fix: preserve gemini thought signatures (#25933) (#26169) · coder/coder@9595e6c

"io"

"net/http"

"strings"

"github.com/coder/coder/v2/internal/googleopenai"

)

// OpenAI-compatible providers share an API shape but differ in the exact JSON

// they accept. These patches adjust Fantasy's serialized request body at the

// transport boundary so higher-level generation code can stay provider agnostic.

//

// googleOpenAICompatDummyThoughtSignature is Google's documented last-resort

// bypass for callers that cannot preserve a real Gemini thought signature.

// See https://ai.google.dev/gemini-api/docs/thought-signatures.

const googleOpenAICompatDummyThoughtSignature = "skip_thought_signature_validator"

func withOpenAICompatRequestPatches(

client *http.Client,

}

changed := rewriteOpenAICompatSingleToolChoice(payload)

if shouldAddGoogleOpenAICompatThoughtSignatures(baseURL, modelID) {

changed = addGoogleOpenAICompatThoughtSignatures(payload) || changed

if googleopenai.ShouldPatchOpenAICompatRequest(baseURL, modelID) {

changed = googleopenai.AddThoughtSignaturesToLatestTurn(payload) || changed

}

if !changed {

return body

payload["tool_choice"] = "required"

return true

}

// shouldAddGoogleOpenAICompatThoughtSignatures detects direct Gemini OpenAI

// endpoints and Coder AI Bridge Gemini routes. Other gateways, such as Vercel,

// keep their own provider-specific compatibility behavior.

func shouldAddGoogleOpenAICompatThoughtSignatures(baseURL string, modelID string) bool {

parsed, ok := parseProviderBaseURL(baseURL)

if !ok {

return false

}

host := strings.ToLower(parsed.Hostname())

path := strings.ToLower(parsed.EscapedPath())

if host == "generativelanguage.googleapis.com" && strings.Contains(path, "/openai") {

return true

}

return host == "coder-aibridge" && isGeminiModelID(modelID)

}

func isGeminiModelID(modelID string) bool {

modelID = strings.ToLower(strings.TrimSpace(modelID))

return strings.HasPrefix(modelID, "gemini-") || strings.Contains(modelID, "/gemini-")

}

// addGoogleOpenAICompatThoughtSignatures adds a dummy thought signature to the

// first tool call on each assistant tool-call message in the latest user turn.

// Gemini validates tool-call history with thought signatures, but

// OpenAI-compatible serialization can drop the original provider metadata.

func addGoogleOpenAICompatThoughtSignatures(payload map[string]any) bool {

messages, ok := payload["messages"].([]any)

if !ok {

return false

}

currentTurnStart := -1

for i, raw := range messages {

message, ok := raw.(map[string]any)

if !ok {

continue

}

if role, _ := message["role"].(string); role == "user" {

currentTurnStart = i

}

}

if currentTurnStart == -1 {

return false

}

changed := false

for _, raw := range messages[currentTurnStart+1:] {

message, ok := raw.(map[string]any)

if !ok || !isOpenAICompatAssistantRole(message["role"]) {

continue

}

toolCalls, ok := message["tool_calls"].([]any)

if !ok || len(toolCalls) == 0 {

continue

}

firstToolCall, ok := toolCalls[0].(map[string]any)

if !ok {

continue

}

if ensureGoogleOpenAICompatThoughtSignature(firstToolCall) {

changed = true

}

}

return changed

}

func isOpenAICompatAssistantRole(role any) bool {

roleValue, _ := role.(string)

return roleValue == "assistant" || roleValue == "model"

}

func ensureGoogleOpenAICompatThoughtSignature(toolCall map[string]any) bool {

extraContent, _ := toolCall["extra_content"].(map[string]any)

google, _ := extraContent["google"].(map[string]any)

if signature, _ := google["thought_signature"].(string); signature != "" {

return false

}

if extraContent == nil {

extraContent = map[string]any{}

toolCall["extra_content"] = extraContent

}

if google == nil {

google = map[string]any{}

extraContent["google"] = google

}

google["thought_signature"] = googleOpenAICompatDummyThoughtSignature

return true

}