diff --git a/.github/workflows/actionlint.yml b/.github/workflows/actionlint.yml
new file mode 100644
index 000000000..b4b6b8272
--- /dev/null
+++ b/.github/workflows/actionlint.yml
@@ -0,0 +1,32 @@
+name: Actionlint
+
+# Lints the GitHub Actions workflow YAML on every change so a malformed
+# workflow / bad action ref / missing-permission bug is caught before it ships
+# a broken pipeline. gbrain edits .github/workflows/* often (sharding, cache,
+# timeouts); this is the cheap guard that keeps those edits honest.
+
+on:
+  push:
+    branches: [master]
+    paths:
+      - '.github/workflows/**'
+  pull_request:
+    branches: [master]
+    paths:
+      - '.github/workflows/**'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  actionlint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+      - uses: rhysd/actionlint@393031adb9afb225ee52ae2ccd7a5af5525e03e8  # v1.7.11
diff --git a/.github/workflows/e2e.yml b/.github/workflows/e2e.yml
index 556afcf42..3857043ba 100644
--- a/.github/workflows/e2e.yml
+++ b/.github/workflows/e2e.yml
@@ -12,10 +12,18 @@ on:
 permissions:
   contents: read
 
+# Cancel a superseded run when a newer commit lands on the same PR/branch.
+# PR number for pull_request events (fork-safe), github.ref fallback for
+# push/scheduled runs.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   tier1:
     name: Tier 1 (Mechanical)
     runs-on: ubuntu-latest
+    timeout-minutes: 20
     services:
       postgres:
         image: pgvector/pgvector:pg16
@@ -49,6 +57,7 @@ jobs:
     # from repo/org secrets. Nightly + manual triggers still supported via
     # the workflow-level `on:` list.
     needs: tier1
+    timeout-minutes: 30
     services:
       postgres:
         image: pgvector/pgvector:pg16
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 62004cd6b..4b6430895 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -14,6 +14,15 @@ on:
 permissions:
   contents: read
 
+# Cancel a superseded run when a newer commit lands on the same PR/branch.
+# Keyed on the PR number for pull_request events (unique per PR, so two PRs
+# from forks sharing a branch name don't cancel each other) and falls back to
+# github.ref for push/scheduled runs. Mirrors heavy-tests.yml; frees runners
+# and stops a stale-SHA run from reporting a flaky failure on an obsolete commit.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   # ──────────────────────────────────────────────────────────────────────
   # cache-check: runs first, computes the content hash of every tracked
@@ -29,6 +38,7 @@ jobs:
   # ──────────────────────────────────────────────────────────────────────
   cache-check:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     outputs:
       hit: ${{ steps.lookup.outputs.cache-hit }}
       hash: ${{ steps.compute.outputs.hash }}
@@ -72,6 +82,7 @@ jobs:
     needs: cache-check
     if: needs.cache-check.outputs.hit != 'true'
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
         with:
@@ -90,6 +101,7 @@ jobs:
     needs: cache-check
     if: needs.cache-check.outputs.hit != 'true'
     runs-on: ubuntu-latest
+    timeout-minutes: 12
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
       - uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6  # v2
@@ -110,6 +122,7 @@ jobs:
     needs: cache-check
     if: needs.cache-check.outputs.hit != 'true'
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
       - uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6  # v2
@@ -134,6 +147,7 @@ jobs:
     needs: cache-check
     if: needs.cache-check.outputs.hit != 'true'
     runs-on: ubuntu-latest
+    timeout-minutes: 12
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
       - uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6  # v2
@@ -156,6 +170,7 @@ jobs:
     needs: cache-check
     if: needs.cache-check.outputs.hit != 'true'
     runs-on: ubuntu-latest
+    timeout-minutes: 12
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
       - uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6  # v2
@@ -204,6 +219,7 @@ jobs:
     needs: cache-check
     if: needs.cache-check.outputs.hit != 'true'
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     strategy:
       fail-fast: false
       matrix:
@@ -233,6 +249,7 @@ jobs:
     needs: [cache-check, gitleaks, verify, serial-tests, slow-eval-longmemeval, slow-entity-resolve-perf, test]
     if: success() && needs.cache-check.outputs.hit != 'true'
     runs-on: ubuntu-latest
+    timeout-minutes: 5
     steps:
       - name: Create cache marker
         run: |
@@ -255,6 +272,7 @@ jobs:
     needs: [cache-check, gitleaks, verify, serial-tests, slow-eval-longmemeval, slow-entity-resolve-perf, test]
     if: always()
     runs-on: ubuntu-latest
+    timeout-minutes: 5
     steps:
       - name: Aggregate result
         run: |
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 41cf5760b..60121f394 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -49,6 +49,21 @@ complete operation catalog — both speak the verbs). Run `gbrain protocol confo
 to self-certify, and `gbrain protocol stats` to watch adoption. Memories your agent
 saves are readable by every agent connected to the brain by default; pass
 `visibility: "private"` for local-only facts.
+## [0.42.50.0] - 2026-06-17
+
+**CI reliability hardening — a wedged job can no longer run for six hours, a superseded run no longer reports a stale flaky failure, and broken workflow YAML is caught before it ships.** gbrain's CI already had the deep machinery (content-hash run-skip cache, weight-aware shard balancing, test-isolation guards, hermetic E2E). What it lacked was the cheap GitHub-Actions hygiene that was already wired into `heavy-tests.yml` but never into the two hot-path workflows. This pass closes that gap, porting the patterns from the sibling GStack project's CI-reliability work.
+
+### Changed
+- **`test.yml` and `e2e.yml` cancel a superseded run** when a newer commit lands on the same PR (`concurrency` keyed on the PR number — fork-safe — with a `github.ref` fallback so push and scheduled runs always complete). Frees runners and stops a run against an obsolete commit from reporting a flaky failure.
+- **Every job in `test.yml`/`e2e.yml` now has a `timeout-minutes` bound** (test matrix 15, verify 12, serial 15, slow jobs 12, E2E tier 1 20 / tier 2 30, trivial jobs 5-10). A wedged job is converted from a six-hour zombie (GitHub's default) into a fast, legible failure.
+- **`scripts/run-e2e.sh` scrubs operator/agent environment before E2E.** A dev or Conductor shell exporting `CONDUCTOR_*` / `MCP_*` / `GBRAIN_*` config overrides no longer bleeds into E2E child processes (which made "hermetic" E2E non-hermetic and its failures unreproducible across machines). Denylist scrub — `PATH`/`HOME`/`TMPDIR`/`DATABASE_URL` survive; `GBRAIN_HOME` is preserved for the existing HOME isolation.
+
+### Added
+- **`actionlint` workflow** (`rhysd/actionlint`, SHA-pinned) lints all workflow YAML on `.github/workflows/**` changes, catching a malformed workflow / bad action ref / missing-permission bug before it ships a broken pipeline.
+
+### To take advantage of v0.42.50.0
+Nothing to do — these are CI/test-infra changes that take effect automatically on the next push. Contributors running the suite locally get the same hermetic-E2E env scrub via `bash scripts/run-e2e.sh` (or `bun run ci:local`).
+
 ## [0.42.49.0] - 2026-06-16
 
 **Big embed backfills and syncs now throttle themselves when the database gets busy, so clearing a backlog can't starve the job queue — no more external babysitter scripts.** A naive `gbrain embed --stale` or large `gbrain sync` against a PgBouncer transaction-mode pooler could saturate it and starve the minion supervisor's lock renewals, cascading `lock-renewal-failed` into dead jobs. The field workaround was an external wrapper that SIGSTOP/SIGCONT'd the process off a side-pool latency probe. That approach was blind (the side pool read low latency while the pool that mattered starved), unsafe (SIGSTOP can freeze a process mid-transaction holding locks), and couldn't touch peak pressure. gbrain now does this natively, and better.
diff --git a/scripts/run-e2e.sh b/scripts/run-e2e.sh
index d945ea2e2..4cb075084 100755
--- a/scripts/run-e2e.sh
+++ b/scripts/run-e2e.sh
@@ -66,6 +66,24 @@ export HOME="$E2E_TMP_HOME"
 export GBRAIN_HOME="$E2E_TMP_HOME"
 mkdir -p "$E2E_TMP_HOME/.gbrain"
 
+# --- Hermetic env scrub: operator/agent context must not bleed into E2E ---
+# A dev shell or a Conductor workspace exports CONDUCTOR_*, MCP_*, OPENCLAW_*,
+# and GBRAIN_* config overrides (e.g. a stray GBRAIN_BRAIN_ID, GBRAIN_SOURCE,
+# GBRAIN_*_THRESHOLD, GBRAIN_SUPERVISOR_PID_FILE) that would silently change
+# test behavior — making "hermetic" E2E non-hermetic and its failures
+# unreproducible across machines. Drop them before bun starts. This is a
+# DENYLIST of operator-context prefixes (not an allowlist rebuild), so PATH,
+# HOME, TMPDIR, CI, DATABASE_URL, and bun internals survive untouched. We keep
+# GBRAIN_HOME (just set above for HOME isolation); everything else GBRAIN_* is
+# an operator override the suite must not inherit. Adapts GStack's
+# buildHermeticEnv() allowlist to gbrain's shell E2E runner.
+for _e2e_var in $(env | grep -oE '^(CONDUCTOR_|MCP_|OPENCLAW_|GBRAIN_)[A-Za-z0-9_]*' | sort -u); do
+  case "$_e2e_var" in
+    GBRAIN_HOME) ;;  # required for HOME isolation (set above) — keep
+    *) unset "$_e2e_var" || true ;;
+  esac
+done
+
 # --dry-run-list: print the resolved file list (one per line) and exit. Used
 # by scripts/ci-local.sh to smoke-test the argv branching at startup.
 DRY_RUN_LIST=0