diff --git a/README.md b/README.md
index 67c708a7..c0265f5d 100644
--- a/README.md
+++ b/README.md
@@ -39,31 +39,31 @@ Specifically, `_RegexParser` contains the parser for regular expression literals
 
 ### Branching scheme
 
-#### Development branch
-
 The `main` branch is the branch for day-to-day development. Generally, you should create PRs against this branch.
 
-#### Swift integration branches
-
 Branches whose name starts with `swift/` are Swift integration branches similar to those in [apple/llvm-project](https://github.com/apple/llvm-project). For each branch, dropping the `swift/` prefix is the corresponding branch in [apple/swift](https://github.com/apple/swift).
 
+This package's `main` branch will automatically integrate with Swift's `main` branch.
+
 | apple/swift branch  | apple/swift-experimental-string-processing branch     |
 | ------------------- | ----------------------------------------------------- |
-| main                | swift/main                                            |
+| main                | main                                                  |
 | release/5.7         | swift/release/5.7                                     |
 | ...                 | swift/...                                             |
 
 A pair of corresponding branches are expected to build successfully together and pass all tests.
 
-### Integration workflow
+### Running Package CI and full Swift CI
 
 To integrate the latest changes in apple/swift-experimental-string-processing to apple/swift, carefully follow the workflow: 
 
-- Create pull requests.
-  - Create a branch from a commit on `main` that you would like to integrate into `swift/main`.
-  - Create a pull request in apple/swift-experimental-string-processing from that branch to `swift/main`, e.g. "[Integration] main (<commit>) -> swift/main".
+- Run package CI
+  - In the pull request, trigger package CI using
+```
+@swift-ci please test
+```
+- Run full Swift CI for any changes to public or SPI interfaces or the `_RegexParser` module.
   - If apple/swift needs to be modified to work with the latest `main` in apple/swift-experimental-string-processing, create a pull request in apple/swift.  **Note:** Since CI in apple/swift-experimental-string-processing has not yet been set up to run full toolchain tests, you should create a PR in apple/swift regardless; if the integartion does not require changing apple/swift, create a dummy PR in apple/swift by changing the README and just not merge it in the end.
-- Trigger CI.
   - In the apple/swift-experimental-string-processing pull request, trigger CI using the following command (replacing `<PR NUMBER>` with the apple/swift pull request number, if any):
     ```
     apple/swift#<PR NUMBER> # use this line only if there is an corresponding apple/swift PR
@@ -75,7 +75,9 @@ To integrate the latest changes in apple/swift-experimental-string-processing to
     @swift-ci please test
     ```
 - Merge when approved.
-  - Merge the pull request in apple/swift-experimental-string-processing as a **merge commit**.
+  - Merge the PR in apple/swift-experimental-string-processing:
+    - as a squash or rebase if against main (the development branch).
+    - as a merge commit if it's a merge from main to swift/release/x.y.
   - Merge the pull request in apple/swift (if any).
 
 ### Development notes
diff --git a/Sources/_RegexParser/Regex/Parse/Parse.swift b/Sources/_RegexParser/Regex/Parse/Parse.swift
index 1fdadd8d..3ec852aa 100644
--- a/Sources/_RegexParser/Regex/Parse/Parse.swift
+++ b/Sources/_RegexParser/Regex/Parse/Parse.swift
@@ -523,6 +523,19 @@ extension Parser {
   mutating func parseCustomCharacterClass(
     _ start: Source.Located<CustomCC.Start>
   ) -> CustomCC {
+    // Excessively nested recursion is a common DOS attack, so limit
+    // our recursion.
+    context.parseDepth += 1
+    defer { context.parseDepth -= 1 }
+    guard context.parseDepth < context.maxParseDepth else {
+      self.errorAtCurrentPosition(.nestingTooDeep)
+
+      // This is not generally recoverable and further errors will be
+      // incorrect
+      diags.suppressFurtherDiagnostics = true
+      return .init(start, [], start.location)
+    }
+
     let alreadyInCCC = context.isInCustomCharacterClass
     context.isInCustomCharacterClass = true
     defer { context.isInCustomCharacterClass = alreadyInCCC }
diff --git a/Tests/RegexTests/ParseTests.swift b/Tests/RegexTests/ParseTests.swift
index cbb9e6b3..7f0dd811 100644
--- a/Tests/RegexTests/ParseTests.swift
+++ b/Tests/RegexTests/ParseTests.swift
@@ -3335,6 +3335,13 @@ extension RegexTests {
       + "a"
       + String(repeating: ")*", count: 500),
       .nestingTooDeep)
+
+    diagnosticTest(
+      String(repeating: "[", count: 500)
+      + "a"
+      + String(repeating: "]*", count: 500),
+      .nestingTooDeep)
+
   }
 
   func testDelimiterLexingErrors() {