Theory Of Constraints

Theory of Constraints

A diagnostic runbook for optimizing any process — a CI/build pipeline, a dev value stream, an Agent Skill or plugin, or a runtime code path — through Eliyahu Goldratt's Theory of Constraints (ToC).

The one idea that makes ToC powerful: every system has exactly one binding constraint at a time, and global throughput rises only when you improve that constraint. Effort spent anywhere else produces nothing — "an hour saved at a non-bottleneck is a mirage." This runbook finds the constraint with measurement, then walks the Five Focusing Steps to relieve it without creating new problems.

When to Apply

Use this skill when the user wants to optimize a process or workflow and any of these are true:

• They want to optimize but don't know where to start ("make this faster", "why is this slow", "reduce the cost of this").
• A local speedup didn't move the end-to-end result (you optimized the wrong thing).
• Work, queues, or WIP pile up at one stage while others sit idle.
• Everything looks 100% busy but little ships (high utilization, low throughput).
• They added capacity, parallelism, or resources and it didn't help.
• Fixing one bottleneck just surfaces another.
• The real limiter is a policy or rule, not a resource (a mandatory full test suite, serialized review, a "read every reference" instruction, batch-everything releases).
• They're stuck in a tradeoff that blocks the obvious fix ("faster vs safer", "smaller context vs more coverage").

Do not use this skill for:

• A specific, already-localized hotspot where the constraint is known — go straight to the fix (e.g. an O(n²) loop → complexity-optimizer).
• Pure correctness/quality review with no throughput goal — use a code-review skill.
• Micro-optimizing a stage you have not yet proven is the constraint. That is the cardinal ToC error; this skill exists to stop it.

The Process of Ongoing Improvement (POOGI)

ToC is a loop, not a one-shot. Always run it in order — exploiting before elevating is what separates ToC from "just throw resources at it."

        ┌─────────────────────────────────────────────────┐
        │                                                   │
        ▼                                                   │
1. IDENTIFY the constraint  ── the one stage that gates global throughput
        │
        ▼
2. EXPLOIT it               ── get the most from it with NO new spend
        │                       (remove waste/idle on the constraint)
        ▼
3. SUBORDINATE everything   ── pace all non-constraints to the constraint;
   else to the constraint      let them idle rather than build WIP
        │
        ▼
4. ELEVATE the constraint   ── only now add capacity / invest / parallelize
        │
        ▼
5. REPEAT                   ── the constraint has moved; go to step 1.
        │                       Do NOT let inertia (old policies) be the
        └───────────────────────new constraint.

The most common mistakes map directly to skipped steps: jumping to step 4 (elevate) before step 2 (exploit), or never reaching step 1 (optimizing whatever is most visible instead of what is binding).

Common Symptoms

Start here. Match the symptom, open its decision tree, run the quick check.

For Agent Skills / plugins specifically, the constraint is most often the always-loaded context budget (a bloated SKILL.md) or a weak description (the skill never triggers, so its throughput is zero). Run queries/skill-context-cost.sh <skill-dir>.

How to Use

1. Identify the symptom in the table above and open its tree in references/.
2. Define the goal and throughput metric first. ToC is meaningless without a global metric to improve (PRs merged/week, requests/sec, task completions per agent session, build wall-clock). The trees assume you have one — set it via config.json or ask the user.
3. Run the quick-check query the tree points to. Queries live in references/queries/; each has a header explaining parameters and how to read the output.
4. Follow the tree to a terminal action. Every path ends in a concrete ToC move (exploit / subordinate / elevate / change-the-policy / repeat).
5. Record the finding using assets/templates/report.md. Append a one-line entry to the investigation log so recurring constraints become visible over time.

Read references/symptoms.md for the full catalog with entry points and severity.

Setup

This skill uses config.json to know what "throughput" means for the system under study and how to measure each stage. On first use, if goal_metric or value_stream_stages are empty, ask the user (via AskUserQuestion) for:

• the goal metric (the global throughput to maximize), and
• the ordered stages of the workflow being optimized.

Then save them to config.json. If config cannot be filled, the skill still works — fall back to asking the user inline and measuring stages manually. Never block on missing config.

Gotchas

The classic ToC traps (measuring local efficiency, elevating before exploiting, optimizing the most-visible stage) are captured in gotchas.md. Read it before your first investigation — these errors are the whole reason ToC exists.

Related Skills

• complexity-optimizer — once ToC identifies a code stage as the constraint, use this to find and fix the algorithmic hotspot inside it.
• dx-harness — when the constraint is a developer-experience chore (slow bootstrap, manual steps), this audits and fixes the harness.
• dev-skill:evolve — when the constraint is an Agent Skill itself (bloated context, weak triggering), this improves it.