KnickKnackLabs · junior-ricon · Jul 16, 2026 · Jul 16, 2026 · Jul 16, 2026 · Jul 16, 2026
diff --git a/.mise/tasks/run b/.mise/tasks/run
@@ -25,7 +25,8 @@ SYSTEM_PROMPT_FILE="${usage_system_prompt_file:-}"
 TIMEOUT="${usage_timeout:-}"
 MODEL="${usage_model:-}"
 SESSION="${usage_session:-}"
-CWD="${usage_cwd:-${SESSIONS_CALLER_PWD:-${CALLER_PWD:-.}}}"
+CALLER_CWD="${SESSIONS_CALLER_PWD:-.}"
+CWD="${usage_cwd:-$CALLER_CWD}"
 HEADLESS="${usage_headless:-false}"
 INTERACTIVE="${usage_interactive:-false}"
 PROJECT_TRUST="${usage_project_trust:-inherit}"
@@ -59,6 +60,8 @@ source "$MISE_CONFIG_ROOT/lib/processes.sh"
 
 PROMPT_TEMP_FILE=""
 PROCESS_START_ID=""
+HARNESS_NAME=""
+HARNESS_EXECUTABLE=""
 # shellcheck disable=SC2329  # Invoked by EXIT trap below.
 cleanup_prompt_temp() {
   if [ -n "$PROMPT_TEMP_FILE" ]; then
@@ -234,6 +237,29 @@ fi
 
 sessions_validate_project_trust "$PROJECT_TRUST" || exit 1
 
+# Mise tasks run from Sessions' package root. Resolve relative child paths from
+# the invoking caller before either launch path changes directories again.
+case "$CWD" in
+  /*) ;;
+  *) CWD="$CALLER_CWD/$CWD" ;;
+esac
+CWD=$(cd "$CWD" 2>/dev/null && pwd -P) || {
+  echo "Error: --cwd directory not found: ${usage_cwd:-$CALLER_CWD}" >&2
+  exit 1
+}
+
+# Resolve the selected harness and its Sessions-owned executable before any
+# launch environment is sanitized. Unsupported skeleton adapters may return no
+# executable and retain their adapter-level rejection in the Elixir boundary.
+if [ -n "$SESSION" ]; then
+  HARNESS_NAME=$(harness_resolve --session "$SESSION") || exit 1
+else
+  HARNESS_NAME=$(harness_resolve) || exit 1
+fi
+# shellcheck source=/dev/null
+source "$MISE_CONFIG_ROOT/lib/harness/$HARNESS_NAME.sh"
+HARNESS_EXECUTABLE=$(harness_call "$HARNESS_NAME" executable "$MISE_CONFIG_ROOT") || exit 1
+
 # Prompt resolution order:
 #   1. Explicit --system-prompt-file
 #   2. Latest system_prompt entry baked into --session by `sessions new`
@@ -284,33 +310,16 @@ HEADLESS_EOF
 fi
 
 run_interactive() {
-  # shellcheck source=../../lib/harness/dispatch.sh
-  source "$MISE_CONFIG_ROOT/lib/harness/dispatch.sh"
-
-  local harness_name
-  if [ -n "$SESSION" ]; then
-    harness_name=$(harness_resolve --session "$SESSION") || exit 1
-  else
-    harness_name=$(harness_resolve) || exit 1
-  fi
-  # shellcheck source=/dev/null
-  source "$MISE_CONFIG_ROOT/lib/harness/$harness_name.sh"
-
-  if [ "$harness_name" != "pi" ]; then
-    echo "sessions: '$harness_name' harness does not support interactive no-message run yet" >&2
+  if [ "$HARNESS_NAME" != "pi" ]; then
+    echo "sessions: '$HARNESS_NAME' harness does not support interactive no-message run yet" >&2
     exit "$HARNESS_UNSUPPORTED_EXIT"
   fi
 
   sessions_prepare_harness_env
 
-  local -a pi_command=(mise -C "$MISE_CONFIG_ROOT" exec -- pi)
-  if ! command -v mise >/dev/null 2>&1; then
-    echo "Error: mise not found on PATH for sessions-owned pi harness" >&2
-    exit 1
-  fi
-
+  local -a pi_command=("$HARNESS_EXECUTABLE")
   local project_trust_flag
-  project_trust_flag=$(harness_call "$harness_name" project_trust_flag "$PROJECT_TRUST") || exit 1
+  project_trust_flag=$(harness_call "$HARNESS_NAME" project_trust_flag "$PROJECT_TRUST") || exit 1
 
   local pi_args=(--model "$MODEL")
   [ -n "$project_trust_flag" ] && pi_args+=("$project_trust_flag")
@@ -354,6 +363,7 @@ CLI_ARGS=(--cwd "$CWD")
 [ -n "$TIMEOUT" ] && CLI_ARGS+=(--timeout "$TIMEOUT")
 CLI_ARGS+=(--model "$MODEL")
 [ -n "$SESSION" ] && CLI_ARGS+=(--session "$SESSION")
+[ -n "$HARNESS_EXECUTABLE" ] && CLI_ARGS+=(--harness-executable "$HARNESS_EXECUTABLE")
 CLI_ARGS+=(--project-trust "$PROJECT_TRUST")
 [ "$EXTENSIONS" != "true" ] && CLI_ARGS+=(--no-extensions)
 [ "$SKILLS" != "true" ] && CLI_ARGS+=(--no-skills)

diff --git a/.mise/tasks/wake b/.mise/tasks/wake
@@ -30,13 +30,8 @@ NO_EXTENSIONS="${usage_no_extensions:-false}"
 NO_SKILLS="${usage_no_skills:-false}"
 NO_PROMPT_TEMPLATES="${usage_no_prompt_templates:-false}"
 
-scrub_caller_pwd_env() {
-  local name
-  while IFS= read -r name; do
-    case "$name" in
-      CALLER_PWD|*_CALLER_PWD) unset "$name" ;;
-    esac
-  done < <(compgen -e)
+scrub_sessions_caller_pwd_env() {
+  unset SESSIONS_CALLER_PWD
 }
 
 if [ -z "$SESSION_ID" ]; then
@@ -246,7 +241,7 @@ if [ -n "$OS_USER" ]; then
   RUN_CMD=("$HOST_RUN_AS_USER" --user "$OS_USER" -- "${RUN_CMD[@]}")
 fi
 
-scrub_caller_pwd_env
+scrub_sessions_caller_pwd_env
 
 if [ "$BACKGROUND" = "true" ]; then
   # Background: launch via shell/zmx (fire-and-forget)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -12,6 +12,7 @@ Keep these generic in core task/library code:
 
 Keep harness-specific knowledge in `lib/harness/<name>.sh` and `lib/harness/<name>.py`:
 
+- exact executable resolution from Sessions' declared tool context;
 - session file locations and path encoding;
 - native JSONL message schemas;
 - launch arguments for a harness binary;

diff --git a/README.md b/README.md
@@ -8,7 +8,7 @@ Create sessions with structured metadata, wake agents into them,
 observe transcripts in real time, and query your history.
 
 ![lang: bash + python](https://img.shields.io/badge/lang-bash%20%2B%20python-4EAA25?style=flat&logo=gnubash&logoColor=white)
-[![tests: 321 passing](https://img.shields.io/badge/tests-321%20passing-brightgreen?style=flat)](test/)
+[![tests: 322 passing](https://img.shields.io/badge/tests-322%20passing-brightgreen?style=flat)](test/)
 ![commands: 19](https://img.shields.io/badge/commands-19-blue?style=flat)
 ![license: MIT](https://img.shields.io/badge/license-MIT-blue?style=flat)
 
@@ -115,6 +115,8 @@ sessions wake review/pr-50 --model openai-codex/gpt-5.5 --message "You missed th
 
 The spawning stack uses [shell](https://github.com/KnickKnackLabs/shell) for persistent zmx sessions. `sessions wake` calls `sessions run` as its hidden low-level executor. For profile-specific sessions, use `new` + `wake`: bake profile or task instructions into the session with `--system-prompt-file` at creation, then wake it with task messages. If no explicit or baked prompt exists, the harness starts without an appended prompt and can rely on its native cwd context discovery.
 
+Before launch, Sessions resolves the selected harness executable from its own declared toolchain. The child then starts in the requested `--cwd` with Sessions' mise task context and direct tool-install paths removed. This keeps the harness version pinned without replacing the target project or agent home's own tool and resource context.
+
 `sessions run` remains available as an advanced/compatibility command. It accepts an explicit `--system-prompt-file`, uses any prompt baked into the session, and otherwise starts without appending a system prompt. Caller-provided context belongs to the caller, not to `sessions`.
 
 `--model` on `sessions wake` is required and is not remembered across wakes — pass a provider-qualified model (for example `openai-codex/gpt-5.5`) on each wake.
@@ -272,7 +274,7 @@ cd sessions && mise trust && mise install
 mise run test
 ```
 
-**321 tests** across 21 suites, using [BATS 1.13.0](https://github.com/bats-core/bats-core). Tasks are bash scripts (session creation, wake, metadata) and Python scripts with [Rich](https://github.com/Textualize/rich) output (list, read, wait, usage, inspect, search). The shared Python support library is 2740 lines in `lib/`.
+**322 tests** across 21 suites, using [BATS 1.13.0](https://github.com/bats-core/bats-core). Tasks are bash scripts (session creation, wake, metadata) and Python scripts with [Rich](https://github.com/Textualize/rich) output (list, read, wait, usage, inspect, search). The shared Python support library is 2740 lines in `lib/`.
 
 Python code is checked with [Ruff](https://docs.astral.sh/ruff/) via `mise run lint:python`, and CI runs the same lint/format check in addition to the BATS and Elixir suites.
 
@@ -311,7 +313,7 @@ sessions/
 │   └── harness/        # Per-harness adapters (pi, …)
 ├── queries/            # Packaged sessions query SQL presets
 └── test/
-    └── *.bats          # 321 tests
+    └── *.bats          # 322 tests
 ```
 
 </details>

diff --git a/README.tsx b/README.tsx
@@ -232,6 +232,12 @@ sessions wake review/pr-50 --model openai-codex/gpt-5.5 --message "You missed th
         {" at creation, then wake it with task messages. If no explicit or baked prompt exists, the harness starts without an appended prompt and can rely on its native cwd context discovery."}
       </Paragraph>
 
+      <Paragraph>
+        {"Before launch, Sessions resolves the selected harness executable from its own declared toolchain. The child then starts in the requested "}
+        <Code>--cwd</Code>
+        {" with Sessions' mise task context and direct tool-install paths removed. This keeps the harness version pinned without replacing the target project or agent home's own tool and resource context."}
+      </Paragraph>
+
       <Paragraph>
         <Code>sessions run</Code>
         {" remains available as an advanced/compatibility command. It accepts an explicit "}

diff --git a/cli/lib/cli.ex b/cli/lib/cli.ex
@@ -55,6 +55,7 @@ defmodule Cli do
     skills = opts[:no_skills] != true
     prompt_templates = opts[:no_prompt_templates] != true
     project_trust = opts[:project_trust] || "inherit"
+    harness_executable = opts[:harness_executable]
 
     print_header(opts, message, timeout, model)
 
@@ -75,7 +76,8 @@ defmodule Cli do
           extensions: extensions,
           skills: skills,
           prompt_templates: prompt_templates,
-          project_trust: project_trust
+          project_trust: project_trust,
+          harness_executable: harness_executable
         )
     end
   end
@@ -129,6 +131,7 @@ defmodule Cli do
           no_skills: :boolean,
           no_prompt_templates: :boolean,
           project_trust: :string,
+          harness_executable: :string,
           help: :boolean
         ],
         aliases: [h: :help]

diff --git a/cli/lib/cli/engine.ex b/cli/lib/cli/engine.ex
@@ -20,7 +20,8 @@ defmodule Cli.Engine do
            extensions: boolean(),
            skills: boolean(),
            prompt_templates: boolean(),
-           project_trust: String.t()
+           project_trust: String.t(),
+           harness_executable: String.t() | nil
          ]
 
   @doc """
@@ -91,13 +92,17 @@ defmodule Cli.Engine do
   end
 
   defp harness_env do
-    caller_pwd_env_scrub() ++ path_env()
+    inherited_task_env_scrub() ++ path_env()
   end
 
-  defp caller_pwd_env_scrub do
+  defp inherited_task_env_scrub do
     System.get_env()
     |> Map.keys()
-    |> Enum.filter(&(&1 == "CALLER_PWD" or String.ends_with?(&1, "_CALLER_PWD")))
+    |> Enum.filter(fn name ->
+      name == "SESSIONS_CALLER_PWD" or
+        (String.starts_with?(name, "MISE_") and name != "MISE_DATA_DIR") or
+        String.starts_with?(name, "usage_")
+    end)
     |> Enum.map(&{String.to_charlist(&1), false})
   end
 

diff --git a/cli/lib/harness/pi/command.ex b/cli/lib/harness/pi/command.ex
@@ -3,9 +3,9 @@ defmodule Cli.Harness.Pi.Command do
   Pi command construction — builds the shell invocation passed to the
   port under `/bin/sh -c <script> -- $1 $2 ...`.
 
-  User-controlled strings (message, model, system prompt file, session
-  path) are passed as positional `$1`/`$2`/... args so they never enter
-  the shell script as interpolated text.
+  User-controlled strings and the Sessions-selected Pi executable are passed
+  as positional `$1`/`$2`/... args so they never enter the shell script as
+  interpolated text.
 
   Part of the pi harness adapter — see sessions#50 for the
   multi-harness plan.
@@ -15,7 +15,8 @@ defmodule Cli.Harness.Pi.Command do
            extensions: boolean(),
            skills: boolean(),
            prompt_templates: boolean(),
-           project_trust: String.t()
+           project_trust: String.t(),
+           harness_executable: String.t()
          ]
 
   @doc """
@@ -40,6 +41,7 @@ defmodule Cli.Harness.Pi.Command do
     skills = Keyword.get(opts, :skills, true)
     prompt_templates = Keyword.get(opts, :prompt_templates, true)
     project_trust_flag = project_trust_flag(Keyword.get(opts, :project_trust, "inherit"))
+    executable = harness_executable(opts)
 
     qualified_model = model
 
@@ -59,6 +61,9 @@ defmodule Cli.Harness.Pi.Command do
         {" --no-session", positional_after_prompt}
       end
 
+    executable_arg = "$#{length(positional) + 1}"
+    positional = positional ++ [executable]
+
     pi_flags =
       [
         prompt_flag,
@@ -72,7 +77,7 @@ defmodule Cli.Harness.Pi.Command do
       ]
       |> Enum.join("")
 
-    pi_cmd = ~s(mise -C "$MISE_CONFIG_ROOT" exec -- pi -p "$1"#{pi_flags})
+    pi_cmd = ~s("#{executable_arg}" -p "$1"#{pi_flags})
 
     # `echo |` pipes empty stdin so pi doesn't block waiting for a TTY.
     shell_script =
@@ -85,6 +90,20 @@ defmodule Cli.Harness.Pi.Command do
     {shell_script, positional}
   end
 
+  defp harness_executable(opts) do
+    case Keyword.fetch(opts, :harness_executable) do
+      {:ok, executable} when is_binary(executable) and executable != "" ->
+        if Path.type(executable) == :absolute do
+          executable
+        else
+          raise ArgumentError, "pi harness executable must be an absolute path"
+        end
+
+      _ ->
+        raise ArgumentError, "pi harness executable is required"
+    end
+  end
+
   defp project_trust_flag("inherit"), do: ""
   defp project_trust_flag("approve"), do: " --approve"
   defp project_trust_flag("deny"), do: " --no-approve"