diff --git a/.agent/skills/simplicity-first/SKILL.md b/.agent/skills/simplicity-first/SKILL.md
new file mode 100644
index 00000000..a3b5a31b
--- /dev/null
+++ b/.agent/skills/simplicity-first/SKILL.md
@@ -0,0 +1,59 @@
+---
+name: simplicity-first
+description: Simplicity and traceability gate for all TransferQueue code written, fixed, or reviewed. Invoke before changing code or reviewing a diff, especially across public APIs, controller and metadata logic, samplers, storage backends, asynchronous execution, or metrics.
+---
+
+# Put simplicity first
+
+Keep code readable in one pass. Make each behavior traceable from a public API
+or configuration entry through controller, metadata, sampler, and storage
+logic to its tests and observability. Treat hidden control flow and unnecessary
+indirection as correctness problems, especially across asynchronous or
+distributed boundaries.
+
+1. **Keep execution paths explicit.** Make state transitions, partition and
+   sample ownership, retry or cleanup behavior, and async boundaries visible at
+   the point where they matter. Avoid clever control flow that obscures which
+   component mutates metadata or moves data.
+
+2. **Use the smallest readable change.** Delete redundancy before adding new
+   machinery. Do not add configuration, return fields, or extension points for
+   hypothetical future needs.
+
+3. **Preserve the control-plane/data-plane boundary.** Keep metadata and
+   scheduling in the controller layer and payload movement in storage managers,
+   clients, and backends. Do not route payloads through the controller or bind a
+   public API to one backend merely to shorten a local implementation.
+
+4. **Avoid thin abstractions.** Keep one-off logic inline when it remains clear.
+   Add a helper or type only when it removes real nontrivial duplication, names
+   an important invariant, or implements an existing interface such as a
+   sampler, storage manager, or storage client.
+
+5. **Preserve contracts and capabilities.** Keep public KV, client, and
+   dataloader behavior; metadata and sampler semantics; supported storage
+   backends; async and distributed behavior; metrics; and existing defaults.
+   Simplify implementations without silently narrowing the behavior surface.
+
+6. **Work from reachable behavior.** Prioritize issues reproducible through
+   supported APIs, configurations, backends, tutorials, or tests. Still protect
+   internal invariants required for concurrency, cleanup, and data consistency;
+   do not invent fixes for states the system cannot enter.
+
+## Checklist before finishing any change
+
+- Can a reader trace the change from `transfer_queue.interface`,
+  `TransferQueueClient`, or `StreamingDataLoader` through the controller and
+  storage path to a focused test?
+- Are control-plane metadata and data-plane payload responsibilities still
+  separate?
+- Are partition isolation, production and consumption status, sampler behavior,
+  cleanup, and async failure handling preserved where relevant?
+- Could this diff be half the size? If unsure, make it smaller.
+- Does every new abstraction remove real complexity or implement an existing
+  TransferQueue interface?
+- Does any public API, configuration default, metadata shape, or backend
+  contract change? If so, verify every affected caller and test.
+- Keep comments to concise reasons or invariants; omit run-specific data and
+  internal paths, while retaining useful upstream issue or PR links.
+- One problem = one minimal diff. Do not batch unrelated "improvements".
diff --git a/.claude/skills/simplicity-first/SKILL.md b/.claude/skills/simplicity-first/SKILL.md
new file mode 120000
index 00000000..7dc09ad2
--- /dev/null
+++ b/.claude/skills/simplicity-first/SKILL.md
@@ -0,0 +1 @@
+../../../.agent/skills/simplicity-first/SKILL.md
\ No newline at end of file
diff --git a/.codex/skills/simplicity-first/SKILL.md b/.codex/skills/simplicity-first/SKILL.md
new file mode 120000
index 00000000..7dc09ad2
--- /dev/null
+++ b/.codex/skills/simplicity-first/SKILL.md
@@ -0,0 +1 @@
+../../../.agent/skills/simplicity-first/SKILL.md
\ No newline at end of file
diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 00000000..c508824a
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,36 @@
+# Working rules for AI assistants
+
+## Code standards (hard rules, not preferences)
+
+The priority order is explicit: **human readability comes first; coding-agent
+traceability is the minimum gate.** A human should understand code in one pass,
+and an agent must be able to trace a feature from a public API or configuration
+entry through controller, metadata, sampler, and storage logic to observability
+and tests without reconstructing hidden control flow.
+
+1. Over-complex or hard-to-follow code is a **bug**, not a style issue.
+2. Reduce complexity and line count — prefer deleting code over adding it.
+3. Preserve the control-plane/data-plane boundary: controllers manage metadata
+   and scheduling; storage managers, clients, and backends move payloads.
+4. No over-encapsulation: add an abstraction only for real nontrivial reuse, an
+   important invariant, or an existing sampler/storage interface.
+5. Do NOT remove public APIs, backend support, async/distributed behavior,
+   metadata semantics, defaults, or observability in the name of simplicity.
+6. Prioritize behavior reachable through supported APIs, configurations,
+   backends, tutorials, or tests; do not fix states the system cannot enter.
+
+Details: `.claude/skills/simplicity-first` (invoke before any code change).
+
+## Comments
+
+Concise "why" only, 2-4 lines, written for an external reader: no job ids,
+commit hashes, single-run metrics, or internal cluster paths; keep upstream
+issue/PR links.
+
+## Workflow
+
+- Reviews report findings only; fixes ship as one minimal diff per issue
+  after approval.
+- Verify with `python -m compileall -q transfer_queue tutorial tests` and
+  `python -m pytest -q`; use the relevant optional-backend environment for
+  integration tests and validate shell scripts with `bash -n`.
diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 00000000..43c994c2
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1 @@
+@AGENTS.md