diff --git a/.claude/scripts/log-worker-tool.sh b/.claude/scripts/log-worker-tool.sh
new file mode 100755
index 0000000..9a69c26
--- /dev/null
+++ b/.claude/scripts/log-worker-tool.sh
@@ -0,0 +1,144 @@
+#!/usr/bin/env bash
+# log-worker-tool.sh — PostToolUse mirror hook (issue #71, Cockpit 3c SPIKE).
+#
+# NOT ENABLED BY DEFAULT — see the "Wiring (disabled by default)" section
+# below for the copy-paste snippet that turns it on. This is a spike to
+# gather evidence on signal/noise and log growth before committing to always-
+# on tool mirroring.
+#
+# Reads the PostToolUse hook event JSON on STDIN and mirrors ONLY the tools
+# Bash, Edit, Write (every other tool — Read, Grep, Glob, ... — is silently
+# ignored, no record written). This is OBSERVABILITY ONLY: it never gates
+# anything, never affects control flow, and must never break the caller —
+# always exits 0, even on malformed/empty stdin, missing node, missing
+# fields, or an unwritable log directory.
+#
+# Appends exactly ONE JSON object per line (JSONL) to the log, schema:
+#   {"ts":"<ISO-8601 UTC>","tool":"Bash|Edit|Write","summary":"<one-line>",
+#    "path":"<file path for Edit/Write, or cwd for Bash>"}
+# - summary: for Bash, the command (collapsed to one line, truncated to a
+#   sane cap); for Edit/Write, the target file path.
+# - path: for Bash, the hook event's `cwd` (the worktree-path attribution
+#   key — workers are worktree-isolated); for Edit/Write, `tool_input.file_path`.
+# The JSON line is built with `node` (never hand-rolled string
+# interpolation), mirroring log-event.sh EXACTLY, so quotes/backslashes/
+# newlines/HTML are always safely escaped and the summary is collapsed to a
+# single line.
+#
+# Log file: defaults to <repo-root>/.claude/state/worker-tools.jsonl.
+# Override with CLAUDE_WORKER_TOOLS_FILE=<absolute path> (used by tests to
+# point at a temp file instead of the real, gitignored state dir). The parent
+# directory is created if missing.
+#
+# Rotation/retention: after appending, the file is capped to the last
+# ${WORKER_TOOLS_MAX_LINES:-2000} lines (oldest dropped first), via a temp
+# file + atomic `mv`, mirroring log-event.sh's rotation node block exactly —
+# so unattended multi-day runs never grow the log unbounded and a crash
+# mid-rotation never leaves a truncated/corrupt log in place.
+#
+# Zero-token / harness-side rationale: this hook is invoked by the Claude
+# Code harness itself (PostToolUse), OUTSIDE the agent's sandbox and context
+# window — it reads the tool-call event off stdin and writes a log line; the
+# agent never sees this happen and it costs zero agent tokens.
+#
+# ---------------------------------------------------------------------------
+# Wiring (DISABLED by default — copy into .claude/settings.json to enable):
+#
+#   "PostToolUse": [
+#     {
+#       "matcher": "Bash|Edit|Write",
+#       "hooks": [
+#         {
+#           "type": "command",
+#           "command": "bash \"$CLAUDE_PROJECT_DIR/.claude/scripts/log-worker-tool.sh\""
+#         }
+#       ]
+#     }
+#   ]
+#
+# A "go" decision is this one array entry — nothing else to wire up.
+# ---------------------------------------------------------------------------
+set -u
+
+# Two-root derivation (issue #63) — resolve-roots.sh never fails, matching
+# this script's never-block contract.
+# shellcheck source=resolve-roots.sh
+. "$(cd "$(dirname "${BASH_SOURCE[0]}")" 2>/dev/null && pwd)/resolve-roots.sh" 2>/dev/null || exit 0
+
+worker_tools_file="${CLAUDE_WORKER_TOOLS_FILE:-$root/.claude/state/worker-tools.jsonl}"
+max_lines="${WORKER_TOOLS_MAX_LINES:-2000}"
+
+# Read the hook event JSON off stdin once; never let a hang or huge payload
+# block the caller.
+event_json="$(cat 2>/dev/null)" || exit 0
+
+mkdir -p "$(dirname "$worker_tools_file")" 2>/dev/null || exit 0
+
+ts="$(date -u +%Y-%m-%dT%H:%M:%SZ 2>/dev/null)" || ts=""
+
+CLAUDE_WT_TS="$ts" \
+CLAUDE_WT_EVENT="$event_json" \
+node -e '
+  let event;
+  try {
+    event = JSON.parse(process.env.CLAUDE_WT_EVENT || "");
+  } catch (e) {
+    process.exit(0); // malformed/empty stdin — silent no-op
+  }
+  if (!event || typeof event !== "object") process.exit(0);
+
+  const toolName = event.tool_name;
+  if (toolName !== "Bash" && toolName !== "Edit" && toolName !== "Write") {
+    process.exit(0); // not a mirrored tool — silent no-op
+  }
+
+  const input = event.tool_input || {};
+  const collapse = (s) =>
+    String(s == null ? "" : s)
+      .replace(/\r?\n/g, " ")
+      .replace(/\s+/g, " ")
+      .trim();
+  const truncate = (s, cap) => (s.length > cap ? s.slice(0, cap) : s);
+
+  let summary = "";
+  let path = "";
+  if (toolName === "Bash") {
+    summary = truncate(collapse(input.command), 200);
+    path = event.cwd || "";
+  } else {
+    // Edit or Write
+    path = input.file_path || "";
+    summary = collapse(path);
+  }
+
+  const line = JSON.stringify({
+    ts: process.env.CLAUDE_WT_TS || "",
+    tool: toolName,
+    summary,
+    path,
+  });
+  process.stdout.write(line + "\n");
+' >>"$worker_tools_file" 2>/dev/null || exit 0
+
+# ---- rotation: cap to the last $max_lines lines, atomically -----------------
+node -e '
+  const fs = require("fs");
+  const file = process.argv[1];
+  const max = parseInt(process.argv[2], 10);
+  const tmp = process.argv[3];
+  try {
+    if (!Number.isFinite(max) || max <= 0) process.exit(0);
+    const text = fs.readFileSync(file, "utf8");
+    const lines = text.split("\n");
+    // drop a single trailing empty string from the final newline, if present
+    if (lines.length && lines[lines.length - 1] === "") lines.pop();
+    if (lines.length <= max) process.exit(0);
+    const kept = lines.slice(lines.length - max);
+    fs.writeFileSync(tmp, kept.join("\n") + "\n");
+    fs.renameSync(tmp, file);
+  } catch (e) {
+    process.exit(0);
+  }
+' "$worker_tools_file" "$max_lines" "$worker_tools_file.tmp.$$" 2>/dev/null
+
+exit 0
diff --git a/.claude/scripts/log-worker-tool.test.sh b/.claude/scripts/log-worker-tool.test.sh
new file mode 100755
index 0000000..ebe149a
--- /dev/null
+++ b/.claude/scripts/log-worker-tool.test.sh
@@ -0,0 +1,177 @@
+#!/usr/bin/env bash
+# log-worker-tool.test.sh — offline smoke test for log-worker-tool.sh
+# (issue #71, Cockpit 3c SPIKE).
+#
+# Asserts: Bash/Edit/Write tool calls yield exactly one valid-JSON record
+# each with the expected tool/summary/path fields; non-mirrored tools (Read,
+# Grep) and malformed/empty stdin produce NO record and still exit 0;
+# multi-line Bash commands collapse to a single-line summary; quotes/
+# backslashes in a command still round-trip as valid JSON; and rotation caps
+# the log to the last WORKER_TOOLS_MAX_LINES lines.
+#
+# Exit 0 on success, non-zero if any assertion fails. Runnable bare:
+#   bash .claude/scripts/log-worker-tool.test.sh
+set -uo pipefail
+
+script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+log_worker_tool="$script_dir/log-worker-tool.sh"
+
+work="$(mktemp -d "${TMPDIR:-/tmp}/log-worker-tool-test.XXXXXX")"
+trap 'rm -rf "$work"' EXIT
+
+fail=0
+ok=0
+check() {
+  local desc="$1"; shift
+  if "$@"; then
+    ok=$((ok + 1))
+    echo "ok - $desc"
+  else
+    fail=1
+    echo "FAIL - $desc"
+  fi
+}
+
+emit() {
+  # emit <log_file> <event_json>
+  printf '%s' "$2" | CLAUDE_WORKER_TOOLS_FILE="$1" bash "$log_worker_tool" >/dev/null 2>&1
+}
+
+# ---------------------------------------------------------------------------
+# 1. Bash tool call -> one record, tool=Bash, summary=command, path=cwd.
+# ---------------------------------------------------------------------------
+bash_file="$work/bash.jsonl"
+emit "$bash_file" '{"tool_name":"Bash","tool_input":{"command":"echo hello world"},"cwd":"/wt/task-1"}'
+
+check "bash call yields exactly 1 line" bash -c '[ "$(wc -l < "$1" | tr -d " ")" -eq 1 ]' _ "$bash_file"
+check "bash record has expected fields" node -e '
+  const fs = require("fs");
+  const obj = JSON.parse(fs.readFileSync(process.argv[1], "utf8").trim());
+  if (obj.tool !== "Bash") throw new Error("tool mismatch: " + obj.tool);
+  if (obj.summary !== "echo hello world") throw new Error("summary mismatch: " + obj.summary);
+  if (obj.path !== "/wt/task-1") throw new Error("path mismatch: " + obj.path);
+  if (!/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/.test(obj.ts)) throw new Error("ts not ISO-8601 UTC: " + obj.ts);
+' "$bash_file"
+
+# ---------------------------------------------------------------------------
+# 2. Edit and Write -> record with correct tool + path=file_path.
+# ---------------------------------------------------------------------------
+edit_file="$work/edit.jsonl"
+emit "$edit_file" '{"tool_name":"Edit","tool_input":{"file_path":"/wt/task-1/src/foo.js","old_string":"a","new_string":"b"},"cwd":"/wt/task-1"}'
+check "edit record has correct tool + path" node -e '
+  const fs = require("fs");
+  const obj = JSON.parse(fs.readFileSync(process.argv[1], "utf8").trim());
+  if (obj.tool !== "Edit") throw new Error("tool mismatch: " + obj.tool);
+  if (obj.path !== "/wt/task-1/src/foo.js") throw new Error("path mismatch: " + obj.path);
+' "$edit_file"
+
+write_file="$work/write.jsonl"
+emit "$write_file" '{"tool_name":"Write","tool_input":{"file_path":"/wt/task-1/src/bar.js","content":"..."},"cwd":"/wt/task-1"}'
+check "write record has correct tool + path" node -e '
+  const fs = require("fs");
+  const obj = JSON.parse(fs.readFileSync(process.argv[1], "utf8").trim());
+  if (obj.tool !== "Write") throw new Error("tool mismatch: " + obj.tool);
+  if (obj.path !== "/wt/task-1/src/bar.js") throw new Error("path mismatch: " + obj.path);
+' "$write_file"
+
+# ---------------------------------------------------------------------------
+# 3. A non-target tool (Read, Grep) -> NO record appended, exit 0.
+# ---------------------------------------------------------------------------
+nontarget_file="$work/nontarget.jsonl"
+printf '%s' '{"tool_name":"Read","tool_input":{"file_path":"/wt/task-1/src/foo.js"},"cwd":"/wt/task-1"}' | \
+  CLAUDE_WORKER_TOOLS_FILE="$nontarget_file" bash "$log_worker_tool" >/dev/null 2>&1
+check "Read call exits 0" [ "$?" -eq 0 ]
+printf '%s' '{"tool_name":"Grep","tool_input":{"pattern":"foo"},"cwd":"/wt/task-1"}' | \
+  CLAUDE_WORKER_TOOLS_FILE="$nontarget_file" bash "$log_worker_tool" >/dev/null 2>&1
+check "Grep call exits 0" [ "$?" -eq 0 ]
+check "no record written for non-target tools" bash -c '[ ! -s "$1" ]' _ "$nontarget_file"
+
+# ---------------------------------------------------------------------------
+# 4. Empty stdin / malformed JSON -> exit 0 AND no spurious line written.
+# ---------------------------------------------------------------------------
+malformed_file="$work/malformed.jsonl"
+printf '' | CLAUDE_WORKER_TOOLS_FILE="$malformed_file" bash "$log_worker_tool" >/dev/null 2>&1
+check "empty stdin exits 0" [ "$?" -eq 0 ]
+printf 'not json at all {{{' | CLAUDE_WORKER_TOOLS_FILE="$malformed_file" bash "$log_worker_tool" >/dev/null 2>&1
+check "malformed JSON exits 0" [ "$?" -eq 0 ]
+check "no spurious line written for empty/malformed stdin" bash -c '[ ! -s "$1" ]' _ "$malformed_file"
+
+# ---------------------------------------------------------------------------
+# 5. Multi-line Bash command -> summary collapsed to a single line.
+# ---------------------------------------------------------------------------
+multiline_file="$work/multiline.jsonl"
+multiline_event="$(node -e '
+  process.stdout.write(JSON.stringify({
+    tool_name: "Bash",
+    tool_input: { command: "echo one\necho two\necho three" },
+    cwd: "/wt/task-1",
+  }));
+')"
+printf '%s' "$multiline_event" | CLAUDE_WORKER_TOOLS_FILE="$multiline_file" bash "$log_worker_tool" >/dev/null 2>&1
+check "multi-line command yields exactly 1 line in the log" bash -c '[ "$(wc -l < "$1" | tr -d " ")" -eq 1 ]' _ "$multiline_file"
+check "multi-line command collapsed to single-line summary (no raw newline)" node -e '
+  const fs = require("fs");
+  const raw = fs.readFileSync(process.argv[1], "utf8");
+  if (raw.split("\n").filter(Boolean).length !== 1) throw new Error("expected exactly 1 non-empty line, got: " + JSON.stringify(raw));
+  const obj = JSON.parse(raw.trim());
+  if (obj.summary.includes("\n")) throw new Error("summary contains raw newline: " + JSON.stringify(obj.summary));
+  if (obj.summary !== "echo one echo two echo three") throw new Error("summary mismatch: " + obj.summary);
+' "$multiline_file"
+
+# ---------------------------------------------------------------------------
+# 6. JSON escaping: quotes/backslashes in a command still produce valid JSON.
+# ---------------------------------------------------------------------------
+escapes_file="$work/escapes.jsonl"
+escapes_event="$(node -e '
+  process.stdout.write(JSON.stringify({
+    tool_name: "Bash",
+    tool_input: { command: String.raw`echo "hi" \ then </script> tags` },
+    cwd: "/wt/task-1",
+  }));
+')"
+printf '%s' "$escapes_event" | CLAUDE_WORKER_TOOLS_FILE="$escapes_file" bash "$log_worker_tool" >/dev/null 2>&1
+check "command with quotes/backslashes yields valid parseable JSON" node -e '
+  const fs = require("fs");
+  const line = fs.readFileSync(process.argv[1], "utf8").trim();
+  const obj = JSON.parse(line); // throws (fails the check) if not valid JSON
+  if (!obj.summary.includes(String.raw`"hi"`)) throw new Error("summary missing expected content: " + obj.summary);
+' "$escapes_file"
+
+# ---------------------------------------------------------------------------
+# 7. Rotation: WORKER_TOOLS_MAX_LINES small caps the file to the last N lines.
+# ---------------------------------------------------------------------------
+rotate_file="$work/rotate.jsonl"
+for i in $(seq 1 12); do
+  event="$(node -e "process.stdout.write(JSON.stringify({tool_name:'Bash',tool_input:{command:'echo t-$i'},cwd:'/wt/task-1'}))")"
+  WORKER_TOOLS_MAX_LINES=5 CLAUDE_WORKER_TOOLS_FILE="$rotate_file" bash "$log_worker_tool" <<<"$event" >/dev/null 2>&1
+done
+
+check "rotation caps the file to exactly 5 lines" bash -c '[ "$(wc -l < "$1" | tr -d " ")" -eq 5 ]' _ "$rotate_file"
+check "rotation keeps the LAST 5 records (most recent), in order" node -e '
+  const fs = require("fs");
+  const lines = fs.readFileSync(process.argv[1], "utf8").split("\n").filter(Boolean);
+  const summaries = lines.map((l) => JSON.parse(l).summary);
+  const want = ["echo t-8", "echo t-9", "echo t-10", "echo t-11", "echo t-12"];
+  if (JSON.stringify(summaries) !== JSON.stringify(want)) {
+    throw new Error("got " + JSON.stringify(summaries) + " want " + JSON.stringify(want));
+  }
+' "$rotate_file"
+
+# ---------------------------------------------------------------------------
+# 8. Best-effort: never blocks the caller (always exits 0).
+# ---------------------------------------------------------------------------
+best_effort_file="$work/best-effort.jsonl"
+printf '{"tool_name":"Bash"' | CLAUDE_WORKER_TOOLS_FILE="$best_effort_file" bash "$log_worker_tool" >/dev/null 2>&1
+check "truncated JSON still exits 0" [ "$?" -eq 0 ]
+
+CLAUDE_WORKER_TOOLS_FILE="/nonexistent/unwritable/dir/log.jsonl" bash "$log_worker_tool" <<<'{"tool_name":"Bash","tool_input":{"command":"x"},"cwd":"/"}' >/dev/null 2>&1
+check "unwritable log directory still exits 0" [ "$?" -eq 0 ]
+
+echo ""
+if [ "$fail" -eq 0 ]; then
+  echo "log-worker-tool.test.sh: PASS ($ok checks)"
+  exit 0
+else
+  echo "log-worker-tool.test.sh: FAIL (see FAIL lines above)"
+  exit 1
+fi