1 · Runtime
Check the Node version
node --versionUse Node 22.19.0 or newer for the current Inspector v2 package.
Independent MCP diagnostic
Prove the browser connection before debugging the agent.
The official MCP Inspector can connect directly to Hronaut's local endpoint and list its tools without involving Codex, Claude Code, an editor, or an LLM. One short probe separates a server or transport failure from client configuration.
MCP Inspector is maintained by the Model Context Protocol project. It is not bundled with Hronaut, and running it with npx downloads and executes that separate package.
What this isolates
Hronaut → loopback → MCP
Run the Inspector on the same computer as Hronaut. A hosted Inspector, cloud agent, remote VM, or container without explicit host networking cannot reach your desktop's 127.0.0.1.
Read-only connection check
List tools without calling one.
Current MCP Inspector v2 requires Node.js 22.19 or newer. Start Hronaut, confirm MCP server online on Hronaut Home, then run the CLI on the same machine.
2 · Transport
Ask for Hronaut's tool catalog
npx @modelcontextprotocol/inspector@latest --cli http://127.0.0.1:47812/mcp --transport http --method tools/listtools/list initializes the connection and reads tool definitions. It does not navigate, click, or modify a browser workspace.
The explicit --transport http selects Streamable HTTP. Inspector's CLI is one-shot: it connects, runs the requested method, prints the result, disconnects, and returns a non-zero exit code for protocol or tool errors.
Visual protocol inspection
Use the web UI when you need to inspect schemas and responses.
Start the current Inspector without a target, add a Streamable HTTP server in its local catalog, and connect it to Hronaut.
Local Inspector UI
Keep both developer tools on loopback
npx @modelcontextprotocol/inspector@latest- Open the local URL printed by Inspector.
- Add a server named hronaut.
- Select Streamable HTTP and enter
http://127.0.0.1:47812/mcp. - Connect, open Tools, then inspect the catalog before calling anything.
Inspector v2 stores server entries in ~/.mcp-inspector/mcp.json. Hronaut's optional bearer token and Inspector's own local API token protect different boundaries. Never disable either product's authentication to make a valuable signed-in profile easier to debug.
Failure matrix
Fix the layer that actually failed.
| Observed result | What it proves | Next check |
|---|---|---|
| Connection refused | No process accepted the configured loopback connection. | Confirm Hronaut is running, MCP is online, and the active port on Hronaut Home matches the URL. |
| Unauthorized | The endpoint is reachable, but the Hronaut profile requires authentication. | Keep authentication enabled. Use Hronaut Home's token-aware snippet in a supported client; do not paste an owner token into shell history or a support ticket. |
tools/list succeeds | Hronaut, Streamable HTTP negotiation, and tool discovery work independently of the coding agent. | Reload the client configuration, verify its local/user scope, and check that it points to the same port and transport. |
| Client connects, task fails | The transport is no longer the first suspect. | Inspect the exact tool arguments and result, then retry in a disposable named workspace rather than the human Default workspace. |
Two local control surfaces
Do not weaken security for a diagnostic.
Inspector can connect to MCP servers and its backend can launch local processes. Keep its default API authentication enabled, leave it bound to loopback, and never set DANGEROUSLY_OMIT_AUTH. Do not expose its web server to a LAN or the public internet.
This unauthenticated Hronaut example is appropriate for a new, non-sensitive profile where local processes are equally trusted. For a signed-in or sensitive profile, keep Hronaut authentication enabled and troubleshoot through a client configuration that reads the owner-only token safely. Pause MCP before entering passwords, security keys, payment data, or other human-only information.
Primary sources
Commands, lifecycle, and security evidence.
- MCP Inspector CLI reference — current Streamable HTTP flags, supported methods, one-shot behavior, output, exit semantics, and Node requirement.
- Inspector v1-to-v2 migration — the current v2 package, default catalog, local API token, and changed web architecture.
- Inspector web-client reference — loopback binding, API authentication, persisted server settings, and warnings against network exposure.
- MCP Streamable HTTP specification — independent server transport, single endpoint behavior, Origin validation, loopback binding, and authentication guidance.
From protocol proof to browser proof
After discovery passes, verify one isolated browser task.
Return to your coding agent and ask it to create a named first-check workspace, open https://example.com, and report the page title and workspace ID without touching Default. That tests tool use and browser behavior after the independent transport probe.