diff --git a/AGENTS.md b/AGENTS.md
index 4ba75ba..8f5c18d 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -21,7 +21,7 @@ implementing it one task at a time.
 ## Files you must never edit
 
 - `PLAN.md`, `docs/plans/`, `AGENTS.md`
-- Anything a task told you to copy from `docs/plans/**/files/`: tests, testdata, `Makefile`,
+- Anything a task told you to copy from `docs/plans/**/_files/`: tests, testdata, `Makefile`,
   scripts, `example.toml`, `cmd/fakeupstream`. If a copied test fails, your code is wrong.
 
 ## Code rules
diff --git a/docs/plans/v0/01-module-gate-config.md b/docs/plans/v0/01-module-gate-config.md
index a08ad55..49f4cba 100644
--- a/docs/plans/v0/01-module-gate-config.md
+++ b/docs/plans/v0/01-module-gate-config.md
@@ -103,10 +103,10 @@ Rules the tests check:
 ```sh
 git switch -c v0
 mkdir -p scripts internal/config/testdata
-cp docs/plans/v0/files/Makefile docs/plans/v0/files/go.sum .
-cp docs/plans/v0/files/scripts/check-lines.sh scripts/
-cp docs/plans/v0/files/internal/config/config_test.go internal/config/
-cp docs/plans/v0/files/internal/config/testdata/*.toml internal/config/testdata/
+cp docs/plans/v0/_files/Makefile docs/plans/v0/_files/go.sum .
+cp docs/plans/v0/_files/scripts/check-lines.sh scripts/
+cp docs/plans/v0/_files/internal/config/config_test.go internal/config/
+cp docs/plans/v0/_files/internal/config/testdata/*.toml internal/config/testdata/
 ```
 
 Read `Makefile` and `internal/config/config_test.go`. The test names every rule above.
@@ -139,7 +139,7 @@ git commit
 ## Done when
 
 - `go test ./internal/config/` is `ok`; `make gate` prints `gate: ok`.
-- `cmp internal/config/config_test.go docs/plans/v0/files/internal/config/config_test.go` prints nothing.
+- `cmp internal/config/config_test.go docs/plans/v0/_files/internal/config/config_test.go` prints nothing.
 
 ## Stop and report if
 
diff --git a/docs/plans/v0/02-health.md b/docs/plans/v0/02-health.md
index 83f0b0d..5d49748 100644
--- a/docs/plans/v0/02-health.md
+++ b/docs/plans/v0/02-health.md
@@ -81,7 +81,7 @@ Rules the tests check:
 
 ```sh
 git switch v0
-cp docs/plans/v0/files/internal/health/health_test.go internal/health/
+cp docs/plans/v0/_files/internal/health/health_test.go internal/health/
 ```
 
 Read the test. `newFake` is the router stand-in; `TestFailureThenRecoveryNeedsTwoPolls` is rule 3
@@ -102,7 +102,7 @@ git commit
 ## Done when
 
 - `go test -race -count=1 ./internal/health/` is `ok`; `make gate` prints `gate: ok`.
-- `cmp internal/health/health_test.go docs/plans/v0/files/internal/health/health_test.go` prints nothing.
+- `cmp internal/health/health_test.go docs/plans/v0/_files/internal/health/health_test.go` prints nothing.
 
 ## Stop and report if
 
diff --git a/docs/plans/v0/03-proxy.md b/docs/plans/v0/03-proxy.md
index 2932b39..8ac725f 100644
--- a/docs/plans/v0/03-proxy.md
+++ b/docs/plans/v0/03-proxy.md
@@ -92,7 +92,7 @@ Rules the tests check, in the order `ServeHTTP` applies them. Every error answer
 
 ```sh
 git switch v0
-cp docs/plans/v0/files/internal/proxy/proxy_test.go internal/proxy/
+cp docs/plans/v0/_files/internal/proxy/proxy_test.go internal/proxy/
 ```
 
 Read the test. `fakeHealth` stands in for the table; `newUpstream` records what arrived.
@@ -113,7 +113,7 @@ git commit
 ## Done when
 
 - `go test -race -count=1 ./internal/proxy/` is `ok`; `make gate` prints `gate: ok`.
-- `cmp internal/proxy/proxy_test.go docs/plans/v0/files/internal/proxy/proxy_test.go` prints nothing.
+- `cmp internal/proxy/proxy_test.go docs/plans/v0/_files/internal/proxy/proxy_test.go` prints nothing.
 
 ## Stop and report if
 
diff --git a/docs/plans/v0/04-admin-main.md b/docs/plans/v0/04-admin-main.md
index 69956c9..9ee00fa 100644
--- a/docs/plans/v0/04-admin-main.md
+++ b/docs/plans/v0/04-admin-main.md
@@ -82,9 +82,9 @@ not change it.
 ```sh
 git switch v0
 mkdir -p cmd/fakeupstream cmd/crossbar internal/admin
-cp docs/plans/v0/files/cmd/fakeupstream/main.go cmd/fakeupstream/
-cp docs/plans/v0/files/example.toml .
-cp docs/plans/v0/files/internal/admin/admin_test.go internal/admin/
+cp docs/plans/v0/_files/cmd/fakeupstream/main.go cmd/fakeupstream/
+cp docs/plans/v0/_files/example.toml .
+cp docs/plans/v0/_files/internal/admin/admin_test.go internal/admin/
 ```
 
 - [ ] **2. See the test fail.** `go test ./internal/admin/`. Expected: it does not compile.
@@ -119,7 +119,7 @@ git commit
 
 - The admin test passes, the three-second run exits 0 with both log lines, the missing-config
   run exits 1, `make gate` prints `gate: ok`.
-- `cmp cmd/fakeupstream/main.go docs/plans/v0/files/cmd/fakeupstream/main.go` and the same for
+- `cmp cmd/fakeupstream/main.go docs/plans/v0/_files/cmd/fakeupstream/main.go` and the same for
   `example.toml` and `internal/admin/admin_test.go` print nothing.
 
 ## Stop and report if
diff --git a/docs/plans/v0/05-smoke-readme-deploy.md b/docs/plans/v0/05-smoke-readme-deploy.md
index 896e963..2f0deb7 100644
--- a/docs/plans/v0/05-smoke-readme-deploy.md
+++ b/docs/plans/v0/05-smoke-readme-deploy.md
@@ -32,7 +32,7 @@ spread over at least 600 ms, not in one burst; and crossbar wrote a request log
 ```sh
 git switch v0
 mkdir -p tools deploy
-cp docs/plans/v0/files/tools/smoke.sh tools/
+cp docs/plans/v0/_files/tools/smoke.sh tools/
 make smoke
 ```
 
@@ -111,7 +111,7 @@ git commit
 ## Done when
 
 - `make smoke` prints `smoke: ok (…)`; `make gate` prints `gate: ok`; `README.md` has the seven
-  sections; `cmp tools/smoke.sh docs/plans/v0/files/tools/smoke.sh` prints nothing.
+  sections; `cmp tools/smoke.sh docs/plans/v0/_files/tools/smoke.sh` prints nothing.
 
 ## Stop and report if
 
diff --git a/docs/plans/v0/README.md b/docs/plans/v0/README.md
index 72e039a..73418dc 100644
--- a/docs/plans/v0/README.md
+++ b/docs/plans/v0/README.md
@@ -12,7 +12,7 @@ no `/slots`, no queueing.
 **Architecture:** four small packages under `internal/` — `config` (TOML + validation), `health`
 (poller + table), `proxy` (route → host → `httputil.ReverseProxy`), `admin` (read-only JSON) —
 and two binaries under `cmd/`: `crossbar` and the given `fakeupstream`. Behaviour is pinned by
-the tests in `files/`, which were run against a private reference implementation at each task's
+the tests in `_files/`, which were run against a private reference implementation at each task's
 end state; the reference is not in this repository and the implementer must not look for it.
 
 **Tech stack:** Go 1.26, standard library, `github.com/BurntSushi/toml` v1.6.0. Nothing else.
@@ -53,10 +53,19 @@ stops at the first task that does not end with a commit, a clean tree and a `don
 
 1. `git log --oneline master..v0`: five commits with the `Implemented-By` trailer.
 2. Copied files are unchanged:
-   `for f in $(cd docs/plans/v0/files && find . -type f); do cmp "docs/plans/v0/files/$f" "$f"; done`
+   `for f in $(cd docs/plans/v0/_files && find . -type f); do cmp "docs/plans/v0/_files/$f" "$f"; done`
 3. `git diff master..v0 --stat -- PLAN.md AGENTS.md docs/plans` is empty.
 4. `make gate` and `make smoke` on straylight.
 5. Read every source file against its task. Probe from outside with inputs the tests do not
    contain: a route with query strings and encoded characters, a host that hangs after headers, a
    3 MB request body, `/_crossbar/hosts` while a poll is in flight, SIGTERM during a stream.
 6. Write findings under "Reviews" in `docs/implementer-log.md`.
+
+## Changes during the run
+
+- 2026-09-25, task 01, first attempt: the given files lived under `docs/plans/v0/files/`, which
+  Go's `./...` pattern includes, so `go vet ./...` in the gate tried to build the tests of tasks
+  02–04 against packages that did not exist yet. Ornith diagnosed this correctly and stopped
+  investigating instead of editing the Makefile. Fixed by moving the directory to `_files/`
+  (directories starting with `_` are ignored by the go tool); every task file updated. Task 01
+  restarted from a clean tree.
diff --git a/docs/plans/v0/files/Makefile b/docs/plans/v0/_files/Makefile
similarity index 100%
rename from docs/plans/v0/files/Makefile
rename to docs/plans/v0/_files/Makefile
diff --git a/docs/plans/v0/files/cmd/fakeupstream/main.go b/docs/plans/v0/_files/cmd/fakeupstream/main.go
similarity index 100%
rename from docs/plans/v0/files/cmd/fakeupstream/main.go
rename to docs/plans/v0/_files/cmd/fakeupstream/main.go
diff --git a/docs/plans/v0/files/example.toml b/docs/plans/v0/_files/example.toml
similarity index 100%
rename from docs/plans/v0/files/example.toml
rename to docs/plans/v0/_files/example.toml
diff --git a/docs/plans/v0/files/go.sum b/docs/plans/v0/_files/go.sum
similarity index 100%
rename from docs/plans/v0/files/go.sum
rename to docs/plans/v0/_files/go.sum
diff --git a/docs/plans/v0/files/internal/admin/admin_test.go b/docs/plans/v0/_files/internal/admin/admin_test.go
similarity index 100%
rename from docs/plans/v0/files/internal/admin/admin_test.go
rename to docs/plans/v0/_files/internal/admin/admin_test.go
diff --git a/docs/plans/v0/files/internal/config/config_test.go b/docs/plans/v0/_files/internal/config/config_test.go
similarity index 100%
rename from docs/plans/v0/files/internal/config/config_test.go
rename to docs/plans/v0/_files/internal/config/config_test.go
diff --git a/docs/plans/v0/files/internal/config/testdata/bad-default-model.toml b/docs/plans/v0/_files/internal/config/testdata/bad-default-model.toml
similarity index 100%
rename from docs/plans/v0/files/internal/config/testdata/bad-default-model.toml
rename to docs/plans/v0/_files/internal/config/testdata/bad-default-model.toml
diff --git a/docs/plans/v0/files/internal/config/testdata/bad-listen.toml b/docs/plans/v0/_files/internal/config/testdata/bad-listen.toml
similarity index 100%
rename from docs/plans/v0/files/internal/config/testdata/bad-listen.toml
rename to docs/plans/v0/_files/internal/config/testdata/bad-listen.toml
diff --git a/docs/plans/v0/files/internal/config/testdata/bad-unknown-host.toml b/docs/plans/v0/_files/internal/config/testdata/bad-unknown-host.toml
similarity index 100%
rename from docs/plans/v0/files/internal/config/testdata/bad-unknown-host.toml
rename to docs/plans/v0/_files/internal/config/testdata/bad-unknown-host.toml
diff --git a/docs/plans/v0/files/internal/config/testdata/bad-unknown-key.toml b/docs/plans/v0/_files/internal/config/testdata/bad-unknown-key.toml
similarity index 100%
rename from docs/plans/v0/files/internal/config/testdata/bad-unknown-key.toml
rename to docs/plans/v0/_files/internal/config/testdata/bad-unknown-key.toml
diff --git a/docs/plans/v0/files/internal/config/testdata/good.toml b/docs/plans/v0/_files/internal/config/testdata/good.toml
similarity index 100%
rename from docs/plans/v0/files/internal/config/testdata/good.toml
rename to docs/plans/v0/_files/internal/config/testdata/good.toml
diff --git a/docs/plans/v0/files/internal/health/health_test.go b/docs/plans/v0/_files/internal/health/health_test.go
similarity index 100%
rename from docs/plans/v0/files/internal/health/health_test.go
rename to docs/plans/v0/_files/internal/health/health_test.go
diff --git a/docs/plans/v0/files/internal/proxy/proxy_test.go b/docs/plans/v0/_files/internal/proxy/proxy_test.go
similarity index 100%
rename from docs/plans/v0/files/internal/proxy/proxy_test.go
rename to docs/plans/v0/_files/internal/proxy/proxy_test.go
diff --git a/docs/plans/v0/files/scripts/check-lines.sh b/docs/plans/v0/_files/scripts/check-lines.sh
similarity index 100%
rename from docs/plans/v0/files/scripts/check-lines.sh
rename to docs/plans/v0/_files/scripts/check-lines.sh
diff --git a/docs/plans/v0/files/tools/smoke.sh b/docs/plans/v0/_files/tools/smoke.sh
similarity index 100%
rename from docs/plans/v0/files/tools/smoke.sh
rename to docs/plans/v0/_files/tools/smoke.sh