Fallout-build · ChrisonSimtian · Jul 24, 2026 · Jul 24, 2026 · Jul 24, 2026 · dennisdoomen
diff --git a/build.ps1 b/build.ps1
@@ -22,7 +22,6 @@ $DotNetChannel = "STS"
 $env:DOTNET_CLI_TELEMETRY_OPTOUT = 1
 $env:DOTNET_NOLOGO = 1
 $env:DOTNET_ROLL_FORWARD = "Major"
-$env:FALLOUT_TELEMETRY_OPTOUT = 1
 
 ###########################################################################
 # EXECUTION

diff --git a/build.sh b/build.sh
@@ -18,7 +18,6 @@ DOTNET_CHANNEL="STS"
 export DOTNET_CLI_TELEMETRY_OPTOUT=1
 export DOTNET_NOLOGO=1
 export DOTNET_ROLL_FORWARD="Major"
-export FALLOUT_TELEMETRY_OPTOUT=1
 
 ###########################################################################
 # EXECUTION

diff --git a/build/Build.cs b/build/Build.cs
@@ -103,9 +103,6 @@ from framework in project.GetTargetFrameworks()
     [Parameter]
     public int TestDegreeOfParallelism { get; } = 1;
 
-    Configure<DotNetTestSettings> ITest.TestSettings => _ => _
-        .SetProcessEnvironmentVariable("FALLOUT_TELEMETRY_OPTOUT", bool.TrueString);
-
     Target ITest.Test => _ => _
         .Inherit<ITest>()
         .Partition(2);

diff --git a/build/_build.csproj b/build/_build.csproj
@@ -9,7 +9,6 @@
     <RootNamespace></RootNamespace>
     <NoWarn>CS0649;CS0169</NoWarn>
     <FalloutRootDirectory>.\..</FalloutRootDirectory>
-    <FalloutTelemetryVersion>1</FalloutTelemetryVersion>
     <ManagePackageVersionsCentrally>false</ManagePackageVersionsCentrally>
     <IsPackable>false</IsPackable>
   </PropertyGroup>

diff --git a/docs/01-getting-started/07-telemetry.md b/docs/01-getting-started/07-telemetry.md
diff --git a/docs/02-fundamentals/04-builds.md b/docs/02-fundamentals/04-builds.md
@@ -116,7 +116,7 @@ You can examine the status of targets by using any of the appropriate `ICollecti
 
 ## Build Events
 
-For implementing cross-cutting concerns, like telemetry and similar, you can hook into various build events:
+For implementing cross-cutting concerns, like logging or notifications, you can hook into various build events:
 
 ```csharp title="FalloutBuild.cs"
 abstract class FalloutBuild

diff --git a/docs/adr/0010-no-telemetry-collection.md b/docs/adr/0010-no-telemetry-collection.md
@@ -0,0 +1,72 @@
+# ADR-0010 — Fallout collects no telemetry
+
+- **Status:** Accepted
+- **Date:** 2026-07-24
+- **Deciders:** Fallout maintainers
+- **Relates to:** [#79](https://github.com/Fallout-build/Fallout/issues/79) (drop the dead `Microsoft.ApplicationInsights` dependency — subsumed by this decision), the removed `docs/01-getting-started/07-telemetry.md`.
+
+## Context
+
+NUKE shipped a telemetry subsystem (added upstream in 2021): a `[Telemetry]` build extension plus global-tool hooks that gathered anonymous usage data — OS/SDK versions, build shape (target/component counts), hashed repo/commit fingerprints — and sent it to an **Azure Application Insights** instance owned personally by the original maintainer, behind a first-run disclosure/consent flow and a `NUKE_TELEMETRY_OPTOUT` opt-out.
+
+Fallout inherited all of it, but it has been **inert since the fork**:
+
+- The Application Insights instrumentation key was matkoch-owned and cannot be reused, so `Microsoft.ApplicationInsights` was dropped from dependencies ([#79](https://github.com/Fallout-build/Fallout/issues/79)) and `TrackEvent` became a stub that discards its inputs.
+- The static constructor short-circuits before the consent flow ever runs — no disclosure prompt, no awareness cookie.
+- Nothing is collected and nothing is transmitted anywhere.
+
+The scaffolding was nonetheless **kept on purpose**, on the stated intent of wiring up a "Fallout-controlled backend later." That intent never acquired an owner, an endpoint, or a concrete plan — it was a standing *maybe*. Meanwhile the dormant code was a liability: it still assembled usage properties on the hot build path, it carried a re-enable comment that invited someone to flip it back on, and it kept a consumer-facing surface (`FALLOUT_TELEMETRY_OPTOUT`, `FalloutTelemetryVersion`, disclosure copy) alive for a feature that does nothing.
+
+## Decision
+
+**Fallout collects no telemetry — now or as a matter of standing policy for this fork — and the inherited subsystem is removed in full rather than left dormant.**
+
+- No usage data is gathered, and nothing phones home. A build framework people run in CI and on their own machines should not be a data-collection channel; for a hard-fork rebuilding trust, "we collect nothing" is a simpler and stronger promise than "we collect anonymized data you can opt out of."
+- Because there is nothing to opt out of, there is no opt-out. The `FALLOUT_TELEMETRY_OPTOUT` / legacy `NUKE_TELEMETRY_OPTOUT` env vars and the `FalloutTelemetryVersion` / `NukeTelemetryVersion` MSBuild property are removed along with the code that read them.
+- Dormant scaffolding is not kept "just in case." If Fallout ever wants usage insight, that is a fresh decision requiring its own ADR and an **opt-in**, fully-documented design with a named endpoint and owner — not the revival of this code.
+
+### Removed surface
+
+- The `Telemetry` subsystem (`Telemetry`, `Telemetry.Events`, `Telemetry.Properties`) and the `[Telemetry]` build extension.
+- All call sites: the `[Telemetry]` attribute on `FalloutBuild`, the config-generation hook, and the `setup` / `add-package` / `cake-convert` CLI events.
+- `FALLOUT_TELEMETRY_OPTOUT` / `NUKE_TELEMETRY_OPTOUT`, `FalloutTelemetryVersion` / `NukeTelemetryVersion`, the `FalloutTelemetryDocsUrl` constant, and the test-run opt-out plumbing.
+- The telemetry documentation page.
+- The `fallout migrate` tool now **strips** NUKE's telemetry knobs from migrated projects instead of renaming them to dead `Fallout*` equivalents.
+
+## Consequences
+
+### Positive
+
+- **Zero data collection**, and no privacy footgun — the "someone re-enables it incorrectly" path is gone because there is no code to re-enable.
+- Smaller surface: dead code, a dead dependency ([#79](https://github.com/Fallout-build/Fallout/issues/79)), a consent UX, and several consumer-facing knobs all removed.
+- Migrated NUKE projects come out clean — no telemetry-branded cruft carried across.
+
+### Negative
+
+- We forgo the aggregate usage insight telemetry could (in principle) have provided. Accepted: it was never actually flowing, and prioritization has done fine without it.
+- Reintroducing any metrics later means starting from a clean, opt-in design — deliberately more work than flipping a dormant switch. That friction is the point.
+
+### Neutral
+
+- Removing the opt-out env var and the MSBuild property is **not a breaking change**: both only ever gated a no-op, and an unset/unknown env var or MSBuild property is silently ignored — no consumer build errors. The `FALLOUT001` legacy-property warning simply stops firing for `NukeTelemetryVersion`.
+- `DOTNET_CLI_TELEMETRY_OPTOUT` (the **.NET SDK's** telemetry, unrelated to Fallout's) is left in place in the bootstrap scripts and generated CI — we still disable that.
+
+## Alternatives considered
+
+### A. Keep the scaffolding dormant, wire up a Fallout-owned endpoint later (the prior stance — rejected)
+
+This is what the code and docs described. **Rejected** because the "later" had no owner, endpoint, or timeline; the dormant code was a live liability (hot-path property assembly, a re-enable invitation, consumer-facing knobs for a no-op); and keeping consent/opt-out machinery for a feature that does nothing is confusing. A future decision to collect data should be made explicitly, not pre-wired.
+
+### B. Ship opt-in telemetry with a Fallout endpoint (rejected for now)
+
+Stand up an opt-in, Fallout-owned analytics pipeline. **Rejected** — no compelling need for a build framework, and it is out of scope for the rebrand/foundation work. Not foreclosed forever: it would require its own ADR superseding this one, and would have to be opt-in by construction.
+
+### C. Local-only anonymized stats (rejected)
+
+Collect stats to a local file for the user's own inspection, never transmitted. **Rejected** as scope creep with no demonstrated demand; nothing stops a consumer from building this themselves via the public build-event hooks.
+
+## References
+
+- [#79](https://github.com/Fallout-build/Fallout/issues/79) — drop the dead `Microsoft.ApplicationInsights` dependency (subsumed here)
+- [docs/agents/conventions.md](../agents/conventions.md) — "No telemetry" convention
+- [docs/migration/from-nuke.md](../migration/from-nuke.md) — telemetry knobs are stripped on migration
diff --git a/docs/adr/README.md b/docs/adr/README.md
@@ -40,3 +40,4 @@ If you change a decision, do NOT silently rewrite the old ADR — add a new one
 | [0004](0004-calendar-versioning-and-dual-pace-channels.md) | Calendar versioning + dual-pace channels (edge/stable) + experimental APIs | Accepted (§3 amended by 0007; channel ladder §2 superseded by 0008) |
 | [0007](0007-cut-release-branch-on-demand.md) | Cut `release/YYYY` on demand, not preemptively | Accepted |
 | [0008](0008-collapse-experimental-into-main.md) | Collapse `experimental` into `main`; `main` is the sole prerelease lane | Accepted |
+| [0010](0010-no-telemetry-collection.md) | Fallout collects no telemetry | Accepted |
diff --git a/docs/agents/conventions.md b/docs/agents/conventions.md
@@ -10,7 +10,7 @@ Three groups: conventions to respect, things never to do, and the tool-wrapper r
 - **Tool wrappers**: copy/paste from neighbours; cover full commands; use `<c>`, `<a>`, `<ul>`/`<ol>`, `<em>`, `<para/>` in `help`; don't write `secret: false` or `default: xxx`. See [Tool wrapper recipe](#tool-wrapper-recipe) below.
 - **Tests next to code, separate folder**: every `Foo` project under `src/` has a sibling `Foo.Tests` project under `tests/`. Mirror the namespace.
 - **No IDE-specific style files committed.** `.editorconfig` and `*.DotSettings` were removed during the takeover — relying on `dotnet format` defaults and review.
-- **Telemetry opt-out is set in test runs** (`FALLOUT_TELEMETRY_OPTOUT=true`). Keep it that way.
+- **No telemetry.** Fallout collects no usage data ([ADR-0010](../adr/0010-no-telemetry-collection.md)). The inherited NUKE telemetry subsystem, its opt-out env var, and the `FalloutTelemetryVersion` property were removed — don't reintroduce any of them.
 - **No per-file license headers.** The MIT notice lives in [`LICENSE`](https://github.com/Fallout-build/Fallout/blob/main/LICENSE) at the repo root, and NuGet packages declare MIT via `PackageLicenseExpression`. Per-file headers were stripped in v11 (one source of truth + the header URL would have rotted on the repo-org transfer). Vendored third-party code keeps its own copyright headers — don't touch those (e.g. files under `src/Persistence/Fallout.Persistence.Solution/` retain Microsoft's MIT notice).
 - **`[Experimental]` for opt-in unstable public APIs.** Not-yet-stable public surface is marked with `[Experimental("FALLOUT0xx")]` rather than held back or shipped silently. See [the `[Experimental]` convention](#experimental-for-opt-in-unstable-apis) below and the [diagnostic-ID registry](../experimental-apis.md).
 - **`[Obsolete]` with a `DiagnosticId` for deprecations.** Deprecated public surface carries `[Obsolete(..., DiagnosticId = "FALLOUTOBS0xx")]` so `TreatWarningsAsErrors` consumers can suppress a single deprecation. See [the `[Obsolete]` convention](#obsolete-for-deprecating-public-apis) below and the [diagnostic-ID registry](../obsolete_apis.md).

diff --git a/docs/dependencies.md b/docs/dependencies.md
@@ -64,12 +64,6 @@ Central package versions are pinned in `Directory.Packages.props`; this page lin
 |---|---|
 | `NuGet.Packaging` | Read .nupkg metadata. Used by `NuGetVersionResolver`, `ProjectUpdater`. |
 
-## Telemetry — currently inactive
-
-| Package | Purpose | Status |
-|---|---|---|
-| `Microsoft.ApplicationInsights` | Telemetry client | **Dead weight today.** `Telemetry.cs` short-circuits because `InstrumentationKey = ""` (the original NUKE key was matkoch-owned, we don't reuse). Removal tracked in [#79](https://github.com/Fallout-build/Fallout/issues/79). Re-introduce when we stand up a Fallout-owned endpoint. |
-
 ## Vendored source
 
 | Package | Source | Why vendored |

diff --git a/docs/migration/from-nuke.md b/docs/migration/from-nuke.md
@@ -66,8 +66,9 @@ If your build had previously worked against NUKE, it should now work against Fal
 | Fully-qualified type refs | `Nuke.Common.AbsolutePath` | `Fallout.Common.AbsolutePath` |
 | Base class name | `: NukeBuild` | `: FalloutBuild` |
 | Base interface name | `: INukeBuild` | `: IFalloutBuild` |
-| MSBuild properties in `_build.csproj` | `<NukeRootDirectory>`, `<NukeTelemetryVersion>` | `<FalloutRootDirectory>`, `<FalloutTelemetryVersion>` |
-| Bootstrap scripts | `dotnet nuke`, `NUKE_TELEMETRY_OPTOUT`, `.nuke/temp` | `dotnet fallout`, `FALLOUT_TELEMETRY_OPTOUT`, `.fallout/temp` |
+| MSBuild properties in `_build.csproj` | `<NukeRootDirectory>` | `<FalloutRootDirectory>` |
+| Bootstrap scripts | `dotnet nuke`, `.nuke/temp` | `dotnet fallout`, `.fallout/temp` |
+| Telemetry knobs (removed) | `<NukeTelemetryVersion>`, `NUKE_TELEMETRY_OPTOUT` | *dropped* — Fallout has no telemetry ([ADR-0010](../adr/0010-no-telemetry-collection.md)); `fallout migrate` strips them |
 | Config directory | `.nuke/` | `.fallout/` (contents preserved) |
 
 The 1:1 namespace prefix swap is the only structural change. Type names (other than `NukeBuild` / `INukeBuild`) keep their identifiers — `[Parameter]`, `[Solution]`, `[GitHubActions]`, `Solution`, `GitRepository`, etc. all stay the same.
@@ -103,9 +104,9 @@ You'll need a GitHub Personal Access Token with the `read:packages` scope. Then
 
 If you'd rather drive the rewrite by hand (small projects, or you want to learn what the tool does):
 
-1. Edit `build/_build.csproj`. For every `<PackageReference Include="Nuke.X" ...>`, change `Nuke.X` → `Fallout.X`. Same for `<NukeRootDirectory>` / `<NukeTelemetryVersion>` MSBuild properties.
+1. Edit `build/_build.csproj`. For every `<PackageReference Include="Nuke.X" ...>`, change `Nuke.X` → `Fallout.X`. Same for the `<NukeRootDirectory>` MSBuild property. Delete any `<NukeTelemetryVersion>` — Fallout has no telemetry ([ADR-0010](../adr/0010-no-telemetry-collection.md)).
 2. In every `.cs` file under `build/`, change `using Nuke.X.Y;` to `using Fallout.X.Y;`. Replace `: NukeBuild` with `: FalloutBuild` and `INukeBuild` with `IFalloutBuild`.
-3. In `build.ps1`, `build.sh`, `build.cmd`: `dotnet nuke` → `dotnet fallout`, `NUKE_TELEMETRY_OPTOUT` → `FALLOUT_TELEMETRY_OPTOUT`, `.nuke/temp` → `.fallout/temp`.
+3. In `build.ps1`, `build.sh`, `build.cmd`: `dotnet nuke` → `dotnet fallout`, `.nuke/temp` → `.fallout/temp`. Delete any `NUKE_TELEMETRY_OPTOUT` line (no telemetry to opt out of).
 4. Rename the `.nuke/` directory to `.fallout/`. Contents are preserved.
 5. Run `./build.ps1` to verify.