diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index be631e9..e58ca07 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -43,7 +43,7 @@ repos:
         - black==23.10.1
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.1.14
+    rev: v0.1.15
     hooks:
       - id: ruff
         args: [--fix, --exit-non-zero-on-fix]
diff --git a/phir/model.py b/phir/model.py
index b94d447..aa63645 100644
--- a/phir/model.py
+++ b/phir/model.py
@@ -79,6 +79,24 @@ class ExportVar(Data):
 
 DataMgmt: TypeAlias = CVarDefine | QVarDefine | ExportVar
 
+# Meta Instructions
+
+
+class Meta(BaseModel, abc.ABC):
+    """Meta instructions base class."""
+
+    model_config = ConfigDict(extra="forbid")
+
+    meta: str
+
+
+class Barrier(Meta):
+    """Barrier instruction."""
+
+    meta: Literal["barrier"]
+    args: list[Bit]
+
+
 # Operations
 
 
@@ -243,14 +261,14 @@ class MOp(Op):
 
 
 QOp: TypeAlias = MeasOp | SQOp | TQOp
-OpType: TypeAlias = FFCall | COp | QOp | MOp
+OpType: TypeAlias = FFCall | COp | QOp | MOp | Barrier
 
 
 # Blocks
 
 
 class Block(BaseModel, abc.ABC):
-    """General block type."""
+    """Base class for block type."""
 
     model_config = ConfigDict(extra="forbid")
 
@@ -277,8 +295,8 @@ class IfBlock(Block):
 
     block: Literal["if"]
     condition: COp
-    true_branch: list[OpType]
-    false_branch: list[OpType] | None = None
+    true_branch: list[OpType | BlockType]
+    false_branch: list[OpType | BlockType] | None = None
 
 
 BlockType: TypeAlias = SeqBlock | QParBlock | IfBlock
diff --git a/requirements.txt b/requirements.txt
index 4415045..7ef1703 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,11 +2,11 @@ autodoc-pydantic==2.0.1
 build==1.0.3
 mypy==1.8.0
 pre-commit==3.6.0
-pydantic==2.5.3
+pydantic==2.6.0
 pydata_sphinx_theme==0.15.2
 pytest==8.0.0
 rich==13.7.0
-ruff==0.1.14
+ruff==0.1.15
 setuptools-scm==8.0.4
 sphinx==7.2.6
 wheel==0.42.0
diff --git a/ruff.toml b/ruff.toml
index 9637fbb..d538e10 100644
--- a/ruff.toml
+++ b/ruff.toml
@@ -61,6 +61,8 @@ select = [
   "YTT",  # flake8-2020
 ]
 
+ignore = ["COM812", "ISC001"]  # conflicting with the formatter
+
 [per-file-ignores]
 "__init__.py" = ["F401", "CPY001"]
 "docs/*"      = [
@@ -71,8 +73,6 @@ select = [
     "INP001",
     ]
 
-ignore = ["COM812", "ISC001"]  # conflicting with the formatter
-
 [pydocstyle]
 convention = "google"
 
diff --git a/schema.json b/schema.json
index 20d17ca..afd720e 100644
--- a/schema.json
+++ b/schema.json
@@ -1,5 +1,39 @@
 {
   "$defs": {
+    "Barrier": {
+      "additionalProperties": false,
+      "description": "Barrier instruction.",
+      "properties": {
+        "meta": {
+          "const": "barrier",
+          "title": "Meta"
+        },
+        "args": {
+          "items": {
+            "maxItems": 2,
+            "minItems": 2,
+            "prefixItems": [
+              {
+                "type": "string"
+              },
+              {
+                "minimum": 0,
+                "type": "integer"
+              }
+            ],
+            "type": "array"
+          },
+          "title": "Args",
+          "type": "array"
+        }
+      },
+      "required": [
+        "meta",
+        "args"
+      ],
+      "title": "Barrier",
+      "type": "object"
+    },
     "COp": {
       "additionalProperties": false,
       "description": "Classical operation.",
@@ -374,6 +408,18 @@
               },
               {
                 "$ref": "#/$defs/MOp"
+              },
+              {
+                "$ref": "#/$defs/Barrier"
+              },
+              {
+                "$ref": "#/$defs/SeqBlock"
+              },
+              {
+                "$ref": "#/$defs/QParBlock"
+              },
+              {
+                "$ref": "#/$defs/IfBlock"
               }
             ]
           },
@@ -402,6 +448,18 @@
                   },
                   {
                     "$ref": "#/$defs/MOp"
+                  },
+                  {
+                    "$ref": "#/$defs/Barrier"
+                  },
+                  {
+                    "$ref": "#/$defs/SeqBlock"
+                  },
+                  {
+                    "$ref": "#/$defs/QParBlock"
+                  },
+                  {
+                    "$ref": "#/$defs/IfBlock"
                   }
                 ]
               },
@@ -776,6 +834,9 @@
               {
                 "$ref": "#/$defs/MOp"
               },
+              {
+                "$ref": "#/$defs/Barrier"
+              },
               {
                 "$ref": "#/$defs/SeqBlock"
               },
@@ -966,6 +1027,9 @@
           {
             "$ref": "#/$defs/MOp"
           },
+          {
+            "$ref": "#/$defs/Barrier"
+          },
           {
             "$ref": "#/$defs/SeqBlock"
           },
diff --git a/spec.md b/spec.md
index 031ff65..51a28a9 100644
--- a/spec.md
+++ b/spec.md
@@ -547,6 +547,24 @@ bitwise/logical operations, or comparisons between two variables and/or bits. In
 *Note:* While PHIR/PECOS can effectively manage nested if/else statements, extended OpenQASM 2.0 strictly permits only
 non-nested if statements. Consequently, such nesting should be sidestepped when converting from OpenQASM 2.0 to PHIR.
 
+## Meta Instructions
+
+Instructions that communicate information such as a compiler hints and debugging commands that have influence beyond
+a quantum program.
+
+### Barrier
+
+A barrier instruction provides a hint to the compiler/emulator that qubits involved in barrier may not be optimized or
+parallelized across the barrier. Effectively, it enforces an ordering in time for how quantum state is manipulated by
+the machine.
+
+```json5
+{
+  "meta": "barrier",
+  "args": [qubit_id, ...] // list of qubit IDs
+}
+```
+
 ## Overall PHIR Example with Quantinuum's Extended OpenQASM 2.0
 
 A simple quantum program might look like:
diff --git a/tests/cond_barrier_qparallel.json b/tests/cond_barrier_qparallel.json
new file mode 100644
index 0000000..a85705a
--- /dev/null
+++ b/tests/cond_barrier_qparallel.json
@@ -0,0 +1,54 @@
+{
+  "format": "PHIR/JSON",
+  "version": "0.1.0",
+  "metadata": { "strict_parallelism": "true" },
+  "ops": [
+    {
+      "data": "qvar_define",
+      "data_type": "qubits",
+      "variable": "q",
+      "size": 2
+    },
+    { "data": "cvar_define", "data_type": "u32", "variable": "m", "size": 2 },
+    {
+      "block": "sequence",
+      "ops": [
+        {
+          "block": "if",
+          "condition": { "cop": "==", "args": ["m", 0] },
+          "true_branch": [
+            {
+              "meta": "barrier",
+              "args": [
+                ["q", 0],
+                ["q", 1]
+              ]
+            }
+          ]
+        },
+        {
+          "block": "if",
+          "condition": { "cop": "==", "args": ["m", 1] },
+          "true_branch": [
+            {
+              "block": "qparallel",
+              "ops": [
+                { "qop": "SZdg", "args": [["q", 0]] },
+                { "qop": "SZ", "args": [["q", 1]] }
+              ]
+            }
+          ],
+          "false_branch": [
+            {
+              "block": "qparallel",
+              "ops": [
+                { "qop": "SZdg", "args": [["q", 0]] },
+                { "qop": "SZ", "args": [["q", 1]] }
+              ]
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
diff --git a/tests/test_model.py b/tests/test_model.py
index 583a379..06801e8 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -6,6 +6,8 @@
 #
 ##############################################################################
 
+# mypy: disable-error-code="misc"
+
 """Basic validation tests."""
 
 import json
@@ -14,9 +16,20 @@
 from phir.model import PHIRModel
 
 
-def test_spec_example() -> None:  # noqa: D103
-    # From https://github.com/CQCL/phir/blob/main/spec.md#overall-phir-example-with-quantinuums-extended-openqasm-20
+def test_spec_example() -> None:
+    """From https://github.com/CQCL/phir/blob/main/spec.md .
+
+    Specifically "Overall PHIR Example with Quantinuum's Extended OpenQASM 2.0"
+    """
     with Path("tests/example.json").open() as f:
-        data = json.load(f)  # type: ignore [misc]
+        data = json.load(f)
+
+    PHIRModel.model_validate(data)
+
+
+def test_conditional_barrier() -> None:
+    """Checks for barriers and qparallel blocks inside conditionals."""
+    with Path("tests/cond_barrier_qparallel.json").open() as f:
+        data = json.load(f)
 
-    PHIRModel.model_validate(data)  # type: ignore [misc]
+    PHIRModel.model_validate(data)