diff --git a/pkg/parser/schemas/main_workflow_schema.json b/pkg/parser/schemas/main_workflow_schema.json
index ee9505e6388..8eca1627c10 100644
--- a/pkg/parser/schemas/main_workflow_schema.json
+++ b/pkg/parser/schemas/main_workflow_schema.json
@@ -4766,9 +4766,18 @@
                   }
                 },
                 "mode": {
-                  "type": "string",
-                  "description": "Integration mode: 'cli' (recommended) installs @playwright/cli via npm for token-efficient CLI invocations \u2014 use playwright-cli commands in bash and localhost to reach local servers; 'mcp' (deprecated) runs a Docker-based MCP server.",
-                  "enum": ["cli", "mcp"]
+                  "description": "Integration mode: 'cli' (recommended) installs @playwright/cli via npm for token-efficient CLI invocations \u2014 use playwright-cli commands in bash and localhost to reach local servers; 'mcp' (deprecated) runs a Docker-based MCP server. Must be a literal value; GitHub Actions expressions are rejected.",
+                  "oneOf": [
+                    {
+                      "type": "string",
+                      "enum": ["cli", "mcp"]
+                    },
+                    {
+                      "type": "string",
+                      "pattern": "^\\$\\{\\{.*\\}\\}$",
+                      "description": "Not allowed at runtime: mode must be a literal 'cli' or 'mcp' value, not a GitHub Actions expression."
+                    }
+                  ]
                 }
               },
               "additionalProperties": false
diff --git a/pkg/workflow/playwright_validation.go b/pkg/workflow/playwright_validation.go
index 0989c09e4e2..a7f3463ba12 100644
--- a/pkg/workflow/playwright_validation.go
+++ b/pkg/workflow/playwright_validation.go
@@ -37,9 +37,9 @@ import (
 
 var playwrightValidationLog = logger.New("workflow:playwright_validation")
 
-// validatePlaywrightMode warns when the playwright tool is configured in MCP
-// mode. MCP mode is deprecated; use mode: cli instead for token-efficient,
-// container-free browser automation.
+// validatePlaywrightMode validates that Playwright mode is static, then warns
+// when the tool is configured in MCP mode. MCP mode is deprecated; use mode:
+// cli instead for token-efficient, container-free browser automation.
 func (c *Compiler) validatePlaywrightMode(workflowData *WorkflowData) error {
 	if workflowData == nil || workflowData.Tools == nil {
 		return nil
@@ -49,6 +49,16 @@ func (c *Compiler) validatePlaywrightMode(workflowData *WorkflowData) error {
 	if !ok || playwrightTool == false {
 		return nil
 	}
+	if config, ok := playwrightTool.(map[string]any); ok {
+		if mode, ok := config["mode"].(string); ok && hasExpressionMarker(mode) {
+			return NewValidationError(
+				"tools.playwright.mode",
+				mode,
+				"mode must be a literal value; expressions are not allowed",
+				"Set mode to either mcp or cli",
+			)
+		}
+	}
 
 	if isPlaywrightCLIMode(workflowData.Tools) {
 		playwrightValidationLog.Print("playwright mode: cli — no deprecation warning")
diff --git a/pkg/workflow/playwright_validation_test.go b/pkg/workflow/playwright_validation_test.go
index b6d9bee762d..faf664d294a 100644
--- a/pkg/workflow/playwright_validation_test.go
+++ b/pkg/workflow/playwright_validation_test.go
@@ -3,6 +3,8 @@
 package workflow
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -54,6 +56,12 @@ func TestValidatePlaywrightMode(t *testing.T) {
 			tools:      map[string]any{"playwright": map[string]any{"mode": "CLI"}},
 			expectWarn: false,
 		},
+		{
+			name:        "playwright mode expression is rejected",
+			tools:       map[string]any{"playwright": map[string]any{"mode": "${{ inputs.playwright-mode }}"}},
+			expectError: true,
+			errorSubstr: "mode must be a literal value; expressions are not allowed",
+		},
 		{
 			name:       "playwright mcp mode in strict mode warns only",
 			tools:      map[string]any{"playwright": map[string]any{"mode": "mcp"}},
@@ -90,6 +98,36 @@ func TestValidatePlaywrightMode(t *testing.T) {
 	}
 }
 
+// TestCompileWorkflowRejectsPlaywrightModeExpression ensures that a full compile
+// of a workflow with an expression-valued tools.playwright.mode surfaces the
+// field-specific error from validatePlaywrightMode, rather than the generic
+// JSON schema enum error. This guards against the schema's enum constraint
+// preempting the dedicated validator.
+func TestCompileWorkflowRejectsPlaywrightModeExpression(t *testing.T) {
+	tmpDir := t.TempDir()
+	mdPath := filepath.Join(tmpDir, "test-workflow.md")
+	content := `---
+on: push
+engine: claude
+tools:
+  playwright:
+    mode: ${{ inputs.playwright-mode }}
+---
+
+# Test Workflow
+
+Test playwright mode expression rejection.
+`
+	require.NoError(t, os.WriteFile(mdPath, []byte(content), 0644))
+
+	compiler := NewCompiler()
+	err := compiler.CompileWorkflow(mdPath)
+
+	require.Error(t, err, "expected compilation to fail for expression-valued playwright mode")
+	assert.Contains(t, err.Error(), "tools.playwright.mode")
+	assert.Contains(t, err.Error(), "mode must be a literal value; expressions are not allowed")
+}
+
 // TestValidatePlaywrightModeNilWorkflow ensures no panic on nil/empty input.
 func TestValidatePlaywrightModeNilWorkflow(t *testing.T) {
 	compiler := NewCompiler()