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…nce deployments Use NeverSessionManager + stateful_mode(false) so every POST request is handled independently. Previously the default LocalSessionManager stored sessions in memory per process, causing Cursor (and any load-balanced client) to receive 404 "Session not found" when a request landed on a different instance than the one that created the session. Clients that cache the Mcp-Session-Id then fell back to legacy SSE V1, which this server does not implement, producing a 400 error. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
MCP spec requires structuredContent to be a record (JSON object). Tools that return Vec<T> serialize to a JSON array, which Cursor validates strictly and rejects with "expected record, received array". Filter structured_content to None for non-object values so array responses (static_info, quote, trades, candlesticks, etc.) no longer violate the spec. The fix is centralized in tool_result so all tools are covered without per-tool changes. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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…olation (#38) ## Summary - Switch MCP server to stateless mode to fix session-not-found errors on multi-instance deployments - Fix `structuredContent` type violation that caused Cursor to reject array tool responses ## Fix 1 — Stateless mode (`src/auth/mod.rs`) **Root cause**: The server is designed for stateless multi-instance deployment, but was using `stateful_mode: true` (the rmcp default) with an in-memory `LocalSessionManager`. Under a load balancer, sessions created on Instance A are unknown to Instance B, triggering a failure chain in Cursor: 1. POST with cached `Mcp-Session-Id` → **404 Session not found** (session lives on another instance) 2. Cursor falls back to legacy SSE V1 protocol (GET without session ID) → **400 Session ID is required** Claude Code and Codex are unaffected because they re-initialize on every connection rather than caching session IDs. **Fix**: Replace `LocalSessionManager` with `NeverSessionManager` and set `stateful_mode(false)`. The `Mcp-Session-Id` header is completely ignored in stateless mode; each POST is handled independently with no session state. ## Fix 2 — `structuredContent` type (`src/tools/mod.rs`) **Root cause**: `tool_result` unconditionally assigned the parsed JSON value to `structured_content`. Tools returning `Vec<T>` (e.g. `quote`, `static_info`, `trades`, `candlesticks`, `participants`) serialize to a JSON array. The MCP spec requires `structuredContent` to be a JSON **object** (record); Cursor validates this strictly and rejects array values with: ``` Invalid input: expected record, received array ``` **Fix**: Added `.filter(serde_json::Value::is_object)` so `structured_content` is only set for JSON object responses. Array responses leave it as `None`, which is valid per spec. The fix is centralized in `tool_result` and covers all tools. 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
structuredContenttype violation that caused Cursor to reject array tool responsesFix 1 — Stateless mode (
src/auth/mod.rs)Root cause: The server is designed for stateless multi-instance deployment, but was using
stateful_mode: true(the rmcp default) with an in-memoryLocalSessionManager. Under a load balancer, sessions created on Instance A are unknown to Instance B, triggering a failure chain in Cursor:Mcp-Session-Id→ 404 Session not found (session lives on another instance)Claude Code and Codex are unaffected because they re-initialize on every connection rather than caching session IDs.
Fix: Replace
LocalSessionManagerwithNeverSessionManagerand setstateful_mode(false). TheMcp-Session-Idheader is completely ignored in stateless mode; each POST is handled independently with no session state.Fix 2 —
structuredContenttype (src/tools/mod.rs)Root cause:
tool_resultunconditionally assigned the parsed JSON value tostructured_content. Tools returningVec<T>(e.g.quote,static_info,trades,candlesticks,participants) serialize to a JSON array. The MCP spec requiresstructuredContentto be a JSON object (record); Cursor validates this strictly and rejects array values with:Fix: Added
.filter(serde_json::Value::is_object)sostructured_contentis only set for JSON object responses. Array responses leave it asNone, which is valid per spec. The fix is centralized intool_resultand covers all tools.🤖 Generated with Claude Code