diff --git a/control_plane/src/intent_algebra/expr_ir.rs b/control_plane/src/intent_algebra/expr_ir.rs
new file mode 100644
index 00000000..41736d68
--- /dev/null
+++ b/control_plane/src/intent_algebra/expr_ir.rs
@@ -0,0 +1,36 @@
+//! Language-independent scalar expression IR.
+//!
+//! ## Phase 2 step 2 (docs/migration-plan-backend-plan.md)
+//!
+//! New file, re-exported from ASAPController's `asap-ir` crate. This is
+//! the D2 decision from `ASAPController/docs/intent-algebra-reconciliation.md`
+//! (already validated by ASAPController's own evolution — control_plane
+//! had no equivalent generic-over-column-type scalar IR before this):
+//! `Predicate` and `HavingPredicate` in `query_expr.rs` are currently ad
+//! hoc, control_plane-only types; `relational.rs`'s `ScalarExpr` is a
+//! separate, L2-only scalar type. Once `query_expr.rs`/`relational.rs`
+//! are merged (next Phase 2 step), both collapse onto this one
+//! `Expr<C>` — `L2Expr = Expr<ColumnRef>` for the front-end-emitted L2
+//! tree, `L3Expr = Expr<ColumnId>` for the canonical positional L3 tree.
+//! Nothing in this repo constructs `Expr<C>` yet — that lands with the
+//! `query_expr.rs`/`relational.rs` merge, not here. This step only makes
+//! the type available.
+//!
+//! One generic [`Expr<C>`] spans the lowering boundary; the two layers are
+//! aliases that differ only in the column-reference type `C`:
+//!
+//! - [`L2Expr`] = `Expr<ColumnRef>` — name-based. The per-language front ends
+//!   emit it (PromQL label matchers, SQL `WHERE` / projection / sort-key
+//!   expressions) on the Layer-2 `relational` tree.
+//! - [`L3Expr`] = `Expr<ColumnId>` — **positional**. The canonical L3
+//!   `query_expr` tree carries it; the converter resolves every `ColumnRef`
+//!   against the in-scope schema to produce it, so L3 column identity is
+//!   unambiguous (no name collisions across a join).
+//!
+//! `Expr<C>` shares the scalar/operator vocabulary
+//! ([`L3Scalar`], [`CompareOp`], [`ArithOp`]) — the **union** of what the two
+//! front ends need: PromQL contributes `Regex` / `NotRegex` (`=~` / `!~`); SQL
+//! contributes arithmetic, `CASE`, `IN`, `CAST`, `IS [NOT] NULL`, scalar
+//! function calls, and the `LIKE` / `ILIKE` comparison family.
+
+pub use asap_ir::intent_algebra::{ArithOp, ColumnRef, CompareOp, Expr, L2Expr, L3Expr, L3Scalar};
diff --git a/control_plane/src/intent_algebra/mod.rs b/control_plane/src/intent_algebra/mod.rs
index 533c2df5..c3c675a9 100644
--- a/control_plane/src/intent_algebra/mod.rs
+++ b/control_plane/src/intent_algebra/mod.rs
@@ -73,6 +73,12 @@
 
 pub mod agg_intent;
 pub mod cse;
+// Not yet re-exported into the crate::intent_algebra::* top-level surface
+// below -- `query_expr::ColumnRef` already claims that name, and this
+// module is unused until the query_expr.rs/relational.rs merge (next
+// Phase 2 step) retargets `Predicate`/`ScalarExpr` onto `L3Expr`/`L2Expr`.
+// Reachable today only via the full `intent_algebra::expr_ir::` path.
+pub mod expr_ir;
 pub mod query_expr;
 pub mod schema;