fix: preserve correct parent references in explode merge anchor reconstruction

When explode resolves merge anchors (<<:), items copied from the
alias target retained the original parent pointer instead of being
set to the enclosing node being reconstructed. This caused GetPath()
to return wrong paths for children of merge-anchored nodes, making
subsequent merge operations target the wrong LHS keys.

In fixedReconstructAliasedMap, set copied.Parent = node after copy.

In reconstructAliasedMap (non-spec path), replace AddChild (which
creates sequence-style numeric-index entries) with AddKeyValueChild
to properly reconstruct mapping key-value pairs. AddKeyValueChild
also correctly sets parent references via SetParent.

.github/workflows/codeql.yml

@@ -44,7 +44,7 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@95e58e9a2cdfd71adc6e0353d5c52f41a045d225 # v4.35.2
+      uses: github/codeql-action/init@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4.36.2
       with:
         languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
@@ -55,7 +55,7 @@ jobs:
     # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@95e58e9a2cdfd71adc6e0353d5c52f41a045d225 # v4.35.2
+      uses: github/codeql-action/autobuild@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4.36.2
 
     # ℹ️ Command-line programs to run using the OS shell.
     # 📚 See https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsrun
@@ -69,4 +69,4 @@ jobs:
     #   make release
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@95e58e9a2cdfd71adc6e0353d5c52f41a045d225 # v4.35.2
+      uses: github/codeql-action/analyze@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4.36.2

.github/workflows/release.yml

@@ -43,7 +43,7 @@ jobs:
             man.md
 
       - name: Install cosign
-        uses: sigstore/cosign-installer@7e8b541eb2e61bf99390e1afd4be13a184e9ebc5 # v3.10.1
+        uses: sigstore/cosign-installer@6f9f17788090df1f26f669e9d70d6ae9567deba6 # v4.1.2
 
       - name: Cross compile
         run: |

.github/workflows/scorecard.yml

@@ -73,6 +73,6 @@ jobs:
       # Upload the results to GitHub's code scanning dashboard (optional).
       # Commenting out will disable upload of results to your repo's Code Scanning dashboard
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@95e58e9a2cdfd71adc6e0353d5c52f41a045d225 # v4.35.2
+        uses: github/codeql-action/upload-sarif@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4.36.2
         with:
           sarif_file: results.sarif

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.26.4@sha256:68cb6d68bed024785b69195b89af7ac7a444f27791435f98647edff595aa0479 AS builder
+FROM golang:1.26.4@sha256:11fd8f7f63db3b6fb198797042ba4c40a4a34dc83325d3328ca3bc4bb7726786 AS builder
 
 WORKDIR /go/src/mikefarah/yq
 
@@ -10,7 +10,7 @@ RUN ./scripts/acceptance.sh
 
 # Choose alpine as a base image to make this useful for CI, as many
 # CI tools expect an interactive shell inside the container
-FROM alpine:3@sha256:5b10f432ef3da1b8d4c7eb6c487f2f5a8f096bc91145e68878dd4a5019afde11 AS production
+FROM alpine:3@sha256:a2d49ea686c2adfe3c992e47dc3b5e7fa6e6b5055609400dc2acaeb241c829f4 AS production
 LABEL maintainer="Mike Farah <mikefarah@users.noreply.github.com>"
 
 COPY --from=builder /go/src/mikefarah/yq/yq /usr/bin/yq

Dockerfile.dev

@@ -1,4 +1,4 @@
-FROM golang:1.26.4@sha256:68cb6d68bed024785b69195b89af7ac7a444f27791435f98647edff595aa0479
+FROM golang:1.26.4@sha256:11fd8f7f63db3b6fb198797042ba4c40a4a34dc83325d3328ca3bc4bb7726786
 
 COPY scripts/devtools.sh /opt/devtools.sh
 

go.mod

@@ -19,10 +19,10 @@ require (
 	github.com/spf13/pflag v1.0.10
 	github.com/yuin/gopher-lua v1.1.2
 	github.com/zclconf/go-cty v1.18.1
-	go.yaml.in/yaml/v4 v4.0.0-rc.4
+	go.yaml.in/yaml/v4 v4.0.0-rc.5
 	golang.org/x/mod v0.36.0
 	golang.org/x/net v0.55.0
-	golang.org/x/text v0.37.0
+	golang.org/x/text v0.38.0
 )
 
 require (
@@ -33,9 +33,9 @@ require (
 	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/mitchellh/go-wordwrap v1.0.1 // indirect
-	golang.org/x/sync v0.20.0 // indirect
+	golang.org/x/sync v0.21.0 // indirect
 	golang.org/x/sys v0.45.0 // indirect
-	golang.org/x/tools v0.44.0 // indirect
+	golang.org/x/tools v0.45.0 // indirect
 )
 
 go 1.25.0

go.sum

@@ -68,21 +68,21 @@ github.com/zclconf/go-cty v1.18.1/go.mod h1:qpnV6EDNgC1sns/AleL1fvatHw72j+S+nS+M
 github.com/zclconf/go-cty-debug v0.0.0-20240509010212-0d6042c53940 h1:4r45xpDWB6ZMSMNJFMOjqrGHynW3DIBuR2H9j0ug+Mo=
 github.com/zclconf/go-cty-debug v0.0.0-20240509010212-0d6042c53940/go.mod h1:CmBdvvj3nqzfzJ6nTCIwDTPZ56aVGvDrmztiO5g3qrM=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
-go.yaml.in/yaml/v4 v4.0.0-rc.4 h1:UP4+v6fFrBIb1l934bDl//mmnoIZEDK0idg1+AIvX5U=
-go.yaml.in/yaml/v4 v4.0.0-rc.4/go.mod h1:aZqd9kCMsGL7AuUv/m/PvWLdg5sjJsZ4oHDEnfPPfY0=
+go.yaml.in/yaml/v4 v4.0.0-rc.5 h1:JVliQq9EGOYaTgMi+k8BhUJyqcGk4ZqeuiN1Cirba9c=
+go.yaml.in/yaml/v4 v4.0.0-rc.5/go.mod h1:aZqd9kCMsGL7AuUv/m/PvWLdg5sjJsZ4oHDEnfPPfY0=
 golang.org/x/mod v0.36.0 h1:JJjpVx6myfUsUdAzZuOSTTmRE0PfZeNWzzvKrP7amb4=
 golang.org/x/mod v0.36.0/go.mod h1:moc6ELqsWcOw5Ef3xVprK5ul/MvtVvkIXLziUOICjUQ=
 golang.org/x/net v0.55.0 h1:bcvxaJn3e1U6InsFWt1JUq1aSjnRxLzT2rtD2KfkDF8=
 golang.org/x/net v0.55.0/go.mod h1:L5U2KuzuOe1lY7Z+aWVIKK6qEeJXnXV9yzGA+WCHJww=
-golang.org/x/sync v0.20.0 h1:e0PTpb7pjO8GAtTs2dQ6jYa5BWYlMuX047Dco/pItO4=
-golang.org/x/sync v0.20.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
+golang.org/x/sync v0.21.0 h1:HLII4xRRTtCRkxYp4HNFF0Js/Og6q2i++KXbg0gHCwM=
+golang.org/x/sync v0.21.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.45.0 h1:dO4czNzziLiiXplLQgBCEpCvXQ3dnkn0SdaZSYdQ+FY=
 golang.org/x/sys v0.45.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
-golang.org/x/text v0.37.0 h1:Cqjiwd9eSg8e0QAkyCaQTNHFIIzWtidPahFWR83rTrc=
-golang.org/x/text v0.37.0/go.mod h1:a5sjxXGs9hsn/AJVwuElvCAo9v8QYLzvavO5z2PiM38=
-golang.org/x/tools v0.44.0 h1:UP4ajHPIcuMjT1GqzDWRlalUEoY+uzoZKnhOjbIPD2c=
-golang.org/x/tools v0.44.0/go.mod h1:KA0AfVErSdxRZIsOVipbv3rQhVXTnlU6UhKxHd1seDI=
+golang.org/x/text v0.38.0 h1:sXmwo9DwP3OK9EZ7PqAdaooSGozfl/3a6/xJcbzPRhE=
+golang.org/x/text v0.38.0/go.mod h1:YXZt3QhHUKYT53r2lLKFIVi6Ao1jdzrTR/KQ09qyxF4=
+golang.org/x/tools v0.45.0 h1:18qN3FAooORvApf5XjCXgsuayZOEtXf6JK18I3+ONa8=
+golang.org/x/tools v0.45.0/go.mod h1:LuUGqqaXcXMEFEruIVJVm5mgDD8vww/z/SR1gQ4uE/0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

pkg/yqlib/candidate_node.go

@@ -46,7 +46,11 @@ const (
 func createStringScalarNode(stringValue string) *CandidateNode {
 	var node = &CandidateNode{Kind: ScalarNode}
 	node.Value = stringValue
-	node.Tag = "!!str"
+	if stringValue == "<<" {
+		node.Tag = "!!merge"
+	} else {
+		node.Tag = "!!str"
+	}
 	return node
 }
 

pkg/yqlib/candidate_node_test.go

@@ -106,6 +106,31 @@ func TestCreateScalarNodeScenarios(t *testing.T) {
 	}
 }
 
+type createStringScalarNodeScenario struct {
+	stringValue string
+	expectedTag string
+}
+
+var createStringScalarNodeScenarios = []createStringScalarNodeScenario{
+	{
+		stringValue: "yourKey",
+		expectedTag: "!!str",
+	},
+	{
+		stringValue: "<<",
+		expectedTag: "!!merge",
+	},
+}
+
+func TestCreateStringScalarNodeScenarios(t *testing.T) {
+	for _, tt := range createStringScalarNodeScenarios {
+		actual := createStringScalarNode(tt.stringValue)
+		test.AssertResultWithContext(t, tt.stringValue, actual.Value, fmt.Sprintf("Value for: %v", tt.stringValue))
+		test.AssertResultWithContext(t, tt.expectedTag, actual.Tag, fmt.Sprintf("Tag for: %v", tt.stringValue))
+		test.AssertResultWithContext(t, ScalarNode, actual.Kind, fmt.Sprintf("Kind for: %v", tt.stringValue))
+	}
+}
+
 func TestGetKeyForMapValue(t *testing.T) {
 	key := createStringScalarNode("yourKey")
 	n := CandidateNode{Key: key, Value: "meow", document: 3}

pkg/yqlib/doc/operators/anchor-and-alias-operators.md

@@ -2,7 +2,7 @@
 
 Use the `alias` and `anchor` operators to read and write yaml aliases and anchors. The `explode` operator normalises a yaml file (dereference (or expands) aliases and remove anchor names).
 
-`yq` supports merge aliases (like `<<: *blah`) however this is no longer in the standard yaml spec (1.2) and so `yq` will automatically add the `!!merge` tag to these nodes as it is effectively a custom tag.
+`yq` supports merge keys (like `<<: *blah`) from YAML 1.1. These are no longer part of the YAML 1.2 standard, but remain common in practice. Plain `<<:` keys are recognised as merge keys and round-trip as `<<:` without an explicit `!!merge` tag. When the source uses an explicit `!!merge` tag, that is preserved on output. Internally, when `yq` synthesises a `<<` map key (for example during merge operations), it tags the key as `!!merge` rather than `!!str`.
 
 
 ## NOTE --yaml-fix-merge-anchor-to-spec flag
@@ -32,7 +32,7 @@ Given a sample.yml file of:
   r: 10
 - &SMALL
   r: 1
-- !!merge <<: *CENTRE
+- <<: *CENTRE
   r: 10
 ```
 then
@@ -213,10 +213,10 @@ item_value: &item_value
   value: true
 thingOne:
   name: item_1
-  !!merge <<: *item_value
+  <<: *item_value
 thingTwo:
   name: item_2
-  !!merge <<: *item_value
+  <<: *item_value
 ```
 then
 ```bash
@@ -231,7 +231,7 @@ thingOne:
   value: false
 thingTwo:
   name: item_2
-  !!merge <<: *item_value
+  <<: *item_value
 ```
 
 ## LEGACY: Explode with merge anchors
@@ -249,13 +249,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -298,7 +298,7 @@ Given a sample.yml file of:
   r: 10
 - &SMALL
   r: 1
-- !!merge <<:
+- <<:
     - *CENTRE
     - *BIG
 ```
@@ -328,7 +328,7 @@ Given a sample.yml file of:
   r: 10
 - &SMALL
   r: 1
-- !!merge <<:
+- <<:
     - *BIG
     - *LEFT
     - *SMALL
@@ -361,13 +361,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -411,7 +411,7 @@ Given a sample.yml file of:
   r: 10
 - &SMALL
   r: 1
-- !!merge <<:
+- <<:
     - *CENTRE
     - *BIG
 ```
@@ -442,7 +442,7 @@ Given a sample.yml file of:
   r: 10
 - &SMALL
   r: 1
-- !!merge <<:
+- <<:
     - *BIG
     - *LEFT
     - *SMALL
@@ -467,7 +467,7 @@ Given a sample.yml file of:
 ```yaml
 a:
   b: &b 42
-!!merge <<:
+<<:
   c: *b
 ```
 then

pkg/yqlib/doc/operators/divide.md

@@ -55,7 +55,7 @@ yq '.a = .a / 0 | .b = .b / 0' sample.yml
 ```
 will output
 ```yaml
-a: !!float +Inf
-b: !!float -Inf
+a: +Inf
+b: -Inf
 ```
 

pkg/yqlib/doc/operators/headers/anchor-and-alias-operators.md

@@ -2,7 +2,7 @@
 
 Use the `alias` and `anchor` operators to read and write yaml aliases and anchors. The `explode` operator normalises a yaml file (dereference (or expands) aliases and remove anchor names).
 
-`yq` supports merge aliases (like `<<: *blah`) however this is no longer in the standard yaml spec (1.2) and so `yq` will automatically add the `!!merge` tag to these nodes as it is effectively a custom tag.
+`yq` supports merge keys (like `<<: *blah`) from YAML 1.1. These are no longer part of the YAML 1.2 standard, but remain common in practice. Plain `<<:` keys are recognised as merge keys and round-trip as `<<:` without an explicit `!!merge` tag. When the source uses an explicit `!!merge` tag, that is preserved on output. Internally, when `yq` synthesises a `<<` map key (for example during merge operations), it tags the key as `!!merge` rather than `!!str`.
 
 
 ## NOTE --yaml-fix-merge-anchor-to-spec flag

pkg/yqlib/doc/operators/modulo.md

@@ -34,7 +34,7 @@ yq '.a = .a % .b' sample.yml
 ```
 will output
 ```yaml
-a: !!float 2
+a: 2
 b: 2.5
 ```
 
@@ -69,7 +69,7 @@ yq '.a = .a % .b' sample.yml
 ```
 will output
 ```yaml
-a: !!float NaN
+a: NaN
 b: 0
 ```
 

pkg/yqlib/doc/operators/multiply-merge.md

@@ -471,13 +471,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -487,7 +487,7 @@ yq '.foobar * .foobarList' sample.yml
 will output
 ```yaml
 c: foobarList_c
-!!merge <<:
+<<:
   - *foo
   - *bar
 thing: foobar_thing

pkg/yqlib/doc/operators/recursive-descent-glob.md

@@ -131,13 +131,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -147,7 +147,7 @@ yq '.foobar | [..]' sample.yml
 will output
 ```yaml
 - c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 - foobar_c
 - *foo

pkg/yqlib/doc/operators/traverse-read.md

@@ -294,13 +294,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -325,13 +325,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -376,13 +376,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -409,13 +409,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -442,13 +442,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -477,13 +477,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -513,13 +513,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -546,13 +546,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -579,13 +579,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then
@@ -614,13 +614,13 @@ bar: &bar
   c: bar_c
 foobarList:
   b: foobarList_b
-  !!merge <<:
+  <<:
     - *foo
     - *bar
   c: foobarList_c
 foobar:
   c: foobar_c
-  !!merge <<: *foo
+  <<: *foo
   thing: foobar_thing
 ```
 then

pkg/yqlib/goccy_yaml_test.go

@@ -230,8 +230,7 @@ var goccyYamlFormatScenarios = []formatScenario{
 		description: "merge anchor",
 		skipDoc:     true,
 		input:       "a: &remember\n  c: mike\nb:\n  <<: *remember",
-		// fine to have !!merge as that's what the current impl does
-		expected: "a: &remember\n  c: mike\nb:\n  !!merge <<: *remember\n",
+		expected:    "a: &remember\n  c: mike\nb:\n  <<: *remember\n",
 	},
 	{
 		description: "custom tag",

pkg/yqlib/lib_test.go

@@ -24,7 +24,7 @@ type parseSnippetScenario struct {
 var parseSnippetScenarios = []parseSnippetScenario{
 	{
 		snippet:       ":",
-		expectedError: "yaml: while parsing a block mapping at <unknown position>: did not find expected key",
+		expectedError: "go-yaml load error in parser (while parsing a block mapping) at L1.C1: did not find expected key",
 	},
 	{
 		snippet: "",

pkg/yqlib/operator_anchors_aliases_test.go

@@ -31,7 +31,7 @@ thingOne:
     value: false
 thingTwo:
     name: item_2
-    !!merge <<: *item_value
+    <<: *item_value
 `
 
 var explodeMergeAnchorsFixedExpected = `D0, P[], (!!map)::foo:
@@ -311,7 +311,63 @@ var badAnchorOperatorScenarios = []expressionScenario{
 	},
 }
 
+var mixedMergeTagStyleDocument = `
+constants:
+    errorResponse: &errorResponse
+        status: 200
+endpoints:
+    - condition: true
+      !!merge <<: *errorResponse
+    - condition: false
+      <<: *errorResponse
+other:
+    !!merge <<: *errorResponse
+somethingElse:
+    <<: *errorResponse
+`
+
+var mixedMergeTagStyleExplodedDocument = `
+constants:
+    errorResponse:
+        status: 200
+endpoints:
+    - condition: true
+      status: 200
+    - condition: false
+      status: 200
+other:
+    status: 200
+somethingElse:
+    status: 200
+`
+
 var anchorOperatorScenarios = []expressionScenario{
+	{
+		// mergeObjects previously skipped all !!merge-tagged nodes. Since !!merge only appears on
+		// << map keys, this meant applyAssignment was never called for the << key. It was later
+		// autocreated by createStringScalarNode("<<") with tag !!str, silently dropping !!merge.
+		// DontFollowAlias:true already prevents aliases being followed, so the skip was redundant.
+		// Old (buggy) output: "D0, P[], (!!map)::base: &base\n    x: 1\ndest:\n    <<: *base\n"
+		skipDoc:     true,
+		description: "direct *+ preserves explicit !!merge tag on << key (regression for issue 2677)",
+		document:    "base: &base\n    x: 1\ndest:\n    !!merge <<: *base\n",
+		expression:  `. as $d | {} *+ $d`,
+		expected:    []string{"D0, P[], (!!map)::base: &base\n    x: 1\ndest:\n    !!merge <<: *base\n"},
+	},
+	{
+		skipDoc:     true,
+		description: "explicit !!merge tag on << key is preserved through ireduce merge",
+		document:    mixedMergeTagStyleDocument,
+		expression:  `. as $item ireduce ({}; . *+ $item)`,
+		expected:    []string{"D0, P[], (!!map)::" + mixedMergeTagStyleDocument},
+	},
+	{
+		skipDoc:     true,
+		description: "explode expands << merge keys regardless of explicit tag style (!!merge or plain)",
+		document:    mixedMergeTagStyleDocument,
+		expression:  `explode(.)`,
+		expected:    []string{"D0, P[], (!!map)::" + mixedMergeTagStyleExplodedDocument},
+	},
 	{
 		skipDoc:     true,
 		description: "merge anchor to alias alias",

pkg/yqlib/operator_divide_test.go

@@ -45,7 +45,7 @@ var divideOperatorScenarios = []expressionScenario{
 		document:       `{a: 1, b: -1}`,
 		expression:     `.a = .a / 0 | .b = .b / 0`,
 		expected: []string{
-			"D0, P[], (!!map)::{a: !!float +Inf, b: !!float -Inf}\n",
+			"D0, P[], (!!map)::{a: +Inf, b: -Inf}\n",
 		},
 	},
 	{

pkg/yqlib/operator_load_test.go

@@ -77,7 +77,7 @@ var loadScenarios = []expressionScenario{
 		document:       `{something: {file: "thing.yml"}, over: {here: [{file: "thing.yml"}]}}`,
 		expression:     `(.. | select(has("file"))) |= load("../../examples/" + .file)`,
 		expected: []string{
-			"D0, P[], (!!map)::{something: {a: apple is included, b: cool.}, over: {here: [{a: apple is included, b: cool.}]}}\n",
+			"D0, P[], (!!map)::{something: {a: apple is included, b: cool.}, over: {here: [{a: apple is included,\n                b: cool.}]}}\n",
 		},
 	},
 	{

pkg/yqlib/operator_modulo_test.go

@@ -37,7 +37,7 @@ var moduloOperatorScenarios = []expressionScenario{
 		document:       `{a: 12, b: 2.5}`,
 		expression:     `.a = .a % .b`,
 		expected: []string{
-			"D0, P[], (!!map)::{a: !!float 2, b: 2.5}\n",
+			"D0, P[], (!!map)::{a: 2, b: 2.5}\n",
 		},
 	},
 	{
@@ -53,7 +53,7 @@ var moduloOperatorScenarios = []expressionScenario{
 		document:       `{a: 1.1, b: 0}`,
 		expression:     `.a = .a % .b`,
 		expected: []string{
-			"D0, P[], (!!map)::{a: !!float NaN, b: 0}\n",
+			"D0, P[], (!!map)::{a: NaN, b: 0}\n",
 		},
 	},
 	{
@@ -70,7 +70,7 @@ var moduloOperatorScenarios = []expressionScenario{
 		document:   "a: 2\nb: !goat 2.3",
 		expression: `.a = .a % .b`,
 		expected: []string{
-			"D0, P[], (!!map)::a: !!float 2\nb: !goat 2.3\n",
+			"D0, P[], (!!map)::a: 2\nb: !goat 2.3\n",
 		},
 	},
 	{

pkg/yqlib/operator_multiply.go

@@ -189,10 +189,6 @@ func mergeObjects(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs
 
 		log.Debugf("going to applied assignment to LHS: %v with RHS: %v", NodeToString(lhs), NodeToString(candidate))
 
-		if candidate.Tag == "!!merge" {
-			continue
-		}
-
 		err := applyAssignment(d, context, pathIndexToStartFrom, lhs, candidate, preferences)
 		if err != nil {
 			return nil, err

pkg/yqlib/operator_multiply_test.go

@@ -121,7 +121,7 @@ var multiplyOperatorScenarios = []expressionScenario{
 		document:   mergeArrayWithAnchors,
 		expression: `. * .`,
 		expected: []string{
-			"D0, P[], (!!map)::sample:\n    - &a\n    - !!merge <<: *a\n",
+			"D0, P[], (!!map)::sample:\n    - &a\n    - <<: *a\n",
 		},
 	},
 	{
@@ -514,7 +514,7 @@ var multiplyOperatorScenarios = []expressionScenario{
 		environmentVariables: map[string]string{"originalPath": ".myArray", "otherPath": ".newArray", "idPath": ".a"},
 		expression:           mergeExpression,
 		expected: []string{
-			"D0, P[], (!!map)::{myArray: [{a: apple, b: appleB2}, {a: kiwi, b: kiwiB}, {a: banana, b: bananaB, c: bananaC}, {a: dingo, c: dingoC}], something: else}\n",
+			"D0, P[], (!!map)::{myArray: [{a: apple, b: appleB2}, {a: kiwi, b: kiwiB}, {a: banana, b: bananaB, c: bananaC},\n        {a: dingo, c: dingoC}], something: else}\n",
 		},
 	},
 	{
@@ -546,7 +546,7 @@ var multiplyOperatorScenarios = []expressionScenario{
 		document:    mergeDocSample,
 		expression:  `.foobar * .foobarList`,
 		expected: []string{
-			"D0, P[foobar], (!!map)::c: foobarList_c\n!!merge <<: [*foo, *bar]\nthing: foobar_thing\nb: foobarList_b\n",
+			"D0, P[foobar], (!!map)::c: foobarList_c\n<<: [*foo, *bar]\nthing: foobar_thing\nb: foobarList_b\n",
 		},
 	},
 	{
@@ -554,7 +554,7 @@ var multiplyOperatorScenarios = []expressionScenario{
 		document:   document,
 		expression: `.b * .c`,
 		expected: []string{
-			"D0, P[b], (!!map)::{name: dog, \"<<\": *cat}\n",
+			"D0, P[b], (!!map)::{name: dog, <<: *cat}\n",
 		},
 	},
 	{
@@ -581,7 +581,7 @@ var multiplyOperatorScenarios = []expressionScenario{
 		document:    "a: 2\nb: !goat 3.5",
 		expression:  ".a = .a * .b",
 		expected: []string{
-			"D0, P[], (!!map)::a: !!float 7\nb: !goat 3.5\n",
+			"D0, P[], (!!map)::a: 7\nb: !goat 3.5\n",
 		},
 	},
 	{

pkg/yqlib/operator_recursive_descent_test.go

@@ -187,7 +187,7 @@ var recursiveDescentOperatorScenarios = []expressionScenario{
 		document:    mergeDocSample,
 		expression:  `.foobar | [..]`,
 		expected: []string{
-			"D0, P[foobar], (!!seq)::- c: foobar_c\n  !!merge <<: *foo\n  thing: foobar_thing\n- foobar_c\n- *foo\n- foobar_thing\n",
+			"D0, P[foobar], (!!seq)::- c: foobar_c\n  <<: *foo\n  thing: foobar_thing\n- foobar_c\n- *foo\n- foobar_thing\n",
 		},
 	},
 	{
@@ -195,7 +195,7 @@ var recursiveDescentOperatorScenarios = []expressionScenario{
 		document:   mergeDocSample,
 		expression: `.foobar | [...]`,
 		expected: []string{
-			"D0, P[foobar], (!!seq)::- c: foobar_c\n  !!merge <<: *foo\n  thing: foobar_thing\n- c\n- foobar_c\n- !!merge <<\n- *foo\n- thing\n- foobar_thing\n",
+			"D0, P[foobar], (!!seq)::- c: foobar_c\n  <<: *foo\n  thing: foobar_thing\n- c\n- foobar_c\n- <<\n- *foo\n- thing\n- foobar_thing\n",
 		},
 	},
 	{
@@ -203,7 +203,7 @@ var recursiveDescentOperatorScenarios = []expressionScenario{
 		document:   mergeDocSample,
 		expression: `.foobarList | ..`,
 		expected: []string{
-			"D0, P[foobarList], (!!map)::b: foobarList_b\n!!merge <<: [*foo, *bar]\nc: foobarList_c\n",
+			"D0, P[foobarList], (!!map)::b: foobarList_b\n<<: [*foo, *bar]\nc: foobarList_c\n",
 			"D0, P[foobarList b], (!!str)::foobarList_b\n",
 			"D0, P[foobarList <<], (!!seq)::[*foo, *bar]\n",
 			"D0, P[foobarList << 0], (alias)::*foo\n",
@@ -216,7 +216,7 @@ var recursiveDescentOperatorScenarios = []expressionScenario{
 		document:   mergeDocSample,
 		expression: `.foobarList | ...`,
 		expected: []string{
-			"D0, P[foobarList], (!!map)::b: foobarList_b\n!!merge <<: [*foo, *bar]\nc: foobarList_c\n",
+			"D0, P[foobarList], (!!map)::b: foobarList_b\n<<: [*foo, *bar]\nc: foobarList_c\n",
 			"D0, P[foobarList b], (!!str)::b\n",
 			"D0, P[foobarList b], (!!str)::foobarList_b\n",
 			"D0, P[foobarList <<], (!!merge)::<<\n",

pkg/yqlib/operator_select_test.go

@@ -98,7 +98,7 @@ var selectOperatorScenarios = []expressionScenario{
 		document:    `[{animal: cat, legs: {cool: true}}, {animal: fish}]`,
 		expression:  `(.[] | select(.legs.cool == true).canWalk) = true | (.[] | .alive.things) = "yes"`,
 		expected: []string{
-			"D0, P[], (!!seq)::[{animal: cat, legs: {cool: true}, canWalk: true, alive: {things: yes}}, {animal: fish, alive: {things: yes}}]\n",
+			"D0, P[], (!!seq)::[{animal: cat, legs: {cool: true}, canWalk: true, alive: {things: yes}}, {animal: fish,\n        alive: {things: yes}}]\n",
 		},
 	},
 	{

pkg/yqlib/operator_sort_keys_test.go

@@ -37,7 +37,7 @@ var sortKeysOperatorScenarios = []expressionScenario{
 		document:       `{bParent: {c: dog, array: [3,1,2]}, aParent: {z: donkey, x: [{c: yum, b: delish}, {b: ew, a: apple}]}}`,
 		expression:     `sort_keys(..)`,
 		expected: []string{
-			"D0, P[], (!!map)::{aParent: {x: [{b: delish, c: yum}, {a: apple, b: ew}], z: donkey}, bParent: {array: [3, 1, 2], c: dog}}\n",
+			"D0, P[], (!!map)::{aParent: {x: [{b: delish, c: yum}, {a: apple, b: ew}], z: donkey}, bParent: {array: [\n            3, 1, 2], c: dog}}\n",
 		},
 	},
 }

pkg/yqlib/operator_style_test.go

@@ -50,7 +50,7 @@ var styleOperatorScenarios = []expressionScenario{
 		document:   "bing: &foo {x: z}\na:\n  c: cat\n  <<: [*foo]",
 		expression: `(... | select(tag=="!!str")) style="single"`,
 		expected: []string{
-			"D0, P[], (!!map)::'bing': &foo {'x': 'z'}\n'a':\n    'c': 'cat'\n    !!merge <<: [*foo]\n",
+			"D0, P[], (!!map)::'bing': &foo {'x': 'z'}\n'a':\n    'c': 'cat'\n    <<: [*foo]\n",
 		},
 	},
 	{

pkg/yqlib/operator_traverse_path_test.go

@@ -494,7 +494,7 @@ var traversePathOperatorScenarios = []expressionScenario{
 		document:   mergeDocSample,
 		expression: `.foobar`,
 		expected: []string{
-			"D0, P[foobar], (!!map)::c: foobar_c\n!!merge <<: *foo\nthing: foobar_thing\n",
+			"D0, P[foobar], (!!map)::c: foobar_c\n<<: *foo\nthing: foobar_thing\n",
 		},
 	},
 	{
@@ -518,7 +518,7 @@ var traversePathOperatorScenarios = []expressionScenario{
 		document:   mergeDocSample,
 		expression: `.foobarList`,
 		expected: []string{
-			"D0, P[foobarList], (!!map)::b: foobarList_b\n!!merge <<: [*foo, *bar]\nc: foobarList_c\n",
+			"D0, P[foobarList], (!!map)::b: foobarList_b\n<<: [*foo, *bar]\nc: foobarList_c\n",
 		},
 	},
 	{