feat: ADR-0036 Phase 3a — live typed-slot hints + highlighting for SQL SET values

Wire the DSL's column-typed value slots into the advanced-mode SQL
UPDATE/UPSERT `SET col = <rhs>` value position so a learner gets the same
per-column hint ("for `Email`: type a quoted string") and live numeric-
shape mismatch highlight the simple-mode DSL gives.

Discriminate literal-vs-expression with a boundary-aware lookahead
(shared::SET_VALUE), NOT the naive `Choice(typed-slot, sql_expr)` the ADR
originally sketched: the walker's Choice is first-match-wins with no
backtrack, so a typed slot would greedily match the leading `1` of `1 + 2`
and commit, regressing valid SQL (e.g. the existing `values (1, 1 + 2)`
test). The lookahead peeks the whole value position: a literal routes to
the typed slot only when it fills the position up to the next
`,`/`)`/`;`/`where`/`returning`/end; everything else falls through to the
full sql_expr grammar unchanged. The SET column ident gets
`writes_column: true` so `current_column` drives the slot + hint.

Scope: Phase 3a covers UPDATE's assignment list and INSERT's ON CONFLICT
DO UPDATE SET. Phase 3b (INSERT VALUES — needs a per-position grammar
restructure + multi-row) is deferred. Records ADR-0036 Amendment 1 with
the mechanism correction + the 3a/3b split.

Tests: 1939 passing (+5), 0 failed, 0 skipped, 1 ignored; clippy clean.

docs/adr/0036-typed-dml-values-vs-verbatim.md

@@ -16,8 +16,12 @@ validation + offending-value retention; the same capture-at-parse technique
 on the SET assignment list — `capture_set_literals` in `data.rs` —
 classifying each top-level RHS literal-vs-expression, validating literals in
 `do_sql_update`, and reading them in `user_value_for_column`; `WHERE` is not
-validated, execution stays verbatim). Phase 3 (completion
-hinting/highlighting — the only part needing a grammar change) pending.
+validated, execution stays verbatim). **Phase 3a implemented 2026-05-26**
+— live typed-slot hints + numeric-shape highlighting for advanced-mode
+`UPDATE`/UPSERT `SET col = <literal>` value positions, via a
+**boundary-aware lookahead** (not the naive `Choice` this ADR originally
+sketched in §5 — see **Amendment 1**). Phase 3b (`INSERT … VALUES` typed
+slots — needs a per-position grammar restructure + multi-row) pending.
 
 **Augments** **ADR-0030 §4** and **ADR-0033 §10** — it does **not**
 supersede them and does **not** change the execution model. Advanced-mode
@@ -265,13 +269,17 @@ execution), only its `Result` is used.
   verbatim update; `user_value_for_column` reads them so a constraint error
   names the offending value. `WHERE` is deliberately not validated (§2).
 - **Phase 3 — completion hinting / highlighting.** This is the *only*
-  part that needs a grammar change: a `Choice(typed-literal-slot,
-  sql_expr)` at each value position (reusing the DSL's live
-  `column_value_list` / `TypedValueSlot`s — `data.rs:141`/`189`/`269`),
-  so the column type drives a live hint and a mismatch highlights while
-  typing. When Phase 3 lands, the typed slot supersedes Phase 1's
-  classification of literals (the validation/enrichment built on top is
-  unaffected — that is the only throwaway, by design).
+  part that needs a grammar change: a typed-literal slot vs `sql_expr` at
+  each value position (reusing the DSL's live `column_value_list` /
+  `TypedValueSlot`s — `data.rs:141`/`189`/`269`), so the column type
+  drives a live hint and a mismatch highlights while typing. When Phase 3
+  lands, the typed slot supersedes Phase 1/2's classification of literals
+  (the validation/enrichment built on top is unaffected — that is the
+  only throwaway, by design). **The literal-vs-expression discriminator
+  is a boundary-aware *lookahead*, not a naive `Choice(typed-slot,
+  sql_expr)` — see Amendment 1, which corrects this section's mechanism
+  and splits Phase 3 into 3a (`SET`, implemented 2026-05-26) and 3b
+  (`VALUES`, pending).**
 
 ### 6. Non-goals
 
@@ -315,6 +323,69 @@ execution), only its `Result` is used.
   validation/enrichment built on it is permanent; only the detection is
   provisional — a deliberate, documented small throwaway.
 
+## Amendment 1 — Phase 3 mechanism is a boundary-aware lookahead, not a naive `Choice`; Phase 3 split into 3a/3b (2026-05-26)
+
+**Status:** Accepted (agreed with the user in conversation, 2026-05-26).
+**Phase 3a implemented the same day.**
+
+§5 Phase 3 sketched the mechanism as "a `Choice(typed-literal-slot,
+sql_expr)` at each value position." Implementation found that sketch is
+**wrong as written** and would regress valid SQL, so it is corrected here.
+
+**Why the naive `Choice` is broken.** The walker's `Node::Choice` is
+first-match-wins with **no cross-branch backtracking** once a branch has
+committed a `Matched` (a later failure in the enclosing `Seq` does not
+re-enter the Choice). At, say, an `int` column, the value `1 + 2`:
+
+- Branch 0 (the typed slot) matches just the `1` and commits, leaving
+  `+ 2` dangling — the enclosing tuple/assignment then fails on `+`.
+- The Choice never falls through to `sql_expr`, so a **valid, currently
+  parsing SQL expression is rejected**.
+
+This is not hypothetical: `tests/sql_insert.rs::sql_insert_expression_value_is_not_validated_and_runs`
+exercises exactly `values (1, 1 + 2)`. Putting `sql_expr` first instead
+makes the typed slot unreachable (sql_expr matches bare literals too),
+defeating the purpose. So the discriminator must know whether a literal
+**fills the whole value position** before choosing the typed slot.
+
+**The correction.** Discriminate by a **boundary-aware lookahead**
+(`shared::SET_VALUE` → `set_value_node`): peek the value position and
+route to the column-typed slot only when it is empty, a partial string
+still being typed, or a single complete literal token whose next token is
+a position boundary (`,` / `)` / `;` / `where` / `returning` / end);
+otherwise route to `Subgrammar(sql_expr)`. The empty case still routes to
+the slot so the per-column hint shows while the cursor sits right after
+`=`. A leading sign folds into the literal (the slot's `NumberLit` uses
+the same `consume_number_literal` that eats a `-`), so signed literals get
+typed treatment too. `Node::Lookahead` already exists and is used the same
+way by `insert_first_paren` (`data.rs`). The validation/enrichment from
+Phases 1–2 is unchanged; only the *live-feedback detection* uses this
+lookahead — consistent with §5's note that Phase 3's detection is the one
+deliberate throwaway.
+
+**Phase 3 split into 3a + 3b.** The two halves differ structurally:
+
+- **Phase 3a (implemented) — `UPDATE` / UPSERT `SET col = <rhs>`.** Low
+  risk: the preceding `SET` column ident gets `writes_column: true` so
+  `current_column` (and the `pending_value_column` hint framing) is set
+  per assignment; the RHS becomes `shared::SET_VALUE`. Covers both
+  `sql_update`'s assignment list and `sql_insert`'s `ON CONFLICT … DO
+  UPDATE SET`. Mismatch examples now caught **live** (e.g. `set k = 3.14`
+  at an `int` column), matching what simple mode already does — earlier,
+  better feedback than Phase 2's execution-time catch.
+- **Phase 3b (pending) — `INSERT … VALUES (…)`.** Harder: the values list
+  is `Repeated(VALUE_EXPR)` with **no per-position column identity**, and
+  multi-row `values (..),(..)` must be handled. It needs the DSL-style
+  per-position restructure (a `DynamicSubgrammar` emitting one
+  boundary-aware position per column), tracked as its own step.
+
+**Known limitation (both phases, matches the DSL).** `date` / `shortid` /
+`datetime` **format** is still not validated at parse — those slots accept
+any quoted string; the format is checked at bind/execution time (Phase 2).
+So the live highlight catches *numeric-shape* mismatches (`int`/`decimal`/
+`bool`), not malformed dates. The column-type **hint** still shows for
+every type.
+
 ## See also
 
 - ADR-0030 §4 / ADR-0033 §10 — the execute-path this ADR **augments**

src/dsl/grammar/shared.rs

@@ -456,3 +456,114 @@ pub fn column_value_list(ctx: &WalkContext) -> Node {
     }
     Node::Seq(Box::leak(children.into_boxed_slice()))
 }
+
+// =================================================================
+// Advanced-mode SQL `SET col = <rhs>` value slot (ADR-0036 Phase 3a)
+// =================================================================
+//
+// A SQL UPDATE / UPSERT `SET col = <rhs>` value position routes a
+// *lone literal* (a string / number / `null` / `true` / `false` that
+// fills the whole position up to the next `,` / `where` / `returning`
+// / `;` / end-of-input) to the column-typed slot — so the learner gets
+// the same per-column hint + numeric-shape highlight the DSL gives —
+// and routes anything else (an expression: arithmetic, a literal-
+// prefixed form like `1 + 2`, a function call, a scalar subquery, a
+// column / `excluded` reference) to the full `sql_expr` grammar,
+// unchanged (ADR-0030 §4).
+//
+// Discrimination is by *lookahead*, NOT `Choice([typed_slot,
+// sql_expr])`. A naive Choice would let the typed slot greedily match
+// the leading literal of `1 + 2` and commit, leaving `+ 2` dangling —
+// the walker's `Choice` is first-match-wins with no cross-branch
+// backtrack — turning a valid expression into a parse error. The
+// lookahead peeks the whole value position first, so a literal routes
+// to the typed slot only when it is the *entire* value (ADR-0036
+// Amendment 1).
+
+/// Lookahead factory for a SQL `SET col = <rhs>` value position
+/// (ADR-0036 Phase 3a). Routes a lone literal to the column-typed slot
+/// (live hint + highlight) and everything else to `sql_expr`.
+fn set_value_node(_ctx: &WalkContext, source: &str, pos: usize) -> Node {
+    if set_rhs_is_lone_literal(source, pos) {
+        // The column type was resolved into `current_column` by the
+        // preceding `SET` column ident (`writes_column: true`), so the
+        // typed slot drives the per-column hint + highlight.
+        Node::DynamicSubgrammar(current_column_value)
+    } else {
+        // An expression — the engine evaluates it; keep the full
+        // `sql_expr` surface. Returned from a `fn` (not a `const`) so
+        // the reference doesn't enter the sql_expr ⇄ sql_select
+        // const-evaluation cycle (see the matching note in `data.rs`).
+        Node::Subgrammar(&crate::dsl::grammar::sql_expr::SQL_OR_EXPR)
+    }
+}
+
+/// The SQL `SET col = <rhs>` value slot (ADR-0036 Phase 3a). Shared by
+/// `sql_update`'s assignment list and the `sql_insert` UPSERT
+/// `DO UPDATE SET`.
+pub const SET_VALUE: Node = Node::Lookahead(set_value_node);
+
+/// True when the `SET` RHS starting at `pos` is empty, a partial string
+/// still being typed, or exactly one complete literal token that fills
+/// the value position (the next token is a position boundary). Such
+/// positions route to the column-typed slot so its hint/highlight fire;
+/// everything else is an expression and routes to `sql_expr`.
+///
+/// An empty RHS counts as lone-literal so the typed-slot hint shows
+/// while the cursor sits right after `=`. A signed number (`-5`) counts
+/// too: `consume_number_literal` — the same consumer the slot's
+/// `NumberLit` uses — folds the leading sign into the literal, so the
+/// slot can match it.
+fn set_rhs_is_lone_literal(source: &str, pos: usize) -> bool {
+    use crate::dsl::walker::lex_helpers::{
+        consume_ident, consume_number_literal, consume_string_literal, skip_whitespace,
+    };
+    let p = skip_whitespace(source, pos);
+    if p >= source.len() {
+        return true; // empty RHS — show the typed-slot hint
+    }
+    // A string literal — single-quoted (SQL strings). Complete (a
+    // boundary must follow) or a partial one still being typed (route
+    // to the slot so the hint persists while typing).
+    if source.as_bytes()[p] == b'\'' {
+        return match consume_string_literal(source, p) {
+            Some(((_, end), _)) => next_is_set_boundary(source, end),
+            None => true, // unterminated string, mid-typing
+        };
+    }
+    // A number literal (incl. a leading sign) that fills the position.
+    if let Some((_, end)) = consume_number_literal(source, p) {
+        return next_is_set_boundary(source, end);
+    }
+    // `null` / `true` / `false` filling the position.
+    if let Some((s, e)) = consume_ident(source, p) {
+        let word = &source[s..e];
+        if word.eq_ignore_ascii_case("null")
+            || word.eq_ignore_ascii_case("true")
+            || word.eq_ignore_ascii_case("false")
+        {
+            return next_is_set_boundary(source, e);
+        }
+        return false; // any other identifier → column ref / function → expression
+    }
+    false // punctuation / sign-then-space / `(` → expression
+}
+
+/// True when the next non-whitespace token after `pos` ends a `SET`
+/// value position: `,` (next assignment), `)` / `;` / end-of-input, or
+/// a `where` / `returning` clause keyword.
+fn next_is_set_boundary(source: &str, pos: usize) -> bool {
+    use crate::dsl::walker::lex_helpers::{consume_ident, skip_whitespace};
+    let p = skip_whitespace(source, pos);
+    let Some(b) = source.as_bytes().get(p) else {
+        return true; // end of input
+    };
+    if *b == b',' || *b == b';' || *b == b')' {
+        return true;
+    }
+    if let Some((s, e)) = consume_ident(source, p) {
+        let word = &source[s..e];
+        return word.eq_ignore_ascii_case("where") || word.eq_ignore_ascii_case("returning");
+    }
+    false
+}

src/dsl/grammar/sql_insert.rs

@@ -13,6 +13,7 @@
 //! (3g), and `ON CONFLICT … ` UPSERT (3h) land in later
 //! sub-phases.
 
+use crate::dsl::grammar::shared::SET_VALUE;
 use crate::dsl::grammar::sql_expr;
 use crate::dsl::grammar::sql_select::{
     RETURNING_CLAUSE, SQL_SELECT_COMPOUND, WHERE_CLAUSE, reject_internal_table,
@@ -146,30 +147,31 @@ const OPTIONAL_CONFLICT_TARGET: Node = Node::Optional(&Node::Seq(CONFLICT_TARGET
 /// The column on the left of one `DO UPDATE SET col = expr`
 /// assignment. Mirrors `sql_update`'s `ASSIGN_COLUMN` shape (same
 /// `update_set_column` role so it gets the same column completion /
-/// diagnostics against the target table).
+/// diagnostics against the target table). `writes_column: true`
+/// resolves the column type into `current_column` so the RHS
+/// `SET_VALUE` lookahead can dispatch the typed slot for a lone
+/// literal (ADR-0036 Phase 3a).
 const UPSERT_SET_COLUMN: Node = Node::Ident {
     source: IdentSource::Columns,
     role: "update_set_column",
     validator: None,
     highlight_override: None,
     writes_table: false,
-    writes_column: false,
+    writes_column: true,
     writes_user_listed_column: false,
     writes_table_alias: false,
     writes_cte_name: false,
     writes_projection_alias: false,
 };
 
-/// `column '=' sql_expr` — the RHS reuses the shared expression
-/// grammar (ADR-0031), so `excluded.col`, literals, operators,
-/// `CASE`, and function calls are all admitted. `excluded` is the
-/// would-have-been-inserted row (ADR-0033 §9); it parses as a
+/// `column '=' <value>` — the RHS is the boundary-aware `SET_VALUE`
+/// slot (ADR-0036 Phase 3a), shared with `sql_update`: a lone literal
+/// routes to the column-typed slot (live hint + highlight) while an
+/// expression — `excluded.col`, operators, `CASE`, function calls —
+/// falls through to the full `sql_expr` grammar (ADR-0031). `excluded`
+/// is the would-have-been-inserted row (ADR-0033 §9); it parses as a
 /// qualified ref via `sql_expr` and the engine resolves it.
-static UPSERT_ASSIGNMENT_NODES: &[Node] = &[
-    UPSERT_SET_COLUMN,
-    Node::Punct('='),
-    Node::Subgrammar(&sql_expr::SQL_OR_EXPR),
-];
+static UPSERT_ASSIGNMENT_NODES: &[Node] = &[UPSERT_SET_COLUMN, Node::Punct('='), SET_VALUE];
 static UPSERT_ASSIGNMENT: Node = Node::Seq(UPSERT_ASSIGNMENT_NODES);
 // `const` — used by value in `DO_UPDATE_NODES` (static-vs-const
 // rule: a `Node` referenced by value in a `static [...]` must be

src/dsl/grammar/sql_update.rs

@@ -15,7 +15,7 @@
 //! `--all-rows` rail — a SQL `UPDATE` without `WHERE` runs as
 //! written (ADR-0030 §12). `RETURNING` (3g) lands later.
 
-use crate::dsl::grammar::sql_expr;
+use crate::dsl::grammar::shared::SET_VALUE;
 use crate::dsl::grammar::sql_select::{RETURNING_CLAUSE, WHERE_CLAUSE, reject_internal_table};
 use crate::dsl::grammar::{IdentSource, Node, Word};
 
@@ -44,28 +44,33 @@ const TARGET_TABLE: Node = Node::Ident {
 };
 
 /// The column on the left of one `SET col = expr` assignment.
+///
+/// `writes_column: true` resolves the column's type into
+/// `current_column` (and frames the value-slot hint via
+/// `pending_value_column`), so the RHS `SET_VALUE` lookahead can
+/// dispatch the column-typed slot for a lone literal (ADR-0036
+/// Phase 3a).
 const ASSIGN_COLUMN: Node = Node::Ident {
     source: IdentSource::Columns,
     role: "update_set_column",
     validator: None,
     highlight_override: None,
     writes_table: false,
-    writes_column: false,
+    writes_column: true,
     writes_user_listed_column: false,
     writes_table_alias: false,
     writes_cte_name: false,
     writes_projection_alias: false,
 };
 
-/// `column_name '=' sql_expr` — the RHS reuses the shared
-/// expression grammar (ADR-0031), so literals, operators, `CASE`,
-/// function calls, and scalar subqueries are all admitted; the
-/// engine evaluates them at execution time.
-static ASSIGNMENT_NODES: &[Node] = &[
-    ASSIGN_COLUMN,
-    Node::Punct('='),
-    Node::Subgrammar(&sql_expr::SQL_OR_EXPR),
-];
+/// `column_name '=' <value>` — the RHS is the boundary-aware
+/// `SET_VALUE` slot (ADR-0036 Phase 3a): a lone literal routes to the
+/// column-typed slot (live per-column hint + numeric-shape highlight,
+/// shared with the DSL), while any expression — arithmetic, a
+/// literal-prefixed form, `CASE`, function calls, scalar subqueries —
+/// falls through to the full `sql_expr` grammar (ADR-0031), which the
+/// engine evaluates at execution time.
+static ASSIGNMENT_NODES: &[Node] = &[ASSIGN_COLUMN, Node::Punct('='), SET_VALUE];
 static ASSIGNMENT: Node = Node::Seq(ASSIGNMENT_NODES);
 
 /// `assignment ( ',' assignment )*`.

tests/sql_insert.rs

@@ -20,9 +20,12 @@
 //! worker-level tests call `db.run_sql_insert` directly with the
 //! real reconstructed SQL.
 
+use rdbms_playground::completion::{SchemaCache, TableColumn};
 use rdbms_playground::db::{Database, DbError, InsertResult};
 use rdbms_playground::dsl::{ColumnSpec, Command, Type, Value, parse_command};
 use rdbms_playground::event::AppEvent;
+use rdbms_playground::input_render::{AmbientHint, ambient_hint_in_mode};
+use rdbms_playground::mode::Mode;
 use rdbms_playground::persistence::Persistence;
 use rdbms_playground::project;
 use rdbms_playground::runtime::run_replay;
@@ -1182,3 +1185,35 @@ fn sql_insert_natural_order_validates_against_schema_columns() {
         "natural-order insert validates the date against column `d`; events: {events:?}"
     );
 }
+
+// =================================================================
+// ADR-0036 Phase 3a — live typed-slot hint for the UPSERT
+// `ON CONFLICT … DO UPDATE SET col = <rhs>` value position.
+// =================================================================
+
+#[test]
+fn advanced_upsert_do_update_set_offers_typed_slot_hint() {
+    // ADR-0036 Phase 3a: the `DO UPDATE SET col = ` value position
+    // shares the SQL UPDATE `SET` treatment, so it drives the same
+    // column-typed slot hint (boundary-aware lookahead → typed slot).
+    let mut cache = SchemaCache::default();
+    let cols = vec![
+        TableColumn { name: "id".to_string(), user_type: Type::Int, not_null: false, has_default: false },
+        TableColumn { name: "Name".to_string(), user_type: Type::Text, not_null: false, has_default: false },
+    ];
+    cache.tables.push("Customers".to_string());
+    cache.columns.push("id".to_string());
+    cache.columns.push("Name".to_string());
+    cache.table_columns.insert("Customers".to_string(), cols);
+
+    let input = "insert into Customers (id, Name) values (1, 'x') on conflict (id) do update set Name=";
+    let hint = ambient_hint_in_mode(input, input.len(), None, &cache, Mode::Advanced);
+    let Some(AmbientHint::Prose(prose)) = hint else {
+        panic!("expected a Prose hint at the UPSERT SET value slot, got {hint:?}");
+    };
+    assert!(prose.contains("Name"), "hint names the column `Name`: {prose:?}");
+    assert!(
+        prose.contains("quoted string"),
+        "text-column hint says `quoted string`: {prose:?}"
+    );
+}

tests/sql_update.rs

@@ -7,9 +7,14 @@
 //! append `history.log`). A SQL `UPDATE` without `WHERE` runs
 //! across all rows with no rail (ADR-0030 §12).
 
+use rdbms_playground::completion::{SchemaCache, TableColumn};
 use rdbms_playground::db::{Database, DbError, UpdateResult};
 use rdbms_playground::dsl::{ColumnSpec, Command, Type, Value, parse_command};
 use rdbms_playground::event::AppEvent;
+use rdbms_playground::input_render::{
+    AmbientHint, InputState, ambient_hint_in_mode, classify_input_with_schema_in_mode,
+};
+use rdbms_playground::mode::Mode;
 use rdbms_playground::persistence::Persistence;
 use rdbms_playground::project;
 use rdbms_playground::runtime::run_replay;
@@ -368,3 +373,118 @@ fn update_returning_matching_no_rows_is_ok_and_empty() {
     assert!(result.data.rows.is_empty(), "no rows returned");
     assert_eq!(result.data.columns, vec!["id".to_string(), "v".to_string()], "columns still present");
 }
+
+// =================================================================
+// ADR-0036 Phase 3a — live typed-slot hints + highlighting for
+// advanced-mode `SET col = <rhs>` (boundary-aware lookahead).
+// =================================================================
+
+/// Build a `SchemaCache` for the advanced-mode typing-surface tests
+/// (mirrors `tests/typing_surface`'s `build_schema`).
+fn schema_cache(tables: &[(&str, &[(&str, Type)])]) -> SchemaCache {
+    let mut cache = SchemaCache::default();
+    for (table, cols) in tables {
+        let table_cols: Vec<TableColumn> = cols
+            .iter()
+            .map(|(n, t)| TableColumn {
+                name: (*n).to_string(),
+                user_type: *t,
+                not_null: false,
+                has_default: false,
+            })
+            .collect();
+        cache.tables.push((*table).to_string());
+        for c in &table_cols {
+            if !cache.columns.contains(&c.name) {
+                cache.columns.push(c.name.clone());
+            }
+        }
+        cache.table_columns.insert((*table).to_string(), table_cols);
+    }
+    cache
+}
+
+#[test]
+fn advanced_update_set_value_offers_typed_slot_hint_for_column() {
+    // ADR-0036 Phase 3a: at a `SET col = ` value position the
+    // advanced-mode SQL UPDATE now drives the same column-typed slot
+    // hint the DSL gives — "for `Email`: type a quoted string …" —
+    // instead of the type-blind sql_expr surface.
+    let schema = schema_cache(&[(
+        "Customers",
+        &[("id", Type::Serial), ("Name", Type::Text), ("Email", Type::Text)],
+    )]);
+    let input = "update Customers set Email=";
+    let hint = ambient_hint_in_mode(input, input.len(), None, &schema, Mode::Advanced);
+    let Some(AmbientHint::Prose(prose)) = hint else {
+        panic!("expected a Prose hint at the typed value slot, got {hint:?}");
+    };
+    assert!(prose.contains("Email"), "hint names the column `Email`: {prose:?}");
+    assert!(
+        prose.contains("quoted string"),
+        "text-column hint says `quoted string`: {prose:?}"
+    );
+}
+
+#[test]
+fn advanced_update_set_date_value_hint_says_yyyy_mm_dd() {
+    let schema = schema_cache(&[("Things", &[("k", Type::Int), ("dt", Type::Date)])]);
+    let input = "update Things set dt=";
+    let hint = ambient_hint_in_mode(input, input.len(), None, &schema, Mode::Advanced);
+    let Some(AmbientHint::Prose(prose)) = hint else {
+        panic!("expected a Prose hint at the date value slot, got {hint:?}");
+    };
+    assert!(
+        prose.contains("YYYY-MM-DD"),
+        "date-column hint references the YYYY-MM-DD format: {prose:?}"
+    );
+}
+
+#[test]
+fn advanced_update_set_int_value_type_mismatch_is_caught_live() {
+    // A decimal literal at an `int` column now fails to parse in
+    // advanced mode (the typed slot's integer validator fires while
+    // typing) — previously the verbatim sql_expr surface accepted it
+    // and only Phase 2's execution-time validation caught it.
+    let schema = schema_cache(&[("Things", &[("k", Type::Int), ("note", Type::Text)])]);
+    let bad = classify_input_with_schema_in_mode(
+        "update Things set k = 3.14 where k = 0",
+        &schema,
+        Mode::Advanced,
+    );
+    assert!(
+        !matches!(bad, InputState::Valid),
+        "a decimal at an int column is rejected live (typed slot), got {bad:?}"
+    );
+    // A well-formed integer literal still parses cleanly.
+    let ok = classify_input_with_schema_in_mode(
+        "update Things set k = 5 where k = 0",
+        &schema,
+        Mode::Advanced,
+    );
+    assert!(matches!(ok, InputState::Valid), "a valid int literal parses: {ok:?}");
+}
+
+#[test]
+fn advanced_update_set_expression_still_parses_via_sql_expr() {
+    // Regression guard: the boundary-aware lookahead must fall through
+    // to sql_expr for anything that is not a lone literal — arithmetic,
+    // a literal-prefixed expression, a function call, a scalar subquery.
+    // None of these may be stolen by the typed slot.
+    let schema = schema_cache(&[
+        ("Things", &[("k", Type::Int), ("note", Type::Text)]),
+        ("other", &[("n", Type::Int)]),
+    ]);
+    for input in [
+        "update Things set k = 3 + 2 where k = 0",      // literal-prefixed expression
+        "update Things set k = (select max(n) from other) where k = 0", // scalar subquery
+        "update Things set note = upper(note) where k = 0", // function call
+        "update Things set k = -5 where k = 0",         // signed number → sql_expr
+    ] {
+        let state = classify_input_with_schema_in_mode(input, &schema, Mode::Advanced);
+        assert!(
+            matches!(state, InputState::Valid),
+            "{input:?} must still parse via sql_expr, got {state:?}"
+        );
+    }
+}