Protocol eras changeddocs/draft/tools/inspector/protocol-eras
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Upstream edited this page at 2 Aug 2026 23:45 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 28 Sep 2026 22:07 UTC.
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99Each server carries a `protocolEra` of `legacy`, `auto`, or `modern`. In the web client it lives in **Server Settings**; in a catalog or config file it is the `protocolEra` field; in the CLI and TUI it comes from that same file.
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11| Era | What the Inspector does at connect |
12| -------- | --------------------------------------------------------------------------------------- |
13| `legacy` | **The default.** Plain `initialize`, no probing at all. |
14| `auto` | Probe `server/discover` first, and fall back to `initialize` on any non-modern outcome. |
15| `modern` | Pin exactly `2026-07-28`. No fallback, so a non-modern server fails loudly. |
11| Era | What the Inspector does at connect |
12| - | - |
13| `legacy` | **The default.** Plain `initialize`, no probing at all. |
14| `auto` | Probe `server/discover` first, and fall back to `initialize` on any non-modern outcome. |
15| `modern` | Pin exactly `2026-07-28`. No fallback, so a non-modern server fails loudly. |
1616
1717<Note>
1818 **Why `legacy` is the default, and not `auto`.** A debugging tool must not
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142142`test-servers/configs/mrtr-showcase-http.json` bundles every shape in one modern server:
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144| Tool | What it exercises |
145| --------------- | ----------------------------------------------------------------------------- |
146| `mrtr_confirm` | A single elicitation round. |
147| `mrtr_two_step` | Two elicitation rounds, threaded through `requestState`. |
148| `mrtr_sample` | An embedded sampling request, routed to the Sampling panel. |
149| `mrtr_roots` | An embedded `roots/list`, answered silently from configured roots (no modal). |
150| `mrtr_edge` | An `inputRequests`-only round, then a `requestState`-only round. |
151| `mrtr_loop` | Never completes, so the client stops at its `MRTR_MAX_ROUNDS` limit. |
144| Tool | What it exercises |
145| - | - |
146| `mrtr_confirm` | A single elicitation round. |
147| `mrtr_two_step` | Two elicitation rounds, threaded through `requestState`. |
148| `mrtr_sample` | An embedded sampling request, routed to the Sampling panel. |
149| `mrtr_roots` | An embedded `roots/list`, answered silently from configured roots (no modal). |
150| `mrtr_edge` | An `inputRequests`-only round, then a `requestState`-only round. |
151| `mrtr_loop` | Never completes, so the client stops at its `MRTR_MAX_ROUNDS` limit. |
152152
153153<Note>
154154 The legacy `collect_elicitation` pattern (a server calling
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208208
209209`test-servers/configs/modern-network-http.json` serves four tools that produce a real HTTP status plus a JSON-RPC error body, one per class:
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211| Tool | HTTP | JSON-RPC code | Meaning |
212| ----------------------------- | ----- | ------------- | ------------------------------------------------------------ |
213| `trigger_header_mismatch` | `400` | `-32020` | A required mirrored header was missing or wrong. |
214| `trigger_missing_capability` | `400` | `-32021` | The request omitted a client capability the server requires. |
215| `trigger_unsupported_version` | `400` | `-32022` | Unsupported version; supported versions in `data.supported`. |
216| `trigger_method_not_found` | `404` | `-32601` | Method not found. |
211| Tool | HTTP | JSON-RPC code | Meaning |
212| - | - | - | - |
213| `trigger_header_mismatch` | `400` | `-32020` | A required mirrored header was missing or wrong. |
214| `trigger_missing_capability` | `400` | `-32021` | The request omitted a client capability the server requires. |
215| `trigger_unsupported_version` | `400` | `-32022` | Unsupported version; supported versions in `data.supported`. |
216| `trigger_method_not_found` | `404` | `-32601` | Method not found. |
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218218<Frame caption="The Network tab shows the HTTP layer; here, the 400 Bad Request the strict server answered with.">
219219 <img src="https://mintcdn.com/mcp/gk28X8wi_tbRYzej/images/inspector/network-modern-headers.png?fit=max&auto=format&n=gk28X8wi_tbRYzej&q=85&s=7df4c01f5ab68aa7632ac3b5a5866b42" width="3840" height="2160" data-path="images/inspector/network-modern-headers.png" />
No line in this hunk matches that.