diff --git a/.github/workflows/conformance.yml b/.github/workflows/conformance.yml
new file mode 100644
index 0000000..fb8073a
--- /dev/null
+++ b/.github/workflows/conformance.yml
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: MPL-2.0
+# conformance.yml — parser conformance gate for the Phronesis grammar.
+#
+# Runs the real parser (Phronesis.parse/1 = Lexer.tokenize |> Parser.parse) over
+# the conformance corpus:
+#   * conformance/valid/*.phr   MUST parse  (exit 0)
+#   * conformance/invalid/*.phr MUST fail   (exit non-zero)
+# The corpus is the executable contract for spec/grammar.ebnf (v0.2.0). Any drift
+# between the parser and the documented grammar turns this gate red.
+name: Conformance
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+  workflow_dispatch:
+
+# Estate guardrail: cancel superseded runs (read-only check, safe to cancel).
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  conformance:
+    name: Grammar conformance (parser vs corpus)
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - name: Checkout
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      # Match the project toolchain (.tool-versions: elixir 1.16.0 / erlang 26.2.1).
+      # Pinned to the estate-vetted setup-beam SHA already used by hypatia-scan.yml.
+      - name: Setup Elixir
+        uses: erlef/setup-beam@fc68ffb90438ef2936bbb3251622353b3dcb2f93 # v1.18.2
+        with:
+          elixir-version: '1.16'
+          otp-version: '26'
+
+      - name: Fetch dependencies
+        run: mix deps.get
+
+      # Compile without --warnings-as-errors: the gate measures conformance, not
+      # lint. A genuine compile break still fails here (mix compile exits non-zero).
+      - name: Compile
+        run: mix compile
+
+      - name: Run conformance corpus
+        run: ./conformance/run_conformance.sh
diff --git a/conformance/run_conformance.sh b/conformance/run_conformance.sh
index 452e88f..6e740de 100755
--- a/conformance/run_conformance.sh
+++ b/conformance/run_conformance.sh
@@ -20,7 +20,7 @@ if [[ -n "${1:-}" ]]; then
     # shellcheck disable=SC2206 # deliberate word-splitting of caller's string
     PARSER_CMD=(${1})
 else
-    PARSER_CMD=(mix run -e 'Phronesis.CLI.parse(System.argv())' --)
+    PARSER_CMD=(mix run --no-start -e 'System.halt(case Phronesis.parse(File.read!(Enum.at(System.argv(), 0))) do {:ok, _} -> 0; _ -> 1 end)' --)
 fi
 
 PASS=0
diff --git a/conformance/valid/v02_if_then.phr b/conformance/valid/v02_if_then.phr
index 9d8e647..264f418 100644
--- a/conformance/valid/v02_if_then.phr
+++ b/conformance/valid/v02_if_then.phr
@@ -1,11 +1,9 @@
 # SPDX-License-Identifier: MPL-2.0
-# Conformance: IF/THEN/ELSE conditional in policy
+# Conformance: IF/THEN/ELSE conditional action (grammar §5 conditional_action)
 
 POLICY conditional_check:
-  IF status == :valid THEN
-    ACCEPT "Status is valid"
-  ELSE
-    REJECT "Status is invalid"
-PRIORITY 50
-EXPIRES "2030-12-31"
-CREATED_BY "test_suite"
+  value > 0
+  THEN IF value > 100 THEN ACCEPT("High value") ELSE REJECT("Low value")
+  PRIORITY: 50
+  EXPIRES: never
+  CREATED_BY: test_suite
diff --git a/conformance/valid/v03_and_or.phr b/conformance/valid/v03_and_or.phr
index 87ef28f..ea51e4d 100644
--- a/conformance/valid/v03_and_or.phr
+++ b/conformance/valid/v03_and_or.phr
@@ -1,11 +1,11 @@
 # SPDX-License-Identifier: MPL-2.0
-# Conformance: compound conditions with AND/OR
+# Conformance: compound conditions with AND/OR (grammar §6 logical_expr)
+# AND/OR are equal-precedence, left-associative, so this parses as
+#   ((score > 50 AND status == "active") OR override == true).
 
 POLICY compound_logic:
-  IF (score > 50 AND status == :active) OR override == true THEN
-    ACCEPT "Conditions met"
-  ELSE
-    REJECT "Conditions not met"
-PRIORITY 75
-EXPIRES "2030-12-31"
-CREATED_BY "test_suite"
+  score > 50 AND status == "active" OR override == true
+  THEN ACCEPT("Conditions met")
+  PRIORITY: 75
+  EXPIRES: never
+  CREATED_BY: test_suite
diff --git a/conformance/valid/v05_import.phr b/conformance/valid/v05_import.phr
index cca9cae..efca951 100644
--- a/conformance/valid/v05_import.phr
+++ b/conformance/valid/v05_import.phr
@@ -1,15 +1,12 @@
 # SPDX-License-Identifier: MPL-2.0
-# Conformance: IMPORT clause
+# Conformance: IMPORT clause + module-qualified call (grammar §3, §8)
 
 IMPORT Std.BGP
 IMPORT Std.RPKI
 
 POLICY import_test:
-  rpki_result = Std.RPKI.validate(route)
-  IF rpki_result == :valid THEN
-    ACCEPT "RPKI validation passed"
-  ELSE
-    REJECT "RPKI validation failed"
-PRIORITY 100
-EXPIRES "2030-12-31"
-CREATED_BY "test_suite"
+  Std.RPKI.validate(route) == "valid"
+  THEN ACCEPT("RPKI validation passed")
+  PRIORITY: 100
+  EXPIRES: never
+  CREATED_BY: test_suite
diff --git a/conformance/valid/v07_nested.phr b/conformance/valid/v07_nested.phr
index b20bead..fc5ea57 100644
--- a/conformance/valid/v07_nested.phr
+++ b/conformance/valid/v07_nested.phr
@@ -1,14 +1,9 @@
 # SPDX-License-Identifier: MPL-2.0
-# Conformance: nested conditions
+# Conformance: nested conditional actions (grammar §5 conditional_action)
 
 POLICY nested_check:
-  IF level > 1 THEN
-    IF score > 80 THEN
-      ACCEPT "High score at high level"
-    ELSE
-      REJECT "Low score at high level"
-  ELSE
-    ACCEPT "Any score at base level"
-PRIORITY 150
-EXPIRES "2030-12-31"
-CREATED_BY "test_suite"
+  level > 1
+  THEN IF score > 80 THEN ACCEPT("High score at high level") ELSE REJECT("Low score at high level")
+  PRIORITY: 150
+  EXPIRES: never
+  CREATED_BY: test_suite