Adding in first pass with copilot at doing nightly builds.

cli/azd/docs/extensions/extension-framework.md

@@ -84,6 +84,26 @@ azd extension source add -n dev -t url -l "https://aka.ms/azd/extensions/registr
 
 Extensions installed from the dev registry are automatically promoted to the main registry when a newer version becomes available there. See the [Dev/Experimental Extension Registry](./extension-resolution-and-versioning.md#devexperimental-extension-registry) section for full details on stability expectations, submission guidelines, promotion behavior, and troubleshooting.
 
+#### Nightly Registry
+
+> [!CAUTION]
+> The nightly registry contains automated pre-release builds. They come with **no stability guarantees** and are **not covered by Azure support**. Expect breaking changes between nights.
+
+The nightly registry is an opt-in source containing daily pre-release builds of first-party extensions, published every night from the latest `main`. It lives on the `nightly-registry` branch of the [`azd` GitHub repo](https://github.com/Azure/azure-dev/blob/nightly-registry/cli/azd/extensions/registry.nightly.json) and is **not** configured by default.
+
+To opt-in for the nightly registry run the following command:
+
+```bash
+# Add a new extension source named 'nightly' to your `azd` configuration.
+azd extension source add -n nightly -t url \
+  -l "https://raw.githubusercontent.com/Azure/azure-dev/nightly-registry/cli/azd/extensions/registry.nightly.json"
+
+# Install the nightly build of an extension.
+azd extension install <extension-id> --source nightly
+```
+
+Nightly builds use a `<base>-nightly.<yyyyMMdd>.<buildId>` version format, so the matching stable release always supersedes them — running `azd extension upgrade` moves you back to the `azd` source automatically once that stable version ships. See [Choosing Stable vs. Nightly](./extension-resolution-and-versioning.md#choosing-stable-vs-nightly) for the full workflow, including how to switch channels and opt back out.
+
 #### `azd extension source list`
 
 Displays a list of installed extension sources.

cli/azd/docs/extensions/extension-resolution-and-versioning.md

@@ -547,6 +547,91 @@ If the dev registry URL is unreachable (network issue, DNS failure), operations
 azd extension source remove dev
 ```
 
+## Nightly Extension Registry
+
+The nightly registry is a separate, opt-in extension source that contains automated daily
+pre-release builds of first-party extensions. A scheduled pipeline builds each extension from
+the latest `main` and publishes a new prerelease version to the registry every night, so the
+nightly source always tracks the most recent in-development code.
+
+Like `dev`, the nightly source is **not** configured by default and is **not** a replacement for
+the stable `azd` registry. It is a parallel pre-release channel for early adopters who want to
+validate upcoming changes before they ship.
+
+| Property | Main Registry | Nightly Registry |
+|----------|---------------|------------------|
+| Source file | `cli/azd/extensions/registry.json` | `cli/azd/extensions/registry.nightly.json` |
+| Location | `https://aka.ms/azd/extensions/registry` | `https://raw.githubusercontent.com/Azure/azure-dev/nightly-registry/cli/azd/extensions/registry.nightly.json` |
+| Source name | `azd` (built-in default) | `nightly` (opt-in) |
+| Cadence | On stable release | Every night from `main` |
+| Stability | Stable releases | **Pre-release; may change or break nightly** |
+| Support | Covered by Azure support | **Not covered** |
+
+### Nightly Version Format
+
+Nightly builds are stamped by [`eng/scripts/Set-ExtensionVersionVariable.ps1`](../../../../eng/scripts/Set-ExtensionVersionVariable.ps1)
+into a semver-valid prerelease derived from the extension's `version.txt`:
+
+```text
+<base>-nightly.<yyyyMMdd>.<buildId>     e.g. 0.1.0-nightly.20260618.1234
+<base>.nightly.<yyyyMMdd>.<buildId>     (when <base> already has a prerelease label)
+```
+
+Because these are valid prereleases, semver precedence orders them the way you would expect:
+
+- A stable release always outranks any nightly built from the same base
+  (`0.1.0-nightly.20260618.1234` < `0.1.0`), so the stable version supersedes the nightly once it ships.
+- A later nightly outranks an earlier one, comparing the date and then the build id numerically
+  (`...20260618.1234` < `...20260618.5678` and `...20260618.9999` < `...20260619.1000`).
+
+### Choosing Stable vs. Nightly
+
+The two channels coexist; you decide per extension which one to install from.
+
+**Stay on stable (default):** Do nothing. Without the `nightly` source configured, every
+`azd extension install` and `azd extension upgrade` resolves against the official `azd` registry only.
+
+**Opt in to nightly:** Add the source, then install with `--source nightly`:
+
+```bash
+# Add the nightly source once.
+azd extension source add -n nightly -t url \
+  -l "https://raw.githubusercontent.com/Azure/azure-dev/nightly-registry/cli/azd/extensions/registry.nightly.json"
+
+# Install the nightly build of an extension.
+azd extension install <extension-id> --source nightly
+
+# Confirm both sources are configured.
+azd extension source list
+```
+
+When an extension exists in both `azd` and `nightly` and you omit `--source`, `azd` prompts you to
+choose (interactive) or errors with `"found in multiple sources"` (non-interactive). See
+[Troubleshooting Multi-Registry Scenarios](#troubleshooting-multi-registry-scenarios).
+
+**Switch back to stable:** The nightly source uses the same one-way promotion logic as the dev
+registry — see [Upgrade and Dev→Main Promotion](#upgrade-and-devmain-promotion). Because a stable
+release always outranks the nightly built from the same base, running `azd extension upgrade` moves
+you from `nightly` back to the `azd` source automatically once the corresponding stable version is
+published. The extension's stored source flips from `nightly` to `azd`, and it stays on stable
+from then on. To force the switch immediately (for example, to leave a nightly that is ahead of the
+current stable), reinstall explicitly:
+
+```bash
+# --force is required only when the stable version is lower than the installed nightly.
+azd extension install <extension-id> --source azd --force
+```
+
+**Leave nightly entirely:** Remove the source to stop pulling nightly builds:
+
+```bash
+azd extension source remove nightly
+```
+
+> [!CAUTION]
+> Nightly builds come with **no stability guarantees** and are **not covered by Azure support**.
+> Expect breaking changes between nights. Use a stable source for production workflows.
+
 ## Related Documentation
 
 | Document | Description |

cli/azd/pkg/extensions/update_checker_test.go

@@ -249,3 +249,139 @@ func Test_UpdateChecker_InvalidVersions(t *testing.T) {
 	require.NoError(t, err)
 	require.False(t, result.HasUpdate) // Should gracefully handle invalid version
 }
+
+// Test_UpdateChecker_NightlyVersions verifies that the update checker correctly
+// orders the nightly prerelease versions produced by Set-ExtensionVersionVariable.ps1.
+//
+// Nightly versions built from a base without an existing prerelease take the shape:
+//
+//	<base>-nightly.<yyyyMMdd>.<buildId>   e.g. 0.1.0-nightly.20260618.1234
+//
+// Several transitions must hold for the upgrade experience to work:
+//   - nightly -> stable: once the stable <base> ships it must supersede any nightly
+//     built from that base (semver: a release outranks its prereleases).
+//   - nightly -> next nightly: a later nightly (newer date, or same date with a
+//     higher build id) must supersede an earlier one, and an earlier nightly must
+//     never be offered as an update over a newer one.
+//   - nightly vs. milestone prereleases: for a clean base, semver orders
+//     alpha < beta < nightly < rc < stable, so a nightly supersedes alpha/beta of the
+//     same base but is itself superseded by rc and the final release. When the base
+//     already carries a prerelease label (e.g. 0.1.0-beta), the appended ".nightly"
+//     segment outranks every numbered beta of that base, so only the final release
+//     (or a higher base) supersedes it.
+func Test_UpdateChecker_NightlyVersions(t *testing.T) {
+	tests := []struct {
+		name       string
+		installed  string
+		available  []string
+		wantUpdate bool
+	}{
+		{
+			name:       "nightly to stable",
+			installed:  "0.1.0-nightly.20260618.1234",
+			available:  []string{"0.1.0-nightly.20260618.1234", "0.1.0"},
+			wantUpdate: true,
+		},
+		{
+			name:       "nightly to next nightly newer date",
+			installed:  "0.1.0-nightly.20260618.1234",
+			available:  []string{"0.1.0-nightly.20260618.1234", "0.1.0-nightly.20260619.1234"},
+			wantUpdate: true,
+		},
+		{
+			name:       "nightly to next nightly same date higher build",
+			installed:  "0.1.0-nightly.20260618.1234",
+			available:  []string{"0.1.0-nightly.20260618.1234", "0.1.0-nightly.20260618.5678"},
+			wantUpdate: true,
+		},
+		{
+			name:       "same nightly is not an update",
+			installed:  "0.1.0-nightly.20260618.1234",
+			available:  []string{"0.1.0-nightly.20260618.1234"},
+			wantUpdate: false,
+		},
+		{
+			name:       "older nightly is not offered over newer installed",
+			installed:  "0.1.0-nightly.20260619.1234",
+			available:  []string{"0.1.0-nightly.20260618.1234"},
+			wantUpdate: false,
+		},
+		{
+			// Clean base: nightly outranks beta of the same base (b < n).
+			name:       "nightly supersedes beta of same base",
+			installed:  "0.1.0-beta.1",
+			available:  []string{"0.1.0-beta.1", "0.1.0-nightly.20260618.1234"},
+			wantUpdate: true,
+		},
+		{
+			// Clean base: an older beta must never be offered over an installed nightly.
+			name:       "beta is not offered over installed nightly",
+			installed:  "0.1.0-nightly.20260618.1234",
+			available:  []string{"0.1.0-beta.5", "0.1.0-nightly.20260618.1234"},
+			wantUpdate: false,
+		},
+		{
+			// Clean base: rc outranks nightly of the same base (n < r).
+			name:       "rc supersedes nightly of same base",
+			installed:  "0.1.0-nightly.20260618.1234",
+			available:  []string{"0.1.0-nightly.20260618.1234", "0.1.0-rc.1"},
+			wantUpdate: true,
+		},
+		{
+			// Prerelease base gotcha: "0.1.0-beta.nightly..." outranks every numbered
+			// beta of that base because numeric identifiers lose to alphanumeric ones,
+			// so a later beta.N is NOT offered as an update.
+			name:       "numbered beta does not supersede beta-base nightly",
+			installed:  "0.1.0-beta.nightly.20260618.1234",
+			available:  []string{"0.1.0-beta.2", "0.1.0-beta.nightly.20260618.1234"},
+			wantUpdate: false,
+		},
+		{
+			// Prerelease base: only the final stable release supersedes the beta-base nightly.
+			name:       "stable supersedes beta-base nightly",
+			installed:  "0.1.0-beta.nightly.20260618.1234",
+			available:  []string{"0.1.0-beta.nightly.20260618.1234", "0.1.0"},
+			wantUpdate: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tempDir := t.TempDir()
+			t.Setenv("AZD_CONFIG_DIR", tempDir)
+
+			cacheManager, err := NewRegistryCacheManager()
+			require.NoError(t, err)
+
+			ctx := t.Context()
+			sourceName := "test-source"
+
+			versions := make([]ExtensionVersion, 0, len(tt.available))
+			for _, v := range tt.available {
+				versions = append(versions, ExtensionVersion{Version: v})
+			}
+
+			err = cacheManager.Set(ctx, sourceName, []*ExtensionMetadata{
+				{
+					Id:          "test.extension",
+					DisplayName: "Test Extension",
+					Versions:    versions,
+				},
+			})
+			require.NoError(t, err)
+
+			updateChecker := NewUpdateChecker(cacheManager)
+
+			extension := &Extension{
+				Id:          "test.extension",
+				DisplayName: "Test Extension",
+				Version:     tt.installed,
+				Source:      sourceName,
+			}
+
+			result, err := updateChecker.CheckForUpdate(ctx, extension)
+			require.NoError(t, err)
+			require.Equal(t, tt.wantUpdate, result.HasUpdate)
+		})
+	}
+}

docs/architecture/extension-framework.md

@@ -25,6 +25,7 @@ Extensions are discovered from registries — JSON manifests that list available
 
 - **Official registry:** `https://aka.ms/azd/extensions/registry` — Stable, signed, production-ready extensions vetted by the azd team.
 - **Dev registry:** `https://aka.ms/azd/extensions/registry/dev` — Experimental and pre-release extensions (unsigned builds, backed by `cli/azd/extensions/registry.dev.json`). Not configured by default; users opt in with `azd extension source add`.
+- **Nightly registry:** `https://raw.githubusercontent.com/Azure/azure-dev/nightly-registry/cli/azd/extensions/registry.nightly.json` — Automated daily pre-release builds of first-party extensions, published from the latest `main` and backed by `registry.nightly.json` on the `nightly-registry` branch. Not configured by default; users opt in with `azd extension source add -n nightly`. See [Choosing Stable vs. Nightly](../../cli/azd/docs/extensions/extension-resolution-and-versioning.md#choosing-stable-vs-nightly).
 - **Local sources:** File-based manifests for development
 
 The dev registry serves as a staging area for extensions before they graduate to the main registry. Extensions installed from the dev registry are automatically promoted to the main registry when a newer stable version becomes available there. See the [Extension Resolution and Versioning](../../cli/azd/docs/extensions/extension-resolution-and-versioning.md#devexperimental-extension-registry) guide for detailed criteria, stability expectations, and submission guidelines.