make xhigh the sandbox's thinking, and stop settings.json freezing

Two changes, one bug found through the other.

Thinking is policy now: defaultThinkingLevel is xhigh unless you say otherwise
(thinking / --thinking / AISB_THINKING, with pi's levels plus 'host' to decline
and 'off' meaning pi's own no-reasoning level). It is written into the bridged
settings and re-applied by the entrypoint on every run, so a run cannot set its
own reasoning down for the runs after it. Unknown levels are refused with the
list to pick from. Nothing is written for codex, claude or a command after --,
and --no-pi-config declines it along with the bridge, because pi's own defaults
are what that flag asks for.

The reason xhigh had never reached a sandbox is worse than a missing default:
settings.json was managed as one whole file, and pi rewrites its own settings
(a theme change, "seen the changelog"), so the first such write matched nothing
and froze every host preference out permanently -- provider, model, thinking
budgets and level included, a real session left holding just
{"lastChangelogVersion": "1.4.0"}. It is merged per key instead, against a copy
of what we last wrote: a key edited in the sandbox stays edited, a key never
touched follows the host again, an untouched key the host dropped is dropped, a
key pi invented survives, and a file with no base copy takes the host values --
which repairs the volumes already frozen. Unparseable JSON is re-seeded with a
warning since pi cannot use it either; a file the container cannot read is
reported with the fix, because nothing inside the sandbox can repair one.

One trap worth remembering: the seeding script is passed to bash -c in single
quotes, so a single quote inside it closes the argument early and the rest runs
in the outer shell -- valid bash, wrong program, clean bash -n and clean
shellcheck. tests/unit/06_entrypoint.sh extracts the seeding script and asserts
it is quote-free, and extracts the merge program to test its semantics without
a container; tests/e2e/12_sandbox.sh does the same in a real run, including
forcing the level back after the sandbox sets it to off.

LLM-Generated: true

AGENTS.md

@@ -105,6 +105,11 @@ networking or the image, `make e2e` green too.
 * `entrypoint_script()` — the enforcement half. It is rendered into the image and
   runs as root there. A bug here is a security bug. `tests/unit/06_entrypoint.sh`
   checks the generated rule shape; `tests/e2e/11_net.sh` checks it in a container.
+  Its pi-seeding block is passed to `bash -c` inside single quotes, so a single quote
+  anywhere in there silently closes the argument and the rest runs in the *outer* shell
+  — valid bash, wrong program, clean `bash -n` and clean shellcheck. Nothing in it may
+  use `'`; jq programs there are written unquoted (`.defaultThinkingLevel=\$lvl`), and
+  `tests/unit/06_entrypoint.sh` fails the build if that ever changes.
 * `split_target()` / `classify_allows()` — the mapping from what the user typed to
   what the firewall and the proxy enforce.
 * `build_argv()` — every isolation flag lives here.

PLAN.md

@@ -127,6 +127,33 @@ the same destination wins because podman refuses duplicates. A missing or unread
 directory is a silent skip like the pi bridge's; an explicit `--agents-dir` that resolves
 to nothing is a hard error.
 
+### 11 — Thinking level as policy, and a settings merge that does not freeze
+`defaultThinkingLevel` is now `xhigh` by default (`thinking`, `--thinking`,
+`AISB_THINKING`; pi's own default is `medium`), written into the bridged settings and
+re-applied by the entrypoint on every run, so a run cannot lower the reasoning of the runs
+after it. `--thinking host` hands the key back to `settings.json`, `off` is pi's own
+"no reasoning" level, and an unknown value is refused with the list to pick from. Nothing
+is written for codex, claude or a command after `--`, and `--no-pi-config` declines the
+policy along with the bridge.
+
+Getting there found a worse bug. `settings.json` was managed as one managed file, and pi
+rewrites its own settings (a theme change, "seen the changelog"), so the first such write
+matched nothing and froze *every* host preference out of the sandbox for good -- provider, model,
+thinking budgets and the level included, with a real session left holding
+`{"lastChangelogVersion": "1.4.0"}`. It is merged per key instead, against a copy of what
+we last wrote (`.aisb-settings.json.wrote`): sandbox edits win per key, untouched keys
+follow the host again, untouched keys the host dropped are dropped, keys pi invented
+survive, and a file that is missing a base copy takes the host values -- which is what
+repairs the volumes already frozen. Unparseable JSON is re-seeded with a warning (pi
+cannot use it either); a file the container cannot *read* is reported with the fix, because
+nothing inside the sandbox can repair it.
+
+One trap worth remembering: the seeding script is passed to `bash -c` in single quotes, so
+a single quote anywhere inside it closes the argument early and the remainder becomes code
+in the outer shell -- valid bash, wrong program, invisible to `bash -n` and shellcheck.
+`tests/unit/06_entrypoint.sh` now extracts the seeding script and asserts it is quote-free,
+and extracts the merge program to test its semantics without a container.
+
 ## Follow-ups (not yet done)
 
 * **`--net unix` mode**: `--network=none` plus a unix-socket proxy and an in-container
@@ -150,6 +177,9 @@ to nothing is a hard error.
 * **Scoped sandbox tokens**: if the gateway can mint a short-lived, per-sandbox key,
   `--pi-token-env` should ask for one rather than forwarding the long-lived host
   credential. The bridge deliberately does not guess a minting endpoint.
+* **`--thinking` for the other harnesses**: codex and claude have their own reasoning
+  knobs; a policy that spans harnesses needs to know each one's config shape rather than
+  assume pi's.
 * **Bridging extensions/skills on request**: `--pi-mount-ext` or similar for the
   extension paths named in `enabledExtensionPaths`, which are host paths and therefore
   currently dropped; needs the same explicit-grant shape as `--mount`.

README.md

@@ -154,14 +154,41 @@ purpose is to be unable to use it:
 | `apiKey: "sk-..."` or `apiKey: "!pass show ..."` | `apiKey: "$AI_API_TOKEN"` -- pi resolves it itself, no value is written to disk |
 | a header like `X-Trace: "!date +%s"` | dropped, and reported: a host command is not run in the sandbox |
 | `baseUrl: "https://aipi.reeseapps.com/v1"` | unchanged, along with every model, limit and thinking level |
-| settings: provider, model, theme, thinking budgets, telemetry | unchanged |
+| settings: provider, model, theme, thinking budgets, telemetry | unchanged, merged per key |
 | a settings value pointing into `~` | dropped, and reported: that path is not mounted |
 | `auth.json`, `models-store.json`, sessions, extensions | never touched |
 
 The rewritten pair is seeded into `/home/sandbox/.pi/agent` at container start, owned by
-your uid, mode `600`. It is a managed file: a change on the host is picked up on the
-next run, an edit made *inside* the sandbox is left alone, and deleting it inside
-re-seeds from the host.
+your uid, mode `600`. The two files are managed differently, because they are different
+kinds of thing:
+
+| file | rule | why |
+|---|---|---|
+| `models.json` | replaced when missing or unchanged, left alone once you edit it in the sandbox | it is a catalog; a partial merge of a provider list is worse than either choice |
+| `settings.json` | **merged per key** | pi rewrites its own settings — a theme change, "seen the changelog" — and managing the file whole meant that one write froze *every* host preference out of the sandbox permanently |
+
+So in `settings.json`: a key you change inside the sandbox stays yours, a key you never
+touched follows the host again, a key the host drops disappears unless you had changed
+it, and a key pi added (`lastChangelogVersion`) survives.
+
+### Thinking is xhigh, and it is policy
+
+`defaultThinkingLevel` is the one setting `ai-sandbox` insists on, because pi's own
+default is `medium` and a sandbox run is usually the kind of work you want reasoned
+about hard:
+
+```bash
+pi --allow aipi.reeseapps.com        # xhigh, whatever your host settings.json says
+pi --thinking max ...                # this run only
+pi --thinking off ...                # no reasoning, e.g. a mechanical refactor at scale
+pi --thinking host ...               # stop forcing it; your settings.json decides
+```
+
+`--thinking` is a policy, not a preference: it is written over the merged settings on
+every run, so a run cannot set its own thinking level down for the runs after it. It is
+`pi`-only — codex, claude and anything you put after `--` read their own config, and
+ai-sandbox leaves that alone. `--no-pi-config` declines the policy too, since "pi starts
+with its own defaults" is what that flag is for.
 
 The token itself follows the normal rule -- it is the one variable the bridged config
 names, so it is passed by name (never by value, and never into `ps`):

bin/ai-sandbox

@@ -42,6 +42,7 @@ AISB_PI_PACKAGE="${AISB_PI_PACKAGE:-@earendil-works/pi-coding-agent}"
 #   AISB_TMPFS_SIZE AISB_BASE_IMAGE AISB_NODE_VERSION AISB_PI_VERSION
 #   AISB_BASE_TTL_DAYS AISB_BASE_AUTO_UPDATE AISB_BASE_PULL_FALLBACK AISB_SKOPEO
 #   AISB_SELINUX AISB_GATE_ADDR AISB_GATE_PORT AISB_HOME_CACHE AISB_EXTRA_ARGS
+#   AISB_PI_CONFIG AISB_PI_TOKEN_ENV AISB_PI_TOKEN_AUTO AISB_PI_AGENT_DIR AISB_THINKING
 #   AISB_AGENTS AISB_AGENTS_DIR AISB_AGENTS_DEST
 AISB_UID="${AISB_UID:-1000}"
 AISB_GID="${AISB_GID:-1000}"
@@ -233,6 +234,17 @@ PI CONFIG
   --no-pi-token-env         Do not pass it automatically; then pass it with --env or
                             the run is refused rather than starting a pi with no key.
   --no-pi-config            Do not bridge at all; pi starts with its own defaults.
+  --thinking LEVEL          Default thinking level in the sandbox: off, minimal, low,
+                            medium, high, xhigh (the default) or host. It is policy, not
+                            a preference: it is written over the bridged settings on
+                            every run, so an edit inside the sandbox cannot quietly lower
+                            it for the next one. 'host' leaves the key to your
+                            settings.json. pi only -- codex, claude and your own command
+                            read their own config and ai-sandbox does not touch it.
+
+  settings.json is merged per key rather than managed as a whole file: keys you edit
+  inside the sandbox stay yours, every key you did not touch follows the host again, keys
+  the host dropped go away, and keys the sandbox invented survive.
 
 LIMITS
   --cpus N (4)   --memory SIZE (4g)   --pids N (512)   --tmpfs-size SIZE (1g)
@@ -274,7 +286,7 @@ CONFIG
   \$HOME/.config/ai-sandbox/{config,allow}  and  ./.ai-sandbox/{config,allow}
   Every default can also be set as an environment variable:
   AISB_NET, AISB_ALLOW (comma list), AISB_ENV (comma list), AISB_CPUS, AISB_MEMORY,
-  AISB_PIDS, AISB_HARNESS, AISB_EXTRA_ARGS, AISB_SELINUX, AISB_HOME_CACHE,
+  AISB_PIDS, AISB_HARNESS, AISB_EXTRA_ARGS, AISB_SELINUX, AISB_HOME_CACHE, AISB_THINKING,
   AISB_AGENTS, AISB_AGENTS_DIR, AISB_AGENTS_DEST, ...
   Base images: AISB_BASE_IMAGE, AISB_BASE_TTL_DAYS (7; 0 every build, -1 never),
   AISB_BASE_AUTO_UPDATE (0 keeps the recorded digest), AISB_BASE_PULL_FALLBACK
@@ -315,7 +327,7 @@ cfg_read_kv() { # `key = value` file
     case "$key" in
       net|harness|workdir|cpus|memory|pids|tmpfs_size|base_image|node_version|pi_version|\
       project_dest|selinux|home_cache|gate_addr|gate_port|extra_args|base_ttl_days|base_auto_update|\
-      pi_config|pi_token_env|pi_token_auto|pi_agent_dir|agents|agents_dir|agents_dest) CFG["$key"]="$val" ;;
+      pi_config|pi_token_env|pi_token_auto|pi_agent_dir|thinking|agents|agents_dir|agents_dest) CFG["$key"]="$val" ;;
       *) warn "$file: unknown key: $key" ;;
     esac
   done < "$file"
@@ -354,7 +366,7 @@ OPT_NO_CWD=0 OPT_SHELL=0 OPT_DRY=0 OPT_PRINT=0 OPT_NO_BUILD=0 OPT_KEEP=0 OPT_REA
 OPT_HOME_CACHE="" OPT_STRICT="${AISB_STRICT_ARGS:-0}" OPT_UNENFORCED=0 OPT_KEEP_ROOT=0
 OPT_TTY="" OPT_INTERACTIVE="" OPT_PRINT_EP=0 OPT_PRINT_CF=0 OPT_PASSTHROUGH=0
 OPT_AGENTS="" OPT_AGENTS_DIR=""
-OPT_PI_CONFIG="" OPT_PI_TOKEN_AUTO="" OPT_PI_TOKEN_ENV=""
+OPT_PI_CONFIG="" OPT_PI_TOKEN_AUTO="" OPT_PI_TOKEN_ENV="" OPT_THINKING=""
 declare -a OPT_allow=() OPT_env=() OPT_mount=() OPT_install=() OPT_label=() OPT_allow_files=()
 COMMAND=()
 
@@ -365,7 +377,8 @@ KNOWN_OPTS=(
   workdir home-cache ephemeral-home
   harness install base-image cpus memory pids tmpfs-size name label keep read-only shell
   interactive no-tty dry-run print-policy no-build allow-unenforced strict-args insecure-keep-root
-  print-entrypoint print-containerfile pi-token-env no-pi-config no-pi-token-env help version
+  print-entrypoint print-containerfile pi-token-env no-pi-config no-pi-token-env thinking
+  help version
 )
 suggest() {
   local given="$1" o hit=0 hits=""
@@ -389,6 +402,8 @@ parse_args() {
       --no-pi-token-env) OPT_PI_TOKEN_AUTO=0; shift ;;
       --pi-token-env)    need "$1" "${2:-}"; OPT_PI_TOKEN_ENV="$2"; shift 2 ;;
       --pi-token-env=*)  OPT_PI_TOKEN_ENV="${1#*=}"; shift ;;
+      --thinking)     need "$1" "${2:-}"; OPT_THINKING="$2"; shift 2 ;;
+      --thinking=*)   OPT_THINKING="${1#*=}"; shift ;;
       --harness=*)  OPT_HARNESS="${1#*=}"; shift ;;
       --allow)      need "$1" "${2:-}"; OPT_allow+=("$2"); shift 2 ;;
       --allow=*)    OPT_allow+=("${1#*=}"); shift ;;
@@ -513,6 +528,17 @@ resolve_opts() {
     || die "pi token variable name is not a valid identifier: '${POL[pi_token_env]}'"
   POL[pi_token_auto]="${OPT_PI_TOKEN_AUTO:-${AISB_PI_TOKEN_AUTO:-$(cfgv pi_token_auto 1)}}"
   case "${POL[pi_token_auto]}" in 0|false|no) POL[pi_token_auto]=0 ;; *) POL[pi_token_auto]=1 ;; esac
+  # --- thinking level (policy, not preference: see pi_config_bridge) ----------
+  # pi's own default is medium, which is not what an agentic sandbox run is for, so
+  # ai-sandbox states one. 'host' hands the decision back to settings.json; the entrypoint
+  # enforces the value on every run unless it is empty.
+  POL[thinking]="${OPT_THINKING:-${AISB_THINKING:-$(cfgv thinking xhigh)}}"
+  case "${POL[thinking]}" in
+    off|minimal|low|medium|high|xhigh|max) ;;
+    host|inherit)   POL[thinking]=host ;;
+    *) die "--thinking must be off, minimal, low, medium, high, xhigh, max or host (got '${POL[thinking]}')" ;;
+  esac
+  POL[thinking_eff]=""     # set by pi_config_bridge: the level actually written, if any
 
   POL[base_ttl]="${AISB_BASE_TTL_DAYS:-$(cfgv base_ttl_days 7)}"
   [[ "${POL[base_ttl]}" =~ ^-?[0-9]+$ ]] || { warn "base_ttl_days must be an integer, using 7"; POL[base_ttl]=7; }
@@ -745,6 +771,7 @@ write_policy_files() {
     printf 'AISB_ALLOW_DNS=%s\n'      "$ALLOW_DNS"
     printf 'AISB_PROXY_IPS=%s\n'      "${PROXY_IPS[*]-}"
     printf 'AISB_PROXY_PORTS=%s\n'    "${PROXY_PORTS[*]-}"
+    printf 'AISB_PI_THINKING=%s\n'    "${POL[thinking_eff]:-}"
   } > "$SESSION_MOUNT/policy.env"
   chmod 644 "$SESSION_MOUNT/policy.env"
   printf '%s\n' ${DIRECT4[@]+"${DIRECT4[@]}"}   > "$SESSION_MOUNT/direct4.list"
@@ -867,20 +894,56 @@ command -v setpriv >/dev/null || fail "setpriv is missing from the image; rebuil
 # the entrypoint has no CAP_DAC_OVERRIDE, so root could not write there anyway. It is
 # also the honest identity -- these are the user's own files.
 #
-# A file is only replaced when it is missing or still identical to what we seeded last
-# time, so an edit made inside the sandbox survives; a change on the host wins next run.
+# The two files are managed differently, on purpose.
+#
+# models.json is a catalog, so it is managed whole: replaced when it is missing or still
+# identical to what we seeded, left alone once the sandbox has edited it.
+#
+# settings.json is a flat bag of preferences, and managing it whole went badly: pi
+# rewrites it itself (a theme change, "I have seen this changelog"), and from that moment
+# *every* host preference was frozen out -- provider, model, thinking budgets included,
+# with only the changelog line left in the file. So it is merged per key against a copy of
+# what we last wrote (.aisb-settings.json.wrote): a key the sandbox changed stays theirs,
+# a key it did not touch follows the host again, a key the host dropped disappears unless
+# the sandbox had changed it, and a key the sandbox invented survives.
+#
+# defaultThinkingLevel is the exception inside that merge: it is policy the host set for
+# the sandbox, so AISB_PI_THINKING is written over the result every run however the file
+# was edited. Empty (from --thinking host) makes it an ordinary preference again.
+
+# The merge itself, as an argument rather than a heredoc: the seeding script below is
+# passed to bash -c in single quotes, so nesting a here-document inside it is unreadable.
+# Nothing inside that script may contain a single quote either -- one closes the argument
+# and the rest of the file silently becomes code in the *outer* shell, where $lvl is not
+# set. jq programs there are written unquoted (.defaultThinkingLevel=\$lvl) for that
+# reason, and tests/unit/06_entrypoint.sh checks the quoting rather than trusting it.
+# T = what is in the sandbox now, B = what we last wrote, N = what the host says now.
+SETTINGS_MERGE_JQ='
+  ($T[0] // {}) as $t | ($B[0] // {}) as $b | ($N[0] // {}) as $n
+  | reduce ($t | keys[]) as $k ($t;
+      if ($b | has($k)) and ($n | has($k) | not) and ($t[$k] == $b[$k])
+      then del(.[$k]) else . end)
+  | . as $kept
+  | reduce ($n | keys[]) as $k ($kept;
+      if ($b | has($k)) and ($kept | has($k)) and ($kept[$k] != $b[$k])
+      then . else .[$k] = $n[$k] end)
+'
+
 if [[ -d "$POLICY_DIR/pi" ]]; then
   setpriv --reuid="$UID_TARGET" --regid="$GID_TARGET" --clear-groups -- /bin/bash -c '
-    dst="$HOME/.pi/agent"
+    dst="$HOME/.pi/agent"; lvl="$2"; jq_merge="$3"
     mkdir -p "$dst" || { echo "[aisb] pi config: cannot create $dst" >&2; exit 0; }
-    for f in models.json settings.json; do
-      src="$1/pi/$f"
-      [ -f "$src" ] || continue
+
+    # --- models.json: a catalog, managed as a whole file
+    f=models.json; src="$1/pi/$f"
+    if [ -f "$src" ]; then
       tgt="$dst/$f"; mark="$dst/.aisb-$f.seeded"
       want="$(sha256sum "$src" | cut -c1-16)"
       cur="";  [ -f "$tgt" ]  && cur="$(sha256sum "$tgt" | cut -c1-16)"
       prev=""; [ -f "$mark" ] && prev="$(cat "$mark" 2>/dev/null)"
-      if [ -z "$cur" ]; then
+      if [ -e "$tgt" ] && [ ! -r "$tgt" ]; then
+        echo "[aisb] pi config: cannot read $f -- its mode or SELinux label blocks this container, and nothing inside can repair it (remove it from the host, or use --ephemeral-home)" >&2
+      elif [ -z "$cur" ]; then
         install -m 600 "$src" "$tgt" && printf %s "$want" > "$mark"
         echo "[aisb] pi config: seeded $f"
       elif [ "$cur" = "$prev" ]; then
@@ -889,8 +952,47 @@ if [[ -d "$POLICY_DIR/pi" ]]; then
       else
         echo "[aisb] pi config: left $f alone (changed inside the sandbox; delete it to take the host version again)"
       fi
-    done
-  ' aisb-seed "$POLICY_DIR" || log "pi config: seeding failed"
+    fi
+
+    # --- settings.json: merged per key, then the policy level on top
+    f=settings.json; src="$1/pi/$f"
+    if [ -f "$src" ]; then
+      tgt="$dst/$f"; wrote="$dst/.aisb-$f.wrote"; tmp="$dst/.aisb-$f.tmp"
+      rm -f "$dst/.aisb-$f.seeded"        # the whole-file marker is .wrote now
+      if [ ! -e "$tgt" ]; then
+        install -m 600 "$src" "$tgt" && cp "$tgt" "$wrote"
+        echo "[aisb] pi config: seeded $f"
+      elif [ ! -r "$tgt" ]; then
+        echo "[aisb] pi config: cannot read $f -- its mode or SELinux label blocks this container, and nothing inside can repair it (remove it from the host, or use --ephemeral-home)" >&2
+      else
+        base=/dev/null; [ -f "$wrote" ] && base="$wrote"
+        had=""; [ -n "$lvl" ] && had="$(jq -r ".defaultThinkingLevel // \"\"" "$tgt" 2>/dev/null)"
+        if merged="$(jq -n --slurpfile T "$tgt" --slurpfile B "$base" --slurpfile N "$src" \
+                          -f <(printf %s "$jq_merge") 2>/dev/null)" && [ -n "$merged" ]; then
+          if [ -n "$lvl" ]; then
+            merged="$(printf %s "$merged" | jq --arg lvl "$lvl" .defaultThinkingLevel=\$lvl 2>/dev/null)"
+            [ -z "$merged" ] && merged="$(printf null | jq --arg lvl "$lvl" .defaultThinkingLevel=\$lvl)"
+          fi
+        else
+          # Unparseable, so pi could not have used it either, and this file is ours to
+          # manage: take the host version rather than leave a broken one in place.
+          if [ -n "$lvl" ]; then
+            merged="$(jq --arg lvl "$lvl" .defaultThinkingLevel=\$lvl "$src" 2>/dev/null)"
+          else
+            merged="$(jq . "$src" 2>/dev/null)"
+          fi
+          [ -n "$merged" ] && echo "[aisb] pi config: $f was not usable JSON -- re-seeded from the host config, your in-sandbox changes to it are gone" >&2
+        fi
+        if [ -n "$merged" ] && printf "%s\n" "$merged" > "$tmp" \
+           && install -m 600 "$tmp" "$tgt" && rm -f "$tmp" && cp "$tgt" "$wrote"; then
+          if [ -n "$lvl" ] && [ "$had" != "$lvl" ]; then
+            echo "[aisb] pi config: thinking -> $lvl (policy: --thinking, or host)"
+          fi
+        fi
+      fi
+    fi
+  ' aisb-seed "$POLICY_DIR" "${AISB_PI_THINKING:-}" "$SETTINGS_MERGE_JQ" \
+    || log "pi config: seeding failed"
 fi
 
 exec setpriv --reuid="$UID_TARGET" --regid="$GID_TARGET" --clear-groups \
@@ -1328,6 +1430,8 @@ pi_config_bridge() {
   fi
 
   # --- settings.json: preferences travel, host paths do not
+  local lvl="${POL[thinking]}"
+  [[ "$lvl" == host ]] && lvl=""
   if [[ -r "$src/settings.json" ]]; then
     if ! jq -e . "$src/settings.json" > /dev/null 2>&1; then
       warn "pi config: $src/settings.json is not valid JSON -- pi starts without it"
@@ -1336,12 +1440,28 @@ pi_config_bridge() {
       jq --arg home "$homep" '
         with_entries(select(((.value | type) == "string" and (.value | contains($home))) | not))
       ' "$src/settings.json" > "$dst/settings.json" || die "pi config: could not rewrite $src/settings.json"
-      chmod 644 "$dst/settings.json"
       dropped="$(jq -r --arg home "$homep" '[to_entries[]
                  | select((.value | type) == "string" and (.value | contains($home))) | .key] | join(", ")' "$src/settings.json")"
       [[ -n "$dropped" ]] && warn "pi config: dropped settings $dropped -- they point inside the host home, which is not mounted"
     fi
   fi
+  # The thinking level is applied to whatever survived, and on its own if the host has no
+  # settings.json at all -- a sandbox that silently thinks at pi's default of medium is
+  # not what --thinking is for. It is written here *and* carried to the entrypoint, which
+  # re-applies it to a settings.json that already exists in the sandbox home.
+  if [[ -n "$lvl" ]]; then
+    if [[ -f "$dst/settings.json" ]]; then
+      jq --arg lvl "$lvl" '.defaultThinkingLevel = $lvl' "$dst/settings.json" \
+        > "$dst/settings.json.new" || die "pi config: could not set the thinking level"
+      mv "$dst/settings.json.new" "$dst/settings.json"
+    else
+      jq -n --arg lvl "$lvl" '{defaultThinkingLevel: $lvl}' > "$dst/settings.json" \
+        || die "pi config: could not write the thinking level"
+    fi
+    chmod 644 "$dst/settings.json"
+    POL[thinking_eff]="$lvl"
+    log "pi config: thinking -> $lvl (policy; --thinking host to let settings.json decide)"
+  fi
 
   [[ -f "$dst/models.json" || -f "$dst/settings.json" ]] || { rmdir "$dst" 2>/dev/null || true; PI_GEN_DIR=""; return 0; }
 
@@ -1697,6 +1817,12 @@ print_policy() {
   printf 'mounts=%s\n'         "$(join ';'  ${P_mount[@]+"${P_mount[@]}"})"
   printf 'agents=%s\n'         "${POL[agents_src]:-off}"
   if [[ -n "${POL[agents_src]:-}" ]]; then printf 'agents_dest=%s\n' "${POL[agents_dest]}"; fi
+  if [[ -n "${POL[thinking_eff]:-}" ]]; then
+    printf 'thinking=%s (enforced on every run)\n' "${POL[thinking]}"
+  else
+    printf 'thinking=%s (not applied: %s)\n' "${POL[thinking]}" \
+      "$([[ "${POL[thinking]}" == host ]] && printf 'the config decides' || printf 'pi config bridging is off')"
+  fi
 }
 
 # ===========================================================================
@@ -1857,6 +1983,14 @@ cmd_doctor() {
       chk WARN "pi credential: \$$ptok is unset or empty -- a bridged pi run is refused (export it, add it to $(cfg_or_home), or use --no-pi-config)"
     fi
   fi
+  # The thinking policy: what a pi run in this directory will reason at, and whether
+  # anything is actually there to say so.
+  if [[ -n "${POL[thinking_eff]:-}" ]]; then
+    chk INFO "pi thinking: ${POL[thinking]} (policy, re-applied every run; --thinking host lets settings.json decide)"
+  else
+    chk INFO "pi thinking: ${POL[thinking]} -- $([[ "${POL[thinking]}" == host ]] && printf 'pi takes it from the bridged settings.json' || printf 'not written, pi config bridging is off')"
+  fi
+
   # The .agents bridge, reported read-only like the pi bridge: doctor never mounts.
   if [[ -z "${POL[agents_src]:-}" ]]; then
     chk INFO "agents: your skills are not shared (agents=0, --no-agents, or no ${POL[agents_dir]})"

config/config.example

@@ -62,6 +62,12 @@ net = allow
 # pi_token_env = AI_API_TOKEN
 # pi_token_auto = 1
 #
+# The thinking level a sandboxed pi reasons at: off, minimal, low, medium, high, xhigh
+# or max.  pi's own default is medium; ai-sandbox states xhigh and re-applies it on every
+# run, so one run cannot lower the thinking of the next. 'host' stops forcing it and lets
+# settings.json decide.  pi only -- other harnesses read their own config.
+# thinking = xhigh
+#
 # Where to read the host config from (default ~/.pi/agent).
 # pi_agent_dir = ~/.pi/agent
 

contrib/ai-sandbox.bash

@@ -0,0 +1,81 @@
+# bash completion for ai-sandbox.
+#
+# Install (either):
+#   mkdir -p ~/.local/share/bash-completion/completions
+#   cp contrib/ai-sandbox.bash ~/.local/share/bash-completion/completions/ai-sandbox
+# or source it from ~/.bashrc -- put the `source` line *after* the alias, since
+# bash needs `complete` registered under the alias name (`alias pi=ai-sandbox`).
+#
+# The flag list mirrors parse_args() in bin/ai-sandbox -- keep them in sync.
+_ai_sandbox_completions() {
+  local cur prev word first="" sub="" i
+  if type _get_comp_words_by_ref >/dev/null 2>&1; then
+    _get_comp_words_by_ref -n : cur prev
+  else
+    cur="${COMP_WORDS[COMP_CWORD]}"; prev="${COMP_WORDS[COMP_CWORD-1]:-}"
+  fi
+
+  local subs="build update doctor gate ps clean inspect version help"
+  # flags that consume the next word, so their values are not mistaken for
+  # positional (harness) arguments.
+  local value_flags=" --net --allow --allow-file --proxy --mount --workdir --agents-dir
+    --env --env-file --base-image --install --harness --pi-token-env --cpus --memory
+    --pids --tmpfs-size --name --label "
+
+  # Walk the words before the cursor to find the subcommand, skipping option values.
+  local skip=0
+  for ((i = 1; i < COMP_CWORD; i++)); do
+    word="${COMP_WORDS[i]}"
+    if (( skip )); then skip=0; continue; fi
+    if [[ "$word" == --* && "$value_flags" == *" $word "* ]]; then skip=1; continue; fi
+    [[ "$word" == -* ]] && continue
+    [[ -z "$first" ]] && first="$word"
+  done
+  [[ " $subs " == *" $first "* ]] && sub="$first"
+
+  case "$prev" in                                   # values of the flag just typed
+    --net)     COMPREPLY=( $(compgen -W "none allow full" -- "$cur") ); return ;;
+    --harness) COMPREPLY=( $(compgen -W "pi codex claude none" -- "$cur") ); return ;;
+    --env)     COMPREPLY=( $(compgen -A export -- "$cur") ); return ;;
+    --allow)   # hosts already in the allow files; no DNS, no network
+      local hosts
+      hosts="$(sed 's/#.*//' "$HOME/.config/ai-sandbox/allow" ./.ai-sandbox/allow 2>/dev/null | tr ',[:space:]' '\n\n')"
+      COMPREPLY=( $(compgen -W "$hosts" -- "$cur") )
+      (( ${#COMPREPLY[@]} )) || COMPREPLY=( "$cur" )   # don't fall back to filenames
+      return ;;
+    --proxy)   COMPREPLY=( "$cur" ); return ;;
+    --allow-file|--env-file)     COMPREPLY=( $(compgen -f -- "$cur") ); return ;;
+    --mount|--agents-dir|--workdir) COMPREPLY=( $(compgen -d -- "$cur") ); return ;;
+  esac
+
+  # A non-flag word before the cursor that is not a subcommand means the rest goes
+  # to the harness: ai-sandbox stops parsing there, so offer nothing, not sandbox flags.
+  [[ -n "$first" && -z "$sub" ]] && return 1
+
+  [[ -z "$first" && "$cur" != -* ]] && { COMPREPLY=( $(compgen -W "$subs" -- "$cur") ); return; }
+
+  # subcommand-specific flags (each subcommand dies on anything else);
+  # `inspect` takes the full policy flag set, so it falls through to the list below.
+  case "$sub" in
+    build)   COMPREPLY=( $(compgen -W "--rebuild -f --refresh-base -B --gate" -- "$cur") ); return ;;
+    update)  COMPREPLY=( $(compgen -W "--check --no-gate" -- "$cur") ); return ;;
+    doctor)  COMPREPLY=( $(compgen -W "--deep -d" -- "$cur") ); return ;;
+    clean)   COMPREPLY=( $(compgen -W "--all -a --volumes -V" -- "$cur") ); return ;;
+    gate)    COMPREPLY=( $(compgen -W "up down status logs" -- "$cur") ); return ;;
+    ps|version) return 1 ;;
+  esac
+
+  COMPREPLY=( $(compgen -W \
+    "--net --allow --allow-file --proxy --no-gate --mount --no-cwd --workdir --home-cache --ephemeral-home --read-only --agents --no-agents --agents-dir --env --env-file --base-image --install --harness --pi-token-env --no-pi-token-env --no-pi-config --cpus --memory --pids --tmpfs-size --shell --interactive --no-tty --keep --name --label --no-build --dry-run --print-policy --print-entrypoint --print-containerfile --allow-unenforced --insecure-keep-root --strict-args -h --help -V" \
+    -- "$cur") )
+}
+
+complete -o default -F _ai_sandbox_completions ai-sandbox 2>/dev/null || true
+if [[ $- == *i* ]]; then                             # also complete the harness alias
+  for _aisb in $(compgen -A alias 2>/dev/null); do
+    if alias "$_aisb" 2>/dev/null | grep -q 'ai-sandbox'; then
+      complete -o default -F _ai_sandbox_completions "$_aisb" 2>/dev/null || true
+    fi
+  done
+  unset _aisb
+fi

docs/recipes.md

@@ -50,12 +50,37 @@ pi --allow aipi.reeseapps.com --pi-token-env GW_TOKEN
 # pass it yourself, which is what you want in shared scripts
 pi --allow aipi.reeseapps.com --env AI_API_TOKEN --no-pi-token-env
 
-# no bridge: pi starts with its own defaults inside the volume
+# no bridge: pi starts with its own defaults inside the volume (and no thinking policy)
 pi --no-pi-config --allow aipi.reeseapps.com
 ```
 
-Edits made inside the sandbox are kept; changes to the host config are picked up on
-the next run; deleting `~/.pi/agent/models.json` inside the sandbox re-seeds it.
+`models.json` is kept in step with the host unless you edit it in the sandbox, where your
+edit then wins; deleting it inside the sandbox re-seeds it. `settings.json` is merged per
+key, so a preference you changed in the sandbox stays changed and every one you did not
+touch follows the host again.
+
+### How hard it thinks
+
+`defaultThinkingLevel` is policy, not preference: `xhigh` unless you say otherwise, and
+re-applied every run rather than remembered from whatever the last sandbox set.
+
+```bash
+# the everyday case: xhigh
+pi --allow aipi.reeseapps.com
+
+# one-off: the top of pi's range, or no reasoning at all for a mechanical job
+pi --thinking max --allow aipi.reeseapps.com
+pi --thinking off --net allow --allow registry.npmjs.org -- npm ci
+
+# let settings.json decide, the way it did before this was policy
+pi --thinking host --allow aipi.reeseapps.com
+
+# per repo, chosen by .ai-sandbox/config
+#   thinking = high
+```
+
+Nothing is written for `codex`, `claude` or a command after `--`: those read their own
+configuration and ai-sandbox does not touch it.
 
 ## Your skills and standing instructions
 

docs/threat-model.md

@@ -88,10 +88,14 @@ Be honest about these, and design your work accordingly.
     uses is your real one. So the bridged config is a convenience, not a narrower
     credential: prefer a per-sandbox token from your gateway if it can mint one, and
     note that a bridged run whose token variable is unset or empty is refused rather
-    than started. Sandboxed edits to `~/.pi/agent` persist in the home volume and are
-    kept over later host changes (see the README), which is convenience with a
-    consequence: a hostile run could rewrite the sandboxed pi config for later runs of
-    that volume. `--ephemeral-home` removes that.
+    than started. Sandboxed edits to `~/.pi/agent` persist in the home volume and win
+    over later host changes (see the README), which is convenience with a consequence: a
+    hostile run could rewrite the sandboxed pi config for later runs of that volume —
+    point `baseUrl` at a host it controls, swap a model, change the provider. Merging
+    `settings.json` per key limits this (a run can only pin the keys it actually writes,
+    and everything else keeps following your host config), and `defaultThinkingLevel` is
+    re-forced every run so a run cannot quietly lower the reasoning of the next. It is
+    not eliminated: `--ephemeral-home` removes it, and `inspect` shows what is bridged.
 
 ## Residual risk rating
 

tests/e2e/12_sandbox.sh

@@ -245,6 +245,55 @@ sb $DARK --harness pi -- bash -c 'rm -f "$HOME/.pi/agent/models.json"; echo rese
 sb $DARK --harness pi -- bash -lc 'grep -q 524288 "$HOME/.pi/agent/models.json" && echo reseeded || echo not_reseeded'
 assert_contains "reseeded" "deleting it inside the sandbox takes the host version again"
 
+t_name "settings.json follows the host per key, and the thinking level is policy"
+# The host file says medium and no ai-sandbox policy is in it: anything that arrives as
+# xhigh can only have been written by the policy.
+printf '{ "defaultProvider": "gateway", "defaultModel": "turbo", "theme": "dark/dark",\n  "defaultThinkingLevel": "medium", "thinkingBudgets": { "xhigh": 65536 } }\n' > "$AGENT/settings.json"
+sb $DARK --harness pi -- bash -lc 'jq -c . "$HOME/.pi/agent/settings.json"'
+assert_contains '"defaultThinkingLevel":"xhigh"' "xhigh is enforced over the host file's medium"
+assert_contains '"thinkingBudgets":{"xhigh":65536}' "and the rest of the preferences come along"
+
+# What pi does to its own settings: rewrites the file, adding a key of its own. That used
+# to freeze every host preference out of the sandbox for good.
+sb $DARK --harness pi -- bash -c '
+  f="$HOME/.pi/agent/settings.json"
+  jq ".theme=\"light/light\" | .defaultThinkingLevel=\"off\" | .lastChangelogVersion=\"9.9.9\"" "$f" > "$f.n" && mv "$f.n" "$f"
+  echo edited' >/dev/null
+# the host then moves the model and the budgets, drops the provider entirely, and says
+# medium itself -- so a later --thinking host run has something to hand over
+printf '{ "defaultModel": "deepthink", "theme": "sepia/sepia",\n  "defaultThinkingLevel": "medium", "thinkingBudgets": { "xhigh": 131072 } }\n' > "$AGENT/settings.json"
+sb $DARK --harness pi -- bash -lc 'jq -c . "$HOME/.pi/agent/settings.json"'
+MERGED="$OUT"
+printf '%s' "$MERGED" | grep -qF '"theme":"light/light"' && _ok "the theme edited in the sandbox survives" \
+  || _bad "the theme edited in the sandbox survives" "$MERGED"
+printf '%s' "$MERGED" | grep -qF '"lastChangelogVersion":"9.9.9"' && _ok "a key only pi wrote survives" \
+  || _bad "a key only pi wrote survives" "$MERGED"
+printf '%s' "$MERGED" | grep -qF '"defaultModel":"deepthink"' && _ok "an untouched model follows the host again" \
+  || _bad "an untouched model follows the host again" "$MERGED"
+printf '%s' "$MERGED" | grep -qF '"xhigh":131072' && _ok "and so do the thinking budgets" \
+  || _bad "and so do the thinking budgets" "$MERGED"
+printf '%s' "$MERGED" | grep -qF 'defaultProvider' && _bad "an untouched key the host dropped is dropped" \
+  || _ok "an untouched key the host dropped is dropped"
+printf '%s' "$MERGED" | grep -qF '"defaultThinkingLevel":"xhigh"' && _ok "thinking is forced back to xhigh after the sandbox set off" \
+  || _bad "thinking is forced back to xhigh after the sandbox set off" "$MERGED"
+
+# (the jq programs below avoid `{a, b}` object construction: bash brace-expands an
+# unquoted word containing a comma before jq ever sees it)
+sb $DARK --harness pi --thinking host -- bash -lc 'jq -r .defaultThinkingLevel "$HOME/.pi/agent/settings.json"'
+assert_eq "medium" "$(printf '%s' "$OUT" | tail -1)" "with --thinking host the host's own medium is handed over"
+
+sb $DARK --harness pi -- bash -c 'printf "{oops" > "$HOME/.pi/agent/settings.json"' >/dev/null
+sb $DARK --harness pi -- bash -lc 'jq -c . "$HOME/.pi/agent/settings.json"'
+assert_contains "deepthink" "a settings.json that is not JSON is re-seeded rather than left broken"
+assert_contains '"defaultThinkingLevel":"xhigh"' "with the policy still applied"
+sb $DARK --harness pi -- bash -lc 'jq -r .defaultThinkingLevel "$HOME/.pi/agent/settings.json"'
+assert_eq "xhigh" "$(printf '%s' "$OUT" | tail -1)" "and it stays xhigh, not the medium that came back"
+
+sb $DARK --harness pi -- bash -c 'chmod 000 "$HOME/.pi/agent/settings.json"' >/dev/null
+sb $DARK --harness pi -- bash -lc 'echo ran'
+assert_contains "cannot read settings.json" "a file this container cannot read is reported, not blamed on JSON"
+assert_contains "--ephemeral-home" "and the report names a way out"
+
 unset AI_API_TOKEN
 sb_timeout 90 $DARK --harness pi
 assert_rc 1 "a run without the credential is refused before anything starts"

tests/run.sh

@@ -79,7 +79,7 @@ for f in "${FILES[@]}"; do
     # test should depend on or accidentally share. Files that exercise the .agents
     # bridge point AISB_AGENTS_DIR at a fixture of their own.
     export AISB_AGENTS_DIR="${AISB_AGENTS_DIR:-$W/absent-agents-dir}"
-    unset AI_API_TOKEN AISB_PI_TOKEN_ENV AISB_PI_CONFIG AISB_PI_TOKEN_AUTO
+    unset AI_API_TOKEN AISB_PI_TOKEN_ENV AISB_PI_CONFIG AISB_PI_TOKEN_AUTO AISB_THINKING
     # NOTE: HOME is deliberately not overridden -- podman storage lives there.
     unset AISB_ALLOW AISB_ENV AISB_MOUNT AISB_INSTALL AISB_NET AISB_EXTRA_ARGS AISB_SESSION_OVERRIDE
     unset AISB_AGENTS AISB_AGENTS_DEST

tests/unit/06_entrypoint.sh

@@ -61,6 +61,83 @@ grep -c 'accept comment "aisb-direct"' "$RULES" | grep -qx 3 && _ok "exactly 3 d
 t_name "no DNS hole when the gate is in front"
 grep -E 'th dport 53' "$RULES" >/dev/null && _bad "DNS is closed in gate mode" || _ok "DNS is closed in gate mode"
 
+t_name "the seeding script survives being passed in single quotes"
+# Everything between `bash -c '` and `' aisb-seed` is one single-quoted argument of the
+# outer script. One quote inside it closes that argument early and the rest of the file
+# silently becomes code in the *outer* shell -- valid bash, wrong program, so neither
+# `bash -n` nor shellcheck notices. Hence this test.
+INNER="$WORK/seeding-inner.sh"
+awk "/setpriv .*bash -c '/{f=1;next} /^ *' aisb-seed/{f=0} f" "$EP" > "$INNER"
+[[ -s "$INNER" ]] && _ok "the seeding script was extracted" || _bad "the seeding script was extracted"
+if grep -q "'" "$INNER"; then
+  _bad "it contains no single quote" "found: $(grep -n "'" "$INNER" | head -2 | tr '\n' ' ')"
+else
+  _ok "it contains no single quote"
+fi
+bash -n "$INNER" && _ok "and it is valid bash on its own" || _bad "and it is valid bash on its own"
+grep -q '\$lvl' "$INNER" && _ok "the thinking level is enforced inside it" || _bad "thinking level enforced"
+
+t_name "settings.json is merged per key, not managed whole"
+# Run the merge exactly as the entrypoint does, with the program extracted from the image
+# script: T = what the sandbox has, B = what we last wrote, N = what the host says now.
+MJQ="$WORK/merge.jq"
+awk '/^SETTINGS_MERGE_JQ=/{f=1;next} f && /^.$/{exit} f' "$EP" > "$MJQ"
+[[ "$(wc -l < "$MJQ")" -gt 3 ]] && _ok "the merge program was extracted" || _bad "the merge program was extracted"
+M_IN="$WORK/m"; mkdir -p "$M_IN"
+cat > "$M_IN/new.json" <<'EOF'
+{ "defaultProvider": "gateway", "defaultModel": "turbo", "theme": "dark/dark",
+  "thinkingBudgets": { "xhigh": 65536 } }
+EOF
+cat > "$M_IN/wrote.json" <<'EOF'
+{ "defaultProvider": "gateway", "defaultModel": "turbo", "theme": "dark/dark",
+  "thinkingBudgets": { "xhigh": 65536 } }
+EOF
+cat > "$M_IN/sandbox.json" <<'EOF'
+{ "defaultProvider": "gateway", "defaultModel": "turbo", "theme": "light/light",
+  "thinkingBudgets": { "xhigh": 65536 }, "lastChangelogVersion": "1.4.0", "mine": 7 }
+EOF
+merge_out() { jq -c -n --slurpfile T "$1" --slurpfile B "$2" --slurpfile N "$3" -f "$MJQ"; }
+M="$(merge_out "$M_IN/sandbox.json" "$M_IN/wrote.json" "$M_IN/new.json")"
+[[ "$(printf '%s' "$M" | jq -r .theme)" == "light/light" ]] \
+  && _ok "a key edited in the sandbox stays edited" || _bad "sandbox edit kept: $M"
+[[ "$(printf '%s' "$M" | jq -r .lastChangelogVersion)" == "1.4.0" ]] \
+  && _ok "a key only pi wrote survives" || _bad "sandbox-only key: $M"
+[[ "$(printf '%s' "$M" | jq -r .mine)" == "7" ]] \
+  && _ok "and so does one the sandbox invented" || _bad "invented key: $M"
+
+# host moves two keys, drops a third, keeps one the sandbox changed
+cat > "$M_IN/new2.json" <<'EOF'
+{ "defaultProvider": "gateway", "defaultModel": "deepthink",
+  "thinkingBudgets": { "xhigh": 131072 } }
+EOF
+M2="$(merge_out "$M_IN/sandbox.json" "$M_IN/wrote.json" "$M_IN/new2.json")"
+[[ "$(printf '%s' "$M2" | jq -r .defaultModel)" == "deepthink" ]] \
+  && _ok "an untouched key follows the host again" || _bad "host key arrives: $M2"
+[[ "$(printf '%s' "$M2" | jq -r .thinkingBudgets.xhigh)" == "131072" ]] \
+  && _ok "including a nested one (whole key, whole value)" || _bad "nested key: $M2"
+[[ "$(printf '%s' "$M2" | jq -r 'has("theme")')" == "true" ]] \
+  && _ok "a key the host dropped stays if the sandbox had changed it" || _bad "dropped-but-edited key: $M2"
+# the same drop against a file the sandbox never touched: it goes away, as it did when
+# the whole file was re-seeded -- otherwise settings only ever accumulate
+cat > "$M_IN/clean.json" <<'EOF'
+{ "defaultProvider": "gateway", "defaultModel": "turbo", "theme": "dark/dark",
+  "thinkingBudgets": { "xhigh": 65536 } }
+EOF
+M3="$(merge_out "$M_IN/clean.json" "$M_IN/wrote.json" "$M_IN/new2.json")"
+[[ "$(printf '%s' "$M3" | jq -r 'has("theme")')" == "false" ]] \
+  && _ok "an untouched key the host dropped is dropped" || _bad "untouched dropped key: $M3"
+# no base copy (the first run after this shipped, or .wrote deleted): the host wins on
+# every key it has, which is what repairs a settings file pi had frozen.
+M4="$(merge_out "$M_IN/sandbox.json" /dev/null "$M_IN/new.json")"
+[[ "$(printf '%s' "$M4" | jq -r '.thinkingBudgets.xhigh')" == "65536" ]] \
+  && _ok "with no base, host preferences come back (the frozen-file repair)" || _bad "no-base merge: $M4"
+[[ "$(printf '%s' "$M4" | jq -r .lastChangelogVersion)" == "1.4.0" ]] \
+  && _ok "and pi's own keys are kept" || _bad "no-base, pi key: $M4"
+printf '{oops' > "$M_IN/broken.json"
+jq -n --slurpfile T "$M_IN/broken.json" --slurpfile B /dev/null --slurpfile N "$M_IN/new.json" \
+   -f "$MJQ" > /dev/null 2>&1 \
+  && _bad "unparseable input fails loudly for the caller to handle" || _ok "unparseable input fails loudly for the caller to handle"
+
 t_name "privilege drop is the last thing that happens"
 tail -5 "$EP" | grep -q 'setpriv' && _ok "exec setpriv at the end" || _bad "setpriv last: $(tail -3 "$EP" | tr '\n' ' ')"
 grep -q -- '--bounding-set=-all' "$EP"  && _ok "bounding set cleared"   || _bad "bounding set cleared"

tests/unit/08_pi_config.sh

@@ -37,12 +37,15 @@ cat > "$AGENT/models.json" <<EOF
 EOF
 # sessionDir points at the *real* host home on purpose: that is the case the bridge
 # has to drop, and HOME must stay the real home for podman's sake.
+# defaultThinkingLevel is deliberately NOT xhigh here: the host has to disagree with the
+# ai-sandbox policy, otherwise "the policy wrote xhigh" cannot be told apart from "the
+# host said xhigh and we copied it".
 cat > "$AGENT/settings.json" <<EOF
 {
   "defaultProvider": "gateway",
   "defaultModel": "turbo",
   "theme": "dark/dark",
-  "defaultThinkingLevel": "xhigh",
+  "defaultThinkingLevel": "medium",
   "enableInstallTelemetry": false,
   "thinkingBudgets": { "xhigh": 65536 },
   "sessionDir": "$HOME/pi-sessions"
@@ -110,13 +113,74 @@ t_name "settings travel, host paths do not"
 S="$(gen_file settings.json)"
 if [[ -n "$S" ]]; then
   for pair in '"defaultProvider": "gateway"' '"defaultModel": "turbo"' '"theme": "dark/dark"' \
-              '"defaultThinkingLevel": "xhigh"' '"xhigh": 65536' '"enableInstallTelemetry": false'; do
+              '"xhigh": 65536' '"enableInstallTelemetry": false'; do   # the thinking level is policy, not a preference that travels
     grep -qF "$pair" "$S" && _ok "kept $pair" || _bad "kept $pair"
   done
   grep -qF 'sessionDir' "$S" && _bad "a value pointing at the host home is dropped" || _ok "a value pointing at the host home is dropped"
 fi
 assert_contains "dropped settings sessionDir" "and it says so"
 
+# `--print-policy --keep` renders the bridge into the session directory and stops there:
+# a unit file never starts a container, and --keep keeps the rendered files to look at.
+rendered_level() { # rendered_level <level-or-default>
+  clear_sessions
+  sb --keep --print-policy --net none ${1:+--thinking "$1"}
+  local f; f="$(gen_file settings.json)"
+  [[ -n "$f" ]] || { printf 'none'; return; }
+  jq -r '.defaultThinkingLevel // "absent"' "$f" 2>/dev/null || printf 'invalid'
+}
+
+t_name "the thinking level is policy, written over the settings that travel"
+sb --keep --print-policy --net none
+assert_contains "thinking=xhigh (enforced on every run)" "xhigh is the default, not pi's medium"
+assert_contains "pi config: thinking -> xhigh" "and it is announced"
+# the fixture says medium, so an xhigh here can only have come from the policy
+assert_eq "xhigh" "$(rendered_level '')" "the policy beats the host file's medium"
+# the level is a preference, so it belongs to settings.json and nowhere else
+clear_sessions
+sb --keep --print-policy --net none
+if grep -q 'defaultThinkingLevel' "${M:-/nonexistent}" 2>/dev/null; then
+  _bad "models.json is untouched by it" "the key appeared in the model catalog"
+else
+  _ok "models.json is untouched by it"
+fi
+S="$(gen_file settings.json)"
+grep -qF '"defaultProvider": "gateway"' "${S:-/nonexistent}" \
+  && _ok "the rest of the settings still travel" || _bad "the rest of the settings still travel"
+grep -qF '"xhigh": 65536' "${S:-/nonexistent}" \
+  && _ok "including the host's thinking budgets" || _bad "the host's thinking budgets"
+grep -qF 'sessionDir' "${S:-/nonexistent}" \
+  && _bad "and a host path is still dropped while the level is added" || _ok "and a host path is still dropped while the level is added"
+
+t_name "every level, including 'host' and 'off', and nothing in between"
+assert_eq "low"    "$(rendered_level low)" "a level of your choosing"
+assert_eq "max"    "$(rendered_level max)" "and the top of pi's range"
+assert_eq "off"    "$(rendered_level off)" "off is pi's own level, not 'do not manage it'"
+assert_eq "medium" "$(rendered_level host)" "host leaves the key to settings.json (medium there)"
+rendered_level host >/dev/null
+assert_contains "thinking=host (not applied: the config decides)" "and says so"
+rendered_level bogus >/dev/null
+assert_rc 1 "an unknown level is refused"
+assert_contains "must be off, minimal, low, medium, high, xhigh, max or host" "with the list to pick from"
+sb_env AISB_THINKING=medium --print-policy --net none
+assert_contains "thinking=medium" "AISB_THINKING works"
+sb_env AISB_THINKING=medium --thinking max --print-policy --net none
+assert_contains "thinking=max" "the flag beats the environment"
+
+t_name "a host with no settings.json still gets the policy"
+mv "$AGENT/settings.json" "$WORK/settings-away.json"
+assert_eq "xhigh" "$(rendered_level '')" "the level does not depend on the host having the file"
+clear_sessions
+sb --keep --print-policy --net none
+assert_contains "pi_endpoints" "the model bridge still happened alongside it"
+mv "$WORK/settings-away.json" "$AGENT/settings.json"
+
+t_name "no bridge means no policy either, and it says so"
+clear_sessions
+sb --keep --no-pi-config --print-policy --net none
+assert_contains "thinking=xhigh (not applied: pi config bridging is off)" "--no-pi-config declines the thinking policy too"
+if [[ -n "$(gen_file settings.json)" ]]; then _bad "nothing is rendered for pi at all"; else _ok "nothing is rendered for pi at all"; fi
+
 t_name "auth.json and the credential store are never bridged"
 if find "$AISB_STATE_DIR/sessions" \( -name auth.json -o -name models-store.json \) | grep -q .; then
   _bad "only models.json and settings.json are bridged"
@@ -130,6 +194,7 @@ else
 fi
 
 t_name "the token is passed by name, once, and announced"
+sb --keep --print-policy --net none
 assert_contains "passing \$AI_API_TOKEN from the host" "the auto-pass is announced"
 assert_eq "env_names=AI_API_TOKEN" "$(printf '%s' "$OUT" | grep '^env_names=' || true)" "exactly one variable is passed"
 assert_absent "$AI_API_TOKEN" "and only its name is reported"