diff --git a/CHANGELOG.md b/CHANGELOG.md
index 79383e1..51f310e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.4.0] - 2026-08-28
+
+### Added
+
+- `devpub upload --json` prints a machine-readable result object (`uploaded` /
+  `failed` arrays) to stdout for scripting; human output goes to stderr and the
+  command exits non-zero if any file failed. Mutually exclusive with `--markdown`.
+
+### Fixed
+
+- `devpub push` now sends `tags` as an array. It was joining them into a
+  comma-separated string, which Dev.to accepts but silently drops, publishing
+  articles with no tags.
+
 ## [0.3.0] - 2026-08-27
 
 ### Added
diff --git a/pyproject.toml b/pyproject.toml
index cd5da55..ac311fb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "devpub"
-version = "0.3.0"
+version = "0.4.0"
 description = "Write in your editor. Publish to Dev.to. Track what works."
 readme = "README.md"
 license = {text = "MIT"}
diff --git a/src/devpub/__init__.py b/src/devpub/__init__.py
index a87bbdb..4207a1f 100644
--- a/src/devpub/__init__.py
+++ b/src/devpub/__init__.py
@@ -1,3 +1,3 @@
 """devpub - Write in your editor. Publish to Dev.to. Track what works."""
 
-__version__ = "0.3.0"
+__version__ = "0.4.0"
diff --git a/src/devpub/cli/__init__.py b/src/devpub/cli/__init__.py
index ab9db9e..cca5106 100644
--- a/src/devpub/cli/__init__.py
+++ b/src/devpub/cli/__init__.py
@@ -67,7 +67,10 @@ def pull(pull_all, folder):
 @click.option(
     "--markdown", "-m", is_flag=True, help="Print Markdown image tags instead of a table."
 )
-def upload(files, markdown):
+@click.option(
+    "--json", "as_json", is_flag=True, help="Print a JSON result object (for scripting)."
+)
+def upload(files, markdown, as_json):
     """Upload images to Dev.to and get their URLs.
 
     \b
@@ -76,9 +79,12 @@ def upload(files, markdown):
     DEVPUB_SESSION_COOKIE and DEVPUB_CSRF_TOKEN rather than your API key --
     run it once without them for instructions on where to find them.
     """
+    if markdown and as_json:
+        raise click.UsageError("--markdown and --json are mutually exclusive.")
+
     from devpub.cli.images import upload_images
 
-    upload_images(files=files, markdown=markdown)
+    upload_images(files=files, markdown=markdown, as_json=as_json)
 
 
 @cli.command()
diff --git a/src/devpub/cli/images.py b/src/devpub/cli/images.py
index f336188..f15b3f3 100644
--- a/src/devpub/cli/images.py
+++ b/src/devpub/cli/images.py
@@ -1,5 +1,7 @@
 """Image upload commands for devpub."""
 
+import json
+import sys
 from pathlib import Path
 
 from rich.console import Console
@@ -10,18 +12,23 @@
 from devpub.core.config import ensure_session_credentials
 
 
-def upload_images(files: tuple, markdown: bool = False):
+def upload_images(files: tuple, markdown: bool = False, as_json: bool = False):
     """Upload image files to Dev.to and print their public URLs.
 
     Args:
         files: Paths to upload, in the order given.
         markdown: Print ready-to-paste Markdown instead of a table.
+        as_json: Print a machine-readable JSON result to stdout (for scripting).
+
+    Exits non-zero if any file failed to upload.
     """
     console = Console()
+    # In --json mode, keep stdout pure JSON; send all human output to stderr.
+    log = Console(stderr=True) if as_json else console
 
     if not files:
-        console.print("[yellow]No files given.[/]")
-        console.print("  Example: [cyan]devpub upload cover.png diagram.png[/]")
+        log.print("[yellow]No files given.[/]")
+        log.print("  Example: [cyan]devpub upload cover.png diagram.png[/]")
         return
 
     session_cookie, csrf_token = ensure_session_credentials()
@@ -36,11 +43,28 @@ def upload_images(files: tuple, markdown: bool = False):
                 url = uploader.upload(path)
             except APIError as e:
                 failed.append((path, e.message))
-                console.print(f"  [red]Failed:[/] {path.name} -- {e.message}")
+                log.print(f"  [red]Failed:[/] {path.name} -- {e.message}")
                 continue
             uploaded.append((path, url))
-            console.print(f"  [green]Uploaded:[/] {path.name}")
+            log.print(f"  [green]Uploaded:[/] {path.name}")
+
+    if as_json:
+        print(json.dumps(_json_result(uploaded, failed), indent=2))
+    else:
+        _print_human(console, uploaded, failed, markdown=markdown)
+
+    if failed:
+        sys.exit(1)
+
+
+def _json_result(uploaded, failed) -> dict:
+    return {
+        "uploaded": [{"file": p.name, "path": str(p), "url": url} for p, url in uploaded],
+        "failed": [{"file": p.name, "path": str(p), "error": err} for p, err in failed],
+    }
+
 
+def _print_human(console: Console, uploaded, failed, markdown: bool):
     if uploaded:
         if markdown:
             console.print()
@@ -56,6 +80,4 @@ def upload_images(files: tuple, markdown: bool = False):
             console.print()
             console.print(table)
 
-    console.print(
-        f"\n[dim]Done. {len(uploaded)} uploaded, {len(failed)} failed.[/]"
-    )
+    console.print(f"\n[dim]Done. {len(uploaded)} uploaded, {len(failed)} failed.[/]")
diff --git a/src/devpub/core/article.py b/src/devpub/core/article.py
index 38845c7..4ed46cc 100644
--- a/src/devpub/core/article.py
+++ b/src/devpub/core/article.py
@@ -221,9 +221,11 @@ def article_to_api_payload(article: dict) -> dict:
         "published": article["published"],
     }
 
-    if article.get("tags"):
-        tags = article["tags"]
-        payload["tags"] = tags if isinstance(tags, str) else ", ".join(tags)
+    tags = _parse_tags(article.get("tags"))
+    if tags:
+        # Dev.to expects an array of tags; a comma-joined string is accepted
+        # by the API but silently produces an empty tag_list on the article.
+        payload["tags"] = tags
     if article.get("description"):
         payload["description"] = article["description"]
     if article.get("series"):
diff --git a/tests/test_articles.py b/tests/test_articles.py
index df6e083..db49b66 100644
--- a/tests/test_articles.py
+++ b/tests/test_articles.py
@@ -117,7 +117,7 @@ def test_full_article(self):
         payload = article_to_api_payload(article)
         assert payload["title"] == "Full Post"
         assert payload["published"] is True
-        assert payload["tags"] == "python, tutorial"
+        assert payload["tags"] == ["python", "tutorial"]
         assert payload["description"] == "A full article"
         assert payload["series"] == "My Series"
         assert payload["canonical_url"] == "https://myblog.com/post"
@@ -125,6 +125,34 @@ def test_full_article(self):
         assert payload["organization_id"] == 42
 
 
+class TestPayloadTags:
+    """Dev.to expects `tags` as an array; a comma-joined string is silently
+    dropped, leaving the published article with no tags."""
+
+    def test_list_is_sent_as_array(self):
+        payload = article_to_api_payload(
+            {"title": "T", "body": "B", "published": False, "tags": ["a", "b"]}
+        )
+        assert payload["tags"] == ["a", "b"]
+
+    def test_comma_string_is_split_into_array(self):
+        payload = article_to_api_payload(
+            {"title": "T", "body": "B", "published": False, "tags": "python, tutorial"}
+        )
+        assert payload["tags"] == ["python", "tutorial"]
+
+    def test_empty_tags_are_omitted(self):
+        for empty in ([], "", "  ", None):
+            payload = article_to_api_payload(
+                {"title": "T", "body": "B", "published": False, "tags": empty}
+            )
+            assert "tags" not in payload
+
+    def test_no_tags_key_is_omitted(self):
+        payload = article_to_api_payload({"title": "T", "body": "B", "published": False})
+        assert "tags" not in payload
+
+
 class TestCreateArticle:
     def test_create_default(self, tmp_path, monkeypatch):
         monkeypatch.chdir(tmp_path)
diff --git a/tests/test_cli_upload.py b/tests/test_cli_upload.py
new file mode 100644
index 0000000..d09c8e2
--- /dev/null
+++ b/tests/test_cli_upload.py
@@ -0,0 +1,80 @@
+"""CLI-level tests for `devpub upload`, focused on output modes."""
+
+import json
+
+import pytest
+from click.testing import CliRunner
+
+from devpub.cli import cli
+
+
+@pytest.fixture(autouse=True)
+def _fake_session(monkeypatch):
+    """Bypass the real credential lookup so the command can run offline.
+
+    Patched on the images module, where the name is actually resolved.
+    """
+    import devpub.cli.images as images_mod
+
+    monkeypatch.setattr(
+        images_mod, "ensure_session_credentials", lambda: ("session", "csrf")
+    )
+
+
+def _stub_uploads(monkeypatch, results):
+    """Make ImageUploader.upload return a URL per filename, or raise for errors.
+
+    `results` maps a filename to either a URL string or an Exception to raise.
+    """
+    from pathlib import Path
+
+    def fake_upload(self, path):
+        outcome = results[Path(path).name]
+        if isinstance(outcome, Exception):
+            raise outcome
+        return outcome
+
+    monkeypatch.setattr("devpub.api.uploads.ImageUploader.upload", fake_upload)
+
+
+def test_json_output_is_pure_json_on_stdout(monkeypatch):
+    _stub_uploads(monkeypatch, {"a.png": "https://img/a.png", "b.png": "https://img/b.png"})
+    runner = CliRunner()
+    result = runner.invoke(cli, ["upload", "a.png", "b.png", "--json"])
+
+    assert result.exit_code == 0
+    payload = json.loads(result.stdout)  # must parse cleanly -> no rich noise
+    assert [u["file"] for u in payload["uploaded"]] == ["a.png", "b.png"]
+    assert payload["uploaded"][0]["url"] == "https://img/a.png"
+    assert payload["failed"] == []
+
+
+def test_json_reports_failures_and_exits_nonzero(monkeypatch):
+    from devpub.api.devto import APIError
+
+    _stub_uploads(
+        monkeypatch,
+        {"ok.png": "https://img/ok.png", "bad.png": APIError(422, "nope")},
+    )
+    runner = CliRunner()
+    result = runner.invoke(cli, ["upload", "ok.png", "bad.png", "--json"])
+
+    assert result.exit_code == 1
+    payload = json.loads(result.stdout)
+    assert [u["file"] for u in payload["uploaded"]] == ["ok.png"]
+    assert payload["failed"][0]["file"] == "bad.png"
+    assert payload["failed"][0]["error"] == "nope"
+
+
+def test_markdown_and_json_are_mutually_exclusive():
+    runner = CliRunner()
+    result = runner.invoke(cli, ["upload", "a.png", "--markdown", "--json"])
+    assert result.exit_code != 0
+    assert "mutually exclusive" in result.output
+
+
+def test_all_success_exits_zero(monkeypatch):
+    _stub_uploads(monkeypatch, {"a.png": "https://img/a.png"})
+    runner = CliRunner()
+    result = runner.invoke(cli, ["upload", "a.png", "--json"])
+    assert result.exit_code == 0