Strip It To Foundation

The Thin Bundle discipline, caught in the act

The Stakes

Composition is Amplifier's superpower — but freedom without discipline lets bundles rot

Anyone can wire agents, tools, and hooks into a bundle in minutes. The foundation team named the cure for what happens when that freedom runs unchecked.

The cure has a name — and it's already written down.

And — compose a bundle in minutes
But — that freedom lets bundles rot
Therefore — the keystone Thin Bundle Pattern

It's Documented

The Thin Bundle isn't a slogan — it's a "Recommended" section in foundation's guide

In amplifier-foundation's 1436-line BUNDLE_GUIDE.md: "Most bundles should be thin — inheriting from foundation and adding only their unique capabilities."

Real and documented. So what exactly goes wrong without it?

1436

lines in BUNDLE_GUIDE.md

"Rec."

The Thin Bundle Pattern (Recommended)

The Rot

Foundation names the failure modes directly — fat bundles and vague agents

A "Fat bundle that duplicates foundation" is an explicit anti-pattern. And the agent meta.description is "the ONLY discovery mechanism" — poor descriptions cause delegation failures.

So who has actually lived this and stripped their way out?

Creates maintenance burden — update in two places
Can cause version conflicts
Misses foundation updates automatically
Poor descriptions cause delegation failures

The Worked Example

Meet codex-patterns — a public bundle that learned the discipline the hard way

michaeljabbour/amplifier-bundle-codex-patterns is a small, public, primary-source repo: 2 shipped modules, 2 behaviors, and 5–6 documented patterns. Its git history is the story.

The cure it landed on fits in one line.

2

shipped modules (checkpoint, cost-tracker)

2

behaviors

5–6

documented patterns

The Cure, In One Line

The final bundle is just 26 lines and delegates everything with one include

The whole thin bundle.md is 26 lines: it inherits from foundation and adds only one unique thing. The center stays still so the edges can move.

It didn't start that way.

# bundle.md — 26 lines total
includes:
  - bundle: foundation

# plus one unique thing:
# swap Opus for Sonnet
default_model: claude-sonnet-4

Caught In The Act

The git history started fat — five modules inline, no foundation include

The first commit declared 5 modules inline with no foundation include. Then came the tell-tale commits: "strip to bare minimum," "absolute minimum bundle," "include foundation bundle."

Watch where that strip-down lands.

feat: initial codex-patterns bundle (5 modules inline)
fix: strip to bare minimum to diagnose parsing error
fix: absolute minimum bundle — no includes
fix: include foundation bundle for orchestrator/tools

The Strip-Down, Resolved

Across 9 commits it went from 5 inline modules to zero — keeping one unique swap

The arc converged: from 5 modules declared inline to none, delegating all of them to foundation. The one thing it kept: swapping Opus for Sonnet (~70% cheaper). That's the Thin Bundle, earned.

And the rule it leaves you with is portable.

5 → 0

inline modules: first commit → final

9

commits on main to converge

~70%

cheaper: Sonnet vs Opus (author's figure)

The Portable Rule

Inherit the foundation; add only what's uniquely yours

"Mechanism, Not Policy" keeps your bundle thin, current, and easy to route — the kernel provides protocols, your bundle adds only its policy.

Strip it to foundation, and let the edges move fast.

Sources

Research Methodology

Data as of: February 2026 (repo pushedAt 2026-02-06).

Feature status: codex-patterns bundle is public and early on GitHub (9 commits on main). The Thin Bundle Pattern is documented and canonical in amplifier-foundation.

Commands run:

cd /tmp/codex-patterns && wc -l bundle.md && cat bundle.md → 26 lines; includes: - bundle: foundation
git rev-list HEAD --count → 9; git rev-list --all --count → 10
git --no-pager log --all --format='%ci | %an | %h | %s' — fat→thin commit arc
git show 92d8690:bundle.md && git show HEAD:bundle.md — 5 inline modules → 0
grep -n -i 'thin bundle' docs/BUNDLE_GUIDE.md && wc -l docs/BUNDLE_GUIDE.md → 1436 lines
sed -n '28,60p' docs/BUNDLE_GUIDE.md — "BAD: Fat bundle that duplicates foundation"
sed -n '408,416p' agents/foundation-expert.md — meta.description = ONLY discovery mechanism
gh repo view michaeljabbour/amplifier-bundle-codex-patterns --json createdAt,pushedAt

Gaps: The "~70% cheaper" (Sonnet vs Opus) is the author's stated figure; the pricing table (Opus in $15/out $75 vs Sonnet in $3/out $15) implies closer to ~80%. Some patterns referenced in the README are config-illustrative — only checkpoint and cost-tracker ship as module files.

Primary contributors: Michael J. Jabbour — sole author of codex-patterns (all 9–10 commits). Brian Krabach — author of the Thin Bundle Pattern docs (454 of 502 foundation commits).