attune/work-summary/2026-02-20-native-runtime-refactor.md

Work Summary: Native Runtime Refactor, Shell Wrapper Cleanup & Stdin Protocol Fixes (2026-02-20)

Problem

Python sensors (e.g., python_example.counter_sensor) were being executed by /bin/sh instead of python3, causing import: not found errors. Root cause was two-fold:

1. All sensors hardcoded to core.builtin runtime — PackComponentLoader::load_sensors() ignored the sensor YAML's runner_type field and assigned every sensor the core.builtin runtime.
2. core.builtin runtime defaulted to /bin/sh — The InterpreterConfig default was /bin/sh, so runtimes with no execution_config (like core.builtin) got shell as their interpreter, causing Python scripts to be interpreted as shell.

Additionally, the shell wrapper script had a hard dependency on python3 for JSON secret parsing, and pre-existing security test failures were discovered caused by a stdin protocol conflict between parameters and secrets.

Changes

Architecture: Remove "builtin" runtime concept

Replaced the separate core.builtin runtime with core.native. Runtime detection is now purely data-driven via execution_config in the runtime table — no special-cased runtime names.

• Deleted packs/core/runtimes/sensor_builtin.yaml
• Fixed packs/core/runtimes/native.yaml — removed /bin/sh -c interpreter; empty execution_config signals direct binary execution
• Changed InterpreterConfig default binary from "/bin/sh" to "" (empty = native)
• Updated interval_timer_sensor.yaml — runner_type: native

Sensor runtime resolution

• Fixed PackComponentLoader::load_sensors() — reads runner_type from each sensor's YAML definition and resolves to the correct runtime via resolve_runtime(). Defaults to native.
• Added resolve_runtime() method returning (Id, String) — both ID and ref
• Updated runtime mappings — builtin, standalone → core.native
• Updated load_core_pack.py — per-sensor runtime resolution from YAML instead of hardcoded core.builtin
• Updated seed_core_pack.sql — references core.native instead of core.builtin

Shell wrapper: remove Python dependency

The shell wrapper script (generate_wrapper_script) previously used python3 -c to parse JSON secrets from stdin into a bash associative array. This created a hard dependency on Python being installed, which violates the principle that core services must operate without supplemental runtimes.

• Replaced runtime JSON parsing with Rust-side secret injection — secrets are now embedded directly as ATTUNE_SECRETS['key']='value' entries at script generation time
• Added bash_single_quote_escape() helper for safe bash string embedding
• Changed wrapper execution from bash -c <script> to writing a temp file and executing it, keeping secrets out of /proc/<pid>/cmdline
• Removed unused execute_shell_code() method (wrapper now uses execute_shell_file)
• Also applied bash single-quote escaping to parameter values embedded in the wrapper
• Un-ignored test_shell_runtime_with_secrets — it now passes

Stdin protocol fixes (pre-existing bugs)

• Process executor: Skip writing empty/trivial parameter content ({}, "", []) to stdin to avoid breaking scripts that read secrets via readline()
• Shell streaming executor: Same empty-params skip applied
• Worker env tests: Replaced flaky env-var-manipulating tests with pure parsing tests to eliminate parallel test interference

Files Changed

File	Change
crates/common/src/models.rs	Default interpreter binary: "/bin/sh" → ""
crates/common/src/pack_registry/loader.rs	Sensors read runner_type from YAML; added resolve_runtime(); removed builtin mapping
crates/common/src/runtime_detection.rs	Comment update
crates/common/src/schema.rs	Test: core.builtin → core.native
crates/sensor/src/sensor_manager.rs	Updated is_native comments
crates/worker/src/env_setup.rs	Fixed flaky env var tests
crates/worker/src/runtime/shell.rs	Rewrote wrapper to embed secrets from Rust (no Python); temp file execution; removed execute_shell_code; un-ignored secrets test
crates/worker/src/runtime/process_executor.rs	Skip empty params on stdin
crates/worker/src/service.rs	Comment update
packs/core/runtimes/native.yaml	Removed /bin/sh interpreter; empty execution_config
packs/core/runtimes/sensor_builtin.yaml	Deleted
packs/core/runtimes/README.md	Removed sensor_builtin reference
packs/core/sensors/interval_timer_sensor.yaml	runner_type: native
scripts/load_core_pack.py	Per-sensor runtime resolution from YAML
scripts/seed_core_pack.sql	core.native references
AGENTS.md	Updated runtime documentation

Test Results

• All 7 security tests pass (2 previously failing now fixed)
• All 82 worker unit tests pass (1 previously ignored now un-ignored and passing)
• All 17 dependency isolation tests pass
• All 8 log truncation tests pass
• All 145 common unit tests pass
• Zero compiler warnings