Language server performance issues can be difficult to diagnose because
request timings are not shown alongside the corresponding JSON-RPC
traffic. Annotate responses in the "LSP Logs / RPC Messages" view with
their end-to-end duration, making it easier to identify slow methods,
latency outliers, and cancellation behavior in the language server
process launched by Zed.

Capture timestamps at the transport boundary, correlate decoded request
IDs separately by direction, preserve timing across cancellation, bound
stale request tracking, and forward host-measured durations to remote
clients.

## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and relxability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

## Showcase

<details>
<summary>Example trace</summary>

```
// Send:
{"jsonrpc":"2.0","id":61,"method":"textDocument/documentHighlight","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":378,"character":3}}}

// Receive (took 7.698042ms):
{"jsonrpc":"2.0","id":61,"result":[]}

// Send:
{"jsonrpc":"2.0","id":62,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"range":{"start":{"line":378,"character":3},"end":{"line":378,"character":3}},"context":{"diagnostics":[]}}}

// Receive (took 5.632167ms):
{"jsonrpc":"2.0","id":62,"result":[{"title":"Show macro expansion for `@static`","command":{"title":"Show macro expansion for `@static`","command":"jetls.openMacroExpansion","arguments":["jetls-macro-expansion:/macro-expanded.jl?source=file%253A%252F%252F%252FUsers%252Faviatesk%252Fjulia%252Fpackages%252Fworktrees%252FJETLS%252Fplacid-wren%252FJETLS%252Fsrc%252Fanalysis%252FAnalyzer.jl&start=14278&stop=15609"]}},{"title":"Expand all macros in this top-level form","command":{"title":"Expand all macros in this top-level form","command":"jetls.openMacroExpansion","arguments":["jetls-macro-expansion:/macro-expanded.jl?source=file%253A%252F%252F%252FUsers%252Faviatesk%252Fjulia%252Fpackages%252Fworktrees%252FJETLS%252Fplacid-wren%252FJETLS%252Fsrc%252Fanalysis%252FAnalyzer.jl&start=14278&stop=15609&mode=toplevel"]}},{"title":"Show inferred type annotations","command":{"title":"Show inferred type annotations","command":"jetls.openTypeAnnotation","arguments":["jetls-type-annotation:/type-annotated.jl?source=file%253A%252F%252F%252FUsers%252Faviatesk%252Fjulia%252Fpackages%252Fworktrees%252FJETLS%252Fplacid-wren%252FJETLS%252Fsrc%252Fanalysis%252FAnalyzer.jl&start=14278&stop=15609"]}}]}

// Send:
{"jsonrpc":"2.0","id":63,"method":"textDocument/documentHighlight","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":379,"character":3}}}

// Receive (took 3.473792ms):
{"jsonrpc":"2.0","id":63,"result":[]}

// Send:
{"jsonrpc":"2.0","id":64,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"range":{"start":{"line":379,"character":3},"end":{"line":379,"character":3}},"context":{"diagnostics":[]}}}

// Receive (took 4.472375ms):
{"jsonrpc":"2.0","id":64,"result":[{"title":"Show macro expansion for `@static`","command":{"title":"Show macro expansion for `@static`","command":"jetls.openMacroExpansion","arguments":["jetls-macro-expansion:/macro-expanded.jl?source=file%253A%252F%252F%252FUsers%252Faviatesk%252Fjulia%252Fpackages%252Fworktrees%252FJETLS%252Fplacid-wren%252FJETLS%252Fsrc%252Fanalysis%252FAnalyzer.jl&start=14278&stop=15609"]}},{"title":"Expand all macros in this top-level form","command":{"title":"Expand all macros in this top-level form","command":"jetls.openMacroExpansion","arguments":["jetls-macro-expansion:/macro-expanded.jl?source=file%253A%252F%252F%252FUsers%252Faviatesk%252Fjulia%252Fpackages%252Fworktrees%252FJETLS%252Fplacid-wren%252FJETLS%252Fsrc%252Fanalysis%252FAnalyzer.jl&start=14278&stop=15609&mode=toplevel"]}},{"title":"Show inferred type annotations","command":{"title":"Show inferred type annotations","command":"jetls.openTypeAnnotation","arguments":["jetls-type-annotation:/type-annotated.jl?source=file%253A%252F%252F%252FUsers%252Faviatesk%252Fjulia%252Fpackages%252Fworktrees%252FJETLS%252Fplacid-wren%252FJETLS%252Fsrc%252Fanalysis%252FAnalyzer.jl&start=14278&stop=15609"]}}]}

// Send:
{"jsonrpc":"2.0","id":65,"method":"textDocument/documentHighlight","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":380,"character":0}}}

// Receive (took 1.186541ms):
{"jsonrpc":"2.0","id":65,"result":[]}

// Send:
{"jsonrpc":"2.0","id":66,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"range":{"start":{"line":380,"character":0},"end":{"line":380,"character":0}},"context":{"diagnostics":[]}}}

// Receive (took 2.552708ms):
{"jsonrpc":"2.0","id":66,"result":[]}

// Send:
{"jsonrpc":"2.0","id":67,"method":"textDocument/documentHighlight","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":401,"character":0}}}

// Receive (took 1.490084ms):
{"jsonrpc":"2.0","id":67,"result":[]}

// Send:
{"jsonrpc":"2.0","id":68,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"range":{"start":{"line":401,"character":0},"end":{"line":401,"character":0}},"context":{"diagnostics":[]}}}

// Receive (took 2.819125ms):
{"jsonrpc":"2.0","id":68,"result":[]}

// Send:
{"jsonrpc":"2.0","id":69,"method":"textDocument/documentHighlight","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":400,"character":0}}}

// Receive (took 3.501375ms):
{"jsonrpc":"2.0","id":69,"result":[]}

// Send:
{"jsonrpc":"2.0","id":70,"method":"textDocument/documentHighlight","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":399,"character":0}}}

// Receive (took 2.903333ms):
{"jsonrpc":"2.0","id":70,"result":[]}

// Send:
{"jsonrpc":"2.0","id":71,"method":"textDocument/documentHighlight","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":399,"character":14}}}

// Receive (took 3.166ms):
{"jsonrpc":"2.0","id":71,"result":[{"range":{"start":{"line":389,"character":19},"end":{"line":389,"character":22}},"kind":3},{"range":{"start":{"line":399,"character":11},"end":{"line":399,"character":14}},"kind":2}]}

// Send:
{"jsonrpc":"2.0","id":72,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"range":{"start":{"line":399,"character":14},"end":{"line":399,"character":14}},"context":{"diagnostics":[]}}}

// Receive (took 3.169625ms):
{"jsonrpc":"2.0","id":72,"result":[{"title":"Show inferred type annotations","command":{"title":"Show inferred type annotations","command":"jetls.openTypeAnnotation","arguments":["jetls-type-annotation:/type-annotated.jl?source=file%253A%252F%252F%252FUsers%252Faviatesk%252Fjulia%252Fpackages%252Fworktrees%252FJETLS%252Fplacid-wren%252FJETLS%252Fsrc%252Fanalysis%252FAnalyzer.jl&start=15676&stop=16556"]}}]}

// Send:
{"jsonrpc":"2.0","id":73,"method":"textDocument/hover","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":399,"character":14}}}

// Receive (took 1.234396208s):
{"jsonrpc":"2.0","id":73,"result":{"contents":{"kind":"markdown","value":"```julia\n(local) ret :: Compiler.RTEffects  # Core.PartialStruct(Compiler.RTEffects, Any[Any, Any, Compiler.Effects, Core.Const(nothing)])\n```\n"},"range":{"start":{"line":399,"character":11},"end":{"line":399,"character":14}}}}

// Send:
{"jsonrpc":"2.0","id":74,"method":"textDocument/hover","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":399,"character":14}}}

// Receive (took 11.429875ms):
{"jsonrpc":"2.0","id":74,"result":{"contents":{"kind":"markdown","value":"```julia\n(local) ret :: Compiler.RTEffects  # Core.PartialStruct(Compiler.RTEffects, Any[Any, Any, Compiler.Effects, Core.Const(nothing)])\n```\n"},"range":{"start":{"line":399,"character":11},"end":{"line":399,"character":14}}}}

// Send:
{"jsonrpc":"2.0","id":75,"method":"textDocument/documentHighlight","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"position":{"line":401,"character":0}}}

// Receive (took 1.098667ms):
{"jsonrpc":"2.0","id":75,"result":[]}

// Send:
{"jsonrpc":"2.0","id":76,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///Users/aviatesk/julia/packages/worktrees/JETLS/placid-wren/JETLS/src/analysis/Analyzer.jl"},"range":{"start":{"line":401,"character":0},"end":{"line":401,"character":0}},"context":{"diagnostics":[]}}}

// Receive (took 4.117459ms):
{"jsonrpc":"2.0","id":76,"result":[]}
```

</details>

---

Release Notes:

- Improved LSP Logs by showing request durations alongside RPC
responses, making slow language server behavior easier to diagnose.

---------

Co-authored-by: Kirill Bulatov <kirill@zed.dev>