Verified: shell-expanded command name deobfuscation is correct and well-tested.

Reviewed the full diff — this is a solid security hardening. Key observations:

1. _deobfuscate_shell_word_for_detection() correctly iterates (max 2 passes) to collapse nested shell quoting/escaping + simple $(echo ...) and ${var/pat/repl} expansions into their literal form. The convergence guard (if deobfuscated == previous: break) prevents infinite loops.

2. _read_shell_word() properly skips $(...), ${...}, backtick substitutions, and quote-delimited spans without executing them — this is detection-only, not execution. The _scan_dollar_paren_end() handles balanced nesting with correct quote-awareness.

3. _iter_shell_command_starts() correctly identifies command-position starts after ;, &&, ||, |, \n, and nested $(...). The seen set deduplicates overlapping starts (e.g., $(echo rm) yields both position 0 and the inner command start).

4. _command_detection_variants() only yields deobfuscated variants that differ from the original — no unnecessary pattern re-evaluation.

5. Test coverage is thorough: backslash escapes (r\m), empty-quote literals (r''m, r""m), $(echo rm) substitution, ${0/x/r}m parameter replacement, and the negative case (echo $(echo rm) stays as echo, not promoted to command).

6. The 12-word prefix cap in _iter_shell_command_word_spans() prevents quadratic blowup on pathological inputs while still handling sudo -u user env VAR=val rm -rf /.

One minor observation: _iter_shell_command_starts() could yield a position inside a double-quoted $(...) context (the quote == '"' branch does starts.append(i + 2) for $(...) inside double quotes), but since the deobfuscation is detection-only and the outer quoting would prevent execution, this is a false-positive-safe over-approximation — not a bug.

LGTM from a security perspective.

Verified: shell-expanded command name deobfuscation is correct and well-tested.

Reviewed the full diff — this is a solid security hardening for the approval system's command detection layer. Key observations:

1. _command_detection_variants() correctly generates deobfuscated variants of shell commands by collapsing quoting, backslash escapes, and simple $(echo ...) / ${var/pat/repl} expansions. The two-pass iteration in _deobfuscate_shell_word_for_detection() handles nested obfuscation (e.g., r''m → rm).

2. _iter_shell_command_word_spans() properly skips wrapper commands (sudo, env, exec, etc.) and their options to find the actual command name at any position. The _SUDO_OPTIONS_WITH_ARG set correctly handles -u, -g, etc. that consume the next token.

3. _iter_shell_command_starts() handles compound commands (;, &&, ||, |, newlines) and nested $(...) substitutions, so $(echo rm) -rf / correctly identifies rm as the command name inside the substitution.

4. Non-overreach: The test test_echo_argument_substitution_not_promoted_to_command verifies that echo $(echo rm) -rf / is NOT flagged — command-name deobfuscation only applies to command-position words, not ordinary arguments. This prevents false positives.

5. Hardline blocklist integration: Both detect_dangerous_command() and detect_hardline_command() now iterate over variants, so all existing pattern checks automatically benefit from deobfuscation.

6. Test coverage is thorough: backslash escapes, empty quote pairs, $(echo ...) substitution, ${0/x/r}m parameter replacement, and negative cases for echo arguments. The hardline blocklist tests add corresponding obfuscated dangerous commands and non-dangerous echo cases.

LGTM.

Thanks for the detailed review. Yes, the double-quoted substitution case is intentionally conservative in the detection layer: it never executes shell code, and the regression tests keep argument-only cases like echo $(echo rm) -rf / from being promoted into command execution. Appreciate the careful check.

Thanks for catching this. I reproduced the failure on the GitHub merge result rather than the standalone PR head, and updated the branch accordingly.

What changed:

• Removed the global shell backslash / empty-quote stripping from _normalize_command_for_detection(), so argument text like echo r\m -rf / and echo r''m -rf / is no longer rewritten into echo rm -rf / before scanning.
• Kept shell deobfuscation scoped to command-position words in _command_detection_variants(), so command-position forms like r\m -rf / and r''m -rf / are still blocked.
• Preserved the current-main absolute HERMES_HOME config/env protection and made that rewrite understand Windows path separators too, so the cross-platform focused suite stays green.

Verification:

python -m pytest -o addopts="" -p no:cacheprovider tests\tools\test_hardline_blocklist.py -q
# 108 passed

python -m pytest -o addopts="" -p no:cacheprovider tests\tools\test_approval.py tests\tools\test_hardline_blocklist.py -q
# 321 passed

git diff --check
# passed

I also added Co-authored-by: egilewski <1078345+egilewski@users.noreply.github.com> to the follow-up commit for the fix direction from this review.

Thanks again, this was a good catch. I pushed a follow-up that keeps the command-position-only scanner but broadens the literal, non-executing shell-substitution folding.

What changed:

• Added command-word folding for literal printf substitutions: $(printf rm), $(printf %s rm), and split forms like $(printf r)m.
• Added support for echo -n rm inside command substitution.
• Added support for simple default parameter expansion in command position, e.g. ${unset:-rm}.
• Kept the folding scoped to command-position words only, with allowlist coverage for echo $(printf rm) -rf /, echo $(printf %s rm) -rf /, echo $(echo -n rm) -rf /, and echo ${unset:-rm} -rf /.

Verification:

python -B -m pytest -o addopts="" -p no:cacheprovider tests\tools\test_hardline_blocklist.py tests\tools\test_approval.py tests\tools\test_command_guards.py -q
# 353 passed

python -m pytest -o addopts="" -p no:cacheprovider tests\tools\test_approval.py tests\tools\test_hardline_blocklist.py -q
# 335 passed

git diff --check
# passed

The follow-up commit also includes the same Co-authored-by trailer for your review-driven fix direction.

Hi, human here: very nice of you to add me to co-authored-by, stealing that for my AGENTS.md.

I opened #43658 as a quickfix for the original issue, aimed at a faster merge with a smaller and narrower patch.

It does not cover as much as this PR: #40663 still has the broader command-position deobfuscation direction and more complete shell-word modeling. My recommendation is to keep #40663 open rather than treating #43658 as a replacement, and also open a new broader issue to track the remaining/generalized command-position shell-expansion coverage after the quickfix lands.