From 29d527af562f0a3b739ed72c6a1fd92432bbac90 Mon Sep 17 00:00:00 2001
From: Zach Vorhies <zachvorhies@protonmail.com>
Date: Tue, 29 Sep 2026 00:32:16 -0700
Subject: [PATCH 1/4] perf(test): one integration-test binary each for core,
 cli, packages, library-select

14 top-level tests/*.rs files become modules of tests/it/main.rs in their
crates (FastLED/fbuild#1577, zackees/ci.yml RUST-005). Test counts are
unchanged (the one gap in fbuild-core is a #[cfg(windows)] test).
Dylint allowlists, boundary ledgers and --test references follow the
move. Workspace test binaries 47 -> 37.

Local cargo test --no-run for the four crates after a clean, alternating
runs: 18.3-20.2s vs 20.9-21.4s before.
---
 ci/platform_boundary_ledger.tsv                        |  4 ++--
 ci/platform_boundary_research.tsv                      |  4 ++--
 crates/fbuild-cli/tests/it/README.md                   |  7 +++++++
 crates/fbuild-cli/tests/{ => it}/ci_command.rs         |  0
 .../fbuild-cli/tests/{ => it}/daemon_crash_recovery.rs |  0
 crates/fbuild-cli/tests/{ => it}/lib_select.rs         |  0
 crates/fbuild-cli/tests/it/main.rs                     |  8 ++++++++
 crates/fbuild-cli/tests/{ => it}/test_emu_exit_code.rs |  0
 crates/fbuild-core/tests/it/README.md                  |  7 +++++++
 crates/fbuild-core/tests/{ => it}/cpu_profiling.rs     |  0
 crates/fbuild-core/tests/{ => it}/dep_identity.rs      |  0
 crates/fbuild-core/tests/it/main.rs                    | 10 ++++++++++
 .../tests/{ => it}/platformio_avr_resolution.rs        |  0
 .../tests/{ => it}/platformio_ch32v_resolution.rs      |  0
 .../tests/{ => it}/platformio_esp8266_resolution.rs    |  0
 .../tests/{ => it}/platformio_package_resolution.rs    |  0
 crates/fbuild-library-select/tests/it/README.md        |  7 +++++++
 crates/fbuild-library-select/tests/it/main.rs          |  6 ++++++
 .../fbuild-library-select/tests/{ => it}/perf_tdd.rs   |  0
 .../tests/{ => it}/teensy41_ldf_diag.rs                |  2 +-
 crates/fbuild-packages/tests/it/README.md              |  7 +++++++
 .../tests/{ => it}/disk_cache_schema_migration.rs      |  0
 crates/fbuild-packages/tests/{ => it}/lnk_e2e.rs       |  0
 crates/fbuild-packages/tests/it/main.rs                |  6 ++++++
 dylints/ban_raw_path_prefix_compare/src/lib.rs         |  2 +-
 dylints/ban_raw_subprocess/src/lib.rs                  |  2 +-
 dylints/ban_std_pathbuf/src/allowlist.txt              |  6 +++---
 dylints/enforce_platform_boundary/src/baseline.txt     |  4 ++--
 28 files changed, 70 insertions(+), 12 deletions(-)
 create mode 100644 crates/fbuild-cli/tests/it/README.md
 rename crates/fbuild-cli/tests/{ => it}/ci_command.rs (100%)
 rename crates/fbuild-cli/tests/{ => it}/daemon_crash_recovery.rs (100%)
 rename crates/fbuild-cli/tests/{ => it}/lib_select.rs (100%)
 create mode 100644 crates/fbuild-cli/tests/it/main.rs
 rename crates/fbuild-cli/tests/{ => it}/test_emu_exit_code.rs (100%)
 create mode 100644 crates/fbuild-core/tests/it/README.md
 rename crates/fbuild-core/tests/{ => it}/cpu_profiling.rs (100%)
 rename crates/fbuild-core/tests/{ => it}/dep_identity.rs (100%)
 create mode 100644 crates/fbuild-core/tests/it/main.rs
 rename crates/fbuild-core/tests/{ => it}/platformio_avr_resolution.rs (100%)
 rename crates/fbuild-core/tests/{ => it}/platformio_ch32v_resolution.rs (100%)
 rename crates/fbuild-core/tests/{ => it}/platformio_esp8266_resolution.rs (100%)
 rename crates/fbuild-core/tests/{ => it}/platformio_package_resolution.rs (100%)
 create mode 100644 crates/fbuild-library-select/tests/it/README.md
 create mode 100644 crates/fbuild-library-select/tests/it/main.rs
 rename crates/fbuild-library-select/tests/{ => it}/perf_tdd.rs (100%)
 rename crates/fbuild-library-select/tests/{ => it}/teensy41_ldf_diag.rs (98%)
 create mode 100644 crates/fbuild-packages/tests/it/README.md
 rename crates/fbuild-packages/tests/{ => it}/disk_cache_schema_migration.rs (100%)
 rename crates/fbuild-packages/tests/{ => it}/lnk_e2e.rs (100%)
 create mode 100644 crates/fbuild-packages/tests/it/main.rs

diff --git a/ci/platform_boundary_ledger.tsv b/ci/platform_boundary_ledger.tsv
index f47962701..d69b2cc3a 100644
--- a/ci/platform_boundary_ledger.tsv
+++ b/ci/platform_boundary_ledger.tsv
@@ -1,6 +1,6 @@
 path	kind	normalized	ordinal	capability	classification
-crates/fbuild-core/tests/platformio_package_resolution.rs	attr_cfg	#[cfg(windows)]	0	host	host_mechanic
-crates/fbuild-core/tests/platformio_package_resolution.rs	attr_cfg	#[cfg(windows)]	1	host	host_mechanic
+crates/fbuild-core/tests/it/platformio_package_resolution.rs	attr_cfg	#[cfg(windows)]	0	host	host_mechanic
+crates/fbuild-core/tests/it/platformio_package_resolution.rs	attr_cfg	#[cfg(windows)]	1	host	host_mechanic
 crates/fbuild-daemon/Cargo.toml	native_dependency	libc	0	process	host_mechanic
 crates/fbuild-daemon/src/handlers/emulator/tests_npm_cache.rs	attr_cfg	#[cfg(windows)]	0	host_executable	host_artifact_policy
 crates/fbuild-daemon/src/handlers/emulator/tests_process.rs	attr_cfg	#[cfg(not(windows))]	0	host_executable	host_artifact_policy
diff --git a/ci/platform_boundary_research.tsv b/ci/platform_boundary_research.tsv
index 801f40bfd..e9828c4d3 100644
--- a/ci/platform_boundary_research.tsv
+++ b/ci/platform_boundary_research.tsv
@@ -71,8 +71,8 @@ crates/fbuild-core/src/platform/windows/usb_pnp.rs	32	native_path	windows_sys::
 crates/fbuild-core/src/platform/windows/usb_pnp.rs	35	native_path	windows_sys::	process	host_mechanic
 crates/fbuild-core/src/platform/windows/usb_pnp.rs	39	native_path	windows_sys::	process	host_mechanic
 crates/fbuild-core/src/platform/windows/usb_pnp.rs	40	native_path	windows_sys::	process	host_mechanic
-crates/fbuild-core/tests/platformio_package_resolution.rs	5	attr_cfg	#[cfg(windows)]	host	host_mechanic
-crates/fbuild-core/tests/platformio_package_resolution.rs	107	attr_cfg	#[cfg(windows)]	host	host_mechanic
+crates/fbuild-core/tests/it/platformio_package_resolution.rs	5	attr_cfg	#[cfg(windows)]	host	host_mechanic
+crates/fbuild-core/tests/it/platformio_package_resolution.rs	107	attr_cfg	#[cfg(windows)]	host	host_mechanic
 crates/fbuild-daemon/Cargo.toml	68	native_dependency	libc	process	host_mechanic
 crates/fbuild-daemon/src/handlers/emulator/tests_npm_cache.rs	146	attr_cfg	#[cfg(windows)]	host_executable	host_artifact_policy
 crates/fbuild-daemon/src/handlers/emulator/tests_process.rs	9	attr_cfg	#[cfg(windows)]	host_executable	host_artifact_policy
diff --git a/crates/fbuild-cli/tests/it/README.md b/crates/fbuild-cli/tests/it/README.md
new file mode 100644
index 000000000..45624633f
--- /dev/null
+++ b/crates/fbuild-cli/tests/it/README.md
@@ -0,0 +1,7 @@
+# fbuild-cli integration tests
+
+All integration tests for `fbuild-cli` compile into this single `it` binary; each
+`*.rs` here is a module listed in `main.rs`. Add new integration tests
+as a module here, not as a new top-level `tests/*.rs` file: every top-level
+file is a separate binary that re-links the crate's whole dependency graph
+(zackees/ci.yml RUST-005).
diff --git a/crates/fbuild-cli/tests/ci_command.rs b/crates/fbuild-cli/tests/it/ci_command.rs
similarity index 100%
rename from crates/fbuild-cli/tests/ci_command.rs
rename to crates/fbuild-cli/tests/it/ci_command.rs
diff --git a/crates/fbuild-cli/tests/daemon_crash_recovery.rs b/crates/fbuild-cli/tests/it/daemon_crash_recovery.rs
similarity index 100%
rename from crates/fbuild-cli/tests/daemon_crash_recovery.rs
rename to crates/fbuild-cli/tests/it/daemon_crash_recovery.rs
diff --git a/crates/fbuild-cli/tests/lib_select.rs b/crates/fbuild-cli/tests/it/lib_select.rs
similarity index 100%
rename from crates/fbuild-cli/tests/lib_select.rs
rename to crates/fbuild-cli/tests/it/lib_select.rs
diff --git a/crates/fbuild-cli/tests/it/main.rs b/crates/fbuild-cli/tests/it/main.rs
new file mode 100644
index 000000000..511f5598e
--- /dev/null
+++ b/crates/fbuild-cli/tests/it/main.rs
@@ -0,0 +1,8 @@
+//! One integration-test binary for this crate (zackees/ci.yml RUST-005):
+//! each top-level `tests/*.rs` file links the crate's whole dependency
+//! graph separately, so these modules share one link instead.
+
+mod ci_command;
+mod daemon_crash_recovery;
+mod lib_select;
+mod test_emu_exit_code;
diff --git a/crates/fbuild-cli/tests/test_emu_exit_code.rs b/crates/fbuild-cli/tests/it/test_emu_exit_code.rs
similarity index 100%
rename from crates/fbuild-cli/tests/test_emu_exit_code.rs
rename to crates/fbuild-cli/tests/it/test_emu_exit_code.rs
diff --git a/crates/fbuild-core/tests/it/README.md b/crates/fbuild-core/tests/it/README.md
new file mode 100644
index 000000000..b9c7ba122
--- /dev/null
+++ b/crates/fbuild-core/tests/it/README.md
@@ -0,0 +1,7 @@
+# fbuild-core integration tests
+
+All integration tests for `fbuild-core` compile into this single `it` binary; each
+`*.rs` here is a module listed in `main.rs`. Add new integration tests
+as a module here, not as a new top-level `tests/*.rs` file: every top-level
+file is a separate binary that re-links the crate's whole dependency graph
+(zackees/ci.yml RUST-005).
diff --git a/crates/fbuild-core/tests/cpu_profiling.rs b/crates/fbuild-core/tests/it/cpu_profiling.rs
similarity index 100%
rename from crates/fbuild-core/tests/cpu_profiling.rs
rename to crates/fbuild-core/tests/it/cpu_profiling.rs
diff --git a/crates/fbuild-core/tests/dep_identity.rs b/crates/fbuild-core/tests/it/dep_identity.rs
similarity index 100%
rename from crates/fbuild-core/tests/dep_identity.rs
rename to crates/fbuild-core/tests/it/dep_identity.rs
diff --git a/crates/fbuild-core/tests/it/main.rs b/crates/fbuild-core/tests/it/main.rs
new file mode 100644
index 000000000..80ded676f
--- /dev/null
+++ b/crates/fbuild-core/tests/it/main.rs
@@ -0,0 +1,10 @@
+//! One integration-test binary for this crate (zackees/ci.yml RUST-005):
+//! each top-level `tests/*.rs` file links the crate's whole dependency
+//! graph separately, so these modules share one link instead.
+
+mod cpu_profiling;
+mod dep_identity;
+mod platformio_avr_resolution;
+mod platformio_ch32v_resolution;
+mod platformio_esp8266_resolution;
+mod platformio_package_resolution;
diff --git a/crates/fbuild-core/tests/platformio_avr_resolution.rs b/crates/fbuild-core/tests/it/platformio_avr_resolution.rs
similarity index 100%
rename from crates/fbuild-core/tests/platformio_avr_resolution.rs
rename to crates/fbuild-core/tests/it/platformio_avr_resolution.rs
diff --git a/crates/fbuild-core/tests/platformio_ch32v_resolution.rs b/crates/fbuild-core/tests/it/platformio_ch32v_resolution.rs
similarity index 100%
rename from crates/fbuild-core/tests/platformio_ch32v_resolution.rs
rename to crates/fbuild-core/tests/it/platformio_ch32v_resolution.rs
diff --git a/crates/fbuild-core/tests/platformio_esp8266_resolution.rs b/crates/fbuild-core/tests/it/platformio_esp8266_resolution.rs
similarity index 100%
rename from crates/fbuild-core/tests/platformio_esp8266_resolution.rs
rename to crates/fbuild-core/tests/it/platformio_esp8266_resolution.rs
diff --git a/crates/fbuild-core/tests/platformio_package_resolution.rs b/crates/fbuild-core/tests/it/platformio_package_resolution.rs
similarity index 100%
rename from crates/fbuild-core/tests/platformio_package_resolution.rs
rename to crates/fbuild-core/tests/it/platformio_package_resolution.rs
diff --git a/crates/fbuild-library-select/tests/it/README.md b/crates/fbuild-library-select/tests/it/README.md
new file mode 100644
index 000000000..35bf6bbef
--- /dev/null
+++ b/crates/fbuild-library-select/tests/it/README.md
@@ -0,0 +1,7 @@
+# fbuild-library-select integration tests
+
+All integration tests for `fbuild-library-select` compile into this single `it` binary; each
+`*.rs` here is a module listed in `main.rs`. Add new integration tests
+as a module here, not as a new top-level `tests/*.rs` file: every top-level
+file is a separate binary that re-links the crate's whole dependency graph
+(zackees/ci.yml RUST-005).
diff --git a/crates/fbuild-library-select/tests/it/main.rs b/crates/fbuild-library-select/tests/it/main.rs
new file mode 100644
index 000000000..c85f34b3c
--- /dev/null
+++ b/crates/fbuild-library-select/tests/it/main.rs
@@ -0,0 +1,6 @@
+//! One integration-test binary for this crate (zackees/ci.yml RUST-005):
+//! each top-level `tests/*.rs` file links the crate's whole dependency
+//! graph separately, so these modules share one link instead.
+
+mod perf_tdd;
+mod teensy41_ldf_diag;
diff --git a/crates/fbuild-library-select/tests/perf_tdd.rs b/crates/fbuild-library-select/tests/it/perf_tdd.rs
similarity index 100%
rename from crates/fbuild-library-select/tests/perf_tdd.rs
rename to crates/fbuild-library-select/tests/it/perf_tdd.rs
diff --git a/crates/fbuild-library-select/tests/teensy41_ldf_diag.rs b/crates/fbuild-library-select/tests/it/teensy41_ldf_diag.rs
similarity index 98%
rename from crates/fbuild-library-select/tests/teensy41_ldf_diag.rs
rename to crates/fbuild-library-select/tests/it/teensy41_ldf_diag.rs
index 738ac5d49..584836520 100644
--- a/crates/fbuild-library-select/tests/teensy41_ldf_diag.rs
+++ b/crates/fbuild-library-select/tests/it/teensy41_ldf_diag.rs
@@ -6,7 +6,7 @@
 //! only runs on explicit demand:
 //!
 //!     soldr cargo test -p fbuild-library-select \
-//!         --test teensy41_ldf_diag -- --ignored --nocapture
+//!         --test it teensy41_ldf_diag:: -- --ignored --nocapture
 //!
 //! Requires:
 //!   * Cached Teensyduino framework at:
diff --git a/crates/fbuild-packages/tests/it/README.md b/crates/fbuild-packages/tests/it/README.md
new file mode 100644
index 000000000..0a26c1b17
--- /dev/null
+++ b/crates/fbuild-packages/tests/it/README.md
@@ -0,0 +1,7 @@
+# fbuild-packages integration tests
+
+All integration tests for `fbuild-packages` compile into this single `it` binary; each
+`*.rs` here is a module listed in `main.rs`. Add new integration tests
+as a module here, not as a new top-level `tests/*.rs` file: every top-level
+file is a separate binary that re-links the crate's whole dependency graph
+(zackees/ci.yml RUST-005).
diff --git a/crates/fbuild-packages/tests/disk_cache_schema_migration.rs b/crates/fbuild-packages/tests/it/disk_cache_schema_migration.rs
similarity index 100%
rename from crates/fbuild-packages/tests/disk_cache_schema_migration.rs
rename to crates/fbuild-packages/tests/it/disk_cache_schema_migration.rs
diff --git a/crates/fbuild-packages/tests/lnk_e2e.rs b/crates/fbuild-packages/tests/it/lnk_e2e.rs
similarity index 100%
rename from crates/fbuild-packages/tests/lnk_e2e.rs
rename to crates/fbuild-packages/tests/it/lnk_e2e.rs
diff --git a/crates/fbuild-packages/tests/it/main.rs b/crates/fbuild-packages/tests/it/main.rs
new file mode 100644
index 000000000..b275293fa
--- /dev/null
+++ b/crates/fbuild-packages/tests/it/main.rs
@@ -0,0 +1,6 @@
+//! One integration-test binary for this crate (zackees/ci.yml RUST-005):
+//! each top-level `tests/*.rs` file links the crate's whole dependency
+//! graph separately, so these modules share one link instead.
+
+mod disk_cache_schema_migration;
+mod lnk_e2e;
diff --git a/dylints/ban_raw_path_prefix_compare/src/lib.rs b/dylints/ban_raw_path_prefix_compare/src/lib.rs
index 95657d61f..ec8738aa5 100644
--- a/dylints/ban_raw_path_prefix_compare/src/lib.rs
+++ b/dylints/ban_raw_path_prefix_compare/src/lib.rs
@@ -222,7 +222,7 @@ mod tests {
     #[test]
     fn in_production_scope_rejects_non_src() {
         assert!(!in_production_scope(
-            "crates/fbuild-cli/tests/lib_select.rs"
+            "crates/fbuild-cli/tests/it/lib_select.rs"
         ));
         assert!(!in_production_scope(
             "dylints/ban_raw_path_prefix_compare/src/lib.rs"
diff --git a/dylints/ban_raw_subprocess/src/lib.rs b/dylints/ban_raw_subprocess/src/lib.rs
index 67acc4093..c6d0dc35c 100644
--- a/dylints/ban_raw_subprocess/src/lib.rs
+++ b/dylints/ban_raw_subprocess/src/lib.rs
@@ -245,7 +245,7 @@ mod tests {
     #[test]
     fn in_production_scope_rejects_non_src() {
         assert!(!in_production_scope(
-            "crates/fbuild-cli/tests/lib_select.rs"
+            "crates/fbuild-cli/tests/it/lib_select.rs"
         ));
         assert!(!in_production_scope("crates/fbuild-build/examples/demo.rs"));
         assert!(!in_production_scope(
diff --git a/dylints/ban_std_pathbuf/src/allowlist.txt b/dylints/ban_std_pathbuf/src/allowlist.txt
index 5be64224f..b0bba370b 100644
--- a/dylints/ban_std_pathbuf/src/allowlist.txt
+++ b/dylints/ban_std_pathbuf/src/allowlist.txt
@@ -159,7 +159,7 @@ crates/fbuild-library-select/src/lib.rs
 # (FastLED/fbuild#1371). A file move must not silently drop the
 # exception the moved code already had.
 crates/fbuild-library-select/src/lib_tests.rs
-crates/fbuild-library-select/tests/teensy41_ldf_diag.rs
+crates/fbuild-library-select/tests/it/teensy41_ldf_diag.rs
 crates/fbuild-packages-fetch/src/cache.rs
 crates/fbuild-packages-fetch/src/disk_cache/gc.rs
 crates/fbuild-packages-fetch/src/disk_cache/index/mod.rs
@@ -218,8 +218,8 @@ crates/fbuild-toolchain/src/toolchain/riscv.rs
 crates/fbuild-toolchain/src/toolchain/rp2040_picotool.rs
 crates/fbuild-toolchain/src/toolchain/rp2040_pqt.rs
 crates/fbuild-toolchain/src/toolchain/teensy_arm.rs
-crates/fbuild-packages/tests/disk_cache_schema_migration.rs
-crates/fbuild-packages/tests/lnk_e2e.rs
+crates/fbuild-packages/tests/it/disk_cache_schema_migration.rs
+crates/fbuild-packages/tests/it/lnk_e2e.rs
 crates/fbuild-paths/src/lib.rs
 crates/fbuild-paths/src/running_process.rs
 crates/fbuild-python/src/daemon.rs
diff --git a/dylints/enforce_platform_boundary/src/baseline.txt b/dylints/enforce_platform_boundary/src/baseline.txt
index b10d9c6d4..a3083a999 100644
--- a/dylints/enforce_platform_boundary/src/baseline.txt
+++ b/dylints/enforce_platform_boundary/src/baseline.txt
@@ -1,6 +1,6 @@
 # path<TAB>kind<TAB>normalized<TAB>ordinal
-crates/fbuild-core/tests/platformio_package_resolution.rs	attr_cfg	windows	0
-crates/fbuild-core/tests/platformio_package_resolution.rs	attr_cfg	windows	1
+crates/fbuild-core/tests/it/platformio_package_resolution.rs	attr_cfg	windows	0
+crates/fbuild-core/tests/it/platformio_package_resolution.rs	attr_cfg	windows	1
 crates/fbuild-daemon/src/handlers/emulator/tests_npm_cache.rs	attr_cfg	windows	0
 crates/fbuild-daemon/src/handlers/emulator/tests_process.rs	attr_cfg	windows	0
 crates/fbuild-daemon/src/handlers/emulator/tests_process.rs	attr_cfg	windows	1

From a0f56ee49f21af23096a7805f1a4830cb2348a60 Mon Sep 17 00:00:00 2001
From: Zach Vorhies <zachvorhies@protonmail.com>
Date: Tue, 29 Sep 2026 22:10:37 -0700
Subject: [PATCH 2/4] perf(test): finish #1577 -- 8 integration-test binaries
 workspace-wide

Categories (ci/check_test_layout.py is the list):
  fbuild-build/tests/it            build
  fbuild-build/tests/env_isolated  tests that mutate FBUILD_*/ZCCACHE_* env,
                                   all behind one ENV_LOCK: avr_build,
                                   eh_frame_strip_esp32, include-farm parity,
                                   build-engine dev_daemon_namespace_isolation
  fbuild-daemon/tests/it           daemon
  fbuild-cli/tests/it              cli
  fbuild-core/tests/it             config_resolution
  fbuild-packages/tests/it         packages (+ toolchain qemu_linux_runtime)
  fbuild-library-select/tests/it   library_select
  fbuild-python/tests/python_facades  python (+ pyo3_policy)

- test = false on harnesses that ran 0 tests: fbuild-packages lib,
  enrich_boards, containment_harness, bench-fastled-examples.
- fbuild_build_engine::zccache::daemon_endpoint() so the namespace test can
  move without a second zccache pin.
- ci/check_test_layout.py (crate-gate.yml): fails on a new top-level
  tests/*.rs, an unknown category dir, [[test]] targets, or a #[test] inside
  a test = false target.
- select_boards: test-only paths (crates/*/tests/**, *_tests.rs,
  ci/test_*.py) never select platform boards.
- Workflows, Dylint allowlist/baseline and run instructions follow the move.

Workspace test binaries 47 -> 29 (8 integration + unit-test harnesses).
Test counts unchanged: 3588 passed, 91 ignored.

Closes #1577.
---
 .github/workflows/acceptance-205.yml          | 11 ++-
 .github/workflows/crate-gate.yml              |  5 +
 .github/workflows/qemu-linux-runtime.yml      |  2 +-
 bench/fastled-examples/Cargo.toml             |  2 +
 ci/check_test_layout.py                       | 99 +++++++++++++++++++
 ci/select_boards.py                           | 14 +++
 ci/test_check_test_layout.py                  | 75 ++++++++++++++
 ci/test_select_boards.py                      | 19 ++++
 .../fbuild-build-engine/src/include_farm.rs   |  2 +-
 crates/fbuild-build-engine/src/zccache.rs     |  7 ++
 crates/fbuild-build-engine/tests/README.md    | 12 ---
 .../fbuild-build/tests/env_isolated/README.md |  9 ++
 .../tests/{ => env_isolated}/avr_build.rs     |  7 +-
 .../dev_daemon_namespace_isolation.rs         | 21 ++--
 .../eh_frame_strip_esp32.rs                   |  3 +-
 .../esp32_include_farm_parity.rs              |  9 +-
 .../fbuild-build/tests/env_isolated/main.rs   | 14 +++
 .../tests/it/clangd_check_parity.rs           |  4 +-
 .../tests/it/compile_many_two_stage.rs        |  2 +-
 crates/fbuild-build/tests/it/main.rs          |  1 -
 crates/fbuild-config/Cargo.toml               |  2 +
 crates/fbuild-daemon/Cargo.toml               |  6 ++
 crates/fbuild-packages/Cargo.toml             |  6 ++
 crates/fbuild-packages/tests/it/main.rs       |  1 +
 .../tests/it}/qemu_linux_runtime.rs           |  0
 .../fbuild-paths/src/dev_daemon_namespace.rs  |  2 +-
 crates/fbuild-python/Cargo.toml               |  2 +-
 crates/fbuild-python/tests/README.md          |  6 +-
 .../main.rs}                                  |  3 +-
 .../tests/{ => python_facades}/pyo3_policy.rs |  0
 crates/fbuild-toolchain/tests/README.md       | 18 ----
 dylints/ban_std_pathbuf/src/allowlist.txt     |  2 +-
 .../src/baseline.txt                          |  2 +-
 33 files changed, 305 insertions(+), 63 deletions(-)
 create mode 100644 ci/check_test_layout.py
 create mode 100644 ci/test_check_test_layout.py
 delete mode 100644 crates/fbuild-build-engine/tests/README.md
 create mode 100644 crates/fbuild-build/tests/env_isolated/README.md
 rename crates/fbuild-build/tests/{ => env_isolated}/avr_build.rs (98%)
 rename crates/{fbuild-build-engine/tests => fbuild-build/tests/env_isolated}/dev_daemon_namespace_isolation.rs (78%)
 rename crates/fbuild-build/tests/{ => env_isolated}/eh_frame_strip_esp32.rs (98%)
 rename crates/fbuild-build/tests/{it => env_isolated}/esp32_include_farm_parity.rs (96%)
 create mode 100644 crates/fbuild-build/tests/env_isolated/main.rs
 rename crates/{fbuild-toolchain/tests => fbuild-packages/tests/it}/qemu_linux_runtime.rs (100%)
 rename crates/fbuild-python/tests/{python_facades.rs => python_facades/main.rs} (99%)
 rename crates/fbuild-python/tests/{ => python_facades}/pyo3_policy.rs (100%)
 delete mode 100644 crates/fbuild-toolchain/tests/README.md

diff --git a/.github/workflows/acceptance-205.yml b/.github/workflows/acceptance-205.yml
index 56fb4a1cf..07a784315 100644
--- a/.github/workflows/acceptance-205.yml
+++ b/.github/workflows/acceptance-205.yml
@@ -51,30 +51,39 @@ jobs:
             test_fn: teensy41_cold_library_selection_meets_205_ac6
           # FastLED/fbuild#1588: GCC resolves the same headers with and without the include farm.
           - gate: esp32dev include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32dev
           - gate: esp32s2 include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32s2
           - gate: esp32s3 include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32s3
           - gate: esp32c2 include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32c2
           - gate: esp32c3 include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32c3
           - gate: esp32c5 include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32c5
           - gate: esp32c6 include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32c6
           - gate: esp32h2 include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32h2
           - gate: esp32p4 include-farm parity
+            test_target: env_isolated
             test_bin: esp32_include_farm_parity
             test_fn: farm_parity_esp32p4
     steps:
@@ -101,4 +110,4 @@ jobs:
 
       - name: Run ${{ matrix.gate }} acceptance gate
         run: |
-          soldr cargo test -p fbuild-build --test it -- --ignored --exact ${{ matrix.test_bin }}::${{ matrix.test_fn }} --nocapture --test-threads=1
+          soldr cargo test -p fbuild-build --test ${{ matrix.test_target || 'it' }} -- --ignored --exact ${{ matrix.test_bin }}::${{ matrix.test_fn }} --nocapture --test-threads=1
diff --git a/.github/workflows/crate-gate.yml b/.github/workflows/crate-gate.yml
index 92c6b708a..ca69f2e05 100644
--- a/.github/workflows/crate-gate.yml
+++ b/.github/workflows/crate-gate.yml
@@ -39,3 +39,8 @@ jobs:
         # which requires `soldr` (absent in this job) and fails the gate for an
         # unrelated reason. The script declares its own inline metadata.
         run: uv run --script ci/check_workspace_crates.py
+
+      - name: Check integration tests stay in their 8 category binaries
+        # FastLED/fbuild#1577: a new top-level crates/*/tests/*.rs is a new
+        # test binary that re-links the whole dependency graph.
+        run: uv run --script ci/check_test_layout.py
diff --git a/.github/workflows/qemu-linux-runtime.yml b/.github/workflows/qemu-linux-runtime.yml
index e88db1f74..f45d9a4eb 100644
--- a/.github/workflows/qemu-linux-runtime.yml
+++ b/.github/workflows/qemu-linux-runtime.yml
@@ -72,5 +72,5 @@ jobs:
 
       - name: QEMU runtime provisioning test
         run: |
-          soldr cargo test -p fbuild-toolchain --test qemu_linux_runtime -- \
+          soldr cargo test -p fbuild-packages --test it -- qemu_linux_runtime:: \
             --ignored --nocapture
diff --git a/bench/fastled-examples/Cargo.toml b/bench/fastled-examples/Cargo.toml
index 599e92e8b..4fab3c934 100644
--- a/bench/fastled-examples/Cargo.toml
+++ b/bench/fastled-examples/Cargo.toml
@@ -10,6 +10,8 @@ publish = false
 [[bin]]
 name = "bench-fastled-examples"
 path = "src/main.rs"
+# No #[test] in this bin; skip its empty harness (FastLED/fbuild#1577).
+test = false
 
 [[bin]]
 name = "bench-build-comparison"
diff --git a/ci/check_test_layout.py b/ci/check_test_layout.py
new file mode 100644
index 000000000..3e6d83204
--- /dev/null
+++ b/ci/check_test_layout.py
@@ -0,0 +1,99 @@
+#!/usr/bin/env -S uv run --script
+# /// script
+# requires-python = ">=3.10"
+# ///
+"""Linter: keep the workspace at no more than 8 integration-test binaries.
+
+Every top-level `crates/<crate>/tests/*.rs` file, and every
+`tests/<dir>/main.rs`, is a separate test binary. Each one links its crate's
+whole dependency graph again, and before FastLED/fbuild#1577 that linking took
+most of CI's `Test` step. The workspace now has a fixed set of category
+binaries (soldr's layout, zackees/ci.yml RUST-005). A new integration test goes
+into one of them as a module, never into a new top-level file or directory.
+
+Adding a category is a deliberate act: add it to `CATEGORIES` below with a
+one-line reason, and keep the total at no more than `MAX_CATEGORIES`.
+
+Usage:
+    uv run --script ci/check_test_layout.py
+"""
+
+from __future__ import annotations
+
+import re
+import sys
+from pathlib import Path
+
+MAX_CATEGORIES = 8
+
+# (crate dir, tests/ subdir) -> what belongs there.
+CATEGORIES: dict[tuple[str, str], str] = {
+    ("fbuild-build", "it"): "build: real and synthetic build pipelines",
+    ("fbuild-build", "env_isolated"): "tests that mutate FBUILD_*/ZCCACHE_* env vars, behind ENV_LOCK",
+    ("fbuild-daemon", "it"): "daemon: HTTP/WS server and managers",
+    ("fbuild-cli", "it"): "cli: command-line front end",
+    ("fbuild-core", "it"): "config_resolution: PlatformIO resolution and core types",
+    ("fbuild-packages", "it"): "packages: caches, lnk, toolchain provisioning",
+    ("fbuild-library-select", "it"): "library_select: LDF and library selection",
+    ("fbuild-python", "python_facades"): "python: needs libpython at link time",
+}
+
+REPO = Path(__file__).resolve().parent.parent
+
+
+def violations(repo: Path = REPO) -> list[str]:
+    problems: list[str] = []
+    if len(CATEGORIES) > MAX_CATEGORIES:
+        problems.append(f"{len(CATEGORIES)} categories declared; the limit is {MAX_CATEGORIES}")
+    for tests in sorted((repo / "crates").glob("*/tests")):
+        crate = tests.parent.name
+        for entry in sorted(tests.iterdir()):
+            rel = entry.relative_to(repo).as_posix()
+            if entry.is_file() and entry.suffix == ".rs":
+                problems.append(f"{rel}: top-level test file is its own binary; add it as a module of a category in ci/check_test_layout.py")
+            elif entry.is_dir() and (entry / "main.rs").exists() and (crate, entry.name) not in CATEGORIES:
+                problems.append(f"{rel}/main.rs: unknown test category; use an existing one")
+    manifests = sorted((repo / "crates").glob("*/Cargo.toml")) + sorted((repo / "bench").glob("*/Cargo.toml"))
+    for manifest in manifests:
+        text = manifest.read_text(encoding="utf-8")
+        rel = manifest.relative_to(repo).as_posix()
+        if re.search(r"^\[\[test\]\]", text, re.MULTILINE):
+            problems.append(f"{rel}: [[test]] targets bypass the category layout")
+        for source in test_disabled_sources(manifest, text):
+            if TEST_ATTR.search(source.read_text(encoding="utf-8")):
+                problems.append(
+                    f"{source.relative_to(repo).as_posix()}: has #[test] but its target sets `test = false` in {rel}, so it never runs"
+                )
+    return problems
+
+
+TEST_ATTR = re.compile(r"#\[(tokio::)?test\b")
+
+
+def test_disabled_sources(manifest: Path, text: str) -> list[Path]:
+    """Source files of `[lib]`/`[[bin]]` targets that set `test = false`."""
+    crate = manifest.parent
+    sources: list[Path] = []
+    for header, body in re.findall(r"^(\[lib\]|\[\[bin\]\])\n((?:(?!\[).*\n?)*)", text, re.MULTILINE):
+        if not re.search(r"^test\s*=\s*false", body, re.MULTILINE):
+            continue
+        path = re.search(r'^path\s*=\s*"([^"]+)"', body, re.MULTILINE)
+        entry = crate / (path.group(1) if path else ("src/lib.rs" if header == "[lib]" else "src/main.rs"))
+        # A lib's unit tests can live anywhere under src/; a bin's in its file.
+        sources.extend(sorted(entry.parent.rglob("*.rs")) if header == "[lib]" else [entry])
+    return [s for s in sources if s.is_file()]
+
+
+def main() -> int:
+    problems = violations()
+    for problem in problems:
+        print(f"error: {problem}", file=sys.stderr)
+    if problems:
+        print(f"\n{len(problems)} test-layout violation(s); see FastLED/fbuild#1577", file=sys.stderr)
+        return 1
+    print(f"ok: {len(CATEGORIES)} integration-test categories, no stray test binaries")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/ci/select_boards.py b/ci/select_boards.py
index 181c48176..311444280 100644
--- a/ci/select_boards.py
+++ b/ci/select_boards.py
@@ -53,10 +53,24 @@ def path_matches(pattern: str, path: str) -> bool:
     return _compile(pattern).match(path) is not None
 
 
+# Test-only paths never select boards (FastLED/fbuild#1577): the Linux test
+# job runs them, and a test refactor must not fan out to every platform.
+TEST_ONLY_PATTERNS = (
+    "crates/*/tests/**",
+    "crates/**/*_tests.rs",
+    "ci/test_*.py",
+)
+
+
+def is_test_only(path: str) -> bool:
+    return any(path_matches(p, path) for p in TEST_ONLY_PATTERNS)
+
+
 def select_workflows(boards, families, common_paths, changed):
     """Workflows to run for `changed` files; `None` means the diff is unknown."""
     if changed is None:
         return sorted(b["workflow"] for b in boards)
+    changed = [f for f in changed if not is_test_only(f)]
     selected = []
     for board in boards:
         patterns = render_paths_for_board(board, families, common_paths)
diff --git a/ci/test_check_test_layout.py b/ci/test_check_test_layout.py
new file mode 100644
index 000000000..a471e920d
--- /dev/null
+++ b/ci/test_check_test_layout.py
@@ -0,0 +1,75 @@
+"""Tests for ci/check_test_layout.py (FastLED/fbuild#1577)."""
+from __future__ import annotations
+
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+
+from check_test_layout import CATEGORIES, MAX_CATEGORIES, violations  # noqa: E402
+
+
+def make(root: Path, rel: str, body: str = "") -> None:
+    path = root / rel
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text(body, encoding="utf-8")
+
+
+class LayoutTests(unittest.TestCase):
+    def test_repository_is_clean(self):
+        self.assertEqual([], violations())
+
+    def test_at_most_eight_categories(self):
+        self.assertLessEqual(len(CATEGORIES), MAX_CATEGORIES)
+        self.assertEqual(8, MAX_CATEGORIES)
+
+    def test_top_level_test_file_is_rejected(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            make(root, "crates/fbuild-core/tests/it/main.rs")
+            make(root, "crates/fbuild-core/tests/new_thing.rs")
+            problems = violations(root)
+        self.assertEqual(1, len(problems))
+        self.assertIn("new_thing.rs", problems[0])
+
+    def test_unknown_category_dir_is_rejected(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            make(root, "crates/fbuild-core/tests/extra/main.rs")
+            self.assertIn("unknown test category", violations(root)[0])
+
+    def test_explicit_test_target_is_rejected(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            make(root, "crates/fbuild-core/Cargo.toml", '[package]\nname = "x"\n\n[[test]]\nname = "y"\n')
+            self.assertIn("[[test]]", violations(root)[0])
+
+    def test_helper_dirs_without_main_are_allowed(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            make(root, "crates/fbuild-core/tests/it/main.rs")
+            make(root, "crates/fbuild-core/tests/fixtures/data.json")
+            self.assertEqual([], violations(root))
+
+    def test_test_false_target_with_tests_is_rejected(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            make(root, "crates/fbuild-x/Cargo.toml", '[package]\nname = "x"\n\n[lib]\ntest = false\n\n[dependencies]\n')
+            make(root, "crates/fbuild-x/src/lib.rs", "mod a;\n")
+            make(root, "crates/fbuild-x/src/a.rs", "#[test]\nfn t() {}\n")
+            problems = violations(root)
+        self.assertEqual(1, len(problems))
+        self.assertIn("never runs", problems[0])
+
+    def test_test_false_target_without_tests_is_fine(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            make(root, "crates/fbuild-x/Cargo.toml", '[package]\nname = "x"\n\n[[bin]]\nname = "b"\npath = "src/bin/b.rs"\ntest = false\n')
+            make(root, "crates/fbuild-x/src/bin/b.rs", "fn main() {}\n")
+            self.assertEqual([], violations(root))
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/ci/test_select_boards.py b/ci/test_select_boards.py
index 4233696e2..b3297fbba 100644
--- a/ci/test_select_boards.py
+++ b/ci/test_select_boards.py
@@ -62,6 +62,25 @@ def test_shared_code_selects_core_boards_only(self):
     def test_own_workflow_file_selects_board(self):
         self.assertEqual(["build-esp32c3.yml"], select([".github/workflows/build-esp32c3.yml"]))
 
+    def test_test_only_changes_select_nothing(self):
+        # FastLED/fbuild#1577: moving or editing tests must not fan out to
+        # platform builds; the Linux test job already runs them.
+        self.assertEqual(
+            [],
+            select([
+                "crates/fbuild-core/tests/it/main.rs",
+                "crates/fbuild-build/tests/env_isolated/avr_build.rs",
+                "crates/fbuild-build-mcu/src/avr/orchestrator_tests.rs",
+                "ci/test_select_boards.py",
+            ]),
+        )
+
+    def test_test_change_alongside_source_still_selects(self):
+        self.assertEqual(
+            ["build-attiny85.yml", "build-uno.yml"],
+            select(["crates/fbuild-core/tests/it/main.rs", "crates/fbuild-build-mcu/src/avr/mod.rs"]),
+        )
+
     def test_unknown_diff_selects_everything(self):
         self.assertEqual(sorted(b["workflow"] for b in BOARDS), select(None))
 
diff --git a/crates/fbuild-build-engine/src/include_farm.rs b/crates/fbuild-build-engine/src/include_farm.rs
index c1bc477aa..8684a2a3f 100644
--- a/crates/fbuild-build-engine/src/include_farm.rs
+++ b/crates/fbuild-build-engine/src/include_farm.rs
@@ -22,7 +22,7 @@
 //! Callers skip farms on Windows, where symlinks usually need elevated rights,
 //! and when `FBUILD_INCLUDE_FARM=0`. The text-level checks above cannot see
 //! macro includes; the real-SDK parity test in
-//! `fbuild-build/tests/it/esp32_include_farm_parity.rs` compares GCC's own
+//! `fbuild-build/tests/env_isolated/esp32_include_farm_parity.rs` compares GCC's own
 //! depfiles with and without the farm (FastLED/fbuild#1588).
 
 use std::collections::{BTreeMap, HashMap};
diff --git a/crates/fbuild-build-engine/src/zccache.rs b/crates/fbuild-build-engine/src/zccache.rs
index 0aef3bb0a..ed6717233 100644
--- a/crates/fbuild-build-engine/src/zccache.rs
+++ b/crates/fbuild-build-engine/src/zccache.rs
@@ -86,3 +86,10 @@ pub fn mark_fingerprint_success(watch: &FingerprintWatch) -> Result<()> {
         ))
     })
 }
+
+/// The compile daemon's IPC endpoint for the current environment, including
+/// the `ZCCACHE_DAEMON_NAMESPACE` stamp (FastLED/fbuild#1285). Two checkouts
+/// with different stamps must get different endpoints.
+pub fn daemon_endpoint() -> String {
+    ::zccache::ipc::default_endpoint()
+}
diff --git a/crates/fbuild-build-engine/tests/README.md b/crates/fbuild-build-engine/tests/README.md
deleted file mode 100644
index 59510eeb2..000000000
--- a/crates/fbuild-build-engine/tests/README.md
+++ /dev/null
@@ -1,12 +0,0 @@
-# `fbuild-build-engine` integration tests
-
-Tests that need a separate final executable, or that exercise a contract
-spanning this crate and one of its external dependencies.
-
-- **`dev_daemon_namespace_isolation.rs`** — proves the dev daemon-identity
-  stamp `fbuild-paths` exports actually changes the zccache IPC endpoint
-  (FastLED/fbuild#1285). It lives here because this is the crate that depends
-  on both sides: `fbuild-paths` produces the stamp but cannot see zccache, and
-  zccache consumes it but is a pinned external dependency. A repin that
-  dropped endpoint namespacing would otherwise pass every other test in the
-  tree while quietly restoring the `displace-stale` daemon war.
diff --git a/crates/fbuild-build/tests/env_isolated/README.md b/crates/fbuild-build/tests/env_isolated/README.md
new file mode 100644
index 000000000..b9834868a
--- /dev/null
+++ b/crates/fbuild-build/tests/env_isolated/README.md
@@ -0,0 +1,9 @@
+# env_isolated integration tests
+
+One test binary (FastLED/fbuild#1577) for `fbuild-build` integration tests
+that mutate process-wide environment variables (`FBUILD_*`,
+`ZCCACHE_DAEMON_NAMESPACE`). Every test takes `ENV_LOCK` from `main.rs` for
+its whole body. Add env-mutating tests here as a module; everything else goes
+in `../it`.
+
+Run one test: `soldr cargo test -p fbuild-build --test env_isolated -- --ignored --exact <module>::<test> --nocapture`
diff --git a/crates/fbuild-build/tests/avr_build.rs b/crates/fbuild-build/tests/env_isolated/avr_build.rs
similarity index 98%
rename from crates/fbuild-build/tests/avr_build.rs
rename to crates/fbuild-build/tests/env_isolated/avr_build.rs
index 475eb0814..b069924fa 100644
--- a/crates/fbuild-build/tests/avr_build.rs
+++ b/crates/fbuild-build/tests/env_isolated/avr_build.rs
@@ -3,7 +3,7 @@
 //! Downloads avr-gcc + Arduino core (cached after first run), compiles a
 //! minimal blink sketch, and validates the output firmware.hex.
 //!
-//! Run with: `soldr cargo test -p fbuild-build --test avr_build -- --ignored`
+//! Run with: `soldr cargo test -p fbuild-build --test env_isolated -- --ignored avr_build::`
 //!
 //! ## Timeout cap (FastLED/fbuild#806, MEDIUM)
 //!
@@ -71,6 +71,7 @@ async fn install_test_compile_backend() {
 /// Verify stem/hash cache path format produces readable, unique paths.
 #[test]
 fn cache_paths_stem_hash() {
+    let _env = crate::ENV_LOCK.blocking_lock();
     use fbuild_packages::cache::{hash_url, url_stem};
 
     // Toolchain: stem from base URL
@@ -107,6 +108,7 @@ fn cache_paths_stem_hash() {
 #[tokio::test(flavor = "multi_thread", worker_threads = 4)]
 #[ignore = "downloads AVR toolchain + Arduino-AVR core; requires ~/dev/fbuild/tests/uno_minimal"]
 async fn build_uno_minimal() {
+    let _env = crate::ENV_LOCK.lock().await;
     let project_dir = home_dir().join("dev/fbuild/tests/uno_minimal");
 
     if !project_dir.exists() {
@@ -212,6 +214,7 @@ async fn build_uno_minimal() {
 #[tokio::test(flavor = "multi_thread", worker_threads = 4)]
 #[ignore = "downloads AVR toolchain; requires Python fbuild reference output at ~/dev/fbuild/tests/uno_minimal"]
 async fn compare_with_python_output() {
+    let _env = crate::ENV_LOCK.lock().await;
     let project_dir = home_dir().join("dev/fbuild/tests/uno_minimal");
 
     let python_hex = project_dir.join(format!(
@@ -298,6 +301,7 @@ async fn compare_with_python_output() {
 #[tokio::test(flavor = "multi_thread", worker_threads = 4)]
 #[ignore = "downloads AVR toolchain + Arduino-AVR core"]
 async fn build_self_contained_blink() {
+    let _env = crate::ENV_LOCK.lock().await;
     install_test_compile_backend().await;
     let tmp = tempfile::TempDir::new().unwrap();
     let project_dir = tmp.path();
@@ -511,6 +515,7 @@ impl Drop for EnvVarGuard {
 #[tokio::test(flavor = "multi_thread", worker_threads = 4)]
 #[ignore = "downloads AVR toolchain + Arduino-AVR core; exercises tar-extract cache path"]
 async fn cache_survives_tar_extract_uno() {
+    let _env = crate::ENV_LOCK.lock().await;
     install_test_compile_backend().await;
     let tmp_a = tempfile::TempDir::new().unwrap();
     let proj_a = tmp_a.path().join("proj");
diff --git a/crates/fbuild-build-engine/tests/dev_daemon_namespace_isolation.rs b/crates/fbuild-build/tests/env_isolated/dev_daemon_namespace_isolation.rs
similarity index 78%
rename from crates/fbuild-build-engine/tests/dev_daemon_namespace_isolation.rs
rename to crates/fbuild-build/tests/env_isolated/dev_daemon_namespace_isolation.rs
index 449d573b1..86a50a381 100644
--- a/crates/fbuild-build-engine/tests/dev_daemon_namespace_isolation.rs
+++ b/crates/fbuild-build/tests/env_isolated/dev_daemon_namespace_isolation.rs
@@ -11,31 +11,32 @@
 //! export was inert until fbuild repinned zccache. It is not; it has been
 //! live since the stamp landed.
 //!
-//! This test is the place that can tell. It lives in `fbuild-build-engine`
-//! because that is the crate depending on both sides. A zccache repin that
+//! This test is the place that can tell. It reaches zccache through
+//! `fbuild_build_engine::zccache::daemon_endpoint`, the crate depending on
+//! both sides. A zccache repin that
 //! silently dropped endpoint namespacing would take the `displace-stale` war
 //! from zackees/soldr#2352 with it, and nothing else in the tree would
 //! notice.
 
 use fbuild_paths::dev_daemon_namespace::ZCCACHE_DAEMON_NAMESPACE_ENV;
 
-/// One test, not three: the variable is process-global, so parallel cases
-/// would race each other's `set_var`.
+/// One test, not three: the variable is process-global.
 #[test]
 fn the_exported_stamp_changes_the_zccache_daemon_endpoint() {
-    // SAFETY: this test binary contains one test, so no peer thread can
-    // observe the process-wide environment change.
+    let _env = crate::ENV_LOCK.blocking_lock();
+    // SAFETY: every test in this binary holds crate::ENV_LOCK, so no peer
+    // test observes the process-wide environment change.
     unsafe { std::env::remove_var(ZCCACHE_DAEMON_NAMESPACE_ENV) };
-    let bare = zccache::ipc::default_endpoint();
+    let bare = fbuild_build_engine::zccache::daemon_endpoint();
 
     unsafe { std::env::set_var(ZCCACHE_DAEMON_NAMESPACE_ENV, "2.5.0-aaaaaaaaaaaaaaaa") };
-    let first = zccache::ipc::default_endpoint();
+    let first = fbuild_build_engine::zccache::daemon_endpoint();
 
     unsafe { std::env::set_var(ZCCACHE_DAEMON_NAMESPACE_ENV, "2.5.0-bbbbbbbbbbbbbbbb") };
-    let second = zccache::ipc::default_endpoint();
+    let second = fbuild_build_engine::zccache::daemon_endpoint();
 
     unsafe { std::env::remove_var(ZCCACHE_DAEMON_NAMESPACE_ENV) };
-    let bare_again = zccache::ipc::default_endpoint();
+    let bare_again = fbuild_build_engine::zccache::daemon_endpoint();
 
     // The property that matters: two checkouts with different stamps do not
     // meet on one pipe. Without this, each displaces the other as
diff --git a/crates/fbuild-build/tests/eh_frame_strip_esp32.rs b/crates/fbuild-build/tests/env_isolated/eh_frame_strip_esp32.rs
similarity index 98%
rename from crates/fbuild-build/tests/eh_frame_strip_esp32.rs
rename to crates/fbuild-build/tests/env_isolated/eh_frame_strip_esp32.rs
index f595fef37..185b10cf4 100644
--- a/crates/fbuild-build/tests/eh_frame_strip_esp32.rs
+++ b/crates/fbuild-build/tests/env_isolated/eh_frame_strip_esp32.rs
@@ -6,7 +6,7 @@
 //! of MB on first run) and is not headless-CI-friendly. Run with:
 //!
 //! ```
-//! soldr cargo test -p fbuild-build --test eh_frame_strip_esp32 -- --ignored
+//! soldr cargo test -p fbuild-build --test env_isolated -- --ignored eh_frame_strip_esp32::
 //! ```
 //!
 //! The orchestrator invocation pattern mirrors
@@ -114,6 +114,7 @@ void loop() {
 #[tokio::test(flavor = "multi_thread", worker_threads = 4)]
 #[ignore = "downloads ESP32 toolchain (~hundreds of MB)"]
 async fn eh_frame_strip_drops_firmware_at_least_150kb() {
+    let _env = crate::ENV_LOCK.lock().await;
     install_test_compile_backend().await;
     // Use two separate tempdirs so .fbuild/build/... paths don't collide.
     let preserve_tmp = tempfile::TempDir::new().unwrap();
diff --git a/crates/fbuild-build/tests/it/esp32_include_farm_parity.rs b/crates/fbuild-build/tests/env_isolated/esp32_include_farm_parity.rs
similarity index 96%
rename from crates/fbuild-build/tests/it/esp32_include_farm_parity.rs
rename to crates/fbuild-build/tests/env_isolated/esp32_include_farm_parity.rs
index fc34c4bcc..1e7eff5b2 100644
--- a/crates/fbuild-build/tests/it/esp32_include_farm_parity.rs
+++ b/crates/fbuild-build/tests/env_isolated/esp32_include_farm_parity.rs
@@ -8,7 +8,7 @@
 //! header files.
 //!
 //! Run one variant with:
-//! `soldr cargo test -p fbuild-build --test it -- --ignored --exact
+//! `soldr cargo test -p fbuild-build --test env_isolated -- --ignored --exact
 //!  esp32_include_farm_parity::farm_parity_esp32dev --nocapture --test-threads=1`
 
 use std::collections::{BTreeMap, BTreeSet};
@@ -21,9 +21,6 @@ use fbuild_core::path::NormalizedPath;
 
 const REAL_BUILD_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(900);
 
-/// `FBUILD_INCLUDE_FARM` is process-wide; serialize the builds that flip it.
-static FARM_ENV: tokio::sync::Mutex<()> = tokio::sync::Mutex::const_new(());
-
 async fn install_test_compile_backend() {
     static INSTALL: tokio::sync::OnceCell<()> = tokio::sync::OnceCell::const_new();
     INSTALL
@@ -83,7 +80,7 @@ async fn build(project_dir: &Path, env_name: &str, farm: bool) -> NormalizedPath
         bloat_analysis: false,
         caller_path: None,
     };
-    // Process-wide; FARM_ENV keeps the other parity tests out meanwhile.
+    // Process-wide; the caller holds crate::ENV_LOCK.
     std::env::set_var("FBUILD_INCLUDE_FARM", if farm { "1" } else { "0" });
     let result = tokio::time::timeout(
         REAL_BUILD_TIMEOUT,
@@ -192,7 +189,7 @@ fn mentions_farm(build_dir: &Path) -> bool {
 
 async fn assert_farm_parity(fixture: &str, env_name: &str) {
     install_test_compile_backend().await;
-    let _guard = FARM_ENV.lock().await;
+    let _env = crate::ENV_LOCK.lock().await;
     let fixtures = Path::new(env!("CARGO_MANIFEST_DIR")).join("../../tests/platform");
     let tmp = tempfile::TempDir::new().unwrap();
     let project_dir = tmp.path().join(fixture);
diff --git a/crates/fbuild-build/tests/env_isolated/main.rs b/crates/fbuild-build/tests/env_isolated/main.rs
new file mode 100644
index 000000000..0db0953df
--- /dev/null
+++ b/crates/fbuild-build/tests/env_isolated/main.rs
@@ -0,0 +1,14 @@
+//! Integration tests that change process-wide `FBUILD_*` / `ZCCACHE_*`
+//! environment variables (FastLED/fbuild#1577 category `env_isolated`).
+//!
+//! They live apart from `tests/it` so an env change can never leak into an
+//! unrelated test, and every test here holds [`ENV_LOCK`] for its whole body
+//! so they cannot race each other either.
+
+mod avr_build;
+mod dev_daemon_namespace_isolation;
+mod eh_frame_strip_esp32;
+mod esp32_include_farm_parity;
+
+/// Held by every test in this binary for its whole body.
+pub(crate) static ENV_LOCK: tokio::sync::Mutex<()> = tokio::sync::Mutex::const_new(());
diff --git a/crates/fbuild-build/tests/it/clangd_check_parity.rs b/crates/fbuild-build/tests/it/clangd_check_parity.rs
index 44df073b7..f17c968d8 100644
--- a/crates/fbuild-build/tests/it/clangd_check_parity.rs
+++ b/crates/fbuild-build/tests/it/clangd_check_parity.rs
@@ -36,7 +36,7 @@ use fbuild_core::BuildProfile;
 /// indexing). Generous — cold AVR toolchain/core downloads can take a few
 /// minutes; a warm cache (the common case once #1194-era CI has run once)
 /// finishes in seconds. Mirrors the pattern in
-/// `crates/fbuild-build/tests/avr_build.rs` (FastLED/fbuild#806).
+/// `crates/fbuild-build/tests/env_isolated/avr_build.rs` (FastLED/fbuild#806).
 const HARNESS_TIMEOUT: Duration = Duration::from_secs(600);
 
 /// Diagnostic substrings that are known-benign and must never fail the
@@ -126,7 +126,7 @@ fn unexpected_error_diagnostics(output: &str) -> Vec<&str> {
 }
 
 /// Generate the IDE-flavored `compile_commands.json` for `tests/platform/uno`
-/// via the same in-process orchestrator path `avr_build.rs` uses (no daemon,
+/// via the same in-process orchestrator path `env_isolated/avr_build.rs` uses (no daemon,
 /// no CLI subprocess — `compiledb_only: true` skips actual compilation and
 /// linking, so this is the "lighter path" mentioned in FastLED/fbuild#1076:
 /// generate the DB without paying for a full AVR link).
diff --git a/crates/fbuild-build/tests/it/compile_many_two_stage.rs b/crates/fbuild-build/tests/it/compile_many_two_stage.rs
index 5ec686337..bc0c1db06 100644
--- a/crates/fbuild-build/tests/it/compile_many_two_stage.rs
+++ b/crates/fbuild-build/tests/it/compile_many_two_stage.rs
@@ -4,7 +4,7 @@
 //! These tests inject a mock [`SketchBuilder`] so we exercise the
 //! orchestration layer (stage counts, parallelism, output-path
 //! uniqueness, input ordering) without dragging in a real toolchain.
-//! Real-toolchain coverage lives in `avr_build.rs` etc. and is
+//! Real-toolchain coverage lives in `../env_isolated/avr_build.rs` etc. and is
 //! `#[ignore]`-gated to keep `uv run test` fast.
 
 use std::collections::HashSet;
diff --git a/crates/fbuild-build/tests/it/main.rs b/crates/fbuild-build/tests/it/main.rs
index 9eb201b18..1d5cea594 100644
--- a/crates/fbuild-build/tests/it/main.rs
+++ b/crates/fbuild-build/tests/it/main.rs
@@ -7,7 +7,6 @@ mod clangd_check_parity;
 mod compile_many_stage2_perf;
 mod compile_many_two_stage;
 mod esp32_build;
-mod esp32_include_farm_parity;
 mod esp32s3_size_parity;
 mod flag_escaping_lint;
 mod lite_scons_acceptance;
diff --git a/crates/fbuild-config/Cargo.toml b/crates/fbuild-config/Cargo.toml
index dbe69caf9..e36580a25 100644
--- a/crates/fbuild-config/Cargo.toml
+++ b/crates/fbuild-config/Cargo.toml
@@ -12,6 +12,8 @@ publish = false
 [[bin]]
 name = "enrich_boards"
 path = "src/bin/enrich_boards.rs"
+# No #[test] in the tool; skip its empty harness (FastLED/fbuild#1577).
+test = false
 
 [dependencies]
 fbuild-core = { path = "../fbuild-core" }
diff --git a/crates/fbuild-daemon/Cargo.toml b/crates/fbuild-daemon/Cargo.toml
index aeec687ef..c1a7d5cb6 100644
--- a/crates/fbuild-daemon/Cargo.toml
+++ b/crates/fbuild-daemon/Cargo.toml
@@ -13,6 +13,12 @@ publish = false
 name = "fbuild-daemon"
 path = "src/main.rs"
 
+[[bin]]
+name = "containment_harness"
+path = "src/bin/containment_harness.rs"
+# No #[test] in the harness; skip its empty test binary (FastLED/fbuild#1577).
+test = false
+
 [lib]
 name = "fbuild_daemon"
 path = "src/lib.rs"
diff --git a/crates/fbuild-packages/Cargo.toml b/crates/fbuild-packages/Cargo.toml
index cbadfc151..2e446b86b 100644
--- a/crates/fbuild-packages/Cargo.toml
+++ b/crates/fbuild-packages/Cargo.toml
@@ -9,6 +9,12 @@ license.workspace = true
 # this member exists purely for internal compile parallelism. FastLED/fbuild#1008.
 publish = false
 
+# The lib has no unit tests (its tests live in tests/it), so don't build and
+# link an empty harness. FastLED/fbuild#1577; ci/check_test_layout.py fails if
+# a #[test] is added to src/ while this is set.
+[lib]
+test = false
+
 [dependencies]
 # FastLED/fbuild#1008 Phase B — this crate is now a thin facade re-exporting
 # the fetch primitives + the parallel library / toolchain crates.
diff --git a/crates/fbuild-packages/tests/it/main.rs b/crates/fbuild-packages/tests/it/main.rs
index b275293fa..12084a109 100644
--- a/crates/fbuild-packages/tests/it/main.rs
+++ b/crates/fbuild-packages/tests/it/main.rs
@@ -4,3 +4,4 @@
 
 mod disk_cache_schema_migration;
 mod lnk_e2e;
+mod qemu_linux_runtime;
diff --git a/crates/fbuild-toolchain/tests/qemu_linux_runtime.rs b/crates/fbuild-packages/tests/it/qemu_linux_runtime.rs
similarity index 100%
rename from crates/fbuild-toolchain/tests/qemu_linux_runtime.rs
rename to crates/fbuild-packages/tests/it/qemu_linux_runtime.rs
diff --git a/crates/fbuild-paths/src/dev_daemon_namespace.rs b/crates/fbuild-paths/src/dev_daemon_namespace.rs
index de89d95ad..2b14af26d 100644
--- a/crates/fbuild-paths/src/dev_daemon_namespace.rs
+++ b/crates/fbuild-paths/src/dev_daemon_namespace.rs
@@ -15,7 +15,7 @@
 //! This module previously claimed the export was "inert until fbuild repins
 //! a zccache release containing it". That was wrong: endpoint namespacing is
 //! already present at the pinned rev, and the isolation has worked since the
-//! stamp landed. `crates/fbuild-build-engine/tests/
+//! stamp landed. `crates/fbuild-build/tests/env_isolated/
 //! dev_daemon_namespace_isolation.rs` pins the contract so a future repin
 //! cannot drop it silently. What remains zccache-side (zccache#1362) is
 //! zccache *deriving its own* stamp when nothing exported one — which fbuild
diff --git a/crates/fbuild-python/Cargo.toml b/crates/fbuild-python/Cargo.toml
index fa1b6cf92..1ad2d526d 100644
--- a/crates/fbuild-python/Cargo.toml
+++ b/crates/fbuild-python/Cargo.toml
@@ -44,7 +44,7 @@ tracing = { workspace = true }
 [dev-dependencies]
 tempfile = { workspace = true }
 tracing-subscriber = { workspace = true }
-# Only pulled in for the `tests/python_facades.rs` integration binary, which
+# Only pulled in for the `tests/python_facades/` integration binary, which
 # embeds CPython to exercise the Python-visible facades under real GIL and
 # asyncio behavior (FastLED/fbuild#1485 §5.2). Cargo's per-target feature
 # resolution keeps this out of the normal `cdylib`/`rlib` build.
diff --git a/crates/fbuild-python/tests/README.md b/crates/fbuild-python/tests/README.md
index dfbbac8a4..434b15fab 100644
--- a/crates/fbuild-python/tests/README.md
+++ b/crates/fbuild-python/tests/README.md
@@ -2,8 +2,10 @@
 
 Repository-level contract tests for the `fbuild-python` PyO3 extension.
 
-- `pyo3_policy.rs` keeps the PyO3 dependency family and cross-build workflow policy in sync.
-- `python_facades.rs` — embedded-CPython integration tests for `SerialMonitor` /
+One test binary, `python_facades/` (FastLED/fbuild#1577):
+
+- `python_facades/pyo3_policy.rs` keeps the PyO3 dependency family and cross-build workflow policy in sync (runs in the normal test sweep).
+- `python_facades/main.rs`, `cases.rs`, `extended.rs` — embedded-CPython integration tests for `SerialMonitor` /
   `AsyncSerialMonitor` (FastLED/fbuild#1485 §5.2, "AT-P" tests). Needs
   `libpython` at link and run time (the `pyo3` `auto-initialize`
   dev-dependency feature), so every test is `#[ignore]`d and run separately
diff --git a/crates/fbuild-python/tests/python_facades.rs b/crates/fbuild-python/tests/python_facades/main.rs
similarity index 99%
rename from crates/fbuild-python/tests/python_facades.rs
rename to crates/fbuild-python/tests/python_facades/main.rs
index 568d77cda..c2a9d3f4a 100644
--- a/crates/fbuild-python/tests/python_facades.rs
+++ b/crates/fbuild-python/tests/python_facades/main.rs
@@ -387,10 +387,9 @@ fn run_snippet(py: pyo3::Python<'_>, code: &str) {
         });
 }
 
-#[path = "python_facades/cases.rs"]
 mod cases;
-#[path = "python_facades/extended.rs"]
 mod extended;
+mod pyo3_policy;
 
 /// FastLED/fbuild#1487: the test binary must load the `libpython` belonging to
 /// the interpreter it embeds, found through its own RUNPATH rather than a
diff --git a/crates/fbuild-python/tests/pyo3_policy.rs b/crates/fbuild-python/tests/python_facades/pyo3_policy.rs
similarity index 100%
rename from crates/fbuild-python/tests/pyo3_policy.rs
rename to crates/fbuild-python/tests/python_facades/pyo3_policy.rs
diff --git a/crates/fbuild-toolchain/tests/README.md b/crates/fbuild-toolchain/tests/README.md
deleted file mode 100644
index 0afada345..000000000
--- a/crates/fbuild-toolchain/tests/README.md
+++ /dev/null
@@ -1,18 +0,0 @@
-# fbuild-toolchain integration tests
-
-Tests that exercise toolchain resolution against the real network and the real
-package cache, rather than in-process fixtures.
-
-- **`qemu_linux_runtime.rs`** — Linux-only. Proves fbuild can start Espressif
-  QEMU on a host that carries none of libslirp / libSDL2 / libpixman, by
-  provisioning its own runtime-library bundle. `#[ignore]`d by default because
-  it downloads QEMU (~15 MB) and, when needed, the bundle (~5 MB). Run in CI by
-  `.github/workflows/qemu-linux-runtime.yml` on a stock `ubuntu-latest` runner
-  with **no** apt preinstall step — that missing preinstall is the point of the
-  test.
-
-Run locally on Linux:
-
-```bash
-soldr cargo test -p fbuild-toolchain --test qemu_linux_runtime -- --ignored --nocapture
-```
diff --git a/dylints/ban_std_pathbuf/src/allowlist.txt b/dylints/ban_std_pathbuf/src/allowlist.txt
index b0bba370b..459e2bd37 100644
--- a/dylints/ban_std_pathbuf/src/allowlist.txt
+++ b/dylints/ban_std_pathbuf/src/allowlist.txt
@@ -91,7 +91,7 @@ crates/fbuild-build-arm/src/teensy/teensy_compiler.rs
 crates/fbuild-build-arm/src/teensy/teensy_linker.rs
 crates/fbuild-build-engine/src/zccache.rs
 crates/fbuild-build-engine/src/zccache_embedded.rs
-crates/fbuild-build/tests/avr_build.rs
+crates/fbuild-build/tests/env_isolated/avr_build.rs
 crates/fbuild-build/tests/it/cache_survives_tar_extract.rs
 crates/fbuild-build/tests/it/compile_many_stage2_perf.rs
 crates/fbuild-build/tests/it/compile_many_two_stage.rs
diff --git a/dylints/enforce_platform_boundary/src/baseline.txt b/dylints/enforce_platform_boundary/src/baseline.txt
index a3083a999..28d83d2a5 100644
--- a/dylints/enforce_platform_boundary/src/baseline.txt
+++ b/dylints/enforce_platform_boundary/src/baseline.txt
@@ -41,4 +41,4 @@ crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	windows	5
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	target_os	0
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	target_os	1
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	target_os	2
-crates/fbuild-toolchain/tests/qemu_linux_runtime.rs	attr_cfg	target_os	0
+crates/fbuild-packages/tests/it/qemu_linux_runtime.rs	attr_cfg	target_os	0

From b333ef12c26c40e9486f97b72e998dbeca62558b Mon Sep 17 00:00:00 2001
From: Zach Vorhies <zachvorhies@protonmail.com>
Date: Tue, 29 Sep 2026 22:28:38 -0700
Subject: [PATCH 3/4] chore(platform-boundary): follow the moved test files in
 ledger, baseline, inventory

---
 ci/platform_boundary_ledger.tsv                    | 4 ++--
 ci/platform_boundary_research.tsv                  | 6 +++---
 dylints/enforce_platform_boundary/src/baseline.txt | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/ci/platform_boundary_ledger.tsv b/ci/platform_boundary_ledger.tsv
index d69b2cc3a..e59f0ec5c 100644
--- a/ci/platform_boundary_ledger.tsv
+++ b/ci/platform_boundary_ledger.tsv
@@ -24,6 +24,7 @@ crates/fbuild-daemon/src/handlers/websockets_tests.rs	native_path	libc::	6	proce
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	native_path	libc::	7	process	host_mechanic
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	native_path	libc::	8	process	host_mechanic
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	native_path	libc::	9	process	host_mechanic
+crates/fbuild-packages/tests/it/qemu_linux_runtime.rs	attr_cfg	#![cfg(target_os=)]	0	host	host_mechanic
 crates/fbuild-paths/src/dev_daemon_namespace.rs	native_path	std::env::current_exe	0	host_executable	host_mechanic
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	#[cfg(all(test,unix))]	0	host	host_mechanic
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	#[cfg(not(unix))]	0	host	host_mechanic
@@ -32,7 +33,7 @@ crates/fbuild-paths/src/executable_hash.rs	attr_cfg	#[cfg(unix)]	1	host	host_mec
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	#[cfg(unix)]	2	host	host_mechanic
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	#[cfg(unix)]	3	host	host_mechanic
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	#[cfg(unix)]	4	host	host_mechanic
-crates/fbuild-python/tests/python_facades.rs	native_path	std::env::current_exe	0	host_executable	host_mechanic
+crates/fbuild-python/tests/python_facades/main.rs	native_path	std::env::current_exe	0	host_executable	host_mechanic
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	#[cfg(not(windows))]	0	host_executable	host_mechanic
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	#[cfg(not(windows))]	1	host_executable	host_mechanic
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	#[cfg(windows)]	0	host_executable	host_mechanic
@@ -42,4 +43,3 @@ crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	#[cfg(windows)]	3	hos
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	#[cfg(not(target_os=))]	0	host_executable	host_artifact_policy
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	#[cfg(target_os=)]	0	host_executable	host_artifact_policy
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	#[cfg_attr(not(target_os=),allow(dead_code))]	0	host_executable	host_artifact_policy
-crates/fbuild-toolchain/tests/qemu_linux_runtime.rs	attr_cfg	#![cfg(target_os=)]	0	host_executable	host_artifact_policy
diff --git a/ci/platform_boundary_research.tsv b/ci/platform_boundary_research.tsv
index e9828c4d3..2463c3189 100644
--- a/ci/platform_boundary_research.tsv
+++ b/ci/platform_boundary_research.tsv
@@ -73,7 +73,7 @@ crates/fbuild-core/src/platform/windows/usb_pnp.rs	39	native_path	windows_sys::
 crates/fbuild-core/src/platform/windows/usb_pnp.rs	40	native_path	windows_sys::	process	host_mechanic
 crates/fbuild-core/tests/it/platformio_package_resolution.rs	5	attr_cfg	#[cfg(windows)]	host	host_mechanic
 crates/fbuild-core/tests/it/platformio_package_resolution.rs	107	attr_cfg	#[cfg(windows)]	host	host_mechanic
-crates/fbuild-daemon/Cargo.toml	68	native_dependency	libc	process	host_mechanic
+crates/fbuild-daemon/Cargo.toml	74	native_dependency	libc	process	host_mechanic
 crates/fbuild-daemon/src/handlers/emulator/tests_npm_cache.rs	146	attr_cfg	#[cfg(windows)]	host_executable	host_artifact_policy
 crates/fbuild-daemon/src/handlers/emulator/tests_process.rs	9	attr_cfg	#[cfg(windows)]	host_executable	host_artifact_policy
 crates/fbuild-daemon/src/handlers/emulator/tests_process.rs	21	attr_cfg	#[cfg(not(windows))]	host_executable	host_artifact_policy
@@ -96,6 +96,7 @@ crates/fbuild-daemon/src/handlers/websockets_tests.rs	340	native_path	libc::	pro
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	342	native_path	libc::	process	host_mechanic
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	345	native_path	libc::	process	host_mechanic
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	348	native_path	libc::	process	host_mechanic
+crates/fbuild-packages/tests/it/qemu_linux_runtime.rs	18	attr_cfg	#![cfg(target_os=)]	host	host_mechanic
 crates/fbuild-paths/src/dev_daemon_namespace.rs	91	native_path	std::env::current_exe	host_executable	host_mechanic
 crates/fbuild-paths/src/executable_hash.rs	6	attr_cfg	#[cfg(unix)]	host	host_mechanic
 crates/fbuild-paths/src/executable_hash.rs	9	attr_cfg	#[cfg(unix)]	host	host_mechanic
@@ -104,7 +105,7 @@ crates/fbuild-paths/src/executable_hash.rs	66	attr_cfg	#[cfg(not(unix))]	host	ho
 crates/fbuild-paths/src/executable_hash.rs	71	attr_cfg	#[cfg(unix)]	host	host_mechanic
 crates/fbuild-paths/src/executable_hash.rs	76	attr_cfg	#[cfg(unix)]	host	host_mechanic
 crates/fbuild-paths/src/executable_hash.rs	85	attr_cfg	#[cfg(all(test,unix))]	host	host_mechanic
-crates/fbuild-python/tests/python_facades.rs	317	native_path	std::env::current_exe	host_executable	host_mechanic
+crates/fbuild-python/tests/python_facades/main.rs	317	native_path	std::env::current_exe	host_executable	host_mechanic
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	528	attr_cfg	#[cfg(windows)]	host_executable	host_mechanic
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	534	attr_cfg	#[cfg(windows)]	host_executable	host_mechanic
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	565	attr_cfg	#[cfg(not(windows))]	host_executable	host_mechanic
@@ -114,4 +115,3 @@ crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	755	attr_cfg	#[cfg(windows)]	h
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	253	attr_cfg	#[cfg_attr(not(target_os=),allow(dead_code))]	host_executable	host_artifact_policy
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	295	attr_cfg	#[cfg(not(target_os=))]	host_executable	host_artifact_policy
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	301	attr_cfg	#[cfg(target_os=)]	host_executable	host_artifact_policy
-crates/fbuild-toolchain/tests/qemu_linux_runtime.rs	18	attr_cfg	#![cfg(target_os=)]	host_executable	host_artifact_policy
diff --git a/dylints/enforce_platform_boundary/src/baseline.txt b/dylints/enforce_platform_boundary/src/baseline.txt
index 28d83d2a5..38e408194 100644
--- a/dylints/enforce_platform_boundary/src/baseline.txt
+++ b/dylints/enforce_platform_boundary/src/baseline.txt
@@ -23,6 +23,7 @@ crates/fbuild-daemon/src/handlers/websockets_tests.rs	native_import	libc	6
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	native_import	libc	7
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	native_import	libc	8
 crates/fbuild-daemon/src/handlers/websockets_tests.rs	native_import	libc	9
+crates/fbuild-packages/tests/it/qemu_linux_runtime.rs	attr_cfg	target_os	0
 crates/fbuild-paths/src/dev_daemon_namespace.rs	native_import	std::env::current_exe	0
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	unix	0
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	unix	1
@@ -31,7 +32,7 @@ crates/fbuild-paths/src/executable_hash.rs	attr_cfg	unix	3
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	unix	4
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	unix	5
 crates/fbuild-paths/src/executable_hash.rs	attr_cfg	unix	6
-crates/fbuild-python/tests/python_facades.rs	native_import	std::env::current_exe	0
+crates/fbuild-python/tests/python_facades/main.rs	native_import	std::env::current_exe	0
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	windows	0
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	windows	1
 crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	windows	2
@@ -41,4 +42,3 @@ crates/fbuild-toolchain/src/toolchain/esp_qemu.rs	attr_cfg	windows	5
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	target_os	0
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	target_os	1
 crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs	attr_cfg	target_os	2
-crates/fbuild-packages/tests/it/qemu_linux_runtime.rs	attr_cfg	target_os	0

From fc4b6cd1291501465e875175385d5cf38cbc35bd Mon Sep 17 00:00:00 2001
From: Zach Vorhies <zachvorhies@protonmail.com>
Date: Tue, 29 Sep 2026 22:31:01 -0700
Subject: [PATCH 4/4] ci(check-ubuntu): give the check and python-facade jobs
 their own build-cache store

setup-soldr keys the zccache build cache on toolchain + job suffix +
Cargo.lock. With no suffix these jobs shared one key with ~10 other
workflows; the first small job to save it froze a 165 MB entry (an exact
hit never re-saves), so every run of the PR gate restored it and
recompiled ~240 crates (28-32% hit rate, ~380 s of the Test step).
---
 .github/workflows/check-ubuntu.yml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/.github/workflows/check-ubuntu.yml b/.github/workflows/check-ubuntu.yml
index 9d0577797..c1ba342eb 100644
--- a/.github/workflows/check-ubuntu.yml
+++ b/.github/workflows/check-ubuntu.yml
@@ -44,6 +44,11 @@ jobs:
         id: setup-soldr
         uses: zackees/setup-soldr@67ed4018aca013f8388050ac9bc264244f9b742c
         with:
+          # Own build-cache store (setup-soldr#237): with no suffix this job
+          # shared one Cargo.lock-keyed entry with ~10 other workflows, and
+          # the first small job to save it (165 MB) froze it -- an exact hit
+          # never re-saves -- so every run recompiled ~240 crates.
+          cache-key-suffix: check-ubuntu
           cache: true
           build-cache: true
           target-cache: true
@@ -103,6 +108,7 @@ jobs:
       - name: Setup soldr
         uses: zackees/setup-soldr@67ed4018aca013f8388050ac9bc264244f9b742c
         with:
+          cache-key-suffix: python-facades
           cache: true
           build-cache: true
           target-cache: true