diff --git a/cli/src/guidance/skills.gen.ts b/cli/src/guidance/skills.gen.ts
index 4e8cc464d5..fff7df1153 100644
--- a/cli/src/guidance/skills.gen.ts
+++ b/cli/src/guidance/skills.gen.ts
@@ -1106,6 +1106,9 @@ async sleep(seconds: number): Promise<void>
  * \`fn\`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a \`Date\`
  * comes back as a string, a \`Map\` as \`{}\`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, \`fn\` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
@@ -1949,6 +1952,9 @@ async sleep(seconds: number): Promise<void>
  * \`fn\`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a \`Date\`
  * comes back as a string, a \`Map\` as \`{}\`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, \`fn\` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
@@ -2898,6 +2904,9 @@ async sleep(seconds: number): Promise<void>
  * \`fn\`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a \`Date\`
  * comes back as a string, a \`Map\` as \`{}\`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, \`fn\` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
@@ -5073,7 +5082,9 @@ def parse_sql_client_name(name: str) -> tuple[str, Optional[str]]
 # 
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 # 
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a \`\`datetime\`\` comes back as a
@@ -5159,12 +5170,15 @@ def workflow(func)
 # \`\`fn\`\`'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a \`\`datetime\`\` comes back as a string, a tuple as a list.
+# 
+# Called from inside a task body, \`\`fn\`\` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 # 
 # Inside a @workflow, the parent job suspends and auto-resumes after \`\`seconds\`\`.
-# Outside a workflow, falls back to \`\`asyncio.sleep\`\`.
+# Outside a workflow, or inside a task body, falls back to \`\`asyncio.sleep\`\`.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
@@ -7436,6 +7450,8 @@ async def enrich(customer_id: str):
 
 In TypeScript, prefer assigning each task to a named top-level const. In Python, prefer top-level async functions decorated with \`@task()\` or \`@task\`.
 
+Only the workflow body dispatches steps. A task runs as a single job, so a task or \`step()\` called from inside a task body runs in place in that job, as a plain function call: no child job, no checkpoint, and its task options (retry, timeout, tag) do not apply. \`sleep()\` there waits in the job, and \`taskScript()\` / \`taskFlow()\` / \`waitForApproval()\` (\`task_script()\` / \`task_flow()\` / \`wait_for_approval()\`) throw. To get separate jobs, call the tasks one after another from the workflow body and pass results between them.
+
 For existing scripts:
 
 \`\`\`typescript
@@ -7601,8 +7617,9 @@ export async function getResumeUrls(approver?: string, flowLevel?: boolean): Pro
  * const call_api = task(fetchOrders, { retry: { attempts: 3, delay: 30, multiplier: 2 } });
  *
  * Inside a \`workflow()\`, calling a task dispatches it as a step.
- * Outside a workflow, the function body executes directly and
- * {@link TaskOptions} — retry included — does not apply.
+ * Outside a workflow, or called from inside another task, the function body
+ * executes directly and {@link TaskOptions} — retry included — does not apply:
+ * a task runs as a single job, so the tasks it calls run in that same job.
  *
  * A task runs as its own job, so its result is always encoded as JSON and
  * decoded back before the caller sees it: a \`Date\` comes back as a string, a
@@ -7646,6 +7663,9 @@ export function workflow<T>(fn: (...args: any[]) => Promise<T>)
  * \`fn\`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a \`Date\`
  * comes back as a string, a \`Map\` as \`{}\`. {@link Jsonified} is that shape.
+ *
+ * Called from inside a task body, \`fn\` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 export async function step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
@@ -7744,7 +7764,9 @@ def get_resume_urls(approver: str = None, flow_level: bool = None) -> dict
 #
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 #
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a \`\`datetime\`\` comes back as a
@@ -7830,12 +7852,15 @@ def workflow(func)
 # \`\`fn\`\`'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a \`\`datetime\`\` comes back as a string, a tuple as a list.
+#
+# Called from inside a task body, \`\`fn\`\` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 #
 # Inside a @workflow, the parent job suspends and auto-resumes after \`\`seconds\`\`.
-# Outside a workflow, falls back to \`\`asyncio.sleep\`\`.
+# Outside a workflow, or inside a task body, falls back to \`\`asyncio.sleep\`\`.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
diff --git a/python-client/wmill/tests/test_workflow.py b/python-client/wmill/tests/test_workflow.py
index ceed39bfeb..d32ae1458b 100644
--- a/python-client/wmill/tests/test_workflow.py
+++ b/python-client/wmill/tests/test_workflow.py
@@ -7,7 +7,7 @@ import pytest
 
 from datetime import datetime, timezone
 
-from wmill.client import WorkflowCtx, _StepSuspend, TaskError, workflow, task, step, sleep, parallel, wait_for_approval, _run_workflow, _run_workflow_async
+from wmill.client import WorkflowCtx, _StepSuspend, TaskError, workflow, task, task_script, step, sleep, parallel, wait_for_approval, _run_workflow, _run_workflow_async
 
 
 class _FakeItems(dict):
@@ -752,6 +752,84 @@ class TestChildModeParallel:
         assert result["result"] == 8
 
 
+class TestSdkCallsInsideTaskBody:
+    """A task body runs as one child job, so the SDK calls it makes cannot be
+    dispatched as steps of their own."""
+
+    def _run_child(self, wf, key):
+        async def bounded():
+            return await asyncio.wait_for(
+                _run_workflow_async(wf, {"completed_steps": {}, "_executing_key": key}, {}),
+                timeout=2,
+            )
+
+        return asyncio.run(bounded())
+
+    def test_nested_task_and_step_run_in_the_tasks_own_job(self):
+        @task
+        async def inner(x: str):
+            return f"inner:{x}"
+
+        @task
+        def sync_leaf(x: str):
+            return f"sync:{x}"
+
+        # A sync body calls its tasks without awaiting, whatever called it.
+        @task
+        def sync_inner(x: str):
+            return sync_leaf(x).upper().lower()
+
+        @task
+        async def outer(x: str):
+            via_task = await inner(x)
+            via_sync = await sync_inner(x)
+            via_step = await step("s", lambda: "stepped")
+            return f"{via_task}+{via_sync}+{via_step}"
+
+        @workflow
+        async def wf():
+            return await outer("a")
+
+        result = self._run_child(wf, "outer")
+        assert result == {"type": "complete", "result": "inner:a+sync:a+stepped"}
+
+    def test_sibling_task_of_the_workflow_body_is_not_run(self):
+        # The workflow body keeps replaying beside the task body, and its own
+        # calls must stay parked: running them would execute a sibling task in
+        # this job.
+        ran = []
+
+        @task
+        async def inner(x: str):
+            ran.append(x)
+            return x
+
+        @task
+        async def outer(x: str):
+            await asyncio.sleep(0)
+            return await inner("nested")
+
+        @workflow
+        async def wf():
+            return await asyncio.gather(outer("a"), inner("sibling"))
+
+        result = self._run_child(wf, "outer")
+        assert result == {"type": "complete", "result": "nested"}
+        assert ran == ["nested"]
+
+    def test_step_that_would_need_a_dispatch_fails_instead_of_hanging(self):
+        @task
+        async def dispatching():
+            return await task_script("f/other/script")()
+
+        @workflow
+        async def wf():
+            return await dispatching()
+
+        with pytest.raises(RuntimeError, match="cannot be called from inside a task"):
+            self._run_child(wf, "dispatching")
+
+
 class TestKeyDeterminism:
     def test_keys_consistent_across_replays(self):
         r1 = _run_workflow(det_wf, {}, {"n": 3})
diff --git a/python-client/wmill/wmill/client.py b/python-client/wmill/wmill/client.py
index 97da60aadc..824db9741f 100644
--- a/python-client/wmill/wmill/client.py
+++ b/python-client/wmill/wmill/client.py
@@ -2766,6 +2766,7 @@ def parse_sql_client_name(name: str) -> tuple[str, Optional[str]]:
 
 import asyncio as _asyncio
 import contextvars as _contextvars
+import inspect as _inspect
 import sys as _sys
 import traceback as _traceback
 
@@ -2993,6 +2994,64 @@ _workflow_ctx: _contextvars.ContextVar["WorkflowCtx"] = _contextvars.ContextVar(
     "_workflow_ctx"
 )
 
+# Set while a task body runs in its child job: ``"async"`` or ``"sync"`` after
+# the kind of function the body is. A flag on the ctx cannot stand in: under
+# ``asyncio.gather`` the workflow body keeps replaying beside the task body, and
+# its calls must still park rather than run a sibling task's body in this job.
+_in_task_body: _contextvars.ContextVar[Optional[str]] = _contextvars.ContextVar(
+    "_in_task_body", default=None
+)
+
+
+def _dispatch_ctx() -> "WorkflowCtx | None":
+    """The ctx SDK calls dispatch through, or None where they run in place:
+    outside a workflow, and inside a task body, which is one job and has no
+    rounds of its own to dispatch or checkpoint a step in."""
+    if _in_task_body.get():
+        return None
+    return _workflow_ctx.get(None)
+
+
+async def _resolved(value):
+    return value
+
+
+def _call_in_task_body(func, caller: str, args, kwargs):
+    """Run a task called from inside a task body in place, round-tripping its
+    result as a dispatched one would be.
+
+    The workflow body awaits every task, sync ones included, so an async caller
+    gets an awaitable back either way; a sync caller gets the value. The scope
+    is re-marked for the nested body, which may be of the other kind."""
+
+    async def run_async(coro):
+        token = _in_task_body.set("async")
+        try:
+            return _json_round_trip(await coro)
+        finally:
+            _in_task_body.reset(token)
+
+    if _inspect.iscoroutinefunction(func):
+        return run_async(func(*args, **kwargs))
+    token = _in_task_body.set("sync")
+    try:
+        result = func(*args, **kwargs)
+    finally:
+        _in_task_body.reset(token)
+    if _asyncio.iscoroutine(result):
+        return run_async(result)
+    result = _json_round_trip(result)
+    return _resolved(result) if caller == "async" else result
+
+
+def _assert_not_inside_task_body(what: str) -> None:
+    if _in_task_body.get():
+        raise RuntimeError(
+            f"{what} cannot be called from inside a task: a task runs as a single "
+            "job and cannot suspend or dispatch steps. Call it from the @workflow "
+            "body instead."
+        )
+
 
 class WorkflowCtx:
     """Internal context for workflow replay/suspension.
@@ -3117,15 +3176,20 @@ class WorkflowCtx:
         raise _StepSuspend({"mode": "sleep", "key": key, "seconds": seconds, "steps": []})
 
     async def _resolved(self, value):
-        return value
+        return await _resolved(value)
 
     async def _execute_directly(self, func, **kwargs):
+        token = _in_task_body.set(
+            "async" if _inspect.iscoroutinefunction(func) else "sync"
+        )
         try:
             result = func(**kwargs)
             if _asyncio.iscoroutine(result):
                 result = await result
         except Exception as exc:
             raise _StepFailure(exc) from exc
+        finally:
+            _in_task_body.reset(token)
         raise _StepSuspend({"mode": "step_complete", "steps": [], "result": result})
 
     async def _never_resolve(self):
@@ -3367,7 +3431,9 @@ def task(
 
     - **v2 (inside @workflow)**: dispatches as a checkpoint step.
     - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-    - **Standalone**: executes the function body directly.
+    - **Standalone, or called from inside another v2 task**: executes the
+      function body directly. A task runs as a single job, so the tasks it
+      calls run in that same job, without their own options.
 
     A task runs as its own job, so its result is always encoded as JSON and
     decoded back before the caller sees it: a ``datetime`` comes back as a
@@ -3447,12 +3513,16 @@ def task(
         @functools.wraps(func)
         def wrapper(*args, **kwargs):
             # WAC v2: inside a @workflow context
-            ctx = _workflow_ctx.get(None)
+            ctx = _dispatch_ctx()
             if ctx is not None:
                 script = task_path if task_path else task_name
                 merged = _merge_args(args, kwargs)
                 return ctx._next_step(task_name, script, func, _task_options=_task_opts, **merged)
 
+            caller = _in_task_body.get()
+            if caller is not None:
+                return _call_in_task_body(func, caller, args, kwargs)
+
             # WAC v1: running inside a Windmill job but not in a @workflow
             if (
                 os.environ.get("WM_JOB_ID") is not None
@@ -3531,6 +3601,7 @@ def task_script(
     _opts = {k: v for k, v in {"timeout": timeout, "tag": tag, "cache_ttl": cache_ttl, "priority": priority, "concurrent_limit": concurrency_limit, "concurrency_key": concurrency_key, "concurrency_time_window_s": concurrency_time_window_s, "retry": _checked_retry(retry)}.items() if v is not None} or None
 
     def wrapper(**kwargs):
+        _assert_not_inside_task_body(f'task_script("{path}")')
         ctx = _workflow_ctx.get(None)
         if ctx is not None:
             return ctx._next_step(name, path, dispatch_type="script", _task_options=_opts, **kwargs)
@@ -3570,6 +3641,7 @@ def task_flow(
     _opts = {k: v for k, v in {"timeout": timeout, "tag": tag, "cache_ttl": cache_ttl, "priority": priority, "concurrent_limit": concurrency_limit, "concurrency_key": concurrency_key, "concurrency_time_window_s": concurrency_time_window_s, "retry": _checked_retry(retry)}.items() if v is not None} or None
 
     def wrapper(**kwargs):
+        _assert_not_inside_task_body(f'task_flow("{path}")')
         ctx = _workflow_ctx.get(None)
         if ctx is not None:
             return ctx._next_step(name, path, dispatch_type="flow", _task_options=_opts, **kwargs)
@@ -3604,8 +3676,11 @@ async def step(name: str, fn):
     ``fn``'s result is encoded as JSON and decoded back before it is returned,
     so the round that runs the body sees the same types every replay sees:
     a ``datetime`` comes back as a string, a tuple as a list.
+
+    Called from inside a task body, ``fn`` runs in place and nothing is
+    checkpointed: a task is a single job and is never replayed.
     """
-    ctx: WorkflowCtx | None = _workflow_ctx.get(None)
+    ctx = _dispatch_ctx()
     if ctx is not None:
         return await ctx._run_inline_step(name, fn)
     result = fn()
@@ -3620,9 +3695,9 @@ async def sleep(seconds: int):
     """Server-side sleep — suspend the workflow for the given duration without holding a worker.
 
     Inside a @workflow, the parent job suspends and auto-resumes after ``seconds``.
-    Outside a workflow, falls back to ``asyncio.sleep``.
+    Outside a workflow, or inside a task body, falls back to ``asyncio.sleep``.
     """
-    ctx: WorkflowCtx | None = _workflow_ctx.get(None)
+    ctx = _dispatch_ctx()
     if ctx is not None:
         return await ctx._sleep(seconds)
     await _asyncio.sleep(seconds)
@@ -3660,6 +3735,7 @@ async def wait_for_approval(
         await step("notify", lambda: send_email(urls["resume"], urls["cancel"]))
         result = await wait_for_approval(key="manager", timeout=3600)
     """
+    _assert_not_inside_task_body("wait_for_approval()")
     ctx: WorkflowCtx | None = _workflow_ctx.get(None)
     if ctx is not None:
         return await ctx._wait_for_approval(
diff --git a/system_prompts/auto-generated/prompts.ts b/system_prompts/auto-generated/prompts.ts
index cfa3415e35..393b724f6b 100644
--- a/system_prompts/auto-generated/prompts.ts
+++ b/system_prompts/auto-generated/prompts.ts
@@ -1427,6 +1427,8 @@ async def enrich(customer_id: str):
 
 In TypeScript, prefer assigning each task to a named top-level const. In Python, prefer top-level async functions decorated with \`@task()\` or \`@task\`.
 
+Only the workflow body dispatches steps. A task runs as a single job, so a task or \`step()\` called from inside a task body runs in place in that job, as a plain function call: no child job, no checkpoint, and its task options (retry, timeout, tag) do not apply. \`sleep()\` there waits in the job, and \`taskScript()\` / \`taskFlow()\` / \`waitForApproval()\` (\`task_script()\` / \`task_flow()\` / \`wait_for_approval()\`) throw. To get separate jobs, call the tasks one after another from the workflow body and pass results between them.
+
 For existing scripts:
 
 \`\`\`typescript
@@ -2029,6 +2031,9 @@ async sleep(seconds: number): Promise<void>
  * \`fn\`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a \`Date\`
  * comes back as a string, a \`Map\` as \`{}\`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, \`fn\` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
@@ -2871,7 +2876,9 @@ def parse_sql_client_name(name: str) -> tuple[str, Optional[str]]
 # 
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 # 
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a \`\`datetime\`\` comes back as a
@@ -2957,12 +2964,15 @@ def workflow(func)
 # \`\`fn\`\`'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a \`\`datetime\`\` comes back as a string, a tuple as a list.
+# 
+# Called from inside a task body, \`\`fn\`\` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 # 
 # Inside a @workflow, the parent job suspends and auto-resumes after \`\`seconds\`\`.
-# Outside a workflow, falls back to \`\`asyncio.sleep\`\`.
+# Outside a workflow, or inside a task body, falls back to \`\`asyncio.sleep\`\`.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
@@ -3084,8 +3094,9 @@ export async function getResumeUrls(approver?: string, flowLevel?: boolean): Pro
  * const call_api = task(fetchOrders, { retry: { attempts: 3, delay: 30, multiplier: 2 } });
  *
  * Inside a \`workflow()\`, calling a task dispatches it as a step.
- * Outside a workflow, the function body executes directly and
- * {@link TaskOptions} — retry included — does not apply.
+ * Outside a workflow, or called from inside another task, the function body
+ * executes directly and {@link TaskOptions} — retry included — does not apply:
+ * a task runs as a single job, so the tasks it calls run in that same job.
  *
  * A task runs as its own job, so its result is always encoded as JSON and
  * decoded back before the caller sees it: a \`Date\` comes back as a string, a
@@ -3129,6 +3140,9 @@ export function workflow<T>(fn: (...args: any[]) => Promise<T>)
  * \`fn\`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a \`Date\`
  * comes back as a string, a \`Map\` as \`{}\`. {@link Jsonified} is that shape.
+ *
+ * Called from inside a task body, \`fn\` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 export async function step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
@@ -3227,7 +3241,9 @@ def get_resume_urls(approver: str = None, flow_level: bool = None) -> dict
 #
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 #
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a \`\`datetime\`\` comes back as a
@@ -3313,12 +3329,15 @@ def workflow(func)
 # \`\`fn\`\`'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a \`\`datetime\`\` comes back as a string, a tuple as a list.
+#
+# Called from inside a task body, \`\`fn\`\` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 #
 # Inside a @workflow, the parent job suspends and auto-resumes after \`\`seconds\`\`.
-# Outside a workflow, falls back to \`\`asyncio.sleep\`\`.
+# Outside a workflow, or inside a task body, falls back to \`\`asyncio.sleep\`\`.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
diff --git a/system_prompts/auto-generated/script.md b/system_prompts/auto-generated/script.md
index 14ca869180..a4064c3d9e 100644
--- a/system_prompts/auto-generated/script.md
+++ b/system_prompts/auto-generated/script.md
@@ -1906,6 +1906,9 @@ async sleep(seconds: number): Promise<void>
  * `fn`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a `Date`
  * comes back as a string, a `Map` as `{}`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, `fn` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
@@ -2748,7 +2751,9 @@ def parse_sql_client_name(name: str) -> tuple[str, Optional[str]]
 # 
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 # 
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a ``datetime`` comes back as a
@@ -2834,12 +2839,15 @@ def workflow(func)
 # ``fn``'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a ``datetime`` comes back as a string, a tuple as a list.
+# 
+# Called from inside a task body, ``fn`` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 # 
 # Inside a @workflow, the parent job suspends and auto-resumes after ``seconds``.
-# Outside a workflow, falls back to ``asyncio.sleep``.
+# Outside a workflow, or inside a task body, falls back to ``asyncio.sleep``.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
diff --git a/system_prompts/auto-generated/sdks/python.md b/system_prompts/auto-generated/sdks/python.md
index 13a93ed063..1964c88685 100644
--- a/system_prompts/auto-generated/sdks/python.md
+++ b/system_prompts/auto-generated/sdks/python.md
@@ -669,7 +669,9 @@ def parse_sql_client_name(name: str) -> tuple[str, Optional[str]]
 # 
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 # 
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a ``datetime`` comes back as a
@@ -755,12 +757,15 @@ def workflow(func)
 # ``fn``'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a ``datetime`` comes back as a string, a tuple as a list.
+# 
+# Called from inside a task body, ``fn`` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 # 
 # Inside a @workflow, the parent job suspends and auto-resumes after ``seconds``.
-# Outside a workflow, falls back to ``asyncio.sleep``.
+# Outside a workflow, or inside a task body, falls back to ``asyncio.sleep``.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
diff --git a/system_prompts/auto-generated/sdks/typescript.md b/system_prompts/auto-generated/sdks/typescript.md
index 55df35ccf7..da9e79ec94 100644
--- a/system_prompts/auto-generated/sdks/typescript.md
+++ b/system_prompts/auto-generated/sdks/typescript.md
@@ -463,6 +463,9 @@ async sleep(seconds: number): Promise<void>
  * `fn`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a `Date`
  * comes back as a string, a `Map` as `{}`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, `fn` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
diff --git a/system_prompts/auto-generated/sdks/wac-python.md b/system_prompts/auto-generated/sdks/wac-python.md
index a8e98a9d4f..6dd307dd24 100644
--- a/system_prompts/auto-generated/sdks/wac-python.md
+++ b/system_prompts/auto-generated/sdks/wac-python.md
@@ -36,7 +36,9 @@ def get_resume_urls(approver: str = None, flow_level: bool = None) -> dict
 #
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 #
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a ``datetime`` comes back as a
@@ -122,12 +124,15 @@ def workflow(func)
 # ``fn``'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a ``datetime`` comes back as a string, a tuple as a list.
+#
+# Called from inside a task body, ``fn`` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 #
 # Inside a @workflow, the parent job suspends and auto-resumes after ``seconds``.
-# Outside a workflow, falls back to ``asyncio.sleep``.
+# Outside a workflow, or inside a task body, falls back to ``asyncio.sleep``.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
diff --git a/system_prompts/auto-generated/sdks/wac-typescript.md b/system_prompts/auto-generated/sdks/wac-typescript.md
index 608d75d18c..dd04a64de0 100644
--- a/system_prompts/auto-generated/sdks/wac-typescript.md
+++ b/system_prompts/auto-generated/sdks/wac-typescript.md
@@ -67,8 +67,9 @@ export async function getResumeUrls(approver?: string, flowLevel?: boolean): Pro
  * const call_api = task(fetchOrders, { retry: { attempts: 3, delay: 30, multiplier: 2 } });
  *
  * Inside a `workflow()`, calling a task dispatches it as a step.
- * Outside a workflow, the function body executes directly and
- * {@link TaskOptions} — retry included — does not apply.
+ * Outside a workflow, or called from inside another task, the function body
+ * executes directly and {@link TaskOptions} — retry included — does not apply:
+ * a task runs as a single job, so the tasks it calls run in that same job.
  *
  * A task runs as its own job, so its result is always encoded as JSON and
  * decoded back before the caller sees it: a `Date` comes back as a string, a
@@ -112,6 +113,9 @@ export function workflow<T>(fn: (...args: any[]) => Promise<T>)
  * `fn`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a `Date`
  * comes back as a string, a `Map` as `{}`. {@link Jsonified} is that shape.
+ *
+ * Called from inside a task body, `fn` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 export async function step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
diff --git a/system_prompts/auto-generated/skills/write-script-bun/SKILL.md b/system_prompts/auto-generated/skills/write-script-bun/SKILL.md
index 6ad44db068..055b1613b2 100644
--- a/system_prompts/auto-generated/skills/write-script-bun/SKILL.md
+++ b/system_prompts/auto-generated/skills/write-script-bun/SKILL.md
@@ -659,6 +659,9 @@ async sleep(seconds: number): Promise<void>
  * `fn`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a `Date`
  * comes back as a string, a `Map` as `{}`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, `fn` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
diff --git a/system_prompts/auto-generated/skills/write-script-bunnative/SKILL.md b/system_prompts/auto-generated/skills/write-script-bunnative/SKILL.md
index a5f599a946..beaf7817bb 100644
--- a/system_prompts/auto-generated/skills/write-script-bunnative/SKILL.md
+++ b/system_prompts/auto-generated/skills/write-script-bunnative/SKILL.md
@@ -671,6 +671,9 @@ async sleep(seconds: number): Promise<void>
  * `fn`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a `Date`
  * comes back as a string, a `Map` as `{}`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, `fn` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
diff --git a/system_prompts/auto-generated/skills/write-script-deno/SKILL.md b/system_prompts/auto-generated/skills/write-script-deno/SKILL.md
index ce0c610da7..afefb7e987 100644
--- a/system_prompts/auto-generated/skills/write-script-deno/SKILL.md
+++ b/system_prompts/auto-generated/skills/write-script-deno/SKILL.md
@@ -661,6 +661,9 @@ async sleep(seconds: number): Promise<void>
  * `fn`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a `Date`
  * comes back as a string, a `Map` as `{}`. {@link Jsonified} is that shape.
+ * 
+ * Called from inside a task body, `fn` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 async step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
diff --git a/system_prompts/auto-generated/skills/write-script-python3/SKILL.md b/system_prompts/auto-generated/skills/write-script-python3/SKILL.md
index 4946ed0f6e..ee50b6d62d 100644
--- a/system_prompts/auto-generated/skills/write-script-python3/SKILL.md
+++ b/system_prompts/auto-generated/skills/write-script-python3/SKILL.md
@@ -877,7 +877,9 @@ def parse_sql_client_name(name: str) -> tuple[str, Optional[str]]
 # 
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 # 
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a ``datetime`` comes back as a
@@ -963,12 +965,15 @@ def workflow(func)
 # ``fn``'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a ``datetime`` comes back as a string, a tuple as a list.
+# 
+# Called from inside a task body, ``fn`` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 # 
 # Inside a @workflow, the parent job suspends and auto-resumes after ``seconds``.
-# Outside a workflow, falls back to ``asyncio.sleep``.
+# Outside a workflow, or inside a task body, falls back to ``asyncio.sleep``.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
diff --git a/system_prompts/auto-generated/skills/write-workflow-as-code/SKILL.md b/system_prompts/auto-generated/skills/write-workflow-as-code/SKILL.md
index 13d305c74e..09789b388a 100644
--- a/system_prompts/auto-generated/skills/write-workflow-as-code/SKILL.md
+++ b/system_prompts/auto-generated/skills/write-workflow-as-code/SKILL.md
@@ -143,6 +143,8 @@ async def enrich(customer_id: str):
 
 In TypeScript, prefer assigning each task to a named top-level const. In Python, prefer top-level async functions decorated with `@task()` or `@task`.
 
+Only the workflow body dispatches steps. A task runs as a single job, so a task or `step()` called from inside a task body runs in place in that job, as a plain function call: no child job, no checkpoint, and its task options (retry, timeout, tag) do not apply. `sleep()` there waits in the job, and `taskScript()` / `taskFlow()` / `waitForApproval()` (`task_script()` / `task_flow()` / `wait_for_approval()`) throw. To get separate jobs, call the tasks one after another from the workflow body and pass results between them.
+
 For existing scripts:
 
 ```typescript
@@ -308,8 +310,9 @@ export async function getResumeUrls(approver?: string, flowLevel?: boolean): Pro
  * const call_api = task(fetchOrders, { retry: { attempts: 3, delay: 30, multiplier: 2 } });
  *
  * Inside a `workflow()`, calling a task dispatches it as a step.
- * Outside a workflow, the function body executes directly and
- * {@link TaskOptions} — retry included — does not apply.
+ * Outside a workflow, or called from inside another task, the function body
+ * executes directly and {@link TaskOptions} — retry included — does not apply:
+ * a task runs as a single job, so the tasks it calls run in that same job.
  *
  * A task runs as its own job, so its result is always encoded as JSON and
  * decoded back before the caller sees it: a `Date` comes back as a string, a
@@ -353,6 +356,9 @@ export function workflow<T>(fn: (...args: any[]) => Promise<T>)
  * `fn`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a `Date`
  * comes back as a string, a `Map` as `{}`. {@link Jsonified} is that shape.
+ *
+ * Called from inside a task body, `fn` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 export async function step<T>(name: string, fn: () => T | Promise<T>,): Promise<Jsonified<Awaited<T>>>
 
@@ -451,7 +457,9 @@ def get_resume_urls(approver: str = None, flow_level: bool = None) -> dict
 #
 # - **v2 (inside @workflow)**: dispatches as a checkpoint step.
 # - **v1 (WM_JOB_ID set, no @workflow)**: dispatches via HTTP API.
-# - **Standalone**: executes the function body directly.
+# - **Standalone, or called from inside another v2 task**: executes the
+#   function body directly. A task runs as a single job, so the tasks it
+#   calls run in that same job, without their own options.
 #
 # A task runs as its own job, so its result is always encoded as JSON and
 # decoded back before the caller sees it: a ``datetime`` comes back as a
@@ -537,12 +545,15 @@ def workflow(func)
 # ``fn``'s result is encoded as JSON and decoded back before it is returned,
 # so the round that runs the body sees the same types every replay sees:
 # a ``datetime`` comes back as a string, a tuple as a list.
+#
+# Called from inside a task body, ``fn`` runs in place and nothing is
+# checkpointed: a task is a single job and is never replayed.
 async def step(name: str, fn)
 
 # Server-side sleep — suspend the workflow for the given duration without holding a worker.
 #
 # Inside a @workflow, the parent job suspends and auto-resumes after ``seconds``.
-# Outside a workflow, falls back to ``asyncio.sleep``.
+# Outside a workflow, or inside a task body, falls back to ``asyncio.sleep``.
 async def sleep(seconds: int)
 
 # Suspend the workflow and wait for an external approval.
diff --git a/system_prompts/base/workflow-as-code.md b/system_prompts/base/workflow-as-code.md
index 0e529f6803..efc29df360 100644
--- a/system_prompts/base/workflow-as-code.md
+++ b/system_prompts/base/workflow-as-code.md
@@ -95,6 +95,8 @@ async def enrich(customer_id: str):
 
 In TypeScript, prefer assigning each task to a named top-level const. In Python, prefer top-level async functions decorated with `@task()` or `@task`.
 
+Only the workflow body dispatches steps. A task runs as a single job, so a task or `step()` called from inside a task body runs in place in that job, as a plain function call: no child job, no checkpoint, and its task options (retry, timeout, tag) do not apply. `sleep()` there waits in the job, and `taskScript()` / `taskFlow()` / `waitForApproval()` (`task_script()` / `task_flow()` / `wait_for_approval()`) throw. To get separate jobs, call the tasks one after another from the workflow body and pass results between them.
+
 For existing scripts:
 
 ```typescript
diff --git a/typescript-client/client.ts b/typescript-client/client.ts
index 3f7b03117a..da957239cf 100644
--- a/typescript-client/client.ts
+++ b/typescript-client/client.ts
@@ -1832,6 +1832,52 @@ export function setWorkflowCtx(ctx: WorkflowCtx | null) {
   Reflect.set(globalThis, "__wmill_wf_ctx", ctx);
 }
 
+type TaskBodyScope = { run<R>(store: true, fn: () => R): R; getStore(): true | undefined };
+
+/** Marks the async context of a task body running in its child job. A flag on
+ *  the ctx cannot stand in: the workflow body keeps replaying beside the task
+ *  body (`Promise.all([a(), b()])`), and its calls must still park rather than
+ *  run a sibling task's body in this job. Kept on `globalThis`, like the ctx,
+ *  so a bundle holding two copies of this module shares one scope. Resolved
+ *  through `process.getBuiltinModule` because a `node:` import would break
+ *  browser bundles of this package. */
+function taskBodyScope(): TaskBodyScope | null {
+  const existing = Reflect.get(globalThis, "__wmill_wf_task_body");
+  if (existing !== undefined) return existing;
+  let scope: TaskBodyScope | null = null;
+  try {
+    const AsyncLocalStorage = (globalThis as any).process?.getBuiltinModule?.("node:async_hooks")?.AsyncLocalStorage;
+    if (AsyncLocalStorage) scope = new AsyncLocalStorage();
+  } catch {}
+  Reflect.set(globalThis, "__wmill_wf_task_body", scope);
+  return scope;
+}
+
+function runTaskBody<R>(fn: () => R): R {
+  const scope = taskBodyScope();
+  return scope ? scope.run(true, fn) : fn();
+}
+
+function insideTaskBody(): boolean {
+  return taskBodyScope()?.getStore() === true;
+}
+
+/** The ctx SDK calls dispatch through, or null where they run in place: outside
+ *  a workflow, and inside a task body, which is one job and has no rounds of its
+ *  own to dispatch or checkpoint a step in. */
+function dispatchCtx(): WorkflowCtx | null {
+  if (insideTaskBody()) return null;
+  return _workflowCtx ?? Reflect.get(globalThis, "__wmill_wf_ctx");
+}
+
+function assertNotInsideTaskBody(what: string): void {
+  if (insideTaskBody()) {
+    throw new Error(
+      `${what} cannot be called from inside a task: a task runs as a single job and cannot suspend or dispatch steps. Call it from the workflow() body instead.`,
+    );
+  }
+}
+
 
 export class WorkflowCtx {
   private completed: Record<string, any>;
@@ -2304,11 +2350,11 @@ export class WorkflowCtx {
 }
 
 export async function sleep(seconds: number): Promise<void> {
-  const ctx: WorkflowCtx | null = _workflowCtx ?? Reflect.get(globalThis, "__wmill_wf_ctx");
+  const ctx = dispatchCtx();
   if (ctx) {
     return ctx._sleep(seconds) as Promise<void>;
   }
-  // Outside workflow context, just wait locally
+  // Outside a workflow, or inside a task body, just wait locally
   await new Promise((r) => setTimeout(r, seconds * 1000));
 }
 
@@ -2319,12 +2365,15 @@ export async function sleep(seconds: number): Promise<void> {
  * `fn`'s result is encoded as JSON and decoded back before it is returned, so
  * the round that runs the body sees the same types every replay sees: a `Date`
  * comes back as a string, a `Map` as `{}`. {@link Jsonified} is that shape.
+ *
+ * Called from inside a task body, `fn` runs in place and nothing is
+ * checkpointed: a task is a single job and is never replayed.
  */
 export async function step<T>(
   name: string,
   fn: () => T | Promise<T>,
 ): Promise<Jsonified<Awaited<T>>> {
-  const ctx: WorkflowCtx | null = _workflowCtx ?? Reflect.get(globalThis, "__wmill_wf_ctx");
+  const ctx = dispatchCtx();
   if (ctx) {
     return ctx._runInlineStep(name, fn) as Promise<Jsonified<Awaited<T>>>;
   }
@@ -2342,8 +2391,9 @@ export async function step<T>(
  * const call_api = task(fetchOrders, { retry: { attempts: 3, delay: 30, multiplier: 2 } });
  *
  * Inside a `workflow()`, calling a task dispatches it as a step.
- * Outside a workflow, the function body executes directly and
- * {@link TaskOptions} — retry included — does not apply.
+ * Outside a workflow, or called from inside another task, the function body
+ * executes directly and {@link TaskOptions} — retry included — does not apply:
+ * a task runs as a single job, so the tasks it calls run in that same job.
  *
  * A task runs as its own job, so its result is always encoded as JSON and
  * decoded back before the caller sees it: a `Date` comes back as a string, a
@@ -2377,7 +2427,7 @@ export function task<T extends (...args: any[]) => Promise<any>>(
   // .then() which throws StepSuspend and empties pending before the caller
   // can flush.
   const wrapper = function (...args: any[]) {
-    const ctx: WorkflowCtx | null = _workflowCtx ?? Reflect.get(globalThis, "__wmill_wf_ctx");
+    const ctx = dispatchCtx();
     if (ctx) {
       // Inside a workflow with checkpoint/replay context — dispatch as step
       const script = taskPath ?? taskName;
@@ -2397,7 +2447,7 @@ export function task<T extends (...args: any[]) => Promise<any>>(
         return (async () => {
           let result: any;
           try {
-            result = await fn(...args);
+            result = await runTaskBody(() => fn(...args));
           } catch (e) {
             if (isSuspendSignal(e, StepSuspend)) throw e;
             ctx._raiseStepFailure(e);
@@ -2406,7 +2456,7 @@ export function task<T extends (...args: any[]) => Promise<any>>(
         })();
       }
       return stepResult;
-    } else if (getEnv("WM_JOB_ID") && !getEnv("WM_FLOW_JOB_ID")) {
+    } else if (!insideTaskBody() && getEnv("WM_JOB_ID") && !getEnv("WM_FLOW_JOB_ID")) {
       // Inside a Windmill root job without checkpoint context — v1 HTTP dispatch
       // WM_FLOW_JOB_ID is set on child jobs, so we skip dispatch for those
       return (async () => {
@@ -2456,7 +2506,8 @@ export function taskScript(path: string, options?: TaskOptions): (...args: any[]
   assertUsableRetry(options?.retry);
   const name = path.split("/").pop() || path;
   const wrapper = function (...args: any[]) {
-    const ctx: WorkflowCtx | null = _workflowCtx ?? Reflect.get(globalThis, "__wmill_wf_ctx");
+    assertNotInsideTaskBody(`taskScript("${path}")`);
+    const ctx = dispatchCtx();
     if (ctx) {
       const kwargs = args.length === 1 && typeof args[0] === "object" && args[0] !== null
         ? args[0]
@@ -2482,7 +2533,8 @@ export function taskFlow(path: string, options?: TaskOptions): (...args: any[])
   assertUsableRetry(options?.retry);
   const name = path.split("/").pop() || path;
   const wrapper = function (...args: any[]) {
-    const ctx: WorkflowCtx | null = _workflowCtx ?? Reflect.get(globalThis, "__wmill_wf_ctx");
+    assertNotInsideTaskBody(`taskFlow("${path}")`);
+    const ctx = dispatchCtx();
     if (ctx) {
       const kwargs = args.length === 1 && typeof args[0] === "object" && args[0] !== null
         ? args[0]
@@ -2535,7 +2587,8 @@ export function waitForApproval(options?: {
   skin?: "detailed" | "minimal";
   description?: string | object;
 }): PromiseLike<{ value: any; approver: string; approved: boolean }> {
-  const ctx: WorkflowCtx | null = _workflowCtx ?? Reflect.get(globalThis, "__wmill_wf_ctx");
+  assertNotInsideTaskBody("waitForApproval()");
+  const ctx = dispatchCtx();
   if (!ctx) {
     throw new Error("waitForApproval can only be called inside a workflow()");
   }
diff --git a/typescript-client/tests/workflow_nested_task.test.ts b/typescript-client/tests/workflow_nested_task.test.ts
new file mode 100644
index 0000000000..39ac2185d8
--- /dev/null
+++ b/typescript-client/tests/workflow_nested_task.test.ts
@@ -0,0 +1,91 @@
+/**
+ * A task body runs as one child job, so the SDK calls it makes cannot be
+ * dispatched as steps of their own. Against the real client.
+ *
+ * Run with: bun test typescript-client/tests/workflow_nested_task.test.ts
+ */
+import { expect, test, describe, mock, afterEach } from "bun:test";
+
+mock.module("../services.gen", () => ({
+  ResourceService: {},
+  VariableService: {},
+  JobService: {},
+  HelpersService: {},
+  AppService: {},
+  MetricsService: {},
+  OidcService: {},
+  UserService: {},
+  KafkaTriggerService: {},
+}));
+mock.module("../core/OpenAPI", () => ({
+  OpenAPI: { BASE: "http://localhost:8000/api", TOKEN: "tok" },
+}));
+
+const { WorkflowCtx, StepSuspend, task, taskScript, step, setWorkflowCtx } = await import(
+  "../client.ts"
+);
+
+let ran: string[] = [];
+
+const inner = task(async function inner(x: string) {
+  ran.push("inner");
+  return `inner:${x}`;
+});
+
+const outer = task(async function outer(x: string) {
+  ran.push("outer");
+  await Promise.resolve();
+  const viaTask = await inner(x);
+  const viaStep = await step("s", () => "stepped");
+  return `${viaTask}+${viaStep}`;
+});
+
+const dispatching = task(async function dispatching() {
+  return await taskScript("f/other/script")({});
+});
+
+/** Run `body` as the child round executing `key`, and hand back what it raised. */
+async function childRound(key: string, body: () => Promise<unknown>): Promise<any> {
+  setWorkflowCtx(new WorkflowCtx({ completed_steps: {}, _executing_key: key }));
+  const hung = new Promise((r) => setTimeout(() => r("hung"), 500));
+  return await Promise.race([body().then(() => "returned", (e) => e), hung]);
+}
+
+afterEach(() => {
+  ran = [];
+  setWorkflowCtx(null);
+});
+
+describe("SDK calls inside a task body", () => {
+  test("a nested task and step run in the task's own job", async () => {
+    const raised = await childRound("outer", async () => {
+      await outer("a");
+    });
+
+    expect(raised).toBeInstanceOf(StepSuspend);
+    expect(raised.dispatchInfo).toMatchObject({
+      mode: "step_complete",
+      result: "inner:a+stepped",
+    });
+  });
+
+  // The workflow body keeps replaying beside the task body, and its own calls
+  // must stay parked: running them would execute a sibling task in this job.
+  test("a sibling task of the workflow body is not run", async () => {
+    const raised = await childRound("outer", async () => {
+      await Promise.all([outer("a"), inner("sibling")]);
+    });
+
+    expect(raised.dispatchInfo).toMatchObject({ mode: "step_complete" });
+    expect(ran).toEqual(["outer", "inner"]);
+  });
+
+  test("a step that would need a dispatch fails instead of hanging", async () => {
+    const raised = await childRound("dispatching", async () => {
+      await dispatching();
+    });
+
+    expect(raised).toBeInstanceOf(Error);
+    expect(raised.message).toContain("cannot be called from inside a task");
+  });
+});