diff --git a/.gitea/workflows/docker-publish.yml b/.gitea/workflows/docker-publish.yml
index 968a267..c17d938 100644
--- a/.gitea/workflows/docker-publish.yml
+++ b/.gitea/workflows/docker-publish.yml
@@ -58,6 +58,9 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
+      - name: Guard — base *_REF args must be folded into the base hash
+        run: bash scripts/check-base-hash.sh
+
       - name: Compute base tag from Dockerfile.base + dependencies
         id: compute
         run: |
@@ -127,52 +130,70 @@ jobs:
       - name: Resolve pi version + companion refs
         id: resolve
         run: |
-          set -eu
-          # Query npm registry directly; catthehacker/ubuntu:act-latest's npm
-          # is not reliably on PATH in act_runner job containers.
-          PI_VERSION=$(curl -sf "https://registry.npmjs.org/@earendil-works%2Fpi-coding-agent/latest" | jq -r '.version')
+          set -euo pipefail
+          AUTH_HEADER="Authorization: token ${GITEA_BUILD_TOKEN:-${GITHUB_TOKEN:-}}"
+
+          # Fail loud rather than silently shipping a floating branch. A
+          # transient network/API failure must ABORT the release, not bake
+          # an unpinned ref that defeats both cache-busting AND after-the-
+          # fact reproducibility. (Previously each lookup fell back to
+          # `main`/`master` via `|| echo`.)
+          require_sha() { # $1=label $2=value
+            if ! printf '%s' "${2:-}" | grep -qiE '^[0-9a-f]{40}$'; then
+              echo "::error::Could not resolve $1 to a commit SHA (got '${2:-<empty>}'). Refusing to fall back to a floating ref — published images must stay reproducible. Check connectivity and GITEA_BUILD_TOKEN/GITHUB_TOKEN."
+              exit 1
+            fi
+          }
+
+          # pi version from npm (catthehacker/ubuntu:act-latest's npm is not
+          # reliably on PATH in act_runner job containers, so query directly).
+          PI_VERSION=$(curl -sf "https://registry.npmjs.org/@earendil-works%2Fpi-coding-agent/latest" | jq -r '.version' 2>/dev/null || true)
+          if ! printf '%s' "${PI_VERSION:-}" | grep -qE '^[0-9]+\.[0-9]+\.[0-9]+'; then
+            echo "::error::Could not resolve pi version from npm (got '${PI_VERSION:-<empty>}')."
+            exit 1
+          fi
           echo "pi_version=${PI_VERSION}" >> "$GITHUB_OUTPUT"
-          # Resolve pi-fork / pi-observational-memory git refs to commit
-          # SHAs so the build-arg string changes whenever upstream moves.
+
+          # pi-fork / pi-observational-memory (GitHub) → commit SHAs.
           FORK_REF=$(curl -sf -H "Accept: application/vnd.github.sha" \
-            "https://api.github.com/repos/elpapi42/pi-fork/commits/master" || echo "master")
+            "https://api.github.com/repos/elpapi42/pi-fork/commits/master" || true)
+          require_sha PI_FORK_REF "$FORK_REF"
           OBSMEM_REF=$(curl -sf -H "Accept: application/vnd.github.sha" \
-            "https://api.github.com/repos/elpapi42/pi-observational-memory/commits/master" || echo "master")
-          [ -n "$FORK_REF" ]   || FORK_REF=master
-          [ -n "$OBSMEM_REF" ] || OBSMEM_REF=master
+            "https://api.github.com/repos/elpapi42/pi-observational-memory/commits/master" || true)
+          require_sha PI_OBSMEM_REF "$OBSMEM_REF"
           echo "fork_ref=${FORK_REF}"     >> "$GITHUB_OUTPUT"
           echo "obsmem_ref=${OBSMEM_REF}" >> "$GITHUB_OUTPUT"
-          # Also resolve pi-toolkit / pi-extensions main HEADs to SHAs so a
-          # workflow_dispatch re-run produces byte-identical images when
-          # those repos haven't moved (and a clean diff in build-arg strings
-          # when they have, defeating the registry buildcache footgun).
-          # Gitea API requires auth even for public-repo commit listing.
-          TOOLKIT_REF=$(curl -sf -H "Authorization: token ${GITEA_BUILD_TOKEN:-${GITHUB_TOKEN:-}}" \
+
+          # pi-toolkit / pi-extensions (Gitea) → commit SHAs. Gitea API
+          # requires auth even for public-repo commit listing.
+          TOOLKIT_REF=$(curl -sf -H "$AUTH_HEADER" \
             "https://gitea.jordbo.se/api/v1/repos/joakimp/pi-toolkit/commits?limit=1&sha=main" \
-            | jq -r '.[0].sha // "main"' 2>/dev/null || echo "main")
-          EXTENSIONS_REF=$(curl -sf -H "Authorization: token ${GITEA_BUILD_TOKEN:-${GITHUB_TOKEN:-}}" \
+            | jq -r '.[0].sha // empty' 2>/dev/null || true)
+          require_sha PI_TOOLKIT_REF "$TOOLKIT_REF"
+          EXTENSIONS_REF=$(curl -sf -H "$AUTH_HEADER" \
             "https://gitea.jordbo.se/api/v1/repos/joakimp/pi-extensions/commits?limit=1&sha=main" \
-            | jq -r '.[0].sha // "main"' 2>/dev/null || echo "main")
-          [ -n "$TOOLKIT_REF" ]    || TOOLKIT_REF=main
-          [ -n "$EXTENSIONS_REF" ] || EXTENSIONS_REF=main
+            | jq -r '.[0].sha // empty' 2>/dev/null || true)
+          require_sha PI_EXTENSIONS_REF "$EXTENSIONS_REF"
           echo "toolkit_ref=${TOOLKIT_REF}"        >> "$GITHUB_OUTPUT"
           echo "extensions_ref=${EXTENSIONS_REF}"  >> "$GITHUB_OUTPUT"
-          # Resolve mempalace-toolkit main HEAD to a SHA. UNLIKE the others,
-          # mempalace-toolkit is cloned in Dockerfile.base, so this SHA is
-          # ALSO folded into the base-decide hash to force a base rebuild
-          # when the toolkit moves (without it, a toolkit-only fix silently
-          # fails to land unless Dockerfile.base itself changes).
-          MEMPALACE_TOOLKIT_REF=$(curl -sf -H "Authorization: token ${GITEA_BUILD_TOKEN:-${GITHUB_TOKEN:-}}" \
+
+          # mempalace-toolkit (Gitea) → commit SHA. UNLIKE the others this
+          # is cloned in Dockerfile.base, so the SAME SHA is ALSO folded
+          # into the base-decide hash (see that job) to force a base rebuild
+          # when the toolkit moves — otherwise a toolkit-only fix silently
+          # fails to land unless Dockerfile.base itself changes.
+          MEMPALACE_TOOLKIT_REF=$(curl -sf -H "$AUTH_HEADER" \
             "https://gitea.jordbo.se/api/v1/repos/joakimp/mempalace-toolkit/commits?limit=1&sha=main" \
-            | jq -r '.[0].sha // "main"' 2>/dev/null || echo "main")
-          [ -n "$MEMPALACE_TOOLKIT_REF" ] || MEMPALACE_TOOLKIT_REF=main
+            | jq -r '.[0].sha // empty' 2>/dev/null || true)
+          require_sha MEMPALACE_TOOLKIT_REF "$MEMPALACE_TOOLKIT_REF"
           echo "mempalace_toolkit_ref=${MEMPALACE_TOOLKIT_REF}" >> "$GITHUB_OUTPUT"
-          # Resolve pi-studio (omaclaren/pi-studio) main HEAD to a SHA for
-          # the :latest-studio variant — same cache-busting rationale.
+
+          # pi-studio (omaclaren/pi-studio) → commit SHA for :latest-studio.
           STUDIO_REF=$(curl -sf -H "Accept: application/vnd.github.sha" \
-            "https://api.github.com/repos/omaclaren/pi-studio/commits/main" || echo "main")
-          [ -n "$STUDIO_REF" ] || STUDIO_REF=main
+            "https://api.github.com/repos/omaclaren/pi-studio/commits/main" || true)
+          require_sha PI_STUDIO_REF "$STUDIO_REF"
           echo "studio_ref=${STUDIO_REF}" >> "$GITHUB_OUTPUT"
+
           echo "Resolved PI_VERSION=${PI_VERSION}"
           echo "Resolved PI_FORK_REF=${FORK_REF}, PI_OBSMEM_REF=${OBSMEM_REF}"
           echo "Resolved PI_TOOLKIT_REF=${TOOLKIT_REF}, PI_EXTENSIONS_REF=${EXTENSIONS_REF}"
@@ -299,6 +320,9 @@ jobs:
             PI_OBSMEM_REF=${{ needs.resolve-versions.outputs.obsmem_ref }}
             PI_TOOLKIT_REF=${{ needs.resolve-versions.outputs.toolkit_ref }}
             PI_EXTENSIONS_REF=${{ needs.resolve-versions.outputs.extensions_ref }}
+            MEMPALACE_TOOLKIT_REF=${{ needs.resolve-versions.outputs.mempalace_toolkit_ref }}
+            RELEASE_TAG=smoke
+            SOURCE_REVISION=${{ github.sha }}
       - name: Smoke test (amd64)
         env:
           EXPECTED_PI_VERSION: ${{ needs.resolve-versions.outputs.pi_version }}
@@ -355,6 +379,9 @@ jobs:
             PI_EXTENSIONS_REF=${{ needs.resolve-versions.outputs.extensions_ref }}
             INSTALL_STUDIO=true
             PI_STUDIO_REF=${{ needs.resolve-versions.outputs.studio_ref }}
+            MEMPALACE_TOOLKIT_REF=${{ needs.resolve-versions.outputs.mempalace_toolkit_ref }}
+            RELEASE_TAG=smoke-studio
+            SOURCE_REVISION=${{ github.sha }}
       - name: Smoke test studio (amd64)
         env:
           EXPECTED_PI_VERSION: ${{ needs.resolve-versions.outputs.pi_version }}
@@ -406,10 +433,12 @@ jobs:
           OBSMEM_REF: ${{ needs.resolve-versions.outputs.obsmem_ref }}
           TOOLKIT_REF: ${{ needs.resolve-versions.outputs.toolkit_ref }}
           EXTENSIONS_REF: ${{ needs.resolve-versions.outputs.extensions_ref }}
+          MEMPALACE_TOOLKIT_REF: ${{ needs.resolve-versions.outputs.mempalace_toolkit_ref }}
         run: |
           set -euo pipefail
           TAG_FLAGS=()
           while IFS= read -r t; do [[ -n "$t" ]] && TAG_FLAGS+=( -t "$t" ); done <<< "${TAGS}"
+          BUILD_DATE=$(date -u +%Y-%m-%dT%H:%M:%SZ)
           # 3-attempt retry (see build-base step for rationale).
           for attempt in 1 2 3; do
             echo "==> Build+push attempt ${attempt}/3"
@@ -423,6 +452,10 @@ jobs:
                 --build-arg "PI_OBSMEM_REF=${OBSMEM_REF}" \
                 --build-arg "PI_TOOLKIT_REF=${TOOLKIT_REF}" \
                 --build-arg "PI_EXTENSIONS_REF=${EXTENSIONS_REF}" \
+                --build-arg "MEMPALACE_TOOLKIT_REF=${MEMPALACE_TOOLKIT_REF}" \
+                --build-arg "RELEASE_TAG=${RELEASE_TAG}" \
+                --build-arg "BUILD_DATE=${BUILD_DATE}" \
+                --build-arg "SOURCE_REVISION=${GITHUB_SHA:-}" \
                 "${TAG_FLAGS[@]}" \
                 .; then
               echo "==> Attempt ${attempt} succeeded"
@@ -487,10 +520,12 @@ jobs:
           TOOLKIT_REF: ${{ needs.resolve-versions.outputs.toolkit_ref }}
           EXTENSIONS_REF: ${{ needs.resolve-versions.outputs.extensions_ref }}
           STUDIO_REF: ${{ needs.resolve-versions.outputs.studio_ref }}
+          MEMPALACE_TOOLKIT_REF: ${{ needs.resolve-versions.outputs.mempalace_toolkit_ref }}
         run: |
           set -euo pipefail
           TAG_FLAGS=()
           while IFS= read -r t; do [[ -n "$t" ]] && TAG_FLAGS+=( -t "$t" ); done <<< "${TAGS}"
+          BUILD_DATE=$(date -u +%Y-%m-%dT%H:%M:%SZ)
           # 3-attempt retry (see build-base step for rationale).
           for attempt in 1 2 3; do
             echo "==> Build+push attempt ${attempt}/3"
@@ -504,8 +539,12 @@ jobs:
                 --build-arg "PI_OBSMEM_REF=${OBSMEM_REF}" \
                 --build-arg "PI_TOOLKIT_REF=${TOOLKIT_REF}" \
                 --build-arg "PI_EXTENSIONS_REF=${EXTENSIONS_REF}" \
+                --build-arg "MEMPALACE_TOOLKIT_REF=${MEMPALACE_TOOLKIT_REF}" \
                 --build-arg "INSTALL_STUDIO=true" \
                 --build-arg "PI_STUDIO_REF=${STUDIO_REF}" \
+                --build-arg "RELEASE_TAG=${RELEASE_TAG}" \
+                --build-arg "BUILD_DATE=${BUILD_DATE}" \
+                --build-arg "SOURCE_REVISION=${GITHUB_SHA:-}" \
                 "${TAG_FLAGS[@]}" \
                 .; then
               echo "==> Attempt ${attempt} succeeded"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa529ac..ab7f6e1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,72 @@ Pre-v1.0.0 tags followed the pi npm version (`v{pi_version}[letter]`).
 
 ## Unreleased
 
+## v1.1.6 — 2026-06-19
+
+Build provenance + reproducibility hardening, plus pi `0.79.7` → `0.79.8`
+(auto-resolved at build). Companion refs are auto-resolved to SHAs at build
+as before.
+
+### Bumped: pi 0.79.7 → 0.79.8
+
+Notable upstream changes (from [pi releases](https://github.com/earendil-works/pi/releases/tag/v0.79.8)):
+
+- **Selective provider base entry points** — SDK users can pair
+  `@earendil-works/pi-ai/base` and `@earendil-works/pi-agent-core/base` with
+  explicit provider registration to keep bundled apps from including unused
+  provider transports.
+- **Mistral prompt caching** — Mistral sessions use provider-side prompt
+  caching keyed on the pi session ID, with cached-token usage/cost
+  accounting.
+- **Post-compaction token estimates** — compact results and compaction
+  events now include estimated post-compaction token counts.
+- **OpenRouter Fusion alias** — `openrouter/fusion` available as a built-in
+  OpenRouter model alias.
+
+### Added
+
+- **Self-describing images: OCI labels + on-disk build manifest.** The
+  variant build now records exactly which pi version and companion-repo
+  commits were baked into each image. Previously the SHAs resolved by CI
+  only ever reached the build log (which rotates), so a published tag was
+  not reconstructable after the fact — confirming what shipped meant
+  triangulating from `git`, `pi --version`, and extension source.
+  - OCI labels: `org.opencontainers.image.{version,revision,created}` plus
+    `se.jordbo.pi-devbox.{pi,pi-toolkit,pi-extensions,pi-fork,pi-obsmem,mempalace-toolkit,pi-studio}-*ref` —
+    inspect with `docker inspect`.
+  - `/etc/pi-devbox/build-manifest.json` written from **ground truth** (the
+    actual checked-out `HEAD` of each `/opt` clone + live `pi --version`),
+    not just the intended build-args, so it also exposes a clone that
+    silently resolved to the wrong ref. The provenance ARGs are declared
+    last so a changing `BUILD_DATE` never invalidates the expensive
+    install/clone layers.
+- **`scripts/check-base-hash.sh` — base-rebuild invariant guard.** Every
+  floating `ARG *_REF` consumed by `Dockerfile.base` must be folded into the
+  `base_tag` hash, or a ref-only change won't trigger a base rebuild (the
+  v1.1.2 mempalace-toolkit staleness footgun). The guard fails CI the moment
+  someone adds an `ARG *_REF` to `Dockerfile.base` without folding it in; it
+  runs in the `base-decide` job and locally. Smoke-test gained assertions for
+  the manifest (present, no `"unknown"` components) and the OCI labels.
+- **Overridable companion repo URLs.** The three gitea-hosted companions
+  (`pi-toolkit`, `pi-extensions`, `mempalace-toolkit`) gained `*_REPO`
+  build-args defaulting to their canonical `gitea.jordbo.se` origin —
+  matching the existing `PI_FORK_REPO` / `PI_OBSMEM_REPO` / `PI_STUDIO_REPO`
+  pattern. A relocated or forked build can now repoint a companion at a
+  mirror, another host, or a local path (`--build-arg PI_EXTENSIONS_REPO=...`)
+  without editing the Dockerfiles. Defaults are unchanged, so the canonical
+  CI build is byte-identical.
+
+### Changed
+
+- **`resolve-versions` now fails loud instead of falling back to a floating
+  branch.** Each pi-version / companion-ref lookup previously degraded to
+  `main`/`master` on a transient API/network failure (`|| echo "main"`),
+  silently shipping an unpinned ref that defeats both cache-busting and
+  reproducibility. Resolution now validates each result is a 40-hex commit
+  SHA (and pi a real semver) and aborts the release otherwise.
+
+---
+
 ## v1.1.5 — 2026-06-18
 
 Patch release: SSH ControlMaster read-only-socket fix + pi `0.79.6` → `0.79.7`
diff --git a/Dockerfile.base b/Dockerfile.base
index cb9e8ef..eb94a27 100644
--- a/Dockerfile.base
+++ b/Dockerfile.base
@@ -351,6 +351,11 @@ RUN if [ "${INSTALL_MEMPALACE}" = "true" ]; then \
 # ── mempalace-toolkit — bash wrappers for session/docs mining ────────
 ARG INSTALL_MEMPALACE_TOOLKIT=true
 ARG MEMPALACE_TOOLKIT_REF=main
+# MEMPALACE_TOOLKIT_REPO defaults to the canonical gitea origin but is
+# overridable so a relocated/forked build can clone from a mirror or a
+# different host without editing this Dockerfile (mirrors the
+# PI_FORK_REPO / PI_OBSMEM_REPO / PI_STUDIO_REPO pattern in the variant).
+ARG MEMPALACE_TOOLKIT_REPO=https://gitea.jordbo.se/joakimp/mempalace-toolkit.git
 # MEMPALACE_TOOLKIT_REF accepts EITHER a branch name OR a commit SHA. CI
 # resolves it to a SHA (resolve-versions job) and folds that SHA into the
 # base-decide hash so the base rebuilds when the toolkit moves. `git clone
@@ -360,7 +365,7 @@ ARG MEMPALACE_TOOLKIT_REF=main
 RUN if [ "${INSTALL_MEMPALACE}" = "true" ] && [ "${INSTALL_MEMPALACE_TOOLKIT}" = "true" ]; then \
       rm -rf /opt/mempalace-toolkit && mkdir -p /opt/mempalace-toolkit && \
       git -C /opt/mempalace-toolkit init -q && \
-      git -C /opt/mempalace-toolkit remote add origin https://gitea.jordbo.se/joakimp/mempalace-toolkit.git && \
+      git -C /opt/mempalace-toolkit remote add origin "${MEMPALACE_TOOLKIT_REPO}" && \
       ok=0; for i in 1 2 3 4 5; do \
         if git -C /opt/mempalace-toolkit fetch --depth 1 origin "${MEMPALACE_TOOLKIT_REF}" && \
            git -C /opt/mempalace-toolkit checkout -q FETCH_HEAD; then ok=1; break; fi; \
diff --git a/Dockerfile.variant b/Dockerfile.variant
index e7c0132..3d3db31 100644
--- a/Dockerfile.variant
+++ b/Dockerfile.variant
@@ -41,6 +41,12 @@ ARG USER_NAME=developer
 ARG PI_VERSION=latest
 ARG PI_TOOLKIT_REF=main
 ARG PI_EXTENSIONS_REF=main
+# Repo URLs default to the canonical gitea origin but are overridable so a
+# relocated/forked build can clone from a mirror or a different host
+# without editing this Dockerfile — same pattern as PI_FORK_REPO /
+# PI_OBSMEM_REPO / PI_STUDIO_REPO below.
+ARG PI_TOOLKIT_REPO=https://gitea.jordbo.se/joakimp/pi-toolkit.git
+ARG PI_EXTENSIONS_REPO=https://gitea.jordbo.se/joakimp/pi-extensions.git
 # pi-fork (fork tool) + pi-observational-memory (recall tool) live on GitHub
 # under elpapi42. CI resolves these to commit SHAs to defeat the same
 # cache-hit footgun that affects PI_VERSION.
@@ -77,8 +83,8 @@ RUN set -e && \
       NPM_CONFIG_PREFIX=/usr npm install -g @earendil-works/pi-coding-agent@${PI_VERSION} ; \
     fi && \
     pi --version && \
-    git_fetch_ref   "https://gitea.jordbo.se/joakimp/pi-toolkit.git"    "${PI_TOOLKIT_REF}"    /opt/pi-toolkit && \
-    git_fetch_ref   "https://gitea.jordbo.se/joakimp/pi-extensions.git" "${PI_EXTENSIONS_REF}" /opt/pi-extensions && \
+    git_fetch_ref   "${PI_TOOLKIT_REPO}"    "${PI_TOOLKIT_REF}"    /opt/pi-toolkit && \
+    git_fetch_ref   "${PI_EXTENSIONS_REPO}" "${PI_EXTENSIONS_REF}" /opt/pi-extensions && \
     git_fetch_ref   "${PI_FORK_REPO}"   "${PI_FORK_REF}"   /opt/pi-fork && \
     git_fetch_ref   "${PI_OBSMEM_REPO}" "${PI_OBSMEM_REF}" /opt/pi-observational-memory && \
     (cd /opt/pi-fork && npm install --omit=dev --no-audit --no-fund) && \
@@ -154,4 +160,60 @@ RUN if [ "${INSTALL_GO}" = "true" ]; then \
       ln -s /usr/local/go/bin/gofmt /usr/local/bin/gofmt; \
     fi
 
+# ── Build provenance: OCI labels + on-disk build manifest ────────────
+# Records exactly which pi version and companion-repo commits were baked
+# into THIS image, so a published tag is self-describing and reproducible
+# after the fact (CI logs rotate; a released image must not depend on
+# them). Previously the resolved SHAs only ever reached the CI build log.
+#
+# These ARGs are declared LAST, immediately before the layer that uses
+# them, so a changing BUILD_DATE / RELEASE_TAG / SOURCE_REVISION never
+# invalidates the expensive pi-install / clone layers above.
+ARG RELEASE_TAG=dev
+ARG BUILD_DATE=
+ARG SOURCE_REVISION=
+# MEMPALACE_TOOLKIT_REF is consumed in Dockerfile.base; re-declared here
+# only so its intended ref lands in the label set alongside the others.
+ARG MEMPALACE_TOOLKIT_REF=main
+
+LABEL org.opencontainers.image.version="${RELEASE_TAG}" \
+      org.opencontainers.image.revision="${SOURCE_REVISION}" \
+      org.opencontainers.image.created="${BUILD_DATE}" \
+      se.jordbo.pi-devbox.pi-version="${PI_VERSION}" \
+      se.jordbo.pi-devbox.pi-toolkit-ref="${PI_TOOLKIT_REF}" \
+      se.jordbo.pi-devbox.pi-extensions-ref="${PI_EXTENSIONS_REF}" \
+      se.jordbo.pi-devbox.pi-fork-ref="${PI_FORK_REF}" \
+      se.jordbo.pi-devbox.pi-obsmem-ref="${PI_OBSMEM_REF}" \
+      se.jordbo.pi-devbox.mempalace-toolkit-ref="${MEMPALACE_TOOLKIT_REF}" \
+      se.jordbo.pi-devbox.pi-studio-ref="${PI_STUDIO_REF}"
+
+# The manifest is written from GROUND TRUTH — the actual checked-out HEAD
+# of each /opt clone and the live `pi --version` — not merely the intended
+# build-args. That way it also exposes a clone that silently resolved to
+# something other than the requested ref. pi-studio is present only in the
+# studio variant (JSON null otherwise).
+RUN set -e; \
+    mkdir -p /etc/pi-devbox; \
+    rev() { git -C "$1" rev-parse HEAD 2>/dev/null || echo "unknown"; }; \
+    PI_V="$(pi --version 2>/dev/null | head -n1 | tr -d '\r\n')"; \
+    STUDIO_REV='null'; \
+    if [ -d /opt/pi-studio/.git ]; then STUDIO_REV="\"$(rev /opt/pi-studio)\""; fi; \
+    { \
+      echo '{'; \
+      echo "  \"release_tag\": \"${RELEASE_TAG}\","; \
+      echo "  \"build_date\": \"${BUILD_DATE}\","; \
+      echo "  \"source_revision\": \"${SOURCE_REVISION}\","; \
+      echo "  \"pi_version\": \"${PI_V}\","; \
+      echo "  \"components\": {"; \
+      echo "    \"pi-toolkit\": \"$(rev /opt/pi-toolkit)\","; \
+      echo "    \"pi-extensions\": \"$(rev /opt/pi-extensions)\","; \
+      echo "    \"pi-fork\": \"$(rev /opt/pi-fork)\","; \
+      echo "    \"pi-observational-memory\": \"$(rev /opt/pi-observational-memory)\","; \
+      echo "    \"mempalace-toolkit\": \"$(rev /opt/mempalace-toolkit)\","; \
+      echo "    \"pi-studio\": ${STUDIO_REV}"; \
+      echo "  }"; \
+      echo '}'; \
+    } > /etc/pi-devbox/build-manifest.json; \
+    echo "── build manifest ──"; cat /etc/pi-devbox/build-manifest.json
+
 # WORKDIR / ENTRYPOINT / CMD inherited from base.
diff --git a/README.md b/README.md
index bfc2787..74545c1 100644
--- a/README.md
+++ b/README.md
@@ -537,6 +537,68 @@ pi-coding-agent@latest` (the build-arg string would otherwise be
 byte-identical across releases and the layer would silently reuse the
 previous version's bytes).
 
+### Building a fork / relocated build
+
+The canonical build clones its companions from `gitea.jordbo.se`. Every
+companion repo URL is an overridable build-arg (defaulting to the canonical
+origin), so a fork or a build on a host that can't reach that gitea can
+repoint each one at a mirror, another host, or a local `file://` path
+**without editing the Dockerfiles**:
+
+| Build-arg | Default | Dockerfile |
+|---|---|---|
+| `PI_TOOLKIT_REPO` | `https://gitea.jordbo.se/joakimp/pi-toolkit.git` | variant |
+| `PI_EXTENSIONS_REPO` | `https://gitea.jordbo.se/joakimp/pi-extensions.git` | variant |
+| `MEMPALACE_TOOLKIT_REPO` | `https://gitea.jordbo.se/joakimp/mempalace-toolkit.git` | base |
+| `PI_FORK_REPO` | `https://github.com/elpapi42/pi-fork.git` | variant |
+| `PI_OBSMEM_REPO` | `https://github.com/elpapi42/pi-observational-memory.git` | variant |
+| `PI_STUDIO_REPO` | `https://github.com/omaclaren/pi-studio.git` | variant |
+
+Each has a matching `*_REF` arg (branch name or commit SHA). Example — build
+the variant against forked toolkit/extensions and a pinned pi:
+
+```bash
+# base first (mempalace-toolkit lives here)
+docker build -f Dockerfile.base -t myorg/pi-devbox:base-dev \
+  --build-arg MEMPALACE_TOOLKIT_REPO=https://github.com/myorg/mempalace-toolkit.git .
+
+# then the variant FROM that base
+docker build -f Dockerfile.variant -t myorg/pi-devbox:dev \
+  --build-arg BASE_IMAGE=myorg/pi-devbox:base-dev \
+  --build-arg PI_VERSION=0.79.7 \
+  --build-arg PI_TOOLKIT_REPO=https://github.com/myorg/pi-toolkit.git \
+  --build-arg PI_EXTENSIONS_REPO=https://github.com/myorg/pi-extensions.git .
+```
+
+Note: the gitea companions clone anonymously (no token needed); only the
+`resolve-versions` CI job calls the gitea *API* (which needs a token even
+for public repos). A plain `docker build` like the above skips that job
+entirely, so no credentials are required for a local/forked build.
+
+Provenance build-args (all optional; populate the OCI labels and
+`/etc/pi-devbox/build-manifest.json` — see below): `RELEASE_TAG`,
+`BUILD_DATE`, `SOURCE_REVISION`. CI sets these automatically; a manual build
+leaves them at harmless defaults.
+
+### Build provenance (labels + manifest)
+
+Every published image is self-describing. Inspect the OCI labels without
+pulling the filesystem:
+
+```bash
+docker inspect --format '{{json .Config.Labels}}' joakimp/pi-devbox:latest | jq .
+```
+
+`org.opencontainers.image.{version,revision,created}` plus
+`se.jordbo.pi-devbox.*-ref` record the intended pi version and companion
+refs. The on-disk `/etc/pi-devbox/build-manifest.json` records **ground
+truth** — the actual checked-out commit of each `/opt` clone and the live
+`pi --version` — so a tag is reconstructable after CI logs rotate:
+
+```bash
+docker run --rm --entrypoint= joakimp/pi-devbox:latest cat /etc/pi-devbox/build-manifest.json
+```
+
 ## Troubleshooting
 
 ### Image grew unexpectedly
diff --git a/scripts/check-base-hash.sh b/scripts/check-base-hash.sh
new file mode 100755
index 0000000..74080c6
--- /dev/null
+++ b/scripts/check-base-hash.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+# check-base-hash.sh — guard the base-rebuild invariant.
+#
+# Every floating `ARG *_REF` consumed by Dockerfile.base MUST be folded
+# into the base_tag hash in the docker-publish workflow. Otherwise a
+# ref-only change to that dependency does not change the base hash, the
+# Docker Hub probe finds the old base tag, and the base is NOT rebuilt —
+# the dependency fix silently fails to land. This is the v1.1.2-class
+# staleness footgun (then it was mempalace-toolkit; this guard stops the
+# next one before it ships).
+#
+# Runs in CI (base-decide job) and locally:  bash scripts/check-base-hash.sh
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+WF=".gitea/workflows/docker-publish.yml"
+DF="Dockerfile.base"
+
+# Extract the hash-compute block: the `HASH=$( … ) | sha256sum | cut`
+# brace-group in the "Compute base tag" step. This lives in a separate
+# file from the workflow, so scanning $WF here is free of the self-match
+# hazard an inline workflow step would have.
+block=$(awk '/HASH=\$\(/{f=1} f{print} f && /cut -c1-12/{exit}' "$WF")
+if [ -z "$block" ]; then
+  echo "::error::could not locate the HASH=\$( … ) | sha256sum block in $WF"
+  exit 1
+fi
+
+refs=$(grep -oE '^ARG [A-Z0-9_]+_REF' "$DF" | awk '{print $2}' | sort -u)
+fail=0
+for r in $refs; do
+  lc=$(printf '%s' "$r" | tr '[:upper:]' '[:lower:]')
+  if ! printf '%s' "$block" | grep -q "outputs.$lc"; then
+    echo "::error::Dockerfile.base declares '$r' but it is NOT folded into the base_tag hash in $WF."
+    echo "::error::Add  echo \"\${{ needs.resolve-versions.outputs.$lc }}\"  inside the HASH=\$( … ) | sha256sum block, or a $r-only change will silently fail to rebuild the base."
+    fail=1
+  fi
+done
+
+if [ "$fail" = 0 ]; then
+  echo "OK: all Dockerfile.base *_REF args are folded into base_tag (${refs:-none})."
+fi
+exit $fail
diff --git a/scripts/smoke-test.sh b/scripts/smoke-test.sh
index 507b468..0ff4465 100755
--- a/scripts/smoke-test.sh
+++ b/scripts/smoke-test.sh
@@ -113,6 +113,28 @@ else
   echo "  ℹ️   pi-studio not present (non-studio variant) — skipping studio clone checks"
 fi
 
+# ── Build provenance (manifest + OCI labels) ─────────────────────────
+echo ""
+echo "── Build provenance ──"
+run "/etc/pi-devbox/build-manifest.json present" \
+    "test -f /etc/pi-devbox/build-manifest.json"
+run_expect "manifest records pi-extensions component" \
+    "cat /etc/pi-devbox/build-manifest.json" '"pi-extensions"'
+run_expect "manifest records pi_version" \
+    "cat /etc/pi-devbox/build-manifest.json" '"pi_version"'
+# Every component must be a resolved commit (or null for pi-studio in the
+# non-studio variant) — 'unknown' means a clone silently failed to resolve.
+run "manifest has no unresolved ('unknown') components" \
+    "! grep -q '\"unknown\"' /etc/pi-devbox/build-manifest.json"
+# OCI labels live in the image config, not the container fs — inspect them
+# from the host docker rather than via `docker run`.
+LBL=$(docker inspect --format '{{ index .Config.Labels "se.jordbo.pi-devbox.pi-extensions-ref" }}' "$IMAGE" 2>/dev/null || true)
+if [ -n "$LBL" ] && [ "$LBL" != "<no value>" ]; then
+  printf "  ✅  OCI label se.jordbo.pi-devbox.pi-extensions-ref=%s\n" "$LBL"; PASS=$((PASS+1))
+else
+  printf "  ❌  OCI label se.jordbo.pi-devbox.pi-extensions-ref missing or empty\n"; FAIL=$((FAIL+1))
+fi
+
 # ── Runtime deployment (needs entrypoint to run) ──────────────────────
 echo ""
 echo "── Runtime deployment ──"