From df86435847f77b14b94dfb6577eabf9958297ec5 Mon Sep 17 00:00:00 2001
From: kevin Heifner <kevin@wire.network>
Date: Wed, 16 Sep 2026 17:54:09 -0500
Subject: [PATCH 1/5] feat(sdk-core): consume slug_name's canonical string
 carrier
MIME-Version: 1.0
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A slug field now arrives and leaves as its canonical spelling, matching
the depot's ABI builtin (wire-sysio#619). The two row unwrappers and the
two {value} writers are gone, and chainSlugValue/reserveSlugValue no
longer read a digit-only string as a decimal — "12345678" is a valid slug
whose packed value is nothing like it, so that branch silently mis-decoded.

ChainsSlugName and ReservSlugName stop being Struct subclasses and become
ABISerializableObject types modelled on Name. A Struct cannot express this:
the object decoder dispatches on type.fields before consulting a class's
own from(), so a struct-shaped slug can only ever be written {value}. Wire
bytes are unchanged — a struct of one uint64 packs as that uint64.

Regenerates SysioContractTypes against the generator's new slug_name
builtin mapping; the diff is slug-only.

Change-Id: Id1e57c61100d20daa53d6275ed39c886a02e04d8
---
 .../src/contracts/sysio/chains/Actions.ts     |   8 +-
 .../src/contracts/sysio/chains/Client.ts      |   8 +-
 .../src/contracts/sysio/chains/Slug.ts        |  23 +-
 .../src/contracts/sysio/chains/Structs.ts     |  67 +++++-
 .../src/contracts/sysio/reserv/Actions.ts     |  20 +-
 .../src/contracts/sysio/reserv/Client.ts      |  18 +-
 .../src/contracts/sysio/reserv/Slug.ts        |  26 +--
 .../src/contracts/sysio/reserv/Structs.ts     |  67 +++++-
 .../src/contracts/sysio/tokens/Client.ts      |  12 +-
 .../src/contracts/sysio/uwrit/Actions.ts      |   8 +-
 .../src/contracts/sysio/uwrit/Client.ts       |  22 +-
 .../sdk-core/src/types/SysioContractTypes.ts  | 206 +++++++++---------
 .../contracts/sysio/chains/Actions.test.ts    |  11 +-
 .../contracts/sysio/chains/Client.test.ts     |   6 +-
 .../tests/contracts/sysio/chains/Slug.test.ts |  19 +-
 .../contracts/sysio/reserv/Client.test.ts     |  12 +-
 .../contracts/sysio/tokens/Client.test.ts     |  14 +-
 .../contracts/sysio/uwrit/Client.test.ts      |  28 ++-
 18 files changed, 335 insertions(+), 240 deletions(-)

diff --git a/packages/sdk-core/src/contracts/sysio/chains/Actions.ts b/packages/sdk-core/src/contracts/sysio/chains/Actions.ts
index 5f52ea33..7e3d2441 100644
--- a/packages/sdk-core/src/contracts/sysio/chains/Actions.ts
+++ b/packages/sdk-core/src/contracts/sysio/chains/Actions.ts
@@ -4,7 +4,7 @@ import { buildContractAction } from "../../Contract.js"
 
 import { DEFAULT_CHAINS_CONTRACT, MAX_EXTERNAL_CHAIN_ID } from "./Constants.js"
 import { descriptor } from "./Descriptor.js"
-import { chainSlugData } from "./Slug.js"
+import { chainSlugString } from "./Slug.js"
 import type {
   ChainOutpostAddresses,
   ChainRegistration,
@@ -44,7 +44,7 @@ export function createRegisterChainActionData(
 ): SysioContracts.SysioChainsRegchainAction {
   return {
     kind: registration.kind,
-    code: chainSlugData(registration.code),
+    code: chainSlugString(registration.code),
     external_chain_id: assertExternalChainId(registration.externalChainId),
     name: registration.name,
     description: registration.description,
@@ -69,7 +69,7 @@ export function createSetOutpostActionData(
   code: CreateSetOutpostActionOptions["code"],
   outpost: CreateSetOutpostActionOptions["outpost"]
 ): SysioContracts.SysioChainsSetoutpostAction {
-  return { code: chainSlugData(code), outpost: outpostAddressData(outpost) }
+  return { code: chainSlugString(code), outpost: outpostAddressData(outpost) }
 }
 
 /** Creates an unsigned privileged `sysio.chains::setoutpost` action. */
@@ -88,7 +88,7 @@ export function createSetOutpostAction(
 export function createActivateChainActionData(
   code: CreateActivateChainActionOptions["code"]
 ): SysioContracts.SysioChainsActivchainAction {
-  return { code: chainSlugData(code) }
+  return { code: chainSlugString(code) }
 }
 
 /** Creates an unsigned privileged `sysio.chains::activchain` action. */
diff --git a/packages/sdk-core/src/contracts/sysio/chains/Client.ts b/packages/sdk-core/src/contracts/sysio/chains/Client.ts
index 167f5638..fef30a4c 100644
--- a/packages/sdk-core/src/contracts/sysio/chains/Client.ts
+++ b/packages/sdk-core/src/contracts/sysio/chains/Client.ts
@@ -45,15 +45,11 @@ function chainKindValue(
   return Number(mapped) as SysioContracts.SysioChainsChainkind
 }
 
-function rowSlugValue(value: SysioContracts.SysioChainsSlugNameType): number {
-  return chainSlugValue(value.value)
-}
-
 /** Normalizes a generated chain registry row into application-friendly values. */
 export function normalizeChainRow(
   row: SysioContracts.SysioChainsChainRowType
 ): ChainRecord {
-  const codeValue = rowSlugValue(row.code)
+  const codeValue = chainSlugValue(row.code)
 
   return {
     code: chainSlugString(codeValue),
@@ -156,7 +152,7 @@ export class ChainsClient {
   async getChain(code: ChainSlugName): Promise<ChainRecord> {
     const codeValue = chainSlugValue(code),
       rows = await this.listChainRows({ limit: Number.MAX_SAFE_INTEGER }),
-      row = rows.find(candidate => rowSlugValue(candidate.code) === codeValue)
+      row = rows.find(candidate => chainSlugValue(candidate.code) === codeValue)
 
     return row ? normalizeChainRow(row) : null
   }
diff --git a/packages/sdk-core/src/contracts/sysio/chains/Slug.ts b/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
index bd5b1def..926d1017 100644
--- a/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
+++ b/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
@@ -1,16 +1,16 @@
 import { SlugName } from "../../../SlugName.js"
-import type * as SysioContracts from "../../../types/SysioContractTypes.js"
 
 import type { ChainSlugName } from "./Types.js"
 
-/** Converts a friendly chain slug or packed value to its safe numeric form. */
+/**
+ * Converts a friendly chain slug or packed value to its safe numeric form.
+ *
+ * A string is ALWAYS parsed as a slug, never as a decimal: the slug alphabet
+ * contains digits, so `"12345678"` is a legitimate code whose packed value is
+ * nothing like 12345678. Pass a `number` to supply an already-packed value.
+ */
 export function chainSlugValue(value: ChainSlugName): number {
-  const numericString = typeof value === "string" && /^[0-9]+$/.test(value),
-    packed = numericString
-      ? Number(value)
-      : typeof value === "string"
-        ? SlugName.from(value)
-        : Number(value)
+  const packed = typeof value === "string" ? SlugName.from(value) : Number(value)
 
   if (!Number.isSafeInteger(packed) || packed <= 0) {
     throw new Error(
@@ -21,13 +21,6 @@ export function chainSlugValue(value: ChainSlugName): number {
   return packed
 }
 
-/** Converts a friendly chain slug to generated `slug_name` action data. */
-export function chainSlugData(
-  value: ChainSlugName
-): SysioContracts.SysioChainsSlugNameType {
-  return { value: chainSlugValue(value) }
-}
-
 /** Returns the display form of a packed chain slug. */
 export function chainSlugString(value: ChainSlugName): string {
   return SlugName.toString(chainSlugValue(value))
diff --git a/packages/sdk-core/src/contracts/sysio/chains/Structs.ts b/packages/sdk-core/src/contracts/sysio/chains/Structs.ts
index ab5b6eb3..5f4c8929 100644
--- a/packages/sdk-core/src/contracts/sysio/chains/Structs.ts
+++ b/packages/sdk-core/src/contracts/sysio/chains/Structs.ts
@@ -1,11 +1,68 @@
+import { ABIDecoder } from "../../../serializer/Decoder.js"
+import { ABIEncoder } from "../../../serializer/Encoder.js"
+import { ABISerializableObject } from "../../../serializer/Serializable.js"
 import { Int32, UInt32, UInt64 } from "../../../chain/Integer.js"
 import { Struct } from "../../../chain/Struct.js"
+import { SlugName } from "../../../SlugName.js"
+import { isInstanceOf } from "../../../Utils.js"
 
-/** Runtime serializer for the Wire `slug_name` wrapper used by `sysio.chains`. */
-@Struct.type("slug_name")
-export class ChainsSlugName extends Struct {
-  /** Packed eight-character chain code. */
-  @Struct.field("uint64") declare value: UInt64
+/**
+ * Runtime serializer for the Wire `slug_name` chain type used by `sysio.chains`.
+ *
+ * Modelled on `Name`, not on `Struct`: `slug_name` is an ABI BUILTIN on the
+ * chain, so it has one wire form (a packed `uint64` — unchanged, the bytes are
+ * what the depot stores) and one JSON form (the canonical spelling, the only
+ * carrier the builtin emits or accepts). A `Struct` subclass cannot express
+ * that — the object decoder dispatches on `type.fields` before consulting a
+ * class's own `from`, so a struct-shaped slug can only ever be written as
+ * `{ value }`.
+ */
+export class ChainsSlugName implements ABISerializableObject {
+  static abiName = "slug_name"
+
+  /** Packed eight-symbol code — the wire form. */
+  value: UInt64
+
+  /** Builds from the canonical spelling, an already-packed value, or itself. */
+  static from(value: ChainsSlugName | UInt64 | string | number): ChainsSlugName {
+    if (isInstanceOf(value, ChainsSlugName)) return value
+    if (isInstanceOf(value, UInt64)) return new ChainsSlugName(value)
+
+    return new ChainsSlugName(
+      UInt64.from(typeof value === "string" ? SlugName.from(value) : value)
+    )
+  }
+
+  static fromABI(decoder: ABIDecoder) {
+    return new ChainsSlugName(UInt64.fromABI(decoder))
+  }
+
+  static abiDefault() {
+    return new this(UInt64.from(0))
+  }
+
+  constructor(value: UInt64) {
+    this.value = value
+  }
+
+  /** Return true if this slug is equal to the passed slug. */
+  equals(other: ChainsSlugName | UInt64 | string | number): boolean {
+    return this.value.equals(ChainsSlugName.from(other).value)
+  }
+
+  /** The canonical spelling — `""` for the zero sentinel. */
+  toString(): string {
+    return SlugName.toString(Number(this.value))
+  }
+
+  toABI(encoder: ABIEncoder) {
+    this.value.toABI(encoder)
+  }
+
+  /** @internal */
+  toJSON() {
+    return this.toString()
+  }
 }
 
 /**
diff --git a/packages/sdk-core/src/contracts/sysio/reserv/Actions.ts b/packages/sdk-core/src/contracts/sysio/reserv/Actions.ts
index 6f7703fe..40f99470 100644
--- a/packages/sdk-core/src/contracts/sysio/reserv/Actions.ts
+++ b/packages/sdk-core/src/contracts/sysio/reserv/Actions.ts
@@ -6,7 +6,7 @@ import { SysioContractName } from "../../../types/SysioContractTypes.js"
 import { assertEncodedAction, getSysioContract } from "../Client.js"
 
 import { DEFAULT_RESERV_CONTRACT } from "./Constants.js"
-import { reserveSlugData } from "./Slug.js"
+import { reserveSlugString } from "./Slug.js"
 import type { MatchReserveOptions, ReserveQuoteOptions } from "./Types.js"
 
 /** Any value with a string form — an amount as a number, string, bigint, or a BN/Decimal-like object. */
@@ -23,9 +23,9 @@ export function matchReserveActionData(
   options: MatchReserveOptions
 ): SysioContracts.SysioReservMatchreserveAction {
   return {
-    chain_code: reserveSlugData(options.chainCode),
-    token_code: reserveSlugData(options.tokenCode),
-    reserve_code: reserveSlugData(options.reserveCode),
+    chain_code: reserveSlugString(options.chainCode),
+    token_code: reserveSlugString(options.tokenCode),
+    reserve_code: reserveSlugString(options.reserveCode),
     matcher: Name.from(options.matcher).toString(),
     wire_amount: amountString(options.wireAmount)
   }
@@ -54,13 +54,13 @@ export function swapQuoteActionData(
   options: ReserveQuoteOptions
 ): SysioContracts.SysioReservSwapquoteAction {
   return {
-    from_chain_code: reserveSlugData(options.from.chainCode),
-    from_token_code: reserveSlugData(options.from.tokenCode),
-    from_reserve_code: reserveSlugData(options.from.reserveCode),
+    from_chain_code: reserveSlugString(options.from.chainCode),
+    from_token_code: reserveSlugString(options.from.tokenCode),
+    from_reserve_code: reserveSlugString(options.from.reserveCode),
     from_amount: amountString(options.fromAmount),
-    to_chain_code: reserveSlugData(options.to.chainCode),
-    to_token_code: reserveSlugData(options.to.tokenCode),
-    to_reserve_code: reserveSlugData(options.to.reserveCode)
+    to_chain_code: reserveSlugString(options.to.chainCode),
+    to_token_code: reserveSlugString(options.to.tokenCode),
+    to_reserve_code: reserveSlugString(options.to.reserveCode)
   }
 }
 
diff --git a/packages/sdk-core/src/contracts/sysio/reserv/Client.ts b/packages/sdk-core/src/contracts/sysio/reserv/Client.ts
index a425e7f2..0600b973 100644
--- a/packages/sdk-core/src/contracts/sysio/reserv/Client.ts
+++ b/packages/sdk-core/src/contracts/sysio/reserv/Client.ts
@@ -23,11 +23,7 @@ import {
   DEFAULT_RESERV_CONTRACT,
   DEFAULT_RESERVE_QUERY_LIMIT
 } from "./Constants.js"
-import {
-  reserveRowSlugValue,
-  reserveSlugString,
-  reserveSlugValue
-} from "./Slug.js"
+import { reserveSlugString, reserveSlugValue } from "./Slug.js"
 import type {
   ListReservesOptions,
   PushMatchReserveOptions,
@@ -74,9 +70,9 @@ function optionalAccountString(value: NameType): string {
 export function normalizeReserveRow(
   row: SysioContracts.SysioReservReserveRowType
 ): ReserveRecord {
-  const chainCodeValue = reserveRowSlugValue(row.chain_code),
-    tokenCodeValue = reserveRowSlugValue(row.token_code),
-    reserveCodeValue = reserveRowSlugValue(row.reserve_code)
+  const chainCodeValue = reserveSlugValue(row.chain_code),
+    tokenCodeValue = reserveSlugValue(row.token_code),
+    reserveCodeValue = reserveSlugValue(row.reserve_code)
 
   return {
     chainCode: reserveSlugString(chainCodeValue),
@@ -186,11 +182,11 @@ export class ReserveClient {
           const status = enumValue(SysioReservReservestatus, row.status),
             chainMatches =
               options.chainCode == null ||
-              reserveRowSlugValue(row.chain_code) ===
+              reserveSlugValue(row.chain_code) ===
                 reserveSlugValue(options.chainCode),
             tokenMatches =
               options.tokenCode == null ||
-              reserveRowSlugValue(row.token_code) ===
+              reserveSlugValue(row.token_code) ===
                 reserveSlugValue(options.tokenCode),
             statusMatches = options.status == null || status === options.status,
             ownerMatches = !owner || optionalAccountString(row.owner) === owner,
@@ -235,7 +231,7 @@ export class ReserveClient {
         limit: Number.MAX_SAFE_INTEGER
       }),
       row = rows.find(
-        candidate => reserveRowSlugValue(candidate.reserve_code) === reserveCode
+        candidate => reserveSlugValue(candidate.reserve_code) === reserveCode
       )
 
     return row ? normalizeReserveRow(row) : null
diff --git a/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts b/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
index 62e34e47..7e2b9d0e 100644
--- a/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
+++ b/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
@@ -1,9 +1,14 @@
 import { SlugName } from "../../../SlugName.js"
-import type * as SysioContracts from "../../../types/SysioContractTypes.js"
 
 import type { ReserveSlugName } from "./Types.js"
 
-/** Converts a friendly slug string or packed value to its safe numeric form. */
+/**
+ * Converts a friendly slug string or packed value to its safe numeric form.
+ *
+ * A string is ALWAYS parsed as a slug, never as a decimal: the slug alphabet
+ * contains digits, so `"12345678"` is a legitimate code whose packed value is
+ * nothing like 12345678. Pass a `number` to supply an already-packed value.
+ */
 export function reserveSlugValue(value: ReserveSlugName): number {
   const packed =
     typeof value === "string" ? SlugName.from(value) : Number(value)
@@ -17,23 +22,6 @@ export function reserveSlugValue(value: ReserveSlugName): number {
   return packed
 }
 
-/** Converts a generated row slug, including JSON-serialized uint64 strings. */
-export function reserveRowSlugValue(
-  value: SysioContracts.SysioReservSlugNameType
-): number {
-  const packed = value.value
-  return typeof packed === "string" && /^[0-9]+$/.test(packed)
-    ? reserveSlugValue(Number(packed))
-    : reserveSlugValue(packed)
-}
-
-/** Converts a friendly reserve slug to generated `slug_name` action data. */
-export function reserveSlugData(
-  value: ReserveSlugName
-): SysioContracts.SysioReservSlugNameType {
-  return { value: reserveSlugValue(value) }
-}
-
 /** Returns the display form of a packed reserve slug. */
 export function reserveSlugString(value: ReserveSlugName): string {
   return SlugName.toString(reserveSlugValue(value))
diff --git a/packages/sdk-core/src/contracts/sysio/reserv/Structs.ts b/packages/sdk-core/src/contracts/sysio/reserv/Structs.ts
index 2597afdb..158e263a 100644
--- a/packages/sdk-core/src/contracts/sysio/reserv/Structs.ts
+++ b/packages/sdk-core/src/contracts/sysio/reserv/Structs.ts
@@ -1,12 +1,69 @@
+import { ABIDecoder } from "../../../serializer/Decoder.js"
+import { ABIEncoder } from "../../../serializer/Encoder.js"
+import { ABISerializableObject } from "../../../serializer/Serializable.js"
 import { UInt64 } from "../../../chain/Integer.js"
 import { Name } from "../../../chain/Name.js"
 import { Struct } from "../../../chain/Struct.js"
+import { SlugName } from "../../../SlugName.js"
+import { isInstanceOf } from "../../../Utils.js"
 
-/** Runtime serializer for the Wire `slug_name` wrapper used by `sysio.reserv`. */
-@Struct.type("slug_name")
-export class ReservSlugName extends Struct {
-  /** Packed eight-character reserve slug. */
-  @Struct.field("uint64") declare value: UInt64
+/**
+ * Runtime serializer for the Wire `slug_name` chain type used by `sysio.reserv`.
+ *
+ * Modelled on `Name`, not on `Struct`: `slug_name` is an ABI BUILTIN on the
+ * chain, so it has one wire form (a packed `uint64` — unchanged, the bytes are
+ * what the depot stores) and one JSON form (the canonical spelling, the only
+ * carrier the builtin emits or accepts). A `Struct` subclass cannot express
+ * that — the object decoder dispatches on `type.fields` before consulting a
+ * class's own `from`, so a struct-shaped slug can only ever be written as
+ * `{ value }`.
+ */
+export class ReservSlugName implements ABISerializableObject {
+  static abiName = "slug_name"
+
+  /** Packed eight-symbol code — the wire form. */
+  value: UInt64
+
+  /** Builds from the canonical spelling, an already-packed value, or itself. */
+  static from(value: ReservSlugName | UInt64 | string | number): ReservSlugName {
+    if (isInstanceOf(value, ReservSlugName)) return value
+    if (isInstanceOf(value, UInt64)) return new ReservSlugName(value)
+
+    return new ReservSlugName(
+      UInt64.from(typeof value === "string" ? SlugName.from(value) : value)
+    )
+  }
+
+  static fromABI(decoder: ABIDecoder) {
+    return new ReservSlugName(UInt64.fromABI(decoder))
+  }
+
+  static abiDefault() {
+    return new this(UInt64.from(0))
+  }
+
+  constructor(value: UInt64) {
+    this.value = value
+  }
+
+  /** Return true if this slug is equal to the passed slug. */
+  equals(other: ReservSlugName | UInt64 | string | number): boolean {
+    return this.value.equals(ReservSlugName.from(other).value)
+  }
+
+  /** The canonical spelling — `""` for the zero sentinel. */
+  toString(): string {
+    return SlugName.toString(Number(this.value))
+  }
+
+  toABI(encoder: ABIEncoder) {
+    this.value.toABI(encoder)
+  }
+
+  /** @internal */
+  toJSON() {
+    return this.toString()
+  }
 }
 
 /** Runtime serializer for `sysio.reserv::matchreserve`. */
diff --git a/packages/sdk-core/src/contracts/sysio/tokens/Client.ts b/packages/sdk-core/src/contracts/sysio/tokens/Client.ts
index e8bc6c7d..df024a60 100644
--- a/packages/sdk-core/src/contracts/sysio/tokens/Client.ts
+++ b/packages/sdk-core/src/contracts/sysio/tokens/Client.ts
@@ -5,11 +5,7 @@ import {
 } from "../../../types/SysioContractTypes.js"
 import type * as SysioContracts from "../../../types/SysioContractTypes.js"
 import { getSysioContract, type SysioContractClient } from "../Client.js"
-import {
-  reserveRowSlugValue,
-  reserveSlugString,
-  reserveSlugValue
-} from "../reserv/Slug.js"
+import { reserveSlugString, reserveSlugValue } from "../reserv/Slug.js"
 
 import {
   DEFAULT_TOKENS_CONTRACT,
@@ -44,7 +40,7 @@ function enumValue<T extends Record<string, string | number>>(
 export function normalizeTokenRow(
   row: SysioContracts.SysioTokensTokenRowType
 ): TokenRecord {
-  const codeValue = reserveRowSlugValue(row.code)
+  const codeValue = reserveSlugValue(row.code)
 
   return {
     code: reserveSlugString(codeValue),
@@ -69,8 +65,8 @@ export function normalizeTokenRow(
 export function normalizeChainTokenRow(
   row: SysioContracts.SysioTokensChainTokenRowType
 ): ChainTokenRecord {
-  const chainCodeValue = reserveRowSlugValue(row.chain_code),
-    tokenCodeValue = reserveRowSlugValue(row.token_code)
+  const chainCodeValue = reserveSlugValue(row.chain_code),
+    tokenCodeValue = reserveSlugValue(row.token_code)
 
   return {
     chainCode: reserveSlugString(chainCodeValue),
diff --git a/packages/sdk-core/src/contracts/sysio/uwrit/Actions.ts b/packages/sdk-core/src/contracts/sysio/uwrit/Actions.ts
index 3793d7cf..03e087fd 100644
--- a/packages/sdk-core/src/contracts/sysio/uwrit/Actions.ts
+++ b/packages/sdk-core/src/contracts/sysio/uwrit/Actions.ts
@@ -1,6 +1,6 @@
 import { Name } from "../../../chain/Name.js"
 import type * as SysioContracts from "../../../types/SysioContractTypes.js"
-import { reserveSlugData } from "../reserv/Slug.js"
+import { reserveSlugString } from "../reserv/Slug.js"
 
 import type { SwapFromWireOptions } from "./Types.js"
 
@@ -11,9 +11,9 @@ export function swapFromWireActionData(
   return {
     user: Name.from(options.user).toString(),
     wire_amount: options.wireAmount.toString(),
-    dst_chain_code: reserveSlugData(options.destination.chainCode),
-    dst_token_code: reserveSlugData(options.destination.tokenCode),
-    dst_reserve_code: reserveSlugData(options.destination.reserveCode),
+    dst_chain_code: reserveSlugString(options.destination.chainCode),
+    dst_token_code: reserveSlugString(options.destination.tokenCode),
+    dst_reserve_code: reserveSlugString(options.destination.reserveCode),
     target_amount: options.targetAmount.toString(),
     target_tolerance_bps: options.targetToleranceBps,
     recipient_kind: options.recipientKind,
diff --git a/packages/sdk-core/src/contracts/sysio/uwrit/Client.ts b/packages/sdk-core/src/contracts/sysio/uwrit/Client.ts
index 6b879f1b..bbbb9733 100644
--- a/packages/sdk-core/src/contracts/sysio/uwrit/Client.ts
+++ b/packages/sdk-core/src/contracts/sysio/uwrit/Client.ts
@@ -8,11 +8,7 @@ import {
 } from "../../../types/SysioContractTypes.js"
 import type * as SysioContracts from "../../../types/SysioContractTypes.js"
 import { getSysioContract, type SysioContractClient } from "../Client.js"
-import {
-  reserveRowSlugValue,
-  reserveSlugString,
-  reserveSlugValue
-} from "../reserv/Slug.js"
+import { reserveSlugString, reserveSlugValue } from "../reserv/Slug.js"
 
 import { swapFromWireActionData } from "./Actions.js"
 import {
@@ -30,10 +26,14 @@ import type {
   UnderwritingRequestRecord
 } from "./Types.js"
 
+/**
+ * The three slug fields that identify a reserve leg on a `uwreqs` row. Typed by
+ * indexed access off the generated row so a codegen change propagates here.
+ */
 interface ReserveIdentitySlugs {
-  chain: SysioContracts.SysioUwritSlugNameType
-  token: SysioContracts.SysioUwritSlugNameType
-  reserve: SysioContracts.SysioUwritSlugNameType
+  chain: SysioContracts.SysioUwritUwRequestTType["src_chain_code"]
+  token: SysioContracts.SysioUwritUwRequestTType["src_token_code"]
+  reserve: SysioContracts.SysioUwritUwRequestTType["src_reserve_code"]
 }
 
 function bigintValue(value: number | string): bigint {
@@ -58,9 +58,9 @@ function identity(
   reserve: ReserveIdentitySlugs["reserve"]
 ) {
   return {
-    chainCode: reserveSlugString(reserveRowSlugValue(chain)),
-    tokenCode: reserveSlugString(reserveRowSlugValue(token)),
-    reserveCode: reserveSlugString(reserveRowSlugValue(reserve))
+    chainCode: reserveSlugString(chain),
+    tokenCode: reserveSlugString(token),
+    reserveCode: reserveSlugString(reserve)
   }
 }
 
diff --git a/packages/sdk-core/src/types/SysioContractTypes.ts b/packages/sdk-core/src/types/SysioContractTypes.ts
index 22841332..191d78df 100644
--- a/packages/sdk-core/src/types/SysioContractTypes.ts
+++ b/packages/sdk-core/src/types/SysioContractTypes.ts
@@ -298,17 +298,17 @@ export enum SysioChainsChainkind {
 
 /** sysio.chains::activchain (action) */
 export interface SysioChainsActivchainAction {
-  code: SysioChainsSlugNameType
+  code: string
 }
 
 /** sysio.chains::chain_key (type) */
 export interface SysioChainsChainKeyType {
-  code: SysioChainsSlugNameType
+  code: string
 }
 
 /** sysio.chains::chain_row (type) */
 export interface SysioChainsChainRowType {
-  code: SysioChainsSlugNameType
+  code: string
   kind: SysioChainsChainkind | keyof typeof SysioChainsChainkind
   external_chain_id: number
   name: string
@@ -331,7 +331,7 @@ export interface SysioChainsOutpostAddrsType {
 /** sysio.chains::regchain (action) */
 export interface SysioChainsRegchainAction {
   kind: SysioChainsChainkind | keyof typeof SysioChainsChainkind
-  code: SysioChainsSlugNameType
+  code: string
   external_chain_id: number
   name: string
   description: string
@@ -340,7 +340,7 @@ export interface SysioChainsRegchainAction {
 
 /** sysio.chains::setoutpost (action) */
 export interface SysioChainsSetoutpostAction {
-  code: SysioChainsSlugNameType
+  code: string
   outpost: SysioChainsOutpostAddrsType
 }
 
@@ -1786,14 +1786,14 @@ export interface SysioOpregTokenamountType {
 /** sysio.opreg::available (action) */
 export interface SysioOpregAvailableAction {
   account: string
-  chain_code: SysioOpregSlugNameType
-  token_code: SysioOpregSlugNameType
+  chain_code: string
+  token_code: string
 }
 
 /** sysio.opreg::balance_entry (type) */
 export interface SysioOpregBalanceEntryType {
-  chain_code: SysioOpregSlugNameType
-  token_code: SysioOpregSlugNameType
+  chain_code: string
+  token_code: string
   balance: number | string
   last_updated_ms: number | string
 }
@@ -1806,8 +1806,8 @@ export interface SysioOpregCancelwtdwAction {
 
 /** sysio.opreg::chain_min_bond (type) */
 export interface SysioOpregChainMinBondType {
-  chain_code: SysioOpregSlugNameType
-  token_code: SysioOpregSlugNameType
+  chain_code: string
+  token_code: string
   min_bond: number | string
   config_timestamp_ms: number | string
 }
@@ -1840,8 +1840,8 @@ export interface SysioOpregDepositAction {
 /** sysio.opreg::depositinle (action) */
 export interface SysioOpregDepositinleAction {
   account: string
-  chain_code: SysioOpregSlugNameType
-  token_code: SysioOpregSlugNameType
+  chain_code: string
+  token_code: string
   amount: number | string
   actor_chain: SysioOpregChainkind | keyof typeof SysioOpregChainkind
   actor_address: string
@@ -1935,8 +1935,8 @@ export interface SysioOpregRegoperatorAction {
 /** sysio.opreg::releaselock (action) */
 export interface SysioOpregReleaselockAction {
   account: string
-  chain_code: SysioOpregSlugNameType
-  token_code: SysioOpregSlugNameType
+  chain_code: string
+  token_code: string
   amount: number | string
 }
 
@@ -2013,8 +2013,8 @@ export interface SysioOpregWithdrawKeyType {
 export interface SysioOpregWithdrawRequestType {
   request_id: number | string
   account: string
-  chain_code: SysioOpregSlugNameType
-  token_code: SysioOpregSlugNameType
+  chain_code: string
+  token_code: string
   amount: number | string
   eligible_at_epoch: number
   requested_at_epoch: number
@@ -2023,8 +2023,8 @@ export interface SysioOpregWithdrawRequestType {
 /** sysio.opreg::withdrawinle (action) */
 export interface SysioOpregWithdrawinleAction {
   account: string
-  chain_code: SysioOpregSlugNameType
-  token_code: SysioOpregSlugNameType
+  chain_code: string
+  token_code: string
   amount: number | string
 }
 
@@ -2087,9 +2087,9 @@ export interface SysioReservChainaddressType {
 
 /** sysio.reserv::applyfromwire (action) */
 export interface SysioReservApplyfromwireAction {
-  dst_chain_code: SysioReservSlugNameType
-  dst_token_code: SysioReservSlugNameType
-  dst_reserve_code: SysioReservSlugNameType
+  dst_chain_code: string
+  dst_token_code: string
+  dst_reserve_code: string
   wire_in: number | string
   dst_amount: number | string
   underwriter: string
@@ -2097,22 +2097,22 @@ export interface SysioReservApplyfromwireAction {
 
 /** sysio.reserv::applyswap (action) */
 export interface SysioReservApplyswapAction {
-  src_chain_code: SysioReservSlugNameType
-  src_token_code: SysioReservSlugNameType
-  src_reserve_code: SysioReservSlugNameType
+  src_chain_code: string
+  src_token_code: string
+  src_reserve_code: string
   src_amount: number | string
-  dst_chain_code: SysioReservSlugNameType
-  dst_token_code: SysioReservSlugNameType
-  dst_reserve_code: SysioReservSlugNameType
+  dst_chain_code: string
+  dst_token_code: string
+  dst_reserve_code: string
   dst_amount: number | string
   underwriter: string
 }
 
 /** sysio.reserv::claimrsvfee (action) */
 export interface SysioReservClaimrsvfeeAction {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
 }
 
 /** sysio.reserv::claimuwfee (action) */
@@ -2127,9 +2127,9 @@ export interface SysioReservClaimwireAction {
 
 /** sysio.reserv::debit (action) */
 export interface SysioReservDebitAction {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
   amount: number | string
 }
 
@@ -2140,27 +2140,27 @@ export interface SysioReservDrainrewardsAction {
 
 /** sysio.reserv::matchreserve (action) */
 export interface SysioReservMatchreserveAction {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
   matcher: string
   wire_amount: number | string
 }
 
 /** sysio.reserv::oncnclrsv (action) */
 export interface SysioReservOncnclrsvAction {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
   creator_chain_kind: SysioReservChainkind | keyof typeof SysioReservChainkind
   creator_chain_addr: string
 }
 
 /** sysio.reserv::oncrtreserve (action) */
 export interface SysioReservOncrtreserveAction {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
   name: string
   description: string
   external_token_amount: number | string
@@ -2175,9 +2175,9 @@ export interface SysioReservOncrtreserveAction {
 
 /** sysio.reserv::paywire (action) */
 export interface SysioReservPaywireAction {
-  src_chain_code: SysioReservSlugNameType
-  src_token_code: SysioReservSlugNameType
-  src_reserve_code: SysioReservSlugNameType
+  src_chain_code: string
+  src_token_code: string
+  src_reserve_code: string
   src_amount: number | string
   recipient: string
   wire_out: number | string
@@ -2193,9 +2193,9 @@ export interface SysioReservRefundwireAction {
 
 /** sysio.reserv::regreserve (action) */
 export interface SysioReservRegreserveAction {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
   name: string
   description: string
   initial_chain_amount: number | string
@@ -2213,16 +2213,16 @@ export interface SysioReservReserveConfigType {
 
 /** sysio.reserv::reserve_key (type) */
 export interface SysioReservReserveKeyType {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
 }
 
 /** sysio.reserv::reserve_row (type) */
 export interface SysioReservReserveRowType {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
   name: string
   description: string
   status: SysioReservReservestatus | keyof typeof SysioReservReservestatus
@@ -2256,9 +2256,9 @@ export interface SysioReservRewardsBucketType {
 
 /** sysio.reserv::rsvfeebal (action) */
 export interface SysioReservRsvfeebalAction {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
 }
 
 /** sysio.reserv::setconfig (action) */
@@ -2268,9 +2268,9 @@ export interface SysioReservSetconfigAction {
 
 /** sysio.reserv::setrsvfee (action) */
 export interface SysioReservSetrsvfeeAction {
-  chain_code: SysioReservSlugNameType
-  token_code: SysioReservSlugNameType
-  reserve_code: SysioReservSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
   owner_fee_bps: number
 }
 
@@ -2281,13 +2281,13 @@ export interface SysioReservSlugNameType {
 
 /** sysio.reserv::swapquote (action) */
 export interface SysioReservSwapquoteAction {
-  from_chain_code: SysioReservSlugNameType
-  from_token_code: SysioReservSlugNameType
-  from_reserve_code: SysioReservSlugNameType
+  from_chain_code: string
+  from_token_code: string
+  from_reserve_code: string
   from_amount: number | string
-  to_chain_code: SysioReservSlugNameType
-  to_token_code: SysioReservSlugNameType
-  to_reserve_code: SysioReservSlugNameType
+  to_chain_code: string
+  to_token_code: string
+  to_reserve_code: string
 }
 
 /** sysio.reserv::sweepclaims (action) */
@@ -3806,25 +3806,25 @@ export interface SysioTokensChainaddressType {
 
 /** sysio.tokens::activctok (action) */
 export interface SysioTokensActivctokAction {
-  chain_code: SysioTokensSlugNameType
-  token_code: SysioTokensSlugNameType
+  chain_code: string
+  token_code: string
 }
 
 /** sysio.tokens::activtoken (action) */
 export interface SysioTokensActivtokenAction {
-  code: SysioTokensSlugNameType
+  code: string
 }
 
 /** sysio.tokens::chain_token_key (type) */
 export interface SysioTokensChainTokenKeyType {
-  chain_code: SysioTokensSlugNameType
-  token_code: SysioTokensSlugNameType
+  chain_code: string
+  token_code: string
 }
 
 /** sysio.tokens::chain_token_row (type) */
 export interface SysioTokensChainTokenRowType {
-  chain_code: SysioTokensSlugNameType
-  token_code: SysioTokensSlugNameType
+  chain_code: string
+  token_code: string
   contract_addr: string
   is_native: boolean
   active: boolean
@@ -3834,8 +3834,8 @@ export interface SysioTokensChainTokenRowType {
 
 /** sysio.tokens::regctok (action) */
 export interface SysioTokensRegctokAction {
-  chain_code: SysioTokensSlugNameType
-  token_code: SysioTokensSlugNameType
+  chain_code: string
+  token_code: string
   contract_addr: string
   is_native: boolean
 }
@@ -3843,7 +3843,7 @@ export interface SysioTokensRegctokAction {
 /** sysio.tokens::regtoken (action) */
 export interface SysioTokensRegtokenAction {
   kind: SysioTokensTokenkind | keyof typeof SysioTokensTokenkind
-  code: SysioTokensSlugNameType
+  code: string
   symbol_name: string
   description: string
   precision: number
@@ -3857,12 +3857,12 @@ export interface SysioTokensSlugNameType {
 
 /** sysio.tokens::token_key (type) */
 export interface SysioTokensTokenKeyType {
-  code: SysioTokensSlugNameType
+  code: string
 }
 
 /** sysio.tokens::token_row (type) */
 export interface SysioTokensTokenRowType {
-  code: SysioTokensSlugNameType
+  code: string
   kind: SysioTokensTokenkind | keyof typeof SysioTokensTokenkind
   symbol_name: string
   description: string
@@ -3992,9 +3992,9 @@ export interface SysioUwritFromwireQType {
   id: number | string
   user: string
   wire_amount: number | string
-  dst_chain_code: SysioUwritSlugNameType
-  dst_token_code: SysioUwritSlugNameType
-  dst_reserve_code: SysioUwritSlugNameType
+  dst_chain_code: string
+  dst_token_code: string
+  dst_reserve_code: string
   target_amount: number | string
   variance_tolerance_bps: number
   recipient_kind: SysioUwritChainkind | keyof typeof SysioUwritChainkind
@@ -4024,9 +4024,9 @@ export interface SysioUwritLockEntryType {
   lock_id: number | string
   uwreq_id: number | string
   underwriter: string
-  chain_code: SysioUwritSlugNameType
-  token_code: SysioUwritSlugNameType
-  reserve_code: SysioUwritSlugNameType
+  chain_code: string
+  token_code: string
+  reserve_code: string
   amount: number | string
   created_at_ms: number | string
   expires_at_ms: number | string
@@ -4041,16 +4041,16 @@ export interface SysioUwritLockKeyType {
 /** sysio.uwrit::lock_sum (type) */
 export interface SysioUwritLockSumType {
   underwriter: string
-  chain_code: SysioUwritSlugNameType
-  token_code: SysioUwritSlugNameType
+  chain_code: string
+  token_code: string
   amount: number | string
 }
 
 /** sysio.uwrit::lock_sum_key (type) */
 export interface SysioUwritLockSumKeyType {
   underwriter: string
-  chain_code: SysioUwritSlugNameType
-  token_code: SysioUwritSlugNameType
+  chain_code: string
+  token_code: string
 }
 
 /** sysio.uwrit::pruneuwreqs (action) */
@@ -4063,9 +4063,9 @@ export interface SysioUwritRcrdcommitAction {
   uwreq_id: number | string
   underwriter: string
   chain_code: number | string
-  from_chain_code: SysioUwritSlugNameType
-  from_token_code: SysioUwritSlugNameType
-  reserve_code: SysioUwritSlugNameType
+  from_chain_code: string
+  from_token_code: string
+  reserve_code: string
   uic_bytes: string
 }
 
@@ -4087,17 +4087,17 @@ export interface SysioUwritSlugNameType {
 /** sysio.uwrit::sumlocks (action) */
 export interface SysioUwritSumlocksAction {
   underwriter: string
-  chain_code: SysioUwritSlugNameType
-  token_code: SysioUwritSlugNameType
+  chain_code: string
+  token_code: string
 }
 
 /** sysio.uwrit::swapfromwire (action) */
 export interface SysioUwritSwapfromwireAction {
   user: string
   wire_amount: number | string
-  dst_chain_code: SysioUwritSlugNameType
-  dst_token_code: SysioUwritSlugNameType
-  dst_reserve_code: SysioUwritSlugNameType
+  dst_chain_code: string
+  dst_token_code: string
+  dst_reserve_code: string
   target_amount: number | string
   target_tolerance_bps: number
   recipient_kind: SysioUwritChainkind | keyof typeof SysioUwritChainkind
@@ -4131,13 +4131,13 @@ export interface SysioUwritUwRequestTType {
   id: number | string
   type: SysioUwritAttestationtype | keyof typeof SysioUwritAttestationtype
   status: SysioUwritUnderwriterequeststatus | keyof typeof SysioUwritUnderwriterequeststatus
-  src_chain_code: SysioUwritSlugNameType
-  src_token_code: SysioUwritSlugNameType
-  src_reserve_code: SysioUwritSlugNameType
+  src_chain_code: string
+  src_token_code: string
+  src_reserve_code: string
   src_amount: number | string
-  dst_chain_code: SysioUwritSlugNameType
-  dst_token_code: SysioUwritSlugNameType
-  dst_reserve_code: SysioUwritSlugNameType
+  dst_chain_code: string
+  dst_token_code: string
+  dst_reserve_code: string
   dst_amount: number | string
   target_amount: number | string
   variance_tolerance_bps: number
diff --git a/packages/sdk-core/tests/contracts/sysio/chains/Actions.test.ts b/packages/sdk-core/tests/contracts/sysio/chains/Actions.test.ts
index e98b6345..2bd1a153 100644
--- a/packages/sdk-core/tests/contracts/sysio/chains/Actions.test.ts
+++ b/packages/sdk-core/tests/contracts/sysio/chains/Actions.test.ts
@@ -37,7 +37,7 @@ describe("sysio.chains action helpers", () => {
   test("creates generated register and activation action data", () => {
     expect(createRegisterChainActionData(REGISTRATION)).toEqual({
       kind: SysioChainsChainkind.CHAIN_KIND_EVM,
-      code: { value: SlugName.from("POLYGON") },
+      code: "POLYGON",
       external_chain_id: 137,
       name: "Polygon",
       description: "Polygon EVM outpost",
@@ -46,7 +46,7 @@ describe("sysio.chains action helpers", () => {
       outpost: EMPTY_OUTPOST
     })
     expect(createActivateChainActionData("POLYGON")).toEqual({
-      code: { value: SlugName.from("POLYGON") }
+      code: "POLYGON"
     })
   })
 
@@ -66,12 +66,16 @@ describe("sysio.chains action helpers", () => {
     expect(register.name.toString()).toBe("regchain")
     expect(register.authorization.map(String)).toEqual(["sysio.chains@active"])
     expect(Number(registerData.kind)).toBe(SysioChainsChainkind.CHAIN_KIND_EVM)
+    // Both forms of the one type: the packed wire value, and the canonical
+    // spelling that is its only JSON carrier.
     expect(Number(registerData.code.value)).toBe(SlugName.from("POLYGON"))
+    expect(registerData.code.toJSON()).toBe("POLYGON")
     expect(Number(registerData.external_chain_id)).toBe(137)
     expect(registerData.name).toBe("Polygon")
     expect(registerData.description).toBe("Polygon EVM outpost")
     expect(registerData.outpost.opp_addr).toBe("")
     expect(Number(activateData.code.value)).toBe(SlugName.from("POLYGON"))
+    expect(activateData.code.toJSON()).toBe("POLYGON")
   })
 
   test("carries every EVM contract role through regchain", () => {
@@ -99,7 +103,7 @@ describe("sysio.chains action helpers", () => {
     expect(
       createSetOutpostActionData("SOLANA", { oppAddress: SVM_PROGRAM })
     ).toEqual({
-      code: { value: SlugName.from("SOLANA") },
+      code: "SOLANA",
       outpost: { ...EMPTY_OUTPOST, opp_addr: SVM_PROGRAM }
     })
   })
@@ -120,6 +124,7 @@ describe("sysio.chains action helpers", () => {
     expect(action.account.toString()).toBe("sysio.chains")
     expect(action.name.toString()).toBe("setoutpost")
     expect(Number(data.code.value)).toBe(SlugName.from("POLYGON"))
+    expect(data.code.toJSON()).toBe("POLYGON")
     expect(data.outpost.opp_addr).toBe(EVM_OPP)
     expect(data.outpost.opp_inbound_addr).toBe(EVM_INBOUND)
     expect(data.outpost.operator_registry_addr).toBe(EVM_OPREG)
diff --git a/packages/sdk-core/tests/contracts/sysio/chains/Client.test.ts b/packages/sdk-core/tests/contracts/sysio/chains/Client.test.ts
index 6f1bfbe4..38036a17 100644
--- a/packages/sdk-core/tests/contracts/sysio/chains/Client.test.ts
+++ b/packages/sdk-core/tests/contracts/sysio/chains/Client.test.ts
@@ -5,7 +5,7 @@ const { ChainsClient } = contracts.sysio.chains
 
 const CHAIN_ROWS = [
   {
-    code: { value: String(SlugName.from("ETHEREUM")) },
+    code: "ETHEREUM",
     kind: "CHAIN_KIND_EVM",
     external_chain_id: 31337,
     name: "Ethereum (anvil)",
@@ -16,7 +16,7 @@ const CHAIN_ROWS = [
     activated_at_ms: "1784345978000"
   },
   {
-    code: { value: SlugName.from("SOLANA") },
+    code: "SOLANA",
     kind: SysioChainsChainkind.CHAIN_KIND_SVM,
     external_chain_id: 0,
     name: "Solana",
@@ -27,7 +27,7 @@ const CHAIN_ROWS = [
     activated_at_ms: "0"
   },
   {
-    code: { value: SlugName.from("WIRE") },
+    code: "WIRE",
     kind: "CHAIN_KIND_WIRE",
     external_chain_id: 0,
     name: "Wire",
diff --git a/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts b/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
index d88e5170..647f6de2 100644
--- a/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
+++ b/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
@@ -1,18 +1,29 @@
 import { contracts, SlugName } from "@wireio/sdk-core"
 
-const { chainSlugData, chainSlugString, chainSlugValue } =
-  contracts.sysio.chains
+const { chainSlugString, chainSlugValue } = contracts.sysio.chains
 
 describe("sysio.chains slug helpers", () => {
   test("round-trips friendly and packed chain codes", () => {
     const packed = SlugName.from("ETHEREUM")
 
     expect(chainSlugValue("ETHEREUM")).toBe(packed)
-    expect(chainSlugValue(String(packed))).toBe(packed)
-    expect(chainSlugData("ETHEREUM")).toEqual({ value: packed })
+    expect(chainSlugValue(packed)).toBe(packed)
+    expect(chainSlugString("ETHEREUM")).toBe("ETHEREUM")
     expect(chainSlugString(packed)).toBe("ETHEREUM")
   })
 
+  test("reads a digit-only code as a slug, never as its own decimal", () => {
+    // The slug alphabet contains digits, so "12345678" is a legitimate code
+    // whose packed value is nothing like 12345678. A decimal string is
+    // therefore not a second spelling of a packed value — it is a slug, or it
+    // is invalid. The packed form is passed as a number.
+    expect(chainSlugValue("12345678")).toBe(SlugName.from("12345678"))
+    expect(chainSlugValue("12345678")).not.toBe(12345678)
+    expect(() => chainSlugValue(String(SlugName.from("ETHEREUM")))).toThrow(
+      "longer than 8"
+    )
+  })
+
   test("rejects empty, invalid, and unsafe values", () => {
     expect(() => chainSlugValue(0)).toThrow("non-zero safe integer")
     expect(() => chainSlugValue("ethereum")).toThrow("outside [A-Z0-9_]")
diff --git a/packages/sdk-core/tests/contracts/sysio/reserv/Client.test.ts b/packages/sdk-core/tests/contracts/sysio/reserv/Client.test.ts
index a52a6068..365fc96f 100644
--- a/packages/sdk-core/tests/contracts/sysio/reserv/Client.test.ts
+++ b/packages/sdk-core/tests/contracts/sysio/reserv/Client.test.ts
@@ -1,15 +1,15 @@
 import { UInt64 } from "@wireio/sdk-core/chain/Integer"
 import { Serializer } from "@wireio/sdk-core/serializer"
-import { contracts, SlugName } from "@wireio/sdk-core"
+import { contracts } from "@wireio/sdk-core"
 import { SysioReservReservestatus } from "@wireio/sdk-core/types/SysioContractTypes"
 
 const { ReserveClient } = contracts.sysio.reserv
 
 function reserveRow(overrides: Record<string, unknown> = {}) {
   return {
-    chain_code: { value: String(SlugName.from("ETHEREUM")) },
-    token_code: { value: SlugName.from("ETH") },
-    reserve_code: { value: SlugName.from("PRIMARY") },
+    chain_code: "ETHEREUM",
+    token_code: "ETH",
+    reserve_code: "PRIMARY",
     name: "Primary ETH",
     description: "Public ETH liquidity",
     status: "RESERVE_STATUS_PENDING",
@@ -125,9 +125,7 @@ describe("ReserveClient", () => {
     getTableRows.mockImplementation(async (params: any) => ({
       rows: [
         reserveRow({
-          reserve_code: {
-            value: SlugName.from(params.lower_bound ? "PRIMARY" : "OTHER")
-          }
+          reserve_code: params.lower_bound ? "PRIMARY" : "OTHER"
         })
       ],
       more: !params.lower_bound,
diff --git a/packages/sdk-core/tests/contracts/sysio/tokens/Client.test.ts b/packages/sdk-core/tests/contracts/sysio/tokens/Client.test.ts
index f0de471f..e336774a 100644
--- a/packages/sdk-core/tests/contracts/sysio/tokens/Client.test.ts
+++ b/packages/sdk-core/tests/contracts/sysio/tokens/Client.test.ts
@@ -1,4 +1,4 @@
-import { contracts, SlugName } from "@wireio/sdk-core"
+import { contracts } from "@wireio/sdk-core"
 import {
   SysioTokensChainkind,
   SysioTokensTokenkind
@@ -13,7 +13,7 @@ interface TableQuery {
 
 function tokenRow(overrides: Record<string, unknown> = {}) {
   return {
-    code: { value: SlugName.from("ETH") },
+    code: "ETH",
     kind: "TOKEN_KIND_NATIVE",
     symbol_name: "ETH",
     description: "Ether",
@@ -28,8 +28,8 @@ function tokenRow(overrides: Record<string, unknown> = {}) {
 
 function chainTokenRow(overrides: Record<string, unknown> = {}) {
   return {
-    chain_code: { value: SlugName.from("ETHEREUM") },
-    token_code: { value: SlugName.from("ETH") },
+    chain_code: "ETHEREUM",
+    token_code: "ETH",
     contract_addr: "0x",
     is_native: true,
     active: true,
@@ -70,14 +70,14 @@ describe("TokenRegistryClient", () => {
   test("normalizes packed slugs serialized as uint64 strings", () => {
     expect(
       normalizeTokenRow(
-        tokenRow({ code: { value: String(SlugName.from("ETH")) } }) as any
+        tokenRow({ code: "ETH" }) as any
       )
     ).toMatchObject({ code: "ETH" })
     expect(
       normalizeChainTokenRow(
         chainTokenRow({
-          chain_code: { value: String(SlugName.from("ETHEREUM")) },
-          token_code: { value: String(SlugName.from("ETH")) }
+          chain_code: "ETHEREUM",
+          token_code: "ETH"
         }) as any
       )
     ).toMatchObject({ chainCode: "ETHEREUM", tokenCode: "ETH" })
diff --git a/packages/sdk-core/tests/contracts/sysio/uwrit/Client.test.ts b/packages/sdk-core/tests/contracts/sysio/uwrit/Client.test.ts
index c832b1c3..90f176c6 100644
--- a/packages/sdk-core/tests/contracts/sysio/uwrit/Client.test.ts
+++ b/packages/sdk-core/tests/contracts/sysio/uwrit/Client.test.ts
@@ -1,4 +1,4 @@
-import { contracts, SlugName } from "@wireio/sdk-core"
+import { contracts } from "@wireio/sdk-core"
 import {
   SysioUwritChainkind,
   SysioUwritUnderwriterequeststatus
@@ -16,20 +16,18 @@ interface TableQuery {
   table: string
 }
 
-const slug = (value: string) => ({ value: String(SlugName.from(value)) })
-
 function requestRow(overrides: Record<string, unknown> = {}) {
   return {
     id: "7",
     type: "ATTESTATION_TYPE_SWAP_REQUEST",
     status: "UNDERWRITE_REQUEST_STATUS_PENDING",
-    src_chain_code: slug("ETHEREUM"),
-    src_token_code: slug("ETH"),
-    src_reserve_code: slug("PRIMARY"),
+    src_chain_code: "ETHEREUM",
+    src_token_code: "ETH",
+    src_reserve_code: "PRIMARY",
     src_amount: "100",
-    dst_chain_code: slug("SOLANA"),
-    dst_token_code: slug("SOL"),
-    dst_reserve_code: slug("PRIMARY"),
+    dst_chain_code: "SOLANA",
+    dst_token_code: "SOL",
+    dst_reserve_code: "PRIMARY",
     dst_amount: "90",
     variance_tolerance_bps: 500,
     source_tx_id: "000000000000002a",
@@ -50,9 +48,9 @@ function queueRow(overrides: Record<string, unknown> = {}) {
     id: "8",
     user: "alice",
     wire_amount: "5000000000",
-    dst_chain_code: slug("SOLANA"),
-    dst_token_code: slug("SOL"),
-    dst_reserve_code: slug("PRIMARY"),
+    dst_chain_code: "SOLANA",
+    dst_token_code: "SOL",
+    dst_reserve_code: "PRIMARY",
     target_amount: "80",
     variance_tolerance_bps: 500,
     recipient_kind: "CHAIN_KIND_SVM",
@@ -135,9 +133,9 @@ describe("UnderwritingClient", () => {
 
   test("decodes the synthetic WIRE request id and depositor account", () => {
     const row = requestRow({
-      src_chain_code: slug("WIRE"),
-      src_token_code: slug("WIRE"),
-      src_reserve_code: slug("WIRE"),
+      src_chain_code: "WIRE",
+      src_token_code: "WIRE",
+      src_reserve_code: "WIRE",
       source_tx_id: "0700000000000080",
       depositor: "776972656e6f2e616263"
     })

From 637b20ca6da55f5969d272cb82d546a61d2927a8 Mon Sep 17 00:00:00 2001
From: kevin Heifner <kevin@wire.network>
Date: Thu, 17 Sep 2026 13:17:51 -0500
Subject: [PATCH 2/5] fix(sdk-core): mirror the chain's leading-letter rule in
 SlugName
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

A code must start with a letter, so SlugName.from refuses a digit- or
underscore-leading spelling rather than packing one the depot will reject —
the failure surfaces at the parse with its reason instead of at pushAction
as an opaque ABI error.

toString stays total: it is a reader, and a throwing renderer in a scan loop
is what stalls a consumer.

Change-Id: Ibfcfee56719a9800f1ab7e41719f1dd527062576
---
 packages/sdk-core/src/SlugName.ts             | 29 +++++++++++++--
 .../src/contracts/sysio/chains/Slug.ts        |  6 +--
 .../src/contracts/sysio/reserv/Slug.ts        |  6 +--
 packages/sdk-core/tests/SlugName.test.ts      | 37 ++++++++++++++++---
 .../tests/contracts/sysio/chains/Slug.test.ts | 15 ++++----
 5 files changed, 70 insertions(+), 23 deletions(-)

diff --git a/packages/sdk-core/src/SlugName.ts b/packages/sdk-core/src/SlugName.ts
index 6a353d87..957c2cc3 100644
--- a/packages/sdk-core/src/SlugName.ts
+++ b/packages/sdk-core/src/SlugName.ts
@@ -1,3 +1,12 @@
+/** Every character a slug_name may contain — `slug_name_traits::alphabet`. */
+const SlugAlphabetPattern = /^[A-Z0-9_]+$/
+
+/**
+ * The characters a slug_name may START with —
+ * `slug_name_traits::leading_alphabet`.
+ */
+const SlugLeadingAlphabetPattern = /^[A-Z]/
+
 /**
  * SlugName — TypeScript counterpart to the `sysio::slug_name` (contract) /
  * `fc::slug_name` (host) packed 8-byte type used as the primary key for
@@ -12,7 +21,14 @@
  * `A..Z`, slots 27..36 hold `0..9`, slot 37 holds `_`. Characters outside the
  * alphabet are a parse error. Inputs longer than 8 chars are a parse error.
  *
- * Mirrors the encoding in `wire-sysio/contracts/sysio.opp.common/include/sysio.opp.common/slug_name.hpp`.
+ * A code must START with a letter. That is what makes the chain's string
+ * carrier unambiguous — no legal code can be spelled like a number, so a bare
+ * JSON string is always a code and never a decimal. Digits and `_` stay legal
+ * in every position after the first (`V1`, `USDC`, `TRAIL_`).
+ *
+ * Mirrors the encoding in `wire-sysio/contracts/sysio.opp.common/include/sysio.opp.common/slug_name.hpp`,
+ * and the leading rule in `fc::slug_name_traits::leading_alphabet` (host) /
+ * `sysio::slug_name_traits::leading_alphabet` (CDT).
  */
 export class SlugName {
   /**
@@ -23,8 +39,10 @@ export class SlugName {
    * slug_name occupies 48 bits, well above the 32-bit boundary but safely
    * under `Number.MAX_SAFE_INTEGER` (53 bits) — arithmetic stays exact.
    *
-   * @param s   uppercase letters, digits, and underscore; ≤8 chars
-   * @throws   on empty input, length > 8, or any out-of-alphabet character
+   * @param s   uppercase letters, digits, and underscore; ≤8 chars, and the
+   *            first character must be a letter ([A-Z])
+   * @throws   on empty input, length > 8, any out-of-alphabet character, or a
+   *           first character that is not a letter
    */
   static from(s: string): number {
     if (s.length === 0) {
@@ -33,9 +51,12 @@ export class SlugName {
     if (s.length > 8) {
       throw new Error(`SlugName.from: '${s}' is longer than 8 chars`)
     }
-    if (!/^[A-Z0-9_]+$/.test(s)) {
+    if (!SlugAlphabetPattern.test(s)) {
       throw new Error(`SlugName.from: '${s}' has chars outside [A-Z0-9_]`)
     }
+    if (!SlugLeadingAlphabetPattern.test(s)) {
+      throw new Error(`SlugName.from: '${s}' must start with a letter ([A-Z])`)
+    }
     let v = 0
     for (let i = 0; i < s.length; ++i) {
       const c = s.charCodeAt(i)
diff --git a/packages/sdk-core/src/contracts/sysio/chains/Slug.ts b/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
index 926d1017..ba54bce1 100644
--- a/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
+++ b/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
@@ -5,9 +5,9 @@ import type { ChainSlugName } from "./Types.js"
 /**
  * Converts a friendly chain slug or packed value to its safe numeric form.
  *
- * A string is ALWAYS parsed as a slug, never as a decimal: the slug alphabet
- * contains digits, so `"12345678"` is a legitimate code whose packed value is
- * nothing like 12345678. Pass a `number` to supply an already-packed value.
+ * A string is ALWAYS parsed as a slug, never as a decimal — and that is
+ * unambiguous because a code must start with a letter, so no legal spelling can
+ * be read as a number. Pass a `number` to supply an already-packed value.
  */
 export function chainSlugValue(value: ChainSlugName): number {
   const packed = typeof value === "string" ? SlugName.from(value) : Number(value)
diff --git a/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts b/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
index 7e2b9d0e..aaba5639 100644
--- a/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
+++ b/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
@@ -5,9 +5,9 @@ import type { ReserveSlugName } from "./Types.js"
 /**
  * Converts a friendly slug string or packed value to its safe numeric form.
  *
- * A string is ALWAYS parsed as a slug, never as a decimal: the slug alphabet
- * contains digits, so `"12345678"` is a legitimate code whose packed value is
- * nothing like 12345678. Pass a `number` to supply an already-packed value.
+ * A string is ALWAYS parsed as a slug, never as a decimal — and that is
+ * unambiguous because a code must start with a letter, so no legal spelling can
+ * be read as a number. Pass a `number` to supply an already-packed value.
  */
 export function reserveSlugValue(value: ReserveSlugName): number {
   const packed =
diff --git a/packages/sdk-core/tests/SlugName.test.ts b/packages/sdk-core/tests/SlugName.test.ts
index 9f01edcc..ad0b6d24 100644
--- a/packages/sdk-core/tests/SlugName.test.ts
+++ b/packages/sdk-core/tests/SlugName.test.ts
@@ -14,12 +14,12 @@ describe("SlugName", () => {
       expect(SlugName.from("Z")).toBe(26 * SLOT0)
     })
 
-    it("encodes digit '0' to slot 27", () => {
-      expect(SlugName.from("0")).toBe(27 * SLOT0)
+    it("encodes digit '0' to slot 27, behind a leading letter", () => {
+      expect(SlugName.from("A0")).toBe(1 * SLOT0 + 27 * SLOT1)
     })
 
-    it("encodes '_' to slot 37", () => {
-      expect(SlugName.from("_")).toBe(37 * SLOT0)
+    it("encodes '_' to slot 37, behind a leading letter", () => {
+      expect(SlugName.from("A_")).toBe(1 * SLOT0 + 37 * SLOT1)
     })
 
     it("encodes a multi-char string with 6-bit MSB-first packing", () => {
@@ -54,6 +54,28 @@ describe("SlugName", () => {
       expect(() => SlugName.from("ETH!")).toThrow(/outside/)
       expect(() => SlugName.from("E-T")).toThrow(/outside/)
     })
+
+    it("rejects a code that does not start with a letter", () => {
+      // The rule that makes the chain's string carrier unambiguous: no legal
+      // code can be spelled like a number. Mirrors
+      // `fc::slug_name_traits::leading_alphabet`.
+      const leadingLetter = /must start with a letter/
+      expect(() => SlugName.from("0")).toThrow(leadingLetter)
+      expect(() => SlugName.from("7")).toThrow(leadingLetter)
+      expect(() => SlugName.from("101")).toThrow(leadingLetter)
+      expect(() => SlugName.from("1E3")).toThrow(leadingLetter)
+      expect(() => SlugName.from("0X10")).toThrow(leadingLetter)
+      expect(() => SlugName.from("12345678")).toThrow(leadingLetter)
+      expect(() => SlugName.from("_")).toThrow(leadingLetter)
+      expect(() => SlugName.from("_LEAD")).toThrow(leadingLetter)
+    })
+
+    it("keeps digits and '_' legal after the first character", () => {
+      expect(SlugName.toString(SlugName.from("V1"))).toBe("V1")
+      expect(SlugName.toString(SlugName.from("TRAIL_"))).toBe("TRAIL_")
+      expect(SlugName.toString(SlugName.from("Z1234567"))).toBe("Z1234567")
+      expect(SlugName.toString(SlugName.from("Z_______"))).toBe("Z_______")
+    })
   })
 
   describe("toString", () => {
@@ -68,7 +90,10 @@ describe("SlugName", () => {
       expect(SlugName.toString(26 * SLOT0)).toBe("Z")
     })
 
-    it("decodes digit slots", () => {
+    // `toString` stays TOTAL on purpose: it is a READER. A throwing renderer in
+    // a scan loop is what stalls a consumer (wire-sysio #619 thread 3), so the
+    // leading rule is enforced on the WRITE path (`from`) only.
+    it("decodes digit slots even though such a value is not a writable code", () => {
       expect(SlugName.toString(27 * SLOT0)).toBe("0")
       expect(SlugName.toString(36 * SLOT0)).toBe("9")
     })
@@ -84,7 +109,7 @@ describe("SlugName", () => {
   })
 
   describe("round-trip", () => {
-    const inputs = ["ETH", "WIRE", "SOL", "USDC", "LIQETH", "LIQSOL", "PRIMARY", "ETHEREUM", "SOLANA", "0", "_", "A", "Z9_"]
+    const inputs = ["ETH", "WIRE", "SOL", "USDC", "LIQETH", "LIQSOL", "PRIMARY", "ETHEREUM", "SOLANA", "A0", "A_", "A", "Z9_"]
     inputs.forEach(s => {
       it(`round-trips '${s}'`, () => {
         const encoded = SlugName.from(s)
diff --git a/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts b/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
index 647f6de2..ff118dda 100644
--- a/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
+++ b/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
@@ -12,16 +12,17 @@ describe("sysio.chains slug helpers", () => {
     expect(chainSlugString(packed)).toBe("ETHEREUM")
   })
 
-  test("reads a digit-only code as a slug, never as its own decimal", () => {
-    // The slug alphabet contains digits, so "12345678" is a legitimate code
-    // whose packed value is nothing like 12345678. A decimal string is
-    // therefore not a second spelling of a packed value — it is a slug, or it
-    // is invalid. The packed form is passed as a number.
-    expect(chainSlugValue("12345678")).toBe(SlugName.from("12345678"))
-    expect(chainSlugValue("12345678")).not.toBe(12345678)
+  test("refuses a digit-leading string, so a decimal is never read as a slug", () => {
+    // A code must start with a letter, which is what makes the string carrier
+    // unambiguous: a decimal spelling can never also be a code. The packed form
+    // is passed as a number, never as its decimal string.
+    expect(() => chainSlugValue("12345678")).toThrow("must start with a letter")
+    expect(() => chainSlugValue("7")).toThrow("must start with a letter")
     expect(() => chainSlugValue(String(SlugName.from("ETHEREUM")))).toThrow(
       "longer than 8"
     )
+    // Digits after the leading letter are ordinary.
+    expect(chainSlugValue("Z1234567")).toBe(SlugName.from("Z1234567"))
   })
 
   test("rejects empty, invalid, and unsafe values", () => {

From 9e012fef869cb397ada55dbc8a2b052c8bde12cf Mon Sep 17 00:00:00 2001
From: kevin Heifner <kevin@wire.network>
Date: Tue, 22 Sep 2026 16:51:15 -0500
Subject: [PATCH 3/5] feat(sdk-core): accept the transitional { value } slug
 carrier
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

A pre-builtin depot emits a slug_name as an object — the reflected struct
is object-only — and the depot still accepts that shape inbound. A
string-only reader cannot straddle the landing window, so #83 could not
merge before the node change; with this it can.

slugValue is now the one decoder for every carrier (string, number,
bigint, or the { value } object) and both per-contract readers delegate
to it instead of duplicating the body. Matches wire-tools' slugUtils,
which already takes all three. Delete SlugNameObject once no depot emits
the object form.

Change-Id: Icfbe2e544e4416194ab12e2434e90cb795189c7a
---
 packages/sdk-core/src/SlugName.ts             | 53 +++++++++++++++++++
 .../src/contracts/sysio/chains/Slug.ts        | 19 ++-----
 .../src/contracts/sysio/chains/Types.ts       |  5 +-
 .../src/contracts/sysio/reserv/Slug.ts        | 20 ++-----
 .../src/contracts/sysio/reserv/Types.ts       |  5 +-
 packages/sdk-core/tests/SlugName.test.ts      | 45 +++++++++++++++-
 6 files changed, 111 insertions(+), 36 deletions(-)

diff --git a/packages/sdk-core/src/SlugName.ts b/packages/sdk-core/src/SlugName.ts
index 957c2cc3..bc05d420 100644
--- a/packages/sdk-core/src/SlugName.ts
+++ b/packages/sdk-core/src/SlugName.ts
@@ -1,3 +1,5 @@
+import { match, P } from "ts-pattern"
+
 /** Every character a slug_name may contain — `slug_name_traits::alphabet`. */
 const SlugAlphabetPattern = /^[A-Z0-9_]+$/
 
@@ -116,3 +118,54 @@ export class SlugName {
     return out
   }
 }
+
+/**
+ * The transitional object carrier for a packed slug_name.
+ *
+ * With the ABI builtin absent, a slug converts through
+ * `FC_REFLECT_TEMPLATE(basic_name<Traits>, (value))` and is therefore
+ * object-only, so a pre-builtin depot emits this shape. The depot still
+ * ACCEPTS it (`fc::slug_name::from_variant`), which is what lets a READER
+ * straddle the landing window — a JSON writer cannot, since no value both
+ * spellings accept.
+ *
+ * Delete this once no depot emits the object form; the bare string is the one
+ * canonical carrier.
+ */
+export interface SlugNameObject {
+  /** The packed uint64. `fc::json` quotes it once it exceeds `0xffffffff`. */
+  value: number | string
+}
+
+/** Every carrier a slug_name cell can arrive in. */
+export type SlugNameValue = string | number | bigint | SlugNameObject
+
+/**
+ * The packed numeric value of a slug cell, whatever carrier it arrived in.
+ *
+ * A bare string is ALWAYS parsed as a slug, never as a decimal — unambiguous
+ * because a code must start with a letter, so no legal spelling can be read as
+ * a number. A number or bigint is an already-packed value. An object is the
+ * transitional {@link SlugNameObject} carrier.
+ *
+ * @param value  the cell, in any carrier
+ * @param label  names the slug in the failure message (`Chain`, `Reserve`)
+ * @throws if the result is not a non-zero safe integer, or a string is not a
+ *         valid slug_name spelling
+ */
+export function slugValue(value: SlugNameValue, label: string): number {
+  const packed = match(value)
+    .with(P.string, spelling => SlugName.from(spelling))
+    .with({ value: P.union(P.string, P.number) }, wrapped =>
+      Number(wrapped.value)
+    )
+    .otherwise(alreadyPacked => Number(alreadyPacked))
+
+  if (!Number.isSafeInteger(packed) || packed <= 0) {
+    throw new Error(
+      `${label} slug must be a non-zero safe integer or valid slug_name string.`
+    )
+  }
+
+  return packed
+}
diff --git a/packages/sdk-core/src/contracts/sysio/chains/Slug.ts b/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
index ba54bce1..9d92deb4 100644
--- a/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
+++ b/packages/sdk-core/src/contracts/sysio/chains/Slug.ts
@@ -1,24 +1,13 @@
-import { SlugName } from "../../../SlugName.js"
+import { SlugName, slugValue } from "../../../SlugName.js"
 
 import type { ChainSlugName } from "./Types.js"
 
 /**
- * Converts a friendly chain slug or packed value to its safe numeric form.
- *
- * A string is ALWAYS parsed as a slug, never as a decimal — and that is
- * unambiguous because a code must start with a letter, so no legal spelling can
- * be read as a number. Pass a `number` to supply an already-packed value.
+ * Converts a chain slug cell to its safe numeric form, in any carrier —
+ * see {@link slugValue} for how each one is read.
  */
 export function chainSlugValue(value: ChainSlugName): number {
-  const packed = typeof value === "string" ? SlugName.from(value) : Number(value)
-
-  if (!Number.isSafeInteger(packed) || packed <= 0) {
-    throw new Error(
-      "Chain slug must be a non-zero safe integer or valid slug_name string."
-    )
-  }
-
-  return packed
+  return slugValue(value, "Chain")
 }
 
 /** Returns the display form of a packed chain slug. */
diff --git a/packages/sdk-core/src/contracts/sysio/chains/Types.ts b/packages/sdk-core/src/contracts/sysio/chains/Types.ts
index 6b29dc26..c0093153 100644
--- a/packages/sdk-core/src/contracts/sysio/chains/Types.ts
+++ b/packages/sdk-core/src/contracts/sysio/chains/Types.ts
@@ -2,9 +2,10 @@ import type { NameType } from "../../../chain/Name.js"
 import type { ContractPermissionLevel } from "../../Contract.js"
 import type * as SysioContracts from "../../../types/SysioContractTypes.js"
 import type { APIClient } from "../../../api/Client.js"
+import type { SlugNameValue } from "../../../SlugName.js"
 
-/** Friendly string or packed numeric `slug_name` accepted by chain helpers. */
-export type ChainSlugName = string | number | bigint
+/** Every carrier a chain `slug_name` may arrive in — see {@link SlugNameValue}. */
+export type ChainSlugName = SlugNameValue
 
 /** Configuration for `ChainsClient`. */
 export interface ChainsClientOptions {
diff --git a/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts b/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
index aaba5639..d2709c31 100644
--- a/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
+++ b/packages/sdk-core/src/contracts/sysio/reserv/Slug.ts
@@ -1,25 +1,13 @@
-import { SlugName } from "../../../SlugName.js"
+import { SlugName, slugValue } from "../../../SlugName.js"
 
 import type { ReserveSlugName } from "./Types.js"
 
 /**
- * Converts a friendly slug string or packed value to its safe numeric form.
- *
- * A string is ALWAYS parsed as a slug, never as a decimal — and that is
- * unambiguous because a code must start with a letter, so no legal spelling can
- * be read as a number. Pass a `number` to supply an already-packed value.
+ * Converts a reserve slug cell to its safe numeric form, in any carrier —
+ * see {@link slugValue} for how each one is read.
  */
 export function reserveSlugValue(value: ReserveSlugName): number {
-  const packed =
-    typeof value === "string" ? SlugName.from(value) : Number(value)
-
-  if (!Number.isSafeInteger(packed) || packed <= 0) {
-    throw new Error(
-      "Reserve slug must be a non-zero safe integer or valid slug_name string."
-    )
-  }
-
-  return packed
+  return slugValue(value, "Reserve")
 }
 
 /** Returns the display form of a packed reserve slug. */
diff --git a/packages/sdk-core/src/contracts/sysio/reserv/Types.ts b/packages/sdk-core/src/contracts/sysio/reserv/Types.ts
index ed5b2658..f059d17e 100644
--- a/packages/sdk-core/src/contracts/sysio/reserv/Types.ts
+++ b/packages/sdk-core/src/contracts/sysio/reserv/Types.ts
@@ -3,9 +3,10 @@ import type { TransactionExtraOptions } from "../../../api/Types.js"
 import type { UInt64Type } from "../../../chain/Integer.js"
 import type { NameType } from "../../../chain/Name.js"
 import type * as SysioContracts from "../../../types/SysioContractTypes.js"
+import type { SlugNameValue } from "../../../SlugName.js"
 
-/** Friendly string or packed numeric `slug_name` accepted by reserve helpers. */
-export type ReserveSlugName = string | number | bigint
+/** Every carrier a reserve `slug_name` may arrive in — see {@link SlugNameValue}. */
+export type ReserveSlugName = SlugNameValue
 
 /** Three-part identity that uniquely addresses one reserve. */
 export interface ReserveIdentity {
diff --git a/packages/sdk-core/tests/SlugName.test.ts b/packages/sdk-core/tests/SlugName.test.ts
index ad0b6d24..a39275b6 100644
--- a/packages/sdk-core/tests/SlugName.test.ts
+++ b/packages/sdk-core/tests/SlugName.test.ts
@@ -1,4 +1,4 @@
-import { SlugName } from "@wireio/sdk-core/SlugName"
+import { SlugName, slugValue } from "@wireio/sdk-core/SlugName"
 
 describe("SlugName", () => {
   describe("from", () => {
@@ -126,4 +126,47 @@ describe("SlugName", () => {
       expect(SlugName.from("WIRE")).not.toBe(SlugName.from("ETH"))
     })
   })
+
+  describe("slugValue", () => {
+    const packedEthereum = SlugName.from("ETHEREUM")
+
+    it("parses a bare string as a SPELLING, never a decimal", () => {
+      expect(slugValue("ETHEREUM", "Chain")).toBe(packedEthereum)
+    })
+
+    it("passes an already-packed number through", () => {
+      expect(slugValue(packedEthereum, "Chain")).toBe(packedEthereum)
+    })
+
+    it("accepts a bigint, since a generated field may carry one", () => {
+      expect(slugValue(BigInt(packedEthereum), "Chain")).toBe(packedEthereum)
+    })
+
+    it("accepts the transitional { value } object carrier", () => {
+      // The shape a pre-builtin depot emits: FC_REFLECT_TEMPLATE makes the
+      // reflected struct object-only, so a reader must take both carriers.
+      expect(slugValue({ value: packedEthereum }, "Chain")).toBe(packedEthereum)
+    })
+
+    it("accepts the object carrier quoted, as fc::json emits it above 0xffffffff", () => {
+      expect(slugValue({ value: String(packedEthereum) }, "Chain")).toBe(
+        packedEthereum
+      )
+    })
+
+    it("rejects a spelling that does not lead with a letter", () => {
+      expect(() => slugValue("7", "Chain")).toThrow(/must start with a letter/)
+    })
+
+    it("names the slug in the failure, so the caller knows which one", () => {
+      expect(() => slugValue(0, "Reserve")).toThrow(/^Reserve slug must be/)
+      expect(() => slugValue(0, "Chain")).toThrow(/^Chain slug must be/)
+    })
+
+    it("rejects an object carrying a non-numeric value", () => {
+      expect(() => slugValue({ value: "not-a-number" }, "Chain")).toThrow(
+        /must be a non-zero safe integer/
+      )
+    })
+  })
 })

From d9ed2328c3d4e7f481f550d6452f4fe8efac7b83 Mon Sep 17 00:00:00 2001
From: kevin Heifner <kevin@wire.network>
Date: Fri, 25 Sep 2026 08:57:07 -0500
Subject: [PATCH 4/5] chore(sdk-core): regenerate SysioContractTypes after
 rebasing onto master

Generated from the wire-sysio#619 ABIs, which carry master's sysio.liq and
sysio.swap contracts; slug_name fields are the builtin string carrier.

Change-Id: Ia77e57d060a151de76b36d5bbfc4f74a8cd7d50b
---
 .../sdk-core/src/types/SysioContractTypes.ts  | 60 +++++--------------
 1 file changed, 15 insertions(+), 45 deletions(-)

diff --git a/packages/sdk-core/src/types/SysioContractTypes.ts b/packages/sdk-core/src/types/SysioContractTypes.ts
index 191d78df..332c90c9 100644
--- a/packages/sdk-core/src/types/SysioContractTypes.ts
+++ b/packages/sdk-core/src/types/SysioContractTypes.ts
@@ -344,11 +344,6 @@ export interface SysioChainsSetoutpostAction {
   outpost: SysioChainsOutpostAddrsType
 }
 
-/** sysio.chains::slug_name (type) */
-export interface SysioChainsSlugNameType {
-  value: number | string
-}
-
 /** sysio.chains - action + table surface for the typed contract client. */
 export interface SysioChainsContract {
   actions: {
@@ -1079,15 +1074,15 @@ export interface SysioLiqCloseAction {
 /** sysio.liq::create (action) */
 export interface SysioLiqCreateAction {
   sym: string
-  chain_code: SysioLiqSlugNameType
-  token_code: SysioLiqSlugNameType
+  chain_code: string
+  token_code: string
 }
 
 /** sysio.liq::currency_stats (type) */
 export interface SysioLiqCurrencyStatsType {
   supply: string
-  chain_code: SysioLiqSlugNameType
-  token_code: SysioLiqSlugNameType
+  chain_code: string
+  token_code: string
   pair_symbol: string
 }
 
@@ -1114,8 +1109,8 @@ export interface SysioLiqImportdoneAction {
 
 /** sysio.liq::importsynd (action) */
 export interface SysioLiqImportsyndAction {
-  chain_code: SysioLiqSlugNameType
-  token_code: SysioLiqSlugNameType
+  chain_code: string
+  token_code: string
   credits: SysioLiqImportCreditType[]
 }
 
@@ -1139,26 +1134,26 @@ export interface SysioLiqLiqCountersType {
 
 /** sysio.liq::liq_cursor (type) */
 export interface SysioLiqLiqCursorType {
-  chain_code: SysioLiqSlugNameType
+  chain_code: string
   last_sequence: number | string
   last_epoch: number | string
 }
 
 /** sysio.liq::mintsynd (action) */
 export interface SysioLiqMintsyndAction {
-  chain_code: SysioLiqSlugNameType
+  chain_code: string
   sequence: number | string
   account: string
-  token_code: SysioLiqSlugNameType
+  token_code: string
   amount: number | string
 }
 
 /** sysio.liq::mintyield (action) */
 export interface SysioLiqMintyieldAction {
-  chain_code: SysioLiqSlugNameType
+  chain_code: string
   sequence: number | string
   epoch: number | string
-  token_code: SysioLiqSlugNameType
+  token_code: string
   amount: number | string
 }
 
@@ -1171,11 +1166,11 @@ export interface SysioLiqOpenAction {
 
 /** sysio.liq::park (action) */
 export interface SysioLiqParkAction {
-  chain_code: SysioLiqSlugNameType
+  chain_code: string
   sequence: number | string
   chain_kind: SysioLiqChainkind | keyof typeof SysioLiqChainkind
   pubkey: string
-  token_code: SysioLiqSlugNameType
+  token_code: string
   amount: number | string
 }
 
@@ -1211,8 +1206,8 @@ export interface SysioLiqRecreditAction {
 
 /** sysio.liq::regliqpool (action) */
 export interface SysioLiqRegliqpoolAction {
-  chain_code: SysioLiqSlugNameType
-  token_code: SysioLiqSlugNameType
+  chain_code: string
+  token_code: string
   pair_symbol: string
   initial_chain_amount: number | string
   initial_wire_amount: number | string
@@ -1228,11 +1223,6 @@ export interface SysioLiqSetkickerAction {
   bps: number
 }
 
-/** sysio.liq::slug_name (type) */
-export interface SysioLiqSlugNameType {
-  value: number | string
-}
-
 /** sysio.liq::sweep (action) */
 export interface SysioLiqSweepAction {
   account: string
@@ -1972,11 +1962,6 @@ export interface SysioOpregSlashAction {
   reason: string
 }
 
-/** sysio.opreg::slug_name (type) */
-export interface SysioOpregSlugNameType {
-  value: number | string
-}
-
 /** sysio.opreg::termcheck (action) */
 export interface SysioOpregTermcheckAction {
   account: string
@@ -2274,11 +2259,6 @@ export interface SysioReservSetrsvfeeAction {
   owner_fee_bps: number
 }
 
-/** sysio.reserv::slug_name (type) */
-export interface SysioReservSlugNameType {
-  value: number | string
-}
-
 /** sysio.reserv::swapquote (action) */
 export interface SysioReservSwapquoteAction {
   from_chain_code: string
@@ -3850,11 +3830,6 @@ export interface SysioTokensRegtokenAction {
   address: SysioTokensChainaddressType
 }
 
-/** sysio.tokens::slug_name (type) */
-export interface SysioTokensSlugNameType {
-  value: number | string
-}
-
 /** sysio.tokens::token_key (type) */
 export interface SysioTokensTokenKeyType {
   code: string
@@ -4079,11 +4054,6 @@ export interface SysioUwritSetconfigAction {
   uwreq_retention_epochs: number
 }
 
-/** sysio.uwrit::slug_name (type) */
-export interface SysioUwritSlugNameType {
-  value: number | string
-}
-
 /** sysio.uwrit::sumlocks (action) */
 export interface SysioUwritSumlocksAction {
   underwriter: string

From 7420cd268e1f96da555061b2aeb20873e1a349a0 Mon Sep 17 00:00:00 2001
From: kevin Heifner <kevin@wire.network>
Date: Fri, 25 Sep 2026 08:57:07 -0500
Subject: [PATCH 5/5] fix(sdk-core): parse a packed slug value strictly

Number() coerces "", " 12 ", "0x10" and "1e3", and parseInt stops at the
first non-digit, so neither rejects a malformed { value } carrier. Parse through
UInt64.from, which accepts only a base-10 integer or a safe integer, and convert
the slug structs with toNumber(), which throws past 53 bits instead of rounding.

Change-Id: Iff04918124c7dce134becefa1cc9e1a53ebf9e1e
---
 packages/sdk-core/src/SlugName.ts             | 37 ++++++++++++++++---
 .../src/contracts/sysio/chains/Structs.ts     |  2 +-
 .../src/contracts/sysio/reserv/Structs.ts     |  2 +-
 packages/sdk-core/tests/SlugName.test.ts      | 18 +++++++++
 .../tests/contracts/sysio/chains/Slug.test.ts | 12 +++++-
 .../tests/contracts/sysio/reserv/Slug.test.ts | 13 +++++++
 6 files changed, 74 insertions(+), 10 deletions(-)
 create mode 100644 packages/sdk-core/tests/contracts/sysio/reserv/Slug.test.ts

diff --git a/packages/sdk-core/src/SlugName.ts b/packages/sdk-core/src/SlugName.ts
index bc05d420..374b4ebb 100644
--- a/packages/sdk-core/src/SlugName.ts
+++ b/packages/sdk-core/src/SlugName.ts
@@ -1,5 +1,10 @@
+import { Either } from "@3fv/prelude-ts"
 import { match, P } from "ts-pattern"
 
+import { NestedError } from "@wireio/shared"
+
+import { UInt64 } from "./chain/Integer.js"
+
 /** Every character a slug_name may contain — `slug_name_traits::alphabet`. */
 const SlugAlphabetPattern = /^[A-Z0-9_]+$/
 
@@ -157,15 +162,35 @@ export function slugValue(value: SlugNameValue, label: string): number {
   const packed = match(value)
     .with(P.string, spelling => SlugName.from(spelling))
     .with({ value: P.union(P.string, P.number) }, wrapped =>
-      Number(wrapped.value)
+      packedValue(wrapped.value, label)
     )
-    .otherwise(alreadyPacked => Number(alreadyPacked))
+    .otherwise(alreadyPacked => packedValue(alreadyPacked, label))
 
-  if (!Number.isSafeInteger(packed) || packed <= 0) {
-    throw new Error(
-      `${label} slug must be a non-zero safe integer or valid slug_name string.`
-    )
+  if (packed <= 0) {
+    throw new Error(slugValueMessage(label))
   }
 
   return packed
 }
+
+/** The failure message every rejected slug carrier shares. */
+function slugValueMessage(label: string): string {
+  return `${label} slug must be a non-zero safe integer or valid slug_name string.`
+}
+
+/**
+ * An already-packed slug value, parsed strictly. `UInt64.from` accepts only a
+ * base-10 integer string or a safe integer, so `""`, `" 12 "`, `"0x10"`,
+ * `"1e3"` and `"12abc"` are rejected rather than coerced the way `Number()` or
+ * `parseInt()` would; `toNumber()` rejects anything past 53 bits.
+ */
+function packedValue(packed: string | number | bigint, label: string): number {
+  return Either.try(() => UInt64.from(packed).toNumber())
+    .ifLeft(cause => {
+      throw new NestedError(slugValueMessage(label), {
+        cause,
+        context: { packed: String(packed) }
+      })
+    })
+    .getOrThrow()
+}
diff --git a/packages/sdk-core/src/contracts/sysio/chains/Structs.ts b/packages/sdk-core/src/contracts/sysio/chains/Structs.ts
index 5f4c8929..3bd2fddf 100644
--- a/packages/sdk-core/src/contracts/sysio/chains/Structs.ts
+++ b/packages/sdk-core/src/contracts/sysio/chains/Structs.ts
@@ -52,7 +52,7 @@ export class ChainsSlugName implements ABISerializableObject {
 
   /** The canonical spelling — `""` for the zero sentinel. */
   toString(): string {
-    return SlugName.toString(Number(this.value))
+    return SlugName.toString(this.value.toNumber())
   }
 
   toABI(encoder: ABIEncoder) {
diff --git a/packages/sdk-core/src/contracts/sysio/reserv/Structs.ts b/packages/sdk-core/src/contracts/sysio/reserv/Structs.ts
index 158e263a..071bc1d0 100644
--- a/packages/sdk-core/src/contracts/sysio/reserv/Structs.ts
+++ b/packages/sdk-core/src/contracts/sysio/reserv/Structs.ts
@@ -53,7 +53,7 @@ export class ReservSlugName implements ABISerializableObject {
 
   /** The canonical spelling — `""` for the zero sentinel. */
   toString(): string {
-    return SlugName.toString(Number(this.value))
+    return SlugName.toString(this.value.toNumber())
   }
 
   toABI(encoder: ABIEncoder) {
diff --git a/packages/sdk-core/tests/SlugName.test.ts b/packages/sdk-core/tests/SlugName.test.ts
index a39275b6..b25c5063 100644
--- a/packages/sdk-core/tests/SlugName.test.ts
+++ b/packages/sdk-core/tests/SlugName.test.ts
@@ -168,5 +168,23 @@ describe("SlugName", () => {
         /must be a non-zero safe integer/
       )
     })
+
+    it.each(["", " 12 ", "0x10", "1e3", "12abc", "-5", "1.5"])(
+      "rejects the loosely numeric carrier %j instead of coercing it",
+      loose => {
+        expect(() => slugValue({ value: loose }, "Chain")).toThrow(
+          /must be a non-zero safe integer/
+        )
+      }
+    )
+
+    it("rejects a packed value past 53 bits rather than rounding it", () => {
+      expect(() =>
+        slugValue({ value: "18446744073709551615" }, "Chain")
+      ).toThrow(/must be a non-zero safe integer/)
+      expect(() => slugValue(BigInt(2) ** BigInt(60), "Chain")).toThrow(
+        /must be a non-zero safe integer/
+      )
+    })
   })
 })
diff --git a/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts b/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
index ff118dda..a0a5a930 100644
--- a/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
+++ b/packages/sdk-core/tests/contracts/sysio/chains/Slug.test.ts
@@ -1,6 +1,6 @@
-import { contracts, SlugName } from "@wireio/sdk-core"
+import { contracts, SlugName, UInt64 } from "@wireio/sdk-core"
 
-const { chainSlugString, chainSlugValue } = contracts.sysio.chains
+const { ChainsSlugName, chainSlugString, chainSlugValue } = contracts.sysio.chains
 
 describe("sysio.chains slug helpers", () => {
   test("round-trips friendly and packed chain codes", () => {
@@ -32,4 +32,12 @@ describe("sysio.chains slug helpers", () => {
       "non-zero safe integer"
     )
   })
+
+  test("ChainsSlugName renders its canonical spelling and refuses an unsafe value", () => {
+    expect(ChainsSlugName.from("ETHEREUM").toString()).toBe("ETHEREUM")
+    expect(ChainsSlugName.abiDefault().toString()).toBe("")
+    // Past 53 bits the packed value cannot be a canonical slug; converting it
+    // throws instead of silently rounding to a different code.
+    expect(() => ChainsSlugName.from(UInt64.from("18446744073709551615")).toString()).toThrow()
+  })
 })
diff --git a/packages/sdk-core/tests/contracts/sysio/reserv/Slug.test.ts b/packages/sdk-core/tests/contracts/sysio/reserv/Slug.test.ts
new file mode 100644
index 00000000..52472204
--- /dev/null
+++ b/packages/sdk-core/tests/contracts/sysio/reserv/Slug.test.ts
@@ -0,0 +1,13 @@
+import { contracts, UInt64 } from "@wireio/sdk-core"
+
+const { ReservSlugName } = contracts.sysio.reserv
+
+describe("sysio.reserv slug struct", () => {
+  test("ReservSlugName renders its canonical spelling and refuses an unsafe value", () => {
+    expect(ReservSlugName.from("PRIMARY").toString()).toBe("PRIMARY")
+    expect(ReservSlugName.abiDefault().toString()).toBe("")
+    // Past 53 bits the packed value cannot be a canonical slug; converting it
+    // throws instead of silently rounding to a different code.
+    expect(() => ReservSlugName.from(UInt64.from("18446744073709551615")).toString()).toThrow()
+  })
+})