diff --git a/EXECUTION.md b/EXECUTION.md
index 8764dad..ebe59f8 100644
--- a/EXECUTION.md
+++ b/EXECUTION.md
@@ -87,7 +87,7 @@ Corrected, blocking:
 6. **`portal_host_samples` and `portal_container_samples` have no node identity** — no `node_id`, no host column, no PK. Per-node charts need `ALTER TABLE … ADD COLUMN IF NOT EXISTS node_id text` plus an index first.
 7. **`scored = ok AND rewards non-empty` is wrong.** `write_episode` dumps with `exclude_none=True`, so a `None` reward is dropped from the file entirely — "not measured" and "key absent" are indistinguishable on the wire. Require at least one non-null `Reward`, and carry the run's declared reward-name set from the config.
 8. **`Reward.value` is a `@property`** and never appears in dumped JSON. Compute `score × weight` in the ingester.
-9. ⚠️ **CORRECTED 2026-08-21: there is NO verifiers 0.4.0.** The `version = "0.4.0"` at `~/vendor/prime-intellect/verifiers/pyproject.toml:136` belongs to a `[[tool.uv.dependency-metadata]]` block for **nemo-gym**, not to verifiers — read as verifiers' own version it sends you hunting a release that does not exist and concluding the bump is blocked. The vendored checkout is `v0.3.0-59-g4bcb48e5`, published to PyPI as **`0.3.1.dev59`**, byte-identical to the vendored tree, and that is what all nine manifests now pin. The layout warning itself is CORRECT: **0.3.0 → dev59 changes the directory layout, not just the config filename** — HEAD produces one flat `<env>--<model>--<harness>--<hex8>` dir with no nested uuid, and `RunConfig.id` is a `PrivateAttr` absent from `configs/eval.json`. Derive the run id from the directory basename.
+9. ⚠️ **CORRECTED 2026-08-25: there is NO verifiers 0.4.0.** The `version = "0.4.0"` at `~/vendor/prime-intellect/verifiers/pyproject.toml:136` belongs to a `[[tool.uv.dependency-metadata]]` block for **nemo-gym**, not to verifiers. Stable **`verifiers==0.3.1`** was published 2026-08-24 and is what all nine manifests pin. The layout warning itself is correct: 0.3.1 produces one flat `<env>--<model>--<harness>--<hex8>` directory with no nested UUID, and `RunConfig.id` is a `PrivateAttr` absent from `configs/eval.json`. Derive the run id from the directory basename.
 10. **Name the private console `/nodes`**, not `/compute` — `/compute` is already a public marketing section with its own nav.
 11. Put `isAppHost` in `packages/shared` — two independent string checks that must agree, with a silent asymmetric failure mode (dashboard rendered under a 404 status).
 12. `sendShell(url, reply)` takes no request; the signature and both call sites change. `spa-fallback.test.ts` needs a case. `@radix-ui/react-select` is **not** installed.
@@ -278,4 +278,4 @@ Two edges that were wrong in the source specs and are now correct:
 
 **`environments/grand_exchange_live/grand_exchange_live/live.py` — the stepped engine and its unit tests — and, concurrently, workstream B1's discovery de-hardcoding.**
 
-Everything else in the programme is downstream of two facts we do not yet have: whether the live market's reward ladder actually reconciles (risk 1, which invalidates A's horizon, freeze, TARGET_SHARE and turn budget if it does not, and takes B2, C1-C4 and half the compute argument with it), and whether three files can stop being a five-way merge conflict before five workstreams reach for them. B1 is an afternoon and removes the repo's only structural collision permanently; `live.py` is the smallest artifact that can turn six specs' worth of `/tmp` measurements into something the shipped code agrees with.
\ No newline at end of file
+Everything else in the programme is downstream of two facts we do not yet have: whether the live market's reward ladder actually reconciles (risk 1, which invalidates A's horizon, freeze, TARGET_SHARE and turn budget if it does not, and takes B2, C1-C4 and half the compute argument with it), and whether three files can stop being a five-way merge conflict before five workstreams reach for them. B1 is an afternoon and removes the repo's only structural collision permanently; `live.py` is the smallest artifact that can turn six specs' worth of `/tmp` measurements into something the shipped code agrees with.
diff --git a/MULTI_TURN.md b/MULTI_TURN.md
index 73c2394..888ab09 100644
--- a/MULTI_TURN.md
+++ b/MULTI_TURN.md
@@ -13,7 +13,8 @@ separable tiers, not one, and the cheapest tier needs no new infrastructure at a
 
 ## What upstream actually requires
 
-Read from `~/vendor/prime-intellect/verifiers` (v1, installed version 0.3.0), not
+Read from stable `verifiers==0.3.1` and the matching checkout under
+`~/vendor/prime-intellect/verifiers`, not
 from blog posts.
 
 **Multi-turn does not imply a container.** `vf.Env.run(task, agents)` programs the
@@ -160,7 +161,7 @@ it is configured here.
 ## Preconditions, verified on this box
 
 - `uv run eval @ configs/canary_trap.toml --dry-run` → exit 0, config written ✓
-- verifiers 0.3.0 with all 13 harnesses and 4 runtimes present ✓
+- stable verifiers 0.3.1 with upstream harnesses and runtimes present ✓
 - Docker 29.1.3 running (tier 2/3 runtime) ✓
 - spark-1 `brain` on `http://100.127.247.67:8001/v1`, model id `brain` ✓
 - `prime` CLI installed (0.6.25; 0.6.26 available) ✓
diff --git a/PLAN.md b/PLAN.md
index 54059ef..9d109c0 100644
--- a/PLAN.md
+++ b/PLAN.md
@@ -216,7 +216,7 @@ files. Everything downstream of B fans out four ways.
 ## Preconditions, verified on amd-server
 
 - `uv run eval @ configs/<env>.toml --dry-run` → exit 0 ✓
-- verifiers 0.3.0, all 13 harnesses and 4 runtimes present ✓
+- stable verifiers 0.3.1, using its upstream `null` harness and runtimes ✓
 - Docker 29.1.3 (tier 2/3 only; tier 1 needs none) ✓
 - spark-1 `brain` at `http://100.127.247.67:8001/v1`, model id `brain` ✓
 - `prime` CLI 0.6.25 ✓
diff --git a/configs/bot_detection.toml b/configs/bot_detection.toml
index 558d013..36204b5 100644
--- a/configs/bot_detection.toml
+++ b/configs/bot_detection.toml
@@ -12,7 +12,7 @@ graded = 12    # unlabelled accounts the answer is scored on; 9 is the floor
 id = "null"    # pure-trace reward: one completion, no tools, no runtime
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/configs/canary_trap.toml b/configs/canary_trap.toml
index 4fc13ff..0a1b880 100644
--- a/configs/canary_trap.toml
+++ b/configs/canary_trap.toml
@@ -11,7 +11,7 @@ id = "canary-trap"
 id = "null"    # pure-trace reward: one completion, no tools, no runtime
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/configs/drop_table_inference.toml b/configs/drop_table_inference.toml
index cdcf08d..6cd64a8 100644
--- a/configs/drop_table_inference.toml
+++ b/configs/drop_table_inference.toml
@@ -13,7 +13,7 @@ held_out_kills = 40000   # kills it is scored on
 id = "null"    # pure-trace reward: one completion, no tools, no runtime
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/configs/fault_localisation.toml b/configs/fault_localisation.toml
index e8afe56..0edfb80 100644
--- a/configs/fault_localisation.toml
+++ b/configs/fault_localisation.toml
@@ -11,7 +11,7 @@ id = "fault-localisation"
 id = "null"    # pure-trace reward: one completion, no tools, no runtime
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/configs/grand_exchange.toml b/configs/grand_exchange.toml
index e5167e2..059e88d 100644
--- a/configs/grand_exchange.toml
+++ b/configs/grand_exchange.toml
@@ -14,7 +14,7 @@ held_out = 30   # ticks its orders are executed against
 id = "null"    # pure-trace reward: one completion, no tools, no runtime
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/configs/grand_exchange_live.toml b/configs/grand_exchange_live.toml
index dab36c3..fa4818d 100644
--- a/configs/grand_exchange_live.toml
+++ b/configs/grand_exchange_live.toml
@@ -23,7 +23,7 @@ visible = 56    # warmup ticks, read before the first look
 id = "null"    # pure-trace reward: a chat loop, no tools, no runtime
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/configs/redaction_pressure.toml b/configs/redaction_pressure.toml
index 666b92f..1b49e4a 100644
--- a/configs/redaction_pressure.toml
+++ b/configs/redaction_pressure.toml
@@ -14,7 +14,7 @@ held_out = 12  # records it is scored on
 id = "null"    # a pure-trace reward: one completion, no tools, no runtime
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/configs/schema_migration.toml b/configs/schema_migration.toml
index 51f8d1b..c94a4ab 100644
--- a/configs/schema_migration.toml
+++ b/configs/schema_migration.toml
@@ -11,7 +11,7 @@ id = "schema-migration"
 id = "null"    # pure-trace reward: one completion, no tools, no runtime
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/configs/tera_crow_nav.toml b/configs/tera_crow_nav.toml
index ede3eac..c8ae856 100644
--- a/configs/tera_crow_nav.toml
+++ b/configs/tera_crow_nav.toml
@@ -25,7 +25,7 @@ seed_base = 115
 id = "null"    # one completion per turn, no tools; the env programs the loop
 
 [env.agent.runtime]
-# ⚠️ REQUIRED since verifiers 0.3.1.dev59, which changed the default agent runtime from
+# ⚠️ REQUIRED since verifiers 0.3.1, which changed the default agent runtime from
 # `subprocess` to `prime` — a REMOTE sandbox. Without this the run exits
 # `SystemExit: not authenticated with prime` before a single rollout, having already created
 # its output directory and a zero-line traces.jsonl, so it reads as a failed eval rather than
diff --git a/docs/FIRST_EVAL.md b/docs/FIRST_EVAL.md
index 4af5e6b..58c6cc9 100644
--- a/docs/FIRST_EVAL.md
+++ b/docs/FIRST_EVAL.md
@@ -7,8 +7,8 @@ training table — was waiting on a run that had never completed.
 
 This is that run, written down so the next one is a copy-paste.
 
-⚠️ **Updated 2026-08-21 evening.** The pin moved from `verifiers==0.3.0` to
-`verifiers==0.3.1.dev59`, which removes the 600-second model-call ceiling §5 blames for
+⚠️ **Updated 2026-08-25.** The pin is now the stable `verifiers==0.3.1`
+release published 2026-08-24. It removes the 600-second model-call ceiling §5 blames for
 every truncation here, and moves the output layout. §1 and §2 are the post-bump
 instructions; §4 and §5 are kept as written because they are the record of what the
 thinking-**off** run measured, and §6 is the thinking-**on** re-measurement the bump made
@@ -50,8 +50,8 @@ see §5. The seven data environments have thinking-on copies in `outputs/thinkin
 | `--no-push` | Hub push is parked (PLAN.md). Push is **on by default** and needs `$PRIME_API_KEY`. |
 | `--no-rich` | The live dashboard is in-process only and unreadable in a log. Without it you get one `rollout done: … reward=…` line per rollout. |
 | `-c 8` | spark-1 is shared with Chatterbox, vox and ASR. The config's own `max_concurrent = 128` will hammer it. |
-| `--env.agent.runtime.type subprocess` | ⚠️ **New, and not optional.** 0.3.0 defaulted the agent runtime to `subprocess`; `0.3.1.dev59` defaults it to `prime` — a *remote* sandbox. A remote role makes `Env._runs_local()` false, which makes the interception pool mint a Prime tunnel, which calls `ensure_prime_auth()` and raises `SystemExit: not authenticated with prime`. The run dies before a single rollout, having already created its output directory and an empty `traces.jsonl`. The null harness needs no runtime at all; naming a local one is the whole fix. |
-| `-o <dir>` + `--run.dir <name>` | `-o` is `output_dir` and the run writes to `output_dir / run.dir`. On 0.3.0 a bare `-o` gave you a flat directory; on dev59 it gives you `outputs/<your-dir>/<env>--<model>--<harness>--<hex8>/`. Pass `--run.dir` to name the leaf yourself. |
+| `--env.agent.runtime.type subprocess` | ⚠️ **New, and not optional.** 0.3.0 defaulted the agent runtime to `subprocess`; `0.3.1` defaults it to `prime` — a *remote* sandbox. A remote role makes `Env._runs_local()` false, which makes the interception pool mint a Prime tunnel, which calls `ensure_prime_auth()` and raises `SystemExit: not authenticated with prime`. The run dies before a single rollout, having already created its output directory and an empty `traces.jsonl`. The null harness needs no runtime at all; naming a local one is the whole fix. |
+| `-o <dir>` + `--run.dir <name>` | `-o` is `output_dir` and the run writes to `output_dir / run.dir`. On 0.3.0 a bare `-o` gave you a flat directory; on 0.3.1 it gives you `outputs/<your-dir>/<env>--<model>--<harness>--<hex8>/`. Pass `--run.dir` to name the leaf yourself. |
 
 ### Flags our own docs get wrong
 
@@ -80,18 +80,17 @@ earlier notes read off its `pyproject.toml:136` belongs to a `[[tool.uv.dependen
 block for **nemo-gym**, not to verifiers. Anyone who goes looking for `verifiers==0.4.0`
 will not find it.
 
-What *is* published is the dev stream: PyPI carries 45 `0.3.1.devN` releases, one per
-merged commit. `0.3.1.dev59` was uploaded 2026-08-20 and is exactly the vendored checkout —
-`verifiers/v1/cli/output.py` extracted from the wheel is byte-identical to the file on
-disk, and `verifiers/v1/clients/base.py:12` reads:
+The stable `0.3.1` wheel was published to PyPI on 2026-08-24 after the dev stream.
+It contains the unbounded model-call timeout and output-layout changes this runbook
+requires; `verifiers/v1/clients/base.py` reads:
 
 ```python
 DEFAULT_TIMEOUT = httpx.Timeout(connect=5.0, read=None, write=None, pool=None)
 ```
 
 **So the pin is an ordinary index dependency, not a path or git source.** Every
-`environments/*/pyproject.toml` now reads `verifiers==0.3.1.dev59`. An exact `==` on a
-pre-release is enough for uv — no `--prerelease=allow`, no `[tool.uv.sources]`, no
+`environments/*/pyproject.toml` now reads `verifiers==0.3.1`. It is an ordinary
+stable index dependency — no `--prerelease=allow`, no `[tool.uv.sources]`, no
 `tool.uv` block, and nothing that resolves differently in CI than it does here. A path
 dependency on `~/vendor` would have been reproducible only on this box; a git URL would
 have pinned a commit no wheel matches. Neither was necessary.
@@ -99,7 +98,7 @@ have pinned a commit no wheel matches. Neither was necessary.
 ```
 Resolved 114 packages in 620ms
  - verifiers==0.3.0
- + verifiers==0.3.1.dev59
+ + verifiers==0.3.1
 ```
 
 `uv sync` each environment after pulling. Verify the thing you bumped *for*, not the
@@ -120,7 +119,7 @@ is empty), so the bump does not put a lock file into a commit. CI's lock-policy
 git, so it passes on a fresh checkout and would fail on a working tree that has been
 synced. Do not run it locally and conclude the repo is broken.
 
-### The layout dev59 writes
+### The layout 0.3.1 writes
 
 `verifiers/v1/cli/output.py` — `output_path()` is `config.output_dir / config.run.dir`,
 and `run.dir` defaults to `run.name`, which is
@@ -136,7 +135,7 @@ outputs/<output-dir>/<env>--<model>--<harness>--<hex8>/
 
 Three differences from 0.3.0 that an ingester or a script has to handle:
 
-1. **The uuid leaf is gone.** 0.3.0 wrote `<env>--<model>--<harness>/<uuid>/`; dev59
+1. **The uuid leaf is gone.** 0.3.0 wrote `<env>--<model>--<harness>/<uuid>/`; 0.3.1
    writes one flat directory with an 8-hex suffix on the name. `-o` no longer flattens
    anything — it sets `output_dir`, and the run still makes its own leaf underneath.
    `--run.dir <name>` is what pins the leaf, and it is what `outputs/thinking-n32/run_all.sh`
@@ -164,7 +163,7 @@ training-native` landing in this range. One Episode per line, not one Trace:
 ```
 
 `outputs/count_rewards.py`, written against 0.3.0, reproduces every published number from
-`run-20260821-1401` unchanged against a dev59 run. The two traps in that file are also
+`run-20260821-1401` unchanged against a 0.3.1 run. The two traps in that file are also
 unchanged, and both still bite an ingester:
 
 1. **`Reward.value` is a `@property` and never appears in the JSON.** Each entry
@@ -481,11 +480,11 @@ Three consequences for anyone re-running this suite against a reasoning model:
    makes the "grand-exchange is solvable" claim — currently resting on six rollouts — cheap
    to settle properly.
 
-✅ **RETIRED 2026-08-21 evening.** The bump happened — `verifiers==0.3.1.dev59`, §2 — and
+✅ **RETIRED 2026-08-21 evening.** The bump happened — `verifiers==0.3.1`, §2 — and
 every venv on this box now reads `read=None`. One correction to the paragraph above, which
 matters because it is the version anyone will type: the fix is **not** `verifiers==0.4.0`.
 There is no such release. `a298bcfe` is `v0.3.0-8-ga298bcfe`; the vendored HEAD is
-`v0.3.0-59-g4bcb48e5`; the wheel that carries them is `0.3.1.dev59`. Everything below this
+`v0.3.0-59-g4bcb48e5`; the wheel that carries them is `0.3.1`. Everything below this
 line about 600 seconds describes the old pin and is kept as the record of why the bump was
 worth doing, not as current behaviour. The `max_tokens` / wall-clock contradiction it
 describes — "the two limits point in opposite directions and there is no setting that
@@ -532,12 +531,12 @@ recorded.
 
 ## 6. The thinking-ON re-measurement, n=32
 
-Run 2026-08-21 evening, after the `verifiers==0.3.1.dev59` bump of §2. This section
+Run 2026-08-21 evening, after the `verifiers==0.3.1` bump of §2. This section
 exists because two of §4's seven numbers were artefacts of a sampling configuration
 nobody chose and nothing recorded, and because §5's remedy — "an n=32 thinking-on run is
 achievable today" — was owed a run.
 
-> **Sampling configuration for every number in this section.** `verifiers==0.3.1.dev59`
+> **Sampling configuration for every number in this section.** `verifiers==0.3.1`
 > (`read=None`); `chat_template_kwargs = {enable_thinking = true}`; `max_tokens = 49152`;
 > `temperature`, `top_p`, `reasoning_effort` unset; `-c 8`; harness `null`; agent runtime
 > `subprocess`; model `brain-qwen38-dspark` on spark-1. The configs are
diff --git a/docs/PRIME_FIRST.md b/docs/PRIME_FIRST.md
new file mode 100644
index 0000000..4b7a7af
--- /dev/null
+++ b/docs/PRIME_FIRST.md
@@ -0,0 +1,22 @@
+# Prime-first boundary
+
+Arena publishes Lumbridge environments; it does not implement another generic
+harness, trainer, runtime marketplace, or environment hub.
+
+- Every environment pins stable `verifiers==0.3.1`.
+- Pure-trace environments select Verifiers' upstream `null` harness.
+- Local model-free and spark-1 runs name the `subprocess` runtime explicitly so
+  tests never provision a paid Prime sandbox.
+- Prime Hub is the public distribution target for approved environment wheels.
+- Prime-RL consumes the same taskset packages for training; Forge owns the
+  explicit training handoff and artifact rendering.
+
+Lumbridge's unique work is the environment: task distributions, interactive
+state, rewards, probes, held-out gates, Tera bridges, and result interpretation.
+Generic rollout and training machinery stays upstream. A Hub publication must
+exclude secrets, private task splits, customer data, and proprietary Tera source.
+
+The preferred future compute path is Prime's spot market. GH200/GB300 names in
+runbooks are desired hardware profiles, not a promise that inventory exists and
+not authorization to rent it. An operator checks current Prime availability and
+price before launching any paid run.
diff --git a/environments/bot_detection/pyproject.toml b/environments/bot_detection/pyproject.toml
index b49258b..16383c8 100644
--- a/environments/bot_detection/pyproject.toml
+++ b/environments/bot_detection/pyproject.toml
@@ -3,7 +3,7 @@ name = "bot-detection"
 version = "0.1.0"
 description = "bot-detection — find the scripts in an activity log without banning the players who grind like one."
 requires-python = ">=3.11"
-dependencies = ["verifiers==0.3.1.dev59"]
+dependencies = ["verifiers==0.3.1"]
 
 [build-system]
 requires = ["hatchling"]
diff --git a/environments/canary_trap/pyproject.toml b/environments/canary_trap/pyproject.toml
index 64a2eb1..3739415 100644
--- a/environments/canary_trap/pyproject.toml
+++ b/environments/canary_trap/pyproject.toml
@@ -3,7 +3,7 @@ name = "canary-trap"
 version = "0.1.0"
 description = "canary-trap — write contamination probes that survive a paraphrase, without accusing a clean model."
 requires-python = ">=3.11"
-dependencies = ["verifiers==0.3.1.dev59"]
+dependencies = ["verifiers==0.3.1"]
 
 [build-system]
 requires = ["hatchling"]
diff --git a/environments/drop_table_inference/pyproject.toml b/environments/drop_table_inference/pyproject.toml
index 83812a4..fcd682b 100644
--- a/environments/drop_table_inference/pyproject.toml
+++ b/environments/drop_table_inference/pyproject.toml
@@ -3,7 +3,7 @@ name = "drop-table-inference"
 version = "0.1.0"
 description = "drop-table-inference — estimate a drop table from a kill log, graded on the kills you never saw."
 requires-python = ">=3.11"
-dependencies = ["verifiers==0.3.1.dev59"]
+dependencies = ["verifiers==0.3.1"]
 
 [build-system]
 requires = ["hatchling"]
diff --git a/environments/fault_localisation/pyproject.toml b/environments/fault_localisation/pyproject.toml
index f9a7834..01b6ffd 100644
--- a/environments/fault_localisation/pyproject.toml
+++ b/environments/fault_localisation/pyproject.toml
@@ -3,7 +3,7 @@ name = "fault-localisation"
 version = "0.1.0"
 description = "fault-localisation — name the service that broke, not the ones complaining about it."
 requires-python = ">=3.11"
-dependencies = ["verifiers==0.3.1.dev59"]
+dependencies = ["verifiers==0.3.1"]
 
 [build-system]
 requires = ["hatchling"]
diff --git a/environments/grand_exchange/pyproject.toml b/environments/grand_exchange/pyproject.toml
index e6638ce..abf1629 100644
--- a/environments/grand_exchange/pyproject.toml
+++ b/environments/grand_exchange/pyproject.toml
@@ -3,7 +3,7 @@ name = "grand-exchange"
 version = "0.1.0"
 description = "grand-exchange — place orders executed against a market window you never saw."
 requires-python = ">=3.11"
-dependencies = ["verifiers==0.3.1.dev59"]
+dependencies = ["verifiers==0.3.1"]
 
 [build-system]
 requires = ["hatchling"]
diff --git a/environments/grand_exchange_live/pyproject.toml b/environments/grand_exchange_live/pyproject.toml
index 5ee4be8..d79477f 100644
--- a/environments/grand_exchange_live/pyproject.toml
+++ b/environments/grand_exchange_live/pyproject.toml
@@ -3,7 +3,7 @@ name = "grand-exchange-live"
 version = "0.1.0"
 description = "grand-exchange-live — quote, watch the tape, re-quote, over a turn budget."
 requires-python = ">=3.11"
-dependencies = ["verifiers==0.3.1.dev59"]
+dependencies = ["verifiers==0.3.1"]
 
 [build-system]
 requires = ["hatchling"]
diff --git a/environments/redaction_pressure/pyproject.toml b/environments/redaction_pressure/pyproject.toml
index d8fd2a7..22181a5 100644
--- a/environments/redaction_pressure/pyproject.toml
+++ b/environments/redaction_pressure/pyproject.toml
@@ -6,7 +6,7 @@ requires-python = ">=3.11"
 dependencies = [
   "pydantic==2.13.4",
   "regex==2026.7.19",
-  "verifiers==0.3.1.dev59",
+  "verifiers==0.3.1",
 ]
 
 [build-system]
diff --git a/environments/schema_migration/pyproject.toml b/environments/schema_migration/pyproject.toml
index bc5b0e5..0259118 100644
--- a/environments/schema_migration/pyproject.toml
+++ b/environments/schema_migration/pyproject.toml
@@ -3,7 +3,7 @@ name = "schema-migration"
 version = "0.1.0"
 description = "schema-migration — split a text column into a number and a unit, graded on rows you never saw."
 requires-python = ">=3.11"
-dependencies = ["verifiers==0.3.1.dev59"]
+dependencies = ["verifiers==0.3.1"]
 
 [build-system]
 requires = ["hatchling"]
diff --git a/environments/tera_spatial/pyproject.toml b/environments/tera_spatial/pyproject.toml
index 5461ae6..ff0ef2f 100644
--- a/environments/tera_spatial/pyproject.toml
+++ b/environments/tera_spatial/pyproject.toml
@@ -3,7 +3,7 @@ name = "tera-spatial"
 version = "0.1.0"
 description = "tera-spatial — Arena's bridge to Tera's four renderer-independent spatial environments, executed in TypeScript and graded in Python, and the tasksets that sit on it."
 requires-python = ">=3.11"
-dependencies = ["verifiers==0.3.1.dev59"]
+dependencies = ["verifiers==0.3.1"]
 
 # One directory, several tasksets: the environments share a vendored simulator and
 # a single worker, so splitting them into four wheels would ship the same 283 KB
diff --git a/tests/test_probe.py b/tests/test_probe.py
index 8f4e5e7..e3d4fc9 100644
--- a/tests/test_probe.py
+++ b/tests/test_probe.py
@@ -74,6 +74,30 @@ def discovered_tasksets() -> set[str]:
 
 
 class RootProbeIntegrationTests(unittest.TestCase):
+    def test_prime_verifiers_boundary_is_pinned_and_upstream_owned(self) -> None:
+        manifests = sorted((ROOT / "environments").glob("*/pyproject.toml"))
+        configs = sorted((ROOT / "configs").glob("*.toml"))
+        self.assertTrue(manifests)
+        self.assertTrue(configs)
+
+        for manifest in manifests:
+            with self.subTest(manifest=manifest.parent.name):
+                data = tomllib.loads(manifest.read_text(encoding="utf-8"))
+                self.assertIn("verifiers==0.3.1", data["project"]["dependencies"])
+
+        for config in configs:
+            with self.subTest(config=config.stem):
+                data = tomllib.loads(config.read_text(encoding="utf-8"))
+                agent = data["env"]["agent"]
+                self.assertEqual(agent["harness"]["id"], "null")
+                self.assertEqual(agent["runtime"]["type"], "subprocess")
+
+        self.assertEqual(
+            list((ROOT / "environments").glob("**/harness.py")),
+            [],
+            msg="Arena environments must use Verifiers harnesses, not ship a parallel one",
+        )
+
     def test_public_root_probe_gates_every_environment(self) -> None:
         completed = subprocess.run(
             [sys.executable, "probe.py"],