diff --git a/CLAUDE.md b/CLAUDE.md
index b27dfcf..d2662b1 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -21,7 +21,7 @@ Uses `corral` for dependency management. `make` automatically runs `corral fetch
 - `github.com/ponylang/http.git` -- HTTP client
 - `github.com/ponylang/net_ssl.git` (via http) -- SSL/TLS
 - `github.com/kulibali/kiuatan.git` -- PEG parsing (for URI templates and Link headers)
-- `github.com/ponylang/json.git` -- JSON parsing
+- `github.com/ponylang/json-ng.git` -- JSON parsing (immutable, persistent collections)
 
 ## Source Layout
 
@@ -45,6 +45,7 @@ github_rest_api/
   search.pony              -- SearchIssues + SearchResults generic
   user.pony                -- User model
   license.pony             -- License model
+  json_nav_util.pony       -- JsonNavUtil (string_or_none for nullable JSON fields)
   paginated_list.pony      -- PaginatedList[A] with prev/next page navigation
   request/                 -- HTTP request infrastructure (temporary home, intended to be extracted to its own library)
     http.pony              -- Credentials, ResultReceiver, RequestFactory
@@ -52,7 +53,7 @@ github_rest_api/
     http_post.pony         -- HTTPPost (POST with JSON response)
     http_delete.pony       -- HTTPDelete (DELETE, expects 204)
     request_error.pony     -- RequestError (status, response_body, message)
-    json.pony              -- JsonConverter interface
+    json.pony              -- JsonConverter interface, JsonTypeString utility
     query_params.pony      -- QueryParams (URL query string builder with percent-encoding)
     _test.pony             -- QueryParams tests (example + property-based)
   simple_uri_template/     -- RFC 6570 path segment expansion (PEG-based; temporary home, intended to be extracted to its own library)
diff --git a/corral.json b/corral.json
index 66f872d..da9cada 100644
--- a/corral.json
+++ b/corral.json
@@ -15,8 +15,8 @@
       "version": "0.6.4"
     },
     {
-      "locator": "github.com/ponylang/json.git",
-      "version": "0.2.0"
+      "locator": "github.com/ponylang/json-ng.git",
+      "version": "0.1.0"
     }
   ],
   "info": {
diff --git a/github_rest_api/asset.pony b/github_rest_api/asset.pony
index 774328e..597096d 100644
--- a/github_rest_api/asset.pony
+++ b/github_rest_api/asset.pony
@@ -50,22 +50,20 @@ class val Asset
     browser_download_url = browser_download_url'
 
 primitive AssetJsonConverter is req.JsonConverter[Asset]
-  fun apply(json: JsonType val, creds: req.Credentials): Asset ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let id = JsonExtractor(obj("id")?).as_i64()?
-    let node_id = JsonExtractor(obj("node_id")?).as_string()?
-    let name = JsonExtractor(obj("name")?).as_string()?
-    let label = JsonExtractor(obj("label")?).as_string_or_none()?
-    let uploader = UserJsonConverter(obj("uploader")?, creds)?
-    let content_type = JsonExtractor(obj("content_type")?).as_string()?
-    let state = JsonExtractor(obj("state")?).as_string()?
-    let size = JsonExtractor(obj("size")?).as_i64()?
-    let download_count = JsonExtractor(obj("download_count")?).as_i64()?
-    let created_at = JsonExtractor(obj("created_at")?).as_string()?
-    let updated_at = JsonExtractor(obj("updated_at")?).as_string()?
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let browser_download_url =
-      JsonExtractor(obj("browser_download_url")?).as_string()?
+  fun apply(json: JsonNav, creds: req.Credentials): Asset ? =>
+    let id = json("id").as_i64()?
+    let node_id = json("node_id").as_string()?
+    let name = json("name").as_string()?
+    let label = JsonNavUtil.string_or_none(json("label"))?
+    let uploader = UserJsonConverter(json("uploader"), creds)?
+    let content_type = json("content_type").as_string()?
+    let state = json("state").as_string()?
+    let size = json("size").as_i64()?
+    let download_count = json("download_count").as_i64()?
+    let created_at = json("created_at").as_string()?
+    let updated_at = json("updated_at").as_string()?
+    let url = json("url").as_string()?
+    let browser_download_url = json("browser_download_url").as_string()?
 
     Asset(creds,
       id,
diff --git a/github_rest_api/commit.pony b/github_rest_api/commit.pony
index d7b2d14..9d648cc 100644
--- a/github_rest_api/commit.pony
+++ b/github_rest_api/commit.pony
@@ -67,20 +67,19 @@ primitive GetCommit
     p
 
 primitive CommitJsonConverter is req.JsonConverter[Commit]
-  fun apply(json: JsonType val, creds: req.Credentials): Commit ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let sha = JsonExtractor(obj("sha")?).as_string()?
+  fun apply(json: JsonNav, creds: req.Credentials): Commit ? =>
+    let sha = json("sha").as_string()?
 
     let files = recover trn Array[CommitFile] end
-    for f in JsonExtractor(obj("files")?).as_array()?.values() do
-      let file = CommitFileJsonConverter(f, creds)?
+    for f in json("files").as_array()?.values() do
+      let file = CommitFileJsonConverter(JsonNav(f), creds)?
       files.push(file)
     end
 
-    let git_commit = GitCommitJsonConverter(obj("commit")?, creds)?
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let html_url = JsonExtractor(obj("html_url")?).as_string()?
-    let comments_url = JsonExtractor(obj("comments_url")?).as_string()?
+    let git_commit = GitCommitJsonConverter(json("commit"), creds)?
+    let url = json("url").as_string()?
+    let html_url = json("html_url").as_string()?
+    let comments_url = json("comments_url").as_string()?
 
     Commit(creds,
       sha,
diff --git a/github_rest_api/commit_file.pony b/github_rest_api/commit_file.pony
index 63ee956..4619585 100644
--- a/github_rest_api/commit_file.pony
+++ b/github_rest_api/commit_file.pony
@@ -19,12 +19,11 @@ class val CommitFile
     filename = filename'
 
 primitive CommitFileJsonConverter is req.JsonConverter[CommitFile]
-  fun apply(json: JsonType val,
+  fun apply(json: JsonNav,
     creds: req.Credentials): CommitFile ?
   =>
-    let obj = JsonExtractor(json).as_object()?
-    let sha = JsonExtractor(obj("sha")?).as_string()?
-    let status = JsonExtractor(obj("status")?).as_string()?
-    let filename = JsonExtractor(obj("filename")?).as_string()?
+    let sha = json("sha").as_string()?
+    let status = json("status").as_string()?
+    let filename = json("filename").as_string()?
 
     CommitFile(creds, sha, status, filename)
diff --git a/github_rest_api/git_commit.pony b/github_rest_api/git_commit.pony
index a237742..83d486c 100644
--- a/github_rest_api/git_commit.pony
+++ b/github_rest_api/git_commit.pony
@@ -21,11 +21,10 @@ class val GitCommit
     url = url'
 
 primitive GitCommitJsonConverter is req.JsonConverter[GitCommit]
-  fun apply(json: JsonType val, creds: req.Credentials): GitCommit ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let author = GitPersonJsonConverter(obj("author")?, creds)?
-    let committer = GitPersonJsonConverter(obj("committer")?, creds)?
-    let message = JsonExtractor(obj("message")?).as_string()?
-    let url = JsonExtractor(obj("url")?).as_string()?
+  fun apply(json: JsonNav, creds: req.Credentials): GitCommit ? =>
+    let author = GitPersonJsonConverter(json("author"), creds)?
+    let committer = GitPersonJsonConverter(json("committer"), creds)?
+    let message = json("message").as_string()?
+    let url = json("url").as_string()?
 
     GitCommit(creds, author, committer, message, url)
diff --git a/github_rest_api/git_person.pony b/github_rest_api/git_person.pony
index 56404cf..750ca6e 100644
--- a/github_rest_api/git_person.pony
+++ b/github_rest_api/git_person.pony
@@ -10,9 +10,8 @@ class val GitPerson
     email = email'
 
 primitive GitPersonJsonConverter is req.JsonConverter[GitPerson]
-  fun apply(json: JsonType val, creds: req.Credentials): GitPerson ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let name = JsonExtractor(obj("name")?).as_string()?
-    let email = JsonExtractor(obj("email")?).as_string()?
+  fun apply(json: JsonNav, creds: req.Credentials): GitPerson ? =>
+    let name = json("name").as_string()?
+    let email = json("email").as_string()?
 
     GitPerson(name, email)
diff --git a/github_rest_api/issue.pony b/github_rest_api/issue.pony
index 4c4c081..3c96112 100644
--- a/github_rest_api/issue.pony
+++ b/github_rest_api/issue.pony
@@ -1,4 +1,3 @@
-use "collections"
 use "json"
 use "promises"
 use req = "request"
@@ -147,34 +146,33 @@ primitive GetRepositoryIssues
 
 
 primitive IssueJsonConverter is req.JsonConverter[Issue]
-  fun apply(json: JsonType val, creds: req.Credentials): Issue ? =>
-    let obj = JsonExtractor(json).as_object()?
-
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let respository_url = JsonExtractor(obj("repository_url")?).as_string()?
-    let labels_url = JsonExtractor(obj("labels_url")?).as_string()?
-    let comments_url = JsonExtractor(obj("comments_url")?).as_string()?
-    let events_url = JsonExtractor(obj("events_url")?).as_string()?
-    let html_url = JsonExtractor(obj("html_url")?).as_string()?
-
-    let number = JsonExtractor(obj("number")?).as_i64()?
-    let title = JsonExtractor(obj("title")?).as_string()?
-    let user = UserJsonConverter(obj("user")?, creds)?
-    let state = JsonExtractor(obj("state")?).as_string_or_none()?
-    let body = JsonExtractor(obj("body")?).as_string_or_none()?
+  fun apply(json: JsonNav, creds: req.Credentials): Issue ? =>
+    let url = json("url").as_string()?
+    let respository_url = json("repository_url").as_string()?
+    let labels_url = json("labels_url").as_string()?
+    let comments_url = json("comments_url").as_string()?
+    let events_url = json("events_url").as_string()?
+    let html_url = json("html_url").as_string()?
+
+    let number = json("number").as_i64()?
+    let title = json("title").as_string()?
+    let user = UserJsonConverter(json("user"), creds)?
+    let state = JsonNavUtil.string_or_none(json("state"))?
+    let body = JsonNavUtil.string_or_none(json("body"))?
 
     let labels = recover trn Array[Label] end
-    for i in JsonExtractor(obj("labels")?).as_array()?.values() do
-      let l = LabelJsonConverter(i, creds)?
+    for i in json("labels").as_array()?.values() do
+      let l = LabelJsonConverter(JsonNav(i), creds)?
       labels.push(l)
     end
 
-    let pull_request =
-      if obj.contains("pull_request") then
-        IssuePullRequestJsonConverter(obj("pull_request")?, creds)?
-      else
-        None
-      end
+    let pr_json = json("pull_request")
+    let pull_request = match pr_json.json()
+    | let _: JsonType =>
+      IssuePullRequestJsonConverter(pr_json, creds)?
+    else
+      None
+    end
 
     Issue(creds,
       url,
diff --git a/github_rest_api/issue_comment.pony b/github_rest_api/issue_comment.pony
index a357646..9ed6b95 100644
--- a/github_rest_api/issue_comment.pony
+++ b/github_rest_api/issue_comment.pony
@@ -1,4 +1,3 @@
-use "collections"
 use "json"
 use "net"
 use "promises"
@@ -54,13 +53,11 @@ primitive CreateIssueComment
       p,
       IssueCommentJsonConverter)
 
-    let m: Map[String, JsonType] = m.create()
-    m.update("body", comment)
-    let json = JsonObject.from_map(m).string()
+    let json = JsonObject.update("body", comment).string()
 
     try
       req.HTTPPost(creds.auth)(url,
-        json,
+        consume json,
         r,
         creds.token)?
     else
@@ -115,25 +112,24 @@ primitive IssueCommentsURL
       end)
 
 primitive IssueCommentJsonConverter is req.JsonConverter[IssueComment]
-  fun apply(json: JsonType val,
+  fun apply(json: JsonNav,
     creds: req.Credentials): IssueComment ?
   =>
-    let obj = JsonExtractor(json).as_object()?
-    let body = JsonExtractor(obj("body")?).as_string()?
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let html_url = JsonExtractor(obj("html_url")?).as_string()?
-    let issue_url = JsonExtractor(obj("issue_url")?).as_string()?
+    let body = json("body").as_string()?
+    let url = json("url").as_string()?
+    let html_url = json("html_url").as_string()?
+    let issue_url = json("issue_url").as_string()?
 
     IssueComment(creds, body, url, html_url, issue_url)
 
 primitive IssueCommentsJsonConverter is req.JsonConverter[Array[IssueComment] val]
-  fun apply(json: JsonType val,
+  fun apply(json: JsonNav,
     creds: req.Credentials): Array[IssueComment] val ?
   =>
     let comments = recover trn Array[IssueComment] end
 
-    for i in JsonExtractor(json).as_array()?.values() do
-      let comment = IssueCommentJsonConverter(i, creds)?
+    for i in json.as_array()?.values() do
+      let comment = IssueCommentJsonConverter(JsonNav(i), creds)?
       comments.push(comment)
     end
 
diff --git a/github_rest_api/issue_pull_request.pony b/github_rest_api/issue_pull_request.pony
index 5757653..9d139fb 100644
--- a/github_rest_api/issue_pull_request.pony
+++ b/github_rest_api/issue_pull_request.pony
@@ -29,12 +29,11 @@ class val IssuePullRequest
     merged_at = merged_at'
 
 primitive IssuePullRequestJsonConverter is req.JsonConverter[IssuePullRequest]
-  fun apply(json: JsonType val, creds: req.Credentials): IssuePullRequest ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let html_url = JsonExtractor(obj("html_url")?).as_string()?
-    let diff_url = JsonExtractor(obj("diff_url")?).as_string()?
-    let patch_url = JsonExtractor(obj("patch_url")?).as_string()?
-    let merged_at = JsonExtractor(obj("merged_at")?).as_string_or_none()?
+  fun apply(json: JsonNav, creds: req.Credentials): IssuePullRequest ? =>
+    let url = json("url").as_string()?
+    let html_url = json("html_url").as_string()?
+    let diff_url = json("diff_url").as_string()?
+    let patch_url = json("patch_url").as_string()?
+    let merged_at = JsonNavUtil.string_or_none(json("merged_at"))?
 
     IssuePullRequest(url, html_url, diff_url, patch_url, merged_at)
diff --git a/github_rest_api/json_nav_util.pony b/github_rest_api/json_nav_util.pony
new file mode 100644
index 0000000..49387a6
--- /dev/null
+++ b/github_rest_api/json_nav_util.pony
@@ -0,0 +1,18 @@
+use "json"
+
+primitive JsonNavUtil
+  """
+  Utility for extracting optional string fields from JSON.
+
+  json-ng's JsonNav does not have an as_string_or_none() method. This
+  primitive provides equivalent functionality: given a JsonNav positioned on a
+  field, it returns the String value if present or None if the JSON value is
+  null. Raises an error if the navigation failed (key missing) or the value is
+  any other type.
+  """
+  fun string_or_none(json: JsonNav): (String | None) ? =>
+    match json.json()
+    | let s: String => s
+    | JsonNull => None
+    else error
+    end
diff --git a/github_rest_api/label.pony b/github_rest_api/label.pony
index dab9e43..17e11a7 100644
--- a/github_rest_api/label.pony
+++ b/github_rest_api/label.pony
@@ -1,4 +1,3 @@
-use "collections"
 use "json"
 use "promises"
 use req = "request"
@@ -69,19 +68,18 @@ primitive CreateLabel
       p,
       LabelJsonConverter)
 
-    let m: Map[String, JsonType] = m.create()
-    m.update("name", name)
+    var obj = JsonObject.update("name", name)
     match color
-    | let c: String => m.update("color", c)
+    | let c: String => obj = obj.update("color", c)
     end
     match description
-    | let d: String => m.update("description", d)
+    | let d: String => obj = obj.update("description", d)
     end
-    let json = JsonObject.from_map(m).string()
+    let json = obj.string()
 
     try
       req.HTTPPost(creds.auth)(url,
-        json,
+        consume json,
         r,
         creds.token)?
     else
@@ -133,15 +131,14 @@ primitive DeleteLabel
     p
 
 primitive LabelJsonConverter is req.JsonConverter[Label]
-  fun apply(json: JsonType val, creds: req.Credentials): Label ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let id = JsonExtractor(obj("id")?).as_i64()?
-    let node_id = JsonExtractor(obj("node_id")?).as_string()?
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let name = JsonExtractor(obj("name")?).as_string()?
-    let color = JsonExtractor(obj("color")?).as_string()?
-    let default = JsonExtractor(obj("default")?).as_bool()?
-    let description = JsonExtractor(obj("description")?).as_string_or_none()?
+  fun apply(json: JsonNav, creds: req.Credentials): Label ? =>
+    let id = json("id").as_i64()?
+    let node_id = json("node_id").as_string()?
+    let url = json("url").as_string()?
+    let name = json("name").as_string()?
+    let color = json("color").as_string()?
+    let default = json("default").as_bool()?
+    let description = JsonNavUtil.string_or_none(json("description"))?
 
     Label(creds,
       id,
diff --git a/github_rest_api/license.pony b/github_rest_api/license.pony
index 5751006..55c6ba9 100644
--- a/github_rest_api/license.pony
+++ b/github_rest_api/license.pony
@@ -24,13 +24,12 @@ class val License
     url = url'
 
 primitive LicenseJsonConverter is req.JsonConverter[License]
-  fun apply(json: JsonType val, creds: req.Credentials): License ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let node_id = JsonExtractor(obj("node_id")?).as_string()?
-    let name = JsonExtractor(obj("name")?).as_string()?
-    let key = JsonExtractor(obj("key")?).as_string()?
-    let spdx_id = JsonExtractor(obj("spdx_id")?).as_string()?
-    let url = JsonExtractor(obj("url")?).as_string()?
+  fun apply(json: JsonNav, creds: req.Credentials): License ? =>
+    let node_id = json("node_id").as_string()?
+    let name = json("name").as_string()?
+    let key = json("key").as_string()?
+    let spdx_id = json("spdx_id").as_string()?
+    let url = json("url").as_string()?
 
     License(creds,
       node_id,
diff --git a/github_rest_api/paginated_list.pony b/github_rest_api/paginated_list.pony
index ee7708b..a59b3ae 100644
--- a/github_rest_api/paginated_list.pony
+++ b/github_rest_api/paginated_list.pony
@@ -74,14 +74,14 @@ class val PaginatedListJsonConverter[A: Any val]
     _creds = creds
     _converter = converter
 
-  fun apply(json: JsonType val,
+  fun apply(json: JsonNav,
     link_header: String,
     creds: req.Credentials): PaginatedList[A] ?
   =>
     let entries = recover trn Array[A] end
 
-    for i in JsonExtractor(json).as_array()?.values() do
-      let e = _converter(i, creds)?
+    for i in json.as_array()?.values() do
+      let e = _converter(JsonNav(i), creds)?
       entries.push(e)
     end
 
@@ -114,12 +114,12 @@ actor PaginatedResultReceiver[A: Any val]
     _p = p
     _converter = c
 
-  be success(json: JsonDoc val, link_header: String) =>
+  be success(json: JsonNav, link_header: String) =>
     try
-      _p(_converter(json.data, link_header, _creds)?)
+      _p(_converter(json, link_header, _creds)?)
     else
       let m = recover val
-        "Unable to convert json for " + json.string()
+        "Unable to convert json for " + req.JsonTypeString(json)
       end
 
       _p(req.RequestError(where message' = m))
@@ -224,13 +224,10 @@ class PaginatedJsonRequesterHandler[A: Any val] is HTTPHandler
     let y: String iso = String.from_iso_array(consume x)
 
     if _status == 200 then
-      try
-        let json = recover val
-          JsonDoc.>parse(consume y)?
-        end
-        _receiver.success(json, _link_header)
-      else
-        _receiver.failure(_status, "", "Failed to parse response")
+      match JsonParser.parse(consume y)
+      | let json: JsonType => _receiver.success(JsonNav(json), _link_header)
+      | let _: JsonParseError => _receiver.failure(_status, "",
+        "Failed to parse response")
       end
     elseif (_status != 301) and (_status != 307) then
       _receiver.failure(_status, consume y, "")
diff --git a/github_rest_api/pull_request.pony b/github_rest_api/pull_request.pony
index 3756a27..397cc1c 100644
--- a/github_rest_api/pull_request.pony
+++ b/github_rest_api/pull_request.pony
@@ -86,25 +86,23 @@ primitive GetPullRequest
     p
 
 primitive PullRequestJsonConverter is req.JsonConverter[PullRequest]
-  fun apply(json: JsonType val, creds: req.Credentials): PullRequest ? =>
-    let obj = JsonExtractor(json).as_object()?
-
-    let number = JsonExtractor(obj("number")?).as_i64()?
-    let title = JsonExtractor(obj("title")?).as_string()?
-    let body = JsonExtractor(obj("body")?).as_string_or_none()?
-    let state = JsonExtractor(obj("state")?).as_string()?
+  fun apply(json: JsonNav, creds: req.Credentials): PullRequest ? =>
+    let number = json("number").as_i64()?
+    let title = json("title").as_string()?
+    let body = JsonNavUtil.string_or_none(json("body"))?
+    let state = json("state").as_string()?
 
     let labels = recover trn Array[Label] end
-    for i in JsonExtractor(obj("labels")?).as_array()?.values() do
-      let l = LabelJsonConverter(i, creds)?
+    for i in json("labels").as_array()?.values() do
+      let l = LabelJsonConverter(JsonNav(i), creds)?
       labels.push(l)
     end
 
-    let base = PullRequestBaseJsonConverter(obj("base")?, creds)?
+    let base = PullRequestBaseJsonConverter(json("base"), creds)?
 
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let html_url = JsonExtractor(obj("html_url")?).as_string()?
-    let comments_url = JsonExtractor(obj("comments_url")?).as_string()?
+    let url = json("url").as_string()?
+    let html_url = json("html_url").as_string()?
+    let comments_url = json("comments_url").as_string()?
 
     PullRequest(creds,
       number,
diff --git a/github_rest_api/pull_request_base.pony b/github_rest_api/pull_request_base.pony
index 3427831..3fe8b70 100644
--- a/github_rest_api/pull_request_base.pony
+++ b/github_rest_api/pull_request_base.pony
@@ -24,12 +24,11 @@ class val PullRequestBase
     repo = repo'
 
 primitive PullRequestBaseJsonConverter is req.JsonConverter[PullRequestBase]
-  fun apply(json: JsonType val, creds: req.Credentials): PullRequestBase ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let label = JsonExtractor(obj("label")?).as_string()?
-    let reference = JsonExtractor(obj("ref")?).as_string()?
-    let sha = JsonExtractor(obj("sha")?).as_string()?
-    let user = UserJsonConverter(obj("user")?, creds)?
-    let repo = RepositoryJsonConverter(obj("repo")?, creds)?
+  fun apply(json: JsonNav, creds: req.Credentials): PullRequestBase ? =>
+    let label = json("label").as_string()?
+    let reference = json("ref").as_string()?
+    let sha = json("sha").as_string()?
+    let user = UserJsonConverter(json("user"), creds)?
+    let repo = RepositoryJsonConverter(json("repo"), creds)?
 
     PullRequestBase(creds, label, reference, sha, user, repo)
diff --git a/github_rest_api/pull_request_file.pony b/github_rest_api/pull_request_file.pony
index 309afc8..eddad8c 100644
--- a/github_rest_api/pull_request_file.pony
+++ b/github_rest_api/pull_request_file.pony
@@ -59,14 +59,14 @@ primitive GetPullRequestFiles
 
 primitive PullRequestFilesJsonConverter is
   req.JsonConverter[Array[PullRequestFile] val]
-  fun apply(json: JsonType val,
+  fun apply(json: JsonNav,
     creds: req.Credentials): Array[PullRequestFile] val ?
   =>
     let files = recover trn Array[PullRequestFile] end
 
-    for i in JsonExtractor(json).as_array()?.values() do
-      let j = JsonExtractor(i).as_object()?
-      let filename = JsonExtractor(j("filename")?).as_string()?
+    for i in json.as_array()?.values() do
+      let json_i = JsonNav(i)
+      let filename = json_i("filename").as_string()?
       let file = PullRequestFile(creds, filename)
       files.push(file)
     end
diff --git a/github_rest_api/release.pony b/github_rest_api/release.pony
index 6583fab..1a1f49b 100644
--- a/github_rest_api/release.pony
+++ b/github_rest_api/release.pony
@@ -1,4 +1,3 @@
-use "collections"
 use "json"
 use "promises"
 use req = "request"
@@ -117,21 +116,20 @@ primitive CreateRelease
       p,
       ReleaseJsonConverter)
 
-    let m: Map[String, JsonType] = m.create()
-    m.update("tag_name", tag_name)
-    m.update("name", name)
-    m.update("body", body)
+    var obj = JsonObject
+      .update("tag_name", tag_name)
+      .update("name", name)
+      .update("body", body)
     match target_commitish
     | let tc: String =>
-      m.update("target_commitish", tc)
+      obj = obj.update("target_commitish", tc)
     end
-    m.update("draft", draft)
-    m.update("prerelease", prerelease)
-    let json = JsonObject.from_map(m).string()
+    obj = obj.update("draft", draft).update("prerelease", prerelease)
+    let json = obj.string()
 
     try
       req.HTTPPost(creds.auth)(url,
-        json,
+        consume json,
         r,
         creds.token)?
     else
@@ -142,32 +140,31 @@ primitive CreateRelease
     p
 
 primitive ReleaseJsonConverter is req.JsonConverter[Release]
-  fun apply(json: JsonType val, creds: req.Credentials): Release ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let id = JsonExtractor(obj("id")?).as_i64()?
-    let node_id = JsonExtractor(obj("node_id")?).as_string()?
-    let author = UserJsonConverter(obj("author")?, creds)?
-    let tag_name = JsonExtractor(obj("tag_name")?).as_string()?
-    let target_commitish = JsonExtractor(obj("target_commitish")?).as_string()?
-    let name = JsonExtractor(obj("name")?).as_string()?
-    let body = JsonExtractor(obj("body")?).as_string()?
-    let draft = JsonExtractor(obj("draft")?).as_bool()?
-    let prerelease = JsonExtractor(obj("prerelease")?).as_bool()?
-    let created_at = JsonExtractor(obj("created_at")?).as_string()?
-    let published_at = JsonExtractor(obj("published_at")?).as_string()?
+  fun apply(json: JsonNav, creds: req.Credentials): Release ? =>
+    let id = json("id").as_i64()?
+    let node_id = json("node_id").as_string()?
+    let author = UserJsonConverter(json("author"), creds)?
+    let tag_name = json("tag_name").as_string()?
+    let target_commitish = json("target_commitish").as_string()?
+    let name = json("name").as_string()?
+    let body = json("body").as_string()?
+    let draft = json("draft").as_bool()?
+    let prerelease = json("prerelease").as_bool()?
+    let created_at = json("created_at").as_string()?
+    let published_at = json("published_at").as_string()?
 
     let assets = recover trn Array[Asset] end
-    for i in JsonExtractor(obj("assets")?).as_array()?.values() do
-      let a = AssetJsonConverter(i, creds)?
+    for i in json("assets").as_array()?.values() do
+      let a = AssetJsonConverter(JsonNav(i), creds)?
       assets.push(a)
     end
 
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let assets_url = JsonExtractor(obj("assets_url")?).as_string()?
-    let upload_url = JsonExtractor(obj("upload_url")?).as_string()?
-    let html_url = JsonExtractor(obj("html_url")?).as_string()?
-    let tarball_url = JsonExtractor(obj("tarball_url")?).as_string()?
-    let zipball_url = JsonExtractor(obj("zipball_url")?).as_string()?
+    let url = json("url").as_string()?
+    let assets_url = json("assets_url").as_string()?
+    let upload_url = json("upload_url").as_string()?
+    let html_url = json("html_url").as_string()?
+    let tarball_url = json("tarball_url").as_string()?
+    let zipball_url = json("zipball_url").as_string()?
 
     Release(creds,
       id,
diff --git a/github_rest_api/repository.pony b/github_rest_api/repository.pony
index ba3610e..662c7c4 100644
--- a/github_rest_api/repository.pony
+++ b/github_rest_api/repository.pony
@@ -463,99 +463,96 @@ primitive GetOrganizationRepositories
     p
 
 primitive RepositoryJsonConverter is req.JsonConverter[Repository]
-  fun apply(json: JsonType val,
+  fun apply(json: JsonNav,
     creds: req.Credentials): Repository ?
   =>
-    let obj = JsonExtractor(json).as_object()?
-    let id = JsonExtractor(obj("id")?).as_i64()?
-    let node_id = JsonExtractor(obj("node_id")?).as_string()?
-    let name = JsonExtractor(obj("name")?).as_string()?
-    let full_name = JsonExtractor(obj("full_name")?).as_string()?
-    let description = JsonExtractor(obj("description")?).as_string_or_none()?
-    let owner = UserJsonConverter(obj("owner")?, creds)?
-    let private = JsonExtractor(obj("private")?).as_bool()?
-    let fork = JsonExtractor(obj("fork")?).as_bool()?
-    let created_at = JsonExtractor(obj("created_at")?).as_string()?
-    let pushed_at = JsonExtractor(obj("pushed_at")?).as_string()?
-    let updated_at = JsonExtractor(obj("updated_at")?).as_string()?
-    let homepage = JsonExtractor(obj("homepage")?).as_string_or_none()?
-    let default_branch = JsonExtractor(obj("default_branch")?).as_string()?
+    let id = json("id").as_i64()?
+    let node_id = json("node_id").as_string()?
+    let name = json("name").as_string()?
+    let full_name = json("full_name").as_string()?
+    let description = JsonNavUtil.string_or_none(json("description"))?
+    let owner = UserJsonConverter(json("owner"), creds)?
+    let private = json("private").as_bool()?
+    let fork = json("fork").as_bool()?
+    let created_at = json("created_at").as_string()?
+    let pushed_at = json("pushed_at").as_string()?
+    let updated_at = json("updated_at").as_string()?
+    let homepage = JsonNavUtil.string_or_none(json("homepage"))?
+    let default_branch = json("default_branch").as_string()?
     let organization = try
-      UserJsonConverter(obj("organization")?, creds)?
+      UserJsonConverter(json("organization"), creds)?
     else
       None
     end
 
-    let size = JsonExtractor(obj("size")?).as_i64()?
-    let forks = JsonExtractor(obj("forks")?).as_i64()?
-    let forks_count = JsonExtractor(obj("forks_count")?).as_i64()?
+    let size = json("size").as_i64()?
+    let forks = json("forks").as_i64()?
+    let forks_count = json("forks_count").as_i64()?
     let network_count =
-      try JsonExtractor(obj("network_count")?).as_i64()? else None end
-    let open_issues = JsonExtractor(obj("open_issues")?).as_i64()?
-    let open_issues_count = JsonExtractor(obj("open_issues_count")?).as_i64()?
-    let stargazers_count = JsonExtractor(obj("stargazers_count")?).as_i64()?
+      try json("network_count").as_i64()? else None end
+    let open_issues = json("open_issues").as_i64()?
+    let open_issues_count = json("open_issues_count").as_i64()?
+    let stargazers_count = json("stargazers_count").as_i64()?
     let subscribers_count =
-      try JsonExtractor(obj("subscribers_count")?).as_i64()? else None end
-    let watchers = JsonExtractor(obj("watchers")?).as_i64()?
-    let watchers_count = JsonExtractor(obj("watchers_count")?).as_i64()?
-    let language = JsonExtractor(obj("language")?).as_string_or_none()?
+      try json("subscribers_count").as_i64()? else None end
+    let watchers = json("watchers").as_i64()?
+    let watchers_count = json("watchers_count").as_i64()?
+    let language = JsonNavUtil.string_or_none(json("language"))?
     let license = try
-      LicenseJsonConverter(obj("license")?, creds)?
+      LicenseJsonConverter(json("license"), creds)?
     else
       None
     end
 
-    let archived = JsonExtractor(obj("archived")?).as_bool()?
-    let disabled = JsonExtractor(obj("disabled")?).as_bool()?
-    let has_downloads = JsonExtractor(obj("has_downloads")?).as_bool()?
-    let has_issues = JsonExtractor(obj("has_issues")?).as_bool()?
-    let has_pages = JsonExtractor(obj("has_pages")?).as_bool()?
-    let has_projects = JsonExtractor(obj("has_projects")?).as_bool()?
-    let has_wiki = JsonExtractor(obj("has_wiki")?).as_bool()?
-
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let html_url = JsonExtractor(obj("html_url")?).as_string()?
-    let archive_url = JsonExtractor(obj("archive_url")?).as_string()?
-    let assignees_url = JsonExtractor(obj("assignees_url")?).as_string()?
-    let blobs_url = JsonExtractor(obj("blobs_url")?).as_string()?
-    let branches_url = JsonExtractor(obj("branches_url")?).as_string()?
-    let comments_url = JsonExtractor(obj("comments_url")?).as_string()?
-    let commits_url = JsonExtractor(obj("commits_url")?).as_string()?
-    let compare_url = JsonExtractor(obj("compare_url")?).as_string()?
-    let contents_url = JsonExtractor(obj("contents_url")?).as_string()?
-    let contributors_url = JsonExtractor(obj("contributors_url")?).as_string()?
-    let deployments_url = JsonExtractor(obj("deployments_url")?).as_string()?
-    let downloads_url = JsonExtractor(obj("downloads_url")?).as_string()?
-    let events_url = JsonExtractor(obj("events_url")?).as_string()?
-    let forks_url = JsonExtractor(obj("forks_url")?).as_string()?
-    let git_commits_url = JsonExtractor(obj("git_commits_url")?).as_string()?
-    let git_refs_url = JsonExtractor(obj("git_refs_url")?).as_string()?
-    let git_tags_url = JsonExtractor(obj("git_tags_url")?).as_string()?
-    let issue_comment_url =
-      JsonExtractor(obj("issue_comment_url")?).as_string()?
-    let issue_events_url = JsonExtractor(obj("issue_events_url")?).as_string()?
-    let issues_url = JsonExtractor(obj("issues_url")?).as_string()?
-    let keys_url = JsonExtractor(obj("keys_url")?).as_string()?
-    let labels_url = JsonExtractor(obj("labels_url")?).as_string()?
-    let languages_url = JsonExtractor(obj("languages_url")?).as_string()?
-    let merges_url = JsonExtractor(obj("merges_url")?).as_string()?
-    let milestones_url = JsonExtractor(obj("milestones_url")?).as_string()?
-    let notifications_url =
-      JsonExtractor(obj("notifications_url")?).as_string()?
-    let pulls_url = JsonExtractor(obj("pulls_url")?).as_string()?
-    let releases_url = JsonExtractor(obj("releases_url")?).as_string()?
-    let stargazers_url = JsonExtractor(obj("stargazers_url")?).as_string()?
-    let statuses_url = JsonExtractor(obj("statuses_url")?).as_string()?
-    let subscribers_url = JsonExtractor(obj("subscribers_url")?).as_string()?
-    let subscription_url = JsonExtractor(obj("subscription_url")?).as_string()?
-    let tags_url = JsonExtractor(obj("tags_url")?).as_string()?
-    let trees_url = JsonExtractor(obj("trees_url")?).as_string()?
-
-    let clone_url = JsonExtractor(obj("clone_url")?).as_string()?
-    let git_url = JsonExtractor(obj("git_url")?).as_string()?
-    let mirror_url = JsonExtractor(obj("mirror_url")?).as_string_or_none()?
-    let ssh_url = JsonExtractor(obj("ssh_url")?).as_string()?
-    let svn_url = JsonExtractor(obj("svn_url")?).as_string()?
+    let archived = json("archived").as_bool()?
+    let disabled = json("disabled").as_bool()?
+    let has_downloads = json("has_downloads").as_bool()?
+    let has_issues = json("has_issues").as_bool()?
+    let has_pages = json("has_pages").as_bool()?
+    let has_projects = json("has_projects").as_bool()?
+    let has_wiki = json("has_wiki").as_bool()?
+
+    let url = json("url").as_string()?
+    let html_url = json("html_url").as_string()?
+    let archive_url = json("archive_url").as_string()?
+    let assignees_url = json("assignees_url").as_string()?
+    let blobs_url = json("blobs_url").as_string()?
+    let branches_url = json("branches_url").as_string()?
+    let comments_url = json("comments_url").as_string()?
+    let commits_url = json("commits_url").as_string()?
+    let compare_url = json("compare_url").as_string()?
+    let contents_url = json("contents_url").as_string()?
+    let contributors_url = json("contributors_url").as_string()?
+    let deployments_url = json("deployments_url").as_string()?
+    let downloads_url = json("downloads_url").as_string()?
+    let events_url = json("events_url").as_string()?
+    let forks_url = json("forks_url").as_string()?
+    let git_commits_url = json("git_commits_url").as_string()?
+    let git_refs_url = json("git_refs_url").as_string()?
+    let git_tags_url = json("git_tags_url").as_string()?
+    let issue_comment_url = json("issue_comment_url").as_string()?
+    let issue_events_url = json("issue_events_url").as_string()?
+    let issues_url = json("issues_url").as_string()?
+    let keys_url = json("keys_url").as_string()?
+    let labels_url = json("labels_url").as_string()?
+    let languages_url = json("languages_url").as_string()?
+    let merges_url = json("merges_url").as_string()?
+    let milestones_url = json("milestones_url").as_string()?
+    let notifications_url = json("notifications_url").as_string()?
+    let pulls_url = json("pulls_url").as_string()?
+    let releases_url = json("releases_url").as_string()?
+    let stargazers_url = json("stargazers_url").as_string()?
+    let statuses_url = json("statuses_url").as_string()?
+    let subscribers_url = json("subscribers_url").as_string()?
+    let subscription_url = json("subscription_url").as_string()?
+    let tags_url = json("tags_url").as_string()?
+    let trees_url = json("trees_url").as_string()?
+
+    let clone_url = json("clone_url").as_string()?
+    let git_url = json("git_url").as_string()?
+    let mirror_url = JsonNavUtil.string_or_none(json("mirror_url"))?
+    let ssh_url = json("ssh_url").as_string()?
+    let svn_url = json("svn_url").as_string()?
 
     Repository(creds,
       id,
diff --git a/github_rest_api/request/http.pony b/github_rest_api/request/http.pony
index 50b2cfc..5bc54f3 100644
--- a/github_rest_api/request/http.pony
+++ b/github_rest_api/request/http.pony
@@ -24,12 +24,12 @@ actor ResultReceiver[A: Any val]
     _p = p
     _converter = c
 
-  be success(json: JsonDoc val) =>
+  be success(json: JsonNav) =>
     try
-      _p(_converter(json.data, _creds)?)
+      _p(_converter(json, _creds)?)
     else
       let m = recover val
-        "Unable to convert json for " + json.string()
+        "Unable to convert json for " + JsonTypeString(json)
       end
 
       _p(RequestError(where message' = m))
diff --git a/github_rest_api/request/http_get.pony b/github_rest_api/request/http_get.pony
index 45e89fa..a093d96 100644
--- a/github_rest_api/request/http_get.pony
+++ b/github_rest_api/request/http_get.pony
@@ -29,7 +29,7 @@ class JsonRequester
     client(consume r)?
 
 interface tag JsonRequesterResultReceiver
-  be success(json: JsonDoc val)
+  be success(json: JsonNav)
   be failure(status: U16, response_body: String, message: String)
 
 class JsonRequesterHandlerFactory is HandlerFactory
@@ -96,13 +96,10 @@ class JsonRequesterHandler is HTTPHandler
     let y: String iso = String.from_iso_array(consume x)
 
     if _status == 200 then
-      try
-        let json = recover val
-          JsonDoc.>parse(consume y)?
-        end
-        _receiver.success(json)
-      else
-        _receiver.failure(_status, "", "Failed to parse response")
+      match JsonParser.parse(consume y)
+      | let json: JsonType => _receiver.success(JsonNav(json))
+      | let _: JsonParseError => _receiver.failure(_status, "",
+        "Failed to parse response")
       end
     elseif (_status != 301) and (_status != 307) then
       _receiver.failure(_status, consume y, "")
diff --git a/github_rest_api/request/http_post.pony b/github_rest_api/request/http_post.pony
index 03616bc..05b454a 100644
--- a/github_rest_api/request/http_post.pony
+++ b/github_rest_api/request/http_post.pony
@@ -4,7 +4,7 @@ use "net"
 use "ssl/net"
 
 interface tag PostResultReceiver
-  be success(json: JsonDoc val)
+  be success(json: JsonNav)
   be failure(status: U16, response_body: String, message: String)
 
 class HTTPPost
@@ -82,13 +82,10 @@ class HTTPPostHandler is HTTPHandler
     let y = String.from_iso_array(consume x)
 
     if _status == 201 then
-      try
-        let json = recover val
-          JsonDoc.>parse(consume y)?
-        end
-        _receiver.success(json)
-      else
-        _receiver.failure(_status, "", "Failed to parse response")
+      match JsonParser.parse(consume y)
+      | let json: JsonType => _receiver.success(JsonNav(json))
+      | let _: JsonParseError => _receiver.failure(_status, "",
+        "Failed to parse response")
       end
     else
       _receiver.failure(_status, consume y, "")
diff --git a/github_rest_api/request/json.pony b/github_rest_api/request/json.pony
index 7896bb5..513581e 100644
--- a/github_rest_api/request/json.pony
+++ b/github_rest_api/request/json.pony
@@ -1,6 +1,19 @@
-use "collections"
 use "json"
 use "net"
 
 interface val JsonConverter[A: Any #share]
-  fun apply(json: JsonType val, creds: Credentials): A ?
+  fun apply(json: JsonNav, creds: Credentials): A ?
+
+primitive JsonTypeString
+  """Convert a JsonNav's value to its JSON string representation for error messages."""
+  fun apply(json: JsonNav): String =>
+    match json.json()
+    | let o: JsonObject => o.string()
+    | let a: JsonArray => a.string()
+    | let s: String => s
+    | let i: I64 => i.string()
+    | let f: F64 => f.string()
+    | let b: Bool => b.string()
+    | JsonNull => "null"
+    | NotFound => "NotFound"
+    end
diff --git a/github_rest_api/search.pony b/github_rest_api/search.pony
index 744dbf1..562212e 100644
--- a/github_rest_api/search.pony
+++ b/github_rest_api/search.pony
@@ -93,17 +93,16 @@ class val PaginatedSearchJsonConverter[A: Any val]
     _creds = creds
     _converter = converter
 
-  fun apply(json: JsonType val,
+  fun apply(json: JsonNav,
     link_header: String,
     creds: req.Credentials): SearchResults[A] ?
   =>
-    let obj = JsonExtractor(json).as_object()?
-    let total_count = JsonExtractor(obj("total_count")?).as_i64()?
-    let incomplete = JsonExtractor(obj("incomplete_results")?).as_bool()?
+    let total_count = json("total_count").as_i64()?
+    let incomplete = json("incomplete_results").as_bool()?
 
     let items = recover trn Array[A] end
-    for i in JsonExtractor(obj("items")?).as_array()?.values() do
-      let item = _converter(i, creds)?
+    for i in json("items").as_array()?.values() do
+      let item = _converter(JsonNav(i), creds)?
       items.push(item)
     end
 
@@ -135,12 +134,12 @@ actor SearchResultReceiver[A: Any val]
     _p = p
     _converter = c
 
-  be success(json: JsonDoc val, link_header: String) =>
+  be success(json: JsonNav, link_header: String) =>
     try
-      _p(_converter(json.data, link_header, _creds)?)
+      _p(_converter(json, link_header, _creds)?)
     else
       let m = recover val
-        "Unable to convert json for " + json.string()
+        "Unable to convert json for " + req.JsonTypeString(json)
       end
 
       _p(req.RequestError(where message' = m))
@@ -244,13 +243,10 @@ class SearchJsonRequesterHandler[A: Any val] is HTTPHandler
     let y: String iso = String.from_iso_array(consume x)
 
     if _status == 200 then
-      try
-        let json = recover val
-          JsonDoc.>parse(consume y)?
-        end
-        _receiver.success(json, _link_header)
-      else
-        _receiver.failure(_status, "", "Failed to parse response")
+      match JsonParser.parse(consume y)
+      | let json: JsonType => _receiver.success(JsonNav(json), _link_header)
+      | let _: JsonParseError => _receiver.failure(_status, "",
+        "Failed to parse response")
       end
     elseif (_status != 301) and (_status != 307) then
       _receiver.failure(_status, consume y, "")
diff --git a/github_rest_api/user.pony b/github_rest_api/user.pony
index 50f0ccc..9e649da 100644
--- a/github_rest_api/user.pony
+++ b/github_rest_api/user.pony
@@ -63,29 +63,25 @@ class val User
     site_admin = site_admin'
 
 primitive UserJsonConverter is req.JsonConverter[User]
-  fun apply(json: JsonType val, creds: req.Credentials): User ? =>
-    let obj = JsonExtractor(json).as_object()?
-    let login = JsonExtractor(obj("login")?).as_string()?
-    let id = JsonExtractor(obj("id")?).as_i64()?
-    let node_id = JsonExtractor(obj("node_id")?).as_string()?
-    let avatar_url = JsonExtractor(obj("avatar_url")?).as_string()?
-    let gravatar_id = JsonExtractor(obj("gravatar_id")?).as_string()?
-    let url = JsonExtractor(obj("url")?).as_string()?
-    let html_url = JsonExtractor(obj("html_url")?).as_string()?
-    let followers_url = JsonExtractor(obj("followers_url")?).as_string()?
-    let following_url = JsonExtractor(obj("following_url")?).as_string()?
-    let gists_url = JsonExtractor(obj("gists_url")?).as_string()?
-    let starred_url = JsonExtractor(obj("starred_url")?).as_string()?
-    let subscriptions_url =
-      JsonExtractor(obj("subscriptions_url")?).as_string()?
-    let organizations_url =
-      JsonExtractor(obj("organizations_url")?).as_string()?
-    let repos_url = JsonExtractor(obj("repos_url")?).as_string()?
-    let events_url = JsonExtractor(obj("events_url")?).as_string()?
-    let received_events_url =
-      JsonExtractor(obj("received_events_url")?).as_string()?
-    let user_type = JsonExtractor(obj("type")?).as_string()?
-    let site_admin = JsonExtractor(obj("site_admin")?).as_bool()?
+  fun apply(json: JsonNav, creds: req.Credentials): User ? =>
+    let login = json("login").as_string()?
+    let id = json("id").as_i64()?
+    let node_id = json("node_id").as_string()?
+    let avatar_url = json("avatar_url").as_string()?
+    let gravatar_id = json("gravatar_id").as_string()?
+    let url = json("url").as_string()?
+    let html_url = json("html_url").as_string()?
+    let followers_url = json("followers_url").as_string()?
+    let following_url = json("following_url").as_string()?
+    let gists_url = json("gists_url").as_string()?
+    let starred_url = json("starred_url").as_string()?
+    let subscriptions_url = json("subscriptions_url").as_string()?
+    let organizations_url = json("organizations_url").as_string()?
+    let repos_url = json("repos_url").as_string()?
+    let events_url = json("events_url").as_string()?
+    let received_events_url = json("received_events_url").as_string()?
+    let user_type = json("type").as_string()?
+    let site_admin = json("site_admin").as_bool()?
 
     User(creds,
       login,