diff --git a/internal/auth/devin/devin_auth.go b/internal/auth/devin/devin_auth.go
index bb2788fe9..53ad58ba7 100644
--- a/internal/auth/devin/devin_auth.go
+++ b/internal/auth/devin/devin_auth.go
@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"html"
 	"io"
 	"net"
 	"net/http"
@@ -289,7 +290,7 @@ func (s *OAuthServer) handleCallback(w http.ResponseWriter, r *http.Request) {
 			errMsg = "missing authorization code"
 		}
 		w.WriteHeader(http.StatusBadRequest)
-		_, _ = w.Write([]byte(fmt.Sprintf(loginFailureHTML, errMsg)))
+		_, _ = w.Write([]byte(fmt.Sprintf(loginFailureHTML, html.EscapeString(errMsg))))
 		select {
 		case s.resultChan <- &OAuthResult{Error: errMsg}:
 		default:
diff --git a/internal/auth/devin/user_status.go b/internal/auth/devin/user_status.go
index 31892c93b..eb34a3117 100644
--- a/internal/auth/devin/user_status.go
+++ b/internal/auth/devin/user_status.go
@@ -2,6 +2,7 @@ package devin
 
 import (
 	"context"
+	"crypto/rand"
 	"crypto/sha256"
 	"encoding/hex"
 	"errors"
@@ -40,9 +41,15 @@ type DevinUserStatus struct {
 	PlanEnd                     time.Time `json:"plan_end,omitempty"`
 }
 
-// GenerateDeviceFingerprint generates a stable 732-character hex device fingerprint.
+// GenerateDeviceFingerprint generates a 732-character hex device fingerprint.
+// When seed is empty, it generates a cryptographically random 732-character hex string per request.
+// When seed is provided, it derives a deterministic 732-character hex fingerprint.
 func GenerateDeviceFingerprint(seed string) string {
 	if seed == "" {
+		var b [devinFingerprintHexLen / 2]byte
+		if _, err := rand.Read(b[:]); err == nil {
+			return hex.EncodeToString(b[:])
+		}
 		seed = uuid.New().String()
 	}
 	var sb strings.Builder
@@ -346,6 +353,8 @@ func (s *DevinAuthService) FetchUserStatus(ctx context.Context, sessionToken, de
 	req.Header.Set("Authorization", fmt.Sprintf("Basic %s-%s", sessionToken, sessionToken))
 	req.Header.Set("Connect-Protocol-Version", "1")
 	req.Header.Set("Content-Type", "application/proto")
+	req.Header.Set("Accept", "*/*")
+	req.Header["User-Agent"] = []string{""}
 
 	resp, errDo := s.client.Do(req)
 	if errDo != nil {
diff --git a/internal/auth/devin/user_status_test.go b/internal/auth/devin/user_status_test.go
index 0af8907c3..30eeb08ec 100644
--- a/internal/auth/devin/user_status_test.go
+++ b/internal/auth/devin/user_status_test.go
@@ -193,6 +193,9 @@ func TestFetchUserStatusLiveMock(t *testing.T) {
 }
 
 func TestLiveDevinUserStatus(t *testing.T) {
+	if os.Getenv("CPA_LIVE_TEST") != "true" {
+		t.Skip("skipping live test; set CPA_LIVE_TEST=true to run")
+	}
 	authPath := "../../../auths/devin-cli.json"
 	data, err := os.ReadFile(authPath)
 	if err != nil {
diff --git a/internal/cache/bounded_lru.go b/internal/cache/bounded_lru.go
index 458853be7..a50c69a77 100644
--- a/internal/cache/bounded_lru.go
+++ b/internal/cache/bounded_lru.go
@@ -76,6 +76,24 @@ func (cache *BoundedLRU[K, V]) Get(key K) (V, bool) {
 	return zero, false
 }
 
+func (cache *BoundedLRU[K, V]) Delete(key K) bool {
+	cache.mu.Lock()
+	element, ok := cache.entries[key]
+	if !ok {
+		cache.mu.Unlock()
+		return false
+	}
+	entry := element.Value.(boundedLRUEntry[K, V])
+	delete(cache.entries, key)
+	cache.order.Remove(element)
+	cache.mu.Unlock()
+
+	if cache.onEvict != nil {
+		cache.onEvict(entry.key, entry.value)
+	}
+	return true
+}
+
 func (cache *BoundedLRU[K, V]) Len() int {
 	cache.mu.Lock()
 	defer cache.mu.Unlock()
diff --git a/internal/registry/models/devin_models.json b/internal/registry/models/devin_models.json
index 39957e28b..8e5cdd89d 100644
--- a/internal/registry/models/devin_models.json
+++ b/internal/registry/models/devin_models.json
@@ -7,7 +7,7 @@
       "owned_by": "cognition",
       "display_name": "SWE-2",
       "context_length": 262000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -30,7 +30,7 @@
       "owned_by": "cognition",
       "display_name": "SWE-1.7",
       "context_length": 262000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -52,7 +52,7 @@
       "owned_by": "cognition",
       "display_name": "SWE-1.6",
       "context_length": 200000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -67,7 +67,7 @@
       "owned_by": "zhipu",
       "display_name": "GLM-5.2",
       "context_length": 200000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -88,7 +88,7 @@
       "owned_by": "zhipu",
       "display_name": "GLM-5.3",
       "context_length": 1048576,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -110,7 +110,7 @@
       "owned_by": "zhipu",
       "display_name": "GLM-5.3 Flash",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -132,7 +132,7 @@
       "owned_by": "deepseek",
       "display_name": "DeepSeek V4 Flash",
       "context_length": 1048576,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -153,7 +153,7 @@
       "owned_by": "deepseek",
       "display_name": "DeepSeek V4.1 Flash",
       "context_length": 1048576,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -174,7 +174,7 @@
       "owned_by": "deepseek",
       "display_name": "DeepSeek V4 Pro",
       "context_length": 1048576,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -195,7 +195,7 @@
       "owned_by": "google",
       "display_name": "Gemini 3.8 Flash",
       "context_length": 1048576,
-      "max_completion_tokens": 65536,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -218,7 +218,7 @@
       "owned_by": "google",
       "display_name": "Gemini 3.7 Flash",
       "context_length": 1048576,
-      "max_completion_tokens": 65536,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -240,7 +240,7 @@
       "owned_by": "google",
       "display_name": "Gemini 3.6 Flash",
       "context_length": 1048576,
-      "max_completion_tokens": 65536,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -264,7 +264,7 @@
       "owned_by": "google",
       "display_name": "Gemini 3.5 Flash",
       "context_length": 1048576,
-      "max_completion_tokens": 65536,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -288,7 +288,7 @@
       "owned_by": "google",
       "display_name": "Gemini 3 Flash",
       "context_length": 1048576,
-      "max_completion_tokens": 65536,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -312,7 +312,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Fable 5.1",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -337,7 +337,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude 5 Fable",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -362,7 +362,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Sonnet 5",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -387,7 +387,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Opus 5",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -412,7 +412,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Opus 4.8",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -437,7 +437,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Opus 4.7",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -462,7 +462,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Opus 4.6",
       "context_length": 200000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -478,7 +478,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Sonnet 4.6",
       "context_length": 200000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -494,7 +494,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Haiku 4.5",
       "context_length": 200000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -510,7 +510,7 @@
       "owned_by": "anthropic",
       "display_name": "Claude Sonnet 4.5",
       "context_length": 200000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -526,7 +526,7 @@
       "owned_by": "openai",
       "display_name": "GPT-6 Astra",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -551,7 +551,7 @@
       "owned_by": "openai",
       "display_name": "GPT-5.6 Sol",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -577,7 +577,7 @@
       "owned_by": "openai",
       "display_name": "GPT-5.6 Terra",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -603,7 +603,7 @@
       "owned_by": "openai",
       "display_name": "GPT-5.6 Luna",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -629,7 +629,7 @@
       "owned_by": "openai",
       "display_name": "GPT-5.5",
       "context_length": 272000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -654,7 +654,7 @@
       "owned_by": "openai",
       "display_name": "GPT-5.4",
       "context_length": 272000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -679,7 +679,7 @@
       "owned_by": "openai",
       "display_name": "GPT-5.4 Mini",
       "context_length": 400000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -703,7 +703,7 @@
       "owned_by": "openai",
       "display_name": "GPT-5.3-Codex",
       "context_length": 400000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -727,7 +727,7 @@
       "owned_by": "openai",
       "display_name": "GPT-4.1",
       "context_length": 1047576,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text",
         "image"
@@ -790,7 +790,7 @@
       "owned_by": "moonshot",
       "display_name": "Kimi K3",
       "context_length": 1048576,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -812,7 +812,7 @@
       "owned_by": "moonshot",
       "display_name": "Kimi K2.7",
       "context_length": 262144,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -827,7 +827,7 @@
       "owned_by": "moonshot",
       "display_name": "Kimi K2.6",
       "context_length": 262144,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
@@ -842,7 +842,7 @@
       "owned_by": "nvidia",
       "display_name": "Nemotron 3 Ultra",
       "context_length": 1000000,
-      "max_completion_tokens": 64000,
+      "max_completion_tokens": 128000,
       "supportedInputModalities": [
         "text"
       ],
diff --git a/internal/runtime/executor/devin_executor.go b/internal/runtime/executor/devin_executor.go
index 1f9eb49d4..48c570770 100644
--- a/internal/runtime/executor/devin_executor.go
+++ b/internal/runtime/executor/devin_executor.go
@@ -8,6 +8,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"strconv"
 	"strings"
@@ -97,7 +98,15 @@ func (e *DevinExecutor) PrepareRequest(req *http.Request, auth *cliproxyauth.Aut
 	}
 	req.Header.Set("Content-Type", "application/connect+proto")
 	req.Header.Set("Connect-Protocol-Version", "1")
-	req.Header.Set("User-Agent", "connect-go/1.19.1 (go1.25.0)")
+	req.Header.Set("Accept", "*/*")
+	// Native devin-cli attaches Sentry-Trace only to chat streaming, omitting it on unary status/catalog calls.
+	isUnary := req.URL != nil && (strings.Contains(req.URL.Path, "GetUserStatus") || strings.Contains(req.URL.Path, "GetCliModelConfigs") || strings.Contains(req.URL.Path, "SeatManagementService"))
+	if !isUnary && req.Header.Get("Sentry-Trace") == "" {
+		req.Header.Set("Sentry-Trace", helps.GenerateDevinSentryTrace())
+	}
+	// Native devin-cli suppresses User-Agent header entirely on the wire.
+	// In Go net/http, setting the header slice to empty string suppresses default Go-http-client injection.
+	req.Header["User-Agent"] = []string{""}
 
 	var attrs map[string]string
 	if auth != nil {
@@ -119,7 +128,7 @@ func (e *DevinExecutor) HttpRequest(ctx context.Context, auth *cliproxyauth.Auth
 	if err := e.PrepareRequest(httpReq, auth); err != nil {
 		return nil, err
 	}
-	httpClient := helps.NewProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
+	httpClient := helps.NewDevinHTTPClient(ctx, e.cfg, auth, 0)
 	return httpClient.Do(httpReq)
 }
 
@@ -147,7 +156,7 @@ func (e *DevinExecutor) Refresh(ctx context.Context, auth *cliproxyauth.Auth) (*
 		return auth, nil
 	}
 
-	httpClient := helps.NewProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
+	httpClient := helps.NewDevinHTTPClient(ctx, e.cfg, auth, 0)
 	authService := devinauth.NewDevinAuthService(httpClient)
 	if baseURL := strings.TrimSpace(auth.Attributes["base_url"]); baseURL != "" {
 		authService.SetServerBaseURL(baseURL)
@@ -276,7 +285,7 @@ func (e *DevinExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, re
 		AuthValue: authValue,
 	})
 
-	httpClient := reporter.TrackHTTPClient(helps.NewProxyAwareHTTPClient(ctx, e.cfg, auth, 0))
+	httpClient := reporter.TrackHTTPClient(helps.NewDevinHTTPClient(ctx, e.cfg, auth, 0))
 	httpResp, errDo := httpClient.Do(httpReq)
 	if errDo != nil {
 		helps.RecordAPIResponseError(ctx, e.cfg, errDo)
@@ -288,7 +297,7 @@ func (e *DevinExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, re
 
 	helps.RecordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
 	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
-		errData, _ := io.ReadAll(httpResp.Body)
+		errData, _ := io.ReadAll(io.LimitReader(httpResp.Body, 1<<20))
 		helps.AppendAPIResponseChunk(ctx, e.cfg, errData)
 		return resp, newDevinStatusError(httpResp.StatusCode, httpResp.Header, errData)
 	}
@@ -340,7 +349,7 @@ func (e *DevinExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 		AuthValue: authValue,
 	})
 
-	httpClient := reporter.TrackHTTPClient(helps.NewProxyAwareHTTPClient(ctx, e.cfg, auth, 0))
+	httpClient := reporter.TrackHTTPClient(helps.NewDevinHTTPClient(ctx, e.cfg, auth, 0))
 	httpResp, errDo := httpClient.Do(httpReq)
 	if errDo != nil {
 		helps.RecordAPIResponseError(ctx, e.cfg, errDo)
@@ -348,10 +357,10 @@ func (e *DevinExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 	}
 	helps.RecordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
 	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
-		errData, _ := io.ReadAll(httpResp.Body)
+		errData, _ := io.ReadAll(io.LimitReader(httpResp.Body, 1<<20))
 		_ = httpResp.Body.Close()
 		helps.AppendAPIResponseChunk(ctx, e.cfg, errData)
-		return nil, statusErr{code: httpResp.StatusCode, msg: string(errData)}
+		return nil, newDevinStatusError(httpResp.StatusCode, httpResp.Header, errData)
 	}
 
 	out := make(chan cliproxyexecutor.StreamChunk)
@@ -359,6 +368,11 @@ func (e *DevinExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 
 	streamCtx, cancelStream := context.WithCancel(ctx)
 
+	go func() {
+		<-streamCtx.Done()
+		_ = httpResp.Body.Close()
+	}()
+
 	go func() {
 		defer close(out)
 		defer cancelStream()
@@ -382,9 +396,6 @@ func (e *DevinExecutor) prepareDevinHTTPRequest(ctx context.Context, auth *clipr
 	if apiKey == "" {
 		return nil, "", nil, fmt.Errorf("devin credentials missing: api_key or session_token required")
 	}
-	if deviceSeed == "" {
-		deviceSeed = apiKey
-	}
 
 	payload := req.Payload
 	isInteractionsSource := opts.SourceFormat == "" || opts.SourceFormat == sdktranslator.FormatInteractions
@@ -394,7 +405,8 @@ func (e *DevinExecutor) prepareDevinHTTPRequest(ctx context.Context, auth *clipr
 	systemPrompt, prompts, tools, temp, maxTokens, sessionID, cascadeID, thinkingLevel, budgetTokens := parseInteractionsPayload(payload, opts.OriginalRequest)
 	sessionID, cascadeID = resolveDevinSessionAndCascadeIDs(ctx, sessionID, cascadeID, opts)
 
-	if modelInfo := registry.LookupModelInfo(req.Model, "devin"); modelInfo != nil && modelInfo.MaxCompletionTokens > 0 {
+	baseModel := thinking.ParseSuffix(req.Model).ModelName
+	if modelInfo := registry.LookupModelInfo(baseModel, "devin"); modelInfo != nil && modelInfo.MaxCompletionTokens > 0 {
 		if maxTokens > modelInfo.MaxCompletionTokens || maxTokens <= 0 {
 			maxTokens = modelInfo.MaxCompletionTokens
 		}
@@ -469,7 +481,7 @@ func (e *DevinExecutor) streamDevinFrames(
 	stepIndex := 0
 	thoughtStarted := false
 	contentStarted := false
-	currentToolCallActive := false
+	toolCallSteps := make(map[int]int) // maps tc.Index -> stepIndex
 	thinkingBuf := &helps.UTF8SplitBuffer{}
 	contentBuf := &helps.UTF8SplitBuffer{}
 	var accumulatedThinking strings.Builder
@@ -533,15 +545,17 @@ func (e *DevinExecutor) streamDevinFrames(
 	}
 
 	thoughtStepIndex := -1
+	var streamErr error
 
 	// 2. Consume streaming Connect-proto frames
 	for {
 		flag, payload, errRead := helps.ReadConnectFrame(body)
 		if errRead != nil {
-			if errors.Is(errRead, io.EOF) || errors.Is(errRead, io.ErrUnexpectedEOF) {
+			if errors.Is(errRead, io.EOF) || errors.Is(errRead, net.ErrClosed) || ctx.Err() != nil {
 				break
 			}
-			log.Debugf("devin executor: read connect frame error: %v", errRead)
+			streamErr = errRead
+			log.Warnf("devin executor: stream read error: %v", errRead)
 			break
 		}
 		streamFrameCount++
@@ -551,6 +565,7 @@ func (e *DevinExecutor) streamDevinFrames(
 			code, errTrailer := helps.ParseDevinTrailerError(payload)
 			if errTrailer != nil {
 				log.Warnf("devin executor: trailer error (%d): %v", code, errTrailer)
+				helps.RecordAPIResponseError(ctx, e.cfg, errTrailer)
 				failedEvent, _ := sjson.SetBytes([]byte(`{"event_type":"response.failed","error":{"message":"","code":""}}`), "error.message", errTrailer.Error())
 				failedEvent, _ = sjson.SetBytes(failedEvent, "error.code", fmt.Sprintf("%d", code))
 				_ = emitInteractionsEvent(failedEvent)
@@ -600,14 +615,23 @@ func (e *DevinExecutor) streamDevinFrames(
 
 		// Emit thinking signature delta targeting the thought step
 		if len(frameRes.DeltaSignature) > 0 {
-			targetIdx := thoughtStepIndex
-			if targetIdx < 0 {
-				targetIdx = 0
+			if !thoughtStarted {
+				thoughtStepIndex = stepIndex
+				startEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.start","index":0,"step":{"type":"thought"}}`), "index", stepIndex)
+				if !emitInteractionsEvent(startEvent) {
+					return
+				}
+				thoughtStarted = true
 			}
 			sigEvent := []byte(`{"event_type":"step.delta","index":0,"delta":{"type":"thought_signature","signature":""}}`)
-			sigEvent, _ = sjson.SetBytes(sigEvent, "index", targetIdx)
+			sigEvent, _ = sjson.SetBytes(sigEvent, "index", thoughtStepIndex)
 			sigEvent, _ = sjson.SetBytes(sigEvent, "delta.signature", string(frameRes.DeltaSignature))
-			_ = emitInteractionsEvent(sigEvent)
+			if frameRes.DeltaSignatureType != "" {
+				sigEvent, _ = sjson.SetBytes(sigEvent, "delta.signature_type", frameRes.DeltaSignatureType)
+			}
+			if !emitInteractionsEvent(sigEvent) {
+				return
+			}
 		}
 
 		// Emit content text delta
@@ -653,23 +677,22 @@ func (e *DevinExecutor) streamDevinFrames(
 				stepIndex++
 			}
 
-			if tc.Name != "" || tc.ID != "" {
-				if currentToolCallActive {
-					stopEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.stop","index":0}`), "index", stepIndex)
-					_ = emitInteractionsEvent(stopEvent)
-					stepIndex++
-				}
-				startEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.start","index":0,"step":{"type":"function_call","name":"","id":"","call_id":"","arguments":{}}}`), "index", stepIndex)
+			sIdx, exists := toolCallSteps[tc.Index]
+			if !exists {
+				sIdx = stepIndex
+				stepIndex++
+				toolCallSteps[tc.Index] = sIdx
+				startEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.start","index":0,"step":{"type":"function_call","name":"","id":"","call_id":"","arguments":{}}}`), "index", sIdx)
 				startEvent, _ = sjson.SetBytes(startEvent, "step.name", tc.Name)
 				startEvent, _ = sjson.SetBytes(startEvent, "step.id", tc.ID)
 				startEvent, _ = sjson.SetBytes(startEvent, "step.call_id", tc.ID)
 				if !emitInteractionsEvent(startEvent) {
 					return
 				}
-				currentToolCallActive = true
 			}
+
 			if tc.Arguments != "" {
-				deltaEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.delta","index":0,"delta":{"type":"arguments_delta","arguments":""}}`), "index", stepIndex)
+				deltaEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.delta","index":0,"delta":{"type":"arguments_delta","arguments":""}}`), "index", sIdx)
 				deltaEvent, _ = sjson.SetBytes(deltaEvent, "delta.arguments", tc.Arguments)
 				if !emitInteractionsEvent(deltaEvent) {
 					return
@@ -678,26 +701,23 @@ func (e *DevinExecutor) streamDevinFrames(
 		}
 	}
 
-	// 3. Emit accumulated signature if present
-	if len(accumulatedSignature) > 0 {
-		targetIdx := thoughtStepIndex
-		if targetIdx < 0 {
-			targetIdx = 0
-		}
-		sigBase64 := base64.StdEncoding.EncodeToString(accumulatedSignature)
-		sigEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.delta","index":0,"delta":{"type":"thought_signature","signature":""}}`), "index", targetIdx)
-		sigEvent, _ = sjson.SetBytes(sigEvent, "delta.signature", sigBase64)
-		if signatureType != "" {
-			sigEvent, _ = sjson.SetBytes(sigEvent, "delta.signature_type", signatureType)
-		}
-		_ = emitInteractionsEvent(sigEvent)
-	}
-
-	// 4. Close open steps
-	if thoughtStarted || contentStarted || currentToolCallActive {
+	// 3. Close open steps
+	if thoughtStarted || contentStarted {
 		stopEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.stop","index":0}`), "index", stepIndex)
 		_ = emitInteractionsEvent(stopEvent)
 	}
+	for _, sIdx := range toolCallSteps {
+		stopEvent, _ := sjson.SetBytes([]byte(`{"event_type":"step.stop","index":0}`), "index", sIdx)
+		_ = emitInteractionsEvent(stopEvent)
+	}
+
+	// If stream encountered an abnormal read error mid-flight, record failure and emit response.failed
+	if streamErr != nil && ctx.Err() == nil {
+		helps.RecordAPIResponseError(ctx, e.cfg, streamErr)
+		failedEvent, _ := sjson.SetBytes([]byte(`{"event_type":"response.failed","error":{"message":"","code":"stream_read_error"}}`), "error.message", streamErr.Error())
+		_ = emitInteractionsEvent(failedEvent)
+		return
+	}
 
 	// 5. Emit interaction.completed with final usage
 	completedEvent := []byte(`{"event_type":"interaction.completed","interaction":{"id":"","model":"","status":"completed","usage":{"total_input_tokens":0,"total_output_tokens":0,"total_cached_tokens":0}}}`)
@@ -775,7 +795,7 @@ func consumeDevinFramesToInteractions(body io.Reader, model, chatModelUID string
 	for {
 		flag, payload, errRead := helps.ReadConnectFrame(body)
 		if errRead != nil {
-			if errors.Is(errRead, io.EOF) || errors.Is(errRead, io.ErrUnexpectedEOF) {
+			if errors.Is(errRead, io.EOF) {
 				break
 			}
 			respLog := &helps.DevinUpstreamResponseLog{
@@ -840,14 +860,18 @@ func consumeDevinFramesToInteractions(body io.Reader, model, chatModelUID string
 			textParts = append(textParts, frameRes.ContentText)
 		}
 		for _, tc := range frameRes.ToolCallDeltas {
-			if tc.Name != "" || tc.ID != "" {
-				toolCalls = append(toolCalls, helps.DevinToolCall{
-					ID:        tc.ID,
-					Name:      tc.Name,
-					Arguments: tc.Arguments,
-				})
-			} else if len(toolCalls) > 0 {
-				toolCalls[len(toolCalls)-1].Arguments += tc.Arguments
+			idx := tc.Index
+			for len(toolCalls) <= idx {
+				toolCalls = append(toolCalls, helps.DevinToolCall{})
+			}
+			if tc.ID != "" {
+				toolCalls[idx].ID = tc.ID
+			}
+			if tc.Name != "" {
+				toolCalls[idx].Name = tc.Name
+			}
+			if tc.Arguments != "" {
+				toolCalls[idx].Arguments += tc.Arguments
 			}
 		}
 	}
@@ -858,9 +882,13 @@ func consumeDevinFramesToInteractions(body io.Reader, model, chatModelUID string
 
 	var steps [][]byte
 
-	if len(thinkingParts) > 0 {
+	if len(thinkingParts) > 0 || len(accumulatedSignature) > 0 {
 		thoughtStep := []byte(`{"type":"thought","content":[{"type":"text","text":""}]}`)
-		thoughtStep, _ = sjson.SetBytes(thoughtStep, "content.0.text", strings.Join(thinkingParts, ""))
+		if len(thinkingParts) > 0 {
+			thoughtStep, _ = sjson.SetBytes(thoughtStep, "content.0.text", strings.Join(thinkingParts, ""))
+		} else {
+			thoughtStep, _ = sjson.DeleteBytes(thoughtStep, "content")
+		}
 		if len(accumulatedSignature) > 0 {
 			sigStr := string(accumulatedSignature)
 			thoughtStep, _ = sjson.SetBytes(thoughtStep, "signature", sigStr)
@@ -972,19 +1000,22 @@ func parseInteractionsPayload(payload, originalRequest []byte) (
 	}
 
 	// 3. Session and Cascade ID
+	// Prioritize stable session identifiers across turns (session_id, sessionId, conversation_id)
+	// to ensure upstream session ID and cascade ID remain stable, preserving prompt caching.
+	// Fall back to previous_interaction_id only when no stable session identifier exists.
 	sessionID = strings.TrimSpace(firstNonEmpty(
-		root.Get("previous_interaction_id").String(),
 		root.Get("session_id").String(),
 		root.Get("sessionId").String(),
 		root.Get("conversation_id").String(),
+		root.Get("previous_interaction_id").String(),
 	))
 	if sessionID == "" && len(originalRequest) > 0 {
 		origRoot := gjson.ParseBytes(originalRequest)
 		sessionID = strings.TrimSpace(firstNonEmpty(
-			origRoot.Get("previous_interaction_id").String(),
 			origRoot.Get("session_id").String(),
 			origRoot.Get("sessionId").String(),
 			origRoot.Get("conversation_id").String(),
+			origRoot.Get("previous_interaction_id").String(),
 		))
 	}
 	cascadeID = sessionID
@@ -1403,16 +1434,22 @@ func detectSignatureType(sig string) string {
 	return "sealed"
 }
 
+type originalAssistantMeta struct {
+	signature     []byte
+	signatureType string
+	thinking      string
+}
+
 func supplementSignaturesFromOriginal(original []byte, prompts []helps.DevinPrompt) {
 	origRoot := gjson.ParseBytes(original)
 	messages := origRoot.Get("messages")
 	if !messages.IsArray() {
 		return
 	}
-	var assistantSigs [][]byte
-	var assistantSigTypes []string
+	var originalAssistants []originalAssistantMeta
 	for _, m := range messages.Array() {
 		if strings.EqualFold(m.Get("role").String(), "assistant") {
+			var meta originalAssistantMeta
 			content := m.Get("content")
 			if content.IsArray() {
 				for _, part := range content.Array() {
@@ -1420,22 +1457,34 @@ func supplementSignaturesFromOriginal(original []byte, prompts []helps.DevinProm
 						if sig := part.Get("signature").String(); sig != "" {
 							bytes, sType := parseSignatureBytes(sig)
 							if len(bytes) > 0 {
-								assistantSigs = append(assistantSigs, bytes)
-								assistantSigTypes = append(assistantSigTypes, sType)
+								meta.signature = bytes
+								meta.signatureType = sType
 							}
 						}
+						if t := part.Get("thinking").String(); t != "" {
+							meta.thinking = t
+						}
 					}
 				}
 			}
+			originalAssistants = append(originalAssistants, meta)
 		}
 	}
 
-	sigIdx := 0
+	asstIdx := 0
 	for i := range prompts {
-		if prompts[i].Source == 2 && len(prompts[i].Signature) == 0 && sigIdx < len(assistantSigs) {
-			prompts[i].Signature = assistantSigs[sigIdx]
-			prompts[i].SignatureType = assistantSigTypes[sigIdx]
-			sigIdx++
+		if prompts[i].Source == 2 {
+			if asstIdx < len(originalAssistants) {
+				orig := originalAssistants[asstIdx]
+				if len(prompts[i].Signature) == 0 && len(orig.signature) > 0 {
+					prompts[i].Signature = orig.signature
+					prompts[i].SignatureType = orig.signatureType
+				}
+				if prompts[i].Thinking == "" && orig.thinking != "" {
+					prompts[i].Thinking = orig.thinking
+				}
+				asstIdx++
+			}
 		}
 	}
 }
@@ -1497,6 +1546,9 @@ func devinAuthCredentials(auth *cliproxyauth.Auth) (apiKey string, baseURL strin
 		if v, ok := auth.Metadata["base_url"].(string); ok && strings.TrimSpace(v) != "" && baseURL == helps.DevinDefaultBaseURL {
 			baseURL = strings.TrimSpace(v)
 		}
+		if v, ok := auth.Metadata["device_seed"].(string); ok && strings.TrimSpace(v) != "" && deviceSeed == "" {
+			deviceSeed = strings.TrimSpace(v)
+		}
 	}
 	return
 }
diff --git a/internal/runtime/executor/devin_executor_test.go b/internal/runtime/executor/devin_executor_test.go
index 0ce245434..101650633 100644
--- a/internal/runtime/executor/devin_executor_test.go
+++ b/internal/runtime/executor/devin_executor_test.go
@@ -61,6 +61,41 @@ func TestDevinExecutorPrepareRequest(t *testing.T) {
 	if req.Header.Get("Connect-Protocol-Version") != "1" {
 		t.Fatalf("Connect-Protocol-Version = %q, want 1", req.Header.Get("Connect-Protocol-Version"))
 	}
+	if req.Header.Get("Accept") != "*/*" {
+		t.Fatalf("Accept = %q, want */*", req.Header.Get("Accept"))
+	}
+	sentryTrace := req.Header.Get("Sentry-Trace")
+	if sentryTrace == "" {
+		t.Fatalf("Sentry-Trace header missing")
+	}
+	parts := strings.Split(sentryTrace, "-")
+	if len(parts) != 3 || len(parts[0]) != 32 || len(parts[1]) != 16 || parts[2] != "1" {
+		t.Fatalf("invalid Sentry-Trace format: %q", sentryTrace)
+	}
+
+	// Verify User-Agent suppression on the wire
+	var receivedUA []string
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		receivedUA = r.Header["User-Agent"]
+	}))
+	defer ts.Close()
+
+	wireReq, err := http.NewRequest(http.MethodPost, ts.URL, nil)
+	if err != nil {
+		t.Fatalf("NewRequest failed: %v", err)
+	}
+	if err := exec.PrepareRequest(wireReq, auth); err != nil {
+		t.Fatalf("PrepareRequest failed: %v", err)
+	}
+	resp, err := ts.Client().Do(wireReq)
+	if err != nil {
+		t.Fatalf("Do request failed: %v", err)
+	}
+	_ = resp.Body.Close()
+
+	if len(receivedUA) != 0 {
+		t.Errorf("expected User-Agent to be completely omitted on wire, got: %v", receivedUA)
+	}
 }
 
 func TestDevinAuthCredentials(t *testing.T) {
diff --git a/internal/runtime/executor/helps/devin_models.go b/internal/runtime/executor/helps/devin_models.go
index 0c29a9054..e9b66e2fc 100644
--- a/internal/runtime/executor/helps/devin_models.go
+++ b/internal/runtime/executor/helps/devin_models.go
@@ -20,6 +20,7 @@ var (
 
 // knownDevinSuffixes lists recognized model uid suffixes.
 var knownDevinSuffixes = []string{
+	"-none",
 	"-low",
 	"-medium",
 	"-high",
diff --git a/internal/runtime/executor/helps/devin_wire.go b/internal/runtime/executor/helps/devin_wire.go
index f67f29223..cadde89a4 100644
--- a/internal/runtime/executor/helps/devin_wire.go
+++ b/internal/runtime/executor/helps/devin_wire.go
@@ -3,6 +3,7 @@ package helps
 import (
 	"bytes"
 	"compress/gzip"
+	"crypto/rand"
 	"crypto/sha256"
 	"encoding/base64"
 	"encoding/binary"
@@ -14,9 +15,11 @@ import (
 	"net/http"
 	"runtime"
 	"strings"
+	"sync/atomic"
 	"unicode/utf8"
 
 	"github.com/google/uuid"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/cache"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/util"
 	"google.golang.org/protobuf/encoding/protowire"
 )
@@ -117,9 +120,15 @@ type DevinFrameResult struct {
 	UnknownFieldNumbers     []int
 }
 
-// GenerateDevinDeviceFingerprint generates a stable 732-character hex device fingerprint.
+// GenerateDevinDeviceFingerprint generates a 732-character hex device fingerprint.
+// When seed is empty, it generates a cryptographically random 732-character hex string per request (matching native devin-cli).
+// When seed is provided, it derives a deterministic 732-character hex fingerprint.
 func GenerateDevinDeviceFingerprint(seed string) string {
 	if seed == "" {
+		var b [DevinFingerprintHexLen / 2]byte
+		if _, err := rand.Read(b[:]); err == nil {
+			return hex.EncodeToString(b[:])
+		}
 		seed = uuid.New().String()
 	}
 	var sb strings.Builder
@@ -133,6 +142,45 @@ func GenerateDevinDeviceFingerprint(seed string) string {
 	return sb.String()[:DevinFingerprintHexLen]
 }
 
+// GenerateDevinSentryTrace generates a Sentry distributed tracing header in the format:
+// "<32-hex-trace-id>-<16-hex-span-id>-1"
+func GenerateDevinSentryTrace() string {
+	var b [24]byte
+	if _, err := rand.Read(b[:]); err != nil {
+		u1 := strings.ReplaceAll(uuid.New().String(), "-", "")
+		u2 := strings.ReplaceAll(uuid.New().String(), "-", "")[:16]
+		return u1 + "-" + u2 + "-1"
+	}
+	traceID := hex.EncodeToString(b[:16])
+	spanID := hex.EncodeToString(b[16:24])
+	return traceID + "-" + spanID + "-1"
+}
+
+const defaultMaxSessionTurnCounters = 5000
+
+var sessionTurnLRU = cache.NewBoundedLRU[string, *atomic.Uint64](defaultMaxSessionTurnCounters, nil)
+
+// NextDevinSessionTurnIndex returns the next 0-based request ordinal for a session (Field 15.2).
+// In native devin-cli, the counter is process-scoped per session:
+// First request in a session returns 0 (which is omitted on the wire).
+// Subsequent requests return 1, 2, 3... monotonically.
+func NextDevinSessionTurnIndex(sessionID string) int {
+	cleanID := strings.TrimSpace(sessionID)
+	if cleanID == "" {
+		return 0
+	}
+
+	counter := sessionTurnLRU.GetOrAdd(cleanID, func() *atomic.Uint64 {
+		return &atomic.Uint64{}
+	})
+	return int(counter.Add(1) - 1)
+}
+
+// ResetDevinSessionTurnIndex clears the session counter (used for testing or explicit session reset).
+func ResetDevinSessionTurnIndex(sessionID string) {
+	sessionTurnLRU.Delete(strings.TrimSpace(sessionID))
+}
+
 // WrapConnectEnvelope wraps raw payload bytes into a standard 5-byte Connect envelope:
 // [1 byte flag: 0x00] + [4 byte big-endian length] + [payload].
 func WrapConnectEnvelope(protoBytes []byte) []byte {
@@ -373,7 +421,7 @@ func BuildDevinGetChatMessageRequest(
 	f8Bytes = protowire.AppendVarint(f8Bytes, 40)
 
 	f8Bytes = protowire.AppendTag(f8Bytes, 8, protowire.Fixed64Type)
-	f8Bytes = protowire.AppendFixed64(f8Bytes, math.Float64bits(0.95))
+	f8Bytes = protowire.AppendFixed64(f8Bytes, math.Float64bits(float64(float32(0.95))))
 
 	reqBytes = protowire.AppendTag(reqBytes, 8, protowire.BytesType)
 	reqBytes = protowire.AppendBytes(reqBytes, f8Bytes)
@@ -402,18 +450,32 @@ func BuildDevinGetChatMessageRequest(
 	}
 
 	// 7. Thread session metadata (Field 15)
+	// In native devin-cli:
+	// Field 1: sessionID (UUID string)
+	// Field 2: turnIndex (per-session request ordinal, omitted when 0)
+	// Field 3: 4 (varint)
+	// Field 4: 14 (emitted conditionally on user-turn boundaries)
+	turnIndex := NextDevinSessionTurnIndex(sessionID)
+
 	var f15Bytes []byte
 	f15Bytes = protowire.AppendTag(f15Bytes, 1, protowire.BytesType)
 	f15Bytes = protowire.AppendString(f15Bytes, sessionID)
 
-	f15Bytes = protowire.AppendTag(f15Bytes, 2, protowire.VarintType)
-	f15Bytes = protowire.AppendVarint(f15Bytes, 53)
+	if turnIndex > 0 {
+		f15Bytes = protowire.AppendTag(f15Bytes, 2, protowire.VarintType)
+		f15Bytes = protowire.AppendVarint(f15Bytes, uint64(turnIndex))
+	}
 
 	f15Bytes = protowire.AppendTag(f15Bytes, 3, protowire.VarintType)
 	f15Bytes = protowire.AppendVarint(f15Bytes, 4)
 
-	f15Bytes = protowire.AppendTag(f15Bytes, 4, protowire.VarintType)
-	f15Bytes = protowire.AppendVarint(f15Bytes, 14)
+	// In native devin-cli, Field 15.4=14 is emitted on user-turn boundaries
+	if len(prompts) > 0 && prompts[len(prompts)-1].Source == 1 {
+		if turnIndex == 0 || len(prompts) < 2 || prompts[len(prompts)-2].Source != 1 {
+			f15Bytes = protowire.AppendTag(f15Bytes, 4, protowire.VarintType)
+			f15Bytes = protowire.AppendVarint(f15Bytes, 14)
+		}
+	}
 
 	reqBytes = protowire.AppendTag(reqBytes, 15, protowire.BytesType)
 	reqBytes = protowire.AppendBytes(reqBytes, f15Bytes)
diff --git a/internal/runtime/executor/helps/devin_wire_test.go b/internal/runtime/executor/helps/devin_wire_test.go
index 4194640a9..c7b1aeff0 100644
--- a/internal/runtime/executor/helps/devin_wire_test.go
+++ b/internal/runtime/executor/helps/devin_wire_test.go
@@ -4,6 +4,9 @@ import (
 	"bytes"
 	"strings"
 	"testing"
+
+	"github.com/google/uuid"
+	"google.golang.org/protobuf/encoding/protowire"
 )
 
 func TestConnectEnvelopeFraming(t *testing.T) {
@@ -255,10 +258,10 @@ func TestParseDevinTrailerError(t *testing.T) {
 
 func TestUTF8SplitBuffer(t *testing.T) {
 	buf := &UTF8SplitBuffer{}
-	// "你好" in UTF-8: \xe4\xbd\xa0 \xe5\xa5\xbd (3 bytes each)
-	chunk1 := []byte{0xe4, 0xbd}       // first 2 bytes of 你
-	chunk2 := []byte{0xa0, 0xe5, 0xa5} // last 1 byte of 你, first 2 bytes of 好
-	chunk3 := []byte{0xbd}             // last 1 byte of 好
+	// Multi-byte UTF-8 test: \xe4\xbd\xa0 \xe5\xa5\xbd (3 bytes each)
+	chunk1 := []byte{0xe4, 0xbd}       // first 2 bytes of char 1
+	chunk2 := []byte{0xa0, 0xe5, 0xa5} // last 1 byte of char 1, first 2 bytes of char 2
+	chunk3 := []byte{0xbd}             // last 1 byte of char 2
 
 	s1 := buf.Feed(chunk1)
 	if s1 != "" {
@@ -374,3 +377,178 @@ func TestBuildDevinUpstreamLogBody(t *testing.T) {
 		t.Errorf("expected direct body to contain model UID")
 	}
 }
+
+func TestGenerateDevinSentryTrace(t *testing.T) {
+	st1 := GenerateDevinSentryTrace()
+	st2 := GenerateDevinSentryTrace()
+	if st1 == st2 {
+		t.Fatalf("traces should be randomly generated: %s == %s", st1, st2)
+	}
+	parts := strings.Split(st1, "-")
+	if len(parts) != 3 {
+		t.Fatalf("sentry-trace should have 3 parts separated by hyphen, got %q", st1)
+	}
+	if len(parts[0]) != 32 {
+		t.Errorf("traceID len = %d, want 32", len(parts[0]))
+	}
+	if len(parts[1]) != 16 {
+		t.Errorf("spanID len = %d, want 16", len(parts[1]))
+	}
+	if parts[2] != "1" {
+		t.Errorf("sampled = %q, want 1", parts[2])
+	}
+}
+
+func TestBuildDevinGetChatMessageRequest_Field15TurnIndex(t *testing.T) {
+	sessID0 := "sess-turn0-" + uuid.New().String()
+	defer ResetDevinSessionTurnIndex(sessID0)
+
+	// 1. Turn 0 with user prompt: turnIndex=0 (omitted), 15.4=14 emitted on user boundary
+	promptsTurn0 := []DevinPrompt{
+		{MessageID: "u1", Source: 1, Content: "hello"},
+	}
+	req0 := BuildDevinGetChatMessageRequest("tok", "seed", "swe-2-high", "", promptsTurn0, nil, nil, 1000, sessID0, "casc-turn0", nil)
+	gotSess0, f15Sub0 := extractField15Subfields(t, req0)
+	if gotSess0 != sessID0 {
+		t.Errorf("Field 1 sessionID = %q, want %q", gotSess0, sessID0)
+	}
+	if _, hasF2 := f15Sub0[2]; hasF2 {
+		t.Errorf("turn 0 should omit Field 2, got %v", f15Sub0[2])
+	}
+	if f15Sub0[3] != 4 {
+		t.Errorf("Field 3 = %d, want 4", f15Sub0[3])
+	}
+	if f15Sub0[4] != 14 {
+		t.Errorf("Field 4 = %d, want 14 on user turn boundary", f15Sub0[4])
+	}
+
+	sessIDTool := "sess-tool-" + uuid.New().String()
+	defer ResetDevinSessionTurnIndex(sessIDTool)
+
+	// 2. Tool-result continuation (source=4): 15.4 should be omitted
+	promptsTool := []DevinPrompt{
+		{MessageID: "u1", Source: 1, Content: "read file"},
+		{MessageID: "a1", Source: 2, Content: "calling tool"},
+		{MessageID: "t1", Source: 4, Content: "file content", ToolCallID: "call_1"},
+	}
+	reqTool := BuildDevinGetChatMessageRequest("tok", "seed", "swe-2-high", "", promptsTool, nil, nil, 1000, sessIDTool, "casc-tool", nil)
+	_, f15SubTool := extractField15Subfields(t, reqTool)
+	if _, hasF4 := f15SubTool[4]; hasF4 {
+		t.Errorf("Field 4 should be omitted on tool result continuation, got %v", f15SubTool[4])
+	}
+}
+
+func TestBuildDevinGetChatMessageRequest_Field15SequentialCounter(t *testing.T) {
+	sessionID := "sess-sequential-test-" + uuid.New().String()
+	defer ResetDevinSessionTurnIndex(sessionID)
+
+	prompts := []DevinPrompt{
+		{MessageID: "u1", Source: 1, Content: "hi"},
+	}
+
+	// Request 1: fresh session -> turnIndex 0 (omitted from wire)
+	req1 := BuildDevinGetChatMessageRequest("tok", "seed", "swe-2-high", "", prompts, nil, nil, 1000, sessionID, "casc-1", nil)
+	_, sub1 := extractField15Subfields(t, req1)
+	if _, hasF2 := sub1[2]; hasF2 {
+		t.Errorf("Request 1 in fresh session should omit 15.2, got %v", sub1[2])
+	}
+
+	// Request 2: turnIndex 1
+	req2 := BuildDevinGetChatMessageRequest("tok", "seed", "swe-2-high", "", prompts, nil, nil, 1000, sessionID, "casc-1", nil)
+	_, sub2 := extractField15Subfields(t, req2)
+	if sub2[2] != 1 {
+		t.Errorf("Request 2 should have 15.2 = 1, got %v", sub2[2])
+	}
+
+	// Request 3: turnIndex 2
+	req3 := BuildDevinGetChatMessageRequest("tok", "seed", "swe-2-high", "", prompts, nil, nil, 1000, sessionID, "casc-1", nil)
+	_, sub3 := extractField15Subfields(t, req3)
+	if sub3[2] != 2 {
+		t.Errorf("Request 3 should have 15.2 = 2, got %v", sub3[2])
+	}
+}
+
+func TestGenerateDevinDeviceFingerprint_RandomWhenEmptySeed(t *testing.T) {
+	fp1 := GenerateDevinDeviceFingerprint("")
+	fp2 := GenerateDevinDeviceFingerprint("")
+	if len(fp1) != DevinFingerprintHexLen {
+		t.Fatalf("fp1 len = %d, want %d", len(fp1), DevinFingerprintHexLen)
+	}
+	if len(fp2) != DevinFingerprintHexLen {
+		t.Fatalf("fp2 len = %d, want %d", len(fp2), DevinFingerprintHexLen)
+	}
+	if fp1 == fp2 {
+		t.Fatalf("fingerprints without explicit seed must be unique per call: %q == %q", fp1, fp2)
+	}
+
+	// With explicit seed, it must be deterministic
+	seeded1 := GenerateDevinDeviceFingerprint("my-stable-seed")
+	seeded2 := GenerateDevinDeviceFingerprint("my-stable-seed")
+	if seeded1 != seeded2 {
+		t.Fatalf("seeded fingerprints must be identical: %q != %q", seeded1, seeded2)
+	}
+}
+
+func extractField15Subfields(t *testing.T, reqBytes []byte) (string, map[int]uint64) {
+	t.Helper()
+	b := reqBytes
+	var f15Bytes []byte
+	for len(b) > 0 {
+		num, typ, n := protowire.ConsumeTag(b)
+		if n < 0 {
+			break
+		}
+		b = b[n:]
+		if num == 15 && typ == protowire.BytesType {
+			sub, m := protowire.ConsumeBytes(b)
+			if m < 0 {
+				t.Fatalf("failed to consume field 15 bytes")
+			}
+			f15Bytes = sub
+			break
+		}
+		m := protowire.ConsumeFieldValue(num, typ, b)
+		if m < 0 {
+			break
+		}
+		b = b[m:]
+	}
+	if len(f15Bytes) == 0 {
+		t.Fatalf("field 15 not found in request")
+	}
+
+	var sessionID string
+	subfields := make(map[int]uint64)
+	sb := f15Bytes
+	for len(sb) > 0 {
+		num, typ, n := protowire.ConsumeTag(sb)
+		if n < 0 {
+			break
+		}
+		sb = sb[n:]
+		if typ == protowire.VarintType {
+			val, m := protowire.ConsumeVarint(sb)
+			if m < 0 {
+				break
+			}
+			subfields[int(num)] = val
+			sb = sb[m:]
+		} else if typ == protowire.BytesType {
+			val, m := protowire.ConsumeBytes(sb)
+			if m < 0 {
+				break
+			}
+			if num == 1 {
+				sessionID = string(val)
+			}
+			sb = sb[m:]
+		} else {
+			m := protowire.ConsumeFieldValue(num, typ, sb)
+			if m < 0 {
+				break
+			}
+			sb = sb[m:]
+		}
+	}
+	return sessionID, subfields
+}
diff --git a/internal/runtime/executor/helps/proxy_helpers.go b/internal/runtime/executor/helps/proxy_helpers.go
index 572f87c7a..404877b0d 100644
--- a/internal/runtime/executor/helps/proxy_helpers.go
+++ b/internal/runtime/executor/helps/proxy_helpers.go
@@ -61,6 +61,24 @@ func NewProxyAwareHTTPClient(ctx context.Context, cfg *config.Config, auth *clip
 	return httpClient
 }
 
+// NewDevinHTTPClient creates an HTTP client customized for Devin Connect-RPC upstream.
+// Suppresses automatic Accept-Encoding: gzip while preserving robust HTTP/2 streaming.
+func NewDevinHTTPClient(ctx context.Context, cfg *config.Config, auth *cliproxyauth.Auth, timeout time.Duration) *http.Client {
+	httpClient := NewProxyAwareHTTPClient(ctx, cfg, auth, timeout)
+	if httpClient.Transport == nil {
+		if dt, ok := http.DefaultTransport.(*http.Transport); ok {
+			httpClient.Transport = dt.Clone()
+		}
+	} else if tr, ok := httpClient.Transport.(*http.Transport); ok {
+		// Clone transport to avoid mutating a shared or cached roundtripper
+		httpClient.Transport = tr.Clone()
+	}
+	if tr, ok := httpClient.Transport.(*http.Transport); ok {
+		tr.DisableCompression = true
+	}
+	return httpClient
+}
+
 // buildProxyTransport creates an HTTP transport configured for the given proxy URL.
 // It supports SOCKS5, HTTP, and HTTPS proxy protocols.
 //
diff --git a/sdk/auth/devin.go b/sdk/auth/devin.go
index fce08dbfe..8da1dfe19 100644
--- a/sdk/auth/devin.go
+++ b/sdk/auth/devin.go
@@ -132,7 +132,7 @@ waitForResult:
 			if res.Error != "" {
 				return nil, fmt.Errorf("devin oauth error: %s", res.Error)
 			}
-			if state != "" && res.State != "" && res.State != state {
+			if state != "" && res.State != state {
 				return nil, fmt.Errorf("devin oauth state mismatch (possible CSRF)")
 			}
 			authCode = res.Code
@@ -180,7 +180,7 @@ waitForResult:
 			// 2. Full callback redirect URL
 			parsed, errParse := misc.ParseOAuthCallback(trimmed)
 			if errParse == nil && parsed != nil && parsed.Code != "" {
-				if state != "" && parsed.State != "" && parsed.State != state {
+				if state != "" && parsed.State != state {
 					return nil, fmt.Errorf("devin oauth state mismatch (possible CSRF)")
 				}
 				authCode = parsed.Code