diff --git a/backend/internal/service/openai_tool_continuation.go b/backend/internal/service/openai_tool_continuation.go
index a50721370..3b2356c97 100644
--- a/backend/internal/service/openai_tool_continuation.go
+++ b/backend/internal/service/openai_tool_continuation.go
@@ -235,16 +235,16 @@ func AnalyzeToolCallOutputContextCoverageBytes(body []byte) ToolCallOutputContex
 		return coverage
 	}
 	input := parseRawJSONView(body).Get("input")
-	if !input.IsArray() {
+	if !input.IsArray() && !input.IsObject() {
 		return coverage
 	}
 
 	missingCallID := false
 	var outputCallIDs map[string]struct{}
 	var contextIDs map[string]struct{}
-	input.ForEach(func(_, item gjson.Result) bool {
+	analyzeItem := func(item gjson.Result) {
 		if !item.IsObject() {
-			return true
+			return
 		}
 		itemType := item.Get("type").String()
 		switch {
@@ -253,7 +253,7 @@ func AnalyzeToolCallOutputContextCoverageBytes(body []byte) ToolCallOutputContex
 			callID := strings.TrimSpace(item.Get("call_id").String())
 			if callID == "" {
 				missingCallID = true
-				return true
+				return
 			}
 			if outputCallIDs == nil {
 				outputCallIDs = make(map[string]struct{})
@@ -262,7 +262,7 @@ func AnalyzeToolCallOutputContextCoverageBytes(body []byte) ToolCallOutputContex
 		case isCodexToolCallContextItemType(itemType):
 			callID := strings.TrimSpace(item.Get("call_id").String())
 			if callID == "" {
-				return true
+				return
 			}
 			if contextIDs == nil {
 				contextIDs = make(map[string]struct{})
@@ -271,15 +271,22 @@ func AnalyzeToolCallOutputContextCoverageBytes(body []byte) ToolCallOutputContex
 		case itemType == "item_reference":
 			idValue := strings.TrimSpace(item.Get("id").String())
 			if idValue == "" {
-				return true
+				return
 			}
 			if contextIDs == nil {
 				contextIDs = make(map[string]struct{})
 			}
 			contextIDs[idValue] = struct{}{}
 		}
-		return true
-	})
+	}
+	if input.IsArray() {
+		input.ForEach(func(_, item gjson.Result) bool {
+			analyzeItem(item)
+			return true
+		})
+	} else {
+		analyzeItem(input)
+	}
 
 	if !coverage.HasFunctionCallOutput || missingCallID {
 		return coverage
diff --git a/backend/internal/service/openai_tool_continuation_test.go b/backend/internal/service/openai_tool_continuation_test.go
index 569d89eff..460a659c2 100644
--- a/backend/internal/service/openai_tool_continuation_test.go
+++ b/backend/internal/service/openai_tool_continuation_test.go
@@ -206,6 +206,14 @@ func TestAnalyzeToolCallOutputContextCoverageBytes(t *testing.T) {
 			hasOutput:    false,
 			coversAllIDs: false,
 		},
+		{
+			name: "object_tool_output_requires_context_replay",
+			body: map[string]any{"input": map[string]any{
+				"type": "custom_tool_call_output", "call_id": "call_a",
+			}},
+			hasOutput:    true,
+			coversAllIDs: false,
+		},
 		{
 			name: "all_outputs_covered_by_context",
 			body: map[string]any{"input": []any{
diff --git a/backend/internal/service/openai_ws_forwarder_ingress.go b/backend/internal/service/openai_ws_forwarder_ingress.go
index 4b0fe5a01..f02ad2513 100644
--- a/backend/internal/service/openai_ws_forwarder_ingress.go
+++ b/backend/internal/service/openai_ws_forwarder_ingress.go
@@ -511,7 +511,9 @@ func (s *OpenAIGatewayService) ProxyResponsesWebSocketFromClient(
 			}
 			bridgePayloadRaw := currentBridgePayload.payloadRaw
 			bridgePayloadBytes := currentBridgePayload.payloadBytes
-			needsBridgeReplay := currentBridgePayload.previousResponseID != "" || openAIWSRawPayloadHasToolCallOutput(currentBridgePayload.payloadRaw)
+			toolOutputCoverage := AnalyzeToolCallOutputContextCoverageBytes(currentBridgePayload.payloadRaw)
+			needsBridgeReplay := currentBridgePayload.previousResponseID != "" ||
+				(toolOutputCoverage.HasFunctionCallOutput && !toolOutputCoverage.ContextCoversAllCallIDs)
 			turnReplayInput, turnReplayInputExists, replayInputErr := buildOpenAIWSReplayInputSequence(
 				bridgeReplayInput,
 				bridgeReplayInputExists,
diff --git a/backend/internal/service/openai_ws_forwarder_ingress_test.go b/backend/internal/service/openai_ws_forwarder_ingress_test.go
index a13248e39..a7bdf31b7 100644
--- a/backend/internal/service/openai_ws_forwarder_ingress_test.go
+++ b/backend/internal/service/openai_ws_forwarder_ingress_test.go
@@ -809,6 +809,35 @@ func TestBuildOpenAIWSReplayInputSequence(t *testing.T) {
 		require.Equal(t, "new", gjson.GetBytes(items[0], "text").String())
 	})
 
+	t.Run("no_previous_response_id_custom_tool_history_does_not_accumulate", func(t *testing.T) {
+		previousFull := []json.RawMessage{
+			json.RawMessage(`{"type":"input_text","text":"stale"}`),
+			json.RawMessage(`{"type":"custom_tool_call","id":"stale_item","call_id":"stale_call","name":"exec","input":"stale"}`),
+		}
+		currentPayload := []byte(`{"input":[
+			{"type":"custom_tool_call","id":"item_1","call_id":"call_1","name":"exec","input":"pwd"},
+			{"type":"custom_tool_call_output","call_id":"call_1","output":"/tmp"},
+			{"type":"input_text","text":"continue"}
+		]}`)
+
+		for range 3 {
+			items, exists, err := buildOpenAIWSReplayInputSequence(
+				previousFull,
+				true,
+				currentPayload,
+				false,
+			)
+			require.NoError(t, err)
+			require.True(t, exists)
+			require.Len(t, items, 3)
+			require.Equal(t, "custom_tool_call", gjson.GetBytes(items[0], "type").String())
+			require.Equal(t, "call_1", gjson.GetBytes(items[0], "call_id").String())
+			require.Equal(t, "custom_tool_call_output", gjson.GetBytes(items[1], "type").String())
+			require.Equal(t, "call_1", gjson.GetBytes(items[1], "call_id").String())
+			previousFull = append(items, json.RawMessage(`{"type":"custom_tool_call","id":"replayed_item","call_id":"replayed_call","name":"exec","input":"ignored"}`))
+		}
+	})
+
 	t.Run("previous_response_id_delta_append", func(t *testing.T) {
 		items, exists, err := buildOpenAIWSReplayInputSequence(
 			lastFull,
diff --git a/backend/internal/service/openai_ws_http_bridge_test.go b/backend/internal/service/openai_ws_http_bridge_test.go
index 49b4c7073..74838026c 100644
--- a/backend/internal/service/openai_ws_http_bridge_test.go
+++ b/backend/internal/service/openai_ws_http_bridge_test.go
@@ -413,6 +413,191 @@ func TestOpenAIWSHTTPBridgeAPIKeyReusesClientToolMappingWhenFollowupOmitsTools(t
 	require.False(t, secondInput[2].Get("id").Exists())
 }
 
+func TestOpenAIWSHTTPBridgeFullCustomToolHistoryWithoutPreviousResponseIDDoesNotReplay(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	completed := func(responseID string, output string) string {
+		return "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"" + responseID + "\",\"model\":\"gpt-5.1\",\"output\":" + output + ",\"usage\":{\"input_tokens\":1,\"output_tokens\":1}}}\n\n"
+	}
+	upstream := &httpUpstreamRecorder{responses: []*http.Response{
+		{StatusCode: http.StatusOK, Header: http.Header{"Content-Type": []string{"text/event-stream"}}, Body: io.NopCloser(strings.NewReader(completed("resp_1", `[{"type":"custom_tool_call","id":"item_1","call_id":"call_1","name":"exec","input":"pwd"}]`)))},
+		{StatusCode: http.StatusOK, Header: http.Header{"Content-Type": []string{"text/event-stream"}}, Body: io.NopCloser(strings.NewReader(completed("resp_2", `[]`)))},
+		{StatusCode: http.StatusOK, Header: http.Header{"Content-Type": []string{"text/event-stream"}}, Body: io.NopCloser(strings.NewReader(completed("resp_3", `[]`)))},
+	}}
+	cfg := &config.Config{}
+	cfg.Security.URLAllowlist.Enabled = false
+	cfg.Security.URLAllowlist.AllowInsecureHTTP = true
+	cfg.Gateway.OpenAIWS.Enabled = true
+	cfg.Gateway.OpenAIWS.OAuthEnabled = true
+	cfg.Gateway.OpenAIWS.ResponsesWebsocketsV2 = true
+	cfg.Gateway.OpenAIWS.HTTPBridgeEnabled = true
+	cfg.Gateway.OpenAIWS.HTTPBridgeThresholdBytes = 1
+	cfg.Gateway.OpenAIWS.ReadTimeoutSeconds = 3
+	cfg.Gateway.OpenAIWS.WriteTimeoutSeconds = 3
+
+	svc := &OpenAIGatewayService{
+		cfg: cfg, httpUpstream: upstream, cache: &stubGatewayCache{},
+		openaiWSResolver: NewOpenAIWSProtocolResolver(cfg), toolCorrector: NewCodexToolCorrector(),
+	}
+	account := &Account{
+		ID: 9002, Name: "oauth-full-context", Platform: PlatformOpenAI, Type: AccountTypeOAuth,
+		Credentials: map[string]any{"access_token": "test-token"}, Extra: map[string]any{"responses_websockets_v2_enabled": true},
+		Concurrency: 1, Status: StatusActive, Schedulable: true,
+	}
+
+	errCh := make(chan error, 1)
+	wsServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		conn, err := coderws.Accept(w, r, nil)
+		if err != nil {
+			errCh <- err
+			return
+		}
+		defer func() { _ = conn.CloseNow() }()
+		readCtx, cancelRead := context.WithTimeout(r.Context(), 3*time.Second)
+		_, firstMessage, err := conn.Read(readCtx)
+		cancelRead()
+		if err != nil {
+			errCh <- err
+			return
+		}
+		rec := httptest.NewRecorder()
+		ginCtx, _ := gin.CreateTestContext(rec)
+		ginCtx.Request = r.Clone(r.Context())
+		errCh <- svc.ProxyResponsesWebSocketFromClient(r.Context(), ginCtx, conn, account, "test-token", firstMessage, nil)
+	}))
+	defer wsServer.Close()
+
+	dialCtx, cancelDial := context.WithTimeout(context.Background(), 3*time.Second)
+	clientConn, _, err := coderws.Dial(dialCtx, "ws"+strings.TrimPrefix(wsServer.URL, "http"), nil)
+	cancelDial()
+	require.NoError(t, err)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	writeAndRead := func(payload string) {
+		writeCtx, cancelWrite := context.WithTimeout(context.Background(), 3*time.Second)
+		require.NoError(t, clientConn.Write(writeCtx, coderws.MessageText, []byte(payload)))
+		cancelWrite()
+		readCtx, cancelRead := context.WithTimeout(context.Background(), 3*time.Second)
+		_, event, readErr := clientConn.Read(readCtx)
+		cancelRead()
+		require.NoError(t, readErr)
+		require.Equal(t, "response.completed", gjson.GetBytes(event, "type").String())
+	}
+
+	writeAndRead(`{"type":"response.create","model":"gpt-5.1","input":"run pwd"}`)
+	fullContext := `{"type":"response.create","model":"gpt-5.1","input":[{"type":"custom_tool_call","id":"item_1","call_id":"call_1","name":"exec","input":"pwd"},{"type":"custom_tool_call_output","call_id":"call_1","output":"/tmp"},{"role":"user","content":"continue"}]}`
+	writeAndRead(fullContext)
+	writeAndRead(fullContext)
+
+	require.NoError(t, clientConn.Close(coderws.StatusNormalClosure, "done"))
+	select {
+	case proxyErr := <-errCh:
+		require.NoError(t, proxyErr)
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for websocket bridge proxy to finish")
+	}
+
+	require.Len(t, upstream.bodies, 3)
+	for _, body := range upstream.bodies[1:] {
+		input := gjson.GetBytes(body, "input").Array()
+		require.Len(t, input, 3)
+		require.Equal(t, "custom_tool_call", input[0].Get("type").String())
+		require.Equal(t, "call_1", input[0].Get("call_id").String())
+		require.Equal(t, "custom_tool_call_output", input[1].Get("type").String())
+		require.Equal(t, "call_1", input[1].Get("call_id").String())
+	}
+}
+
+func TestOpenAIWSHTTPBridgeObjectToolOutputWithoutPreviousResponseIDReplaysMatchingCall(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	completed := func(responseID string, output string) string {
+		return "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"" + responseID + "\",\"model\":\"gpt-5.1\",\"output\":" + output + ",\"usage\":{\"input_tokens\":1,\"output_tokens\":1}}}\n\n"
+	}
+	upstream := &httpUpstreamRecorder{responses: []*http.Response{
+		{StatusCode: http.StatusOK, Header: http.Header{"Content-Type": []string{"text/event-stream"}}, Body: io.NopCloser(strings.NewReader(completed("resp_1", `[{"type":"custom_tool_call","id":"item_1","call_id":"call_1","name":"exec","input":"pwd"}]`)))},
+		{StatusCode: http.StatusOK, Header: http.Header{"Content-Type": []string{"text/event-stream"}}, Body: io.NopCloser(strings.NewReader(completed("resp_2", `[]`)))},
+	}}
+	cfg := &config.Config{}
+	cfg.Security.URLAllowlist.Enabled = false
+	cfg.Security.URLAllowlist.AllowInsecureHTTP = true
+	cfg.Gateway.OpenAIWS.Enabled = true
+	cfg.Gateway.OpenAIWS.OAuthEnabled = true
+	cfg.Gateway.OpenAIWS.ResponsesWebsocketsV2 = true
+	cfg.Gateway.OpenAIWS.HTTPBridgeEnabled = true
+	cfg.Gateway.OpenAIWS.HTTPBridgeThresholdBytes = 1
+	cfg.Gateway.OpenAIWS.ReadTimeoutSeconds = 3
+	cfg.Gateway.OpenAIWS.WriteTimeoutSeconds = 3
+
+	svc := &OpenAIGatewayService{
+		cfg: cfg, httpUpstream: upstream, cache: &stubGatewayCache{},
+		openaiWSResolver: NewOpenAIWSProtocolResolver(cfg), toolCorrector: NewCodexToolCorrector(),
+	}
+	account := &Account{
+		ID: 9003, Name: "oauth-output-only", Platform: PlatformOpenAI, Type: AccountTypeOAuth,
+		Credentials: map[string]any{"access_token": "test-token"}, Extra: map[string]any{"responses_websockets_v2_enabled": true},
+		Concurrency: 1, Status: StatusActive, Schedulable: true,
+	}
+
+	errCh := make(chan error, 1)
+	wsServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		conn, err := coderws.Accept(w, r, nil)
+		if err != nil {
+			errCh <- err
+			return
+		}
+		defer func() { _ = conn.CloseNow() }()
+		readCtx, cancelRead := context.WithTimeout(r.Context(), 3*time.Second)
+		_, firstMessage, err := conn.Read(readCtx)
+		cancelRead()
+		if err != nil {
+			errCh <- err
+			return
+		}
+		rec := httptest.NewRecorder()
+		ginCtx, _ := gin.CreateTestContext(rec)
+		ginCtx.Request = r.Clone(r.Context())
+		errCh <- svc.ProxyResponsesWebSocketFromClient(r.Context(), ginCtx, conn, account, "test-token", firstMessage, nil)
+	}))
+	defer wsServer.Close()
+
+	dialCtx, cancelDial := context.WithTimeout(context.Background(), 3*time.Second)
+	clientConn, _, err := coderws.Dial(dialCtx, "ws"+strings.TrimPrefix(wsServer.URL, "http"), nil)
+	cancelDial()
+	require.NoError(t, err)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	writeAndRead := func(payload string) {
+		writeCtx, cancelWrite := context.WithTimeout(context.Background(), 3*time.Second)
+		require.NoError(t, clientConn.Write(writeCtx, coderws.MessageText, []byte(payload)))
+		cancelWrite()
+		readCtx, cancelRead := context.WithTimeout(context.Background(), 3*time.Second)
+		_, event, readErr := clientConn.Read(readCtx)
+		cancelRead()
+		require.NoError(t, readErr)
+		require.Equal(t, "response.completed", gjson.GetBytes(event, "type").String())
+	}
+
+	writeAndRead(`{"type":"response.create","model":"gpt-5.1","input":"run pwd"}`)
+	writeAndRead(`{"type":"response.create","model":"gpt-5.1","input":{"type":"custom_tool_call_output","call_id":"call_1","output":"/tmp"}}`)
+
+	require.NoError(t, clientConn.Close(coderws.StatusNormalClosure, "done"))
+	select {
+	case proxyErr := <-errCh:
+		require.NoError(t, proxyErr)
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for websocket bridge proxy to finish")
+	}
+
+	require.Len(t, upstream.bodies, 2)
+	secondInput := gjson.GetBytes(upstream.bodies[1], "input").Array()
+	require.Len(t, secondInput, 3)
+	require.Equal(t, "custom_tool_call", secondInput[1].Get("type").String())
+	require.Equal(t, "call_1", secondInput[1].Get("call_id").String())
+	require.Equal(t, "custom_tool_call_output", secondInput[2].Get("type").String())
+	require.Equal(t, "call_1", secondInput[2].Get("call_id").String())
+}
+
 func TestOpenAIWSHTTPBridgeDecisionKeepsSmallFramesOnWS(t *testing.T) {
 	svc := &OpenAIGatewayService{
 		cfg: &config.Config{