<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019cbba8-0528-7eb8-a967-f07dd1c5d759,g:cbd54f26-db03-42cb-98f5-1213fb8bcfe4-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="https://xbrl.org/2023/arcrole/summation-item" xlink:type="simple" xlink:href="https://www.xbrl.org/2023/calculation-1.1.xsd#summation-item"/>
  <link:roleRef roleURI="http://gig.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="gct-20260331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:calculationLink xlink:role="http://gig.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019cbba8-0653-73a7-a239-05dbe0e74641" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019cbba8-0653-7036-9bb0-797e983c93ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019cbba8-0653-73a7-a239-05dbe0e74641" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019cbba8-0653-7036-9bb0-797e983c93ee" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019cbba8-0653-7853-942c-c39c67831f43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019cbba8-0653-73a7-a239-05dbe0e74641" xlink:to="loc_us-gaap_CommonStockValue_019cbba8-0653-7853-942c-c39c67831f43" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7861-ad51-5808823d32c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019cbba8-0653-73a7-a239-05dbe0e74641" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7861-ad51-5808823d32c5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonValue_019cbba8-0653-7a28-8e67-63318af5cf99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonValue"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019cbba8-0653-73a7-a239-05dbe0e74641" xlink:to="loc_us-gaap_TreasuryStockCommonValue_019cbba8-0653-7a28-8e67-63318af5cf99" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019cbba8-0653-7d12-a39a-a371d7cef8ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019cbba8-0653-73a7-a239-05dbe0e74641" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019cbba8-0653-7d12-a39a-a371d7cef8ef" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019cbba8-0653-75c1-86ba-486e4e8b823a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019cbba8-0653-7e1d-a41e-916b80994101" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019cbba8-0653-75c1-86ba-486e4e8b823a" xlink:to="loc_us-gaap_LiabilitiesCurrent_019cbba8-0653-7e1d-a41e-916b80994101" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrent_019cbba8-0653-7e0b-bebc-4c3ce961e274" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019cbba8-0653-75c1-86ba-486e4e8b823a" xlink:to="loc_us-gaap_LiabilitiesNoncurrent_019cbba8-0653-7e0b-bebc-4c3ce961e274" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019cbba8-0653-76e4-bef2-167056c6e901" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019cbba8-0653-7310-9acc-fa1b22937e70" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019cbba8-0653-76e4-bef2-167056c6e901" xlink:to="loc_us-gaap_Liabilities_019cbba8-0653-7310-9acc-fa1b22937e70" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019ce195-3020-7f70-8025-acbdf5ee641d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019cbba8-0653-76e4-bef2-167056c6e901" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019ce195-3020-7f70-8025-acbdf5ee641d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019cbba8-0653-7663-b79b-f765423c4fcc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019cbba8-0653-76e4-bef2-167056c6e901" xlink:to="loc_us-gaap_StockholdersEquity_019cbba8-0653-7663-b79b-f765423c4fcc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrent_019cbba8-0653-7624-a1a1-aa8e30ac9a5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019cbba8-0653-7085-b51a-8fc645ff47c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesNoncurrent_019cbba8-0653-7624-a1a1-aa8e30ac9a5c" xlink:to="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019cbba8-0653-7085-b51a-8fc645ff47c2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesNoncurrent_019cbba8-0653-7d3a-994d-7b99558ad79a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedIncomeTaxesNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesNoncurrent_019cbba8-0653-7624-a1a1-aa8e30ac9a5c" xlink:to="loc_us-gaap_AccruedIncomeTaxesNoncurrent_019cbba8-0653-7d3a-994d-7b99558ad79a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019cbba8-0653-7755-825f-b191274f8827" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesNoncurrent_019cbba8-0653-7624-a1a1-aa8e30ac9a5c" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019cbba8-0653-7755-825f-b191274f8827" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019cbba8-0653-7762-95f1-8dcaced9104e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesNoncurrent_019cbba8-0653-7624-a1a1-aa8e30ac9a5c" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019cbba8-0653-7762-95f1-8dcaced9104e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_ContingentConsiderationLiabilityNoncurrent_019da8ab-95b0-768f-a1fe-b38036bb81b9" xlink:href="gct-20260331.xsd#gct_ContingentConsiderationLiabilityNoncurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesNoncurrent_019cbba8-0653-7624-a1a1-aa8e30ac9a5c" xlink:to="loc_gct_ContingentConsiderationLiabilityNoncurrent_019da8ab-95b0-768f-a1fe-b38036bb81b9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019cbba8-0653-712d-85fc-92d6447318c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-7c71-a246-dc6289f1f2c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019cbba8-0653-712d-85fc-92d6447318c4" xlink:to="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-7c71-a246-dc6289f1f2c2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019cbba8-0653-7710-8cc4-d0fdbdc9b066" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019cbba8-0653-712d-85fc-92d6447318c4" xlink:to="loc_us-gaap_AssetsCurrent_019cbba8-0653-7710-8cc4-d0fdbdc9b066" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019cbba8-0653-7e46-85bd-7c3f79a3d1fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019cbba8-0653-710e-9b7c-57748605b6b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019cbba8-0653-7e46-85bd-7c3f79a3d1fc" xlink:to="loc_us-gaap_AccountsPayableCurrent_019cbba8-0653-710e-9b7c-57748605b6b0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019cbba8-0653-7963-a88c-7b2511625d76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019cbba8-0653-7e46-85bd-7c3f79a3d1fc" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019cbba8-0653-7963-a88c-7b2511625d76" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_019cbba8-0653-7d91-b697-201477a82662" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019cbba8-0653-7e46-85bd-7c3f79a3d1fc" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_019cbba8-0653-7d91-b697-201477a82662" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_AccruedLiabilitiesAndOtherCurrentLiabilities_019cbba8-0653-79aa-b78e-6e8a61769b6a" xlink:href="gct-20260331.xsd#gct_AccruedLiabilitiesAndOtherCurrentLiabilities"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019cbba8-0653-7e46-85bd-7c3f79a3d1fc" xlink:to="loc_gct_AccruedLiabilitiesAndOtherCurrentLiabilities_019cbba8-0653-79aa-b78e-6e8a61769b6a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxes_019cbba8-0653-7d07-8dc2-8f76610e7a7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedIncomeTaxes"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019cbba8-0653-7e46-85bd-7c3f79a3d1fc" xlink:to="loc_us-gaap_AccruedIncomeTaxes_019cbba8-0653-7d07-8dc2-8f76610e7a7b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-76e0-8515-faa6203ee164" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019cbba8-0653-73bb-b8be-2413182e04cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-76e0-8515-faa6203ee164" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019cbba8-0653-73bb-b8be-2413182e04cf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_019cbba8-0653-749b-9cdc-e70035910cc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-76e0-8515-faa6203ee164" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_019cbba8-0653-749b-9cdc-e70035910cc2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019cbba8-0653-78df-b6dc-0c232f871b9f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-76e0-8515-faa6203ee164" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_019cbba8-0653-78df-b6dc-0c232f871b9f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019cbba8-0653-76f7-a518-64a65c08f733" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-76e0-8515-faa6203ee164" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019cbba8-0653-76f7-a518-64a65c08f733" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019cbba8-0653-71dc-a8c1-cdd00d844c85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-76e0-8515-faa6203ee164" xlink:to="loc_us-gaap_Goodwill_019cbba8-0653-71dc-a8c1-cdd00d844c85" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019cbba8-0653-7a3e-8eef-6d34eb6f8af4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrent_019cbba8-0653-76e0-8515-faa6203ee164" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019cbba8-0653-7a3e-8eef-6d34eb6f8af4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019cbba8-0653-7c27-a672-b86259c9a97a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019cbba8-0653-7dc0-bf47-ac51ce791a12" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019cbba8-0653-7c27-a672-b86259c9a97a" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019cbba8-0653-7dc0-bf47-ac51ce791a12" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_019cbba8-0653-75d8-b59a-f2ea6a994332" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermInvestments"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019cbba8-0653-7c27-a672-b86259c9a97a" xlink:to="loc_us-gaap_ShortTermInvestments_019cbba8-0653-75d8-b59a-f2ea6a994332" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_019cbba8-0653-729b-9631-dd4af58f3ba9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNet"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019cbba8-0653-7c27-a672-b86259c9a97a" xlink:to="loc_us-gaap_InventoryNet_019cbba8-0653-729b-9631-dd4af58f3ba9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019cbba8-0653-701f-806d-5def86647898" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019cbba8-0653-7c27-a672-b86259c9a97a" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019cbba8-0653-701f-806d-5def86647898" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019cbba8-0653-7b07-a3e1-a29e0303abf8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019cbba8-0653-7c27-a672-b86259c9a97a" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_019cbba8-0653-7b07-a3e1-a29e0303abf8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_019cbba8-0653-7e0b-8c14-10d7f4e0bee8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019cbba8-0653-7c27-a672-b86259c9a97a" xlink:to="loc_us-gaap_RestrictedCashCurrent_019cbba8-0653-7e0b-8c14-10d7f4e0bee8" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME" xlink:type="simple" xlink:href="gct-20260331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME"/>
  <link:calculationLink xlink:role="http://gig.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7d79-bdc8-404a7b7c79d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_019cbba8-0653-7f93-be97-233181adf654" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7d79-bdc8-404a7b7c79d9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_019cbba8-0653-7f93-be97-233181adf654" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_019cbba8-0653-7ef2-a01d-7fc108584cc4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7d79-bdc8-404a7b7c79d9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_019cbba8-0653-7ef2-a01d-7fc108584cc4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentForLongTermIntercompanyTransactionsNetOfTax_019cbba8-0653-7370-bdce-83ed03252026" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentForLongTermIntercompanyTransactionsNetOfTax"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7d79-bdc8-404a7b7c79d9" xlink:to="loc_us-gaap_AdjustmentForLongTermIntercompanyTransactionsNetOfTax_019cbba8-0653-7370-bdce-83ed03252026" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax_019cbba8-0653-777c-9389-78014cc55090" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7d79-bdc8-404a7b7c79d9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax_019cbba8-0653-777c-9389-78014cc55090" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019cbba8-0653-73ad-986e-3c9de491c25e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7482-8ca3-c6efe3cfb2d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019cbba8-0653-73ad-986e-3c9de491c25e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cbba8-0653-7482-8ca3-c6efe3cfb2d5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019cbba8-0653-75d6-8441-1c9ccc9813b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019cbba8-0653-73ad-986e-3c9de491c25e" xlink:to="loc_us-gaap_NetIncomeLoss_019cbba8-0653-75d6-8441-1c9ccc9813b1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019cbba8-0653-785b-9148-9dd769909e71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossProfit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019cbba8-0653-7c30-8359-e8550c9a1e24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_GrossProfit_019cbba8-0653-785b-9148-9dd769909e71" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019cbba8-0653-7c30-8359-e8550c9a1e24" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_CostOfRevenues_019cbba8-0653-7996-9921-d9637fa7aa7e" xlink:href="gct-20260331.xsd#gct_CostOfRevenues"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_GrossProfit_019cbba8-0653-785b-9148-9dd769909e71" xlink:to="loc_gct_CostOfRevenues_019cbba8-0653-7996-9921-d9637fa7aa7e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019cbba8-0653-706f-a22b-8c6499113be0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019cbba8-0653-79a4-a613-86d28a4bd34a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossProfit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_019cbba8-0653-706f-a22b-8c6499113be0" xlink:to="loc_us-gaap_GrossProfit_019cbba8-0653-79a4-a613-86d28a4bd34a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019cbba8-0653-7278-a30d-65989e596a0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpenses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_019cbba8-0653-706f-a22b-8c6499113be0" xlink:to="loc_us-gaap_OperatingExpenses_019cbba8-0653-7278-a30d-65989e596a0e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019cbba8-0653-7d72-9664-9415e2c22780" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_019cbba8-0653-7e84-89dc-9e4cc788cf7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019cbba8-0653-7d72-9664-9415e2c22780" xlink:to="loc_us-gaap_InvestmentIncomeInterest_019cbba8-0653-7e84-89dc-9e4cc788cf7b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019cbba8-0653-729d-b85f-0a91d9f23764" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019cbba8-0653-7d72-9664-9415e2c22780" xlink:to="loc_us-gaap_OperatingIncomeLoss_019cbba8-0653-729d-b85f-0a91d9f23764" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019cbba8-0653-79ff-88a5-c821cf571761" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019cbba8-0653-7d72-9664-9415e2c22780" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019cbba8-0653-79ff-88a5-c821cf571761" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_019cbba8-0653-7b33-ac2b-c5ed367b0432" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019cbba8-0653-7d72-9664-9415e2c22780" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_019cbba8-0653-7b33-ac2b-c5ed367b0432" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019cbba8-0653-7f6d-a678-06c243e4990b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019cbba8-0653-7d72-9664-9415e2c22780" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019cbba8-0653-7f6d-a678-06c243e4990b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019cbba8-0653-762f-88d7-2f002eda80b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpenses"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019cbba8-0653-7cc8-abb6-9aeaafe6ee9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019cbba8-0653-762f-88d7-2f002eda80b4" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019cbba8-0653-7cc8-abb6-9aeaafe6ee9e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_019cbba8-0653-767c-8abf-8118fdabdbce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019cbba8-0653-762f-88d7-2f002eda80b4" xlink:to="loc_us-gaap_SellingAndMarketingExpense_019cbba8-0653-767c-8abf-8118fdabdbce" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019cbba8-0653-730f-af2c-1efde0bbad67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019cbba8-0653-762f-88d7-2f002eda80b4" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019cbba8-0653-730f-af2c-1efde0bbad67" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019cbba8-0653-7b8e-90b3-f780a3a93bf3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019cbba8-0653-762f-88d7-2f002eda80b4" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019cbba8-0653-7b8e-90b3-f780a3a93bf3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019cbba8-0653-7b68-bf41-b9228b6f9f65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019cbba8-0653-7073-9426-f6c62071b394" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019cbba8-0653-7b68-bf41-b9228b6f9f65" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019cbba8-0653-7073-9426-f6c62071b394" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019cbba8-0653-7307-ae2b-83e53f223e08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019cbba8-0653-7b68-bf41-b9228b6f9f65" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019cbba8-0653-7307-ae2b-83e53f223e08" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="simple" xlink:href="gct-20260331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:calculationLink xlink:role="http://gig.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019cbba8-0653-7755-ba12-50386f93cfa5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019cbba8-0653-7c78-9c87-b06eb28b6afb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019cbba8-0653-7755-ba12-50386f93cfa5" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019cbba8-0653-7c78-9c87-b06eb28b6afb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireInvestments_019cbba8-0653-73ac-8206-a5f62938acb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireInvestments"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019cbba8-0653-7755-ba12-50386f93cfa5" xlink:to="loc_us-gaap_PaymentsToAcquireInvestments_019cbba8-0653-73ac-8206-a5f62938acb7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities_019cbba8-0653-7cd6-b6c1-9ca3497c6fea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019cbba8-0653-7755-ba12-50386f93cfa5" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities_019cbba8-0653-7cd6-b6c1-9ca3497c6fea" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019cbba8-0653-7a9e-9262-2bd60f3717c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019cbba8-0653-7755-ba12-50386f93cfa5" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019cbba8-0653-7a9e-9262-2bd60f3717c0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019da887-8ae0-7757-93f4-3af8350bdda6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019cbba8-0653-7755-ba12-50386f93cfa5" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019da887-8ae0-7757-93f4-3af8350bdda6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019cbba8-0653-7387-b065-6521176de66f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensation"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_ShareBasedCompensation_019cbba8-0653-7387-b065-6521176de66f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_019cbba8-0653-731c-9e11-a133bd7dacf9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_019cbba8-0653-731c-9e11-a133bd7dacf9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_019cbba8-0653-7b69-bba5-be3f2491907c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_019cbba8-0653-7b69-bba5-be3f2491907c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_019cbba8-0653-78e4-893c-e05ded8b918b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_019cbba8-0653-78e4-893c-e05ded8b918b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_IncreaseDecreaseInAccountsPayableAccruedExpensesAndOtherCurrentLiabilities_019cbba8-0653-7a75-8e0d-ffa603cece77" xlink:href="gct-20260331.xsd#gct_IncreaseDecreaseInAccountsPayableAccruedExpensesAndOtherCurrentLiabilities"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_gct_IncreaseDecreaseInAccountsPayableAccruedExpensesAndOtherCurrentLiabilities_019cbba8-0653-7a75-8e0d-ffa603cece77" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingActivitiesCashFlowStatement_019cbba8-0653-7374-a709-c54b06b04ee9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherOperatingActivitiesCashFlowStatement"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_OtherOperatingActivitiesCashFlowStatement_019cbba8-0653-7374-a709-c54b06b04ee9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019cbba8-0653-7d94-bc9c-a1298ad37705" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019cbba8-0653-7d94-bc9c-a1298ad37705" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_019cbba8-0653-7864-8924-08cbd6e8db87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_019cbba8-0653-7864-8924-08cbd6e8db87" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019cbba8-0653-7321-9365-bb465bd60d20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_NetIncomeLoss_019cbba8-0653-7321-9365-bb465bd60d20" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes_019cbba8-0653-73d8-8513-826f1a70f83b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInDeferredIncomeTaxes"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes_019cbba8-0653-73d8-8513-826f1a70f83b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019cbba8-0653-73fa-8561-458711b07f19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019cbba8-0653-73fa-8561-458711b07f19" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_019cbba8-0653-773d-bd82-87d3fbbfc92e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-7572-a2d6-c95632d4734d" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_019cbba8-0653-773d-bd82-87d3fbbfc92e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019cbba8-0653-7c8b-99c9-a0e0ccc2cd44" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019cbba8-0653-7996-95b4-6d60c10ebe58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019cbba8-0653-7c8b-99c9-a0e0ccc2cd44" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019cbba8-0653-7996-95b4-6d60c10ebe58" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_019cbba8-0653-7001-a677-8276010630fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019cbba8-0653-7c8b-99c9-a0e0ccc2cd44" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_019cbba8-0653-7001-a677-8276010630fa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019cbba8-0653-7d28-8593-0d00f3f22e4e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019cbba8-0653-7c8b-99c9-a0e0ccc2cd44" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019cbba8-0653-7d28-8593-0d00f3f22e4e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-71a6-b3d0-5256a9572c34" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019cbba8-0653-7c8b-99c9-a0e0ccc2cd44" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019cbba8-0653-71a6-b3d0-5256a9572c34" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019cbba8-0653-796b-ac24-5becc97e3db3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfEquity_019cbba8-0653-7164-a18a-4690d7e532ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForRepurchaseOfEquity"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019cbba8-0653-796b-ac24-5becc97e3db3" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfEquity_019cbba8-0653-7164-a18a-4690d7e532ff" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_019cbba8-0653-7456-8e46-a2e0c750fe88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeasePrincipalPayments"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019cbba8-0653-796b-ac24-5becc97e3db3" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_019cbba8-0653-7456-8e46-a2e0c750fe88" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofReconciliationofCashandRestrictedCashDetails" xlink:type="simple" xlink:href="gct-20260331.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofReconciliationofCashandRestrictedCashDetails"/>
  <link:calculationLink xlink:role="http://gig.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofReconciliationofCashandRestrictedCashDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019cbba8-0653-7a9f-ae24-07b9a1b7f210" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019cbba8-0653-7746-a2ff-9121337a871c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019cbba8-0653-7a9f-ae24-07b9a1b7f210" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019cbba8-0653-7746-a2ff-9121337a871c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019cbba8-0653-7daa-b9ca-4d8fa18f52bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019cbba8-0653-7a9f-ae24-07b9a1b7f210" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019cbba8-0653-7daa-b9ca-4d8fa18f52bc" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/BUSINESSCOMBINATIONScheduleofBusinessCombinationRecognizedAssetAcquiredandLiabilityAssumedDetails" xlink:type="simple" xlink:href="gct-20260331.xsd#BUSINESSCOMBINATIONScheduleofBusinessCombinationRecognizedAssetAcquiredandLiabilityAssumedDetails"/>
  <link:calculationLink xlink:role="http://gig.com/role/BUSINESSCOMBINATIONScheduleofBusinessCombinationRecognizedAssetAcquiredandLiabilityAssumedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019dffa3-7189-7f27-8513-dc0754783a4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_019dffa3-7189-725b-8895-94e23ffdf8a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019dffa3-7189-7f27-8513-dc0754783a4c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_019dffa3-7189-725b-8895-94e23ffdf8a9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiabilitiesCurrent_019dffa3-7189-711f-9f60-841e2a0b4136" xlink:href="gct-20260331.xsd#gct_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019dffa3-7189-7f27-8513-dc0754783a4c" xlink:to="loc_gct_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiabilitiesCurrent_019dffa3-7189-711f-9f60-841e2a0b4136" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_BusinessCombinationRecognizedLiabilityAssumedAccruedExpensesAndOtherCurrentLiabilities_019dffa3-7189-7ebd-9337-255b1a2e374c" xlink:href="gct-20260331.xsd#gct_BusinessCombinationRecognizedLiabilityAssumedAccruedExpensesAndOtherCurrentLiabilities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019dffa3-7189-7f27-8513-dc0754783a4c" xlink:to="loc_gct_BusinessCombinationRecognizedLiabilityAssumedAccruedExpensesAndOtherCurrentLiabilities_019dffa3-7189-7ebd-9337-255b1a2e374c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiabilitiesNonCurrent_019dffa3-7189-7738-a9be-c60a1211a94e" xlink:href="gct-20260331.xsd#gct_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiabilitiesNonCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019dffa3-7189-7f27-8513-dc0754783a4c" xlink:to="loc_gct_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiabilitiesNonCurrent_019dffa3-7189-7738-a9be-c60a1211a94e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_BusinessCombinationRecognizedLiabilitiesAssumedFinanceLeaseObligationsNonCurrent_019dffa3-7189-71e9-a9e2-f04186822ae0" xlink:href="gct-20260331.xsd#gct_BusinessCombinationRecognizedLiabilitiesAssumedFinanceLeaseObligationsNonCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019dffa3-7189-7f27-8513-dc0754783a4c" xlink:to="loc_gct_BusinessCombinationRecognizedLiabilitiesAssumedFinanceLeaseObligationsNonCurrent_019dffa3-7189-71e9-a9e2-f04186822ae0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019ce6a8-5fdf-7d0c-8377-63377daf4277" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ce6a8-5fdf-77bc-8826-2525dc032b43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019ce6a8-5fdf-7d0c-8377-63377daf4277" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ce6a8-5fdf-77bc-8826-2525dc032b43" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019ce6a8-5fdf-7999-b658-7433e3d8270e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019ce6a8-5fdf-7d0c-8377-63377daf4277" xlink:to="loc_us-gaap_Goodwill_019ce6a8-5fdf-7999-b658-7433e3d8270e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019dffa5-5924-722e-8f5d-d66af486d551" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-5924-7a24-9912-2011a2090359" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019dffa5-5924-722e-8f5d-d66af486d551" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-5924-7a24-9912-2011a2090359" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019dffa5-5924-7509-8707-1fce8fabb00b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019dffa5-5924-722e-8f5d-d66af486d551" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019dffa5-5924-7509-8707-1fce8fabb00b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019dffa5-1cba-7d11-9751-4321f22ea248" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019dffa5-1cba-7d11-9751-4321f22ea248" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019dffa5-1cba-79d2-a6ee-203b215aa5a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019dffa5-1cba-79d2-a6ee-203b215aa5a1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_019dffa5-1cba-7ab8-94db-068935aed9b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_019dffa5-1cba-7ab8-94db-068935aed9b6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_019dffa5-1cba-7cef-b1c9-83c225b12058" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_019dffa5-1cba-7cef-b1c9-83c225b12058" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_BusinessCombinationRecognizedAssetsAcquiredOperatingLeaseRightOfUseAssets_019dffa5-1cba-78c4-90d2-512e4270f8b8" xlink:href="gct-20260331.xsd#gct_BusinessCombinationRecognizedAssetsAcquiredOperatingLeaseRightOfUseAssets"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:to="loc_gct_BusinessCombinationRecognizedAssetsAcquiredOperatingLeaseRightOfUseAssets_019dffa5-1cba-78c4-90d2-512e4270f8b8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019dffa5-1cba-7826-aa62-96ba2abc0b15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019dffa5-1cba-7826-aa62-96ba2abc0b15" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019dffa5-1cba-7243-aa5a-144c854b45d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019dffa5-1cba-7243-aa5a-144c854b45d9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_019dffa5-1cba-7c50-90d8-c0a9b89b9dba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019dffa5-1cba-7d0d-ab57-4563a934d803" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_019dffa5-1cba-7c50-90d8-c0a9b89b9dba" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/ACCOUNTSRECEIVABLENETScheduleofAccountsReceivableNetDetails" xlink:type="simple" xlink:href="gct-20260331.xsd#ACCOUNTSRECEIVABLENETScheduleofAccountsReceivableNetDetails"/>
  <link:calculationLink xlink:role="http://gig.com/role/ACCOUNTSRECEIVABLENETScheduleofAccountsReceivableNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_019cbba8-0653-7d5e-88a7-dae5882ba07f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableGross_019cbba8-0653-7e1d-8234-fdb146080bf2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableNet_019cbba8-0653-7d5e-88a7-dae5882ba07f" xlink:to="loc_us-gaap_AccountsReceivableGross_019cbba8-0653-7e1d-8234-fdb146080bf2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019cbba8-0653-79cf-9832-911409b93ef0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableNet_019cbba8-0653-7d5e-88a7-dae5882ba07f" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019cbba8-0653-79cf-9832-911409b93ef0" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/INVENTORIESDetails" xlink:type="simple" xlink:href="gct-20260331.xsd#INVENTORIESDetails"/>
  <link:calculationLink xlink:role="http://gig.com/role/INVENTORIESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_019cbba8-0653-732f-ab17-377ed260a616" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryFinishedGoods_019cbba8-0653-79dc-969e-e204ebdf0158" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryFinishedGoods"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryNet_019cbba8-0653-732f-ab17-377ed260a616" xlink:to="loc_us-gaap_InventoryFinishedGoods_019cbba8-0653-79dc-969e-e204ebdf0158" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherInventoryInTransit_019cbba8-0653-7c8b-aef6-e7caa669a874" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherInventoryInTransit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryNet_019cbba8-0653-732f-ab17-377ed260a616" xlink:to="loc_us-gaap_OtherInventoryInTransit_019cbba8-0653-7c8b-aef6-e7caa669a874" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/LEASESScheduleofAssetsandLiabilitiesRelatedtobothOperatingandFinanceLeasesDetails" xlink:type="simple" xlink:href="gct-20260331.xsd#LEASESScheduleofAssetsandLiabilitiesRelatedtobothOperatingandFinanceLeasesDetails"/>
  <link:calculationLink xlink:role="http://gig.com/role/LEASESScheduleofAssetsandLiabilitiesRelatedtobothOperatingandFinanceLeasesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_gct_LeaseLiabilities_019cbba8-0653-7540-9f0b-03f62f5142cf" xlink:href="gct-20260331.xsd#gct_LeaseLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019cbba8-0653-7394-9b36-36b7d4cab049" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_gct_LeaseLiabilities_019cbba8-0653-7540-9f0b-03f62f5142cf" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019cbba8-0653-7394-9b36-36b7d4cab049" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019cbba8-0653-7a40-961f-0a88a5a0579d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_gct_LeaseLiabilities_019cbba8-0653-7540-9f0b-03f62f5142cf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019cbba8-0653-7a40-961f-0a88a5a0579d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityCurrent_019cbba8-0653-70fc-80e3-9c302412927f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_gct_LeaseLiabilities_019cbba8-0653-7540-9f0b-03f62f5142cf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityCurrent_019cbba8-0653-70fc-80e3-9c302412927f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_019cbba8-0653-7a8b-9c30-e162fc08942b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_gct_LeaseLiabilities_019cbba8-0653-7540-9f0b-03f62f5142cf" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_019cbba8-0653-7a8b-9c30-e162fc08942b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_RightOfUseAssets_019cbba8-0653-7eb5-981b-cac8802f82bf" xlink:href="gct-20260331.xsd#gct_RightOfUseAssets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019cbba8-0653-7326-a8d3-a93e66142da9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_gct_RightOfUseAssets_019cbba8-0653-7eb5-981b-cac8802f82bf" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019cbba8-0653-7326-a8d3-a93e66142da9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAsset_019cbba8-0653-7639-b7cc-984828fb94e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseRightOfUseAsset"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_gct_RightOfUseAssets_019cbba8-0653-7eb5-981b-cac8802f82bf" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAsset_019cbba8-0653-7639-b7cc-984828fb94e3" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/LEASESScheduleofLeaseCostDetails" xlink:type="simple" xlink:href="gct-20260331.xsd#LEASESScheduleofLeaseCostDetails"/>
  <link:calculationLink xlink:role="http://gig.com/role/LEASESScheduleofLeaseCostDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCost_019cbba8-0653-7a12-a383-47f463d0b211" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeaseCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_019cbba8-0653-7c7a-aa28-5a776692b795" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseCost"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019cbba8-0653-7a12-a383-47f463d0b211" xlink:to="loc_us-gaap_OperatingLeaseCost_019cbba8-0653-7c7a-aa28-5a776692b795" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAssetAmortization_019cbba8-0653-7ec5-9e09-4d82216cc17e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseRightOfUseAssetAmortization"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019cbba8-0653-7a12-a383-47f463d0b211" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAssetAmortization_019cbba8-0653-7ec5-9e09-4d82216cc17e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseInterestExpense_019cbba8-0653-7809-8516-338f5adce201" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseInterestExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019cbba8-0653-7a12-a383-47f463d0b211" xlink:to="loc_us-gaap_FinanceLeaseInterestExpense_019cbba8-0653-7809-8516-338f5adce201" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermLeaseCost_019cbba8-0653-77ba-8479-379d6fa3be23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermLeaseCost"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019cbba8-0653-7a12-a383-47f463d0b211" xlink:to="loc_us-gaap_ShortTermLeaseCost_019cbba8-0653-77ba-8479-379d6fa3be23" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/LEASESScheduleofFutureMinimumLeasePaymentsDetails" xlink:type="simple" xlink:href="gct-20260331.xsd#LEASESScheduleofFutureMinimumLeasePaymentsDetails"/>
  <link:calculationLink xlink:role="http://gig.com/role/LEASESScheduleofFutureMinimumLeasePaymentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019d2c7d-cfd4-70da-ad98-779d5f600ec5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019d2c7d-cfd4-7a64-bb30-58e98f5f3df5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019d2c7d-cfd4-70da-ad98-779d5f600ec5" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019d2c7d-cfd4-7a64-bb30-58e98f5f3df5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019d2c7d-cfd4-7fa3-8d51-7d64840fc412" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019d2c7d-cfd4-70da-ad98-779d5f600ec5" xlink:to="loc_us-gaap_OperatingLeaseLiability_019d2c7d-cfd4-7fa3-8d51-7d64840fc412" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019cbba8-0725-70c8-8565-61a42ea1974a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_019cbba8-0725-7dd7-be6a-d1253add2ad2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019cbba8-0725-70c8-8565-61a42ea1974a" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_019cbba8-0725-7dd7-be6a-d1253add2ad2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_FinanceLeaseLiabilityPaymentsDueAfterYearFour_019cbba8-0725-7be1-8fe4-2c16dc7ebc8b" xlink:href="gct-20260331.xsd#gct_FinanceLeaseLiabilityPaymentsDueAfterYearFour"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019cbba8-0725-70c8-8565-61a42ea1974a" xlink:to="loc_gct_FinanceLeaseLiabilityPaymentsDueAfterYearFour_019cbba8-0725-7be1-8fe4-2c16dc7ebc8b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_019cbba8-0725-7733-9f90-48e377e73d80" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019cbba8-0725-70c8-8565-61a42ea1974a" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_019cbba8-0725-7733-9f90-48e377e73d80" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear_019cbba8-0725-7e38-a359-1c54a7101ac7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019cbba8-0725-70c8-8565-61a42ea1974a" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear_019cbba8-0725-7e38-a359-1c54a7101ac7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_019cbba8-0725-7e63-bd76-ed1adda7406d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019cbba8-0725-70c8-8565-61a42ea1974a" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_019cbba8-0725-7e63-bd76-ed1adda7406d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_019cbba8-0725-7f11-943f-46460bf68953" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019cbba8-0725-70c8-8565-61a42ea1974a" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_019cbba8-0725-7f11-943f-46460bf68953" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://gig.com/role/LEASESScheduleofFutureMinimumLeasePaymentsDetails_1" xlink:type="simple" xlink:href="gct-20260331.xsd#LEASESScheduleofFutureMinimumLeasePaymentsDetails_1"/>
  <link:calculationLink xlink:role="http://gig.com/role/LEASESScheduleofFutureMinimumLeasePaymentsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019cbba8-0725-747d-8aee-47a74d625ab8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019cbba8-0725-764e-bff3-d0aae6426eda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019cbba8-0725-747d-8aee-47a74d625ab8" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019cbba8-0725-764e-bff3-d0aae6426eda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gct_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour_019cbba8-0725-750a-9dfe-d789da0a9472" xlink:href="gct-20260331.xsd#gct_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019cbba8-0725-747d-8aee-47a74d625ab8" xlink:to="loc_gct_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour_019cbba8-0725-750a-9dfe-d789da0a9472" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019cbba8-0725-7f10-acfb-9b07afa7d055" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019cbba8-0725-747d-8aee-47a74d625ab8" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019cbba8-0725-7f10-acfb-9b07afa7d055" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019cbba8-0725-7c41-8600-d90455e29849" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019cbba8-0725-747d-8aee-47a74d625ab8" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019cbba8-0725-7c41-8600-d90455e29849" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_019cbba8-0725-719a-8bbd-b626d41230a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019cbba8-0725-747d-8aee-47a74d625ab8" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_019cbba8-0725-719a-8bbd-b626d41230a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019cbba8-0725-78aa-a3a4-04db7bd2e287" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019cbba8-0725-747d-8aee-47a74d625ab8" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019cbba8-0725-78aa-a3a4-04db7bd2e287" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
