tauri-apps/tauri · error · DecodingError

Invalid channel ID from \(channelDef)

Error message

Invalid channel ID from \(channelDef)

What it means

Tauri's iOS Channel initializer decodes a channel definition string of the form '<prefix><numeric-id>' (e.g. '__CHANNEL__:123'). The numeric portion could not be parsed as a UInt64, so DecodingError.dataCorruptedError is thrown with this message. It indicates the channel definition string passed through the IPC bridge was malformed or a different format than expected.

Solutions

1. Ensure the channel definition string is generated by Tauri's own channel machinery and includes a numeric ID after the prefix (e.g. __CHANNEL__:42).
2. Align the Rust and iOS Tauri versions so the channel wire format/prefix matches on both sides.
3. Log the received channelDef string to confirm the actual format being decoded.
4. Check custom plugin code for hand-built channel identifiers and replace them with Channel instances from the plugin API.

Example fix

// before: building the channel string by hand
const channel = `__CHANNEL__:${myCustomId}`
// after: let Tauri create it
const channel = new Channel(handler)

function isValidChannelDef(def) {
  return typeof def === 'string' && /^__CHANNEL__:\d+$/.test(def) && BigInt(def.split(':')[1]) <= 18446744073709551615n
}

const isChannelDef = (v) => typeof v === 'string' && /^__CHANNEL__:\d+$/.test(v)

When it happens

Trigger: Decoding a Channel from JSON where components[1] (the part after the channel prefix) is not a valid UInt64: non-numeric text, negative numbers, an ID exceeding UInt64 range, or a string missing the ID segment entirely.

Common situations: Mismatched channel-serialization formats between the Rust core and the iOS webview layer (e.g. after upgrading Tauri versions so prefix/format changed), custom plugins hand-rolling channel strings, or a corrupted/truncated IPC payload.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Invalid channel definition from \(channelDef)
• missing userInfo for Channel handler. This is a Tauri issue
• unexpected channel value $channelDef
• Arch specified by Xcode was invalid.
• failed to read missing addr file

AI-assisted analysis of tauri-apps/tauri@460ec35447 (2026-09-18). Data as JSON: /api/errors/9b236b72c704c131. Report an issue: GitHub.

Appendix: source

Thrown at crates/tauri/mobile/ios-api/Sources/Tauri/Channel.swift:27

public class Channel: Decodable {
  public let id: UInt64
  let handler: (UInt64, String) -> Void

  public required init(from decoder: Decoder) throws {
    let container = try decoder.singleValueContainer()
    let channelDef = try container.decode(String.self)

    let components = channelDef.components(separatedBy: CHANNEL_PREFIX)
    if components.count < 2 {
      throw DecodingError.dataCorruptedError(
        in: container,
        debugDescription: "Invalid channel definition from \(channelDef)"
      )

    }
    guard let channelId = UInt64(components[1]) else {
      throw DecodingError.dataCorruptedError(
        in: container,
        debugDescription: "Invalid channel ID from \(channelDef)"
      )
    }

    guard let handler = decoder.userInfo[channelDataKey] as? (UInt64, String) -> Void else {
      throw DecodingError.dataCorruptedError(
        in: container,
        debugDescription: "missing userInfo for Channel handler. This is a Tauri issue"
      )
    }

    self.id = channelId
    self.handler = handler
  }

  func serialize(_ data: JsonValue) -> String {
    do {

View on GitHub (pinned to 460ec35447)