diff --git a/.github/workflows/smoke-soak.yml b/.github/workflows/smoke-soak.yml
index c70a7839..250d9403 100644
--- a/.github/workflows/smoke-soak.yml
+++ b/.github/workflows/smoke-soak.yml
@@ -106,7 +106,7 @@ jobs:
         with:
           # The fork/exec surface PR #206 introduced and epic #501 is
           # actively de-risking, plus the reproducer harness itself — a
-          # change to `scripts/repro-fork.sh`, `userspace/repro_fork/`,
+          # change to `scripts/repro-fork.sh`, `tests/userspace/repro_fork/`,
           # or the `repro-fork` xtask subcommand could silently
           # invalidate the soak, so it must trigger too.
           # Deliberately does NOT include this workflow file — a
@@ -120,7 +120,7 @@ jobs:
               - 'kernel/src/process/**'
               - 'xtask/src/main.rs'
               - 'scripts/repro-fork.sh'
-              - 'userspace/repro_fork/**'
+              - 'tests/userspace/repro_fork/**'
 
       - name: Decide
         id: decide
diff --git a/Cargo.toml b/Cargo.toml
index 5c8b1bef..fd2df575 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,16 +16,16 @@ members = [
     # dispatches to its `bench-page-cache` binary.
     "bench/page-cache",
     "xtask",
-    "userspace/hello",
-    "userspace/init",
-    "userspace/pjdfstest_runner",
-    "userspace/repro_fork",
-    "userspace/shell_pipeline",
-    "userspace/vibix_abi",
-    "userspace/vibix_libc",
-    "userspace/vibix_libc_defs",
-    "userspace/ld_vibix",
-    "userspace/hello_dyn",
+    "base/init",
+    "base/vibix_abi",
+    "base/vibix_libc",
+    "base/vibix_libc_defs",
+    "base/ld_vibix",
+    "tests/userspace/hello",
+    "tests/userspace/hello_dyn",
+    "tests/userspace/pjdfstest_runner",
+    "tests/userspace/repro_fork",
+    "tests/userspace/shell_pipeline",
 ]
 # tests/pjdfstest is a vendored copy of saidsay-so/pjdfstest (2-clause BSD). It
 # is intentionally kept outside the workspace until #581 wires it into xtask —
@@ -38,7 +38,7 @@ members = [
 # `host-fuzz` feature; pulling it into the workspace would force the host
 # feature surface on the kernel-target build graph. `cargo xtask fuzz ext2`
 # drives it directly.
-exclude = ["tests/pjdfstest", "kernel/fuzz", "userspace/std_hello"]
+exclude = ["tests/pjdfstest", "kernel/fuzz", "tests/userspace/std_hello"]
 resolver = "2"
 
 [workspace.package]
diff --git a/userspace/init/Cargo.toml b/base/init/Cargo.toml
similarity index 100%
rename from userspace/init/Cargo.toml
rename to base/init/Cargo.toml
diff --git a/userspace/init/link.ld b/base/init/link.ld
similarity index 100%
rename from userspace/init/link.ld
rename to base/init/link.ld
diff --git a/userspace/init/src/main.rs b/base/init/src/main.rs
similarity index 100%
rename from userspace/init/src/main.rs
rename to base/init/src/main.rs
diff --git a/userspace/ld_vibix/Cargo.toml b/base/ld_vibix/Cargo.toml
similarity index 100%
rename from userspace/ld_vibix/Cargo.toml
rename to base/ld_vibix/Cargo.toml
diff --git a/userspace/ld_vibix/link.ld b/base/ld_vibix/link.ld
similarity index 100%
rename from userspace/ld_vibix/link.ld
rename to base/ld_vibix/link.ld
diff --git a/userspace/ld_vibix/src/elf.rs b/base/ld_vibix/src/elf.rs
similarity index 100%
rename from userspace/ld_vibix/src/elf.rs
rename to base/ld_vibix/src/elf.rs
diff --git a/userspace/ld_vibix/src/main.rs b/base/ld_vibix/src/main.rs
similarity index 100%
rename from userspace/ld_vibix/src/main.rs
rename to base/ld_vibix/src/main.rs
diff --git a/userspace/ld_vibix/src/reloc.rs b/base/ld_vibix/src/reloc.rs
similarity index 100%
rename from userspace/ld_vibix/src/reloc.rs
rename to base/ld_vibix/src/reloc.rs
diff --git a/userspace/ld_vibix/src/serial.rs b/base/ld_vibix/src/serial.rs
similarity index 100%
rename from userspace/ld_vibix/src/serial.rs
rename to base/ld_vibix/src/serial.rs
diff --git a/userspace/lib/ld-musl-x86_64.so.1 b/base/lib/ld-musl-x86_64.so.1
similarity index 100%
rename from userspace/lib/ld-musl-x86_64.so.1
rename to base/lib/ld-musl-x86_64.so.1
diff --git a/userspace/vibix_abi/Cargo.toml b/base/vibix_abi/Cargo.toml
similarity index 100%
rename from userspace/vibix_abi/Cargo.toml
rename to base/vibix_abi/Cargo.toml
diff --git a/userspace/vibix_abi/src/alloc.rs b/base/vibix_abi/src/alloc.rs
similarity index 100%
rename from userspace/vibix_abi/src/alloc.rs
rename to base/vibix_abi/src/alloc.rs
diff --git a/userspace/vibix_abi/src/errno.rs b/base/vibix_abi/src/errno.rs
similarity index 100%
rename from userspace/vibix_abi/src/errno.rs
rename to base/vibix_abi/src/errno.rs
diff --git a/userspace/vibix_abi/src/fs.rs b/base/vibix_abi/src/fs.rs
similarity index 100%
rename from userspace/vibix_abi/src/fs.rs
rename to base/vibix_abi/src/fs.rs
diff --git a/userspace/vibix_abi/src/futex.rs b/base/vibix_abi/src/futex.rs
similarity index 100%
rename from userspace/vibix_abi/src/futex.rs
rename to base/vibix_abi/src/futex.rs
diff --git a/userspace/vibix_abi/src/lib.rs b/base/vibix_abi/src/lib.rs
similarity index 100%
rename from userspace/vibix_abi/src/lib.rs
rename to base/vibix_abi/src/lib.rs
diff --git a/userspace/vibix_abi/src/process.rs b/base/vibix_abi/src/process.rs
similarity index 100%
rename from userspace/vibix_abi/src/process.rs
rename to base/vibix_abi/src/process.rs
diff --git a/userspace/vibix_abi/src/stdio.rs b/base/vibix_abi/src/stdio.rs
similarity index 100%
rename from userspace/vibix_abi/src/stdio.rs
rename to base/vibix_abi/src/stdio.rs
diff --git a/userspace/vibix_abi/src/syscall.rs b/base/vibix_abi/src/syscall.rs
similarity index 100%
rename from userspace/vibix_abi/src/syscall.rs
rename to base/vibix_abi/src/syscall.rs
diff --git a/userspace/vibix_abi/src/thread.rs b/base/vibix_abi/src/thread.rs
similarity index 100%
rename from userspace/vibix_abi/src/thread.rs
rename to base/vibix_abi/src/thread.rs
diff --git a/userspace/vibix_libc/Cargo.toml b/base/vibix_libc/Cargo.toml
similarity index 100%
rename from userspace/vibix_libc/Cargo.toml
rename to base/vibix_libc/Cargo.toml
diff --git a/userspace/vibix_libc/src/errno.rs b/base/vibix_libc/src/errno.rs
similarity index 100%
rename from userspace/vibix_libc/src/errno.rs
rename to base/vibix_libc/src/errno.rs
diff --git a/userspace/vibix_libc/src/fcntl.rs b/base/vibix_libc/src/fcntl.rs
similarity index 100%
rename from userspace/vibix_libc/src/fcntl.rs
rename to base/vibix_libc/src/fcntl.rs
diff --git a/userspace/vibix_libc/src/helpers.rs b/base/vibix_libc/src/helpers.rs
similarity index 100%
rename from userspace/vibix_libc/src/helpers.rs
rename to base/vibix_libc/src/helpers.rs
diff --git a/userspace/vibix_libc/src/lib.rs b/base/vibix_libc/src/lib.rs
similarity index 100%
rename from userspace/vibix_libc/src/lib.rs
rename to base/vibix_libc/src/lib.rs
diff --git a/userspace/vibix_libc/src/stat.rs b/base/vibix_libc/src/stat.rs
similarity index 100%
rename from userspace/vibix_libc/src/stat.rs
rename to base/vibix_libc/src/stat.rs
diff --git a/userspace/vibix_libc/src/unistd.rs b/base/vibix_libc/src/unistd.rs
similarity index 100%
rename from userspace/vibix_libc/src/unistd.rs
rename to base/vibix_libc/src/unistd.rs
diff --git a/userspace/vibix_libc_defs/Cargo.toml b/base/vibix_libc_defs/Cargo.toml
similarity index 100%
rename from userspace/vibix_libc_defs/Cargo.toml
rename to base/vibix_libc_defs/Cargo.toml
diff --git a/userspace/vibix_libc_defs/src/lib.rs b/base/vibix_libc_defs/src/lib.rs
similarity index 100%
rename from userspace/vibix_libc_defs/src/lib.rs
rename to base/vibix_libc_defs/src/lib.rs
diff --git a/docs/RFC/0009-std-on-vibix.md b/docs/RFC/0009-std-on-vibix.md
index 639dc101..4a2fe367 100644
--- a/docs/RFC/0009-std-on-vibix.md
+++ b/docs/RFC/0009-std-on-vibix.md
@@ -251,7 +251,7 @@ Key choices:
 #### vibix_abi crate structure
 
 ```
-userspace/vibix_abi/
+base/vibix_abi/
 ├── Cargo.toml          # #![no_std], no deps
 └── src/
     ├── lib.rs          # pub mod syscall, alloc, thread, ...
@@ -268,7 +268,7 @@ userspace/vibix_abi/
 #### vibix_libc crate structure
 
 ```
-userspace/vibix_libc/
+base/vibix_libc/
 ├── Cargo.toml          # cdylib + staticlib, depends on vibix_abi
 ├── cbindgen.toml       # generates libc-compatible C headers
 └── src/
@@ -599,7 +599,7 @@ Porting it to vibix would give immediate ecosystem compatibility.
 musl introduces 100K lines of C that must be audited, cross-compiled,
 and maintained. The Rust-based approach (`vibix_libc`) is smaller,
 memory-safe, and can share syscall stubs with `vibix_abi`. The
-`ld-musl-x86_64.so.1` already present in `userspace/lib/` was
+`ld-musl-x86_64.so.1` already present in `base/lib/` was
 shipped for PT_INTERP testing (#762), not as a long-term libc
 strategy.
 
diff --git a/docs/design/dst-478-investigation.md b/docs/design/dst-478-investigation.md
index 002305f0..15ed4cc8 100644
--- a/docs/design/dst-478-investigation.md
+++ b/docs/design/dst-478-investigation.md
@@ -17,7 +17,7 @@ on the failure being scheduler-driven rather than hardware-fault-driven.
 [#478](https://github.com/dburkart/vibix/issues/478)'s production
 evidence is unambiguous about the failure shape: the kernel emits
 `init: iretq to ring-3` to the serial port, then **no userspace output
-ever appears**. In particular, the `userspace/init/src/main.rs::_start`
+ever appears**. In particular, the `base/init/src/main.rs::_start`
 diagnostic markers `init: pre-write marker` (a `write(2, …)` immediately
 on entry, before any other userspace work) never appear in failing
 runs. That makes the failure window strictly the gap between IRETQ
@@ -175,5 +175,5 @@ analogue of #478.
   [`kernel/src/arch/x86_64/syscall.rs`](../../kernel/src/arch/x86_64/syscall.rs)
   `jump_to_ring3` — the kernel-side seam the trap-frame surface would
   intercept.
-- [`userspace/init/src/main.rs`](../../userspace/init/src/main.rs)
+- [`base/init/src/main.rs`](../../base/init/src/main.rs)
   `_start` (~line 103) — the userspace side of the failure window.
diff --git a/docs/repros/fork-loop.md b/docs/repros/fork-loop.md
index 55840dba..71d35774 100644
--- a/docs/repros/fork-loop.md
+++ b/docs/repros/fork-loop.md
@@ -9,7 +9,7 @@ reproducer.
 
 ## What it does
 
-Replaces PID 1 with a userspace binary (`userspace/repro_fork/`) that runs
+Replaces PID 1 with a userspace binary (`tests/userspace/repro_fork/`) that runs
 a tight `fork → child execve → parent wait4` loop for `CYCLES` iterations
 (default 500).  Every 50 cycles it writes `repro: cycle K alive` to serial;
 every cycle it reads the TSC before and after and prints a watchdog
@@ -72,7 +72,7 @@ exits 0.  Failure: any of —
   to a large value for soak runs.  (Implemented as `option_env!` inside
   the binary, so cargo rebuilds when the value changes.)
 - The per-cycle TSC budget is a compile-time constant
-  (`STALL_TSC_BUDGET` in `userspace/repro_fork/src/main.rs`).  Bump it
+  (`STALL_TSC_BUDGET` in `tests/userspace/repro_fork/src/main.rs`).  Bump it
   if unaccelerated CI QEMU is hitting spurious watchdog trips on a
   healthy kernel.
 
@@ -105,7 +105,7 @@ invocation per iteration, with `SOAK_COUNT` iterations per job run
 Nightly `schedule` and manual `workflow_dispatch` runs exercise this
 path today; the `pull_request` trigger is still gated off while the
 fork flake is live (see #517).  Changes to this harness — either the
-wrapper script or `userspace/repro_fork/` — trigger the workflow's
+wrapper script or `tests/userspace/repro_fork/` — trigger the workflow's
 path filter so the soak runs on any PR that touches them.
 
   The harness amplifies opportunity to hit the hang; whether it trips
diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml
index 51f334b7..1209bc83 100644
--- a/library/std/Cargo.toml
+++ b/library/std/Cargo.toml
@@ -79,7 +79,7 @@ hermit-abi = { version = "0.5.0", features = [
 ], public = true }
 
 [target.'cfg(target_os = "vibix")'.dependencies]
-vibix_abi = { path = "../../userspace/vibix_abi", features = [
+vibix_abi = { path = "../../base/vibix_abi", features = [
     'rustc-dep-of-std',
 ] }
 
diff --git a/userspace/hello/Cargo.toml b/tests/userspace/hello/Cargo.toml
similarity index 100%
rename from userspace/hello/Cargo.toml
rename to tests/userspace/hello/Cargo.toml
diff --git a/userspace/hello/link.ld b/tests/userspace/hello/link.ld
similarity index 100%
rename from userspace/hello/link.ld
rename to tests/userspace/hello/link.ld
diff --git a/userspace/hello/src/main.rs b/tests/userspace/hello/src/main.rs
similarity index 100%
rename from userspace/hello/src/main.rs
rename to tests/userspace/hello/src/main.rs
diff --git a/userspace/hello_dyn/Cargo.toml b/tests/userspace/hello_dyn/Cargo.toml
similarity index 85%
rename from userspace/hello_dyn/Cargo.toml
rename to tests/userspace/hello_dyn/Cargo.toml
index 112f437d..a48a74ba 100644
--- a/userspace/hello_dyn/Cargo.toml
+++ b/tests/userspace/hello_dyn/Cargo.toml
@@ -11,4 +11,4 @@ name = "userspace_hello_dyn"
 path = "src/main.rs"
 
 [dependencies]
-vibix_libc = { path = "../vibix_libc" }
+vibix_libc = { path = "../../../base/vibix_libc" }
diff --git a/userspace/hello_dyn/link.ld b/tests/userspace/hello_dyn/link.ld
similarity index 100%
rename from userspace/hello_dyn/link.ld
rename to tests/userspace/hello_dyn/link.ld
diff --git a/userspace/hello_dyn/src/main.rs b/tests/userspace/hello_dyn/src/main.rs
similarity index 100%
rename from userspace/hello_dyn/src/main.rs
rename to tests/userspace/hello_dyn/src/main.rs
diff --git a/userspace/pjdfstest_runner/Cargo.toml b/tests/userspace/pjdfstest_runner/Cargo.toml
similarity index 100%
rename from userspace/pjdfstest_runner/Cargo.toml
rename to tests/userspace/pjdfstest_runner/Cargo.toml
diff --git a/userspace/pjdfstest_runner/link.ld b/tests/userspace/pjdfstest_runner/link.ld
similarity index 100%
rename from userspace/pjdfstest_runner/link.ld
rename to tests/userspace/pjdfstest_runner/link.ld
diff --git a/userspace/pjdfstest_runner/src/main.rs b/tests/userspace/pjdfstest_runner/src/main.rs
similarity index 100%
rename from userspace/pjdfstest_runner/src/main.rs
rename to tests/userspace/pjdfstest_runner/src/main.rs
diff --git a/userspace/repro_fork/Cargo.toml b/tests/userspace/repro_fork/Cargo.toml
similarity index 100%
rename from userspace/repro_fork/Cargo.toml
rename to tests/userspace/repro_fork/Cargo.toml
diff --git a/userspace/repro_fork/link.ld b/tests/userspace/repro_fork/link.ld
similarity index 100%
rename from userspace/repro_fork/link.ld
rename to tests/userspace/repro_fork/link.ld
diff --git a/userspace/repro_fork/src/main.rs b/tests/userspace/repro_fork/src/main.rs
similarity index 100%
rename from userspace/repro_fork/src/main.rs
rename to tests/userspace/repro_fork/src/main.rs
diff --git a/userspace/shell_pipeline/Cargo.toml b/tests/userspace/shell_pipeline/Cargo.toml
similarity index 100%
rename from userspace/shell_pipeline/Cargo.toml
rename to tests/userspace/shell_pipeline/Cargo.toml
diff --git a/userspace/shell_pipeline/link.ld b/tests/userspace/shell_pipeline/link.ld
similarity index 100%
rename from userspace/shell_pipeline/link.ld
rename to tests/userspace/shell_pipeline/link.ld
diff --git a/userspace/shell_pipeline/src/main.rs b/tests/userspace/shell_pipeline/src/main.rs
similarity index 100%
rename from userspace/shell_pipeline/src/main.rs
rename to tests/userspace/shell_pipeline/src/main.rs
diff --git a/userspace/std_hello/Cargo.toml b/tests/userspace/std_hello/Cargo.toml
similarity index 100%
rename from userspace/std_hello/Cargo.toml
rename to tests/userspace/std_hello/Cargo.toml
diff --git a/userspace/std_hello/src/main.rs b/tests/userspace/std_hello/src/main.rs
similarity index 100%
rename from userspace/std_hello/src/main.rs
rename to tests/userspace/std_hello/src/main.rs
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
index 167feb50..a1fba4ee 100644
--- a/xtask/src/main.rs
+++ b/xtask/src/main.rs
@@ -577,13 +577,13 @@ fn build_userspace_binary(package: &str, link_ld: &str) -> R<PathBuf> {
 }
 
 fn build_userspace_init() -> R<PathBuf> {
-    build_userspace_binary("userspace_init", "userspace/init/link.ld")
+    build_userspace_binary("userspace_init", "base/init/link.ld")
 }
 
 /// Build the hello binary — the exec() target for the fork+exec+wait test.
 /// Links at 0x400000 (lower half) just like init so load_user_elf accepts it.
 fn build_userspace_hello() -> R<PathBuf> {
-    build_userspace_binary("userspace_hello", "userspace/hello/link.ld")
+    build_userspace_binary("userspace_hello", "tests/userspace/hello/link.ld")
 }
 
 /// Build the fork-loop reproducer harness (issue #506).
@@ -592,7 +592,7 @@ fn build_userspace_hello() -> R<PathBuf> {
 /// this binary runs a tight fork+exec+wait loop as PID 1 to amplify the
 /// ~50 %-rate flake bisected to PR #206 into a deterministic repro.
 fn build_userspace_repro_fork() -> R<PathBuf> {
-    build_userspace_binary("userspace_repro_fork", "userspace/repro_fork/link.ld")
+    build_userspace_binary("userspace_repro_fork", "tests/userspace/repro_fork/link.ld")
 }
 
 /// Build the shell-pipeline integration binary (issue #462).
@@ -600,12 +600,12 @@ fn build_userspace_repro_fork() -> R<PathBuf> {
 /// Shipped as `userspace_init.elf` when `cargo xtask shell-pipeline` is
 /// used — the binary internally simulates `echo foo | cat | wc -c`
 /// using pipe2/fork/dup2/close/wait4 and prints `SHELL_PIPELINE_OK: 4`
-/// on success. See `userspace/shell_pipeline/src/main.rs` for the
+/// on success. See `tests/userspace/shell_pipeline/src/main.rs` for the
 /// rationale on why all three pipeline stages live in one binary.
 fn build_userspace_shell_pipeline() -> R<PathBuf> {
     build_userspace_binary(
         "userspace_shell_pipeline",
-        "userspace/shell_pipeline/link.ld",
+        "tests/userspace/shell_pipeline/link.ld",
     )
 }
 
@@ -614,7 +614,10 @@ fn build_userspace_shell_pipeline() -> R<PathBuf> {
 /// `cargo xtask pjdfstest`. Same link layout as `userspace_init` so
 /// the kernel's ELF loader doesn't need any new code paths.
 pub(crate) fn build_pjdfstest_runner() -> R<PathBuf> {
-    build_userspace_binary("pjdfstest_runner", "userspace/pjdfstest_runner/link.ld")
+    build_userspace_binary(
+        "pjdfstest_runner",
+        "tests/userspace/pjdfstest_runner/link.ld",
+    )
 }
 
 /// Build the vibix dynamic linker (`ld-vibix.so`).
@@ -624,7 +627,7 @@ pub(crate) fn build_pjdfstest_runner() -> R<PathBuf> {
 /// Uses `-C relocation-model=pic` and `-C link-arg=-shared` to get
 /// position-independent code in a shared-object container.
 fn build_ld_vibix() -> R<PathBuf> {
-    let link_ld = "userspace/ld_vibix/link.ld";
+    let link_ld = "base/ld_vibix/link.ld";
     let rustflags = [
         &format!("-C link-arg=-T{link_ld}"),
         "-C relocation-model=pic",
@@ -713,7 +716,7 @@ fn build_libc_so() -> R<PathBuf> {
 /// The kernel loads ld-vibix.so and transfers control to it, which then
 /// processes relocations and jumps to this binary's entry point.
 fn build_userspace_hello_dyn() -> R<PathBuf> {
-    let link_ld = "userspace/hello_dyn/link.ld";
+    let link_ld = "tests/userspace/hello_dyn/link.ld";
     let rustflags = [
         &format!("-C link-arg=-T{link_ld}"),
         "-C relocation-model=pic",
@@ -751,7 +754,7 @@ fn build_userspace_hello_dyn() -> R<PathBuf> {
 fn build_userspace_std_hello() -> R<PathBuf> {
     let ws = workspace_root();
     let target_spec = ws.join(VIBIX_USERSPACE_TARGET);
-    let manifest = ws.join("userspace/std_hello/Cargo.toml");
+    let manifest = ws.join("tests/userspace/std_hello/Cargo.toml");
     let library_root = ws.join("library");
 
     let target_dir = ws.join("target");
@@ -1283,7 +1286,7 @@ fn ensure_initrd() -> R<PathBuf> {
                                                       // DIRS headers + 4 file headers + (3 small + LDSO_BLOCKS) data blocks + 2 end blocks.
     const EXPECTED_SIZE: u64 = (DIRS.len() as u64 + 4 + 3 + LDSO_BLOCKS + 2) * 512;
 
-    let ldso_src = workspace_root().join("userspace/lib/ld-musl-x86_64.so.1");
+    let ldso_src = workspace_root().join("base/lib/ld-musl-x86_64.so.1");
 
     // Size + magic aren't sufficient — changing MOTD_PAYLOAD to another
     // equal-or-shorter string would leave the old payload on disk (same
@@ -1551,7 +1554,7 @@ fn make_iso_inner(
     fs::copy(userspace_hello, iso_root.join("boot/userspace_hello.elf"))?;
     fs::copy(&initrd, iso_root.join("boot/rootfs.tar"))?;
     fs::copy(
-        workspace_root().join("userspace/lib/ld-musl-x86_64.so.1"),
+        workspace_root().join("base/lib/ld-musl-x86_64.so.1"),
         iso_root.join("boot/ld-musl-x86_64.so.1"),
     )?;
     // #764: stub dynamic-linker fixture for the dynlinker_stub integration test.
@@ -2275,7 +2278,7 @@ fn repro_fork_build(opts: &BuildOpts) -> R<PathBuf> {
 /// heartbeat-aware watchdog.  Issue #506 / epic #501.
 ///
 /// Replaces `/boot/userspace_init.elf` in the ISO with the
-/// `userspace_repro_fork` binary (see `userspace/repro_fork/`).  That
+/// `userspace_repro_fork` binary (see `tests/userspace/repro_fork/`).  That
 /// binary runs `CYCLES` fork+exec+wait iterations, emitting
 /// `repro: cycle K alive` every 50 cycles and `repro: fork loop
 /// complete` on success.  The loop in this function follows those
@@ -3687,6 +3690,7 @@ repro: starting fork loop cycles=500 hb=50
     fn repro_fork_default_cycles_is_500() {
         let source = std::fs::read_to_string(
             workspace_root()
+                .join("tests")
                 .join("userspace")
                 .join("repro_fork")
                 .join("src")
@@ -3701,7 +3705,7 @@ repro: starting fork loop cycles=500 hb=50
         // timing budget / this test."
         assert!(
             source.contains("None => 500,"),
-            "userspace/repro_fork/src/main.rs must keep the default CYCLES=500; \
+            "tests/userspace/repro_fork/src/main.rs must keep the default CYCLES=500; \
              if you genuinely need to change this, also update \
              .github/workflows/smoke-soak.yml timing budgets and issue #531's context"
         );
@@ -3720,6 +3724,7 @@ repro: starting fork loop cycles=500 hb=50
     fn repro_fork_syscall_blocks_clobber_all_sysv_caller_saved() {
         let source = std::fs::read_to_string(
             workspace_root()
+                .join("tests")
                 .join("userspace")
                 .join("repro_fork")
                 .join("src")