diff --git a/api/core/dify_builder/handlers_fix.py b/api/core/dify_builder/handlers_fix.py
index 5c943a00ca0..0e1518976dd 100644
--- a/api/core/dify_builder/handlers_fix.py
+++ b/api/core/dify_builder/handlers_fix.py
@@ -466,14 +466,16 @@ _ENDPOINT_TEMPLATE_RE = re.compile(r"\{\{#([^.#{}]+)\.([^.#{}]+)#\}\}")
 
 
 def endpoint_variable_names(graph: Graph) -> set[str]:
-    """Names of the start variables an http-request node reads its URL from.
+    """Names of the start variables an http-request node reads its URL,
+    headers, params, or API-key authorization from.
 
-    Nothing can invent a real endpoint any more than it can invent an upload
-    (ESQ1-302 / build.py's ``_ground_placeholder_endpoints``), so these are
-    values a human still has to supply even when every other field is mocked
-    for them. Only a reference to the graph's own START node counts -- a
-    reference to some other node's output is an ordinary wired value, not an
-    endpoint waiting on the user.
+    Nothing can invent a real endpoint or credential any more than it can
+    invent an upload (ESQ1-302 / build.py's ``_ground_placeholder_endpoints``
+    and Task 3's credential grounding), so these are values a human still has
+    to supply even when every other field is mocked for them. Only a
+    reference to the graph's own START node counts -- a reference to some
+    other node's output is an ordinary wired value, not an endpoint/credential
+    waiting on the user.
     """
     start_id = ""
     for node in graph.get("nodes", []):
@@ -484,14 +486,23 @@ def endpoint_variable_names(graph: Graph) -> set[str]:
     if not start_id:
         return set()
     names: set[str] = set()
+
+    def _collect(text: str) -> None:
+        for node_id, var_name in _ENDPOINT_TEMPLATE_RE.findall(text):
+            if node_id == start_id:
+                names.add(var_name)
+
     for node in graph.get("nodes", []):
         data = node.get("data") or {}
         if data.get("type") != "http-request":
             continue
-        url = str(data.get("url") or "")
-        for node_id, var_name in _ENDPOINT_TEMPLATE_RE.findall(url):
-            if node_id == start_id:
-                names.add(var_name)
+        _collect(str(data.get("url") or ""))
+        _collect(str(data.get("headers") or ""))
+        _collect(str(data.get("params") or ""))
+        authorization = data.get("authorization")
+        auth_config = authorization.get("config") if isinstance(authorization, dict) else None
+        if isinstance(auth_config, dict):
+            _collect(str(auth_config.get("api_key") or ""))
     return names
 
 
diff --git a/api/services/dify_builder/agent/build.py b/api/services/dify_builder/agent/build.py
index 1273d3e0a82..c1242297831 100644
--- a/api/services/dify_builder/agent/build.py
+++ b/api/services/dify_builder/agent/build.py
@@ -664,6 +664,10 @@ def build_nodes(
         _ground(intents, grounding_mc, tenant_id, plan_items)
         for node_id in _ground_placeholder_endpoints(intents, trusted_text=trusted_text):
             logger.info("Dify Builder: http-request %s had a placeholder URL; now read from a start variable", node_id)
+        for node_id in _ground_placeholder_credentials(intents, trusted_text=trusted_text):
+            logger.info(
+                "Dify Builder: http-request %s had a placeholder credential; now read from a start variable", node_id
+            )
         applicable, rejected = graph_ops.filter_applicable({"nodes": [], "edges": []}, intents, _ALLOWED_NODE_TYPES)
         if not applicable:
             reason = rejected[0][1] if rejected else "no applicable node intents"
@@ -761,6 +765,24 @@ def _is_placeholder_endpoint(url: str) -> bool:
     return _PLACEHOLDER_URL_RE.search(text) is not None or _is_localhost_host(text)
 
 
+def _add_required_start_variable(variables: list[dict], var_name: str, label: str) -> None:
+    """Append a REQUIRED text-input start variable (max 2048 chars) named
+    ``var_name`` to ``variables`` if not already present -- the write shared
+    by every grounding pass that turns an invented literal (URL, credential)
+    into a start-node input, so it is not duplicated per pass."""
+    if any(isinstance(v, dict) and v.get("variable") == var_name for v in variables):
+        return
+    variables.append(
+        {
+            "variable": var_name,
+            "label": label,
+            "type": "text-input",
+            "required": True,
+            "max_length": 2048,
+        }
+    )
+
+
 def _ground_placeholder_endpoints(intents: list[MutationIntent], *, trusted_text: str = "") -> list[str]:
     """Replace every http-request URL the user didn't supply with a REQUIRED
     start-node variable and a template reference to it.
@@ -801,16 +823,7 @@ def _ground_placeholder_endpoints(intents: list[MutationIntent], *, trusted_text
             continue
         node_id = str(intent.args.get("node_id") or "")
         var_name = f"{node_id}_url"
-        if not any(v.get("variable") == var_name for v in variables if isinstance(v, dict)):
-            variables.append(
-                {
-                    "variable": var_name,
-                    "label": f"{node_config.get('title') or node_id} URL",
-                    "type": "text-input",
-                    "required": True,
-                    "max_length": 2048,
-                }
-            )
+        _add_required_start_variable(variables, var_name, f"{node_config.get('title') or node_id} URL")
         node_config["url"] = f"{{{{#{start_id}.{var_name}#}}}}"
         intent.args["config"] = node_config
         grounded.append(node_id)
@@ -820,6 +833,146 @@ def _ground_placeholder_endpoints(intents: list[MutationIntent], *, trusted_text
     return grounded
 
 
+def _is_invented_credential(value: str, trusted_text: str) -> bool:
+    """Mirrors ``_ground_placeholder_endpoints``'s OR-of-two-checks shape, but
+    for a credential value (a header/param 'Value' half, or an
+    ``authorization.config.api_key``): an unmistakable placeholder
+    (``CREDENTIAL_PLACEHOLDER_RE``, after stripping a leading ``Bearer
+    ``/``Basic ``/``Token `` scheme) grounds even in placeholder-only mode
+    (``trusted_text == ""``, mirroring how a shaped-like-invented URL grounds
+    with no goal text at all); otherwise, with ``trusted_text`` non-empty, a
+    value that never appears verbatim in it also grounds (S5b-style
+    plausible-looking secret the model invented). An empty value has nothing
+    to ground.
+    """
+    stripped_value = value.strip()
+    remainder = user_supplied.strip_auth_scheme(stripped_value)
+    if not remainder:
+        return False
+    if user_supplied.CREDENTIAL_PLACEHOLDER_RE.search(remainder):
+        return True
+    return bool(trusted_text) and not user_supplied.is_user_supplied_secret(stripped_value, trusted_text)
+
+
+def _replace_credential_value(value: str, template_ref: str) -> str:
+    """Rebuild a header/param 'Value' half with its secret swapped for
+    ``template_ref``, preserving surrounding whitespace and a leading
+    ``Bearer ``/``Basic ``/``Token `` auth-scheme prefix exactly as written
+    (e.g. ``" Bearer YOUR_API_KEY"`` -> ``" Bearer {{#s.h_api_key#}}"``)."""
+    lstripped = value.lstrip(" \t")
+    leading_ws = value[: len(value) - len(lstripped)]
+    core = lstripped.rstrip(" \t")
+    trailing_ws = lstripped[len(core) :]
+    remainder = user_supplied.strip_auth_scheme(core)
+    scheme_prefix = core[: len(core) - len(remainder)]
+    return f"{leading_ws}{scheme_prefix}{template_ref}{trailing_ws}"
+
+
+def _ground_credential_text(text: str, template_ref: str, *, trusted_text: str) -> tuple[str, bool]:
+    """Ground each ``Key: Value`` line of an http-request ``headers``/
+    ``params`` text block whose key names a credential
+    (``user_supplied.is_credential_key``, decided by the key's LAST segment)
+    and whose value the user didn't supply (``_is_invented_credential``),
+    replacing only the secret part of that line with ``template_ref``. Every
+    other line -- including a credential line the user DID supply -- passes
+    through byte-identical. Returns ``(new_text, changed)``.
+    """
+    if not text:
+        return text, False
+    lines = text.split("\n")
+    changed = False
+    new_lines: list[str] = []
+    for line in lines:
+        if ":" not in line:
+            new_lines.append(line)
+            continue
+        key, _sep, value = line.partition(":")
+        if not user_supplied.is_credential_key(key.strip()) or not _is_invented_credential(value, trusted_text):
+            new_lines.append(line)
+            continue
+        new_lines.append(f"{key}:{_replace_credential_value(value, template_ref)}")
+        changed = True
+    return "\n".join(new_lines), changed
+
+
+def _ground_placeholder_credentials(intents: list[MutationIntent], *, trusted_text: str = "") -> list[str]:
+    """Replace every http-request credential literal the user didn't supply
+    -- a header/param whose key names a credential, or an ``api-key``
+    authorization's ``config.api_key`` -- with a REQUIRED start-node variable
+    and a template reference to it. Sibling to ``_ground_placeholder_endpoints``,
+    called right after it in ``build_nodes`` and sharing its start-variable
+    insertion write (``_add_required_start_variable``); reads the start
+    node's config fresh, so a variable that pass already added (e.g.
+    ``<node>_url``) is seen and not clobbered.
+
+    S5b/F2: requirements analysis invented an ``Authorization: Bearer
+    YOUR_API_KEY`` header for a goal that named no credential. Turning it
+    into an input makes the test-data gate ask the user for the real key --
+    or, when mocked, drop it (``without_endpoint_values`` -> now
+    ``endpoint_variable_names``, extended to also scan headers/params/
+    authorization) so the run fails on a missing required input instead of
+    an invented secret the target API rejects.
+
+    A single ``<node>_api_key`` variable covers every credential grounded on
+    that node, however many lines/fields triggered it. Returns the ids of the
+    http-request nodes it re-pointed.
+    """
+    start = next((i for i in intents if i.op == "create_node" and i.args.get("node_type") == "start"), None)
+    if start is None:
+        return []
+    start_id = str(start.args.get("node_id") or "")
+    if not start_id:
+        return []
+    config = dict(start.args.get("config") or {})
+    variables = list(config.get("variables") or [])
+    grounded: list[str] = []
+    for intent in intents:
+        if intent.op != "create_node" or intent.args.get("node_type") != "http-request":
+            continue
+        node_config = dict(intent.args.get("config") or {})
+        node_id = str(intent.args.get("node_id") or "")
+        var_name = f"{node_id}_api_key"
+        template_ref = f"{{{{#{start_id}.{var_name}#}}}}"
+        changed = False
+
+        new_headers, headers_changed = _ground_credential_text(
+            str(node_config.get("headers") or ""), template_ref, trusted_text=trusted_text
+        )
+        if headers_changed:
+            node_config["headers"] = new_headers
+            changed = True
+
+        new_params, params_changed = _ground_credential_text(
+            str(node_config.get("params") or ""), template_ref, trusted_text=trusted_text
+        )
+        if params_changed:
+            node_config["params"] = new_params
+            changed = True
+
+        authorization = node_config.get("authorization")
+        auth_config = authorization.get("config") if isinstance(authorization, dict) else None
+        if (
+            isinstance(authorization, dict)
+            and authorization.get("type") == "api-key"
+            and isinstance(auth_config, dict)
+            and _is_invented_credential(str(auth_config.get("api_key") or ""), trusted_text)
+        ):
+            new_auth_config = dict(auth_config)
+            new_auth_config["api_key"] = template_ref
+            node_config["authorization"] = {**authorization, "config": new_auth_config}
+            changed = True
+
+        if not changed:
+            continue
+        _add_required_start_variable(variables, var_name, f"{node_config.get('title') or node_id} API key")
+        intent.args["config"] = node_config
+        grounded.append(node_id)
+    if grounded:
+        config["variables"] = variables
+        start.args["config"] = config
+    return grounded
+
+
 def _ground(intents: list[MutationIntent], mc: ModelConfig, tenant_id: str, plan_items: list[str]) -> None:
     mode = mc.mode.value if hasattr(mc.mode, "value") else str(mc.mode)
     datasets = resources.list_tenant_resources(tenant_id).datasets
diff --git a/api/tests/unit_tests/core/dify_builder/test_handlers_build.py b/api/tests/unit_tests/core/dify_builder/test_handlers_build.py
index 574f7d47769..399ce03b562 100644
--- a/api/tests/unit_tests/core/dify_builder/test_handlers_build.py
+++ b/api/tests/unit_tests/core/dify_builder/test_handlers_build.py
@@ -1639,6 +1639,56 @@ def test_run_test_prefill_omits_a_placeholder_endpoint_but_keeps_other_fields():
     assert [f["type"] for f in form.payload["fields"]] == ["text-input", "text-input"]  # both still asked for
 
 
+def test_run_test_prefill_omits_a_placeholder_credential_but_keeps_other_fields():
+    """The credential counterpart of the placeholder-endpoint prefill guard
+    (Task 3): a mocked API key would let the run launch with an invented
+    secret and fail deep inside the http-request node instead of at input
+    validation -- so, like an invented URL, it must stay empty while an
+    ordinary text field is still pre-filled."""
+    from core.dify_builder.handlers_build import handle_execution
+    from tests.unit_tests.core.dify_builder.fakes import FakeBuildDifyPort
+
+    env, _ = _new_env()
+    env.dify = FakeBuildDifyPort()
+    env.dify.graph = {
+        "nodes": [
+            {
+                "id": "s",
+                "data": {
+                    "type": "start",
+                    "variables": [
+                        {"variable": "topic", "type": "text-input"},
+                        {"variable": "h_api_key", "type": "text-input", "required": True, "max_length": 2048},
+                    ],
+                },
+            },
+            {
+                "id": "h",
+                "data": {
+                    "type": "http-request",
+                    "title": "Call PPT API",
+                    "url": "https://api.acme.com/v1/render",
+                    "headers": "Authorization: Bearer {{#s.h_api_key#}}",
+                    "params": "",
+                    "authorization": {"type": "no-auth", "config": None},
+                },
+            },
+        ],
+        "edges": [],
+    }
+    env.agent.generate_mock_inputs = lambda _schema, _prior: {
+        "topic": "quarterly report",
+        "h_api_key": "sk-mock-invented",
+    }
+    s = _session(entry_mode=EntryMode.BUILD, current_state=PcState.BUILD_EXECUTION)
+    fc = DifyBuilderContext(test_input_ref="")
+    result = handle_execution(env, Turn(actor=_actor(), action=Action(kind="run_test")), s, fc)
+    assert result.next == PcState.BUILD_AWAIT_TESTDATA
+    form = next(i for i in result.items if i.kind == "form")
+    assert form.payload["values"] == {"topic": "quarterly report"}  # h_api_key dropped, topic kept
+    assert [f["type"] for f in form.payload["fields"]] == ["text-input", "text-input"]  # both still asked for
+
+
 def test_run_test_still_asks_when_a_file_is_declared_among_other_variables():
     """Mixed schema: text can be mocked, but the file variable cannot -- the
     gate must still fire so a human can supply the upload."""
diff --git a/api/tests/unit_tests/core/dify_builder/test_handlers_fix.py b/api/tests/unit_tests/core/dify_builder/test_handlers_fix.py
index 9df06d7b65a..776391e7267 100644
--- a/api/tests/unit_tests/core/dify_builder/test_handlers_fix.py
+++ b/api/tests/unit_tests/core/dify_builder/test_handlers_fix.py
@@ -825,6 +825,75 @@ def test_endpoint_variable_names_empty_when_there_is_no_http_request_node():
     assert endpoint_variable_names(graph) == set()
 
 
+def test_endpoint_variable_names_collects_headers_too():
+    """A node whose url and header both read the start node counts both; a
+    header reading another node's output is an ordinary wired value, not a
+    credential waiting on the user."""
+    from core.dify_builder.handlers_fix import endpoint_variable_names
+
+    graph = {
+        "nodes": [
+            {
+                "id": "s",
+                "data": {
+                    "type": "start",
+                    "variables": [
+                        {"variable": "h_url", "type": "text-input"},
+                        {"variable": "h_api_key", "type": "text-input"},
+                    ],
+                },
+            },
+            {"id": "llm1", "data": {"type": "llm"}},
+            {
+                "id": "h",
+                "data": {
+                    "type": "http-request",
+                    "url": "{{#s.h_url#}}",
+                    "headers": "Authorization: Bearer {{#s.h_api_key#}}\nX-Trace: {{#llm1.text#}}",
+                    "params": "",
+                    "authorization": {"type": "no-auth", "config": None},
+                },
+            },
+        ],
+        "edges": [],
+    }
+    assert endpoint_variable_names(graph) == {"h_url", "h_api_key"}
+
+
+def test_endpoint_variable_names_also_collects_params_and_authorization_api_key():
+    from core.dify_builder.handlers_fix import endpoint_variable_names
+
+    graph = {
+        "nodes": [
+            {
+                "id": "s",
+                "data": {
+                    "type": "start",
+                    "variables": [
+                        {"variable": "p_key", "type": "text-input"},
+                        {"variable": "auth_key", "type": "text-input"},
+                    ],
+                },
+            },
+            {
+                "id": "h",
+                "data": {
+                    "type": "http-request",
+                    "url": "https://api.acme.com/v1",
+                    "headers": "",
+                    "params": "api_key: {{#s.p_key#}}",
+                    "authorization": {
+                        "type": "api-key",
+                        "config": {"type": "bearer", "api_key": "{{#s.auth_key#}}"},
+                    },
+                },
+            },
+        ],
+        "edges": [],
+    }
+    assert endpoint_variable_names(graph) == {"p_key", "auth_key"}
+
+
 # ---- without_endpoint_values -------------------------------------------------
 
 
diff --git a/api/tests/unit_tests/services/dify_builder/test_build_nodes.py b/api/tests/unit_tests/services/dify_builder/test_build_nodes.py
index 9f97e47620a..1bd09016132 100644
--- a/api/tests/unit_tests/services/dify_builder/test_build_nodes.py
+++ b/api/tests/unit_tests/services/dify_builder/test_build_nodes.py
@@ -583,7 +583,15 @@ def test_build_nodes_grounds_a_placeholder_endpoint_into_a_required_start_variab
     assert "Call PPT API" in var["label"]
 
 
-def _http_node(node_id: str, title: str, url: str) -> dict:
+def _http_node(
+    node_id: str,
+    title: str,
+    url: str,
+    *,
+    headers: str = "",
+    params: str = "",
+    authorization: dict | None = None,
+) -> dict:
     return {
         "id": node_id,
         "type": "custom",
@@ -592,14 +600,35 @@ def _http_node(node_id: str, title: str, url: str) -> dict:
             "title": title,
             "method": "post",
             "url": url,
-            "authorization": {"type": "no-auth", "config": None},
-            "headers": "",
-            "params": "",
+            "authorization": authorization or {"type": "no-auth", "config": None},
+            "headers": headers,
+            "params": params,
             "body": _HTTP_BODY,
         },
     }
 
 
+def _gen_graph_with_http_full(
+    url: str,
+    *,
+    headers: str = "",
+    params: str = "",
+    authorization: dict | None = None,
+) -> dict:
+    return {
+        "graph": {
+            "nodes": [
+                {"id": "s", "type": "custom", "data": {"type": "start", "title": "Start", "variables": []}},
+                _http_node("h", "Call PPT API", url, headers=headers, params=params, authorization=authorization),
+                {"id": "e", "type": "custom", "data": {"type": "end", "title": "End", "outputs": []}},
+            ],
+            "edges": [{"id": "e1", "source": "s", "target": "h"}, {"id": "e2", "source": "h", "target": "e"}],
+        },
+        "error": "",
+        "errors": [],
+    }
+
+
 def test_build_nodes_grounds_each_placeholder_endpoint_into_its_own_start_variable():
     gen_graph = _gen_graph_with_http("https://api.example.com/ppt/generate")
     nodes = gen_graph["graph"]["nodes"]
@@ -685,3 +714,78 @@ def test_is_placeholder_endpoint_recognises_the_usual_inventions():
     assert not build._is_placeholder_endpoint(
         "https://abc123.localhost.run/webhook"
     )  # a real tunnel domain, not the localhost host
+
+
+# ---- Task 3: invented credentials become an input ---------------------------
+
+
+def test_build_nodes_grounds_an_invented_credential_header_into_a_required_start_variable():
+    """S5b/F2: requirements analysis invented an ``Authorization: Bearer
+    YOUR_API_KEY`` header the goal never supplied. Grounding it into a start
+    variable means the test-data gate asks the user for the real key instead
+    of the workflow shipping a header the run can never satisfy. The
+    Content-Type line is not a credential and must pass through byte-identical."""
+    intents = _build_with(
+        _gen_graph_with_http_full(
+            "https://api.acme.com/v1/render",
+            headers="Content-Type: application/json\nAuthorization: Bearer YOUR_API_KEY",
+        )
+    )
+
+    http = next(i for i in intents if i.args.get("node_type") == "http-request")
+    start = next(i for i in intents if i.args.get("node_type") == "start")
+    assert http.args["config"]["headers"] == ("Content-Type: application/json\nAuthorization: Bearer {{#s.h_api_key#}}")
+    var = next(v for v in start.args["config"]["variables"] if v["variable"] == "h_api_key")
+    assert var["type"] == "text-input"
+    assert var["required"] is True
+    assert var["max_length"] == 2048
+    assert "Call PPT API" in var["label"]
+
+
+def test_build_nodes_leaves_a_header_credential_alone_when_the_user_actually_supplied_it():
+    """The mirror case: the goal literally names the secret, so it is not a
+    fabrication and must be left alone."""
+    goal = "Call https://api.acme.com/v1/render with Authorization: Bearer sk-live-abc123."
+    intents = _build_with(
+        _gen_graph_with_http_full(
+            "https://api.acme.com/v1/render",
+            headers="Authorization: Bearer sk-live-abc123",
+        ),
+        trusted_text=goal,
+    )
+
+    http = next(i for i in intents if i.args.get("node_type") == "http-request")
+    start = next(i for i in intents if i.args.get("node_type") == "start")
+    assert http.args["config"]["headers"] == "Authorization: Bearer sk-live-abc123"
+    assert start.args["config"]["variables"] == []
+
+
+def test_build_nodes_grounds_an_invented_api_key_authorization_config():
+    intents = _build_with(
+        _gen_graph_with_http_full(
+            "https://api.acme.com/v1/render",
+            authorization={"type": "api-key", "config": {"type": "bearer", "api_key": "YOUR_TOKEN"}},
+        )
+    )
+
+    http = next(i for i in intents if i.args.get("node_type") == "http-request")
+    start = next(i for i in intents if i.args.get("node_type") == "start")
+    assert http.args["config"]["authorization"]["config"]["api_key"] == "{{#s.h_api_key#}}"
+    assert http.args["config"]["authorization"]["config"]["type"] == "bearer"  # untouched
+    var = next(v for v in start.args["config"]["variables"] if v["variable"] == "h_api_key")
+    assert var["required"] is True
+
+
+def test_build_nodes_grounds_an_invented_api_key_param():
+    intents = _build_with(
+        _gen_graph_with_http_full(
+            "https://api.acme.com/v1/render",
+            params="api_key: xxxxxxxx",
+        )
+    )
+
+    http = next(i for i in intents if i.args.get("node_type") == "http-request")
+    start = next(i for i in intents if i.args.get("node_type") == "start")
+    assert http.args["config"]["params"] == "api_key: {{#s.h_api_key#}}"
+    var = next(v for v in start.args["config"]["variables"] if v["variable"] == "h_api_key")
+    assert var["required"] is True