diff --git a/CHANGELOG.md b/CHANGELOG.md
index 654ab2b52..07112e9ea 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,20 @@
 # Changelog
 
+## [1.92.69.0] - 2026-11-02
+
+**Background `--derive` runs no longer drop /office-hours sessions or fail with ENOENT when they overlap (#3437).** `gstack-question-log` starts a background `gstack-developer-profile --derive` after every append, and a multi-question AskUserQuestion logs several rows at once. Every derive wrote the same `developer-profile.json.tmp` and rewrote the whole profile without a lock. On main at 3bfe566, 30 rounds of 8 overlapping derives plus one `--log-session` saw 9 of 270 runs fail with `ENOENT` on rename, and 2 of the 30 sessions disappeared. With this change the same run has 0 failures and keeps 30 of 30 sessions.
+
+### Fixed
+- **`bin/gstack-developer-profile`**: `--derive`, `--log-session`, `--reconcile` and `--migrate` hold `developer-profile.json.lock` from before they read the profile until after they rename it, and each writes its own `mktemp` file. The owner file names the holder's process ID, and the lock is ownership-checked on release. A lock is taken over when its holder process is gone, or once it is 5 minutes old even if a process with that ID is running, since no writer takes that long and the ID may have been reused. Takeovers go one at a time under `developer-profile.json.lock.takeover`, so two waiters can't both take over. A writer that can't get the lock within 10 seconds writes nothing and exits 5. An unwritable state directory is reported right away instead of after the wait. A relative state root is anchored once, so the lock is released under the same path it was taken. Windows drive-letter roots stay as they are.
+### Removed
+- **`scripts/psychographic-signals.ts`**: `applySignal` and `newDimensionTotals`, which lost their last production caller when `--derive` moved onto `accumulateSignals` (#3435), and their three unit tests.
+
+### Not covered yet
+- `gstack-distill-apply` and /plan-tune's declared edits still write the profile without the lock.
+
+### Tests
+- `test/gstack-developer-profile.test.ts`: a directory at the old fixed temp path; a held lock blocking `--derive` and `--log-session`; takeover of an ownerless stale lock, of a dead holder's lock, and of a 5-minute-old lock whose process ID is alive; a takeover already in progress; a takeover that can't remove the lock still giving up; a relative state root; and 6 rounds of 6 derives plus a `--log-session` keeping every session. Each test failed on the code before its fix.
+
 ## [1.92.68.0] - 2026-11-02
 
 **`/health` now finds its tools with gstack's detector, the same one `/verify` uses, and a test proves it still finds every check it found before.** /health Step 1 used to carry its own shell block for detecting a type checker, linter, test runner, knip, shellcheck and gbrain, a second copy of the list in `lib/checks.ts`. It now runs `gstack-checks detect --for health`. Scoring, the gbrain sub-score and history are unchanged. GST-116, PR 2 of 2.
diff --git a/VERSION b/VERSION
index 75a21384c..d44ae96df 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.92.68.0
+1.92.69.0
diff --git a/agents-digest/gstack-AGENTS.md b/agents-digest/gstack-AGENTS.md
index f898c2f84..72187e385 100644
--- a/agents-digest/gstack-AGENTS.md
+++ b/agents-digest/gstack-AGENTS.md
@@ -1,4 +1,4 @@
-# gstack digest v1.92.68.0 — regenerate/re-copy after upgrading gstack
+# gstack digest v1.92.69.0 — regenerate/re-copy after upgrading gstack
 
 Behavioral rules from gstack (https://github.com/garrytan/gstack), compressed
 for agent hosts without a full skill install. The full skills add workflows,
diff --git a/bin/gstack-developer-profile b/bin/gstack-developer-profile
index f64178e2b..bc489c5c1 100755
--- a/bin/gstack-developer-profile
+++ b/bin/gstack-developer-profile
@@ -25,6 +25,10 @@
 #                       `completed` events in projects/*/timeline.jsonl.
 #                       Idempotent; backfilled rows count for tenure only.
 #
+# Writers (--derive, --log-session, --reconcile, --migrate) hold
+# developer-profile.json.lock for their read-modify-write and exit 5 when
+# another writer keeps it past the give-up window (#3437).
+#
 # Profile file: ~/.gstack/developer-profile.json (unified schema — see
 # docs/designs/PLAN_TUNING_V0.md). Event file: ~/.gstack/projects/{SLUG}/
 # question-events.jsonl.
@@ -37,6 +41,10 @@ ROOT_DIR="$(cd "$SCRIPT_DIR/.." && pwd)"
 . "$(dirname "$0")/gstack-state-root.sh" 2>/dev/null || { echo "$0: cannot resolve the gstack state root: $(dirname "$0")/gstack-state-root.sh is missing. fix: reinstall with ./setup or /gstack-upgrade (docs/state-root.md)" >&2; exit 1; }
 gstack_state_root_select
 GSTACK_HOME="$_gstack_sr_root"
+# A relative state root is anchored to the starting directory once, here:
+# do_derive changes directory, and the profile lock must name the same path
+# when it is taken and when it is released.
+case "$GSTACK_HOME" in /*|[A-Za-z]:[\\/]*) ;; *) GSTACK_HOME="$PWD/$GSTACK_HOME" ;; esac
 # Windows git-bash: GSTACK_HOME resolves to an MSYS path (/c/Users/...), which
 # Bun on Windows cannot open as a filesystem path (bites --derive). Normalize
 # once, here, before PROFILE_FILE/LEGACY_FILE are derived from it below —
@@ -52,10 +60,100 @@ SLUG="${SLUG:-unknown}"
 CMD="${1:---read}"
 shift || true
 
+# -----------------------------------------------------------------------
+# Profile lock (#3437). Every subcommand that rewrites the profile reads,
+# changes and renames the whole file, and gstack-question-log starts a
+# background --derive after every append, so writers overlap: a shared temp
+# name made renames fail and an unlocked rewrite dropped a concurrent
+# --log-session. Writers hold a mkdir lock (<profile>.lock/, whose owner file
+# names the holder's pid and a random token; release is ownership-checked)
+# from before their read until after their rename, and write a unique temp
+# file. A lock whose holder process is gone is taken over at once; one older
+# than 5 minutes is taken over even when its pid is alive, since no writer
+# runs that long and the pid may have been reused. Takeovers are serialized by a second mkdir lock
+# (<profile>.lock.takeover/) and re-read the owner under it, so two waiters
+# cannot both take over or remove a lock a third writer just took. A lock or
+# takeover directory older than 30 s with no owner belongs to a writer that
+# died before writing one; cleanup removes a takeover lock this writer holds. A writer that cannot get the lock within the
+# give-up window writes nothing and exits 5. Writers outside this binary
+# (gstack-distill-apply, /plan-tune's declared edits) do not take it yet.
+# -----------------------------------------------------------------------
+LOCK_DIR="$PROFILE_FILE.lock"
+TAKEOVER_DIR="$LOCK_DIR.takeover"
+LOCK_TOKEN=""
+HOLDS_TAKEOVER=""
+PROFILE_TMP=""
+
+cleanup() {
+  if [ -n "$PROFILE_TMP" ]; then rm -f "$PROFILE_TMP"; fi
+  if [ -n "$HOLDS_TAKEOVER" ]; then rmdir "$TAKEOVER_DIR" 2>/dev/null || true; fi
+  if [ -n "$LOCK_TOKEN" ] && [ "$(cat "$LOCK_DIR/owner" 2>/dev/null || true)" = "$LOCK_TOKEN" ]; then
+    rm -rf "$LOCK_DIR"
+  fi
+}
+trap cleanup EXIT
+trap 'exit 130' INT
+trap 'exit 143' TERM
+
+dir_age_s() {
+  local mtime
+  # GNU stat first: BSD-style stat -f on Linux prints a filesystem block.
+  mtime=$(stat -c %Y "$1" 2>/dev/null || stat -f %m "$1" 2>/dev/null || echo "")
+  case "$mtime" in ""|*[!0-9]*) echo 0 ;; *) echo $(( $(date +%s) - mtime )) ;; esac
+}
+
+lock_abandoned() {
+  if [ -n "$1" ]; then
+    ! kill -0 "${1%%-*}" 2>/dev/null || [ "$(dir_age_s "$LOCK_DIR")" -gt 300 ]
+  else
+    [ "$(dir_age_s "$LOCK_DIR")" -gt 30 ]
+  fi
+}
+
+acquire_lock() {
+  if [ -n "$LOCK_TOKEN" ]; then return 0; fi
+  mkdir -p "$GSTACK_HOME"
+  # GSTACK_PROFILE_LOCK_TIMEOUT_MS: test-only override for the give-up.
+  local give_up_ms="${GSTACK_PROFILE_LOCK_TIMEOUT_MS:-10000}" waited_ms=0 started=$SECONDS vanished=0 owner
+  local token="$$-$RANDOM$RANDOM"
+  until mkdir "$LOCK_DIR" 2>/dev/null; do
+    # mkdir failed with no lock to wait for: retry once in case a holder just
+    # released it, then report the directory instead of waiting out the window.
+    if [ ! -e "$LOCK_DIR" ]; then
+      if [ "$vanished" -eq 0 ]; then vanished=1; continue; fi
+      echo "gstack-developer-profile: cannot create $LOCK_DIR (is $GSTACK_HOME writable?), so nothing was written (exit 5)." >&2
+      exit 5
+    fi
+    vanished=0
+    owner=$(cat "$LOCK_DIR/owner" 2>/dev/null || true)
+    if [ -d "$LOCK_DIR" ] && lock_abandoned "$owner"; then
+      if [ -d "$TAKEOVER_DIR" ] && [ "$(dir_age_s "$TAKEOVER_DIR")" -gt 30 ]; then rmdir "$TAKEOVER_DIR" 2>/dev/null || true; fi
+      if mkdir "$TAKEOVER_DIR" 2>/dev/null; then
+        HOLDS_TAKEOVER=1
+        if [ "$(cat "$LOCK_DIR/owner" 2>/dev/null || true)" = "$owner" ] && lock_abandoned "$owner"; then
+          rm -rf "$LOCK_DIR" 2>/dev/null || true
+        fi
+        rmdir "$TAKEOVER_DIR" 2>/dev/null || true
+        HOLDS_TAKEOVER=""
+        if [ ! -e "$LOCK_DIR" ]; then continue; fi
+      fi
+    fi
+    if [ "$waited_ms" -ge "$give_up_ms" ] || [ $(( SECONDS - started )) -gt $(( give_up_ms / 1000 )) ]; then
+      echo "gstack-developer-profile: another writer held $LOCK_DIR for ${give_up_ms} ms, so nothing was written (exit 5)." >&2
+      exit 5
+    fi
+    sleep 0.05
+    waited_ms=$(( waited_ms + 50 ))
+  done
+  printf '%s\n' "$token" > "$LOCK_DIR/owner"
+  LOCK_TOKEN="$token"
+}
+
 # -----------------------------------------------------------------------
 # Migration: builder-profile.jsonl → developer-profile.json
 # -----------------------------------------------------------------------
 do_migrate() {
+  acquire_lock
   if [ ! -f "$LEGACY_FILE" ]; then
     echo "MIGRATE: no legacy file to migrate"
     return 0
@@ -68,9 +166,7 @@ do_migrate() {
   fi
 
   # Run migration in a temp file, then atomic rename.
-  local TMPOUT
-  TMPOUT=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
-  trap 'rm -f "$TMPOUT"' EXIT
+  PROFILE_TMP=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
 
   cat "$LEGACY_FILE" | bun --no-env-file --config="${GSTACK_BUN_CONFIG:-/dev/null}" -e "
     const lines = (await Bun.stdin.text()).trim().split('\n').filter(Boolean);
@@ -113,11 +209,11 @@ do_migrate() {
       schema_version: 1,
     };
     console.log(JSON.stringify(profile, null, 2));
-  " > "$TMPOUT"
+  " > "$PROFILE_TMP"
 
   # Atomic rename.
-  mv "$TMPOUT" "$PROFILE_FILE"
-  trap - EXIT
+  mv "$PROFILE_TMP" "$PROFILE_FILE"
+  PROFILE_TMP=""
 
   # gbrain-sync: enqueue the migrated file for cross-machine sync (no-op if off).
   SCRIPT_DIR_E="$(cd "$(dirname "$0")" && pwd)"
@@ -205,13 +301,12 @@ do_log_session() {
     *) echo "gstack-developer-profile: bun printed no verdict while validating the session; nothing was logged" >&2; return 1 ;;
   esac
 
+  acquire_lock
   ensure_profile
 
-  local TMPOUT
-  TMPOUT=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
-  trap 'rm -f "$TMPOUT"' EXIT
+  PROFILE_TMP=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
 
-  PROFILE_FILE_PATH="$PROFILE_FILE" RECORD_INPUT="$INPUT" TMPOUT_PATH="$TMPOUT" bun --no-env-file --config="${GSTACK_BUN_CONFIG:-/dev/null}" -e "
+  PROFILE_FILE_PATH="$PROFILE_FILE" RECORD_INPUT="$INPUT" TMPOUT_PATH="$PROFILE_TMP" bun --no-env-file --config="${GSTACK_BUN_CONFIG:-/dev/null}" -e "
     const fs = require('fs');
     const entry = JSON.parse(process.env.RECORD_INPUT);
     if (!entry.ts) entry.ts = new Date().toISOString();
@@ -238,8 +333,8 @@ do_log_session() {
     fs.writeFileSync(process.env.TMPOUT_PATH, JSON.stringify(profile, null, 2));
   "
 
-  mv "$TMPOUT" "$PROFILE_FILE"
-  trap - EXIT
+  mv "$PROFILE_TMP" "$PROFILE_FILE"
+  PROFILE_TMP=""
   "$SCRIPT_DIR/gstack-brain-enqueue" "developer-profile.json" 2>/dev/null &
 }
 
@@ -252,13 +347,12 @@ do_log_session() {
 # rewritten only when something was added.
 # -----------------------------------------------------------------------
 do_reconcile() {
+  acquire_lock
   ensure_profile
 
-  local TMPOUT
-  TMPOUT=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
-  trap 'rm -f "$TMPOUT"' EXIT
+  PROFILE_TMP=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
 
-  PROFILE_FILE_PATH="$PROFILE_FILE" PROJECTS_DIR="$GSTACK_HOME/projects" TMPOUT_PATH="$TMPOUT" bun --no-env-file --config="${GSTACK_BUN_CONFIG:-/dev/null}" -e "
+  PROFILE_FILE_PATH="$PROFILE_FILE" PROJECTS_DIR="$GSTACK_HOME/projects" TMPOUT_PATH="$PROFILE_TMP" bun --no-env-file --config="${GSTACK_BUN_CONFIG:-/dev/null}" -e "
     const fs = require('fs');
     const path = require('path');
     const profile = JSON.parse(fs.readFileSync(process.env.PROFILE_FILE_PATH, 'utf-8'));
@@ -313,13 +407,13 @@ do_reconcile() {
     console.log('RECONCILE: ' + added + ' backfilled from ' + runs.length + ' office-hours run(s)');
   "
 
-  if [ -s "$TMPOUT" ]; then
-    mv "$TMPOUT" "$PROFILE_FILE"
-    trap - EXIT
+  if [ -s "$PROFILE_TMP" ]; then
+    mv "$PROFILE_TMP" "$PROFILE_FILE"
+    PROFILE_TMP=""
     "$SCRIPT_DIR/gstack-brain-enqueue" "developer-profile.json" 2>/dev/null &
   else
-    rm -f "$TMPOUT"
-    trap - EXIT
+    rm -f "$PROFILE_TMP"
+    PROFILE_TMP=""
   fi
 }
 
@@ -506,6 +600,7 @@ function accumulateSignals(lines, QUESTIONS, SIGNAL_MAP, dims) {
 # Derive: recompute inferred dimensions from question-events.jsonl
 # -----------------------------------------------------------------------
 do_derive() {
+  acquire_lock
   ensure_profile
   local EVENTS="$GSTACK_HOME/projects/$SLUG/question-log.jsonl"
   local REGISTRY="$ROOT_DIR/scripts/question-registry.ts"
@@ -515,8 +610,9 @@ do_derive() {
     exit 1
   fi
 
+  PROFILE_TMP=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
   cd "$ROOT_DIR"
-  PROFILE_FILE_PATH="$PROFILE_FILE" EVENTS_PATH="$EVENTS" bun --no-env-file --config="${GSTACK_BUN_CONFIG:-/dev/null}" -e "
+  PROFILE_FILE_PATH="$PROFILE_FILE" EVENTS_PATH="$EVENTS" TMPOUT_PATH="$PROFILE_TMP" bun --no-env-file --config="${GSTACK_BUN_CONFIG:-/dev/null}" -e "
     import('./scripts/question-registry.ts').then(async (regmod) => {
       const sigmod = await import('./scripts/psychographic-signals.ts');
       const fs = require('fs');
@@ -568,12 +664,12 @@ do_derive() {
       profile.gap = gap;
       profile.derived_at = new Date().toISOString();
 
-      const tmp = profilePath + '.tmp';
-      fs.writeFileSync(tmp, JSON.stringify(profile, null, 2));
-      fs.renameSync(tmp, profilePath);
+      fs.writeFileSync(process.env.TMPOUT_PATH, JSON.stringify(profile, null, 2));
       console.log('DERIVE: ok — ' + count + ' events, ' + skills.size + ' skills, ' + qids.size + ' questions');
     }).catch(err => { console.error('DERIVE:', err.message); process.exit(1); });
   "
+  mv "$PROFILE_TMP" "$PROFILE_FILE"
+  PROFILE_TMP=""
 }
 
 # -----------------------------------------------------------------------
diff --git a/package.json b/package.json
index 883d131b3..766188b87 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "1.92.68",
+  "version": "1.92.69",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",
diff --git a/scripts/psychographic-signals.ts b/scripts/psychographic-signals.ts
index 43d4a89ab..d6a479497 100644
--- a/scripts/psychographic-signals.ts
+++ b/scripts/psychographic-signals.ts
@@ -306,29 +306,6 @@ export function resolveOptionKey(question_id: string, choice: string): string |
   return tie ? undefined : best;
 }
 
-/**
- * Apply a user choice for a question to the running dimension totals.
- *
- * @param dims - running total of dimension nudges (mutated)
- * @param signal_key - from the question registry entry
- * @param user_choice - the option key the user selected
- * @returns list of dimension deltas applied (empty if no mapping)
- */
-export function applySignal(
-  dims: Record<Dimension, number>,
-  signal_key: string,
-  user_choice: string,
-): DimensionDelta[] {
-  const subMap = SIGNAL_MAP[signal_key];
-  if (!subMap) return [];
-  const deltas = subMap[user_choice];
-  if (!deltas) return [];
-  for (const { dim, delta } of deltas) {
-    dims[dim] = (dims[dim] ?? 0) + delta;
-  }
-  return deltas;
-}
-
 /**
  * Validate that every signal_key referenced in the registry has a matching
  * entry in SIGNAL_MAP. Called by tests to catch drift.
@@ -353,17 +330,6 @@ export function validateRegistrySignalKeys(): {
   return { missing, extra };
 }
 
-/** Empty dimension totals — starting point for derivation. */
-export function newDimensionTotals(): Record<Dimension, number> {
-  return {
-    scope_appetite: 0,
-    risk_tolerance: 0,
-    detail_preference: 0,
-    autonomy: 0,
-    architecture_care: 0,
-  };
-}
-
 /** Sigmoid clamp: map accumulated delta total to [0, 1]. */
 export function normalizeToDimensionValue(total: number): number {
   // Simple sigmoid: each 1.0 of accumulated delta approaches saturation.
diff --git a/test/gstack-developer-profile.test.ts b/test/gstack-developer-profile.test.ts
index 46a945508..df23a9c3b 100644
--- a/test/gstack-developer-profile.test.ts
+++ b/test/gstack-developer-profile.test.ts
@@ -770,6 +770,155 @@ describe('gstack-developer-profile --log-session (#1671 fix)', () => {
   });
 });
 
+// -----------------------------------------------------------------------
+// Concurrent writers (#3437). gstack-question-log starts a background
+// --derive after every append, and a multi-question AskUserQuestion logs
+// several rows at once, so derives overlap each other and /office-hours'
+// --log-session. Each subcommand rewrites the whole profile, so every
+// read-modify-write holds the profile lock and writes a unique temp file.
+// -----------------------------------------------------------------------
+
+async function runDevAsync(...args: string[]): Promise<{ stdout: string; stderr: string; status: number }> {
+  const proc = Bun.spawn([BIN_DEV, ...args], {
+    env: { ...process.env, GSTACK_HOME: tmpHome },
+    cwd: ROOT,
+    stdout: 'pipe',
+    stderr: 'pipe',
+  });
+  const timer = setTimeout(() => proc.kill(), 60_000);
+  const [stdout, stderr, status] = await Promise.all([
+    new Response(proc.stdout).text(),
+    new Response(proc.stderr).text(),
+    proc.exited,
+  ]);
+  clearTimeout(timer);
+  return { stdout, stderr, status };
+}
+
+describe('gstack-developer-profile concurrent writers (#3437)', () => {
+  const lockDir = () => path.join(tmpHome, 'developer-profile.json.lock');
+
+  test('--derive does not write through a fixed temp path', () => {
+    fs.mkdirSync(path.join(tmpHome, 'developer-profile.json.tmp'));
+    const r = runDev('--derive');
+    expect(r.stderr).toBe('');
+    expect(r.status).toBe(0);
+    expect(typeof (readProfile() as { derived_at?: string }).derived_at).toBe('string');
+  });
+
+  test('a held profile lock keeps --derive and --log-session from writing', () => {
+    expect(runDev('--derive').status).toBe(0);
+    const before = fs.readFileSync(path.join(tmpHome, 'developer-profile.json'), 'utf-8');
+    fs.mkdirSync(lockDir());
+    fs.writeFileSync(path.join(lockDir(), 'owner'), process.pid + '-held\n');
+    const env = { ...process.env, GSTACK_HOME: tmpHome, GSTACK_PROFILE_LOCK_TIMEOUT_MS: '300' };
+    for (const args of [['--derive'], ['--log-session', JSON.stringify({ date: '2026-10-31', mode: 'builder' })]]) {
+      const res = spawnSync(BIN_DEV, args, { env, encoding: 'utf-8', cwd: ROOT, timeout: 30_000 });
+      expect(res.status).toBe(5);
+      expect(res.stderr).toContain('developer-profile.json.lock');
+    }
+    expect(fs.readFileSync(path.join(tmpHome, 'developer-profile.json'), 'utf-8')).toBe(before);
+    expect(fs.readFileSync(path.join(lockDir(), 'owner'), 'utf-8')).toBe(process.pid + '-held\n');
+  });
+
+  test('a stale lock left by a crashed writer is taken over', () => {
+    fs.mkdirSync(lockDir());
+    const old = new Date(Date.now() - 120_000);
+    fs.utimesSync(lockDir(), old, old);
+    const r = runDev('--log-session', JSON.stringify({ date: '2026-10-31', mode: 'builder', project_slug: 'p' }));
+    expect(r.status).toBe(0);
+    expect((readProfile() as { sessions: unknown[] }).sessions.length).toBe(1);
+    expect(fs.existsSync(lockDir())).toBe(false);
+  });
+
+  test('a lock whose holder process is gone is taken over at once', () => {
+    const gone = spawnSync('true', [], { timeout: 10_000 }).pid;
+    fs.mkdirSync(lockDir());
+    fs.writeFileSync(path.join(lockDir(), 'owner'), gone + '-crashed\n');
+    const env = { ...process.env, GSTACK_HOME: tmpHome, GSTACK_PROFILE_LOCK_TIMEOUT_MS: '300' };
+    const res = spawnSync(BIN_DEV, ['--log-session', JSON.stringify({ date: '2026-10-31', mode: 'builder', project_slug: 'p' })], { env, encoding: 'utf-8', cwd: ROOT, timeout: 30_000 });
+    expect(res.stderr).toBe('');
+    expect(res.status).toBe(0);
+    expect((readProfile() as { sessions: unknown[] }).sessions.length).toBe(1);
+    expect(fs.existsSync(lockDir())).toBe(false);
+  });
+
+  test('a lock older than 5 minutes is taken over even when its pid is alive (pid reuse)', () => {
+    fs.mkdirSync(lockDir());
+    fs.writeFileSync(path.join(lockDir(), 'owner'), process.pid + '-reused\n');
+    const old = new Date(Date.now() - 10 * 60_000);
+    fs.utimesSync(lockDir(), old, old);
+    const env = { ...process.env, GSTACK_HOME: tmpHome, GSTACK_PROFILE_LOCK_TIMEOUT_MS: '300' };
+    const res = spawnSync(BIN_DEV, ['--log-session', JSON.stringify({ date: '2026-10-31', mode: 'builder', project_slug: 'p' })], { env, encoding: 'utf-8', cwd: ROOT, timeout: 30_000 });
+    expect(res.stderr).toBe('');
+    expect(res.status).toBe(0);
+    expect((readProfile() as { sessions: unknown[] }).sessions.length).toBe(1);
+    expect(fs.existsSync(lockDir())).toBe(false);
+  });
+
+  test('a takeover already in progress is not repeated', () => {
+    const gone = spawnSync('true', [], { timeout: 10_000 }).pid;
+    fs.mkdirSync(lockDir());
+    fs.writeFileSync(path.join(lockDir(), 'owner'), gone + '-crashed\n');
+    fs.mkdirSync(lockDir() + '.takeover');
+    const env = { ...process.env, GSTACK_HOME: tmpHome, GSTACK_PROFILE_LOCK_TIMEOUT_MS: '300' };
+    const res = spawnSync(BIN_DEV, ['--log-session', JSON.stringify({ date: '2026-10-31', mode: 'builder' })], { env, encoding: 'utf-8', cwd: ROOT, timeout: 30_000 });
+    expect(res.status).toBe(5);
+    expect(fs.readFileSync(path.join(lockDir(), 'owner'), 'utf-8')).toBe(gone + '-crashed\n');
+  });
+
+  test('a takeover that cannot remove the lock still gives up', () => {
+    expect(runDev('--derive').status).toBe(0);
+    fs.mkdirSync(lockDir());
+    const old = new Date(Date.now() - 120_000);
+    fs.utimesSync(lockDir(), old, old);
+    fs.chmodSync(tmpHome, 0o555);
+    try {
+      const env = { ...process.env, GSTACK_HOME: tmpHome, GSTACK_PROFILE_LOCK_TIMEOUT_MS: '300' };
+      const res = spawnSync(BIN_DEV, ['--derive'], { env, encoding: 'utf-8', cwd: ROOT, timeout: 10_000 });
+      expect(res.signal).toBeNull();
+      expect([0, 5]).toContain(res.status ?? -1);
+    } finally {
+      fs.chmodSync(tmpHome, 0o755);
+    }
+  }, 20_000);
+
+  test('a relative state root does not leave the lock behind', () => {
+    const env = { ...process.env, GSTACK_HOME: 'state' };
+    for (const args of [['--derive'], ['--log-session', JSON.stringify({ date: '2026-10-31', mode: 'builder', project_slug: 'p' })]]) {
+      const res = spawnSync(BIN_DEV, args, { env, encoding: 'utf-8', cwd: tmpHome, timeout: 30_000 });
+      expect(res.stderr).toBe('');
+      expect(res.status).toBe(0);
+    }
+    const p = JSON.parse(fs.readFileSync(path.join(tmpHome, 'state', 'developer-profile.json'), 'utf-8'));
+    expect(p.sessions.length).toBe(1);
+    expect(typeof p.derived_at).toBe('string');
+    expect(fs.existsSync(path.join(tmpHome, 'state', 'developer-profile.json.lock'))).toBe(false);
+  });
+
+  test('overlapping derives and log-sessions keep every session and leave valid JSON', async () => {
+    for (let i = 0; i < 5; i++) {
+      logQuestion({ skill: 'plan-ceo-review', question_id: 'plan-ceo-review-mode', question_summary: 'mode', user_choice: 'expand', session_id: 's' + i });
+    }
+    expect(runDev('--derive').status).toBe(0);
+    const rounds = 6;
+    for (let round = 0; round < rounds; round++) {
+      const runs = await Promise.all([
+        ...Array.from({ length: 6 }, () => runDevAsync('--derive')),
+        runDevAsync('--log-session', JSON.stringify({ date: '2026-10-31', mode: 'builder', project_slug: 'round-' + round })),
+      ]);
+      for (const r of runs) {
+        expect(r.stderr).toBe('');
+        expect(r.status).toBe(0);
+      }
+    }
+    const p = readProfile() as { sessions: Array<{ project_slug: string }>; inferred: { sample_size: number } };
+    expect(p.sessions.map((s) => s.project_slug).sort()).toEqual(Array.from({ length: rounds }, (_, i) => 'round-' + i).sort());
+    expect(p.inferred.sample_size).toBe(5);
+    expect(fs.readdirSync(tmpHome).filter((f) => f.startsWith('developer-profile.json.'))).toEqual([]);
+  }, 120_000);
+});
+
 // -----------------------------------------------------------------------
 // SESSION_COUNT / TIER / NUDGE_ELIGIBLE must ignore mode:resources entries.
 //
diff --git a/test/plan-tune.test.ts b/test/plan-tune.test.ts
index 413ed07f9..467ec8b91 100644
--- a/test/plan-tune.test.ts
+++ b/test/plan-tune.test.ts
@@ -29,9 +29,7 @@ import {
 } from '../scripts/one-way-doors';
 import {
   SIGNAL_MAP,
-  applySignal,
   validateRegistrySignalKeys,
-  newDimensionTotals,
   normalizeToDimensionValue,
   resolveOptionKey,
   ALL_DIMENSIONS,
@@ -246,26 +244,6 @@ describe('psychographic signal map', () => {
     expect(missing).toEqual([]);
   });
 
-  test('applySignal mutates dimension totals per mapping', () => {
-    const dims = newDimensionTotals();
-    const applied = applySignal(dims, 'scope-appetite', 'expand');
-    expect(applied.length).toBeGreaterThan(0);
-    expect(dims.scope_appetite).toBeCloseTo(0.06, 5);
-  });
-
-  test('applySignal returns [] for unknown signal_key', () => {
-    const dims = newDimensionTotals();
-    const applied = applySignal(dims, 'no-such-signal', 'anything');
-    expect(applied).toEqual([]);
-    expect(dims.scope_appetite).toBe(0);
-  });
-
-  test('applySignal returns [] for unknown user_choice', () => {
-    const dims = newDimensionTotals();
-    const applied = applySignal(dims, 'scope-appetite', 'definitely-not-a-real-choice');
-    expect(applied).toEqual([]);
-  });
-
   test('normalizeToDimensionValue maps 0 → 0.5 (neutral)', () => {
     expect(normalizeToDimensionValue(0)).toBeCloseTo(0.5, 5);
   });