diff --git a/internal/cache/codex_reasoning_replay_cache.go b/internal/cache/codex_reasoning_replay_cache.go
new file mode 100644
index 000000000..820f7f1d1
--- /dev/null
+++ b/internal/cache/codex_reasoning_replay_cache.go
@@ -0,0 +1,253 @@
+package cache
+
+import (
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/signature"
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
+)
+
+const (
+	// CodexReasoningReplayCacheTTL limits how long encrypted reasoning replay
+	// items stay in process memory.
+	CodexReasoningReplayCacheTTL = 1 * time.Hour
+
+	// CodexReasoningReplayCacheMaxEntries bounds process memory for replay
+	// continuity. Oldest entries are evicted first.
+	CodexReasoningReplayCacheMaxEntries = 10240
+
+	// CodexReasoningReplayCacheEvictBatchSize leaves headroom after the cache
+	// reaches capacity so high write volume does not rescan the map every turn.
+	CodexReasoningReplayCacheEvictBatchSize = 128
+)
+
+type codexReasoningReplayEntry struct {
+	Items     [][]byte
+	Timestamp time.Time
+}
+
+var (
+	codexReasoningReplayMu      sync.Mutex
+	codexReasoningReplayEntries = make(map[string]codexReasoningReplayEntry)
+)
+
+// CacheCodexReasoningReplayItem 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 CacheCodexReasoningReplayItem(modelName, sessionKey string, item []byte) bool {
+	return CacheCodexReasoningReplayItems(modelName, sessionKey, [][]byte{item})
+}
+
+// CacheCodexReasoningReplayItems stores the final GPT/Codex assistant output
+// items needed to replay a stateless next turn.
+func CacheCodexReasoningReplayItems(modelName, sessionKey string, items [][]byte) bool {
+	key := codexReasoningReplayCacheKey(modelName, sessionKey)
+	if key == "" {
+		return false
+	}
+	normalized, ok := normalizeCodexReasoningReplayItems(items)
+	if !ok {
+		return false
+	}
+
+	cacheCleanupOnce.Do(startCacheCleanup)
+	now := time.Now()
+	codexReasoningReplayMu.Lock()
+	defer codexReasoningReplayMu.Unlock()
+	codexReasoningReplayEntries[key] = codexReasoningReplayEntry{
+		Items:     normalized,
+		Timestamp: now,
+	}
+	if len(codexReasoningReplayEntries) > CodexReasoningReplayCacheMaxEntries {
+		evictOldestCodexReasoningReplayEntries(CodexReasoningReplayCacheEvictBatchSize)
+	}
+	return true
+}
+
+// GetCodexReasoningReplayItem retrieves a normalized reasoning replay item.
+func GetCodexReasoningReplayItem(modelName, sessionKey string) ([]byte, bool) {
+	items, ok := GetCodexReasoningReplayItems(modelName, sessionKey)
+	if !ok || len(items) == 0 {
+		return nil, false
+	}
+	return items[0], true
+}
+
+// GetCodexReasoningReplayItems retrieves normalized assistant output items.
+func GetCodexReasoningReplayItems(modelName, sessionKey string) ([][]byte, bool) {
+	key := codexReasoningReplayCacheKey(modelName, sessionKey)
+	if key == "" {
+		return nil, false
+	}
+
+	cacheCleanupOnce.Do(startCacheCleanup)
+	now := time.Now()
+	codexReasoningReplayMu.Lock()
+	defer codexReasoningReplayMu.Unlock()
+	entry, ok := codexReasoningReplayEntries[key]
+	if !ok {
+		return nil, false
+	}
+	if now.Sub(entry.Timestamp) > CodexReasoningReplayCacheTTL {
+		delete(codexReasoningReplayEntries, key)
+		return nil, false
+	}
+	entry.Timestamp = now
+	codexReasoningReplayEntries[key] = entry
+	return cloneCodexReasoningReplayItems(entry.Items), true
+}
+
+// DeleteCodexReasoningReplayItem removes one replay item after upstream rejects
+// it or the caller otherwise knows it is stale.
+func DeleteCodexReasoningReplayItem(modelName, sessionKey string) {
+	key := codexReasoningReplayCacheKey(modelName, sessionKey)
+	if key == "" {
+		return
+	}
+	codexReasoningReplayMu.Lock()
+	delete(codexReasoningReplayEntries, key)
+	codexReasoningReplayMu.Unlock()
+}
+
+// ClearCodexReasoningReplayCache clears all Codex reasoning replay state.
+func ClearCodexReasoningReplayCache() {
+	codexReasoningReplayMu.Lock()
+	codexReasoningReplayEntries = make(map[string]codexReasoningReplayEntry)
+	codexReasoningReplayMu.Unlock()
+}
+
+func codexReasoningReplayCacheKey(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{"codex-reasoning-replay", modelName, sessionKey}, "\x00")
+}
+
+func normalizeCodexReasoningReplayItems(items [][]byte) ([][]byte, bool) {
+	normalized := make([][]byte, 0, len(items))
+	for _, item := range items {
+		normalizedItem, ok := normalizeCodexReasoningReplayItem(item)
+		if ok {
+			normalized = append(normalized, normalizedItem)
+		}
+	}
+	return normalized, len(normalized) > 0
+}
+
+func normalizeCodexReasoningReplayItem(item []byte) ([]byte, bool) {
+	itemResult := gjson.ParseBytes(item)
+	switch strings.TrimSpace(itemResult.Get("type").String()) {
+	case "reasoning":
+		return normalizeCodexReasoningReplayReasoningItem(itemResult)
+	case "function_call":
+		return normalizeCodexReasoningReplayFunctionCallItem(itemResult)
+	case "custom_tool_call":
+		return normalizeCodexReasoningReplayCustomToolCallItem(itemResult)
+	default:
+		return nil, false
+	}
+}
+
+func normalizeCodexReasoningReplayReasoningItem(itemResult gjson.Result) ([]byte, bool) {
+	encryptedContentResult := itemResult.Get("encrypted_content")
+	if encryptedContentResult.Type != gjson.String {
+		return nil, false
+	}
+	encryptedContent := encryptedContentResult.String()
+	if encryptedContent != strings.TrimSpace(encryptedContent) {
+		return nil, false
+	}
+	if _, err := signature.InspectGPTReasoningSignature(encryptedContent); err != nil {
+		return nil, false
+	}
+
+	normalized := []byte(`{"type":"reasoning","summary":[],"content":null}`)
+	normalized, _ = sjson.SetBytes(normalized, "encrypted_content", encryptedContent)
+	return normalized, true
+}
+
+func normalizeCodexReasoningReplayFunctionCallItem(itemResult gjson.Result) ([]byte, bool) {
+	callID := strings.TrimSpace(itemResult.Get("call_id").String())
+	name := strings.TrimSpace(itemResult.Get("name").String())
+	arguments := itemResult.Get("arguments")
+	if callID == "" || name == "" || arguments.Type != gjson.String {
+		return nil, false
+	}
+
+	normalized := []byte(`{"type":"function_call"}`)
+	normalized, _ = sjson.SetBytes(normalized, "call_id", callID)
+	normalized, _ = sjson.SetBytes(normalized, "name", name)
+	normalized, _ = sjson.SetBytes(normalized, "arguments", arguments.String())
+	return normalized, true
+}
+
+func normalizeCodexReasoningReplayCustomToolCallItem(itemResult gjson.Result) ([]byte, bool) {
+	callID := strings.TrimSpace(itemResult.Get("call_id").String())
+	name := strings.TrimSpace(itemResult.Get("name").String())
+	input := itemResult.Get("input")
+	if callID == "" || name == "" || !input.Exists() {
+		return nil, false
+	}
+
+	normalized := []byte(`{"type":"custom_tool_call","status":"completed"}`)
+	if status := strings.TrimSpace(itemResult.Get("status").String()); status != "" {
+		normalized, _ = sjson.SetBytes(normalized, "status", status)
+	}
+	normalized, _ = sjson.SetBytes(normalized, "call_id", callID)
+	normalized, _ = sjson.SetBytes(normalized, "name", name)
+	if input.Type == gjson.String {
+		normalized, _ = sjson.SetBytes(normalized, "input", input.String())
+	} else {
+		normalized, _ = sjson.SetRawBytes(normalized, "input", []byte(input.Raw))
+	}
+	return normalized, true
+}
+
+func cloneCodexReasoningReplayItems(items [][]byte) [][]byte {
+	cloned := make([][]byte, 0, len(items))
+	for _, item := range items {
+		cloned = append(cloned, append([]byte(nil), item...))
+	}
+	return cloned
+}
+
+func evictOldestCodexReasoningReplayEntries(count int) {
+	if count <= 0 || len(codexReasoningReplayEntries) == 0 {
+		return
+	}
+	type candidate struct {
+		key       string
+		timestamp time.Time
+	}
+	candidates := make([]candidate, 0, len(codexReasoningReplayEntries))
+	for key, entry := range codexReasoningReplayEntries {
+		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(codexReasoningReplayEntries, candidates[i].key)
+	}
+}
+
+func purgeExpiredCodexReasoningReplayCache(now time.Time) {
+	codexReasoningReplayMu.Lock()
+	for key, entry := range codexReasoningReplayEntries {
+		if now.Sub(entry.Timestamp) > CodexReasoningReplayCacheTTL {
+			delete(codexReasoningReplayEntries, key)
+		}
+	}
+	codexReasoningReplayMu.Unlock()
+}
diff --git a/internal/cache/codex_reasoning_replay_cache_test.go b/internal/cache/codex_reasoning_replay_cache_test.go
new file mode 100644
index 000000000..cc43ed414
--- /dev/null
+++ b/internal/cache/codex_reasoning_replay_cache_test.go
@@ -0,0 +1,73 @@
+package cache
+
+import (
+	"encoding/base64"
+	"fmt"
+	"testing"
+)
+
+func validCodexReasoningReplayEncryptedContentForTest(seed byte) string {
+	payload := make([]byte, 1+8+16+16+32)
+	payload[0] = 0x80
+	for i := 9; i < len(payload); i++ {
+		payload[i] = seed + byte(i)
+	}
+	return base64.RawURLEncoding.EncodeToString(payload)
+}
+
+func TestCodexReasoningReplayCacheRejectsInvalidItems(t *testing.T) {
+	ClearCodexReasoningReplayCache()
+	t.Cleanup(ClearCodexReasoningReplayCache)
+
+	if CacheCodexReasoningReplayItem("gpt-5.4", "session", []byte(`{"type":"reasoning","encrypted_content":"bad","summary":[]}`)) {
+		t.Fatal("invalid encrypted_content should not be cached")
+	}
+	if _, ok := GetCodexReasoningReplayItem("gpt-5.4", "session"); ok {
+		t.Fatal("invalid item was cached")
+	}
+}
+
+func TestCodexReasoningReplayCacheScopesByModelAndSession(t *testing.T) {
+	ClearCodexReasoningReplayCache()
+	t.Cleanup(ClearCodexReasoningReplayCache)
+
+	encryptedContent := validCodexReasoningReplayEncryptedContentForTest(7)
+	if !CacheCodexReasoningReplayItem("gpt-5.4", "session-a", []byte(`{"type":"reasoning","summary":[],"content":null,"encrypted_content":"`+encryptedContent+`"}`)) {
+		t.Fatal("valid item was not cached")
+	}
+
+	if _, ok := GetCodexReasoningReplayItem("gpt-5.5", "session-a"); ok {
+		t.Fatal("cache should not hit across models")
+	}
+	if _, ok := GetCodexReasoningReplayItem("gpt-5.4", "session-b"); ok {
+		t.Fatal("cache should not hit across sessions")
+	}
+
+	item, ok := GetCodexReasoningReplayItem("gpt-5.4", "session-a")
+	if !ok {
+		t.Fatal("cache miss for original model and session")
+	}
+	if string(item) != `{"type":"reasoning","summary":[],"content":null,"encrypted_content":"`+encryptedContent+`"}` {
+		t.Fatalf("normalized item = %s", string(item))
+	}
+}
+
+func TestCodexReasoningReplayCacheBatchEvictsWhenFull(t *testing.T) {
+	ClearCodexReasoningReplayCache()
+	t.Cleanup(ClearCodexReasoningReplayCache)
+
+	encryptedContent := validCodexReasoningReplayEncryptedContentForTest(9)
+	item := []byte(`{"type":"reasoning","summary":[],"content":null,"encrypted_content":"` + encryptedContent + `"}`)
+	for i := 0; i <= CodexReasoningReplayCacheMaxEntries; i++ {
+		if !CacheCodexReasoningReplayItem("gpt-5.4", fmt.Sprintf("session-%d", i), item) {
+			t.Fatalf("cache insert %d failed", i)
+		}
+	}
+
+	codexReasoningReplayMu.Lock()
+	gotLen := len(codexReasoningReplayEntries)
+	codexReasoningReplayMu.Unlock()
+	if gotLen >= CodexReasoningReplayCacheMaxEntries {
+		t.Fatalf("cache entries = %d, want batch eviction below max %d", gotLen, CodexReasoningReplayCacheMaxEntries)
+	}
+}
diff --git a/internal/cache/signature_cache.go b/internal/cache/signature_cache.go
index fd2ccab7c..42020ae72 100644
--- a/internal/cache/signature_cache.go
+++ b/internal/cache/signature_cache.go
@@ -94,6 +94,7 @@ func purgeExpiredCaches() {
 		}
 		return true
 	})
+	purgeExpiredCodexReasoningReplayCache(now)
 }
 
 // CacheSignature stores a thinking signature for a given model group and text.
diff --git a/internal/runtime/executor/codex_executor.go b/internal/runtime/executor/codex_executor.go
index d3c3925ed..2b243db8a 100644
--- a/internal/runtime/executor/codex_executor.go
+++ b/internal/runtime/executor/codex_executor.go
@@ -4,17 +4,22 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"crypto/sha256"
+	"encoding/hex"
 	"fmt"
 	"io"
 	"net/http"
+	"regexp"
 	"sort"
 	"strings"
 	"time"
 
 	codexauth "github.com/router-for-me/CLIProxyAPI/v7/internal/auth/codex"
+	internalcache "github.com/router-for-me/CLIProxyAPI/v7/internal/cache"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/misc"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/runtime/executor/helps"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/signature"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/thinking"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/util"
 	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/auth"
@@ -36,6 +41,7 @@ const (
 )
 
 var dataTag = []byte("data:")
+var codexClaudeCodeSessionPattern = regexp.MustCompile(`_session_([a-f0-9-]+)$`)
 
 // Streamed Codex responses may emit response.output_item.done events while leaving
 // response.completed.response.output empty. Keep the stream path aligned with the
@@ -101,6 +107,14 @@ func patchCodexCompletedOutput(eventData []byte, outputItemsByIndex map[int64][]
 }
 
 func codexTerminalStreamContextLengthErr(eventData []byte) (statusErr, bool) {
+	streamErr, body, ok := codexTerminalStreamErr(eventData)
+	if !ok || !codexTerminalErrorIsContextLength(body) {
+		return statusErr{}, false
+	}
+	return streamErr, true
+}
+
+func codexTerminalStreamErr(eventData []byte) (statusErr, []byte, bool) {
 	eventType := gjson.GetBytes(eventData, "type").String()
 	var body []byte
 	switch eventType {
@@ -115,15 +129,23 @@ func codexTerminalStreamContextLengthErr(eventData []byte) (statusErr, bool) {
 			body = codexTerminalErrorBody(eventData, "error")
 		}
 	default:
-		return statusErr{}, false
+		return statusErr{}, nil, false
 	}
 	if len(body) == 0 {
-		return statusErr{}, false
+		return statusErr{}, nil, false
 	}
-	if !codexTerminalErrorIsContextLength(body) {
-		return statusErr{}, false
+	if !codexTerminalStreamErrShouldHandle(body) {
+		return statusErr{}, nil, false
 	}
-	return newCodexStatusErr(http.StatusBadRequest, body), true
+	return newCodexStatusErr(http.StatusBadRequest, body), body, true
+}
+
+func codexTerminalStreamErrShouldHandle(body []byte) bool {
+	if codexTerminalErrorIsContextLength(body) {
+		return true
+	}
+	code, _, ok := codexStatusErrorClassification(http.StatusBadRequest, body)
+	return ok && code == "thinking_signature_invalid"
 }
 
 func codexTerminalErrorBody(eventData []byte, path string) []byte {
@@ -217,6 +239,482 @@ func translateCodexRequestPair(from, to sdktranslator.Format, model string, orig
 	return originalTranslated, body
 }
 
+type codexReasoningReplayScope struct {
+	modelName  string
+	sessionKey string
+}
+
+func (s codexReasoningReplayScope) valid() bool {
+	return strings.TrimSpace(s.modelName) != "" && strings.TrimSpace(s.sessionKey) != ""
+}
+
+func applyCodexReasoningReplayCache(ctx context.Context, from sdktranslator.Format, req cliproxyexecutor.Request, opts cliproxyexecutor.Options, body []byte) ([]byte, codexReasoningReplayScope) {
+	scope := codexReasoningReplayScopeFromRequest(ctx, from, req, opts, body)
+	if !scope.valid() {
+		return body, scope
+	}
+	items, ok := internalcache.GetCodexReasoningReplayItems(scope.modelName, scope.sessionKey)
+	if !ok {
+		return body, scope
+	}
+	items = filterCodexReasoningReplayItemsForInput(body, items)
+	if len(items) == 0 {
+		return body, scope
+	}
+	updated, ok := insertCodexReasoningReplayItems(body, items)
+	if !ok {
+		return body, scope
+	}
+	return updated, scope
+}
+
+func codexReasoningReplayScopeFromRequest(ctx context.Context, from sdktranslator.Format, req cliproxyexecutor.Request, opts cliproxyexecutor.Options, body []byte) codexReasoningReplayScope {
+	if !codexReasoningReplayEnabledForSource(from) {
+		return codexReasoningReplayScope{}
+	}
+	return codexReasoningReplayScope{
+		modelName:  thinking.ParseSuffix(req.Model).ModelName,
+		sessionKey: codexReasoningReplaySessionKey(ctx, from, req, opts, body),
+	}
+}
+
+func codexReasoningReplayEnabledForSource(from sdktranslator.Format) bool {
+	return sourceFormatEqual(from, sdktranslator.FormatClaude)
+}
+
+func sourceFormatEqual(from, want sdktranslator.Format) bool {
+	return strings.EqualFold(strings.TrimSpace(from.String()), want.String())
+}
+
+func codexClaudeCodeReplaySessionKey(payload []byte) string {
+	sessionID := extractClaudeCodeSessionIDForCodexReplay(payload)
+	if sessionID == "" {
+		return ""
+	}
+	return "claude:" + sessionID
+}
+
+func codexClaudeCodePromptCacheStorageKey(req cliproxyexecutor.Request) string {
+	sessionID := extractClaudeCodeSessionIDForCodexReplay(req.Payload)
+	if sessionID == "" {
+		return ""
+	}
+	return fmt.Sprintf("%s-claude:%s", req.Model, sessionID)
+}
+
+func codexClaudeCodePromptCache(req cliproxyexecutor.Request) (helps.CodexCache, bool) {
+	key := codexClaudeCodePromptCacheStorageKey(req)
+	if key == "" {
+		return helps.CodexCache{}, false
+	}
+	if cache, ok := helps.GetCodexCache(key); ok {
+		return cache, true
+	}
+	cache := helps.CodexCache{
+		ID:     uuid.New().String(),
+		Expire: time.Now().Add(1 * time.Hour),
+	}
+	helps.SetCodexCache(key, cache)
+	return cache, true
+}
+
+func extractClaudeCodeSessionIDForCodexReplay(payload []byte) string {
+	if len(payload) == 0 {
+		return ""
+	}
+	userID := gjson.GetBytes(payload, "metadata.user_id").String()
+	if userID == "" {
+		return ""
+	}
+	if matches := codexClaudeCodeSessionPattern.FindStringSubmatch(userID); len(matches) >= 2 {
+		return matches[1]
+	}
+	if len(userID) > 0 && userID[0] == '{' {
+		return gjson.Get(userID, "session_id").String()
+	}
+	return ""
+}
+
+func codexReasoningReplaySessionKey(ctx context.Context, from sdktranslator.Format, req cliproxyexecutor.Request, opts cliproxyexecutor.Options, body []byte) string {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	if value := metadataString(opts.Metadata, cliproxyexecutor.ExecutionSessionMetadataKey); value != "" {
+		return "execution:" + value
+	}
+	if value := metadataString(req.Metadata, cliproxyexecutor.ExecutionSessionMetadataKey); value != "" {
+		return "execution:" + value
+	}
+	if value := codexReasoningReplaySessionKeyFromPayload(body); value != "" {
+		return value
+	}
+	if value := codexReasoningReplaySessionKeyFromPayload(req.Payload); value != "" {
+		return value
+	}
+	if value := codexReasoningReplaySessionKeyFromHeaders(opts.Headers); value != "" {
+		return value
+	}
+	if ginCtx, ok := ctx.Value("gin").(*gin.Context); ok && ginCtx != nil && ginCtx.Request != nil {
+		if value := codexReasoningReplaySessionKeyFromHeaders(ginCtx.Request.Header); value != "" {
+			return value
+		}
+	}
+	if sourceFormatEqual(from, sdktranslator.FormatClaude) {
+		return codexClaudeCodeReplaySessionKey(req.Payload)
+	}
+	if sourceFormatEqual(from, sdktranslator.FormatOpenAI) {
+		if apiKey := strings.TrimSpace(helps.APIKeyFromContext(ctx)); apiKey != "" {
+			return "prompt-cache:" + uuid.NewSHA1(uuid.NameSpaceOID, []byte("cli-proxy-api:codex:prompt-cache:"+apiKey)).String()
+		}
+	}
+	return ""
+}
+
+func metadataString(metadata map[string]any, key string) string {
+	if len(metadata) == 0 {
+		return ""
+	}
+	raw, ok := metadata[key]
+	if !ok || raw == nil {
+		return ""
+	}
+	switch v := raw.(type) {
+	case string:
+		return strings.TrimSpace(v)
+	case []byte:
+		return strings.TrimSpace(string(v))
+	default:
+		return ""
+	}
+}
+
+func codexReasoningReplaySessionKeyFromPayload(payload []byte) string {
+	if len(payload) == 0 {
+		return ""
+	}
+	if promptCacheKey := strings.TrimSpace(gjson.GetBytes(payload, "prompt_cache_key").String()); promptCacheKey != "" {
+		return "prompt-cache:" + promptCacheKey
+	}
+	if windowID := strings.TrimSpace(gjson.GetBytes(payload, "client_metadata.x-codex-window-id").String()); windowID != "" {
+		return "window:" + windowID
+	}
+	if turnMetadata := strings.TrimSpace(gjson.GetBytes(payload, "client_metadata.x-codex-turn-metadata").String()); turnMetadata != "" {
+		return codexReasoningReplaySessionKeyFromTurnMetadata(turnMetadata)
+	}
+	return ""
+}
+
+func codexReasoningReplaySessionKeyFromHeaders(headers http.Header) string {
+	if headers == nil {
+		return ""
+	}
+	if turnMetadata := strings.TrimSpace(headers.Get("X-Codex-Turn-Metadata")); turnMetadata != "" {
+		if key := codexReasoningReplaySessionKeyFromTurnMetadata(turnMetadata); key != "" {
+			return key
+		}
+	}
+	if windowID := strings.TrimSpace(headerValueCaseInsensitive(headers, "X-Codex-Window-Id")); windowID != "" {
+		return "window:" + windowID
+	}
+	for _, headerName := range []string{"Session_id", "session_id", "Session-Id"} {
+		if value := strings.TrimSpace(headerValueCaseInsensitive(headers, headerName)); value != "" {
+			return "session-id:" + value
+		}
+	}
+	if conversationID := strings.TrimSpace(headerValueCaseInsensitive(headers, "Conversation_id")); conversationID != "" {
+		return "conversation_id:" + conversationID
+	}
+	return ""
+}
+
+func codexReasoningReplaySessionKeyFromTurnMetadata(turnMetadata string) string {
+	if promptCacheKey := strings.TrimSpace(gjson.Get(turnMetadata, "prompt_cache_key").String()); promptCacheKey != "" {
+		return "prompt-cache:" + promptCacheKey
+	}
+	if windowID := strings.TrimSpace(gjson.Get(turnMetadata, "window_id").String()); windowID != "" {
+		return "window:" + windowID
+	}
+	return ""
+}
+
+func codexInputHasValidReasoningEncryptedContent(body []byte) bool {
+	input := gjson.GetBytes(body, "input")
+	if !input.IsArray() {
+		return false
+	}
+	for _, item := range input.Array() {
+		if strings.TrimSpace(item.Get("type").String()) != "reasoning" {
+			continue
+		}
+		encryptedContent := item.Get("encrypted_content")
+		if encryptedContent.Type != gjson.String {
+			continue
+		}
+		if _, err := signature.InspectGPTReasoningSignature(encryptedContent.String()); err == nil {
+			return true
+		}
+	}
+	return false
+}
+
+func filterCodexReasoningReplayItemsForInput(body []byte, items [][]byte) [][]byte {
+	input := gjson.GetBytes(body, "input")
+	if !input.IsArray() {
+		return nil
+	}
+
+	hasInputReasoning := codexInputHasValidReasoningEncryptedContent(body)
+	existingCalls := make(map[string]bool)
+	for _, inputItem := range input.Array() {
+		for _, key := range codexReplayToolCallKeys(inputItem) {
+			existingCalls[key] = true
+		}
+	}
+
+	filtered := make([][]byte, 0, len(items))
+	for _, item := range items {
+		itemResult := gjson.ParseBytes(item)
+		switch strings.TrimSpace(itemResult.Get("type").String()) {
+		case "reasoning":
+			if hasInputReasoning {
+				continue
+			}
+		case "function_call", "custom_tool_call":
+			keys := codexReplayToolCallKeys(itemResult)
+			if len(keys) == 0 || codexReplayAnyToolCallKeyExists(existingCalls, keys) {
+				continue
+			}
+			for _, key := range keys {
+				existingCalls[key] = true
+			}
+		default:
+			continue
+		}
+		filtered = append(filtered, item)
+	}
+	return filtered
+}
+
+func insertCodexReasoningReplayItems(body []byte, replayItems [][]byte) ([]byte, bool) {
+	input := gjson.GetBytes(body, "input")
+	if !input.IsArray() || len(replayItems) == 0 {
+		return body, false
+	}
+	inputItems := input.Array()
+	insertIndex := codexReasoningReplayInsertIndex(inputItems, replayItems)
+	replayItems = codexAlignReasoningReplayToolCallIDs(inputItems, replayItems)
+	items := make([]string, 0, len(inputItems)+len(replayItems))
+	for i, inputItem := range inputItems {
+		if i == insertIndex {
+			for _, replayItem := range replayItems {
+				items = append(items, string(replayItem))
+			}
+		}
+		items = append(items, inputItem.Raw)
+	}
+	if insertIndex == len(inputItems) {
+		for _, replayItem := range replayItems {
+			items = append(items, string(replayItem))
+		}
+	}
+	updated, err := sjson.SetRawBytes(body, "input", []byte("["+strings.Join(items, ",")+"]"))
+	if err != nil {
+		return body, false
+	}
+	return updated, true
+}
+
+func codexReasoningReplayInsertIndex(inputItems []gjson.Result, replayItems [][]byte) int {
+	replayCallIDs := make(map[string]bool)
+	for _, replayItem := range replayItems {
+		itemResult := gjson.ParseBytes(replayItem)
+		itemType := strings.TrimSpace(itemResult.Get("type").String())
+		if itemType != "function_call" && itemType != "custom_tool_call" {
+			continue
+		}
+		for _, callID := range codexReplayComparableCallIDs(itemResult.Get("call_id").String()) {
+			replayCallIDs[callID] = true
+		}
+	}
+	if len(replayCallIDs) > 0 {
+		for index, inputItem := range inputItems {
+			itemType := strings.TrimSpace(inputItem.Get("type").String())
+			if itemType != "function_call_output" && itemType != "custom_tool_call_output" {
+				continue
+			}
+			callID := strings.TrimSpace(inputItem.Get("call_id").String())
+			if callID == "" || replayCallIDs[callID] {
+				return index
+			}
+		}
+	}
+	for index := len(inputItems) - 1; index >= 0; index-- {
+		inputItem := inputItems[index]
+		if strings.TrimSpace(inputItem.Get("type").String()) == "message" && strings.TrimSpace(inputItem.Get("role").String()) == "assistant" {
+			return index
+		}
+	}
+	for index, inputItem := range inputItems {
+		if shouldInsertCodexReasoningReplayBefore(inputItem) {
+			return index
+		}
+	}
+	return len(inputItems)
+}
+
+func codexAlignReasoningReplayToolCallIDs(inputItems []gjson.Result, replayItems [][]byte) [][]byte {
+	outputCallIDs := codexReplayOutputCallIDs(inputItems)
+	if len(outputCallIDs) == 0 {
+		return replayItems
+	}
+
+	aligned := make([][]byte, 0, len(replayItems))
+	for _, replayItem := range replayItems {
+		itemResult := gjson.ParseBytes(replayItem)
+		itemType := strings.TrimSpace(itemResult.Get("type").String())
+		if itemType != "function_call" && itemType != "custom_tool_call" {
+			aligned = append(aligned, replayItem)
+			continue
+		}
+
+		callID := strings.TrimSpace(itemResult.Get("call_id").String())
+		outputCallID := ""
+		for _, candidate := range codexReplayComparableCallIDs(callID) {
+			if value := outputCallIDs[candidate]; value != "" {
+				outputCallID = value
+				break
+			}
+		}
+		if outputCallID == "" || outputCallID == callID {
+			aligned = append(aligned, replayItem)
+			continue
+		}
+
+		updated, err := sjson.SetBytes(replayItem, "call_id", outputCallID)
+		if err != nil {
+			aligned = append(aligned, replayItem)
+			continue
+		}
+		aligned = append(aligned, updated)
+	}
+	return aligned
+}
+
+func codexReplayOutputCallIDs(inputItems []gjson.Result) map[string]string {
+	outputCallIDs := make(map[string]string)
+	for _, inputItem := range inputItems {
+		itemType := strings.TrimSpace(inputItem.Get("type").String())
+		if itemType != "function_call_output" && itemType != "custom_tool_call_output" {
+			continue
+		}
+		callID := strings.TrimSpace(inputItem.Get("call_id").String())
+		if callID == "" {
+			continue
+		}
+		for _, candidate := range codexReplayComparableCallIDs(callID) {
+			outputCallIDs[candidate] = callID
+		}
+	}
+	return outputCallIDs
+}
+
+func shouldInsertCodexReasoningReplayBefore(item gjson.Result) bool {
+	if strings.TrimSpace(item.Get("type").String()) != "message" {
+		return true
+	}
+	switch strings.TrimSpace(item.Get("role").String()) {
+	case "developer", "system":
+		return false
+	default:
+		return true
+	}
+}
+
+func codexReplayToolCallKeys(item gjson.Result) []string {
+	itemType := strings.TrimSpace(item.Get("type").String())
+	if itemType != "function_call" && itemType != "custom_tool_call" {
+		return nil
+	}
+	callIDs := codexReplayComparableCallIDs(item.Get("call_id").String())
+	if len(callIDs) == 0 {
+		return nil
+	}
+	keys := make([]string, 0, len(callIDs))
+	for _, callID := range callIDs {
+		keys = append(keys, itemType+":"+callID)
+	}
+	return keys
+}
+
+func codexReplayAnyToolCallKeyExists(existing map[string]bool, keys []string) bool {
+	for _, key := range keys {
+		if existing[key] {
+			return true
+		}
+	}
+	return false
+}
+
+func codexReplayComparableCallIDs(callID string) []string {
+	callID = strings.TrimSpace(callID)
+	if callID == "" {
+		return nil
+	}
+
+	claudeVisibleCallID := shortenCodexReplayCallIDIfNeeded(util.SanitizeClaudeToolID(callID))
+	if claudeVisibleCallID == "" || claudeVisibleCallID == callID {
+		return []string{callID}
+	}
+	return []string{callID, claudeVisibleCallID}
+}
+
+func shortenCodexReplayCallIDIfNeeded(id string) string {
+	const limit = 64
+	if len(id) <= limit {
+		return id
+	}
+
+	sum := sha256.Sum256([]byte(id))
+	suffix := "_" + hex.EncodeToString(sum[:8])
+	prefixLen := limit - len(suffix)
+	if prefixLen <= 0 {
+		return suffix[len(suffix)-limit:]
+	}
+	return id[:prefixLen] + suffix
+}
+
+func cacheCodexReasoningReplayFromCompleted(scope codexReasoningReplayScope, completedData []byte) {
+	if !scope.valid() {
+		return
+	}
+	output := gjson.GetBytes(completedData, "response.output")
+	if !output.IsArray() {
+		return
+	}
+	items := make([][]byte, 0, len(output.Array()))
+	for _, item := range output.Array() {
+		switch strings.TrimSpace(item.Get("type").String()) {
+		case "reasoning", "function_call", "custom_tool_call":
+			items = append(items, []byte(item.Raw))
+		default:
+			continue
+		}
+	}
+	if !internalcache.CacheCodexReasoningReplayItems(scope.modelName, scope.sessionKey, items) {
+		internalcache.DeleteCodexReasoningReplayItem(scope.modelName, scope.sessionKey)
+	}
+}
+
+func clearCodexReasoningReplayOnInvalidSignature(scope codexReasoningReplayScope, statusCode int, body []byte) {
+	if !scope.valid() {
+		return
+	}
+	code, _, ok := codexStatusErrorClassification(statusCode, body)
+	if ok && code == "thinking_signature_invalid" {
+		internalcache.DeleteCodexReasoningReplayItem(scope.modelName, scope.sessionKey)
+	}
+}
+
 // PrepareRequest injects Codex credentials into the outgoing HTTP request.
 func (e *CodexExecutor) PrepareRequest(req *http.Request, auth *cliproxyauth.Auth) error {
 	if req == nil {
@@ -295,6 +793,7 @@ func (e *CodexExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, re
 		body = ensureImageGenerationTool(body, baseModel, auth)
 	}
 	body = sanitizeOpenAIResponsesReasoningEncryptedContent(ctx, "codex executor", body)
+	body, replayScope := applyCodexReasoningReplayCache(ctx, from, req, opts, body)
 	reporter.SetTranslatedReasoningEffort(body, to.String())
 
 	url := strings.TrimSuffix(baseURL, "/") + "/responses"
@@ -338,6 +837,7 @@ func (e *CodexExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, re
 	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
 		b, _ := io.ReadAll(httpResp.Body)
 		b = applyCodexIdentityConfuseResponsePayload(b, identityState)
+		clearCodexReasoningReplayOnInvalidSignature(replayScope, httpResp.StatusCode, b)
 		helps.AppendAPIResponseChunk(ctx, e.cfg, b)
 		helps.LogWithRequestID(ctx).Debugf("request error, error status: %d, error message: %s", httpResp.StatusCode, helps.SummarizeErrorBody(httpResp.Header.Get("Content-Type"), b))
 		err = newCodexStatusErr(httpResp.StatusCode, b)
@@ -362,7 +862,8 @@ func (e *CodexExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, re
 		eventData := bytes.TrimSpace(line[5:])
 		eventType := gjson.GetBytes(eventData, "type").String()
 
-		if streamErr, ok := codexTerminalStreamContextLengthErr(eventData); ok {
+		if streamErr, terminalBody, ok := codexTerminalStreamErr(eventData); ok {
+			clearCodexReasoningReplayOnInvalidSignature(replayScope, streamErr.StatusCode(), terminalBody)
 			err = streamErr
 			return resp, err
 		}
@@ -412,6 +913,7 @@ func (e *CodexExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, re
 			}
 			completedData = completedDataPatched
 		}
+		cacheCodexReasoningReplayFromCompleted(replayScope, completedData)
 
 		var param any
 		clientCompletedData := applyCodexIdentityExposeResponsePayload(completedData, identityState)
@@ -566,6 +1068,7 @@ func (e *CodexExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 		body = ensureImageGenerationTool(body, baseModel, auth)
 	}
 	body = sanitizeOpenAIResponsesReasoningEncryptedContent(ctx, "codex executor", body)
+	body, replayScope := applyCodexReasoningReplayCache(ctx, from, req, opts, body)
 	reporter.SetTranslatedReasoningEffort(body, to.String())
 
 	url := strings.TrimSuffix(baseURL, "/") + "/responses"
@@ -612,6 +1115,7 @@ func (e *CodexExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 			return nil, readErr
 		}
 		data = applyCodexIdentityConfuseResponsePayload(data, identityState)
+		clearCodexReasoningReplayOnInvalidSignature(replayScope, httpResp.StatusCode, data)
 		helps.AppendAPIResponseChunk(ctx, e.cfg, data)
 		helps.LogWithRequestID(ctx).Debugf("request error, error status: %d, error message: %s", httpResp.StatusCode, helps.SummarizeErrorBody(httpResp.Header.Get("Content-Type"), data))
 		err = newCodexStatusErr(httpResp.StatusCode, data)
@@ -637,7 +1141,8 @@ func (e *CodexExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 
 			if bytes.HasPrefix(line, dataTag) {
 				data := bytes.TrimSpace(line[5:])
-				if streamErr, ok := codexTerminalStreamContextLengthErr(data); ok {
+				if streamErr, terminalBody, ok := codexTerminalStreamErr(data); ok {
+					clearCodexReasoningReplayOnInvalidSignature(replayScope, streamErr.StatusCode(), terminalBody)
 					helps.RecordAPIResponseError(ctx, e.cfg, streamErr)
 					reporter.PublishFailure(ctx, streamErr)
 					select {
@@ -655,6 +1160,7 @@ func (e *CodexExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 					}
 					publishCodexImageToolUsage(ctx, reporter, body, data)
 					data = patchCodexCompletedOutput(data, outputItemsByIndex, outputItemsFallback)
+					cacheCodexReasoningReplayFromCompleted(replayScope, data)
 					translatedLine = append([]byte("data: "), data...)
 				}
 			}
@@ -895,25 +1401,16 @@ type codexIdentityReplacement struct {
 
 func (e *CodexExecutor) cacheHelper(ctx context.Context, from sdktranslator.Format, url string, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, userPayload []byte, rawJSON []byte) (*http.Request, []byte, codexIdentityConfuseState, error) {
 	var cache helps.CodexCache
-	if from == "claude" {
-		userIDResult := gjson.GetBytes(req.Payload, "metadata.user_id")
-		if userIDResult.Exists() {
-			key := fmt.Sprintf("%s-%s", req.Model, userIDResult.String())
-			var ok bool
-			if cache, ok = helps.GetCodexCache(key); !ok {
-				cache = helps.CodexCache{
-					ID:     uuid.New().String(),
-					Expire: time.Now().Add(1 * time.Hour),
-				}
-				helps.SetCodexCache(key, cache)
-			}
+	if sourceFormatEqual(from, sdktranslator.FormatClaude) {
+		if cached, ok := codexClaudeCodePromptCache(req); ok {
+			cache = cached
 		}
-	} else if from == "openai-response" {
+	} else if sourceFormatEqual(from, sdktranslator.FormatOpenAIResponse) {
 		promptCacheKey := gjson.GetBytes(req.Payload, "prompt_cache_key")
 		if promptCacheKey.Exists() {
 			cache.ID = promptCacheKey.String()
 		}
-	} else if from == "openai" {
+	} else if sourceFormatEqual(from, sdktranslator.FormatOpenAI) {
 		if apiKey := strings.TrimSpace(helps.APIKeyFromContext(ctx)); apiKey != "" {
 			cache.ID = uuid.NewSHA1(uuid.NameSpaceOID, []byte("cli-proxy-api:codex:prompt-cache:"+apiKey)).String()
 		}
@@ -978,10 +1475,7 @@ func applyCodexIdentityConfuseHeaders(headers http.Header, state *codexIdentityC
 		return
 	}
 
-	setHeaderCasePreserved(headers, "Session-Id", state.promptCacheKey)
-	if headerValueCaseInsensitive(headers, "session_id") != "" {
-		setHeaderCasePreserved(headers, "session_id", state.promptCacheKey)
-	}
+	setCodexSessionHeaderCasePreserved(headers, "Session_id", state.promptCacheKey)
 	if headerValueCaseInsensitive(headers, "Conversation_id") != "" {
 		setHeaderCasePreserved(headers, "Conversation_id", state.promptCacheKey)
 	}
diff --git a/internal/runtime/executor/codex_executor_cache_test.go b/internal/runtime/executor/codex_executor_cache_test.go
index 3f7d412ba..d33d7fc64 100644
--- a/internal/runtime/executor/codex_executor_cache_test.go
+++ b/internal/runtime/executor/codex_executor_cache_test.go
@@ -47,8 +47,11 @@ func TestCodexExecutorCacheHelper_OpenAIChatCompletions_StablePromptCacheKeyFrom
 	if gotConversation := httpReq.Header.Get("Conversation_id"); gotConversation != "" {
 		t.Fatalf("Conversation_id = %q, want empty", gotConversation)
 	}
-	if gotSession := httpReq.Header.Get("Session_id"); gotSession != expectedKey {
-		t.Fatalf("Session_id = %q, want %q", gotSession, expectedKey)
+	if gotSession := httpReq.Header["Session_id"]; len(gotSession) != 1 || gotSession[0] != expectedKey {
+		t.Fatalf("Session_id = %#v, want [%q]", gotSession, expectedKey)
+	}
+	if gotCanonicalSession := httpReq.Header.Get("Session-Id"); gotCanonicalSession != "" {
+		t.Fatalf("Session-Id = %q, want empty", gotCanonicalSession)
 	}
 
 	httpReq2, _, _, err := executor.cacheHelper(ctx, sdktranslator.FromString("openai"), url, nil, req, req.Payload, rawJSON)
@@ -65,6 +68,88 @@ func TestCodexExecutorCacheHelper_OpenAIChatCompletions_StablePromptCacheKeyFrom
 	}
 }
 
+func TestCodexExecutorCacheHelper_ClaudeUsesClaudeCodeSessionID(t *testing.T) {
+	executor := &CodexExecutor{}
+	ctx := context.Background()
+	url := "https://example.com/responses"
+	rawJSON := []byte(`{"model":"gpt-5.4","stream":true}`)
+	firstReq := cliproxyexecutor.Request{
+		Model: "gpt-5.4-claude-cache-session",
+		Payload: []byte(`{
+			"model":"gpt-5.4",
+			"metadata":{"user_id":"{\"device_id\":\"device-a\",\"account_uuid\":\"\",\"session_id\":\"cache-session-1\"}"},
+			"messages":[{"role":"user","content":[{"type":"text","text":"first"}]}]
+		}`),
+	}
+	secondReq := cliproxyexecutor.Request{
+		Model: "gpt-5.4-claude-cache-session",
+		Payload: []byte(`{
+			"model":"gpt-5.4",
+			"metadata":{"user_id":"{\"device_id\":\"device-b\",\"account_uuid\":\"\",\"session_id\":\"cache-session-1\"}"},
+			"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]
+		}`),
+	}
+
+	firstHTTPReq, _, _, err := executor.cacheHelper(ctx, sdktranslator.FromString("claude"), url, nil, firstReq, firstReq.Payload, rawJSON)
+	if err != nil {
+		t.Fatalf("cacheHelper first error: %v", err)
+	}
+	secondHTTPReq, _, _, err := executor.cacheHelper(ctx, sdktranslator.FromString("claude"), url, nil, secondReq, secondReq.Payload, rawJSON)
+	if err != nil {
+		t.Fatalf("cacheHelper second error: %v", err)
+	}
+
+	firstBody, errRead := io.ReadAll(firstHTTPReq.Body)
+	if errRead != nil {
+		t.Fatalf("read first request body: %v", errRead)
+	}
+	secondBody, errRead := io.ReadAll(secondHTTPReq.Body)
+	if errRead != nil {
+		t.Fatalf("read second request body: %v", errRead)
+	}
+	firstKey := gjson.GetBytes(firstBody, "prompt_cache_key").String()
+	secondKey := gjson.GetBytes(secondBody, "prompt_cache_key").String()
+	if firstKey == "" {
+		t.Fatalf("first prompt_cache_key is empty; body=%s", string(firstBody))
+	}
+	if secondKey != firstKey {
+		t.Fatalf("same Claude Code session_id produced different prompt_cache_key: first=%q second=%q", firstKey, secondKey)
+	}
+	if gotSession := firstHTTPReq.Header["Session_id"]; len(gotSession) != 1 || gotSession[0] != firstKey {
+		t.Fatalf("first Session_id = %#v, want [%q]", gotSession, firstKey)
+	}
+	if gotSession := secondHTTPReq.Header["Session_id"]; len(gotSession) != 1 || gotSession[0] != firstKey {
+		t.Fatalf("second Session_id = %#v, want [%q]", gotSession, firstKey)
+	}
+}
+
+func TestCodexExecutorCacheHelper_ClaudeRejectsBareUserID(t *testing.T) {
+	executor := &CodexExecutor{}
+	req := cliproxyexecutor.Request{
+		Model:   "gpt-5.4-claude-cache-bare-user",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"same-user-across-chats"},"messages":[{"role":"user","content":[{"type":"text","text":"first"}]}]}`),
+	}
+
+	httpReq, _, _, err := executor.cacheHelper(context.Background(), sdktranslator.FromString("claude"), "https://example.com/responses", nil, req, req.Payload, []byte(`{"model":"gpt-5.4","stream":true}`))
+	if err != nil {
+		t.Fatalf("cacheHelper error: %v", err)
+	}
+
+	body, errRead := io.ReadAll(httpReq.Body)
+	if errRead != nil {
+		t.Fatalf("read request body: %v", errRead)
+	}
+	if got := gjson.GetBytes(body, "prompt_cache_key").String(); got != "" {
+		t.Fatalf("bare metadata.user_id must not create prompt_cache_key, got %q; body=%s", got, string(body))
+	}
+	if got := httpReq.Header["Session_id"]; len(got) != 0 {
+		t.Fatalf("bare metadata.user_id must not create Session_id, got %#v", got)
+	}
+	if got := httpReq.Header.Get("Session-Id"); got != "" {
+		t.Fatalf("bare metadata.user_id must not create Session-Id, got %q", got)
+	}
+}
+
 func TestCodexExecutorCacheHelper_IdentityConfuseRemapsBodyAndHeaders(t *testing.T) {
 	recorder := httptest.NewRecorder()
 	ginCtx, _ := gin.CreateTestContext(recorder)
@@ -114,13 +199,16 @@ func TestCodexExecutorCacheHelper_IdentityConfuseRemapsBodyAndHeaders(t *testing
 	if gotWindowID := gjson.GetBytes(body, "client_metadata.x-codex-window-id").String(); gotWindowID != expectedPromptCacheKey+":0" {
 		t.Fatalf("client_metadata.x-codex-window-id = %q, want %q", gotWindowID, expectedPromptCacheKey+":0")
 	}
-	for _, headerName := range []string{"Session-Id", "X-Client-Request-Id", "Thread-Id"} {
+	if gotHeader := httpReq.Header["Session_id"]; len(gotHeader) != 1 || gotHeader[0] != expectedPromptCacheKey {
+		t.Fatalf("Session_id = %#v, want [%q]", gotHeader, expectedPromptCacheKey)
+	}
+	for _, headerName := range []string{"X-Client-Request-Id", "Thread-Id"} {
 		if gotHeader := httpReq.Header.Get(headerName); gotHeader != expectedPromptCacheKey {
 			t.Fatalf("%s = %q, want %q", headerName, gotHeader, expectedPromptCacheKey)
 		}
 	}
-	if gotSession := httpReq.Header.Get("Session_id"); gotSession != expectedPromptCacheKey {
-		t.Fatalf("Session_id = %q, want %q", gotSession, expectedPromptCacheKey)
+	if gotCanonicalSession := httpReq.Header.Get("Session-Id"); gotCanonicalSession != "" {
+		t.Fatalf("Session-Id = %q, want empty", gotCanonicalSession)
 	}
 	if gotWindow := httpReq.Header.Get("X-Codex-Window-Id"); gotWindow != expectedPromptCacheKey+":0" {
 		t.Fatalf("X-Codex-Window-Id = %q, want %q", gotWindow, expectedPromptCacheKey+":0")
diff --git a/internal/runtime/executor/codex_executor_reasoning_replay_cache_test.go b/internal/runtime/executor/codex_executor_reasoning_replay_cache_test.go
new file mode 100644
index 000000000..a15007ed3
--- /dev/null
+++ b/internal/runtime/executor/codex_executor_reasoning_replay_cache_test.go
@@ -0,0 +1,803 @@
+package executor
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	internalcache "github.com/router-for-me/CLIProxyAPI/v7/internal/cache"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
+	_ "github.com/router-for-me/CLIProxyAPI/v7/internal/translator"
+	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"
+	"github.com/tidwall/gjson"
+)
+
+func validCodexReasoningEncryptedContentForTestSeed(seed byte) string {
+	payload := make([]byte, 1+8+16+16+32)
+	payload[0] = 0x80
+	for i := 9; i < len(payload); i++ {
+		payload[i] = seed + byte(i)
+	}
+	return base64.RawURLEncoding.EncodeToString(payload)
+}
+
+func shortenedCodexReplayCallIDForTest(id string) string {
+	const limit = 64
+	if len(id) <= limit {
+		return id
+	}
+
+	sum := sha256.Sum256([]byte(id))
+	suffix := "_" + hex.EncodeToString(sum[:8])
+	prefixLen := limit - len(suffix)
+	if prefixLen <= 0 {
+		return suffix[len(suffix)-limit:]
+	}
+	return id[:prefixLen] + suffix
+}
+
+func TestCodexExecutorReasoningReplayCacheStoresFinalDoneAndInjectsNextClaudeRequest(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	addedEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(1)
+	doneEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(2)
+	var bodies [][]byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, errRead := io.ReadAll(r.Body)
+		if errRead != nil {
+			t.Fatalf("read body: %v", errRead)
+		}
+		bodies = append(bodies, body)
+
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.added","item":{"id":"rs_added","type":"reasoning","status":"in_progress","summary":[],"encrypted_content":"` + addedEncryptedContent + `"},"output_index":0}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.done","item":{"id":"rs_done","type":"reasoning","summary":[],"encrypted_content":"` + doneEncryptedContent + `"},"output_index":0}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[],"usage":{"input_tokens":1,"output_tokens":1,"total_tokens":2}}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	auth := &cliproxyauth.Auth{
+		ID: "auth-replay-1",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}
+	opts := cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       false,
+	}
+
+	_, err := executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-1\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"hello"}]}]}`),
+	}, opts)
+	if err != nil {
+		t.Fatalf("first Execute error: %v", err)
+	}
+
+	_, err = executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-1\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]}`),
+	}, opts)
+	if err != nil {
+		t.Fatalf("second Execute error: %v", err)
+	}
+
+	if len(bodies) != 2 {
+		t.Fatalf("upstream request count = %d, want 2", len(bodies))
+	}
+	secondBody := bodies[1]
+	if got := gjson.GetBytes(secondBody, "input.0.type").String(); got != "reasoning" {
+		t.Fatalf("input.0.type = %q, want reasoning; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.0.encrypted_content").String(); got != doneEncryptedContent {
+		t.Fatalf("injected encrypted_content = %q, want final done %q; body=%s", got, doneEncryptedContent, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.1.role").String(); got != "user" {
+		t.Fatalf("input.1.role = %q, want user; body=%s", got, string(secondBody))
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheSharesSameSessionAcrossClientKeys(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	from := sdktranslator.FromString("claude")
+	req := cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-only\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]}`),
+	}
+	opts := cliproxyexecutor.Options{SourceFormat: from}
+	body := []byte(`{"model":"gpt-5.4","input":[{"type":"message","role":"user","content":[{"type":"input_text","text":"next"}]}]}`)
+	encryptedContent := validCodexReasoningEncryptedContentForTestSeed(11)
+
+	firstScope := codexReasoningReplayScopeFromRequest(codexReplaySessionOnlyContext("client-key-a"), from, req, opts, body)
+	if !firstScope.valid() {
+		t.Fatalf("first replay scope is invalid: %#v", firstScope)
+	}
+	cacheCodexReasoningReplayFromCompleted(firstScope, []byte(`{"response":{"output":[{"type":"reasoning","summary":[],"content":null,"encrypted_content":"`+encryptedContent+`"}]}}`))
+
+	secondBody, secondScope := applyCodexReasoningReplayCache(codexReplaySessionOnlyContext("client-key-b"), from, req, opts, body)
+	if secondScope != firstScope {
+		t.Fatalf("replay scope should ignore client API key for the same session: first=%#v second=%#v", firstScope, secondScope)
+	}
+	if got := gjson.GetBytes(secondBody, "input.0.type").String(); got != "reasoning" {
+		t.Fatalf("input.0.type = %q, want same-session replay; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.0.encrypted_content").String(); got != encryptedContent {
+		t.Fatalf("injected encrypted_content = %q, want cached value", got)
+	}
+}
+
+func TestCodexExecutorReasoningReplaySessionKeyUsesClaudeCodeJSONSessionID(t *testing.T) {
+	from := sdktranslator.FromString("claude")
+	req := cliproxyexecutor.Request{
+		Model: "gpt-5.4",
+		Payload: []byte(`{
+			"model":"gpt-5.4",
+			"metadata":{"user_id":"{\"device_id\":\"device-a\",\"account_uuid\":\"\",\"session_id\":\"session-json-1\"}"},
+			"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]
+		}`),
+	}
+	body := []byte(`{"model":"gpt-5.4","input":[{"type":"message","role":"user","content":[{"type":"input_text","text":"next"}]}]}`)
+
+	got := codexReasoningReplaySessionKey(context.Background(), from, req, cliproxyexecutor.Options{SourceFormat: from}, body)
+	if got != "claude:session-json-1" {
+		t.Fatalf("codexReasoningReplaySessionKey() = %q, want claude:session-json-1", got)
+	}
+}
+
+func TestCodexExecutorReasoningReplaySessionKeyRejectsBareClaudeUserID(t *testing.T) {
+	from := sdktranslator.FromString("claude")
+	req := cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"same-user-across-chats"},"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]}`),
+	}
+	body := []byte(`{"model":"gpt-5.4","input":[{"type":"message","role":"user","content":[{"type":"input_text","text":"next"}]}]}`)
+
+	got := codexReasoningReplaySessionKey(context.Background(), from, req, cliproxyexecutor.Options{SourceFormat: from}, body)
+	if got != "" {
+		t.Fatalf("bare metadata.user_id must not become replay session key, got %q", got)
+	}
+}
+
+func TestCodexExecutorReasoningReplaySessionKeyCanonicalizesSessionHeaderAliases(t *testing.T) {
+	legacy := http.Header{"Session_id": []string{"session-alias"}}
+	lowercase := http.Header{"session_id": []string{"session-alias"}}
+	canonical := http.Header{"Session-Id": []string{"session-alias"}}
+
+	gotLegacy := codexReasoningReplaySessionKeyFromHeaders(legacy)
+	gotLowercase := codexReasoningReplaySessionKeyFromHeaders(lowercase)
+	gotCanonical := codexReasoningReplaySessionKeyFromHeaders(canonical)
+
+	if gotLegacy != gotLowercase || gotLowercase != gotCanonical {
+		t.Fatalf("session header aliases produced different keys: legacy=%q lowercase=%q canonical=%q", gotLegacy, gotLowercase, gotCanonical)
+	}
+	if gotCanonical != "session-id:session-alias" {
+		t.Fatalf("canonical session key = %q, want session-id:session-alias", gotCanonical)
+	}
+}
+
+func TestCodexExecutorReasoningReplaySessionKeyCanonicalizesWindowHeaderWithPayload(t *testing.T) {
+	payload := []byte(`{"client_metadata":{"x-codex-window-id":"window-1"}}`)
+	headers := http.Header{"X-Codex-Window-Id": []string{"window-1"}}
+
+	gotPayload := codexReasoningReplaySessionKeyFromPayload(payload)
+	gotHeader := codexReasoningReplaySessionKeyFromHeaders(headers)
+
+	if gotPayload != gotHeader {
+		t.Fatalf("window replay keys differ: payload=%q header=%q", gotPayload, gotHeader)
+	}
+	if gotHeader != "window:window-1" {
+		t.Fatalf("window replay key = %q, want window:window-1", gotHeader)
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheSharesSameSessionAcrossCodexAuths(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	encryptedContent := validCodexReasoningEncryptedContentForTestSeed(12)
+	var bodies [][]byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, errRead := io.ReadAll(r.Body)
+		if errRead != nil {
+			t.Fatalf("read body: %v", errRead)
+		}
+		bodies = append(bodies, body)
+
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.done","item":{"id":"rs_done","type":"reasoning","summary":[],"encrypted_content":"` + encryptedContent + `"},"output_index":0}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[]}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	firstAuth := &cliproxyauth.Auth{
+		ID: "auth-replay-session-auth-a",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test-a",
+		},
+	}
+	secondAuth := &cliproxyauth.Auth{
+		ID: "auth-replay-session-auth-b",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test-b",
+		},
+	}
+	opts := cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       false,
+	}
+
+	_, err := executor.Execute(context.Background(), firstAuth, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-auth-switch\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"hello"}]}]}`),
+	}, opts)
+	if err != nil {
+		t.Fatalf("first Execute error: %v", err)
+	}
+
+	_, err = executor.Execute(context.Background(), secondAuth, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-auth-switch\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]}`),
+	}, opts)
+	if err != nil {
+		t.Fatalf("second Execute error: %v", err)
+	}
+
+	if len(bodies) != 2 {
+		t.Fatalf("upstream request count = %d, want 2", len(bodies))
+	}
+	secondBody := bodies[1]
+	if got := gjson.GetBytes(secondBody, "input.0.type").String(); got != "reasoning" {
+		t.Fatalf("input.0.type = %q, want same-session replay across auths; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.0.encrypted_content").String(); got != encryptedContent {
+		t.Fatalf("injected encrypted_content = %q, want cached value", got)
+	}
+}
+
+func codexReplaySessionOnlyContext(apiKey string) context.Context {
+	recorder := httptest.NewRecorder()
+	ginCtx, _ := gin.CreateTestContext(recorder)
+	ginCtx.Set("userApiKey", apiKey)
+	ginCtx.Set("accessProvider", "config-inline")
+	ginCtx.Request = httptest.NewRequest("POST", "/v1/messages", nil)
+	return context.WithValue(context.Background(), "gin", ginCtx)
+}
+
+func TestCodexExecutorReasoningReplayCacheDoesNotInjectNativeResponsesRequest(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	cachedEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(3)
+	internalcache.CacheCodexReasoningReplayItem("gpt-5.4", "prompt-cache:native-session", []byte(`{"type":"reasoning","summary":[],"content":null,"encrypted_content":"`+cachedEncryptedContent+`"}`))
+
+	var gotBody []byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, errRead := io.ReadAll(r.Body)
+		if errRead != nil {
+			t.Fatalf("read body: %v", errRead)
+		}
+		gotBody = body
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[]}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	_, err := executor.Execute(context.Background(), &cliproxyauth.Auth{
+		ID: "auth-replay-native",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","prompt_cache_key":"native-session","input":[{"role":"user","content":"native"}]}`),
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("openai-response"),
+		Stream:       false,
+	})
+	if err != nil {
+		t.Fatalf("Execute error: %v", err)
+	}
+
+	if got := gjson.GetBytes(gotBody, "input.0.type").String(); got == "reasoning" {
+		t.Fatalf("native Responses request should not receive cached reasoning; body=%s", string(gotBody))
+	}
+	if got := gjson.GetBytes(gotBody, "input.0.role").String(); got != "user" {
+		t.Fatalf("input.0.role = %q, want user; body=%s", got, string(gotBody))
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheDoesNotStoreNativeResponsesRequest(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	nativeEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(4)
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = io.ReadAll(r.Body)
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[{"id":"rs_native","type":"reasoning","summary":[],"encrypted_content":"` + nativeEncryptedContent + `"}]}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	_, err := executor.Execute(context.Background(), &cliproxyauth.Auth{
+		ID: "auth-replay-native-store",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","prompt_cache_key":"native-store","input":[{"role":"user","content":"native"}]}`),
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("openai-response"),
+		Stream:       false,
+	})
+	if err != nil {
+		t.Fatalf("Execute error: %v", err)
+	}
+
+	if _, ok := internalcache.GetCodexReasoningReplayItem("gpt-5.4", "prompt-cache:native-store"); ok {
+		t.Fatal("native Responses request should not populate Codex reasoning replay cache")
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheDoesNotDuplicateClaudeClientReasoning(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	cachedEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(5)
+	clientEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(6)
+	internalcache.CacheCodexReasoningReplayItem("gpt-5.4", "claude:session-2", []byte(`{"type":"reasoning","summary":[],"content":null,"encrypted_content":"`+cachedEncryptedContent+`"}`))
+
+	var gotBody []byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, errRead := io.ReadAll(r.Body)
+		if errRead != nil {
+			t.Fatalf("read body: %v", errRead)
+		}
+		gotBody = body
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[]}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	_, err := executor.Execute(context.Background(), &cliproxyauth.Auth{
+		ID: "auth-replay-2",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-2\"}"},"messages":[{"role":"assistant","content":[{"type":"thinking","thinking":"client summary","signature":"` + clientEncryptedContent + `"},{"type":"text","text":"answer"}]},{"role":"user","content":[{"type":"text","text":"next"}]}]}`),
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       false,
+	})
+	if err != nil {
+		t.Fatalf("Execute error: %v", err)
+	}
+
+	if got := gjson.GetBytes(gotBody, "input.0.encrypted_content").String(); got != clientEncryptedContent {
+		t.Fatalf("client reasoning should be preserved, got %q want %q; body=%s", got, clientEncryptedContent, string(gotBody))
+	}
+	reasoningCount := 0
+	for _, item := range gjson.GetBytes(gotBody, "input").Array() {
+		if item.Get("type").String() == "reasoning" {
+			reasoningCount++
+		}
+	}
+	if reasoningCount != 1 {
+		t.Fatalf("reasoning item count = %d, want 1; body=%s", reasoningCount, string(gotBody))
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheInsertsReasoningBeforeAssistantOutputInClaudeHistory(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	cachedEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(7)
+	internalcache.CacheCodexReasoningReplayItem("gpt-5.4", "claude:session-history", []byte(`{"type":"reasoning","summary":[],"content":null,"encrypted_content":"`+cachedEncryptedContent+`"}`))
+
+	var gotBody []byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, errRead := io.ReadAll(r.Body)
+		if errRead != nil {
+			t.Fatalf("read body: %v", errRead)
+		}
+		gotBody = body
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[]}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	_, err := executor.Execute(context.Background(), &cliproxyauth.Auth{
+		ID: "auth-replay-history",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}, cliproxyexecutor.Request{
+		Model: "gpt-5.4",
+		Payload: []byte(`{
+			"model":"gpt-5.4",
+			"metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-history\"}"},
+			"messages":[
+				{"role":"user","content":[{"type":"text","text":"first"}]},
+				{"role":"assistant","content":[{"type":"text","text":"answer"}]},
+				{"role":"user","content":[{"type":"text","text":"next"}]}
+			]
+		}`),
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       false,
+	})
+	if err != nil {
+		t.Fatalf("Execute error: %v", err)
+	}
+
+	if got := gjson.GetBytes(gotBody, "input.0.role").String(); got != "user" {
+		t.Fatalf("input.0.role = %q, want first user message; body=%s", got, string(gotBody))
+	}
+	if got := gjson.GetBytes(gotBody, "input.1.type").String(); got != "reasoning" {
+		t.Fatalf("input.1.type = %q, want cached reasoning before assistant output; body=%s", got, string(gotBody))
+	}
+	if got := gjson.GetBytes(gotBody, "input.1.encrypted_content").String(); got != cachedEncryptedContent {
+		t.Fatalf("input.1.encrypted_content = %q, want cached reasoning; body=%s", got, string(gotBody))
+	}
+	if got := gjson.GetBytes(gotBody, "input.2.role").String(); got != "assistant" {
+		t.Fatalf("input.2.role = %q, want assistant output after cached reasoning; body=%s", got, string(gotBody))
+	}
+	if got := gjson.GetBytes(gotBody, "input.3.role").String(); got != "user" {
+		t.Fatalf("input.3.role = %q, want final user message; body=%s", got, string(gotBody))
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheExecuteStreamStoresFinalDoneForClaude(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	addedEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(7)
+	doneEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(8)
+	var bodies [][]byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, errRead := io.ReadAll(r.Body)
+		if errRead != nil {
+			t.Fatalf("read body: %v", errRead)
+		}
+		bodies = append(bodies, body)
+
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.added","item":{"id":"rs_added","type":"reasoning","status":"in_progress","summary":[],"encrypted_content":"` + addedEncryptedContent + `"},"output_index":0}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.done","item":{"id":"rs_done","type":"reasoning","summary":[],"encrypted_content":"` + doneEncryptedContent + `"},"output_index":0}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[]}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	auth := &cliproxyauth.Auth{
+		ID: "auth-replay-stream",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}
+
+	streamResult, err := executor.ExecuteStream(context.Background(), auth, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"stream-session-1\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"hello"}]}]}`),
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       true,
+	})
+	if err != nil {
+		t.Fatalf("ExecuteStream error: %v", err)
+	}
+	for chunk := range streamResult.Chunks {
+		if chunk.Err != nil {
+			t.Fatalf("stream chunk error: %v", chunk.Err)
+		}
+	}
+
+	_, err = executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"stream-session-1\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]}`),
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       false,
+	})
+	if err != nil {
+		t.Fatalf("Execute error: %v", err)
+	}
+
+	if len(bodies) != 2 {
+		t.Fatalf("upstream request count = %d, want 2", len(bodies))
+	}
+	secondBody := bodies[1]
+	if got := gjson.GetBytes(secondBody, "input.0.encrypted_content").String(); got != doneEncryptedContent {
+		t.Fatalf("stream cached encrypted_content = %q, want final done %q; body=%s", got, doneEncryptedContent, string(secondBody))
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheClearsOnNonStreamResponseFailedInvalidSignature(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	cachedEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(9)
+	internalcache.CacheCodexReasoningReplayItem("gpt-5.4", "claude:session-invalid-nonstream", []byte(`{"type":"reasoning","summary":[],"content":null,"encrypted_content":"`+cachedEncryptedContent+`"}`))
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = io.ReadAll(r.Body)
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.failed","response":{"id":"resp_1","status":"failed","error":{"message":"Invalid signature in thinking block","type":"invalid_request_error","code":"invalid_request_error"}}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	_, err := executor.Execute(context.Background(), &cliproxyauth.Auth{
+		ID: "auth-replay-invalid-nonstream",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-invalid-nonstream\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]}`),
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       false,
+	})
+	if err == nil {
+		t.Fatal("expected invalid signature error")
+	}
+	if _, ok := internalcache.GetCodexReasoningReplayItem("gpt-5.4", "claude:session-invalid-nonstream"); ok {
+		t.Fatal("invalid signature response.failed should clear cached replay item")
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheClearsOnStreamResponseFailedInvalidSignature(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	cachedEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(10)
+	internalcache.CacheCodexReasoningReplayItem("gpt-5.4", "claude:session-invalid-stream", []byte(`{"type":"reasoning","summary":[],"content":null,"encrypted_content":"`+cachedEncryptedContent+`"}`))
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = io.ReadAll(r.Body)
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.failed","response":{"id":"resp_1","status":"failed","error":{"message":"Invalid signature in thinking block","type":"invalid_request_error","code":"invalid_request_error"}}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	streamResult, err := executor.ExecuteStream(context.Background(), &cliproxyauth.Auth{
+		ID: "auth-replay-invalid-stream",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}, cliproxyexecutor.Request{
+		Model:   "gpt-5.4",
+		Payload: []byte(`{"model":"gpt-5.4","metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"session-invalid-stream\"}"},"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]}`),
+	}, cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       true,
+	})
+	if err != nil {
+		t.Fatalf("ExecuteStream setup error: %v", err)
+	}
+
+	gotChunkErr := false
+	for chunk := range streamResult.Chunks {
+		if chunk.Err != nil {
+			gotChunkErr = true
+		}
+	}
+	if !gotChunkErr {
+		t.Fatal("expected stream chunk error for invalid signature response.failed")
+	}
+	if _, ok := internalcache.GetCodexReasoningReplayItem("gpt-5.4", "claude:session-invalid-stream"); ok {
+		t.Fatal("invalid signature response.failed should clear cached replay item")
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheReplaysFunctionCallForClaudeToolResult(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	reasoningEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(8)
+	var bodies [][]byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, errRead := io.ReadAll(r.Body)
+		if errRead != nil {
+			t.Fatalf("read body: %v", errRead)
+		}
+		bodies = append(bodies, body)
+
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.done","item":{"id":"rs_1","type":"reasoning","summary":[],"encrypted_content":"` + reasoningEncryptedContent + `"},"output_index":0}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.added","item":{"id":"fc_1","type":"function_call","call_id":"call_1","name":"lookup","arguments":"{\"q\":\"weather\"}","status":"in_progress"},"output_index":1}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.done","item":{"id":"fc_1","type":"function_call","call_id":"call_1","name":"lookup","arguments":"{\"q\":\"weather\"}","status":"completed"},"output_index":1}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[]}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	auth := &cliproxyauth.Auth{
+		ID: "auth-replay-claude-tool",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}
+	opts := cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       false,
+	}
+
+	_, err := executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+		Model: "gpt-5.4",
+		Payload: []byte(`{
+			"model":"gpt-5.4",
+			"metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"claude-session-tool\"}"},
+			"messages":[{"role":"user","content":[{"type":"text","text":"call lookup"}]}],
+			"tools":[{"name":"lookup","input_schema":{"type":"object","properties":{"q":{"type":"string"}}}}]
+		}`),
+	}, opts)
+	if err != nil {
+		t.Fatalf("first Execute error: %v", err)
+	}
+
+	_, err = executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+		Model: "gpt-5.4",
+		Payload: []byte(`{
+			"model":"gpt-5.4",
+			"metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"claude-session-tool\"}"},
+			"messages":[
+				{"role":"user","content":[{"type":"text","text":"call lookup"}]},
+				{"role":"user","content":[{"type":"tool_result","tool_use_id":"call_1","content":"sunny"}]}
+			],
+			"tools":[{"name":"lookup","input_schema":{"type":"object","properties":{"q":{"type":"string"}}}}]
+		}`),
+	}, opts)
+	if err != nil {
+		t.Fatalf("second Execute error: %v", err)
+	}
+
+	if len(bodies) != 2 {
+		t.Fatalf("upstream request count = %d, want 2", len(bodies))
+	}
+	secondBody := bodies[1]
+	if got := gjson.GetBytes(secondBody, "input.0.type").String(); got != "message" {
+		t.Fatalf("input.0.type = %q, want initial user message; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.1.type").String(); got != "reasoning" {
+		t.Fatalf("input.1.type = %q, want cached reasoning; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.2.type").String(); got != "function_call" {
+		t.Fatalf("input.2.type = %q, want cached function_call; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.2.call_id").String(); got != "call_1" {
+		t.Fatalf("input.2.call_id = %q, want call_1; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.3.type").String(); got != "function_call_output" {
+		t.Fatalf("input.3.type = %q, want function_call_output after cached call; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.3.call_id").String(); got != "call_1" {
+		t.Fatalf("input.3.call_id = %q, want call_1; body=%s", got, string(secondBody))
+	}
+}
+
+func TestCodexExecutorReasoningReplayCacheMatchesShortenedClaudeToolResultCallID(t *testing.T) {
+	internalcache.ClearCodexReasoningReplayCache()
+	t.Cleanup(internalcache.ClearCodexReasoningReplayCache)
+
+	longCallID := "call_" + strings.Repeat("a", 62)
+	shortCallID := shortenedCodexReplayCallIDForTest(longCallID)
+	if len(longCallID) <= 64 || len(shortCallID) > 64 || shortCallID == longCallID {
+		t.Fatalf("invalid test setup: long=%q short=%q", longCallID, shortCallID)
+	}
+
+	reasoningEncryptedContent := validCodexReasoningEncryptedContentForTestSeed(13)
+	var bodies [][]byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, errRead := io.ReadAll(r.Body)
+		if errRead != nil {
+			t.Fatalf("read body: %v", errRead)
+		}
+		bodies = append(bodies, body)
+
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.done","item":{"id":"rs_long","type":"reasoning","summary":[],"encrypted_content":"` + reasoningEncryptedContent + `"},"output_index":0}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.output_item.done","item":{"id":"fc_long","type":"function_call","call_id":"` + longCallID + `","name":"lookup","arguments":"{\"q\":\"weather\"}","status":"completed"},"output_index":1}` + "\n"))
+		_, _ = w.Write([]byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","created_at":0,"status":"completed","model":"gpt-5.4","output":[]}}` + "\n\n"))
+	}))
+	defer server.Close()
+
+	executor := NewCodexExecutor(&config.Config{})
+	auth := &cliproxyauth.Auth{
+		ID: "auth-replay-claude-short-tool",
+		Attributes: map[string]string{
+			"base_url": server.URL,
+			"api_key":  "test",
+		},
+	}
+	opts := cliproxyexecutor.Options{
+		SourceFormat: sdktranslator.FromString("claude"),
+		Stream:       false,
+	}
+
+	_, err := executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+		Model: "gpt-5.4",
+		Payload: []byte(`{
+			"model":"gpt-5.4",
+			"metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"claude-session-short-tool\"}"},
+			"messages":[{"role":"user","content":[{"type":"text","text":"call lookup"}]}],
+			"tools":[{"name":"lookup","input_schema":{"type":"object","properties":{"q":{"type":"string"}}}}]
+		}`),
+	}, opts)
+	if err != nil {
+		t.Fatalf("first Execute error: %v", err)
+	}
+
+	_, err = executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+		Model: "gpt-5.4",
+		Payload: []byte(`{
+			"model":"gpt-5.4",
+			"metadata":{"user_id":"{\"device_id\":\"device-test\",\"account_uuid\":\"\",\"session_id\":\"claude-session-short-tool\"}"},
+			"messages":[
+				{"role":"user","content":[{"type":"text","text":"call lookup"}]},
+				{"role":"user","content":[{"type":"tool_result","tool_use_id":"` + shortCallID + `","content":"sunny"}]}
+			],
+			"tools":[{"name":"lookup","input_schema":{"type":"object","properties":{"q":{"type":"string"}}}}]
+		}`),
+	}, opts)
+	if err != nil {
+		t.Fatalf("second Execute error: %v", err)
+	}
+
+	if len(bodies) != 2 {
+		t.Fatalf("upstream request count = %d, want 2", len(bodies))
+	}
+	secondBody := bodies[1]
+	if got := gjson.GetBytes(secondBody, "input.0.type").String(); got != "message" {
+		t.Fatalf("input.0.type = %q, want initial user message; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.1.type").String(); got != "reasoning" {
+		t.Fatalf("input.1.type = %q, want cached reasoning; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.2.type").String(); got != "function_call" {
+		t.Fatalf("input.2.type = %q, want cached function_call; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.2.call_id").String(); got != shortCallID {
+		t.Fatalf("input.2.call_id = %q, want shortened call_id %q; body=%s", got, shortCallID, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.3.type").String(); got != "function_call_output" {
+		t.Fatalf("input.3.type = %q, want function_call_output after cached call; body=%s", got, string(secondBody))
+	}
+	if got := gjson.GetBytes(secondBody, "input.3.call_id").String(); got != shortCallID {
+		t.Fatalf("input.3.call_id = %q, want shortened call_id %q; body=%s", got, shortCallID, string(secondBody))
+	}
+}
diff --git a/internal/runtime/executor/codex_executor_stream_output_test.go b/internal/runtime/executor/codex_executor_stream_output_test.go
index 983f915bc..46a227924 100644
--- a/internal/runtime/executor/codex_executor_stream_output_test.go
+++ b/internal/runtime/executor/codex_executor_stream_output_test.go
@@ -159,6 +159,13 @@ func TestCodexTerminalStreamContextLengthErrIgnoresOtherTerminalErrors(t *testin
 	}
 }
 
+func TestCodexTerminalStreamErrIgnoresRateLimitTerminalErrors(t *testing.T) {
+	_, _, ok := codexTerminalStreamErr([]byte(`{"type":"error","error":{"type":"rate_limit_error","code":"rate_limit_exceeded","message":"Rate limit reached."}}`))
+	if ok {
+		t.Fatal("rate limit terminal error should not be handled by replay terminal error path")
+	}
+}
+
 func statusCodeFromTestError(t *testing.T, err error) int {
 	t.Helper()
 
diff --git a/internal/runtime/executor/codex_websockets_executor.go b/internal/runtime/executor/codex_websockets_executor.go
index e1c9ce344..8d68a251e 100644
--- a/internal/runtime/executor/codex_websockets_executor.go
+++ b/internal/runtime/executor/codex_websockets_executor.go
@@ -835,21 +835,11 @@ func applyCodexPromptCacheHeaders(from sdktranslator.Format, req cliproxyexecuto
 	}
 
 	var cache helps.CodexCache
-	if from == "claude" {
-		userIDResult := gjson.GetBytes(req.Payload, "metadata.user_id")
-		if userIDResult.Exists() {
-			key := fmt.Sprintf("%s-%s", req.Model, userIDResult.String())
-			if cached, ok := helps.GetCodexCache(key); ok {
-				cache = cached
-			} else {
-				cache = helps.CodexCache{
-					ID:     uuid.New().String(),
-					Expire: time.Now().Add(1 * time.Hour),
-				}
-				helps.SetCodexCache(key, cache)
-			}
+	if sourceFormatEqual(from, sdktranslator.FormatClaude) {
+		if cached, ok := codexClaudeCodePromptCache(req); ok {
+			cache = cached
 		}
-	} else if from == "openai-response" {
+	} else if sourceFormatEqual(from, sdktranslator.FormatOpenAIResponse) {
 		if promptCacheKey := gjson.GetBytes(req.Payload, "prompt_cache_key"); promptCacheKey.Exists() {
 			cache.ID = promptCacheKey.String()
 		}
@@ -899,10 +889,11 @@ func applyCodexWebsocketHeaders(ctx context.Context, headers http.Header, auth *
 		betaHeader = codexResponsesWebsocketBetaHeaderValue
 	}
 	headers.Set("OpenAI-Beta", betaHeader)
+	sessionFallback := ""
 	if strings.Contains(headers.Get("User-Agent"), "Mac OS") {
-		ensureHeaderCasePreserved(headers, ginHeaders, "session_id", "", uuid.NewString())
+		sessionFallback = uuid.NewString()
 	}
-	ensureHeaderCasePreserved(headers, ginHeaders, "session_id", "", "")
+	ensureCodexWebsocketSessionHeader(headers, ginHeaders, sessionFallback)
 	if originator := strings.TrimSpace(ginHeaders.Get("Originator")); originator != "" {
 		headers.Set("Originator", originator)
 	} else if !isAPIKey {
@@ -927,6 +918,32 @@ func applyCodexWebsocketHeaders(ctx context.Context, headers http.Header, auth *
 	return headers
 }
 
+func ensureCodexWebsocketSessionHeader(target http.Header, source http.Header, fallbackValue string) {
+	if target == nil {
+		return
+	}
+	sessionID := codexSessionHeaderValue(target)
+	if sessionID == "" {
+		sessionID = codexSessionHeaderValue(source)
+	}
+	if sessionID == "" {
+		sessionID = strings.TrimSpace(fallbackValue)
+	}
+	if sessionID != "" {
+		setHeaderCasePreserved(target, "session_id", sessionID)
+	}
+	deleteHeaderCaseInsensitive(target, "Session-Id")
+}
+
+func codexSessionHeaderValue(headers http.Header) string {
+	for _, key := range []string{"Session-Id", "Session_id", "session_id"} {
+		if value := strings.TrimSpace(headerValueCaseInsensitive(headers, key)); value != "" {
+			return value
+		}
+	}
+	return ""
+}
+
 func codexAuthUsesAPIKey(auth *cliproxyauth.Auth) bool {
 	if auth == nil || auth.Attributes == nil {
 		return false
@@ -969,6 +986,47 @@ func setHeaderCasePreserved(headers http.Header, key string, value string) {
 	headers[key] = []string{value}
 }
 
+func setCodexSessionHeaderCasePreserved(headers http.Header, fallbackKey string, value string) {
+	if headers == nil {
+		return
+	}
+	fallbackKey = strings.TrimSpace(fallbackKey)
+	value = strings.TrimSpace(value)
+	if fallbackKey == "" || value == "" {
+		return
+	}
+
+	selectedKey := ""
+	if _, ok := headers[fallbackKey]; ok && codexSessionHeaderKeyUsesUnderscore(fallbackKey) {
+		selectedKey = fallbackKey
+	} else {
+		for existingKey := range headers {
+			if codexSessionHeaderKeyUsesUnderscore(existingKey) {
+				selectedKey = existingKey
+				break
+			}
+		}
+	}
+	if selectedKey == "" {
+		selectedKey = fallbackKey
+	}
+	for existingKey := range headers {
+		if codexSessionHeaderKey(existingKey) && existingKey != selectedKey {
+			delete(headers, existingKey)
+		}
+	}
+	headers[selectedKey] = []string{value}
+}
+
+func codexSessionHeaderKey(key string) bool {
+	normalized := strings.ToLower(strings.TrimSpace(key))
+	return normalized == "session_id" || normalized == "session-id"
+}
+
+func codexSessionHeaderKeyUsesUnderscore(key string) bool {
+	return strings.ToLower(strings.TrimSpace(key)) == "session_id"
+}
+
 func headerValueCaseInsensitive(headers http.Header, key string) string {
 	key = strings.TrimSpace(key)
 	if headers == nil || key == "" {
diff --git a/internal/runtime/executor/codex_websockets_executor_test.go b/internal/runtime/executor/codex_websockets_executor_test.go
index 5dbfbce94..a3d3a5525 100644
--- a/internal/runtime/executor/codex_websockets_executor_test.go
+++ b/internal/runtime/executor/codex_websockets_executor_test.go
@@ -197,7 +197,7 @@ func TestApplyCodexWebsocketHeadersPassesThroughClientIdentityHeaders(t *testing
 		"Version":               "0.115.0-alpha.27",
 		"X-Codex-Turn-Metadata": `{"turn_id":"turn-1"}`,
 		"X-Client-Request-Id":   "019d2233-e240-7162-992d-38df0a2a0e0d",
-		"session_id":            "legacy-session",
+		"session-id":            "legacy-session",
 	})
 
 	headers := applyCodexWebsocketHeaders(ctx, http.Header{}, auth, "", nil)
@@ -217,11 +217,32 @@ func TestApplyCodexWebsocketHeadersPassesThroughClientIdentityHeaders(t *testing
 	if got := headers.Get("X-Client-Request-Id"); got != "019d2233-e240-7162-992d-38df0a2a0e0d" {
 		t.Fatalf("X-Client-Request-Id = %s, want %s", got, "019d2233-e240-7162-992d-38df0a2a0e0d")
 	}
-	if got := headerValueCaseInsensitive(headers, "session_id"); got != "legacy-session" {
-		t.Fatalf("session_id = %s, want legacy-session", got)
+	if got := headers["session_id"]; len(got) != 1 || got[0] != "legacy-session" {
+		t.Fatalf("session_id = %#v, want [legacy-session]", got)
 	}
-	if _, ok := headers["session_id"]; !ok {
-		t.Fatalf("expected lowercase session_id header key, got %#v", headers)
+	if got := headers.Get("Session-Id"); got != "" {
+		t.Fatalf("Session-Id = %s, want empty", got)
+	}
+}
+
+func TestApplyCodexWebsocketHeadersCanonicalizesLegacyUnderscoreSessionHeader(t *testing.T) {
+	auth := &cliproxyauth.Auth{
+		Provider: "codex",
+		Metadata: map[string]any{"email": "user@example.com"},
+	}
+	ctx := contextWithGinHeaders(map[string]string{
+		"Originator": "Codex Desktop",
+		"User-Agent": "codex_cli_rs/0.1.0",
+		"Session_id": "legacy-underscore-session",
+	})
+
+	headers := applyCodexWebsocketHeaders(ctx, http.Header{}, auth, "", nil)
+
+	if got := headers["session_id"]; len(got) != 1 || got[0] != "legacy-underscore-session" {
+		t.Fatalf("session_id = %#v, want [legacy-underscore-session]", got)
+	}
+	if got := headers.Get("Session-Id"); got != "" {
+		t.Fatalf("Session-Id = %s, want empty", got)
 	}
 }
 
@@ -361,22 +382,79 @@ func TestApplyCodexWebsocketHeadersUsesCanonicalAccountHeader(t *testing.T) {
 	}
 }
 
-func TestApplyCodexPromptCacheHeadersSetsLowercaseSessionAndLegacyConversation(t *testing.T) {
+func TestApplyCodexPromptCacheHeadersSetsSessionIDAndLegacyConversation(t *testing.T) {
 	req := cliproxyexecutor.Request{Model: "gpt-5-codex", Payload: []byte(`{"prompt_cache_key":"cache-1"}`)}
 
 	_, headers := applyCodexPromptCacheHeaders("openai-response", req, []byte(`{"model":"gpt-5-codex"}`))
 
-	if got := headerValueCaseInsensitive(headers, "session_id"); got != "cache-1" {
-		t.Fatalf("session_id = %s, want cache-1", got)
+	if got := headers["session_id"]; len(got) != 1 || got[0] != "cache-1" {
+		t.Fatalf("session_id = %#v, want [cache-1]", got)
 	}
-	if _, ok := headers["session_id"]; !ok {
-		t.Fatalf("expected lowercase session_id key, got %#v", headers)
+	if got := headers.Get("Session-Id"); got != "" {
+		t.Fatalf("Session-Id = %s, want empty", got)
 	}
 	if got := headers.Get("Conversation_id"); got != "cache-1" {
 		t.Fatalf("Conversation_id = %s, want cache-1", got)
 	}
 }
 
+func TestApplyCodexPromptCacheHeadersClaudeUsesClaudeCodeSessionID(t *testing.T) {
+	firstReq := cliproxyexecutor.Request{
+		Model: "gpt-5-codex-claude-ws-cache-session",
+		Payload: []byte(`{
+			"metadata":{"user_id":"{\"device_id\":\"device-a\",\"account_uuid\":\"\",\"session_id\":\"ws-cache-session-1\"}"},
+			"messages":[{"role":"user","content":[{"type":"text","text":"first"}]}]
+		}`),
+	}
+	secondReq := cliproxyexecutor.Request{
+		Model: "gpt-5-codex-claude-ws-cache-session",
+		Payload: []byte(`{
+			"metadata":{"user_id":"{\"device_id\":\"device-b\",\"account_uuid\":\"\",\"session_id\":\"ws-cache-session-1\"}"},
+			"messages":[{"role":"user","content":[{"type":"text","text":"next"}]}]
+		}`),
+	}
+
+	firstBody, firstHeaders := applyCodexPromptCacheHeaders("claude", firstReq, []byte(`{"model":"gpt-5-codex"}`))
+	secondBody, secondHeaders := applyCodexPromptCacheHeaders("claude", secondReq, []byte(`{"model":"gpt-5-codex"}`))
+
+	firstKey := gjson.GetBytes(firstBody, "prompt_cache_key").String()
+	secondKey := gjson.GetBytes(secondBody, "prompt_cache_key").String()
+	if firstKey == "" {
+		t.Fatalf("first prompt_cache_key is empty; body=%s", string(firstBody))
+	}
+	if secondKey != firstKey {
+		t.Fatalf("same Claude Code session_id produced different websocket prompt_cache_key: first=%q second=%q", firstKey, secondKey)
+	}
+	if got := firstHeaders["session_id"]; len(got) != 1 || got[0] != firstKey {
+		t.Fatalf("first session_id = %#v, want [%q]", got, firstKey)
+	}
+	if got := secondHeaders["session_id"]; len(got) != 1 || got[0] != firstKey {
+		t.Fatalf("second session_id = %#v, want [%q]", got, firstKey)
+	}
+}
+
+func TestApplyCodexPromptCacheHeadersClaudeRejectsBareUserID(t *testing.T) {
+	req := cliproxyexecutor.Request{
+		Model:   "gpt-5-codex-claude-ws-cache-bare-user",
+		Payload: []byte(`{"metadata":{"user_id":"same-user-across-chats"},"messages":[{"role":"user","content":[{"type":"text","text":"first"}]}]}`),
+	}
+
+	body, headers := applyCodexPromptCacheHeaders("claude", req, []byte(`{"model":"gpt-5-codex"}`))
+
+	if got := gjson.GetBytes(body, "prompt_cache_key").String(); got != "" {
+		t.Fatalf("bare metadata.user_id must not create websocket prompt_cache_key, got %q; body=%s", got, string(body))
+	}
+	if got := headers["session_id"]; len(got) != 0 {
+		t.Fatalf("bare metadata.user_id must not create websocket session_id, got %#v", got)
+	}
+	if got := headers.Get("Session-Id"); got != "" {
+		t.Fatalf("bare metadata.user_id must not create websocket Session-Id, got %q", got)
+	}
+	if got := headers.Get("Conversation_id"); got != "" {
+		t.Fatalf("bare metadata.user_id must not create websocket Conversation_id, got %q", got)
+	}
+}
+
 func TestApplyCodexWebsocketHeadersIdentityConfuseRemapsPromptCacheKey(t *testing.T) {
 	cfg := &config.Config{
 		Routing: config.RoutingConfig{SessionAffinity: true},
@@ -402,8 +480,11 @@ func TestApplyCodexWebsocketHeadersIdentityConfuseRemapsPromptCacheKey(t *testin
 	if gotKey := gjson.GetBytes(body, "prompt_cache_key").String(); gotKey != expectedPromptCacheKey {
 		t.Fatalf("prompt_cache_key = %q, want %q", gotKey, expectedPromptCacheKey)
 	}
-	if gotSession := headerValueCaseInsensitive(headers, "session_id"); gotSession != expectedPromptCacheKey {
-		t.Fatalf("session_id = %q, want %q", gotSession, expectedPromptCacheKey)
+	if gotSession := headers["session_id"]; len(gotSession) != 1 || gotSession[0] != expectedPromptCacheKey {
+		t.Fatalf("session_id = %#v, want [%q]", gotSession, expectedPromptCacheKey)
+	}
+	if gotCanonicalSession := headers.Get("Session-Id"); gotCanonicalSession != "" {
+		t.Fatalf("Session-Id = %q, want empty", gotCanonicalSession)
 	}
 	if gotRequestID := headers.Get("X-Client-Request-Id"); gotRequestID != expectedPromptCacheKey {
 		t.Fatalf("X-Client-Request-Id = %q, want %q", gotRequestID, expectedPromptCacheKey)