diff --git a/docs/content/docs/guide/authoringprs.md b/docs/content/docs/guide/authoringprs.md
index 267e74eef8..ddc0937e8b 100644
--- a/docs/content/docs/guide/authoringprs.md
+++ b/docs/content/docs/guide/authoringprs.md
@@ -187,6 +187,77 @@ for example, this will show the GitHub event type for a GitHub event:
 
 and then you can do the same conditional or access as described above for the `body` keyword.
 
+## Using the cel: prefix for advanced CEL expressions
+
+For more complex CEL expressions that go beyond simple property access, you can
+use the `cel:` prefix. This allows you to write arbitrary CEL expressions with
+access to all available data sources.
+
+The `cel:` prefix provides access to:
+
+- `body` - The full webhook payload
+- `headers` - HTTP request headers
+- `files` - Changed files information (`files.all`, `files.added`, `files.deleted`, `files.modified`, `files.renamed`)
+- `pac` - Standard PAC parameters (`pac.revision`, `pac.target_branch`, `pac.source_branch`, etc.)
+
+### Examples
+
+**Conditional values based on event action:**
+
+```yaml
+params:
+  - name: pr-status
+    value: "{{ cel: body.action == \"opened\" ? \"new-pr\" : \"updated-pr\" }}"
+```
+
+**Environment selection based on target branch:**
+
+```yaml
+params:
+  - name: environment
+    value: "{{ cel: pac.target_branch == \"main\" ? \"production\" : \"staging\" }}"
+```
+
+**Safe field access with has() function:**
+
+Use the `has()` function to safely check if a field exists before accessing it:
+
+```yaml
+params:
+  - name: commit-type
+    value: "{{ cel: has(body.head_commit) && body.head_commit.message.startsWith(\"Merge\") ? \"merge\" : \"regular\" }}"
+```
+
+**Check if Go files were modified:**
+
+```yaml
+params:
+  - name: run-go-tests
+    value: "{{ cel: files.all.exists(f, f.endsWith(\".go\")) ? \"true\" : \"false\" }}"
+```
+
+**String concatenation:**
+
+```yaml
+params:
+  - name: greeting
+    value: "{{ cel: \"Build for \" + pac.repo_name + \" on \" + pac.target_branch }}"
+```
+
+**Count changed files:**
+
+```yaml
+params:
+  - name: file-count
+    value: "{{ cel: files.all.size() }}"
+```
+
+{{< hint info >}}
+If a `cel:` expression has a syntax error or fails to evaluate, it returns an
+empty string. This allows PipelineRuns to continue even if an optional dynamic
+value cannot be computed.
+{{< /hint >}}
+
 ## Using the temporary GitHub APP Token for GitHub API operations
 
 You can use the temporary installation token that is generated by Pipelines as
diff --git a/pkg/cel/cel.go b/pkg/cel/cel.go
index 320a431528..8f8a4aa583 100644
--- a/pkg/cel/cel.go
+++ b/pkg/cel/cel.go
@@ -1,6 +1,7 @@
 package cel
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 
@@ -38,14 +39,29 @@ func evaluate(expr string, env *cel.Env, data map[string]any) (ref.Val, error) {
 // / pacParams, it will output a Cel value or an error if selectedjm.
 func Value(query string, body any, headers, pacParams map[string]string, changedFiles map[string]any) (ref.Val, error) {
 	// Marshal/Unmarshal the body to a map[string]any so we can access it from the CEL
-	nbody, err := json.Marshal(body)
-	if err != nil {
-		return nil, err
-	}
 	var jsonMap map[string]any
-	err = json.Unmarshal(nbody, &jsonMap)
-	if err != nil {
-		return nil, err
+	switch b := body.(type) {
+	case nil:
+		jsonMap = map[string]any{}
+	case map[string]any:
+		jsonMap = b
+	default:
+		nbody, err := json.Marshal(body)
+		if err != nil {
+			return nil, err
+		}
+		trimmed := bytes.TrimSpace(nbody)
+		if len(trimmed) == 0 || bytes.Equal(trimmed, []byte("null")) {
+			jsonMap = map[string]any{}
+		} else {
+			err = json.Unmarshal(nbody, &jsonMap)
+			if err != nil {
+				return nil, err
+			}
+			if jsonMap == nil {
+				jsonMap = map[string]any{}
+			}
+		}
 	}
 
 	mapStrDyn := types.NewMapType(types.StringType, types.DynType)
diff --git a/pkg/cel/cel_test.go b/pkg/cel/cel_test.go
index 1a9a86ff48..1159188af4 100644
--- a/pkg/cel/cel_test.go
+++ b/pkg/cel/cel_test.go
@@ -39,6 +39,11 @@ func TestValue(t *testing.T) {
 	assert.NilError(t, err)
 	assert.Equal(t, ref.Val(val), val)
 
+	// Test pac-only query with nil body
+	val, err = Value("pac.param", nil, headers, pacParams, changedFiles)
+	assert.NilError(t, err)
+	assert.Equal(t, val.Value(), "value")
+
 	// Test an invalid query
 	_, err = Value("invalid query", body, headers, pacParams, changedFiles)
 	assert.ErrorContains(t, err, "failed to parse expression")
diff --git a/pkg/templates/templating.go b/pkg/templates/templating.go
index 24c280c3cb..63c0cf8510 100644
--- a/pkg/templates/templating.go
+++ b/pkg/templates/templating.go
@@ -27,10 +27,12 @@ var (
 // value.
 //
 // The function first checks if the key in the placeholder has a prefix of
-// "body", "headers", or "files". If it does and both `rawEvent` and `headers`
+// "body", "headers", "files", or "cel:". If it does and both `rawEvent` and `headers`
 // are not nil, it attempts to retrieve the value for the key using the
 // `cel.Value` function and returns the corresponding string
-// representation. If the key does not have any of the mentioned prefixes, the
+// representation. The "cel:" prefix allows evaluating arbitrary CEL expressions
+// with access to body, headers, files, and pac (standard PAC parameters) namespaces.
+// If the key does not have any of the mentioned prefixes, the
 // function checks if the key exists in the `dico` map. If it does, the
 // function replaces the placeholder with the corresponding value from the
 // `dico` map.
@@ -52,10 +54,18 @@ func ReplacePlaceHoldersVariables(template string, dico map[string]string, rawEv
 	return keys.ParamsRe.ReplaceAllStringFunc(template, func(s string) string {
 		parts := keys.ParamsRe.FindStringSubmatch(s)
 		key := strings.TrimSpace(parts[1])
-		if strings.HasPrefix(key, "body") || strings.HasPrefix(key, "headers") || strings.HasPrefix(key, "files") {
+
+		// Check for cel: prefix first - it allows arbitrary CEL expressions
+		isCelExpr := strings.HasPrefix(key, "cel:")
+
+		if strings.HasPrefix(key, "body") || strings.HasPrefix(key, "headers") || strings.HasPrefix(key, "files") || isCelExpr {
 			// Check specific requirements for each prefix
 			canEvaluate := false
+			celExpr := key
 			switch {
+			case isCelExpr:
+				canEvaluate = true
+				celExpr = strings.TrimSpace(strings.TrimPrefix(key, "cel:"))
 			case strings.HasPrefix(key, "body") && rawEvent != nil:
 				canEvaluate = true
 			case strings.HasPrefix(key, "headers") && headers != nil:
@@ -70,8 +80,17 @@ func ReplacePlaceHoldersVariables(template string, dico map[string]string, rawEv
 				for k, v := range headers {
 					headerMap[k] = v[0]
 				}
-				val, err := cel.Value(key, rawEvent, headerMap, map[string]string{}, changedFiles)
+				// For cel: prefix, pass dico as pacParams so pac.* variables are available
+				pacParams := map[string]string{}
+				if isCelExpr {
+					pacParams = dico
+				}
+				val, err := cel.Value(celExpr, rawEvent, headerMap, pacParams, changedFiles)
 				if err != nil {
+					// For cel: prefix, return empty string on error
+					if isCelExpr {
+						return ""
+					}
 					return s
 				}
 				var raw any
diff --git a/pkg/templates/templating_test.go b/pkg/templates/templating_test.go
index 29770d0b49..00122c4208 100644
--- a/pkg/templates/templating_test.go
+++ b/pkg/templates/templating_test.go
@@ -286,6 +286,255 @@ func TestReplacePlaceHoldersVariablesJSONOutput(t *testing.T) {
 	}
 }
 
+func TestReplacePlaceHoldersVariablesCelPrefix(t *testing.T) {
+	tests := []struct {
+		name         string
+		template     string
+		expected     string
+		dicto        map[string]string
+		headers      http.Header
+		changedFiles map[string]any
+		rawEvent     any
+	}{
+		{
+			name:         "cel: prefix with simple body access",
+			template:     `result: {{ cel: body.hello }}`,
+			expected:     `result: world`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]string{
+				"hello": "world",
+			},
+		},
+		{
+			name:         "cel: prefix with ternary expression",
+			template:     `status: {{ cel: body.action == "opened" ? "new-pr" : "updated-pr" }}`,
+			expected:     `status: new-pr`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]any{
+				"action": "opened",
+			},
+		},
+		{
+			name:         "cel: prefix with ternary expression - else branch",
+			template:     `status: {{ cel: body.action == "opened" ? "new-pr" : "updated-pr" }}`,
+			expected:     `status: updated-pr`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]any{
+				"action": "synchronize",
+			},
+		},
+		{
+			name:     "cel: prefix with pac namespace access",
+			template: `branch: {{ cel: pac.target_branch }}`,
+			expected: `branch: main`,
+			dicto: map[string]string{
+				"target_branch": "main",
+			},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent:     map[string]any{},
+		},
+		{
+			name:     "cel: prefix with pac namespace conditional",
+			template: `env: {{ cel: pac.target_branch == "main" ? "production" : "staging" }}`,
+			expected: `env: production`,
+			dicto: map[string]string{
+				"target_branch": "main",
+			},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent:     map[string]any{},
+		},
+		{
+			name:     "cel: prefix with pac namespace - staging branch",
+			template: `env: {{ cel: pac.target_branch == "main" ? "production" : "staging" }}`,
+			expected: `env: staging`,
+			dicto: map[string]string{
+				"target_branch": "develop",
+			},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent:     map[string]any{},
+		},
+		{
+			name:         "cel: prefix with has() function",
+			template:     `has_field: {{ cel: has(body.optional_field) ? body.optional_field : "default" }}`,
+			expected:     `has_field: custom_value`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]any{
+				"optional_field": "custom_value",
+			},
+		},
+		{
+			name:         "cel: prefix with has() function - field missing",
+			template:     `has_field: {{ cel: has(body.optional_field) ? body.optional_field : "default" }}`,
+			expected:     `has_field: default`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent:     map[string]any{},
+		},
+		{
+			name:     "cel: prefix with files access",
+			template: `go_files: {{ cel: files.all.exists(f, f.endsWith(".go")) ? "yes" : "no" }}`,
+			expected: `go_files: yes`,
+			dicto:    map[string]string{},
+			changedFiles: map[string]any{
+				"all": []string{"main.go", "README.md"},
+			},
+			headers:  http.Header{},
+			rawEvent: map[string]any{},
+		},
+		{
+			name:     "cel: prefix with files access - no go files",
+			template: `go_files: {{ cel: files.all.exists(f, f.endsWith(".go")) ? "yes" : "no" }}`,
+			expected: `go_files: no`,
+			dicto:    map[string]string{},
+			changedFiles: map[string]any{
+				"all": []string{"README.md", "config.yaml"},
+			},
+			headers:  http.Header{},
+			rawEvent: map[string]any{},
+		},
+		{
+			name:         "cel: prefix with headers access",
+			template:     `event: {{ cel: headers["X-GitHub-Event"] }}`,
+			expected:     `event: push`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers: http.Header{
+				"X-GitHub-Event": []string{"push"},
+			},
+			rawEvent: map[string]any{},
+		},
+		{
+			name:         "cel: prefix with boolean result",
+			template:     `is_draft: {{ cel: body.draft == true }}`,
+			expected:     `is_draft: false`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]any{
+				"draft": false,
+			},
+		},
+		{
+			name:         "cel: prefix with invalid expression returns empty string",
+			template:     `invalid: {{ cel: invalid.syntax[ }}`,
+			expected:     `invalid: `,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent:     map[string]any{},
+		},
+		{
+			name:         "cel: prefix with evaluation error returns empty string",
+			template:     `error: {{ cel: body.nonexistent.deep.field }}`,
+			expected:     `error: `,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent:     map[string]any{},
+		},
+		{
+			name:         "cel: prefix with extra whitespace",
+			template:     `result: {{ cel:    body.hello   }}`,
+			expected:     `result: world`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]string{
+				"hello": "world",
+			},
+		},
+		{
+			name:         "cel: prefix with string concatenation",
+			template:     `greeting: {{ cel: "Hello, " + body.name + "!" }}`,
+			expected:     `greeting: Hello, World!`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]any{
+				"name": "World",
+			},
+		},
+		{
+			name:         "cel: prefix with size function",
+			template:     `count: {{ cel: body.items.size() }}`,
+			expected:     `count: 3`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]any{
+				"items": []string{"a", "b", "c"},
+			},
+		},
+		{
+			name:         "cel: prefix with complex nested conditional (merge commit detection)",
+			template:     `commit_type: {{ cel: has(body.head_commit) && body.head_commit.message.startsWith("Merge") ? "merge" : "regular" }}`,
+			expected:     `commit_type: merge`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]any{
+				"head_commit": map[string]any{
+					"message": "Merge pull request #123",
+				},
+			},
+		},
+		{
+			name:         "cel: prefix with complex nested conditional - regular commit",
+			template:     `commit_type: {{ cel: has(body.head_commit) && body.head_commit.message.startsWith("Merge") ? "merge" : "regular" }}`,
+			expected:     `commit_type: regular`,
+			dicto:        map[string]string{},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent: map[string]any{
+				"head_commit": map[string]any{
+					"message": "Fix bug in parser",
+				},
+			},
+		},
+		{
+			name:     "cel: prefix mixed with regular placeholders",
+			template: `branch: {{ target_branch }}, check: {{ cel: pac.target_branch == "main" ? "prod" : "dev" }}`,
+			expected: `branch: main, check: prod`,
+			dicto: map[string]string{
+				"target_branch": "main",
+			},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent:     map[string]any{},
+		},
+		{
+			name:         "cel: prefix with nil rawEvent still works",
+			template:     `result: {{ cel: pac.revision }}`,
+			expected:     `result: abc123`,
+			dicto:        map[string]string{"revision": "abc123"},
+			changedFiles: map[string]any{},
+			headers:      http.Header{},
+			rawEvent:     nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := ReplacePlaceHoldersVariables(tt.template, tt.dicto, tt.rawEvent, tt.headers, tt.changedFiles)
+			if d := cmp.Diff(got, tt.expected); d != "" {
+				t.Fatalf("-got, +want: %v", d)
+			}
+		})
+	}
+}
+
 func TestReplacePlaceHoldersVariablesEdgeCases(t *testing.T) {
 	tests := []struct {
 		name         string
diff --git a/test/gitea_params_test.go b/test/gitea_params_test.go
index ead963de31..c8f4143029 100644
--- a/test/gitea_params_test.go
+++ b/test/gitea_params_test.go
@@ -526,3 +526,45 @@ func TestGiteaParamsChangedFilesCEL(t *testing.T) {
 		fmt.Sprintf("tekton.dev/pipelineRun=%s,tekton.dev/pipelineTask=changed-files-push-params", sortedstatus[0].PipelineRunName),
 		"step-test-changed-files-params-push", strings.ReplaceAll(fmt.Sprintf("%s-changed-files-push-params-2.golden", t.Name()), "/", "-"), 2)
 }
+
+// TestGiteaParamsCelPrefix tests the cel: prefix for arbitrary CEL expressions.
+// The cel: prefix allows evaluating full CEL expressions with access to body, headers, files, and pac namespaces.
+func TestGiteaParamsCelPrefix(t *testing.T) {
+	topts := &tgitea.TestOpts{
+		Regexp:      successRegexp,
+		TargetEvent: "pull_request",
+		YAMLFiles: map[string]string{
+			".tekton/pr.yaml": "testdata/pipelinerun-cel-prefix-test.yaml",
+		},
+		CheckForStatus: "success",
+		ExpectEvents:   false,
+	}
+	_, f := tgitea.TestPR(t, topts)
+	defer f()
+
+	// check the repos CR only one pr should have run
+	repo, err := topts.ParamsRun.Clients.PipelineAsCode.PipelinesascodeV1alpha1().Repositories(topts.TargetNS).Get(context.Background(), topts.TargetNS, metav1.GetOptions{})
+	assert.NilError(t, err)
+	assert.Equal(t, len(repo.Status), 1, repo.Status)
+
+	// Verify cel: prefix expressions evaluated correctly
+	// Expected output:
+	// cel_ternary: new-pr (body.action == "opened" for a new PR)
+	// cel_pac_branch: matched (pac.target_branch matches the target branch)
+	// cel_has_function: has-pr (body.pull_request exists)
+	// cel_string_concat: Build on <target_branch>
+	// cel_files_check: has-files (files.all.size() > 0 since we have changed files)
+	// cel_error_handling: (empty string - cel: prefix returns empty on error)
+	// if this change you need to run that e2e test with -test.update-golden=true
+	err = twait.RegexpMatchingInPodLog(
+		context.Background(),
+		topts.ParamsRun,
+		topts.TargetNS,
+		fmt.Sprintf("tekton.dev/pipelineRun=%s,tekton.dev/pipelineTask=cel-prefix-test", repo.Status[0].PipelineRunName),
+		"step-test-cel-prefix-values",
+		regexp.Regexp{},
+		t.Name(),
+		2,
+	)
+	assert.NilError(t, err)
+}
diff --git a/test/github_pullrequest_test.go b/test/github_pullrequest_test.go
index 04241e6bf7..f51ec30dff 100644
--- a/test/github_pullrequest_test.go
+++ b/test/github_pullrequest_test.go
@@ -685,6 +685,51 @@ func TestGithubIgnoreTagPushCommitsFromSkipPushEventsSetting(t *testing.T) {
 	g.Cnx.Clients.Log.Infof("Tag %s has been deleted", tag)
 }
 
+// TestGithubPullRequestCelPrefix tests the cel: prefix for arbitrary CEL expressions.
+// The cel: prefix allows evaluating full CEL expressions with access to body, headers, files, and pac namespaces.
+func TestGithubPullRequestCelPrefix(t *testing.T) {
+	ctx := context.Background()
+	g := &tgithub.PRTest{
+		Label:     "Github CEL Prefix",
+		YamlFiles: []string{"testdata/pipelinerun-cel-prefix-github.yaml"},
+	}
+	g.RunPullRequest(ctx, t)
+	defer g.TearDown(ctx, t)
+
+	// Wait for repository status to be updated
+	waitOpts := twait.Opts{
+		RepoName:        g.TargetNamespace,
+		Namespace:       g.TargetNamespace,
+		MinNumberStatus: 1,
+		PollTimeout:     twait.DefaultTimeout,
+		TargetSHA:       g.SHA,
+	}
+	repo, err := twait.UntilRepositoryUpdated(ctx, g.Cnx.Clients, waitOpts)
+	assert.NilError(t, err)
+	assert.Assert(t, len(repo.Status) >= 1, "Expected at least one status")
+
+	// Verify cel: prefix expressions evaluated correctly using golden file
+	// Expected output:
+	// cel_ternary: new-pr (body.action == "opened" for a new PR)
+	// cel_pac_branch: matched (pac.target_branch matches the target branch)
+	// cel_has_function: has-pr (body.pull_request exists)
+	// cel_string_concat: Build on <target_branch>
+	// cel_files_check: has-files (files.all.size() > 0 since we have changed files)
+	// cel_github_header: pull_request (X-Github-Event header value)
+	// cel_error_handling: (empty string - cel: prefix returns empty on error)
+	err = twait.RegexpMatchingInPodLog(
+		ctx,
+		g.Cnx,
+		g.TargetNamespace,
+		fmt.Sprintf("tekton.dev/pipelineRun=%s,tekton.dev/pipelineTask=cel-prefix-test", repo.Status[0].PipelineRunName),
+		"step-test-cel-prefix-values",
+		regexp.Regexp{},
+		t.Name(),
+		2,
+	)
+	assert.NilError(t, err)
+}
+
 // Local Variables:
 // compile-command: "go test -tags=e2e -v -info TestGithubPullRequest$ ."
 // End:
diff --git a/test/gitlab_merge_request_test.go b/test/gitlab_merge_request_test.go
index 07132667cc..9c65321a0c 100644
--- a/test/gitlab_merge_request_test.go
+++ b/test/gitlab_merge_request_test.go
@@ -951,6 +951,96 @@ func TestGitlabConsistentCommitStatusOnMR(t *testing.T) {
 	}
 }
 
+// TestGitlabMergeRequestCelPrefix tests the cel: prefix for arbitrary CEL expressions.
+// The cel: prefix allows evaluating full CEL expressions with access to body, headers, files, and pac namespaces.
+func TestGitlabMergeRequestCelPrefix(t *testing.T) {
+	targetNS := names.SimpleNameGenerator.RestrictLengthWithRandomSuffix("pac-e2e-ns")
+	ctx := context.Background()
+	runcnx, opts, glprovider, err := tgitlab.Setup(ctx)
+	assert.NilError(t, err)
+	ctx, err = cctx.GetControllerCtxInfo(ctx, runcnx)
+	assert.NilError(t, err)
+	runcnx.Clients.Log.Info("Testing cel: prefix with GitLab")
+
+	projectinfo, resp, err := glprovider.Client().Projects.GetProject(opts.ProjectID, nil)
+	assert.NilError(t, err)
+	if resp != nil && resp.StatusCode == http.StatusNotFound {
+		t.Errorf("Repository %s not found in %s", opts.Organization, opts.Repo)
+	}
+
+	err = tgitlab.CreateCRD(ctx, projectinfo, runcnx, opts, targetNS, nil)
+	assert.NilError(t, err)
+
+	entries, err := payload.GetEntries(map[string]string{
+		".tekton/pipelinerun.yaml": "testdata/pipelinerun-cel-prefix-gitlab.yaml",
+	}, targetNS, projectinfo.DefaultBranch,
+		triggertype.PullRequest.String(), map[string]string{})
+	assert.NilError(t, err)
+
+	targetRefName := names.SimpleNameGenerator.RestrictLengthWithRandomSuffix("pac-e2e-test")
+
+	gitCloneURL, err := scm.MakeGitCloneURL(projectinfo.WebURL, opts.UserName, opts.Password)
+	assert.NilError(t, err)
+	commitTitle := "Testing cel: prefix on " + targetRefName
+	scmOpts := &scm.Opts{
+		GitURL:        gitCloneURL,
+		CommitTitle:   commitTitle,
+		Log:           runcnx.Clients.Log,
+		WebURL:        projectinfo.WebURL,
+		TargetRefName: targetRefName,
+		BaseRefName:   projectinfo.DefaultBranch,
+	}
+	_ = scm.PushFilesToRefGit(t, scmOpts, entries)
+
+	runcnx.Clients.Log.Infof("Branch %s has been created and pushed with cel: prefix test files", targetRefName)
+	mrTitle := "TestCelPrefix - " + targetRefName
+	mrID, err := tgitlab.CreateMR(glprovider.Client(), opts.ProjectID, targetRefName, projectinfo.DefaultBranch, mrTitle)
+	assert.NilError(t, err)
+	runcnx.Clients.Log.Infof("MergeRequest %s/-/merge_requests/%d has been created", projectinfo.WebURL, mrID)
+	defer tgitlab.TearDown(ctx, t, runcnx, glprovider, mrID, targetRefName, targetNS, opts.ProjectID)
+
+	sopt := twait.SuccessOpt{
+		Title:           commitTitle,
+		OnEvent:         "Merge Request",
+		TargetNS:        targetNS,
+		NumberofPRMatch: 1,
+		SHA:             "",
+	}
+	twait.Succeeded(ctx, t, runcnx, opts, sopt)
+
+	// Get the MR to fetch the SHA
+	mr, _, err := glprovider.Client().MergeRequests.GetMergeRequest(opts.ProjectID, mrID, nil)
+	assert.NilError(t, err)
+
+	// Get repository to find the pipelinerun name
+	repo, err := runcnx.Clients.PipelineAsCode.PipelinesascodeV1alpha1().Repositories(targetNS).Get(ctx, targetNS, metav1.GetOptions{})
+	assert.NilError(t, err)
+	assert.Assert(t, len(repo.Status) >= 1, "Expected at least one status, got %d", len(repo.Status))
+
+	// Verify cel: prefix expressions evaluated correctly using golden file
+	// Expected output:
+	// cel_ternary: new-mr (body.object_attributes.action == "open" for a new MR)
+	// cel_pac_branch: matched (pac.target_branch matches the target branch)
+	// cel_has_function: has-mr (body.object_attributes exists)
+	// cel_string_concat: Build on <target_branch>
+	// cel_files_check: has-files (files.all.size() > 0 since we have changed files)
+	// cel_gitlab_header: Merge Request Hook (X-Gitlab-Event header value)
+	// cel_error_handling: (empty string - cel: prefix returns empty on error)
+	err = twait.RegexpMatchingInPodLog(
+		ctx,
+		runcnx,
+		targetNS,
+		fmt.Sprintf("tekton.dev/pipelineRun=%s,tekton.dev/pipelineTask=cel-prefix-test", repo.Status[0].PipelineRunName),
+		"step-test-cel-prefix-values",
+		regexp.Regexp{},
+		t.Name(),
+		2,
+	)
+	assert.NilError(t, err)
+
+	_ = mr // use mr variable to avoid unused variable error
+}
+
 // Local Variables:
 // compile-command: "go test -tags=e2e -v -run ^TestGitlabMergeRequest$"
 // End:
diff --git a/test/testdata/TestGiteaParamsCelPrefix.golden b/test/testdata/TestGiteaParamsCelPrefix.golden
new file mode 100644
index 0000000000..91fb9b047a
--- /dev/null
+++ b/test/testdata/TestGiteaParamsCelPrefix.golden
@@ -0,0 +1,6 @@
+cel_ternary: new-pr
+cel_pac_branch: matched
+cel_has_function: has-pr
+cel_string_concat: Build on main
+cel_files_check: has-files
+cel_error_handling: 
diff --git a/test/testdata/TestGithubPullRequestCelPrefix.golden b/test/testdata/TestGithubPullRequestCelPrefix.golden
new file mode 100644
index 0000000000..93ca82c561
--- /dev/null
+++ b/test/testdata/TestGithubPullRequestCelPrefix.golden
@@ -0,0 +1,7 @@
+cel_ternary: new-pr
+cel_pac_branch: matched
+cel_has_function: has-pr
+cel_string_concat: Build on main
+cel_files_check: has-files
+cel_github_header: pull_request
+cel_error_handling: 
diff --git a/test/testdata/TestGitlabMergeRequestCelPrefix.golden b/test/testdata/TestGitlabMergeRequestCelPrefix.golden
new file mode 100644
index 0000000000..e02367b404
--- /dev/null
+++ b/test/testdata/TestGitlabMergeRequestCelPrefix.golden
@@ -0,0 +1,7 @@
+cel_ternary: new-mr
+cel_pac_branch: matched
+cel_has_function: has-mr
+cel_string_concat: Build on main
+cel_files_check: has-files
+cel_gitlab_header: Merge Request Hook
+cel_error_handling: 
diff --git a/test/testdata/pipelinerun-cel-prefix-github.yaml b/test/testdata/pipelinerun-cel-prefix-github.yaml
new file mode 100644
index 0000000000..95702b3f48
--- /dev/null
+++ b/test/testdata/pipelinerun-cel-prefix-github.yaml
@@ -0,0 +1,36 @@
+---
+apiVersion: tekton.dev/v1beta1
+kind: PipelineRun
+metadata:
+  name: "\\ .PipelineName //"
+  annotations:
+    pipelinesascode.tekton.dev/target-namespace: "\\ .TargetNamespace //"
+    pipelinesascode.tekton.dev/on-cel-expression: |
+      target_branch == "\\ .TargetBranch //" && event == "\\ .TargetEvent //"
+spec:
+  pipelineSpec:
+    tasks:
+      - name: cel-prefix-test
+        taskSpec:
+          steps:
+            - name: test-cel-prefix-values
+              image: registry.access.redhat.com/ubi9/ubi-micro
+              script: |
+                # Test cel: prefix with various expressions for GitHub
+                # Expected output:
+                # cel_ternary: new-pr
+                # cel_pac_branch: matched
+                # cel_has_function: has-pr
+                # cel_string_concat: Build on <target_branch>
+                # cel_files_check: has-files
+                # cel_github_header: pull_request
+                # cel_error_handling: (empty - error returns empty string)
+                cat <<EOF
+                cel_ternary: {{ cel: body.action == "opened" ? "new-pr" : "updated-pr" }}
+                cel_pac_branch: {{ cel: pac.target_branch == "\\ .TargetBranch //" ? "matched" : "not-matched" }}
+                cel_has_function: {{ cel: has(body.pull_request) ? "has-pr" : "no-pr" }}
+                cel_string_concat: {{ cel: "Build on " + pac.target_branch }}
+                cel_files_check: {{ cel: files.all.size() > 0 ? "has-files" : "no-files" }}
+                cel_github_header: {{ cel: headers["X-Github-Event"] }}
+                cel_error_handling: {{ cel: nonexistent.field.access }}
+                EOF
diff --git a/test/testdata/pipelinerun-cel-prefix-gitlab.yaml b/test/testdata/pipelinerun-cel-prefix-gitlab.yaml
new file mode 100644
index 0000000000..ee58547ce0
--- /dev/null
+++ b/test/testdata/pipelinerun-cel-prefix-gitlab.yaml
@@ -0,0 +1,36 @@
+---
+apiVersion: tekton.dev/v1beta1
+kind: PipelineRun
+metadata:
+  name: "\\ .PipelineName //"
+  annotations:
+    pipelinesascode.tekton.dev/target-namespace: "\\ .TargetNamespace //"
+    pipelinesascode.tekton.dev/on-cel-expression: |
+      target_branch == "\\ .TargetBranch //" && event == "\\ .TargetEvent //"
+spec:
+  pipelineSpec:
+    tasks:
+      - name: cel-prefix-test
+        taskSpec:
+          steps:
+            - name: test-cel-prefix-values
+              image: registry.access.redhat.com/ubi9/ubi-micro
+              script: |
+                # Test cel: prefix with various expressions for GitLab
+                # Expected output:
+                # cel_ternary: new-mr
+                # cel_pac_branch: matched
+                # cel_has_function: has-mr
+                # cel_string_concat: Build on <target_branch>
+                # cel_files_check: has-files
+                # cel_gitlab_header: Merge Request Hook
+                # cel_error_handling: (empty - error returns empty string)
+                cat <<EOF
+                cel_ternary: {{ cel: body.object_attributes.action == "open" ? "new-mr" : "updated-mr" }}
+                cel_pac_branch: {{ cel: pac.target_branch == "\\ .TargetBranch //" ? "matched" : "not-matched" }}
+                cel_has_function: {{ cel: has(body.object_attributes) ? "has-mr" : "no-mr" }}
+                cel_string_concat: {{ cel: "Build on " + pac.target_branch }}
+                cel_files_check: {{ cel: files.all.size() > 0 ? "has-files" : "no-files" }}
+                cel_gitlab_header: {{ cel: headers["X-Gitlab-Event"] }}
+                cel_error_handling: {{ cel: nonexistent.field.access }}
+                EOF
diff --git a/test/testdata/pipelinerun-cel-prefix-test.yaml b/test/testdata/pipelinerun-cel-prefix-test.yaml
new file mode 100644
index 0000000000..2d7bebe284
--- /dev/null
+++ b/test/testdata/pipelinerun-cel-prefix-test.yaml
@@ -0,0 +1,34 @@
+---
+apiVersion: tekton.dev/v1beta1
+kind: PipelineRun
+metadata:
+  name: "\\ .PipelineName //"
+  annotations:
+    pipelinesascode.tekton.dev/target-namespace: "\\ .TargetNamespace //"
+    pipelinesascode.tekton.dev/on-cel-expression: |
+      target_branch == "\\ .TargetBranch //" && event == "\\ .TargetEvent //"
+spec:
+  pipelineSpec:
+    tasks:
+      - name: cel-prefix-test
+        taskSpec:
+          steps:
+            - name: test-cel-prefix-values
+              image: alpine
+              script: |
+                # Test cel: prefix with various expressions
+                # Expected output:
+                # cel_ternary: new-pr
+                # cel_pac_branch: matched
+                # cel_has_function: has-pr
+                # cel_string_concat: Build on <target_branch>
+                # cel_files_check: has-files
+                # cel_error_handling: (empty - error returns empty string)
+                cat <<EOF
+                cel_ternary: {{ cel: body.action == "opened" ? "new-pr" : "updated-pr" }}
+                cel_pac_branch: {{ cel: pac.target_branch == "\\ .TargetBranch //" ? "matched" : "not-matched" }}
+                cel_has_function: {{ cel: has(body.pull_request) ? "has-pr" : "no-pr" }}
+                cel_string_concat: {{ cel: "Build on " + pac.target_branch }}
+                cel_files_check: {{ cel: files.all.size() > 0 ? "has-files" : "no-files" }}
+                cel_error_handling: {{ cel: nonexistent.field.access }}
+                EOF