diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 000000000..cc1690152
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,33 @@
+# EditorConfig helps maintain consistent coding styles across editors
+# https://editorconfig.org
+
+root = true
+
+[*]
+indent_style = space
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[Makefile]
+indent_style = tab
+
+[*.Makefile]
+indent_style = tab
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.yml]
+indent_size = 2
+
+[*.yaml]
+indent_size = 2
+
+[*.json]
+indent_size = 2
+
+[*.toml]
+indent_size = 2
diff --git a/BUILDING.md b/BUILDING.md
index 8f80dd11d..19e014de0 100644
--- a/BUILDING.md
+++ b/BUILDING.md
@@ -189,3 +189,7 @@ Attach debugger to the XPC helpers using their launchd service labels:
 ## Pre-commit hook
 
 Run `make pre-commit` to install a pre-commit hook that ensures that your changes have correct formatting and license headers when you run `git commit`.
+
+## Troubleshooting
+
+If you run into build or runtime issues, check the [troubleshooting guide](TROUBLESHOOTING.md).
diff --git a/TROUBLESHOOTING.md b/TROUBLESHOOTING.md
new file mode 100644
index 000000000..57b684267
--- /dev/null
+++ b/TROUBLESHOOTING.md
@@ -0,0 +1,84 @@
+# Troubleshooting
+
+Known issues and workarounds. If your problem isn't listed here, check the [open issues](https://github.com/apple/container/issues) or file a new one.
+
+## Xcode or developer tools not found
+
+Build errors about missing compilers usually mean `xcode-select` is pointing at the Command Line Tools instead of a full Xcode installation:
+
+```bash
+xcode-select --print-path
+```
+
+If this returns `/Library/Developer/CommandLineTools`, switch it to Xcode:
+
+```bash
+sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer
+```
+
+On macOS 26 you'll want the latest Xcode:
+
+```bash
+sudo xcode-select --switch /Applications/Xcode-latest.app/Contents/Developer
+```
+
+## Wrong Swift version
+
+Swift 6.1+ is required. Check with `swift --version`.
+
+If you have multiple toolchains, SPM picks whatever `swift` is first in `$PATH`. You can also just set `DEVELOPER_DIR` before building:
+
+```bash
+DEVELOPER_DIR=/Applications/Xcode-latest.app/Contents/Developer make all
+```
+
+## Permission errors during install
+
+`make install` builds a `.pkg` and runs `sudo installer` to put binaries in `/usr/local`. If you don't have sudo or prefer a different location:
+
+```bash
+DEST_DIR=~/.local/ SUDO= make install
+```
+
+Don't forget to add `~/.local/bin` to your `$PATH` afterwards.
+
+See also [#1281](https://github.com/apple/container/issues/1281) for Homebrew-specific permission issues.
+
+## Network errors in integration tests
+
+Integration tests spin up VMs that need outbound network access. Corporate proxies can interfere — try excluding the local ranges:
+
+```bash
+export NO_PROXY="${NO_PROXY},192.168.0.0/16,fe80::/10"
+export no_proxy="${no_proxy},192.168.0.0/16,fe80::/10"
+make test integration
+```
+
+VPN can also cause issues, see [#1307](https://github.com/apple/container/issues/1307).
+
+## Kernel install hangs
+
+The `install-kernel` target starts the container system and waits for the kernel to finish installing. If it times out:
+
+1. Stop the system: `bin/container system stop`
+2. Give launchd a few seconds to clean up
+3. Try again with a longer timeout: `bin/container --debug system start --timeout 120`
+4. Run `make install-kernel` again
+
+Still stuck? Check for stale launchd services:
+
+```bash
+launchctl list | grep com.apple.container
+```
+
+You can clean these up with `scripts/ensure-container-stopped.sh -a`. See [#1280](https://github.com/apple/container/issues/1280) and [#1306](https://github.com/apple/container/issues/1306) for related issues.
+
+## vmnet fails under ~/Documents or ~/Desktop
+
+macOS 26 has a bug in the `vmnet` framework — network creation fails if the project or helper binaries sit under `~/Documents` or `~/Desktop`. Move the project somewhere else:
+
+```bash
+mv ~/Documents/container ~/projects/container
+```
+
+Alternatively, `make install` puts binaries in `/usr/local` which isn't affected.