diff --git a/tests/test_qa_progress.py b/tests/test_qa_progress.py
new file mode 100644
index 0000000..1d5fde2
--- /dev/null
+++ b/tests/test_qa_progress.py
@@ -0,0 +1,226 @@
+"""Tests for ``arborist.qa.progress`` — stage-level state-machine
+emitter for ``arborist query``.
+
+Module was zero-coverage. 85 LOC of pure stdlib emitter +
+env/TTY/cli-override resolution. Surface:
+
+  - Progress.emit (formatting, key=value tail, stream redirect)
+  - disabled() singleton (true no-op, no formatting cost)
+  - from_env(cli_override=...) precedence resolution
+  - ARBORIST_PROGRESS env var (multiple truthy/falsy spellings)
+  - TTY auto-detect fallback
+"""
+
+from __future__ import annotations
+
+import io
+import time
+
+import pytest
+
+from arborist.qa.progress import Progress, disabled, from_env
+
+
+# --- Progress.emit --------------------------------------------------
+
+
+def test_progress_emit_writes_to_stream():
+    buf = io.StringIO()
+    p = Progress(enabled=True, t_start=time.monotonic(), stream=buf)
+    p.emit("stage.name", k="v")
+    out = buf.getvalue()
+    assert "stage.name" in out
+    assert "k=v" in out
+    assert "arborist" in out  # prefix
+
+
+def test_progress_emit_disabled_writes_nothing():
+    """`enabled=False` is a true no-op — no string formatting,
+    no stream write."""
+    buf = io.StringIO()
+    p = Progress(enabled=False, t_start=time.monotonic(), stream=buf)
+    p.emit("stage", a=1)
+    assert buf.getvalue() == ""
+
+
+def test_progress_emit_no_kv_writes_bare_prefix():
+    """emit('stage') with no kwargs → just the timestamp + stage."""
+    buf = io.StringIO()
+    p = Progress(enabled=True, t_start=time.monotonic(), stream=buf)
+    p.emit("stage.bare")
+    out = buf.getvalue()
+    assert "stage.bare" in out
+    assert "=" not in out  # no key=value tail
+
+
+def test_progress_emit_includes_elapsed_seconds():
+    """Elapsed is wall-clock since t_start. Format `NN.NNs`."""
+    t0 = time.monotonic() - 1.5  # pretend started 1.5s ago
+    buf = io.StringIO()
+    p = Progress(enabled=True, t_start=t0, stream=buf)
+    p.emit("now")
+    out = buf.getvalue()
+    # Format includes "1.5" or higher; exact value drifts but the
+    # decimal format is fixed at 6.2f.
+    assert "s]" in out  # closing bracket on elapsed
+    # Token before "s]" should parse as a positive float.
+    head = out.split("s]")[0]
+    elapsed_str = head.split()[-1]
+    assert float(elapsed_str) >= 1.5
+
+
+def test_progress_emit_multiple_kv_pairs_space_separated():
+    buf = io.StringIO()
+    p = Progress(enabled=True, t_start=time.monotonic(), stream=buf)
+    p.emit("multi", a=1, b="two", c=3.14)
+    out = buf.getvalue()
+    assert "a=1" in out
+    assert "b=two" in out
+    assert "c=3.14" in out
+
+
+def test_progress_emit_default_stream_is_stderr(capsys):
+    """When stream kwarg is None, default is sys.stderr."""
+    p = Progress(enabled=True, t_start=time.monotonic(), stream=None)
+    p.emit("default-stream")
+    captured = capsys.readouterr()
+    assert captured.out == ""
+    assert "default-stream" in captured.err
+
+
+def test_progress_emit_default_t_start_is_now():
+    """If t_start kwarg is None, defaults to monotonic() at
+    construction. Elapsed at first emit() should be ~0."""
+    buf = io.StringIO()
+    p = Progress(enabled=True, t_start=None, stream=buf)
+    p.emit("right-after-init")
+    out = buf.getvalue()
+    elapsed_str = out.split("s]")[0].split()[-1]
+    assert float(elapsed_str) < 0.1  # virtually no time elapsed
+
+
+# --- disabled() singleton -------------------------------------------
+
+
+def test_disabled_returns_singleton():
+    """disabled() returns the same Progress instance on every call.
+    Suitable as a default kwarg value with no allocation."""
+    a = disabled()
+    b = disabled()
+    assert a is b
+    assert a.enabled is False
+
+
+def test_disabled_emits_nothing():
+    p = disabled()
+    # disabled() singleton has no test-injectable stream; emit must
+    # still no-op without raising.
+    p.emit("stage", k="v")
+    # No assertion — just confirming no exception path.
+
+
+# --- from_env precedence --------------------------------------------
+
+
+def test_from_env_cli_override_on(monkeypatch):
+    """cli_override='on' wins over env + TTY."""
+    monkeypatch.setenv("ARBORIST_PROGRESS", "0")
+    p = from_env(cli_override="on")
+    assert p.enabled is True
+
+
+def test_from_env_cli_override_off(monkeypatch):
+    """cli_override='off' wins over env."""
+    monkeypatch.setenv("ARBORIST_PROGRESS", "1")
+    p = from_env(cli_override="off")
+    assert p.enabled is False
+
+
+@pytest.mark.parametrize("env_value", ["1", "true", "on", "yes",
+                                        "TRUE", "On", "YES"])
+def test_from_env_truthy_env_enables(monkeypatch, env_value):
+    """ARBORIST_PROGRESS in {1, true, on, yes} (case-insensitive)
+    → enabled=True."""
+    monkeypatch.setenv("ARBORIST_PROGRESS", env_value)
+    p = from_env()
+    assert p.enabled is True
+
+
+@pytest.mark.parametrize("env_value", ["0", "false", "off", "no",
+                                        "FALSE", "Off", "NO"])
+def test_from_env_falsy_env_disables(monkeypatch, env_value):
+    monkeypatch.setenv("ARBORIST_PROGRESS", env_value)
+    p = from_env()
+    assert p.enabled is False
+
+
+def test_from_env_unknown_env_falls_through_to_tty(monkeypatch):
+    """ARBORIST_PROGRESS=garbage → fall through to TTY auto-detect."""
+    monkeypatch.setenv("ARBORIST_PROGRESS", "maybe")
+    # Force stderr to be non-TTY (we're in a test, so usually it is).
+    class _NonTTY:
+        def isatty(self):
+            return False
+    monkeypatch.setattr("arborist.qa.progress.sys.stderr", _NonTTY())
+    p = from_env()
+    assert p.enabled is False
+
+
+def test_from_env_unset_env_falls_through_to_tty(monkeypatch):
+    """No ARBORIST_PROGRESS in env → TTY detect."""
+    monkeypatch.delenv("ARBORIST_PROGRESS", raising=False)
+    class _IsATTY:
+        def isatty(self):
+            return True
+    monkeypatch.setattr("arborist.qa.progress.sys.stderr", _IsATTY())
+    p = from_env()
+    assert p.enabled is True
+
+
+def test_from_env_isatty_attribute_error_disables(monkeypatch):
+    """If sys.stderr lacks .isatty (replaced with a buffer), the
+    fallback is enabled=False (fail-closed)."""
+    monkeypatch.delenv("ARBORIST_PROGRESS", raising=False)
+
+    class _NoIsATTY:
+        pass
+
+    monkeypatch.setattr("arborist.qa.progress.sys.stderr", _NoIsATTY())
+    p = from_env()
+    assert p.enabled is False
+
+
+def test_from_env_returns_fresh_instance(monkeypatch):
+    """Each from_env() call returns a new Progress with a fresh
+    t_start; never shares state with prior calls."""
+    monkeypatch.setenv("ARBORIST_PROGRESS", "1")
+    a = from_env()
+    time.sleep(0.001)
+    b = from_env()
+    assert a is not b
+    assert b.t_start >= a.t_start
+
+
+# --- empty-string env -----------------------------------------------
+
+
+def test_from_env_empty_string_falls_through(monkeypatch):
+    """ARBORIST_PROGRESS='' (empty) → fall through to TTY."""
+    monkeypatch.setenv("ARBORIST_PROGRESS", "")
+    class _NonTTY:
+        def isatty(self):
+            return False
+    monkeypatch.setattr("arborist.qa.progress.sys.stderr", _NonTTY())
+    p = from_env()
+    assert p.enabled is False
+
+
+def test_from_env_whitespace_env_falls_through(monkeypatch):
+    """ARBORIST_PROGRESS='  ' (whitespace) → strip → empty → TTY."""
+    monkeypatch.setenv("ARBORIST_PROGRESS", "   ")
+    class _IsATTY:
+        def isatty(self):
+            return True
+    monkeypatch.setattr("arborist.qa.progress.sys.stderr", _IsATTY())
+    p = from_env()
+    assert p.enabled is True