diff --git a/lib/entry-points.js b/lib/entry-points.js
index 83c1d99b3..0901767d7 100644
--- a/lib/entry-points.js
+++ b/lib/entry-points.js
@@ -149268,6 +149268,22 @@ var DEFAULT_SETUP_CONFIG_SCHEMA = {
     object(DEFAULT_SETUP_SCHEMA)
   )
 };
+function matchesDefaultSetupConfigSchema(contents) {
+  let config;
+  try {
+    config = load(contents);
+  } catch (error3) {
+    if (error3 instanceof YAMLException) {
+      return false;
+    }
+    throw error3;
+  }
+  if (!isObject(config)) {
+    return false;
+  }
+  const result = checkSchema(DEFAULT_SETUP_CONFIG_SCHEMA, config);
+  return result.valid && result.unknownKeys.length === 0;
+}
 function mergeDefaultSetupAndUserConfigs(logger, fromConfigInput, fromConfigFile) {
   logger.debug(
     "Combining configuration files from 'config' and 'config-file' inputs"
@@ -151614,7 +151630,7 @@ function getOtherLanguagePacksReason(inputs) {
   if (inputs.configFile !== void 0) {
     return `the configuration file '${inputs.configFile}' may use queries that need library packs for other languages`;
   }
-  if (inputs.configInput !== void 0 && !inputs.isDynamicWorkflow) {
+  if (inputs.configInput !== void 0 && !matchesDefaultSetupConfigSchema(inputs.configInput)) {
     return "the 'config' input may use queries that need library packs for other languages";
   }
   const query = findNonBuiltInQuery(
@@ -162399,8 +162415,7 @@ async function run3(actionState) {
       configFile,
       configInput,
       queriesInput,
-      extraQueriesProperty: repositoryProperties["github-codeql-extra-queries" /* EXTRA_QUERIES */],
-      isDynamicWorkflow: isDynamicWorkflow(actionState.env)
+      extraQueriesProperty: repositoryProperties["github-codeql-extra-queries" /* EXTRA_QUERIES */]
     });
     const useOverlayAwareDefaultCliVersion = analysisKinds?.length === 1 && analysisKinds[0] === "code-scanning" /* CodeScanning */;
     const initCodeQLResult = await initCodeQL(
diff --git a/src/config/db-config.test.ts b/src/config/db-config.test.ts
index 63d9d2ffe..ecf77194a 100644
--- a/src/config/db-config.test.ts
+++ b/src/config/db-config.test.ts
@@ -625,3 +625,43 @@ test("mergeDefaultSetupAndUserConfigs - warns about invalid keys from Default Se
     `Invalid keys in Default Setup configuration: ${expectedInvalidKeys}`,
   ]);
 });
+
+test("matchesDefaultSetupConfigSchema - returns true for configurations that only use Default Setup properties", (t) => {
+  for (const contents of [
+    [
+      "default-setup:",
+      "  org:",
+      "    model-packs: [ github/immutable-actions-list@0.0.1 ]",
+      "threat-models: [  ]",
+    ].join("\n"),
+    "threat-models: [ local ]",
+    "{}",
+  ]) {
+    t.true(dbConfig.matchesDefaultSetupConfigSchema(contents), contents);
+  }
+});
+
+test("matchesDefaultSetupConfigSchema - returns false for configurations that use other properties", (t) => {
+  for (const contents of [
+    "queries: [ { uses: ./queries/show_ifs.ql } ]",
+    "paths-ignore: [ tests ]",
+    "default-setup: { org: { model-packs: [], queries: [] } }",
+  ]) {
+    t.false(dbConfig.matchesDefaultSetupConfigSchema(contents), contents);
+  }
+});
+
+test("matchesDefaultSetupConfigSchema - returns false for invalid Default Setup properties", (t) => {
+  for (const contents of [
+    "threat-models: local",
+    "default-setup: { org: { model-packs: [ 1 ] } }",
+  ]) {
+    t.false(dbConfig.matchesDefaultSetupConfigSchema(contents), contents);
+  }
+});
+
+test("matchesDefaultSetupConfigSchema - returns false for contents that aren't a YAML object", (t) => {
+  for (const contents of ["threat-models: [", "- threat-models", "local", ""]) {
+    t.false(dbConfig.matchesDefaultSetupConfigSchema(contents), contents);
+  }
+});
diff --git a/src/config/db-config.ts b/src/config/db-config.ts
index 4b1ed5479..38cc74ab2 100644
--- a/src/config/db-config.ts
+++ b/src/config/db-config.ts
@@ -94,6 +94,28 @@ const DEFAULT_SETUP_CONFIG_SCHEMA = {
   ),
 } as const satisfies json.Schema;
 
+/**
+ * Returns whether `contents` is a YAML mapping that only sets the properties that Default Setup
+ * uses, which are threat models and model packs, to valid values. Returns `false` otherwise,
+ * including if `contents` isn't valid YAML.
+ */
+export function matchesDefaultSetupConfigSchema(contents: string): boolean {
+  let config: unknown;
+  try {
+    config = yaml.load(contents);
+  } catch (error) {
+    if (error instanceof yaml.YAMLException) {
+      return false;
+    }
+    throw error;
+  }
+  if (!json.isObject(config)) {
+    return false;
+  }
+  const result = json.checkSchema(DEFAULT_SETUP_CONFIG_SCHEMA, config);
+  return result.valid && result.unknownKeys.length === 0;
+}
+
 /**
  * Merges supported properties from two configuration files. This is intended only for
  * use with merging the `config` input provided by Default Setup with a potentially
diff --git a/src/init-action.ts b/src/init-action.ts
index 311127024..e1ac5df5e 100644
--- a/src/init-action.ts
+++ b/src/init-action.ts
@@ -13,7 +13,6 @@ import {
   getOptionalInput,
   getRequiredInput,
   getTemporaryDirectory,
-  isDynamicWorkflow,
   persistInputs,
 } from "./actions-util";
 import { AnalysisKind, getAnalysisKinds } from "./analyses";
@@ -315,7 +314,6 @@ async function run(
       queriesInput,
       extraQueriesProperty:
         repositoryProperties[RepositoryPropertyName.EXTRA_QUERIES],
-      isDynamicWorkflow: isDynamicWorkflow(actionState.env),
     });
     const useOverlayAwareDefaultCliVersion =
       analysisKinds?.length === 1 &&
diff --git a/src/per-language-bundles.test.ts b/src/per-language-bundles.test.ts
index 63e01d0dc..c94b8d6db 100644
--- a/src/per-language-bundles.test.ts
+++ b/src/per-language-bundles.test.ts
@@ -199,7 +199,6 @@ const NO_QUERY_CONFIG: QueryConfigInputs = {
   configInput: undefined,
   queriesInput: undefined,
   extraQueriesProperty: undefined,
-  isDynamicWorkflow: false,
 };
 
 test("getOtherLanguagePacksReason returns undefined when no queries are configured", (t) => {
@@ -224,33 +223,34 @@ test("getOtherLanguagePacksReason returns undefined for built-in query suites",
   }
 });
 
-test("getOtherLanguagePacksReason returns undefined for the config input in a dynamic workflow", (t) => {
+test("getOtherLanguagePacksReason returns undefined for a config input that only uses default setup properties", (t) => {
   t.is(
     getOtherLanguagePacksReason({
       ...NO_QUERY_CONFIG,
-      configInput: "threat-models: [ local ]",
-      isDynamicWorkflow: true,
+      // The shape of the `config` input that default setup passes.
+      configInput: [
+        "default-setup:",
+        "  org:",
+        "    model-packs: [ github/immutable-actions-list@0.0.1 ]",
+        "threat-models: [  ]",
+      ].join("\n"),
     }),
     undefined,
   );
 });
 
-test("getOtherLanguagePacksReason explains a configuration file, including in a dynamic workflow", (t) => {
-  // Default setup can get a configuration file from a repository property.
-  for (const isDynamicWorkflow of [false, true]) {
-    t.is(
-      getOtherLanguagePacksReason({
-        ...NO_QUERY_CONFIG,
-        configFile: "./.github/codeql/codeql-config.yml",
-        isDynamicWorkflow,
-      }),
-      "the configuration file './.github/codeql/codeql-config.yml' may use queries that need " +
-        "library packs for other languages",
-    );
-  }
+test("getOtherLanguagePacksReason explains a configuration file", (t) => {
+  t.is(
+    getOtherLanguagePacksReason({
+      ...NO_QUERY_CONFIG,
+      configFile: "./.github/codeql/codeql-config.yml",
+    }),
+    "the configuration file './.github/codeql/codeql-config.yml' may use queries that need " +
+      "library packs for other languages",
+  );
 });
 
-test("getOtherLanguagePacksReason explains the config input outside a dynamic workflow", (t) => {
+test("getOtherLanguagePacksReason explains a config input that uses other properties", (t) => {
   t.is(
     getOtherLanguagePacksReason({
       ...NO_QUERY_CONFIG,
diff --git a/src/per-language-bundles.ts b/src/per-language-bundles.ts
index d85c3f892..371787901 100644
--- a/src/per-language-bundles.ts
+++ b/src/per-language-bundles.ts
@@ -4,6 +4,7 @@ import { ActionState } from "./action-common";
 import { isGitHubHostedRunner } from "./actions-util";
 import {
   defaultSuites,
+  matchesDefaultSetupConfigSchema,
   parseExtraQueriesProperty,
   parseQueriesInput,
   QuerySpec,
@@ -48,8 +49,6 @@ export interface QueryConfigInputs {
   queriesInput: string | undefined;
   /** The `github-codeql-extra-queries` repository property. */
   extraQueriesProperty: string | undefined;
-  /** Whether the Action is running in a dynamic workflow, such as default setup. */
-  isDynamicWorkflow: boolean;
 }
 
 /**
@@ -58,8 +57,9 @@ export interface QueryConfigInputs {
  * queries that these inputs add are built-in query suites. The `packs` input doesn't matter, since
  * query packs are downloaded together with their dependencies.
  *
- * The configuration isn't loaded until CodeQL is set up, so any configuration file or `config`
- * input is assumed to configure such queries, except for the `config` input in dynamic workflows.
+ * Any configuration file is assumed to configure such queries, since reading it may need file or API
+ * access. The `config` input is only assumed to if it sets anything other than valid threat models
+ * and model packs, which are the properties that default setup uses.
  *
  * @throws A `ConfigurationError` if the `queries` input or the `github-codeql-extra-queries`
  *   repository property is a '+' with no queries after it, unless an input that's checked earlier
@@ -75,10 +75,12 @@ export function getOtherLanguagePacksReason(
     );
   }
 
-  // The `config` input can configure queries in the same way as a configuration file. We assume
-  // that dynamic workflows, which GitHub manages, don't use it to add queries. For example, default
-  // setup only uses it for threat models and model packs.
-  if (inputs.configInput !== undefined && !inputs.isDynamicWorkflow) {
+  // The `config` input can configure queries in the same way as a configuration file. Default
+  // setup only uses it for threat models and model packs, neither of which adds queries.
+  if (
+    inputs.configInput !== undefined &&
+    !matchesDefaultSetupConfigSchema(inputs.configInput)
+  ) {
     return "the 'config' input may use queries that need library packs for other languages";
   }