RA performs some sort of (re)load when opening ui tests in a rustc checkout

Every time I open a new ui test that I haven't opened before, the status bar flashes like this:
https://github.com/user-attachments/assets/4a9bce84-4eaf-41d2-a5d6-1ef9205db890

It seems to be doing a bunch of work, including running ra-checks which is my configured check-on-save command.
This didn't use to happen, but I don't know exactly when it started. I tried older versions of the extension and I am still seeing this, so it seems like something outside RA changed, though I can't explain what that could be. (It definitely wasn't a VSCodium update, I didn't update VSCodium in forever. Though I now did update it and that didn't fix the problem either.) There's nothing appearing in the server logs under "output" either.

rust-analyzer version: rust-analyzer version: 0.3.2997-standalone [/home/r/.vscode-oss/extensions/rust-lang.rust-analyzer-0.3.2997-linux-x64/server/rust-analyzer]
but this also happens with nightly (0.4.3014)

rustc version: in a rustc checkout, so bootstrap I guess?

editor or extension: VSCodium

relevant settings:

{
    "rust-analyzer.linkedProjects": [
        "Cargo.toml",
        "library/Cargo.toml",
        "src/bootstrap/Cargo.toml",
        "compiler/rustc_codegen_cranelift/Cargo.toml",
        "compiler/rustc_codegen_gcc/Cargo.toml",
    ],
    "rust-analyzer.check.invocationStrategy": "once",
    "rust-analyzer.check.overrideCommand": [
        "./ra-check", "--json-output"
    ],
    "rust-analyzer.rustfmt.overrideCommand": [
        "${workspaceFolder}/build/host/rustfmt/bin/rustfmt",
        "--edition=2024",
    ],
    "rust-analyzer.procMacro.server": "${workspaceFolder}/build/host/stage0/libexec/rust-analyzer-proc-macro-srv",
    "rust-analyzer.cargo.buildScripts.invocationStrategy": "once",
    "rust-analyzer.cargo.buildScripts.overrideCommand": [
        "python3", "x.py", "check",
        "library", "compiler", "miri",
        "--json-output",
        "--compile-time-deps",
        "--set", "rust.download-rustc=false",
    ],
    "rust-analyzer.server.extraEnv": {
        "RUSTC": "${workspaceFolder}/build/host/stage0/bin/rustc",
        "CARGO": "${workspaceFolder}/build/host/stage0/bin/cargo",
    },
    "rust-analyzer.rustc.source": "./Cargo.toml",
    "rust-analyzer.cargo.sysrootSrc": "./library",
    "rust-analyzer.cargo.extraEnv": {
        "RUSTC_BOOTSTRAP": "1"
    },
    // Some diagnostics don't work properly here
    "rust-analyzer.diagnostics.enable": false, // due to <https://github.com/rust-lang/rust-analyzer/issues/13504>, we have too many errors
    //
    "files.watcherExclude": {
        "build": true,
    },
    "files.exclude": {
        "build": true
    },
}

repository link (if public, optional): https://github.com/rust-lang/rust/

Start by reproducing the reload/status-bar activity when opening a previously unopened UI test in the rustc checkout, using the listed linkedProjects, ra-check, x.py, and overrideCommand settings. Compare the behavior with server logs and check-on-save activity; done means identifying the trigger and preventing unintended reload or check work when opening the file.