diff --git a/README.md b/README.md
index 533dca7..51337c1 100644
--- a/README.md
+++ b/README.md
@@ -146,6 +146,27 @@ soleil bench --suite smoke
 soleil bench --suite core --runs 3 --json
 ```
 
+### PowerShell tab completion
+
+Windows PowerShell users can load deterministic completions for the `soleil`
+command:
+
+```powershell
+. "$PWD\completions\soleil.ps1"
+```
+
+To keep it available, add the same line to your PowerShell profile:
+
+```powershell
+notepad $PROFILE
+```
+
+Remove the line from `$PROFILE` to uninstall the completion hook. The script
+completes the documented commands (`doctor`, `setup`, `language`, `run`,
+`bench`), common options (`--cwd`, `--mode`, `--language`, `--yes`, `--json`,
+`--suite`, `--runs`), and known values for `--mode`, `--language`, and
+`--suite`.
+
 Benchmarks use the configured free/local routes and therefore consume their quota.
 Each case runs in a new temporary project that is removed after verification.
 See the [benchmark methodology and latest verified snapshot](docs/BENCHMARKS.md).
diff --git a/completions/soleil.ps1 b/completions/soleil.ps1
new file mode 100644
index 0000000..960ad65
--- /dev/null
+++ b/completions/soleil.ps1
@@ -0,0 +1,73 @@
+# SoleilCode PowerShell tab completion.
+# Load with: . "$PWD\completions\soleil.ps1"
+
+$script:SoleilCommands = @(
+  'doctor',
+  'setup',
+  'language',
+  'languages',
+  'run',
+  'bench',
+  'benchmark'
+)
+
+$script:SoleilOptions = @(
+  '--cwd',
+  '--mode',
+  '--language',
+  '--lang',
+  '--yes',
+  '-y',
+  '--json',
+  '--prompt-file',
+  '--suite',
+  '--runs',
+  '--version',
+  '-v',
+  '--help',
+  '-h'
+)
+
+$script:SoleilModes = @('auto', 'free', 'local', 'private')
+$script:SoleilLanguages = @('en', 'tr', 'es', 'fr', 'de', 'it', 'pt', 'ru', 'ja', 'ko')
+$script:SoleilSuites = @('smoke', 'core')
+
+function script:New-SoleilCompletionResult {
+  param(
+    [string] $Value,
+    [string] $ToolTip = $Value
+  )
+
+  [System.Management.Automation.CompletionResult]::new(
+    $Value,
+    $Value,
+    [System.Management.Automation.CompletionResultType]::ParameterValue,
+    $ToolTip
+  )
+}
+
+Register-ArgumentCompleter -Native -CommandName soleil -ScriptBlock {
+  param($wordToComplete, $commandAst, $cursorPosition)
+
+  $elements = @($commandAst.CommandElements | ForEach-Object { $_.ToString() })
+  $previous = if ($elements.Count -ge 2) { $elements[$elements.Count - 2] } else { '' }
+
+  $candidates = switch ($previous) {
+    '--mode' { $script:SoleilModes; break }
+    '--language' { $script:SoleilLanguages; break }
+    '--lang' { $script:SoleilLanguages; break }
+    '--suite' { $script:SoleilSuites; break }
+    default {
+      if ($wordToComplete -like '-*') {
+        $script:SoleilOptions
+      } else {
+        @($script:SoleilCommands + $script:SoleilOptions)
+      }
+    }
+  }
+
+  $candidates |
+    Where-Object { $_ -like "$wordToComplete*" } |
+    Sort-Object -Unique |
+    ForEach-Object { script:New-SoleilCompletionResult $_ }
+}
diff --git a/package.json b/package.json
index 8168abb..d49046c 100644
--- a/package.json
+++ b/package.json
@@ -16,6 +16,7 @@
   },
   "files": [
     "bin",
+    "completions",
     "dist",
     "README.md",
     "CHANGELOG.md",
diff --git a/tests/powershell-completion.test.ts b/tests/powershell-completion.test.ts
new file mode 100644
index 0000000..a73bd96
--- /dev/null
+++ b/tests/powershell-completion.test.ts
@@ -0,0 +1,36 @@
+import assert from "node:assert/strict";
+import { readFile } from "node:fs/promises";
+import path from "node:path";
+import test from "node:test";
+
+const completionPath = path.resolve("completions/soleil.ps1");
+
+test("PowerShell completion covers documented commands and options", async () => {
+  const script = await readFile(completionPath, "utf8");
+
+  for (const command of ["doctor", "setup", "language", "run", "bench"]) {
+    assert.match(script, new RegExp(`'${command}'`));
+  }
+
+  for (const option of ["--cwd", "--mode", "--language", "--yes", "--json", "--suite", "--runs"]) {
+    assert.match(script, new RegExp(`'${option}'`));
+  }
+
+  for (const value of ["auto", "free", "local", "private", "smoke", "core"]) {
+    assert.match(script, new RegExp(`'${value}'`));
+  }
+
+  assert.match(script, /Register-ArgumentCompleter -Native -CommandName soleil/);
+});
+
+test("PowerShell completion candidate lists are deterministic and unique", async () => {
+  const script = await readFile(completionPath, "utf8");
+  const listMatches = script.matchAll(/\$script:Soleil(?:Commands|Options|Modes|Languages|Suites) = @\((?<body>[\s\S]*?)\)/g);
+
+  for (const match of listMatches) {
+    const body = match.groups?.body ?? "";
+    const values = [...body.matchAll(/'([^']+)'/g)].map((entry) => entry[1]);
+    assert.deepEqual(values, [...new Set(values)], `duplicate completion values in ${match[0].split(" = ")[0]}`);
+    assert.ok(values.length > 0);
+  }
+});