René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"New Client (all-versions, low-level + high-level)","articleBody":"The reworked Client that speaks every version: a connect sequence that probes `server/discover` and falls back to `initialize`, stamps the `_meta` envelope on modern requests, and exposes both a low-level interface (raw requests, handle MRTR yourself) and a high-level one (negotiation/MRTR/etc. handled). Relationship to `ClientSession` is part of this design.\n\n## What's in it\n\n- Low-level + high-level interface; relationship to `ClientSession` (replaces? wraps? grows 2026 under the hood?).\n- Connect sequence: probe `server/discover` → fall back to legacy `initialize`; cache era per origin.\n- Stamp the `_meta` envelope on every modern request.\n- Emit `Mcp-Method` / `Mcp-Name` / `Mcp-Param-*` on modern HTTP (consumes the helpers from #2900).\n- Own the client-side wiring of the MRTR loop (_MRTR (multi-round-trip requests)_), listen stream (_subscriptions/listen_), and caching parse (_Caching hints (ttlMs / cacheScope)_) — those issues supply the helpers.\n- Never send session-id / open GET / DELETE against modern servers.\n\n## Conformance\n\n- `request-metadata`\n- `http-standard-headers` (runs and passes, not skips)\n- `http-custom-headers`, `http-invalid-tool-headers` (with #2900)\n- `sep-2322-client-request-state` (with #2898)\n\n## Dependencies\n\n- Depends on: #2892\n\n## References\n\n- [Versioning](https://modelcontextprotocol.io/specification/draft/basic/versioning)\n- [server/discover](https://modelcontextprotocol.io/specification/draft/server/discover)\n- [SEP-2575](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2575)\n- [client/request-metadata.ts](https://github.com/modelcontextprotocol/conformance/blob/main/src/scenarios/client/request-metadata.ts)\n","author":{"url":"https://github.com/maxisbey","@type":"Person","name":"maxisbey"},"datePublished":"2026-06-17T11:11:56.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/2894/python-sdk/issues/2894"}