avoid serializing field: null + docs

big guy rambles.md

@@ -0,0 +1,93 @@
+# lda rambles
+
+that was surprisingly tuff response from our first user. it made me think about how we handle @node atm.
+
+atm only one way is allowed: path. If you want to inbuilt a value; please use the the graph input.
+
+our first user doesnt understand this. AT ALL.
+
+this calls to several problems.
+
+## dict use, instead of list[InputMap]
+
+why dict, when we can:
+
+```python
+class InputMap(BaseModel, Generic[TypeT]):
+  key: SupportToValue[TypeT]
+  input: Path
+```
+
+same thing
+
+```python
+class OutputMap(BaseModel, Generic[TypeT]):
+  output: Pathexpr
+  key (give me a better key name): SupportToValue[TypeT] 
+```
+
+look at this support to value, or use another fitting name.
+what it does is:
+
+Path("state.foo") -> TypeT
+Literal(TypeT) -> TypeT
+
+two modes that we currently need to PATCH IN. we do not PATCH wf_core if there isnt a greater problem.
+
+### default arguments, and literal()
+
+expand on literal, in wf_authoring we can have some Field bs:
+
+```python
+@node(
+  in_map = [
+    InputMap(dont support this either, use g.use()),
+  ]
+)
+def baz(spam: InputT = "literal input", egg: Input2T = Path(do not support this.)):
+  ...
+```
+
+so that means wf_authoring.node shouldnt do any field augmentation.
+
+```python
+g.use(
+  baz,
+  in_map = [
+    now were talking
+  ]
+)
+```
+
+this SHOULD support both path and literal.
+
+## Context, of some sort
+
+langgraph has 3 ways of storage, if you read tests/rewrite
+
+lets copy that over:
+```
+ According to https://docs.langchain.com/oss/python/concepts/context, there are three types:
+
+ | type | mut | lifetime |
+ | --- | --- | --- |
+ |static runtime (context) | static | single run |
+ |dynamic runtime (state) | mut | single run |
+ |dynamic cross-convo (store) | mut | cross-conversation |
+
+ now what the hell is store
+## store
+
+ store is used in langgraph-demo for debugging. but it can be used for more things.
+ it saves every turn. every graph nodes. I use InMemoryStore, you can use psql store!
+ This allows for picking the work up again after a while for example.
+ a lot more versatility there.
+```
+
+now we 100% has state. we kinda have store if you skim it (trace), but trace is no store. and Context is patched in through state.
+
+this can be done with support for async, because lowk store is going to give us superpowers.
+
+## complaints come when user uses
+
+not a lot from me rn.

docs/wf_mcp_troubleshooting.md

@@ -353,6 +353,21 @@ be explicit, for example:
 }
 ```
 
+For node inputs:
+
+- `in` is path mapping only, in source-to-destination order such as
+  `"input.url": "url"`.
+- `with` is for static node-local values such as
+  `"value": "CLICKED"`.
+- Do not put literal objects inside `in`. Invalid `use` step payloads should be
+  rejected, not silently treated as joins.
+
+For strict MCP servers such as Playwright, unmapped optional tool arguments
+should be omitted. If a trace shows optional keys being sent as `null`, capture
+the capability name, the node trace `resolved_input`, and the upstream error;
+that points at the workflow capability wrapper boundary rather than the raw MCP
+tool.
+
 ## MCP Resources Or Prompts Are Missing
 
 First ask whether the upstream server actually supports them.

docs/workflow_drafts.md

@@ -93,6 +93,75 @@ Important details:
 - When saved with source bindings, concrete refs can be normalized to logical
   refs such as `demo.echo_tool`.
 
+## Mapping Shape
+
+Draft maps are JSON objects whose keys and values are strings:
+
+```ts
+type InMap = Record<string, string>
+type OutMap = Record<string, string>
+```
+
+Both maps are source-to-destination.
+
+| Map | Key | Value | Example |
+| --- | --- | --- | --- |
+| `in` | graph source path | node-local input path | `"input.text": "message"` |
+| `out` | node-local output path | graph state destination path | `"echoed": "state.echoed"` |
+
+Graph source paths in `in` normally start with `input.`, `state.`, or
+`context.`. Node-local paths do not use those prefixes; they are paths inside
+the target capability's input or output payload.
+
+For example:
+
+```json
+{
+  "in": {
+    "input.user.name": "user.name",
+    "state.job.title": "job.title"
+  },
+  "out": {
+    "user.age": "state.person.age",
+    "job.years": "state.experience.years"
+  }
+}
+```
+
+Read that as:
+
+- `input.user.name` -> local input `user.name`
+- `state.job.title` -> local input `job.title`
+- local output `user.age` -> `state.person.age`
+- local output `job.years` -> `state.experience.years`
+
+Do not reverse the direction. This is wrong:
+
+```json
+{
+  "in": {
+    "message": "input.text"
+  }
+}
+```
+
+That asks the runtime to read from graph path `message` and write into a
+node-local input field literally named `input.text`.
+
+Do not put constants in `in`. This is also wrong:
+
+```json
+{
+  "in": {
+    "value": {
+      "value": "CLICKED"
+    }
+  }
+}
+```
+
+Use `with` for static node-local values instead.
+
 ## Step Kinds
 
 ### `use`
@@ -114,6 +183,27 @@ Calls a workflow capability.
 Use this for normal node calls, including generated workflow wrappers around
 MCP tools and local `wf.std` capabilities.
 
+`use` steps can also provide static node-local input values with `with`.
+Use this for hardcoded strings, booleans, numbers, and small JSON values that
+are part of the graph definition:
+
+```json
+{
+  "use": "wf.std.constant",
+  "with": {
+    "value": "CLICKED"
+  },
+  "out": {
+    "value": "state.wait_text"
+  }
+}
+```
+
+Static values are not path mappings. Do not put `{"value": "CLICKED"}` inside
+`in`. The `in` object only maps graph paths such as `input.url` or
+`state.wait_text` to node-local input fields. Invalid draft step shapes are
+rejected instead of silently compiling to `join`.
+
 Generated MCP tool wrappers are intentionally naive. They normally expose both
 `ok` and `error` outcomes, because MCP tool calls can report transport/provider
 errors separately from useful output. Drafts should wire both outcomes:

src/wf_artifacts/drafts/adapter.py

@@ -42,6 +42,7 @@ def _add_step(builder: WorkflowBuilder, step_id: str, step: DraftStep):
             step.use,
             id=step_id,
             in_map=step.in_,
+            input_values=step.with_,
             out_map=step.out,
             desc=step.desc,
         )

src/wf_artifacts/drafts/models.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 
 from typing import Any, Literal
 
-from pydantic import BaseModel, Field, model_validator
+from pydantic import BaseModel, ConfigDict, Field, model_validator
 
 from wf_core.models.conditions import Condition
 
@@ -15,9 +15,33 @@ STEP_KIND_KEYS = frozenset(
 class DraftUseStep(BaseModel):
     """Draft step that calls one externally resolvable workflow capability."""
 
+    model_config = ConfigDict(extra="forbid", populate_by_name=True)
+
     use: str
-    in_: dict[str, str] = Field(default_factory=dict, alias="in")
+    in_: dict[str, str] = Field(
-    out: dict[str, str] = Field(default_factory=dict)
+        default_factory=dict,
+        alias="in",
+        description=(
+            "Source-to-destination map from graph paths to node-local input "
+            "paths. Example: {'input.text': 'message'}. Values must be strings; "
+            "use 'with' for literals."
+        ),
+    )
+    with_: dict[str, Any] = Field(
+        default_factory=dict,
+        alias="with",
+        description=(
+            "Static node-local input values keyed by destination input field/path. "
+            "Example: {'value': 'CLICKED'}."
+        ),
+    )
+    out: dict[str, str] = Field(
+        default_factory=dict,
+        description=(
+            "Source-to-destination map from node-local output paths to workflow "
+            "state destinations. Example: {'echoed': 'state.echoed'}."
+        ),
+    )
     desc: str | None = None
     retry: int | None = Field(default=None, ge=0)
     timeout_seconds: int | None = Field(default=None, gt=0)
@@ -26,6 +50,8 @@ class DraftUseStep(BaseModel):
 class DraftForeachPayload(BaseModel):
     """Payload for one draft foreach step."""
 
+    model_config = ConfigDict(extra="forbid", populate_by_name=True)
+
     over: str
     as_: str = Field(alias="as")
     mode: Literal["serial", "parallel"] = "serial"
@@ -35,12 +61,16 @@ class DraftForeachPayload(BaseModel):
 class DraftForeachStep(BaseModel):
     """Draft step that delegates foreach construction to `WorkflowBuilder`."""
 
+    model_config = ConfigDict(extra="forbid")
+
     foreach: DraftForeachPayload
 
 
 class DraftInterruptPayload(BaseModel):
     """Payload for one draft interrupt step."""
 
+    model_config = ConfigDict(extra="forbid")
+
     kind: str
     request: dict[str, str] = Field(default_factory=dict)
     resume: dict[str, str] = Field(default_factory=dict)
@@ -50,18 +80,24 @@ class DraftInterruptPayload(BaseModel):
 class DraftInterruptStep(BaseModel):
     """Draft step that pauses execution and waits for resume input."""
 
+    model_config = ConfigDict(extra="forbid")
+
     interrupt: DraftInterruptPayload
 
 
 class DraftJoinStep(BaseModel):
     """Draft step that emits the current core join node."""
 
+    model_config = ConfigDict(extra="forbid")
+
     join: JsonObject = Field(default_factory=dict)
 
 
 class DraftWhenPayload(BaseModel):
     """Payload for one boolean draft decision."""
 
+    model_config = ConfigDict(extra="forbid", populate_by_name=True)
+
     if_: Condition = Field(alias="if")
     then: str
     otherwise: str = "__end__"
@@ -70,12 +106,16 @@ class DraftWhenPayload(BaseModel):
 class DraftWhenStep(BaseModel):
     """Draft step that delegates one boolean decision to `WorkflowBuilder.when`."""
 
+    model_config = ConfigDict(extra="forbid")
+
     when: DraftWhenPayload
 
 
 class DraftChooseClause(BaseModel):
     """One ordered boolean clause in a draft choose decision."""
 
+    model_config = ConfigDict(extra="forbid", populate_by_name=True)
+
     if_: Condition = Field(alias="if")
     then: str
 
@@ -83,6 +123,8 @@ class DraftChooseClause(BaseModel):
 class DraftChoosePayload(BaseModel):
     """Payload for an ordered first-true draft decision."""
 
+    model_config = ConfigDict(extra="forbid")
+
     clauses: list[DraftChooseClause] = Field(min_length=1)
     default: str = "__end__"
 
@@ -90,12 +132,16 @@ class DraftChoosePayload(BaseModel):
 class DraftChooseStep(BaseModel):
     """Draft step that delegates ordered decisions to `WorkflowBuilder.choose`."""
 
+    model_config = ConfigDict(extra="forbid")
+
     choose: DraftChoosePayload
 
 
 class DraftMatchCase(BaseModel):
     """One ordered equality case in a draft match decision."""
 
+    model_config = ConfigDict(extra="forbid")
+
     equals: Any
     then: str
 
@@ -103,6 +149,8 @@ class DraftMatchCase(BaseModel):
 class DraftMatchPayload(BaseModel):
     """Payload for matching one graph value against ordered equality cases."""
 
+    model_config = ConfigDict(extra="forbid")
+
     value: str
     cases: list[DraftMatchCase] = Field(min_length=1)
     default: str = "__end__"
@@ -111,6 +159,8 @@ class DraftMatchPayload(BaseModel):
 class DraftMatchStep(BaseModel):
     """Draft step that delegates equality decisions to `WorkflowBuilder.match`."""
 
+    model_config = ConfigDict(extra="forbid")
+
     match: DraftMatchPayload
 
 

src/wf_authoring/builder/core.py

@@ -84,6 +84,7 @@ class WorkflowBuilder:
         *,
         id: str | None = None,
         in_map: MapArg | None = None,
+        input_values: Mapping[str, Any] | None = None,
         out_map: MapArg | None = None,
         desc: str | None = None,
     ) -> NodeUse:
@@ -104,6 +105,7 @@ class WorkflowBuilder:
                 if in_map is None
                 else normalize_mapping(in_map)
             ),
+            input_values=dict(input_values or {}),
             out_map=(
                 auto_output_map(spec, state_schema=normalized_state_schema)
                 if out_map is None
@@ -119,6 +121,7 @@ class WorkflowBuilder:
         *,
         id: str | None = None,
         in_map: MapArg | None = None,
+        input_values: Mapping[str, Any] | None = None,
         out_map: MapArg | None = None,
         desc: str | None = None,
     ) -> NodeUse:
@@ -135,6 +138,7 @@ class WorkflowBuilder:
             node=name,
             desc=desc,
             in_map=normalize_mapping(in_map),
+            input_values=dict(input_values or {}),
             out_map=normalize_mapping(out_map),
         )
         self.nodes.append(node)

src/wf_core/models/steps.py

@@ -14,8 +14,29 @@ class NodeUse(BaseModel):
     type: Literal["node"]
     node: str
     desc: str | None = None
-    in_map: dict[str, str] = Field(default_factory=dict)
+    in_map: dict[str, str] = Field(
-    out_map: dict[str, str] = Field(default_factory=dict)
+        default_factory=dict,
+        description=(
+            "Map graph source paths to node-local input paths. Keys are paths "
+            "such as input.text, state.user.name, or context.item; values are "
+            "input fields/paths inside the node payload."
+        ),
+    )
+    input_values: dict[str, object] = Field(
+        default_factory=dict,
+        description=(
+            "Static node-local input values keyed by destination input field/path. "
+            "Use this for graph-defined constants; use in_map only for graph paths."
+        ),
+    )
+    out_map: dict[str, str] = Field(
+        default_factory=dict,
+        description=(
+            "Map node-local output paths to workflow state destinations. Keys "
+            "are output fields/paths inside the node payload; values must be "
+            "state.* destination paths."
+        ),
+    )
     retry: int | None = Field(default=None, ge=0)
     timeout_seconds: int | None = Field(default=None, gt=0)
 

src/wf_core/runtime/ops/nodes.py

@@ -33,6 +33,11 @@ def _resolve_node_execution(
     frame = run.current_frame()
     context_values = frame_context_values(frame)
     resolved_input: dict[str, Any] = {}
+    for destination_field, value in node.input_values.items():
+        try:
+            set_local_value(resolved_input, destination_field, value)
+        except LocalPathError as exc:
+            raise WorkflowExecutionError(str(exc)) from exc
     for source_path, destination_field in node.in_map.items():
         value = safe_resolve_path(
             source_path,

src/wf_core/validation/steps.py

@@ -38,6 +38,17 @@ def validate_node_use(
     state_fields = set(workflow.state_schema.fields)
     input_root_fields = set(workflow.input_schema.properties)
 
+    for destination_field in node.input_values:
+        destination_root = _local_root(destination_field)
+        if destination_root is None or (
+            destination_root != "." and destination_root not in input_fields
+        ):
+            report.add(
+                ValidationIssueCode.INVALID_NODE_INPUT_FIELD,
+                f"nodes[{index}].input_values[{destination_field!r}]",
+                f"destination field {destination_field!r} is not declared in node input schema",
+            )
+
     for source_path, destination_field in node.in_map.items():
         destination_root = _local_root(destination_field)
         if destination_root is None or (
@@ -63,6 +74,12 @@ def validate_node_use(
             f"nodes[{index}].in_map",
             "in_map has overlapping node-local input paths",
         )
+    if has_overlapping_paths([*node.input_values, *node.in_map.values()]):
+        report.add(
+            ValidationIssueCode.INVALID_NODE_INPUT_FIELD,
+            f"nodes[{index}].input_values",
+            "static input_values overlap with path-based in_map destinations",
+        )
 
     for source_field, destination_path in node.out_map.items():
         source_root = _local_root(source_field)

src/wf_mcp/workflow/wrappers.py

@@ -126,14 +126,16 @@ def wrap_discovered_tool(
                     "tool_call_started",
                     connection_id=connection.id,
                     capability_id=f"{connection.id}.{tool.name}",
-                    payload={"input": payload.model_dump()},
+                    payload={"input": payload.model_dump(exclude_unset=True)},
                 )
             )
         result = await adapter.call_tool(
             connection=connection,
             auth=auth,
             tool_name=tool.name,
-            payload=payload.model_dump(),
+            # Pydantic fills absent optional fields with None, but strict MCP
+            # servers such as Playwright distinguish omitted from explicit null.
+            payload=payload.model_dump(exclude_unset=True),
         )
         if emit_event is not None:
             emit_event(

tests/artifacts/test_draft_adapter.py

@@ -1,6 +1,9 @@
 from __future__ import annotations
 
+from pydantic import ValidationError
+
 from wf_artifacts.drafts import WorkflowDraft
+from wf_artifacts.drafts.api import compile_workflow_draft, validate_workflow_draft
 from wf_artifacts.drafts.adapter import build_workflow_from_draft
 from wf_core import ConditionNode, NodeUse
 
@@ -29,6 +32,62 @@ def test_adapter_lowers_keyed_use_steps_and_routes_through_builder() -> None:
     assert workflow.edges[0].to == "__end__"
 
 
+def test_adapter_lowers_static_inputs_for_constant_like_steps() -> None:
+    draft = WorkflowDraft.model_validate(
+        {
+            "name": "constant",
+            "input_schema": {},
+            "state_schema": {"fields": {"message": {"type": "string"}}},
+            "output_schema": {},
+            "start": "constant",
+            "steps": {
+                "constant": {
+                    "use": "wf.std.constant",
+                    "with": {"value": "CLICKED"},
+                    "out": {"value": "state.message"},
+                }
+            },
+            "routes": {"constant": {"ok": "__end__"}},
+        }
+    )
+
+    workflow = build_workflow_from_draft(draft)
+    node = workflow.nodes[0]
+
+    assert isinstance(node, NodeUse)
+    assert node.node == "wf.std.constant"
+    assert node.input_values["value"] == "CLICKED"
+    assert node.in_map == {}
+
+
+def test_invalid_literal_input_map_does_not_fall_through_to_join() -> None:
+    draft = {
+        "name": "bad_constant",
+        "input_schema": {},
+        "state_schema": {"fields": {}},
+        "output_schema": {},
+        "start": "constant",
+        "steps": {
+            "constant": {
+                "use": "wf.std.constant",
+                "in": {"value": {"value": "CLICKED"}},
+            }
+        },
+        "routes": {"constant": {"ok": "__end__"}},
+    }
+
+    result = validate_workflow_draft(draft)
+
+    assert result["status"] == "invalid"
+    assert "steps.constant" in result["diagnostics"][0]["path"]
+    try:
+        compile_workflow_draft(draft)
+    except ValidationError:
+        pass
+    else:  # pragma: no cover - kept explicit because silent join fallback was the bug.
+        raise AssertionError("invalid use step compiled instead of failing")
+
+
 def test_adapter_lowers_when_step_through_builder() -> None:
     draft = WorkflowDraft.model_validate(
         {

tests/core/test_nested_mappings.py

@@ -113,6 +113,55 @@ def test_root_node_local_paths_map_whole_input_and_output_payloads() -> None:
     assert run.state["rates"] == {"r_1": 0.0, "r_10": 0.1}
 
 
+def test_static_input_values_are_merged_into_node_local_input() -> None:
+    workflow = Workflow(
+        name="static_input_values",
+        input_schema=SchemaRef.model_validate({"type": "object", "properties": {}}),
+        state_schema=StateSchema(fields={"message": StateField(type="string")}),
+        output_schema=SchemaRef(type="object", properties={}),
+        node_defs=[
+            NodeDef(
+                name="constant",
+                input_schema=SchemaRef.model_validate(
+                    {
+                        "type": "object",
+                        "properties": {"value": {"type": "string"}},
+                        "required": ["value"],
+                    }
+                ),
+                output_schema=SchemaRef.model_validate(
+                    {
+                        "type": "object",
+                        "properties": {"value": {"type": "string"}},
+                        "required": ["value"],
+                    }
+                ),
+                outcomes=["ok"],
+            )
+        ],
+        start="constant",
+        nodes=[
+            NodeUse(
+                id="constant",
+                type="node",
+                node="constant",
+                input_values={"value": "CLICKED"},
+                out_map={"value": "state.message"},
+            )
+        ],
+        edges=[Edge.model_validate({"from": "constant", "outcome": "ok", "to": END})],
+    )
+
+    run = execute_workflow(
+        workflow,
+        {},
+        {"constant": lambda payload, _ctx: {"outcome": "ok", "output": payload}},
+    )
+
+    assert run.trace[0].resolved_input["value"] == "CLICKED"
+    assert run.state["message"] == "CLICKED"
+
+
 def _nested_mapping_workflow() -> Workflow:
     return Workflow(
         name="nested_mapping",

tests/wf_mcp/test_workflow_wrappers.py

@@ -0,0 +1,67 @@
+from __future__ import annotations
+
+import asyncio
+from typing import Any, cast
+
+from wf_authoring import build_async_registry
+from wf_core import RuntimeContext
+from wf_mcp.capabilities import DiscoveredTool
+from wf_mcp.models import AuthRecord, ConnectionConfig
+from wf_mcp.sdk import BackendAdapter, ToolCallResult
+from wf_mcp.workflow import wrap_discovered_tool
+
+
+class RecordingAdapter:
+    """Tiny adapter fake that records exactly what MCP payload would be sent."""
+
+    def __init__(self) -> None:
+        self.payloads: list[dict[str, Any]] = []
+
+    async def call_tool(
+        self,
+        connection: ConnectionConfig,
+        auth: AuthRecord | None,
+        tool_name: str,
+        payload: dict[str, Any],
+    ) -> ToolCallResult:
+        self.payloads.append(payload)
+        return ToolCallResult(outcome="ok", output={})
+
+
+def test_discovered_tool_wrapper_omits_unset_optional_arguments() -> None:
+    adapter = RecordingAdapter()
+    spec = wrap_discovered_tool(
+        connection=ConnectionConfig(
+            id="playwright.default",
+            server="playwright",
+            account="default",
+        ),
+        auth=None,
+        adapter=cast(BackendAdapter, adapter),
+        tool=DiscoveredTool(
+            name="browser_snapshot",
+            title=None,
+            description=None,
+            input_schema={
+                "type": "object",
+                "properties": {
+                    "target": {"type": "string"},
+                    "depth": {"type": "integer"},
+                },
+            },
+            output_schema={"type": "object", "properties": {}},
+        ),
+    )
+    handler = build_async_registry(spec)[spec.name]
+
+    async def run_calls() -> None:
+        await handler({}, RuntimeContext(current_node_id="snapshot"))
+        await handler(
+            {"target": "main"},
+            RuntimeContext(current_node_id="snapshot"),
+        )
+
+    asyncio.run(run_calls())
+
+    assert adapter.payloads[0] == {}
+    assert adapter.payloads[1] == {"target": "main"}

wf_mcp.config.json

@@ -9,9 +9,7 @@
       "metadata": {
         "transport": "stdio",
         "command": "pnpx",
-        "args": [
+        "args": ["@upstash/context7-mcp"],
-          "@upstash/context7-mcp"
-        ],
         "env": {}
       }
     },
@@ -23,10 +21,7 @@
       "metadata": {
         "transport": "stdio",
         "command": "pnpx",
-        "args": [
+        "args": ["@playwright/mcp@latest"],
-          "@playwright/mcp@latest",
-          "--isolated"
-        ],
         "env": {}
       }
     },
@@ -38,9 +33,7 @@
       "metadata": {
         "transport": "stdio",
         "command": "pnpx",
-        "args": [
+        "args": ["@modelcontextprotocol/server-everything"],
-          "@modelcontextprotocol/server-everything"
-        ],
         "env": {}
       }
     },
@@ -52,10 +45,7 @@
       "metadata": {
         "transport": "stdio",
         "command": "serena",
-        "args": [
+        "args": ["start-mcp-server", "--project-from-cwd"],
-          "start-mcp-server",
-          "--project-from-cwd"
-        ],
         "env": {}
       }
     }