diff --git a/acceptance/localenv/constraints-only/out.test.toml b/acceptance/localenv/constraints-only/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/constraints-only/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/constraints-only/output.txt b/acceptance/localenv/constraints-only/output.txt
new file mode 100644
index 0000000000..d2f12be5db
--- /dev/null
+++ b/acceptance/localenv/constraints-only/output.txt
@@ -0,0 +1,53 @@
+
+>>> [CLI] local-env python sync --serverless v4 --constraints-only --check --output json
+{
+  "schemaVersion": 1,
+  "command": "local-env python sync",
+  "ok": true,
+  "mode": "constraints-only",
+  "dryRun": true,
+  "target": {
+    "source": "serverless",
+    "serverlessVersion": "v4",
+    "envKey": "serverless/serverless-v4"
+  },
+  "resolved": {
+    "pythonVersion": "3.12",
+    "artifactSource": "network"
+  },
+  "greenfield": true,
+  "plan": {
+    "wouldWrite": "[TEST_TMP_DIR]/pyproject.toml",
+    "wouldInstallPython": "3.12",
+    "diff": "--- pyproject.toml\n+++ pyproject.toml\n@@ -1 +1,15 @@\n+[project]\n+name = \"001\"\n+version = \"0.0.0\"\n+requires-python = \"\u003e=3.12\"\n+\n+[dependency-groups]\n+dev = []\n+\n+# managed by databricks local-env python sync — do not edit\n+[tool.uv]\n+constraint-dependencies = [\n+    \"pyarrow\u003c19\",\n+    \"pandas\u003c3\",\n+]\n+# end managed by databricks local-env python sync\n"
+  },
+  "phases": [
+    {
+      "phase": "preflight",
+      "status": "ok"
+    },
+    {
+      "phase": "resolve",
+      "status": "ok"
+    },
+    {
+      "phase": "fetch",
+      "status": "ok"
+    },
+    {
+      "phase": "merge",
+      "status": "ok"
+    },
+    {
+      "phase": "provision",
+      "status": "ok"
+    },
+    {
+      "phase": "validate",
+      "status": "ok"
+    }
+  ],
+  "warnings": [],
+  "error": null,
+  "durationMs": 0
+}
diff --git a/acceptance/localenv/constraints-only/script b/acceptance/localenv/constraints-only/script
new file mode 100644
index 0000000000..354eac4996
--- /dev/null
+++ b/acceptance/localenv/constraints-only/script
@@ -0,0 +1 @@
+trace $CLI local-env python sync --serverless v4 --constraints-only --check --output json
diff --git a/acceptance/localenv/constraints-only/test.toml b/acceptance/localenv/constraints-only/test.toml
new file mode 100644
index 0000000000..e2b12fc95b
--- /dev/null
+++ b/acceptance/localenv/constraints-only/test.toml
@@ -0,0 +1,21 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
+
+[Env]
+DATABRICKS_LOCALENV_CONSTRAINT_SOURCE = "$DATABRICKS_HOST"
+
+[[Server]]
+Pattern = "GET /serverless/serverless-v4/pyproject.toml"
+Response.Body = '''
+[project]
+requires-python = ">=3.12"
+
+[dependency-groups]
+dev = ["databricks-connect~=17.2.0"]
+
+[tool.uv]
+constraint-dependencies = ["pyarrow<19", "pandas<3"]
+'''
+
+[[Repls]]
+Old = 'uv uv \S+(?: \([^)]+\))?'
+New = 'uv [UV_VERSION]'
diff --git a/acceptance/localenv/env-unsupported/out.test.toml b/acceptance/localenv/env-unsupported/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/env-unsupported/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/env-unsupported/output.txt b/acceptance/localenv/env-unsupported/output.txt
new file mode 100644
index 0000000000..39e540600d
--- /dev/null
+++ b/acceptance/localenv/env-unsupported/output.txt
@@ -0,0 +1,8 @@
+preflight  ok  check
+resolve    ok  source=cluster envKey=dbr/15.4.x-scala2.12
+fetch      error  no published environment for "dbr/15.4.x-scala2.12". If this is a new runtime, try the latest LTS target (e.g. --serverless v4 or a supported --cluster DBR): GET [DATABRICKS_URL]/dbr/15.4.x-scala2.12/pyproject.toml: environment key not found
+merge      pending
+provision  pending
+validate   pending
+For more detail, re-run with --debug, or --output json to share a structured report.
+Error: no published environment for "dbr/15.4.x-scala2.12". If this is a new runtime, try the latest LTS target (e.g. --serverless v4 or a supported --cluster DBR): GET [DATABRICKS_URL]/dbr/15.4.x-scala2.12/pyproject.toml: environment key not found
diff --git a/acceptance/localenv/env-unsupported/script b/acceptance/localenv/env-unsupported/script
new file mode 100644
index 0000000000..924f04b9d9
--- /dev/null
+++ b/acceptance/localenv/env-unsupported/script
@@ -0,0 +1 @@
+musterr $CLI local-env python sync --cluster test-cluster-id --check
diff --git a/acceptance/localenv/env-unsupported/test.toml b/acceptance/localenv/env-unsupported/test.toml
new file mode 100644
index 0000000000..7823db924d
--- /dev/null
+++ b/acceptance/localenv/env-unsupported/test.toml
@@ -0,0 +1,22 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
+
+[Env]
+DATABRICKS_LOCALENV_CONSTRAINT_SOURCE = "$DATABRICKS_HOST"
+
+[[Server]]
+Pattern = "GET /api/2.1/clusters/get"
+Response.Body = '''
+{
+  "cluster_id": "test-cluster-id",
+  "spark_version": "15.4.x-scala2.12"
+}
+'''
+
+[[Server]]
+Pattern = "GET /dbr/15.4.x-scala2.12/pyproject.toml"
+Response.StatusCode = 404
+Response.Body = '{"message": "Not found"}'
+
+[[Repls]]
+Old = 'uv uv \S+(?: \([^)]+\))?'
+New = 'uv [UV_VERSION]'
diff --git a/acceptance/localenv/flag-conflict/out.test.toml b/acceptance/localenv/flag-conflict/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/flag-conflict/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/flag-conflict/output.txt b/acceptance/localenv/flag-conflict/output.txt
new file mode 100644
index 0000000000..141152ae1c
--- /dev/null
+++ b/acceptance/localenv/flag-conflict/output.txt
@@ -0,0 +1 @@
+Error: if any flags in the group [cluster serverless job] are set none of the others can be; [cluster serverless] were all set
diff --git a/acceptance/localenv/flag-conflict/script b/acceptance/localenv/flag-conflict/script
new file mode 100644
index 0000000000..3309cd5220
--- /dev/null
+++ b/acceptance/localenv/flag-conflict/script
@@ -0,0 +1 @@
+musterr $CLI local-env python sync --cluster abc --serverless v4
diff --git a/acceptance/localenv/flag-conflict/test.toml b/acceptance/localenv/flag-conflict/test.toml
new file mode 100644
index 0000000000..c63fe3fe10
--- /dev/null
+++ b/acceptance/localenv/flag-conflict/test.toml
@@ -0,0 +1 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/help/out.test.toml b/acceptance/localenv/help/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/help/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/help/output.txt b/acceptance/localenv/help/output.txt
new file mode 100644
index 0000000000..03fffb2be7
--- /dev/null
+++ b/acceptance/localenv/help/output.txt
@@ -0,0 +1,43 @@
+Manage the local Python environment matched to a Databricks compute target.
+
+Usage:
+  databricks local-env python [flags]
+  databricks local-env python [command]
+
+Available Commands:
+  sync        Provision a local Python environment matched to a Databricks compute target
+
+Flags:
+  -h, --help   help for python
+
+Global Flags:
+      --debug            enable debug logging
+  -o, --output type      output type: text or json (default text)
+  -p, --profile string   ~/.databrickscfg profile
+  -t, --target string    bundle target to use (if applicable)
+
+Use "databricks local-env python [command] --help" for more information about a command.
+Provision (or update) a local Python environment matched to a Databricks compute target.
+
+Resolves the target to an environment key, fetches the pinned Python version,
+databricks-connect version, and dependency constraints published for that key,
+then provisions a matched .venv with uv. A project with no pyproject.toml is
+initialized from scratch; an existing pyproject.toml is merged in place (its
+env-owned sections are refreshed, user-owned content is preserved).
+
+Usage:
+  databricks local-env python sync [flags]
+
+Flags:
+      --check               compute the plan without writing files or provisioning
+      --cluster string      cluster ID to use as the compute target
+      --constraints-only    apply the Python version and constraints without adding the databricks-connect dependency
+  -h, --help                help for sync
+      --job string          job ID to use as the compute target
+      --serverless string   serverless version to use as the compute target (e.g. v4)
+
+Global Flags:
+      --debug            enable debug logging
+  -o, --output type      output type: text or json (default text)
+  -p, --profile string   ~/.databrickscfg profile
+  -t, --target string    bundle target to use (if applicable)
diff --git a/acceptance/localenv/help/script b/acceptance/localenv/help/script
new file mode 100644
index 0000000000..cca1e85aad
--- /dev/null
+++ b/acceptance/localenv/help/script
@@ -0,0 +1,2 @@
+$CLI local-env python --help
+$CLI local-env python sync --help
diff --git a/acceptance/localenv/help/test.toml b/acceptance/localenv/help/test.toml
new file mode 100644
index 0000000000..c63fe3fe10
--- /dev/null
+++ b/acceptance/localenv/help/test.toml
@@ -0,0 +1 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/json-error/out.test.toml b/acceptance/localenv/json-error/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/json-error/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/json-error/output.txt b/acceptance/localenv/json-error/output.txt
new file mode 100644
index 0000000000..e76a8f7479
--- /dev/null
+++ b/acceptance/localenv/json-error/output.txt
@@ -0,0 +1,42 @@
+{
+  "schemaVersion": 1,
+  "command": "local-env python sync",
+  "ok": false,
+  "mode": "default",
+  "dryRun": false,
+  "greenfield": false,
+  "phases": [
+    {
+      "phase": "preflight",
+      "status": "ok"
+    },
+    {
+      "phase": "resolve",
+      "status": "error"
+    },
+    {
+      "phase": "fetch",
+      "status": "pending"
+    },
+    {
+      "phase": "merge",
+      "status": "pending"
+    },
+    {
+      "phase": "provision",
+      "status": "pending"
+    },
+    {
+      "phase": "validate",
+      "status": "pending"
+    }
+  ],
+  "warnings": [],
+  "error": {
+    "code": "E_NO_TARGET",
+    "failurePhase": "resolve",
+    "message": "No compute target is selected. Select a cluster or serverless target, or pass --cluster / --serverless / --job",
+    "diskMutated": false
+  },
+  "durationMs": 0
+}
diff --git a/acceptance/localenv/json-error/script b/acceptance/localenv/json-error/script
new file mode 100644
index 0000000000..bffcc264af
--- /dev/null
+++ b/acceptance/localenv/json-error/script
@@ -0,0 +1 @@
+musterr $CLI local-env python sync --output json
diff --git a/acceptance/localenv/json-error/test.toml b/acceptance/localenv/json-error/test.toml
new file mode 100644
index 0000000000..0d0481fb83
--- /dev/null
+++ b/acceptance/localenv/json-error/test.toml
@@ -0,0 +1,5 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
+
+[[Repls]]
+Old = 'uv uv \S+(?: \([^)]+\))?'
+New = 'uv [UV_VERSION]'
diff --git a/acceptance/localenv/manager-unsupported/environment.yml b/acceptance/localenv/manager-unsupported/environment.yml
new file mode 100644
index 0000000000..d5364e4706
--- /dev/null
+++ b/acceptance/localenv/manager-unsupported/environment.yml
@@ -0,0 +1,3 @@
+name: demo
+dependencies:
+  - python=3.10
diff --git a/acceptance/localenv/manager-unsupported/out.test.toml b/acceptance/localenv/manager-unsupported/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/manager-unsupported/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/manager-unsupported/output.txt b/acceptance/localenv/manager-unsupported/output.txt
new file mode 100644
index 0000000000..4a5b3b2c08
--- /dev/null
+++ b/acceptance/localenv/manager-unsupported/output.txt
@@ -0,0 +1,8 @@
+preflight  error  detected a conda project; automated setup for conda is not yet available (P1). Use a uv project (add a pyproject.toml with a [tool.uv] table, or run `uv init`) to provision automatically
+resolve    pending
+fetch      pending
+merge      pending
+provision  pending
+validate   pending
+For more detail, re-run with --debug, or --output json to share a structured report.
+Error: detected a conda project; automated setup for conda is not yet available (P1). Use a uv project (add a pyproject.toml with a [tool.uv] table, or run `uv init`) to provision automatically
diff --git a/acceptance/localenv/manager-unsupported/script b/acceptance/localenv/manager-unsupported/script
new file mode 100644
index 0000000000..aae187d00c
--- /dev/null
+++ b/acceptance/localenv/manager-unsupported/script
@@ -0,0 +1 @@
+musterr $CLI local-env python sync --serverless v4 --check
diff --git a/acceptance/localenv/manager-unsupported/test.toml b/acceptance/localenv/manager-unsupported/test.toml
new file mode 100644
index 0000000000..0d0481fb83
--- /dev/null
+++ b/acceptance/localenv/manager-unsupported/test.toml
@@ -0,0 +1,5 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
+
+[[Repls]]
+Old = 'uv uv \S+(?: \([^)]+\))?'
+New = 'uv [UV_VERSION]'
diff --git a/acceptance/localenv/no-target/out.test.toml b/acceptance/localenv/no-target/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/no-target/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/no-target/output.txt b/acceptance/localenv/no-target/output.txt
new file mode 100644
index 0000000000..f17c350c8f
--- /dev/null
+++ b/acceptance/localenv/no-target/output.txt
@@ -0,0 +1,8 @@
+preflight  ok  uv [UV_VERSION]
+resolve    error  No compute target is selected. Select a cluster or serverless target, or pass --cluster / --serverless / --job
+fetch      pending
+merge      pending
+provision  pending
+validate   pending
+For more detail, re-run with --debug, or --output json to share a structured report.
+Error: No compute target is selected. Select a cluster or serverless target, or pass --cluster / --serverless / --job
diff --git a/acceptance/localenv/no-target/script b/acceptance/localenv/no-target/script
new file mode 100644
index 0000000000..3460d1b8cf
--- /dev/null
+++ b/acceptance/localenv/no-target/script
@@ -0,0 +1 @@
+musterr $CLI local-env python sync
diff --git a/acceptance/localenv/no-target/test.toml b/acceptance/localenv/no-target/test.toml
new file mode 100644
index 0000000000..0d0481fb83
--- /dev/null
+++ b/acceptance/localenv/no-target/test.toml
@@ -0,0 +1,5 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
+
+[[Repls]]
+Old = 'uv uv \S+(?: \([^)]+\))?'
+New = 'uv [UV_VERSION]'
diff --git a/acceptance/localenv/serverless-check/out.test.toml b/acceptance/localenv/serverless-check/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/serverless-check/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/serverless-check/output.txt b/acceptance/localenv/serverless-check/output.txt
new file mode 100644
index 0000000000..927da068d4
--- /dev/null
+++ b/acceptance/localenv/serverless-check/output.txt
@@ -0,0 +1,13 @@
+
+>>> [CLI] local-env python sync --serverless v4 --check
+preflight  ok  check
+resolve    ok  source=serverless envKey=serverless/serverless-v4
+fetch      ok  source=[DATABRICKS_URL]/serverless/serverless-v4/pyproject.toml fromCache=false
+merge      ok
+provision  ok
+validate   ok
+Plan: [TEST_TMP_DIR]/pyproject.toml
+  changed region: requires-python
+  changed region: tool.uv.constraint-dependencies
+  changed region: databricks-connect
+Check complete. No files were modified.
diff --git a/acceptance/localenv/serverless-check/script b/acceptance/localenv/serverless-check/script
new file mode 100644
index 0000000000..8c202ab129
--- /dev/null
+++ b/acceptance/localenv/serverless-check/script
@@ -0,0 +1 @@
+trace $CLI local-env python sync --serverless v4 --check
diff --git a/acceptance/localenv/serverless-check/test.toml b/acceptance/localenv/serverless-check/test.toml
new file mode 100644
index 0000000000..e2b12fc95b
--- /dev/null
+++ b/acceptance/localenv/serverless-check/test.toml
@@ -0,0 +1,21 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
+
+[Env]
+DATABRICKS_LOCALENV_CONSTRAINT_SOURCE = "$DATABRICKS_HOST"
+
+[[Server]]
+Pattern = "GET /serverless/serverless-v4/pyproject.toml"
+Response.Body = '''
+[project]
+requires-python = ">=3.12"
+
+[dependency-groups]
+dev = ["databricks-connect~=17.2.0"]
+
+[tool.uv]
+constraint-dependencies = ["pyarrow<19", "pandas<3"]
+'''
+
+[[Repls]]
+Old = 'uv uv \S+(?: \([^)]+\))?'
+New = 'uv [UV_VERSION]'
diff --git a/acceptance/localenv/serverless-json/out.test.toml b/acceptance/localenv/serverless-json/out.test.toml
new file mode 100644
index 0000000000..d6187dcb04
--- /dev/null
+++ b/acceptance/localenv/serverless-json/out.test.toml
@@ -0,0 +1,3 @@
+Local = true
+Cloud = false
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
diff --git a/acceptance/localenv/serverless-json/output.txt b/acceptance/localenv/serverless-json/output.txt
new file mode 100644
index 0000000000..c53fa61031
--- /dev/null
+++ b/acceptance/localenv/serverless-json/output.txt
@@ -0,0 +1,54 @@
+
+>>> [CLI] local-env python sync --serverless v4 --check --output json
+{
+  "schemaVersion": 1,
+  "command": "local-env python sync",
+  "ok": true,
+  "mode": "default",
+  "dryRun": true,
+  "target": {
+    "source": "serverless",
+    "serverlessVersion": "v4",
+    "envKey": "serverless/serverless-v4"
+  },
+  "resolved": {
+    "pythonVersion": "3.12",
+    "dbconnectVersion": "17.2.0",
+    "artifactSource": "network"
+  },
+  "greenfield": true,
+  "plan": {
+    "wouldWrite": "[TEST_TMP_DIR]/pyproject.toml",
+    "wouldInstallPython": "3.12",
+    "diff": "--- pyproject.toml\n+++ pyproject.toml\n@@ -1 +1,17 @@\n+[project]\n+name = \"001\"\n+version = \"0.0.0\"\n+requires-python = \"\u003e=3.12\"\n+\n+[dependency-groups]\n+dev = [\n+    \"databricks-connect~=17.2.0\",\n+]\n+\n+# managed by databricks local-env python sync — do not edit\n+[tool.uv]\n+constraint-dependencies = [\n+    \"pyarrow\u003c19\",\n+    \"pandas\u003c3\",\n+]\n+# end managed by databricks local-env python sync\n"
+  },
+  "phases": [
+    {
+      "phase": "preflight",
+      "status": "ok"
+    },
+    {
+      "phase": "resolve",
+      "status": "ok"
+    },
+    {
+      "phase": "fetch",
+      "status": "ok"
+    },
+    {
+      "phase": "merge",
+      "status": "ok"
+    },
+    {
+      "phase": "provision",
+      "status": "ok"
+    },
+    {
+      "phase": "validate",
+      "status": "ok"
+    }
+  ],
+  "warnings": [],
+  "error": null,
+  "durationMs": 0
+}
diff --git a/acceptance/localenv/serverless-json/script b/acceptance/localenv/serverless-json/script
new file mode 100644
index 0000000000..84ff562045
--- /dev/null
+++ b/acceptance/localenv/serverless-json/script
@@ -0,0 +1 @@
+trace $CLI local-env python sync --serverless v4 --check --output json
diff --git a/acceptance/localenv/serverless-json/test.toml b/acceptance/localenv/serverless-json/test.toml
new file mode 100644
index 0000000000..e2b12fc95b
--- /dev/null
+++ b/acceptance/localenv/serverless-json/test.toml
@@ -0,0 +1,21 @@
+EnvMatrix.DATABRICKS_BUNDLE_ENGINE = []
+
+[Env]
+DATABRICKS_LOCALENV_CONSTRAINT_SOURCE = "$DATABRICKS_HOST"
+
+[[Server]]
+Pattern = "GET /serverless/serverless-v4/pyproject.toml"
+Response.Body = '''
+[project]
+requires-python = ">=3.12"
+
+[dependency-groups]
+dev = ["databricks-connect~=17.2.0"]
+
+[tool.uv]
+constraint-dependencies = ["pyarrow<19", "pandas<3"]
+'''
+
+[[Repls]]
+Old = 'uv uv \S+(?: \([^)]+\))?'
+New = 'uv [UV_VERSION]'