diff --git a/weed/s3api/auth_credentials.go b/weed/s3api/auth_credentials.go
index 85002377b..54293e95a 100644
--- a/weed/s3api/auth_credentials.go
+++ b/weed/s3api/auth_credentials.go
@@ -513,7 +513,8 @@ func (iam *IdentityAccessManagement) authRequest(r *http.Request, action Action)
 		// - No policy or indeterminate → fall through to IAM checks
 		if iam.policyEngine != nil && bucket != "" {
 			principal := buildPrincipalARN(identity)
-			allowed, evaluated, err := iam.policyEngine.EvaluatePolicy(bucket, object, string(action), principal)
+			// Use context-aware policy evaluation to get the correct S3 action
+			allowed, evaluated, err := iam.policyEngine.EvaluatePolicyWithContext(bucket, object, string(action), principal, r)
 			
 			if err != nil {
 				// SECURITY: Fail-close on policy evaluation errors
diff --git a/weed/s3api/s3_action_resolver.go b/weed/s3api/s3_action_resolver.go
new file mode 100644
index 000000000..83431424c
--- /dev/null
+++ b/weed/s3api/s3_action_resolver.go
@@ -0,0 +1,334 @@
+package s3api
+
+import (
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
+)
+
+// ResolveS3Action determines the specific S3 action from HTTP request context.
+// This is the unified implementation used by both the bucket policy engine
+// and the IAM integration for consistent action resolution.
+//
+// It examines the HTTP method, path, query parameters, and headers to determine
+// the most specific S3 action string (e.g., "s3:DeleteObject", "s3:PutObjectTagging").
+//
+// Parameters:
+//   - r: HTTP request containing method, URL, query params, and headers
+//   - baseAction: Coarse-grained action constant (e.g., ACTION_WRITE, ACTION_READ)
+//   - bucket: Bucket name from the request path
+//   - object: Object key from the request path (may be empty for bucket operations)
+//
+// Returns:
+//   - Specific S3 action string (e.g., "s3:DeleteObject")
+//   - Falls back to base action mapping if no specific resolution is possible
+//   - Always returns a valid S3 action string (never empty)
+func ResolveS3Action(r *http.Request, baseAction string, bucket string, object string) string {
+	if r == nil || r.URL == nil {
+		// No HTTP context available: fall back to coarse-grained mapping
+		// This ensures consistent behavior and avoids returning empty strings
+		return mapBaseActionToS3Format(baseAction)
+	}
+
+	method := r.Method
+	query := r.URL.Query()
+
+	// Determine if this is an object or bucket operation
+	// Note: "/" is treated as bucket-level, not object-level
+	hasObject := object != "" && object != "/"
+
+	// Priority 1: Check for specific query parameters that indicate specific actions
+	// These override everything else because they explicitly indicate the operation type
+	if action := resolveFromQueryParameters(query, method, hasObject); action != "" {
+		return action
+	}
+
+	// Priority 2: Handle basic operations based on method and resource type
+	// Only use the result if a specific action was resolved; otherwise fall through to Priority 3
+	if hasObject {
+		if action := resolveObjectLevelAction(method, baseAction); action != "" {
+			return action
+		}
+	} else if bucket != "" {
+		if action := resolveBucketLevelAction(method, baseAction); action != "" {
+			return action
+		}
+	}
+
+	// Priority 3: Fallback to legacy action mapping
+	return mapBaseActionToS3Format(baseAction)
+}
+
+// bucketQueryActions maps bucket-level query parameters to their corresponding S3 actions by HTTP method
+var bucketQueryActions = map[string]map[string]string{
+	"policy": {
+		http.MethodGet:    s3_constants.S3_ACTION_GET_BUCKET_POLICY,
+		http.MethodPut:    s3_constants.S3_ACTION_PUT_BUCKET_POLICY,
+		http.MethodDelete: s3_constants.S3_ACTION_DELETE_BUCKET_POLICY,
+	},
+	"cors": {
+		http.MethodGet:    s3_constants.S3_ACTION_GET_BUCKET_CORS,
+		http.MethodPut:    s3_constants.S3_ACTION_PUT_BUCKET_CORS,
+		http.MethodDelete: s3_constants.S3_ACTION_DELETE_BUCKET_CORS,
+	},
+	"lifecycle": {
+		http.MethodGet:    s3_constants.S3_ACTION_GET_BUCKET_LIFECYCLE,
+		http.MethodPut:    s3_constants.S3_ACTION_PUT_BUCKET_LIFECYCLE,
+		http.MethodDelete: s3_constants.S3_ACTION_PUT_BUCKET_LIFECYCLE, // DELETE uses same permission as PUT
+	},
+	"versioning": {
+		http.MethodGet: s3_constants.S3_ACTION_GET_BUCKET_VERSIONING,
+		http.MethodPut: s3_constants.S3_ACTION_PUT_BUCKET_VERSIONING,
+	},
+	"notification": {
+		http.MethodGet: s3_constants.S3_ACTION_GET_BUCKET_NOTIFICATION,
+		http.MethodPut: s3_constants.S3_ACTION_PUT_BUCKET_NOTIFICATION,
+	},
+	"object-lock": {
+		http.MethodGet: s3_constants.S3_ACTION_GET_BUCKET_OBJECT_LOCK,
+		http.MethodPut: s3_constants.S3_ACTION_PUT_BUCKET_OBJECT_LOCK,
+	},
+}
+
+// resolveFromQueryParameters checks query parameters to determine specific S3 actions
+func resolveFromQueryParameters(query url.Values, method string, hasObject bool) string {
+	// Multipart upload operations with uploadId parameter (object-level only)
+	// All multipart operations require an object in the path
+	if hasObject && query.Has("uploadId") {
+		switch method {
+		case http.MethodPut:
+			if query.Has("partNumber") {
+				return s3_constants.S3_ACTION_UPLOAD_PART
+			}
+		case http.MethodPost:
+			return s3_constants.S3_ACTION_COMPLETE_MULTIPART
+		case http.MethodDelete:
+			return s3_constants.S3_ACTION_ABORT_MULTIPART
+		case http.MethodGet:
+			return s3_constants.S3_ACTION_LIST_PARTS
+		}
+	}
+
+	// Multipart upload operations
+	// CreateMultipartUpload: POST /bucket/object?uploads (object-level)
+	// ListMultipartUploads: GET /bucket?uploads (bucket-level)
+	if query.Has("uploads") {
+		if method == http.MethodPost && hasObject {
+			return s3_constants.S3_ACTION_CREATE_MULTIPART
+		} else if method == http.MethodGet && !hasObject {
+			return s3_constants.S3_ACTION_LIST_MULTIPART_UPLOADS
+		}
+	}
+
+	// ACL operations
+	if query.Has("acl") {
+		switch method {
+		case http.MethodGet, http.MethodHead:
+			if hasObject {
+				return s3_constants.S3_ACTION_GET_OBJECT_ACL
+			}
+			return s3_constants.S3_ACTION_GET_BUCKET_ACL
+		case http.MethodPut:
+			if hasObject {
+				return s3_constants.S3_ACTION_PUT_OBJECT_ACL
+			}
+			return s3_constants.S3_ACTION_PUT_BUCKET_ACL
+		}
+	}
+
+	// Tagging operations
+	if query.Has("tagging") {
+		switch method {
+		case http.MethodGet:
+			if hasObject {
+				return s3_constants.S3_ACTION_GET_OBJECT_TAGGING
+			}
+			return s3_constants.S3_ACTION_GET_BUCKET_TAGGING
+		case http.MethodPut:
+			if hasObject {
+				return s3_constants.S3_ACTION_PUT_OBJECT_TAGGING
+			}
+			return s3_constants.S3_ACTION_PUT_BUCKET_TAGGING
+		case http.MethodDelete:
+			if hasObject {
+				return s3_constants.S3_ACTION_DELETE_OBJECT_TAGGING
+			}
+			return s3_constants.S3_ACTION_DELETE_BUCKET_TAGGING
+		}
+	}
+
+	// Versioning operations - distinguish between versionId (specific version) and versions (list versions)
+	// versionId: Used to access/delete a specific version of an object (e.g., GET /bucket/key?versionId=xyz)
+	if query.Has("versionId") {
+		if hasObject {
+			switch method {
+			case http.MethodGet, http.MethodHead:
+				return s3_constants.S3_ACTION_GET_OBJECT_VERSION
+			case http.MethodDelete:
+				return s3_constants.S3_ACTION_DELETE_OBJECT_VERSION
+			}
+		}
+	}
+
+	// versions: Used to list all versions of objects in a bucket (e.g., GET /bucket?versions)
+	if query.Has("versions") {
+		if method == http.MethodGet && !hasObject {
+			return s3_constants.S3_ACTION_LIST_BUCKET_VERSIONS
+		}
+	}
+
+	// Check bucket-level query parameters using data-driven approach
+	// These are strictly bucket-level operations, so only apply when !hasObject
+	if !hasObject {
+		for param, actions := range bucketQueryActions {
+			if query.Has(param) {
+				if action, ok := actions[method]; ok {
+					return action
+				}
+			}
+		}
+	}
+
+	// Location (GET only, bucket-level)
+	if query.Has("location") && method == http.MethodGet && !hasObject {
+		return s3_constants.S3_ACTION_GET_BUCKET_LOCATION
+	}
+
+	// Object retention and legal hold operations (object-level only)
+	if hasObject {
+		if query.Has("retention") {
+			switch method {
+			case http.MethodGet:
+				return s3_constants.S3_ACTION_GET_OBJECT_RETENTION
+			case http.MethodPut:
+				return s3_constants.S3_ACTION_PUT_OBJECT_RETENTION
+			}
+		}
+
+		if query.Has("legal-hold") {
+			switch method {
+			case http.MethodGet:
+				return s3_constants.S3_ACTION_GET_OBJECT_LEGAL_HOLD
+			case http.MethodPut:
+				return s3_constants.S3_ACTION_PUT_OBJECT_LEGAL_HOLD
+			}
+		}
+	}
+
+	// Batch delete - POST request with delete query parameter (bucket-level operation)
+	// Example: POST /bucket?delete (not POST /bucket/object?delete)
+	if query.Has("delete") && method == http.MethodPost && !hasObject {
+		return s3_constants.S3_ACTION_DELETE_OBJECT
+	}
+
+	return ""
+}
+
+// resolveObjectLevelAction determines the S3 action for object-level operations
+func resolveObjectLevelAction(method string, baseAction string) string {
+	switch method {
+	case http.MethodGet, http.MethodHead:
+		if baseAction == s3_constants.ACTION_READ {
+			return s3_constants.S3_ACTION_GET_OBJECT
+		}
+
+	case http.MethodPut:
+		if baseAction == s3_constants.ACTION_WRITE {
+			// Note: CopyObject operations also use s3:PutObject permission (same as MinIO/AWS)
+			// Copy requires s3:PutObject on destination and s3:GetObject on source
+			return s3_constants.S3_ACTION_PUT_OBJECT
+		}
+
+	case http.MethodDelete:
+		// CRITICAL: Map DELETE method to s3:DeleteObject
+		// This fixes the architectural limitation where ACTION_WRITE was mapped to s3:PutObject
+		if baseAction == s3_constants.ACTION_WRITE {
+			return s3_constants.S3_ACTION_DELETE_OBJECT
+		}
+
+	case http.MethodPost:
+		// POST without query params is typically multipart or form upload
+		if baseAction == s3_constants.ACTION_WRITE {
+			return s3_constants.S3_ACTION_PUT_OBJECT
+		}
+	}
+
+	return ""
+}
+
+// resolveBucketLevelAction determines the S3 action for bucket-level operations
+func resolveBucketLevelAction(method string, baseAction string) string {
+	switch method {
+	case http.MethodGet, http.MethodHead:
+		if baseAction == s3_constants.ACTION_LIST || baseAction == s3_constants.ACTION_READ {
+			return s3_constants.S3_ACTION_LIST_BUCKET
+		}
+
+	case http.MethodPut:
+		if baseAction == s3_constants.ACTION_WRITE {
+			return s3_constants.S3_ACTION_CREATE_BUCKET
+		}
+
+	case http.MethodDelete:
+		if baseAction == s3_constants.ACTION_DELETE_BUCKET {
+			return s3_constants.S3_ACTION_DELETE_BUCKET
+		}
+
+	case http.MethodPost:
+		// POST to bucket is typically form upload
+		if baseAction == s3_constants.ACTION_WRITE {
+			return s3_constants.S3_ACTION_PUT_OBJECT
+		}
+	}
+
+	return ""
+}
+
+// mapBaseActionToS3Format converts coarse-grained base actions to S3 format
+// This is the fallback when no specific resolution is found
+func mapBaseActionToS3Format(baseAction string) string {
+	// Handle actions that already have s3: prefix
+	if strings.HasPrefix(baseAction, "s3:") {
+		return baseAction
+	}
+
+	// Map coarse-grained actions to their most common S3 equivalent
+	// Note: The s3_constants values ARE the string values (e.g., ACTION_READ = "Read")
+	switch baseAction {
+	case s3_constants.ACTION_READ: // "Read"
+		return s3_constants.S3_ACTION_GET_OBJECT
+	case s3_constants.ACTION_WRITE: // "Write"
+		return s3_constants.S3_ACTION_PUT_OBJECT
+	case s3_constants.ACTION_LIST: // "List"
+		return s3_constants.S3_ACTION_LIST_BUCKET
+	case s3_constants.ACTION_TAGGING: // "Tagging"
+		return s3_constants.S3_ACTION_PUT_OBJECT_TAGGING
+	case s3_constants.ACTION_ADMIN: // "Admin"
+		return s3_constants.S3_ACTION_ALL
+	case s3_constants.ACTION_READ_ACP: // "ReadAcp"
+		return s3_constants.S3_ACTION_GET_OBJECT_ACL
+	case s3_constants.ACTION_WRITE_ACP: // "WriteAcp"
+		return s3_constants.S3_ACTION_PUT_OBJECT_ACL
+	case s3_constants.ACTION_DELETE_BUCKET: // "DeleteBucket"
+		return s3_constants.S3_ACTION_DELETE_BUCKET
+	case s3_constants.ACTION_BYPASS_GOVERNANCE_RETENTION:
+		return s3_constants.S3_ACTION_BYPASS_GOVERNANCE
+	case s3_constants.ACTION_GET_OBJECT_RETENTION:
+		return s3_constants.S3_ACTION_GET_OBJECT_RETENTION
+	case s3_constants.ACTION_PUT_OBJECT_RETENTION:
+		return s3_constants.S3_ACTION_PUT_OBJECT_RETENTION
+	case s3_constants.ACTION_GET_OBJECT_LEGAL_HOLD:
+		return s3_constants.S3_ACTION_GET_OBJECT_LEGAL_HOLD
+	case s3_constants.ACTION_PUT_OBJECT_LEGAL_HOLD:
+		return s3_constants.S3_ACTION_PUT_OBJECT_LEGAL_HOLD
+	case s3_constants.ACTION_GET_BUCKET_OBJECT_LOCK_CONFIG:
+		return s3_constants.S3_ACTION_GET_BUCKET_OBJECT_LOCK
+	case s3_constants.ACTION_PUT_BUCKET_OBJECT_LOCK_CONFIG:
+		return s3_constants.S3_ACTION_PUT_BUCKET_OBJECT_LOCK
+	default:
+		// For unknown actions, prefix with s3: to maintain format consistency
+		return "s3:" + baseAction
+	}
+}
diff --git a/weed/s3api/s3_constants/s3_action_strings.go b/weed/s3api/s3_constants/s3_action_strings.go
new file mode 100644
index 000000000..c7d5541c9
--- /dev/null
+++ b/weed/s3api/s3_constants/s3_action_strings.go
@@ -0,0 +1,84 @@
+package s3_constants
+
+// S3 action strings for bucket policy evaluation
+// These match the official AWS S3 action format used in IAM and bucket policies
+const (
+	// Object operations
+	S3_ACTION_GET_OBJECT            = "s3:GetObject"
+	S3_ACTION_PUT_OBJECT            = "s3:PutObject"
+	S3_ACTION_DELETE_OBJECT         = "s3:DeleteObject"
+	S3_ACTION_DELETE_OBJECT_VERSION = "s3:DeleteObjectVersion"
+	S3_ACTION_GET_OBJECT_VERSION    = "s3:GetObjectVersion"
+
+	// Object ACL operations
+	S3_ACTION_GET_OBJECT_ACL = "s3:GetObjectAcl"
+	S3_ACTION_PUT_OBJECT_ACL = "s3:PutObjectAcl"
+
+	// Object tagging operations
+	S3_ACTION_GET_OBJECT_TAGGING    = "s3:GetObjectTagging"
+	S3_ACTION_PUT_OBJECT_TAGGING    = "s3:PutObjectTagging"
+	S3_ACTION_DELETE_OBJECT_TAGGING = "s3:DeleteObjectTagging"
+
+	// Object retention and legal hold
+	S3_ACTION_GET_OBJECT_RETENTION  = "s3:GetObjectRetention"
+	S3_ACTION_PUT_OBJECT_RETENTION  = "s3:PutObjectRetention"
+	S3_ACTION_GET_OBJECT_LEGAL_HOLD = "s3:GetObjectLegalHold"
+	S3_ACTION_PUT_OBJECT_LEGAL_HOLD = "s3:PutObjectLegalHold"
+	S3_ACTION_BYPASS_GOVERNANCE     = "s3:BypassGovernanceRetention"
+
+	// Multipart upload operations
+	S3_ACTION_CREATE_MULTIPART   = "s3:CreateMultipartUpload"
+	S3_ACTION_UPLOAD_PART        = "s3:UploadPart"
+	S3_ACTION_COMPLETE_MULTIPART = "s3:CompleteMultipartUpload"
+	S3_ACTION_ABORT_MULTIPART    = "s3:AbortMultipartUpload"
+	S3_ACTION_LIST_PARTS         = "s3:ListMultipartUploadParts"
+
+	// Bucket operations
+	S3_ACTION_CREATE_BUCKET          = "s3:CreateBucket"
+	S3_ACTION_DELETE_BUCKET          = "s3:DeleteBucket"
+	S3_ACTION_LIST_BUCKET            = "s3:ListBucket"
+	S3_ACTION_LIST_BUCKET_VERSIONS   = "s3:ListBucketVersions"
+	S3_ACTION_LIST_MULTIPART_UPLOADS = "s3:ListBucketMultipartUploads"
+
+	// Bucket ACL operations
+	S3_ACTION_GET_BUCKET_ACL = "s3:GetBucketAcl"
+	S3_ACTION_PUT_BUCKET_ACL = "s3:PutBucketAcl"
+
+	// Bucket policy operations
+	S3_ACTION_GET_BUCKET_POLICY    = "s3:GetBucketPolicy"
+	S3_ACTION_PUT_BUCKET_POLICY    = "s3:PutBucketPolicy"
+	S3_ACTION_DELETE_BUCKET_POLICY = "s3:DeleteBucketPolicy"
+
+	// Bucket tagging operations
+	S3_ACTION_GET_BUCKET_TAGGING    = "s3:GetBucketTagging"
+	S3_ACTION_PUT_BUCKET_TAGGING    = "s3:PutBucketTagging"
+	S3_ACTION_DELETE_BUCKET_TAGGING = "s3:DeleteBucketTagging"
+
+	// Bucket CORS operations
+	S3_ACTION_GET_BUCKET_CORS    = "s3:GetBucketCors"
+	S3_ACTION_PUT_BUCKET_CORS    = "s3:PutBucketCors"
+	S3_ACTION_DELETE_BUCKET_CORS = "s3:DeleteBucketCors"
+
+	// Bucket lifecycle operations
+	// Note: Both PUT and DELETE lifecycle operations use s3:PutLifecycleConfiguration
+	S3_ACTION_GET_BUCKET_LIFECYCLE = "s3:GetLifecycleConfiguration"
+	S3_ACTION_PUT_BUCKET_LIFECYCLE = "s3:PutLifecycleConfiguration"
+
+	// Bucket versioning operations
+	S3_ACTION_GET_BUCKET_VERSIONING = "s3:GetBucketVersioning"
+	S3_ACTION_PUT_BUCKET_VERSIONING = "s3:PutBucketVersioning"
+
+	// Bucket location
+	S3_ACTION_GET_BUCKET_LOCATION = "s3:GetBucketLocation"
+
+	// Bucket notification
+	S3_ACTION_GET_BUCKET_NOTIFICATION = "s3:GetBucketNotification"
+	S3_ACTION_PUT_BUCKET_NOTIFICATION = "s3:PutBucketNotification"
+
+	// Bucket object lock operations
+	S3_ACTION_GET_BUCKET_OBJECT_LOCK = "s3:GetBucketObjectLockConfiguration"
+	S3_ACTION_PUT_BUCKET_OBJECT_LOCK = "s3:PutBucketObjectLockConfiguration"
+
+	// Wildcard for all S3 actions
+	S3_ACTION_ALL = "s3:*"
+)
diff --git a/weed/s3api/s3_granular_action_security_test.go b/weed/s3api/s3_granular_action_security_test.go
index 404638d14..3def7e9d2 100644
--- a/weed/s3api/s3_granular_action_security_test.go
+++ b/weed/s3api/s3_granular_action_security_test.go
@@ -3,12 +3,49 @@ package s3api
 import (
 	"net/http"
 	"net/url"
+	"strings"
 	"testing"
 
 	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
 	"github.com/stretchr/testify/assert"
 )
 
+// createTestRequestWithQueryParams creates a test HTTP request with query parameters
+// and extracts bucket/object from the path. This helper reduces duplication in test setup.
+func createTestRequestWithQueryParams(method, path string, queryParams map[string]string) (*http.Request, string, string, error) {
+	// Parse the URL
+	u, err := url.Parse(path)
+	if err != nil {
+		return nil, "", "", err
+	}
+
+	// Add query parameters
+	q := u.Query()
+	for k, v := range queryParams {
+		q.Add(k, v)
+	}
+	u.RawQuery = q.Encode()
+
+	// Create HTTP request
+	req, err := http.NewRequest(method, u.String(), nil)
+	if err != nil {
+		return nil, "", "", err
+	}
+
+	// Parse path to extract bucket and object
+	parts := strings.Split(strings.TrimPrefix(u.Path, "/"), "/")
+	bucket := ""
+	object := ""
+	if len(parts) > 0 {
+		bucket = parts[0]
+	}
+	if len(parts) > 1 {
+		object = "/" + strings.Join(parts[1:], "/")
+	}
+
+	return req, bucket, object, nil
+}
+
 // TestGranularActionMappingSecurity demonstrates how the new granular action mapping
 // fixes critical security issues that existed with the previous coarse mapping
 func TestGranularActionMappingSecurity(t *testing.T) {
@@ -83,10 +120,10 @@ func TestGranularActionMappingSecurity(t *testing.T) {
 			bucket:      "inventory-bucket",
 			objectKey:   "",
 			queryParams: map[string]string{"uploads": ""},
-			description: "Listing multipart uploads should map to s3:ListMultipartUploads",
+			description: "Listing multipart uploads should map to s3:ListBucketMultipartUploads",
 			problemWithOldMapping: "Old mapping would use generic s3:ListBucket for all bucket operations, " +
 				"preventing fine-grained control over who can see ongoing multipart operations",
-			granularActionResult: "s3:ListMultipartUploads",
+			granularActionResult: "s3:ListBucketMultipartUploads",
 		},
 		{
 			name:        "delete_object_tagging_precision",
@@ -116,8 +153,8 @@ func TestGranularActionMappingSecurity(t *testing.T) {
 			}
 			req.URL.RawQuery = query.Encode()
 
-			// Test the new granular action determination
-			result := determineGranularS3Action(req, s3_constants.ACTION_WRITE, tt.bucket, tt.objectKey)
+			// Test the granular action determination
+			result := ResolveS3Action(req, string(s3_constants.ACTION_WRITE), tt.bucket, tt.objectKey)
 
 			assert.Equal(t, tt.granularActionResult, result,
 				"Security Fix Test: %s\n"+
@@ -191,7 +228,7 @@ func TestBackwardCompatibilityFallback(t *testing.T) {
 				URL:    &url.URL{Path: "/" + tt.bucket + "/" + tt.objectKey},
 			}
 
-			result := determineGranularS3Action(req, tt.fallbackAction, tt.bucket, tt.objectKey)
+			result := ResolveS3Action(req, string(tt.fallbackAction), tt.bucket, tt.objectKey)
 
 			assert.Equal(t, tt.expectedResult, result,
 				"Backward Compatibility Test: %s\nDescription: %s\nExpected: %s, Got: %s",
@@ -292,16 +329,281 @@ func TestPolicyEnforcementScenarios(t *testing.T) {
 			}
 			req.URL.RawQuery = query.Encode()
 
-			result := determineGranularS3Action(req, s3_constants.ACTION_WRITE, scenario.bucket, scenario.objectKey)
+			result := ResolveS3Action(req, string(s3_constants.ACTION_WRITE), scenario.bucket, scenario.objectKey)
 
 			assert.Equal(t, scenario.expectedAction, result,
 				"Policy Enforcement Scenario: %s\nExpected Action: %s, Got: %s",
 				scenario.name, scenario.expectedAction, result)
 
-			t.Logf("🔒 SECURITY SCENARIO: %s", scenario.name)
+			t.Logf("SECURITY SCENARIO: %s", scenario.name)
 			t.Logf("   Expected Action: %s", result)
 			t.Logf("   Security Benefit: %s", scenario.securityBenefit)
 			t.Logf("   Policy Example:\n%s", scenario.policyExample)
 		})
 	}
 }
+
+// TestDeleteObjectPolicyEnforcement demonstrates that the architectural limitation has been fixed
+// Previously, DeleteObject operations were mapped to s3:PutObject, preventing fine-grained policies from working
+func TestDeleteObjectPolicyEnforcement(t *testing.T) {
+	tests := []struct {
+		name             string
+		method           string
+		bucket           string
+		objectKey        string
+		baseAction       Action
+		expectedS3Action string
+		policyScenario   string
+	}{
+		{
+			name:             "delete_object_maps_to_correct_action",
+			method:           http.MethodDelete,
+			bucket:           "test-bucket",
+			objectKey:        "test-object.txt",
+			baseAction:       s3_constants.ACTION_WRITE,
+			expectedS3Action: "s3:DeleteObject",
+			policyScenario:   "Policy that denies s3:DeleteObject but allows s3:PutObject should now work correctly",
+		},
+		{
+			name:             "put_object_maps_to_correct_action",
+			method:           http.MethodPut,
+			bucket:           "test-bucket",
+			objectKey:        "test-object.txt",
+			baseAction:       s3_constants.ACTION_WRITE,
+			expectedS3Action: "s3:PutObject",
+			policyScenario:   "Policy that allows s3:PutObject but denies s3:DeleteObject should allow uploads",
+		},
+		{
+			name:             "batch_delete_maps_to_delete_action",
+			method:           http.MethodPost,
+			bucket:           "test-bucket",
+			objectKey:        "",
+			baseAction:       s3_constants.ACTION_WRITE,
+			expectedS3Action: "s3:DeleteObject",
+			policyScenario:   "Batch delete operations should also map to s3:DeleteObject",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Create HTTP request
+			req := &http.Request{
+				Method: tt.method,
+				URL:    &url.URL{Path: "/" + tt.bucket + "/" + tt.objectKey},
+				Header: http.Header{},
+			}
+
+			// For batch delete, add the delete query parameter
+			if tt.method == http.MethodPost && tt.expectedS3Action == "s3:DeleteObject" {
+				query := req.URL.Query()
+				query.Set("delete", "")
+				req.URL.RawQuery = query.Encode()
+			}
+
+			// Test the action resolution
+			result := ResolveS3Action(req, string(tt.baseAction), tt.bucket, tt.objectKey)
+
+			assert.Equal(t, tt.expectedS3Action, result,
+				"Action Resolution Test: %s\n"+
+					"HTTP Method: %s\n"+
+					"Base Action: %s\n"+
+					"Policy Scenario: %s\n"+
+					"Expected: %s, Got: %s",
+				tt.name, tt.method, tt.baseAction, tt.policyScenario, tt.expectedS3Action, result)
+
+			t.Logf("ARCHITECTURAL FIX VERIFIED: %s", tt.name)
+			t.Logf("   Method: %s -> S3 Action: %s", tt.method, result)
+			t.Logf("   Policy Scenario: %s", tt.policyScenario)
+		})
+	}
+}
+
+// TestFineGrainedPolicyExample demonstrates a real-world use case that now works
+// This test verifies the exact scenario described in the original TODO comment
+func TestFineGrainedPolicyExample(t *testing.T) {
+	// Example policy: Allow PutObject but Deny DeleteObject
+	// This is a common pattern for "append-only" buckets or write-once scenarios
+	policyExample := `{
+		"Version": "2012-10-17",
+		"Statement": [
+			{
+				"Sid": "AllowObjectUploads",
+				"Effect": "Allow",
+				"Action": "s3:PutObject",
+				"Resource": "arn:aws:s3:::test-bucket/*"
+			},
+			{
+				"Sid": "DenyObjectDeletion",
+				"Effect": "Deny",
+				"Action": "s3:DeleteObject",
+				"Resource": "arn:aws:s3:::test-bucket/*"
+			}
+		]
+	}`
+
+	testCases := []struct {
+		operation       string
+		method          string
+		objectKey       string
+		queryParams     map[string]string
+		baseAction      Action
+		expectedAction  string
+		shouldBeAllowed bool
+		rationale       string
+	}{
+		{
+			operation:       "PUT object",
+			method:          http.MethodPut,
+			objectKey:       "document.txt",
+			queryParams:     map[string]string{},
+			baseAction:      s3_constants.ACTION_WRITE,
+			expectedAction:  "s3:PutObject",
+			shouldBeAllowed: true,
+			rationale:       "Policy explicitly allows s3:PutObject - upload should succeed",
+		},
+		{
+			operation:       "DELETE object",
+			method:          http.MethodDelete,
+			objectKey:       "document.txt",
+			queryParams:     map[string]string{},
+			baseAction:      s3_constants.ACTION_WRITE,
+			expectedAction:  "s3:DeleteObject",
+			shouldBeAllowed: false,
+			rationale:       "Policy explicitly denies s3:DeleteObject - deletion should be blocked",
+		},
+		{
+			operation:       "Batch DELETE",
+			method:          http.MethodPost,
+			objectKey:       "",
+			queryParams:     map[string]string{"delete": ""},
+			baseAction:      s3_constants.ACTION_WRITE,
+			expectedAction:  "s3:DeleteObject",
+			shouldBeAllowed: false,
+			rationale:       "Policy explicitly denies s3:DeleteObject - batch deletion should be blocked",
+		},
+	}
+
+	t.Logf("\nTesting Fine-Grained Policy:")
+	t.Logf("%s\n", policyExample)
+
+	for _, tc := range testCases {
+		t.Run(tc.operation, func(t *testing.T) {
+			// Create HTTP request
+			req := &http.Request{
+				Method: tc.method,
+				URL:    &url.URL{Path: "/test-bucket/" + tc.objectKey},
+				Header: http.Header{},
+			}
+
+			// Add query parameters
+			query := req.URL.Query()
+			for key, value := range tc.queryParams {
+				query.Set(key, value)
+			}
+			req.URL.RawQuery = query.Encode()
+
+			// Determine the S3 action
+			actualAction := ResolveS3Action(req, string(tc.baseAction), "test-bucket", tc.objectKey)
+
+			// Verify the action mapping is correct
+			assert.Equal(t, tc.expectedAction, actualAction,
+				"Operation: %s\nExpected Action: %s\nGot: %s",
+				tc.operation, tc.expectedAction, actualAction)
+
+			// Log the result
+			allowStatus := "[DENIED]"
+			if tc.shouldBeAllowed {
+				allowStatus = "[ALLOWED]"
+			}
+
+			t.Logf("%s %s -> %s", allowStatus, tc.operation, actualAction)
+			t.Logf("   Rationale: %s", tc.rationale)
+		})
+	}
+
+	t.Logf("\nARCHITECTURAL LIMITATION RESOLVED!")
+	t.Logf("   Fine-grained policies like 'allow PUT but deny DELETE' now work correctly")
+	t.Logf("   The policy engine can distinguish between s3:PutObject and s3:DeleteObject")
+}
+
+// TestCoarseActionResolution verifies that ResolveS3Action correctly maps
+// coarse-grained ACTION_WRITE to specific S3 actions based on HTTP context.
+// This demonstrates the fix for the architectural limitation where ACTION_WRITE
+// was always mapped to s3:PutObject, preventing fine-grained policies from working.
+func TestCoarseActionResolution(t *testing.T) {
+	testCases := []struct {
+		name             string
+		method           string
+		path             string
+		queryParams      map[string]string
+		coarseAction     Action
+		expectedS3Action string
+		policyScenario   string
+	}{
+		{
+			name:             "PUT_with_ACTION_WRITE_resolves_to_PutObject",
+			method:           http.MethodPut,
+			path:             "/test-bucket/test-file.txt",
+			queryParams:      map[string]string{},
+			coarseAction:     s3_constants.ACTION_WRITE,
+			expectedS3Action: "s3:PutObject",
+			policyScenario:   "Policy allowing s3:PutObject should match PUT requests",
+		},
+		{
+			name:             "DELETE_with_ACTION_WRITE_resolves_to_DeleteObject",
+			method:           http.MethodDelete,
+			path:             "/test-bucket/test-file.txt",
+			queryParams:      map[string]string{},
+			coarseAction:     s3_constants.ACTION_WRITE,
+			expectedS3Action: "s3:DeleteObject",
+			policyScenario:   "Policy denying s3:DeleteObject should block DELETE requests",
+		},
+		{
+			name:             "batch_DELETE_with_ACTION_WRITE_resolves_to_DeleteObject",
+			method:           http.MethodPost,
+			path:             "/test-bucket",
+			queryParams:      map[string]string{"delete": ""},
+			coarseAction:     s3_constants.ACTION_WRITE,
+			expectedS3Action: "s3:DeleteObject",
+			policyScenario:   "Policy denying s3:DeleteObject should block batch DELETE",
+		},
+		{
+			name:             "POST_multipart_with_ACTION_WRITE_resolves_to_CreateMultipartUpload",
+			method:           http.MethodPost,
+			path:             "/test-bucket/large-file.mp4",
+			queryParams:      map[string]string{"uploads": ""},
+			coarseAction:     s3_constants.ACTION_WRITE,
+			expectedS3Action: "s3:CreateMultipartUpload",
+			policyScenario:   "Policy allowing s3:PutObject but denying s3:CreateMultipartUpload can now work",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Create test request with query parameters and extract bucket/object
+			req, bucket, object, err := createTestRequestWithQueryParams(tc.method, tc.path, tc.queryParams)
+			assert.NoError(t, err)
+
+			// Call ResolveS3Action with coarse action constant
+			resolvedAction := ResolveS3Action(req, string(tc.coarseAction), bucket, object)
+
+			// Verify correct S3 action is resolved
+			assert.Equal(t, tc.expectedS3Action, resolvedAction,
+				"Coarse action %s with method %s should resolve to %s",
+				tc.coarseAction, tc.method, tc.expectedS3Action)
+
+			t.Logf("SUCCESS: %s", tc.name)
+			t.Logf("  Input:  %s %s + ACTION_WRITE", tc.method, tc.path)
+			t.Logf("  Output: %s", resolvedAction)
+			t.Logf("  Policy impact: %s", tc.policyScenario)
+		})
+	}
+
+	t.Log("\n=== ARCHITECTURAL LIMITATION RESOLVED ===")
+	t.Log("Handlers can use coarse ACTION_WRITE constant, and the context-aware")
+	t.Log("resolver will map it to the correct specific S3 action (PutObject,")
+	t.Log("DeleteObject, CreateMultipartUpload, etc.) based on HTTP method and")
+	t.Log("query parameters. This enables fine-grained bucket policies like:")
+	t.Log("  - Allow s3:PutObject but Deny s3:DeleteObject (append-only)")
+	t.Log("  - Allow regular uploads but Deny multipart (size limits)")
+}
diff --git a/weed/s3api/s3_iam_middleware.go b/weed/s3api/s3_iam_middleware.go
index 230b2d2cb..4cb14490a 100644
--- a/weed/s3api/s3_iam_middleware.go
+++ b/weed/s3api/s3_iam_middleware.go
@@ -184,7 +184,7 @@ func (s3iam *S3IAMIntegration) AuthorizeAction(ctx context.Context, identity *IA
 	requestContext := extractRequestContext(r)
 
 	// Determine the specific S3 action based on the HTTP request details
-	specificAction := determineGranularS3Action(r, action, bucket, objectKey)
+	specificAction := ResolveS3Action(r, string(action), bucket, objectKey)
 
 	// Create action request
 	actionRequest := &integration.ActionRequest{
@@ -246,176 +246,11 @@ func buildS3ResourceArn(bucket string, objectKey string) string {
 	}
 
 	// Remove leading slash from object key if present
-	if strings.HasPrefix(objectKey, "/") {
-		objectKey = objectKey[1:]
-	}
+	objectKey = strings.TrimPrefix(objectKey, "/")
 
 	return "arn:aws:s3:::" + bucket + "/" + objectKey
 }
 
-// determineGranularS3Action determines the specific S3 IAM action based on HTTP request details
-// This provides granular, operation-specific actions for accurate IAM policy enforcement
-func determineGranularS3Action(r *http.Request, fallbackAction Action, bucket string, objectKey string) string {
-	method := r.Method
-	query := r.URL.Query()
-
-	// Check if there are specific query parameters indicating granular operations
-	// If there are, always use granular mapping regardless of method-action alignment
-	hasGranularIndicators := hasSpecificQueryParameters(query)
-
-	// Only check for method-action mismatch when there are NO granular indicators
-	// This provides fallback behavior for cases where HTTP method doesn't align with intended action
-	if !hasGranularIndicators && isMethodActionMismatch(method, fallbackAction) {
-		return mapLegacyActionToIAM(fallbackAction)
-	}
-
-	// Handle object-level operations when method and action are aligned
-	if objectKey != "" && objectKey != "/" {
-		switch method {
-		case "GET", "HEAD":
-			// Object read operations - check for specific query parameters
-			if _, hasAcl := query["acl"]; hasAcl {
-				return "s3:GetObjectAcl"
-			}
-			if _, hasTagging := query["tagging"]; hasTagging {
-				return "s3:GetObjectTagging"
-			}
-			if _, hasRetention := query["retention"]; hasRetention {
-				return "s3:GetObjectRetention"
-			}
-			if _, hasLegalHold := query["legal-hold"]; hasLegalHold {
-				return "s3:GetObjectLegalHold"
-			}
-			if _, hasVersions := query["versions"]; hasVersions {
-				return "s3:GetObjectVersion"
-			}
-			if _, hasUploadId := query["uploadId"]; hasUploadId {
-				return "s3:ListParts"
-			}
-			// Default object read
-			return "s3:GetObject"
-
-		case "PUT", "POST":
-			// Object write operations - check for specific query parameters
-			if _, hasAcl := query["acl"]; hasAcl {
-				return "s3:PutObjectAcl"
-			}
-			if _, hasTagging := query["tagging"]; hasTagging {
-				return "s3:PutObjectTagging"
-			}
-			if _, hasRetention := query["retention"]; hasRetention {
-				return "s3:PutObjectRetention"
-			}
-			if _, hasLegalHold := query["legal-hold"]; hasLegalHold {
-				return "s3:PutObjectLegalHold"
-			}
-			// Check for multipart upload operations
-			if _, hasUploads := query["uploads"]; hasUploads {
-				return "s3:CreateMultipartUpload"
-			}
-			if _, hasUploadId := query["uploadId"]; hasUploadId {
-				if _, hasPartNumber := query["partNumber"]; hasPartNumber {
-					return "s3:UploadPart"
-				}
-				return "s3:CompleteMultipartUpload" // Complete multipart upload
-			}
-			// Default object write
-			return "s3:PutObject"
-
-		case "DELETE":
-			// Object delete operations
-			if _, hasTagging := query["tagging"]; hasTagging {
-				return "s3:DeleteObjectTagging"
-			}
-			if _, hasUploadId := query["uploadId"]; hasUploadId {
-				return "s3:AbortMultipartUpload"
-			}
-			// Default object delete
-			return "s3:DeleteObject"
-		}
-	}
-
-	// Handle bucket-level operations
-	if bucket != "" {
-		switch method {
-		case "GET", "HEAD":
-			// Bucket read operations - check for specific query parameters
-			if _, hasAcl := query["acl"]; hasAcl {
-				return "s3:GetBucketAcl"
-			}
-			if _, hasPolicy := query["policy"]; hasPolicy {
-				return "s3:GetBucketPolicy"
-			}
-			if _, hasTagging := query["tagging"]; hasTagging {
-				return "s3:GetBucketTagging"
-			}
-			if _, hasCors := query["cors"]; hasCors {
-				return "s3:GetBucketCors"
-			}
-			if _, hasVersioning := query["versioning"]; hasVersioning {
-				return "s3:GetBucketVersioning"
-			}
-			if _, hasNotification := query["notification"]; hasNotification {
-				return "s3:GetBucketNotification"
-			}
-			if _, hasObjectLock := query["object-lock"]; hasObjectLock {
-				return "s3:GetBucketObjectLockConfiguration"
-			}
-			if _, hasUploads := query["uploads"]; hasUploads {
-				return "s3:ListMultipartUploads"
-			}
-			if _, hasVersions := query["versions"]; hasVersions {
-				return "s3:ListBucketVersions"
-			}
-			// Default bucket read/list
-			return "s3:ListBucket"
-
-		case "PUT":
-			// Bucket write operations - check for specific query parameters
-			if _, hasAcl := query["acl"]; hasAcl {
-				return "s3:PutBucketAcl"
-			}
-			if _, hasPolicy := query["policy"]; hasPolicy {
-				return "s3:PutBucketPolicy"
-			}
-			if _, hasTagging := query["tagging"]; hasTagging {
-				return "s3:PutBucketTagging"
-			}
-			if _, hasCors := query["cors"]; hasCors {
-				return "s3:PutBucketCors"
-			}
-			if _, hasVersioning := query["versioning"]; hasVersioning {
-				return "s3:PutBucketVersioning"
-			}
-			if _, hasNotification := query["notification"]; hasNotification {
-				return "s3:PutBucketNotification"
-			}
-			if _, hasObjectLock := query["object-lock"]; hasObjectLock {
-				return "s3:PutBucketObjectLockConfiguration"
-			}
-			// Default bucket creation
-			return "s3:CreateBucket"
-
-		case "DELETE":
-			// Bucket delete operations - check for specific query parameters
-			if _, hasPolicy := query["policy"]; hasPolicy {
-				return "s3:DeleteBucketPolicy"
-			}
-			if _, hasTagging := query["tagging"]; hasTagging {
-				return "s3:DeleteBucketTagging"
-			}
-			if _, hasCors := query["cors"]; hasCors {
-				return "s3:DeleteBucketCors"
-			}
-			// Default bucket delete
-			return "s3:DeleteBucket"
-		}
-	}
-
-	// Fallback to legacy mapping for specific known actions
-	return mapLegacyActionToIAM(fallbackAction)
-}
-
 // hasSpecificQueryParameters checks if the request has query parameters that indicate specific granular operations
 func hasSpecificQueryParameters(query url.Values) bool {
 	// Check for object-level operation indicators
@@ -525,9 +360,9 @@ func mapLegacyActionToIAM(legacyAction Action) string {
 	case s3_constants.ACTION_ABORT_MULTIPART:
 		return "s3:AbortMultipartUpload"
 	case s3_constants.ACTION_LIST_MULTIPART_UPLOADS:
-		return "s3:ListMultipartUploads"
+		return s3_constants.S3_ACTION_LIST_MULTIPART_UPLOADS
 	case s3_constants.ACTION_LIST_PARTS:
-		return "s3:ListParts"
+		return s3_constants.S3_ACTION_LIST_PARTS
 
 	default:
 		// If it's already a properly formatted S3 action, return as-is
diff --git a/weed/s3api/s3_iam_simple_test.go b/weed/s3api/s3_iam_simple_test.go
index 36691bb8f..41dbbbed8 100644
--- a/weed/s3api/s3_iam_simple_test.go
+++ b/weed/s3api/s3_iam_simple_test.go
@@ -294,7 +294,7 @@ func TestDetermineGranularS3Action(t *testing.T) {
 			objectKey:      "",
 			queryParams:    map[string]string{"uploads": ""},
 			fallbackAction: s3_constants.ACTION_LIST,
-			expected:       "s3:ListMultipartUploads",
+			expected:       "s3:ListBucketMultipartUploads",
 			description:    "List multipart uploads in bucket",
 		},
 
@@ -336,8 +336,8 @@ func TestDetermineGranularS3Action(t *testing.T) {
 			}
 			req.URL.RawQuery = query.Encode()
 
-			// Test the granular action determination
-			result := determineGranularS3Action(req, tt.fallbackAction, tt.bucket, tt.objectKey)
+			// Test the action determination
+			result := ResolveS3Action(req, string(tt.fallbackAction), tt.bucket, tt.objectKey)
 
 			assert.Equal(t, tt.expected, result,
 				"Test %s failed: %s. Expected %s but got %s",
diff --git a/weed/s3api/s3_list_parts_action_test.go b/weed/s3api/s3_list_parts_action_test.go
index c0e9aa8a1..e83be9be7 100644
--- a/weed/s3api/s3_list_parts_action_test.go
+++ b/weed/s3api/s3_list_parts_action_test.go
@@ -39,8 +39,8 @@ func TestListPartsActionMapping(t *testing.T) {
 			objectKey:      "test-object.txt",
 			queryParams:    map[string]string{"uploadId": "test-upload-id"},
 			fallbackAction: s3_constants.ACTION_READ,
-			expectedAction: "s3:ListParts",
-			description:    "GET request with uploadId should map to s3:ListParts (this was the missing mapping)",
+			expectedAction: "s3:ListMultipartUploadParts",
+			description:    "GET request with uploadId should map to s3:ListMultipartUploadParts (this was the missing mapping)",
 		},
 		{
 			name:      "get_object_with_uploadId_and_other_params",
@@ -53,18 +53,18 @@ func TestListPartsActionMapping(t *testing.T) {
 				"part-number-marker": "50",
 			},
 			fallbackAction: s3_constants.ACTION_READ,
-			expectedAction: "s3:ListParts",
-			description:    "GET request with uploadId plus other multipart params should map to s3:ListParts",
+			expectedAction: "s3:ListMultipartUploadParts",
+			description:    "GET request with uploadId plus other multipart params should map to s3:ListMultipartUploadParts",
 		},
 		{
-			name:           "get_object_versions",
+			name:           "get_object_with_versionId",
 			method:         "GET",
 			bucket:         "test-bucket",
 			objectKey:      "test-object.txt",
-			queryParams:    map[string]string{"versions": ""},
+			queryParams:    map[string]string{"versionId": "version-123"},
 			fallbackAction: s3_constants.ACTION_READ,
 			expectedAction: "s3:GetObjectVersion",
-			description:    "GET request with versions should still map to s3:GetObjectVersion (precedence check)",
+			description:    "GET request with versionId should map to s3:GetObjectVersion",
 		},
 		{
 			name:           "get_object_acl_without_uploadId",
@@ -103,8 +103,8 @@ func TestListPartsActionMapping(t *testing.T) {
 			}
 			req.URL.RawQuery = query.Encode()
 
-			// Call the granular action determination function
-			action := determineGranularS3Action(req, tc.fallbackAction, tc.bucket, tc.objectKey)
+			// Call the action resolver directly
+			action := ResolveS3Action(req, string(tc.fallbackAction), tc.bucket, tc.objectKey)
 
 			// Verify the action mapping
 			assert.Equal(t, tc.expectedAction, action,
@@ -127,17 +127,17 @@ func TestListPartsActionMappingSecurityScenarios(t *testing.T) {
 		query1 := req1.URL.Query()
 		query1.Set("uploadId", "active-upload-123")
 		req1.URL.RawQuery = query1.Encode()
-		action1 := determineGranularS3Action(req1, s3_constants.ACTION_READ, "secure-bucket", "confidential-document.pdf")
+		action1 := ResolveS3Action(req1, string(s3_constants.ACTION_READ), "secure-bucket", "confidential-document.pdf")
 
 		// Test request 2: Get object without uploadId
 		req2 := &http.Request{
 			Method: "GET",
 			URL:    &url.URL{Path: "/secure-bucket/confidential-document.pdf"},
 		}
-		action2 := determineGranularS3Action(req2, s3_constants.ACTION_READ, "secure-bucket", "confidential-document.pdf")
+		action2 := ResolveS3Action(req2, string(s3_constants.ACTION_READ), "secure-bucket", "confidential-document.pdf")
 
 		// These should be different actions, allowing different permissions
-		assert.Equal(t, "s3:ListParts", action1, "Listing multipart parts should require s3:ListParts permission")
+		assert.Equal(t, "s3:ListMultipartUploadParts", action1, "Listing multipart parts should require s3:ListMultipartUploadParts permission")
 		assert.Equal(t, "s3:GetObject", action2, "Reading object content should require s3:GetObject permission")
 		assert.NotEqual(t, action1, action2, "ListParts and GetObject should be separate permissions for security")
 	})
@@ -155,8 +155,8 @@ func TestListPartsActionMappingSecurityScenarios(t *testing.T) {
 			{
 				description:    "List multipart upload parts",
 				queryParams:    map[string]string{"uploadId": "upload-abc123"},
-				expectedAction: "s3:ListParts",
-				securityNote:   "FIXED: Now correctly maps to s3:ListParts instead of s3:GetObject",
+				expectedAction: "s3:ListMultipartUploadParts",
+				securityNote:   "FIXED: Now correctly maps to s3:ListMultipartUploadParts instead of s3:GetObject",
 			},
 			{
 				description:    "Get actual object content",
@@ -167,7 +167,7 @@ func TestListPartsActionMappingSecurityScenarios(t *testing.T) {
 			{
 				description:    "Get object with complex upload ID",
 				queryParams:    map[string]string{"uploadId": "complex-upload-id-with-hyphens-123-abc-def"},
-				expectedAction: "s3:ListParts",
+				expectedAction: "s3:ListMultipartUploadParts",
 				securityNote:   "FIXED: Complex upload IDs now correctly detected",
 			},
 		}
@@ -184,7 +184,7 @@ func TestListPartsActionMappingSecurityScenarios(t *testing.T) {
 			}
 			req.URL.RawQuery = query.Encode()
 
-			action := determineGranularS3Action(req, s3_constants.ACTION_READ, "test-bucket", "test-object")
+			action := ResolveS3Action(req, string(s3_constants.ACTION_READ), "test-bucket", "test-object")
 
 			assert.Equal(t, tc.expectedAction, action,
 				"%s - %s", tc.description, tc.securityNote)
@@ -205,7 +205,7 @@ func TestListPartsActionRealWorldScenarios(t *testing.T) {
 		query1 := req1.URL.Query()
 		query1.Set("uploads", "")
 		req1.URL.RawQuery = query1.Encode()
-		action1 := determineGranularS3Action(req1, s3_constants.ACTION_WRITE, "data", "large-dataset.csv")
+		action1 := ResolveS3Action(req1, string(s3_constants.ACTION_WRITE), "data", "large-dataset.csv")
 
 		// Step 2: List existing parts (GET with uploadId query) - THIS WAS THE MISSING MAPPING
 		req2 := &http.Request{
@@ -215,7 +215,7 @@ func TestListPartsActionRealWorldScenarios(t *testing.T) {
 		query2 := req2.URL.Query()
 		query2.Set("uploadId", "dataset-upload-20240827-001")
 		req2.URL.RawQuery = query2.Encode()
-		action2 := determineGranularS3Action(req2, s3_constants.ACTION_READ, "data", "large-dataset.csv")
+		action2 := ResolveS3Action(req2, string(s3_constants.ACTION_READ), "data", "large-dataset.csv")
 
 		// Step 3: Upload a part (PUT with uploadId and partNumber)
 		req3 := &http.Request{
@@ -226,7 +226,7 @@ func TestListPartsActionRealWorldScenarios(t *testing.T) {
 		query3.Set("uploadId", "dataset-upload-20240827-001")
 		query3.Set("partNumber", "5")
 		req3.URL.RawQuery = query3.Encode()
-		action3 := determineGranularS3Action(req3, s3_constants.ACTION_WRITE, "data", "large-dataset.csv")
+		action3 := ResolveS3Action(req3, string(s3_constants.ACTION_WRITE), "data", "large-dataset.csv")
 
 		// Step 4: Complete multipart upload (POST with uploadId)
 		req4 := &http.Request{
@@ -236,11 +236,11 @@ func TestListPartsActionRealWorldScenarios(t *testing.T) {
 		query4 := req4.URL.Query()
 		query4.Set("uploadId", "dataset-upload-20240827-001")
 		req4.URL.RawQuery = query4.Encode()
-		action4 := determineGranularS3Action(req4, s3_constants.ACTION_WRITE, "data", "large-dataset.csv")
+		action4 := ResolveS3Action(req4, string(s3_constants.ACTION_WRITE), "data", "large-dataset.csv")
 
 		// Verify each step has the correct action mapping
 		assert.Equal(t, "s3:CreateMultipartUpload", action1, "Step 1: Initiate upload")
-		assert.Equal(t, "s3:ListParts", action2, "Step 2: List parts (FIXED by this PR)")
+		assert.Equal(t, "s3:ListMultipartUploadParts", action2, "Step 2: List parts (FIXED by this PR)")
 		assert.Equal(t, "s3:UploadPart", action3, "Step 3: Upload part")
 		assert.Equal(t, "s3:CompleteMultipartUpload", action4, "Step 4: Complete upload")
 
@@ -277,10 +277,10 @@ func TestListPartsActionRealWorldScenarios(t *testing.T) {
 			query.Set("uploadId", uploadId)
 			req.URL.RawQuery = query.Encode()
 
-			action := determineGranularS3Action(req, s3_constants.ACTION_READ, "test-bucket", "test-file.bin")
+			action := ResolveS3Action(req, string(s3_constants.ACTION_READ), "test-bucket", "test-file.bin")
 
-			assert.Equal(t, "s3:ListParts", action,
-				"Upload ID format %s should be correctly detected and mapped to s3:ListParts", uploadId)
+			assert.Equal(t, "s3:ListMultipartUploadParts", action,
+				"Upload ID format %s should be correctly detected and mapped to s3:ListMultipartUploadParts", uploadId)
 		}
 	})
 }
diff --git a/weed/s3api/s3_multipart_iam_test.go b/weed/s3api/s3_multipart_iam_test.go
index 608d30042..725bd0304 100644
--- a/weed/s3api/s3_multipart_iam_test.go
+++ b/weed/s3api/s3_multipart_iam_test.go
@@ -546,8 +546,8 @@ func setupTestRolesForMultipart(ctx context.Context, manager *integration.IAMMan
 					"s3:UploadPart",
 					"s3:CompleteMultipartUpload",
 					"s3:AbortMultipartUpload",
-					"s3:ListMultipartUploads",
-					"s3:ListParts",
+					"s3:ListBucketMultipartUploads",
+					"s3:ListMultipartUploadParts",
 				},
 				Resource: []string{
 					"arn:aws:s3:::*",
diff --git a/weed/s3api/s3api_bucket_handlers.go b/weed/s3api/s3api_bucket_handlers.go
index 6ccf82e27..5ebb06b21 100644
--- a/weed/s3api/s3api_bucket_handlers.go
+++ b/weed/s3api/s3api_bucket_handlers.go
@@ -610,7 +610,8 @@ func (s3a *S3ApiServer) AuthWithPublicRead(handler http.HandlerFunc, action Acti
 
 			// Check bucket policy for anonymous access using the policy engine
 			principal := "*" // Anonymous principal
-			allowed, evaluated, err := s3a.policyEngine.EvaluatePolicy(bucket, object, string(action), principal)
+			// Use context-aware policy evaluation to get the correct S3 action
+			allowed, evaluated, err := s3a.policyEngine.EvaluatePolicyWithContext(bucket, object, string(action), principal, r)
 			if err != nil {
 				// SECURITY: Fail-close on policy evaluation errors
 				// If we can't evaluate the policy, deny access rather than falling through to IAM
diff --git a/weed/s3api/s3api_bucket_policy_engine.go b/weed/s3api/s3api_bucket_policy_engine.go
index ca1093178..278e3e1ae 100644
--- a/weed/s3api/s3api_bucket_policy_engine.go
+++ b/weed/s3api/s3api_bucket_policy_engine.go
@@ -3,13 +3,12 @@ package s3api
 import (
 	"encoding/json"
 	"fmt"
-	"strings"
+	"net/http"
 
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/iam/policy"
 	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
 	"github.com/seaweedfs/seaweedfs/weed/s3api/policy_engine"
-	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
 )
 
 // BucketPolicyEngine wraps the policy_engine to provide bucket policy evaluation
@@ -102,8 +101,8 @@ func (bpe *BucketPolicyEngine) EvaluatePolicy(bucket, object, action, principal
 		return false, false, fmt.Errorf("action cannot be empty")
 	}
 
-	// Convert action to S3 action format
-	s3Action := convertActionToS3Format(action)
+	// Convert action to S3 action format using base mapping (no HTTP context available)
+	s3Action := mapBaseActionToS3Format(action)
 
 	// Build resource ARN
 	resource := buildResourceARN(bucket, object)
@@ -135,72 +134,52 @@ func (bpe *BucketPolicyEngine) EvaluatePolicy(bucket, object, action, principal
 	}
 }
 
-// convertActionToS3Format converts internal action strings to S3 action format
-//
-// KNOWN LIMITATION: The current Action type uses coarse-grained constants
-// (ACTION_READ, ACTION_WRITE, etc.) that map to specific S3 actions, but these
-// are used for multiple operations. For example, ACTION_WRITE is used for both
-// PutObject and DeleteObject, but this function maps it to only s3:PutObject.
-// This means bucket policies requiring fine-grained permissions (e.g., allowing
-// s3:DeleteObject but not s3:PutObject) will not work correctly.
-//
-// TODO: Refactor to use specific S3 action strings throughout the S3 API handlers
-// instead of coarse-grained Action constants. This is a major architectural change
-// that should be done in a separate PR.
-//
-// This function explicitly maps all known actions to prevent security issues from
-// overly permissive default behavior.
-func convertActionToS3Format(action string) string {
-	// Handle multipart actions that already have s3: prefix
-	if strings.HasPrefix(action, "s3:") {
-		return action
+// EvaluatePolicyWithContext evaluates whether an action is allowed by bucket policy using HTTP request context
+// This version uses the HTTP request to determine the actual S3 action more accurately
+func (bpe *BucketPolicyEngine) EvaluatePolicyWithContext(bucket, object, action, principal string, r *http.Request) (allowed bool, evaluated bool, err error) {
+	// Validate required parameters
+	if bucket == "" {
+		return false, false, fmt.Errorf("bucket cannot be empty")
+	}
+	if action == "" {
+		return false, false, fmt.Errorf("action cannot be empty")
 	}
 
-	// Explicit mapping for all known actions
-	switch action {
-	// Basic operations
-	case s3_constants.ACTION_READ:
-		return "s3:GetObject"
-	case s3_constants.ACTION_WRITE:
-		return "s3:PutObject"
-	case s3_constants.ACTION_LIST:
-		return "s3:ListBucket"
-	case s3_constants.ACTION_TAGGING:
-		return "s3:PutObjectTagging"
-	case s3_constants.ACTION_ADMIN:
-		return "s3:*"
+	// Convert action to S3 action format using request context
+	// ResolveS3Action handles nil request internally (falls back to mapBaseActionToS3Format)
+	s3Action := ResolveS3Action(r, action, bucket, object)
 
-	// ACL operations
-	case s3_constants.ACTION_READ_ACP:
-		return "s3:GetObjectAcl"
-	case s3_constants.ACTION_WRITE_ACP:
-		return "s3:PutObjectAcl"
+	// Build resource ARN
+	resource := buildResourceARN(bucket, object)
 
-	// Bucket operations
-	case s3_constants.ACTION_DELETE_BUCKET:
-		return "s3:DeleteBucket"
+	glog.V(4).Infof("EvaluatePolicyWithContext: bucket=%s, resource=%s, action=%s (from %s), principal=%s", 
+		bucket, resource, s3Action, action, principal)
 
-	// Object Lock operations
-	case s3_constants.ACTION_BYPASS_GOVERNANCE_RETENTION:
-		return "s3:BypassGovernanceRetention"
-	case s3_constants.ACTION_GET_OBJECT_RETENTION:
-		return "s3:GetObjectRetention"
-	case s3_constants.ACTION_PUT_OBJECT_RETENTION:
-		return "s3:PutObjectRetention"
-	case s3_constants.ACTION_GET_OBJECT_LEGAL_HOLD:
-		return "s3:GetObjectLegalHold"
-	case s3_constants.ACTION_PUT_OBJECT_LEGAL_HOLD:
-		return "s3:PutObjectLegalHold"
-	case s3_constants.ACTION_GET_BUCKET_OBJECT_LOCK_CONFIG:
-		return "s3:GetBucketObjectLockConfiguration"
-	case s3_constants.ACTION_PUT_BUCKET_OBJECT_LOCK_CONFIG:
-		return "s3:PutBucketObjectLockConfiguration"
+	// Evaluate using the policy engine
+	args := &policy_engine.PolicyEvaluationArgs{
+		Action:    s3Action,
+		Resource:  resource,
+		Principal: principal,
+	}
 
+	result := bpe.engine.EvaluatePolicy(bucket, args)
+
+	switch result {
+	case policy_engine.PolicyResultAllow:
+		glog.V(3).Infof("EvaluatePolicyWithContext: ALLOW - bucket=%s, action=%s, principal=%s", bucket, s3Action, principal)
+		return true, true, nil
+	case policy_engine.PolicyResultDeny:
+		glog.V(3).Infof("EvaluatePolicyWithContext: DENY - bucket=%s, action=%s, principal=%s", bucket, s3Action, principal)
+		return false, true, nil
+	case policy_engine.PolicyResultIndeterminate:
+		// No policy exists for this bucket
+		glog.V(4).Infof("EvaluatePolicyWithContext: INDETERMINATE (no policy) - bucket=%s", bucket)
+		return false, false, nil
 	default:
-		// Log warning for unmapped actions to help catch issues
-		glog.Warningf("convertActionToS3Format: unmapped action '%s', prefixing with 's3:'", action)
-		// For unknown actions, prefix with s3: to maintain format consistency
-		// This maintains backward compatibility while alerting developers
-		return "s3:" + action
+		return false, false, fmt.Errorf("unknown policy result: %v", result)
 	}
 }
+
+// NOTE: The convertActionToS3Format wrapper has been removed for simplicity.
+// EvaluatePolicy and EvaluatePolicyWithContext now call ResolveS3Action or
+// mapBaseActionToS3Format directly, making the control flow more explicit.