content_block_stop.
closeThinkingBlock()

// Debug: Check if usage data was received
if cfg.Debug {
Expand Down