diff --git a/CLAUDE.md b/CLAUDE.md
index 765cfdb..cdf4db8 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -55,6 +55,7 @@ github_rest_api/
   json_nav_util.pony       -- JsonNavUtil (string_or_none for nullable JSON fields)
   paginated_list.pony      -- PaginatedList[A] with prev/next page navigation, LinkedJsonRequester, LinkedResultReceiver
   _extract_pagination_links.pony -- Extracts prev/next URLs from Link headers (via web_link)
+  _test_json_converters.pony -- Property-based tests for JSON converter primitives
   request/                 -- HTTP request infrastructure (temporary home, intended to be extracted to its own library)
     credentials.pony       -- Credentials (lori.TCPConnectAuth + token), ResultReceiver
     _ssl.pony              -- SSLContextFactory (shared SSL context creation)
@@ -109,7 +110,7 @@ Models have methods that chain to further API calls:
 - JSON converters are primitives implementing `JsonConverter[T]` interface
 - Type aliases for result unions: `RepositoryOrError`, `IssueOrError`, etc.
 - `\nodoc\` annotation on test classes
-- Tests only cover infrastructure (Link header parsing + query params), not API operations
+- Tests cover infrastructure (Link header parsing + query params) and JSON converter primitives, not API operations
 - Keep CLAUDE.md in sync when adding or changing features — update the source layout, OO convenience API, pagination section, and coverage table as part of the PR that introduces the change
 
 ## Known TODOs in Code
diff --git a/github_rest_api/_test.pony b/github_rest_api/_test.pony
index dfa94e3..36d8a66 100644
--- a/github_rest_api/_test.pony
+++ b/github_rest_api/_test.pony
@@ -15,6 +15,14 @@ actor \nodoc\ Main is TestList
     test(_TestExtractPaginationLinksFirstPage)
     test(_TestExtractPaginationLinksLastPage)
     test(_TestExtractPaginationLinksBetweenPages)
+    test(_TestGitPersonJsonConverterPreservesValues)
+    test(_TestGitPersonJsonConverterMissingField)
+    test(_TestLicenseJsonConverterPreservesValues)
+    test(_TestLicenseJsonConverterMissingField)
+    test(_TestCommitFileJsonConverterPreservesValues)
+    test(_TestCommitFileJsonConverterMissingField)
+    test(_TestGistChangeStatusJsonConverterPreservesValues)
+    test(_TestGistChangeStatusJsonConverterMissingField)
     req.QueryParamsTests.make().tests(test)
 
 class \nodoc\ _TestExtractPaginationLinksNoLinks is UnitTest
diff --git a/github_rest_api/_test_json_converters.pony b/github_rest_api/_test_json_converters.pony
new file mode 100644
index 0000000..5313144
--- /dev/null
+++ b/github_rest_api/_test_json_converters.pony
@@ -0,0 +1,214 @@
+use "json"
+use "pony_check"
+use "pony_test"
+use lori = "lori"
+use req = "request"
+
+class \nodoc\ _TestGitPersonJsonConverterPreservesValues is UnitTest
+  fun name(): String => "git-person-json-converter/preserves-values"
+
+  fun ref apply(h: TestHelper) ? =>
+    PonyCheck.for_all[String](
+      recover val Generators.ascii_printable(1, 20) end, h)(
+      {(base, h) =>
+        let auth = lori.TCPConnectAuth(h.env.root)
+        let creds = req.Credentials(auth)
+        let b: String val = base.clone()
+        let name_val: String val = "name_" + b
+        let email_val: String val = "email_" + b
+        let obj = JsonObject
+          .update("name", name_val)
+          .update("email", email_val)
+        let json = JsonNav(obj)
+        try
+          let person = GitPersonJsonConverter(json, creds)?
+          h.assert_eq[String](name_val, person.name)
+          h.assert_eq[String](email_val, person.email)
+        else
+          h.fail("converter raised an error")
+        end
+      })?
+
+class \nodoc\ _TestGitPersonJsonConverterMissingField is UnitTest
+  fun name(): String => "git-person-json-converter/missing-field"
+
+  fun ref apply(h: TestHelper) ? =>
+    PonyCheck.for_all2[String, USize](
+      recover val Generators.ascii_printable(1, 20) end,
+      recover val Generators.usize(0, 1) end, h)(
+      {(base, skip_idx, h) =>
+        let auth = lori.TCPConnectAuth(h.env.root)
+        let creds = req.Credentials(auth)
+        let b: String val = base.clone()
+        var obj = JsonObject
+        if skip_idx != 0 then obj = obj.update("name", "name_" + b) end
+        if skip_idx != 1 then obj = obj.update("email", "email_" + b) end
+        let json = JsonNav(obj)
+        try
+          GitPersonJsonConverter(json, creds)?
+          h.fail("converter should have raised for missing field at index "
+            + skip_idx.string())
+        end
+      })?
+
+class \nodoc\ _TestLicenseJsonConverterPreservesValues is UnitTest
+  fun name(): String => "license-json-converter/preserves-values"
+
+  fun ref apply(h: TestHelper) ? =>
+    PonyCheck.for_all[String](
+      recover val Generators.ascii_printable(1, 20) end, h)(
+      {(base, h) =>
+        let auth = lori.TCPConnectAuth(h.env.root)
+        let creds = req.Credentials(auth)
+        let b: String val = base.clone()
+        let node_id_val: String val = "node_id_" + b
+        let name_val: String val = "name_" + b
+        let key_val: String val = "key_" + b
+        let spdx_id_val: String val = "spdx_id_" + b
+        let url_val: String val = "url_" + b
+        let obj = JsonObject
+          .update("node_id", node_id_val)
+          .update("name", name_val)
+          .update("key", key_val)
+          .update("spdx_id", spdx_id_val)
+          .update("url", url_val)
+        let json = JsonNav(obj)
+        try
+          let license = LicenseJsonConverter(json, creds)?
+          h.assert_eq[String](node_id_val, license.node_id)
+          h.assert_eq[String](name_val, license.name)
+          h.assert_eq[String](key_val, license.key)
+          h.assert_eq[String](spdx_id_val, license.spdx_id)
+          h.assert_eq[String](url_val, license.url)
+        else
+          h.fail("converter raised an error")
+        end
+      })?
+
+class \nodoc\ _TestLicenseJsonConverterMissingField is UnitTest
+  fun name(): String => "license-json-converter/missing-field"
+
+  fun ref apply(h: TestHelper) ? =>
+    PonyCheck.for_all2[String, USize](
+      recover val Generators.ascii_printable(1, 20) end,
+      recover val Generators.usize(0, 4) end, h)(
+      {(base, skip_idx, h) =>
+        let auth = lori.TCPConnectAuth(h.env.root)
+        let creds = req.Credentials(auth)
+        let b: String val = base.clone()
+        var obj = JsonObject
+        if skip_idx != 0 then obj = obj.update("node_id", "node_id_" + b) end
+        if skip_idx != 1 then obj = obj.update("name", "name_" + b) end
+        if skip_idx != 2 then obj = obj.update("key", "key_" + b) end
+        if skip_idx != 3 then obj = obj.update("spdx_id", "spdx_id_" + b) end
+        if skip_idx != 4 then obj = obj.update("url", "url_" + b) end
+        let json = JsonNav(obj)
+        try
+          LicenseJsonConverter(json, creds)?
+          h.fail("converter should have raised for missing field at index "
+            + skip_idx.string())
+        end
+      })?
+
+class \nodoc\ _TestCommitFileJsonConverterPreservesValues is UnitTest
+  fun name(): String => "commit-file-json-converter/preserves-values"
+
+  fun ref apply(h: TestHelper) ? =>
+    PonyCheck.for_all[String](
+      recover val Generators.ascii_printable(1, 20) end, h)(
+      {(base, h) =>
+        let auth = lori.TCPConnectAuth(h.env.root)
+        let creds = req.Credentials(auth)
+        let b: String val = base.clone()
+        let sha_val: String val = "sha_" + b
+        let status_val: String val = "status_" + b
+        let filename_val: String val = "filename_" + b
+        let obj = JsonObject
+          .update("sha", sha_val)
+          .update("status", status_val)
+          .update("filename", filename_val)
+        let json = JsonNav(obj)
+        try
+          let file = CommitFileJsonConverter(json, creds)?
+          h.assert_eq[String](sha_val, file.sha)
+          h.assert_eq[String](status_val, file.status)
+          h.assert_eq[String](filename_val, file.filename)
+        else
+          h.fail("converter raised an error")
+        end
+      })?
+
+class \nodoc\ _TestCommitFileJsonConverterMissingField is UnitTest
+  fun name(): String => "commit-file-json-converter/missing-field"
+
+  fun ref apply(h: TestHelper) ? =>
+    PonyCheck.for_all2[String, USize](
+      recover val Generators.ascii_printable(1, 20) end,
+      recover val Generators.usize(0, 2) end, h)(
+      {(base, skip_idx, h) =>
+        let auth = lori.TCPConnectAuth(h.env.root)
+        let creds = req.Credentials(auth)
+        let b: String val = base.clone()
+        var obj = JsonObject
+        if skip_idx != 0 then obj = obj.update("sha", "sha_" + b) end
+        if skip_idx != 1 then obj = obj.update("status", "status_" + b) end
+        if skip_idx != 2 then
+          obj = obj.update("filename", "filename_" + b)
+        end
+        let json = JsonNav(obj)
+        try
+          CommitFileJsonConverter(json, creds)?
+          h.fail("converter should have raised for missing field at index "
+            + skip_idx.string())
+        end
+      })?
+
+class \nodoc\ _TestGistChangeStatusJsonConverterPreservesValues is UnitTest
+  fun name(): String =>
+    "gist-change-status-json-converter/preserves-values"
+
+  fun ref apply(h: TestHelper) ? =>
+    PonyCheck.for_all3[I64, I64, I64](
+      recover val Generators.i64() end,
+      recover val Generators.i64() end,
+      recover val Generators.i64() end, h)(
+      {(additions, deletions, total, h) =>
+        let auth = lori.TCPConnectAuth(h.env.root)
+        let creds = req.Credentials(auth)
+        let obj = JsonObject
+          .update("additions", additions)
+          .update("deletions", deletions)
+          .update("total", total)
+        let json = JsonNav(obj)
+        try
+          let status = GistChangeStatusJsonConverter(json, creds)?
+          h.assert_eq[I64](additions, status.additions)
+          h.assert_eq[I64](deletions, status.deletions)
+          h.assert_eq[I64](total, status.total)
+        else
+          h.fail("converter raised an error")
+        end
+      })?
+
+class \nodoc\ _TestGistChangeStatusJsonConverterMissingField is UnitTest
+  fun name(): String =>
+    "gist-change-status-json-converter/missing-field"
+
+  fun ref apply(h: TestHelper) ? =>
+    PonyCheck.for_all2[I64, USize](
+      recover val Generators.i64() end,
+      recover val Generators.usize(0, 2) end, h)(
+      {(value, skip_idx, h) =>
+        let auth = lori.TCPConnectAuth(h.env.root)
+        let creds = req.Credentials(auth)
+        var obj = JsonObject
+        if skip_idx != 0 then obj = obj.update("additions", value) end
+        if skip_idx != 1 then obj = obj.update("deletions", value) end
+        if skip_idx != 2 then obj = obj.update("total", value) end
+        let json = JsonNav(obj)
+        try
+          GistChangeStatusJsonConverter(json, creds)?
+          h.fail("converter should have raised for missing field at index "
+            + skip_idx.string())
+        end
+      })?