fixup: address PR #264 review feedback

- CHANGELOG [Unreleased] Changed: document mdlQuote/unquoteString escape-
  sequence behaviour change (now treats \n \r \t \\ as escapes instead of
  literal pairs). Compatibility break flagged for users who intentionally
  embedded raw backslash-letter sequences in MDL string literals.
- Add comment in expressionToString noting the dual use of mdlQuote for
  MDL source output vs Mendix expression strings, and the describe→re-execute
  trade-off it implies.
- Extract defaultLogNodeExpression constant ('Application') so the builder,
  the formatter, and cmd_diff_mdl share a single source of truth for the
  LOG node fallback.
- Add mdl-examples/bug-tests/264-log-node-expression-roundtrip.mdl
  reproducer per CLAUDE.md checklist.

Author: hjothamendix

CHANGELOG.md

@@ -13,6 +13,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 - **Path normalization** — Relative paths in `MetadataUrl` are automatically converted to absolute `file://` URLs for Studio Pro compatibility
 - **ServiceUrl validation** — `ServiceUrl` parameter must now be a constant reference (e.g., `@Module.ConstantName`) to enforce Mendix best practice
 - **Shared URL utilities** — `internal/pathutil` package with `NormalizeURL()`, `URIToPath()`, and `PathFromURL()` for reuse across components
+
+### Changed
+
+- **MDL string literal escapes** — `mdlQuote`/`unquoteString` now treat `\n`, `\r`, `\t`, and `\\` inside single-quoted literals as escape sequences (previously a literal backslash followed by the letter). This is a compatibility break for any MDL script that intentionally embedded a raw `\n` / `\t` / `\\` as two characters; such scripts must now double the backslash (`\\n` to preserve the two-character form). Applies to `LOG` messages, `@caption`/`@annotation` text, and other string literals round-tripped via the describer.
+
 ## [0.7.0] - 2026-04-21
 
 ### Added

mdl-examples/bug-tests/264-log-node-expression-roundtrip.mdl

@@ -0,0 +1,46 @@
+-- ============================================================================
+-- Bug #264: Log node expressions and microflow describe roundtrip
+-- ============================================================================
+--
+-- Three related regressions surfaced together while exercising real .mpr files:
+--
+-- 1. Legacy `NewCaseValue` on sequence flows (Mx 9) was being dropped by the
+--    parser, so re-describing a Mx 9 project silently lost decision labels.
+-- 2. The describer bailed or emitted malformed MDL when it hit partially
+--    understood activity shapes — a single unknown subfield broke the entire
+--    microflow roundtrip.
+-- 3. The MDL grammar didn't accept the `log` activity's expression-typed NODE
+--    parameter, so any microflow containing a log node with a variable or
+--    constant reference failed to re-parse after describe.
+--
+-- Usage:
+--   mxcli exec mdl-examples/bug-tests/264-log-node-expression-roundtrip.mdl -p app.mpr
+--   Then: mxcli describe microflow BugTest264.MF_LogWithNode -p app.mpr
+--   The output must re-execute cleanly against the same project.
+-- ============================================================================
+
+create module BugTest264;
+
+-- String-literal node (backwards-compatible shape)
+create microflow BugTest264.MF_LogWithLiteralNode ()
+begin
+  log info node 'BugTest264' 'started';
+end;
+/
+
+-- Variable-ref node — exercises Node expression path
+create microflow BugTest264.MF_LogWithNode (
+  $nodeName: string
+)
+begin
+  log info node $nodeName 'hello';
+end;
+/
+
+-- Multi-line message with embedded newline — exercises the mdlQuote escape
+-- round-trip (`\n` is decoded on parse, re-encoded on describe).
+create microflow BugTest264.MF_LogMultilineMessage ()
+begin
+  log info node 'BugTest264' 'line 1\nline 2\nline 3';
+end;
+/

mdl/executor/cmd_diff_mdl.go

@@ -345,7 +345,7 @@ func microflowStatementToMDL(ctx *ExecContext, stmt ast.MicroflowStatement, inde
 		lines = append(lines, indentStr+"end loop;")
 
 	case *ast.LogStmt:
-		nodeStr := "'Application'"
+		nodeStr := defaultLogNodeExpression
 		if s.Node != nil {
 			nodeStr = diffExpressionToString(ctx, s.Node)
 		}

mdl/executor/cmd_microflows_builder_calls.go

@@ -14,6 +14,11 @@ import (
 	"github.com/mendixlabs/mxcli/sdk/microflows"
 )
 
+// defaultLogNodeExpression is the quoted Mendix expression used for the log
+// node when none is specified on a LOG statement. Single source of truth shared
+// by the builder, the formatter, and cmd_diff_mdl.
+const defaultLogNodeExpression = "'Application'"
+
 // addLogMessageAction creates a LOG statement as a LogMessageAction.
 func (fb *flowBuilder) addLogMessageAction(s *ast.LogStmt) model.ID {
 	logLevel := microflows.LogLevelInfo
@@ -65,7 +70,7 @@ func (fb *flowBuilder) addLogMessageAction(s *ast.LogStmt) model.ID {
 		templateParams = []string{fb.exprToString(s.Message)}
 	}
 
-	logNodeName := "'Application'"
+	logNodeName := defaultLogNodeExpression
 	if s.Node != nil {
 		logNodeName = fb.exprToString(s.Node)
 	}

mdl/executor/cmd_microflows_format_action.go

@@ -360,7 +360,7 @@ func formatAction(
 		// Output it as-is since it's already stored as an expression
 		node := a.LogNodeName
 		if node == "" {
-			node = "'Application'" // Default value as a string literal expression
+			node = defaultLogNodeExpression
 		}
 		message := "'Message'"
 		if a.MessageTemplate != nil && len(a.MessageTemplate.Translations) > 0 {

mdl/executor/cmd_microflows_helpers.go

@@ -166,6 +166,13 @@ func mendixFunctionName(name string) string {
 }
 
 // expressionToString converts an AST Expression to a Mendix expression string.
+// Note: string literals are quoted via mdlQuote, which escapes backslashes,
+// newlines, tabs, and carriage returns for MDL round-trip safety. Mendix's
+// expression engine does not treat `\n` etc. as escapes, so a string literal
+// with an embedded raw newline round-trips as `\n` in the MDL source (parseable)
+// but is re-serialised into BSON as a two-character `\n` sequence rather than a
+// real newline. This is the correct trade-off for describe→re-execute flows;
+// the alternative (emitting raw control chars in MDL) would break the parser.
 func expressionToString(expr ast.Expression) string {
 	// Check for nil interface
 	if expr == nil {

mdl/executor/roundtrip_microflow_test.go

@@ -148,7 +148,7 @@ func TestRoundtripMicroflow_LogWithNodeExpression(t *testing.T) {
 		t.Fatalf("Failed to describe microflow: %v", err)
 	}
 
-	if !containsProperty(output, "LOG INFO NODE @"+testModule+".SecurityLogNode") {
+	if !containsProperty(output, "log info node @"+testModule+".SecurityLogNode") {
 		t.Fatalf("Expected constant node expression in output, got:\n%s", output)
 	}