diff --git a/.gitea/workflows/backend-build.yml b/.gitea/workflows/backend-build.yml
new file mode 100644
index 0000000..b9fc418
--- /dev/null
+++ b/.gitea/workflows/backend-build.yml
@@ -0,0 +1,70 @@
+name: Backend candidate (Gitea)
+
+# Private Linux candidate only. The reviewed dispatcher supplies the exact Builds
+# head. Fleet admits its exact canonical GitHub source parent before dispatch.
+on:
+  workflow_dispatch:
+    inputs:
+      expected_sha:
+        description: Exact reviewed Builds main commit
+        required: true
+        type: string
+
+env:
+  CARGO_TERM_COLOR: never
+  PYTHONDONTWRITEBYTECODE: '1'
+  EXPECTED_BUILD_SHA: ${{ inputs.expected_sha }}
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  linux:
+    name: Linux candidate
+    runs-on: ubuntu-latest
+    container:
+      image: node:22-bookworm@sha256:0557ac14e0d45d02ed563067b82856ca5e7aa3437fa28d98d4350ea9c3d9494a
+    env:
+      RUSTUP_HOME: ${{ runner.temp }}/rustup-backend-candidate
+      CARGO_HOME: ${{ runner.temp }}/cargo-backend-candidate
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          ref: ${{ inputs.expected_sha }}
+          persist-credentials: false
+      - name: Require reviewed source selectors before setup
+        run: |
+          test "$GITHUB_REPOSITORY" = Builds/smirk-backend-core || { echo 'This repository is not admitted for backend Builds.' >&2; exit 1; }
+          test "$(git rev-parse HEAD)" = "$EXPECTED_BUILD_SHA" || { echo 'Checkout differs from the reviewed event or dispatch head.' >&2; exit 1; }
+      - name: Install isolated container build dependencies
+        run: |
+          apt-get update -qq
+          apt-get install -y --no-install-recommends python3 build-essential pkg-config libssl-dev binutils
+      - name: Admit reviewed source and exact dispatch head
+        run: |
+          if [ "$GITHUB_EVENT_NAME" = pull_request ]; then
+            canonical_source=$(git rev-parse HEAD)
+          else
+            read -r -a parents <<< "$(git show -s --format=%P HEAD)"
+            test "${#parents[@]}" -eq 2 || { echo 'Builds main requires a two-parent source wrapper.' >&2; exit 1; }
+            canonical_source=${parents[1]}
+          fi
+          git fetch --no-tags https://github.com/Such-Software/smirk-backend-core.git "$canonical_source"
+          python3 tools/check-build-source.py
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: x86_64-unknown-linux-gnu
+      - uses: Swatinem/rust-cache@v2
+      - name: Build Linux candidate
+        run: cargo build --locked --release --target x86_64-unknown-linux-gnu --bin smirk-backend-core
+      - name: Stage binary and provenance
+        run: python3 tools/stage-backend-candidate.py --output "$RUNNER_TEMP/backend-candidate"
+      - name: Retain private candidate
+        uses: actions/upload-artifact@v3
+        with:
+          name: smirk-backend-core-linux-x86_64-${{ inputs.expected_sha }}
+          path: ${{ runner.temp }}/backend-candidate/
+          if-no-files-found: error
+          retention-days: 14
diff --git a/.gitea/workflows/ci.yml b/.gitea/workflows/ci.yml
new file mode 100644
index 0000000..8c8369b
--- /dev/null
+++ b/.gitea/workflows/ci.yml
@@ -0,0 +1,110 @@
+name: Backend CI (Gitea)
+
+# GitHub remains canonical source. Builds admits an explicitly reviewed commit;
+# this workflow is the fundless CI gate, not deployment or public publication.
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+env:
+  CARGO_TERM_COLOR: never
+  PYTHONDONTWRITEBYTECODE: '1'
+  EXPECTED_BUILD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  verify:
+    name: backend checks
+    runs-on: ubuntu-latest
+    container:
+      image: node:22-bookworm@sha256:0557ac14e0d45d02ed563067b82856ca5e7aa3437fa28d98d4350ea9c3d9494a
+    env:
+      RUSTUP_HOME: ${{ runner.temp }}/rustup-backend-ci
+      CARGO_HOME: ${{ runner.temp }}/cargo-backend-ci
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha || github.sha }}
+          persist-credentials: false
+      - name: Require reviewed source selectors before setup
+        run: |
+          test "$GITHUB_REPOSITORY" = Builds/smirk-backend-core || { echo 'This repository is not admitted for backend Builds.' >&2; exit 1; }
+          test "$(git rev-parse HEAD)" = "$EXPECTED_BUILD_SHA" || { echo 'Checkout differs from the reviewed event or dispatch head.' >&2; exit 1; }
+      - name: Install isolated container dependencies
+        run: |
+          apt-get update -qq
+          apt-get install -y --no-install-recommends python3 build-essential pkg-config libssl-dev postgresql postgresql-client
+      - name: Admit reviewed canonical source
+        run: |
+          if [ "$GITHUB_EVENT_NAME" = pull_request ]; then
+            canonical_source=$(git rev-parse HEAD)
+          else
+            read -r -a parents <<< "$(git show -s --format=%P HEAD)"
+            test "${#parents[@]}" -eq 2 || { echo 'Builds main requires a two-parent source wrapper.' >&2; exit 1; }
+            canonical_source=${parents[1]}
+          fi
+          git fetch --no-tags https://github.com/Such-Software/smirk-backend-core.git "$canonical_source"
+          python3 tools/check-build-source.py
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+      - uses: Swatinem/rust-cache@v2
+      - name: Source admission and artifact guard regressions
+        run: python3 -m unittest discover -s tools/tests -v
+      - name: Secret shapes
+        run: ./tools/secret-scan.sh
+      - name: Rust format and clippy
+        run: |
+          cargo fmt --all -- --check
+          cargo clippy --locked --all-targets -- -D warnings
+      - name: All fundless tests with disposable PostgreSQL
+        run: ./tools/ci-fundless.sh
+      - name: OpenAPI source agreement
+        run: |
+          cargo run --locked --quiet --bin gen_openapi > "$RUNNER_TEMP/openapi.json"
+          diff openapi.json "$RUNNER_TEMP/openapi.json"
+      - name: Embedded console source agreement
+        working-directory: admin-ui
+        run: |
+          npm ci
+          npm run build
+          git diff --exit-code -- dist
+      - uses: actions/setup-go@v5
+        with:
+          go-version: '1.24.0'
+      - name: Redacted history credential scan
+        run: |
+          go install github.com/zricethezav/gitleaks/v8@v8.18.4
+          "$(go env GOPATH)/bin/gitleaks" detect --no-banner --redact --source .
+
+  supply-chain:
+    name: dependency policy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha || github.sha }}
+          persist-credentials: false
+      - uses: EmbarkStudios/cargo-deny-action@v2
+
+  gate:
+    name: backend gate
+    if: always()
+    needs: [verify, supply-chain]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Require every mandatory check
+        env:
+          VERIFY_RESULT: ${{ needs.verify.result }}
+          DEPENDENCY_RESULT: ${{ needs.supply-chain.result }}
+        run: |
+          if [ "$VERIFY_RESULT" != success ] || [ "$DEPENDENCY_RESULT" != success ]; then
+            echo 'Backend gate refused: required checks failed, were cancelled, or did not run.' >&2
+            exit 1
+          fi
diff --git a/README.md b/README.md
index 39dea37..d13262f 100644
--- a/README.md
+++ b/README.md
@@ -158,3 +158,6 @@ funded or otherwise sensitive wallet seed.
 - [ ] Regenerate OpenAPI and the console bundle from their sources and check drift.
 - [ ] Verify each enabled chain against its configured source.
 - [ ] Use reviewed Fleet plan/apply procedures for company production deployments.
+
+Backend CI and private Linux candidate provenance are described in
+[Building the backend](docs/operations/BUILDING.md).
diff --git a/docs/operations/BUILDING.md b/docs/operations/BUILDING.md
new file mode 100644
index 0000000..e91cee4
--- /dev/null
+++ b/docs/operations/BUILDING.md
@@ -0,0 +1,51 @@
+# Backend builds and candidate provenance
+
+> Status: implemented, enrollment pending · Updated: 2026-09-27 · Applies to: backend maintainers and release operators
+
+GitHub `Such-Software/smirk-backend-core` remains canonical source. Gitea
+`Builds/smirk-backend-core` is private CI and candidate ingress. A workflow file
+in source does not prove that the repository, runner, branch protection or
+required status has been enrolled. Those are reviewed Fleet operations.
+
+`.gitea/workflows/ci.yml` owns the fundless backend gate: formatting, strict
+Clippy, every integration target with disposable PostgreSQL, documentation
+tests, generated OpenAPI and embedded-console agreement, redacted credential
+scanning and dependency policy. Its final gate refuses failed, skipped or
+cancelled mandatory jobs. GitHub Actions is not the build authority.
+
+`tools/ci-fundless.sh` creates a temporary PostgreSQL cluster with a private Unix
+socket and no TCP listener. It never accepts a database URL or a test-command
+override, refuses a local `.env`, supplies `TEST_DATABASE_URL`, and removes its
+cluster on exit. Without a database, ordinary `cargo test` can skip integration
+targets and is not equivalent evidence. Tests use only unfunded fixtures.
+
+## Private Linux candidate
+
+`.gitea/workflows/backend-build.yml` accepts only the required `expected_sha`
+input. The reviewed Fleet dispatcher verifies the admitted canonical GitHub
+commit before dispatch. The workflow checks out that exact Builds commit and
+requires a two-parent merge wrapper with a tree identical to its second parent.
+That parent is recorded as canonical source. It is fetched from the declared
+GitHub repository; an arbitrary tree with different ancestry is refused.
+
+The workflow builds with Rust 1.98.0 in a digest-pinned Debian 12 container.
+`tools/stage-backend-candidate.py` refuses an unexpected binary architecture,
+missing GNU libc evidence, or a binary requiring GNU libc newer than 2.36.
+The private artifact contains the executable and `manifest.json`, which records
+source and Builds commits, source tree, workflow and lockfile digests, compiler,
+target, GNU libc requirements, executable digest and size. Artifact identity is
+`smirk-backend-core-linux-x86_64-<Builds commit>`.
+
+This is a candidate, not a deployment or public release. Fleet must independently
+admit its source, workflow, artifact digest and host compatibility before a
+reviewed plan. A successful upload does not prove production health. The current
+configuration adapter does not install this binary or prepare a new host.
+
+## Reusable build checklist
+
+- [ ] Exact canonical source and Builds wrapper are admitted by reviewed Fleet authority.
+- [ ] Actual Gitea required CI status is green for the selected source.
+- [ ] Every fundless PostgreSQL target ran against disposable data.
+- [ ] Candidate manifest, executable digest and target match the reviewed build.
+- [ ] Host compatibility and deployment evidence are separate from build success.
+- [ ] No credential values, funded wallets or production database were used.
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index 73cb934..aa20bc9 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -1,3 +1,3 @@
 [toolchain]
-channel = "stable"
+channel = "1.98.0"
 components = ["rustfmt", "clippy"]
diff --git a/tools/check-build-source.py b/tools/check-build-source.py
new file mode 100755
index 0000000..3d7f9f2
--- /dev/null
+++ b/tools/check-build-source.py
@@ -0,0 +1,72 @@
+#!/usr/bin/env python3
+"""Admit one reviewed canonical source or its exact Builds merge wrapper."""
+import os
+import re
+import subprocess
+import sys
+
+
+class Refusal(ValueError):
+    pass
+
+
+def git(*args):
+    return subprocess.check_output(["git", *args], text=True, stderr=subprocess.PIPE).strip()
+
+
+def commit(value, label):
+    if not re.fullmatch(r"[0-9a-f]{40}", value or ""):
+        raise Refusal(f"{label} must be a reviewed full lowercase commit SHA")
+    return value
+
+
+def source_for_checkout(require_wrapper):
+    if not require_wrapper:
+        return git("rev-parse", "HEAD")
+    parents = git("show", "-s", "--format=%P", "HEAD").split()
+    if len(parents) != 2:
+        raise Refusal("release or main CI requires a two-parent Builds wrapper")
+    return commit(parents[1], "canonical source parent")
+
+
+def admit(source, expected_head=None, require_wrapper=False):
+    source = commit(source, "canonical source")
+    head = git("rev-parse", "HEAD")
+    if expected_head is not None and head != commit(expected_head, "expected_sha"):
+        raise Refusal("checkout HEAD differs from the reviewed dispatch head")
+    if git("rev-parse", f"{source}^{{commit}}") != source:
+        raise Refusal("reviewed canonical source is not a commit")
+    tree = git("rev-parse", f"{source}^{{tree}}")
+    if git("rev-parse", "HEAD^{tree}") != tree:
+        raise Refusal("Builds checkout tree differs from reviewed canonical source")
+    if head != source or require_wrapper:
+        parents = git("show", "-s", "--format=%P", "HEAD").split()
+        if len(parents) != 2 or parents[1] != source:
+            raise Refusal("Builds HEAD is neither canonical source nor its two-parent wrapper")
+    if git("status", "--porcelain", "--untracked-files=all"):
+        raise Refusal("Builds checkout contains local changes or untracked files")
+    return {"source_commit": source, "build_commit": head, "source_tree": tree}
+
+
+def main():
+    if os.environ.get("GITHUB_REPOSITORY") != "Builds/smirk-backend-core":
+        raise Refusal("this workflow is admitted only on Builds/smirk-backend-core")
+    event = os.environ.get("GITHUB_EVENT_NAME")
+    expected = os.environ.get("EXPECTED_BUILD_SHA")
+    if not expected:
+        raise Refusal("this build requires the exact reviewed event or dispatch head")
+    if event not in {"push", "pull_request", "workflow_dispatch"}:
+        raise Refusal("this build event is not admitted")
+    wrapper = event != "pull_request"
+    canonical = source_for_checkout(wrapper)
+    result = admit(canonical, expected, require_wrapper=wrapper)
+    print(f"Admitted canonical source {result['source_commit']} at Builds {result['build_commit']}")
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except Refusal as error:
+        sys.exit(f"Build source refused: {error}")
+    except subprocess.CalledProcessError:
+        sys.exit("Build source refused: Git could not resolve the reviewed source or checkout")
diff --git a/tools/ci-fundless.sh b/tools/ci-fundless.sh
new file mode 100755
index 0000000..eb55f2c
--- /dev/null
+++ b/tools/ci-fundless.sh
@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+# Own a disposable Unix-socket PostgreSQL cluster. Never use a caller's database.
+set -euo pipefail
+set +x
+if [[ $# != 0 ]]; then
+  echo 'Fundless CI does not accept a database or test-command override.' >&2
+  exit 1
+fi
+if [[ -f .env ]]; then
+  echo 'Fundless CI refuses a checkout containing .env.' >&2
+  exit 1
+fi
+pg_bin=$(pg_config --bindir)
+for tool in initdb pg_ctl createdb psql; do
+  [[ -x "$pg_bin/$tool" ]] || { echo "Fundless CI requires PostgreSQL $tool." >&2; exit 1; }
+done
+ci_pg_dir=$(mktemp -d /tmp/smirk-ci-pg.XXXXXXXX)
+chmod 700 "$ci_pg_dir"
+pg_user=$(id -un)
+if [[ $(id -u) == 0 ]]; then
+  pg_user=postgres
+  id "$pg_user" >/dev/null 2>&1 || { echo 'The isolated CI container requires the postgres service account.' >&2; exit 1; }
+  chown "$pg_user" "$ci_pg_dir"
+fi
+pg_exec() {
+  if [[ $(id -u) == 0 ]]; then
+    runuser -u "$pg_user" -- "$@"
+  else
+    "$@"
+  fi
+}
+cleanup() {
+  pg_exec "$pg_bin/pg_ctl" -D "$ci_pg_dir/data" -m immediate -w stop >/dev/null 2>&1 || true
+  rm -rf "$ci_pg_dir"
+}
+trap cleanup EXIT
+pg_exec "$pg_bin/initdb" -D "$ci_pg_dir/data" --auth-local=trust --auth-host=reject --no-locale >/dev/null
+# No TCP listener and a private socket directory: no password or shared service.
+pg_exec "$pg_bin/pg_ctl" -D "$ci_pg_dir/data" -l "$ci_pg_dir/postgres.log" \
+  -o "-k $ci_pg_dir -c listen_addresses='' -c unix_socket_permissions=0700" -w start >/dev/null
+pg_exec "$pg_bin/createdb" -h "$ci_pg_dir" smirk_ci
+export TEST_DATABASE_URL="postgresql:///smirk_ci?host=$ci_pg_dir&user=$pg_user"
+# A failing or missing DB is an error; tests must not quietly take their no-DB path.
+pg_exec "$pg_bin/psql" -h "$ci_pg_dir" -d smirk_ci -Atc 'SELECT 1' | grep -qx 1
+cargo test --locked --tests
+cargo test --locked --doc
diff --git a/tools/stage-backend-candidate.py b/tools/stage-backend-candidate.py
new file mode 100755
index 0000000..11cdb78
--- /dev/null
+++ b/tools/stage-backend-candidate.py
@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+"""Stage a private Linux candidate with exact source and artifact provenance."""
+import argparse
+import hashlib
+import importlib.util
+import json
+import os
+from pathlib import Path
+import re
+import shutil
+import subprocess
+import sys
+
+ROOT = Path(__file__).resolve().parent.parent
+spec = importlib.util.spec_from_file_location("build_source", ROOT / "tools/check-build-source.py")
+source = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(source)
+
+
+def sha256(path):
+    return hashlib.sha256(Path(path).read_bytes()).hexdigest()
+
+
+def elf_requirements(path):
+    header = Path(path).read_bytes()[:20]
+    if len(header) != 20 or header[:6] != b"\x7fELF\x02\x01" or header[18:20] != b"\x3e\x00":
+        raise source.Refusal("candidate must be a 64-bit little-endian x86_64 ELF binary")
+    versions = subprocess.check_output(["readelf", "--version-info", str(path)], text=True)
+    required = sorted(set(re.findall(r"\bGLIBC_([0-9]+(?:\.[0-9]+)+)\b", versions)),
+                      key=lambda value: tuple(map(int, value.split("."))))
+    if not required:
+        raise source.Refusal("candidate has no readable GNU libc compatibility evidence")
+    if tuple(map(int, required[-1].split("."))) > (2, 36):
+        raise source.Refusal("candidate requires newer GNU libc than the admitted Debian 12 baseline")
+    return required
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--output", type=Path, required=True)
+    args = parser.parse_args()
+    os.chdir(ROOT)
+    admitted = source.admit(source.source_for_checkout(True),
+                            os.environ.get("EXPECTED_BUILD_SHA", ""), require_wrapper=True)
+    binary = ROOT / "target/x86_64-unknown-linux-gnu/release/smirk-backend-core"
+    required = elf_requirements(binary)
+    rustc = subprocess.check_output(["rustc", "--version"], text=True).strip()
+    if not rustc.startswith("rustc 1.98.0 "):
+        raise source.Refusal("candidate compiler differs from the reviewed Rust 1.98.0 pin")
+    args.output.mkdir(mode=0o700, parents=False, exist_ok=False)
+    staged = args.output / "smirk-backend-core"
+    shutil.copyfile(binary, staged)
+    staged.chmod(0o755)
+    manifest = {
+        "schema_version": 1,
+        "product": "smirk-backend-core",
+        "publication": "private_candidate_only",
+        **admitted,
+        "canonical_repository": "https://github.com/Such-Software/smirk-backend-core",
+        "build_repository": "Builds/smirk-backend-core",
+        "workflow_path": ".gitea/workflows/backend-build.yml",
+        "workflow_sha256": sha256(ROOT / ".gitea/workflows/backend-build.yml"),
+        "cargo_lock_sha256": sha256(ROOT / "Cargo.lock"),
+        "rust_toolchain_sha256": sha256(ROOT / "rust-toolchain.toml"),
+        "rustc": rustc,
+        "target": "x86_64-unknown-linux-gnu",
+        "glibc_versions": required,
+        "artifact": {"name": staged.name, "sha256": sha256(staged), "size": staged.stat().st_size},
+    }
+    (args.output / "manifest.json").write_text(json.dumps(manifest, indent=2, sort_keys=True) + "\n")
+    print(f"Staged private candidate for {admitted['source_commit']}; publication requires separate admission.")
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except source.Refusal as error:
+        sys.exit(f"Candidate refused: {error}")
+    except (OSError, subprocess.CalledProcessError):
+        sys.exit("Candidate refused: required build output, compiler, or ELF evidence is unavailable")
diff --git a/tools/tests/test_build_admission.py b/tools/tests/test_build_admission.py
new file mode 100644
index 0000000..1843e4c
--- /dev/null
+++ b/tools/tests/test_build_admission.py
@@ -0,0 +1,134 @@
+"""Fundless Git fixtures prove source admission and binary compatibility guards."""
+import importlib.util
+import os
+from pathlib import Path
+import subprocess
+import tempfile
+import unittest
+from unittest.mock import patch
+
+TOOLS = Path(__file__).resolve().parents[1]
+
+
+def load(name, path):
+    spec = importlib.util.spec_from_file_location(name, path)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+source = load("source", TOOLS / "check-build-source.py")
+stage = load("stage", TOOLS / "stage-backend-candidate.py")
+
+
+class Admission(unittest.TestCase):
+    def setUp(self):
+        self.temp = tempfile.TemporaryDirectory(prefix="smirk-git-admission-")
+        self.previous = Path.cwd()
+        os.chdir(self.temp.name)
+        self.git("init", "-q")
+        self.git("config", "user.name", "Fundless fixture")
+        self.git("config", "user.email", "fixture@example.invalid")
+        Path("source.txt").write_text("baseline\n")
+        self.git("add", ".")
+        self.git("commit", "-qm", "baseline")
+        self.base = self.git("rev-parse", "HEAD")
+        Path("source.txt").write_text("candidate\n")
+        self.git("commit", "-qam", "candidate")
+        self.candidate = self.git("rev-parse", "HEAD")
+
+    def tearDown(self):
+        os.chdir(self.previous)
+        self.temp.cleanup()
+
+    def git(self, *args, input=None):
+        return subprocess.check_output(["git", *args], input=input, text=True,
+                                       stderr=subprocess.PIPE).strip()
+
+    def wrapper(self, second=None, tree=None):
+        tree = tree or self.git("rev-parse", self.candidate + "^{tree}")
+        value = self.git("commit-tree", tree, "-p", self.base, "-p", second or self.candidate,
+                         input="wrapper\n")
+        self.git("reset", "--hard", value)
+        return value
+
+    def test_canonical_and_tree_identical_wrapper_admitted(self):
+        self.assertEqual(source.admit(self.candidate)["build_commit"], self.candidate)
+        wrapper = self.wrapper()
+        admitted = source.admit(self.candidate, wrapper)
+        self.assertEqual(admitted["source_commit"], self.candidate)
+        self.assertEqual(admitted["source_tree"], self.git("rev-parse", "HEAD^{tree}"))
+
+    def test_release_requires_wrapper_and_derives_its_source(self):
+        with self.assertRaises(source.Refusal):
+            source.source_for_checkout(True)
+        with self.assertRaises(source.Refusal):
+            source.admit(self.candidate, self.candidate, require_wrapper=True)
+        wrapper = self.wrapper()
+        self.assertEqual(source.source_for_checkout(True), self.candidate)
+        self.assertEqual(source.admit(self.candidate, wrapper, require_wrapper=True)["build_commit"], wrapper)
+
+    def test_moving_dispatch_head_refused(self):
+        with self.assertRaises(source.Refusal):
+            source.admit(self.candidate, self.base)
+
+    def test_tree_change_refused(self):
+        self.wrapper(tree=self.git("rev-parse", self.base + "^{tree}"))
+        with self.assertRaises(source.Refusal):
+            source.admit(self.candidate)
+
+    def test_tree_identity_without_source_parent_refused(self):
+        tree = self.git("rev-parse", self.candidate + "^{tree}")
+        unrelated = self.git("commit-tree", tree, "-p", self.base, input="unrelated\n")
+        self.wrapper(second=unrelated)
+        with self.assertRaises(source.Refusal):
+            source.admit(self.candidate)
+
+    def test_dirty_surface_and_missing_pin_refused(self):
+        Path("unknown.txt").write_text("unreviewed\n")
+        with self.assertRaises(source.Refusal):
+            source.admit(self.candidate)
+        with self.assertRaises(source.Refusal):
+            source.admit("")
+
+    def test_dispatch_missing_head_or_wrong_repository_refused(self):
+        with patch.dict(os.environ, {"GITHUB_REPOSITORY": "Builds/smirk-backend-core",
+                                    "GITHUB_EVENT_NAME": "workflow_dispatch"}, clear=True):
+            with self.assertRaises(source.Refusal):
+                source.main()
+        with patch.dict(os.environ, {"GITHUB_REPOSITORY": "unreviewed/repository"}, clear=True):
+            with self.assertRaises(source.Refusal):
+                source.main()
+
+
+class BinaryCompatibility(unittest.TestCase):
+    def setUp(self):
+        self.temp = tempfile.TemporaryDirectory(prefix="smirk-elf-fixture-")
+        self.binary = Path(self.temp.name) / "binary"
+        self.binary.write_bytes(b"\x7fELF\x02\x01" + bytes(12) + b"\x3e\x00")
+
+    def tearDown(self):
+        self.temp.cleanup()
+
+    def test_compatible_versions_recorded_in_numeric_order(self):
+        with patch.object(subprocess, "check_output", return_value="GLIBC_2.3 GLIBC_2.36 GLIBC_2.9"):
+            result = stage.elf_requirements(self.binary)
+        self.assertEqual(result[-1], "2.36")
+        self.assertIn("2.9", result)
+
+    def test_incompatible_or_unknown_libc_refused(self):
+        for output in ("GLIBC_2.38", "unreadable"):
+            with self.subTest(output=output), patch.object(subprocess, "check_output", return_value=output):
+                with self.assertRaises(stage.source.Refusal):
+                    stage.elf_requirements(self.binary)
+
+    def test_wrong_binary_format_refused_before_tool_invocation(self):
+        self.binary.write_bytes(b"not ELF")
+        with patch.object(subprocess, "check_output") as probe:
+            with self.assertRaises(stage.source.Refusal):
+                stage.elf_requirements(self.binary)
+            probe.assert_not_called()
+
+
+if __name__ == "__main__":
+    unittest.main()