Internal Changes

optimizer/src/main/java/dev/cel/optimizer/AstMutator.java

@@ -889,14 +889,35 @@ private CelMutableSource normalizeMacroSource(
         }
       }
 
-      if (exprIdToReplace > 0) {
+      // Handle replacing the synthetic single-element list inside a `map` or `filter` loop_step.
+      //
+      // Example: `[1].map(x, 10)`
+      //   - In the main AST, `loop_step` is `@result + [10]` (where `[10]` is a synthetic LIST
+      //     node wrapping the body `10`).
+      //   - In `macro_calls`, the call is `[1].map(x, 10)`, which only references the inner `10`
+      //     node—NOT the synthetic `[10]` LIST node.
+      //
+      // If a mutation replaces the `[10]` LIST node itself (e.g. with `[20]`), the loop above
+      // won't find `[10]`'s ID in `macro_calls`, so we unwrap `20` from `[20]` into the macro
+      // call (`[1].map(x, 20)`).
+      //
+      // We must first verify that:
+      //   1. This macro is actually a COMPREHENSION (e.g. `has(msg.f)` is in `macro_calls` too,
+      //      but expands to a SELECT node, not a COMPREHENSION).
+      //   2. The replaced LIST node is inside *this* comprehension's `loop_step` (not an unrelated
+      //      list replacement elsewhere in the AST, such as folding `[1, 2] + [3, 4]`).
+      if (exprIdToReplace > 0
+          && allExprs.get(callId).getKind().equals(ExprKind.Kind.COMPREHENSION)) {
         long replacedId = idGenerator.generate(exprIdToReplace);
+        CelMutableComprehension comprehension = allExprs.get(callId).comprehension();
         boolean isListExprBeingReplaced =
             allExprs.containsKey(replacedId)
-                && allExprs.get(replacedId).getKind().equals(ExprKind.Kind.LIST);
+                && allExprs.get(replacedId).getKind().equals(ExprKind.Kind.LIST)
+                && CelNavigableMutableExpr.fromExpr(comprehension.loopStep())
+                    .allNodes()
+                    .anyMatch(node -> node.id() == replacedId);
         if (isListExprBeingReplaced) {
-          unwrapListArgumentsInMacroCallExpr(
-              allExprs.get(callId).comprehension(), newMacroCallExpr);
+          unwrapListArgumentsInMacroCallExpr(comprehension, newMacroCallExpr);
         }
       }
 

optimizer/src/test/java/dev/cel/optimizer/AstMutatorTest.java

@@ -579,6 +579,25 @@ public void list_replaceElement() throws Exception {
     assertThat(CEL_UNPARSER.unparse(result.toParsedAst())).isEqualTo("[2, 3, 5]");
   }
 
+  @Test
+  public void list_replaceSubtreeWithListInAstWithHasMacro_success() throws Exception {
+    CelAbstractSyntaxTree ast = CEL.compile("has(msg.single_int64) && 1 in [2]").getAst();
+    CelMutableAst mutableAst = CelMutableAst.fromCelAst(ast);
+    CelMutableExpr foldedList =
+        CelMutableExpr.ofList(
+            CelMutableList.create(
+                CelMutableExpr.ofConstant(CelConstant.ofValue(1)),
+                CelMutableExpr.ofConstant(CelConstant.ofValue(2))));
+
+    // Node 8 is `[2]`; replacing it with a LIST triggers normalizeMacroSource while `has(...)` is
+    // present in macroCalls as a SELECT node rather than a COMPREHENSION node.
+    CelAbstractSyntaxTree replacedAst =
+        AST_MUTATOR.replaceSubtree(mutableAst, foldedList, 8).toParsedAst();
+
+    assertThat(CEL_UNPARSER.unparse(replacedAst)).isEqualTo("has(msg.single_int64) && 1 in [1, 2]");
+    assertConsistentMacroCalls(replacedAst);
+  }
+
   @Test
   public void struct_replaceValue() throws Exception {
     // Tree shape (brackets are expr IDs):

policy/src/main/java/dev/cel/policy/CelPolicyCompilerImpl.java

@@ -38,6 +38,7 @@
 import dev.cel.optimizer.CelOptimizer;
 import dev.cel.optimizer.CelOptimizerFactory;
 import dev.cel.optimizer.optimizers.ConstantFoldingOptimizer;
+import dev.cel.optimizer.optimizers.ConstantFoldingOptimizer.ConstantFoldingOptions;
 import dev.cel.optimizer.optimizers.SubexpressionOptimizer;
 import dev.cel.optimizer.optimizers.SubexpressionOptimizer.SubexpressionOptimizerOptions;
 import dev.cel.policy.CelCompiledRule.CelCompiledMatch;
@@ -419,9 +420,15 @@ static Builder newBuilder(Cel cel) {
         .setIterationLimit(DEFAULT_ITERATION_LIMIT)
         .setOptimizers(
             ImmutableList.of(
-                ConstantFoldingOptimizer.getInstance(),
+                ConstantFoldingOptimizer.newInstance(
+                    ConstantFoldingOptions.newBuilder()
+                        .maxIterationLimit(DEFAULT_ITERATION_LIMIT)
+                        .build()),
                 SubexpressionOptimizer.newInstance(
-                    SubexpressionOptimizerOptions.newBuilder().populateMacroCalls(true).build())));
+                    SubexpressionOptimizerOptions.newBuilder()
+                        .iterationLimit(DEFAULT_ITERATION_LIMIT)
+                        .populateMacroCalls(true)
+                        .build())));
   }
 
   private CelPolicyCompilerImpl(

policy/src/main/java/dev/cel/policy/tools/BUILD.bazel

@@ -25,6 +25,7 @@ java_library(
         "//common:proto_v1alpha1_ast",
         "//extensions",
         "//extensions:optional_library",
+        "//optimizer:ast_optimizer",
         "//optimizer/optimizers:common_subexpression_elimination",
         "//optimizer/optimizers:constant_folding",
         "//optimizer/optimizers:select_optimizer",

policy/src/main/java/dev/cel/policy/tools/CelPolicyCompilerTool.java

@@ -36,7 +36,9 @@
 import dev.cel.common.CelProtoV1Alpha1AbstractSyntaxTree;
 import dev.cel.extensions.CelExtensions;
 import dev.cel.extensions.CelOptionalLibrary;
+import dev.cel.optimizer.CelAstOptimizer;
 import dev.cel.optimizer.optimizers.ConstantFoldingOptimizer;
+import dev.cel.optimizer.optimizers.ConstantFoldingOptimizer.ConstantFoldingOptions;
 import dev.cel.optimizer.optimizers.SelectOptimizer;
 import dev.cel.optimizer.optimizers.SelectOptimizer.SelectOptimizerOptions;
 import dev.cel.optimizer.optimizers.SubexpressionOptimizer;
@@ -125,6 +127,12 @@ public final class CelPolicyCompilerTool implements Callable<Integer> {
       description = "Enable inline variable definitions (e.g., '- var_name: expr') in the policy")
   private boolean simpleVariables = false;
 
+  @Option(
+      names = {"--iteration_limit"},
+      defaultValue = "1000",
+      description = "Maximum iteration limit for composing and optimizing the policy")
+  private int iterationLimit = 1000;
+
   private static final CelOptions CEL_OPTIONS =
       CelOptions.current()
           .populateMacroCalls(true)
@@ -214,19 +222,29 @@ public Integer call() {
     }
 
     try {
-      CelPolicyCompilerBuilder policyCompilerBuilder =
-          CelPolicyCompilerFactory.newPolicyCompiler(cel);
-
+      ImmutableList.Builder<CelAstOptimizer> optimizersBuilder =
+          ImmutableList.<CelAstOptimizer>builder()
+              .add(
+                  ConstantFoldingOptimizer.newInstance(
+                      ConstantFoldingOptions.newBuilder()
+                          .maxIterationLimit(iterationLimit)
+                          .build()),
+                  SubexpressionOptimizer.newInstance(
+                      SubexpressionOptimizerOptions.newBuilder()
+                          .iterationLimit(iterationLimit)
+                          .populateMacroCalls(true)
+                          .build()));
       if (optimizeFieldSelection) {
-        policyCompilerBuilder.setOptimizers(
-            ImmutableList.of(
-                ConstantFoldingOptimizer.getInstance(),
-                SubexpressionOptimizer.newInstance(
-                    SubexpressionOptimizerOptions.newBuilder().populateMacroCalls(true).build()),
-                SelectOptimizer.newInstance(
-                    SelectOptimizerOptions.newBuilder().build(), transitiveFileDescriptors)));
+        optimizersBuilder.add(
+            SelectOptimizer.newInstance(
+                SelectOptimizerOptions.newBuilder().build(), transitiveFileDescriptors));
       }
 
+      CelPolicyCompilerBuilder policyCompilerBuilder =
+          CelPolicyCompilerFactory.newPolicyCompiler(cel)
+              .setIterationLimit(iterationLimit)
+              .setOptimizers(optimizersBuilder.build());
+
       CelPolicyCompiler policyCompiler = policyCompilerBuilder.build();
       CelAbstractSyntaxTree ast = policyCompiler.compile(policy);
 

policy/src/test/java/dev/cel/policy/tools/CelPolicyCompilerToolTest.java

@@ -299,6 +299,34 @@ public void compile_withSimpleVariables_success() throws Exception {
     assertThat(celRuntime.createProgram(ast).eval()).isEqualTo(Optional.of(true));
   }
 
+  @Test
+  public void compile_withIterationLimitReached_returnsError() throws Exception {
+    String configPath = createFile("config.yaml", "name: test-env\n");
+    String policyPath =
+        createFile(
+            "policy.yaml",
+            "name: p\n"
+                + "rule:\n"
+                + "  variables:\n"
+                + "    - a: 1 + 2\n"
+                + "    - b: variables.a + 3\n"
+                + "  match:\n"
+                + "    - condition: variables.b == 6\n"
+                + "      output: 'true'\n");
+
+    String stdErr =
+        executeExpectingError(
+            "--policy",
+            policyPath,
+            "--config",
+            configPath,
+            "--simple_variables",
+            "--iteration_limit",
+            "1");
+
+    assertThat(stdErr).contains("Reason: Unexpected error while composing rules.");
+  }
+
   @Test
   public void compile_withOptimizeFieldSelection_rewritesSelectAndEvaluates() throws Exception {
     String configRlocation =

policy/tools/compile_cel_policy.bzl

@@ -27,6 +27,7 @@ def compile_cel_policy(
         output_version = "canonical",
         optimize_field_selection = False,
         simple_variables = False,
+        iteration_limit = None,
         visibility = None):
     """Compiles a CEL policy into a CheckedExpr binarypb or textpb with optional select optimization.
 
@@ -45,12 +46,14 @@ def compile_cel_policy(
       output_format: (optional) str either "binarypb", "textpb", or "textproto" (default "binarypb")
       output_version: (optional) str either "canonical" or "v1alpha1" (default "canonical")
       optimize_field_selection: (optional) bool whether to enable AST select optimization (default False).
-        When True, embeds field numbers, wire types, and default values directly into the compiled
+        When True, embeds field numbers, field types, and default values directly into the compiled
         `CheckedExpr` AST. This enables version-skew and field-rename resilience (evaluating unknown
         fields from raw wire bytes on older clients) and faster field selections, at the cost of a
         larger serialized AST payload.
       simple_variables: (optional) bool whether to enable inline variable definitions (e.g.,
         `- var_name: expr` instead of `- name: var_name` / `expression: expr`) in the policy (default False)
+      iteration_limit: (optional) int maximum iteration limit for composing and optimizing the policy
+        (default None, which uses the compiler default of 1000)
       visibility: (optional) visibility to use on the genrule macro (default None)
     """
     if output_format not in ("binarypb", "textpb", "textproto"):
@@ -97,6 +100,9 @@ def compile_cel_policy(
     if simple_variables:
         args.append("--simple_variables")
 
+    if iteration_limit != None:
+        args.append("--iteration_limit=%d" % iteration_limit)
+
     cmd = (
         "$(location //policy/tools:cel_policy_compiler_tool) " +
         " ".join(args)