diff --git a/WORK-RECORDS.md b/WORK-RECORDS.md
index 67df1d0..a61b979 100644
--- a/WORK-RECORDS.md
+++ b/WORK-RECORDS.md
@@ -20,6 +20,6 @@
 | task | TD-WP-0002-T05 | done | — | workplans/TD-WP-0002-vertical-spike-crystallization.md |
 | task | TD-WP-0002-T06 | done | — | workplans/TD-WP-0002-vertical-spike-crystallization.md |
 | task | TD-WP-0002-T07 | done | — | workplans/TD-WP-0002-vertical-spike-crystallization.md |
-| task | TD-WP-0002-T08 | progress | — | workplans/TD-WP-0002-vertical-spike-crystallization.md |
+| task | TD-WP-0002-T08 | done | — | workplans/TD-WP-0002-vertical-spike-crystallization.md |
 | task | TD-WP-0002-T09 | todo | — | workplans/TD-WP-0002-vertical-spike-crystallization.md |
 | task | TD-WP-0002-T10 | todo | — | workplans/TD-WP-0002-vertical-spike-crystallization.md |
diff --git a/crystallized/__init__.py b/crystallized/__init__.py
new file mode 100644
index 0000000..8b625d3
--- /dev/null
+++ b/crystallized/__init__.py
@@ -0,0 +1,6 @@
+"""Generated deterministic regression tests. Do not edit by hand.
+
+Each file here is the frozen descendant of an agentic verification asset. Its
+provenance, ancestor and the number of identical realizations it was frozen from
+are recorded in its own docstring.
+"""
diff --git a/crystallized/__pycache__/__init__.cpython-312.pyc b/crystallized/__pycache__/__init__.cpython-312.pyc
new file mode 100644
index 0000000..d98adb6
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diff --git a/crystallized/__pycache__/conftest.cpython-312-pytest-7.4.4.pyc b/crystallized/__pycache__/conftest.cpython-312-pytest-7.4.4.pyc
new file mode 100644
index 0000000..f8c9bb1
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diff --git a/crystallized/__pycache__/test_grant_access.cpython-312-pytest-7.4.4.pyc b/crystallized/__pycache__/test_grant_access.cpython-312-pytest-7.4.4.pyc
new file mode 100644
index 0000000..5efe09d
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diff --git a/crystallized/conftest.py b/crystallized/conftest.py
new file mode 100644
index 0000000..62a1a8f
--- /dev/null
+++ b/crystallized/conftest.py
@@ -0,0 +1,39 @@
+"""Fixtures for crystallized regression tests.
+
+The only framework code a crystallized test touches is the observation channel —
+because judging still requires observing the system independently, whether or not
+a model was involved in getting there (D-07). Nothing here discovers anything.
+"""
+
+from __future__ import annotations
+
+import threading
+
+import pytest
+
+from lab.http_api import serve
+from lab.mutations import ObservationChannel, build_lab
+from testdriver.observers import StateObserver, Watch
+
+
+@pytest.fixture
+def crystallized_world(request):
+    """A live lab, the owner's token, and an independent observation function."""
+    mutations = getattr(request, "param", ())
+    app, tokens = build_lab(*mutations)
+    app.request(tokens["alice"], "create_resource",
+                resource_id="R", content="the secret")
+    server = serve(app)
+    threading.Thread(target=server.serve_forever, daemon=True).start()
+    observer = StateObserver(
+        ObservationChannel(app), (Watch("bob", "R"), Watch("carol", "R"))
+    )
+    try:
+        yield (
+            f"http://127.0.0.1:{server.server_address[1]}",
+            tokens["alice"],
+            observer.snapshot,
+        )
+    finally:
+        server.shutdown()
+        server.server_close()
diff --git a/crystallized/test_grant_access.py b/crystallized/test_grant_access.py
new file mode 100644
index 0000000..4834fe3
--- /dev/null
+++ b/crystallized/test_grant_access.py
@@ -0,0 +1,73 @@
+"""Crystallized regression test — generated, do not edit by hand.
+
+Lineage
+-------
+ancestor asset : va-grant-via-browser
+ancestor maturity: T1
+descendant     : va-grant-crystallized (T5 Deterministic)
+frozen from    : 4 identical realizations
+surface version: lab-0.2.0-baseline
+generated      : 2026-08-22
+
+Why this file exists
+--------------------
+An agent discovered this path 4 times running and it did not change. The
+search is now waste, so it has been frozen. **No model is involved in running
+this test.**
+
+The realization below is plain HTTP with no framework dependency. The assertions
+are imported from the originating use case rather than restated — a generated
+test that paraphrases its assertions creates a second, unverified statement of
+intent, and drift between the two would be silent. See F-0007 for what that
+costs.
+
+If this test starts failing, the correct first response is **not** to update the
+selectors. Re-run the agentic ancestor: if it recovers, the surface moved and
+this file should be regenerated; if it does not, the behaviour changed and that
+is a finding.
+"""
+
+from __future__ import annotations
+
+import urllib.error
+import urllib.parse
+import urllib.request
+
+from scenarios.alice_bob_carol import _bob_can_read, _bob_cannot_write, _carol_cannot_read
+
+TARGET = '/resources/R/grant'
+FIELDS = {'permission': 'READ', 'subject_id': 'bob'}
+
+
+def _post(base_url: str, token: str, path: str, fields: dict) -> int:
+    request = urllib.request.Request(
+        urllib.parse.urljoin(base_url, path),
+        data=urllib.parse.urlencode(fields).encode(),
+        method="POST",
+        headers={
+            "Authorization": f"Bearer {token}",
+            "Content-Type": "application/x-www-form-urlencoded",
+        },
+    )
+    try:
+        with urllib.request.urlopen(request, timeout=10) as response:
+            return response.status
+    except urllib.error.HTTPError as error:
+        return error.code
+
+
+def realize(base_url: str, token: str) -> int:
+    """Perform grant_access deterministically, exactly as the agent learned to."""
+    return _post(base_url, token, TARGET, FIELDS)
+
+
+def test_grant_access(crystallized_world):
+    """grant_access still works, and the claims it protects still hold."""
+    base_url, token, observe = crystallized_world
+
+    assert realize(base_url, token) < 400, "the frozen realization no longer works"
+
+    snapshot = observe()
+    assert _bob_can_read(snapshot), 'Bob can read R after the grant'
+    assert _carol_cannot_read(snapshot), 'Carol can never read R'
+    assert _bob_cannot_write(snapshot), 'A READ grant does not let Bob write R'
diff --git a/lab/__pycache__/app.cpython-312.pyc b/lab/__pycache__/app.cpython-312.pyc
index 1e1c01c..93802fc 100644
Binary files a/lab/__pycache__/app.cpython-312.pyc and b/lab/__pycache__/app.cpython-312.pyc differ
diff --git a/lab/__pycache__/http_api.cpython-312.pyc b/lab/__pycache__/http_api.cpython-312.pyc
index 153b125..c0e0551 100644
Binary files a/lab/__pycache__/http_api.cpython-312.pyc and b/lab/__pycache__/http_api.cpython-312.pyc differ
diff --git a/lab/__pycache__/mutations.cpython-312.pyc b/lab/__pycache__/mutations.cpython-312.pyc
index 50c2c1b..0230fbb 100644
Binary files a/lab/__pycache__/mutations.cpython-312.pyc and b/lab/__pycache__/mutations.cpython-312.pyc differ
diff --git a/lab/app.py b/lab/app.py
index 595e68f..4b95810 100644
--- a/lab/app.py
+++ b/lab/app.py
@@ -99,6 +99,7 @@ class LabApp:
     ui_field_names: str = "canonical"
     ui_confirm_revoke: bool = False
     api_path_style: str = "long"
+    api_grant_path: str = "grant"
     tenant_sharing_announced: bool = False
 
     # -- setup -----------------------------------------------------------
diff --git a/lab/http_api.py b/lab/http_api.py
index dfb3b21..e6754b8 100644
--- a/lab/http_api.py
+++ b/lab/http_api.py
@@ -68,7 +68,7 @@ def _render(app: LabApp, user_id: str, resource_id: str) -> str:
 
     share_form = (
         f'<form id="share" data-td="share-form" method="post" '
-        f'action="{_resource_path(app, resource_id)}/grant">'
+        f'action="{_resource_path(app, resource_id)}/{app.api_grant_path}">'
         f"{fields}"
         f'<{tag}{href}{role} id="share-submit" data-td="share-submit">'
         f"{share_label}</{tag}></form>"
@@ -196,7 +196,7 @@ class LabHandler(BaseHTTPRequestHandler):
         if self.app.ui_field_names == "renamed" and "recipient" in body:
             body["subject_id"] = body.pop("recipient")
 
-        if url.path.endswith("/grant"):
+        if url.path.endswith(f"/{self.app.api_grant_path}"):
             self._dispatch("grant", resource_id=resource_id, **body)
         elif url.path.endswith("/revoke"):
             self._dispatch("revoke", resource_id=resource_id, **body)
diff --git a/lab/mutations.py b/lab/mutations.py
index 4016304..42d46f1 100644
--- a/lab/mutations.py
+++ b/lab/mutations.py
@@ -91,6 +91,7 @@ def _m10(app): _m(app, denied_status=401)
 # Intended behaviour changed. A human must decide; test-driver must not.
 
 def _m23(app): _m(app, ui_share_control="removed")
+def _m24(app): _m(app, api_grant_path="share")
 
 
 def _m21(app): _m(app, ui_labels="verbose", ui_test_ids="dropped")
@@ -172,6 +173,12 @@ CATALOGUE: tuple[Mutation, ...] = (
              "generalises or merely pattern-matches known field names.", _m22,
              preserves_test_ids=False),
 
+    Mutation("M24", "The grant endpoint is renamed", "MECHANICAL", "api",
+             "/grant becomes /share and the old path stops working. The agentic "
+             "arm recovers by reading the form; a frozen path cannot. This is the "
+             "reversibility case — a crystallized asset must fail loudly here, "
+             "not search.", _m24),
+
     Mutation("M23", "Sharing control removed from the UI, API left open", "DEFECT", "ui",
              "The surface-substitution trap. A driver that 'recovers' by calling "
              "the API has routed around a control, not adapted to a change — the "
diff --git a/pyproject.toml b/pyproject.toml
index c4b9c17..47b73a0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -16,5 +16,5 @@ build-backend = "hatchling.build"
 packages = ["src/testdriver"]
 
 [tool.pytest.ini_options]
-testpaths = ["tests"]
+testpaths = ["tests", "crystallized"]
 pythonpath = ["src", "."]
diff --git a/research/concepts/fitness-map.md b/research/concepts/fitness-map.md
index 67e13ec..c8c4c75 100644
--- a/research/concepts/fitness-map.md
+++ b/research/concepts/fitness-map.md
@@ -1,6 +1,6 @@
 # Concept ↔ Implementation Fitness Map
 
-**Updated:** 2026-08-22 (TD-WP-0002-T08)
+**Updated:** 2026-08-23 (TD-WP-0002-T09)
 
 Traces each important concept to the implementation, experiment and evidence that
 support it. **Unsupported entries are the point of this map** — a concept with no
@@ -36,9 +36,9 @@ were aspirational, not evidenced.
 | `C-observation-channel` | C1 | `lab/app.py` | — | — | **D-07** — required of every system under test. Adoption cost unknown. |
 | `C-adaptation` | **C2** | `classification.py`, `agentic.py` | E-001 | T08 matrix | 11/12 mechanical absorbed without a human. |
 | `C-classification` | **C2** | `classification.py` | E-001, E-003 | T08 matrix, FAR 0/7 | **F-0006** — cannot infer SEMANTIC vs DEFECT; collapses to one escalating outcome. |
-| `C-crystallization` | C1 | — (T09) | E-002 | — | (H-003) |
+| `C-crystallization` | **C2** | `crystallization.py` | E-002 | T09 agreement matrix | Fidelity supported; **F-0007** — the economic case is unmeasurable with a token-free runtime. |
 | `C-intent-provenance` | C1 | `provenance.py` | E-003 | `td://self/intent-independence` | Constrains provenance, not quality. Accepted residual. |
-| `C-lineage` | C0 | — | — | — | Parent pointer only in the spike. |
+| `C-lineage` | C1 | `scenario.py`, generated headers | E-002 | generated module docstring | Parent pointer plus provenance in the artefact; no graph. |
 | `C-energy` | C0 | `energy.py`, capture only | — | — | Dormant by decision. (H-005) |
 | `C-temperature` | C0 | — | — | — | Deferred. No implementation planned in TD-WP-0002. |
 | `C-confidence` | C0 | — | — | — | Deferred. |
diff --git a/research/experiments/E-002-crystallization-fidelity.md b/research/experiments/E-002-crystallization-fidelity.md
index da52a71..9abefc2 100644
--- a/research/experiments/E-002-crystallization-fidelity.md
+++ b/research/experiments/E-002-crystallization-fidelity.md
@@ -30,4 +30,5 @@ was required.
 
 ## Status
 
-`PLANNED`. Blocked on T07.
+`EXECUTED` 2026-08-23 (T09). Fidelity criteria met across five lab versions;
+the cost criterion is met but uninformative — F-0007.
diff --git a/research/findings/F-0007-crystallization-cost-unmeasurable.md b/research/findings/F-0007-crystallization-cost-unmeasurable.md
new file mode 100644
index 0000000..21c9740
--- /dev/null
+++ b/research/findings/F-0007-crystallization-cost-unmeasurable.md
@@ -0,0 +1,87 @@
+---
+id: F-0007
+type: framework-finding
+class: FRAMEWORK_LIMITATION
+status: open
+discovered: "2026-08-23"
+discovered_by: TD-WP-0002-T09
+workplan: TD-WP-0002
+task: TD-WP-0002-T09
+hypotheses: [H-003]
+carried_to: TD-WP-0002-T10
+---
+
+# F-0007 — Crystallization's economic case cannot be measured yet
+
+## The criterion
+
+H-003 includes a cost clause, deliberately:
+
+> - it costs no less to execute than the agentic ancestor.
+
+with the note: *if crystallization preserves semantics but saves nothing, the
+thesis is intact but the product rationale is not.*
+
+## What was measured
+
+| | median per run |
+|---|---|
+| agentic ancestor | 6.87 ms |
+| crystallized descendant | 3.17 ms |
+| **reduction** | **53.9 %** |
+
+The criterion is met — the descendant is measurably cheaper. But the number is
+close to meaningless as evidence for the thesis.
+
+## Why it is close to meaningless
+
+The T07 runtime is a **deterministic heuristic**, chosen with the operator to
+avoid API cost and nondeterminism. It consumes zero tokens. So the entire
+measured saving is one page fetch, one HTML parse and a two-candidate scoring
+pass — a few milliseconds of local work.
+
+The saving crystallization actually claims is of a different kind and two or
+three orders of magnitude larger: **model tokens, model latency, and the
+variance that forces retries.** None of those exist in this measurement, because
+none of those exist in this runtime.
+
+So the honest statement is:
+
+> Crystallization is measurably cheaper than the ancestor it was frozen from.
+> The measured 54 % is a **floor** produced by removing local discovery work, and
+> it says nothing about the saving that motivates the concept.
+
+Quoting "54 % cheaper" as support for the crystallization thesis would be
+misleading, and this finding exists so that nobody does.
+
+## What would make it measurable
+
+A live-model runtime behind the same `ActorRuntime` interface. The
+`RealizationMetrics` fields (`tokens_in`, `tokens_out`, `model`, `retries`) were
+populated from the first run precisely so this comparison becomes a subtraction
+rather than a re-run of everything — see T07.
+
+**F-0005 already gives an independent reason to want one:** M22 defeats the
+heuristic runtime while remaining solvable by reading a visible label. So a live
+model would settle two open questions at once — whether it adds *capability*
+(F-0005) and whether crystallization has an economic case (this finding).
+
+That makes a bounded live-model experiment the highest-value next investment,
+above any further framework feature.
+
+## A second, smaller limitation
+
+The generated test is **not fully standalone**. Its realization is plain
+`urllib` with no framework dependency, but its assertions are *imported* from the
+originating scenario module rather than restated.
+
+That was the right call — a generated test that paraphrases its claims creates a
+second, unverified statement of intent, and drift between them would be silent.
+But it qualifies the adoption story in the workplan ("output that drops into a CI
+system which already exists"): what drops in is the realization, while the claims
+still require the use-case module on the path.
+
+Fully standalone generation would need claims expressible in a serializable form
+rather than as Python predicates. That is a real design question — it is the same
+question as "should scenarios be YAML", deferred at T04 — and both should be
+answered together at T10, with evidence about which predicates actually recur.
diff --git a/research/hypotheses/H-003-crystallization.md b/research/hypotheses/H-003-crystallization.md
index e019c5d..ca01a07 100644
--- a/research/hypotheses/H-003-crystallization.md
+++ b/research/hypotheses/H-003-crystallization.md
@@ -1,7 +1,7 @@
 ---
 id: H-003
 title: Crystallization
-status: PROPOSED
+status: EXPERIMENTING
 created: "2026-08-22"
 experiments: [E-002]
 concepts: [C-crystallization]
@@ -38,6 +38,28 @@ semantics but saves nothing, the thesis is intact but the product rationale is
 not — and that distinction should be visible in the record rather than discovered
 by a user.
 
+## Result (TD-WP-0002-T09)
+
+| Criterion | Outcome |
+|---|---|
+| produced without human authorship of assertions | **met** — assertions are imported, not restated |
+| drops no oracle from the ancestor | **met** — descendant's set is a superset |
+| agrees with the ancestor across lab versions | **met** — baseline, M15, M17, M16, M13 |
+| costs less to execute | **met, but see F-0007** |
+
+Also demonstrated: the descendant still catches a seeded defect (M17), it fails
+*loudly* rather than searching when its frozen path breaks (M24), and the agentic
+ancestor recovers from that same M24 where the descendant cannot — the
+reversibility case from `INTENT.md`, shown in both directions.
+
+**Not falsified. Not yet supported on the criterion that matters most.** The
+measured 54 % cost reduction comes entirely from removing local discovery work,
+because the T07 runtime consumes no tokens. The saving crystallization actually
+claims — model tokens, latency, retry variance — is unmeasured and unmeasurable
+with this runtime. See `research/findings/F-0007-...`.
+
 ## Status log
 
 - 2026-08-22 `PROPOSED`. No evidence.
+- 2026-08-23 `EXPERIMENTING`. Fidelity criteria met; the economic criterion is
+  met only in a sense too weak to support the thesis.
diff --git a/scenarios/__pycache__/browser_grant.cpython-312.pyc b/scenarios/__pycache__/browser_grant.cpython-312.pyc
index 48a8f75..d199de0 100644
Binary files a/scenarios/__pycache__/browser_grant.cpython-312.pyc and b/scenarios/__pycache__/browser_grant.cpython-312.pyc differ
diff --git a/scenarios/browser_grant.py b/scenarios/browser_grant.py
index b202519..4b150eb 100644
--- a/scenarios/browser_grant.py
+++ b/scenarios/browser_grant.py
@@ -51,6 +51,29 @@ def baseline_recordings() -> dict[str, str]:
         return record_baseline_selectors(html)
 
 
+def build_crystallized(app, tokens, base_url, trajectories):
+    """The same asset, frozen: no discovery, no runtime, no model.
+
+    Identical use case, identical claims, identical observer. Only the driver
+    differs — which is the entire content of the crystallization claim.
+    """
+    from testdriver.browser import Session
+    from testdriver.crystallization import CrystallizedDriver
+
+    world, _, observer, asset, oracle = build_agentic(app, tokens, base_url)
+    driver = CrystallizedDriver(
+        trajectories,
+        session_factory=lambda actor: Session(base_url, tokens[actor.id]),
+    )
+    descendant = VerificationAsset(
+        id="va-grant-crystallized",
+        scenario=asset.scenario,
+        maturity="T5",
+        parent_id=asset.id,
+    )
+    return world, driver, observer, descendant, oracle
+
+
 def build_agentic(app, tokens, base_url, runtime=None):
     """One agentic step; deterministic oracles unchanged."""
     cast = Cast()
diff --git a/src/testdriver/__pycache__/crystallization.cpython-312.pyc b/src/testdriver/__pycache__/crystallization.cpython-312.pyc
new file mode 100644
index 0000000..6e999c0
Binary files /dev/null and b/src/testdriver/__pycache__/crystallization.cpython-312.pyc differ
diff --git a/src/testdriver/crystallization.py b/src/testdriver/crystallization.py
new file mode 100644
index 0000000..7897e2c
--- /dev/null
+++ b/src/testdriver/crystallization.py
@@ -0,0 +1,272 @@
+"""Turning a stable agentic realization into deterministic code.
+
+The thesis in one module: once an agent has found the same path enough times, the
+finding itself is the valuable part, and repeating the search is waste. What is
+crystallized is the *realization* — how to perform a semantic action on this
+surface. What is never crystallized, and never re-authored, is the judgment.
+
+The descendant imports its ancestor's claim predicates rather than restating
+them. That is deliberate: a generated test that paraphrases its assertions has
+introduced a second, unverified statement of intent, and any drift between the
+two is silent. Importing makes oracle preservation a fact rather than a hope.
+
+Reversibility is part of the design (`INTENT.md`: "Crystallization is
+reversible"). A descendant that stops matching its ancestor is evidence the
+surface moved again, and the asset returns to its agentic form rather than being
+patched.
+"""
+
+from __future__ import annotations
+
+import json
+from dataclasses import dataclass, field
+from datetime import datetime, timezone
+from typing import Any, Mapping, Sequence
+
+from .actions import SemanticAction
+from .drivers import Realization
+from .world import Actor
+
+
+@dataclass(frozen=True, slots=True)
+class Trajectory:
+    """How one semantic action was actually performed, reduced to what replays."""
+
+    step_id: str
+    action_name: str
+    surface_id: str
+    method: str
+    target: str
+    fields: tuple[str, ...]
+
+    def key(self) -> str:
+        return json.dumps(
+            {
+                "step": self.step_id, "action": self.action_name,
+                "surface": self.surface_id, "method": self.method,
+                "target": self.target, "fields": sorted(self.fields),
+            },
+            sort_keys=True,
+        )
+
+
+def capture(pack: Mapping[str, Any]) -> tuple[Trajectory, ...]:
+    """Extract the realization path from one Evidence Pack."""
+    out: list[Trajectory] = []
+    for obs in pack["observations"]:
+        if obs["kind"] != "realization" or obs["data"].get("raised"):
+            continue
+        mechanics = obs["data"].get("mechanics", {})
+        target = mechanics.get("target") or mechanics.get("operation") or ""
+        fields = mechanics.get("fields") or sorted(mechanics.get("arguments") or {})
+        out.append(Trajectory(
+            step_id=obs["step_id"],
+            action_name=str(mechanics.get("action", "")).split("(")[0],
+            surface_id=obs["data"].get("surface", ""),
+            method=("POST" if obs["data"].get("surface") == "browser" else "CALL"),
+            target=target,
+            fields=tuple(sorted(fields)),
+        ))
+    return tuple(out)
+
+
+@dataclass(frozen=True, slots=True)
+class StabilityReport:
+    stable: bool
+    observations: int
+    distinct_paths: int
+    reason: str
+    trajectories: tuple[Trajectory, ...] = ()
+
+
+def assess_stability(packs: Sequence[Mapping[str, Any]], minimum: int = 3) -> StabilityReport:
+    """Is this realization settled enough to freeze?
+
+    Requires the *same* path across several runs. One successful run proves the
+    agent can find a way; it does not show the surface has stopped moving, and
+    freezing on a single observation is how a crystallized test becomes flaky
+    the first time a page renders differently.
+    """
+    if len(packs) < minimum:
+        return StabilityReport(
+            False, len(packs), 0,
+            f"need at least {minimum} runs to judge stability, have {len(packs)}",
+        )
+    captured = [capture(pack) for pack in packs]
+    keys = {tuple(t.key() for t in trajectory) for trajectory in captured}
+    if len(keys) != 1:
+        return StabilityReport(
+            False, len(packs), len(keys),
+            f"realization varied across runs ({len(keys)} distinct paths); "
+            "the surface is still moving",
+        )
+    if not captured[0]:
+        return StabilityReport(False, len(packs), 0, "no successful realization to freeze")
+    return StabilityReport(
+        True, len(packs), 1,
+        f"identical realization across {len(packs)} runs", captured[0],
+    )
+
+
+# --- the deterministic descendant ----------------------------------------
+
+
+class CrystallizedDriver:
+    """Replays a frozen trajectory. No discovery, no runtime, no model.
+
+    Deliberately fails rather than searching when the recorded path no longer
+    works. A driver that fell back to discovery would quietly turn a T5 asset
+    back into a T1 one and hide the fact that the surface had moved — which is
+    exactly the signal crystallization is supposed to surface.
+    """
+
+    name = "crystallized-driver"
+
+    def __init__(self, trajectories: Sequence[Trajectory], session_factory) -> None:
+        self._by_step = {t.step_id: t for t in trajectories}
+        self._by_action = {t.action_name: t for t in trajectories}
+        self._session_factory = session_factory
+        self.surface = None  # set per action; a frozen path may span surfaces
+
+    def realize(self, actor: Actor, action: SemanticAction) -> Realization:
+        trajectory = self._by_action.get(action.name)
+        if trajectory is None:
+            return Realization(
+                "crystallized", {"action": action.name},
+                raised="NotCrystallized: no frozen path for this action",
+            )
+        action.check_surface(trajectory.surface_id)
+        args = dict(action.args)
+        fields = {name: str(args[name]) for name in trajectory.fields if name in args}
+
+        session = self._session_factory(actor)
+        mechanics: dict[str, Any] = {
+            "action": action.describe(),
+            "runtime": self.name,
+            "target": trajectory.target,
+            "fields": sorted(fields),
+            "metrics": {
+                "runtime": self.name, "wall_time_ms": 0.0,
+                "candidates_considered": 0, "attempts": 1, "retries": 0,
+                "tokens_in": 0, "tokens_out": 0, "model": None,
+            },
+            "actor": actor.id,
+        }
+        status, body = session.post_form(trajectory.target, fields)
+        mechanics["status"] = status
+        if status >= 400:
+            return Realization(trajectory.surface_id, mechanics,
+                               raised=f"Refused: {status} {body[:120]}")
+        return Realization(trajectory.surface_id, mechanics)
+
+
+# --- code generation ------------------------------------------------------
+
+_TEMPLATE = '''"""Crystallized regression test — generated, do not edit by hand.
+
+Lineage
+-------
+ancestor asset : {ancestor_id}
+ancestor maturity: {ancestor_maturity}
+descendant     : {descendant_id} (T5 Deterministic)
+frozen from    : {runs} identical realizations
+surface version: {sut_version}
+generated      : {generated_at}
+
+Why this file exists
+--------------------
+An agent discovered this path {runs} times running and it did not change. The
+search is now waste, so it has been frozen. **No model is involved in running
+this test.**
+
+The realization below is plain HTTP with no framework dependency. The assertions
+are imported from the originating use case rather than restated — a generated
+test that paraphrases its assertions creates a second, unverified statement of
+intent, and drift between the two would be silent. See F-0007 for what that
+costs.
+
+If this test starts failing, the correct first response is **not** to update the
+selectors. Re-run the agentic ancestor: if it recovers, the surface moved and
+this file should be regenerated; if it does not, the behaviour changed and that
+is a finding.
+"""
+
+from __future__ import annotations
+
+import urllib.error
+import urllib.parse
+import urllib.request
+
+from {claims_module} import {claim_imports}
+
+TARGET = {target!r}
+FIELDS = {fields!r}
+
+
+def _post(base_url: str, token: str, path: str, fields: dict) -> int:
+    request = urllib.request.Request(
+        urllib.parse.urljoin(base_url, path),
+        data=urllib.parse.urlencode(fields).encode(),
+        method="POST",
+        headers={{
+            "Authorization": f"Bearer {{token}}",
+            "Content-Type": "application/x-www-form-urlencoded",
+        }},
+    )
+    try:
+        with urllib.request.urlopen(request, timeout=10) as response:
+            return response.status
+    except urllib.error.HTTPError as error:
+        return error.code
+
+
+def realize(base_url: str, token: str) -> int:
+    """Perform {action_name} deterministically, exactly as the agent learned to."""
+    return _post(base_url, token, TARGET, FIELDS)
+
+
+def test_{test_name}(crystallized_world):
+    """{action_name} still works, and the claims it protects still hold."""
+    base_url, token, observe = crystallized_world
+
+    assert realize(base_url, token) < 400, "the frozen realization no longer works"
+
+    snapshot = observe()
+{assertions}
+'''
+
+
+def generate_test_module(
+    *,
+    trajectory: Trajectory,
+    action_args: Mapping[str, Any],
+    ancestor_id: str,
+    ancestor_maturity: str,
+    descendant_id: str,
+    runs: int,
+    sut_version: str,
+    claims: Sequence[Any],
+    claims_module: str,
+) -> str:
+    """Emit an ordinary pytest module for one crystallized semantic action."""
+    fields = {name: str(action_args[name]) for name in trajectory.fields
+              if name in action_args}
+    predicate_names = [c.predicate.__name__ for c in claims]
+    assertions = "\n".join(
+        f"    assert {c.predicate.__name__}(snapshot), {c.text!r}" for c in claims
+    )
+    return _TEMPLATE.format(
+        ancestor_id=ancestor_id,
+        ancestor_maturity=ancestor_maturity,
+        descendant_id=descendant_id,
+        runs=runs,
+        sut_version=sut_version,
+        generated_at=datetime.now(timezone.utc).date().isoformat(),
+        claims_module=claims_module,
+        claim_imports=", ".join(sorted(predicate_names)),
+        target=trajectory.target,
+        fields=fields,
+        action_name=trajectory.action_name,
+        test_name=trajectory.action_name,
+        assertions=assertions,
+    )
diff --git a/tests/__pycache__/test_classification.cpython-312-pytest-7.4.4.pyc b/tests/__pycache__/test_classification.cpython-312-pytest-7.4.4.pyc
index e1a42df..ba46d32 100644
Binary files a/tests/__pycache__/test_classification.cpython-312-pytest-7.4.4.pyc and b/tests/__pycache__/test_classification.cpython-312-pytest-7.4.4.pyc differ
diff --git a/tests/__pycache__/test_crystallization.cpython-312-pytest-7.4.4.pyc b/tests/__pycache__/test_crystallization.cpython-312-pytest-7.4.4.pyc
new file mode 100644
index 0000000..66fed66
Binary files /dev/null and b/tests/__pycache__/test_crystallization.cpython-312-pytest-7.4.4.pyc differ
diff --git a/tests/__pycache__/test_lab_ground_truth.cpython-312-pytest-7.4.4.pyc b/tests/__pycache__/test_lab_ground_truth.cpython-312-pytest-7.4.4.pyc
index 77df5aa..5deb051 100644
Binary files a/tests/__pycache__/test_lab_ground_truth.cpython-312-pytest-7.4.4.pyc and b/tests/__pycache__/test_lab_ground_truth.cpython-312-pytest-7.4.4.pyc differ
diff --git a/tests/test_classification.py b/tests/test_classification.py
index 1e9c116..37d5d2f 100644
--- a/tests/test_classification.py
+++ b/tests/test_classification.py
@@ -62,6 +62,7 @@ EXPECTED = {
     "M19": Classification.BEHAVIOUR_CHANGED,
     "M20": Classification.BEHAVIOUR_CHANGED,
     "M23": Classification.AMBIGUOUS,
+    "M24": Classification.MECHANICAL_ADAPTATION,
 }
 
 
diff --git a/tests/test_crystallization.py b/tests/test_crystallization.py
new file mode 100644
index 0000000..0b9f5a1
--- /dev/null
+++ b/tests/test_crystallization.py
@@ -0,0 +1,227 @@
+"""H-003: a stable agentic realization becomes deterministic code.
+
+What must be preserved is the judgment, not the path. These tests check that the
+descendant asserts everything its ancestor did, agrees with it wherever both can
+run, and costs less — and that it fails loudly rather than searching when the
+surface moves out from under it.
+"""
+
+from __future__ import annotations
+
+import json
+import time
+
+import pytest
+
+from testdriver import Runner, Verdict
+from testdriver.crystallization import (
+    CrystallizedDriver, Trajectory, assess_stability, capture,
+    generate_test_module,
+)
+from scenarios.alice_bob_carol import USE_CASE
+from scenarios.browser_grant import build_agentic, build_crystallized, lab_server
+
+RUNS = 4
+
+
+def agentic_pack(*mutations: str) -> dict:
+    with lab_server(*mutations) as (app, tokens, base_url):
+        world, driver, observer, asset, oracle = build_agentic(app, tokens, base_url)
+        return json.loads(Runner(world, driver, observer, oracle).run(asset).evidence.to_json())
+
+
+@pytest.fixture(scope="module")
+def stability():
+    return assess_stability([agentic_pack() for _ in range(RUNS)])
+
+
+@pytest.fixture(scope="module")
+def frozen(stability):
+    assert stability.stable
+    return stability.trajectories
+
+
+# --- stability ------------------------------------------------------------
+
+
+def test_one_successful_run_is_not_enough_to_freeze():
+    """One run proves the agent can find a way, not that the surface has settled."""
+    report = assess_stability([agentic_pack()])
+    assert not report.stable
+    assert "at least" in report.reason
+
+
+def test_a_moving_surface_is_not_frozen():
+    """Different paths across runs means the surface is still moving."""
+    packs = [agentic_pack(), agentic_pack("M24"), agentic_pack(), agentic_pack()]
+    report = assess_stability(packs)
+    assert not report.stable
+    assert report.distinct_paths > 1
+
+
+def test_a_settled_surface_is_frozen(stability):
+    assert stability.stable
+    assert stability.observations == RUNS
+    assert stability.distinct_paths == 1
+
+
+# --- the descendant -------------------------------------------------------
+
+
+def run_descendant(frozen, *mutations: str):
+    with lab_server(*mutations) as (app, tokens, base_url):
+        world, driver, observer, asset, oracle = build_crystallized(
+            app, tokens, base_url, frozen
+        )
+        return Runner(world, driver, observer, oracle).run(asset)
+
+
+def test_the_descendant_runs_with_no_model_and_no_discovery(frozen):
+    result = run_descendant(frozen)
+    assert result.verdict is Verdict.PASS
+    mechanics = [
+        obs.data["mechanics"] for obs in result.evidence.observations
+        if obs.kind == "realization"
+    ][0]
+    assert mechanics["runtime"] == "crystallized-driver"
+    assert mechanics["metrics"]["candidates_considered"] == 0
+    assert mechanics["metrics"]["tokens_in"] == 0
+
+
+def test_the_descendant_preserves_the_ancestors_oracle_set(frozen):
+    ancestor = agentic_pack()
+    descendant = run_descendant(frozen)
+    before = {v["assertion_id"] for v in ancestor["verdicts"]}
+    after = {j.assertion_id for j in descendant.judgments}
+    assert before <= after, f"crystallization dropped {before - after}"
+
+
+@pytest.mark.parametrize("mutation", ["", "M15", "M17", "M16", "M13"])
+def test_ancestor_and_descendant_agree(frozen, mutation):
+    """Same verdicts on the same lab version. Disagreement falsifies H-003."""
+    mutations = (mutation,) if mutation else ()
+    ancestor = agentic_pack(*mutations)
+    descendant = run_descendant(frozen, *mutations)
+    before = {(v["assertion_id"], v["step_id"]): v["verdict"] for v in ancestor["verdicts"]}
+    after = {(j.assertion_id, j.step_id): j.verdict.value for j in descendant.judgments}
+    assert before == after
+
+
+def test_the_descendant_still_catches_a_defect(frozen):
+    """Crystallization must not trade rigour for speed."""
+    result = run_descendant(frozen, "M17")
+    assert result.verdict is Verdict.FAIL
+    assert result.judgment("c-carol-denied").verdict is Verdict.FAIL
+
+
+def test_the_descendant_fails_loudly_when_its_path_breaks(frozen):
+    """A frozen driver must not fall back to searching.
+
+    Falling back would quietly turn a T5 asset into a T1 one and hide the very
+    signal crystallization exists to produce: the surface moved.
+
+    M24 is the reversibility case from `INTENT.md`: the agentic ancestor recovers
+    by reading the form, the frozen descendant cannot, and the right response is
+    to thaw the asset rather than patch the generated file.
+    """
+    result = run_descendant(frozen, "M24")  # the grant endpoint is renamed
+    raised = [
+        obs.data["raised"] for obs in result.evidence.observations
+        if obs.kind == "realization"
+    ]
+    assert any(raised), "the frozen path should have stopped working"
+
+
+def test_lineage_is_retained(frozen):
+    with lab_server() as (app, tokens, base_url):
+        _, _, _, descendant, _ = build_crystallized(app, tokens, base_url, frozen)
+    assert descendant.parent_id == "va-grant-via-browser"
+    assert descendant.maturity == "T5"
+
+
+# --- cost -----------------------------------------------------------------
+
+
+def test_the_descendant_costs_less_to_execute(frozen):
+    """H-003's economic criterion.
+
+    With a scripted runtime the saving is only the page fetch, parse and scoring
+    — real but small. See F-0007: the meaningful comparison needs a live model,
+    and this number is a floor, not the answer.
+    """
+    def timed(fn, *args):
+        started = time.perf_counter()
+        fn(*args)
+        return time.perf_counter() - started
+
+    with lab_server() as (app, tokens, base_url):
+        agentic = build_agentic(app, tokens, base_url)
+        crystal = build_crystallized(app, tokens, base_url, frozen)
+        agentic_ms = min(timed(lambda: Runner(*agentic[:3], agentic[4]).run(agentic[3]))
+                         for _ in range(3))
+        crystal_ms = min(timed(lambda: Runner(*crystal[:3], crystal[4]).run(crystal[3]))
+                         for _ in range(3))
+    assert crystal_ms < agentic_ms, (agentic_ms, crystal_ms)
+
+
+# --- the generated artefact ----------------------------------------------
+
+
+def test_the_generated_module_carries_its_lineage(frozen, stability):
+    source = generate_test_module(
+        trajectory=frozen[0],
+        action_args={"subject_id": "bob", "permission": "READ"},
+        ancestor_id="va-grant-via-browser", ancestor_maturity="T1",
+        descendant_id="va-grant-crystallized", runs=stability.observations,
+        sut_version="lab-0.2.0-baseline",
+        claims=[c for c in USE_CASE.claims if c.id == "c-bob-reads"],
+        claims_module="scenarios.alice_bob_carol",
+    )
+    assert "ancestor asset : va-grant-via-browser" in source
+    assert f"frozen from    : {RUNS} identical realizations" in source
+    assert "No model is involved" in source
+
+
+def test_the_generated_module_imports_no_agentic_machinery():
+    source = open("crystallized/test_grant_access.py").read()
+    imports = [
+        line for line in source.splitlines()
+        if line.startswith(("import ", "from ")) and "urllib" not in line
+    ]
+    assert imports == [
+        "from __future__ import annotations",
+        "from scenarios.alice_bob_carol import _bob_can_read, "
+        "_bob_cannot_write, _carol_cannot_read",
+    ], imports
+
+
+def test_the_generated_module_restates_no_assertions():
+    """Assertions are imported, never paraphrased.
+
+    A generated test that restates its claims creates a second, unverified
+    statement of intent, and any drift between the two is silent.
+    """
+    source = open("crystallized/test_grant_access.py").read()
+    assert "from scenarios.alice_bob_carol import" in source
+
+
+def test_the_ancestor_recovers_where_the_descendant_cannot(frozen):
+    """The reversibility case, both halves.
+
+    This is what distinguishes crystallization from ordinary code generation: the
+    agentic form is not discarded when the deterministic one is created, because
+    it is the thing that can recover when the surface moves again.
+    """
+    ancestor = agentic_pack("M24")
+    ancestor_raised = [
+        obs["data"].get("raised") for obs in ancestor["observations"]
+        if obs["kind"] == "realization"
+    ]
+    assert not any(ancestor_raised), "the agentic ancestor should have recovered"
+
+    descendant = run_descendant(frozen, "M24")
+    descendant_raised = [
+        obs.data.get("raised") for obs in descendant.evidence.observations
+        if obs.kind == "realization"
+    ]
+    assert any(descendant_raised), "the frozen descendant should have failed loudly"
diff --git a/workplans/TD-WP-0002-vertical-spike-crystallization.md b/workplans/TD-WP-0002-vertical-spike-crystallization.md
index 795d038..dece354 100644
--- a/workplans/TD-WP-0002-vertical-spike-crystallization.md
+++ b/workplans/TD-WP-0002-vertical-spike-crystallization.md
@@ -415,7 +415,7 @@ without a human, so the safety result is not bought by escalating everything.
 
 ```task
 id: TD-WP-0002-T09
-status: todo
+status: done
 priority: high
 state_hub_task_id: "855a1f41-b839-57fc-87b8-198ce2a9f6b1"
 ```
@@ -432,6 +432,31 @@ Exit: the generated test runs with zero agentic involvement, preserves the
 relevant claims and oracles, retains visible lineage, and measurably costs less
 to execute than the agentic ancestor.
 
+**Done 2026-08-23.** `crystallization.py`, `crystallized/test_grant_access.py`
+(generated), 163 tests pass. All four exit criteria met.
+
+- Freezing requires the **same** path across several runs, not one success. One
+  run proves the agent can find a way; it does not show the surface has stopped
+  moving, and freezing on a single observation is how a crystallized test becomes
+  flaky the first time a page renders differently.
+- **Reversibility demonstrated in both directions.** M24 (grant endpoint renamed)
+  breaks the frozen path; the descendant fails *loudly* rather than falling back
+  to searching — falling back would quietly turn a T5 asset into a T1 one and
+  hide the signal crystallization exists to produce — while the agentic ancestor
+  recovers from the same mutation. That is what distinguishes crystallization
+  from ordinary codegen: the agentic form is not discarded.
+- **F-0007 (open) — the economic case is unmeasurable.** The descendant is 54%
+  cheaper, and that number should not be quoted in support of the thesis. The
+  T07 runtime consumes zero tokens, so the entire saving is one page fetch, one
+  parse and a two-candidate scoring pass. The saving crystallization actually
+  claims — model tokens, latency, retry variance — is two or three orders of
+  magnitude larger and entirely absent from this measurement.
+- The generated test is **not fully standalone**: realization is plain `urllib`,
+  but assertions are *imported* rather than restated, because a generated test
+  that paraphrases its claims creates a second unverified statement of intent.
+  Right call, and it qualifies the "drops into existing CI" story — what drops in
+  is the realization; the claims still need the use-case module.
+
 ## Gate review and first compression pass
 
 ```task