diff --git a/docs/adr/0006-explicit-fork-and-topology-driven-gather.md b/docs/adr/0006-explicit-fork-and-topology-driven-gather.md
index b7727acf..370a55cf 100644
--- a/docs/adr/0006-explicit-fork-and-topology-driven-gather.md
+++ b/docs/adr/0006-explicit-fork-and-topology-driven-gather.md
@@ -76,10 +76,14 @@ not duplicate the lineage's scope membership.
 
 Lineage remains a virtual worldview: committed scope state plus writes visible
 to one branch. Gathering several lineages does not require turning lineage
-ancestry into a multi-parent graph. A partial gather can create an intermediate
-lineage under the branches' common parent, retaining multi-input provenance in
-activation-token metadata. A final gather can merge that lineage with remaining
-siblings and resume the blocked parent continuation.
+ancestry into a multi-parent graph. Every input lineage must belong to the same
+runtime scope. Because lineages have one parent, their ancestry chains have at
+most one deepest shared lineage: the lowest common ancestor is the deterministic
+merge base. Different scopes or no shared ancestor fail before state mutation.
+A partial gather creates its intermediate lineage under that merge base and
+retains multi-input provenance in activation-token metadata. A final gather can
+merge that lineage with remaining siblings and resume the blocked parent
+continuation.
 
 The first gather merge policy is fail-closed:
 
@@ -92,11 +96,30 @@ State-field reducers remain the source of truth for legitimate concurrent
 merges. The gather policy determines what happens when patches cannot be
 merged; the initial behavior is to fail rather than choose a last writer.
 
+Gather slots have declaration order, and that order is the canonical reducer
+replay order. After choosing the merge base, the runtime applies each selected
+lineage's writes after that base in declared-slot order, never arrival,
+scheduler, or frame-id order. A bucket accepts exactly one token for each slot;
+a second token for the same activation and slot fails the activation instead of
+making an alternative-path race decide the result. Order-sensitive reducers
+such as append are therefore deterministic in synchronous and asynchronous
+execution.
+
 Branch execution order may be deterministic in the synchronous runtime and
 overlap in the asynchronous runtime. Both modes must produce equivalent graph
 semantics. Scheduler order decides when compatible work progresses, never which
 arrivals belong together.
 
+An unhandled branch failure makes its gather activation terminally failed and
+stops further branch admission. The runtime requests cancellation of admitted
+siblings, awaits every sibling's settlement, and accepts no later state or
+trace commits from them; external effects that already occurred cannot be
+rolled back. It then marks the failed activation's uncommitted lineages
+abandoned and permanently non-mergeable, invalidates and removes every pending
+gather token, marks sibling frames cancelled or failed, and persists the failed
+run. Restore may inspect those frames and lineages but cannot schedule them or
+consume a token from the failed activation.
+
 `END` and explicit `EndNode` represent workflow/subgraph termination, not a
 generic way to complete any child frame. A foreach item returns through a
 back-edge targeting its owning `ForeachNode`; the runtime completes that item
@@ -153,9 +176,10 @@ node is a pass-through marker with no barrier contract.
 
 - Edge identity gains gather-slot significance only when its target is a
   gather; ordinary edge semantics stay unchanged.
-- Workflow validation must prove that every gather slot has an incoming edge,
-  reject slots on non-gather targets, and preserve one successor per ordinary
-  `(node, outcome)` pair.
+- Workflow validation must require every gather-target edge to name exactly one
+  declared slot, reject missing or unknown gather slots, prove that every slot
+  has an incoming edge, reject slots on non-gather targets, and preserve one
+  successor per ordinary `(node, outcome)` pair.
 - Checkpoints must persist pending gather arrivals and activation provenance so
   interruption/resume cannot mix loop iterations or subgraph invocations.
 - Runtime operations should resolve a frame, its lineage, and its scope through
@@ -169,8 +193,9 @@ node is a pass-through marker with no barrier contract.
   ordinary node output.
 - Fork/gather should generalize concurrent-foreach lineage and barrier helpers,
   not create a second state-patch system.
-- Runtime branch failures remain execution failures in the first version. Skip,
-  collect, race, first-success, cancellation, and timeout policies are deferred.
+- Runtime branch failures remain execution failures with the terminal cleanup
+  above. Skip, collect, race, first-success, configurable cancellation, and
+  timeout policies are deferred.
 
 ## Open Questions
 
diff --git a/docs/superpowers/specs/2026-09-04-foreach-back-edge-design.md b/docs/superpowers/specs/2026-09-04-foreach-back-edge-design.md
index 9a3e40d9..93812bf0 100644
--- a/docs/superpowers/specs/2026-09-04-foreach-back-edge-design.md
+++ b/docs/superpowers/specs/2026-09-04-foreach-back-edge-design.md
@@ -4,7 +4,8 @@
 
 Implemented on 2026-09-04. This document specifies canonical foreach
 body-return semantics. It does not include the separately planned ergonomic
-Python DSL or authorize fork/gather implementation.
+Python DSL or the explicit fork/gather implementation described by
+[ADR-0006](../../adr/0006-explicit-fork-and-topology-driven-gather.md).
 
 ## Purpose
 
diff --git a/docs/superpowers/specs/2026-09-04-run-step-budget-design.md b/docs/superpowers/specs/2026-09-04-run-step-budget-design.md
index e0d27a2a..749495e4 100644
--- a/docs/superpowers/specs/2026-09-04-run-step-budget-design.md
+++ b/docs/superpowers/specs/2026-09-04-run-step-budget-design.md
@@ -93,6 +93,17 @@ behavior. The counter is incremented before user code or external capability
 code begins, so failures and interrupts still consume the attempt that caused
 them.
 
+For a durable run, admission is checkpointed before dispatch. The checkpoint
+contains the incremented counter, assigned step number, selected frame and
+node, and an admitted-but-not-completed marker. Dispatch may begin only after
+that checkpoint succeeds. If the process stops at that boundary, restore keeps
+the attempt consumed, clears the abandoned admission marker, and requeues the
+frame; a retry is a new attempt with a new step number. The in-memory executor
+applies the same counter transition without requiring a persistence backend.
+As with any crash after external dispatch and before result persistence, retry
+may repeat external effects; the budget records attempts and does not provide
+exactly-once execution.
+
 If `steps_executed == max_steps`, the next attempted dispatch is denied. A
 budget of one therefore admits exactly one step. The denied step does not
 increment the counter and does not invoke a handler.
@@ -132,6 +143,15 @@ Reserved async attempts remain consumed even if one handler raises. This
 matches the rule that admission, rather than successful completion, consumes
 the budget and avoids making counts depend on task completion timing.
 
+The runtime awaits every handler in an admitted batch before finalizing any
+result. It then finalizes in reserved ready-queue order. Handled foreach item
+failures follow their declared `skip` or `collect` policy. At the first
+unhandled failure in that order, preceding successful results have committed,
+the run fails, and later sibling results are discarded without state or trace
+commits. Because all handler tasks have already settled, no sibling can mutate
+the failed checkpoint afterward; external effects performed inside a handler
+remain outside rollback.
+
 ## Exhaustion Behavior
 
 Exhaustion is a runtime failure, not a workflow outcome. The runtime raises a
@@ -160,16 +180,19 @@ administrative rerun can raise the budget is outside ordinary resume semantics.
 
 ## Persistence and Resume
 
-`RunLimits` and `steps_executed` are serialized inside the existing persisted
-`RunState` checkpoint. An interrupted run resumes with its original maximum and
-cumulative count.
+`RunLimits` and `steps_executed` are serialized inside the persisted `RunState`
+checkpoint. An interrupted run resumes with its original maximum and cumulative
+count.
 
-The persisted run envelope may remain at version 1 because adding dataclass
-fields with defaults is structurally additive. Loading an older checkpoint
-that lacks these fields yields the default limit and a zero count. The
-repository has no declared production migration requirement for reconstructing
-historical counts that were never recorded; if real stored checkpoints exist,
-their migration policy must be established before release.
+A checkpoint that predates step budgets receives one explicit, prospective
+upgrade: assign the default limit and `steps_executed = 0`, mark the envelope as
+budget-initialized, and persist the upgraded checkpoint before admitting any
+new work. Attempts made before the upgrade cannot be reconstructed and are
+explicitly outside the new budget; every attempt after it is cumulative. A
+missing counter on an already budget-initialized envelope is corrupt state, not
+another request for defaults. If the one-time upgrade cannot be persisted,
+resume fails before dispatch. The persisted envelope version or equivalent
+migration marker must distinguish these cases.
 
 Subgraph scopes do not receive independent counters. They are part of the same
 run and consume the root run's budget. This prevents an outer workflow from
@@ -258,6 +281,8 @@ with the run.
 - A batch claims no more frames than the remaining budget.
 - Step numbers follow ready-queue order rather than completion order.
 - Reserved attempts remain counted when one async handler fails.
+- A still-running sibling settles before an unhandled handler failure is
+  checkpointed, and its later result does not commit state or trace data.
 - Sync and async runs produce the same count for equivalent serial execution.
 
 ### Persistence and API
@@ -265,7 +290,10 @@ with the run.
 - Limits and counts round-trip through `dump_run_state()` and
   `load_run_state()`.
 - A stored interrupted run resumes without resetting or replacing its budget.
-- Older additive checkpoints receive documented defaults.
+- A pre-budget checkpoint receives its defaults once, persists the upgraded
+  envelope before dispatch, and cannot receive another fresh budget on reload.
+- Stopping after the admission checkpoint but before handler start leaves the
+  attempt consumed; retrying the requeued frame consumes a new attempt.
 - Run inspection exposes effective maximum, executed, and remaining counts.
 - Trace entries expose deterministic step numbers without becoming the source
   of enforcement truth.
diff --git a/docs/wf_authoring_control_flow.md b/docs/wf_authoring_control_flow.md
index 881453a5..355dc590 100644
--- a/docs/wf_authoring_control_flow.md
+++ b/docs/wf_authoring_control_flow.md
@@ -234,6 +234,7 @@ An iteration body returns through its immediate owning foreach:
 g.connect(each, "loop", record)
 g.connect(record, "ok", each)
 g.connect(each, "done", END)
+g.connect(each, "completed_with_errors", END)
 ```
 
 Region conflicts, unreachable nodes, body terminals, non-local returns, empty
diff --git a/skills/wf-python/evals/evals.json b/skills/wf-python/evals/evals.json
index 0a35dd72..ac42a404 100644
--- a/skills/wf-python/evals/evals.json
+++ b/skills/wf-python/evals/evals.json
@@ -22,6 +22,7 @@
         "Loads exact artifact version 3 and edits the seeded builder rather than rebuilding",
         "Warns that step IDs and state paths must be inspected rather than guessed",
         "Validates locally and remotely before saving version 4",
+        "Passes an explicit source binding through bindings=... when creating the deployment",
         "Creates and validates a deployment before starting a durable run"
       ]
     },
diff --git a/skills/wf-python/references/python-lifecycle.md b/skills/wf-python/references/python-lifecycle.md
index 313729bb..f58abb13 100644
--- a/skills/wf-python/references/python-lifecycle.md
+++ b/skills/wf-python/references/python-lifecycle.md
@@ -133,7 +133,7 @@ its real contract; do not assume those names exist.
 ## Deployment Diagnosis And Durable Runs
 
 ```python
-from wf_client import DeploymentRequired, WorkflowClientError
+from wf_client import DeploymentRequired, ProtocolError, WorkflowClientError
 
 artifact = await app.workflow("invoice", version=2)
 
@@ -144,6 +144,12 @@ except DeploymentRequired as error:
     print("unresolved", error.unresolved_logical_sources)
     for diagnostic in error.diagnostics:
         print(diagnostic.code, diagnostic.message)
+except ProtocolError as error:
+    print("server error", error.code, error.message, error.data)
+    raise
+except WorkflowClientError as error:
+    print(type(error).__name__, error)
+    raise
 
 deployment = await artifact.deploy(
     "invoice.production",
diff --git a/src/wf_core/analysis/control_regions.py b/src/wf_core/analysis/control_regions.py
index 8b8063ba..3688fea7 100644
--- a/src/wf_core/analysis/control_regions.py
+++ b/src/wf_core/analysis/control_regions.py
@@ -154,13 +154,14 @@ def analyze_control_regions(workflow: Workflow) -> ControlRegionAnalysis:
                 # unreachable. The `END` token has no node to record.
                 if isinstance(target_node, EndNode):
                     visited_nodes.add(target_id)
-                    recorded_target = owner_stack_by_node.get(target_id)
-                    if recorded_target is None:
-                        owner_stack_by_node[target_id] = target_stack
-                    elif recorded_target != target_stack:
-                        record_region_conflict(
-                            target_id, (recorded_target, target_stack)
-                        )
+                    if target_id not in conflicted:
+                        recorded_target = owner_stack_by_node.get(target_id)
+                        if recorded_target is None:
+                            owner_stack_by_node[target_id] = target_stack
+                        elif recorded_target != target_stack:
+                            record_region_conflict(
+                                target_id, (recorded_target, target_stack)
+                            )
                 if target_stack:
                     issues.append(
                         ControlRegionIssue(
diff --git a/src/wf_core/runtime/lineage.py b/src/wf_core/runtime/lineage.py
index e5657af3..9c5cea17 100644
--- a/src/wf_core/runtime/lineage.py
+++ b/src/wf_core/runtime/lineage.py
@@ -18,9 +18,10 @@ from wf_core.runtime.ops.state import (
 class LineageStateView:
     """Committed state plus writes visible inside one child lineage.
 
-    Today concurrent foreach supplies the writes from barrier metadata. Future
-    native subgraphs and fork/gather should use the same primitive instead of
-    rebuilding foreach-specific overlay logic.
+    Concurrent foreach item writes live in ``RunState.lineages``; the barrier
+    keeps only each item's lineage identity. Future native subgraphs and
+    fork/gather should reuse this primitive instead of rebuilding lineage
+    overlay logic.
     """
 
     base_state: Mapping[str, Any]
diff --git a/src/wf_core/runtime/ops/foreach.py b/src/wf_core/runtime/ops/foreach.py
index 52989dcf..9876dbf4 100644
--- a/src/wf_core/runtime/ops/foreach.py
+++ b/src/wf_core/runtime/ops/foreach.py
@@ -94,7 +94,6 @@ def _step_foreach_serial(
         advance_frame(run, frame, outcome=outcome, next_node_id=next_node_id)
         return run
 
-    loop_start = index.next_node_id(frame.node_id, "loop")
     item = iterable[loop_index]
     loop_start, child_id = _admit_item_frame(
         run=run,
@@ -292,7 +291,6 @@ def _admit_concurrent_children(
         raise WorkflowExecutionError("concurrent foreach requires concurrent policy")
 
     barrier = activation.barrier
-    loop_start = index.next_node_id(frame.node_id, "loop")
     while (
         barrier.next_index < len(iterable)
         and len(barrier.active_frame_ids) < step.concurrent.max_active
diff --git a/src/wf_core/runtime/scheduler.py b/src/wf_core/runtime/scheduler.py
index a8d2b896..35cc8648 100644
--- a/src/wf_core/runtime/scheduler.py
+++ b/src/wf_core/runtime/scheduler.py
@@ -213,10 +213,7 @@ def wake_parent_for_child_progress(run: RunState, child_frame_id: str) -> None:
         load_foreach_activation,
     )
 
-    try:
-        owner = item_frame_owner(child)
-    except WorkflowExecutionError:
-        raise
+    owner = item_frame_owner(child)
     if owner is not None:
         activation = load_foreach_activation(
             parent, owner.foreach_node_id, owner.activation_id
diff --git a/tests/core/test_concurrent_foreach_interrupts.py b/tests/core/test_concurrent_foreach_interrupts.py
index 009f488f..777a4664 100644
--- a/tests/core/test_concurrent_foreach_interrupts.py
+++ b/tests/core/test_concurrent_foreach_interrupts.py
@@ -19,6 +19,7 @@ from wf_core import (
     execute_workflow_async,
     resume_workflow_async,
 )
+from wf_core.runtime.foreach_state import item_frame_owner
 
 
 async def test_concurrent_foreach_interrupt_returns_before_refill() -> None:
@@ -44,6 +45,9 @@ async def test_resume_prioritizes_interrupted_item_before_siblings() -> None:
         {"route": _interrupt_on_b},
     )
     interrupted_trace_len = len(run.trace)
+    interrupted_owner = item_frame_owner(run.frames["root:each#0:1"])
+    assert interrupted_owner is not None
+    interrupted_activation_id = interrupted_owner.activation_id
 
     resumed = await resume_workflow_async(
         workflow,
@@ -52,15 +56,11 @@ async def test_resume_prioritizes_interrupted_item_before_siblings() -> None:
         resume_payload={},
     )
 
-    from wf_core.runtime.foreach_state import item_frame_owner
-
-    interrupted_owner = item_frame_owner(run.frames["root:each#0:1"])
-    assert interrupted_owner is not None
     assert resumed.status is RunStatus.COMPLETED
     assert resumed.state["seen"] == ["a", "b", "c"]
     resumed_owner = item_frame_owner(resumed.frames["root:each#0:1"])
     assert resumed_owner is not None
-    assert resumed_owner.activation_id == interrupted_owner.activation_id
+    assert resumed_owner.activation_id == interrupted_activation_id
     assert resumed.trace[interrupted_trace_len].frame_id == "root:each#0:1"
     assert resumed.trace[interrupted_trace_len].step_type == "interrupt"
     assert resumed.trace[interrupted_trace_len].outcome == "submitted"
diff --git a/tests/core/test_foreach_activations.py b/tests/core/test_foreach_activations.py
index 0bdea28a..22dd7636 100644
--- a/tests/core/test_foreach_activations.py
+++ b/tests/core/test_foreach_activations.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import json
+
 import pytest
 
 from wf_core.errors import WorkflowExecutionError
@@ -65,8 +67,13 @@ def test_closing_stale_activation_fails_closed() -> None:
     second = load_or_begin_foreach_activation(frame, "each", mode="serial")
     save_foreach_activation(frame, second)
 
-    with pytest.raises(WorkflowExecutionError, match="stale|closed|active"):
+    with pytest.raises(
+        WorkflowExecutionError, match="cannot close stale foreach activation"
+    ) as exc_info:
         close_foreach_activation(frame, first)
+    message = str(exc_info.value)
+    assert repr(first.id) in message
+    assert "'root'" in message
 
 
 def test_activation_json_round_trip_through_frame_metadata() -> None:
@@ -75,7 +82,7 @@ def test_activation_json_round_trip_through_frame_metadata() -> None:
     activation.barrier.next_index = 2
     save_foreach_activation(frame, activation)
 
-    dumped = dict(frame.metadata)
+    dumped = json.loads(json.dumps(frame.metadata))
     restored_frame = ExecutionFrame(
         id="root", kind="workflow", node_id="each", metadata=dumped
     )
diff --git a/tests/core/test_foreach_back_edges.py b/tests/core/test_foreach_back_edges.py
index ca19e327..89533438 100644
--- a/tests/core/test_foreach_back_edges.py
+++ b/tests/core/test_foreach_back_edges.py
@@ -28,18 +28,6 @@ from wf_core.runtime.foreach_state import item_frame_owner
 from wf_core.runtime.scheduler import add_frame
 
 
-def _node_use(node_id: str, *, node: str = "record") -> NodeUse:
-    return NodeUse.model_validate(
-        {
-            "id": node_id,
-            "type": "node",
-            "node": node,
-            "input": [{"target": "value", "path": "context.item"}],
-            "output": [{"source": "seen", "target": "state.seen"}],
-        }
-    )
-
-
 def _serial_workflow() -> Workflow:
     foreach = ForeachNode.model_validate(
         {
@@ -1360,8 +1348,14 @@ def test_nonlocal_runtime_return_fails_closed_when_validation_is_bypassed() -> N
 
     from wf_core.runtime.ops.flow import advance_frame
 
-    with pytest.raises(WorkflowExecutionError, match="non-local|ancestor|immediate"):
+    with pytest.raises(
+        WorkflowExecutionError, match="targets non-immediate ancestor"
+    ) as exc_info:
         advance_frame(run, run.frames["inner-item"], outcome="ok", next_node_id="outer")
+    message = str(exc_info.value)
+    assert "'inner-item'" in message
+    assert "'outer'" in message
+    assert "'inner'" in message
 
 
 def test_root_frame_targeting_foreach_enters_normally() -> None:
@@ -1415,8 +1409,13 @@ def test_completed_activation_cannot_consume_later_activation_result_or_wake() -
 
     assert second.id != first.id
 
-    with pytest.raises(WorkflowExecutionError, match="closed|superseded"):
+    with pytest.raises(
+        WorkflowExecutionError, match="closed or superseded"
+    ) as exc_info:
         require_foreach_activation(parent, "each", first.id)
+    message = str(exc_info.value)
+    assert repr(first.id) in message
+    assert "'each'" in message
 
     run = RunState(
         workflow_name="activation_isolation",
diff --git a/tests/core/test_foreach_barrier_state.py b/tests/core/test_foreach_barrier_state.py
index 23dd9a8c..2fbb8d76 100644
--- a/tests/core/test_foreach_barrier_state.py
+++ b/tests/core/test_foreach_barrier_state.py
@@ -361,21 +361,29 @@ def _failed_result(
 
 
 def test_pending_item_result_rejects_error_index_mismatch() -> None:
-    with pytest.raises(WorkflowExecutionError, match="error.*index|index.*error"):
+    with pytest.raises(WorkflowExecutionError, match="error identity") as exc_info:
         PendingItemResult.from_metadata(
             _failed_result(
                 index=0, frame_id="child-0", error_index=7, error_frame="child-0"
             )
         )
+    message = str(exc_info.value)
+    assert "index 7" in message
+    assert "index 0" in message
+    assert "frame 'child-0'" in message
 
 
 def test_pending_item_result_rejects_error_frame_mismatch() -> None:
-    with pytest.raises(WorkflowExecutionError, match="error.*frame|frame.*error"):
+    with pytest.raises(WorkflowExecutionError, match="error identity") as exc_info:
         PendingItemResult.from_metadata(
             _failed_result(
                 index=0, frame_id="child-0", error_index=0, error_frame="other"
             )
         )
+    message = str(exc_info.value)
+    assert "frame 'other'" in message
+    assert "frame 'child-0'" in message
+    assert "index 0" in message
 
 
 def test_pending_item_result_accepts_matching_error_identity() -> None:
diff --git a/tests/core/test_foreach_control_regions.py b/tests/core/test_foreach_control_regions.py
index c48469e5..d87d41e8 100644
--- a/tests/core/test_foreach_control_regions.py
+++ b/tests/core/test_foreach_control_regions.py
@@ -417,6 +417,42 @@ def test_foreach_body_cannot_target_explicit_end_node() -> None:
     assert matching[0].path == "edges[1]"
 
 
+def test_explicit_end_reached_from_three_regions_stays_conflicted() -> None:
+    workflow = _workflow(
+        start="start",
+        nodes=[
+            _node("start"),
+            _foreach("f1"),
+            _node("b1"),
+            _foreach("f2"),
+            _node("b2"),
+            {"id": "stop", "type": "end", "outcome": "ok"},
+        ],
+        edges=[
+            {"from": "start", "outcome": "direct", "to": "stop"},
+            {"from": "start", "outcome": "left", "to": "f1"},
+            {"from": "start", "outcome": "right", "to": "f2"},
+            {"from": "f1", "outcome": "loop", "to": "b1"},
+            {"from": "b1", "outcome": "ok", "to": "stop"},
+            {"from": "f1", "outcome": "done", "to": END},
+            {"from": "f2", "outcome": "loop", "to": "b2"},
+            {"from": "b2", "outcome": "ok", "to": "stop"},
+            {"from": "f2", "outcome": "done", "to": END},
+        ],
+    )
+
+    analysis = analyze_control_regions(workflow)
+
+    conflicts = [
+        issue
+        for issue in analysis.issues
+        if issue.kind == ControlRegionIssueKind.FOREACH_REGION_CONFLICT
+        and issue.path == "nodes[stop]"
+    ]
+    assert len(conflicts) == 1
+    assert "stop" not in analysis.owner_stack_by_node
+
+
 def test_every_unreachable_node_is_reported() -> None:
     workflow = _workflow(
         start="work",