diff --git a/docs/task-execution-mediator-seam.md b/docs/task-execution-mediator-seam.md
new file mode 100644
index 0000000..964688b
--- /dev/null
+++ b/docs/task-execution-mediator-seam.md
@@ -0,0 +1,107 @@
+# Strict task handoff to independent consumption confirmation
+
+RPF-WP-0035-T12 source preparation, 2026-10-16. This seam calls only the existing
+fixed disposable native adapter. It installs no production origin, identity,
+permission, real grant, generic broker or backend default.
+
+## Actual starting gaps and reused owner interfaces
+
+At Platform source base d042d468 and Secrets c80a944 the native fixture used a
+synthetic direct `consume-confirmed` journal transition. No actual strict Secrets
+task handoff existed. Generic Secrets consume accepted a substituted approval ID,
+coerced idempotent values and did not require the original exact decision. Those
+are Secrets-owned defects; Platform did not copy its authorization policy or edit
+that repository. The Secrets owner prepared a separate strict module under
+SECRETS-WP-0013, referenced by exact hashes in this package's manifest.
+
+Approval Engine already provides `ExecutionConfirmationClient.consume_exact` and
+`confirm_consumption`. The latter performs an independently authenticated GET of
+the durable original approval object and filters it to the original consumption
+triplet/time. It is historical PIP evidence, not authorization. It neither validates
+an Access decision nor makes a supplied receipt authoritative. Platform's adapter
+previously assumed its first native call was journal ordinal zero, conflicting
+with a preceding durable CAS/confirmation sequence.
+
+`scripts/task_execution_mediator.py` now performs the narrow owner join:
+
+1. Require the actual `secrets_engine.task_execution_handoff` dependency; absence
+   refuses before provider credentials, journal reservation or native effects.
+   The mediator itself calls `authorize_task_execution`. It accepts neither an
+   inbound authorization object nor a caller-selected authorizer/transport callback.
+2. Independently compile the exact local catalogue/descriptor/grant and compare the
+   strict owner's detached handoff descriptor byte-for-byte. Only authorization_id
+   may be added to approval reference metadata; purpose and source semantics cannot
+   be substituted through an inbound catalogue object. Secrets owns signed Check,
+   claim/native-act/full and approval-free digest joins, caller/subject correspondence
+   and the strict prepared object. Platform does not render or duplicate that decision.
+3. Bind the actual returned full canonical digest into the owner Plan. Reserve the
+   approval/request/operation/Plan tuple and the precommitted cleanup obligations
+   once while holding the same invocation lock through cleanup.
+4. Commit a CAS call intent, invoke Secrets `consume_task_execution` once and require
+   its actual typed result with exact original approval/request/decision/time and
+   `idempotent is False`. A historical idempotent response cannot open native work.
+5. Commit a separate read intent and invoke the actual Approval owner's default
+   isolated transport, with independently installed read credential and exact same
+   owner-admitted origin. Require `confirm_consumption` to match the native act,
+   approval-free digest and original exact triplet/time. Raw approval entries and
+   provider credentials never enter journal evidence or receipts.
+6. Recheck original approval/decision/operation bounds using the existing Secrets
+   time adapter, then persist `consume-confirmed`. Any CAS/read failure, timeout,
+   denied read or mismatch records unknown and causes zero native execution. A
+   subsequent invocation cannot retry the consumed approval or persisted admission.
+7. Only then enter the fixed native grant/metadata adapter. Its next business-call
+   ordinal comes from the same live journal, so CAS and GET occupy ordinals0/1 and
+   native calls continue at2. Pending/unknown/cleanup-closed state cannot supply a
+   next ordinal. Each native request retains its own durable intent and outcome.
+8. Cleanup stays under the original distinct obligations even if business work
+   fails. Returned evidence explicitly says native apply is unverified: six successful
+   native calls do not establish total approved baseline/readback normalization,
+   atomic CAS, service-login provenance or native production owner acceptance.
+
+The owner configuration selects provider route/read credential and the existing
+Secrets configuration. These are independently installed runtime inputs, never
+part of an HTTP body or authority derived from a caller string. Both providers use
+real existing transports. Python import/file checks do not establish runtime
+credential isolation; production custody/enforcement remains an external gate.
+
+## Whole disposable source-server proof
+
+Tests run the actual Access `serve` binary built from the owner source, with its
+real Ed25519 signing implementation and enforce-mode TokenReview client. A local
+synthetic reviewer independently admits only the explicitly fixed service token,
+principal/audience and expiry. This is not actual Kubernetes identity proof.
+Signing keys are generated in private temporary files; the public key and real
+policy digest are independently installed in the Secrets trust file. The policy
+digest comes from an owner-local actual source CLI before any network response.
+
+The positive policy is a separately named local synthetic exact-descriptor Rego
+fixture with a real deny fixture and Rego test. It never edits or enables the
+actual task policy. The actual proposed service task package is exercised unchanged
+and returns genuine signed DENY. There is no fabricated DecisionEnvelope or
+model-only approval. Real Approval WSGI/SQLite plus distinct independently admitted
+synthetic service/human identities create, approve, consume and serve the object.
+The strict Secrets module uses its actual mandatory producer-type signature verifier,
+retained request/claim/envelope and one-shot strict CAS, followed by the independent
+Approval GET and real disposable OpenBao grant/token/metadata/cleanup requests.
+
+Tests also prove actual independent read-scope denial after successful consume:
+the durable approval is consumed, Platform remains unknown with pending read intent,
+no target native objects exist and reinvocation cannot consume again. The native
+journal is checked for known synthetic token leakage. A source purpose substitution
+refuses before authorization/CAS, and a missing strict module refuses before any
+credentials. Actual-policy denial leaves the approval approved and journal empty.
+All identity, policy/registry admission, source-bundle/baseline digests and grant
+approval in these tests are synthetic fixture inputs. These tests do not admit an
+estate caller, real grant, production transport or actual protected custody.
+
+## Remaining production work
+
+Adopt/publish the exact strict Secrets dependency and this owner seam together;
+admit the existing task-execution-grant source projection and actual identity,
+policy package, provider origin/custody and complete source revisions. The current
+actual policy remains hard-closed. Finish target CCR immutable semantics, total
+native expected-state normalization/conflict control, CCR38 provenance, actual
+per-call served-time/use enforcement, audit/outbox and protected uncertain/crash
+recovery. Then obtain and execute the exact founder-scoped attended trial.
+Approval replay prevention and uncertain native-effect reconciliation remain
+separate guarantees. T12, Secrets WP13 and native adoption stay open.
diff --git a/scripts/task_execution_journal.py b/scripts/task_execution_journal.py
index a16291b..8f1b9a2 100644
--- a/scripts/task_execution_journal.py
+++ b/scripts/task_execution_journal.py
@@ -231,6 +231,21 @@ class Journal:
         return {"state": row[3], "evidence_digest": row[4], "dispatch_allowed": False,
                 "external_outcome_unknown": bool(pending)}
 
+    def next_call_ordinal(self, binding: Binding):
+        """Continue the same admitted invocation after owner auth/consume calls.
+
+        This never grants dispatch or resumes a persisted admission. The actual
+        before_call transaction remains the final serialization/intent guard.
+        """
+        if not self._held or self._admission != binding:
+            raise Refused("next call requires same live admission")
+        count,pending=self.db.execute("SELECT COUNT(*),COALESCE(SUM(outcome='pending'),0) FROM calls WHERE operation=?",(binding.operation_id,)).fetchone()
+        cleanup=self.db.execute("SELECT COUNT(*) FROM cleanup WHERE operation=? AND outcome!='owed'",(binding.operation_id,)).fetchone()[0]
+        state=self.db.execute("SELECT state FROM operations WHERE operation=?",(binding.operation_id,)).fetchone()[0]
+        if pending or cleanup or state in {'failed','unknown','cleanup-confirmed'} or count>63:
+            raise Refused("call sequence is uncertain, closed or exhausted")
+        return count
+
     def before_call(self, binding: Binding, ordinal: int, call_digest: str):
         """Persist one exact plan-call intent before the mediator issues it.
 
diff --git a/scripts/task_execution_mediator.py b/scripts/task_execution_mediator.py
new file mode 100644
index 0000000..d42b55f
--- /dev/null
+++ b/scripts/task_execution_mediator.py
@@ -0,0 +1,180 @@
+"""Owner mediator seam for the existing strict Secrets handoff and Approval GET.
+
+Only the disposable NativeFixtureAdapter is callable here. No production backend,
+caller-supplied authorizer/transport, approval boolean or portable receipt exists.
+The strict Secrets module is an explicit external dependency: absence refuses
+before credential-bearing requests or native effects, never a permissive fallback.
+"""
+from __future__ import annotations
+from dataclasses import dataclass
+from datetime import datetime,timezone
+import importlib
+import json
+from pathlib import Path
+from urllib.parse import urlsplit
+
+from task_execution_cleanup import run_cleanup
+from task_execution_journal import Binding,Cleanup,Journal,Refused
+from task_execution_plan import Compiler,encoded,content_hash
+from task_execution_native_fixture import FixtureAdmission,NativeFixtureAdapter
+
+
+@dataclass(frozen=True)
+class ConfirmationConfig:
+    """Owner-installed independent read credential/route, never request fields."""
+    origin: str
+    token_file: Path
+    timeout_seconds: float = 3
+
+
+_HANDOFF_FIELDS={'execution_contract','approval_id','request_digest','decision_id',
+                 'native_binding','approval_binding_digest','submitted_request_digest',
+                 'decision_not_before','decision_expires_at','approval_expires_at'}
+
+
+def _strict_dependency():
+    try:
+        module=importlib.import_module('secrets_engine.task_execution_handoff')
+        for name in ['TaskExecutionAuthorization','TaskExecutionConsumption',
+                     'authorize_task_execution','consume_task_execution']:
+            if not hasattr(module,name):raise ImportError()
+        return module
+    except ImportError:
+        raise Refused('strict Secrets task execution handoff dependency unavailable') from None
+
+
+def _fresh(cfg,handoff,descriptor):
+    from secrets_engine.application_time import read_window,validity_bounds
+    lower,upper=validity_bounds(window=read_window(cfg))
+    try:
+        parse=lambda value:datetime.fromisoformat(value.replace('Z','+00:00'))
+        deadline=parse(descriptor['operation_deadline'])
+        approval=parse(handoff['approval_expires_at']);decision=parse(handoff['decision_expires_at'])
+        start=parse(handoff['decision_not_before']) if handoff['decision_not_before'] else None
+        if any(value.tzinfo is None for value in [deadline,approval,decision]) or (start is not None and start.tzinfo is None):raise ValueError()
+        if upper>=min(deadline,approval,decision) or deadline>min(approval,decision) or (start is not None and lower<start):raise ValueError()
+    except (KeyError,TypeError,ValueError,AttributeError):
+        raise Refused('original task authority deadline refused') from None
+
+
+def _intent(journal,binding,kind,fields):
+    digest=content_hash(encoded({'kind':kind,**fields}))
+    ordinal=journal.next_call_ordinal(binding)
+    journal.before_call(binding,ordinal,digest)
+    return ordinal,digest
+
+
+def _unknown(journal,binding):
+    state=journal.observe(binding)['state']
+    if state not in {'unknown','failed','cleanup-confirmed'}:
+        journal.transition(binding,state,'unknown')
+
+
+def run_native_fixture_task(*,compiler:Compiler,journal:Journal,plan_request:dict,
+                            owner_descriptor:bytes,secrets_cfg,entry,
+                            confirmation:ConfirmationConfig,
+                            native_admission:FixtureAdmission):
+    """Authorize inside owner boundary, reserve, consume once, independently GET.
+
+    Strict authorization is executed here through the actual Secrets-owned module;
+    an inbound TaskExecutionAuthorization or arbitrary callable is never accepted.
+    This function returns closed metadata, not tokens or raw approval/decision data.
+    Positive execution requires the module's real signed PDP path; actual unadmitted
+    Access policy must still deny. Fixture policy/identity admission is independent
+    synthetic setup and cannot become production acceptance.
+    """
+    strict=_strict_dependency()
+    from approval_engine.execution_confirmation import ExecutionConfirmationClient
+    from secrets_engine.execution_contract import ExecutionContract
+    if type(confirmation) is not ConfirmationConfig or type(native_admission) is not FixtureAdmission:
+        raise Refused('independent owner provider configuration required')
+    try:
+        origin=urlsplit(confirmation.origin)
+        if origin.scheme not in {'http','https'} or origin.hostname!='127.0.0.1' or not origin.port or origin.username or origin.password or origin.path or origin.query or origin.fragment:
+            raise ValueError()
+        if confirmation.origin!=str(getattr(secrets_cfg,'approval_url','')).rstrip('/'):
+            raise ValueError()
+        descriptor=ExecutionContract.parse(json.loads(owner_descriptor)).as_dict()
+        if encoded(descriptor)!=owner_descriptor or native_admission.descriptor!=owner_descriptor:
+            raise ValueError()
+    except Exception:
+        raise Refused('exact owner descriptor or provider route refused') from None
+    # An independently pinned owner catalogue must match every engine field. Its
+    # approval IDs are source references, never runtime authority.
+    proposal=compiler.proposal()
+    target={key:getattr(entry,key) for key in proposal['catalog_target']}
+    if encoded(target)!=encoded(proposal['catalog_target']) or entry.id!=proposal['catalog_id'] or entry.stage!='prod':
+        raise Refused('owner catalogue does not match strict task request')
+    snapshot={path:compiler.read(Path(path)) for path in compiler.pins}
+    owner_entry=compiler._catalogue_entry(snapshot)
+    # Only the served approval pointer is added after issue. Purpose or other
+    # source approval semantics cannot be substituted through an inbound entry.
+    without_reference=lambda value:{key:item for key,item in value.items() if key!='authorization_id'}
+    if encoded(without_reference(entry.approval))!=encoded(without_reference(owner_entry.approval)):
+        raise Refused('owner approval metadata differs from source')
+    client=ExecutionConfirmationClient(confirmation.origin,confirmation.token_file,
+                                       timeout_seconds=confirmation.timeout_seconds)
+    with journal.locked():
+        authorization=strict.authorize_task_execution(secrets_cfg,entry,
+                               execution_contract=ExecutionContract.parse(descriptor))
+        if type(authorization) is not strict.TaskExecutionAuthorization:
+            raise Refused('strict task authorization missing')
+        handoff=authorization.as_owner_handoff()
+        if type(handoff) is not dict or set(handoff)!=_HANDOFF_FIELDS or encoded(handoff['execution_contract'])!=owner_descriptor:
+            raise Refused('strict task handoff does not match owner descriptor')
+        _fresh(secrets_cfg,handoff,descriptor)
+        request=dict(plan_request,request_digest=handoff['request_digest'])
+        plan=compiler.bind_execution(compiler.compile(request),descriptor,owner_descriptor)
+        binding=Binding(handoff['approval_id'],handoff['request_digest'],descriptor['operation_id'],plan.content_digest)
+        # Constructor validates fixed native origin/fixture process/grant sources
+        # but performs no native HTTP request or credential acquisition.
+        native=NativeFixtureAdapter(compiler,plan,journal,binding,native_admission)
+        journal.reserve(binding,native.cleanup)
+        fields={key:handoff[key] for key in ['approval_id','request_digest','decision_id']}
+        try:
+            ordinal,digest=_intent(journal,binding,'strict-secrets-task-consume',fields)
+            consumed=strict.consume_task_execution(secrets_cfg,authorization)
+            if type(consumed) is not strict.TaskExecutionConsumption:
+                raise Refused('strict task consumption missing')
+            receipt={key:getattr(consumed,key) for key in ['approval_id','request_digest','decision_id','consumed_at','idempotent']}
+            if any(receipt[key]!=value for key,value in fields.items()) or receipt['idempotent'] is not False:
+                raise Refused('historical or mismatched task consumption refused')
+            stamp=datetime.fromisoformat(receipt['consumed_at'].replace('Z','+00:00'))
+            if stamp.tzinfo is None:raise Refused('consumption timestamp missing')
+            journal.after_call(binding,ordinal,digest,content_hash(encoded(receipt)))
+            _fresh(secrets_cfg,handoff,descriptor)
+            ordinal,digest=_intent(journal,binding,'independent-approval-consumption-read',fields)
+            confirmed=client.confirm_consumption(binding.approval_id,binding.request_digest,
+                       handoff['decision_id'],expected_binding=handoff['native_binding'],
+                       expected_pdp_digest=handoff['approval_binding_digest'])
+            if confirmed!={key:receipt[key] for key in ['approval_id','request_digest','decision_id','consumed_at']}:
+                raise Refused('independent consumption correspondence refused')
+            journal.after_call(binding,ordinal,digest,content_hash(encoded(confirmed)))
+            _fresh(secrets_cfg,handoff,descriptor)
+            journal.transition(binding,'reserved','consume-confirmed',content_hash(encoded(confirmed)))
+        except Exception:
+            _unknown(journal,binding)
+            raise Refused('task consumption or independent confirmation unconfirmed; no native execution') from None
+        result={'operation_id':binding.operation_id,'request_digest':binding.request_digest,
+                'decision_id':handoff['decision_id'],'native_apply':'unverified',
+                'native_calls_completed':0,'cleanup_confirmed':False}
+        try:
+            journal.transition(binding,'consume-confirmed','authenticating')
+            # Fixture identity is independently seeded synthetic setup, not CCR38
+            # provenance proof or a production service login.
+            journal.transition(binding,'authenticating','grant-issuing')
+            native.materialize_grant()
+            journal.transition(binding,'grant-issued','applying')
+            for ordinal in range(6):
+                _fresh(secrets_cfg,handoff,descriptor)
+                native.metadata_call(ordinal)
+                result['native_calls_completed']+=1
+        except Exception:
+            _unknown(journal,binding)
+            result['native_apply']='unknown'
+        finally:
+            result['cleanup_confirmed']=run_cleanup(journal,binding,native)['confirmed']
+        # Native total expected-state normalization/acceptance remains explicitly
+        # absent. Six successful calls cannot be relabelled a verified owner trial.
+        result['business_state']=journal.observe(binding)['state']
+        return result
diff --git a/scripts/task_execution_native_fixture.py b/scripts/task_execution_native_fixture.py
index 29d168d..c9ee244 100644
--- a/scripts/task_execution_native_fixture.py
+++ b/scripts/task_execution_native_fixture.py
@@ -122,8 +122,8 @@ class NativeFixtureAdapter:
             self.used+=1
         evidence_payload = encoded({'token':'owner-retained-task-token'}) if path=='auth/token/lookup' else payload
         digest=content_hash(encoded({'method':method,'path':path,'payload_sha256':'sha256:'+content_hash(evidence_payload),'credential_slot':'task' if task else 'owner'}))
-        ordinal=self._ordinal
-        self.journal.before_call(self.binding,ordinal,digest);self._ordinal+=1
+        ordinal=self.journal.next_call_ordinal(self.binding)
+        self.journal.before_call(self.binding,ordinal,digest);self._ordinal=ordinal+1
         try: status,data=self._http(method,path,token,payload)
         except Exception:
             state=self.journal.observe(self.binding)['state']
diff --git a/tests/task_execution_source_servers.py b/tests/task_execution_source_servers.py
new file mode 100644
index 0000000..3570382
--- /dev/null
+++ b/tests/task_execution_source_servers.py
@@ -0,0 +1,206 @@
+"""Real Approval/Access servers; every admission/key/identity is synthetic local.
+
+The positive fixture policy is separately named and exact-descriptor scoped. It
+never edits either existing unadmitted production task policy or their false gate.
+"""
+import base64
+from contextlib import contextmanager
+from dataclasses import replace
+from datetime import datetime,timedelta,timezone
+import hashlib
+from http.client import HTTPConnection
+from http.server import BaseHTTPRequestHandler,ThreadingHTTPServer
+import json
+import os
+from pathlib import Path
+import shutil
+import socket
+import subprocess
+import threading
+import time
+from types import SimpleNamespace
+from wsgiref.simple_server import make_server,WSGIRequestHandler
+
+from cryptography import x509
+from cryptography.hazmat.primitives import serialization,hashes
+from cryptography.hazmat.primitives.asymmetric import ed25519,rsa
+from cryptography.x509.oid import NameOID
+
+ACCESS=Path(os.environ.get('ACCESS_ENGINE_SOURCE_ROOT','/home/worsch/access-engine'))
+APPROVAL=Path(os.environ.get('APPROVAL_ENGINE_SOURCE_ROOT','/home/worsch/approval-engine'))
+SECRETS=Path(os.environ.get('SECRETS_ENGINE_SOURCE_ROOT','/home/worsch/secrets-engine'))
+FIXTURE_PACKAGE='platform.disposable-task-seam.fixture'
+FIXTURE_VERSION='v1'
+PRINCIPAL='system:serviceaccount:secrets-engine:secrets-engine'
+
+
+def private(path,text):path.write_text(text);path.chmod(0o600);return path
+
+def free_port():
+    with socket.socket() as sock:sock.bind(('127.0.0.1',0));return sock.getsockname()[1]
+
+
+def http(origin,method,path,body=None,token=None):
+    from urllib.parse import urlsplit
+    parsed=urlsplit(origin);conn=HTTPConnection(parsed.hostname,parsed.port,timeout=4)
+    try:
+        headers={'Content-Type':'application/json'}
+        if token is not None:headers['Authorization']='Bearer '+token
+        conn.request(method,path,body=json.dumps(body) if body is not None else None,headers=headers)
+        response=conn.getresponse();raw=response.read(1024*1024)
+        return response.status,json.loads(raw) if raw else {}
+    finally:conn.close()
+
+
+class QuietWSGI(WSGIRequestHandler):
+    def log_message(self,*args):pass
+
+
+@contextmanager
+def approval_server(directory):
+    from approval_engine.api import App
+    from approval_engine.auth import Identity,StaticTokenAuthenticator
+    from approval_engine.store import Engine
+    service='synthetic-source-service';human='synthetic-source-human';no_read='synthetic-source-no-read'
+    def identity(subject,kind,scopes):
+        return Identity(subject,'https://synthetic.invalid',('approval-engine',),kind,'tenant:platform',
+                        frozenset(),frozenset(scopes),{'level':'aal2','methods':['synthetic']},
+                        'fixture:synthetic-identity',tenant_source='directory' if kind=='human' else 'registration')
+    identities={service:identity('secrets-engine','service',['approval:create','approval:read','approval:consume']),
+                human:identity('synthetic-founder','human',['approval:approve','approval:read']),
+                no_read:identity('platform-fixture-confirmation','service',['approval:consume'])}
+    engine=Engine(str(directory/'approval.sqlite'));app=App(engine,StaticTokenAuthenticator(identities))
+    calls=[]
+    def logged(environ,start_response):
+        calls.append((environ['REQUEST_METHOD'],environ['PATH_INFO']))
+        return app(environ,start_response)
+    server=make_server('127.0.0.1',0,logged,handler_class=QuietWSGI)
+    thread=threading.Thread(target=server.serve_forever,daemon=True);thread.start()
+    try:
+        yield SimpleNamespace(origin='http://127.0.0.1:'+str(server.server_port),engine=engine,
+                              service_token=service,human_token=human,no_read_token=no_read,calls=calls)
+    finally:server.shutdown();server.server_close();thread.join(5);engine.close()
+
+
+@contextmanager
+def reviewer_server(directory):
+    # Actual Access TokenReview client consumes this independently admitted
+    # synthetic reviewer. This is not a Kubernetes authentication proof.
+    exp=int(time.time())+900
+    payload=base64.urlsafe_b64encode(json.dumps({'exp':exp}).encode()).decode().rstrip('=')
+    token='synthetic.'+payload+'.synthetic';reviewer='synthetic-reviewer';calls=[]
+    class Handler(BaseHTTPRequestHandler):
+        def log_message(self,*args):pass
+        def do_POST(self):
+            size=int(self.headers.get('Content-Length','0'));data=json.loads(self.rfile.read(size))
+            valid=(self.path=='/apis/authentication.k8s.io/v1/tokenreviews'
+                   and self.headers.get('Authorization')=='Bearer '+reviewer
+                   and data.get('spec',{}).get('token')==token
+                   and 'flex-auth' in data.get('spec',{}).get('audiences',[]))
+            calls.append(valid)
+            result={'apiVersion':'authentication.k8s.io/v1','kind':'TokenReview',
+                    'status':{'authenticated':valid,'audiences':['flex-auth'],
+                              'user':{'username':PRINCIPAL}}}
+            raw=json.dumps(result).encode();self.send_response(201)
+            self.send_header('Content-Type','application/json');self.send_header('Content-Length',str(len(raw)));self.end_headers();self.wfile.write(raw)
+    server=ThreadingHTTPServer(('127.0.0.1',0),Handler);thread=threading.Thread(target=server.serve_forever,daemon=True);thread.start()
+    # The actual reviewer constructor requires a valid CA even for its explicitly
+    # synthetic HTTP endpoint; this CA never trusts an estate endpoint.
+    key=rsa.generate_private_key(public_exponent=65537,key_size=2048)
+    name=x509.Name([x509.NameAttribute(NameOID.COMMON_NAME,'synthetic-local-reviewer')])
+    now=datetime.now(timezone.utc)
+    cert=x509.CertificateBuilder().subject_name(name).issuer_name(name).public_key(key.public_key()).serial_number(x509.random_serial_number()).not_valid_before(now-timedelta(minutes=1)).not_valid_after(now+timedelta(days=1)).sign(key,hashes.SHA256())
+    ca=directory/'fixture-ca.pem';ca.write_bytes(cert.public_bytes(serialization.Encoding.PEM))
+    reviewer_file=private(directory/'reviewer.token',reviewer)
+    try:yield SimpleNamespace(origin='http://127.0.0.1:'+str(server.server_port),caller_token=token,reviewer_file=reviewer_file,ca=ca,calls=calls)
+    finally:server.shutdown();server.server_close();thread.join(5)
+
+
+def fixture_policy(directory,descriptor,request):
+    policy=directory/'fixture-policy.md'
+    fixture=directory/'fixture-cases.json'
+    fixture.write_text(json.dumps([{'id':'synthetic-claim-free-deny','request':request,
+                                   'expect':{'effect':'deny','reason':'fixture_unapproved'}}]))
+    document='''---
+id: platform.disposable-task-seam.fixture
+name: Disposable exact task seam fixture
+namespace: secrets-engine:secret-catalog-lane
+version: v1
+status: proposed
+package: fixture.platform.task_seam
+allow_ttl: 5m
+actions: [execute-ccr]
+owner: team:synthetic-fixture
+fixtures: [fixture-cases.json]
+caring: {profile: caring-0.4.0-rc2, enforce: false}
+activation: {mode: local}
+---
+Synthetic local policy only. No production task policy is edited or enabled.
+
+```rego
+default decision := {"effect":"deny","reason":"fixture_unapproved"}
+decision := {"effect":"allow","reason":"synthetic_exact_task_approved"} {
+  input.action == "execute-ccr"
+  input.tenant == "tenant:platform"
+  input.subject.id == "secrets-engine"
+  input.subject.type == "service"
+  input.resource.system == "secrets-engine"
+  input.context.human_control == true
+  input.context.approval.valid_now == true
+  input.context.approval.consumed == false
+  input.context.approval.binding.human_control == true
+  input.context.execution_contract == DESCRIPTOR
+}
+```
+''' + '''
+```rego test
+import data.fixture.platform.task_seam
+test_missing_approval_denies { task_seam.decision.effect == "deny" with input as {} }
+```
+'''
+    document=document.replace('DESCRIPTOR',json.dumps(descriptor,separators=(',',':')))
+    policy.write_text(document)
+    return policy
+
+
+@contextmanager
+def access_server(directory,descriptor,request,reviewer,*,actual_policy=False):
+    binary=Path(os.environ.get('PLATFORM_ACCESS_FIXTURE_BINARY','/tmp/netkingdom-platform-wave4-access'))
+    verifier=Path(os.environ.get('PLATFORM_PDP_FIXTURE_VERIFIER','/tmp/netkingdom-platform-wave4-verify'))
+    if not binary.is_file() or not verifier.is_file():raise RuntimeError('build source fixture binaries first')
+    registry=directory/'registry.json';registry.write_bytes((ACCESS/'examples/secrets-engine/registry_snapshot.json').read_bytes())
+    policy=ACCESS/'examples/secrets-engine-service-task-execution/policy_package.md' if actual_policy else fixture_policy(directory,descriptor,request)
+    requestfile=directory/'claim-free-request.json';requestfile.write_text(json.dumps(request))
+    # Trusted owner-local source CLI derives the real package pin independently
+    # from the network responder. Its DENY is used only as digest provenance.
+    offline=subprocess.run([str(binary),'check','--registry',str(registry),'--policy',str(policy),'--request',str(requestfile)],capture_output=True,text=True,timeout=15)
+    if offline.returncode!=0:raise RuntimeError('source policy fixture invalid: '+offline.stderr[:300])
+    produced=json.loads(offline.stdout);provenance=produced['provenance']
+    key=ed25519.Ed25519PrivateKey.generate()
+    seed=key.private_bytes(serialization.Encoding.Raw,serialization.PrivateFormat.Raw,serialization.NoEncryption())
+    public=key.public_key().public_bytes(serialization.Encoding.Raw,serialization.PublicFormat.Raw)
+    b64=lambda value:base64.urlsafe_b64encode(value).decode().rstrip('=')
+    seedfile=private(directory/'signing.seed',b64(seed))
+    trust={name:provenance[name] for name in ['evaluator','mode','policy_package','policy_version','policy_package_digest']}
+    trust.update(schema='secrets-engine.pdp-trust.v1',keys={'synthetic-owner-key':b64(public)})
+    trustfile=directory/'pdp-trust.json';trustfile.write_text(json.dumps(trust))
+    port=free_port();origin='http://127.0.0.1:'+str(port)
+    args=[str(binary),'serve','--addr','127.0.0.1:'+str(port),'--registry',str(registry),'--policy',str(policy),
+          '--envelope-signing-key-file',str(seedfile),'--envelope-signing-kid','synthetic-owner-key',
+          '--caller-auth-mode','enforce','--caller-audience','flex-auth','--caller-kubernetes-url',reviewer.origin,
+          '--caller-reviewer-token-file',str(reviewer.reviewer_file),'--caller-ca-file',str(reviewer.ca),
+          '--caller-binding','secrets-engine='+PRINCIPAL]
+    process=subprocess.Popen(args,stdout=subprocess.DEVNULL,stderr=subprocess.DEVNULL)
+    for _ in range(100):
+        if process.poll() is not None:raise RuntimeError('source Access server exited')
+        try:
+            with socket.create_connection(('127.0.0.1',port),timeout=.1):break
+        except OSError:time.sleep(.05)
+    else:process.kill();process.wait();raise RuntimeError('source Access server failed to start')
+    try:yield SimpleNamespace(origin=origin,trustfile=trustfile,verifier=verifier,
+                              package=provenance['policy_package'],version=provenance['policy_version'],
+                              process=process,offline_envelope=produced)
+    finally:
+        process.terminate()
+        try:process.wait(timeout=5)
+        except subprocess.TimeoutExpired:process.kill();process.wait()
diff --git a/tests/test_task_execution_mediation_journal.py b/tests/test_task_execution_mediation_journal.py
new file mode 100644
index 0000000..d0f8e19
--- /dev/null
+++ b/tests/test_task_execution_mediation_journal.py
@@ -0,0 +1,32 @@
+"""Durable CAS/confirmation call prefix cannot overlap native call ordinals."""
+import os
+from pathlib import Path
+import sys
+import uuid
+import pytest
+sys.path.insert(0,str(Path(__file__).resolve().parents[1]/'scripts'))
+from task_execution_journal import Binding,Cleanup,Journal,Refused
+
+
+def test_next_call_continues_auth_prefix_without_replay_or_resume(tmp_path):
+    os.chmod(tmp_path,0o700);journal=Journal(tmp_path)
+    binding=Binding('fixture-approval','sha256:'+'a'*64,str(uuid.uuid4()),'b'*64)
+    try:
+        with pytest.raises(Refused):journal.next_call_ordinal(binding)
+        with journal.locked():
+            journal.reserve(binding,(Cleanup('task-token-revoke','c'*64),))
+            assert journal.next_call_ordinal(binding)==0
+            for ordinal in [0,1]:
+                journal.before_call(binding,ordinal,'d'*64)
+                with pytest.raises(Refused):journal.next_call_ordinal(binding)
+                journal.after_call(binding,ordinal,'d'*64,'e'*64)
+            assert journal.next_call_ordinal(binding)==2
+            journal.transition(binding,'reserved','consume-confirmed')
+            journal.before_call(binding,2,'f'*64)
+            with pytest.raises(Refused):journal.before_call(binding,0,'f'*64)
+            journal.after_call(binding,2,'f'*64,'e'*64)
+            journal.before_cleanup(binding,0,Cleanup('task-token-revoke','c'*64))
+            with pytest.raises(Refused):journal.next_call_ordinal(binding)
+        with journal.locked():
+            with pytest.raises(Refused):journal.next_call_ordinal(binding)
+    finally:journal.close()
diff --git a/tests/test_task_execution_mediator.py b/tests/test_task_execution_mediator.py
new file mode 100644
index 0000000..8ad9045
--- /dev/null
+++ b/tests/test_task_execution_mediator.py
@@ -0,0 +1,160 @@
+"""Whole source-server/native fixture proof, never production owner acceptance."""
+from contextlib import contextmanager
+from dataclasses import replace
+import importlib
+import json
+from pathlib import Path
+import sys
+from types import SimpleNamespace
+import uuid
+
+import pytest
+sys.path.insert(0,str(Path(__file__).resolve().parents[1]/'scripts'))
+from test_task_execution_native_fixture import owner,bao_dev,compiler
+from task_execution_mediator import ConfirmationConfig,run_native_fixture_task
+from task_execution_journal import Refused
+from task_execution_source_servers import approval_server,reviewer_server,access_server,http,private
+from secrets_engine.approval_consume import _request_purpose
+from secrets_engine.approval_claim import binding_from_check_request
+from secrets_engine.authorization import build_action_request
+from secrets_engine.decision_check import check_decision
+from secrets_engine.execution_contract import ExecutionContract
+
+
+@contextmanager
+def whole_fixture(owner,tmp_path,*,actual_policy=False,confirmation_read=True):
+    native,journal,binding,call,compiler,descriptor=owner
+    snapshot={path:compiler.read(Path(path)) for path in compiler.pins}
+    entry=compiler._catalogue_entry(snapshot)
+    approval_id=str(uuid.uuid4())
+    entry=replace(entry,approval={**entry.approval,'authorization_id':approval_id})
+    request=build_action_request(entry,'execute-ccr',subject_id='secrets-engine',subject_type='service',
+                                 purpose=_request_purpose(entry),execution_contract=ExecutionContract.parse(descriptor))
+    with reviewer_server(tmp_path) as reviewer, access_server(tmp_path,descriptor,request,reviewer,actual_policy=actual_policy) as access, approval_server(tmp_path) as approval:
+        issue=access.offline_envelope
+        body={'id':approval_id,'binding':binding_from_check_request(issue['binding']),
+              'pdp_digest':issue['binding']['request_digest'],'pdp_path':True,'human_control':True,
+              'validity':{'not_before':'2026-01-01T00:00:00+00:00',
+                          'expires_at':reviewer_expiry()}}
+        status,obj=http(approval.origin,'POST','/v1/approvals',body,approval.service_token)
+        assert status==201
+        assert http(approval.origin,'POST','/v1/approvals/'+approval_id+'/entries',{},approval.human_token)[0]==200
+        approval_token=private(tmp_path/'approval.token',approval.service_token)
+        pdp_token=private(tmp_path/'pdp.token',reviewer.caller_token)
+        confirmation_token=private(tmp_path/'confirmation.token',approval.service_token if confirmation_read else approval.no_read_token)
+        cfg=SimpleNamespace(approval_url=approval.origin,approval_token_file=approval_token,
+                            approval_client_secret_file=None,pdp_url=access.origin,pdp_token_file=pdp_token,
+                            pdp_trust_file=access.trustfile,pdp_verifier=access.verifier,
+                            authorization_subject_id='secrets-engine',authorization_subject_type='service',
+                            authorization_policy_package=access.package,authorization_policy_version=access.version,
+                            clock_trust_file=None)
+        yield SimpleNamespace(native=native,journal=journal,call=call,compiler=compiler,
+                              descriptor=descriptor,entry=entry,cfg=cfg,approval=approval,
+                              confirmation=ConfirmationConfig(approval.origin,confirmation_token),
+                              approval_id=approval_id,request=request,reviewer=reviewer)
+
+
+def reviewer_expiry():
+    from datetime import datetime,timedelta,timezone
+    return (datetime.now(timezone.utc)+timedelta(minutes=10)).isoformat()
+
+
+def invoke(fixture):
+    return run_native_fixture_task(compiler=fixture.compiler,journal=fixture.journal,
+                plan_request=fixture.native.meta['request'],owner_descriptor=fixture.native.admission.descriptor,
+                secrets_cfg=fixture.cfg,entry=fixture.entry,confirmation=fixture.confirmation,
+                native_admission=fixture.native.admission)
+
+
+def test_real_source_servers_signed_fixture_allow_and_actual_task_policy_deny(owner,tmp_path):
+    # These two Checks test real source servers and independently installed keys;
+    # they are not a fabricated DecisionEnvelope or activation of a real policy.
+    for actual_policy in [False,True]:
+        directory=tmp_path/('actual-policy' if actual_policy else 'fixture-policy');directory.mkdir()
+        with whole_fixture(owner,directory,actual_policy=actual_policy) as fixture:
+            status,claim=http(fixture.approval.origin,'GET','/v1/approvals/'+fixture.approval_id+'/claim',token=fixture.approval.service_token)
+            assert status==200
+            request=json.loads(json.dumps(fixture.request));request['context']['approval']=claim
+            envelope=check_decision(base_url=fixture.cfg.pdp_url,token_file=fixture.cfg.pdp_token_file,request=request,
+                                    trust_file=fixture.cfg.pdp_trust_file,verifier=fixture.cfg.pdp_verifier)
+            assert envelope['effect']==('deny' if actual_policy else 'allow')
+            assert envelope['provenance']['caller']['mode']=='enforce'
+            assert all(fixture.reviewer.calls)
+            assert fixture.approval.engine.get(fixture.approval_id).status=='approved'
+            assert fixture.call('GET','sys/policies/acl/'+fixture.native.policy_name)[0]==404
+
+
+def test_missing_strict_dependency_never_reads_credentials_or_reserves(monkeypatch):
+    original=importlib.import_module
+    def missing(name,*args,**kwargs):
+        if name=='secrets_engine.task_execution_handoff':raise ImportError()
+        return original(name,*args,**kwargs)
+    monkeypatch.setattr(importlib,'import_module',missing)
+    with pytest.raises(Refused,match='dependency unavailable'):
+        run_native_fixture_task(compiler=None,journal=None,plan_request={},owner_descriptor=b'',
+                                secrets_cfg=None,entry=None,confirmation=None,native_admission=None)
+
+
+def test_whole_strict_consume_confirmation_precedes_real_native_effect(owner,tmp_path):
+    with whole_fixture(owner,tmp_path) as fixture:
+        result=invoke(fixture)
+        assert result['native_calls_completed']==6 and result['cleanup_confirmed']
+        assert result['native_apply']=='unverified' # total owner baseline/readback acceptance remains separate
+        obj=fixture.approval.engine.get(fixture.approval_id)
+        assert obj.status=='consumed'
+        assert obj.consumed_digest==result['request_digest']
+        calls=fixture.journal.db.execute('SELECT ordinal,outcome FROM calls ORDER BY ordinal').fetchall()
+        assert calls[:2]==[(0,'complete'),(1,'complete')]
+        assert len(calls)==13 # CAS + GET + five native grant calls + six metadata calls
+        assert fixture.approval.calls.count(('POST','/v1/approvals/'+fixture.approval_id+'/consume'))==1
+        assert fixture.approval.calls.count(('GET','/v1/approvals/'+fixture.approval_id))==1
+        assert fixture.call('GET','sys/policies/acl/'+fixture.native.policy_name)[0]==404
+        raw=(fixture.journal.directory/'journal.sqlite').read_bytes()
+        for token in [fixture.native.admission.owner_token,fixture.native.admission.identity_session.token,
+                      fixture.approval.service_token,fixture.reviewer.caller_token]:
+            assert token.encode() not in raw
+        with pytest.raises(Exception):invoke(fixture)
+        assert fixture.approval.calls.count(('POST','/v1/approvals/'+fixture.approval_id+'/consume'))==1
+
+
+def test_actual_confirmation_read_scope_denial_keeps_native_untouched(owner,tmp_path):
+    with whole_fixture(owner,tmp_path,confirmation_read=False) as fixture:
+        with pytest.raises(Refused,match='confirmation unconfirmed'):invoke(fixture)
+        assert fixture.approval.engine.get(fixture.approval_id).status=='consumed'
+        state=fixture.journal.db.execute('SELECT state FROM operations').fetchone()[0]
+        assert state=='unknown'
+        assert fixture.journal.db.execute("SELECT COUNT(*) FROM calls WHERE outcome='pending'").fetchone()[0]==1
+        assert fixture.call('GET','sys/policies/acl/'+fixture.native.policy_name)[0]==404
+        policy_path=fixture.compiler.before_call(fixture.native.plan,1).path
+        assert fixture.call('GET',policy_path)[0]==404
+        with pytest.raises(Exception):invoke(fixture)
+        assert fixture.approval.calls.count(('POST','/v1/approvals/'+fixture.approval_id+'/consume'))==1
+
+
+def test_actual_unadmitted_policy_refuses_before_cas_and_native(owner,tmp_path):
+    with whole_fixture(owner,tmp_path,actual_policy=True) as fixture:
+        with pytest.raises(Exception):invoke(fixture)
+        assert fixture.approval.engine.get(fixture.approval_id).status=='approved'
+        assert not any(method=='POST' and path.endswith('/consume') for method,path in fixture.approval.calls)
+        assert fixture.journal.db.execute('SELECT COUNT(*) FROM operations').fetchone()[0]==0
+        assert fixture.call('GET','sys/policies/acl/'+fixture.native.policy_name)[0]==404
+
+
+def test_entry_purpose_substitution_refuses_before_authorizer_or_cas(owner,tmp_path):
+    with whole_fixture(owner,tmp_path) as fixture:
+        fixture.entry=replace(fixture.entry,approval={**fixture.entry.approval,'purpose':'caller-substituted-purpose'})
+        before=list(fixture.approval.calls)
+        with pytest.raises(Refused,match='approval metadata differs'):invoke(fixture)
+        assert fixture.approval.calls==before
+        assert fixture.journal.db.execute('SELECT COUNT(*) FROM operations').fetchone()[0]==0
+        assert fixture.call('GET','sys/policies/acl/'+fixture.native.policy_name)[0]==404
+
+
+def test_catalogue_bool_integer_alias_refuses_before_authorizer(owner,tmp_path):
+    with whole_fixture(owner,tmp_path) as fixture:
+        assert fixture.entry.delivery_auth['secret_id_num_uses']==1
+        fixture.entry=replace(fixture.entry,delivery_auth={**fixture.entry.delivery_auth,'secret_id_num_uses':True})
+        before=list(fixture.approval.calls)
+        with pytest.raises(Refused,match='catalogue does not match'):invoke(fixture)
+        assert fixture.approval.calls==before
+        assert fixture.journal.db.execute('SELECT COUNT(*) FROM operations').fetchone()[0]==0
diff --git a/workplans/RPF-WP-0035-credential-lane-implementation.md b/workplans/RPF-WP-0035-credential-lane-implementation.md
index f9af000..4ea8015 100644
--- a/workplans/RPF-WP-0035-credential-lane-implementation.md
+++ b/workplans/RPF-WP-0035-credential-lane-implementation.md
@@ -1262,3 +1262,18 @@ bodies before a native fixture can materialize. Proposed source records gain no
 execution authority; no real grant, policy or legacy applier registration added.
 Details and remaining production gates: docs/task-execution-grant-projection.md.
 T12 remains progress; no owner sync or production effect performed by this package.
+
+2026-10-16 T12 fourth source package: connected the Secrets-owned strict task
+handoff to actual Approval ExecutionConfirmationClient independent GET before
+consume-confirmed/native fixture work. Platform accepts no supplied authorization
+boolean/object/callback and preserves its exact owner descriptor/grant/Plan join.
+Durable CAS/GET intents precede native ordinals through the repaired journal
+prefix API. Actual source-server fixture uses signed Access/enforced synthetic
+TokenReview, real Approval WSGI/SQLite with distinct synthetic human/service
+identities, actual strict Secrets signature/CAS validation and disposable native
+OpenBao. Untouched actual task policy remains signed DENY; separately named
+synthetic fixture policy is never production admission. Read-scope denial after
+CAS records consumed/unknown with zero native effects. Exact dependency/source
+hashes, tests and remaining gates are retained with the source package and in
+docs/task-execution-mediator-seam.md. No real grant/custody, policy default, owner
+sync or native production acceptance is performed; T12 stays progress.