fix: guard ServerRegions/AgentDeployments slice access in agent log streaming

[j0nscalet]

Problem

On v2.16.2, lk agent create . panics immediately after a successful build/deploy if you accept the post-deploy "view logs?" prompt:

Created agent with ID [agt-xxxxxxxxxxxx]
Build completed - You can view build logs later with `lk agent logs --log-type=build`
? Agent deploying. Would you like to view logs? Yes
Tailing runtime logs...safe to exit at any time
panic: runtime error: index out of range [0] with length 0
        github.com/livekit/livekit-cli/v2/cmd/lk/agent.go:646

The agent itself deploys fine — the crash is in the post-deploy log-tailer — so it's cosmetic, but it's a jarring stack trace at the end of an otherwise successful flow.

Diagnosis

Two unguarded slice indexes in cmd/lk/agent.go:

1. Line 646 (the panic): the region for log streaming is read from the first element of the CreateAgent response's ServerRegions slice without a length check. When the server returns an empty ServerRegions, the CLI panics.
2. Line 956 (latent, same class): the agent logs subcommand checks that the Agents slice from ListAgents is non-empty, but then unconditionally reads AgentDeployments[0] on the first agent. An agent with zero deployments would panic the same way.

Fix

cmd/lk/agent.go:646 — before:

} else if viewLogs {
    fmt.Println("Tailing runtime logs...safe to exit at any time")
    return agentsClient.StreamLogs(ctx, "deploy", lkConfig.Agent.ID, os.Stdout, resp.ServerRegions[0])
}

after:

} else if viewLogs {
    fmt.Println("Tailing runtime logs...safe to exit at any time")
    logRegion := region
    if len(resp.ServerRegions) > 0 {
        logRegion = resp.ServerRegions[0]
    }
    return agentsClient.StreamLogs(ctx, "deploy", lkConfig.Agent.ID, os.Stdout, logRegion)
}

region is already resolved earlier in createAgent and is the region the build was targeted at — a sensible fallback for log streaming.

cmd/lk/agent.go:956 — before:

if len(response.Agents) == 0 {
    return fmt.Errorf("no agent deployments found")
}

return agentsClient.StreamLogs(ctx, cmd.String("log-type"), agentID, os.Stdout, response.Agents[0].AgentDeployments[0].ServerRegion)

after:

if len(response.Agents) == 0 {
    return fmt.Errorf("no agent deployments found")
}
if len(response.Agents[0].AgentDeployments) == 0 {
    return fmt.Errorf("agent has no deployments to stream logs from")
}

return agentsClient.StreamLogs(ctx, cmd.String("log-type"), agentID, os.Stdout, response.Agents[0].AgentDeployments[0].ServerRegion)

Definition of Done

• lk agent create . → accept "view logs?" prompt → no panic, even when the CreateAgent response has an empty ServerRegions
• lk agent logs against an agent with zero deployments → returns a clear error instead of panicking