diff --git a/scripts/format.ps1 b/scripts/format.ps1
index 2d61f5170450e..e9860b3f7351c 100644
--- a/scripts/format.ps1
+++ b/scripts/format.ps1
@@ -1,41 +1,142 @@
-# Code formatter.
+# Code formatter - runs targeted formatters based on what changed from trunk.
+# Usage: format.ps1 [-All] [-PreCommit] [-PrePush] [-Lint]
+#   (default)     Check all changes relative to trunk including uncommitted work
+#   -All          Format everything, skip change detection
+#   -PreCommit    Only check staged changes
+#   -PrePush      Only check committed changes relative to trunk
+#   -Lint         Also run linters before formatting
+
+param(
+    [switch]$All,
+    [switch]$PreCommit,
+    [switch]$PrePush,
+    [switch]$Lint
+)
 
 Set-StrictMode -Version 'Latest'
 $ErrorActionPreference = 'Stop'
 
+# Validate mutually exclusive flags
+if ($PreCommit -and $PrePush) {
+    Write-Error "Cannot use both -PreCommit and -PrePush"
+    exit 1
+}
+
 function section($message) {
     Write-Host "- $message" -ForegroundColor Green
 }
 
+# Find what's changed compared to trunk (skip if -All)
+$formatAll = $All
+$trunkRef = git rev-parse --verify trunk 2>$null
+
+if (-not $formatAll -and $trunkRef) {
+    $base = git merge-base HEAD $trunkRef 2>$null
+    if ($base) {
+        if ($PreCommit) {
+            $changed = git diff --name-only --cached
+        } elseif ($PrePush) {
+            $changed = git diff --name-only $base HEAD
+        } else {
+            $committed = git diff --name-only $base HEAD
+            $staged = git diff --name-only --cached
+            $unstaged = git diff --name-only
+            $untracked = git ls-files --others --exclude-standard
+            $changed = ($committed + $staged + $unstaged + $untracked) | Sort-Object -Unique
+        }
+    } else {
+        $formatAll = $true
+    }
+} elseif (-not $formatAll) {
+    # No trunk ref found, format everything
+    $formatAll = $true
+}
+
+# Helper to check if a pattern matches changed files
+function changedMatches($pattern) {
+    if ($formatAll) { return $true }
+    return ($changed | Where-Object { $_ -match $pattern }).Count -gt 0
+}
+
 $WORKSPACE_ROOT = (bazel info workspace)
-$GOOGLE_JAVA_FORMAT = (bazel run --run_under=echo //scripts:google-java-format)
 
+# Capture baseline to detect formatter-introduced changes
+$baseline = git status --porcelain
+
+# Always run buildifier and copyright
 section "Buildifier"
-Write-Host "    buildifier" -ForegroundColor Green
+Write-Host "    buildifier"
 bazel run //:buildifier
 
-section "Java"
-Write-Host "    google-java-format" -ForegroundColor Green
-Get-ChildItem -Path "$PWD/java" -Include "*.java" -Recurse | ForEach-Object {
-    &"$GOOGLE_JAVA_FORMAT" --replace $_.FullName
+section "Copyright"
+Write-Host "    update_copyright"
+bazel run //scripts:update_copyright
+
+# Run language formatters only if those files changed
+if (changedMatches '^java/') {
+    section "Java"
+    Write-Host "    google-java-format"
+    $GOOGLE_JAVA_FORMAT = (bazel run --run_under=echo //scripts:google-java-format)
+    Get-ChildItem -Path "$WORKSPACE_ROOT/java" -Include "*.java" -Recurse | ForEach-Object {
+        & "$GOOGLE_JAVA_FORMAT" --replace $_.FullName
+    }
 }
 
-section "Javascript"
-Write-Host "    javascript/selenium-webdriver - prettier" -ForegroundColor Green
-$NODE_WEBDRIVER = "$WORKSPACE_ROOT/javascript/selenium-webdriver"
-bazel run //javascript:prettier -- "$NODE_WEBDRIVER" --write "$NODE_WEBDRIVER/.prettierrc" --log-level=warn
+if (changedMatches '^javascript/selenium-webdriver/') {
+    section "JavaScript"
+    Write-Host "    prettier"
+    $NODE_WEBDRIVER = "$WORKSPACE_ROOT/javascript/selenium-webdriver"
+    bazel run //javascript:prettier -- "$NODE_WEBDRIVER" --write "$NODE_WEBDRIVER/.prettierrc" --log-level=warn
+}
 
-section "Ruby"
-Write-Host "    rubocop" -ForegroundColor Green
-bazel run //rb:lint
+if (changedMatches '^rb/|^rake_tasks/|^Rakefile') {
+    section "Ruby"
+    Write-Host "    rubocop -a"
+    if ($Lint) {
+        bazel run //rb:rubocop -- -a
+    } else {
+        bazel run //rb:rubocop -- -a --fail-level F
+    }
+}
 
-section "Rust"
-Write-Host "    rustfmt" -ForegroundColor Green
-bazel run @rules_rust//:rustfmt
+if (changedMatches '^rust/') {
+    section "Rust"
+    Write-Host "    rustfmt"
+    bazel run @rules_rust//:rustfmt
+}
 
-section "Python"
-Write-Host "    python - ruff" -ForegroundColor Green
-bazel run //py:ruff-format
+if (changedMatches '^py/') {
+    section "Python"
+    if ($Lint) {
+        Write-Host "    ruff check"
+        bazel run //py:ruff-check
+    }
+    Write-Host "    ruff format"
+    bazel run //py:ruff-format
+}
 
-section "Copyright"
-bazel run //scripts:update_copyright
+if (changedMatches '^dotnet/') {
+    section ".NET"
+    Write-Host "    dotnet format"
+    bazel run //dotnet:format -- style --severity warn
+    bazel run //dotnet:format -- whitespace
+}
+
+# Run shellcheck and actionlint when -Lint is passed
+if ($Lint) {
+    section "Shell/Actions"
+    Write-Host "    actionlint (with shellcheck)"
+    $SHELLCHECK = (bazel run --run_under=echo @multitool//tools/shellcheck)
+    bazel run @multitool//tools/actionlint:cwd -- -shellcheck "$SHELLCHECK"
+}
+
+# Check if formatting introduced new changes (comparing to baseline)
+$after = git status --porcelain
+if ($after -ne $baseline) {
+    Write-Host ""
+    Write-Host "Formatters modified files:" -ForegroundColor Red
+    git diff --name-only
+    exit 1
+}
+
+Write-Host "Format check passed." -ForegroundColor Green
diff --git a/scripts/format.sh b/scripts/format.sh
index a9a271126d71c..66a2183eaed94 100755
--- a/scripts/format.sh
+++ b/scripts/format.sh
@@ -1,39 +1,147 @@
 #!/usr/bin/env bash
-# Code formatter.
+# Code formatter - runs targeted formatters based on what changed from trunk.
+# Usage: format.sh [--all] [--pre-commit] [--pre-push] [--lint]
+#   (default)     Check all changes relative to trunk including uncommitted work
+#   --all         Format everything, skip change detection (previous behavior)
+#   --pre-commit  Only check staged changes
+#   --pre-push    Only check committed changes relative to trunk
+#   --lint        Also run linters before formatting
 set -eufo pipefail
 
-echo "Note: for more flexibility, use './go format' or './go dotnet:format' or './go format -dotnet', etc" >&2
-echo "" >&2
+run_lint=false
+format_all=false
+mode="default"
+for arg in "$@"; do
+    case "$arg" in
+        --lint) run_lint=true ;;
+        --all) format_all=true ;;
+
+        --pre-commit|--pre-push)
+            [[ "$mode" == "default" ]] || { echo "Cannot use both --pre-commit and --pre-push" >&2; exit 1; }
+            mode="${arg#--}"
+            ;;
+        *)
+            echo "Unknown option: $arg" >&2
+            echo "Usage: $0 [--all] [--pre-commit] [--pre-push] [--lint]" >&2
+            exit 1
+            ;;
+    esac
+done
 
 section() {
     echo "- $*" >&2
 }
 
+# Find what's changed compared to trunk (skip if --all)
+trunk_ref="$(git rev-parse --verify trunk 2>/dev/null || echo "")"
+
+if [[ "$format_all" == "false" && -n "$trunk_ref" ]]; then
+    base="$(git merge-base HEAD "$trunk_ref" 2>/dev/null || echo "")"
+    if [[ -n "$base" ]]; then
+        case "$mode" in
+            pre-commit)
+                changed="$(git diff --name-only --cached)"
+                ;;
+            pre-push)
+                changed="$(git diff --name-only "$base" HEAD)"
+                ;;
+            default)
+                committed="$(git diff --name-only "$base" HEAD)"
+                staged="$(git diff --name-only --cached)"
+                unstaged="$(git diff --name-only)"
+                untracked="$(git ls-files --others --exclude-standard)"
+                changed="$(printf '%s\n%s\n%s\n%s' "$committed" "$staged" "$unstaged" "$untracked" | sort -u)"
+                ;;
+        esac
+    else
+        format_all=true
+    fi
+elif [[ "$format_all" == "false" ]]; then
+    # No trunk ref found, format everything
+    format_all=true
+fi
+
+# Helper to check if a pattern matches changed files
+changed_matches() {
+    [[ "$format_all" == "true" ]] || echo "$changed" | grep -qE "$1"
+}
+
 WORKSPACE_ROOT="$(bazel info workspace)"
 
-GOOGLE_JAVA_FORMAT="$(bazel run --run_under=echo //scripts:google-java-format)"
+# Capture baseline to detect formatter-introduced changes (allows pre-existing uncommitted work)
+baseline="$(git status --porcelain)"
 
+# Always run buildifier and copyright
 section "Buildifier"
 echo "    buildifier" >&2
 bazel run //:buildifier
 
-section "Java"
-echo "    google-java-format" >&2
-find "$PWD/java" -type f -name '*.java' | xargs "$GOOGLE_JAVA_FORMAT" --replace
+section "Copyright"
+echo "    update_copyright" >&2
+bazel run //scripts:update_copyright
+
+# Run language formatters only if those files changed
+if changed_matches '^java/'; then
+    section "Java"
+    echo "    google-java-format" >&2
+    GOOGLE_JAVA_FORMAT="$(bazel run --run_under=echo //scripts:google-java-format)"
+    find "${WORKSPACE_ROOT}/java" -type f -name '*.java' -exec "$GOOGLE_JAVA_FORMAT" --replace {} +
+fi
+
+if changed_matches '^javascript/selenium-webdriver/'; then
+    section "JavaScript"
+    echo "    prettier" >&2
+    NODE_WEBDRIVER="${WORKSPACE_ROOT}/javascript/selenium-webdriver"
+    bazel run //javascript:prettier -- "${NODE_WEBDRIVER}" --write "${NODE_WEBDRIVER}/.prettierrc" --log-level=warn
+fi
+
+if changed_matches '^rb/|^rake_tasks/|^Rakefile'; then
+    section "Ruby"
+    echo "    rubocop -a" >&2
+    if [[ "$run_lint" == "true" ]]; then
+        bazel run //rb:rubocop -- -a
+    else
+        bazel run //rb:rubocop -- -a --fail-level F
+    fi
+fi
+
+if changed_matches '^rust/'; then
+    section "Rust"
+    echo "    rustfmt" >&2
+    bazel run @rules_rust//:rustfmt
+fi
+
+if changed_matches '^py/'; then
+    section "Python"
+    if [[ "$run_lint" == "true" ]]; then
+        echo "    ruff check" >&2
+        bazel run //py:ruff-check
+    fi
+    echo "    ruff format" >&2
+    bazel run //py:ruff-format
+fi
 
-section "Javascript"
-echo "    javascript/selenium-webdriver - prettier" >&2
-NODE_WEBDRIVER="${WORKSPACE_ROOT}/javascript/selenium-webdriver"
-bazel run //javascript:prettier -- "${NODE_WEBDRIVER}" --write "${NODE_WEBDRIVER}/.prettierrc" --log-level=warn
+if changed_matches '^dotnet/'; then
+    section ".NET"
+    echo "    dotnet format" >&2
+    bazel run //dotnet:format -- style --severity warn
+    bazel run //dotnet:format -- whitespace
+fi
 
-section "Ruby"
-echo "    rubocop" >&2
-bazel run //rb:rubocop -- -a --fail-level F
+# Run shellcheck and actionlint when --lint is passed
+if [[ "$run_lint" == "true" ]]; then
+    section "Shell/Actions"
+    echo "    actionlint (with shellcheck)" >&2
+    SHELLCHECK="$(bazel run --run_under=echo @multitool//tools/shellcheck)"
+    bazel run @multitool//tools/actionlint:cwd -- -shellcheck "$SHELLCHECK"
+fi
 
-section "Rust"
-echo "   rustfmt" >&2
-bazel run @rules_rust//:rustfmt
+# Check if formatting introduced new changes (comparing to baseline)
+if [[ "$(git status --porcelain)" != "$baseline" ]]; then
+    echo "" >&2
+    echo "Formatters modified files:" >&2
+    git diff --name-only >&2
+    exit 1
+fi
 
-section "Python"
-echo "    python - ruff" >&2
-bazel run //py:ruff-format
+echo "Format check passed." >&2