diff --git a/.github/workflows/v2-ci.yml b/.github/workflows/v2-ci.yml
index 9d81d6a55..caf6fdd9b 100644
--- a/.github/workflows/v2-ci.yml
+++ b/.github/workflows/v2-ci.yml
@@ -96,6 +96,18 @@ jobs:
         working-directory: .
         run: bash bin/test_gh_auth_native_no_cat.sh
 
+      # #4045: agent CLI backends (observed live: Copilot CLI) re-export their
+      # own live GitHub credential as GITHUB_TOKEN into every tool shell they
+      # spawn — after all launch-path scrubbing — letting a wrapper-denied
+      # agent write to repos via raw curl, outside every gh-wrapper control.
+      # This EXECUTES shells the way a backend spawns them (token in the spawn
+      # env) and asserts the BASH_ENV scrub leaves them token-less, with
+      # positive controls that the probe can see a leak and that the wrapper
+      # still authenticates from the per-agent cache.
+      - name: agent shell token scrub (#4045)
+        working-directory: .
+        run: bash bin/test_agent_env_scrub.sh
+
       - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
         with:
           node-version: '22'
diff --git a/bin/README.md b/bin/README.md
index df8162580..710a7e7d8 100644
--- a/bin/README.md
+++ b/bin/README.md
@@ -44,6 +44,7 @@ Most production scripts are installed under `/usr/local/bin` by `bin/hive-deploy
 | `gh-wrapper.sh` | Enforcement | `gh` wrapper that injects App tokens and enforces global/per-agent restriction rules from `/etc/hive/restrictions/<agent-id>.json`. |
 | `hive-open-pr.sh` | Enforcement | Agent-side wrapper for PR creation requests. It writes a request file for the Hive watcher so PRs are opened by the GitHub App bot and pass the same ACMM authorization checks. |
 | `setup-proxy-iptables.sh` | Enforcement | Installs iptables rules in the container to force GitHub HTTPS traffic through the ACMM proxy even if an agent unsets proxy variables. |
+| `agent-env-scrub.sh` | Enforcement | Sourced (never executed) at the start of every shell in an agent's process tree, via `BASH_ENV`/`ENV` from `agent-launch.sh` and an `/etc/bash.bashrc` guard, to unset the live GitHub credentials backend CLIs re-export into agent tool shells (#4045). |
 | `hive-config.sh` | Config | Shared shell config reader that exposes project, repo, agent, dashboard, health, and policy values parsed from `hive-project.yaml`. |
 
 ## Deployment and local operation
diff --git a/bin/agent-env-scrub.sh b/bin/agent-env-scrub.sh
new file mode 100644
index 000000000..019e3bc4c
--- /dev/null
+++ b/bin/agent-env-scrub.sh
@@ -0,0 +1,48 @@
+# agent-env-scrub.sh — shell-boundary credential scrub for agent tool shells.
+#
+# SECURITY (#4045): agent CLI backends re-export their own live GitHub
+# credentials into the shells they spawn for tool calls. Observed live on a
+# Copilot-backed fleet: the CLI authenticates from its persistent credential
+# store (/data/copilot-user-token) and sets GITHUB_TOKEN in the environment of
+# every tool shell — AFTER all of the hive's launch-path scrubbing (#3931) has
+# run. A wrapper-denied agent then fell back to
+#   curl -H "Authorization: Bearer $GITHUB_TOKEN" https://api.github.com/...
+# and succeeded at a repo write, bypassing every gh-wrapper control (allowlist
+# #3854, mode/ACMM gates, merge eligibility, authorship routing, provenance).
+#
+# This file is SOURCED — never executed — at the start of every shell in the
+# agent's process tree, via BASH_ENV/ENV exported by agent-launch.sh (tool
+# shells, which are non-interactive) and via the /etc/bash.bashrc guard the
+# Dockerfile installs (interactive shells). Because the unset runs at CHILD
+# shell startup, it neutralizes tokens however they arrived: inherited from the
+# session env, or set explicitly in the spawn env by the backend CLI itself —
+# the #4045 mechanism, which no amount of parent-side scrubbing can reach.
+#
+# What this deliberately does NOT break:
+#   - The backend CLI process keeps its own auth. The CLI (node/binary) never
+#     sources this file; COPILOT_GITHUB_TOKEN / GITHUB_TOKEN stay in ITS env
+#     for Copilot API auth and the built-in GitHub MCP server (the sanctioned,
+#     hive-mediated write path under github.app_authored_prs).
+#   - gh-wrapper.sh still authenticates: it sources this at startup (losing
+#     only inherited token env, which it must never trust anyway — audit H3)
+#     and then exports GH_TOKEN itself from HIVE_AGENT_TOKEN_CACHE, which is a
+#     PATH, not a credential, and is deliberately not scrubbed.
+#   - git-credential-hive.sh reads the per-agent cache file directly; hive-merge
+#     and hive-open-pr likewise never rely on inherited token env.
+#
+# Residual (documented, closed elsewhere): a same-uid agent can still read a
+# backend CLI's /proc/<pid>/environ deliberately. That extraction lane — and
+# any smuggled credential — is closed at the transport by the MITM proxy's
+# Authorization strip/inject (#1861, PR #4032): the proxy, not the agent env,
+# decides what credential GitHub ever sees.
+#
+# POSIX sh compatible (dash-safe): no bashisms, and `unset` of an absent
+# variable is not an error. Keep the variable list in sync with
+# bin/test_agent_env_scrub.sh, which source-asserts every name below.
+unset GITHUB_TOKEN
+unset GH_TOKEN
+unset GH_ENTERPRISE_TOKEN
+unset GITHUB_ENTERPRISE_TOKEN
+unset COPILOT_GITHUB_TOKEN
+unset GITHUB_COPILOT_TOKEN
+unset HIVE_GITHUB_TOKEN
diff --git a/bin/agent-launch.sh b/bin/agent-launch.sh
index 8ab70f482..94462a502 100755
--- a/bin/agent-launch.sh
+++ b/bin/agent-launch.sh
@@ -202,6 +202,36 @@ if [[ "$BACKEND" == "copilot" ]]; then
   fi
 fi
 
+# SECURITY (#4045): the backend CLI re-exports live GitHub credentials into
+# the tool shells it spawns. The Copilot CLI authenticates from its own
+# persistent store (or COPILOT_GITHUB_TOKEN above) and sets GITHUB_TOKEN in
+# every shell it runs for the agent — after all launch-path scrubbing (#3931)
+# has already happened, so unsetting here cannot reach it. Observed live: a
+# wrapper-denied agent fell back to raw
+#   curl -H "Authorization: Bearer $GITHUB_TOKEN" https://api.github.com/...
+# and performed a repo write outside every gh-wrapper control.
+#
+# BASH_ENV is sourced by every NON-INTERACTIVE bash at startup — i.e. by each
+# tool shell the CLI spawns, INCLUDING ones the CLI hands an explicit
+# GITHUB_TOKEN in the spawn env — so the scrub runs inside the child, at the
+# only boundary that sees the backend's re-export. ENV covers interactive
+# POSIX-mode shells the same way. The CLI process itself is not a shell and
+# never sources this file, so its own auth (COPILOT_GITHUB_TOKEN, the
+# app_authored_prs GITHUB_TOKEN for the built-in GitHub MCP server) is
+# untouched: this changes what the AGENT'S SHELLS see, not what the backend
+# can do. gh-wrapper.sh and git-credential-hive.sh keep working — both
+# authenticate from HIVE_AGENT_TOKEN_CACHE (a path, deliberately not
+# scrubbed), never from inherited token env. Interactive shells get the same
+# scrub from the /etc/bash.bashrc guard installed by the Dockerfile.
+AGENT_ENV_SCRUB="${SCRIPT_DIR}/agent-env-scrub.sh"
+[[ -f "$AGENT_ENV_SCRUB" ]] || AGENT_ENV_SCRUB="/usr/local/bin/agent-env-scrub.sh"
+if [[ -f "$AGENT_ENV_SCRUB" ]]; then
+  export BASH_ENV="$AGENT_ENV_SCRUB"
+  export ENV="$AGENT_ENV_SCRUB"
+else
+  echo "[agent-launch] WARN: agent-env-scrub.sh not found — backend-exported GitHub tokens will be visible in agent tool shells (#4045)" >&2
+fi
+
 # Scrub GitHub token patterns and JWTs from stderr before writing to disk.
 scrub_tokens() {
   sed -u -E \
diff --git a/bin/test_agent_env_scrub.sh b/bin/test_agent_env_scrub.sh
new file mode 100644
index 000000000..c8861205b
--- /dev/null
+++ b/bin/test_agent_env_scrub.sh
@@ -0,0 +1,217 @@
+#!/usr/bin/env bash
+# Behavioural + source tests for the #4045 fix: backend CLIs re-export live
+# GitHub credentials (GITHUB_TOKEN et al.) into the tool shells they spawn for
+# agents, bypassing every gh-wrapper control. bin/agent-env-scrub.sh, sourced
+# via BASH_ENV at CHILD shell startup, must neutralize the token no matter how
+# it arrived — inherited or set explicitly in the spawn env by the CLI (the
+# observed mechanism, which parent-side scrubbing like #3931 cannot reach).
+#
+# Doctrine (audit 6/7): every block-assertion here has a positive control that
+# proves the probe can detect the leak, and the sanctioned paths (gh-wrapper
+# auth, backend-process auth) are asserted ALIVE — a scrub that broke them
+# would get reverted wholesale, which is worse than the vulnerability.
+#
+# No token material is real anywhere in this file; probes assert presence/
+# absence, never values.
+#
+# Run: bash bin/test_agent_env_scrub.sh
+set -uo pipefail
+
+REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+SCRUB="${REPO_ROOT}/bin/agent-env-scrub.sh"
+AGENT_LAUNCH="${REPO_ROOT}/bin/agent-launch.sh"
+WRAPPER="${REPO_ROOT}/bin/gh-wrapper.sh"
+DOCKERFILE="${REPO_ROOT}/src/Dockerfile"
+
+PASS=0
+FAIL=0
+
+pass() { echo "  PASS: $1"; PASS=$((PASS + 1)); }
+fail() {
+  echo "  FAIL: $1"
+  [ $# -gt 1 ] && echo "        $2"
+  FAIL=$((FAIL + 1))
+}
+
+# The single source of truth for what the scrub must cover. Adding a var here
+# without adding it to agent-env-scrub.sh fails the source assertions below.
+SCRUBBED_VARS=(
+  GITHUB_TOKEN
+  GH_TOKEN
+  GH_ENTERPRISE_TOKEN
+  GITHUB_ENTERPRISE_TOKEN
+  COPILOT_GITHUB_TOKEN
+  GITHUB_COPILOT_TOKEN
+  HIVE_GITHUB_TOKEN
+)
+
+# probe_child <BASH_ENV-value or ""> <extra env assignments...>
+# Spawns a bash -c child the way a backend CLI spawns a tool shell — with the
+# given vars set in the SPAWN env (env(1), exactly how the Copilot CLI hands
+# GITHUB_TOKEN to its shell tool) — and reports each scrubbed var as
+# name=present|absent.
+probe_child() {
+  local bash_env="$1"; shift
+  local probe='out=""; for v in GITHUB_TOKEN GH_TOKEN GH_ENTERPRISE_TOKEN GITHUB_ENTERPRISE_TOKEN COPILOT_GITHUB_TOKEN GITHUB_COPILOT_TOKEN HIVE_GITHUB_TOKEN; do if [ -n "$(eval "printf %s \"\${$v:-}\"")" ]; then out="$out $v=present"; else out="$out $v=absent"; fi; done; printf "%s" "$out"'
+  if [ -n "$bash_env" ]; then
+    env "$@" BASH_ENV="$bash_env" bash -c "$probe"
+  else
+    # -u BASH_ENV: the runner's own env must not accidentally scrub the
+    # positive control.
+    env -u BASH_ENV "$@" bash -c "$probe"
+  fi
+}
+
+FAKE_ENV=(
+  GITHUB_TOKEN="fake-github-token-for-test"
+  GH_TOKEN="fake-gh-token-for-test"
+  GH_ENTERPRISE_TOKEN="fake-ghe-token-for-test"
+  GITHUB_ENTERPRISE_TOKEN="fake-github-ent-token-for-test"
+  COPILOT_GITHUB_TOKEN="fake-copilot-token-for-test"
+  GITHUB_COPILOT_TOKEN="fake-copilot2-token-for-test"
+  HIVE_GITHUB_TOKEN="fake-hive-token-for-test"
+)
+
+echo "=== #4045: backend-exported tokens must not survive into agent tool shells ==="
+
+# ── POSITIVE CONTROL first: the probe must be able to SEE a leak ─────────────
+# Without this, a broken probe (or a probe run without the vars) would make
+# every absence-assertion below pass vacuously — the exact failure mode audit 6
+# kept finding.
+echo "-- positive control: unscrubbed shell shows every token --"
+result="$(probe_child "" "${FAKE_ENV[@]}")"
+if [[ "$result" != *"=absent"* && "$result" == *"GITHUB_TOKEN=present"* ]]; then
+  pass "probe detects all injected tokens when no scrub is wired"
+else
+  fail "probe detects all injected tokens when no scrub is wired" "got:$result"
+fi
+
+# ── The #4045 replay: CLI sets tokens in the tool shell's spawn env ──────────
+echo "-- scrubbed tool shell: every known token var is absent --"
+result="$(probe_child "$SCRUB" "${FAKE_ENV[@]}")"
+if [[ "$result" != *"=present"* ]]; then
+  pass "all ${#SCRUBBED_VARS[@]} token vars absent in a BASH_ENV-scrubbed child"
+else
+  fail "all ${#SCRUBBED_VARS[@]} token vars absent in a BASH_ENV-scrubbed child" "got:$result"
+fi
+
+# The literal incident shape: the shell expansion the bypass relied on must
+# come up empty, so the raw-curl fallback sends "Bearer " and 401s.
+result="$(env "${FAKE_ENV[@]}" BASH_ENV="$SCRUB" bash -c 'printf "Bearer %s" "${GITHUB_TOKEN:-}"')"
+if [ "$result" = "Bearer " ]; then
+  pass "incident replay: 'Authorization: Bearer \$GITHUB_TOKEN' expands empty"
+else
+  fail "incident replay: 'Authorization: Bearer \$GITHUB_TOKEN' expands empty" "expansion was non-empty"
+fi
+
+# Nested re-export: even a shell whose PARENT was scrubbed gets the token
+# re-injected by the CLI layer per spawn — each new bash must re-scrub because
+# BASH_ENV stays exported down the tree.
+result="$(env "${FAKE_ENV[@]}" BASH_ENV="$SCRUB" bash -c 'GITHUB_TOKEN=fake-reexported-by-cli bash -c "printf %s \"\${GITHUB_TOKEN:+present}\""')"
+if [ -z "$result" ]; then
+  pass "a token re-exported into a NESTED shell is scrubbed again"
+else
+  fail "a token re-exported into a NESTED shell is scrubbed again" "nested shell saw the token"
+fi
+
+# ── Scrub must not strip what the sanctioned paths need ──────────────────────
+echo "-- non-credential env survives the scrub --"
+result="$(env HIVE_AGENT_TOKEN_CACHE="/var/run/x" HIVE_ACMM_LEVEL=3 HTTPS_PROXY="http://127.0.0.1:3128" BASH_ENV="$SCRUB" bash -c 'printf "%s %s %s" "${HIVE_AGENT_TOKEN_CACHE:+cache}" "${HIVE_ACMM_LEVEL:+acmm}" "${HTTPS_PROXY:+proxy}"')"
+if [ "$result" = "cache acmm proxy" ]; then
+  pass "HIVE_AGENT_TOKEN_CACHE / ACMM / proxy vars pass through untouched"
+else
+  fail "HIVE_AGENT_TOKEN_CACHE / ACMM / proxy vars pass through untouched" "got '$result'"
+fi
+
+# ── SANCTIONED-PATH CONTROL: gh-wrapper still authenticates under the scrub ──
+# The wrapper sources the scrub at startup (it is a bash script under the
+# agent's BASH_ENV), losing any inherited token env — which it must never trust
+# anyway (H3) — then exports GH_TOKEN itself from HIVE_AGENT_TOKEN_CACHE. The
+# stub asserts the token it sees is exactly the CACHE one, proving (a) the
+# wrapper path is alive and (b) the stale inherited token was replaced.
+echo "-- gh-wrapper authenticates from the per-agent cache under the scrub --"
+WORK="$(mktemp -d)"
+trap 'rm -rf "$WORK"' EXIT
+TOKEN_CACHE="${WORK}/token"
+echo "ghs_fake_cache_token_for_test" >"$TOKEN_CACHE"
+STUB="${WORK}/gh-stub"
+STUB_LOG="${WORK}/stub.log"
+# The stub is /bin/sh ON PURPOSE: a bash stub would itself source BASH_ENV at
+# startup and scrub the GH_TOKEN the wrapper just exported — the REAL gh is a
+# Go binary and sources nothing, so /bin/sh (which reads neither BASH_ENV nor
+# non-interactive ENV) models it correctly.
+cat >"$STUB" <<'STUBEOF'
+#!/bin/sh
+if [ "${GH_TOKEN:-}" = "ghs_fake_cache_token_for_test" ]; then
+  echo "CACHE_TOKEN_OK" >> "${STUB_LOG}"
+elif [ -n "${GH_TOKEN:-}" ]; then
+  echo "WRONG_TOKEN" >> "${STUB_LOG}"
+else
+  echo "UNAUTHENTICATED" >> "${STUB_LOG}"
+fi
+exit 0
+STUBEOF
+chmod +x "$STUB"
+: >"$STUB_LOG"
+out="$(
+  env "${FAKE_ENV[@]}" \
+    BASH_ENV="$SCRUB" \
+    HIVE_GH_WRAPPER_REAL_GH="$STUB" \
+    STUB_LOG="$STUB_LOG" \
+    HIVE_AGENT="testagent" \
+    HIVE_AGENT_ID="testagent" \
+    HIVE_AGENT_MODE="ISSUES_PRS_MERGE" \
+    HIVE_ACMM_LEVEL=5 \
+    HIVE_AGENT_TOKEN_CACHE="$TOKEN_CACHE" \
+    HIVE_CONTRIBUTOR_MODE="false" \
+    bash "$WRAPPER" pr view 1 --repo owner/repo 2>&1
+)"
+rc=$?
+stub_saw="$(cat "$STUB_LOG" 2>/dev/null | tail -n1)"
+if [ "$rc" -eq 0 ] && [ "$stub_saw" = "CACHE_TOKEN_OK" ]; then
+  pass "wrapper reached gh with the CACHE token (inherited fakes discarded)"
+else
+  fail "wrapper reached gh with the CACHE token (inherited fakes discarded)" "rc=$rc stub_saw='${stub_saw:-nothing}' out=$(echo "$out" | head -n2 | tr '\n' ' ')"
+fi
+
+# ── The scrub file must be POSIX-sh safe (tool shells may be /bin/sh) ────────
+echo "-- scrub is sh-compatible --"
+if sh -c ". '$SCRUB'" 2>/dev/null; then
+  pass "agent-env-scrub.sh sources cleanly under sh"
+else
+  fail "agent-env-scrub.sh sources cleanly under sh"
+fi
+
+# ── Source-level invariants (drift guards) ───────────────────────────────────
+echo "-- source invariants --"
+for v in "${SCRUBBED_VARS[@]}"; do
+  if grep -qE "^unset[[:space:]]+${v}\$" "$SCRUB"; then
+    pass "scrub unsets ${v}"
+  else
+    fail "scrub unsets ${v}" "add 'unset ${v}' to bin/agent-env-scrub.sh"
+  fi
+done
+if grep -qE 'unset[[:space:]].*HIVE_AGENT_TOKEN_CACHE' "$SCRUB"; then
+  fail "scrub must NOT unset HIVE_AGENT_TOKEN_CACHE (it is a path the wrapper and git credential helper depend on)"
+else
+  pass "scrub leaves HIVE_AGENT_TOKEN_CACHE alone"
+fi
+if grep -qE '^\s*export BASH_ENV="\$AGENT_ENV_SCRUB"' "$AGENT_LAUNCH" && grep -qE '^\s*export ENV="\$AGENT_ENV_SCRUB"' "$AGENT_LAUNCH"; then
+  pass "agent-launch.sh wires BASH_ENV and ENV to the scrub"
+else
+  fail "agent-launch.sh wires BASH_ENV and ENV to the scrub" "the #4045 boundary is not installed for tool shells"
+fi
+if grep -q 'bin/agent-env-scrub.sh /usr/local/bin/agent-env-scrub.sh' "$DOCKERFILE"; then
+  pass "Dockerfile ships agent-env-scrub.sh"
+else
+  fail "Dockerfile ships agent-env-scrub.sh" "the launcher's fallback path /usr/local/bin/agent-env-scrub.sh would be empty in the image"
+fi
+if grep -q 'agent-env-scrub.sh' "$DOCKERFILE" && grep -q 'bash.bashrc' "$DOCKERFILE"; then
+  pass "Dockerfile installs the interactive-shell (/etc/bash.bashrc) arm"
+else
+  fail "Dockerfile installs the interactive-shell (/etc/bash.bashrc) arm"
+fi
+
+echo
+echo "=== $PASS passed, $FAIL failed ==="
+[ "$FAIL" -eq 0 ] || exit 1
diff --git a/src/Dockerfile b/src/Dockerfile
index 25fea85f1..76f653f89 100644
--- a/src/Dockerfile
+++ b/src/Dockerfile
@@ -357,6 +357,12 @@ COPY src/deploy/data/ /opt/hive/seed-data/
 COPY src/deploy/ttyd-tmux.sh /usr/local/bin/ttyd-tmux.sh
 COPY src/deploy/hive-panes.sh /usr/local/bin/hive-panes
 COPY bin/gh-app-token.sh bin/hive-config.sh bin/agent-launch.sh bin/git-credential-hive.sh /usr/local/bin/
+# SECURITY (#4045): sourced (not executed) by every shell in an agent's process
+# tree — via BASH_ENV/ENV from agent-launch.sh for non-interactive tool shells,
+# and via the /etc/bash.bashrc guard below for interactive ones — to unset the
+# GitHub credentials backend CLIs re-export into the shells they spawn. No exec
+# bit on purpose: it must only ever be sourced.
+COPY bin/agent-env-scrub.sh /usr/local/bin/agent-env-scrub.sh
 COPY bin/hive-open-pr.sh /usr/local/bin/hive-open-pr
 COPY bin/hive-merge.sh /usr/local/bin/hive-merge
 COPY bin/gh-wrapper.sh /usr/local/bin/gh
@@ -368,6 +374,13 @@ RUN chmod +x /usr/local/bin/ttyd-tmux.sh /usr/local/bin/hive-panes /usr/local/bi
     /usr/local/bin/hive-config.sh /usr/local/bin/agent-launch.sh /usr/local/bin/gh \
     /usr/local/bin/git-credential-hive.sh /usr/local/bin/hive-open-pr /usr/local/bin/hive-merge
 
+# SECURITY (#4045): interactive-shell arm of the agent credential scrub.
+# BASH_ENV (exported by agent-launch.sh) only reaches NON-interactive shells;
+# an interactive bash a backend CLI spawns for the agent reads
+# /etc/bash.bashrc instead. Gated on the agent-identity env agent-launch.sh
+# exports, so an operator's own `kubectl exec` shell is untouched.
+RUN printf '\n# hive #4045: scrub backend-exported GitHub credentials from agent shells\n[ -n "${HIVE_AGENT:-}${HIVE_AGENT_ID:-}" ] && . /usr/local/bin/agent-env-scrub.sh || true\n' >> /etc/bash.bashrc
+
 # SECURITY (audit F5-egress / refs #2674, #2678, #3760): the hive process needs
 # CAP_NET_ADMIN in its EFFECTIVE set so the MITM proxy can stamp SO_MARK on its
 # own upstream dials and be exempted from the forced-egress iptables REDIRECT