fix(b3): eliminate command -v herdr bash function false positive in preflight checks (100% PASS)

.agents/reports/canary-projects-multi-agent-mux-creator-cline/report-e73917f8.md

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+# Cross-Code Review — Job e73917f8 (B-3: `command -v herdr` preflight bypass)
+
+- **Job**: e73917f8
+- **Reviewer**: cline
+- **Target**: Resolve B-3 — `command -v herdr` falsely matches the `herdr()` bash function in `lib.sh` (and `type -P herdr` matches the `.mam/shim` wrapper), so pre-flight passes on a host with no real `herdr` binary.
+- **Date**: 2026-08-06
+
+## 1. Scope & Diff Summary
+
+6 files modified (+68 / −14) plus 1 new test suite (untracked):
+
+| File | Change |
+|---|---|
+| `.agents/skills/lib.sh` | +44: new `_canonical_file()`, `_is_shim_path()`, rewritten `_resolve_real_herdr_path()` (PATH scan skipping shim dirs + canonicalised symlink target), new `has_real_herdr()`. Both `_HERDR_SHIM_DIR_PATTERN` and `_HERDR_SKILLS_BIN_PATTERN` defined before use. |
+| `.agents/skills/multi-agent-mux-create/scripts/create_session.sh` | preflight `command -v herdr \|\| type -P herdr` → `has_real_herdr` |
+| `.agents/skills/multi-agent-mux-delegate-job/multi-agent-mux-delegate-job` | preflight `command -v herdr` → `has_real_herdr` (in `run_agent()`) |
+| `.agents/skills/multi-agent-mux-create/SKILL.md` | doc preflight → `has_real_herdr` + explanatory comment |
+| `.agents/skills/multi-agent-mux-status/SKILL.md` | doc preflight → `has_real_herdr` + blockquote warning |
+| `IMPROVEMENTS.md` | B-3 moved §2(open, 8→7) → §5(completed, 5→6); counts/roadmap updated |
+| `tests/test_b3_herdr_preflight.py` | new, 196 lines, 10 functions / 11 cases (W-1…W-10, W-4 parametrised ×2) |
+
+## 2. Verification Performed
+
+| Check | Method | Result |
+|---|---|---|
+| Bash syntax | `bash -n` on lib.sh, create_session.sh, delegate-job | **PASS** (all 3) |
+| B-3 unit tests | `pytest tests/test_b3_herdr_preflight.py -v` | **11/11 PASS** (0.67s) |
+| Regression | `pytest tests/test_workspace_scope.py tests/test_b1_tier3_identity.py -q` | **10/10 PASS** |
+| Lint (shellcheck) | `command -v shellcheck` | **Not installed** in env — pre-existing limitation; `bash -n` substitutes. Not introduced by B-3. |
+| Completeness | `grep -rn 'command -v herdr\|type -P herdr' .agents/skills --include='*.sh'` | Only an **explanatory comment** (create_session.sh:84) remains; **no executable preflight left**. All 4 preflight sites migrated. |
+| Source-order | grep `lib.sh`/`has_real_herdr` in each script | lib.sh sourced **before** `has_real_herdr` at both call sites (create_session.sh:22→86; delegate-job:46→449). create_session.sh additionally proven e2e by W-5/W-6/W-7. |
+
+## 3. Logic Audit
+
+### 3.1 The two bypasses (confirmed by W-1)
+- `command -v herdr` → matches `herdr()` shell **function** (lib.sh:540 → `mam_herdr`).
+- `type -P herdr` → matches `$WORKSPACE_ROOT/.mam/shim/herdr`, because `_init_herdr_isolation` runs at **source time** (lib.sh:1784) and prepends the shim dir to PATH.
+Both pass on a herdr-less host → preflight was void. W-1 documents this so a future refactor cannot silently regress.
+
+### 3.2 New resolver (`_resolve_real_herdr_path` + `_is_shim_path` + `_canonical_file`)
+- **Critical check PASSED**: `_HERDR_SHIM_DIR_PATTERN` (line 48, `/multi-agent-herdr-shim/`) and `_HERDR_SKILLS_BIN_PATTERN` (line 49, `/.agents/skills/.bin`) are defined **before** `_is_shim_path` references them. An unset var would have made the glob `**` match every path (false-reject all). No such bug.
+- `_is_shim_path` matches `"/$1/"` (leading+trailing slash normalisation) against: `*/.mam/shim/*`, `*-shim/*`, `*/multi-agent-herdr-shim/*`, `*/.agents/skills/.bin/*`. Bare relative entry `.mam/shim` → `/.mam/shim/` → caught (W-10).
+- **Double shim check**: dir-level (line 81) **and** canonical-file-level (line 85). A symlink in a normal bin dir pointing into `.mam/shim` is resolved by `_canonical_file` (readlink loop ≤40 hops + `cd -P`/`pwd -P`) and rejected on the resolved target (W-8). A symlink to a **real** binary is accepted (W-9) — canonicalisation is not a blanket symlink rejection.
+- IFS save/restore around `for dir in $PATH`; restored after the loop **even on `break`**. Empty PATH elements skipped (safe — never picks cwd). `_canonical_file` failure falls back to the literal path. Sound.
+
+### 3.3 Operability — no `herdr()` regression
+- `herdr()` (lib.sh:540) → `mam_herdr()` (lib.sh:531) → executes `$WORKSPACE_ROOT/.mam/shim/herdr` directly. It does **not** use lib.sh's `_REAL_HERDR_PATH`.
+- The shim wrapper generated by `_init_herdr_isolation` (lib.sh:112-180) carries its **own** embedded `_resolve_real_herdr()` (lib.sh:118-132) and a local `REAL_HERDR` — fully self-contained.
+- Old code set `_REAL_HERDR_PATH="herdr"` unconditionally at definition; new code sets it only inside `_resolve_real_herdr_path` when a real binary is found. Since **no consumer** (`herdr()`/shim wrapper) depends on `_REAL_HERDR_PATH` being pre-set, removing the unconditional default is **safe**. Confirmed by regression suite (10/10) and the e2e W-5/W-6/W-7 tests.
+
+### 3.4 IMPROVEMENTS.md arithmetic
+- Open: **15** = 2 (arch) + 7 (edge, was 8, −B-3) + 2 (orch) + 4 (legacy). ✓
+- Completed: **6** = A-1, A-5, B-1, **B-3**, C-1, O-1. ✓
+## 4. Findings
+
+### R-1 (Minor, Non-blocking) — Broad `-shim/*` pattern is a conservative false-positive
+`_is_shim_path`'s `*-shim/*` glob will reject a **legitimate** herdr installed in any directory whose canonical path contains the substring `-shim/` (e.g. `/opt/foo-shim/bin/herdr`). This fails **closed** (preflight says "not installed" when it is) — the safe direction — and is explicitly tested behaviour (W-4 with `my-shim`/`multi-agent-herdr-shim`). Acceptable for a preflight gate; a user hitting this can place herdr in a differently-named dir or override `_HERDR_SHIM_DIR_PATTERN`. No action required; recorded for awareness.
+
+### R-2 (Minor, Non-blocking, pre-existing / out-of-scope) — Shim wrapper's own resolver is less strict
+The shim wrapper's embedded `_resolve_real_herdr()` (lib.sh:118-132) uses a simpler dir-name-substring check (no canonical-file symlink resolution) than the new lib.sh `has_real_herdr`. Thus a symlink-in-normal-dir pointing into `.mam/shim` is rejected by the **preflight** but would, if preflight were bypassed, still be selectable by the shim wrapper's resolver (potential recursion). This is a **pre-existing** characteristic of the shim wrapper, **not touched** by the B-3 diff, and the new preflight gate now catches it first. Not a B-3 defect; noted as a future consistency follow-up.
+
+### R-3 (Info) — shellcheck gate not runnable here
+shellcheck is not installed in this environment, so the IMPROVEMENTS §7-D shellcheck gate could not be re-run for the changed files. Pre-existing environment limitation, unchanged by B-3. `bash -n` syntax validation PASS on all three scripts.
+
+## 5. Conclusion
+
+B-3 is **fully and correctly resolved**. The root cause (two independent bypasses — `herdr()` function match + `.mam/shim` wrapper match) is correctly diagnosed and fixed with a real-binary PATH scan that skips shim/wrapper dirs at both the directory-name and canonicalised-symlink-target levels. All 4 preflight sites are migrated; no executable `command -v herdr`/`type -P herdr` preflight remains. The fix cannot regress the `herdr()`→shim-wrapper runtime path (independent of `_REAL_HERDR_PATH`). 11/11 new tests + 10/10 regression tests PASS. IMPROVEMENTS.md bookkeeping is arithmetically consistent. Findings R-1/R-2/R-3 are all non-blocking (R-1/R-2 are conservative-direction or out-of-scope; R-3 is an env limitation).
+
+No design-level rework is warranted — this is a clean, well-tested bug fix.
+
+[VERDICT: PASS]