diff --git a/.changeset/v3-supabase-needle-lockcontext-errors.md b/.changeset/v3-supabase-needle-lockcontext-errors.md
new file mode 100644
index 000000000..f4f53c427
--- /dev/null
+++ b/.changeset/v3-supabase-needle-lockcontext-errors.md
@@ -0,0 +1,21 @@
+---
+'@cipherstash/stack-supabase': patch
+'@cipherstash/stack': patch
+---
+
+Three correctness fixes surfaced while documenting the v3 surface:
+
+- **Supabase `matches()` now rejects a short free-text needle.** A needle
+  below the tokenizer's `token_length` blooms to zero tokens, so `bloom @> {}`
+  matched (and the caller decrypted) every row — a fail-open exposure. The
+  guard (`matchNeedleError`) was wired into the Drizzle adapter only; the
+  Supabase adapter now applies it at the same term-resolution choke point, so
+  both first-party surfaces reject identically. (Authoritative FFI-level backstop
+  for the `encryptQuery` paths tracked in cipherstash/protectjs-ffi#138.)
+- **Supabase `.withLockContext()` accepts the plain `{ identityClaim }` form**,
+  not only a `LockContext` instance — matching the stack-level operations and
+  the documented identity-aware example (widened to `LockContextInput`).
+- **`EncryptionErrorTypes` is now `as const`**, so the `StackError` union
+  actually discriminates: `switch (error.type)` narrows and `error.code` is
+  reachable on the relevant branches. Without it every `type` was `string` and
+  the documented exhaustive error handler did not compile.
diff --git a/packages/stack-supabase/__tests__/supabase-v3-builder.test.ts b/packages/stack-supabase/__tests__/supabase-v3-builder.test.ts
index b12d2554f..6ae8b4f31 100644
--- a/packages/stack-supabase/__tests__/supabase-v3-builder.test.ts
+++ b/packages/stack-supabase/__tests__/supabase-v3-builder.test.ts
@@ -203,6 +203,18 @@ describe('encryptedSupabaseV3 wire encoding', () => {
     expect(JSON.parse(gte.args[1] as string).c).toBeDefined()
   })
 
+  it('rejects a short matches needle up front (fail-open guard, mirrors Drizzle)', async () => {
+    const { es } = v3Instance()
+    // A 1-2 char needle blooms to no tokens; `bf @> '{}'` matches every row, so
+    // the query would silently return (and decrypt) the whole table.
+    const { error, status } = await es
+      .from('users', users)
+      .select('id')
+      .matches('email', 'ab')
+    expect(status).toBe(500)
+    expect(error?.message).toMatch(/at least 3 characters|match every row/)
+  })
+
   it('emits encrypted matches as PostgREST cs (bloom-filter containment)', async () => {
     const { es, supabase } = v3Instance()
 
diff --git a/packages/stack-supabase/__tests__/supabase-v3-matrix.test.ts b/packages/stack-supabase/__tests__/supabase-v3-matrix.test.ts
index df1e0f90e..f6cf4e977 100644
--- a/packages/stack-supabase/__tests__/supabase-v3-matrix.test.ts
+++ b/packages/stack-supabase/__tests__/supabase-v3-matrix.test.ts
@@ -98,6 +98,18 @@ function firstSample(spec: DomainSpec): unknown {
   return sample
 }
 
+/** A free-text needle that clears the tokenizer's token_length floor. The text
+ * catalog's `samples[0]` is the empty string (a stored-value edge case), which
+ * the matches() short-needle guard now correctly REJECTS — so the wire tests
+ * for matches()/like() need a real, tokenizable needle instead. */
+function matchNeedle(spec: DomainSpec): string {
+  const needle = spec.samples.find(
+    (s): s is string => typeof s === 'string' && [...s].length >= 3,
+  )
+  expect(needle).toBeDefined()
+  return needle as string
+}
+
 describe('supabase v3 wire encoding, every domain', () => {
   // Guards the tier arithmetic itself. A domain silently dropping out of a
   // tier would otherwise just shrink an `it.each` with no test turning red.
@@ -195,7 +207,7 @@ describe('supabase v3 wire encoding, every domain', () => {
     it('emits matches() as a cs containment filter', async () => {
       const { q, supabase, name } = instanceFor(eqlType, spec)
 
-      await q.select(`id, ${name}`).matches(name, firstSample(spec))
+      await q.select(`id, ${name}`).matches(name, matchNeedle(spec))
 
       const [filter] = supabase.callsFor('filter')
       expect(filter.args[0]).toBe(name)
@@ -219,7 +231,7 @@ describe('supabase v3 wire encoding, every domain', () => {
     it('delegates like() to matches, emitting the same cs filter', async () => {
       const { q, supabase, name } = instanceFor(eqlType, spec)
 
-      await q.select(`id, ${name}`).like(name, firstSample(spec) as string)
+      await q.select(`id, ${name}`).like(name, matchNeedle(spec))
 
       const [filter] = supabase.callsFor('filter')
       expect(filter.args[0]).toBe(name)
diff --git a/packages/stack-supabase/__tests__/supabase-v3.test-d.ts b/packages/stack-supabase/__tests__/supabase-v3.test-d.ts
index 51239b448..2bd1a5724 100644
--- a/packages/stack-supabase/__tests__/supabase-v3.test-d.ts
+++ b/packages/stack-supabase/__tests__/supabase-v3.test-d.ts
@@ -431,3 +431,17 @@ describe('encrypted JSON keys and operands (#650)', () => {
     docsBuilder.contains('note', 'x')
   })
 })
+
+describe('withLockContext accepts the plain { identityClaim } form (not only LockContext)', () => {
+  it('accepts a plain identity-claim object — the canonical documented form', () => {
+    // The identity-aware example chains this exact shape; it must typecheck on
+    // the builder, not only on the stack-level operations.
+    mixedBuilder.withLockContext({ identityClaim: ['sub'] })
+    mixedBuilder.withLockContext({ identityClaim: ['sub', 'org_id'] })
+  })
+
+  it('rejects an object with an unknown key', () => {
+    // @ts-expect-error — `claim` is not `identityClaim`
+    mixedBuilder.withLockContext({ claim: ['sub'] })
+  })
+})
diff --git a/packages/stack-supabase/src/query-builder-v3.ts b/packages/stack-supabase/src/query-builder-v3.ts
index 781ae50b4..1b9b100d4 100644
--- a/packages/stack-supabase/src/query-builder-v3.ts
+++ b/packages/stack-supabase/src/query-builder-v3.ts
@@ -2,6 +2,7 @@ import {
   DATE_LIKE_CASTS,
   EncryptedV3Column,
   logger,
+  matchNeedleError,
   parseSelectorSegments,
   reconstructSelectorDocument,
   unsupportedLeafReason,
@@ -494,6 +495,22 @@ export class EncryptedQueryBuilderV3Impl<
       )
     }
 
+    // Free-text (bloom) needle floor. A needle shorter than the tokenizer's
+    // token_length produces NO tokens, so `bf @> '{}'` holds for every row and
+    // the query would silently return (and the caller decrypt) the whole table
+    // — a fail-open over-exposure. Reject it up front, mirroring the Drizzle v3
+    // adapter (matchNeedleError) so both first-party surfaces guard identically.
+    // JSON containment terms (searchableJson) are validated separately above.
+    if (queryType === 'freeTextSearch') {
+      const match = column.build().indexes?.match
+      const reason = match ? matchNeedleError(term.value, match) : undefined
+      if (reason) {
+        throw new Error(
+          `[supabase v3]: cannot search column "${column.getName()}": ${reason}`,
+        )
+      }
+    }
+
     return column
   }
 
diff --git a/packages/stack-supabase/src/query-builder.ts b/packages/stack-supabase/src/query-builder.ts
index 715877787..1914a3df4 100644
--- a/packages/stack-supabase/src/query-builder.ts
+++ b/packages/stack-supabase/src/query-builder.ts
@@ -7,7 +7,7 @@ import {
 } from '@cipherstash/stack/adapter-kit'
 import type { EncryptionClient } from '@cipherstash/stack/encryption'
 import type { EncryptionError } from '@cipherstash/stack/errors'
-import type { LockContext } from '@cipherstash/stack/identity'
+import type { LockContextInput } from '@cipherstash/stack/identity'
 import type {
   EncryptedTable,
   EncryptedTableColumn,
@@ -94,7 +94,7 @@ export class EncryptedQueryBuilderImpl<
   protected shouldThrowOnError = false
 
   // Encryption-specific state
-  protected lockContext: LockContext | null = null
+  protected lockContext: LockContextInput | null = null
   protected auditConfig: AuditConfig | null = null
 
   constructor(
@@ -370,7 +370,7 @@ export class EncryptedQueryBuilderImpl<
   // Encryption-specific methods
   // ---------------------------------------------------------------------------
 
-  withLockContext(lockContext: LockContext): this {
+  withLockContext(lockContext: LockContextInput): this {
     this.lockContext = lockContext
     return this
   }
diff --git a/packages/stack-supabase/src/types.ts b/packages/stack-supabase/src/types.ts
index c29165cd8..d8af397a2 100644
--- a/packages/stack-supabase/src/types.ts
+++ b/packages/stack-supabase/src/types.ts
@@ -7,7 +7,7 @@ import type {
   QueryTypesForColumn,
 } from '@cipherstash/stack/eql/v3'
 import type { EncryptionError } from '@cipherstash/stack/errors'
-import type { LockContext } from '@cipherstash/stack/identity'
+import type { LockContext, LockContextInput } from '@cipherstash/stack/identity'
 import type {
   EncryptedTable,
   EncryptedTableColumn,
@@ -792,7 +792,10 @@ export interface SupabaseClientLike {
 
 export type { AuditConfig } from '@cipherstash/stack/adapter-kit'
 export type { EncryptionClient } from '@cipherstash/stack/encryption'
-export type { LockContext } from '@cipherstash/stack/identity'
+export type {
+  LockContext,
+  LockContextInput,
+} from '@cipherstash/stack/identity'
 export type {
   EncryptedColumn,
   EncryptedTable,
@@ -927,7 +930,9 @@ export interface EncryptedQueryBuilderCore<
   throwOnError(): Self
   /** Escape hatch: re-types the rows and drops back to the v2 builder surface. */
   returns<U extends Record<string, unknown>>(): EncryptedQueryBuilder<U>
-  withLockContext(lockContext: LockContext): Self
+  /** Bind identity-aware encryption. Accepts either a plain
+   * `{ identityClaim }` (the common form) or a `LockContext` instance. */
+  withLockContext(lockContext: LockContextInput): Self
   audit(config: AuditConfig): Self
 }
 
diff --git a/packages/stack/__tests__/error-discriminated-union.test-d.ts b/packages/stack/__tests__/error-discriminated-union.test-d.ts
new file mode 100644
index 000000000..7bb162986
--- /dev/null
+++ b/packages/stack/__tests__/error-discriminated-union.test-d.ts
@@ -0,0 +1,52 @@
+import {
+  type ClientInitError,
+  type EncryptionError,
+  EncryptionErrorTypes,
+  type StackError,
+} from '@cipherstash/stack/errors'
+import { describe, expectTypeOf, it } from 'vitest'
+
+/**
+ * Regression guard for the `as const` on EncryptionErrorTypes: without it every
+ * member's value widens to `string`, so the StackError `type` fields stop
+ * discriminating and the documented exhaustive `switch (error.type)` — including
+ * `error.code` access on the narrowed branch — fails to compile. This suite is
+ * that documented pattern; if `as const` is dropped it goes red.
+ */
+describe('StackError discriminated union (errors as const)', () => {
+  it('literal member types, not string', () => {
+    expectTypeOf(
+      EncryptionErrorTypes.EncryptionError,
+    ).toEqualTypeOf<'EncryptionError'>()
+    expectTypeOf<EncryptionError['type']>().toEqualTypeOf<
+      | 'ClientInitError'
+      | 'EncryptionError'
+      | 'DecryptionError'
+      | 'LockContextError'
+      | 'CtsTokenError'
+    >()
+  })
+
+  it('narrows on `type` and exhausts', () => {
+    const handle = (error: StackError): string => {
+      switch (error.type) {
+        case EncryptionErrorTypes.ClientInitError: {
+          expectTypeOf(error).toEqualTypeOf<ClientInitError>()
+          return error.message
+        }
+        case EncryptionErrorTypes.EncryptionError:
+        case EncryptionErrorTypes.DecryptionError:
+          // `code` exists only on these branches — proves narrowing works.
+          return error.code ?? error.message
+        case EncryptionErrorTypes.LockContextError:
+        case EncryptionErrorTypes.CtsTokenError:
+          return error.message
+        default: {
+          const _exhaustive: never = error
+          return _exhaustive
+        }
+      }
+    }
+    expectTypeOf(handle).toBeFunction()
+  })
+})
diff --git a/packages/stack/src/errors/index.ts b/packages/stack/src/errors/index.ts
index c3bd280b1..b046d0a46 100644
--- a/packages/stack/src/errors/index.ts
+++ b/packages/stack/src/errors/index.ts
@@ -1,12 +1,16 @@
 import type { ProtectErrorCode } from '@cipherstash/protect-ffi'
 
+// `as const` is load-bearing: without it every member's type widens to `string`,
+// so the `type` fields on the StackError union members below all become `string`
+// and the union stops discriminating — `switch (error.type)` cannot narrow, and
+// the documented exhaustive error-handling pattern fails to compile.
 export const EncryptionErrorTypes = {
   ClientInitError: 'ClientInitError',
   EncryptionError: 'EncryptionError',
   DecryptionError: 'DecryptionError',
   LockContextError: 'LockContextError',
   CtsTokenError: 'CtsTokenError',
-}
+} as const
 
 /**
  * Base error interface returned by all encryption operations.
diff --git a/packages/stack/tsconfig.json b/packages/stack/tsconfig.json
index d0a2140d5..ddc4ca84c 100644
--- a/packages/stack/tsconfig.json
+++ b/packages/stack/tsconfig.json
@@ -52,7 +52,11 @@
       "@cipherstash/stack": ["./src/index.ts"],
       "@cipherstash/stack/eql/v3": ["./src/eql/v3/index.ts"],
       "@cipherstash/stack/schema": ["./src/schema/index.ts"],
-      "@cipherstash/stack/v3": ["./src/encryption/v3.ts"]
+      "@cipherstash/stack/v3": ["./src/encryption/v3.ts"],
+      // Map to source so `.test-d.ts` files typecheck against current source,
+      // not a possibly-stale built `dist/errors` (turbo's `test:types` does not
+      // depend on `build`, so CI can run type tests against an older dist).
+      "@cipherstash/stack/errors": ["./src/errors/index.ts"]
     }
   }
 }