Function appendStreamToolInput

coderd/x/chatd/chatdebug/model.go:810–869

appendStreamToolInput accumulates incremental tool-input deltas per tool call ID so that parallel or sequential tool invocations remain distinguishable in interrupted stream debug payloads.

(
	content []normalizedContentPart,
	part fantasy.StreamPart,
	streamDebugBytes *int,
)

// per tool call ID so that parallel or sequential tool invocations
// remain distinguishable in interrupted stream debug payloads.
func appendStreamToolInput(
	content []normalizedContentPart,
	part fantasy.StreamPart,
	streamDebugBytes *int,
) []normalizedContentPart {
	if part.Delta == "" {
		return content
	}

	remaining := maxStreamDebugTextBytes
	if streamDebugBytes != nil {
		remaining -= *streamDebugBytes
	}
	if remaining <= 0 {
		return content
	}
	delta := part.Delta
	if len(delta) > remaining {
		cut := 0
		for _, r := range delta {
			size := utf8.RuneLen(r)
			if size < 0 {
				size = 1
			}
			if cut+size > remaining {
				break
			}
			cut += size
		}
		delta = delta[:cut]
	}
	if delta == "" {
		return content
	}

	// Find the existing tool_input part for this specific tool call ID.
	// Scan backwards through all content; tool_input deltas for the
	// same call may be separated by text, reasoning, or source parts
	// when streams interleave multiple tool invocations.
	for i := len(content) - 1; i >= 0; i-- {
		if content[i].Type == "tool_input" && content[i].ToolCallID == part.ID {
			content[i].Arguments += delta
			if streamDebugBytes != nil {
				*streamDebugBytes += len(delta)
			}
			return content
		}
	}

	content = append(content, normalizedContentPart{
		Type:       "tool_input",
		ToolCallID: part.ID,
		ToolName:   part.ToolCallName,
		Arguments:  delta,
	})
	if streamDebugBytes != nil {
		*streamDebugBytes += len(delta)
	}