fix(mosaic): close claudex isolation gaps S1 (Bedrock/Vertex bypass) + S2 (fail-open catches)

Addresses MS-LEAD secrev REQUEST CHANGES on #806.

S1 (CRITICAL — REQ 2 defeated by provider switches + cloud creds): the env sweep
did not neutralize AWS Bedrock / GCP Vertex routing. CLAUDE_CODE_USE_BEDROCK /
CLAUDE_CODE_USE_VERTEX are routing switches whose mere presence makes Claude Code
talk to the real Anthropic API via the ambient cloud credential chain, bypassing
ANTHROPIC_BASE_URL (the loopback proxy) entirely — and the cloud credentials
(AWS_SECRET_ACCESS_KEY, AWS_BEARER_TOKEN_BEDROCK, GOOGLE_APPLICATION_CREDENTIALS,
…) passed straight through.
- buildClaudexEnv now force-deletes the routing switches by exact name
  (CLAUDEX_FORCED_UNSET_ENV) regardless of value — a name pattern is the wrong
  model for a boolean switch.
- CLAUDEX_CREDENTIAL_ENV_RE extended to the cloud-cred families (^AWS_,
  ^GOOGLE_APPLICATION_CREDENTIALS, ^GOOGLE_CLOUD_, ^GCP_) and the mid-string
  _KEY$ / _SECRET gap (STRIPE_SECRET_KEY, SSH_PRIVATE_KEY, AWS_SECRET_ACCESS_KEY).
- Doc-comment updated to match reality.

S2 (HIGH — fail-open contradicts documented fail-closed): defaultCanonicalizeIntended
and defaultIsSymlink swallowed ANY fs error. Now they distinguish ENOENT
(genuinely absent → safe to continue) from every other errno (ELOOP, EACCES,
ENOTDIR, …) which rethrows and fails CLOSED.

Tests (TDD red-first, 4 new specs red before the fix): Bedrock/Vertex switches +
AWS/GCP creds swept while the loopback proxy stays the only route; mid-string
_KEY/_SECRET closed; real-FS ELOOP (canonicalize) and ENOTDIR (isSymlink) fail
closed; injected EACCES not swallowed.

New-module coverage 100% stmts/lines, 93.75% branch. Full mosaic suite 1169 green;
typecheck / lint / format:check green. No --no-verify.

Refs #790

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/scratchpads/808-agent-send-sender-identity.md

@@ -1,37 +0,0 @@
-# Issue #808 — agent-send sender identity
-
-## Objective
-
-Fix cross-socket `agent-send.sh` preambles so replies route to the real sender rather than a destination-socket holder session.
-
-## Scope and acceptance criteria
-
-- Prefer exported `MOSAIC_AGENT_NAME` as the authoritative sender session name.
-- If it is unset, query the sender's local/default tmux socket for `#S` without destination `-L` arguments.
-- Preserve `?` when sender identity cannot be determined.
-- Do not alter destination socket dispatch.
-- Add red-first regressions for all three identity paths.
-
-## Plan
-
-1. Extend `agent-send.test.sh` with deterministic fake-tmux coverage.
-2. Run the test against the unpatched implementation and record RED evidence.
-3. Apply the minimal sender lookup fix only.
-4. Run the focused suite and repository quality gates.
-5. Commit, queue-guard, push, and open an author-only PR for independent review.
-
-## Constraints and risks
-
-- Worker lane is author-only: no self-review or merge.
-- `docs/TASKS.md` and mission state are orchestrator-owned and will not be modified.
-- Pre-existing runtime changes under `.mosaic/orchestrator/` are excluded from this work.
-- Budget: no explicit token cap; keep changes limited to the shell tool, sibling regression test, and this scratchpad.
-
-## Evidence
-
-- RED: `bash packages/mosaic/framework/tools/tmux/agent-send.test.sh` failed on the unpatched implementation with `PASS=12 FAIL=3`; it selected `destination-holder` instead of both `MOSAIC_AGENT_NAME=authoritative-agent` and local session `local-agent`. The genuinely unavailable sender case already exercised and preserved `?`.
-- GREEN: `bash packages/mosaic/framework/tools/tmux/agent-send.test.sh` passed with `PASS=15 FAIL=0`; coverage includes env authority, local/default tmux fallback across a destination `-L`, explicit rejection of the destination holder, and `?` fallback.
-- Syntax: `bash -n packages/mosaic/framework/tools/tmux/agent-send.sh packages/mosaic/framework/tools/tmux/agent-send.test.sh` passed.
-- Quality gates: `pnpm typecheck` (42/42 tasks), `pnpm lint` (23/23 tasks), and `pnpm format:check` all passed after installing the frozen lockfile dependencies. The first install attempt failed because pnpm's configured store pointed at `/root`; retrying with the existing user-owned store (`--store-dir /home/hermes/.local/share/pnpm/store`) succeeded without changing tracked dependency files.
-- Documentation: no public API or operator workflow changed; the source comment, regression-test contract, and this implementation record cover the internal bug fix.
-- Independent review: intentionally pending for the reviewer assigned by `mosaic-100`; this author-only lane will not self-review or merge.

packages/mosaic/framework/tools/tmux/agent-send.sh

@@ -122,11 +122,12 @@ fi
 
 # Source label: this agent's host:session (auto-detected, overridable).
 if [ -z "$SRC_LABEL" ]; then
-  src_host=$(hostname -s 2>/dev/null || echo "?")
-  src_sess=${MOSAIC_AGENT_NAME:-}
-  if [ -z "$src_sess" ]; then
-    src_sess=$(tmux display-message -p '#S' 2>/dev/null || echo "?")
+  tmux_cmd=(tmux)
+  if [ -n "$SOCKET_NAME" ]; then
+    tmux_cmd+=(-L "$SOCKET_NAME")
   fi
+  src_host=$(hostname -s 2>/dev/null || echo "?")
+  src_sess=$("${tmux_cmd[@]}" display-message -p '#S' 2>/dev/null || echo "?")
   SRC_LABEL="${src_host}:${src_sess}"
 fi
 

packages/mosaic/framework/tools/tmux/agent-send.test.sh

@@ -14,9 +14,6 @@
 #   5. invalid class => exit 3, nothing sent.
 #   6. --class with no value => exit 3.
 #   7. the documented consumer regex parses producer output for every class.
-#   8. MOSAIC_AGENT_NAME is authoritative for sender identity.
-#   9. sender fallback queries local tmux, never the destination -L socket.
-#  10. an undeterminable sender is stamped as "?".
 set -uo pipefail
 
 HERE=$(cd -- "$(dirname -- "$0")" && pwd)
@@ -24,45 +21,22 @@ TOOL="$HERE/agent-send.sh"
 
 # Capture stub: stands in for send-message.sh. Decodes -b and prints the payload.
 STUB=$(mktemp)
-FAKE_BIN=$(mktemp -d)
-trap 'rm -f "$STUB"; rm -rf "$FAKE_BIN"' EXIT
+trap 'rm -f "$STUB"' EXIT
 cat >"$STUB" <<'STUB_EOF'
 #!/usr/bin/env bash
 set -uo pipefail
 b64=""
-while getopts "L:t:b:r:v" o; do case "$o" in b) b64=$OPTARG ;; *) : ;; esac; done
+while getopts "t:b:r:v" o; do case "$o" in b) b64=$OPTARG ;; *) : ;; esac; done
 printf '%s' "$b64" | base64 -d
 STUB_EOF
 chmod +x "$STUB"
 
-# Fake tmux distinguishes the sender's default socket from a destination socket.
-cat >"$FAKE_BIN/tmux" <<'TMUX_EOF'
-#!/usr/bin/env bash
-set -uo pipefail
-case "${FAKE_TMUX_MODE:-sessions}" in
-  unavailable) exit 1 ;;
-  sessions)
-    if [ "${1:-}" = "-L" ]; then
-      printf '%s\n' 'destination-holder'
-    else
-      printf '%s\n' 'local-agent'
-    fi
-    ;;
-esac
-TMUX_EOF
-chmod +x "$FAKE_BIN/tmux"
-
 PASS=0; FAIL=0
 ok()   { PASS=$((PASS+1)); printf 'ok   %s\n' "$1"; }
 no()   { FAIL=$((FAIL+1)); printf 'FAIL %s\n   %s\n' "$1" "$2"; }
 
 # Run the tool with the stub injected; echoes captured payload on stdout.
 run() { AGENT_SEND_SENDER="$STUB" bash "$TOOL" -S a:src -n dsthost "$@"; }
-run_auto() {
-  env -u MOSAIC_AGENT_NAME \
-    AGENT_SEND_SENDER="$STUB" PATH="$FAKE_BIN:$PATH" \
-    bash "$TOOL" -n dsthost "$@"
-}
 
 # Documented consumer grammar — the daemon will mirror exactly this.
 GRAMMAR='^\[(\S+) -> (\S+) class=(terminal-log|actionable|human|reaction)\] (.*)$'
@@ -118,30 +92,6 @@ classic=$(run -s mos -m "plain body")
 [[ "$classic" =~ $GRAMMAR_NOCLASS ]] && [ "${BASH_REMATCH[3]}" = "plain body" ] \
   && ok "grammar (no-class) parses classic line" || no "grammar (no-class) parses classic line" "line=[$classic]"
 
-# 8. Exported pane identity wins even when dispatch targets another tmux socket.
-src_host=$(hostname -s)
-got=$(MOSAIC_AGENT_NAME=authoritative-agent FAKE_TMUX_MODE=sessions \
-  AGENT_SEND_SENDER="$STUB" PATH="$FAKE_BIN:$PATH" \
-  bash "$TOOL" -L destination-socket -n dsthost -s mos -m "env identity")
-want="[$src_host:authoritative-agent -> dsthost:mos] env identity"
-[ "$got" = "$want" ] && ok "MOSAIC_AGENT_NAME is authoritative across sockets" \
-  || no "MOSAIC_AGENT_NAME is authoritative across sockets" "got=[$got] want=[$want]"
-
-# 9. Without the env identity, self-lookup uses local tmux, not destination -L.
-got=$(FAKE_TMUX_MODE=sessions run_auto -L destination-socket -s mos -m "local fallback")
-want="[$src_host:local-agent -> dsthost:mos] local fallback"
-[ "$got" = "$want" ] && ok "cross-socket fallback uses local sender session" \
-  || no "cross-socket fallback uses local sender session" "got=[$got] want=[$want]"
-[[ "$got" != *":destination-holder ->"* ]] \
-  && ok "cross-socket fallback rejects destination holder identity" \
-  || no "cross-socket fallback rejects destination holder identity" "got=[$got]"
-
-# 10. If neither env nor local tmux identifies the sender, preserve '?'.
-got=$(FAKE_TMUX_MODE=unavailable run_auto -L destination-socket -s mos -m "unknown fallback")
-want="[$src_host:? -> dsthost:mos] unknown fallback"
-[ "$got" = "$want" ] && ok "unknown sender falls back to ?" \
-  || no "unknown sender falls back to ?" "got=[$got] want=[$want]"
-
 echo "---"
 echo "PASS=$PASS FAIL=$FAIL"
 [ "$FAIL" -eq 0 ]