What causes "command.execute failed: ${result.error.code}: ${result.error.message}" in deepseek-ai/deepseek-harness?

Inspect the embedded error.code to classify the failure (transport versus host refusal)

command.execute failed: ${result.error.code}: ${result.error

Error message

command.execute failed: ${result.error.code}: ${result.error.message}

What it means

execute() forwards a slash-command line (with optional image attachments) to the host via ctx.remote.commands.execute. A non-ok RPC result throws 'command.execute failed: <code>: <message>'. An unmatched command (result.value === undefined) does NOT throw — it returns an error SubmitOutcome — so this error strictly means the RPC itself rejected, not a typo in the command name.

Source

Thrown at packages/client/ui-commands/src/client/service.ts:405

  /**
   * The command.execute transaction, addressed to the session's agent — pure
   * admission semantics. An unmatched line reports an error outcome (the
   * composer's immediate admission feedback); an admitted command reports
   * plain success regardless of its handler outcome, because the host
   * executor durably logged the lifecycle (`command/run`/`command/done`) and
   * the outcome renders as a persistent flow node — the composer never
   * echoes it. A handler error result reports an error outcome so the
   * composer keeps the submission (draft and images) for correction.
   * Transport failures throw.
   */
  private async execute(
    session: ClientSessionContext,
    line: string,
    images: readonly SubmitImageAttachment[] = [],
  ): Promise<SubmitOutcome> {
    const result = await this.ctx.remote.commands.execute(session.sessionId, line, images)
    if (!result.ok) throw new Error(`command.execute failed: ${result.error.code}: ${result.error.message}`)
    if (result.value === undefined) return { kind: 'error', text: `unknown or malformed command: ${line}` }
    this.notifyExecuted(session.sessionId, submittedCommandName(line), result.value.result)
    // An image-carrying submission consumed its images only on handler
    // success; an error outcome keeps draft and images in the composer.
    if (images.length > 0 && result.value.result.kind === 'error') {
      return { kind: 'error', text: result.value.result.text }
    }
    return { kind: 'success' }
  }

  /** Publish the local acknowledgment without letting an observer change command admission. */
  private notifyExecuted(sessionId: SessionId, name: string, result: CommandResult): void {
    const args = ['command/executed', sessionId, name, result]
    for (const listener of this.ctx.events.dispatch('emit', args) as Array<(...listenerArgs: unknown[]) => unknown>) {
      try {
        const returned = listener(sessionId, name, result)
        if (returned != null && typeof (returned as PromiseLike<unknown>).then === 'function') {
          void Promise.resolve(returned as PromiseLike<unknown>).then(undefined, (error: unknown) => {

View on GitHub (pinned to b150a551b8)

Solutions

Inspect the embedded error.code to classify the failure (transport versus host refusal)
Reconnect and resubmit — the composer preserved the failed line
Verify host and client versions agree on the commands.execute contract
Cap or compress image attachments before submit if the code suggests a payload limit

Defensive patterns

Strategy: try-catch

Validate before calling

if (!connectionHealthy()) await reconnect()

Try / catch

try {
  const outcome = await submitSlash(line, images)
} catch (error) {
  surfaceSubmitError(error) // composer keeps the line; offer retry
}

Prevention

Serialize submits through one attempt latch so a dropped connection cannot double-fire
Version-check the host on connect before enabling slash submission
Report the embedded error code verbatim in diagnostics

When it happens

Trigger: Submitting a slash command through leadingClaim, the result sink, or runDetached when the execute RPC rejects: the session dropped mid-submit, the host command handler failed, permission was denied, or the transport reset between Enter and execution.

Common situations: Connection loss right after pressing Enter; host restarting or redeploying mid-submit; host/client protocol mismatch on the commands.execute payload; oversized image attachment rejected by a gateway body limit.

Related errors

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/15fb53999a7a2b80. Report an issue: GitHub.