feat: casan chat optz

packages/casan-harness/scripts/bash/loop-run.sh

@@ -27,6 +27,19 @@ set -uo pipefail
 #             4 opt-out refused (prod) · 2 usage error.
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PYTHON_BIN="${CASAN_PYTHON_BIN:-}"
+if [[ -z "$PYTHON_BIN" ]]; then
+  for candidate in /usr/bin/python3 python3 python; do
+    if command -v "$candidate" >/dev/null 2>&1 && "$candidate" --version >/dev/null 2>&1; then
+      PYTHON_BIN="$candidate"
+      break
+    fi
+  done
+fi
+if [[ -z "$PYTHON_BIN" ]]; then
+  echo "LOOP_RUNTIME_UNAVAILABLE: working Python 3 interpreter not found" >&2
+  exit 69
+fi
 GATE="$SCRIPT_DIR/loop-gate.py"
 GOV="$SCRIPT_DIR/loop-governor.py"
 CONV="$SCRIPT_DIR/loop-convergence.py"
@@ -76,7 +89,7 @@ if [[ "$GOVERNANCE" == "off" ]]; then
     exit 4
   fi
   # An allowed opt-out is always audited (never silent).
-  PYTHONPATH="$SCRIPT_DIR" python3 - "$RUN_ID" "${CASAN_LOOP_OPTOUT_REASON:-dev-optout}" <<'PY'
+  PYTHONPATH="$SCRIPT_DIR" "$PYTHON_BIN" - "$RUN_ID" "${CASAN_LOOP_OPTOUT_REASON:-dev-optout}" <<'PY'
 import sys, loop_common as lc
 lc.append_audit({"kind": "loop_governance_optout", "run_id": sys.argv[1], "reason": sys.argv[2]})
 PY
@@ -90,13 +103,13 @@ COST_ACC="0"
 
 for (( step=1; step<=MAX_STEPS; step++ )); do
   CUM_TOKENS=$(( CUM_TOKENS + TOKENS_PER_STEP ))
-  COST_ACC="$(python3 -c "print(round($COST_ACC + $COST_PER_STEP, 6))")"
+  COST_ACC="$("$PYTHON_BIN" -c "print(round($COST_ACC + $COST_PER_STEP, 6))")"
   DECISION="CONTINUE"; VERDICT=""; PROGRESS="0"
 
   if [[ "$GOVERNANCE" == "on" ]]; then
     # 1) Governor: cumulative budget check (loop-breaker) BEFORE more work.
     set +e
-    python3 "$GOV" check --run-id "$RUN_ID" --step "$step" \
+    "$PYTHON_BIN" "$GOV" check --run-id "$RUN_ID" --step "$step" \
       --tokens "$CUM_TOKENS" --cost "$COST_ACC" "${prof_args[@]}" >/dev/null 2>&1
     grc=$?
     set -e 2>/dev/null || true
@@ -106,7 +119,7 @@ for (( step=1; step<=MAX_STEPS; step++ )); do
     if [[ "$DECISION" == "CONTINUE" ]]; then
       # 2) Gate: per-iteration verify contract.
       set +e
-      GATE_OUT="$(python3 "$GATE" verify --run-id "$RUN_ID" --step "$step" \
+      GATE_OUT="$("$PYTHON_BIN" "$GATE" verify --run-id "$RUN_ID" --step "$step" \
         --artifact "$ARTIFACT" ${CRIT:+--success-criteria "$CRIT"} "${prof_args[@]}" 2>/dev/null)"
       set -e 2>/dev/null || true
       VERDICT="$(printf '%s' "$GATE_OUT" | json_field verdict)"
@@ -121,10 +134,10 @@ for (( step=1; step<=MAX_STEPS; step++ )); do
     # 3) Convergence: observe + verdict (no-progress / oscillation breaker).
     if [[ "$DECISION" == "CONTINUE" ]]; then
       AH="$(sha_of "$ARTIFACT")"; AH="${AH:0:16}"
-      python3 "$CONV" observe --run-id "$RUN_ID" --step "$step" \
+      "$PYTHON_BIN" "$CONV" observe --run-id "$RUN_ID" --step "$step" \
         --action-hash "$AH" --progress "$PROGRESS" >/dev/null 2>&1
       set +e
-      python3 "$CONV" verdict --run-id "$RUN_ID" "${prof_args[@]}" >/dev/null 2>&1
+      "$PYTHON_BIN" "$CONV" verdict --run-id "$RUN_ID" "${prof_args[@]}" >/dev/null 2>&1
       cvrc=$?
       set -e 2>/dev/null || true
       if [[ "$cvrc" -eq 3 ]]; then FINAL="HALT"; DECISION="HALT"; RC=3; fi
@@ -136,7 +149,7 @@ for (( step=1; step<=MAX_STEPS; step++ )); do
   fi
 
   # 4) Trace: append the immutable iteration record.
-  python3 "$TRACE" record --run-id "$RUN_ID" --step "$step" \
+  "$PYTHON_BIN" "$TRACE" record --run-id "$RUN_ID" --step "$step" \
     --intent "turn-$step" --action verify --tool loop-run \
     ${VERDICT:+--gate-verdict "$VERDICT"} --decision "$DECISION" --progress "$PROGRESS" \
     --artifact "$ARTIFACT" ${CRIT:+--success-criteria "$CRIT"} \
@@ -144,7 +157,7 @@ for (( step=1; step<=MAX_STEPS; step++ )); do
 
   # 5) Between-turn context compaction (17.21).
   if [[ -n "$CONTEXT" && -f "$CONTEXT" ]]; then
-    python3 "$COMPRESS" --mode structural --input "$CONTEXT" \
+    "$PYTHON_BIN" "$COMPRESS" --mode structural --input "$CONTEXT" \
       > "$(dirname "$ARTIFACT")/.loop-context-compacted.txt" 2>/dev/null || true
   fi