diff --git a/internal/redisqueue/plugin.go b/internal/redisqueue/plugin.go
index 0b3bf108b..4eb8280b6 100644
--- a/internal/redisqueue/plugin.go
+++ b/internal/redisqueue/plugin.go
@@ -65,6 +65,7 @@ func (p *usageQueuePlugin) HandleUsage(ctx context.Context, record coreusage.Rec
 		serviceTier = coreusage.ServiceTierFromContext(ctx)
 	}
 	responseServiceTier := strings.TrimSpace(record.ResponseServiceTier)
+	responseModel := strings.TrimSpace(record.ResponseModel)
 	clientRequestMetadata := internallogging.GetClientRequestMetadata(ctx)
 	sessionID := strings.TrimSpace(record.SessionID)
 	parentSessionID := strings.TrimSpace(record.ParentSessionID)
@@ -138,6 +139,7 @@ func (p *usageQueuePlugin) HandleUsage(ctx context.Context, record coreusage.Rec
 		ReasoningEffort:     reasoningEffort,
 		ServiceTier:         serviceTier,
 		ResponseServiceTier: responseServiceTier,
+		ResponseModel:       responseModel,
 	})
 	if err != nil {
 		return
@@ -162,6 +164,7 @@ type queuedUsageDetail struct {
 	ReasoningEffort     string                   `json:"reasoning_effort"`
 	ServiceTier         string                   `json:"service_tier"`
 	ResponseServiceTier string                   `json:"response_service_tier,omitempty"`
+	ResponseModel       string                   `json:"response_model,omitempty"`
 }
 
 type requestDetail struct {
diff --git a/internal/redisqueue/plugin_test.go b/internal/redisqueue/plugin_test.go
index 248f2a505..78c228565 100644
--- a/internal/redisqueue/plugin_test.go
+++ b/internal/redisqueue/plugin_test.go
@@ -43,6 +43,7 @@ func TestUsageQueuePluginPayloadIncludesStableFieldsAndSuccess(t *testing.T) {
 			ReasoningEffort:     "medium",
 			ServiceTier:         "auto",
 			ResponseServiceTier: "default",
+			ResponseModel:       "gpt-5.6-luna",
 			Generate:            coreusage.GenerateFlag(true),
 			RequestedAt:         time.Date(2026, 4, 25, 0, 0, 0, 0, time.UTC),
 			Latency:             1500 * time.Millisecond,
@@ -72,6 +73,7 @@ func TestUsageQueuePluginPayloadIncludesStableFieldsAndSuccess(t *testing.T) {
 		requireStringField(t, payload, "service_tier", "auto")
 		requireMissingField(t, payload, "request_service_tier")
 		requireStringField(t, payload, "response_service_tier", "default")
+		requireStringField(t, payload, "response_model", "gpt-5.6-luna")
 		requireIntField(t, payload, "accounting_version", coreusage.TokenAccountingSchemaVersion)
 		requireTokenBreakdown(t, payload, coreusage.TokenAccountingQualityComplete, 30)
 		requireTokensBoolField(t, payload, "cache_read_tokens_present", true)
diff --git a/internal/runtime/executor/codex_executor_execute.go b/internal/runtime/executor/codex_executor_execute.go
index 49ef1a127..ab5489247 100644
--- a/internal/runtime/executor/codex_executor_execute.go
+++ b/internal/runtime/executor/codex_executor_execute.go
@@ -140,6 +140,7 @@ func (e *CodexExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, re
 
 		eventData := bytes.TrimSpace(line[5:])
 		eventData = helps.RestoreCodexMultiAgentV2Response(eventData, optimizeMultiAgentV2)
+		reporter.ObserveCodexResponseModel(eventData)
 		eventType := gjson.GetBytes(eventData, "type").String()
 
 		if helps.HasMeaningfulCodexOutputDelta(eventData) {
diff --git a/internal/runtime/executor/codex_executor_terminal.go b/internal/runtime/executor/codex_executor_terminal.go
index a83f01d22..b91b27694 100644
--- a/internal/runtime/executor/codex_executor_terminal.go
+++ b/internal/runtime/executor/codex_executor_terminal.go
@@ -591,9 +591,11 @@ func isCodexEmptyPart(payload []byte) bool {
 	}
 }
 
-// observeCodexTokenEvent inspects a stream payload and marks TTFT on the first substantive token event.
+// observeCodexTokenEvent inspects a stream payload, marks TTFT on the first substantive
+// token event, and records the model the upstream reports serving.
 func observeCodexTokenEvent(reporter *helps.UsageReporter, payload []byte) {
 	helps.ObserveResponsesTokenEvent(reporter, payload)
+	reporter.ObserveCodexResponseModel(payload)
 }
 
 // newCodexBootstrapOverloadErr reports a buffered overload rejection with its real status.
diff --git a/internal/runtime/executor/codex_openai_images.go b/internal/runtime/executor/codex_openai_images.go
index 59ef7a261..d20b00a91 100644
--- a/internal/runtime/executor/codex_openai_images.go
+++ b/internal/runtime/executor/codex_openai_images.go
@@ -154,6 +154,7 @@ func (e *CodexExecutor) executeOpenAIImage(ctx context.Context, auth *cliproxyau
 			continue
 		}
 		eventData := bytes.TrimSpace(line[len(dataTag):])
+		reporter.ObserveCodexResponseModel(eventData)
 		switch gjson.GetBytes(eventData, "type").String() {
 		case "response.output_item.done":
 			collectCodexOutputItemDone(eventData, outputItemsByIndex, &outputItemsFallback)
@@ -278,6 +279,7 @@ func (e *CodexExecutor) executeOpenAIImageStream(ctx context.Context, auth *clip
 				continue
 			}
 			eventData := bytes.TrimSpace(line[len(dataTag):])
+			reporter.ObserveCodexResponseModel(eventData)
 			switch gjson.GetBytes(eventData, "type").String() {
 			case "response.output_item.done":
 				collectCodexOutputItemDone(eventData, outputItemsByIndex, &outputItemsFallback)
diff --git a/internal/runtime/executor/codex_response_model_test.go b/internal/runtime/executor/codex_response_model_test.go
new file mode 100644
index 000000000..97719ddbd
--- /dev/null
+++ b/internal/runtime/executor/codex_response_model_test.go
@@ -0,0 +1,107 @@
+package executor
+
+import (
+	"bytes"
+	"context"
+	"testing"
+	"time"
+
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/runtime/executor/helps"
+	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/auth"
+	coreusage "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/usage"
+)
+
+const codexResponseModelTestStream = `event: response.created
+data: {"type":"response.created","response":{"id":"resp_1","model":"gpt-5.6-luna"}}
+
+data: {"type":"response.output_text.delta","delta":"he"}
+
+data: {"type":"response.output_text.delta","delta":"llo"}
+
+data: {"type":"response.completed","response":{"id":"resp_1","model":"gpt-5.6-luna","usage":{"input_tokens":5,"output_tokens":7,"total_tokens":12}}}
+
+data: [DONE]`
+
+// TestObserveCodexTokenEventRecordsResponseModel guards the wiring between the codex
+// stream loops and the usage reporter: every transport funnels through observeCodexTokenEvent.
+func TestObserveCodexTokenEventRecordsResponseModel(t *testing.T) {
+	reporter := helps.NewExecutorUsageReporter(context.Background(), NewCodexExecutor(&config.Config{}), "gpt-6-astra", nil)
+
+	for _, line := range bytes.Split([]byte(codexResponseModelTestStream), []byte("\n")) {
+		line = bytes.TrimSpace(line)
+		if !bytes.HasPrefix(line, dataTag) {
+			continue
+		}
+		observeCodexTokenEvent(reporter, bytes.TrimSpace(line[len(dataTag):]))
+	}
+
+	if got := reporter.ResponseModel(); got != "gpt-5.6-luna" {
+		t.Fatalf("reporter response model = %q, want %q", got, "gpt-5.6-luna")
+	}
+}
+
+type codexResponseModelUsageCapture struct {
+	alias   string
+	records chan coreusage.Record
+}
+
+func (c *codexResponseModelUsageCapture) HandleUsage(_ context.Context, record coreusage.Record) {
+	if record.Alias != c.alias {
+		return
+	}
+	select {
+	case c.records <- record:
+	default:
+	}
+}
+
+type codexResponseModelNoopUsagePlugin struct{}
+
+func (codexResponseModelNoopUsagePlugin) HandleUsage(context.Context, coreusage.Record) {}
+
+func (c *codexResponseModelUsageCapture) await(t *testing.T) coreusage.Record {
+	t.Helper()
+	select {
+	case record := <-c.records:
+		return record
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for the usage record")
+		return coreusage.Record{}
+	}
+}
+
+// TestCodexUsageRecordsCarryResponseModelPerModel checks that the attempt record reports
+// the served model while the image generation tool record must not claim it.
+func TestCodexUsageRecordsCarryResponseModelPerModel(t *testing.T) {
+	const alias = "codex-response-model-wiring-test"
+	capture := &codexResponseModelUsageCapture{alias: alias, records: make(chan coreusage.Record, 4)}
+	coreusage.RegisterNamedPlugin(t.Name(), capture)
+	t.Cleanup(func() {
+		coreusage.RegisterNamedPlugin(t.Name(), codexResponseModelNoopUsagePlugin{})
+	})
+
+	ctx := coreusage.WithRequestedModelAlias(context.Background(), alias)
+	auth := &cliproxyauth.Auth{ID: "codex-auth-1", Index: "auth-index-7", Provider: "codex"}
+	reporter := helps.NewExecutorUsageReporter(ctx, NewCodexExecutor(&config.Config{}), "gpt-5.4-mini", auth)
+
+	observeCodexTokenEvent(reporter, []byte(`{"type":"response.completed","response":{"model":"gpt-5.4-mini","usage":{"total_tokens":12}}}`))
+	reporter.EnsurePublished(ctx)
+	reporter.PublishAdditionalModel(ctx, "gpt-image-1.5", coreusage.Detail{TotalTokens: 5})
+
+	attemptRecord := capture.await(t)
+	if attemptRecord.Model != "gpt-5.4-mini" {
+		t.Fatalf("attempt record model = %q, want %q", attemptRecord.Model, "gpt-5.4-mini")
+	}
+	if attemptRecord.ResponseModel != "gpt-5.4-mini" {
+		t.Fatalf("attempt record response model = %q, want %q", attemptRecord.ResponseModel, "gpt-5.4-mini")
+	}
+
+	imageRecord := capture.await(t)
+	if imageRecord.Model != "gpt-image-1.5" {
+		t.Fatalf("image record model = %q, want %q", imageRecord.Model, "gpt-image-1.5")
+	}
+	if imageRecord.ResponseModel != "" {
+		t.Fatalf("image record response model = %q, want empty", imageRecord.ResponseModel)
+	}
+}
diff --git a/internal/runtime/executor/helps/response_model.go b/internal/runtime/executor/helps/response_model.go
new file mode 100644
index 000000000..1c2eb1d57
--- /dev/null
+++ b/internal/runtime/executor/helps/response_model.go
@@ -0,0 +1,181 @@
+package helps
+
+import (
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/thinking"
+	"github.com/tidwall/gjson"
+)
+
+const (
+	// maxCodexResponseModelLength is a defensive bound on an upstream-controlled string
+	// reaching logs and usage records; known codex model ids stay under ~30 bytes.
+	maxCodexResponseModelLength = 128
+
+	// codexModelSubstitutionWarnWindow bounds how often one credential and model pair
+	// warns: on an affected credential every request is substituted.
+	codexModelSubstitutionWarnWindow = 10 * time.Minute
+
+	// codexModelSubstitutionWarnMaxEntries caps the throttle state, naturally bounded by
+	// credentials times models; memory safety wins over perfect throttling.
+	codexModelSubstitutionWarnMaxEntries = 1024
+)
+
+// extractCodexResponseModelEvent returns the model a codex upstream reports serving, read
+// from a raw JSON frame or an SSE line, and whether the event terminates the response.
+func extractCodexResponseModelEvent(payload []byte) (model string, terminal bool) {
+	data := jsonPayload(payload)
+	if len(data) == 0 {
+		return "", false
+	}
+	// The event type is checked before the payload is validated, so the hot path
+	// (output deltas) stays a single cheap lookup.
+	carriesModel, terminal := codexResponseModelEventKind(gjson.GetBytes(data, "type").String())
+	if !carriesModel {
+		return "", false
+	}
+	if !gjson.ValidBytes(data) {
+		return "", false
+	}
+	// The value is upstream-controlled: reject non-string and oversized names
+	// rather than propagating them into logs and usage records.
+	modelResult := gjson.GetBytes(data, "response.model")
+	if modelResult.Type != gjson.String {
+		return "", terminal
+	}
+	model = strings.TrimSpace(modelResult.String())
+	if len(model) > maxCodexResponseModelLength {
+		return "", terminal
+	}
+	return model, terminal
+}
+
+// codexResponseModelEventKind reports whether a codex event embeds the authoritative
+// response object, and whether that event terminates the response.
+func codexResponseModelEventKind(eventType string) (carriesModel bool, terminal bool) {
+	switch strings.TrimSpace(eventType) {
+	case "response.created", "response.in_progress":
+		return true, false
+	case "response.completed", "response.incomplete", "response.done":
+		return true, true
+	default:
+		return false, false
+	}
+}
+
+// normalizeCodexModelName lower-cases a model id and drops its thinking suffix,
+// which never reaches the upstream request body.
+func normalizeCodexModelName(model string) string {
+	return strings.TrimSpace(thinking.ParseSuffix(strings.ToLower(strings.TrimSpace(model))).ModelName)
+}
+
+// IsCodexModelSubstituted reports whether the upstream served a model other than the
+// requested one; a dated alias pins a snapshot of the same model and is accepted.
+func IsCodexModelSubstituted(requested, served string) bool {
+	servedModel := normalizeCodexModelName(served)
+	if servedModel == "" {
+		return false
+	}
+	requestedModel := normalizeCodexModelName(requested)
+	if requestedModel == "" {
+		return false
+	}
+	if requestedModel == servedModel {
+		return false
+	}
+	return !isCodexDatedModelAlias(requestedModel, servedModel) &&
+		!isCodexDatedModelAlias(servedModel, requestedModel)
+}
+
+// isCodexDatedModelAlias reports whether dated is base plus a release date suffix,
+// which upstreams use to pin the exact snapshot of the same model.
+func isCodexDatedModelAlias(base, dated string) bool {
+	prefix := base + "-"
+	if !strings.HasPrefix(dated, prefix) {
+		return false
+	}
+	return isCodexModelDateSuffix(dated[len(prefix):])
+}
+
+// isCodexModelDateSuffix reports whether suffix is a YYYY-MM-DD or YYYYMMDD date.
+func isCodexModelDateSuffix(suffix string) bool {
+	switch len(suffix) {
+	case len("YYYY-MM-DD"):
+		if suffix[4] != '-' || suffix[7] != '-' {
+			return false
+		}
+		return isCodexModelDigits(suffix[:4]) && isCodexModelDigits(suffix[5:7]) && isCodexModelDigits(suffix[8:])
+	case len("YYYYMMDD"):
+		return isCodexModelDigits(suffix)
+	default:
+		return false
+	}
+}
+
+// isCodexModelDigits reports whether value is a non-empty run of ASCII digits.
+func isCodexModelDigits(value string) bool {
+	if value == "" {
+		return false
+	}
+	for i := 0; i < len(value); i++ {
+		if value[i] < '0' || value[i] > '9' {
+			return false
+		}
+	}
+	return true
+}
+
+type codexModelSubstitutionKey struct {
+	authID    string
+	requested string
+	served    string
+}
+
+// codexModelSubstitutionThrottle records the last warning per key; nowFunc is
+// injectable so tests can advance the window without sleeping.
+type codexModelSubstitutionThrottle struct {
+	mu       sync.Mutex
+	nowFunc  func() time.Time
+	lastWarn map[codexModelSubstitutionKey]time.Time
+}
+
+func newCodexModelSubstitutionThrottle(nowFunc func() time.Time) *codexModelSubstitutionThrottle {
+	if nowFunc == nil {
+		nowFunc = time.Now
+	}
+	return &codexModelSubstitutionThrottle{
+		nowFunc:  nowFunc,
+		lastWarn: make(map[codexModelSubstitutionKey]time.Time),
+	}
+}
+
+// allow reports whether the key may emit a warning now and records the decision.
+// Suppressed repeats stay silent instead of moving to a lower level.
+func (t *codexModelSubstitutionThrottle) allow(key codexModelSubstitutionKey) bool {
+	if t == nil {
+		return true
+	}
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	now := t.nowFunc()
+	if last, ok := t.lastWarn[key]; ok && now.Sub(last) < codexModelSubstitutionWarnWindow {
+		return false
+	}
+	if len(t.lastWarn) >= codexModelSubstitutionWarnMaxEntries {
+		for storedKey, storedAt := range t.lastWarn {
+			if now.Sub(storedAt) >= codexModelSubstitutionWarnWindow {
+				delete(t.lastWarn, storedKey)
+			}
+		}
+		if len(t.lastWarn) >= codexModelSubstitutionWarnMaxEntries {
+			clear(t.lastWarn)
+		}
+	}
+	t.lastWarn[key] = now
+	return true
+}
+
+// codexModelSubstitutionWarns throttles substitution warnings process-wide.
+var codexModelSubstitutionWarns = newCodexModelSubstitutionThrottle(time.Now)
diff --git a/internal/runtime/executor/helps/response_model_test.go b/internal/runtime/executor/helps/response_model_test.go
new file mode 100644
index 000000000..5d456717d
--- /dev/null
+++ b/internal/runtime/executor/helps/response_model_test.go
@@ -0,0 +1,479 @@
+package helps
+
+import (
+	"context"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/auth"
+	"github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/usage"
+	log "github.com/sirupsen/logrus"
+	logtest "github.com/sirupsen/logrus/hooks/test"
+)
+
+func TestExtractCodexResponseModel(t *testing.T) {
+	tests := []struct {
+		name    string
+		payload string
+		want    string
+	}{
+		{
+			name:    "sse response created",
+			payload: `data: {"type":"response.created","response":{"id":"resp_1","model":"gpt-5.6-luna"}}`,
+			want:    "gpt-5.6-luna",
+		},
+		{
+			name:    "sse response created without space after data prefix",
+			payload: `data:{"type":"response.created","response":{"model":"gpt-6-astra"}}`,
+			want:    "gpt-6-astra",
+		},
+		{
+			name:    "raw json response completed",
+			payload: `{"type":"response.completed","response":{"model":"gpt-5.6-luna","usage":{"total_tokens":12}}}`,
+			want:    "gpt-5.6-luna",
+		},
+		{
+			name:    "response in progress",
+			payload: `{"type":"response.in_progress","response":{"model":"gpt-5.6-terra"}}`,
+			want:    "gpt-5.6-terra",
+		},
+		{
+			name:    "response incomplete",
+			payload: `{"type":"response.incomplete","response":{"model":"gpt-5.6-sol"}}`,
+			want:    "gpt-5.6-sol",
+		},
+		{
+			name:    "response done",
+			payload: `{"type":"response.done","response":{"model":"gpt-5.3-codex-spark"}}`,
+			want:    "gpt-5.3-codex-spark",
+		},
+		{
+			name:    "model value is trimmed",
+			payload: `{"type":"response.created","response":{"model":"  gpt-6-astra  "}}`,
+			want:    "gpt-6-astra",
+		},
+		{
+			name:    "output text delta is ignored",
+			payload: `data: {"type":"response.output_text.delta","delta":"hi","response":{"model":"gpt-5.6-luna"}}`,
+			want:    "",
+		},
+		{
+			name:    "output item done is ignored",
+			payload: `{"type":"response.output_item.done","item":{"type":"message"}}`,
+			want:    "",
+		},
+		{
+			name:    "rate limits event is ignored",
+			payload: `{"type":"codex.rate_limits","rate_limits":{"primary":{"used_percent":12}}}`,
+			want:    "",
+		},
+		{
+			name:    "terminal failure event is ignored",
+			payload: `{"type":"error","error":{"code":"server_is_overloaded"}}`,
+			want:    "",
+		},
+		{
+			// /responses/compact answers with a compaction object that carries no
+			// event type and no response.model, so that route reports nothing.
+			name:    "responses compact object",
+			payload: `{"id":"resp_1","object":"response.compaction","usage":{"input_tokens":1,"output_tokens":2,"total_tokens":3}}`,
+			want:    "",
+		},
+		{
+			// The direct /images/generations and /images/edits endpoints answer in the
+			// Images API shape, which never names the model that served the request.
+			name:    "images api response",
+			payload: `{"created":1745539200,"data":[{"b64_json":"aGk="}]}`,
+			want:    "",
+		},
+		{
+			// Direct image streams emit image_generation.* events only.
+			name:    "image generation completed event",
+			payload: `data: {"type":"image_generation.completed","b64_json":"aGk="}`,
+			want:    "",
+		},
+		{
+			name:    "non string model value",
+			payload: `{"type":"response.created","response":{"model":123}}`,
+			want:    "",
+		},
+		{
+			name:    "object model value",
+			payload: `{"type":"response.created","response":{"model":{"id":"gpt-5.6-luna"}}}`,
+			want:    "",
+		},
+		{
+			name:    "oversized model value",
+			payload: `{"type":"response.created","response":{"model":"` + strings.Repeat("m", maxCodexResponseModelLength+1) + `"}}`,
+			want:    "",
+		},
+		{
+			name:    "model value at the length limit",
+			payload: `{"type":"response.created","response":{"model":"` + strings.Repeat("m", maxCodexResponseModelLength) + `"}}`,
+			want:    strings.Repeat("m", maxCodexResponseModelLength),
+		},
+		{
+			name:    "done marker",
+			payload: "data: [DONE]",
+			want:    "",
+		},
+		{
+			name:    "sse event line",
+			payload: "event: response.created",
+			want:    "",
+		},
+		{
+			name:    "empty payload",
+			payload: "",
+			want:    "",
+		},
+		{
+			name:    "malformed json",
+			payload: `{"type":"response.created","response":{"model":"gpt-5.6-luna"`,
+			want:    "",
+		},
+		{
+			name:    "response without model",
+			payload: `{"type":"response.created","response":{"id":"resp_1"}}`,
+			want:    "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got, _ := extractCodexResponseModelEvent([]byte(tt.payload)); got != tt.want {
+				t.Fatalf("extractCodexResponseModelEvent(%q) = %q, want %q", tt.payload, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestIsCodexModelSubstituted(t *testing.T) {
+	tests := []struct {
+		name      string
+		requested string
+		served    string
+		want      bool
+	}{
+		{name: "silent substitution", requested: "gpt-6-astra", served: "gpt-5.6-luna", want: true},
+		{name: "same model", requested: "gpt-6-astra", served: "gpt-6-astra", want: false},
+		{name: "thinking suffix stripped from requested", requested: "gpt-6-astra(high)", served: "gpt-6-astra", want: false},
+		{name: "thinking suffix stripped from served", requested: "gpt-6-astra", served: "gpt-6-astra(high)", want: false},
+		{name: "thinking suffix on both sides", requested: "gpt-6-astra(high)", served: "gpt-6-astra(low)", want: false},
+		{name: "thinking suffix with substitution", requested: "gpt-6-astra(high)", served: "gpt-5.6-luna", want: true},
+		{name: "numeric thinking suffix", requested: "gpt-5.6-terra(16384)", served: "gpt-5.6-terra", want: false},
+		{name: "case insensitive requested", requested: "GPT-6-Astra", served: "gpt-6-astra", want: false},
+		{name: "case insensitive served", requested: "gpt-6-astra", served: "  GPT-6-ASTRA  ", want: false},
+		{name: "served pins dashed date", requested: "gpt-5.6-terra", served: "gpt-5.6-terra-2026-05-13", want: false},
+		{name: "served pins compact date", requested: "gpt-5.6-sol", served: "gpt-5.6-sol-20260513", want: false},
+		{name: "requested pins dashed date", requested: "gpt-5.6-terra-2026-05-13", served: "gpt-5.6-terra", want: false},
+		{name: "requested pins compact date", requested: "gpt-5.6-sol-20260513", served: "gpt-5.6-sol", want: false},
+		{name: "different dates on both sides", requested: "gpt-5.6-terra-2026-05-13", served: "gpt-5.6-terra-2026-06-01", want: true},
+		{name: "incomplete date suffix", requested: "gpt-5.6-sol", served: "gpt-5.6-sol-2026-5-13", want: true},
+		{name: "non date suffix", requested: "gpt-5.5", served: "gpt-5.5-codex", want: true},
+		{name: "date suffix with trailing tag", requested: "gpt-5.6-luna", served: "gpt-5.6-luna-2026-05-13-preview", want: true},
+		{name: "spark unchanged", requested: "gpt-5.3-codex-spark", served: "gpt-5.3-codex-spark", want: false},
+		{name: "review model unchanged", requested: "codex-auto-review", served: "codex-auto-review", want: false},
+		{name: "review model substituted", requested: "codex-auto-review", served: "gpt-5.6-luna", want: true},
+		{name: "empty served", requested: "gpt-6-astra", served: "", want: false},
+		{name: "blank served", requested: "gpt-6-astra", served: "   ", want: false},
+		{name: "empty requested", requested: "", served: "gpt-5.6-luna", want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := IsCodexModelSubstituted(tt.requested, tt.served); got != tt.want {
+				t.Fatalf("IsCodexModelSubstituted(%q, %q) = %v, want %v", tt.requested, tt.served, got, tt.want)
+			}
+		})
+	}
+}
+
+// setupResponseModelLoggerHook captures warnings from the process-global logrus logger
+// and gives the test its own throttle; both are shared, so callers must not use t.Parallel.
+func setupResponseModelLoggerHook(t *testing.T) *logtest.Hook {
+	t.Helper()
+	logger := log.StandardLogger()
+	oldLevel := logger.GetLevel()
+	logger.SetLevel(log.WarnLevel)
+	savedHooks := logger.ReplaceHooks(make(log.LevelHooks))
+	hook := new(logtest.Hook)
+	logger.AddHook(hook)
+	savedThrottle := codexModelSubstitutionWarns
+	codexModelSubstitutionWarns = newCodexModelSubstitutionThrottle(nil)
+	t.Cleanup(func() {
+		codexModelSubstitutionWarns = savedThrottle
+		logger.SetLevel(oldLevel)
+		logger.ReplaceHooks(savedHooks)
+	})
+	return hook
+}
+
+// codexUsageTestExecutor mirrors the production reporter construction path.
+type codexUsageTestExecutor struct{}
+
+func (codexUsageTestExecutor) Identifier() string { return "codex" }
+
+func newCodexTestReporter(ctx context.Context, model string, auth *cliproxyauth.Auth) *UsageReporter {
+	return NewExecutorUsageReporter(ctx, codexUsageTestExecutor{}, model, auth)
+}
+
+func substitutionWarnings(hook *logtest.Hook) []string {
+	var messages []string
+	for _, entry := range hook.AllEntries() {
+		if entry.Level == log.WarnLevel && strings.Contains(entry.Message, "upstream served model") {
+			messages = append(messages, entry.Message)
+		}
+	}
+	return messages
+}
+
+const codexSubstitutedStream = `data: {"type":"response.created","response":{"id":"resp_1","model":"gpt-5.6-luna"}}
+data: {"type":"response.in_progress","response":{"id":"resp_1","model":"gpt-5.6-luna"}}
+data: {"type":"response.output_text.delta","delta":"hello"}
+data: {"type":"response.completed","response":{"id":"resp_1","model":"gpt-5.6-luna","usage":{"input_tokens":5,"output_tokens":7,"total_tokens":12}}}
+data: [DONE]`
+
+func newSubstitutionTestAuth() *cliproxyauth.Auth {
+	return &cliproxyauth.Auth{
+		ID:       "codex-auth-1",
+		Index:    "auth-index-7",
+		Provider: "codex",
+		FileName: "/auths/codex-user@example.com.json",
+	}
+}
+
+// Relies on the global logrus logger and warning throttle; do not add t.Parallel.
+func TestUsageReporterRecordsSubstitutedCodexResponseModelAndWarnsOnce(t *testing.T) {
+	hook := setupResponseModelLoggerHook(t)
+	ctx := context.Background()
+	reporter := newCodexTestReporter(ctx, "gpt-6-astra", newSubstitutionTestAuth())
+
+	var detail usage.Detail
+	for _, line := range strings.Split(codexSubstitutedStream, "\n") {
+		reporter.ObserveCodexResponseModel([]byte(line))
+		if parsed, ok := ParseCodexUsage(JSONPayload([]byte(line))); ok {
+			detail = parsed
+		}
+	}
+
+	if got := reporter.ResponseModel(); got != "gpt-5.6-luna" {
+		t.Fatalf("reporter response model = %q, want %q", got, "gpt-5.6-luna")
+	}
+	record := reporter.buildRecord(detail, false)
+	if record.ResponseModel != "gpt-5.6-luna" {
+		t.Fatalf("record response model = %q, want %q", record.ResponseModel, "gpt-5.6-luna")
+	}
+	if record.Model != "gpt-6-astra" {
+		t.Fatalf("record model = %q, want %q", record.Model, "gpt-6-astra")
+	}
+	// Observing events must not log anything; the warning belongs to the attempt.
+	if warnings := substitutionWarnings(hook); len(warnings) != 0 {
+		t.Fatalf("expected no warning before the attempt published, got %#v", warnings)
+	}
+
+	reporter.Publish(ctx, detail)
+	reporter.EnsurePublished(ctx)
+
+	warnings := substitutionWarnings(hook)
+	if len(warnings) != 1 {
+		t.Fatalf("substitution warnings = %d, want 1: %#v", len(warnings), warnings)
+	}
+	want := `codex executor: upstream served model "gpt-5.6-luna" for requested model "gpt-6-astra" (auth_index=auth-index-7)`
+	if warnings[0] != want {
+		t.Fatalf("warning = %q, want %q", warnings[0], want)
+	}
+	// The credential file name carries the account e-mail and must stay out of logs.
+	if strings.Contains(warnings[0], "example.com") || strings.Contains(warnings[0], "auth_file") {
+		t.Fatalf("warning leaked credential details: %q", warnings[0])
+	}
+}
+
+// Relies on the global logrus logger and warning throttle; do not add t.Parallel.
+func TestUsageReporterDoesNotWarnWhenCodexResponseModelMatches(t *testing.T) {
+	hook := setupResponseModelLoggerHook(t)
+	ctx := context.Background()
+	reporter := newCodexTestReporter(ctx, "gpt-6-astra(high)", nil)
+
+	reporter.ObserveCodexResponseModel([]byte(`data: {"type":"response.created","response":{"model":"gpt-6-astra-2026-05-13"}}`))
+	reporter.Publish(ctx, usage.Detail{TotalTokens: 3})
+
+	if got := reporter.ResponseModel(); got != "gpt-6-astra-2026-05-13" {
+		t.Fatalf("reporter response model = %q, want %q", got, "gpt-6-astra-2026-05-13")
+	}
+	if warnings := substitutionWarnings(hook); len(warnings) != 0 {
+		t.Fatalf("expected no substitution warning, got %#v", warnings)
+	}
+}
+
+// Relies on the global logrus logger and warning throttle; do not add t.Parallel.
+func TestUsageReporterIgnoresPayloadsWithoutResponseModel(t *testing.T) {
+	hook := setupResponseModelLoggerHook(t)
+	ctx := context.Background()
+	reporter := newCodexTestReporter(ctx, "gpt-6-astra", nil)
+
+	reporter.ObserveCodexResponseModel([]byte(`data: {"type":"response.created","response":{"model":"gpt-5.6-luna"}}`))
+	reporter.ObserveCodexResponseModel([]byte(`data: {"type":"response.output_text.delta","delta":"hello"}`))
+	reporter.Publish(ctx, usage.Detail{TotalTokens: 3})
+
+	if got := reporter.ResponseModel(); got != "gpt-5.6-luna" {
+		t.Fatalf("reporter response model = %q, want %q", got, "gpt-5.6-luna")
+	}
+	warnings := substitutionWarnings(hook)
+	if len(warnings) != 1 {
+		t.Fatalf("substitution warnings = %d, want 1: %#v", len(warnings), warnings)
+	}
+	// A reporter without a credential must still produce a usable label.
+	if !strings.HasSuffix(warnings[0], "(auth_index=nil)") {
+		t.Fatalf("warning = %q, want an auth_index=nil suffix", warnings[0])
+	}
+}
+
+// Relies on the global logrus logger and warning throttle; do not add t.Parallel.
+func TestUsageReporterWarnsOnceUnderConcurrentObservationsAndPublishes(t *testing.T) {
+	hook := setupResponseModelLoggerHook(t)
+	ctx := context.Background()
+	reporter := newCodexTestReporter(ctx, "gpt-6-astra", newSubstitutionTestAuth())
+	created := []byte(`data: {"type":"response.created","response":{"model":"gpt-5.6-luna"}}`)
+	completed := []byte(`data: {"type":"response.completed","response":{"model":"gpt-5.6-luna","usage":{"total_tokens":4}}}`)
+
+	const workers = 32
+	start := make(chan struct{})
+	var wg sync.WaitGroup
+	wg.Add(workers)
+	for i := range workers {
+		go func(worker int) {
+			defer wg.Done()
+			<-start
+			if worker%2 == 0 {
+				reporter.ObserveCodexResponseModel(created)
+			} else {
+				reporter.ObserveCodexResponseModel(completed)
+			}
+			reporter.EnsurePublished(ctx)
+		}(i)
+	}
+	close(start)
+	wg.Wait()
+
+	if got := reporter.ResponseModel(); got != "gpt-5.6-luna" {
+		t.Fatalf("reporter response model = %q, want %q", got, "gpt-5.6-luna")
+	}
+	if warnings := substitutionWarnings(hook); len(warnings) != 1 {
+		t.Fatalf("substitution warnings = %d, want 1: %#v", len(warnings), warnings)
+	}
+}
+
+// Relies on the global logrus logger and warning throttle; do not add t.Parallel.
+func TestUsageReporterThrottlesRepeatedSubstitutionWarnings(t *testing.T) {
+	hook := setupResponseModelLoggerHook(t)
+	ctx := context.Background()
+	now := time.Unix(1_700_000_000, 0)
+	codexModelSubstitutionWarns = newCodexModelSubstitutionThrottle(func() time.Time { return now })
+
+	publishSubstitutedAttempt := func(authID, authIndex string) {
+		auth := &cliproxyauth.Auth{ID: authID, Index: authIndex, Provider: "codex"}
+		reporter := newCodexTestReporter(ctx, "gpt-6-astra", auth)
+		reporter.ObserveCodexResponseModel([]byte(`{"type":"response.completed","response":{"model":"gpt-5.6-luna"}}`))
+		reporter.Publish(ctx, usage.Detail{TotalTokens: 3})
+	}
+
+	publishSubstitutedAttempt("codex-auth-1", "auth-index-7")
+	publishSubstitutedAttempt("codex-auth-1", "auth-index-7")
+	if warnings := substitutionWarnings(hook); len(warnings) != 1 {
+		t.Fatalf("substitution warnings = %d, want 1 inside the window: %#v", len(warnings), warnings)
+	}
+
+	// A different credential is an independent signal.
+	publishSubstitutedAttempt("codex-auth-2", "auth-index-8")
+	if warnings := substitutionWarnings(hook); len(warnings) != 2 {
+		t.Fatalf("substitution warnings = %d, want 2 after a second credential: %#v", len(warnings), warnings)
+	}
+
+	now = now.Add(codexModelSubstitutionWarnWindow - time.Second)
+	publishSubstitutedAttempt("codex-auth-1", "auth-index-7")
+	if warnings := substitutionWarnings(hook); len(warnings) != 2 {
+		t.Fatalf("substitution warnings = %d, want 2 before the window elapsed: %#v", len(warnings), warnings)
+	}
+
+	now = now.Add(time.Second)
+	publishSubstitutedAttempt("codex-auth-1", "auth-index-7")
+	if warnings := substitutionWarnings(hook); len(warnings) != 3 {
+		t.Fatalf("substitution warnings = %d, want 3 once the window elapsed: %#v", len(warnings), warnings)
+	}
+}
+
+// Relies on the global logrus logger and warning throttle; do not add t.Parallel.
+func TestUsageReporterThrottlesSubstitutionWarningsAcrossServedModelCase(t *testing.T) {
+	hook := setupResponseModelLoggerHook(t)
+	ctx := context.Background()
+	now := time.Unix(1_700_000_000, 0)
+	codexModelSubstitutionWarns = newCodexModelSubstitutionThrottle(func() time.Time { return now })
+
+	auth := &cliproxyauth.Auth{ID: "codex-auth-1", Index: "auth-index-7", Provider: "codex"}
+	for _, served := range []string{"gpt-5.6-luna", "GPT-5.6-LUNA"} {
+		reporter := newCodexTestReporter(ctx, "gpt-6-astra", auth)
+		reporter.ObserveCodexResponseModel([]byte(`{"type":"response.completed","response":{"model":"` + served + `"}}`))
+		reporter.Publish(ctx, usage.Detail{TotalTokens: 3})
+	}
+
+	// Both attempts describe one substitution pair, so the casing must not open a
+	// second throttle window while the WARN keeps the raw upstream name.
+	warnings := substitutionWarnings(hook)
+	if len(warnings) != 1 {
+		t.Fatalf("substitution warnings = %d, want 1 for one normalized pair: %#v", len(warnings), warnings)
+	}
+	want := `codex executor: upstream served model "gpt-5.6-luna" for requested model "gpt-6-astra" (auth_index=auth-index-7)`
+	if warnings[0] != want {
+		t.Fatalf("warning = %q, want %q", warnings[0], want)
+	}
+}
+
+func TestCodexModelSubstitutionThrottleBoundsStoredEntries(t *testing.T) {
+	now := time.Unix(1_700_000_000, 0)
+	throttle := newCodexModelSubstitutionThrottle(func() time.Time { return now })
+
+	for i := range codexModelSubstitutionWarnMaxEntries + 16 {
+		key := codexModelSubstitutionKey{
+			authID:    "codex-auth-" + strconv.Itoa(i),
+			requested: "gpt-6-astra",
+			served:    "gpt-5.6-luna",
+		}
+		if !throttle.allow(key) {
+			t.Fatalf("first warning for key %d was suppressed", i)
+		}
+	}
+	throttle.mu.Lock()
+	stored := len(throttle.lastWarn)
+	throttle.mu.Unlock()
+	if stored > codexModelSubstitutionWarnMaxEntries {
+		t.Fatalf("stored throttle entries = %d, want at most %d", stored, codexModelSubstitutionWarnMaxEntries)
+	}
+}
+
+func TestUsageReporterAdditionalModelRecordOmitsResponseModel(t *testing.T) {
+	ctx := context.Background()
+	reporter := newCodexTestReporter(ctx, "gpt-5.4-mini", nil)
+	reporter.ObserveCodexResponseModel([]byte(`data: {"type":"response.completed","response":{"model":"gpt-5.4-mini"}}`))
+
+	mainRecord := reporter.buildRecord(usage.Detail{TotalTokens: 12}, false)
+	if mainRecord.ResponseModel != "gpt-5.4-mini" {
+		t.Fatalf("main record response model = %q, want %q", mainRecord.ResponseModel, "gpt-5.4-mini")
+	}
+
+	additionalRecord, ok := reporter.buildAdditionalModelRecord("gpt-image-1.5", usage.Detail{TotalTokens: 5})
+	if !ok {
+		t.Fatal("expected an additional model record")
+	}
+	if additionalRecord.Model != "gpt-image-1.5" {
+		t.Fatalf("additional record model = %q, want %q", additionalRecord.Model, "gpt-image-1.5")
+	}
+	// The upstream response model describes the main text model, never the image
+	// generation tool model, so consumers must not see a fake substitution here.
+	if additionalRecord.ResponseModel != "" {
+		t.Fatalf("additional record response model = %q, want empty", additionalRecord.ResponseModel)
+	}
+}
diff --git a/internal/runtime/executor/helps/usage_helpers.go b/internal/runtime/executor/helps/usage_helpers.go
index c2a43db29..2bd22fb30 100644
--- a/internal/runtime/executor/helps/usage_helpers.go
+++ b/internal/runtime/executor/helps/usage_helpers.go
@@ -10,6 +10,7 @@ import (
 	"reflect"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/gin-gonic/gin"
@@ -50,6 +51,13 @@ type UsageReporter struct {
 	ttftStart           time.Time
 	ttftSet             bool
 	once                sync.Once
+
+	responseModelMu sync.RWMutex
+	// responseModel holds the latest model name reported by the upstream response.
+	responseModel string
+	// responseModelFinal marks that a terminal event already reported the served
+	// model, so later frames skip parsing entirely.
+	responseModelFinal atomic.Bool
 }
 
 type usageExecutor interface {
@@ -175,6 +183,69 @@ func (r *UsageReporter) accessTokenFingerprint() string {
 	return r.accessTokenHash
 }
 
+// ObserveCodexResponseModel stores the model reported by a codex upstream event and
+// ignores payloads without one; the substitution warning is emitted at publish time.
+func (r *UsageReporter) ObserveCodexResponseModel(payload []byte) {
+	if r == nil || r.responseModelFinal.Load() {
+		return
+	}
+	served, terminal := extractCodexResponseModelEvent(payload)
+	if served == "" {
+		return
+	}
+	r.responseModelMu.Lock()
+	r.responseModel = served
+	r.responseModelMu.Unlock()
+	if terminal {
+		r.responseModelFinal.Store(true)
+	}
+}
+
+// warnCodexModelSubstitution warns about a silent upstream model swap, throttled per
+// credential and model pair, and labels the credential by index only, never by account.
+func (r *UsageReporter) warnCodexModelSubstitution(ctx context.Context) {
+	if r == nil {
+		return
+	}
+	served := r.ResponseModel()
+	if served == "" || !IsCodexModelSubstituted(r.model, served) {
+		return
+	}
+	// The throttle key uses the same normalized names as the substitution check, so
+	// aliases of one pair share a window instead of each warning on its own.
+	requested := normalizeCodexModelName(r.model)
+	servedNormalized := normalizeCodexModelName(served)
+	if !codexModelSubstitutionWarns.allow(codexModelSubstitutionKey{
+		authID:    r.authID,
+		requested: requested,
+		served:    servedNormalized,
+	}) {
+		return
+	}
+	LogWithRequestID(ctx).Warnf("codex executor: upstream served model %q for requested model %q (auth_index=%s)", served, r.model, r.authIndexForLog())
+}
+
+// authIndexForLog labels the credential without exposing its file name or account.
+func (r *UsageReporter) authIndexForLog() string {
+	if r == nil {
+		return "nil"
+	}
+	if authIndex := strings.TrimSpace(r.authIndex); authIndex != "" {
+		return authIndex
+	}
+	return "nil"
+}
+
+// ResponseModel returns the latest model reported by the upstream response.
+func (r *UsageReporter) ResponseModel() string {
+	if r == nil {
+		return ""
+	}
+	r.responseModelMu.RLock()
+	defer r.responseModelMu.RUnlock()
+	return r.responseModel
+}
+
 func ExecutorTypeName(executor any) string {
 	if executor == nil {
 		return ""
@@ -392,7 +463,7 @@ func (r *UsageReporter) publishWithOutcome(ctx context.Context, detail usage.Det
 	}
 	detail = normalizeUsageDetailTotal(detail, r.provider, r.executorType)
 	r.once.Do(func() {
-		r.publishRecord(ctx, r.buildRecord(detail, failed, fail))
+		r.publishAttemptRecord(ctx, r.buildRecord(detail, failed, fail))
 	})
 }
 
@@ -420,10 +491,17 @@ func (r *UsageReporter) EnsurePublished(ctx context.Context) {
 		return
 	}
 	r.once.Do(func() {
-		r.publishRecord(ctx, r.buildRecord(usage.Detail{}, false, usage.Failure{}))
+		r.publishAttemptRecord(ctx, r.buildRecord(usage.Detail{}, false, usage.Failure{}))
 	})
 }
 
+// publishAttemptRecord emits the record for one upstream attempt and the
+// observability warnings that belong to the attempt rather than to a single event.
+func (r *UsageReporter) publishAttemptRecord(ctx context.Context, record usage.Record) {
+	r.publishRecord(ctx, record)
+	r.warnCodexModelSubstitution(ctx)
+}
+
 func (r *UsageReporter) publishRecord(ctx context.Context, record usage.Record) {
 	record.ResponseHeaders = internallogging.GetResponseHeaders(ctx)
 	usage.PublishRecord(ctx, record)
@@ -444,6 +522,12 @@ func (r *UsageReporter) buildRecordForModel(model string, detail usage.Detail, f
 	if r == nil {
 		return usage.Record{Model: model, Detail: detail, Failed: failed, Fail: fail, Generate: usage.GenerateFlag(true)}
 	}
+	// Additional-model records describe a side model (image generation tool usage) that
+	// the upstream response model never refers to, so they must stay empty.
+	responseModel := ""
+	if model == r.model {
+		responseModel = r.ResponseModel()
+	}
 	return usage.Record{
 		Provider:            r.provider,
 		BaseURL:             r.baseURL,
@@ -461,6 +545,7 @@ func (r *UsageReporter) buildRecordForModel(model string, detail usage.Detail, f
 		ReasoningEffort:     r.reasoning,
 		ServiceTier:         r.serviceTier,
 		ResponseServiceTier: strings.TrimSpace(detail.ResponseServiceTier),
+		ResponseModel:       responseModel,
 		Generate:            usage.GenerateFlag(r.generate),
 		Stream:              r.stream,
 		RequestedAt:         r.requestedAt,
diff --git a/sdk/cliproxy/usage/manager.go b/sdk/cliproxy/usage/manager.go
index 5fd800999..5bf39920a 100644
--- a/sdk/cliproxy/usage/manager.go
+++ b/sdk/cliproxy/usage/manager.go
@@ -45,6 +45,8 @@ type Record struct {
 	RequestServiceTier string
 	// ResponseServiceTier stores the final tier reported by the upstream response.
 	ResponseServiceTier string
+	// ResponseModel stores the model name reported by the upstream response, empty when unknown.
+	ResponseModel string
 	// Generate reports whether the client requested actual generation.
 	// nil or true means generation is enabled; only an explicit false disables generation.
 	// Use GenerateFlag to set the value and GenerateEnabled to read it with the default.