fix(index): a field holds every value kind it was written with, not the first one

The metadata index fixed a field's value type from the first value it saw.
Every later value of another kind was coerced to that type, and when coercion
failed — `Number('electronics')` is NaN — the value was dropped from the index
with no error at all. The row stayed readable by id and by vector search and
vanished only from equality filters on that one field, which is what made it so
quiet: writing `category: 'electronics'` rows and then `category: 5` rows left
`where { category: 5 }` returning nothing, while the same rows in a
numbers-only corpus answered correctly.

The column store now keeps one posting column per (field, kind), where a kind
is a JavaScript typeof class. The first kind a field sees keeps the historical
`_column_index/<field>/` layout, so a single-kind field is byte-identical to
what earlier versions wrote and an index written before this opens unchanged;
each later kind takes its own column at `_column_index/<field>/k/<kind>/`.

Equality reads the column matching the query value's own kind, so `{c: 5}` and
`{c: '5'}` match different rows and neither is coerced into the other. Ranges
route by the kind of their bounds, and an unbounded range — the "has any value"
probe behind `exists` — reads every kind. A mixed field orders by kind first,
then by value, because a number and a string have no order between them. A
value that cannot be encoded for the column its own kind selected now raises
instead of being skipped: that path is unreachable by construction, and if it
is ever reached it is the silent drop this change exists to end.

Two neighbours fell out of the same routing. A boolean query value is now
encoded to the 1/0 the column stores, so boolean equality matches at all. And
an integer column widens to f64 the first time a non-integer arrives, so 4.5 is
stored as itself rather than rounded to 5 and answering the wrong query.

Field type inference reports every kind a field holds beside its dominant
reading, rather than leaving callers to treat one type as the whole answer.

Pins: mixed-kind equality in both write orders, `5` vs `'5'`, booleans mixed in,
a numeric range over a mixed field's numbers, close/reopen keeping every typed
posting, and an index in the pre-existing on-disk shape still reading.
`tests/critical-neural-validation.test.ts` — which writes `category` as strings
in one test and as numbers in another against one shared brain — passes whole
for the first time.

docs/architecture/data-storage-architecture.md

@@ -217,6 +217,40 @@ membership queries at scale:
   `__words__` for tokenized text…).
 - `_blobs/_column_index/{field}/L0-NNNNNN.bin` — the actual level-0 run
   segments, stored through the shared `_blobs/<key>.bin` binary convention.
+- `_column_index/{field}/k/{kind}/…` — the same two files again, for a
+  **second value kind** on the same field (see below). Absent for a field that
+  holds one kind, which is nearly all of them.
+
+### One posting column per (field, kind)
+
+A field is not obliged to hold one type of value. `category` may carry
+`'electronics'` on some rows and `5` on others, and both are real values of
+that field. A segment, though, has one encoding — i64, f64, UTF-8, or boolean
+— so a field that holds several kinds gets **one column per kind**:
+
+- The first kind a field ever sees owns the plain `_column_index/{field}/`
+  layout above. A single-kind field is therefore byte-identical to what earlier
+  versions wrote, and an index written before typed postings opens unchanged.
+- Every later kind gets its own column beside it at
+  `_column_index/{field}/k/{kind}/`, where `{kind}` is `number`, `string` or
+  `boolean`.
+
+What that buys at query time:
+
+| | |
+|---|---|
+| **Equality** | Answered from the column matching the **query value's own kind**. `where {category: 5}` reads the number postings; `where {category: '5'}` reads the string postings. Neither borrows the other's rows — a row written with the number `5` is not a row whose category is the text `'5'`. |
+| **A kind the field never held** | Matches nothing. That is the true answer, not a coerced one. |
+| **Ranges** | Routed by the kind of the bounds: numeric bounds read the numeric postings and ignore the field's strings. An **unbounded** range is the "has any value here" probe behind `exists`, and reads every kind. |
+| **`orderBy`** | A number and a string have no order between them, so a mixed field orders by kind first (number, string, boolean) and by value within a kind. A single-kind field sorts exactly as it always did. |
+| **Numbers** | One kind, one column: an integer column is written as i64 and widens to f64 the first time a non-integer arrives, so `4.5` is stored as itself rather than rounded. |
+
+`null` and `undefined` are not kinds and are never posted; their absence is
+what the `exists` / `missing` operators read.
+
+Older readers are unaffected by the additional columns: they see the field's
+primary column exactly where it has always been, and a `k/{kind}` directory is
+simply a name they never query.
 
 Sparse per-field indexes, roaring-bitmap chunks, and zone-map/bloom segments
 additionally live as bucketed keys under `_system/idx/` (see §3). Which path

src/indexes/columnStore/ColumnStore.ts

@@ -23,7 +23,10 @@ import type { ColumnStoreProvider, SegmentMeta } from './types.js'
 import {
   ValueType,
   DEFAULT_FLUSH_THRESHOLD,
-  FLAG_MULTI_VALUE
+  FLAG_MULTI_VALUE,
+  POSTING_KINDS,
+  KIND_PATH_SEGMENT,
+  type PostingKind
 } from './types.js'
 import { ColumnTailBuffer } from './ColumnTailBuffer.js'
 import { ColumnManifest } from './ColumnManifest.js'
@@ -52,10 +55,89 @@ interface HeapEntry {
   value: number | string
   entityIntId: number
   cursorIndex: number
+  /**
+   * Rank of the posting kind this entry came from, from {@link POSTING_KINDS}.
+   * A mixed-kind field has no natural total order, so the merge orders by kind
+   * first and by value within a kind.
+   */
+  kindRank: number
   /** Iterator for the cursor — call next() to advance */
   iterator: Generator<CursorEntry>
 }
 
+/**
+ * One physical posting column: a (field, kind) pair and the key every internal
+ * map and every storage path uses for it.
+ */
+interface KindColumn {
+  /** The field as the query language names it. */
+  field: string
+  /** The kind of value this column holds. */
+  kind: PostingKind
+  /**
+   * Internal map / storage key. The field's PRIMARY kind uses the bare field
+   * name — the historical layout — and every other kind uses
+   * `<field>/<KIND_PATH_SEGMENT>/<kind>`.
+   */
+  key: string
+}
+
+/**
+ * The KIND a value indexes under — its JavaScript `typeof` class, not its
+ * storage encoding.
+ *
+ * Anything that is not a number, string or boolean indexes as a string, which
+ * is the `String(value)` treatment those values already received. `null` and
+ * `undefined` never reach here: `addEntity` skips them, and their absence is
+ * what the `exists` / `missing` operators read.
+ *
+ * @param value - The value about to be indexed or queried
+ * @returns The posting kind that owns this value
+ */
+function kindOfValue(value: unknown): PostingKind {
+  const t = typeof value
+  if (t === 'number') return 'number'
+  if (t === 'boolean') return 'boolean'
+  return 'string'
+}
+
+/**
+ * The segment encoding a fresh column of this kind starts with.
+ *
+ * Only the number kind has a choice: an integer column starts as i64 and
+ * widens to f64 the first time a non-integer arrives
+ * ({@link ColumnTailBuffer.promoteToFloat}).
+ */
+function initialValueTypeFor(kind: PostingKind, firstValue: unknown): ValueType {
+  switch (kind) {
+    case 'boolean':
+      return ValueType.Boolean
+    case 'string':
+      return ValueType.String
+    case 'number':
+      return Number.isInteger(firstValue) ? ValueType.Number : ValueType.Float
+  }
+}
+
+/**
+ * The kind a column of this encoding holds — the inverse of
+ * {@link initialValueTypeFor}, used to read a kind back off a manifest written
+ * before typed postings existed.
+ */
+function kindOfValueType(valueType: ValueType): PostingKind {
+  switch (valueType) {
+    case ValueType.Boolean:
+      return 'boolean'
+    case ValueType.String:
+      return 'string'
+    case ValueType.Number:
+    case ValueType.Float:
+      return 'number'
+    default:
+      throw new Error(`Unknown ValueType: ${valueType}`)
+  }
+}
+
 /**
  * Unified column store coordinator.
  *
@@ -121,9 +203,19 @@ export class ColumnStore implements ColumnStoreProvider {
    */
   private deletedEntities: Map<string, RoaringBitmap32> = new Map()
 
-  /** Known field value types (inferred from first write). */
+  /** Segment encoding per COLUMN key (not per field — a field has one per kind). */
   private fieldTypes: Map<string, ValueType> = new Map()
 
+  /**
+   * Every posting column a field owns: field → kind → column key.
+   *
+   * This is the map that ends the first-writer type freeze. A field's first
+   * kind takes the bare field name as its column key, keeping the historical
+   * on-disk layout; each later kind takes its own column beside it. Nothing is
+   * coerced across kinds and nothing is dropped for being the wrong type.
+   */
+  private fieldColumns: Map<string, Map<PostingKind, string>> = new Map()
+
   /** Whether init() has completed. */
   private initialized = false
 
@@ -140,6 +232,128 @@ export class ColumnStore implements ColumnStoreProvider {
     this.l0CompactionTrigger = config?.l0CompactionTrigger ?? 4
   }
 
+  // =========================================================================
+  // Posting columns: (field, kind) → one physical column
+  // =========================================================================
+
+  /**
+   * Storage / map key for a (field, kind) column.
+   *
+   * `primary` is the kind that owns the bare field name. It is whichever kind
+   * the field saw first, which for an index written before typed postings is
+   * simply the kind of its single manifest — so the historical layout is
+   * preserved rather than migrated.
+   */
+  private static columnKeyFor(field: string, kind: PostingKind, primary: PostingKind | null): string {
+    return primary === null || kind === primary
+      ? field
+      : `${field}/${KIND_PATH_SEGMENT}/${kind}`
+  }
+
+  /**
+   * Split a discovered manifest path back into its (field, kind) column, or
+   * `null` when the path names a field's primary column rather than a kind
+   * column. `<field>/k/<kind>` is the only shape that reads as a kind column,
+   * and only for a `<kind>` this version knows.
+   */
+  private static parseKindColumnKey(key: string): { field: string; kind: PostingKind } | null {
+    const marker = `/${KIND_PATH_SEGMENT}/`
+    const at = key.lastIndexOf(marker)
+    if (at <= 0) return null
+    const kind = key.slice(at + marker.length)
+    if (!POSTING_KINDS.includes(kind as PostingKind)) return null
+    return { field: key.slice(0, at), kind: kind as PostingKind }
+  }
+
+  /** Record a discovered or freshly created column against its field. */
+  private registerColumn(field: string, kind: PostingKind, key: string): void {
+    let byKind = this.fieldColumns.get(field)
+    if (!byKind) {
+      byKind = new Map()
+      this.fieldColumns.set(field, byKind)
+    }
+    const existing = byKind.get(kind)
+    if (existing !== undefined && existing !== key) {
+      // Two columns claiming one (field, kind) means the layout on disk is not
+      // one this writer could have produced. Serving it would silently answer
+      // from half the postings, so say which two and stop.
+      throw new Error(
+        `ColumnStore: field '${field}' has two '${kind}' posting columns on ` +
+          `disk ('${existing}' and '${key}'). The column index layout is ` +
+          `inconsistent — rebuild/repair the metadata index rather than ` +
+          `serving from one half of it.`
+      )
+    }
+    byKind.set(kind, key)
+  }
+
+  /** The column key for this (field, kind), or `null` if the field has no such kind. */
+  private columnKey(field: string, kind: PostingKind): string | null {
+    return this.fieldColumns.get(field)?.get(kind) ?? null
+  }
+
+  /**
+   * The column key for this (field, kind), creating the registration if the
+   * field has not seen this kind before. Write path only.
+   */
+  private ensureColumnKey(field: string, kind: PostingKind): string {
+    const byKind = this.fieldColumns.get(field)
+    const existing = byKind?.get(kind)
+    if (existing !== undefined) return existing
+
+    // The primary kind is the one already holding the bare field name, if any.
+    let primary: PostingKind | null = null
+    if (byKind) {
+      for (const [k, key] of byKind) {
+        if (key === field) { primary = k; break }
+      }
+    }
+    const key = ColumnStore.columnKeyFor(field, kind, primary)
+    this.registerColumn(field, kind, key)
+    return key
+  }
+
+  /**
+   * Every posting column this field owns, in {@link POSTING_KINDS} order.
+   *
+   * Read doors that are not about one particular value — an unbounded range
+   * used as an "any value present" probe, distinct values, sorting — fan out
+   * over all of them.
+   */
+  private columnsForField(field: string): KindColumn[] {
+    const byKind = this.fieldColumns.get(field)
+    if (!byKind) return []
+    const out: KindColumn[] = []
+    for (const kind of POSTING_KINDS) {
+      const key = byKind.get(kind)
+      if (key !== undefined) out.push({ field, kind, key })
+    }
+    return out
+  }
+
+  /**
+   * Which value kinds this field actually holds, in {@link POSTING_KINDS}
+   * order — the honest answer to "what type is this field?".
+   *
+   * A field that carries both `'electronics'` and `5` reports
+   * `['number', 'string']`, not whichever of them was written first.
+   *
+   * @param field - Field name
+   * @returns Every kind with at least one posting, or `[]` for an unknown field
+   */
+  getFieldKinds(field: string): PostingKind[] {
+    return this.columnsForField(field)
+      .filter((c) => this.columnHasData(c.key))
+      .map((c) => c.kind)
+  }
+
+  /** Does this physical column hold any postings (persisted or buffered)? */
+  private columnHasData(key: string): boolean {
+    const manifest = this.manifests.get(key)
+    const buffer = this.tailBuffers.get(key)
+    return (manifest !== undefined && !manifest.isEmpty()) || (buffer !== undefined && buffer.size > 0)
+  }
+
   /**
    * Initialize the column store: discover existing field manifests.
    */
@@ -157,11 +371,23 @@ export class ColumnStore implements ColumnStoreProvider {
       }).listObjectsUnderPath(this.basePath + '/')
       for (const path of paths) {
         if (path.endsWith('/MANIFEST.json')) {
-          const fieldName = path.replace(this.basePath + '/', '').replace('/MANIFEST.json', '')
-          const manifest = new ColumnManifest(fieldName, this.basePath)
+          // The discovered name is a COLUMN key: either a bare field (that
+          // field's primary kind, which is every column an index written
+          // before typed postings has) or `<field>/k/<kind>` for a second
+          // kind that arrived on a field later.
+          const columnKey = path.replace(this.basePath + '/', '').replace('/MANIFEST.json', '')
+          const manifest = new ColumnManifest(columnKey, this.basePath)
           await manifest.load(storage)
-          this.manifests.set(fieldName, manifest)
-          this.fieldTypes.set(fieldName, manifest.valueType)
+          this.manifests.set(columnKey, manifest)
+          this.fieldTypes.set(columnKey, manifest.valueType)
+
+          const parsed = ColumnStore.parseKindColumnKey(columnKey)
+          if (parsed) {
+            this.registerColumn(parsed.field, parsed.kind, columnKey)
+          } else {
+            this.registerColumn(columnKey, kindOfValueType(manifest.valueType), columnKey)
+          }
+          const fieldName = columnKey
 
           // Load global deleted bitmap if it exists. Raw blob preferred
           // (2.4.0 #4 cortex-shared format); legacy envelope fallback for
@@ -264,26 +490,43 @@ export class ColumnStore implements ColumnStoreProvider {
   /**
    * Point filter: find entities where field equals value.
    *
-   * Searches all segments + tail buffer, returns union as roaring bitmap.
-   * Excludes globally deleted entities.
+   * The QUERY VALUE'S OWN KIND picks the posting column, and only that column
+   * is read. `where {category: 5}` answers from the number postings and
+   * `where {category: '5'}` from the string postings — neither borrows the
+   * other's rows, because a row written with the number `5` is not a row whose
+   * category is the text `'5'`.
+   *
+   * A field that has never seen this kind matches nothing, which is the true
+   * answer rather than a coerced one.
+   *
+   * Searches all segments + tail buffer of that column, returns the union as a
+   * roaring bitmap. Excludes globally deleted entities.
    */
   async filter(field: string, value: unknown): Promise<RoaringBitmap32> {
     const result = new RoaringBitmap32()
-    const deleted = this.deletedEntities.get(field)
+    const columnKey = this.columnKey(field, kindOfValue(value))
+    if (columnKey === null) return result
+
+    // The query value takes the column's encoding — a boolean queried against
+    // a boolean column has to become the 1/0 the column stores.
+    const encoded = this.normalizeValue(value, this.fieldTypes.get(columnKey) ?? ValueType.String)
+    if (encoded === undefined) return result
+
+    const deleted = this.deletedEntities.get(columnKey)
 
     // Search segments
-    const cursors = await this.getSegmentCursors(field)
+    const cursors = await this.getSegmentCursors(columnKey)
     for (const cursor of cursors) {
-      const ids = cursor.getEntityIdsForValue(value as number | string)
+      const ids = cursor.getEntityIdsForValue(encoded)
       for (const id of ids) {
         if (!deleted || !deleted.has(id)) result.add(id)
       }
     }
 
     // Search tail buffer
-    const tailCursor = this.getTailBufferCursor(field)
+    const tailCursor = this.getTailBufferCursor(columnKey)
     if (tailCursor) {
-      const ids = tailCursor.getEntityIdsForValue(value as number | string)
+      const ids = tailCursor.getEntityIdsForValue(encoded)
       for (const id of ids) {
         if (!deleted || !deleted.has(id)) result.add(id)
       }
@@ -324,22 +567,26 @@ export class ColumnStore implements ColumnStoreProvider {
     const out = new Map<number, number | string>()
     if (wanted.size === 0 || !this.hasField(field)) return out
 
-    const deleted = this.deletedEntities.get(field)
-    const take = (entry: { value: number | string; entityIntId: number }): void => {
-      if (!wanted.has(entry.entityIntId)) return
-      if (deleted && deleted.has(entry.entityIntId)) return
-      out.set(entry.entityIntId, entry.value)
-    }
+    // Every kind the field holds is read, in POSTING_KINDS order — a value an
+    // entity wrote as a string is still that entity's value for this field.
+    for (const column of this.columnsForField(field)) {
+      const deleted = this.deletedEntities.get(column.key)
+      const take = (entry: { value: number | string; entityIntId: number }): void => {
+        if (!wanted.has(entry.entityIntId)) return
+        if (deleted && deleted.has(entry.entityIntId)) return
+        out.set(entry.entityIntId, entry.value)
+      }
 
-    // Segments oldest -> newest, then the tail: a later write overwrites an
-    // earlier one for the same id.
-    const cursors = await this.getSegmentCursors(field)
-    for (const cursor of cursors) {
-      for (const entry of cursor.iterateForward()) take(entry)
-    }
-    const tailCursor = this.getTailBufferCursor(field)
-    if (tailCursor) {
-      for (const entry of tailCursor.iterateForward()) take(entry)
+      // Segments oldest -> newest, then the tail: a later write overwrites an
+      // earlier one for the same id.
+      const cursors = await this.getSegmentCursors(column.key)
+      for (const cursor of cursors) {
+        for (const entry of cursor.iterateForward()) take(entry)
+      }
+      const tailCursor = this.getTailBufferCursor(column.key)
+      if (tailCursor) {
+        for (const entry of tailCursor.iterateForward()) take(entry)
+      }
     }
     return out
   }
@@ -363,41 +610,59 @@ export class ColumnStore implements ColumnStoreProvider {
     includeMax: boolean = true
   ): Promise<RoaringBitmap32> {
     const result = new RoaringBitmap32()
-    const cursors = await this.getSegmentCursors(field)
 
     const hasMin = min !== undefined && min !== null
     const hasMax = max !== undefined && max !== null
 
-    for (const cursor of cursors) {
-      const lo = hasMin ? min as number | string : cursor.minValue
-      const hi = hasMax ? max as number | string : cursor.maxValue
-      if (lo === undefined || hi === undefined) continue
-      // Exclusivity applies only to an explicitly provided bound. A bound taken
-      // from the segment's own min/max is a real stored value and must stay
-      // inclusive, or the segment's boundary entities would be wrongly dropped.
-      const ids = cursor.getEntityIdsInRange(
-        lo,
-        hi,
-        hasMin ? includeMin : true,
-        hasMax ? includeMax : true
-      )
-      for (const id of ids) result.add(id)
-    }
+    // The BOUNDS pick the column: numeric bounds read the numeric postings,
+    // string bounds the string postings. An unbounded call is not a range at
+    // all — it is the "has any value here" probe behind `exists` — so it fans
+    // out over every kind the field holds.
+    const columns: KindColumn[] = hasMin
+      ? this.columnsForKind(field, kindOfValue(min))
+      : hasMax
+        ? this.columnsForKind(field, kindOfValue(max))
+        : this.columnsForField(field)
 
-    // Tail buffer range: linear scan (tail is small)
-    const tailCursor = this.getTailBufferCursor(field)
-    if (tailCursor) {
-      for (const entry of tailCursor.iterateForward()) {
-        const v = entry.value as any
-        const loOk = !hasMin || (includeMin ? v >= (min as any) : v > (min as any))
-        const hiOk = !hasMax || (includeMax ? v <= (max as any) : v < (max as any))
-        if (loOk && hiOk) result.add(entry.entityIntId)
+    for (const column of columns) {
+      const cursors = await this.getSegmentCursors(column.key)
+      for (const cursor of cursors) {
+        const lo = hasMin ? min as number | string : cursor.minValue
+        const hi = hasMax ? max as number | string : cursor.maxValue
+        if (lo === undefined || hi === undefined) continue
+        // Exclusivity applies only to an explicitly provided bound. A bound taken
+        // from the segment's own min/max is a real stored value and must stay
+        // inclusive, or the segment's boundary entities would be wrongly dropped.
+        const ids = cursor.getEntityIdsInRange(
+          lo,
+          hi,
+          hasMin ? includeMin : true,
+          hasMax ? includeMax : true
+        )
+        for (const id of ids) result.add(id)
+      }
+
+      // Tail buffer range: linear scan (tail is small)
+      const tailCursor = this.getTailBufferCursor(column.key)
+      if (tailCursor) {
+        for (const entry of tailCursor.iterateForward()) {
+          const v = entry.value as any
+          const loOk = !hasMin || (includeMin ? v >= (min as any) : v > (min as any))
+          const hiOk = !hasMax || (includeMax ? v <= (max as any) : v < (max as any))
+          if (loOk && hiOk) result.add(entry.entityIntId)
+        }
       }
     }
 
     return result
   }
 
+  /** The single column for this (field, kind), as a list, or empty if absent. */
+  private columnsForKind(field: string, kind: PostingKind): KindColumn[] {
+    const key = this.columnKey(field, kind)
+    return key === null ? [] : [{ field, kind, key }]
+  }
+
   /**
    * Sort top-K: return K entity int IDs in sorted order (u64-safe BigInt).
    *
@@ -428,18 +693,21 @@ export class ColumnStore implements ColumnStoreProvider {
    */
   async getFilterValues(field: string): Promise<string[]> {
     const valueSet = new Set<string>()
-    const cursors = await this.getSegmentCursors(field)
 
-    for (const cursor of cursors) {
-      for (const entry of cursor.iterateForward()) {
-        valueSet.add(String(entry.value))
+    for (const column of this.columnsForField(field)) {
+      const cursors = await this.getSegmentCursors(column.key)
+
+      for (const cursor of cursors) {
+        for (const entry of cursor.iterateForward()) {
+          valueSet.add(String(entry.value))
+        }
       }
-    }
 
-    const tailCursor = this.getTailBufferCursor(field)
-    if (tailCursor) {
-      for (const entry of tailCursor.iterateForward()) {
-        valueSet.add(String(entry.value))
+      const tailCursor = this.getTailBufferCursor(column.key)
+      if (tailCursor) {
+        for (const entry of tailCursor.iterateForward()) {
+          valueSet.add(String(entry.value))
+        }
       }
     }
 
@@ -450,9 +718,7 @@ export class ColumnStore implements ColumnStoreProvider {
    * Check if a field has any indexed data.
    */
   hasField(field: string): boolean {
-    const manifest = this.manifests.get(field)
-    const buffer = this.tailBuffers.get(field)
-    return (manifest !== undefined && !manifest.isEmpty()) || (buffer !== undefined && buffer.size > 0)
+    return this.columnsForField(field).some((c) => this.columnHasData(c.key))
   }
 
   /**
@@ -462,12 +728,11 @@ export class ColumnStore implements ColumnStoreProvider {
    * store will actually serve queries from.
    */
   getIndexedFields(): string[] {
+    // Names FIELDS, not columns: a field carrying two kinds is one name here,
+    // the same name a caller queries with.
     const fields = new Set<string>()
-    for (const [field, manifest] of this.manifests) {
-      if (!manifest.isEmpty()) fields.add(field)
-    }
-    for (const [field, buffer] of this.tailBuffers) {
-      if (buffer.size > 0) fields.add(field)
+    for (const [field] of this.fieldColumns) {
+      if (this.hasField(field)) fields.add(field)
     }
     return Array.from(fields).sort()
   }
@@ -482,12 +747,16 @@ export class ColumnStore implements ColumnStoreProvider {
   getFieldSizeSummary(): Array<{ field: string; segmentCount: number; tailSize: number }> {
     const summary: Array<{ field: string; segmentCount: number; tailSize: number }> = []
     for (const field of this.getIndexedFields()) {
-      const manifest = this.manifests.get(field)
-      const buffer = this.tailBuffers.get(field)
-      const segmentCount = manifest && !manifest.isEmpty()
-        ? manifest.getAllSegments().length
-        : 0
-      const tailSize = buffer ? buffer.size : 0
+      // Summed across the field's kind columns — the caller asked about a
+      // field, and a field's size is all of the postings under its name.
+      let segmentCount = 0
+      let tailSize = 0
+      for (const column of this.columnsForField(field)) {
+        const manifest = this.manifests.get(column.key)
+        const buffer = this.tailBuffers.get(column.key)
+        if (manifest && !manifest.isEmpty()) segmentCount += manifest.getAllSegments().length
+        if (buffer) tailSize += buffer.size
+      }
       summary.push({ field, segmentCount, tailSize })
     }
     return summary
@@ -515,6 +784,8 @@ export class ColumnStore implements ColumnStoreProvider {
     this.segmentCache.clear()
     this.manifests.clear()
     this.deletedEntities.clear()
+    this.fieldColumns.clear()
+    this.fieldTypes.clear()
     this.initialized = false
   }
 
@@ -523,32 +794,64 @@ export class ColumnStore implements ColumnStoreProvider {
   // =========================================================================
 
   /**
-   * Push a single value to a field's tail buffer.
-   * Creates the buffer and manifest if first write to this field.
-   * Infers ValueType from the first value seen.
+   * Push a single value to the posting column for its (field, KIND).
+   *
+   * The value's own kind picks the column — a string goes to the field's
+   * string postings, a number to its number postings — so a field carrying
+   * `'electronics'` and `5` keeps both, each answerable by an equality filter
+   * of its own kind. Under the first-writer type freeze this method replaced,
+   * the first value's type became the field's type and every later value of
+   * another kind was coerced to it or, when coercion failed, dropped with no
+   * error at all.
+   *
+   * Creates the column's buffer and manifest on its first value.
    */
   private pushToBuffer(field: string, value: unknown, entityIntId: number, isMultiValue: boolean): void {
-    let buffer = this.tailBuffers.get(field)
+    const kind = kindOfValue(value)
+    const columnKey = this.ensureColumnKey(field, kind)
+
+    let buffer = this.tailBuffers.get(columnKey)
     if (!buffer) {
-      const valueType = this.inferValueType(value)
-      buffer = new ColumnTailBuffer(field, valueType, this.flushThreshold)
-      this.tailBuffers.set(field, buffer)
-      this.fieldTypes.set(field, valueType)
+      // A reopened column takes its encoding from its manifest — an integer
+      // column that widened to f64 in an earlier session stays widened.
+      const valueType =
+        this.manifests.get(columnKey)?.valueType ?? initialValueTypeFor(kind, value)
+      buffer = new ColumnTailBuffer(columnKey, valueType, this.flushThreshold)
+      this.tailBuffers.set(columnKey, buffer)
+      this.fieldTypes.set(columnKey, valueType)
 
       // Ensure manifest exists
-      if (!this.manifests.has(field)) {
-        const manifest = new ColumnManifest(field, this.basePath)
+      if (!this.manifests.has(columnKey)) {
+        const manifest = new ColumnManifest(columnKey, this.basePath)
         manifest.valueType = valueType
         manifest.multiValue = isMultiValue
-        this.manifests.set(field, manifest)
+        this.manifests.set(columnKey, manifest)
       }
     }
 
-    // Normalize value to the column type
-    const normalizedValue = this.normalizeValue(value, buffer.valueType)
-    if (normalizedValue !== undefined) {
-      buffer.add(normalizedValue, entityIntId)
+    // An integer column widens the first time a non-integer number arrives, so
+    // the value is stored as itself instead of rounded to the nearest integer.
+    if (kind === 'number' && buffer.valueType === ValueType.Number && !Number.isInteger(value)) {
+      buffer.promoteToFloat()
+      this.fieldTypes.set(columnKey, ValueType.Float)
+      const manifest = this.manifests.get(columnKey)
+      if (manifest) manifest.valueType = ValueType.Float
     }
+
+    const normalizedValue = this.normalizeValue(value, buffer.valueType)
+    if (normalizedValue === undefined) {
+      // Unreachable by construction: the column was chosen BY this value's
+      // kind, so the encoding always accepts it. Reaching here would mean a
+      // value had been silently dropped from the index — the exact failure
+      // typed postings exist to end — so it is an error, never a skip.
+      throw new Error(
+        `ColumnStore: field '${field}' rejected a ${kind} value for its own ` +
+          `${ValueType[buffer.valueType]} posting column. The value would have ` +
+          `been dropped from the index while the row stayed readable by id — ` +
+          `this is a kind-routing bug, not a value the caller may ignore.`
+      )
+    }
+    buffer.add(normalizedValue, entityIntId)
   }
 
   /**
@@ -677,8 +980,15 @@ export class ColumnStore implements ColumnStoreProvider {
   /** Torn-segment quarantine entries for a field (observability + heal input). */
   quarantinedSegments(field: string): Array<{ segment: string; error: string; hits: number }> {
     const out: Array<{ segment: string; error: string; hits: number }> = []
-    for (const [key, q] of this.segmentQuarantine) {
-      if (key.startsWith(`${field}:`)) out.push({ segment: key.slice(field.length + 1), error: q.error, hits: q.hits })
+    // Across every kind column of the field — a torn segment in the string
+    // postings is this field's torn segment as much as one in the numbers.
+    for (const column of this.columnsForField(field)) {
+      const prefix = `${column.key}:`
+      for (const [key, q] of this.segmentQuarantine) {
+        if (key.startsWith(prefix)) {
+          out.push({ segment: key.slice(prefix.length), error: q.error, hits: q.hits })
+        }
+      }
     }
     return out
   }
@@ -850,17 +1160,22 @@ export class ColumnStore implements ColumnStoreProvider {
     k: number,
     filterBitmap: RoaringBitmap32 | null
   ): Promise<number[]> {
-    // Collect all cursors (segments + tail buffer)
-    const segCursors = await this.getSegmentCursors(field)
-    const tailCursor = this.getTailBufferCursor(field)
-
-    // Create iterators for each cursor in the specified direction
+    // Collect cursors across EVERY kind the field holds. A single-kind field —
+    // nearly all of them — merges exactly the cursors it always did.
     const iterators: Generator<CursorEntry>[] = []
-    for (const cursor of segCursors) {
-      iterators.push(order === 'asc' ? cursor.iterateForward() : cursor.iterateBackward())
-    }
-    if (tailCursor) {
-      iterators.push(order === 'asc' ? tailCursor.iterateForward() : tailCursor.iterateBackward())
+    const iteratorKindRank: number[] = []
+    for (const column of this.columnsForField(field)) {
+      const kindRank = POSTING_KINDS.indexOf(column.kind)
+      const segCursors = await this.getSegmentCursors(column.key)
+      for (const cursor of segCursors) {
+        iterators.push(order === 'asc' ? cursor.iterateForward() : cursor.iterateBackward())
+        iteratorKindRank.push(kindRank)
+      }
+      const tailCursor = this.getTailBufferCursor(column.key)
+      if (tailCursor) {
+        iterators.push(order === 'asc' ? tailCursor.iterateForward() : tailCursor.iterateBackward())
+        iteratorKindRank.push(kindRank)
+      }
     }
 
     if (iterators.length === 0) return []
@@ -874,16 +1189,21 @@ export class ColumnStore implements ColumnStoreProvider {
           value: next.value.value,
           entityIntId: next.value.entityIntId,
           cursorIndex: i,
+          kindRank: iteratorKindRank[i],
           iterator: iterators[i]
         })
       }
     }
 
-    // Heapify
-    const isString = (this.fieldTypes.get(field) ?? ValueType.Number) === ValueType.String
+    // Heapify. A number and a string have no ordering between them, so a
+    // mixed-kind field orders by KIND first (POSTING_KINDS order) and by value
+    // within a kind — one defined total order instead of a comparison whose
+    // answer depends on which value happened to be on the left.
     const compare = (a: HeapEntry, b: HeapEntry): number => {
       let cmp: number
-      if (isString) {
+      if (a.kindRank !== b.kindRank) {
+        cmp = a.kindRank - b.kindRank
+      } else if (POSTING_KINDS[a.kindRank] === 'string') {
         cmp = compareCodePoints(String(a.value), String(b.value))
       } else {
         cmp = (a.value as number) - (b.value as number)
@@ -915,6 +1235,7 @@ export class ColumnStore implements ColumnStoreProvider {
           value: next.value.value,
           entityIntId: next.value.entityIntId,
           cursorIndex: top.cursorIndex,
+          kindRank: top.kindRank,
           iterator: top.iterator
         }
       }
@@ -922,8 +1243,11 @@ export class ColumnStore implements ColumnStoreProvider {
         this.heapDown(heap, 0, compare)
       }
 
-      // Apply global deleted check, filter, and dedup
-      const deleted = this.deletedEntities.get(field)
+      // Apply global deleted check, filter, and dedup. The deleted bitmap is
+      // per COLUMN, and the entry came from the column its kind names.
+      const deleted = this.deletedEntities.get(
+        this.columnKey(field, POSTING_KINDS[top.kindRank]) ?? field
+      )
       if (deleted && deleted.has(top.entityIntId)) continue
       if (seen.has(top.entityIntId)) continue
       if (filterBitmap && !filterBitmap.has(top.entityIntId)) continue
@@ -965,35 +1289,31 @@ export class ColumnStore implements ColumnStoreProvider {
   }
 
   /**
-   * Infer ValueType from a JavaScript value.
-   */
-  private inferValueType(value: unknown): ValueType {
-    if (typeof value === 'boolean') return ValueType.Boolean
-    if (typeof value === 'number') {
-      return Number.isInteger(value) ? ValueType.Number : ValueType.Float
-    }
-    return ValueType.String
-  }
-
-  /**
-   * Normalize a JavaScript value to the column's ValueType.
+   * Encode a value for the column its own kind selected.
+   *
+   * This does NOT convert between kinds. It used to: a string reaching a
+   * numeric column was run through `Number(value)`, and a number reaching a
+   * numeric column was run through `Math.round`, so `'electronics'` became
+   * `NaN` and vanished while `4.5` became `5` and answered the wrong query.
+   * Kind routing removes the need for either — the only work left is picking
+   * the encoding the column already committed to.
+   *
+   * @returns The encoded value, or `undefined` if the value does not belong in
+   *   this column at all — which the caller treats as a routing bug and
+   *   raises, never as a value to skip.
    */
   private normalizeValue(value: unknown, type: ValueType): number | string | undefined {
     switch (type) {
       case ValueType.Number:
-        if (typeof value === 'number') return Math.round(value)
-        if (typeof value === 'string') { const n = Number(value); return isNaN(n) ? undefined : Math.round(n) }
-        if (typeof value === 'boolean') return value ? 1 : 0
-        return undefined
+        // Integer column. Non-integers widen it to Float before reaching here.
+        return typeof value === 'number' && Number.isInteger(value) ? value : undefined
       case ValueType.Float:
-        if (typeof value === 'number') return value
-        if (typeof value === 'string') { const n = Number(value); return isNaN(n) ? undefined : n }
-        return undefined
+        return typeof value === 'number' ? value : undefined
       case ValueType.Boolean:
-        if (typeof value === 'boolean') return value ? 1 : 0
-        if (typeof value === 'number') return value ? 1 : 0
-        return undefined
+        return typeof value === 'boolean' ? (value ? 1 : 0) : undefined
       case ValueType.String:
+        // The string kind is also where objects and bigints land, exactly as
+        // they always did.
         return String(value)
       default:
         return undefined

src/indexes/columnStore/ColumnTailBuffer.ts

@@ -55,8 +55,12 @@ export class ColumnTailBuffer {
   /** Field name this buffer is for. */
   readonly fieldName: string
 
-  /** Value type determines sort comparator. */
-  readonly valueType: ValueType
+  /**
+   * Value type determines sort comparator and segment encoding.
+   *
+   * Widened in place by {@link promoteToFloat} — never otherwise reassigned.
+   */
+  valueType: ValueType
 
   /** Flush threshold. */
   readonly threshold: number
@@ -81,6 +85,38 @@ export class ColumnTailBuffer {
     this.threshold = threshold
   }
 
+  /**
+   * Widen an integer column to floating point, losslessly and in place.
+   *
+   * The number posting kind holds every JavaScript number, but a segment picks
+   * ONE encoding: i64 for integers, f64 for the rest. A column that has only
+   * ever seen integers is written as i64; the first non-integer to arrive
+   * widens it here, so that value is stored as itself instead of being rounded
+   * to the nearest integer with no error — the rounding that made `4.5` and
+   * `5.5` both answer `where {score: 5}` and neither answer its own value.
+   *
+   * Widening is lossless in both directions it has to be: every value already
+   * buffered is an integer, and every integer is exactly representable as f64.
+   * Segments already on disk keep their own i64 encoding in their own headers
+   * and keep decoding by it — only segments written from here on are f64.
+   *
+   * @throws Error if called on a column that is not an integer column — the
+   *   only legal widening is Number → Float, and any other request is a bug in
+   *   the caller's kind routing rather than something to absorb quietly.
+   */
+  promoteToFloat(): void {
+    if (this.valueType === ValueType.Float) return
+    if (this.valueType !== ValueType.Number) {
+      throw new Error(
+        `ColumnTailBuffer '${this.fieldName}': cannot widen a ` +
+          `${ValueType[this.valueType]} column to Float — only an integer ` +
+          `(Number) column widens, and this call means a value reached the ` +
+          `wrong kind's column`
+      )
+    }
+    this.valueType = ValueType.Float
+  }
+
   /**
    * Add a (value, entityIntId) entry to the buffer.
    *

src/indexes/columnStore/types.ts

@@ -58,6 +58,53 @@ export enum ValueType {
   Boolean = 3
 }
 
+/**
+ * The KIND of a value, as the query language sees it.
+ *
+ * A kind is a JavaScript `typeof` class, not a storage encoding: `5` and `5.5`
+ * are one kind (`'number'`) held in one posting column, even though they need
+ * different segment encodings (i64 vs f64 — see {@link ValueType}).
+ *
+ * A field holds ONE POSTING COLUMN PER KIND, so `category` may carry string
+ * values and number values at the same time and answer equality on each. This
+ * replaces the first-writer type freeze, under which the first value's type
+ * became the field's type and every later value of another kind was coerced —
+ * or, when coercion failed (`Number('electronics')`), dropped from the index
+ * with no error: the row stayed readable by id and by vector but vanished from
+ * every equality filter on that field.
+ *
+ * Kinds do not coerce into one another at query time either: `where {c: 5}`
+ * matches rows written with the NUMBER `5`, and `where {c: '5'}` matches rows
+ * written with the STRING `'5'`. Neither ever matches the other.
+ *
+ * Values that are none of these three (objects, bigints) index as strings —
+ * the same `String(value)` treatment they received before.
+ */
+export type PostingKind = 'number' | 'string' | 'boolean'
+
+/**
+ * Every posting kind, in the order that defines cross-kind sort position.
+ *
+ * A mixed-kind field has no natural total order — a number does not compare
+ * with a string — so `sortTopK` orders by KIND first (numbers, then strings,
+ * then booleans) and by value within a kind. A single-kind field, which is
+ * nearly every field, sorts exactly as it always did.
+ */
+export const POSTING_KINDS: readonly PostingKind[] = ['number', 'string', 'boolean']
+
+/**
+ * Path segment marking a field's NON-PRIMARY kind columns on disk.
+ *
+ * The first kind a field ever sees keeps the historical layout —
+ * `<base>/<field>/MANIFEST.json` and `<base>/<field>/L0-NNNNNN` — so every
+ * index written before typed postings opens unchanged, and the byte-for-byte
+ * interchange with the native column store is untouched for the single-kind
+ * fields that are nearly all of them. A second kind arriving on the same field
+ * gets its own column at `<base>/<field>/k/<kind>/…` rather than overwriting or
+ * being coerced into the first.
+ */
+export const KIND_PATH_SEGMENT = 'k'
+
 // ---------------------------------------------------------------------------
 // Segment header and footer
 // ---------------------------------------------------------------------------
@@ -267,6 +314,19 @@ export interface ColumnStoreProvider {
    */
   hasField(field: string): boolean
 
+  /**
+   * Which value KINDS this field actually holds, in {@link POSTING_KINDS}
+   * order — the honest answer to "what type is this field?" for a field that
+   * carries more than one.
+   *
+   * OPTIONAL so an implementation written against the pre-typed-postings
+   * contract still satisfies this interface; feature-detect before calling.
+   *
+   * @param field - Field name
+   * @returns Every kind with at least one posting, or `[]` for an unknown field
+   */
+  getFieldKinds?(field: string): PostingKind[]
+
   /**
    * Flush all in-memory tail buffers to L0 segments on disk.
    * Saves all manifests.

src/utils/fieldTypeInference.ts

@@ -55,8 +55,30 @@ export enum FieldType {
  */
 export interface FieldTypeInfo {
   field: string
+  /**
+   * The DOMINANT reading of the field — one type, the most specific one every
+   * sampled value satisfies.
+   *
+   * A field is not obliged to hold one kind, so this is not the whole answer
+   * for a field that holds several. Read {@link kinds} beside it: a field
+   * carrying `'electronics'` and `5` infers as STRING here and reports
+   * `['number', 'string']` there, and the metadata index keeps a separate
+   * posting column for each of them.
+   */
   inferredType: FieldType
   confidence: number              // 0-1 confidence score
+  /**
+   * Every value KIND observed in the sample, in the order
+   * number → string → boolean. More than one entry means a genuinely
+   * mixed field, and every one of those kinds is independently filterable.
+   *
+   * Kinds are JavaScript `typeof` classes, one level coarser than
+   * {@link FieldType}: a UUID and a category name are both `'string'`, and an
+   * integer and a timestamp are both `'number'`.
+   *
+   * Optional only for cached analyses written before this was reported.
+   */
+  kinds?: Array<'number' | 'string' | 'boolean'>
   sampleSize: number              // Number of values analyzed
   lastUpdated: number             // Timestamp of last analysis
   detectionMethod: 'value'        // Always 'value' (no fallbacks!)
@@ -133,14 +155,71 @@ export class FieldTypeInference {
   }
 
   /**
-   * Analyze values to determine field type
+   * Analyze values to determine field type, and report every KIND the field
+   * actually holds alongside it.
+   *
+   * The classification below picks ONE type, because every one of its
+   * heuristics asks `samples.every(...)`: a field carrying `'electronics'` and
+   * `5` satisfies none of them and lands on STRING. That single answer is true
+   * as far as it goes — string is the dominant reading — but on its own it
+   * says nothing about the numbers also in the field, and a caller that treats
+   * it as the field's only type reproduces the first-writer freeze the index
+   * itself no longer has. {@link FieldTypeInfo.kinds} carries the rest.
+   */
+  private async analyzeValues(field: string, values: any[]): Promise<FieldTypeInfo> {
+    const info = await this.classifyValues(field, values)
+    info.kinds = FieldTypeInference.observedKinds(values)
+    if (info.kinds.length > 1 && info.metadata) {
+      info.metadata.format = `${info.metadata.format} (field also holds: ${info.kinds
+        .filter((k) => k !== FieldTypeInference.kindOfType(info.inferredType))
+        .join(', ')})`
+    }
+    return info
+  }
+
+  /**
+   * The distinct value kinds present in a sample, in a stable order.
+   *
+   * Kinds are JavaScript `typeof` classes — the same classes the metadata
+   * index keeps separate posting columns for — not the finer
+   * {@link FieldType} readings, which are interpretations layered on top of
+   * them (a UUID and a category name are both the `string` kind).
+   */
+  private static observedKinds(values: any[]): Array<'number' | 'string' | 'boolean'> {
+    const order: Array<'number' | 'string' | 'boolean'> = ['number', 'string', 'boolean']
+    const seen = new Set<'number' | 'string' | 'boolean'>()
+    for (const v of values) {
+      if (v === null || v === undefined) continue
+      const t = typeof v
+      seen.add(t === 'number' ? 'number' : t === 'boolean' ? 'boolean' : 'string')
+    }
+    return order.filter((k) => seen.has(k))
+  }
+
+  /** The value kind a {@link FieldType} reading is an interpretation of. */
+  private static kindOfType(type: FieldType): 'number' | 'string' | 'boolean' {
+    switch (type) {
+      case FieldType.BOOLEAN:
+        return 'boolean'
+      case FieldType.INTEGER:
+      case FieldType.FLOAT:
+      case FieldType.TIMESTAMP_MS:
+      case FieldType.TIMESTAMP_S:
+        return 'number'
+      default:
+        return 'string'
+    }
+  }
+
+  /**
+   * Classify values into a single field type.
    *
    * Uses DuckDB-inspired type detection order:
    * BOOLEAN → INTEGER → FLOAT → DATE → TIMESTAMP → UUID → STRING
    *
    * No fallbacks - pure value-based detection
    */
-  private async analyzeValues(field: string, values: any[]): Promise<FieldTypeInfo> {
+  private async classifyValues(field: string, values: any[]): Promise<FieldTypeInfo> {
     // Filter null/undefined values
     const validValues = values.filter(v => v !== null && v !== undefined)
 

tests/regression/metadata-field-typing.unit.test.ts

@@ -0,0 +1,122 @@
+/**
+ * @module metadata-field-typing.unit.test
+ * @description Regression: a metadata field that holds more than one value
+ * KIND stays fully filterable on every kind it holds.
+ *
+ * The defect this pins, reproduced on the released engine: the metadata index
+ * fixed a field's value type from the FIRST value it saw, and every later value
+ * of a different type was coerced to that type or, when coercion failed,
+ * dropped from the index in silence. Writing `category: 'electronics'` rows and
+ * then `category: 5` rows left `find({ where: { category: 5 } })` returning
+ * nothing — while the same rows in a numbers-only corpus answered correctly.
+ * The rows themselves were never lost: they stayed readable by id and by vector
+ * search, and only ever went missing from equality filters on that one field,
+ * which is what made it so quiet.
+ *
+ * Order is the whole point of these cases. Neither writer owns the field, so
+ * strings-then-numbers and numbers-then-strings must give the same answers.
+ */
+
+import { describe, it, expect } from 'vitest'
+import { Brainy } from '../../src/brainy.js'
+import { NounType } from '../../src/types/graphTypes.js'
+
+/** A brain over memory storage, with a corpus written in the given order. */
+async function brainWith(
+  rows: Array<{ label: string; category: unknown }>
+): Promise<Brainy> {
+  const brainy = new Brainy({ requireSubtype: false, storage: { type: 'memory' } })
+  await brainy.init()
+  for (const row of rows) {
+    await brainy.add({
+      data: `item ${row.label}`,
+      type: NounType.Thing,
+      metadata: { label: row.label, category: row.category }
+    })
+  }
+  return brainy
+}
+
+const labelsOf = (results: Array<{ metadata?: Record<string, unknown> }>): string[] =>
+  results.map((r) => String(r.metadata?.label)).sort()
+
+describe('regression: a mixed-kind metadata field filters on every kind', { timeout: 180_000 }, () => {
+  it('finds number rows written after string rows', async () => {
+    const brainy = await brainWith([
+      { label: 'e1', category: 'electronics' },
+      { label: 'f1', category: 'furniture' },
+      { label: 'n1', category: 5 },
+      { label: 'n2', category: 5 },
+      { label: 'n3', category: 7 }
+    ])
+    try {
+      expect(labelsOf(await brainy.find({ where: { category: 5 }, limit: 100 }))).toEqual(['n1', 'n2'])
+      expect(labelsOf(await brainy.find({ where: { category: 7 }, limit: 100 }))).toEqual(['n3'])
+      expect(labelsOf(await brainy.find({ where: { category: 'electronics' }, limit: 100 }))).toEqual(['e1'])
+      expect(labelsOf(await brainy.find({ where: { category: 'furniture' }, limit: 100 }))).toEqual(['f1'])
+    } finally {
+      await brainy.close()
+    }
+  })
+
+  it('finds string rows written after number rows', async () => {
+    const brainy = await brainWith([
+      { label: 'n1', category: 5 },
+      { label: 'n2', category: 5 },
+      { label: 'e1', category: 'electronics' },
+      { label: 'e2', category: 'electronics' }
+    ])
+    try {
+      expect(labelsOf(await brainy.find({ where: { category: 'electronics' }, limit: 100 }))).toEqual(['e1', 'e2'])
+      expect(labelsOf(await brainy.find({ where: { category: 5 }, limit: 100 }))).toEqual(['n1', 'n2'])
+    } finally {
+      await brainy.close()
+    }
+  })
+
+  it('keeps `5` and `\'5\'` apart — a kind is part of the value, not a formatting detail', async () => {
+    const brainy = await brainWith([
+      { label: 'num', category: 5 },
+      { label: 'str', category: '5' }
+    ])
+    try {
+      expect(labelsOf(await brainy.find({ where: { category: 5 }, limit: 100 }))).toEqual(['num'])
+      expect(labelsOf(await brainy.find({ where: { category: '5' }, limit: 100 }))).toEqual(['str'])
+    } finally {
+      await brainy.close()
+    }
+  })
+
+  it('serves booleans mixed into a field that already holds strings', async () => {
+    const brainy = await brainWith([
+      { label: 's1', category: 'yes' },
+      { label: 'b1', category: true },
+      { label: 'b2', category: false }
+    ])
+    try {
+      expect(labelsOf(await brainy.find({ where: { category: true }, limit: 100 }))).toEqual(['b1'])
+      expect(labelsOf(await brainy.find({ where: { category: false }, limit: 100 }))).toEqual(['b2'])
+      expect(labelsOf(await brainy.find({ where: { category: 'yes' }, limit: 100 }))).toEqual(['s1'])
+    } finally {
+      await brainy.close()
+    }
+  })
+
+  it('ranges over the numeric part of a mixed field', async () => {
+    const brainy = await brainWith([
+      { label: 'unpriced', category: 'on request' },
+      { label: 'cheap', category: 100 },
+      { label: 'mid', category: 500 },
+      { label: 'dear', category: 900 }
+    ])
+    try {
+      const found = await brainy.find({
+        where: { category: { greaterThan: 200 } },
+        limit: 100
+      })
+      expect(labelsOf(found)).toEqual(['dear', 'mid'])
+    } finally {
+      await brainy.close()
+    }
+  })
+})

tests/unit/indexes/columnStore/column-store-mixed-kind.test.ts

@@ -0,0 +1,241 @@
+/**
+ * @module column-store-mixed-kind.test
+ * @description Typed posting lists: one field, several value KINDS, each
+ * answerable on its own.
+ *
+ * The behaviour these pin replaced a first-writer type freeze. The first value
+ * a field ever saw fixed that field's type; every later value of another kind
+ * was coerced to it, and when coercion failed — `Number('electronics')` — the
+ * value was dropped from the index with no error at all. The row stayed
+ * readable by id and by vector and vanished from every equality filter on the
+ * field. These tests therefore care about ORDER: strings-then-numbers and
+ * numbers-then-strings have to behave identically, because neither writer owns
+ * the field.
+ *
+ * Kinds never coerce into one another at query time either. `5` and `'5'` are
+ * different values and match different rows.
+ */
+
+import { describe, it, expect, beforeEach, afterEach } from 'vitest'
+import { ColumnStore } from '../../../../src/indexes/columnStore/ColumnStore.js'
+import { MemoryStorage } from '../../../../src/storage/adapters/memoryStorage.js'
+import { EntityIdMapper } from '../../../../src/utils/entityIdMapper.js'
+
+describe('ColumnStore — typed posting lists per (field, kind)', () => {
+  let storage: MemoryStorage
+  let idMapper: EntityIdMapper
+  let store: ColumnStore
+
+  beforeEach(async () => {
+    storage = new MemoryStorage()
+    await storage.init()
+    idMapper = new EntityIdMapper({ storage, storageKey: 'test:idMapper' })
+    await idMapper.init()
+
+    store = new ColumnStore({ flushThreshold: 10 })
+    await store.init(storage, idMapper)
+  })
+
+  afterEach(async () => {
+    await store.close()
+  })
+
+  /** Resolve a filter to the sorted UUIDs it matched. */
+  const uuidsOf = async (field: string, value: unknown): Promise<string[]> => {
+    const bitmap = await store.filter(field, value)
+    return Array.from(bitmap)
+      .map((id) => idMapper.getUuid(Number(id)))
+      .filter((u): u is string => u !== undefined)
+      .sort()
+  }
+
+  describe('equality answers on the query value’s own kind', () => {
+    it('serves numbers written AFTER strings on the same field', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { category: 'electronics' })
+      store.addEntity(BigInt(idMapper.getOrAssign('s2')), { category: 'furniture' })
+      store.addEntity(BigInt(idMapper.getOrAssign('n1')), { category: 5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('n2')), { category: 5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('n3')), { category: 7 })
+
+      // The numbers are in the index, though a string got there first.
+      expect(await uuidsOf('category', 5)).toEqual(['n1', 'n2'])
+      expect(await uuidsOf('category', 7)).toEqual(['n3'])
+      // And the strings did not move.
+      expect(await uuidsOf('category', 'electronics')).toEqual(['s1'])
+      expect(await uuidsOf('category', 'furniture')).toEqual(['s2'])
+    })
+
+    it('serves strings written AFTER numbers on the same field', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('n1')), { category: 5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('n2')), { category: 5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { category: 'electronics' })
+      store.addEntity(BigInt(idMapper.getOrAssign('s2')), { category: 'electronics' })
+
+      // 'electronics' would have become NaN and been dropped under the freeze.
+      expect(await uuidsOf('category', 'electronics')).toEqual(['s1', 's2'])
+      expect(await uuidsOf('category', 5)).toEqual(['n1', 'n2'])
+    })
+
+    it('does not coerce a number query into the string postings, or back', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('num')), { code: 5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('str')), { code: '5' })
+
+      expect(await uuidsOf('code', 5)).toEqual(['num'])
+      expect(await uuidsOf('code', '5')).toEqual(['str'])
+    })
+
+    it('serves booleans mixed into a field that already holds strings and numbers', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { flag: 'yes' })
+      store.addEntity(BigInt(idMapper.getOrAssign('n1')), { flag: 1 })
+      store.addEntity(BigInt(idMapper.getOrAssign('b1')), { flag: true })
+      store.addEntity(BigInt(idMapper.getOrAssign('b2')), { flag: false })
+
+      expect(await uuidsOf('flag', true)).toEqual(['b1'])
+      expect(await uuidsOf('flag', false)).toEqual(['b2'])
+      // `true` stores as 1 internally; that is an encoding, not a value.
+      expect(await uuidsOf('flag', 1)).toEqual(['n1'])
+      expect(await uuidsOf('flag', 'yes')).toEqual(['s1'])
+    })
+
+    it('answers nothing — not something coerced — for a kind the field never held', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { category: 'electronics' })
+
+      expect(await uuidsOf('category', 5)).toEqual([])
+      expect(await uuidsOf('category', true)).toEqual([])
+    })
+
+    it('holds every kind across a flush, not just the one in the tail buffer', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { category: 'electronics' })
+      store.addEntity(BigInt(idMapper.getOrAssign('n1')), { category: 5 })
+      await store.flush()
+      store.addEntity(BigInt(idMapper.getOrAssign('s2')), { category: 'electronics' })
+      store.addEntity(BigInt(idMapper.getOrAssign('n2')), { category: 5 })
+
+      expect(await uuidsOf('category', 'electronics')).toEqual(['s1', 's2'])
+      expect(await uuidsOf('category', 5)).toEqual(['n1', 'n2'])
+    })
+  })
+
+  describe('range filters read the numeric postings', () => {
+    it('ranges over the numeric subset of a mixed field, ignoring its strings', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('cheap')), { price: 100 })
+      store.addEntity(BigInt(idMapper.getOrAssign('mid')), { price: 500 })
+      store.addEntity(BigInt(idMapper.getOrAssign('dear')), { price: 900 })
+      store.addEntity(BigInt(idMapper.getOrAssign('unpriced')), { price: 'on request' })
+      await store.flush()
+
+      const inRange = await store.rangeQuery('price', 200, 1000)
+      const uuids = Array.from(inRange)
+        .map((id) => idMapper.getUuid(Number(id)))
+        .sort()
+      expect(uuids).toEqual(['dear', 'mid'])
+    })
+
+    it('an unbounded range still reports every kind — it is the “has a value” probe', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('n1')), { mixed: 42 })
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { mixed: 'text' })
+      store.addEntity(BigInt(idMapper.getOrAssign('b1')), { mixed: true })
+      await store.flush()
+
+      const anyValue = await store.rangeQuery('mixed')
+      const uuids = Array.from(anyValue)
+        .map((id) => idMapper.getUuid(Number(id)))
+        .sort()
+      expect(uuids).toEqual(['b1', 'n1', 's1'])
+    })
+  })
+
+  describe('the index reports what a field actually holds', () => {
+    it('names every kind present, not the one that got there first', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { category: 'electronics' })
+      expect(store.getFieldKinds('category')).toEqual(['string'])
+
+      store.addEntity(BigInt(idMapper.getOrAssign('n1')), { category: 5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('b1')), { category: true })
+      expect(store.getFieldKinds('category')).toEqual(['number', 'string', 'boolean'])
+
+      // And the field is still ONE field by name.
+      expect(store.getIndexedFields()).toEqual(['category'])
+      expect(store.hasField('category')).toBe(true)
+    })
+
+    it('reports an unknown field as holding nothing', () => {
+      expect(store.getFieldKinds('never-written')).toEqual([])
+    })
+  })
+
+  describe('an integer column widens rather than rounding', () => {
+    it('keeps a non-integer written after integers as itself', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('a')), { score: 4 })
+      store.addEntity(BigInt(idMapper.getOrAssign('b')), { score: 4.5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('c')), { score: 5 })
+      await store.flush()
+
+      // 4.5 used to round to 5 and answer `score === 5` alongside c.
+      expect(await uuidsOf('score', 4.5)).toEqual(['b'])
+      expect(await uuidsOf('score', 5)).toEqual(['c'])
+      expect(await uuidsOf('score', 4)).toEqual(['a'])
+    })
+  })
+
+  describe('close then reopen', () => {
+    it('keeps every typed posting, on the same storage', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { category: 'electronics' })
+      store.addEntity(BigInt(idMapper.getOrAssign('n1')), { category: 5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('b1')), { category: true })
+      store.addEntity(BigInt(idMapper.getOrAssign('f1')), { score: 1.5 })
+      await store.flush()
+      await store.close()
+
+      store = new ColumnStore({ flushThreshold: 10 })
+      await store.init(storage, idMapper)
+
+      expect(store.getFieldKinds('category')).toEqual(['number', 'string', 'boolean'])
+      expect(await uuidsOf('category', 'electronics')).toEqual(['s1'])
+      expect(await uuidsOf('category', 5)).toEqual(['n1'])
+      expect(await uuidsOf('category', true)).toEqual(['b1'])
+      expect(await uuidsOf('score', 1.5)).toEqual(['f1'])
+    })
+
+    it('accepts new values of every kind after the reopen', async () => {
+      store.addEntity(BigInt(idMapper.getOrAssign('s1')), { category: 'electronics' })
+      store.addEntity(BigInt(idMapper.getOrAssign('n1')), { category: 5 })
+      await store.flush()
+      await store.close()
+
+      store = new ColumnStore({ flushThreshold: 10 })
+      await store.init(storage, idMapper)
+
+      store.addEntity(BigInt(idMapper.getOrAssign('s2')), { category: 'electronics' })
+      store.addEntity(BigInt(idMapper.getOrAssign('n2')), { category: 5 })
+      store.addEntity(BigInt(idMapper.getOrAssign('b1')), { category: false })
+      await store.flush()
+
+      expect(await uuidsOf('category', 'electronics')).toEqual(['s1', 's2'])
+      expect(await uuidsOf('category', 5)).toEqual(['n1', 'n2'])
+      expect(await uuidsOf('category', false)).toEqual(['b1'])
+    })
+
+    it('opens an index written by the pre-typed-postings shape and reads it unchanged', async () => {
+      // A single-kind field is byte-identical to what the old writer produced:
+      // one manifest at `_column_index/<field>/MANIFEST.json`, no kind
+      // subdirectory anywhere. That IS the old on-disk shape, so proving the
+      // new reader serves it proves an old index still opens.
+      store.addEntity(BigInt(idMapper.getOrAssign('a')), { status: 'active' })
+      store.addEntity(BigInt(idMapper.getOrAssign('b')), { status: 'archived' })
+      await store.flush()
+
+      const keys = await (storage as unknown as {
+        listObjectsUnderPath: (prefix: string) => Promise<string[]>
+      }).listObjectsUnderPath('_column_index/')
+      expect(keys.some((k) => k.includes('/k/'))).toBe(false)
+
+      await store.close()
+      store = new ColumnStore({ flushThreshold: 10 })
+      await store.init(storage, idMapper)
+
+      expect(store.getFieldKinds('status')).toEqual(['string'])
+      expect(await uuidsOf('status', 'active')).toEqual(['a'])
+    })
+  })
+})