fix: restore model from sidecar field when not in cli_args

The save script captures the model from Claude state files, but restore
never used the model field — sessions lost their model setting on every
save/restore cycle. Now adds --model to the resume command when:
- model is present in the sidecar JSON
- tool is claude (only tool that supports --model)
- --model is not already in cli_args (avoids duplication)

Closes #23

Author: timvw

scripts/restore-assistant-sessions.sh

@@ -58,6 +58,7 @@ while read -r entry; do
 	session_id=$(echo "$entry" | jq -r '.session_id')
 	cwd=$(echo "$entry" | jq -r '.cwd')
 	cli_args=$(echo "$entry" | jq -r '.cli_args // empty')
+	model=$(echo "$entry" | jq -r '.model // empty')
 	env_json=$(echo "$entry" | jq -c '.env // {}')
 
 	# Check if the target pane's session exists
@@ -158,11 +159,21 @@ while read -r entry; do
 		set +f
 	fi
 
+	# Add --model from the sidecar model field if not already in cli_args.
+	# Only for Claude — OpenCode and Codex don't support --model.
+	safe_model_arg=""
+	if [ -n "$model" ] && [ "$tool" = "claude" ]; then
+		case "$cli_args" in
+		*--model*) ;;
+		*) safe_model_arg=" --model $(posix_quote "$model")" ;;
+		esac
+	fi
+
 	resume_cmd=""
 	case "$tool" in
 	claude)
-		if [ -n "$safe_cli_args" ]; then
-			resume_cmd="command claude${safe_cli_args} --resume ${safe_sid}"
+		if [ -n "$safe_cli_args" ] || [ -n "$safe_model_arg" ]; then
+			resume_cmd="command claude${safe_cli_args}${safe_model_arg} --resume ${safe_sid}"
 		else
 			resume_cmd="command claude --resume ${safe_sid}"
 		fi

test/run-tests.sh

@@ -2557,6 +2557,112 @@ assert_contains "Empty cli_args: tool identified" "$empty_log" "restoring openco
 
 kill_pane_children test-restore-empty true
 
+# --- Test 10d2: Restore adds --model from sidecar model field ---
+#
+# When model is set in the sidecar JSON but NOT in cli_args (e.g., model
+# was set via config/env, not --model flag), restore should add --model.
+
+echo ""
+echo "=== Test 10d2: restore adds --model from sidecar field ==="
+echo ""
+
+tmux new-session -d -s test-restore-model -c /tmp 2>/dev/null || true
+sleep 0.5
+
+cat >"$HOME/.tmux/resurrect/assistant-sessions.json" <<'RMODEL'
+{
+  "timestamp": "2026-01-01T00:00:00Z",
+  "sessions": [
+    {
+      "pane": "test-restore-model:0.0",
+      "tool": "claude",
+      "session_id": "ses_model_field",
+      "cwd": "/tmp",
+      "pid": "99999",
+      "model": "claude-opus-4-5-20250514",
+      "cli_args": "",
+      "env": {}
+    }
+  ]
+}
+RMODEL
+
+>"$RESTORE_LOG"
+just restore 2>&1
+sleep 5
+
+model_log=$(cat "$RESTORE_LOG")
+assert_contains "Model field: --model added to resume" "$model_log" "--model"
+assert_contains "Model field: correct model value" "$model_log" "claude-opus-4-5-20250514"
+
+# Verify --model is NOT duplicated when already in cli_args
+tmux kill-session -t test-restore-model 2>/dev/null || true
+tmux new-session -d -s test-restore-model -c /tmp 2>/dev/null || true
+sleep 0.5
+
+cat >"$HOME/.tmux/resurrect/assistant-sessions.json" <<'RMODELDUP'
+{
+  "timestamp": "2026-01-01T00:00:00Z",
+  "sessions": [
+    {
+      "pane": "test-restore-model:0.0",
+      "tool": "claude",
+      "session_id": "ses_model_nodup",
+      "cwd": "/tmp",
+      "pid": "99999",
+      "model": "claude-opus-4-5-20250514",
+      "cli_args": "--model claude-opus-4-5-20250514",
+      "env": {}
+    }
+  ]
+}
+RMODELDUP
+
+>"$RESTORE_LOG"
+just restore 2>&1
+sleep 5
+
+nodup_log=$(cat "$RESTORE_LOG")
+# Count occurrences of --model — should be exactly 1 (from cli_args, not doubled)
+nodup_count=$(echo "$nodup_log" | grep -o '\-\-model' | wc -l | tr -d ' ')
+assert_eq "Model field: no duplicate --model when already in cli_args" "1" "$nodup_count"
+
+# Verify model is NOT added for non-Claude tools
+tmux kill-session -t test-restore-model 2>/dev/null || true
+tmux new-session -d -s test-restore-model -c /tmp 2>/dev/null || true
+sleep 0.5
+
+cat >"$HOME/.tmux/resurrect/assistant-sessions.json" <<'RMODELOC'
+{
+  "timestamp": "2026-01-01T00:00:00Z",
+  "sessions": [
+    {
+      "pane": "test-restore-model:0.0",
+      "tool": "opencode",
+      "session_id": "ses_model_oc",
+      "cwd": "/tmp",
+      "pid": "99999",
+      "model": "some-model",
+      "cli_args": "",
+      "env": {}
+    }
+  ]
+}
+RMODELOC
+
+>"$RESTORE_LOG"
+just restore 2>&1
+sleep 5
+
+oc_model_log=$(cat "$RESTORE_LOG")
+if echo "$oc_model_log" | grep -q '\-\-model'; then
+	fail "Model field: --model should NOT be added for opencode"
+else
+	pass "Model field: --model correctly skipped for opencode"
+fi
+
+kill_pane_children test-restore-model true
+
 # --- Test 10e: Restore filters out tmux_pane and shell from env prefix ---
 
 echo ""