diff --git a/docs/CI-RUNNER-ROUTING.md b/docs/CI-RUNNER-ROUTING.md
index aa568e03cc..c281a346d4 100644
--- a/docs/CI-RUNNER-ROUTING.md
+++ b/docs/CI-RUNNER-ROUTING.md
@@ -42,6 +42,32 @@ wheel and SHA-256 in `.github/requirements-ci.txt`, and Dependabot tracks both
 dependency roots. CI consumes those manifests with `npm ci` and hash-required
 `pip`, never mutable global installs.
 
+### Local / workstation ruff
+
+Do **not** trust a bare `ruff` on `PATH` for verification in this repository.
+A workstation `ruff` at a different version from the one CI installs disagrees
+with CI in both directions — it reports findings on an unmodified `main` tree
+that CI accepts, and misses findings CI raises — because a release can move a
+rule into or out of the default set, as 0.16.0 did for eighteen `E`/`F` rules.
+Resolve the tool from the pin instead of from `PATH`:
+
+```shell
+scripts/run-ruff.sh check <paths>
+# equivalent: uvx ruff==$(awk '/^ruff==/{sub(/^ruff==/,""); sub(/[[:space:]\\].*$/,""); print; exit}' .github/requirements-ci.txt) check <paths>
+```
+
+`scripts/run-ruff.sh` uses a PATH `ruff` only when it already reports the pinned
+version (the CI install path); otherwise it runs `uvx ruff==<pin>`. Plugin
+contract tests that lint Python (`engine.test.sh`) invoke that wrapper. The pin
+is read at run time, so the wrapper follows the repository's version wherever it
+goes and carries no copy of its own.
+
+Bumping the pin is a deliberate Dependabot change, and its direction is set
+elsewhere: the pin is held equal to the fleet inventory in
+melodic-software/dotfiles (`.chezmoidata/uv-tools.yaml`), which is what installs
+a developer's local toolchain, so CI never lints with a ruff nobody runs. Do not
+"fix" a clean tree by adopting a newer ruff's new rules in an unrelated PR.
+
 ## Authoritative references
 
 - [Reuse workflows and pin a commit SHA](https://docs.github.com/en/actions/how-tos/reuse-automations/reuse-workflows)
diff --git a/plugins/source-control/.claude-plugin/plugin.json b/plugins/source-control/.claude-plugin/plugin.json
index c8464accef..79c019d81f 100644
--- a/plugins/source-control/.claude-plugin/plugin.json
+++ b/plugins/source-control/.claude-plugin/plugin.json
@@ -1,7 +1,7 @@
 {
   "$schema": "https://json.schemastore.org/claude-code-plugin-manifest.json",
   "name": "source-control",
-  "version": "0.47.1",
+  "version": "0.47.2",
   "description": "Git and GitHub delivery workflow: /commit (Conventional Commits + Co-Authored-By trailer via safe heredoc mechanics), /pull-request (prep, create, CI monitoring, review-comment triage, merge, CI-log fetch), /babysit-prs (self-pacing fleet loop — safe by default; opt-in worker/autopilot tiers add gate-checked merge and thread resolution behind a deterministic Python engine), /babysit-loop (the loop-lane merge lane: a standing or drain loop that invokes babysit-prs per cycle, configured through repo-scoped babysit_loop_* keys on the layered source-control.md seam, with merge authority human-only until the target repo's tracked config adopts the lane, a gate-proven C2-mechanical baseline once adopted, and standing merge-rung raises binding from the team-tracked layer only — with one named exception, where an invocation line explicitly typing both the autopilot tier keyword and the dedicated raise argument --merge c3-this-run widens that single invocation's merge authority up to C3 behind a fresh independent frontier-tier resolver, while C4-structural and C5-untrusted-provenance stay unconditionally human-merge), /worktree (create, status, cleanup, audit for parallel-session isolation), /setup (check the effective commit-subject / PR-title convention merged across its config layers and the babysit-prs config, or apply — interview the repo and write the convention config to a chosen layer), and /resolve-conflicts (intent-first merge/rebase conflict resolution with a semantic-conflict sweep — never --abort). The commit-subject / PR-title convention is configurable via a source-control.md config written by a re-runnable setup skill, layered across a ~/.claude user-global file, the tracked team file, and a gitignored .claude/source-control.local.md personal overlay merged per key; Conventional Commits is the default when no convention is declared.",
   "author": {
     "name": "Melodic Software",
diff --git a/plugins/source-control/CHANGELOG.md b/plugins/source-control/CHANGELOG.md
index d217531488..fb6039b883 100644
--- a/plugins/source-control/CHANGELOG.md
+++ b/plugins/source-control/CHANGELOG.md
@@ -3,6 +3,27 @@
 All notable changes to the `source-control` plugin are documented here. Format follows
 [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); this plugin uses semantic versioning.
 
+## [0.47.2]
+
+### Fixed
+
+- **`babysit-prs` `engine.test.sh` resolves ruff from the declared pin instead of PATH (#1856).**
+  A workstation `ruff` at a different version from the one CI installs made the harness report
+  findings on an unmodified tree that CI does not, or miss findings CI raises — the two disagree in
+  both directions once a release changes the default rule set, as 0.16.0 did. The lint pass now
+  goes through `scripts/run-ruff.sh`, which uses a PATH `ruff` only when it already matches the pin
+  in `.github/requirements-ci.txt` and otherwise runs `uvx ruff==<pin>`. The pin is read at run
+  time, so this follows the repository's version wherever it goes rather than freezing a value
+  here.
+
+- **`engine.test.sh` finds that wrapper on a relative invocation, so the lint pass actually runs.**
+  The suite re-derived the repository root from `BASH_SOURCE` *after* `cd`-ing into its own
+  directory. `BASH_SOURCE` holds the path as invoked, so a relative invocation resolved against the
+  new working directory and landed outside the repository: the wrapper was never found, the harness
+  printed `SKIP: scripts/run-ruff.sh not found (lint pass omitted)`, and the suite exited 0 having
+  linted nothing. `scripts/run-plugin-tests.sh` runs it from the repository root, so that was the
+  path CI took every time. The script directory is now captured once, before the `cd`.
+
 ## [0.47.1]
 
 ### Changed
diff --git a/plugins/source-control/skills/babysit-prs/scripts/engine.test.sh b/plugins/source-control/skills/babysit-prs/scripts/engine.test.sh
index 924f6fc80b..1a04dcdd69 100755
--- a/plugins/source-control/skills/babysit-prs/scripts/engine.test.sh
+++ b/plugins/source-control/skills/babysit-prs/scripts/engine.test.sh
@@ -6,7 +6,11 @@
 # repo test-runner convention for optional toolchains.
 set -uo pipefail
 
-cd "$(dirname "${BASH_SOURCE[0]}")" || exit 1
+# Resolve before the cd: BASH_SOURCE is the path as invoked, so re-deriving it
+# afterwards resolves a relative invocation against the NEW cwd and silently
+# lands somewhere else.
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)" || exit 1
+cd "$SCRIPT_DIR" || exit 1
 
 PY=""
 for candidate in python3 python; do
@@ -30,13 +34,22 @@ if ! "$PY" -m unittest discover -s tests -p 'test_*.py'; then
   FAILED=1
 fi
 
-if command -v ruff >/dev/null 2>&1; then
-  echo "== ruff =="
-  if ! ruff check . tests; then
+# Lint through the repo's CI pin (.github/requirements-ci.txt) rather than a
+# bare PATH ruff: a workstation global that auto-upgraded past the pin false-
+# reds a clean tree with findings CI does not report (#1856).
+REPO_ROOT="$(cd "$SCRIPT_DIR/../../../../.." && pwd)"
+RUN_RUFF="$REPO_ROOT/scripts/run-ruff.sh"
+if [[ -f "$RUN_RUFF" ]]; then
+  echo "== ruff (CI pin via scripts/run-ruff.sh) =="
+  ruff_rc=0
+  bash "$RUN_RUFF" check . tests || ruff_rc=$?
+  if [[ "$ruff_rc" -eq 127 ]]; then
+    echo "SKIP: pinned ruff not available (install uv or the CI pin; lint pass omitted)"
+  elif [[ "$ruff_rc" -ne 0 ]]; then
     FAILED=1
   fi
 else
-  echo "SKIP: ruff not installed (lint pass omitted)"
+  echo "SKIP: scripts/run-ruff.sh not found (lint pass omitted)"
 fi
 
 echo "== guarded-wrapper behavior =="
diff --git a/scripts/run-ruff.sh b/scripts/run-ruff.sh
new file mode 100755
index 0000000000..174792edc4
--- /dev/null
+++ b/scripts/run-ruff.sh
@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+# Run ruff at the version pinned in .github/requirements-ci.txt.
+#
+# CI installs that pin via hash-locked pip (Linux x64 wheels only). Local
+# workstations often carry a newer global ruff that auto-upgraded past the pin;
+# a bare `ruff check` then reports findings CI does not (and that are out of
+# scope for an ordinary lane). This wrapper keeps local verification aligned
+# with the pin without requiring a mass lint cleanup for every ruff minor.
+#
+# Resolution order:
+#   1. `ruff` on PATH when it already reports the pinned version (CI path)
+#   2. `uvx ruff==<pin>` when uv is available (cross-platform local path)
+#   3. exit 2 if PATH ruff exists but drifts and uvx is unavailable
+#   4. exit 127 if neither a matching ruff nor uvx is available
+#
+# Usage: scripts/run-ruff.sh [ruff-args...]
+# Example: scripts/run-ruff.sh check plugins/source-control
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+req="$repo_root/.github/requirements-ci.txt"
+
+if [[ ! -f "$req" ]]; then
+  echo "error: missing $req" >&2
+  exit 2
+fi
+
+# First `ruff==VERSION` line; ignore trailing backslashes / hash pins.
+pin="$(awk '/^ruff==/ {
+  sub(/^ruff==/, "")
+  sub(/[[:space:]\\].*$/, "")
+  print
+  exit
+}' "$req")"
+
+if [[ -z "$pin" ]]; then
+  echo "error: could not parse ruff==VERSION from $req" >&2
+  exit 2
+fi
+
+# `ruff --version` prints "ruff X.Y.Z"; anything else (including a failed probe)
+# is reported as the caller's fallback rather than treated as a version.
+ruff_reported_version() {
+  local out
+  out="$(ruff --version 2>/dev/null)" || return 1
+  printf '%s\n' "${out##* }"
+}
+
+if command -v ruff >/dev/null 2>&1; then
+  # shellcheck disable=SC2310  # the probe's only failure is "no version", handled by the fallback
+  got="$(ruff_reported_version)" || got=""
+  if [[ "$got" == "$pin" ]]; then
+    exec ruff "$@"
+  fi
+fi
+
+if command -v uvx >/dev/null 2>&1; then
+  exec uvx "ruff==${pin}" "$@"
+fi
+
+if command -v ruff >/dev/null 2>&1; then
+  # shellcheck disable=SC2310  # same probe, same fallback — reported, never trusted
+  got="$(ruff_reported_version)" || got="unknown"
+  echo "error: ruff on PATH is ${got}, but CI pins ruff==${pin} (.github/requirements-ci.txt)." >&2
+  echo "error: install the pin, or install uv and re-run (uvx ruff==${pin} ...)." >&2
+  exit 2
+fi
+
+echo "error: ruff==${pin} not available (no matching PATH ruff, no uvx)" >&2
+exit 127