Merge pull request #3900 from sususu98/fix/antigravity-replay-fc-order-upstream-dev

fix(antigravity): HOME Gemini replay and functionCall ordering before functionResponse

.gitignore

@@ -25,6 +25,7 @@ static/*
 
 # Authentication data
 auths/*
+/auths
 !auths/.gitkeep
 
 # Documentation
@@ -38,6 +39,7 @@ GEMINI.md
 .worktrees/
 .codex/*
 .claude/*
+.claude
 .gemini/*
 .serena/*
 .agent/*

internal/cache/antigravity_reasoning_replay_cache.go

@@ -0,0 +1,347 @@
+package cache
+
+import (
+	"context"
+	"encoding/json"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	homekv "github.com/router-for-me/CLIProxyAPI/v7/internal/home"
+	log "github.com/sirupsen/logrus"
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
+)
+
+const (
+	// AntigravityReasoningReplayCacheTTL limits how long encrypted reasoning replay
+	// items stay in process memory.
+	AntigravityReasoningReplayCacheTTL = 1 * time.Hour
+
+	// AntigravityReasoningReplayCacheMaxEntries bounds process memory for replay
+	// continuity. Oldest entries are evicted first.
+	AntigravityReasoningReplayCacheMaxEntries = 10240
+
+	// AntigravityReasoningReplayCacheEvictBatchSize leaves headroom after the cache
+	// reaches capacity so high write volume does not rescan the map every turn.
+	AntigravityReasoningReplayCacheEvictBatchSize = 128
+
+	minAntigravityThoughtSignatureReplayLen = 16
+)
+
+type antigravityReasoningReplayEntry struct {
+	Items     [][]byte
+	Timestamp time.Time
+}
+
+var (
+	antigravityReasoningReplayMu      sync.Mutex
+	antigravityReasoningReplayEntries = make(map[string]antigravityReasoningReplayEntry)
+)
+
+type antigravityReasoningReplayKVClient interface {
+	KVGet(ctx context.Context, key string) ([]byte, bool, error)
+	KVSet(ctx context.Context, key string, value []byte, opts homekv.KVSetOptions) (bool, error)
+	KVDel(ctx context.Context, keys ...string) (int64, error)
+	KVExpire(ctx context.Context, key string, ttl time.Duration) (bool, error)
+}
+
+var currentAntigravityReasoningReplayKVClient = func() (antigravityReasoningReplayKVClient, bool, error) {
+	return homekv.CurrentKVClient()
+}
+
+// CacheAntigravityReasoningReplayItem stores a final GPT/Codex reasoning item for
+// stateless replay. The stored item is normalized to the minimal shape accepted
+// by Responses input replay.
+func CacheAntigravityReasoningReplayItem(modelName, sessionKey string, item []byte) bool {
+	return CacheAntigravityReasoningReplayItems(modelName, sessionKey, [][]byte{item})
+}
+
+// CacheAntigravityReasoningReplayItems stores the final GPT/Codex assistant output
+// items needed to replay a stateless next turn.
+func CacheAntigravityReasoningReplayItems(modelName, sessionKey string, items [][]byte) bool {
+	return CacheAntigravityReasoningReplayItemsBestEffort(context.Background(), modelName, sessionKey, items)
+}
+
+// CacheAntigravityReasoningReplayItemsBestEffort stores replay items for completed response paths.
+func CacheAntigravityReasoningReplayItemsBestEffort(ctx context.Context, modelName, sessionKey string, items [][]byte) bool {
+	key := antigravityReasoningReplayCacheKey(modelName, sessionKey)
+	if key == "" {
+		return false
+	}
+	normalized, ok := normalizeAntigravityReasoningReplayItems(items)
+	if !ok {
+		return false
+	}
+	if client, homeMode, errClient := currentAntigravityReasoningReplayKVClient(); homeMode {
+		if errClient != nil {
+			log.Errorf("home kv best-effort antigravity reasoning replay set failed prefix=cpa:antigravity:*: %v", errClient)
+			return false
+		}
+		raw, errMarshal := json.Marshal(normalized)
+		if errMarshal != nil {
+			log.Errorf("home kv best-effort antigravity reasoning replay set failed prefix=cpa:antigravity:*: %v", errMarshal)
+			return false
+		}
+		written, errSet := client.KVSet(ctx, antigravityReasoningReplayKVKey(modelName, sessionKey), raw, homekv.KVSetOptions{EX: AntigravityReasoningReplayCacheTTL})
+		if errSet != nil {
+			log.Errorf("home kv best-effort antigravity reasoning replay set failed prefix=cpa:antigravity:*: %v", errSet)
+			return false
+		}
+		return written
+	}
+
+	cacheCleanupOnce.Do(startCacheCleanup)
+	now := time.Now()
+	antigravityReasoningReplayMu.Lock()
+	defer antigravityReasoningReplayMu.Unlock()
+	antigravityReasoningReplayEntries[key] = antigravityReasoningReplayEntry{
+		Items:     normalized,
+		Timestamp: now,
+	}
+	if len(antigravityReasoningReplayEntries) > AntigravityReasoningReplayCacheMaxEntries {
+		evictOldestAntigravityReasoningReplayEntries(AntigravityReasoningReplayCacheEvictBatchSize)
+	}
+	return true
+}
+
+// GetAntigravityReasoningReplayItem retrieves a normalized reasoning replay item.
+func GetAntigravityReasoningReplayItem(modelName, sessionKey string) ([]byte, bool) {
+	items, ok := GetAntigravityReasoningReplayItems(modelName, sessionKey)
+	if !ok || len(items) == 0 {
+		return nil, false
+	}
+	return items[0], true
+}
+
+// GetAntigravityReasoningReplayItems retrieves normalized assistant output items.
+func GetAntigravityReasoningReplayItems(modelName, sessionKey string) ([][]byte, bool) {
+	items, ok, err := GetAntigravityReasoningReplayItemsRequired(context.Background(), modelName, sessionKey)
+	if err == nil {
+		return items, ok
+	}
+	return nil, false
+}
+
+// GetAntigravityReasoningReplayItemsRequired retrieves replay items for request-time paths.
+func GetAntigravityReasoningReplayItemsRequired(ctx context.Context, modelName, sessionKey string) ([][]byte, bool, error) {
+	key := antigravityReasoningReplayCacheKey(modelName, sessionKey)
+	if key == "" {
+		return nil, false, nil
+	}
+	client, homeMode, errClient := currentAntigravityReasoningReplayKVClient()
+	if homeMode {
+		if errClient != nil {
+			return nil, false, errClient
+		}
+		raw, found, errGet := client.KVGet(ctx, antigravityReasoningReplayKVKey(modelName, sessionKey))
+		if errGet != nil || !found {
+			return nil, false, errGet
+		}
+		var homeItems [][]byte
+		if errUnmarshal := json.Unmarshal(raw, &homeItems); errUnmarshal != nil {
+			return nil, false, errUnmarshal
+		}
+		if _, errExpire := client.KVExpire(ctx, antigravityReasoningReplayKVKey(modelName, sessionKey), AntigravityReasoningReplayCacheTTL); errExpire != nil {
+			return nil, false, errExpire
+		}
+		return cloneAntigravityReasoningReplayItems(homeItems), true, nil
+	}
+
+	cacheCleanupOnce.Do(startCacheCleanup)
+	now := time.Now()
+	antigravityReasoningReplayMu.Lock()
+	defer antigravityReasoningReplayMu.Unlock()
+	entry, ok := antigravityReasoningReplayEntries[key]
+	if !ok {
+		return nil, false, nil
+	}
+	if now.Sub(entry.Timestamp) > AntigravityReasoningReplayCacheTTL {
+		delete(antigravityReasoningReplayEntries, key)
+		return nil, false, nil
+	}
+	entry.Timestamp = now
+	antigravityReasoningReplayEntries[key] = entry
+	return cloneAntigravityReasoningReplayItems(entry.Items), true, nil
+}
+
+// DeleteAntigravityReasoningReplayItem removes one replay item after upstream rejects
+// it or the caller otherwise knows it is stale.
+func DeleteAntigravityReasoningReplayItem(modelName, sessionKey string) {
+	if errDelete := DeleteAntigravityReasoningReplayItemRequired(context.Background(), modelName, sessionKey); errDelete != nil {
+		return
+	}
+}
+
+// DeleteAntigravityReasoningReplayItemRequired removes one replay item for request-time paths.
+func DeleteAntigravityReasoningReplayItemRequired(ctx context.Context, modelName, sessionKey string) error {
+	key := antigravityReasoningReplayCacheKey(modelName, sessionKey)
+	if key == "" {
+		return nil
+	}
+	client, homeMode, errClient := currentAntigravityReasoningReplayKVClient()
+	if homeMode {
+		if errClient != nil {
+			return errClient
+		}
+		_, errDel := client.KVDel(ctx, antigravityReasoningReplayKVKey(modelName, sessionKey))
+		return errDel
+	}
+	antigravityReasoningReplayMu.Lock()
+	delete(antigravityReasoningReplayEntries, key)
+	antigravityReasoningReplayMu.Unlock()
+	return nil
+}
+
+// ClearAntigravityReasoningReplayCache clears all Antigravity reasoning replay state.
+func ClearAntigravityReasoningReplayCache() {
+	antigravityReasoningReplayMu.Lock()
+	antigravityReasoningReplayEntries = make(map[string]antigravityReasoningReplayEntry)
+	antigravityReasoningReplayMu.Unlock()
+}
+
+func antigravityReasoningReplayCacheKey(modelName, sessionKey string) string {
+	modelName = strings.TrimSpace(modelName)
+	sessionKey = strings.TrimSpace(sessionKey)
+	if modelName == "" || sessionKey == "" {
+		return ""
+	}
+	// The session key is the continuity boundary. Keep this independent from
+	// the selected upstream Codex credential so auth failover can preserve replay.
+	return strings.Join([]string{"antigravity-reasoning-replay", modelName, sessionKey}, "\x00")
+}
+
+func antigravityReasoningReplayKVKey(modelName, sessionKey string) string {
+	return "cpa:antigravity:reasoning-replay:" + homekv.HashKeyPart(strings.TrimSpace(modelName)) + ":" + homekv.HashKeyPart(strings.TrimSpace(sessionKey))
+}
+
+func normalizeAntigravityReasoningReplayItems(items [][]byte) ([][]byte, bool) {
+	normalized := make([][]byte, 0, len(items))
+	for _, item := range items {
+		normalizedItem, ok := normalizeAntigravityReasoningReplayItem(item)
+		if ok {
+			normalized = append(normalized, normalizedItem)
+		}
+	}
+	return normalized, len(normalized) > 0
+}
+
+func normalizeAntigravityReasoningReplayItem(item []byte) ([]byte, bool) {
+	itemResult := gjson.ParseBytes(item)
+	switch strings.TrimSpace(itemResult.Get("type").String()) {
+	case "thought_signature":
+		return normalizeAntigravityThoughtSignatureReplayItem(itemResult)
+	case "function_call_part":
+		return normalizeAntigravityFunctionCallPartReplayItem(itemResult)
+	default:
+		return nil, false
+	}
+}
+
+func normalizeAntigravityThoughtSignatureReplayItem(itemResult gjson.Result) ([]byte, bool) {
+	sig := strings.TrimSpace(itemResult.Get("thoughtSignature").String())
+	if sig == "" {
+		sig = strings.TrimSpace(itemResult.Get("thought_signature").String())
+	}
+	if sig == "" || len(sig) < minAntigravityThoughtSignatureReplayLen {
+		return nil, false
+	}
+	normalized := []byte(`{"type":"thought_signature"}`)
+	normalized, _ = sjson.SetBytes(normalized, "thoughtSignature", sig)
+	if contentIndex := itemResult.Get("contentIndex"); contentIndex.Type == gjson.Number {
+		normalized, _ = sjson.SetBytes(normalized, "contentIndex", contentIndex.Int())
+	}
+	if partIndex := itemResult.Get("partIndex"); partIndex.Type == gjson.Number {
+		normalized, _ = sjson.SetBytes(normalized, "partIndex", partIndex.Int())
+	}
+	return normalized, true
+}
+
+func normalizeAntigravityFunctionCallPartReplayItem(itemResult gjson.Result) ([]byte, bool) {
+	callID := strings.TrimSpace(itemResult.Get("call_id").String())
+	if callID == "" {
+		callID = strings.TrimSpace(itemResult.Get("id").String())
+	}
+	name := strings.TrimSpace(itemResult.Get("name").String())
+	args := itemResult.Get("args")
+	if name == "" || !args.Exists() {
+		fc := itemResult.Get("functionCall")
+		if fc.Exists() {
+			if callID == "" {
+				callID = strings.TrimSpace(fc.Get("id").String())
+			}
+			if name == "" {
+				name = strings.TrimSpace(fc.Get("name").String())
+			}
+			if !args.Exists() {
+				args = fc.Get("args")
+			}
+		}
+	}
+	if name == "" || !args.Exists() {
+		return nil, false
+	}
+	normalized := []byte(`{"type":"function_call_part"}`)
+	if callID != "" {
+		normalized, _ = sjson.SetBytes(normalized, "call_id", callID)
+	}
+	normalized, _ = sjson.SetBytes(normalized, "name", name)
+	if args.Type == gjson.String {
+		normalized, _ = sjson.SetBytes(normalized, "args", args.String())
+	} else {
+		normalized, _ = sjson.SetRawBytes(normalized, "args", []byte(args.Raw))
+	}
+	sig := strings.TrimSpace(itemResult.Get("thoughtSignature").String())
+	if sig != "" {
+		normalized, _ = sjson.SetBytes(normalized, "thoughtSignature", sig)
+	}
+	if contentIndex := itemResult.Get("contentIndex"); contentIndex.Type == gjson.Number {
+		normalized, _ = sjson.SetBytes(normalized, "contentIndex", contentIndex.Int())
+	}
+	if partIndex := itemResult.Get("partIndex"); partIndex.Type == gjson.Number {
+		normalized, _ = sjson.SetBytes(normalized, "partIndex", partIndex.Int())
+	}
+	return normalized, true
+}
+
+func cloneAntigravityReasoningReplayItems(items [][]byte) [][]byte {
+	cloned := make([][]byte, 0, len(items))
+	for _, item := range items {
+		cloned = append(cloned, append([]byte(nil), item...))
+	}
+	return cloned
+}
+
+func evictOldestAntigravityReasoningReplayEntries(count int) {
+	if count <= 0 || len(antigravityReasoningReplayEntries) == 0 {
+		return
+	}
+	type candidate struct {
+		key       string
+		timestamp time.Time
+	}
+	candidates := make([]candidate, 0, len(antigravityReasoningReplayEntries))
+	for key, entry := range antigravityReasoningReplayEntries {
+		candidates = append(candidates, candidate{key: key, timestamp: entry.Timestamp})
+	}
+	sort.Slice(candidates, func(i, j int) bool {
+		return candidates[i].timestamp.Before(candidates[j].timestamp)
+	})
+	if count > len(candidates) {
+		count = len(candidates)
+	}
+	for i := 0; i < count; i++ {
+		delete(antigravityReasoningReplayEntries, candidates[i].key)
+	}
+}
+
+func purgeExpiredAntigravityReasoningReplayCache(now time.Time) {
+	antigravityReasoningReplayMu.Lock()
+	for key, entry := range antigravityReasoningReplayEntries {
+		if now.Sub(entry.Timestamp) > AntigravityReasoningReplayCacheTTL {
+			delete(antigravityReasoningReplayEntries, key)
+		}
+	}
+	antigravityReasoningReplayMu.Unlock()
+}

internal/cache/signature_cache.go

@@ -109,6 +109,7 @@ func purgeExpiredCaches() {
 		return true
 	})
 	purgeExpiredCodexReasoningReplayCache(now)
+	purgeExpiredAntigravityReasoningReplayCache(now)
 }
 
 // CacheSignature stores a thinking signature for a given model group and text.

internal/runtime/executor/antigravity_executor.go

@@ -306,9 +306,6 @@ func validateAntigravityRequestSignatures(ctx context.Context, modelName string,
 	rawJSON = antigravityclaude.StripEmptySignatureThinkingBlocks(rawJSON)
 	logAntigravitySignatureStrip(before, countClaudeThinkingBlocks(rawJSON), "prefix_cleanup", "empty_or_non_claude_signature")
 	if cache.SignatureCacheEnabled() {
-		if errRequire := antigravityclaude.RequireCachedThinkingSignatures(ctx, modelName, rawJSON); errRequire != nil {
-			return nil, homeKVUnavailableStatusErr(errRequire)
-		}
 		return rawJSON, nil
 	}
 	if !cache.SignatureBypassStrictMode() {
@@ -691,6 +688,15 @@ attemptLoop:
 					helps.MarkCreditsUsed(ctx)
 				}
 			}
+			replayScope := antigravityReasoningReplayScope{}
+			if antigravityUsesReasoningReplayCache(baseModel) {
+				var errReplay error
+				requestPayload, replayScope, errReplay = prepareAntigravityGeminiReasoningReplayPayload(ctx, baseModel, req, opts, requestPayload)
+				if errReplay != nil {
+					err = errReplay
+					return resp, err
+				}
+			}
 
 			httpReq, errReq := e.buildRequest(ctx, auth, token, baseModel, requestPayload, false, opts.Alt, baseURL)
 			if errReq != nil {
@@ -798,6 +804,10 @@ attemptLoop:
 						continue attemptLoop
 					}
 				}
+				if errClear := clearAntigravityReasoningReplayOnInvalidSignature(ctx, replayScope, httpResp.StatusCode, bodyBytes); errClear != nil {
+					err = errClear
+					return resp, err
+				}
 				err = newAntigravityStatusErr(httpResp.StatusCode, bodyBytes)
 				return resp, err
 			}
@@ -806,6 +816,7 @@ attemptLoop:
 			if useCredits {
 				clearAntigravityCreditsFailureState(auth)
 			}
+			cacheAntigravityReasoningReplayFromResponse(ctx, replayScope, requestPayload, bodyBytes)
 			bodyBytes = e.resolveWebSearchGroundingURLs(ctx, auth, from, originalPayload, translated, bodyBytes)
 			reporter.Publish(ctx, helps.ParseAntigravityUsage(bodyBytes))
 			var param any
@@ -1369,6 +1380,15 @@ attemptLoop:
 					helps.MarkCreditsUsed(ctx)
 				}
 			}
+			replayScope := antigravityReasoningReplayScope{}
+			if antigravityUsesReasoningReplayCache(baseModel) {
+				var errReplay error
+				requestPayload, replayScope, errReplay = prepareAntigravityGeminiReasoningReplayPayload(ctx, baseModel, req, opts, requestPayload)
+				if errReplay != nil {
+					err = errReplay
+					return nil, err
+				}
+			}
 			httpReq, errReq := e.buildRequest(ctx, auth, token, baseModel, requestPayload, true, opts.Alt, baseURL)
 			if errReq != nil {
 				err = errReq
@@ -1487,6 +1507,10 @@ attemptLoop:
 						continue attemptLoop
 					}
 				}
+				if errClear := clearAntigravityReasoningReplayOnInvalidSignature(ctx, replayScope, httpResp.StatusCode, bodyBytes); errClear != nil {
+					err = errClear
+					return nil, err
+				}
 				err = newAntigravityStatusErr(httpResp.StatusCode, bodyBytes)
 				return nil, err
 			}
@@ -1495,12 +1519,16 @@ attemptLoop:
 			if useCredits {
 				clearAntigravityCreditsFailureState(auth)
 			}
+			replayAccumulator := newAntigravityReasoningReplayAccumulator(replayScope, requestPayload)
 			out := make(chan cliproxyexecutor.StreamChunk)
 			go func(resp *http.Response) {
 				defer close(out)
 				defer func() {
+					if replayAccumulator != nil {
+						replayAccumulator.Flush(ctx)
+					}
 					if errClose := resp.Body.Close(); errClose != nil {
-						log.Errorf("antigravity executor: close response body error: %v", errClose)
+						log.Errorf("antigravity executor: close response line error: %v", errClose)
 					}
 				}()
 				scanner := bufio.NewScanner(resp.Body)
@@ -1509,6 +1537,9 @@ attemptLoop:
 				for scanner.Scan() {
 					line := scanner.Bytes()
 					helps.AppendAPIResponseChunk(ctx, e.cfg, line)
+					if replayAccumulator != nil {
+						replayAccumulator.ObserveSSELine(line)
+					}
 
 					// Filter usage metadata for all models
 					// Only retain usage statistics in the terminal chunk
@@ -2229,9 +2260,10 @@ func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyau
 			payloadStr, _ = sjson.Delete(payloadStr, "request.generationConfig.maxOutputTokens")
 		}
 
-		bodyReader = strings.NewReader(payloadStr)
+		payloadStrBytes := applyAntigravityNativeSignatureReplayIfNeeded(modelName, []byte(payloadStr))
+		bodyReader = bytes.NewReader(payloadStrBytes)
 		if e.cfg != nil && e.cfg.RequestLog {
-			payloadLog = []byte(payloadStr)
+			payloadLog = append([]byte(nil), payloadStrBytes...)
 		}
 	} else {
 		if strings.Contains(modelName, "claude") {
@@ -2240,6 +2272,7 @@ func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyau
 			payload, _ = sjson.DeleteBytes(payload, "request.generationConfig.maxOutputTokens")
 		}
 
+		payload = applyAntigravityNativeSignatureReplayIfNeeded(modelName, payload)
 		bodyReader = bytes.NewReader(payload)
 		if e.cfg != nil && e.cfg.RequestLog {
 			payloadLog = append([]byte(nil), payload...)

internal/runtime/executor/antigravity_reasoning_replay.go

@@ -0,0 +1,607 @@
+package executor
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+
+	internalcache "github.com/router-for-me/CLIProxyAPI/v7/internal/cache"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/runtime/executor/helps"
+	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/executor"
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
+)
+
+type antigravityReasoningReplayScope struct {
+	modelName  string
+	sessionKey string
+}
+
+func (s antigravityReasoningReplayScope) valid() bool {
+	return strings.TrimSpace(s.modelName) != "" && strings.TrimSpace(s.sessionKey) != ""
+}
+
+func antigravityReasoningReplayScopeFromPayload(modelName string, payload []byte) antigravityReasoningReplayScope {
+	sessionID := antigravityReplaySessionIDFromPayload(payload)
+	if sessionID == "" {
+		if stable := strings.TrimSpace(generateStableSessionID(payload)); stable != "" {
+			sessionID = strings.TrimPrefix(stable, "-")
+			if sessionID == "" {
+				sessionID = stable
+			}
+		}
+	}
+	if sessionID == "" {
+		return antigravityReasoningReplayScope{}
+	}
+	return antigravityReasoningReplayScope{
+		modelName:  strings.TrimSpace(modelName),
+		sessionKey: "session:" + sessionID,
+	}
+}
+
+func antigravityReasoningReplayScopeFromRequest(ctx context.Context, modelName string, req cliproxyexecutor.Request, opts cliproxyexecutor.Options, payload []byte) antigravityReasoningReplayScope {
+	if scope := antigravityReasoningReplayScopeFromPayload(modelName, payload); scope.valid() {
+		return scope
+	}
+	if scope := antigravityReasoningReplayScopeFromPayload(modelName, req.Payload); scope.valid() {
+		return scope
+	}
+	if value := metadataString(opts.Metadata, cliproxyexecutor.ExecutionSessionMetadataKey); value != "" {
+		return antigravityReasoningReplayScope{modelName: modelName, sessionKey: "execution:" + value}
+	}
+	if value := metadataString(req.Metadata, cliproxyexecutor.ExecutionSessionMetadataKey); value != "" {
+		return antigravityReasoningReplayScope{modelName: modelName, sessionKey: "execution:" + value}
+	}
+	_ = ctx
+	return antigravityReasoningReplayScope{}
+}
+
+func antigravityReplaySessionIDFromPayload(payload []byte) string {
+	if len(payload) == 0 {
+		return ""
+	}
+	for _, path := range []string{"sessionId", "session_id", "request.sessionId", "request.session_id"} {
+		if id := strings.TrimSpace(gjson.GetBytes(payload, path).String()); id != "" {
+			return id
+		}
+	}
+	return ""
+}
+
+func antigravityReasoningReplayPendingModelContentIndex(payload []byte) (contentIndex int, basePartIndex int) {
+	contents := gjson.GetBytes(payload, "request.contents")
+	if !contents.IsArray() {
+		return 0, 0
+	}
+	arr := contents.Array()
+	if len(arr) == 0 {
+		return 0, 0
+	}
+	last := arr[len(arr)-1]
+	if strings.EqualFold(strings.TrimSpace(last.Get("role").String()), "model") {
+		ci := len(arr) - 1
+		parts := last.Get("parts")
+		base := 0
+		if parts.IsArray() {
+			base = len(parts.Array())
+		}
+		return ci, base
+	}
+	return len(arr), 0
+}
+
+func antigravityReasoningReplayResolveContentIndex(payload []byte, cached int) int {
+	contents := gjson.GetBytes(payload, "request.contents")
+	if !contents.IsArray() {
+		return cached
+	}
+	arr := contents.Array()
+	if cached >= 0 && cached < len(arr) {
+		return cached
+	}
+	for i := len(arr) - 1; i >= 0; i-- {
+		if strings.EqualFold(strings.TrimSpace(arr[i].Get("role").String()), "model") {
+			return i
+		}
+	}
+	if len(arr) == 0 {
+		return 0
+	}
+	return len(arr) - 1
+}
+
+func prepareAntigravityGeminiReasoningReplayPayload(ctx context.Context, modelName string, req cliproxyexecutor.Request, opts cliproxyexecutor.Options, payload []byte) ([]byte, antigravityReasoningReplayScope, error) {
+	if !antigravityUsesReasoningReplayCache(modelName) {
+		return payload, antigravityReasoningReplayScope{}, nil
+	}
+	return applyAntigravityReasoningReplayCache(ctx, modelName, req, opts, payload)
+}
+
+func clearAntigravityReasoningReplayOnInvalidSignature(ctx context.Context, scope antigravityReasoningReplayScope, statusCode int, body []byte) error {
+	if !scope.valid() {
+		return nil
+	}
+	if statusCode != http.StatusBadRequest {
+		return nil
+	}
+	bodyText := strings.ToLower(string(body))
+	if !strings.Contains(bodyText, "thoughtsignature") && !strings.Contains(bodyText, "thought_signature") && !strings.Contains(bodyText, "signature") {
+		return nil
+	}
+	return internalcache.DeleteAntigravityReasoningReplayItemRequired(ctx, scope.modelName, scope.sessionKey)
+}
+
+func applyAntigravityReasoningReplayCache(ctx context.Context, modelName string, req cliproxyexecutor.Request, opts cliproxyexecutor.Options, payload []byte) ([]byte, antigravityReasoningReplayScope, error) {
+	scope := antigravityReasoningReplayScopeFromRequest(ctx, modelName, req, opts, payload)
+	if !scope.valid() {
+		return payload, scope, nil
+	}
+	items, ok, err := internalcache.GetAntigravityReasoningReplayItemsRequired(ctx, scope.modelName, scope.sessionKey)
+	if err != nil || !ok || len(items) == 0 {
+		return payload, scope, err
+	}
+	items = filterAntigravityReasoningReplayItemsForRequest(payload, items)
+	if len(items) == 0 {
+		return payload, scope, nil
+	}
+	updated, okApply := insertAntigravityReasoningReplayItems(payload, items)
+	if !okApply {
+		return payload, scope, nil
+	}
+	return updated, scope, nil
+}
+
+func filterAntigravityReasoningReplayItemsForRequest(payload []byte, items [][]byte) [][]byte {
+	existing := antigravityExistingToolCallKeys(payload)
+	filtered := make([][]byte, 0, len(items))
+	for _, item := range items {
+		itemResult := gjson.ParseBytes(item)
+		switch strings.TrimSpace(itemResult.Get("type").String()) {
+		case "function_call_part":
+			keys := antigravityReplayToolCallKeys(itemResult)
+			if len(keys) == 0 {
+				continue
+			}
+			if antigravityAnyKeyExists(existing, keys) {
+				if !antigravityNeedsSignatureReplayForExistingFunctionCall(payload, itemResult) {
+					continue
+				}
+			}
+			if !antigravityRequestHasMatchingFunctionResponse(payload, itemResult) {
+				continue
+			}
+		case "thought_signature":
+			if antigravityRequestHasThoughtSignatureAt(payload, itemResult) {
+				continue
+			}
+		default:
+			continue
+		}
+		filtered = append(filtered, item)
+	}
+	return filtered
+}
+
+func antigravityExistingToolCallKeys(payload []byte) map[string]bool {
+	existing := make(map[string]bool)
+	contents := gjson.GetBytes(payload, "request.contents")
+	if !contents.IsArray() {
+		return existing
+	}
+	for _, content := range contents.Array() {
+		parts := content.Get("parts")
+		if !parts.IsArray() {
+			continue
+		}
+		for _, part := range parts.Array() {
+			if fc := part.Get("functionCall"); fc.Exists() {
+				for _, key := range antigravityReplayToolCallKeysFromPart(fc) {
+					existing[key] = true
+				}
+			}
+		}
+	}
+	return existing
+}
+
+func antigravityReplayToolCallKeys(itemResult gjson.Result) []string {
+	callID := strings.TrimSpace(itemResult.Get("call_id").String())
+	if callID == "" {
+		callID = strings.TrimSpace(itemResult.Get("id").String())
+	}
+	name := strings.TrimSpace(itemResult.Get("name").String())
+	if name == "" {
+		return nil
+	}
+	args := itemResult.Get("args").Raw
+	key := antigravityFunctionCallKey(name, args, callID)
+	if key == "" {
+		return nil
+	}
+	return []string{key}
+}
+
+func antigravityReplayToolCallKeysFromPart(fc gjson.Result) []string {
+	return antigravityReplayToolCallKeys(gjson.Parse(fc.Raw))
+}
+
+func antigravityFunctionCallKey(name, argsRaw, callID string) string {
+	name = strings.TrimSpace(name)
+	if name == "" {
+		return ""
+	}
+	h := sha256.Sum256([]byte(strings.Join([]string{name, argsRaw, callID}, "\x00")))
+	return fmt.Sprintf("fc:%x", h[:8])
+}
+
+func antigravityAnyKeyExists(existing map[string]bool, keys []string) bool {
+	for _, key := range keys {
+		if existing[key] {
+			return true
+		}
+	}
+	return false
+}
+
+func antigravityNeedsSignatureReplayForExistingFunctionCall(payload []byte, itemResult gjson.Result) bool {
+	callID := strings.TrimSpace(itemResult.Get("call_id").String())
+	if callID == "" {
+		callID = strings.TrimSpace(itemResult.Get("id").String())
+	}
+	sig := strings.TrimSpace(itemResult.Get("thoughtSignature").String())
+	if callID == "" || sig == "" {
+		return false
+	}
+	ci, pi, ok := antigravityFunctionCallPartLocation(payload, callID)
+	if !ok {
+		return false
+	}
+	pathSig := fmt.Sprintf("request.contents.%d.parts.%d.thoughtSignature", ci, pi)
+	return strings.TrimSpace(gjson.GetBytes(payload, pathSig).String()) == ""
+}
+
+func antigravityRequestHasMatchingFunctionResponse(payload []byte, itemResult gjson.Result) bool {
+	callID := strings.TrimSpace(itemResult.Get("call_id").String())
+	if callID == "" {
+		return true
+	}
+	_, ok := antigravityFunctionResponseContentIndex(payload, callID)
+	return ok
+}
+
+func antigravityFunctionResponseContentIndex(payload []byte, callID string) (int, bool) {
+	callID = strings.TrimSpace(callID)
+	if callID == "" {
+		return -1, false
+	}
+	contents := gjson.GetBytes(payload, "request.contents")
+	if !contents.IsArray() {
+		return -1, false
+	}
+	for i, content := range contents.Array() {
+		parts := content.Get("parts")
+		if !parts.IsArray() {
+			continue
+		}
+		for _, part := range parts.Array() {
+			fr := part.Get("functionResponse")
+			if fr.Exists() && strings.TrimSpace(fr.Get("id").String()) == callID {
+				return i, true
+			}
+		}
+	}
+	return -1, false
+}
+
+func antigravityPayloadHasFunctionCallID(payload []byte, callID string) bool {
+	_, _, ok := antigravityFunctionCallPartLocation(payload, callID)
+	return ok
+}
+
+func antigravityFunctionCallPartLocation(payload []byte, callID string) (contentIndex int, partIndex int, ok bool) {
+	callID = strings.TrimSpace(callID)
+	if callID == "" {
+		return -1, -1, false
+	}
+	contents := gjson.GetBytes(payload, "request.contents")
+	if !contents.IsArray() {
+		return -1, -1, false
+	}
+	for ci, content := range contents.Array() {
+		parts := content.Get("parts")
+		if !parts.IsArray() {
+			continue
+		}
+		for pi, part := range parts.Array() {
+			fc := part.Get("functionCall")
+			if fc.Exists() && strings.TrimSpace(fc.Get("id").String()) == callID {
+				return ci, pi, true
+			}
+		}
+	}
+	return -1, -1, false
+}
+
+func insertAntigravityModelFunctionCallBeforeContent(payload []byte, beforeIndex int, name, callID, thoughtSig string, args gjson.Result) ([]byte, bool) {
+	contents := gjson.GetBytes(payload, "request.contents")
+	if !contents.IsArray() {
+		return payload, false
+	}
+	arr := contents.Array()
+	if beforeIndex < 0 || beforeIndex > len(arr) {
+		return payload, false
+	}
+	fc := map[string]any{"name": name}
+	if callID != "" {
+		fc["id"] = callID
+	}
+	if args.Exists() {
+		fc["args"] = args.Value()
+	}
+	part := map[string]any{"functionCall": fc}
+	if thoughtSig != "" {
+		part["thoughtSignature"] = thoughtSig
+	}
+	newContent := map[string]any{
+		"role":  "model",
+		"parts": []any{part},
+	}
+	newArr := make([]any, 0, len(arr)+1)
+	for i := 0; i < beforeIndex; i++ {
+		newArr = append(newArr, arr[i].Value())
+	}
+	newArr = append(newArr, newContent)
+	for i := beforeIndex; i < len(arr); i++ {
+		newArr = append(newArr, arr[i].Value())
+	}
+	updated, err := sjson.SetBytes(payload, "request.contents", newArr)
+	if err != nil {
+		return payload, false
+	}
+	return updated, true
+}
+
+func antigravityRequestHasThoughtSignatureAt(payload []byte, itemResult gjson.Result) bool {
+	ci := int(itemResult.Get("contentIndex").Int())
+	pi := int(itemResult.Get("partIndex").Int())
+	path := fmt.Sprintf("request.contents.%d.parts.%d.thoughtSignature", ci, pi)
+	return strings.TrimSpace(gjson.GetBytes(payload, path).String()) != ""
+}
+
+func insertAntigravityReasoningReplayItems(payload []byte, items [][]byte) ([]byte, bool) {
+	out := payload
+	changed := false
+	for _, item := range items {
+		itemResult := gjson.ParseBytes(item)
+		switch strings.TrimSpace(itemResult.Get("type").String()) {
+		case "thought_signature":
+			ci := antigravityReasoningReplayResolveContentIndex(out, int(itemResult.Get("contentIndex").Int()))
+			pi := int(itemResult.Get("partIndex").Int())
+			sig := strings.TrimSpace(itemResult.Get("thoughtSignature").String())
+			if sig == "" {
+				continue
+			}
+			path := fmt.Sprintf("request.contents.%d.parts.%d.thoughtSignature", ci, pi)
+			if strings.TrimSpace(gjson.GetBytes(out, path).String()) != "" {
+				continue
+			}
+			updated, err := sjson.SetBytes(out, path, sig)
+			if err != nil {
+				continue
+			}
+			out = updated
+			changed = true
+		case "function_call_part":
+			updated, ok := mergeAntigravityFunctionCallPartReplay(out, itemResult)
+			if ok {
+				out = updated
+				changed = true
+			}
+		}
+	}
+	return out, changed
+}
+
+func mergeAntigravityFunctionCallPartReplay(payload []byte, itemResult gjson.Result) ([]byte, bool) {
+	name := strings.TrimSpace(itemResult.Get("name").String())
+	args := itemResult.Get("args")
+	callID := strings.TrimSpace(itemResult.Get("call_id").String())
+	sig := strings.TrimSpace(itemResult.Get("thoughtSignature").String())
+	if name == "" || !args.Exists() {
+		return payload, false
+	}
+	if callID != "" {
+		if ci, pi, exists := antigravityFunctionCallPartLocation(payload, callID); exists {
+			if sig != "" {
+				pathSig := fmt.Sprintf("request.contents.%d.parts.%d.thoughtSignature", ci, pi)
+				if strings.TrimSpace(gjson.GetBytes(payload, pathSig).String()) == "" {
+					if updated, err := sjson.SetBytes(payload, pathSig, sig); err == nil {
+						return updated, true
+					}
+				}
+			}
+			return payload, false
+		}
+		if frIndex, ok := antigravityFunctionResponseContentIndex(payload, callID); ok {
+			return insertAntigravityModelFunctionCallBeforeContent(payload, frIndex, name, callID, sig, args)
+		}
+	}
+
+	ci := antigravityReasoningReplayResolveContentIndex(payload, int(itemResult.Get("contentIndex").Int()))
+	pi := int(itemResult.Get("partIndex").Int())
+	pathSig := fmt.Sprintf("request.contents.%d.parts.%d.thoughtSignature", ci, pi)
+	out := payload
+	changed := false
+	if sig != "" && strings.TrimSpace(gjson.GetBytes(out, pathSig).String()) == "" {
+		if updated, err := sjson.SetBytes(out, pathSig, sig); err == nil {
+			out = updated
+			changed = true
+		}
+	}
+	pathFC := fmt.Sprintf("request.contents.%d.parts.%d.functionCall", ci, pi)
+	if !gjson.GetBytes(out, pathFC).Exists() {
+		fc := map[string]any{"name": name}
+		if callID != "" {
+			fc["id"] = callID
+		}
+		if args.Type == gjson.String {
+			fc["args"] = args.String()
+		} else {
+			var parsed any
+			if json.Unmarshal([]byte(args.Raw), &parsed) == nil {
+				fc["args"] = parsed
+			}
+		}
+		if updated, err := sjson.SetBytes(out, pathFC, fc); err == nil {
+			out = updated
+			changed = true
+		}
+	}
+	return out, changed
+}
+
+type antigravityReasoningReplayAccumulator struct {
+	scope          antigravityReasoningReplayScope
+	requestPayload []byte
+	items          [][]byte
+	seenFC         map[string]bool
+	contentIndex   int
+	nextPartIndex  int
+}
+
+func newAntigravityReasoningReplayAccumulator(scope antigravityReasoningReplayScope, requestPayload []byte) *antigravityReasoningReplayAccumulator {
+	if !scope.valid() {
+		return nil
+	}
+	contentIndex, basePartIndex := antigravityReasoningReplayPendingModelContentIndex(requestPayload)
+	return &antigravityReasoningReplayAccumulator{
+		scope:          scope,
+		requestPayload: append([]byte(nil), requestPayload...),
+		seenFC:         make(map[string]bool),
+		contentIndex:   contentIndex,
+		nextPartIndex:  basePartIndex,
+	}
+}
+
+func (a *antigravityReasoningReplayAccumulator) ObserveSSELine(line []byte) {
+	if a == nil {
+		return
+	}
+	payload := helps.JSONPayload(line)
+	if payload == nil {
+		return
+	}
+	a.observeResponsePayload(payload)
+}
+
+func (a *antigravityReasoningReplayAccumulator) observeResponsePayload(payload []byte) {
+	parts := gjson.GetBytes(payload, "response.candidates.0.content.parts")
+	if !parts.IsArray() {
+		return
+	}
+	parts.ForEach(func(_, part gjson.Result) bool {
+		pi := a.nextPartIndex
+		a.nextPartIndex++
+		sig := antigravityNativePartThoughtSignature(part)
+		if fc := part.Get("functionCall"); fc.Exists() {
+			keys := antigravityReplayToolCallKeysFromPart(fc)
+			for _, k := range keys {
+				if a.seenFC[k] {
+					return true
+				}
+			}
+			for _, k := range keys {
+				a.seenFC[k] = true
+			}
+			item := buildAntigravityFunctionCallPartItem(a.contentIndex, pi, fc, sig)
+			if len(item) > 0 {
+				a.items = append(a.items, item)
+			}
+			return true
+		}
+		if sig != "" {
+			item := buildAntigravityThoughtSignatureItem(a.contentIndex, pi, sig)
+			a.items = append(a.items, item)
+		}
+		return true
+	})
+}
+
+func buildAntigravityThoughtSignatureItem(contentIndex, partIndex int, signature string) []byte {
+	return []byte(fmt.Sprintf(`{"type":"thought_signature","thoughtSignature":%q,"contentIndex":%d,"partIndex":%d}`,
+		signature, contentIndex, partIndex))
+}
+
+func buildAntigravityFunctionCallPartItem(contentIndex, partIndex int, fc gjson.Result, signature string) []byte {
+	item := map[string]any{
+		"type":         "function_call_part",
+		"contentIndex": contentIndex,
+		"partIndex":    partIndex,
+		"name":         fc.Get("name").String(),
+	}
+	if id := strings.TrimSpace(fc.Get("id").String()); id != "" {
+		item["call_id"] = id
+	}
+	if args := fc.Get("args"); args.Exists() {
+		if args.Type == gjson.String {
+			item["args"] = args.String()
+		} else {
+			item["args"] = json.RawMessage(args.Raw)
+		}
+	}
+	if signature != "" {
+		item["thoughtSignature"] = signature
+	}
+	raw, err := json.Marshal(item)
+	if err != nil {
+		return nil
+	}
+	return raw
+}
+
+func (a *antigravityReasoningReplayAccumulator) Flush(ctx context.Context) {
+	if a == nil || !a.scope.valid() || len(a.items) == 0 {
+		return
+	}
+	if !internalcache.CacheAntigravityReasoningReplayItemsBestEffort(ctx, a.scope.modelName, a.scope.sessionKey, a.items) {
+		_ = internalcache.DeleteAntigravityReasoningReplayItemRequired(ctx, a.scope.modelName, a.scope.sessionKey)
+	}
+}
+
+func cacheAntigravityReasoningReplayFromResponse(ctx context.Context, scope antigravityReasoningReplayScope, requestPayload, body []byte) {
+	if !scope.valid() || len(body) == 0 {
+		return
+	}
+	acc := newAntigravityReasoningReplayAccumulator(scope, requestPayload)
+	acc.observeResponsePayload(body)
+	acc.Flush(ctx)
+}
+
+func applyAntigravityNativeSignatureReplayIfNeeded(modelName string, payload []byte) []byte {
+	if antigravityUsesReasoningReplayCache(modelName) {
+		return payload
+	}
+	// Native per-part signature replay is not on upstream/dev; Gemini uses HOME replay only.
+	return payload
+}
+
+func antigravityUsesReasoningReplayCache(modelName string) bool {
+	modelName = strings.ToLower(modelName)
+	if strings.Contains(modelName, "claude") {
+		return false
+	}
+	return strings.Contains(modelName, "gemini") || strings.Contains(modelName, "flash") || strings.Contains(modelName, "agent")
+}
+
+func antigravityNativePartThoughtSignature(part gjson.Result) string {
+	for _, path := range []string{"thoughtSignature", "thought_signature", "extra_content.google.thought_signature"} {
+		if signature := strings.TrimSpace(part.Get(path).String()); signature != "" {
+			return signature
+		}
+	}
+	return ""
+}

internal/runtime/executor/antigravity_reasoning_replay_clear_test.go

@@ -0,0 +1,66 @@
+package executor
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	internalcache "github.com/router-for-me/CLIProxyAPI/v7/internal/cache"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
+	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/auth"
+	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/executor"
+	sdktranslator "github.com/router-for-me/CLIProxyAPI/v7/sdk/translator"
+)
+
+func TestAntigravityReasoningReplayClearsOnInvalidSignature400(t *testing.T) {
+	internalcache.ClearAntigravityReasoningReplayCache()
+	t.Cleanup(internalcache.ClearAntigravityReasoningReplayCache)
+
+	model := "gemini-3-flash-agent"
+	sessionKey := "session:pr3900-invalid-sig"
+	bad := []byte(`{"type":"thought_signature","thoughtSignature":"INVALID_REPLAY_SIGNATURE_PR3900_XXXXXXXXX","contentIndex":1,"partIndex":0}`)
+	if !internalcache.CacheAntigravityReasoningReplayItems(model, sessionKey, [][]byte{bad}) {
+		t.Fatal("failed to seed replay cache")
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = io.ReadAll(r.Body)
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = w.Write([]byte(`{"error":{"message":"Invalid thoughtSignature in model content","code":400}}`))
+	}))
+	defer server.Close()
+
+	exec := NewAntigravityExecutor(&config.Config{RequestRetry: 1})
+	auth := &cliproxyauth.Auth{
+		ID: "auth-pr3900-invalid-sig",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+		},
+		Metadata: map[string]any{
+			"access_token": "token",
+			"project_id":   "project-1",
+			"expired":      time.Now().Add(1 * time.Hour).Format(time.RFC3339),
+		},
+	}
+
+	payload := []byte(`{"sessionId":"pr3900-invalid-sig","request":{"contents":[{"role":"user","parts":[{"text":"hi"}]},{"role":"user","parts":[{"functionResponse":{"id":"id1","name":"Bash","response":{"result":"ok"}}}]}]}}`)
+	_, err := exec.Execute(context.Background(), auth, cliproxyexecutor.Request{
+		Model:   model,
+		Payload: payload,
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FormatAntigravity,
+		Stream:       false,
+	})
+	if err == nil {
+		t.Fatal("expected upstream 400 error")
+	}
+	if _, ok, errGet := internalcache.GetAntigravityReasoningReplayItemsRequired(context.Background(), model, sessionKey); errGet != nil {
+		t.Fatalf("get after clear: %v", errGet)
+	} else if ok {
+		t.Fatal("invalid signature 400 should clear cached replay item")
+	}
+}

internal/runtime/executor/antigravity_reasoning_replay_test.go

@@ -0,0 +1,146 @@
+package executor
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	internalcache "github.com/router-for-me/CLIProxyAPI/v7/internal/cache"
+	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/executor"
+	"github.com/tidwall/gjson"
+)
+
+func TestAntigravityReasoningReplayAccumulatorMultiToolSSEChunks(t *testing.T) {
+	internalcache.ClearAntigravityReasoningReplayCache()
+	t.Cleanup(internalcache.ClearAntigravityReasoningReplayCache)
+
+	requestPayload := []byte(`{"sessionId":"sess-1","request":{"contents":[{"role":"user","parts":[{"text":"hi"}]}]}}`)
+	scope := antigravityReasoningReplayScope{modelName: "gemini-3-flash-agent", sessionKey: "session:sess-1"}
+	acc := newAntigravityReasoningReplayAccumulator(scope, requestPayload)
+	if acc == nil {
+		t.Fatal("accumulator is nil")
+	}
+	if acc.contentIndex != 1 || acc.nextPartIndex != 0 {
+		t.Fatalf("pending model slot = %d/%d, want 1/0", acc.contentIndex, acc.nextPartIndex)
+	}
+
+	line1 := []byte(`data: {"response":{"candidates":[{"content":{"parts":[{"thoughtSignature":"sig-first","functionCall":{"name":"Read","args":{"file_path":"/a"},"id":"id1"}}]}}]}}`)
+	line2 := []byte(`data: {"response":{"candidates":[{"content":{"parts":[{"functionCall":{"name":"Read","args":{"file_path":"/b"},"id":"id2"}}]}}]}}`)
+	acc.ObserveSSELine(line1)
+	acc.ObserveSSELine(line2)
+	acc.Flush(context.Background())
+
+	items, ok := internalcache.GetAntigravityReasoningReplayItems("gemini-3-flash-agent", "session:sess-1")
+	if !ok || len(items) != 2 {
+		t.Fatalf("cached items = %v ok=%v, want 2 items", len(items), ok)
+	}
+	pi0 := int(gjson.GetBytes(items[0], "partIndex").Int())
+	pi1 := int(gjson.GetBytes(items[1], "partIndex").Int())
+	if pi0 != 0 || pi1 != 1 {
+		t.Fatalf("partIndex = %d,%d, want 0,1", pi0, pi1)
+	}
+	if got := gjson.GetBytes(items[0], "thoughtSignature").String(); got != "sig-first" {
+		t.Fatalf("first sig = %q", got)
+	}
+}
+
+func TestPrepareAntigravityGeminiReasoningReplayPayloadInjectsCachedToolPart(t *testing.T) {
+	internalcache.ClearAntigravityReasoningReplayCache()
+	t.Cleanup(internalcache.ClearAntigravityReasoningReplayCache)
+
+	item := []byte(`{"type":"function_call_part","contentIndex":1,"partIndex":0,"name":"Read","call_id":"id1","args":{"file_path":"/a"},"thoughtSignature":"sig-first"}`)
+	if !internalcache.CacheAntigravityReasoningReplayItems("gemini-3-flash-agent", "session:sess-2", [][]byte{item}) {
+		t.Fatal("cache write failed")
+	}
+
+	req := cliproxyexecutor.Request{}
+	opts := cliproxyexecutor.Options{}
+	payload := []byte(`{"sessionId":"sess-2","request":{"contents":[{"role":"user","parts":[{"text":"hi"}]},{"role":"user","parts":[{"functionResponse":{"id":"id1","name":"Read","response":{"result":"ok"}}}]}]}}`)
+	out, scope, err := prepareAntigravityGeminiReasoningReplayPayload(context.Background(), "gemini-3-flash-agent", req, opts, payload)
+	if err != nil {
+		t.Fatalf("prepare error: %v", err)
+	}
+	if !scope.valid() {
+		t.Fatal("scope invalid")
+	}
+	if gjson.GetBytes(out, "request.contents.1.role").String() != "model" {
+		t.Fatalf("functionCall replay must be model role at [1], got %s", string(out))
+	}
+	if got := gjson.GetBytes(out, "request.contents.1.parts.0.thoughtSignature").String(); got != "sig-first" {
+		t.Fatalf("thoughtSignature = %q, want sig-first", got)
+	}
+	if !gjson.GetBytes(out, "request.contents.1.parts.0.functionCall").Exists() {
+		t.Fatalf("functionCall not injected: %s", string(out))
+	}
+	if !gjson.GetBytes(out, "request.contents.2.parts.0.functionResponse").Exists() {
+		t.Fatalf("functionResponse should follow model functionCall at [2]: %s", string(out))
+	}
+}
+
+func TestPrepareAntigravityGeminiReasoningReplayInsertsBeforeModelFunctionResponse(t *testing.T) {
+	internalcache.ClearAntigravityReasoningReplayCache()
+	t.Cleanup(internalcache.ClearAntigravityReasoningReplayCache)
+
+	item := []byte(`{"type":"function_call_part","contentIndex":1,"partIndex":0,"name":"Read","call_id":"id1","args":{"file_path":"/a"},"thoughtSignature":"sig-first"}`)
+	internalcache.CacheAntigravityReasoningReplayItems("gemini-3-flash-agent", "session:sess-3", [][]byte{item})
+
+	payload := []byte(`{"sessionId":"sess-3","request":{"contents":[{"role":"user","parts":[{"text":"hi"}]},{"role":"model","parts":[{"functionResponse":{"id":"id1","name":"Read","response":{"result":"ok"}}}]}]}}`)
+	out, _, err := prepareAntigravityGeminiReasoningReplayPayload(context.Background(), "gemini-3-flash-agent", cliproxyexecutor.Request{}, cliproxyexecutor.Options{}, payload)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !gjson.GetBytes(out, "request.contents.1.parts.0.functionCall").Exists() || gjson.GetBytes(out, "request.contents.1.role").String() != "model" {
+		t.Fatalf("want model functionCall at [1]: %s", string(out))
+	}
+	if !gjson.GetBytes(out, "request.contents.2.parts.0.functionResponse").Exists() {
+		t.Fatalf("functionResponse should be at [2]: %s", string(out))
+	}
+}
+
+func TestMergeAntigravityFunctionCallPartReplayMergesSignatureIntoExistingFunctionCall(t *testing.T) {
+	internalcache.ClearAntigravityReasoningReplayCache()
+	t.Cleanup(internalcache.ClearAntigravityReasoningReplayCache)
+
+	item := []byte(`{"type":"function_call_part","contentIndex":1,"partIndex":0,"name":"Read","call_id":"id1","args":{"file_path":"/a"},"thoughtSignature":"sig-first"}`)
+	internalcache.CacheAntigravityReasoningReplayItems("gemini-3-flash-agent", "session:sess-merge", [][]byte{item})
+
+	payload := []byte(`{"sessionId":"sess-merge","request":{"contents":[{"role":"user","parts":[{"text":"hi"}]},{"role":"model","parts":[{"functionCall":{"id":"id1","name":"Read","args":{"file_path":"/a"}}}]},{"role":"user","parts":[{"functionResponse":{"id":"id1","name":"Read","response":{"result":"ok"}}}]}]}}`)
+	out, _, err := prepareAntigravityGeminiReasoningReplayPayload(context.Background(), "gemini-3-flash-agent", cliproxyexecutor.Request{}, cliproxyexecutor.Options{}, payload)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := gjson.GetBytes(out, "request.contents.1.parts.0.thoughtSignature").String(); got != "sig-first" {
+		t.Fatalf("thoughtSignature = %q, want sig-first; body=%s", got, out)
+	}
+}
+
+func TestAntigravityReasoningReplayScopeUsesStableSessionWithoutSessionId(t *testing.T) {
+	payload := []byte(`{"request":{"contents":[{"role":"user","parts":[{"text":"stable-user-text"}]}]}}`)
+	scope := antigravityReasoningReplayScopeFromPayload("gemini-3-flash-agent", payload)
+	if !scope.valid() {
+		t.Fatal("scope should be valid from stable session hash")
+	}
+	if !strings.HasPrefix(scope.sessionKey, "session:") {
+		t.Fatalf("sessionKey = %q", scope.sessionKey)
+	}
+}
+
+func TestAntigravityReplayToolCallKeysUsesNativeFunctionCallID(t *testing.T) {
+	fc := gjson.Parse(`{"name":"Read","args":{"file_path":"/a"},"id":"id-native"}`)
+	keys := antigravityReplayToolCallKeysFromPart(fc)
+	if len(keys) != 1 {
+		t.Fatalf("keys = %v", keys)
+	}
+	fc2 := gjson.Parse(`{"name":"Read","args":{"file_path":"/a"},"id":"id-native-2"}`)
+	keys2 := antigravityReplayToolCallKeysFromPart(fc2)
+	if keys[0] == keys2[0] {
+		t.Fatalf("parallel tool calls should not share replay key: %v vs %v", keys, keys2)
+	}
+}
+
+func TestAntigravityRequestHasMatchingFunctionResponseWhitespaceCallID(t *testing.T) {
+	item := gjson.Parse(`{"call_id":" "}`)
+	if !antigravityRequestHasMatchingFunctionResponse(nil, item) {
+		t.Fatal("whitespace-only call_id should be treated as empty => true")
+	}
+}