issue-link js-issue-link" data-error-text="Failed to load title" data-id="4609351991" data-permission-text="Title is private" data-url="https://github.com/tableau/hyper-api-rust/issues/118" data-hovercard-type="issue" data-hovercard-url="/tableau/hyper-api-rust/issues/118/hovercard" href="https://github.com/tableau/hyper-api-rust/issues/118">#118) (#126) ## Summary Four fixes on this branch: 1. **Fix heartbeat deadlock.** `maybe_send_heartbeat()` re-locked `self.engine` inside `with_engine()`, which already holds that mutex — under contention this would deadlock and freeze every tool call. The fix passes the daemon health port directly from the caller's already-held engine reference. Fixes #125. 2. **Default chart `inline` to true.** MCP clients (Cursor, Claude Desktop) couldn't render charts without a separate file-read round-trip because the chart tool defaulted to `inline=false`. Flipping the default means charts return base64 image bytes inline for immediate display. Callers can still set `inline=false` for disk-only output. 3. **Remove unused `Duration` import in `connect_named_pipe`** (Windows-only warning from the keepalive change). 4. **Lock-free `status` fast path (partially addresses #118).** The `status` tool previously went through `with_engine`, blocking behind the global engine mutex. If another tool call was stalled (half-open connection, long query), `status` would hang indefinitely. Now `status` uses `try_lock()`: - If the lock is available: full response (table counts, disk, endpoints). - If the lock is held OR engine not yet initialized: returns a **degraded-but-instant** response (daemon health via `discover()` — max ~300ms, no port scan; persistent path; watchers; attachments; version) with `engine_busy: true`. This decouples diagnostics from the data-plane lock so `status` never hangs. Other tool calls (`query`, `execute`, etc.) still serialize behind the engine mutex — the general serialization issue (connection pool / per-op timeout) remains tracked in #118. ## Test plan - [x] `cargo test -p hyperdb-mcp` — all tests pass - [x] `cargo clippy --all-targets -- -D warnings` clean - [ ] Manual: start the MCP, call `status` while a long query is running — confirm instant response with `engine_busy: true` - [ ] Manual: call `status` normally — confirm full response with `engine_busy: false` - [ ] Manual: call `chart(...)` without `inline` — confirm base64 image returned inline - [ ] Manual: run several tool calls in daemon mode to verify heartbeat doesn't hang

Uh oh!

MCP: Windows MCP v0.5.2 is broken. Trying to run queries will hang the MCP. This will be fixed soon. #125

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