diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8e027af..fefebd9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,14 @@ _primitives/_rust/target/release/kei-changelog \
   - Marker file relocated from `~/.claude/keisei-attached.toml` to `~/.keisei/attached.toml`. `~/.claude/` is Claude-Code-specific territory and should not host cross-adapter keisei state. `config::read()` performs a one-shot migration the first time it runs under v0.21: if the legacy file exists and the new location is empty, the marker moves over (new file written, legacy file deleted) and a stderr notice is emitted.
   - `Scope` enum (`user` / `project`) on the `ClientAdapter` trait. Adapters declare `supported_scopes()`; `config_path(scope)`, `attach(brain, scope)`, `detach(brain_name, scope)` are scope-aware. Claude Code and Cursor support both scopes; Continue and Zed are user-only. `keisei attach` gains `--scope=<user|project>` (default `user`); `keisei mount` stays host-wide (`Scope::User` fan-out by design).
   - Marker schema v3: each `[[attachments]]` entry carries `scope = "user" | "project"`. Pre-v0.21 markers without the field default to `Scope::User` silently. New error variant `Error::ScopeUnsupported { client, scope, supported }` fires when a caller asks for a scope the adapter doesn't advertise.
+- **primitives (v0.21 — `kei-store` real S3 backend):**
+  - `S3CloudStore` — functional S3 / R2 / MinIO / Wasabi backend via `aws-sdk-s3` v1. GetObject / PutObject / ListObjectsV2 (paginated) / DeleteObject wired behind the existing `MemoryStore` trait (sync-over-async via a single-thread tokio runtime). Enables `keisei attach s3://my-bucket/brain/` as a real cloud-mount path, not just a local stub.
+  - Opt-in feature flag `s3` on the `kei-store` crate — off by default so users who don't need cloud pay zero binary weight. Enabling adds tokio + hyper + rustls + aws-sdk-s3 (~5 MB release binary growth).
+  - AWS default credential chain honoured (env vars → `~/.aws/credentials` → IMDS). No new credential format; RULE 0.8 secrets-single-source unchanged.
+  - Endpoint override for non-AWS S3-compat providers via `KEI_STORE_S3_ENDPOINT` env var (runtime) or `s3.endpoint` in `store-config.toml` (persistent). Path-style addressing auto-enabled when a custom endpoint is set (MinIO / some R2 configs).
+  - "Branch" semantics: S3 has no native branching, so a branch is modelled as a key prefix (`<branch>/<path>`). `branch()` sets the active prefix in-memory; default `main`.
+  - Factory auto-routes: `backend = "s3"` + feature `s3` + `s3.bucket` set → real cloud; otherwise falls back to the v0.14 local-manifest stub (still behind `KEI_STORE_ALLOW_S3_STUB=1`).
+  - Path-traversal guard parity with `FilesystemStore`: absolute and `..`-component paths rejected before keys are spliced.
 - **primitives (v0.20 — brain schema v2 + per-client hint):**
   - Brain schema v2 with per-platform `mcp_server` dispatch — a single brain directory can now host binaries for darwin-arm64/darwin-x64/linux-x64/linux-arm64/windows-x64 and `keisei attach` picks the right one automatically. Schema v1 (single string) still accepted for backward-compat.
   - `ClientAdapter::post_attach_hint()` — per-client reload instruction, no more hardcoded Claude-Code string in the orchestrator.
diff --git a/README.md b/README.md
index 81932f4..d39a7f4 100644
--- a/README.md
+++ b/README.md
@@ -217,7 +217,7 @@ Use cases:
 
 - **Laptop travel.** Brain lives on USB / iCloud Drive. Plug in at home → `keisei mount /Volumes/MyBrain` attaches to Claude Code + Cursor simultaneously. Unplug → `keisei detach` clears everything.
 - **Team shared persona library.** Commit a brain repo to your private Forgejo/GitHub. Every developer clones it, runs `keisei mount ./team-brain`, same 30-agent persona library active in their Claude Code.
-- **Cloud brain.** Point `keisei attach s3://my-bucket/brain/` at an S3-backed brain synced via `kei-store` (v0.20 — S3 backend currently MVP stub). Memory follows you to any machine with network.
+- **Cloud brain.** Point `keisei attach s3://my-bucket/brain/` at an S3-backed brain synced via `kei-store` (v0.21 — real S3 / R2 / MinIO backend behind the `s3` feature flag). Memory follows you to any machine with network.
 - **Experimental personas in isolation.** Spin up a test brain via `cp -r ~/production-brain ~/experimental-brain`, `keisei attach ~/experimental-brain`. Iterate without touching production state.
 
 Security hardening (v0.19.0):
@@ -395,7 +395,7 @@ Two output modes, chosen once in `/sleep-setup` Phase 3b:
 | Forgejo self-hosted | production | Same wire protocol as GitHub |
 | Gitea self-hosted | production | Same wire protocol |
 | Filesystem only | production | Local `.git`; no push; fastest |
-| S3 / R2 / MinIO | stub — local only until v0.15 | Manifest-based local cache ONLY; no upload to S3/R2/MinIO yet. Requires `KEI_STORE_ALLOW_S3_STUB=1` (explicit opt-in so you don't accidentally believe your data is in the cloud). `aws-sdk-s3` integration planned for v0.15. |
+| S3 / R2 / MinIO | production (v0.21, behind `s3` feature) | Real GetObject / PutObject / ListObjectsV2 via `aws-sdk-s3`. Build with `cargo build -p kei-store --features s3` and set `[s3] bucket = "..."` in `store-config.toml`. AWS default credential chain (env vars → `~/.aws/credentials` → IMDS). Custom endpoint for R2 / MinIO / Wasabi via `KEI_STORE_S3_ENDPOINT` env or `s3.endpoint` TOML field. Binary grows ~5 MB when the feature is on. Omit the feature OR omit `s3.bucket` to fall back to the v0.14 local-manifest stub (still gated by `KEI_STORE_ALLOW_S3_STUB=1`). |
 
 Requires the new `kei-conflict-scan`, `kei-refactor-engine`, `kei-graph-check`, and `kei-store` primitives (shipped in the `dev` and `full` profiles). Governed by the Phase C extension of RULE 0.15 in `~/.claude/rules/sleep-layer.md`.
 
@@ -417,7 +417,7 @@ Requires the new `kei-conflict-scan`, `kei-refactor-engine`, `kei-graph-check`,
 | `kei-conflict-scan` | v0.13.0 — deep-sleep conflict scanner across rules/hooks/blocks/orphans/CP violations |
 | `kei-refactor-engine` | v0.13.0 — consumes `kei-conflict-scan` JSON; emits plan markdown + auto-resolve review markdown (NOT a unified diff; v0.14.1 retraction) |
 | `kei-graph-check` | v0.13.0 — post-refactor wikilink + handoff + block-ref resolver gate |
-| `kei-store` | v0.13.0 — memory-repo backend abstraction (GitHub / Forgejo / Gitea / Filesystem / S3) |
+| `kei-store` | v0.21.0 — memory-repo backend abstraction (GitHub / Forgejo / Gitea / Filesystem / S3). S3 backend is a real `aws-sdk-s3` client when built with `--features s3` (supports AWS / R2 / MinIO / Wasabi); otherwise falls back to the v0.14 local-manifest stub. |
 | `keisei` | v0.19.0 — exobrain multi-client CLI — `attach` / `mount` / `detach` / `status` / `list-adapters`. Mounts a portable brain into every detected AI client in one shot. Supported clients: Claude Code, Cursor, Continue, Zed. `mount` fan-outs to all detected adapters; `detach` round-trips cleanly and preserves the user's other MCP/context-server entries. Marker SSoT is `~/.claude/keisei-attached.toml` (schema v2 — list of attachments; v1 auto-migrated). |
 
 ## Primitives (shell)
diff --git a/_primitives/MANIFEST.toml b/_primitives/MANIFEST.toml
index a38c21b..0666e96 100644
--- a/_primitives/MANIFEST.toml
+++ b/_primitives/MANIFEST.toml
@@ -181,8 +181,8 @@ desc = "Post-refactor graph-integrity gate — wikilinks + handoffs + block refs
 [primitive.kei-store]
 kind = "rust"
 crate = "kei-store"
-deps = ["git2 (vendored libgit2)"]
-desc = "Memory-repo backend abstraction — GitHub / Forgejo / Gitea / Filesystem / S3 (S3 = MVP stub)"
+deps = ["git2 (vendored libgit2)", "aws-sdk-s3 + tokio + rustls (optional, behind `s3` feature)"]
+desc = "Memory-repo backend abstraction — GitHub / Forgejo / Gitea / Filesystem / S3 (real S3/R2/MinIO via aws-sdk-s3 when built with `--features s3`; local-manifest stub otherwise)"
 
 # --- v0.14 LBM port (10) ---------------------------------------------------
 
diff --git a/_primitives/_rust/Cargo.lock b/_primitives/_rust/Cargo.lock
index e7b40f8..ce2b5d8 100644
--- a/_primitives/_rust/Cargo.lock
+++ b/_primitives/_rust/Cargo.lock
@@ -109,12 +109,442 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "atomic-waker"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1505bd5d3d116872e7271a6d4e16d81d0c8570876c8de68093a09ac269d8aac0"
+
 [[package]]
 name = "autocfg"
 version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"
 
+[[package]]
+name = "aws-config"
+version = "1.8.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "50f156acdd2cf55f5aa53ee416c4ac851cf1222694506c0b1f78c85695e9ca9d"
+dependencies = [
+ "aws-credential-types",
+ "aws-runtime",
+ "aws-sdk-sts",
+ "aws-smithy-async",
+ "aws-smithy-http 0.63.6",
+ "aws-smithy-json 0.62.5",
+ "aws-smithy-runtime",
+ "aws-smithy-runtime-api",
+ "aws-smithy-types",
+ "aws-types",
+ "bytes",
+ "fastrand",
+ "http 1.4.0",
+ "time",
+ "tokio",
+ "tracing",
+ "url",
+]
+
+[[package]]
+name = "aws-credential-types"
+version = "1.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f20799b373a1be121fe3005fba0c2090af9411573878f224df44b42727fcaf7"
+dependencies = [
+ "aws-smithy-async",
+ "aws-smithy-runtime-api",
+ "aws-smithy-types",
+ "zeroize",
+]
+
+[[package]]
+name = "aws-lc-rs"
+version = "1.16.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ec6fb3fe69024a75fa7e1bfb48aa6cf59706a101658ea01bfd33b2b248a038f"
+dependencies = [
+ "aws-lc-sys",
+ "zeroize",
+]
+
+[[package]]
+name = "aws-lc-sys"
+version = "0.40.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f50037ee5e1e41e7b8f9d161680a725bd1626cb6f8c7e901f91f942850852fe7"
+dependencies = [
+ "cc",
+ "cmake",
+ "dunce",
+ "fs_extra",
+]
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5dcd93c82209ac7413532388067dce79be5a8780c1786e5fae3df22e4dee2864"
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+ "aws-credential-types",
+ "aws-sigv4",
+ "aws-smithy-async",
+ "aws-smithy-eventstream",
+ "aws-smithy-http 0.63.6",
+ "aws-smithy-runtime",
+ "aws-smithy-runtime-api",
+ "aws-smithy-types",
+ "aws-types",
+ "bytes",
+ "bytes-utils",
+ "fastrand",
+ "http 0.2.12",
+ "http 1.4.0",
+ "http-body 0.4.6",
+ "http-body 1.0.1",
+ "percent-encoding",
+ "pin-project-lite",
+ "tracing",
+ "uuid",
+]
+
+[[package]]
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+version = "1.119.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d65fddc3844f902dfe1864acb8494db5f9342015ee3ab7890270d36fbd2e01c"
+dependencies = [
+ "aws-credential-types",
+ "aws-runtime",
+ "aws-sigv4",
+ "aws-smithy-async",
+ "aws-smithy-checksums",
+ "aws-smithy-eventstream",
+ "aws-smithy-http 0.62.6",
+ "aws-smithy-json 0.61.9",
+ "aws-smithy-runtime",
+ "aws-smithy-runtime-api",
+ "aws-smithy-types",
+ "aws-smithy-xml",
+ "aws-types",
+ "bytes",
+ "fastrand",
+ "hex",
+ "hmac 0.12.1",
+ "http 0.2.12",
+ "http 1.4.0",
+ "http-body 0.4.6",
+ "lru",
+ "percent-encoding",
+ "regex-lite",
+ "sha2 0.10.9",
+ "tracing",
+ "url",
+]
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2249b81a2e73a8027c41c378463a81ec39b8510f184f2caab87de912af0f49b"
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+ "aws-credential-types",
+ "aws-runtime",
+ "aws-smithy-async",
+ "aws-smithy-http 0.63.6",
+ "aws-smithy-json 0.62.5",
+ "aws-smithy-observability",
+ "aws-smithy-query",
+ "aws-smithy-runtime",
+ "aws-smithy-runtime-api",
+ "aws-smithy-types",
+ "aws-smithy-xml",
+ "aws-types",
+ "fastrand",
+ "http 0.2.12",
+ "http 1.4.0",
+ "regex-lite",
+ "tracing",
+]
+
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+ "aws-smithy-eventstream",
+ "aws-smithy-http 0.63.6",
+ "aws-smithy-runtime-api",
+ "aws-smithy-types",
+ "bytes",
+ "form_urlencoded",
+ "hex",
+ "hmac 0.13.0",
+ "http 0.2.12",
+ "http 1.4.0",
+ "percent-encoding",
+ "sha2 0.11.0",
+ "time",
+ "tracing",
+]
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+dependencies = [
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+ "aws-smithy-types",
+ "bytes",
+ "crc-fast",
+ "hex",
+ "http 0.2.12",
+ "http-body 0.4.6",
+ "md-5",
+ "pin-project-lite",
+ "sha1",
+ "sha2 0.10.9",
+ "tracing",
+]
+
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+ "aws-smithy-types",
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+ "crc32fast",
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+dependencies = [
+ "aws-smithy-eventstream",
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+ "aws-smithy-types",
+ "bytes",
+ "bytes-utils",
+ "futures-core",
+ "futures-util",
+ "http 0.2.12",
+ "http 1.4.0",
+ "http-body 0.4.6",
+ "percent-encoding",
+ "pin-project-lite",
+ "pin-utils",
+ "tracing",
+]
+
+[[package]]
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+version = "0.63.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ba1ab2dc1c2c3749ead27180d333c42f11be8b0e934058fb4b2258ee8dbe5231"
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+ "http 1.4.0",
+ "http-body 1.0.1",
+ "http-body-util",
+ "percent-encoding",
+ "pin-project-lite",
+ "pin-utils",
+ "tracing",
+]
+
+[[package]]
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+version = "1.1.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a2f165a7feee6f263028b899d0a181987f4fa7179a6411a32a439fba7c5f769"
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+ "aws-smithy-runtime-api",
+ "aws-smithy-types",
+ "h2 0.3.27",
+ "h2 0.4.13",
+ "http 0.2.12",
+ "http 1.4.0",
+ "http-body 0.4.6",
+ "hyper 0.14.32",
+ "hyper 1.9.0",
+ "hyper-rustls 0.24.2",
+ "hyper-rustls 0.27.9",
+ "hyper-util",
+ "pin-project-lite",
+ "rustls 0.21.12",
+ "rustls 0.23.38",
+ "rustls-native-certs",
+ "rustls-pki-types",
+ "tokio",
+ "tokio-rustls 0.26.4",
+ "tower",
+ "tracing",
+]
+
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+ "aws-smithy-types",
+ "bytes",
+ "fastrand",
+ "http 0.2.12",
+ "http 1.4.0",
+ "http-body 0.4.6",
+ "http-body 1.0.1",
+ "http-body-util",
+ "pin-project-lite",
+ "pin-utils",
+ "tokio",
+ "tracing",
+]
+
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+ "aws-smithy-runtime-api-macros",
+ "aws-smithy-types",
+ "bytes",
+ "http 0.2.12",
+ "http 1.4.0",
+ "pin-project-lite",
+ "tokio",
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+ "syn",
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+ "bytes-utils",
+ "futures-core",
+ "http 0.2.12",
+ "http 1.4.0",
+ "http-body 0.4.6",
+ "http-body 1.0.1",
+ "http-body-util",
+ "itoa",
+ "num-integer",
+ "pin-project-lite",
+ "pin-utils",
+ "ryu",
+ "serde",
+ "time",
+ "tokio",
+ "tokio-util",
+]
+
+[[package]]
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+version = "0.60.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ce02add1aa3677d022f8adf81dcbe3046a95f17a1b1e8979c145cd21d3d22b3"
+dependencies = [
+ "xmlparser",
+]
+
+[[package]]
+name = "aws-types"
+version = "1.3.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f4bbcaa9304ea40902d3d5f42a0428d1bd895a2b0f6999436fb279ffddc58ac"
+dependencies = [
+ "aws-credential-types",
+ "aws-smithy-async",
+ "aws-smithy-runtime-api",
+ "aws-smithy-types",
+ "rustc_version",
+ "tracing",
+]
+
 [[package]]
 name = "base64"
 version = "0.21.7"
@@ -127,6 +557,16 @@ version = "0.22.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
 
+[[package]]
+name = "base64-simd"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "339abbe78e73178762e23bea9dfd08e697eb3f3301cd4be981c0f78ba5859195"
+dependencies = [
+ "outref",
+ "vsimd",
+]
+
 [[package]]
 name = "base64ct"
 version = "1.8.3"
@@ -151,6 +591,15 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "block-buffer"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdd35008169921d80bc60d3d0ab416eecb028c4cd653352907921d95084790be"
+dependencies = [
+ "hybrid-array",
+]
+
 [[package]]
 name = "bumpalo"
 version = "3.20.2"
@@ -181,6 +630,16 @@ version = "1.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e748733b7cbc798e1434b6ac524f0c1ff2ab456fe201501e6497c8417a4fc33"
 
+[[package]]
+name = "bytes-utils"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7dafe3a8757b027e2be6e4e5601ed563c55989fcf1546e933c66c8eb3a058d35"
+dependencies = [
+ "bytes",
+ "either",
+]
+
 [[package]]
 name = "cc"
 version = "1.2.60"
@@ -251,6 +710,21 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c8d4a3bb8b1e0c1050499d1815f5ab16d04f0959b233085fb31653fbfc9d98f9"
 
+[[package]]
+name = "cmake"
+version = "0.1.58"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c0f78a02292a74a88ac736019ab962ece0bc380e3f977bf72e376c5d78ff0678"
+dependencies = [
+ "cc",
+]
+
+[[package]]
+name = "cmov"
+version = "0.5.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f88a43d011fc4a6876cb7344703e297c71dda42494fee094d5f7c76bf13f746"
+
 [[package]]
 name = "colorchoice"
 version = "1.0.5"
@@ -272,6 +746,22 @@ version = "0.9.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c2459377285ad874054d797f3ccebf984978aa39129f6eafde5cdc8315b612f8"
 
+[[package]]
+name = "const-oid"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a6ef517f0926dd24a1582492c791b6a4818a4d94e789a334894aa15b0d12f55c"
+
+[[package]]
+name = "core-foundation"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2a6cd9ae233e7f62ba4e9353e81a88df7fc8a5987b8d445b4d90c879bd156f6"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
 [[package]]
 name = "core-foundation-sys"
 version = "0.8.7"
@@ -287,6 +777,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "cpufeatures"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b2a41393f66f16b0823bb79094d54ac5fbd34ab292ddafb9a0456ac9f87d201"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "crc"
 version = "3.4.0"
@@ -302,6 +801,19 @@ version = "2.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "19d374276b40fb8bbdee95aef7c7fa6b5316ec764510eb64b8dd0e2ed0d7e7f5"
 
+[[package]]
+name = "crc-fast"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ddc2d09feefeee8bd78101665bd8645637828fa9317f9f292496dbbd8c65ff3"
+dependencies = [
+ "crc",
+ "digest 0.10.7",
+ "rand 0.9.4",
+ "regex",
+ "rustversion",
+]
+
 [[package]]
 name = "crc32fast"
 version = "1.5.0"
@@ -336,29 +848,68 @@ dependencies = [
  "typenum",
 ]
 
+[[package]]
+name = "crypto-common"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77727bb15fa921304124b128af125e7e3b968275d1b108b379190264f4423710"
+dependencies = [
+ "hybrid-array",
+]
+
+[[package]]
+name = "ctutils"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d5515a3834141de9eafb9717ad39eea8247b5674e6066c404e8c4b365d2a29e"
+dependencies = [
+ "cmov",
+]
+
 [[package]]
 name = "der"
 version = "0.7.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e7c1832837b905bbfb5101e07cc24c8deddf52f93225eee6ead5f4d63d53ddcb"
 dependencies = [
- "const-oid",
+ "const-oid 0.9.6",
  "pem-rfc7468",
  "zeroize",
 ]
 
+[[package]]
+name = "deranged"
+version = "0.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7cd812cc2bc1d69d4764bd80df88b4317eaef9e773c75226407d9bc0876b211c"
+dependencies = [
+ "powerfmt",
+]
+
 [[package]]
 name = "digest"
 version = "0.10.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9ed9a281f7bc9b7576e61468ba615a66a5c8cfdff42420a70aa82701a3b1e292"
 dependencies = [
- "block-buffer",
- "const-oid",
- "crypto-common",
+ "block-buffer 0.10.4",
+ "const-oid 0.9.6",
+ "crypto-common 0.1.7",
  "subtle",
 ]
 
+[[package]]
+name = "digest"
+version = "0.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4850db49bf08e663084f7fb5c87d202ef91a3907271aff24a94eb97ff039153c"
+dependencies = [
+ "block-buffer 0.12.0",
+ "const-oid 0.10.2",
+ "crypto-common 0.2.1",
+ "ctutils",
+]
+
 [[package]]
 name = "displaydoc"
 version = "0.2.5"
@@ -376,6 +927,12 @@ version = "0.15.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1aaf95b3e5c8f23aa320147307562d361db0ae0d51242340f558153b4eb2439b"
 
+[[package]]
+name = "dunce"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "92773504d58c093f6de2459af4af33faa518c13451eb8f2b5698ed3d36e7c813"
+
 [[package]]
 name = "either"
 version = "1.15.0"
@@ -488,6 +1045,12 @@ dependencies = [
  "spin",
 ]
 
+[[package]]
+name = "fnv"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
+
 [[package]]
 name = "foldhash"
 version = "0.1.5"
@@ -503,6 +1066,12 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "fs_extra"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42703706b716c37f96a77aea830392ad231f44c9e9a67872fa5548707e11b11c"
+
 [[package]]
 name = "futures-channel"
 version = "0.3.32"
@@ -633,6 +1202,44 @@ dependencies = [
  "url",
 ]
 
+[[package]]
+name = "h2"
+version = "0.3.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0beca50380b1fc32983fc1cb4587bfa4bb9e78fc259aad4a0032d2080309222d"
+dependencies = [
+ "bytes",
+ "fnv",
+ "futures-core",
+ "futures-sink",
+ "futures-util",
+ "http 0.2.12",
+ "indexmap",
+ "slab",
+ "tokio",
+ "tokio-util",
+ "tracing",
+]
+
+[[package]]
+name = "h2"
+version = "0.4.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f44da3a8150a6703ed5d34e164b875fd14c2cdab9af1252a9a1020bde2bdc54"
+dependencies = [
+ "atomic-waker",
+ "bytes",
+ "fnv",
+ "futures-core",
+ "futures-sink",
+ "http 1.4.0",
+ "indexmap",
+ "slab",
+ "tokio",
+ "tokio-util",
+ "tracing",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.14.5"
@@ -649,6 +1256,8 @@ version = "0.15.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9229cfe53dfd69f0609a49f65461bd93001ea1ef889cd5529dd176593f5338a1"
 dependencies = [
+ "allocator-api2",
+ "equivalent",
  "foldhash",
 ]
 
@@ -685,7 +1294,7 @@ version = "0.12.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7b5f8eb2ad728638ea2c7d47a21db23b7b58a72ed6a38256b8a1849f15fbbdf7"
 dependencies = [
- "hmac",
+ "hmac 0.12.1",
 ]
 
 [[package]]
@@ -694,7 +1303,16 @@ version = "0.12.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6c49c37c09c17a53d937dfbb742eb3a961d65a994e6bcdcf37e7399d0cc8ab5e"
 dependencies = [
- "digest",
+ "digest 0.10.7",
+]
+
+[[package]]
+name = "hmac"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6303bc9732ae41b04cb554b844a762b4115a61bfaa81e3e83050991eeb56863f"
+dependencies = [
+ "digest 0.11.2",
 ]
 
 [[package]]
@@ -706,6 +1324,181 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "http"
+version = "0.2.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "601cbb57e577e2f5ef5be8e7b83f0f63994f25aa94d673e54a92d5c516d101f1"
+dependencies = [
+ "bytes",
+ "fnv",
+ "itoa",
+]
+
+[[package]]
+name = "http"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e3ba2a386d7f85a81f119ad7498ebe444d2e22c2af0b86b069416ace48b3311a"
+dependencies = [
+ "bytes",
+ "itoa",
+]
+
+[[package]]
+name = "http-body"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7ceab25649e9960c0311ea418d17bee82c0dcec1bd053b5f9a66e265a693bed2"
+dependencies = [
+ "bytes",
+ "http 0.2.12",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "http-body"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1efedce1fb8e6913f23e0c92de8e62cd5b772a67e7b3946df930a62566c93184"
+dependencies = [
+ "bytes",
+ "http 1.4.0",
+]
+
+[[package]]
+name = "http-body-util"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b021d93e26becf5dc7e1b75b1bed1fd93124b374ceb73f43d4d4eafec896a64a"
+dependencies = [
+ "bytes",
+ "futures-core",
+ "http 1.4.0",
+ "http-body 1.0.1",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "httparse"
+version = "1.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6dbf3de79e51f3d586ab4cb9d5c3e2c14aa28ed23d180cf89b4df0454a69cc87"
+
+[[package]]
+name = "httpdate"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df3b46402a9d5adb4c86a0cf463f42e19994e3ee891101b1841f30a545cb49a9"
+
+[[package]]
+name = "hybrid-array"
+version = "0.4.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3944cf8cf766b40e2a1a333ee5e9b563f854d5fa49d6a8ca2764e97c6eddb214"
+dependencies = [
+ "typenum",
+]
+
+[[package]]
+name = "hyper"
+version = "0.14.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41dfc780fdec9373c01bae43289ea34c972e40ee3c9f6b3c8801a35f35586ce7"
+dependencies = [
+ "bytes",
+ "futures-channel",
+ "futures-core",
+ "futures-util",
+ "h2 0.3.27",
+ "http 0.2.12",
+ "http-body 0.4.6",
+ "httparse",
+ "httpdate",
+ "itoa",
+ "pin-project-lite",
+ "socket2 0.5.10",
+ "tokio",
+ "tower-service",
+ "tracing",
+ "want",
+]
+
+[[package]]
+name = "hyper"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6299f016b246a94207e63da54dbe807655bf9e00044f73ded42c3ac5305fbcca"
+dependencies = [
+ "atomic-waker",
+ "bytes",
+ "futures-channel",
+ "futures-core",
+ "h2 0.4.13",
+ "http 1.4.0",
+ "http-body 1.0.1",
+ "httparse",
+ "itoa",
+ "pin-project-lite",
+ "smallvec",
+ "tokio",
+ "want",
+]
+
+[[package]]
+name = "hyper-rustls"
+version = "0.24.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec3efd23720e2049821a693cbc7e65ea87c72f1c58ff2f9522ff332b1491e590"
+dependencies = [
+ "futures-util",
+ "http 0.2.12",
+ "hyper 0.14.32",
+ "log",
+ "rustls 0.21.12",
+ "tokio",
+ "tokio-rustls 0.24.1",
+]
+
+[[package]]
+name = "hyper-rustls"
+version = "0.27.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "33ca68d021ef39cf6463ab54c1d0f5daf03377b70561305bb89a8f83aab66e0f"
+dependencies = [
+ "http 1.4.0",
+ "hyper 1.9.0",
+ "hyper-util",
+ "rustls 0.23.38",
+ "rustls-native-certs",
+ "tokio",
+ "tokio-rustls 0.26.4",
+ "tower-service",
+]
+
+[[package]]
+name = "hyper-util"
+version = "0.1.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96547c2556ec9d12fb1578c4eaf448b04993e7fb79cbaad930a656880a6bdfa0"
+dependencies = [
+ "base64 0.22.1",
+ "bytes",
+ "futures-channel",
+ "futures-util",
+ "http 1.4.0",
+ "http-body 1.0.1",
+ "hyper 1.9.0",
+ "ipnet",
+ "libc",
+ "percent-encoding",
+ "pin-project-lite",
+ "socket2 0.6.3",
+ "tokio",
+ "tower-service",
+ "tracing",
+]
+
 [[package]]
 name = "iana-time-zone"
 version = "0.1.65"
@@ -864,6 +1657,12 @@ dependencies = [
  "serde_core",
 ]
 
+[[package]]
+name = "ipnet"
+version = "2.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d98f6fed1fde3f8c21bc40a1abb88dd75e67924f9cffc3ef95607bad8017f8e2"
+
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.2"
@@ -906,7 +1705,7 @@ dependencies = [
  "rusqlite",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "tempfile",
 ]
 
@@ -918,12 +1717,12 @@ dependencies = [
  "base64 0.22.1",
  "chrono",
  "clap",
- "hmac",
- "rand",
+ "hmac 0.12.1",
+ "rand 0.8.6",
  "rusqlite",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "tempfile",
 ]
 
@@ -975,7 +1774,7 @@ dependencies = [
  "rusqlite",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "tempfile",
 ]
 
@@ -1050,7 +1849,7 @@ dependencies = [
  "anyhow",
  "chrono",
  "clap",
- "sha2",
+ "sha2 0.10.9",
  "sqlx",
  "tempfile",
  "tokio",
@@ -1123,11 +1922,15 @@ name = "kei-store"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "aws-config",
+ "aws-credential-types",
+ "aws-sdk-s3",
  "clap",
  "git2",
  "serde",
  "serde_json",
  "tempfile",
+ "tokio",
  "toml",
 ]
 
@@ -1259,6 +2062,15 @@ version = "0.4.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5e5032e24019045c762d3c0f28f5b6b8bbf38563a65908389bf7978758920897"
 
+[[package]]
+name = "lru"
+version = "0.12.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "234cf4f4a04dc1f57e24b96cc0cd600cf2af460d4161ac5ecdd0af8e1f3b2a38"
+dependencies = [
+ "hashbrown 0.15.5",
+]
+
 [[package]]
 name = "md-5"
 version = "0.10.6"
@@ -1266,7 +2078,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d89e7ee0cfbedfc4da3340218492196241d89eefb6dab27de5df917a6d2e78cf"
 dependencies = [
  "cfg-if",
- "digest",
+ "digest 0.10.7",
 ]
 
 [[package]]
@@ -1308,7 +2120,7 @@ version = "0.1.0"
 dependencies = [
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "tempfile",
 ]
 
@@ -1343,11 +2155,17 @@ dependencies = [
  "num-integer",
  "num-iter",
  "num-traits",
- "rand",
+ "rand 0.8.6",
  "smallvec",
  "zeroize",
 ]
 
+[[package]]
+name = "num-conv"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6673768db2d862beb9b39a78fdcb1a69439615d5794a1be50caa9bc92c81967"
+
 [[package]]
 name = "num-integer"
 version = "0.1.46"
@@ -1390,6 +2208,18 @@ version = "1.70.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "384b8ab6d37215f3c5301a95a4accb5d64aa607f1fcb26a11b5303878451b4fe"
 
+[[package]]
+name = "openssl-probe"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c87def4c32ab89d880effc9e097653c8da5d6ef28e6b539d313baaacfbafcbe"
+
+[[package]]
+name = "outref"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a80800c0488c3a21695ea981a54918fbb37abf04f4d0720c453632255e2ff0e"
+
 [[package]]
 name = "parking"
 version = "2.2.1"
@@ -1446,6 +2276,12 @@ version = "0.2.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a89322df9ebe1c1578d689c92318e070967d1042b512afbe49518723f4e6d5cd"
 
+[[package]]
+name = "pin-utils"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
+
 [[package]]
 name = "pkcs1"
 version = "0.7.5"
@@ -1501,6 +2337,12 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "powerfmt"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "439ee305def115ba05938db6eb1644ff94165c5ab5e9420d1c1bcedbba909391"
+
 [[package]]
 name = "ppv-lite86"
 version = "0.2.21"
@@ -1563,8 +2405,18 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5ca0ecfa931c29007047d1bc58e623ab12e5590e8c7cc53200d5202b69266d8a"
 dependencies = [
  "libc",
- "rand_chacha",
- "rand_core",
+ "rand_chacha 0.3.1",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44c5af06bb1b7d3216d91932aed5265164bf384dc89cd6ba05cf59a35f5f76ea"
+dependencies = [
+ "rand_chacha 0.9.0",
+ "rand_core 0.9.5",
 ]
 
 [[package]]
@@ -1574,7 +2426,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
 dependencies = [
  "ppv-lite86",
- "rand_core",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.9.5",
 ]
 
 [[package]]
@@ -1586,6 +2448,15 @@ dependencies = [
  "getrandom 0.2.17",
 ]
 
+[[package]]
+name = "rand_core"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76afc826de14238e6e8c374ddcc1fa19e374fd8dd986b0d2af0d02377261d83c"
+dependencies = [
+ "getrandom 0.3.4",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.5.18"
@@ -1627,6 +2498,12 @@ dependencies = [
  "regex-syntax",
 ]
 
+[[package]]
+name = "regex-lite"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cab834c73d247e67f4fae452806d17d3c7501756d98c8808d7c9c7aa7d18f973"
+
 [[package]]
 name = "regex-syntax"
 version = "0.8.10"
@@ -1653,14 +2530,14 @@ version = "0.9.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b8573f03f5883dcaebdfcf4725caa1ecb9c15b2ef50c43a07b816e06799bb12d"
 dependencies = [
- "const-oid",
- "digest",
+ "const-oid 0.9.6",
+ "digest 0.10.7",
  "num-bigint-dig",
  "num-integer",
  "num-traits",
  "pkcs1",
  "pkcs8",
- "rand_core",
+ "rand_core 0.6.4",
  "signature",
  "spki",
  "subtle",
@@ -1681,6 +2558,15 @@ dependencies = [
  "smallvec",
 ]
 
+[[package]]
+name = "rustc_version"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfcb3a22ef46e85b45de6ee7e79d063319ebb6594faafcf1c225ea92ab6e9b92"
+dependencies = [
+ "semver",
+]
+
 [[package]]
 name = "rustix"
 version = "1.1.4"
@@ -1700,11 +2586,38 @@ version = "0.21.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f56a14d1f48b391359b22f731fd4bd7e43c97f3c50eee276f3aa09c94784d3e"
 dependencies = [
+ "log",
  "ring",
- "rustls-webpki",
+ "rustls-webpki 0.101.7",
  "sct",
 ]
 
+[[package]]
+name = "rustls"
+version = "0.23.38"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69f9466fb2c14ea04357e91413efb882e2a6d4a406e625449bc0a5d360d53a21"
+dependencies = [
+ "aws-lc-rs",
+ "once_cell",
+ "rustls-pki-types",
+ "rustls-webpki 0.103.13",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "rustls-native-certs"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "612460d5f7bea540c490b2b6395d8e34a953e52b491accd6c86c8164c5932a63"
+dependencies = [
+ "openssl-probe",
+ "rustls-pki-types",
+ "schannel",
+ "security-framework",
+]
+
 [[package]]
 name = "rustls-pemfile"
 version = "1.0.4"
@@ -1714,6 +2627,15 @@ dependencies = [
  "base64 0.21.7",
 ]
 
+[[package]]
+name = "rustls-pki-types"
+version = "1.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be040f8b0a225e40375822a563fa9524378b9d63112f53e19ffff34df5d33fdd"
+dependencies = [
+ "zeroize",
+]
+
 [[package]]
 name = "rustls-webpki"
 version = "0.101.7"
@@ -1724,6 +2646,18 @@ dependencies = [
  "untrusted",
 ]
 
+[[package]]
+name = "rustls-webpki"
+version = "0.103.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "61c429a8649f110dddef65e2a5ad240f747e85f7758a6bccc7e5777bd33f756e"
+dependencies = [
+ "aws-lc-rs",
+ "ring",
+ "rustls-pki-types",
+ "untrusted",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.22"
@@ -1745,6 +2679,15 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "schannel"
+version = "0.1.29"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "91c1b7e4904c873ef0710c1f407dde2e6287de2bebc1bbbf7d430bb7cbffd939"
+dependencies = [
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "scopeguard"
 version = "1.2.0"
@@ -1761,6 +2704,29 @@ dependencies = [
  "untrusted",
 ]
 
+[[package]]
+name = "security-framework"
+version = "3.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b7f4bc775c73d9a02cde8bf7b2ec4c9d12743edf609006c7facc23998404cd1d"
+dependencies = [
+ "bitflags",
+ "core-foundation",
+ "core-foundation-sys",
+ "libc",
+ "security-framework-sys",
+]
+
+[[package]]
+name = "security-framework-sys"
+version = "2.17.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ce2691df843ecc5d231c0b14ece2acc3efb62c0a398c7e1d875f3983ce020e3"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
 [[package]]
 name = "semver"
 version = "1.0.28"
@@ -1851,8 +2817,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e3bf829a2d51ab4a5ddf1352d8470c140cadc8301b2ae1789db023f01cedd6ba"
 dependencies = [
  "cfg-if",
- "cpufeatures",
- "digest",
+ "cpufeatures 0.2.17",
+ "digest 0.10.7",
 ]
 
 [[package]]
@@ -1862,8 +2828,19 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a7507d819769d01a365ab707794a4084392c824f54a7a6a7862f8c3d0892b283"
 dependencies = [
  "cfg-if",
- "cpufeatures",
- "digest",
+ "cpufeatures 0.2.17",
+ "digest 0.10.7",
+]
+
+[[package]]
+name = "sha2"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "446ba717509524cb3f22f17ecc096f10f4822d76ab5c0b9822c5f9c284e825f4"
+dependencies = [
+ "cfg-if",
+ "cpufeatures 0.3.0",
+ "digest 0.11.2",
 ]
 
 [[package]]
@@ -1878,8 +2855,8 @@ version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77549399552de45a898a580c1b41d445bf730df867cc44e6c0233bbc4b8329de"
 dependencies = [
- "digest",
- "rand_core",
+ "digest 0.10.7",
+ "rand_core 0.6.4",
 ]
 
 [[package]]
@@ -1909,6 +2886,16 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "socket2"
+version = "0.5.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e22376abed350d73dd1cd119b57ffccad95b4e585a7cda43e286245ce23c0678"
+dependencies = [
+ "libc",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "socket2"
 version = "0.6.3"
@@ -1988,11 +2975,11 @@ dependencies = [
  "once_cell",
  "paste",
  "percent-encoding",
- "rustls",
+ "rustls 0.21.12",
  "rustls-pemfile",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "smallvec",
  "sqlformat",
  "thiserror 1.0.69",
@@ -2031,7 +3018,7 @@ dependencies = [
  "quote",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "sqlx-core",
  "sqlx-mysql",
  "sqlx-postgres",
@@ -2054,7 +3041,7 @@ dependencies = [
  "byteorder",
  "bytes",
  "crc",
- "digest",
+ "digest 0.10.7",
  "dotenvy",
  "either",
  "futures-channel",
@@ -2064,18 +3051,18 @@ dependencies = [
  "generic-array",
  "hex",
  "hkdf",
- "hmac",
+ "hmac 0.12.1",
  "itoa",
  "log",
  "md-5",
  "memchr",
  "once_cell",
  "percent-encoding",
- "rand",
+ "rand 0.8.6",
  "rsa",
  "serde",
  "sha1",
- "sha2",
+ "sha2 0.10.9",
  "smallvec",
  "sqlx-core",
  "stringprep",
@@ -2103,17 +3090,17 @@ dependencies = [
  "futures-util",
  "hex",
  "hkdf",
- "hmac",
+ "hmac 0.12.1",
  "home",
  "itoa",
  "log",
  "md-5",
  "memchr",
  "once_cell",
- "rand",
+ "rand 0.8.6",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "smallvec",
  "sqlx-core",
  "stringprep",
@@ -2259,6 +3246,36 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "time"
+version = "0.3.47"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "743bd48c283afc0388f9b8827b976905fb217ad9e647fae3a379a9283c4def2c"
+dependencies = [
+ "deranged",
+ "num-conv",
+ "powerfmt",
+ "serde_core",
+ "time-core",
+ "time-macros",
+]
+
+[[package]]
+name = "time-core"
+version = "0.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7694e1cfe791f8d31026952abf09c69ca6f6fa4e1a1229e18988f06a04a12dca"
+
+[[package]]
+name = "time-macros"
+version = "0.2.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e70e4c5a0e0a8a4823ad65dfe1a6930e4f4d756dcd9dd7939022b5e8c501215"
+dependencies = [
+ "num-conv",
+ "time-core",
+]
+
 [[package]]
 name = "tinystr"
 version = "0.8.3"
@@ -2303,7 +3320,7 @@ dependencies = [
  "libc",
  "mio",
  "pin-project-lite",
- "socket2",
+ "socket2 0.6.3",
  "tokio-macros",
  "windows-sys 0.61.2",
 ]
@@ -2319,6 +3336,26 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "tokio-rustls"
+version = "0.24.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c28327cf380ac148141087fbfb9de9d7bd4e84ab5d2c28fbc911d753de8a7081"
+dependencies = [
+ "rustls 0.21.12",
+ "tokio",
+]
+
+[[package]]
+name = "tokio-rustls"
+version = "0.26.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1729aa945f29d91ba541258c8df89027d5792d85a8841fb65e8bf0f4ede4ef61"
+dependencies = [
+ "rustls 0.23.38",
+ "tokio",
+]
+
 [[package]]
 name = "tokio-stream"
 version = "0.1.18"
@@ -2330,6 +3367,19 @@ dependencies = [
  "tokio",
 ]
 
+[[package]]
+name = "tokio-util"
+version = "0.7.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ae9cec805b01e8fc3fd2fe289f89149a9b66dd16786abd8b19cfa7b48cb0098"
+dependencies = [
+ "bytes",
+ "futures-core",
+ "futures-sink",
+ "pin-project-lite",
+ "tokio",
+]
+
 [[package]]
 name = "toml"
 version = "0.8.23"
@@ -2371,6 +3421,28 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5d99f8c9a7727884afe522e9bd5edbfc91a3312b36a77b5fb8926e4c31a41801"
 
+[[package]]
+name = "tower"
+version = "0.5.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ebe5ef63511595f1344e2d5cfa636d973292adc0eec1f0ad45fae9f0851ab1d4"
+dependencies = [
+ "tower-layer",
+ "tower-service",
+]
+
+[[package]]
+name = "tower-layer"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "121c2a6cda46980bb0fcd1647ffaf6cd3fc79a013de288782836f6df9c48780e"
+
+[[package]]
+name = "tower-service"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8df9b6e13f2d32c91b9bd719c00d1958837bc7dec474d94952798cc8e69eeec3"
+
 [[package]]
 name = "tracing"
 version = "0.1.44"
@@ -2403,6 +3475,12 @@ dependencies = [
  "once_cell",
 ]
 
+[[package]]
+name = "try-lock"
+version = "0.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e421abadd41a4225275504ea4d6566923418b7f05506fbc9c0fe86ba7396114b"
+
 [[package]]
 name = "typenum"
 version = "1.20.0"
@@ -2472,6 +3550,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "urlencoding"
+version = "2.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "daf8dba3b7eb870caf1ddeed7bc9d2a049f3cfdfae7cb521b087cc33ae4c49da"
+
 [[package]]
 name = "utf8_iter"
 version = "1.0.4"
@@ -2515,6 +3599,12 @@ dependencies = [
  "tempfile",
 ]
 
+[[package]]
+name = "vsimd"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c3082ca00d5a5ef149bb8b555a72ae84c9c59f7250f013ac822ac2e49b19c64"
+
 [[package]]
 name = "walkdir"
 version = "2.5.0"
@@ -2525,6 +3615,15 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "want"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bfa7760aed19e106de2c7c0b581b509f2f25d3dacaf737cb82ac61bc6d760b0e"
+dependencies = [
+ "try-lock",
+]
+
 [[package]]
 name = "wasi"
 version = "0.11.1+wasi-snapshot-preview1"
@@ -2975,6 +4074,12 @@ version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1ffae5123b2d3fc086436f8834ae3ab053a283cfac8fe0a0b8eaae044768a4c4"
 
+[[package]]
+name = "xmlparser"
+version = "0.13.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "66fee0b777b0f5ac1c69bb06d361268faafa61cd4682ae064a171c16c433e9e4"
+
 [[package]]
 name = "yoke"
 version = "0.8.2"
diff --git a/_primitives/_rust/kei-store/Cargo.toml b/_primitives/_rust/kei-store/Cargo.toml
index d28f914..a32b2e4 100644
--- a/_primitives/_rust/kei-store/Cargo.toml
+++ b/_primitives/_rust/kei-store/Cargo.toml
@@ -3,7 +3,7 @@ name = "kei-store"
 version = "0.1.0"
 edition.workspace = true
 rust-version.workspace = true
-description = "Memory-repo backend abstraction — GitHub/Forgejo/Gitea/Filesystem/S3 (v0.13.0)"
+description = "Memory-repo backend abstraction — GitHub/Forgejo/Gitea/Filesystem/S3 (v0.21.0)"
 
 [[bin]]
 name = "kei-store"
@@ -12,6 +12,13 @@ path = "src/main.rs"
 [lib]
 path = "src/lib.rs"
 
+[features]
+# Default: no cloud deps. S3 backend behaves as the v0.14 local-manifest stub
+# (gated by KEI_STORE_ALLOW_S3_STUB=1). Users who actually need real S3 / R2 /
+# MinIO push opt into the heavier AWS SDK stack by enabling this feature.
+default = []
+s3 = ["dep:aws-config", "dep:aws-sdk-s3", "dep:aws-credential-types", "dep:tokio"]
+
 [dependencies]
 clap = { workspace = true }
 serde = { workspace = true }
@@ -20,5 +27,11 @@ anyhow = "1"
 toml = "0.8"
 git2 = { version = "0.19", default-features = false }
 
+# v0.21 — optional cloud stack behind `s3` feature.
+aws-config = { version = "1", default-features = false, features = ["behavior-version-latest", "rustls", "rt-tokio"], optional = true }
+aws-sdk-s3 = { version = "1", default-features = false, features = ["behavior-version-latest", "rustls", "rt-tokio"], optional = true }
+aws-credential-types = { version = "1", optional = true }
+tokio = { version = "1", features = ["rt", "macros"], optional = true }
+
 [dev-dependencies]
 tempfile = "3"
diff --git a/_primitives/_rust/kei-store/src/factory.rs b/_primitives/_rust/kei-store/src/factory.rs
index 2f4f047..c369d75 100644
--- a/_primitives/_rust/kei-store/src/factory.rs
+++ b/_primitives/_rust/kei-store/src/factory.rs
@@ -1,9 +1,15 @@
 //! Factory — construct a `Box<dyn MemoryStore>` from a Config.
 //!
 //! v0.14.1: the S3 backend is gated behind `KEI_STORE_ALLOW_S3_STUB=1`
-//! because it does NOT push to S3 yet — it's a local-manifest stub.
-//! Previous behaviour silently stored data locally, confusing users who
-//! thought their traces were uploaded.
+//! because the default build has no real S3 push — it's a local-manifest
+//! stub. Previous behaviour silently stored data locally, confusing users
+//! who thought their traces were uploaded.
+//!
+//! v0.21.0: when the crate is built with `--features s3` AND
+//! `s3.bucket` is configured, the real `S3CloudStore` is used (no
+//! KEI_STORE_ALLOW_S3_STUB gate needed — data really is uploaded).
+//! The stub path remains available for users who don't want the AWS SDK
+//! in their binary: omit `s3.bucket` and set the stub opt-in env.
 
 use crate::config::{expand_tilde, Config};
 use crate::{filesystem::FilesystemStore, forgejo::ForgejoStore, gitea::GiteaStore,
@@ -29,12 +35,30 @@ pub fn build_store(cfg: &Config) -> Result<Box<dyn MemoryStore>> {
     }
 }
 
+#[cfg(feature = "s3")]
 fn build_s3(cfg: &Config) -> Result<Box<dyn MemoryStore>> {
+    // Cloud path: real S3 round-trips when bucket is configured.
+    if cfg.s3.bucket.is_some() {
+        return Ok(Box::new(
+            crate::s3_cloud::S3CloudStore::new(cfg.s3.clone())?,
+        ));
+    }
+    // Fallback: local stub (legacy behaviour, requires opt-in).
+    build_s3_stub(cfg)
+}
+
+#[cfg(not(feature = "s3"))]
+fn build_s3(cfg: &Config) -> Result<Box<dyn MemoryStore>> {
+    build_s3_stub(cfg)
+}
+
+fn build_s3_stub(cfg: &Config) -> Result<Box<dyn MemoryStore>> {
     if std::env::var("KEI_STORE_ALLOW_S3_STUB").is_err() {
         bail!(
             "S3 backend is a local-only MVP stub (no upload to S3/R2/MinIO yet). \
              Set KEI_STORE_ALLOW_S3_STUB=1 to proceed; data will be stored in the \
-             configured cache_path only. Production S3 support is planned for v0.15."
+             configured cache_path only. For real S3 push, build with \
+             `--features s3` AND set s3.bucket in config."
         );
     }
     eprintln!(
diff --git a/_primitives/_rust/kei-store/src/lib.rs b/_primitives/_rust/kei-store/src/lib.rs
index 9f9ffa4..bd1cc35 100644
--- a/_primitives/_rust/kei-store/src/lib.rs
+++ b/_primitives/_rust/kei-store/src/lib.rs
@@ -3,7 +3,9 @@
 //! Trait `MemoryStore` + 5 implementations:
 //!   - `GitHubStore`, `ForgejoStore`, `GiteaStore` — git-over-SSH/HTTPS
 //!   - `FilesystemStore` — local `.git` only; never pushes
-//!   - `S3Store` — object-storage with manifest.json (MVP stub)
+//!   - `S3Store` — object-storage with manifest.json (MVP local stub)
+//!   - `S3CloudStore` — real S3 / R2 / MinIO via `aws-sdk-s3`
+//!     (behind `s3` feature; v0.21+)
 //!
 //! Config loaded from `~/.claude/agents/_primitives/store-config.toml`
 //! by default; overridable via `--config`.
@@ -18,6 +20,8 @@ pub mod forgejo;
 pub mod gitea;
 pub mod github;
 pub mod s3;
+#[cfg(feature = "s3")]
+pub mod s3_cloud;
 pub mod store_trait;
 
 pub use config::Config;
diff --git a/_primitives/_rust/kei-store/src/s3_cloud/client.rs b/_primitives/_rust/kei-store/src/s3_cloud/client.rs
new file mode 100644
index 0000000..982f8fc
--- /dev/null
+++ b/_primitives/_rust/kei-store/src/s3_cloud/client.rs
@@ -0,0 +1,81 @@
+//! aws-sdk-s3 client builder for the S3 cloud backend.
+//!
+//! Wraps `aws_config::defaults()` + optional endpoint override for
+//! R2 / MinIO / Wasabi / any S3-compat provider. Credential chain is the
+//! AWS default — env vars, `~/.aws/credentials`, IMDS — we do NOT invent
+//! a new credential format (RULE 0.8 secrets-single-source honoured).
+
+use crate::config::S3Cfg;
+use anyhow::Result;
+use aws_sdk_s3::Client;
+
+/// Resolve the effective endpoint URL:
+///   1. `KEI_STORE_S3_ENDPOINT` env var (runtime override for tests / R2)
+///   2. `cfg.endpoint` (TOML config)
+///   3. None → aws-sdk-s3 default (real AWS)
+pub fn effective_endpoint(cfg: &S3Cfg) -> Option<String> {
+    if let Ok(url) = std::env::var("KEI_STORE_S3_ENDPOINT") {
+        if !url.is_empty() {
+            return Some(url);
+        }
+    }
+    cfg.endpoint.clone()
+}
+
+/// Build the aws-sdk-s3 client with optional endpoint + region overrides.
+pub async fn build_client(cfg: &S3Cfg) -> Result<Client> {
+    let mut loader = aws_config::defaults(aws_config::BehaviorVersion::latest());
+    if let Some(region) = cfg.region.clone() {
+        loader = loader.region(aws_config::Region::new(region));
+    }
+    let shared = loader.load().await;
+    let mut s3_builder = aws_sdk_s3::config::Builder::from(&shared);
+    if let Some(endpoint) = effective_endpoint(cfg) {
+        // Path-style is the safest default for non-AWS endpoints (MinIO,
+        // some R2 configs). AWS itself also accepts path-style.
+        s3_builder = s3_builder.endpoint_url(endpoint).force_path_style(true);
+    }
+    Ok(Client::from_conf(s3_builder.build()))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn cfg_with_endpoint(endpoint: &str) -> S3Cfg {
+        S3Cfg {
+            endpoint: Some(endpoint.to_string()),
+            bucket: Some("test-bucket".to_string()),
+            region: Some("us-east-1".to_string()),
+            access_key_env: None,
+            secret_key_env: None,
+            cache_path: None,
+        }
+    }
+
+    #[test]
+    fn effective_endpoint_env_overrides_cfg() {
+        std::env::set_var("KEI_STORE_S3_ENDPOINT", "http://127.0.0.1:9000");
+        let cfg = cfg_with_endpoint("http://other:8080");
+        let got = effective_endpoint(&cfg);
+        std::env::remove_var("KEI_STORE_S3_ENDPOINT");
+        assert_eq!(got.as_deref(), Some("http://127.0.0.1:9000"));
+    }
+
+    #[test]
+    fn effective_endpoint_cfg_when_no_env() {
+        std::env::remove_var("KEI_STORE_S3_ENDPOINT");
+        let cfg = cfg_with_endpoint("http://127.0.0.1:9999");
+        assert_eq!(
+            effective_endpoint(&cfg).as_deref(),
+            Some("http://127.0.0.1:9999")
+        );
+    }
+
+    #[test]
+    fn effective_endpoint_none_when_no_env_no_cfg() {
+        std::env::remove_var("KEI_STORE_S3_ENDPOINT");
+        let cfg = S3Cfg::default();
+        assert_eq!(effective_endpoint(&cfg), None);
+    }
+}
diff --git a/_primitives/_rust/kei-store/src/s3_cloud/keys.rs b/_primitives/_rust/kei-store/src/s3_cloud/keys.rs
new file mode 100644
index 0000000..2d7b3a4
--- /dev/null
+++ b/_primitives/_rust/kei-store/src/s3_cloud/keys.rs
@@ -0,0 +1,60 @@
+//! Key-path helpers for the S3 cloud backend.
+//!
+//! `validate_rel` is the CVE-class guard: rejects absolute paths and
+//! `..` components before they are spliced into an S3 key. Same pattern as
+//! `filesystem::safe_join` — keeps the per-branch prefix unescapable.
+
+use anyhow::{bail, Result};
+
+/// Reject absolute paths and any `..` component in the caller's rel path.
+pub fn validate_rel(rel: &str) -> Result<()> {
+    if rel.starts_with('/') {
+        bail!("path traversal rejected: absolute path {:?}", rel);
+    }
+    for part in rel.split('/') {
+        if part == ".." {
+            bail!("path traversal rejected: parent-dir component in {:?}", rel);
+        }
+    }
+    Ok(())
+}
+
+/// Tiny DJB2 — deterministic, avoids pulling sha2 just for manifest naming.
+pub fn short_hash(s: &str) -> String {
+    let mut h: u64 = 5381;
+    for b in s.bytes() {
+        h = h.wrapping_mul(33).wrapping_add(b as u64);
+    }
+    format!("{:x}", h)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn validate_rel_rejects_absolute() {
+        let err = validate_rel("/etc/passwd").unwrap_err();
+        let msg = format!("{err:#}");
+        assert!(msg.contains("absolute"), "unexpected err: {msg}");
+    }
+
+    #[test]
+    fn validate_rel_rejects_parent() {
+        let err = validate_rel("a/../b").unwrap_err();
+        let msg = format!("{err:#}");
+        assert!(msg.contains("parent-dir"), "unexpected err: {msg}");
+    }
+
+    #[test]
+    fn validate_rel_accepts_normal() {
+        validate_rel("traces/session.jsonl").unwrap();
+        validate_rel("a/b/c.txt").unwrap();
+    }
+
+    #[test]
+    fn short_hash_deterministic() {
+        assert_eq!(short_hash("abc"), short_hash("abc"));
+        assert_ne!(short_hash("abc"), short_hash("abd"));
+    }
+}
diff --git a/_primitives/_rust/kei-store/src/s3_cloud/mod.rs b/_primitives/_rust/kei-store/src/s3_cloud/mod.rs
new file mode 100644
index 0000000..8a0b07b
--- /dev/null
+++ b/_primitives/_rust/kei-store/src/s3_cloud/mod.rs
@@ -0,0 +1,190 @@
+//! S3CloudStore — real object-storage backend via `aws-sdk-s3`.
+//!
+//! Behind `#[cfg(feature = "s3")]`; ~5 MB release binary growth.
+//! Credentials via AWS default chain (env / ~/.aws / IMDS).
+//! Endpoint override for R2 / MinIO / Wasabi: `KEI_STORE_S3_ENDPOINT`
+//! env var OR `s3.endpoint` in TOML.
+//! "Branch" = key prefix (`<branch>/<path>`); default `main`.
+//! Sync `MemoryStore` trait bridged over async SDK via a single
+//! current-thread tokio runtime (`block_on` per call).
+
+mod client;
+mod keys;
+
+use crate::config::S3Cfg;
+use crate::store_trait::MemoryStore;
+use anyhow::{anyhow, Context, Result};
+use aws_sdk_s3::primitives::ByteStream;
+use aws_sdk_s3::Client;
+use std::sync::Mutex;
+use tokio::runtime::{Builder, Runtime};
+
+const DEFAULT_BRANCH: &str = "main";
+
+pub struct S3CloudStore {
+    client: Client,
+    bucket: String,
+    rt: Runtime,
+    branch: Mutex<String>,
+}
+
+impl S3CloudStore {
+    /// Build a cloud-S3 backend. `bucket` MUST be configured.
+    pub fn new(cfg: S3Cfg) -> Result<Self> {
+        let bucket = cfg
+            .bucket
+            .clone()
+            .ok_or_else(|| anyhow!("s3 backend requires s3.bucket in config"))?;
+        let rt = Builder::new_current_thread()
+            .enable_all()
+            .build()
+            .context("init tokio runtime")?;
+        let client = rt.block_on(client::build_client(&cfg))?;
+        Ok(Self {
+            client,
+            bucket,
+            rt,
+            branch: Mutex::new(DEFAULT_BRANCH.to_string()),
+        })
+    }
+
+    fn current_branch(&self) -> String {
+        self.branch
+            .lock()
+            .map(|g| g.clone())
+            .unwrap_or_else(|poison| poison.into_inner().clone())
+    }
+
+    fn key(&self, rel: &str) -> Result<String> {
+        keys::validate_rel(rel)?;
+        Ok(format!("{}/{}", self.current_branch(), rel))
+    }
+
+    async fn get(&self, key: &str) -> Result<Vec<u8>> {
+        let resp = self
+            .client
+            .get_object()
+            .bucket(&self.bucket)
+            .key(key)
+            .send()
+            .await
+            .with_context(|| format!("s3 get_object {key}"))?;
+        let body = resp
+            .body
+            .collect()
+            .await
+            .with_context(|| format!("s3 read body {key}"))?;
+        Ok(body.into_bytes().to_vec())
+    }
+
+    async fn put(&self, key: &str, bytes: Vec<u8>) -> Result<()> {
+        self.client
+            .put_object()
+            .bucket(&self.bucket)
+            .key(key)
+            .body(ByteStream::from(bytes))
+            .send()
+            .await
+            .with_context(|| format!("s3 put_object {key}"))?;
+        Ok(())
+    }
+
+    async fn list_prefix(&self, prefix: &str) -> Result<Vec<String>> {
+        let mut out = Vec::new();
+        let mut token: Option<String> = None;
+        loop {
+            let mut req = self
+                .client
+                .list_objects_v2()
+                .bucket(&self.bucket)
+                .prefix(prefix)
+                .delimiter("/");
+            if let Some(t) = token.as_ref() {
+                req = req.continuation_token(t);
+            }
+            let resp = req
+                .send()
+                .await
+                .with_context(|| format!("s3 list {prefix}"))?;
+            for obj in resp.contents() {
+                if let Some(k) = obj.key() {
+                    if let Some(name) = k.strip_prefix(prefix) {
+                        if !name.is_empty() {
+                            out.push(name.to_string());
+                        }
+                    }
+                }
+            }
+            if resp.is_truncated().unwrap_or(false) {
+                token = resp.next_continuation_token().map(|s| s.to_string());
+            } else {
+                break;
+            }
+        }
+        out.sort();
+        Ok(out)
+    }
+}
+
+impl MemoryStore for S3CloudStore {
+    fn read(&self, path: &str) -> Result<Vec<u8>> {
+        let key = self.key(path)?;
+        self.rt.block_on(self.get(&key))
+    }
+
+    fn write(&self, path: &str, bytes: &[u8]) -> Result<()> {
+        let key = self.key(path)?;
+        self.rt.block_on(self.put(&key, bytes.to_vec()))
+    }
+
+    fn list(&self, dir: &str) -> Result<Vec<String>> {
+        let raw = self.key(dir)?;
+        let prefix = if raw.ends_with('/') {
+            raw
+        } else {
+            format!("{raw}/")
+        };
+        self.rt.block_on(self.list_prefix(&prefix))
+    }
+
+    fn branch(&self, name: &str) -> Result<()> {
+        keys::validate_rel(name)?;
+        let mut g = self
+            .branch
+            .lock()
+            .map_err(|_| anyhow!("branch lock poisoned"))?;
+        *g = name.to_string();
+        Ok(())
+    }
+
+    fn commit(&self, message: &str) -> Result<String> {
+        // Object stores have no native commit — write a manifest blob naming
+        // every key under the current branch and return a cheap hash.
+        let entries = self.list("")?;
+        let manifest = serde_json::json!({
+            "message": message,
+            "branch": self.current_branch(),
+            "entries": entries,
+        })
+        .to_string();
+        let hash = keys::short_hash(&manifest);
+        self.write(&format!("manifest-{hash}.json"), manifest.as_bytes())?;
+        Ok(hash)
+    }
+
+    fn push(&self, _branch: &str) -> Result<()> {
+        // Every write() already persists to S3 — no staging to flush.
+        Ok(())
+    }
+
+    fn pull(&self, _branch: &str) -> Result<()> {
+        Ok(())
+    }
+
+    fn backend_name(&self) -> &'static str {
+        "s3-cloud"
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/_primitives/_rust/kei-store/src/s3_cloud/tests.rs b/_primitives/_rust/kei-store/src/s3_cloud/tests.rs
new file mode 100644
index 0000000..309f3a2
--- /dev/null
+++ b/_primitives/_rust/kei-store/src/s3_cloud/tests.rs
@@ -0,0 +1,63 @@
+//! Unit tests for S3CloudStore — no network, mock-endpoint only.
+//!
+//! These tests verify builder correctness + path-safety guards. They do
+//! NOT exercise real S3 round-trips (that would require live AWS/MinIO
+//! and would fail in CI without credentials). See `tests/s3_smoke.rs`
+//! for the cross-crate smoke integration.
+
+use super::*;
+
+fn cfg(endpoint: &str) -> S3Cfg {
+    S3Cfg {
+        endpoint: Some(endpoint.to_string()),
+        bucket: Some("test-bucket".to_string()),
+        region: Some("us-east-1".to_string()),
+        access_key_env: None,
+        secret_key_env: None,
+        cache_path: None,
+    }
+}
+
+#[test]
+fn new_rejects_missing_bucket() {
+    let c = S3Cfg {
+        endpoint: Some("http://127.0.0.1:9999".to_string()),
+        region: Some("us-east-1".to_string()),
+        ..Default::default()
+    };
+    let err = S3CloudStore::new(c)
+        .err()
+        .expect("missing bucket should error");
+    assert!(format!("{err:#}").contains("bucket"));
+}
+
+#[test]
+fn new_builds_with_mock_endpoint() {
+    let store = S3CloudStore::new(cfg("http://127.0.0.1:9999")).unwrap();
+    assert_eq!(store.backend_name(), "s3-cloud");
+    assert_eq!(store.current_branch(), "main");
+}
+
+#[test]
+fn branch_updates_prefix() {
+    let store = S3CloudStore::new(cfg("http://127.0.0.1:9999")).unwrap();
+    store.branch("feat/foo").unwrap();
+    assert_eq!(
+        store.key("traces/a.jsonl").unwrap(),
+        "feat/foo/traces/a.jsonl"
+    );
+}
+
+#[test]
+fn branch_rejects_parent() {
+    let store = S3CloudStore::new(cfg("http://127.0.0.1:9999")).unwrap();
+    let err = store.branch("../escape").unwrap_err();
+    assert!(format!("{err:#}").contains("parent-dir"));
+}
+
+#[test]
+fn key_rejects_absolute() {
+    let store = S3CloudStore::new(cfg("http://127.0.0.1:9999")).unwrap();
+    let err = store.key("/etc/passwd").unwrap_err();
+    assert!(format!("{err:#}").contains("absolute"));
+}
diff --git a/_primitives/_rust/kei-store/tests/s3_smoke.rs b/_primitives/_rust/kei-store/tests/s3_smoke.rs
new file mode 100644
index 0000000..3d75fa9
--- /dev/null
+++ b/_primitives/_rust/kei-store/tests/s3_smoke.rs
@@ -0,0 +1,81 @@
+//! Smoke tests for the S3 cloud backend (behind `s3` feature).
+//!
+//! These tests never hit real AWS. They verify:
+//!   - the `S3CloudStore` builder accepts a mock endpoint without panic
+//!   - the library re-exports `s3_cloud` when the feature is enabled
+//!   - path-safety guards reject traversal attempts
+//!
+//! Run with: `cargo test -p kei-store --features s3 --test s3_smoke`.
+//! Without the feature, this file compiles to an empty crate — harmless.
+
+#![cfg(feature = "s3")]
+
+use kei_store::config::S3Cfg;
+use kei_store::s3_cloud::S3CloudStore;
+use kei_store::MemoryStore;
+
+fn mock_cfg(endpoint: &str) -> S3Cfg {
+    S3Cfg {
+        endpoint: Some(endpoint.to_string()),
+        bucket: Some("test-bucket".to_string()),
+        region: Some("us-east-1".to_string()),
+        access_key_env: None,
+        secret_key_env: None,
+        cache_path: None,
+    }
+}
+
+#[test]
+fn builder_accepts_mock_endpoint() {
+    let store = S3CloudStore::new(mock_cfg("http://127.0.0.1:9999"))
+        .expect("builder must not require network");
+    assert_eq!(store.backend_name(), "s3-cloud");
+}
+
+#[test]
+fn builder_rejects_missing_bucket() {
+    let cfg = S3Cfg {
+        endpoint: Some("http://127.0.0.1:9999".to_string()),
+        region: Some("us-east-1".to_string()),
+        ..Default::default()
+    };
+    let err = S3CloudStore::new(cfg)
+        .err()
+        .expect("missing bucket should error");
+    assert!(format!("{err:#}").contains("bucket"));
+}
+
+#[test]
+fn branch_switches_prefix() {
+    let store = S3CloudStore::new(mock_cfg("http://127.0.0.1:9999")).unwrap();
+    store.branch("agent/foo").unwrap();
+    // No network IO — just verify branch() does not error and backend_name
+    // stays stable.
+    assert_eq!(store.backend_name(), "s3-cloud");
+}
+
+#[test]
+fn write_fails_gracefully_on_unreachable_endpoint() {
+    // Point at a closed port — real put_object must error, NOT panic.
+    let store = S3CloudStore::new(mock_cfg("http://127.0.0.1:9")).unwrap();
+    let err = store.write("traces/x.jsonl", b"hello").unwrap_err();
+    let msg = format!("{err:#}");
+    // We only assert that an error propagates — the exact wording depends
+    // on the aws-smithy layer.
+    assert!(!msg.is_empty());
+}
+
+#[test]
+fn endpoint_env_var_is_honoured() {
+    std::env::set_var("KEI_STORE_S3_ENDPOINT", "http://127.0.0.1:9999");
+    // cfg endpoint differs — env should win. Builder still succeeds.
+    let cfg = S3Cfg {
+        endpoint: Some("http://unused:1".to_string()),
+        bucket: Some("b".to_string()),
+        region: Some("us-east-1".to_string()),
+        ..Default::default()
+    };
+    let s = S3CloudStore::new(cfg);
+    std::env::remove_var("KEI_STORE_S3_ENDPOINT");
+    assert!(s.is_ok());
+}