compiler: error on inputs declared under custom jobs

pkg/parser/schema_test.go

@@ -2703,3 +2703,32 @@ func TestValidateMainWorkflowFrontmatter_OnPermissionsUnknownScopeRejected(t *te
 		t.Error("unknown scope in on.permissions should be rejected by schema validation")
 	}
 }
+
+func TestValidateMainWorkflowFrontmatter_JobsInputsRejectedBeforeSchema(t *testing.T) {
+	frontmatter := map[string]any{
+		"on":     "push",
+		"engine": "copilot",
+		"jobs": map[string]any{
+			"my-job": map[string]any{
+				"runs-on": "ubuntu-latest",
+				"inputs": map[string]any{
+					"name": map[string]any{"description": "test"},
+				},
+				"steps": []any{map[string]any{"run": "echo hi"}},
+			},
+		},
+	}
+
+	err := ValidateMainWorkflowFrontmatterWithSchemaAndLocation(frontmatter, "/tmp/gh-aw/jobs-inputs-pre-schema-test.md")
+	if err == nil {
+		t.Fatal("expected jobs.<name>.inputs validation error")
+	}
+
+	errMsg := err.Error()
+	if !strings.Contains(errMsg, "jobs.my-job.inputs: inputs are not supported on jobs") {
+		t.Fatalf("expected actionable jobs.inputs error, got: %v", err)
+	}
+	if strings.Contains(errMsg, "Unknown property: inputs") {
+		t.Fatalf("expected pre-schema validation error instead of schema unknown-property error, got: %v", err)
+	}
+}

pkg/parser/schema_triggers.go

@@ -68,6 +68,30 @@ func validateCommandTriggerConflicts(frontmatter map[string]any) error {
 	return nil
 }
 
+func validateUnsupportedJobInputs(frontmatter map[string]any) error {
+	jobsValue, hasJobs := frontmatter["jobs"]
+	if !hasJobs || jobsValue == nil {
+		return nil
+	}
+
+	jobsMap, ok := jobsValue.(map[string]any)
+	if !ok {
+		return nil
+	}
+
+	for jobName, jobValue := range jobsMap {
+		jobMap, ok := jobValue.(map[string]any)
+		if !ok {
+			continue
+		}
+		if _, hasInputs := jobMap["inputs"]; hasInputs {
+			return fmt.Errorf("jobs.%s.inputs: inputs are not supported on jobs; use 'env' to pass values to job steps", jobName)
+		}
+	}
+
+	return nil
+}
+
 // IsLabelOnlyEvent checks if an event configuration only contains labeled/unlabeled types
 // This is exported for use in the compiler to validate command trigger combinations
 func IsLabelOnlyEvent(eventValue any) bool {

pkg/parser/schema_validation.go

@@ -121,6 +121,9 @@ func ValidateMainWorkflowFrontmatterWithSchemaAndLocation(frontmatter map[string
 	if err := validateCommandTriggerConflicts(filtered); err != nil {
 		return err
 	}
+	if err := validateUnsupportedJobInputs(filtered); err != nil {
+		return err
+	}
 
 	// Then run the standard schema validation with location
 	if err := validateWithSchemaAndLocation(filtered, mainWorkflowSchema, "main workflow file", filePath); err != nil {

pkg/workflow/compiler_custom_jobs.go

@@ -175,6 +175,10 @@ func (c *Compiler) extractCustomJobProperties(job *Job, jobName string, configMa
 }
 
 func (c *Compiler) extractCustomJobCoreProperties(job *Job, jobName string, configMap map[string]any) error {
+	if _, hasInputs := configMap["inputs"]; hasInputs {
+		return fmt.Errorf("jobs.%s.inputs: inputs are not supported on jobs; use 'env' to pass values to job steps", jobName)
+	}
+
 	if err := c.extractCustomJobRunsOn(job, jobName, configMap); err != nil {
 		return err
 	}

pkg/workflow/compiler_custom_jobs_test.go

@@ -202,6 +202,33 @@ func TestBuildCustomJob_InvalidTimeoutMinutesError(t *testing.T) {
 	require.ErrorContains(t, err, "timeout-minutes")
 }
 
+func TestBuildCustomJob_InputsNotSupportedError(t *testing.T) {
+	compiler := NewCompiler()
+	compiler.jobManager = NewJobManager()
+
+	data := &WorkflowData{Name: "Test"}
+	configMap := map[string]any{
+		"runs-on": "ubuntu-latest",
+		"inputs": map[string]any{
+			"my-input": map[string]any{"description": "an input"},
+		},
+		"steps": []any{map[string]any{"run": "echo hello"}},
+	}
+
+	_, err := compiler.buildCustomJob(
+		"my-job",
+		configMap,
+		data,
+		false,
+		map[string]struct{}{},
+		map[string]struct{}{},
+	)
+
+	require.Error(t, err)
+	require.ErrorContains(t, err, "jobs.my-job.inputs")
+	require.ErrorContains(t, err, "inputs are not supported on jobs")
+}
+
 func TestBuildCustomJob_UsesReusableWorkflow(t *testing.T) {
 	compiler := NewCompiler()
 	compiler.jobManager = NewJobManager()

pkg/workflow/compiler_string_api_test.go

@@ -187,6 +187,37 @@ bogus-field: true
 	assert.Contains(t, errorStr, "virtual/workflow.md:3:1: error:")
 }
 
+func TestParseWorkflowString_JobsInputsValidationReportedBeforeSchemaErrors(t *testing.T) {
+	markdown := `---
+name: jobs-inputs-test
+on: push
+engine: copilot
+jobs:
+  my-job:
+    runs-on: ubuntu-latest
+    inputs:
+      greeting:
+        description: Greeting
+    steps:
+      - run: echo hi
+---
+
+# Test
+`
+
+	compiler := NewCompiler(
+		WithNoEmit(true),
+		WithSkipValidation(true),
+	)
+
+	_, err := compiler.ParseWorkflowString(markdown, "virtual/workflow.md")
+	require.Error(t, err)
+
+	errorStr := err.Error()
+	assert.Contains(t, errorStr, "jobs.my-job.inputs: inputs are not supported on jobs")
+	assert.NotContains(t, errorStr, "Unknown property: inputs")
+}
+
 func TestCompileToYAML_BasicCompilation(t *testing.T) {
 	markdown := `---
 name: compile-test