Script Delegation

The Core Principle

• Everything deterministic → script. Everything requiring reasoning → skill/LLM
• If the logic can be expressed as a pure function with known inputs and outputs, it's a script
• If it requires judgment, synthesis, or context-dependent decisions, it stays in the skill

What Belongs in a Script

• Database queries, math operations, file parsing
• JSON normalization, fixed-logic API polling, data transformation
• Any operation where the same input always produces the same output

What Stays in the LLM

• Synthesis across multiple sources, language generation
• Branching decisions that require situational context
• Anything where the "right answer" depends on understanding intent

The Regex Trap

• LLMs are over-eager declaring things deterministic because they think they can regex it
• If the input has too many edge cases for a reasonable regex, it's reasoning — not scripting
• Parsing natural language dates, extracting meaning from unstructured text, classifying ambiguous input — these are not scripting tasks
• A script should only handle patterns that are fully enumerable

Scripts Are Real Files

• Scripts are executable files that live in the tile (e.g., scripts/request-review.sh) — not code blocks in SKILL.md for the agent to copy-paste
• The skill references the script and runs it; the script does the work
• Code blocks in SKILL.md are for showing the agent what command to run, not for embedding logic the agent should reproduce character-by-character

Script Requirements

Scripts follow the baseline in rules/file-hygiene.md (exit codes, stderr, idempotency) plus these Tessl-specific requirements:

• JSON-producing: output structured data, not prose
• Self-error-handling: exit non-zero on failure, write a diagnostic message to stderr
• Single-purpose: one script does one thing — compose scripts, don't build monoliths

Precheck Gating

• Use last-line JSON payload with wake_agent for precheck gating
• The script runs first; the agent only wakes if the script signals it should