diff --git a/gsap_broker/app.py b/gsap_broker/app.py
index a65b172..fbba6d4 100644
--- a/gsap_broker/app.py
+++ b/gsap_broker/app.py
@@ -5,7 +5,7 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from gsap_broker.settings import settings
 from gsap_broker.db import init_db
-from gsap_broker.routers import authorize, complete, session, elevate, health, drivers, connectors
+from gsap_broker.routers import authorize, complete, session, elevate, health, drivers, connectors, functions
 
 logger = structlog.get_logger()
 
@@ -25,4 +25,5 @@ app.include_router(session.router, prefix="/governance", tags=["Session"])
 app.include_router(elevate.router, prefix="/governance", tags=["Elevation"])
 app.include_router(drivers.router, prefix="/governance", tags=["Drivers"])
 app.include_router(connectors.router, prefix="/connectors", tags=["Connectors"])
+app.include_router(functions.router, prefix="/functions", tags=["Functions"])
 app.include_router(health.router, tags=["Health"])
diff --git a/gsap_broker/functions/__init__.py b/gsap_broker/functions/__init__.py
new file mode 100644
index 0000000..ead91c5
--- /dev/null
+++ b/gsap_broker/functions/__init__.py
@@ -0,0 +1,4 @@
+from .base import FunctionPlugin, FunctionContext, FunctionResult
+from .registry import FunctionRegistry
+from .runtime import FunctionRuntime
+from .decorator import governed_function
diff --git a/gsap_broker/functions/base.py b/gsap_broker/functions/base.py
new file mode 100644
index 0000000..324e040
--- /dev/null
+++ b/gsap_broker/functions/base.py
@@ -0,0 +1,116 @@
+"""FunctionPlugin ABC per GCAP-SPEC-FUNCTION-DESCRIPTOR-0001 section 4."""
+from __future__ import annotations
+
+import hashlib
+import json
+from abc import ABC, abstractmethod
+from dataclasses import dataclass, field
+from typing import Any
+
+
+@dataclass
+class FunctionContext:
+    trigger_event_kind: str = ""
+    trigger_event_cid: str = ""
+    chronicle_session_id: str = ""
+    gsap_context_id: str = ""
+    invocation_id: str = ""
+    pipeline_run_id: str = ""
+
+
+@dataclass
+class FunctionResult:
+    success: bool = False
+    data: Any = None
+    error: str | None = None
+    lineage_cid: str = ""
+    duration_ms: float = 0.0
+    metadata: dict[str, Any] = field(default_factory=dict)
+
+    def output_cid(self) -> str:
+        """Compute content-addressable hash of the output data."""
+        canonical = json.dumps(self.data, sort_keys=True, separators=(",", ":"), default=str)
+        return "sha256:" + hashlib.sha256(canonical.encode()).hexdigest()
+
+
+class FunctionPlugin(ABC):
+    """Abstract base for governed serverless functions."""
+
+    function_id: str = ""
+    corpus_entry_cid: str = ""
+    capability_mask: int = 0
+    trigger_events: list[str] = []
+    accord_template: str = ""
+    gsap_required: bool = True
+    chronicle_enabled: bool = True
+    max_duration_seconds: int = 30
+    display_name: str = ""
+    description: str = ""
+    version: str = "0.1.0"
+
+    @abstractmethod
+    async def handle(self, event: dict[str, Any], context: FunctionContext) -> FunctionResult:
+        ...
+
+    @abstractmethod
+    def health_check(self) -> bool:
+        ...
+
+    def descriptor(self) -> dict[str, Any]:
+        """JSON-LD descriptor per GCAP-SPEC-FUNCTION-DESCRIPTOR-0001 §2."""
+        return {
+            "@context": "https://schema.gsap.dev/function/v1",
+            "@type": "FunctionDescriptor",
+            "function_id": self.function_id,
+            "corpus_entry_cid": self.corpus_entry_cid,
+            "capability_mask": self.capability_mask,
+            "trigger_events": self.trigger_events,
+            "accord_template": self.accord_template,
+            "gsap_required": self.gsap_required,
+            "chronicle_enabled": self.chronicle_enabled,
+            "max_duration_seconds": self.max_duration_seconds,
+            "display_name": self.display_name,
+            "description": self.description,
+            "version": self.version,
+        }
+
+    def knative_manifest(self, image: str, namespace: str = "default") -> dict[str, Any]:
+        """Generate Knative Service manifest."""
+        return {
+            "apiVersion": "serving.knative.dev/v1",
+            "kind": "Service",
+            "metadata": {
+                "name": self.function_id,
+                "namespace": namespace,
+                "labels": {
+                    "gcap.dev/function-id": self.function_id,
+                    "gcap.dev/capability-mask": str(self.capability_mask),
+                },
+                "annotations": {
+                    "gcap.dev/corpus-entry-cid": self.corpus_entry_cid,
+                    "gcap.dev/gsap-required": str(self.gsap_required).lower(),
+                },
+            },
+            "spec": {
+                "template": {
+                    "metadata": {
+                        "annotations": {
+                            "autoscaling.knative.dev/minScale": "0",
+                            "autoscaling.knative.dev/maxScale": "10",
+                        },
+                    },
+                    "spec": {
+                        "timeoutSeconds": self.max_duration_seconds,
+                        "containers": [
+                            {
+                                "image": image,
+                                "env": [
+                                    {"name": "GCAP_FUNCTION_ID", "value": self.function_id},
+                                    {"name": "GCAP_CAPABILITY_MASK", "value": str(self.capability_mask)},
+                                ],
+                            }
+                        ],
+                    },
+                },
+            },
+        }
diff --git a/gsap_broker/functions/decorator.py b/gsap_broker/functions/decorator.py
new file mode 100644
index 0000000..e4a4dba
--- /dev/null
+++ b/gsap_broker/functions/decorator.py
@@ -0,0 +1,70 @@
+"""governed_function decorator — wraps async functions as FunctionPlugins."""
+from __future__ import annotations
+
+import functools
+from typing import Any, Callable, Awaitable
+
+from .base import FunctionContext, FunctionPlugin, FunctionResult
+
+
+def governed_function(
+    function_id: str,
+    corpus_entry_cid: str,
+    capability_mask: int = 1,
+    trigger_events: list[str] | None = None,
+    accord_template: str = "",
+    gsap_required: bool = True,
+    chronicle_enabled: bool = True,
+    max_duration_seconds: int = 30,
+    display_name: str = "",
+    description: str = "",
+    version: str = "0.1.0",
+    registry: Any = None,
+) -> Callable:
+    """Decorator that wraps an async function as a governed FunctionPlugin.
+
+    Usage::
+
+        @governed_function(
+            function_id="my-func",
+            corpus_entry_cid="sha256:abc...",
+        )
+        async def my_func(event, context):
+            return FunctionResult(success=True, data=event)
+    """
+
+    def decorator(
+        fn: Callable[[dict[str, Any], FunctionContext], Awaitable[FunctionResult]],
+    ) -> FunctionPlugin:
+
+        class WrappedFunction(FunctionPlugin):
+            pass
+
+        instance = WrappedFunction.__new__(WrappedFunction)
+        instance.function_id = function_id
+        instance.corpus_entry_cid = corpus_entry_cid
+        instance.capability_mask = capability_mask
+        instance.trigger_events = trigger_events or []
+        instance.accord_template = accord_template
+        instance.gsap_required = gsap_required
+        instance.chronicle_enabled = chronicle_enabled
+        instance.max_duration_seconds = max_duration_seconds
+        instance.display_name = display_name or function_id
+        instance.description = description
+        instance.version = version
+
+        async def handle(event: dict[str, Any], context: FunctionContext) -> FunctionResult:
+            return await fn(event, context)
+
+        instance.handle = handle  # type: ignore[assignment]
+        instance.health_check = lambda: True  # type: ignore[assignment]
+
+        # Auto-register if a registry is provided
+        if registry is not None:
+            registry.register(instance)
+
+        # Preserve original function metadata
+        functools.update_wrapper(instance, fn)
+        return instance
+
+    return decorator
diff --git a/gsap_broker/functions/examples/__init__.py b/gsap_broker/functions/examples/__init__.py
new file mode 100644
index 0000000..3e41012
--- /dev/null
+++ b/gsap_broker/functions/examples/__init__.py
@@ -0,0 +1,2 @@
+from .billing import BillingProcessor
+from .echo import EchoFunction
diff --git a/gsap_broker/functions/examples/billing.py b/gsap_broker/functions/examples/billing.py
new file mode 100644
index 0000000..243a18b
--- /dev/null
+++ b/gsap_broker/functions/examples/billing.py
@@ -0,0 +1,62 @@
+"""BillingProcessor — governed billing drain function per §5."""
+from __future__ import annotations
+
+from typing import Any
+
+from gsap_broker.functions.base import FunctionContext, FunctionPlugin, FunctionResult
+
+
+RATE_CARD: dict[str, float] = {
+    "connector_invocation": 0.002,
+    "function_invocation": 0.001,
+    "chronicle_event": 0.0005,
+    "gsap_ac_issued": 0.003,
+    "gsap_cr_completed": 0.005,
+}
+
+
+class BillingProcessor(FunctionPlugin):
+    function_id = "billing-processor"
+    corpus_entry_cid = "sha256:" + "b" * 64
+    capability_mask = 3  # MUTATE
+    trigger_events = ["GSAP_CR_RECEIVED"]
+    accord_template = ""
+    gsap_required = False
+    chronicle_enabled = True
+    max_duration_seconds = 10
+    display_name = "Billing Processor"
+    description = "Governed billing drain — only bills completed outcomes with Chronicle CID reference."
+    version = "0.1.0"
+
+    async def handle(self, event: dict[str, Any], context: FunctionContext) -> FunctionResult:
+        outcome = event.get("outcome", "")
+        if outcome != "completed":
+            return FunctionResult(
+                success=True,
+                data={"billed": False, "reason": f"Outcome '{outcome}' is not billable"},
+                metadata={"function_id": self.function_id},
+            )
+
+        event_type = event.get("event_type", "gsap_cr_completed")
+        rate = RATE_CARD.get(event_type, RATE_CARD["gsap_cr_completed"])
+        quantity = event.get("quantity", 1)
+        amount = rate * quantity
+
+        billing_record = {
+            "billed": True,
+            "event_type": event_type,
+            "rate": rate,
+            "quantity": quantity,
+            "amount": amount,
+            "chronicle_cid": context.trigger_event_cid or event.get("chronicle_cid", ""),
+            "invocation_id": context.invocation_id,
+        }
+
+        return FunctionResult(
+            success=True,
+            data=billing_record,
+            metadata={"function_id": self.function_id},
+        )
+
+    def health_check(self) -> bool:
+        return True
diff --git a/gsap_broker/functions/examples/echo.py b/gsap_broker/functions/examples/echo.py
new file mode 100644
index 0000000..6917e44
--- /dev/null
+++ b/gsap_broker/functions/examples/echo.py
@@ -0,0 +1,26 @@
+"""EchoFunction — minimal governed function example."""
+from __future__ import annotations
+
+from typing import Any
+
+from gsap_broker.functions.base import FunctionContext, FunctionPlugin, FunctionResult
+
+
+class EchoFunction(FunctionPlugin):
+    function_id = "echo-function"
+    corpus_entry_cid = "sha256:" + "e" * 64
+    capability_mask = 1  # READ
+    trigger_events = ["CONNECTOR_INVOKED"]
+    accord_template = ""
+    gsap_required = False
+    chronicle_enabled = True
+    max_duration_seconds = 5
+    display_name = "Echo Function"
+    description = "Returns event data unchanged — used for integration testing."
+    version = "0.1.0"
+
+    async def handle(self, event: dict[str, Any], context: FunctionContext) -> FunctionResult:
+        return FunctionResult(success=True, data=event)
+
+    def health_check(self) -> bool:
+        return True
diff --git a/gsap_broker/functions/registry.py b/gsap_broker/functions/registry.py
new file mode 100644
index 0000000..174ed3a
--- /dev/null
+++ b/gsap_broker/functions/registry.py
@@ -0,0 +1,37 @@
+"""FunctionRegistry — catalogue of governed serverless functions."""
+from __future__ import annotations
+
+from .base import FunctionPlugin
+
+
+class FunctionRegistry:
+    def __init__(self) -> None:
+        self._functions: dict[str, FunctionPlugin] = {}
+        self._trigger_index: dict[str, list[str]] = {}
+
+    def register(self, function: FunctionPlugin) -> None:
+        if not function.function_id:
+            raise ValueError("function_id must be non-empty")
+        if not function.corpus_entry_cid:
+            raise ValueError("corpus_entry_cid must be non-empty")
+        self._functions[function.function_id] = function
+        # Build trigger index
+        for event_kind in function.trigger_events:
+            self._trigger_index.setdefault(event_kind, []).append(function.function_id)
+
+    def get(self, function_id: str) -> FunctionPlugin | None:
+        return self._functions.get(function_id)
+
+    def catalogue(self) -> list[dict]:
+        return [f.descriptor() for f in self._functions.values()]
+
+    def list_ids(self) -> list[str]:
+        return list(self._functions.keys())
+
+    def trigger_index(self) -> dict[str, list[str]]:
+        return dict(self._trigger_index)
+
+    def by_trigger(self, event_kind: str) -> list[FunctionPlugin]:
+        """Return all functions registered for a given trigger event kind."""
+        ids = self._trigger_index.get(event_kind, [])
+        return [self._functions[fid] for fid in ids if fid in self._functions]
diff --git a/gsap_broker/functions/runtime.py b/gsap_broker/functions/runtime.py
new file mode 100644
index 0000000..dfb2eb2
--- /dev/null
+++ b/gsap_broker/functions/runtime.py
@@ -0,0 +1,106 @@
+"""FunctionRuntime — governed invocation with Chronicle emission."""
+from __future__ import annotations
+
+import time
+import uuid
+from typing import Any
+
+from .base import FunctionContext, FunctionResult
+from .registry import FunctionRegistry
+
+
+class FunctionRuntime:
+    def __init__(
+        self, registry: FunctionRegistry, chronicle_client: Any = None
+    ) -> None:
+        self.registry = registry
+        self.chronicle_client = chronicle_client
+
+    async def invoke(
+        self,
+        function_id: str,
+        event: dict[str, Any],
+        context: FunctionContext,
+    ) -> FunctionResult:
+        """Direct invocation of a function by ID."""
+        function = self.registry.get(function_id)
+        if function is None:
+            return FunctionResult(success=False, error=f"Unknown function: {function_id}")
+
+        if function.gsap_required and not context.gsap_context_id:
+            return FunctionResult(success=False, error="GSAP context required but not provided")
+
+        if not context.invocation_id:
+            context.invocation_id = str(uuid.uuid4())
+
+        # Emit FUNCTION_INVOKED (0x2A01) before execution
+        await self._emit_chronicle(
+            "FUNCTION_INVOKED",
+            {
+                "event_code": "0x2A01",
+                "function_id": function_id,
+                "trigger_event_kind": context.trigger_event_kind,
+                "trigger_event_cid": context.trigger_event_cid,
+                "chronicle_session_id": context.chronicle_session_id,
+                "gsap_context_id": context.gsap_context_id,
+                "invocation_id": context.invocation_id,
+                "pipeline_run_id": context.pipeline_run_id,
+            },
+            function,
+        )
+
+        start = time.monotonic()
+        result = await function.handle(event, context)
+        result.duration_ms = (time.monotonic() - start) * 1000
+
+        # Emit FUNCTION_COMPLETED (0x2A02) after execution
+        await self._emit_chronicle(
+            "FUNCTION_COMPLETED",
+            {
+                "event_code": "0x2A02",
+                "function_id": function_id,
+                "invocation_id": context.invocation_id,
+                "success": result.success,
+                "duration_ms": result.duration_ms,
+                "output_cid": result.output_cid() if result.data is not None else "",
+                "error": result.error,
+            },
+            function,
+        )
+
+        return result
+
+    async def dispatch(
+        self,
+        event_kind: str,
+        event_data: dict[str, Any],
+        trigger_cid: str = "",
+    ) -> list[dict[str, Any]]:
+        """Route an event to all functions registered for this event kind."""
+        functions = self.registry.by_trigger(event_kind)
+        results = []
+        for function in functions:
+            context = FunctionContext(
+                trigger_event_kind=event_kind,
+                trigger_event_cid=trigger_cid,
+                invocation_id=str(uuid.uuid4()),
+            )
+            result = await self.invoke(function.function_id, event_data, context)
+            results.append({
+                "function_id": function.function_id,
+                "success": result.success,
+                "data": result.data,
+                "error": result.error,
+                "duration_ms": result.duration_ms,
+                "lineage_cid": result.lineage_cid,
+            })
+        return results
+
+    async def _emit_chronicle(
+        self, event_type: str, payload: dict[str, Any], function: Any
+    ) -> None:
+        if function.chronicle_enabled and self.chronicle_client is not None:
+            try:
+                await self.chronicle_client.emit(event_type, payload)
+            except Exception:
+                pass  # Chronicle failure must not break invocation
diff --git a/gsap_broker/routers/functions.py b/gsap_broker/routers/functions.py
new file mode 100644
index 0000000..974446e
--- /dev/null
+++ b/gsap_broker/routers/functions.py
@@ -0,0 +1,120 @@
+"""Functions router — governed serverless function catalogue and invocation."""
+from __future__ import annotations
+
+from typing import Any
+
+from fastapi import APIRouter, HTTPException
+from pydantic import BaseModel
+
+from gsap_broker.functions.base import FunctionContext
+from gsap_broker.functions.registry import FunctionRegistry
+from gsap_broker.functions.runtime import FunctionRuntime
+from gsap_broker.functions.examples.billing import BillingProcessor
+from gsap_broker.functions.examples.echo import EchoFunction
+
+router = APIRouter()
+
+# Module-level registry and runtime
+_registry = FunctionRegistry()
+_runtime = FunctionRuntime(registry=_registry)
+
+# Register built-in functions
+_registry.register(BillingProcessor())
+_registry.register(EchoFunction())
+
+
+class InvokeRequest(BaseModel):
+    event: dict[str, Any] = {}
+    trigger_event_kind: str = ""
+    trigger_event_cid: str = ""
+    chronicle_session_id: str = ""
+    gsap_context_id: str = ""
+    pipeline_run_id: str = ""
+
+
+class DispatchRequest(BaseModel):
+    event_kind: str
+    event_data: dict[str, Any] = {}
+    trigger_cid: str = ""
+
+
+class InvokeResponse(BaseModel):
+    success: bool
+    data: Any = None
+    error: str | None = None
+    lineage_cid: str = ""
+    function_id: str = ""
+    duration_ms: float = 0.0
+
+
+class DispatchResponse(BaseModel):
+    event_kind: str
+    dispatched_count: int
+    results: list[dict[str, Any]]
+
+
+@router.get("/")
+async def catalogue() -> dict:
+    return {
+        "functions": _registry.catalogue(),
+        "trigger_index": _registry.trigger_index(),
+    }
+
+
+@router.get("/{function_id}/")
+async def get_descriptor(function_id: str) -> dict:
+    function = _registry.get(function_id)
+    if function is None:
+        raise HTTPException(status_code=404, detail=f"Function not found: {function_id}")
+    return function.descriptor()
+
+
+@router.get("/{function_id}/manifest/")
+async def knative_manifest(function_id: str, image: str = "gcr.io/default/function:latest", namespace: str = "default") -> dict:
+    function = _registry.get(function_id)
+    if function is None:
+        raise HTTPException(status_code=404, detail=f"Function not found: {function_id}")
+    return function.knative_manifest(image=image, namespace=namespace)
+
+
+@router.post("/{function_id}/invoke/")
+async def invoke_function(function_id: str, body: InvokeRequest) -> InvokeResponse:
+    function = _registry.get(function_id)
+    if function is None:
+        raise HTTPException(status_code=404, detail=f"Function not found: {function_id}")
+
+    ctx = FunctionContext(
+        trigger_event_kind=body.trigger_event_kind,
+        trigger_event_cid=body.trigger_event_cid,
+        chronicle_session_id=body.chronicle_session_id,
+        gsap_context_id=body.gsap_context_id,
+        pipeline_run_id=body.pipeline_run_id,
+    )
+    result = await _runtime.invoke(function_id, body.event, ctx)
+    return InvokeResponse(
+        success=result.success,
+        data=result.data,
+        error=result.error,
+        lineage_cid=result.lineage_cid,
+        function_id=function_id,
+        duration_ms=result.duration_ms,
+    )
+
+
+@router.post("/dispatch/")
+async def dispatch_event(body: DispatchRequest) -> DispatchResponse:
+    results = await _runtime.dispatch(body.event_kind, body.event_data, body.trigger_cid)
+    return DispatchResponse(
+        event_kind=body.event_kind,
+        dispatched_count=len(results),
+        results=results,
+    )
+
+
+@router.get("/{function_id}/health/")
+async def health_check(function_id: str) -> dict:
+    function = _registry.get(function_id)
+    if function is None:
+        raise HTTPException(status_code=404, detail=f"Function not found: {function_id}")
+    healthy = function.health_check()
+    return {"function_id": function_id, "healthy": healthy}
diff --git a/tests/test_functions.py b/tests/test_functions.py
new file mode 100644
index 0000000..dac0b86
--- /dev/null
+++ b/tests/test_functions.py
@@ -0,0 +1,152 @@
+"""Tests for governed serverless function module."""
+import pytest
+
+
+@pytest.mark.asyncio
+async def test_function_catalogue(client):
+    resp = await client.get("/functions/")
+    assert resp.status_code == 200
+    body = resp.json()
+    ids = [f["function_id"] for f in body["functions"]]
+    assert "billing-processor" in ids
+    assert "echo-function" in ids
+    assert "trigger_index" in body
+
+
+@pytest.mark.asyncio
+async def test_function_descriptor(client):
+    resp = await client.get("/functions/billing-processor/")
+    assert resp.status_code == 200
+    desc = resp.json()
+    assert desc["function_id"] == "billing-processor"
+    assert "trigger_events" in desc
+    assert "GSAP_CR_RECEIVED" in desc["trigger_events"]
+    assert desc["corpus_entry_cid"].startswith("sha256:")
+
+
+@pytest.mark.asyncio
+async def test_knative_manifest(client):
+    resp = await client.get("/functions/billing-processor/manifest/?image=gcr.io/test/billing:v1")
+    assert resp.status_code == 200
+    manifest = resp.json()
+    assert manifest["kind"] == "Service"
+    assert manifest["apiVersion"] == "serving.knative.dev/v1"
+    assert manifest["metadata"]["name"] == "billing-processor"
+    containers = manifest["spec"]["template"]["spec"]["containers"]
+    assert containers[0]["image"] == "gcr.io/test/billing:v1"
+
+
+@pytest.mark.asyncio
+async def test_invoke_echo(client):
+    resp = await client.post(
+        "/functions/echo-function/invoke/",
+        json={"event": {"msg": "hello", "value": 42}},
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["success"] is True
+    assert body["data"]["msg"] == "hello"
+    assert body["data"]["value"] == 42
+    assert body["function_id"] == "echo-function"
+    assert body["duration_ms"] >= 0
+
+
+@pytest.mark.asyncio
+async def test_billing_completed(client):
+    resp = await client.post(
+        "/functions/billing-processor/invoke/",
+        json={
+            "event": {
+                "outcome": "completed",
+                "event_type": "gsap_cr_completed",
+                "quantity": 2,
+                "chronicle_cid": "sha256:abc123",
+            },
+        },
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["success"] is True
+    assert body["data"]["billed"] is True
+    assert body["data"]["amount"] == 0.01  # 0.005 * 2
+    assert body["data"]["chronicle_cid"] == "sha256:abc123"
+
+
+@pytest.mark.asyncio
+async def test_billing_failed_not_billed(client):
+    resp = await client.post(
+        "/functions/billing-processor/invoke/",
+        json={
+            "event": {
+                "outcome": "failed",
+                "event_type": "gsap_cr_completed",
+            },
+        },
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["success"] is True
+    assert body["data"]["billed"] is False
+
+
+@pytest.mark.asyncio
+async def test_dispatch_routes_to_billing(client):
+    resp = await client.post(
+        "/functions/dispatch/",
+        json={
+            "event_kind": "GSAP_CR_RECEIVED",
+            "event_data": {
+                "outcome": "completed",
+                "event_type": "gsap_cr_completed",
+                "quantity": 1,
+            },
+            "trigger_cid": "sha256:trigger001",
+        },
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["event_kind"] == "GSAP_CR_RECEIVED"
+    assert body["dispatched_count"] >= 1
+    # billing-processor should be in the results
+    billing_results = [r for r in body["results"] if r["function_id"] == "billing-processor"]
+    assert len(billing_results) == 1
+    assert billing_results[0]["success"] is True
+
+
+@pytest.mark.asyncio
+async def test_gsap_required_without_ac(client):
+    """A gsap_required function invoked without gsap_context_id returns error."""
+    # We need a function with gsap_required=True. Register one via the runtime.
+    # Use the billing-processor with gsap_required toggled, or invoke directly.
+    # Since billing-processor has gsap_required=False, we test via the runtime directly.
+    from gsap_broker.functions.base import FunctionContext, FunctionPlugin, FunctionResult
+    from gsap_broker.functions.registry import FunctionRegistry
+    from gsap_broker.functions.runtime import FunctionRuntime
+    from typing import Any
+
+    class StrictFunction(FunctionPlugin):
+        function_id = "strict-func"
+        corpus_entry_cid = "sha256:" + "s" * 64
+        capability_mask = 1
+        trigger_events = []
+        gsap_required = True
+        chronicle_enabled = False
+        max_duration_seconds = 5
+        display_name = "Strict"
+        description = "Requires GSAP"
+        version = "0.1.0"
+
+        async def handle(self, event: dict[str, Any], context: FunctionContext) -> FunctionResult:
+            return FunctionResult(success=True, data=event)
+
+        def health_check(self) -> bool:
+            return True
+
+    reg = FunctionRegistry()
+    reg.register(StrictFunction())
+    rt = FunctionRuntime(registry=reg)
+
+    ctx = FunctionContext()  # No gsap_context_id
+    result = await rt.invoke("strict-func", {"test": True}, ctx)
+    assert result.success is False
+    assert "GSAP context required" in (result.error or "")