diff --git a/.github/workflows/performance-contracts.yml b/.github/workflows/performance-contracts.yml
new file mode 100644
index 00000000000..dd4c17c4d9b
--- /dev/null
+++ b/.github/workflows/performance-contracts.yml
@@ -0,0 +1,48 @@
+name: Performance contracts
+
+on:
+  schedule:
+    - cron: '15 9 * * *'
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - '.github/workflows/performance-contracts.yml'
+      - 'config/vitest.performance.config.ts'
+      - 'config/oxlint-performance-audit.json'
+      - 'config/oxlint-plugins/*performance.mjs'
+      - 'config/scripts/*performance-plugin.test.mjs'
+
+permissions:
+  contents: read
+
+concurrency:
+  group: performance-contracts-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  contracts:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+      - uses: ./.github/actions/install-node-dependencies
+      - name: Run operation-count and retention contracts
+        run: pnpm test:perf:contracts --reporter=default --reporter=json --outputFile=performance-contracts.json
+      - name: Audit production performance patterns
+        if: always()
+        shell: bash
+        run: pnpm --silent audit:perf > performance-audit.json
+      - uses: actions/upload-artifact@v7
+        if: always()
+        with:
+          name: performance-contracts-${{ matrix.os }}
+          path: |
+            performance-contracts.json
+            performance-audit.json
+          if-no-files-found: error
diff --git a/.oxlintrc.json b/.oxlintrc.json
index 77a7e43e807..03cc659f494 100644
--- a/.oxlintrc.json
+++ b/.oxlintrc.json
@@ -2,6 +2,10 @@
   "$schema": "./node_modules/oxlint/configuration_schema.json",
   "plugins": ["typescript", "react", "react-hooks", "react-perf", "unicorn"],
   "jsPlugins": [
+    {
+      "name": "sort-comparator-performance",
+      "specifier": "./config/oxlint-plugins/sort-comparator-performance.mjs"
+    },
     {
       "name": "mobile-pairing",
       "specifier": "./config/oxlint-plugins/mobile-pairing-qrcode-import.mjs"
@@ -23,6 +27,7 @@
     "correctness": "error"
   },
   "rules": {
+    "sort-comparator-performance/no-repeated-collator": "warn",
     "app-store-performance/require-selector": "error",
     "app-store-performance/no-identity-selector": "error",
     "app-store-performance/no-fresh-selector-result": "error",
diff --git a/config/oxlint-performance-audit.json b/config/oxlint-performance-audit.json
new file mode 100644
index 00000000000..2912c6b8e03
--- /dev/null
+++ b/config/oxlint-performance-audit.json
@@ -0,0 +1,35 @@
+{
+  "$schema": "../node_modules/oxlint/configuration_schema.json",
+  "plugins": [],
+  "categories": {
+    "correctness": "off",
+    "suspicious": "off",
+    "pedantic": "off",
+    "perf": "off",
+    "style": "off",
+    "restriction": "off",
+    "nursery": "off"
+  },
+  "jsPlugins": [
+    {
+      "name": "app-store-performance",
+      "specifier": "../config/oxlint-plugins/app-store-performance.mjs"
+    },
+    {
+      "name": "quadratic-buffer-concat",
+      "specifier": "../config/oxlint-plugins/quadratic-buffer-concat.mjs"
+    },
+    {
+      "name": "sort-comparator-performance",
+      "specifier": "../config/oxlint-plugins/sort-comparator-performance.mjs"
+    }
+  ],
+  "rules": {
+    "app-store-performance/require-selector": "warn",
+    "app-store-performance/no-identity-selector": "warn",
+    "app-store-performance/no-fresh-selector-result": "warn",
+    "quadratic-buffer-concat/no-loop-carried-concat": "warn",
+    "sort-comparator-performance/no-repeated-collator": "warn"
+  },
+  "ignorePatterns": ["**/node_modules", "**/dist", "**/out", "**/*.test.*", "**/*.spec.*"]
+}
diff --git a/config/oxlint-plugins/sort-comparator-performance.mjs b/config/oxlint-plugins/sort-comparator-performance.mjs
new file mode 100644
index 00000000000..cd3444cf65f
--- /dev/null
+++ b/config/oxlint-plugins/sort-comparator-performance.mjs
@@ -0,0 +1,60 @@
+const FUNCTION_TYPES = new Set([
+  'ArrowFunctionExpression',
+  'FunctionExpression',
+  'FunctionDeclaration'
+])
+
+function propertyName(node) {
+  if (node?.type !== 'MemberExpression') {
+    return null
+  }
+  if (!node.computed && node.property.type === 'Identifier') {
+    return node.property.name
+  }
+  return node.property.type === 'Literal' ? node.property.value : null
+}
+
+function isInlineSortComparator(node) {
+  for (let parent = node.parent; parent; parent = parent.parent) {
+    if (!FUNCTION_TYPES.has(parent.type)) {
+      continue
+    }
+    const call = parent.parent
+    return (
+      call?.type === 'CallExpression' &&
+      call.arguments[0] === parent &&
+      ['sort', 'toSorted'].includes(propertyName(call.callee))
+    )
+  }
+  return false
+}
+
+function isCollatorConstruction(node) {
+  return (
+    node.callee?.object?.type === 'Identifier' &&
+    node.callee.object.name === 'Intl' &&
+    propertyName(node.callee) === 'Collator'
+  )
+}
+
+function createRule(context) {
+  function inspect(node) {
+    const optionedComparison =
+      node.type === 'CallExpression' &&
+      propertyName(node.callee) === 'localeCompare' &&
+      node.arguments.length >= 3
+    if ((optionedComparison || isCollatorConstruction(node)) && isInlineSortComparator(node)) {
+      context.report({
+        node,
+        message:
+          'Create one Intl.Collator before sorting and reuse its compare method; resolving collation options inside the comparator repeats setup for every comparison. Preserve the locale, options, and tie-breaker.'
+      })
+    }
+  }
+  return { CallExpression: inspect, NewExpression: inspect }
+}
+
+export default {
+  meta: { name: 'sort-comparator-performance' },
+  rules: { 'no-repeated-collator': { create: createRule } }
+}
diff --git a/config/performance-audit.md b/config/performance-audit.md
new file mode 100644
index 00000000000..d0187f77486
--- /dev/null
+++ b/config/performance-audit.md
@@ -0,0 +1,37 @@
+# Performance regression checks
+
+`pnpm --silent audit:perf > performance-audit.json` scans production `src/` with
+the existing app-store and buffer-concatenation rules plus the sort-comparator
+rule. Warnings are advisory in this full inventory; tool/parser failures fail.
+New warning findings on changed lines fail `pnpm check:code-quality:changed`.
+Tests, generated files, `mobile/` and `cloud/` are outside this source audit.
+
+The sort rule detects optioned `localeCompare` and `Intl.Collator` construction
+inside inline `sort`/`toSorted` callbacks. Construct one collator outside the
+callback, preserving locale, options and tie-breakers. If the locale changes at
+runtime, reconstruct at the next sort or key the cache by locale. Bare comparisons
+and standalone equality checks are allowed. There is no autofix or interprocedural
+analysis: named comparators, aliases, custom methods and deferred callbacks need
+manual review. A warning identifies repeated setup, not proof of visible lag.
+
+`pnpm test:perf:contracts` runs the explicit selection in
+`vitest.performance.config.ts`: SQLite statement reuse and schema parity, relay
+filesystem concurrency, tokenizer rejection, highlighting cache, queued
+cancellation, terminal backing-memory retention and detector fixtures. Missing
+listed files fail configuration loading. Tests run serially, without retries,
+and inherit the full suite's setup and forced-GC support. This makes existing
+regression coverage easy to run and attribute; it does not create new workload
+coverage by itself.
+
+`.github/workflows/performance-contracts.yml` runs daily and manually on Linux,
+macOS and Windows, and on PRs changing this tooling. It uploads JSON test results
+and the source inventory. Its schedule starts after merge. Run the existing
+`test:e2e:terminal-perf:scale:report` for rendered typing/frame budgets and
+`test:e2e:ssh-docker-perf` for real transport behavior. Relay unit tests do not
+measure SSH RTT, WSL scheduling or a packaged Electron renderer.
+
+To extend coverage, select a production-path regression with an operation-count,
+identity, queue-admission or retained-memory oracle. Confirm it fails with the
+old behavior. Use controlled, counterbalanced benchmark samples for timings;
+avoid new machine-dependent millisecond gates in the normal unit suite. A green
+source scan and these contracts cannot establish that the whole app is fast.
diff --git a/config/scripts/sort-comparator-performance-plugin.test.mjs b/config/scripts/sort-comparator-performance-plugin.test.mjs
new file mode 100644
index 00000000000..a9319c6238d
--- /dev/null
+++ b/config/scripts/sort-comparator-performance-plugin.test.mjs
@@ -0,0 +1,45 @@
+import path from 'node:path'
+import { describe, expect, it } from 'vitest'
+import { runOxlintPluginOnSource } from './oxlint-plugin-test-runner.mjs'
+
+function lint(source) {
+  return runOxlintPluginOnSource({
+    pluginName: 'sort-comparator-performance',
+    pluginPath: path.resolve('config/oxlint-plugins/sort-comparator-performance.mjs'),
+    rules: { 'sort-comparator-performance/no-repeated-collator': 'warn' },
+    source
+  })
+}
+
+describe('sort comparator performance', () => {
+  it('reports repeated collation setup in inline sort and toSorted callbacks', () => {
+    const findings = lint(`
+      rows.sort((a, b) => a.name.localeCompare(b.name, locale, { sensitivity: 'base' }))
+      rows.toSorted(function (a, b) { return new Intl.Collator('sv').compare(a, b) })
+      rows['sort']((a, b) => Intl.Collator('en', { numeric: true }).compare(a, b))
+      rows.sort((a, b) => a['localeCompare'](b, undefined, options))
+    `)
+    expect(findings).toHaveLength(4)
+    expect(
+      findings.every(
+        (finding) => finding.code === 'sort-comparator-performance(no-repeated-collator)'
+      )
+    ).toBe(true)
+  })
+
+  it('allows one collator per sort, bare comparisons, and unrelated callbacks', () => {
+    expect(
+      lint(`
+      const collator = new Intl.Collator(locale, options)
+      rows.sort((a, b) => collator.compare(a.name, b.name) || a.id.localeCompare(b.id))
+      rows.toSorted(collator.compare)
+      const equal = a.localeCompare(b, undefined, { sensitivity: 'accent' }) === 0
+      rows.map(a => new Intl.Collator(a.locale))
+      rows.sort((a, b) => {
+        function deferred() { return new Intl.Collator(locale) }
+        return a - b
+      })
+    `)
+    ).toEqual([])
+  })
+})
diff --git a/config/vitest.performance.config.ts b/config/vitest.performance.config.ts
new file mode 100644
index 00000000000..7682b7b9698
--- /dev/null
+++ b/config/vitest.performance.config.ts
@@ -0,0 +1,33 @@
+import { existsSync } from 'node:fs'
+import { resolve } from 'node:path'
+import { defineConfig } from 'vitest/config'
+import baseConfig from './vitest.config'
+
+const contracts = [
+  'src/main/sqlite/sync-database.test.ts',
+  'src/main/runtime/orchestration/db/row-column-lists.test.ts',
+  'src/relay/fs-path-metadata-symlink-concurrency.test.ts',
+  'src/renderer/src/components/editor/rich-markdown-list-tokenizers.test.ts',
+  'src/renderer/src/components/editor/rich-markdown-lowlight-cache.test.ts',
+  'src/renderer/src/components/terminal-pane/agent-completion-coordinator-queued-inspection-disposal.test.ts',
+  'src/renderer/src/lib/pane-manager/pane-terminal-output-scheduler-queue-retention.test.ts',
+  'config/scripts/app-store-performance-plugin.test.mjs',
+  'config/scripts/quadratic-buffer-concat-plugin.test.mjs',
+  'config/scripts/sort-comparator-performance-plugin.test.mjs'
+]
+
+for (const contract of contracts) {
+  if (!existsSync(resolve(contract))) {
+    throw new Error(`Missing performance contract: ${contract}`)
+  }
+}
+
+export default defineConfig({
+  ...baseConfig,
+  test: {
+    ...baseConfig.test,
+    include: contracts,
+    fileParallelism: false,
+    retry: 0
+  }
+})
diff --git a/package.json b/package.json
index 21636f94e9c..7b27dffc8c7 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,8 @@
   },
   "main": "./out/main/index.js",
   "scripts": {
+    "audit:perf": "oxlint --config config/oxlint-performance-audit.json --format json src",
+    "test:perf:contracts": "vitest run --config config/vitest.performance.config.ts",
     "format": "oxfmt --write .",
     "lint": "oxlint && pnpm run audit:code-quality:native && pnpm run audit:code-quality:type-aware && pnpm run check:reliability-gates && pnpm run check:max-lines-ratchet && pnpm run check:ts-nocheck-ratchet && pnpm run check:runtime-electron-ratchet && pnpm run verify:bundled-skill-guides && pnpm run verify:skill-bundle-manifest && pnpm run verify:localization-catalog && pnpm run verify:localization-runtime-catalog && pnpm run verify:localization-extraction && pnpm run verify:localization-coverage",
     "audit:code-quality": "pnpm run audit:code-quality:native && pnpm run audit:code-quality:type-aware && pnpm run audit:react-doctor",
@@ -144,7 +146,6 @@
     "bench:agent-inspection-cadence": "node config/scripts/agent-inspection-cadence-batching-benchmark.mjs",
     "bench:renderer-quadratic-scans": "node config/scripts/renderer-quadratic-scan-benchmark.mjs",
     "bench:session-write-hot-path": "node config/scripts/session-write-hot-path-benchmark.mjs",
-    "bench:terminal-partial-escape-tail": "node --disable-warning=MODULE_TYPELESS_PACKAGE_JSON config/scripts/terminal-partial-escape-tail-benchmark.mjs",
     "bench:terminal-partial-escape-tail": "node config/scripts/terminal-partial-escape-tail-benchmark.mjs",
     "bench:worktree-refresh-churn": "node --disable-warning=MODULE_TYPELESS_PACKAGE_JSON config/scripts/worktree-refresh-churn-benchmark.mjs",
     "bench:multi-workspace-typing": "pnpm run ensure:electron-runtime && node config/scripts/run-multi-workspace-typing-bench.mjs",