diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 8ae9df0..6141679 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -7,12 +7,26 @@
 
 version: 2
 updates:
+  # All Rust/Cargo directories are grouped into a single entry so that
+  # when a dependency is updated, Dependabot creates ONE PR that bumps it
+  # across the root workspace AND every binding, preventing version skew.
   - package-ecosystem: "cargo"
-    directory: "/" # Location of package manifests
+    directories:
+      - "/"
+      - "/bindings/ffi"
+      - "/bindings/java"
+      - "/bindings/python"
+      - "/bindings/ruby"
+      - "/bindings/ruby/ext/regorusrb"
+      - "/bindings/wasm"
+      - "/tests/ensure_no_std"
+      - "/xtask"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "build(deps)"
     groups:
-      per-dependency:
+      rust-dependencies:
         patterns:
           - "*"
     # Ignore vendored mimalloc crates; updates are managed manually.
@@ -20,82 +34,12 @@ updates:
       - dependency-name: "regorus-mimalloc"
       - dependency-name: "regorus-mimalloc-sys"
 
-  - package-ecosystem: "cargo"
-    directory: "/bindings/ffi"
-    schedule:
-      interval: "weekly"
-    groups:
-      per-dependency:
-        patterns:
-          - "*"
-
-  - package-ecosystem: "cargo"
-    directory: "/bindings/java"
-    schedule:
-      interval: "weekly"
-    groups:
-      per-dependency:
-        patterns:
-          - "*"
-
-  - package-ecosystem: "cargo"
-    directory: "/bindings/python"
-    schedule:
-      interval: "weekly"
-    groups:
-      per-dependency:
-        patterns:
-          - "*"
-
-  - package-ecosystem: "cargo"
-    directory: "/bindings/ruby"
-    schedule:
-      interval: "weekly"
-    groups:
-      per-dependency:
-        patterns:
-          - "*"
-
-  - package-ecosystem: "cargo"
-    directory: "/bindings/ruby/ext/regorusrb"
-    schedule:
-      interval: "weekly"
-    groups:
-      per-dependency:
-        patterns:
-          - "*"
-
-  - package-ecosystem: "cargo"
-    directory: "/bindings/wasm"
-    schedule:
-      interval: "weekly"
-    groups:
-      per-dependency:
-        patterns:
-          - "*"
-
-  - package-ecosystem: "cargo"
-    directory: "/tests/ensure_no_std"
-    schedule:
-      interval: "weekly"
-    groups:
-      per-dependency:
-        patterns:
-          - "*"
-
-  - package-ecosystem: "cargo"
-    directory: "/xtask"
-    schedule:
-      interval: "weekly"
-    groups:
-      per-dependency:
-        patterns:
-          - "*"
-
   - package-ecosystem: "gomod"
     directory: "/bindings/go"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "build(deps)"
     groups:
       per-dependency:
         patterns:
@@ -105,6 +49,8 @@ updates:
     directory: "/bindings/java"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "build(deps)"
     groups:
       per-dependency:
         patterns:
@@ -114,6 +60,8 @@ updates:
     directory: "/bindings/csharp"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "build(deps)"
     groups:
       per-dependency:
         patterns:
@@ -123,6 +71,8 @@ updates:
     directory: "/bindings/python"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "build(deps)"
     groups:
       per-dependency:
         patterns:
@@ -132,6 +82,8 @@ updates:
     directory: "/bindings/ruby"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "build(deps)"
     groups:
       per-dependency:
         patterns:
@@ -141,7 +93,9 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "ci(deps)"
     groups:
-      per-dependency:
+      github-actions:
         patterns:
           - "*"
diff --git a/.github/workflows/feature-matrix.yml b/.github/workflows/feature-matrix.yml
new file mode 100644
index 0000000..df9de6c
--- /dev/null
+++ b/.github/workflows/feature-matrix.yml
@@ -0,0 +1,82 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+#
+# Thorough weekly test of non-default feature combinations.
+# Catches regressions from dependency updates and feature-gating issues
+# that the fast PR CI checks (cargo check only) would miss at runtime.
+name: tests/feature-matrix
+
+on:
+  workflow_dispatch:
+  schedule:
+    # Run at 3:42 AM UTC every Saturday.
+    - cron: "42 3 * * 6"
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  feature-matrix:
+    name: ${{ matrix.name }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # Bare minimum: validates that the core interpreter works
+          # without any builtins or optional subsystems.
+          - name: minimal (std + arc)
+            features: std,arc
+
+          # Common library usage pattern (issue #595): consumer enables
+          # std + arc + rvm and relies on indexmap/std propagation.
+          - name: library (std + arc + rvm)
+            features: std,arc,rvm
+
+          # New default after removing mimalloc from full-opa.
+          # Ensures all builtins compile without the allocator.
+          - name: full-opa (no mimalloc)
+            features: std,arc,full-opa
+
+          # Binding-style usage: full-opa with the vendored allocator.
+          # Mirrors how ffi/java/python/ruby bindings are built.
+          - name: full-opa + allocator
+            features: std,arc,full-opa,allocator-memory-limits
+
+          # Selective builtins without full-opa: validates that popular
+          # features can be cherry-picked independently.
+          - name: cherry-picked builtins
+            features: std,arc,rvm,regex,time,semver,cache
+
+          # Observability features only: coverage + cache without the
+          # heavier builtins (regex, time, etc.).
+          - name: observability
+            features: std,arc,rvm,coverage,cache
+
+          # Azure Policy adds jsonschema + dashmap; test it compiles
+          # and runs on top of full-opa.
+          - name: azure-policy
+            features: std,arc,full-opa,azure_policy
+
+          # Azure RBAC adds regex + time + net on top of full-opa.
+          - name: azure-rbac
+            features: std,arc,full-opa,azure-rbac
+
+          # no_std with the OPA-compatible feature set: exercises the
+          # spin_no_std codepath and absence of std-only dependencies.
+          - name: no_std
+            features: arc,opa-no-std
+
+    steps:
+    - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+    - name: Setup Rust toolchain
+      uses: ./.github/actions/toolchains/rust
+    - name: Cache cargo
+      uses: Swatinem/rust-cache@779680da715d629ac1d338a641029a2f4372abb5 # v2.8.2
+      with:
+        shared-key: ${{ runner.os }}-regorus-features
+    - name: Fetch dependencies
+      run: cargo fetch --locked
+    - name: Build
+      run: cargo build --no-default-features --features "${{ matrix.features }}" --frozen
+    - name: Test
+      run: cargo test --no-default-features --features "${{ matrix.features }}" --frozen
diff --git a/Cargo.toml b/Cargo.toml
index 2dbe5d3..a75c947 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -43,7 +43,7 @@ cache = ["dep:lru"]
 rvm = ["dep:postcard", "dep:indexmap"]
 semver = ["dep:semver"]
 allocator-memory-limits = ["std", "mimalloc", "mimalloc/allocator-memory-limits"]
-std = ["rand/std", "rand/std_rng", "serde_json/std", "msvc_spectre_libs", "dep:parking_lot" ]
+std = ["rand/std", "rand/std_rng", "serde_json/std", "indexmap?/std", "msvc_spectre_libs", "dep:parking_lot" ]
 time = ["dep:chrono", "dep:chrono-tz"]
 uuid = ["dep:uuid"]
 urlquery = ["dep:url"]
@@ -57,8 +57,6 @@ full-opa = [
     "hex",
     "http",
     "jsonschema",
-    "allocator-memory-limits",
-    "mimalloc",
     "net",
     "opa-runtime",
     "regex",
diff --git a/benches/rvm_benchmark.rs b/benches/rvm_benchmark.rs
index 2604be0..ce5092b 100644
--- a/benches/rvm_benchmark.rs
+++ b/benches/rvm_benchmark.rs
@@ -57,6 +57,7 @@ use regorus::{Engine, Rc, Value};
 // hot path (memory_check, execution_timer_tick, instruction-limit compare).
 // ---------------------------------------------------------------------------
 
+#[cfg(feature = "allocator-memory-limits")]
 const MEMORY_LIMIT_BYTES: u64 = 256 * 1024 * 1024;
 const TIME_LIMIT: Duration = Duration::from_secs(30);
 const TIMER_CHECK_INTERVAL: NonZeroU32 = NonZeroU32::new(16).unwrap();
@@ -360,6 +361,7 @@ fn compile_all_programs() -> Vec<BenchmarkProgram> {
 /// Apply or remove production-style limits based on a boolean flag.
 fn configure_limits(vm: &mut RegoVM, limits: bool) {
     if limits {
+        #[cfg(feature = "allocator-memory-limits")]
         regorus::set_global_memory_limit(Some(MEMORY_LIMIT_BYTES));
         vm.set_execution_timer_config(Some(ExecutionTimerConfig {
             limit: TIME_LIMIT,
@@ -367,6 +369,7 @@ fn configure_limits(vm: &mut RegoVM, limits: bool) {
         }));
         vm.set_max_instructions(INSTRUCTION_LIMIT);
     } else {
+        #[cfg(feature = "allocator-memory-limits")]
         regorus::set_global_memory_limit(None);
         vm.set_execution_timer_config(None);
         vm.set_max_instructions(usize::MAX);
diff --git a/bindings/java/Cargo.toml b/bindings/java/Cargo.toml
index 0710448..a32284b 100644
--- a/bindings/java/Cargo.toml
+++ b/bindings/java/Cargo.toml
@@ -14,7 +14,7 @@ keywords = ["interpreter", "opa", "policy-as-code", "rego"]
 crate-type = ["cdylib"]
 
 [features]
-default = ["ast", "cache", "coverage", "regorus/std", "regorus/full-opa"]
+default = ["ast", "cache", "coverage", "regorus/std", "regorus/full-opa", "regorus/allocator-memory-limits"]
 coverage = ["regorus/coverage"]
 ast = ["regorus/ast"]
 cache = ["regorus/cache"]
diff --git a/bindings/python/Cargo.toml b/bindings/python/Cargo.toml
index 87f2c94..f265c66 100644
--- a/bindings/python/Cargo.toml
+++ b/bindings/python/Cargo.toml
@@ -15,7 +15,7 @@ keywords = ["interpreter", "opa", "policy-as-code", "rego"]
 crate-type = ["cdylib"]
 
 [features]
-default = ["ast", "cache", "coverage", "regorus/std", "regorus/full-opa"]
+default = ["ast", "cache", "coverage", "regorus/std", "regorus/full-opa", "regorus/allocator-memory-limits"]
 ast = ["regorus/ast"]
 cache = ["regorus/cache"]
 coverage = ["regorus/coverage"]
diff --git a/bindings/ruby/ext/regorusrb/Cargo.toml b/bindings/ruby/ext/regorusrb/Cargo.toml
index b2f1851..db89b35 100644
--- a/bindings/ruby/ext/regorusrb/Cargo.toml
+++ b/bindings/ruby/ext/regorusrb/Cargo.toml
@@ -11,7 +11,7 @@ crate-type = ["cdylib"]
 path = "src/lib.rs"
 
 [features]
-default = ["ast", "cache", "coverage", "regorus/std", "regorus/full-opa"]
+default = ["ast", "cache", "coverage", "regorus/std", "regorus/full-opa", "regorus/allocator-memory-limits"]
 ast = ["regorus/ast"]
 cache = ["regorus/cache"]
 coverage = ["regorus/coverage"]
diff --git a/xtask/src/tasks/ci/mod.rs b/xtask/src/tasks/ci/mod.rs
index 7250a0d..7834909 100644
--- a/xtask/src/tasks/ci/mod.rs
+++ b/xtask/src/tasks/ci/mod.rs
@@ -242,6 +242,10 @@ fn run_ci_suite(config: CiSuiteConfig) -> Result<()> {
         )?;
     }
 
+    // Verify that important feature subsets compile correctly.
+    // These catch issues like #595 where non-default combinations fail.
+    check_feature_combinations(&workspace, config.release, config.frozen)?;
+
     Ok(())
 }
 
@@ -364,3 +368,48 @@ fn base_cargo_args(
     }
     args
 }
+
+/// Verify that various feature subsets compile.
+///
+/// Library consumers may pick non-default feature combinations.  Running
+/// `cargo check` for each combination is fast and catches regressions like
+/// issue #595 (indexmap/std not propagated) early.
+///
+/// The weekly `feature-matrix.yml` workflow runs a superset of these with
+/// full `cargo test`; these PR checks are intentionally `cargo check` only
+/// to keep CI fast.
+fn check_feature_combinations(workspace: &Path, release: bool, frozen: bool) -> Result<()> {
+    let combos: &[&str] = &[
+        // Issue #595: library consumer with std + arc + rvm but no full-opa.
+        // Validates indexmap/std propagation via the weak-dep syntax.
+        "std,arc,rvm",
+        // full-opa without mimalloc: the new default after removing the
+        // vendored allocator from full-opa. All builtins, no allocator.
+        "std,arc,full-opa",
+        // Binding-style: full-opa plus the explicit allocator opt-in.
+        // Mirrors how ffi/java/python/ruby crates are configured.
+        "std,arc,full-opa,allocator-memory-limits",
+        // no_std codepath: exercises spin_no_std + absence of std deps.
+        "arc,opa-no-std",
+        // Cherry-picked builtins: popular features without full-opa to
+        // ensure individual feature gates compose correctly.
+        "std,arc,rvm,coverage,cache,regex,time",
+    ];
+
+    for features in combos {
+        let label = format!(
+            "cargo check --no-default-features --features {} (ci)",
+            features
+        );
+        run_ci_cargo_step(
+            workspace,
+            "check",
+            release,
+            frozen,
+            Some(features),
+            &["--no-default-features"],
+            &label,
+        )?;
+    }
+    Ok(())
+}