fix(#808): never borrow a session identity for non-tmux senders

When MOSAIC_AGENT_NAME is unset and the sender has no tmux client context
($TMUX empty), agent-send.sh fell back to 'tmux display-message -p #S',
which outside tmux reports the LAST-ACTIVE session on the server. A
nameless sender was silently stamped as whichever seat touched tmux most
recently, forging that seat's identity in the preamble.

Incident (2026-08-20, host sb-it-1-dt): a nameless non-tmux sender was
stamped 'peggy', a live seat, on a message delivered TO peggy. Reproduced
end-to-end before the fix; capture in the seat evidence note.

Fix: the display-message fallback now runs only when $TMUX is set (inside
tmux it resolves the caller's own session — the case #808 built it for).
Outside tmux with no name, the label is host:unverified. Deliberate
identity remains available via -S. Chosen over refusing the send: nameless
senders are legitimate; the defect was borrowing an identity, not lacking
one.

Tests: suite made hermetic (TMUX controlled explicitly; results no longer
depend on the caller's context — previously tests 9/10 inherited the
caller's TMUX). New case 9b: no-tmux sender is labeled unverified and
never a borrowed name (red on original: host:local-agent borrowed from the
fake tmux server; green after). 19/19 in both caller contexts.

AGENTS.md

@@ -81,6 +81,73 @@ pnpm format:check  # Prettier check
 pnpm build         # Build all packages and applications
 ```
 
+## Branch Model and Merge Process — `main` and `next` (CANONICAL)
+
+**Every contribution targets `next` first. No exceptions.** Features, fixes, tests,
+docs, and policy changes all take the same route; urgency changes queue priority,
+never the route. Agents never commit to or merge into `main`.
+
+| Branch | Role                                                             | Who merges into it                                                          |
+| ------ | ---------------------------------------------------------------- | --------------------------------------------------------------------------- |
+| `next` | Integration trunk — the only PR target for contributions         | The designated merge-gate agent, after all gates pass. Never the PR author. |
+| `main` | Stable/release line — receives promotion merges from `next` only | Jason only (or an agent he explicitly delegates for a named promotion).     |
+
+### Contribution sequencing (in order, no skipping)
+
+1. **Issue first.** Work is tracked in a Gitea issue before a branch exists. The
+   issue number appears in the branch name and the PR body.
+2. **Branch from the current `origin/next` head.** Name it
+   `feat/…`, `fix/…`, `docs/…`, or `test/…` with the issue number
+   (e.g. `docs/1214-branch-process`). Record the base SHA in the PR body.
+3. **Develop with evidence.** Applicable tests accompany the change. Hooks are
+   never bypassed (`--no-verify` is prohibited). Stage explicit paths — never
+   `git add -A`.
+4. **Open the PR against `next`.** The body states: scope, base SHA,
+   verification commands with results, and any known pre-existing failures on
+   the base — documented, not retried to green and not absorbed silently.
+5. **CI must be terminal-green on the exact head.** All bounded Woodpecker
+   steps succeed (`verify-terminal-green` contract). Pipelines for fork PRs
+   start `blocked`; a maintainer approves the run — approving CI is not
+   approving the PR.
+6. **Independent review. Self-merge is prohibited** — for every agent, on every
+   PR, including trivial ones. Where the change touches protected or
+   contract-bearing content, the reviewer verifies the exact head
+   (exact-byte/exact-blob comparison), not a description of it. An `AMEND`
+   verdict returns the PR to its author; the reviewer's gate stays held until
+   a fresh exact head passes.
+7. **Merge into `next`** happens only after CI green + review pass, pinned to
+   the reviewed head SHA (a post-review push voids the review).
+8. **Promotion `next` → `main`** is a deliberate, Jason-owned reconciliation
+   merge — not part of any contribution's lifecycle. Contributors are done at
+   step 7.
+
+### Responsibilities
+
+- **Contributor** — base pinning, green CI, evidence in the PR body,
+  responding to AMEND verdicts, never merging own work.
+- **Reviewer / merge gate** — independent verification on the exact head;
+  holds and lifts gates; executes the merge into `next`.
+- **Orchestrator / adjudicator** — cross-PR sequencing, disposition when PRs
+  collide, conflict adjudication.
+- **Jason** — `next` → `main` promotions, merge-authority grants, collaborator
+  and token provisioning. Agents cannot grant themselves or each other any of
+  these.
+
+### Hotfixes and divergence
+
+- A hotfix follows the same path: branch from `next`, PR to `next`, gates,
+  merge, then an expedited Jason-owned promotion if `main` needs it urgently.
+  Committing the fix to `main` directly is prohibited even under pressure.
+- **Never land work on `main` that is not on `next`.** This has happened
+  (issue #1152's goal controller reached `main` without reaching `next`) and
+  every later PR paid for it. If it happens anyway: transplant the work onto
+  a `next`-based branch with provenance-preserving commits
+  (`git cherry-pick -x` or explicit SHA references in the messages), PR it
+  through the normal gates, and let promotion re-align `main`. Do not
+  hand-patch `main` to compensate.
+- Force-pushing a branch you do not own is prohibited; rebasing your own PR
+  branch is fine before review, and voids any review already given.
+
 ## Database and Local Runtime Safety
 
 - Current local data-layer work uses in-process PGlite; leave `DATABASE_URL` unset.

packages/mosaic/framework/tools/fleet/start-agent-session.sh

@@ -292,6 +292,16 @@ esac
 _build_runtime_bin_prefix() {
   local candidates=()
   if [ -n "$MOSAIC_RUNTIME_BIN" ]; then candidates+=("$MOSAIC_RUNTIME_BIN"); fi
+  # A host with no system Node gets one bootstrapped here by tools/install.sh, which
+  # records it in ~/.profile. The fleet unit runs `env -i ... bash --noprofile --norc`
+  # by design, so ~/.profile is never read and the directory has to be named here.
+  # The npm probe below cannot cover this: it reports a package prefix
+  # (~/.npm-global), never a Node runtime directory. It sits ahead of the npm probe so
+  # the bootstrapped runtime wins on a host that has both — that is the one the installer
+  # verified — while an explicit MOSAIC_RUNTIME_BIN still outranks it.
+  # Runtime binaries are `#!/usr/bin/env node`, so without this the pane resolves the
+  # binary and then dies on `env: 'node': No such file or directory`.
+  candidates+=("$PANE_HOME/.mosaic/node/current/bin")
   if command -v npm >/dev/null 2>&1; then
     local npm_prefix
     npm_prefix=$(npm config get prefix 2>/dev/null) || true

packages/mosaic/framework/tools/fleet/test-start-agent-session.sh

@@ -520,6 +520,93 @@ for blocked in LD_PRELOAD= BASH_ENV= MOSAIC_UNTRUSTED_SENTINEL=; do
   contains_literal "$pane_environment" "$blocked" && fail "runtime pane received $blocked"
 done
 
+# #1256. On a host with no system Node, tools/install.sh bootstraps one into
+# ~/.mosaic/node/ and writes that directory to ~/.profile. The fleet unit runs
+# `env -i ... bash --noprofile --norc`, so ~/.profile is never read — correctly, by
+# design — and _build_runtime_bin_prefix does not list the bootstrap directory. Its
+# `npm config get prefix` branch cannot cover the gap either: the installer points
+# npm's prefix at ~/.npm-global, so that branch contributes the npm-global directory
+# and never the Node one, however it resolves.
+#
+# The property under test is not "the string is in PATH". It is that the pane can
+# EXECUTE a Node-shebang runtime binary — which is what `mosaic` is
+# (`#!/usr/bin/env node`) and what actually failed: measured on a greenfield VM as
+# `env: 'node': No such file or directory` after a clean install that reported success.
+#
+# So this case runs the pane for real and requires it to have run. A PATH-substring
+# assertion would pass on a fix that put the directory in the wrong position, and it
+# would keep passing if the pane later stopped running for some unrelated reason.
+: > "$TMUX_CALLS"
+HOME_NODE="$ROOT/bootstrap-node/.config/mosaic"
+write_generated "$HOME_NODE" "coder-node"
+NODE_PANE_HOME="${HOME_NODE%/.config/mosaic}"
+NODE_BOOTSTRAP_BIN="$NODE_PANE_HOME/.mosaic/node/current/bin"
+mkdir -p "$NODE_BOOTSTRAP_BIN"
+
+# The bootstrapped runtime. It records that it ran, which is the evidence this case
+# turns on: no node reachable from the pane means no marker.
+cat > "$NODE_BOOTSTRAP_BIN/node" <<'SHIM'
+#!/usr/bin/env bash
+set -euo pipefail
+env -0 > "${MOSAIC_HOME:?}/fleet/pane-environment"
+SHIM
+chmod +x "$NODE_BOOTSTRAP_BIN/node"
+
+# write_generated plants its symlinks under the MOSAIC_HOME it is given; here the
+# pane's HOME is the trusted parent, so the pane's view of "installed" is this
+# directory instead. `pi` is what #1241 resolves against PANE_PATH; `mosaic` is what
+# the pane then executes, and it is a Node script — not a bash script that would run
+# anywhere and quietly hide the defect.
+mkdir -p "$NODE_PANE_HOME/.npm-global/bin"
+ln -sf "$FAKE_BIN/pi" "$NODE_PANE_HOME/.npm-global/bin/pi"
+printf '#!/usr/bin/env node\n' > "$NODE_PANE_HOME/.npm-global/bin/mosaic"
+chmod +x "$NODE_PANE_HOME/.npm-global/bin/mosaic"
+
+# The npm branch is modelled ALIVE and still cannot close the gap, which is the
+# stronger statement. An earlier draft of this case tried to model npm as absent —
+# true on a real bootstrap host, where npm lives only in the Node directory — and it
+# refused to run anywhere npm is in the system path, i.e. most machines. It was also
+# the weaker claim: it would have proven only that a dead branch supplies nothing.
+#
+# On a bootstrap host the installer sets npm's prefix to ~/.npm-global. So even with
+# `command -v npm` true and the branch executing, `npm config get prefix` yields the
+# npm-global directory and never the Node one. The gap does not depend on whether
+# that branch runs.
+NODE_LAUNCHER_BIN="$ROOT/bootstrap-node-launcher-bin"
+mkdir -p "$NODE_LAUNCHER_BIN"
+ln -sf "$FAKE_BIN/tmux" "$NODE_LAUNCHER_BIN/tmux"
+ln -sf "$FAKE_BIN/npm" "$NODE_LAUNCHER_BIN/npm"
+
+/usr/bin/env -i \
+  "HOME=$NODE_PANE_HOME" \
+  "PATH=$NODE_LAUNCHER_BIN:/usr/bin:/bin" \
+  "MOSAIC_HOME=$HOME_NODE" \
+  "MOSAIC_TEST_TMUX_CALLS=$TMUX_CALLS" \
+  "MOSAIC_TEST_HOME=$NODE_PANE_HOME" \
+  "MOSAIC_TEST_NPM_PREFIX=$NODE_PANE_HOME/.npm-global" \
+  MOSAIC_TEST_FLEET_OWNER=123e4567-e89b-12d3-a456-426614174000 \
+  MOSAIC_TEST_EXECUTE_PANE=1 \
+  "MOSAIC_TEST_PANE_PID=$$" \
+  "$START" coder-node
+
+[ -f "$HOME_NODE/fleet/pane-environment" ] || \
+  fail "pane could not execute a Node-shebang runtime: $NODE_BOOTSTRAP_BIN is absent from PANE_PATH (#1256)"
+node_pane_environment=$(tr '\0' '\n' < "$HOME_NODE/fleet/pane-environment")
+# Colon-pad and match a whole element. A regex with `(^|:)` after `.*` looks like it
+# does this and does not: an anchor cannot match mid-pattern, so it silently requires
+# a leading colon and rejects the directory in FIRST position — which is where THIS
+# FIXTURE puts it: it runs under `env -i` with no MOSAIC_RUNTIME_BIN, so the bootstrap
+# directory leads. That is a property of the fixture, not of the fix — in general the
+# directory sits second, after MOSAIC_RUNTIME_BIN. The colon padding makes the
+# assertion position-independent either way, which is why it is written this way and
+# not with an anchor. That produced a failure reading "pane ran but PANE_PATH does not
+# carry <dir>" against a PATH whose first element was that dir.
+node_pane_path=":$(printf '%s\n' "$node_pane_environment" | sed -n 's/^PATH=//p' | head -1):"
+case "$node_pane_path" in
+  *":$NODE_BOOTSTRAP_BIN:"*) ;;
+  *) fail "pane ran but PANE_PATH does not carry $NODE_BOOTSTRAP_BIN (PATH=$node_pane_path)" ;;
+esac
+
 write_interaction_generated() {
   local home="$1"
   local agent="$2"

packages/mosaic/framework/tools/git/pr-merge.sh

@@ -128,6 +128,7 @@ BASE_BRANCH="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; print(
 HEAD_BRANCH="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; print((json.load(sys.stdin).get("headRefName") or "").strip())')"
 HEAD_SHA="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; print((json.load(sys.stdin).get("headRefOid") or "").strip())')"
 HEAD_REPO="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; value=json.load(sys.stdin).get("headRepository") or ""; print((value.get("nameWithOwner") or value.get("full_name") or "") if isinstance(value, dict) else str(value).strip())')"
+BASE_REPO="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; value=json.load(sys.stdin).get("baseRepository") or ""; print((value.get("nameWithOwner") or value.get("full_name") or "") if isinstance(value, dict) else str(value).strip())')"
 PR_TITLE="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; print((json.load(sys.stdin).get("title") or "").strip())')"
 PR_AUTHOR="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; value=json.load(sys.stdin).get("author") or ""; print((value.get("login") or "").strip() if isinstance(value, dict) else str(value).strip())')"
 if [[ "$BASE_BRANCH" != "main" && "$BASE_BRANCH" != "next" ]]; then
@@ -144,10 +145,19 @@ if [[ -n "$EXPECT_HEAD" && "$HEAD_SHA" != "$EXPECT_HEAD" ]]; then
 fi
 
 if [[ "$DRY_RUN" != true ]]; then
+    # CI statuses for a PR live on the BASE repo (Woodpecker posts there),
+    # even when the head branch lives in a fork. Reading status against the
+    # fork repo yields statuses:null -> malformed for every fork PR (#1215,
+    # gate-merge-01 B1). The head repo is used only for head-sha identity;
+    # when metadata carries no base repository, the origin repo is where CI
+    # posts and remains correct for same-repo PRs.
+    if [[ -z "$BASE_REPO" ]]; then
+        BASE_REPO="$(get_repo_owner)/$(get_repo_name)"
+    fi
     "$SCRIPT_DIR/ci-queue-wait.sh" \
         --purpose merge \
         -B "$HEAD_BRANCH" \
-        -R "$HEAD_REPO" \
+        -R "$BASE_REPO" \
         --sha "$HEAD_SHA" \
         -t "${MOSAIC_CI_QUEUE_TIMEOUT_SEC:-900}" \
         -i "${MOSAIC_CI_QUEUE_POLL_SEC:-15}"

packages/mosaic/framework/tools/git/pr-metadata.sh

@@ -209,6 +209,10 @@ base_ref = first_non_empty(
     data.get('base_ref'),
     data.get('base_label'),
 )
+base_repo = first_non_empty(
+    nested(data, 'base', 'repo', 'full_name'),
+    nested(data, 'base', 'repo', 'name_with_owner'),
+)
 
 if not head_ref or not base_ref:
     available = ', '.join(sorted(data.keys()))
@@ -229,6 +233,7 @@ normalized = {
     'headRefOid': head_sha,
     'headRepository': head_repo,
     'baseRefName': base_ref,
+    'baseRepository': base_repo,
     'labels': [l.get('name', '') for l in data.get('labels', []) if isinstance(l, dict)],
     'assignees': [a.get('login', '') for a in data.get('assignees', []) if isinstance(a, dict)],
     'milestone': nested(data, 'milestone', 'title') or '',

packages/mosaic/framework/tools/git/test-pr-merge-fork-ci-status.sh

@@ -0,0 +1,76 @@
+#!/usr/bin/env bash
+# B1 (stack #1215, gate-merge-01): for a fork PR the merge queue guard must
+# read CI status against the BASE repository. Woodpecker posts statuses on the
+# base repo; pr-metadata's headRepository names the fork, and passing it to
+# ci-queue-wait yields statuses:null -> state=malformed rc=3 on every fork PR.
+#
+# This fixture omits baseRepository entirely (the pre-B1 normalizer's shape),
+# so the guard must fall back to the origin repo — and must NEVER see the fork.
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+WORK_DIR="${MOSAIC_TEST_WORK_DIR:-$PWD/.mosaic-test-work/pr-merge-fork-ci-status}"
+FIXTURE_DIR="$WORK_DIR/tools/git"
+CALL_LOG="$WORK_DIR/queue-call.log"
+
+rm -rf "$WORK_DIR"
+mkdir -p "$FIXTURE_DIR"
+cp "$SCRIPT_DIR/pr-merge.sh" "$FIXTURE_DIR/pr-merge.sh"
+cp "$SCRIPT_DIR/detect-platform.sh" "$FIXTURE_DIR/detect-platform.sh"
+
+cat > "$FIXTURE_DIR/pr-metadata.sh" <<'SH'
+#!/usr/bin/env bash
+printf '%s\n' '{"baseRefName":"next","headRefName":"fix/b1-fork-branch","headRefOid":"fedcba9876543210fedcba9876543210fedcba98","headRepository":"stack-mos-dt-0/stack"}'
+SH
+
+cat > "$FIXTURE_DIR/ci-queue-wait.sh" <<'SH'
+#!/usr/bin/env bash
+printf '%s\n' "$*" > "${MOSAIC_QUEUE_CALL_LOG:?}"
+exit 42
+SH
+chmod +x "$FIXTURE_DIR"/*.sh
+
+# A git repo with an origin remote, so the origin fallback resolves.
+git init -q "$WORK_DIR/upstream"
+git -C "$WORK_DIR/upstream" remote add origin https://git.mosaicstack.dev/mosaicstack/stack.git
+
+set +e
+(
+    cd "$WORK_DIR/upstream"
+    export MOSAIC_QUEUE_CALL_LOG="$CALL_LOG"
+    "$FIXTURE_DIR/pr-merge.sh" -n 1215
+) >/dev/null 2>&1
+rc=$?
+set -e
+
+if [[ "$rc" -ne 42 ]]; then
+    echo "FAIL: expected queue stub rc=42 to propagate, got $rc" >&2
+    exit 1
+fi
+if [[ ! -s "$CALL_LOG" ]]; then
+    echo "FAIL: merge wrapper did not invoke the queue guard" >&2
+    exit 1
+fi
+if grep -q -- '-R stack-mos-dt-0/stack' "$CALL_LOG"; then
+    echo "FAIL: queue guard received the FORK repository for CI status (B1 regression)" >&2
+    cat "$CALL_LOG" >&2
+    exit 1
+fi
+if ! grep -q -- '-R mosaicstack/stack' "$CALL_LOG"; then
+    echo "FAIL: queue guard did not receive the base (origin) repository" >&2
+    cat "$CALL_LOG" >&2
+    exit 1
+fi
+if ! grep -q -- '-B fix/b1-fork-branch' "$CALL_LOG"; then
+    echo "FAIL: queue guard did not receive the PR head branch" >&2
+    cat "$CALL_LOG" >&2
+    exit 1
+fi
+if ! grep -q -- '--sha fedcba9876543210fedcba9876543210fedcba98' "$CALL_LOG"; then
+    echo "FAIL: queue guard did not receive the exact PR head SHA" >&2
+    cat "$CALL_LOG" >&2
+    exit 1
+fi
+
+echo "pr-merge fork-PR CI-status repository regression passed"

packages/mosaic/framework/tools/git/test-pr-merge-queue-branch.sh

@@ -15,7 +15,7 @@ cp "$SCRIPT_DIR/detect-platform.sh" "$FIXTURE_DIR/detect-platform.sh"
 
 cat > "$FIXTURE_DIR/pr-metadata.sh" <<'SH'
 #!/usr/bin/env bash
-printf '%s\n' '{"baseRefName":"main","headRefName":"fix/rm-03-fixture","headRefOid":"0123456789abcdef0123456789abcdef01234567","headRepository":"contributor/widgets-fork"}'
+printf '%s\n' '{"baseRefName":"main","baseRepository":"mosaicstack/stack","headRefName":"fix/rm-03-fixture","headRefOid":"0123456789abcdef0123456789abcdef01234567","headRepository":"contributor/widgets-fork"}'
 SH
 
 cat > "$FIXTURE_DIR/ci-queue-wait.sh" <<'SH'
@@ -52,8 +52,13 @@ if grep -q -- '-B main' "$CALL_LOG"; then
     cat "$CALL_LOG" >&2
     exit 1
 fi
-if ! grep -q -- '-R contributor/widgets-fork' "$CALL_LOG"; then
+if ! grep -q -- '-R mosaicstack/stack' "$CALL_LOG"; then
-    echo "FAIL: merge queue guard did not receive the fork head repository" >&2
+    echo "FAIL: merge queue guard did not receive the BASE repository for CI status" >&2
+    cat "$CALL_LOG" >&2
+    exit 1
+fi
+if grep -q -- '-R contributor/widgets-fork' "$CALL_LOG"; then
+    echo "FAIL: merge queue guard received the fork head repository (B1: statuses are posted on the base repo)" >&2
     cat "$CALL_LOG" >&2
     exit 1
 fi

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

@@ -126,7 +126,16 @@ 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=$(tmux display-message -p '#S' 2>/dev/null || echo "?")
+    if [ -n "${TMUX:-}" ]; then
+      # Inside tmux: display-message resolves against this client's own session.
+      src_sess=$(tmux display-message -p '#S' 2>/dev/null || echo "?")
+    else
+      # Outside tmux with no name: display-message reports the LAST-ACTIVE
+      # session — someone else's identity (measured 2026-08-20: a nameless
+      # non-tmux sender was stamped "peggy", a live seat, forged silently).
+      # Stamp an explicit unverified label instead; deliberate senders use -S.
+      src_sess="unverified"
+    fi
   fi
   SRC_LABEL="${src_host}:${src_sess}"
 fi

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

@@ -61,8 +61,15 @@ 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 "$@"; }
-run_auto() {
+# Hermetic auto-label runs: TMUX is controlled explicitly so results never
-  env -u MOSAIC_AGENT_NAME \
+# depend on whether the caller running this suite sits inside tmux.
+run_auto() {          # models a sender OUTSIDE tmux (no client context)
+  env -u MOSAIC_AGENT_NAME -u TMUX \
+    AGENT_SEND_SENDER="$STUB" PATH="$FAKE_BIN:$PATH" \
+    bash "$TOOL" -n dsthost "$@"
+}
+run_auto_in_tmux() {  # models a sender INSIDE tmux (client context exists)
+  env -u MOSAIC_AGENT_NAME TMUX=/fake/socket \
     AGENT_SEND_SENDER="$STUB" PATH="$FAKE_BIN:$PATH" \
     bash "$TOOL" -n dsthost "$@"
 }
@@ -145,7 +152,9 @@ want="[$src_host:authoritative-agent -> dsthost:mos] env identity"
   || 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=$(FAKE_TMUX_MODE=sessions run_auto -L destination-socket -s mos -m "local fallback")
+#    Sender is INSIDE tmux: the only context where display-message self-lookup
+#    is safe (it resolves against this client's own session).
+got=$(FAKE_TMUX_MODE=sessions run_auto_in_tmux -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=[$want]"
@@ -153,8 +162,17 @@ want="[$src_host:local-agent -> dsthost:mos] local fallback"
   && ok "cross-socket fallback rejects destination holder identity" \
   || no "cross-socket fallback rejects destination holder identity" "got=[$got]"
 
+# 9b. NO tmux context: display-message answers with the LAST-ACTIVE session —
+#     someone else's identity (forgery vector). The label must be `unverified`,
+#     never a borrowed name, even though a tmux server exists here and the fake
+#     would confidently answer `local-agent`.
+got=$(FAKE_TMUX_MODE=sessions run_auto -s mos -m "no tmux context")
+want="[$src_host:unverified -> dsthost:mos] no tmux context"
+[ "$got" = "$want" ] && ok "no-tmux sender labeled unverified, never borrowed" \
+  || no "no-tmux sender labeled unverified, never borrowed" "got=[$got] want=[$want]"
+
 # 10. If neither env nor local tmux identifies the sender, preserve '?'.
-got=$(FAKE_TMUX_MODE=unavailable run_auto -L destination-socket -s mos -m "unknown fallback")
+got=$(FAKE_TMUX_MODE=unavailable run_auto_in_tmux -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]"

packages/mosaic/package.json

@@ -25,7 +25,7 @@
     "lint": "eslint src",
     "typecheck": "tsc --noEmit",
     "test": "vitest run --passWithNoTests && pnpm run test:framework-shell",
-    "test:framework-shell": "bash framework/tools/quality/scripts/check-test-enumeration.sh && bash framework/tools/quality/scripts/test-check-test-enumeration.sh && python3 framework/tools/quality/scripts/test-framework-drift-check.py && bash framework/tools/quality/scripts/test-framework-drift-doctor.sh && bash framework/systemd/user/test-fleet-units.sh && python3 src/lease-broker/daemon_deadline_unittest.py && python3 src/lease-broker/normative_fragments_unittest.py && python3 src/lease-broker/promotion_binding_unittest.py && python3 src/lease-broker/promotion_trigger_unittest.py && python3 src/lease-broker/receipt_challenge_unittest.py && python3 src/lease-broker/context_recovery_unittest.py && python3 src/lease-broker/recovery_runtime_unittest.py && python3 src/lease-broker/recovery_b1_adversarial_unittest.py && python3 src/lease-broker/receipt_observer_client_unittest.py && python3 src/lease-broker/invariant_r_unittest.py && python3 src/lease-broker/framework_skill_portability_unittest.py && python3 src/mutator-gate/runtime_tools_unittest.py && python3 src/mutator-gate/runtime_launch_guard_unittest.py && python3 src/mutator-gate/version_coupling_unittest.py && python3 framework/tools/lease-broker/check-runtime-launches.py --root ../.. && bash framework/tools/codex/test-pr-diff-context.sh && bash framework/tools/qa/test-deps-preflight.sh && bash framework/tools/git/test-pr-edit.sh && bash framework/tools/git/test-pr-review-gitea-comment.sh && bash framework/tools/git/test-pr-review-repo-host-override.sh && bash framework/tools/git/test-ci-queue-wait-no-status.sh && bash framework/tools/git/test-ci-queue-wait-branch-absent.sh && bash framework/tools/git/test-ci-queue-wait-tristate.sh && bash framework/tools/git/test-ci-queue-wait-github-checks.sh && bash framework/tools/git/test-pr-merge-queue-branch.sh && bash framework/tools/git/test-pr-merge-head-pin.sh && bash framework/tools/git/test-pr-merge-message-field.sh && bash framework/tools/git/test-git-credential-mosaic.sh && bash framework/tools/git/test-gitea-token-identity.sh && bash framework/tools/git/test-explain-diagnostic-status-neutral.sh && bash framework/tools/git/test-detect-platform-outside-repo.sh && bash framework/tools/woodpecker/test-terminal-green-contract.sh && bash framework/tools/_scripts/test-install-ordering-guard.sh && bash framework/tools/_scripts/test-mosaic-init-rce.sh && bash framework/tools/tmux/agent-send.test.sh && bash framework/tools/wake/test-wake-store-ack.sh && bash framework/tools/wake/test-wake-store-enqueue-race.sh && bash framework/tools/wake/test-wake-digest-hmac.sh && bash framework/tools/wake/test-wake-digest-quarantine.sh && bash framework/tools/wake/test-wake-detector.sh && bash framework/tools/wake/test-wake-fn-oracle.sh && bash framework/tools/wake/test-wake-reconcile.sh && bash framework/tools/wake/test-wake-beacon.sh && bash framework/tools/wake/test-wake-preimage.sh && bash framework/tools/wake/test-wake-install.sh && bash framework/tools/glpi/test-list-http-status.sh && bash framework/tools/orchestrator/test-board-roll.sh && bash framework/tools/woodpecker/test-ci-wait-exit-matrix.sh && bash framework/tools/_scripts/test-fleet-transport-check.sh && bash framework/tools/_scripts/test-brain-home-check.sh"
+    "test:framework-shell": "bash framework/tools/quality/scripts/check-test-enumeration.sh && bash framework/tools/quality/scripts/test-check-test-enumeration.sh && python3 framework/tools/quality/scripts/test-framework-drift-check.py && bash framework/tools/quality/scripts/test-framework-drift-doctor.sh && bash framework/systemd/user/test-fleet-units.sh && python3 src/lease-broker/daemon_deadline_unittest.py && python3 src/lease-broker/normative_fragments_unittest.py && python3 src/lease-broker/promotion_binding_unittest.py && python3 src/lease-broker/promotion_trigger_unittest.py && python3 src/lease-broker/receipt_challenge_unittest.py && python3 src/lease-broker/context_recovery_unittest.py && python3 src/lease-broker/recovery_runtime_unittest.py && python3 src/lease-broker/recovery_b1_adversarial_unittest.py && python3 src/lease-broker/receipt_observer_client_unittest.py && python3 src/lease-broker/invariant_r_unittest.py && python3 src/lease-broker/framework_skill_portability_unittest.py && python3 src/mutator-gate/runtime_tools_unittest.py && python3 src/mutator-gate/runtime_launch_guard_unittest.py && python3 src/mutator-gate/version_coupling_unittest.py && python3 framework/tools/lease-broker/check-runtime-launches.py --root ../.. && bash framework/tools/codex/test-pr-diff-context.sh && bash framework/tools/qa/test-deps-preflight.sh && bash framework/tools/git/test-pr-edit.sh && bash framework/tools/git/test-pr-review-gitea-comment.sh && bash framework/tools/git/test-pr-review-repo-host-override.sh && bash framework/tools/git/test-ci-queue-wait-no-status.sh && bash framework/tools/git/test-ci-queue-wait-branch-absent.sh && bash framework/tools/git/test-ci-queue-wait-tristate.sh && bash framework/tools/git/test-ci-queue-wait-github-checks.sh && bash framework/tools/git/test-pr-merge-queue-branch.sh && bash framework/tools/git/test-pr-merge-fork-ci-status.sh && bash framework/tools/git/test-pr-merge-head-pin.sh && bash framework/tools/git/test-pr-merge-message-field.sh && bash framework/tools/git/test-git-credential-mosaic.sh && bash framework/tools/git/test-gitea-token-identity.sh && bash framework/tools/git/test-explain-diagnostic-status-neutral.sh && bash framework/tools/git/test-detect-platform-outside-repo.sh && bash framework/tools/woodpecker/test-terminal-green-contract.sh && bash framework/tools/_scripts/test-install-ordering-guard.sh && bash framework/tools/_scripts/test-mosaic-init-rce.sh && bash framework/tools/tmux/agent-send.test.sh && bash framework/tools/wake/test-wake-store-ack.sh && bash framework/tools/wake/test-wake-store-enqueue-race.sh && bash framework/tools/wake/test-wake-digest-hmac.sh && bash framework/tools/wake/test-wake-digest-quarantine.sh && bash framework/tools/wake/test-wake-detector.sh && bash framework/tools/wake/test-wake-fn-oracle.sh && bash framework/tools/wake/test-wake-reconcile.sh && bash framework/tools/wake/test-wake-beacon.sh && bash framework/tools/wake/test-wake-preimage.sh && bash framework/tools/wake/test-wake-install.sh && bash framework/tools/glpi/test-list-http-status.sh && bash framework/tools/orchestrator/test-board-roll.sh && bash framework/tools/woodpecker/test-ci-wait-exit-matrix.sh && bash framework/tools/_scripts/test-fleet-transport-check.sh && bash framework/tools/_scripts/test-brain-home-check.sh"
   },
   "dependencies": {
     "@mosaicstack/brain": "workspace:*",

packages/mosaic/src/stages/finalize-path.spec.ts

@@ -0,0 +1,152 @@
+/**
+ * setupPath profile management (issue #1327, MOSAIC-IMPROVEMENTS 4c / D25).
+ *
+ * The profile append used to be guarded on the binDir value it was about to
+ * write, which is blind to accumulation across different Mosaic homes: every
+ * wizard run against a fresh temp home appended a permanent block to the
+ * operator's real shell profile (1,061 measured appends on sb-it-1-dt).
+ *
+ * Arms below map to the requirements:
+ *   S1 sentinel-managed block, rewritten in place
+ *   S2 a non-default target home never touches the operator profile
+ *   S3 byte-identical profile across repeated runs
+ *   S4 legacy unmarked `# Mosaic` blocks collapse into the managed block
+ *   S5 the Windows ($env:Path) arm shares the same block logic
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { mkdtempSync, mkdirSync, writeFileSync, readFileSync, rmSync } from 'node:fs';
+import { join } from 'node:path';
+import { tmpdir, homedir } from 'node:os';
+
+let profilePathMock: string | null = null;
+
+vi.mock('../platform/detect.js', () => ({
+  getShellProfilePath: (): string | null => profilePathMock,
+}));
+
+import { setupPath, managedBlockFor, stripLegacyPathBlocks } from './finalize.js';
+
+// The real resolved default on this host. Tests use it as the comparator a
+// non-default home must fail against, exactly as the wizard would.
+const REAL_DEFAULT_HOME = join(homedir(), '.config', 'mosaic');
+
+function tempHome(prefix: string): string {
+  const dir = join(tmpdir(), prefix);
+  mkdirSync(join(dir, 'bin'), { recursive: true });
+  return dir;
+}
+
+describe('setupPath profile management (#1327)', () => {
+  let workDir: string;
+  let profileFile: string;
+  let defaultLikeHome: string;
+  let otherHome: string;
+  const baseline = '# existing operator content\nexport EDITOR=vim\n';
+
+  beforeEach(() => {
+    workDir = mkdtempSync(join(tmpdir(), 'setuppath-spec-'));
+    profileFile = join(workDir, '.bashrc');
+    writeFileSync(profileFile, baseline, 'utf-8');
+    profilePathMock = profileFile;
+    defaultLikeHome = tempHome(join(workDir, 'home-a', '.config', 'mosaic'));
+    otherHome = tempHome(join(workDir, 'home-b', '.config', 'mosaic'));
+  });
+
+  afterEach(() => {
+    profilePathMock = null;
+    rmSync(workDir, { recursive: true, force: true });
+  });
+
+  // S2 — the arm that MUST fail against the pre-fix code: a home that is not
+  // the resolved default may not modify the operator profile at all.
+  it('does not touch the operator profile when the target home is not the resolved default', () => {
+    const action = setupPath(otherHome, REAL_DEFAULT_HOME);
+    expect(action).toBe('skipped');
+    expect(readFileSync(profileFile, 'utf-8')).toBe(baseline);
+  });
+
+  it('returns skipped when no shell profile can be resolved', () => {
+    profilePathMock = null;
+    const action = setupPath(defaultLikeHome, defaultLikeHome);
+    expect(action).toBe('skipped');
+  });
+
+  // S1 + S3 — two distinct homes (each run as the resolved default in turn,
+  // the shape of two legitimate installs against one operator profile) and
+  // repeated runs against the same home both leave exactly one block.
+  it('leaves exactly one managed block after runs against two distinct homes', () => {
+    const first = setupPath(defaultLikeHome, defaultLikeHome);
+    expect(first).toBe('added');
+
+    const second = setupPath(otherHome, otherHome);
+    expect(second).toBe('added');
+
+    const content = readFileSync(profileFile, 'utf-8');
+    const beginCount = content.split('# >>> mosaic begin >>>').length - 1;
+    const endCount = content.split('# <<< mosaic end <<<').length - 1;
+    expect(beginCount).toBe(1);
+    expect(endCount).toBe(1);
+    expect(content).toContain(join(otherHome, 'bin'));
+    expect(content).toContain(baseline);
+  });
+
+  it('is byte-identical across repeated runs against the same home', () => {
+    setupPath(defaultLikeHome, defaultLikeHome);
+    const afterFirst = readFileSync(profileFile, 'utf-8');
+
+    const again = setupPath(defaultLikeHome, defaultLikeHome);
+    expect(again).toBe('already');
+    expect(readFileSync(profileFile, 'utf-8')).toBe(afterFirst);
+  });
+
+  // S4 — pre-existing unmarked blocks from the old append logic collapse
+  // into the single managed block instead of accumulating beside it.
+  it('collapses legacy unmarked # Mosaic blocks into the managed block', () => {
+    const legacy =
+      '# existing operator content\n' +
+      '# Mosaic\n' +
+      'export PATH="/tmp/mosaic-dead-wizard-1/bin:$PATH"\n' +
+      'export EDITOR=vim\n' +
+      '# Mosaic\n' +
+      'export PATH="/tmp/mosaic-dead-wizard-2/bin:$PATH"\n';
+    writeFileSync(profileFile, legacy, 'utf-8');
+
+    const action = setupPath(defaultLikeHome, defaultLikeHome);
+    expect(action).toBe('added');
+
+    const content = readFileSync(profileFile, 'utf-8');
+    expect(content).not.toContain('/tmp/mosaic-dead-wizard-1/bin');
+    expect(content).not.toContain('/tmp/mosaic-dead-wizard-2/bin');
+    expect(content).toContain('export EDITOR=vim');
+    expect(content.split('# >>> mosaic begin >>>').length - 1).toBe(1);
+    expect(content).toContain(join(defaultLikeHome, 'bin'));
+  });
+});
+
+describe('managed block helpers (#1327)', () => {
+  // S5 — the Windows arm shares markers and shape with the POSIX arm.
+  it('builds the $env:Path variant inside the same markers', () => {
+    const block = managedBlockFor('C:\\Users\\op\\.config\\mosaic\\bin', true);
+    expect(block).toContain('# >>> mosaic begin >>>');
+    expect(block).toContain('# <<< mosaic end <<<');
+    expect(block).toContain('$env:Path = "C:\\Users\\op\\.config\\mosaic\\bin;$env:Path"');
+  });
+
+  it('builds the POSIX export variant inside the same markers', () => {
+    const block = managedBlockFor('/home/op/.config/mosaic/bin', false);
+    expect(block).toContain('# >>> mosaic begin >>>');
+    expect(block).toContain('export PATH="/home/op/.config/mosaic/bin:$PATH"');
+    expect(block).toContain('# <<< mosaic end <<<');
+  });
+
+  it('strips legacy $env:Path pairs on the Windows arm', () => {
+    const legacy =
+      '# Mosaic\n$env:Path = "C:\\tmp\\dead\\bin;$env:Path"\n' +
+      '# Mosaic\n$env:Path = "C:\\tmp\\dead2\\bin;$env:Path"\n' +
+      'Write-Host hi\n';
+    const stripped = stripLegacyPathBlocks(legacy, true);
+    expect(stripped).not.toContain('C:\\tmp\\dead');
+    expect(stripped).toContain('Write-Host hi');
+  });
+});

packages/mosaic/src/stages/finalize.ts

@@ -1,11 +1,12 @@
 import { spawnSync } from 'node:child_process';
-import { existsSync, readFileSync, appendFileSync } from 'node:fs';
+import { existsSync, readFileSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
 import { platform } from 'node:os';
 import type { WizardPrompter } from '../prompter/interface.js';
 import type { ConfigService } from '../config/config-service.js';
 import type { WizardState } from '../types.js';
 import { getShellProfilePath } from '../platform/detect.js';
+import { DEFAULT_MOSAIC_HOME } from '../constants.js';
 import { ManifestError } from '../framework/manifest.js';
 import {
   getDefaultSkillPaths,
@@ -144,32 +145,87 @@ function runDoctor(mosaicHome: string): DoctorResult {
 
 type PathAction = 'already' | 'added' | 'skipped';
 
-function setupPath(mosaicHome: string, _p: WizardPrompter): PathAction {
+const PATH_BLOCK_BEGIN = '# >>> mosaic begin >>>';
-  const binDir = join(mosaicHome, 'bin');
+const PATH_BLOCK_END = '# <<< mosaic end <<<';
-  const currentPath = process.env['PATH'] ?? '';
+const PATH_BLOCK_NOTE = '# Managed by the Mosaic installer; this block is rewritten on install.';
 
-  if (currentPath.includes(binDir)) {
+/**
-    return 'already';
+ * The managed PATH block written into the operator's shell profile.
+ *
+ * The block is delimited by begin/end sentinels so any number of installs,
+ * against any homes, collapse to exactly one block: the writer replaces the
+ * region between the sentinels instead of appending a second copy (#1327).
+ */
+export function managedBlockFor(binDir: string, isWindows: boolean): string {
+  const exportLine = isWindows
+    ? `$env:Path = "${binDir};$env:Path"`
+    : `export PATH="${binDir}:$PATH"`;
+  return `${PATH_BLOCK_BEGIN}\n${PATH_BLOCK_NOTE}\n${exportLine}\n${PATH_BLOCK_END}\n`;
+}
+
+/**
+ * Remove legacy unmarked `# Mosaic` PATH pairs appended by pre-#1327
+ * installs. Only the exact two-line shape this installer used to write is
+ * removed; any other `# Mosaic` comment line is left alone.
+ */
+export function stripLegacyPathBlocks(content: string, isWindows: boolean): string {
+  const legacyExport = isWindows ? /^\$env:Path = ".*;\$env:Path"$/ : /^export PATH=".*:\$PATH"$/;
+  const lines = content.split('\n');
+  const kept: string[] = [];
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i] ?? '';
+    const next = i + 1 < lines.length ? lines[i + 1] : undefined;
+    if (line === '# Mosaic' && next !== undefined && legacyExport.test(next)) {
+      i += 1;
+      continue;
+    }
+    kept.push(line);
+  }
+  return kept.join('\n');
+}
+
+/** Drop the region between the managed-block sentinels, first occurrence. */
+function withoutManagedBlock(content: string): string {
+  const beginIdx = content.indexOf(PATH_BLOCK_BEGIN);
+  if (beginIdx < 0) return content;
+  const endIdx = content.indexOf(PATH_BLOCK_END, beginIdx);
+  if (endIdx < 0) return content;
+  return content.slice(0, beginIdx) + content.slice(endIdx + PATH_BLOCK_END.length);
+}
+
+export function setupPath(mosaicHome: string, resolvedDefaultHome: string): PathAction {
+  // Never write outside the home under test (#1327 S2): a wizard run against
+  // a non-default home (test harnesses, throwaway installs) must not mutate
+  // the operator's real shell profile.
+  if (mosaicHome !== resolvedDefaultHome) {
+    return 'skipped';
   }
 
+  const binDir = join(mosaicHome, 'bin');
   const profilePath = getShellProfilePath();
   if (!profilePath) return 'skipped';
 
   const isWindows = platform() === 'win32';
-  const exportLine = isWindows
+  const block = managedBlockFor(binDir, isWindows);
-    ? `\n# Mosaic\n$env:Path = "${binDir};$env:Path"\n`
-    : `\n# Mosaic\nexport PATH="${binDir}:$PATH"\n`;
 
-  // Check if already in profile
+  let content = '';
   if (existsSync(profilePath)) {
-    const content = readFileSync(profilePath, 'utf-8');
+    content = readFileSync(profilePath, 'utf-8');
-    if (content.includes(binDir)) {
+  }
-      return 'already';
+
-    }
+  // Migration (#1327 S4): legacy unmarked blocks collapse into the managed
+  // block, and an existing managed block is rewritten in place rather than
+  // appended beside itself (S1/S3).
+  const base = stripLegacyPathBlocks(withoutManagedBlock(content), isWindows);
+  const trimmed = base.replace(/\n+$/, '');
+  const next = trimmed.length === 0 ? block : `${trimmed}\n${block}`;
+
+  if (next === content) {
+    return 'already';
   }
 
   try {
-    appendFileSync(profilePath, exportLine, 'utf-8');
+    writeFileSync(profilePath, next, 'utf-8');
     return 'added';
   } catch {
     return 'skipped';
@@ -286,7 +342,7 @@ export async function finalizeStage(
   }
 
   // 7. PATH setup
-  const pathAction = setupPath(state.mosaicHome, p);
+  const pathAction = setupPath(state.mosaicHome, DEFAULT_MOSAIC_HOME);
 
   let summaryShown = false;
   const showSummary = () => {

scratchpads/2026-08-17-fleet-identity-comms-mosaic-tree.md

@@ -0,0 +1,73 @@
+# 2026-08-17 — Fleet identity, comms delivery, and the ~/.mosaic tree (continuation record)
+
+> **Status:** active continuation record | **Owner:** Jason (rulings) / fleet (delivery) | **Created:** 2026-08-17, sb-it-1-dt session with Jarvis (jarvis-brain)
+> **Audience:** the homelab agents continuing this effort tonight. Read this whole file before acting; it supersedes nothing but preserves structure and decisions that must not be lost.
+
+---
+
+## Why this exists
+
+A session on sb-it-1-dt (2026-08-17) produced three architecture decisions (two awaiting Jason's ruling), one incident postmortem (#1295), interim guardrail edits in the user-owned `~/.mosaic/` contract tree, and one new tool (`ensure-watcher.sh`). The work spans jarvis-brain (P0, not retained) and this repo (the product). **This file is the stack-side anchor so continuation does not depend on jarvis-brain surviving.**
+
+## 1. The `~/.mosaic` tree model — as-built, preserve this structure
+
+Three-tree split (this is design intent, not accident; keep it through all framework work):
+
+| Tree                | Owner     | Rule                                                                                                          |
+| ------------------- | --------- | ------------------------------------------------------------------------------------------------------------- |
+| `~/.config/mosaic/` | framework | upgrade-managed templates; NEVER user-edited; `mosaic upgrade` may overwrite                                  |
+| `~/.mosaic/`        | user      | working contracts, guides, fleet agents; upgrades reconcile with **deny-wins** (user edits never overwritten) |
+| repo satellites     | repos     | bootstrapped per-repo `.mosaic/` state                                                                        |
+
+As-built inventory of `~/.mosaic` on sb-it-1-dt (2026-08-17):
+
+- **Contract core:** `CONSTITUTION.md` (L0 law), `AGENTS.md` (dispatcher + guide router + Fleet Comms Watcher requirement), `SOUL.md` (generic base for ALL fleet agents, zero persona — includes the new **Fleet Boundaries** section), `STANDARDS.md` (universal standards — includes new **session identity** + **comms watcher hygiene** sections), `SYSTEM.md` (pure communication contract, byte-identical to jarvis-brain's prompt-testing `sr_opus_5_system_prompt.md`), `USER.md`, `TOOLS.md`.
+- **`guides/`** — user-owned working copies (E2E-DELIVERY, ORCHESTRATOR(+PROTOCOL,+LEARNINGS), WAKE-DOCTRINE, VAULT-SECRETS, etc.).
+- **`fleet/agents/`** — the per-agent store (this is MOSAIC-D-002's substrate, already in use):
+  - real agent dirs: `fargo/`, `orchestrator/`, `probe/`, `vision/`, `weekly-update/` — shape: `profile.json` (harness/account/overlay pointer) + `overlay.json` + `SOUL.md` (persona) + `scratch/` `work/` `notes/` subdirs (hygiene rules in root SOUL.md)
+  - `*.env.generated` launch overlays: `luna` `sol` `terra` (carry `MOSAIC_AGENT_NAME`, `_CLASS`, `_RUNTIME`, `_MODEL`, `_REASONING`, `_TOOL_POLICY`) — these are the mosaic-fleet seat launch envs; `inbox.env`, `itops.env` also present
+  - `probe/` is the validated layout proof: auth-bundle symlink chain, per-agent sessions, plugin-store symlink (from 2026-08-07)
+- **`auth/`, `config/`, `memory/`, `plugins/`, `skills/`, `skills-local/`** — per-tree copies/links for runtime isolation.
+- Related but outside the tree: watcher units at `~/.config/systemd/user/<agent>-comms-watcher.service`; watcher seen-state at `~/.local/state/comms-watcher-<agent>/`.
+
+## 2. Decisions register (2026-08-17 session)
+
+Full strict records live in jarvis-brain `docs/decisions/mosaic-stack/` (render on its dashboard); both are **Pending Jason's ruling**. Summaries so the content survives P0:
+
+- **MOSAIC-D-001 — SYSTEM.md as canonical harness system prompt.** Static core (Constitution+AGENTS+USER+overlays) in one tracked file; launcher renders dynamic tail (mission/PRD/fleet/persona). Delivery: `--append-system-prompt` (repeatable) for pi/claude; symlinked core file for codex (`$CODEX_HOME/instructions.md`) and opencode (`AGENTS.md`); their dynamic tail via initial prompt (needs live verification). Static-first order is the cache win. `SYSTEM.md` in `~/.mosaic` today is the communication-contract file — D-001's SYSTEM.md is the broader composition; naming to reconcile at implementation.
+- **MOSAIC-D-002 — per-agent harness homes + mechanical profiles.** Launch with targeted config-dir env vars (e.g. `PI_CODING_AGENT_DIR=~/.mosaic/fleet/agents/<name>/pi`), NOT literal HOME. SOUL.md identity mechanically generated from roster (single writer; kills the hand-copy drift measured in `agents/vision/SOUL.md` on jarvis-brain: declared Jarvis, answered Vision). Composes: SYSTEM core → per-agent SOUL → dynamic tail. `MOSAIC_AGENT_NAME` stays load-bearing for comms.
+- **Comms delivery tooling belongs in the STACK framework, not jarvis-brain** (decided in discussion; supersedes the interim placement). jarvis-brain keeps only the transport _data_ (`comms/` tree) while it lives. Agents launch from their own repos (terra from `~/src/stack` etc.) — delivery is transport-repo-relative, so this works; but every installed watcher unit's ExecStart currently points into `~/src/jarvis-brain/scripts/` — that dependency is the P0 trap to remove. Migration = move tools + regenerate units, in one step.
+- **Watcher provisioning is instantiation duty, never running-agent duty.** Interim landed as jarvis-brain `scripts/comms/ensure-watcher.sh` (idempotent ensure + `--status` boot check + interim identity warnings: missing target session, pane `MOSAIC_AGENT_NAME` mismatch via `/proc/<child>/environ`, bare-runtime NOTE). Framework move: fold into `mosaic agent --new` + fleet launch + `mosaic doctor` drift check.
+- **Prose guardrails landed (interim fences until mechanical fixes):** `~/.mosaic/SOUL.md` Fleet Boundaries (wrong-session tripwire; comms ownership; cross-agent investigation requires tasking) · `STANDARDS.md` session identity + watcher hygiene · `AGENTS.md` Fleet Comms Watcher requirement (P0-interim script path marked transitional).
+
+## 3. Incident → #1295 (already tracked here)
+
+`https://git.mosaicstack.dev/mosaicstack/stack/issues/1295` — docs-seat incident: cwd-keyed session files served three lives (dev chat → goals seat → 22 watcher injections into a wedged process); name-based watcher delivery with no identity verification; wedge after pi 0.84.1→0.84.2 update passes every liveness instrument. Proposed fixes enumerated there; provisioning follow-up in comment ID 23027.
+
+## 4. Open work queue (suggested sequence)
+
+1. **Comms tooling migration PR** (lane `next`): move `comms-watcher.sh`, `install-watcher.sh`, `ensure-watcher.sh` into the framework tree → deploy `~/.config/mosaic/tools/comms/`; regenerate existing units' ExecStart to framework paths (one-command sweep); keep `COMMS_WATCH_REPO` per-host config (points at a brain checkout until the queue transport lands). Reference: jarvis-brain commit `701c353b1`.
+2. **Ensure-on-instantiation**: `mosaic agent --new` / fleet launch call ensure semantics; `mosaic doctor` gains the drift check (`--status --all` semantics + `fred`'s hand-written unit as the known drift case; also note daphne/docs/happy/pepper/sanity/tiny/fargo currently have no watcher — cover or consciously exempt).
+3. **MOSAIC-D-002 implementation** (after ruling): per-agent homes via targeted env vars; roster-generated SOUL.md single-writer; extend the existing `*.env.generated` pattern; launch ledger keeps `config_home` audit.
+4. **MOSAIC-D-001 implementation** (after ruling): SYSTEM.md sourcing + per-harness delivery + `compose-contract` becomes render-core+tail with drift check; bench cache-ordering before/after (jarvis-brain `domains/software-dev/mosaic-stack/prompt-testing` has the bench).
+5. **Queue transport + forced separation** (longer term): supersedes watcher path; identity-verification and wedge-detection remain valid regardless of transport.
+6. **Docs inheritance**: jarvis-brain AGENTS.md's durable comms guidance (E7 pi-glyph delivery gotchas, capture-pane rules, comms protocol) must be inherited into stack docs before P0 retirement.
+
+## 5. Rules for tonight's agents
+
+- Lane: **`next`** only; nothing to `main` without Jason (standing ruling).
+- Attribution caveat #1280: Gitea/git identity from this host may misattribute (issue #1295 showed as created by `@mos-dt-0`); prefer per-invocation `git -c user.name=<seat>` and verify what the remote recorded.
+- Do not delete `sb-it-1-dt:docs]` (untracked file at repo root) — it is cited fleet-wide as incident evidence.
+- Edit user contracts in `~/.mosaic/`, never the templates in `~/.config/mosaic/`.
+- Do not restart other fleet seats unilaterally (goals/scrappy/sanity restart decisions are fred's/Jason's per the docs-seat report).
+
+## 6. Artifact map
+
+| Artifact                                                           | Where                                                                                                                    |
+| ------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------ |
+| Decision records D-001/D-002 (strict, pending ruling)              | jarvis-brain `docs/decisions/mosaic-stack/2026-08-17_mosaic-d-00{1,2}_*.md`                                              |
+| Incident issue + provisioning comment                              | stack #1295 + comment 23027                                                                                              |
+| ensure-watcher.sh (reference implementation)                       | jarvis-brain `scripts/comms/ensure-watcher.sh` (commit `701c353b1`)                                                      |
+| Bench for prompt A/B (pi, thinking levels, footer-token semantics) | jarvis-brain `domains/software-dev/mosaic-stack/prompt-testing/` + `docs/reports/2026-08-17-prompt-testing-glm-bench.md` |
+| Launcher inspection basis                                          | `@mosaicstack/mosaic` 0.0.49 `dist/commands/launch.js` (composeContract / ensureRuntimeConfig / harness-home isolation)  |
+| Guardrail edits                                                    | `~/.mosaic/{SOUL,AGENTS,STANDARDS}.md` on sb-it-1-dt (2026-08-17 16:53–17:04)                                            |