test(shellmode): make command lookup independent of host PATH

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  GO_VERSION: "1.27.2"
+  GO_VERSION: "1.27.3"
   # Module resolution: relay is the only GrayCodeAI module dependency and it is
   # published on the public proxy. Direct-VCS fallback is retained for anything
   # else.
@@ -37,6 +37,20 @@ env:
   GOWORK: "off"
 
 jobs:
+  commit-policy:
+    name: commit policy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - name: Enforce signed commits and no AI co-authors
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_EVENT_NAME: ${{ github.event_name }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          PUSH_BEFORE: ${{ github.event.before }}
+          PUSH_AFTER: ${{ github.event.after }}
+        run: bash scripts/check-commit-policy.sh
+
   version:
     name: Canonical version metadata
     runs-on: ubuntu-latest

internal/features/shellmode/classify.go

@@ -159,6 +159,10 @@ var (
 	cmdCache   = make(map[string]bool)
 )
 
+// lookPath is exec.LookPath, indirected so tests can make command lookup
+// deterministic instead of depending on which binaries the host has installed.
+var lookPath = exec.LookPath
+
 // isValidCommand checks if a word exists as a command in PATH (cached).
 func isValidCommand(word string) bool {
 	cmdCacheMu.RLock()
@@ -167,7 +171,7 @@ func isValidCommand(word string) bool {
 		return v
 	}
 	cmdCacheMu.RUnlock()
-	_, err := exec.LookPath(word)
+	_, err := lookPath(word)
 	result := err == nil
 	cmdCacheMu.Lock()
 	cmdCache[word] = result

internal/features/shellmode/classify_test.go

@@ -1,8 +1,45 @@
 package shellmode
 
-import "testing"
+import (
+	"os/exec"
+	"testing"
+)
+
+// stubCommands replaces PATH lookup for the duration of a test, so routing
+// results depend only on the input rather than on which binaries the host
+// happens to have installed. It also clears the package-level lookup cache so
+// earlier tests cannot leak their results into this one.
+func stubCommands(t *testing.T, names ...string) {
+	t.Helper()
+	allowed := make(map[string]bool, len(names))
+	for _, name := range names {
+		allowed[name] = true
+	}
+
+	oldLookPath := lookPath
+	lookPath = func(name string) (string, error) {
+		if allowed[name] {
+			return "/usr/bin/" + name, nil
+		}
+		return "", exec.ErrNotFound
+	}
+
+	cmdCacheMu.Lock()
+	oldCache := cmdCache
+	cmdCache = make(map[string]bool)
+	cmdCacheMu.Unlock()
+
+	t.Cleanup(func() {
+		lookPath = oldLookPath
+		cmdCacheMu.Lock()
+		cmdCache = oldCache
+		cmdCacheMu.Unlock()
+	})
+}
 
 func TestClassifyInput(t *testing.T) {
+	stubCommands(t, "ls", "git", "echo", "find", "kill", "make", "sort")
+
 	tests := []struct {
 		input string
 		want  Classification
@@ -57,6 +94,15 @@ func TestClassifyInput(t *testing.T) {
 // shell-syntax evidence (flags/paths/operators) for these ambiguous
 // command names before trusting them as shell.
 func TestClassifyInput_AmbiguousWordsWithoutShellSyntax(t *testing.T) {
+	// Stub every ambiguous verb so this test exercises the shell-syntax
+	// gate, not whether the host happens to ship these binaries.
+	stubCommands(
+		t,
+		"make", "test", "find", "time", "kill", "man", "more", "less",
+		"true", "date", "file", "look", "expr", "link", "mount",
+		"sort", "diff", "patch",
+	)
+
 	sentences := []string{
 		"make sure this works",
 		"test the login flow",

scripts/check-commit-policy.sh

@@ -0,0 +1,80 @@
+#!/usr/bin/env bash
+# Enforce the repository commit policy:
+#   1. Every commit in the change set has a verified signature.
+#   2. No commit credits an AI assistant as a co-author or generator.
+#
+# Works for pull_request and push events. Requires GH_TOKEN (the workflow's
+# GITHUB_TOKEN is enough) and GITHUB_REPOSITORY.
+set -euo pipefail
+
+repo="${GITHUB_REPOSITORY:?GITHUB_REPOSITORY is required}"
+event="${GITHUB_EVENT_NAME:?GITHUB_EVENT_NAME is required}"
+
+ai_author_re='^[[:space:]]*co-authored-by:.*(claude|anthropic|openai|chatgpt|gpt|copilot|cursor|gemini|codex|aider|devin|windsurf|tabnine|cody|replit|amazon[ -]?q|jetbrains[ -]?ai|sourcegraph)'
+ai_generated_re='generated (with|by).*(claude|anthropic|openai|chatgpt|gpt|copilot|cursor|gemini|codex|aider|devin|windsurf|tabnine|cody|replit|amazon[ -]?q)'
+
+commit_shas() {
+    case "$event" in
+        pull_request | pull_request_target)
+            gh api --paginate "repos/$repo/pulls/${PR_NUMBER:?PR_NUMBER is required}/commits" --jq '.[].sha'
+            ;;
+        push)
+            local before="${PUSH_BEFORE:-}" after="${PUSH_AFTER:?PUSH_AFTER is required}"
+            if [[ -z "$before" || "$before" =~ ^0+$ ]]; then
+                # New branch: check the pushed head only; its history predates
+                # this policy.
+                printf '%s\n' "$after"
+            else
+                gh api "repos/$repo/compare/${before}...${after}" --jq '.commits[].sha'
+            fi
+            ;;
+        *)
+            echo "commit policy: unsupported event '$event'" >&2
+            exit 2
+            ;;
+    esac
+}
+
+failed=0
+checked=0
+
+while IFS= read -r sha; do
+    [[ -z "$sha" ]] && continue
+    checked=$((checked + 1))
+
+    commit_json=$(gh api "repos/$repo/commits/$sha")
+    verified=$(jq -r '.commit.verification.verified' <<<"$commit_json")
+    message=$(jq -r '.commit.message' <<<"$commit_json")
+
+    if [[ "$verified" != "true" ]]; then
+        echo "::error::Commit ${sha:0:12} is not signed with a verified key."
+        failed=1
+    fi
+
+    if grep -Eiq "$ai_author_re" <<<"$message"; then
+        echo "::error::Commit ${sha:0:12} credits an AI assistant as co-author."
+        grep -Ein "$ai_author_re" <<<"$message" | sed 's/^/    /'
+        failed=1
+    fi
+
+    if grep -Eiq "$ai_generated_re" <<<"$message"; then
+        echo "::error::Commit ${sha:0:12} contains an AI generation attribution."
+        grep -Ein "$ai_generated_re" <<<"$message" | sed 's/^/    /'
+        failed=1
+    fi
+done < <(commit_shas)
+
+if [[ "$checked" -eq 0 ]]; then
+    echo "commit policy: no commits to check"
+    exit 0
+fi
+
+if [[ "$failed" -ne 0 ]]; then
+    echo
+    echo "Commit policy failed."
+    echo "  - Sign commits with a key registered on GitHub (git commit -S)."
+    echo "  - Remove AI co-author / generation trailers from the message."
+    exit 1
+fi
+
+echo "commit policy: $checked commit(s) verified, no AI co-author trailers"