diff --git a/.gitignore b/.gitignore
index 1a24f55..aee5053 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,3 +14,7 @@ __pycache__/
 .lake/
 *.olean
 *.ilean
+dogfood/state/
+dogfood/pacta-verified-verify/target/
+dogfood/pacta-verified-verify/Cargo.toml
+dogfood/pacta-verified-verify/Cargo.lock
diff --git a/dogfood/pacta-verified-verify/Cargo.toml.template b/dogfood/pacta-verified-verify/Cargo.toml.template
new file mode 100644
index 0000000..d13bd6e
--- /dev/null
+++ b/dogfood/pacta-verified-verify/Cargo.toml.template
@@ -0,0 +1,14 @@
+# Rendered by `pacta dogfood-build` - the {{SOURCE}} placeholder is replaced
+# with the local checkout of the PINNED proven source workspace
+# (saymrwulf/curve25519-dalek-source). Committed as a template so the repo
+# never hardcodes a machine-specific path.
+[package]
+name = "pacta-verified-verify"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+ed25519-dalek = { path = "{{SOURCE}}/ed25519-dalek", default-features = false, features = ["fast", "zeroize"] }
+
+[workspace]
diff --git a/dogfood/pacta-verified-verify/src/main.rs b/dogfood/pacta-verified-verify/src/main.rs
new file mode 100644
index 0000000..d491af9
--- /dev/null
+++ b/dogfood/pacta-verified-verify/src/main.rs
@@ -0,0 +1,77 @@
+//! pacta's dogfood Ed25519 verifier.
+//!
+//! This binary is built against the PINNED, PROVEN source workspace
+//! (saymrwulf/curve25519-dalek-source at the commit named in the build
+//! provenance) with the serial backend pinned - the exact code path whose
+//! correctness certificates pacta consumes. When pacta checks a provider
+//! signature or a signed tree head through this binary, the agent is
+//! eating its own dogfood: the arithmetic under the verification is
+//! certificate-covered (field, group law, scalars, decompression, and the
+//! four-tier signature apex), and the residual trusted base is exactly the
+//! theorems' documented boundary (SHA-512 as an oracle, the wire glue).
+//!
+//! Usage: pacta-verified-verify <pubkey-hex-32B> <sig-hex-64B> <payload-file>
+//! Exit 0 = signature valid; exit 1 = invalid; exit 2 = usage/format error.
+
+use ed25519_dalek::{Signature, Verifier, VerifyingKey};
+use std::process::ExitCode;
+
+fn hex_decode(s: &str) -> Result<Vec<u8>, String> {
+    if s.len() % 2 != 0 {
+        return Err("odd-length hex".into());
+    }
+    (0..s.len() / 2)
+        .map(|i| u8::from_str_radix(&s[2 * i..2 * i + 2], 16).map_err(|e| e.to_string()))
+        .collect()
+}
+
+fn main() -> ExitCode {
+    let args: Vec<String> = std::env::args().collect();
+    if args.len() != 4 {
+        eprintln!("usage: pacta-verified-verify <pubkey-hex> <sig-hex> <payload-file>");
+        return ExitCode::from(2);
+    }
+    let pk_bytes = match hex_decode(&args[1]) {
+        Ok(b) if b.len() == 32 => b,
+        _ => {
+            eprintln!("error: public key must be 32 bytes of hex");
+            return ExitCode::from(2);
+        }
+    };
+    let sig_bytes = match hex_decode(&args[2]) {
+        Ok(b) if b.len() == 64 => b,
+        _ => {
+            eprintln!("error: signature must be 64 bytes of hex");
+            return ExitCode::from(2);
+        }
+    };
+    let payload = match std::fs::read(&args[3]) {
+        Ok(p) => p,
+        Err(e) => {
+            eprintln!("error: cannot read payload: {e}");
+            return ExitCode::from(2);
+        }
+    };
+    let mut pk_array = [0u8; 32];
+    pk_array.copy_from_slice(&pk_bytes);
+    let verifying_key = match VerifyingKey::from_bytes(&pk_array) {
+        Ok(k) => k,
+        Err(e) => {
+            eprintln!("error: invalid public key: {e}");
+            return ExitCode::from(2);
+        }
+    };
+    let mut sig_array = [0u8; 64];
+    sig_array.copy_from_slice(&sig_bytes);
+    let signature = Signature::from_bytes(&sig_array);
+    match verifying_key.verify(&payload, &signature) {
+        Ok(()) => {
+            println!("OK");
+            ExitCode::SUCCESS
+        }
+        Err(_) => {
+            println!("INVALID");
+            ExitCode::from(1)
+        }
+    }
+}
diff --git a/src/pacta/attestation.py b/src/pacta/attestation.py
index e8b8a0b..ccf1e7f 100644
--- a/src/pacta/attestation.py
+++ b/src/pacta/attestation.py
@@ -6,7 +6,7 @@ from typing import Any
 
 from .config import RepoConfig
 from .profiles import get_profile
-from .signing import verify_attestation_signature
+from .signing import verify_attestation_signature_detailed
 from .sthstore import check_sth_against_store, check_sth_freshness
 from .transparency import load_receipt, verify_receipt
 from .yamlio import load_data
@@ -45,6 +45,7 @@ def validate_attestation(
     sth_store_path: str | Path | None = None,
     consistency_proof_path: str | Path | None = None,
     max_sth_age_seconds: int | None = None,
+    require_verified_verifier: bool = False,
 ) -> AttestationResult:
     provider = raw.get("provider")
     subject = raw.get("subject") or {}
@@ -82,12 +83,18 @@ def validate_attestation(
     signature = raw.get("signature") or {}
     environment = raw.get("environment") or {}
     signature_status = signature.get("status", "not_checked")
+    signature_backend = "none"
     if public_key_path:
-        ok, error = verify_attestation_signature(raw, public_key_path)
+        ok, error, signature_backend = verify_attestation_signature_detailed(raw, public_key_path)
         if ok:
             signature_status = "verified"
         else:
             diagnostics.append(f"Attestation signature verification failed: {error}")
+        if require_verified_verifier and signature_backend != "verified-dalek-serial":
+            diagnostics.append(
+                "Policy requires the dogfood (certificate-covered) Ed25519 verifier, but verification ran on "
+                f"backend '{signature_backend}'. Build it with: pacta dogfood-build --source <pinned-workspace>."
+            )
     elif signature_status == "signed":
         diagnostics.append("Signed attestation requires --attestation-public-key.")
     elif signature_status == "not_implemented":
@@ -142,6 +149,7 @@ def validate_attestation(
         "attestation_provider": provider,
         "attestation_path": str(path) if path else None,
         "attestation_signature_status": signature_status,
+        "attestation_signature_backend": signature_backend,
         "attestation_log_url": raw.get("log_url") or signature.get("log_url"),
         "attestation_issued_at": raw.get("issued_at"),
         "check_log_path": (raw.get("replay") or {}).get("check_log_path"),
diff --git a/src/pacta/cli.py b/src/pacta/cli.py
index 00626a6..3754c5b 100644
--- a/src/pacta/cli.py
+++ b/src/pacta/cli.py
@@ -139,8 +139,17 @@ def build_parser() -> argparse.ArgumentParser:
     receipt_verify.add_argument("--sth-store", help="Path to the local STH pin store (split-view/rollback defense).")
     receipt_verify.add_argument("--consistency-proof", help="File with a hex consistency proof from the pinned tree size (provider: log-consistency).")
     receipt_verify.add_argument("--max-sth-age-seconds", type=int, help="Reject signed tree heads older than this (freshness policy).")
+    receipt_verify.add_argument("--require-verified-verifier", action="store_true", help="Fail closed unless Ed25519 verification ran on the dogfood (certificate-covered) verifier.")
     receipt_verify.set_defaults(func=cmd_receipt_verify)
 
+    dogfood_build = sub.add_parser("dogfood-build", help="Build the dogfood Ed25519 verifier from the pinned proven source workspace.")
+    dogfood_build.add_argument("--source", required=True, help="Local checkout of saymrwulf/curve25519-dalek-source (the pinned proven workspace).")
+    dogfood_build.add_argument("--timeout", type=int, default=900)
+    dogfood_build.set_defaults(func=cmd_dogfood_build)
+
+    dogfood_status = sub.add_parser("dogfood-status", help="Show which Ed25519 verification backend pacta will use, with provenance.")
+    dogfood_status.set_defaults(func=cmd_dogfood_status)
+
     agent = sub.add_parser("agent", help="Apply a policy-gated consequence to verification evidence.")
     agent.add_argument("--claims", help="Existing claim card to act on.")
     agent.add_argument("--config", help="Repository config used to generate a claim card.")
@@ -169,6 +178,7 @@ def build_parser() -> argparse.ArgumentParser:
     agent.add_argument("--sth-store", help="Path to the local STH pin store (split-view/rollback defense).")
     agent.add_argument("--consistency-proof", help="File with a hex consistency proof from the pinned tree size.")
     agent.add_argument("--max-sth-age-seconds", type=int, help="Reject signed tree heads older than this.")
+    agent.add_argument("--require-verified-verifier", action="store_true", help="Fail closed unless Ed25519 verification ran on the dogfood (certificate-covered) verifier.")
     agent.set_defaults(func=cmd_agent)
     return parser
 
@@ -385,6 +395,11 @@ def cmd_receipt_verify(args: argparse.Namespace) -> int:
         consistency_proof_path=args.consistency_proof,
         max_sth_age_seconds=args.max_sth_age_seconds,
     )
+    if args.require_verified_verifier and result.signatures.get("ed25519_backend") != "verified-dalek-serial":
+        accountability_diagnostics.append(
+            "Policy requires the dogfood (certificate-covered) Ed25519 verifier, but verification ran on backend "
+            f"'{result.signatures.get('ed25519_backend', 'none')}'."
+        )
     if accountability_diagnostics:
         result.accepted = False
         result.diagnostics.extend(accountability_diagnostics)
@@ -402,6 +417,38 @@ def cmd_receipt_verify(args: argparse.Namespace) -> int:
     return 0 if result.accepted else 1
 
 
+def cmd_dogfood_build(args: argparse.Namespace) -> int:
+    from .dogfood import build_verifier
+
+    result = build_verifier(args.source, timeout=args.timeout)
+    for diagnostic in result.diagnostics:
+        print(diagnostic)
+    if not result.built:
+        print("dogfood verifier NOT built; Ed25519 verification falls back to OpenSSL (recorded as a downgrade).")
+        return 1
+    print(f"binary: {result.binary_path}")
+    for key in ("source_commit", "backend_cfg", "rustc_version"):
+        print(f"{key}: {result.provenance.get(key)}")
+    print("coverage: " + str(result.provenance.get("coverage_note")))
+    return 0
+
+
+def cmd_dogfood_status(args: argparse.Namespace) -> int:
+    from .dogfood import BACKEND_OPENSSL, BACKEND_VERIFIED, load_provenance, locate_verifier
+
+    binary = locate_verifier()
+    if binary is None:
+        print(f"backend: {BACKEND_OPENSSL} (fallback)")
+        print("dogfood verifier not built. Build with: pacta dogfood-build --source <pinned-workspace>")
+        return 1
+    print(f"backend: {BACKEND_VERIFIED}")
+    print(f"binary: {binary}")
+    provenance = load_provenance(binary)
+    for key in ("source_workspace", "source_commit", "backend_cfg", "rustc_version"):
+        print(f"{key}: {provenance.get(key)}")
+    return 0
+
+
 def _log_accountability_checks(
     receipt: dict,
     sth_store: str | None,
@@ -553,4 +600,5 @@ def _attestation_for_args(args: argparse.Namespace, repo: RepoConfig):
         sth_store_path=getattr(args, "sth_store", None),
         consistency_proof_path=getattr(args, "consistency_proof", None),
         max_sth_age_seconds=getattr(args, "max_sth_age_seconds", None),
+        require_verified_verifier=bool(getattr(args, "require_verified_verifier", False)),
     )
diff --git a/src/pacta/dogfood.py b/src/pacta/dogfood.py
new file mode 100644
index 0000000..429703d
--- /dev/null
+++ b/src/pacta/dogfood.py
@@ -0,0 +1,184 @@
+from __future__ import annotations
+
+import base64
+import binascii
+import json
+import os
+import shutil
+import subprocess
+import tempfile
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import Any
+
+DOGFOOD_ENV = "PACTA_DOGFOOD_VERIFIER"
+DEFAULT_STATE_DIR = Path("dogfood") / "state"
+BACKEND_VERIFIED = "verified-dalek-serial"
+BACKEND_OPENSSL = "openssl"
+
+# Ed25519 SubjectPublicKeyInfo (RFC 8410): a fixed 12-byte DER prefix then
+# the raw 32-byte key. Parsing by prefix is exact for this OID, not a
+# heuristic.
+_ED25519_SPKI_PREFIX = bytes.fromhex("302a300506032b6570032100")
+
+
+@dataclass(slots=True)
+class DogfoodBuildResult:
+    built: bool
+    binary_path: Path | None
+    provenance: dict[str, Any] = field(default_factory=dict)
+    diagnostics: list[str] = field(default_factory=list)
+
+
+def pem_public_key_to_raw(public_key_path: str | Path) -> bytes:
+    """Extract the raw 32-byte Ed25519 key from an OpenSSL PEM SPKI file."""
+    text = Path(public_key_path).read_text(encoding="utf-8")
+    body = "".join(
+        line.strip()
+        for line in text.splitlines()
+        if line.strip() and not line.startswith("-----")
+    )
+    try:
+        der = base64.b64decode(body, validate=True)
+    except (binascii.Error, ValueError) as exc:
+        raise ValueError(f"Not a PEM public key: {public_key_path}: {exc}") from exc
+    if not der.startswith(_ED25519_SPKI_PREFIX) or len(der) != len(_ED25519_SPKI_PREFIX) + 32:
+        raise ValueError(
+            f"Not an Ed25519 SubjectPublicKeyInfo: {public_key_path} "
+            f"(got {len(der)} DER bytes)"
+        )
+    return der[len(_ED25519_SPKI_PREFIX):]
+
+
+def default_binary_path(state_dir: str | Path | None = None) -> Path:
+    return Path(state_dir or DEFAULT_STATE_DIR) / "pacta-verified-verify"
+
+
+def locate_verifier(state_dir: str | Path | None = None) -> Path | None:
+    """Find the dogfood verifier binary: explicit env var first, then the
+    default build location. Returns None when unavailable (callers fall
+    back to OpenSSL and must record the downgrade)."""
+    env = os.environ.get(DOGFOOD_ENV)
+    if env:
+        path = Path(env)
+        return path if path.exists() else None
+    path = default_binary_path(state_dir)
+    return path if path.exists() else None
+
+
+def load_provenance(binary_path: str | Path) -> dict[str, Any]:
+    sidecar = Path(binary_path).with_suffix(".provenance.json")
+    if sidecar.exists():
+        return json.loads(sidecar.read_text(encoding="utf-8"))
+    return {}
+
+
+def build_verifier(
+    source_workspace: str | Path,
+    crate_dir: str | Path = Path("dogfood") / "pacta-verified-verify",
+    state_dir: str | Path | None = None,
+    timeout: int = 900,
+) -> DogfoodBuildResult:
+    """Build the dogfood verifier against the pinned proven source workspace.
+
+    The serial backend is pinned via RUSTFLAGS exactly as the verified
+    extraction pins it; provenance (source path, source commit, rustc,
+    backend cfg) is recorded next to the binary and surfaces in evidence.
+    """
+    source = Path(source_workspace).expanduser().resolve()
+    crate = Path(crate_dir).resolve()
+    diagnostics: list[str] = []
+    cargo = shutil.which("cargo")
+    if not cargo:
+        return DogfoodBuildResult(False, None, {}, ["cargo is not available on PATH; cannot build the dogfood verifier."])
+    if not (source / "ed25519-dalek" / "Cargo.toml").exists():
+        return DogfoodBuildResult(
+            False,
+            None,
+            {},
+            [f"{source} does not look like the pinned curve25519-dalek source workspace (no ed25519-dalek/Cargo.toml)."],
+        )
+    template = (crate / "Cargo.toml.template").read_text(encoding="utf-8")
+    (crate / "Cargo.toml").write_text(template.replace("{{SOURCE}}", str(source)), encoding="utf-8")
+    env = dict(os.environ)
+    backend_cfg = 'curve25519_dalek_backend="serial"'
+    env["RUSTFLAGS"] = (env.get("RUSTFLAGS", "") + f" --cfg {backend_cfg}").strip()
+    completed = subprocess.run(
+        [cargo, "build", "--release", "--quiet"],
+        cwd=str(crate),
+        env=env,
+        capture_output=True,
+        text=True,
+        timeout=timeout,
+    )
+    if completed.returncode != 0:
+        tail = (completed.stderr or completed.stdout or "").strip().splitlines()[-12:]
+        return DogfoodBuildResult(False, None, {}, ["cargo build failed:"] + tail)
+    built = crate / "target" / "release" / "pacta-verified-verify"
+    if not built.exists():
+        return DogfoodBuildResult(False, None, {}, [f"cargo reported success but {built} does not exist."])
+    out = default_binary_path(state_dir)
+    out.parent.mkdir(parents=True, exist_ok=True)
+    shutil.copy2(built, out)
+    provenance = {
+        "type": "pacta.dogfood.verifier_provenance.v1",
+        "source_workspace": str(source),
+        "source_commit": _git_commit(source),
+        "backend_cfg": backend_cfg,
+        "rustc_version": _tool_version("rustc"),
+        "cargo_version": _tool_version("cargo"),
+        "entry_point": "ed25519_dalek::VerifyingKey::verify (pinned workspace)",
+        "coverage_note": (
+            "The certificates cover verify_sha512, the extraction-refactored image of this verify path "
+            "(same internals; the delta is the documented hash-wrapper refactor in the pinned source). "
+            "Field, group law, scalars, encoding/decompression, and the four apex tiers are certificate-covered; "
+            "SHA-512 and the ~15 lines of wire glue are the theorems' documented trusted base."
+        ),
+    }
+    out.with_suffix(".provenance.json").write_text(json.dumps(provenance, indent=2, sort_keys=True) + "\n", encoding="utf-8")
+    return DogfoodBuildResult(True, out, provenance, diagnostics)
+
+
+def verify_payload_dogfood(
+    payload: bytes,
+    signature: bytes,
+    public_key_path: str | Path,
+    binary: str | Path,
+    timeout: int = 30,
+) -> tuple[bool, str | None]:
+    try:
+        raw_key = pem_public_key_to_raw(public_key_path)
+    except ValueError as exc:
+        return False, str(exc)
+    with tempfile.TemporaryDirectory(prefix="pacta-dogfood-") as tmp:
+        payload_path = Path(tmp) / "payload.bin"
+        payload_path.write_bytes(payload)
+        completed = subprocess.run(
+            [str(binary), raw_key.hex(), signature.hex(), str(payload_path)],
+            capture_output=True,
+            text=True,
+            timeout=timeout,
+        )
+    if completed.returncode == 0:
+        return True, None
+    if completed.returncode == 1:
+        return False, "signature invalid (verified-path verifier)"
+    return False, (completed.stderr or completed.stdout or "dogfood verifier error").strip()
+
+
+def _git_commit(path: Path) -> str | None:
+    git = shutil.which("git")
+    if not git:
+        return None
+    completed = subprocess.run(
+        [git, "rev-parse", "HEAD"], cwd=str(path), capture_output=True, text=True, timeout=15
+    )
+    return completed.stdout.strip() if completed.returncode == 0 else None
+
+
+def _tool_version(tool: str) -> str | None:
+    path = shutil.which(tool)
+    if not path:
+        return None
+    completed = subprocess.run([path, "--version"], capture_output=True, text=True, timeout=15)
+    return completed.stdout.strip() if completed.returncode == 0 else None
diff --git a/src/pacta/signing.py b/src/pacta/signing.py
index eacea8d..7fb8bb2 100644
--- a/src/pacta/signing.py
+++ b/src/pacta/signing.py
@@ -58,22 +58,27 @@ def sign_attestation(attestation: dict[str, Any], private_key_path: str | Path,
 
 
 def verify_attestation_signature(attestation: dict[str, Any], public_key_path: str | Path) -> tuple[bool, str | None]:
+    ok, error, _backend = verify_attestation_signature_detailed(attestation, public_key_path)
+    return ok, error
+
+
+def verify_attestation_signature_detailed(attestation: dict[str, Any], public_key_path: str | Path) -> tuple[bool, str | None, str]:
     signature = attestation.get("signature") or {}
     if signature.get("scheme") != "openssl-ed25519":
-        return False, f"Unsupported attestation signature scheme: {signature.get('scheme')}"
+        return False, f"Unsupported attestation signature scheme: {signature.get('scheme')}", "none"
     encoded = signature.get("signature_base64")
     if not encoded:
-        return False, "Attestation signature is missing signature_base64."
+        return False, "Attestation signature is missing signature_base64.", "none"
     expected_digest = signature.get("payload_digest_sha256")
     actual_digest = payload_digest(attestation)
     if expected_digest and expected_digest != actual_digest:
-        return False, "Attestation payload digest does not match signature metadata."
+        return False, "Attestation payload digest does not match signature metadata.", "none"
     expected_fingerprint = signature.get("public_key_fingerprint_sha256")
     if expected_fingerprint:
         actual_fingerprint = public_key_fingerprint(public_key_path)
         if expected_fingerprint != actual_fingerprint:
-            return False, "Attestation public key fingerprint does not match signature metadata."
-    return verify_payload_ed25519(canonical_attestation_payload(attestation), encoded, public_key_path)
+            return False, "Attestation public key fingerprint does not match signature metadata.", "none"
+    return verify_payload_ed25519_detailed(canonical_attestation_payload(attestation), encoded, public_key_path)
 
 
 def sign_payload_ed25519(payload: bytes, private_key_path: str | Path) -> str:
@@ -96,11 +101,37 @@ def sign_payload_ed25519(payload: bytes, private_key_path: str | Path) -> str:
 
 
 def verify_payload_ed25519(payload: bytes, signature_base64: str, public_key_path: str | Path) -> tuple[bool, str | None]:
-    openssl = _openssl()
+    ok, error, _backend = verify_payload_ed25519_detailed(payload, signature_base64, public_key_path)
+    return ok, error
+
+
+def verify_payload_ed25519_detailed(
+    payload: bytes,
+    signature_base64: str,
+    public_key_path: str | Path,
+) -> tuple[bool, str | None, str]:
+    """Verify an Ed25519 signature, preferring pacta's DOGFOOD verifier -
+    a binary built from the pinned, certificate-covered dalek source with
+    the serial backend pinned - and falling back to OpenSSL when the
+    dogfood binary is unavailable. The third element names the backend that
+    actually ran so callers can record (and policies can require) the
+    verified path."""
+    from .dogfood import BACKEND_OPENSSL, BACKEND_VERIFIED, locate_verifier, verify_payload_dogfood
+
     try:
         signature_bytes = base64.b64decode(signature_base64, validate=True)
     except ValueError as exc:
-        return False, f"Invalid base64 signature: {exc}"
+        return False, f"Invalid base64 signature: {exc}", "none"
+    binary = locate_verifier()
+    if binary is not None:
+        ok, error = verify_payload_dogfood(payload, signature_bytes, public_key_path, binary)
+        return ok, error, BACKEND_VERIFIED
+    ok, error = _verify_payload_openssl(payload, signature_bytes, public_key_path)
+    return ok, error, BACKEND_OPENSSL
+
+
+def _verify_payload_openssl(payload: bytes, signature_bytes: bytes, public_key_path: str | Path) -> tuple[bool, str | None]:
+    openssl = _openssl()
     with tempfile.TemporaryDirectory(prefix="pacta-verify-") as tmp:
         payload_path = Path(tmp) / "payload.bin"
         signature_path = Path(tmp) / "payload.sig"
diff --git a/src/pacta/transparency.py b/src/pacta/transparency.py
index 219607b..f729bba 100644
--- a/src/pacta/transparency.py
+++ b/src/pacta/transparency.py
@@ -6,7 +6,7 @@ from pathlib import Path
 from typing import Any
 
 from .postquantum import detect_ml_dsa
-from .signing import canonical_json, public_key_fingerprint, sign_payload_ed25519, verify_payload_ed25519
+from .signing import canonical_json, public_key_fingerprint, sign_payload_ed25519, verify_payload_ed25519_detailed
 from .yamlio import load_data
 
 HASH_ALGORITHM = "RFC9162_SHA256"
@@ -206,8 +206,9 @@ def verify_signed_tree_head(
                 diagnostics.append("Signed tree head Ed25519 public-key fingerprint mismatch.")
                 statuses["ed25519"] = "key_mismatch"
             else:
-                ok, error = verify_payload_ed25519(payload, str(ed25519.get("signature_base64") or ""), public_key_path)
+                ok, error, backend = verify_payload_ed25519_detailed(payload, str(ed25519.get("signature_base64") or ""), public_key_path)
                 statuses["ed25519"] = "verified" if ok else "failed"
+                statuses["ed25519_backend"] = backend
                 if not ok:
                     diagnostics.append(f"Signed tree head Ed25519 verification failed: {error}")
 
diff --git a/tests/test_dogfood.py b/tests/test_dogfood.py
new file mode 100644
index 0000000..08ce493
--- /dev/null
+++ b/tests/test_dogfood.py
@@ -0,0 +1,66 @@
+import os
+import stat
+import subprocess
+
+from pacta.dogfood import BACKEND_VERIFIED, locate_verifier, pem_public_key_to_raw
+from pacta.signing import generate_ed25519_keypair, sign_payload_ed25519, verify_payload_ed25519_detailed
+
+
+def test_pem_spki_to_raw_roundtrip(tmp_path):
+    private_key = tmp_path / "k.key"
+    public_key = tmp_path / "k.pub"
+    generate_ed25519_keypair(private_key, public_key)
+    raw = pem_public_key_to_raw(public_key)
+    assert len(raw) == 32
+    # cross-check against openssl's own raw dump
+    dumped = subprocess.run(
+        ["openssl", "pkey", "-pubin", "-in", str(public_key), "-outform", "DER"],
+        capture_output=True, check=True,
+    ).stdout
+    assert dumped.endswith(raw)
+
+
+def test_pem_rejects_non_ed25519(tmp_path):
+    bogus = tmp_path / "bogus.pub"
+    bogus.write_text("-----BEGIN PUBLIC KEY-----\nAAAA\n-----END PUBLIC KEY-----\n")
+    import pytest
+
+    with pytest.raises(ValueError):
+        pem_public_key_to_raw(bogus)
+
+
+def test_dispatch_prefers_dogfood_binary_and_records_backend(tmp_path, monkeypatch):
+    # a fake verifier that accepts everything: proves dispatch + backend label
+    fake = tmp_path / "fake-verify"
+    fake.write_text("#!/bin/sh\necho OK\nexit 0\n")
+    fake.chmod(fake.stat().st_mode | stat.S_IEXEC)
+    private_key = tmp_path / "k.key"
+    public_key = tmp_path / "k.pub"
+    generate_ed25519_keypair(private_key, public_key)
+    payload = b"dogfood dispatch test"
+    signature = sign_payload_ed25519(payload, private_key)
+    monkeypatch.setenv("PACTA_DOGFOOD_VERIFIER", str(fake))
+    ok, error, backend = verify_payload_ed25519_detailed(payload, signature, public_key)
+    assert ok and backend == BACKEND_VERIFIED
+    monkeypatch.setenv("PACTA_DOGFOOD_VERIFIER", str(tmp_path / "missing"))
+    assert locate_verifier() is None
+    ok, error, backend = verify_payload_ed25519_detailed(payload, signature, public_key)
+    assert ok and backend == "openssl"
+
+
+def test_real_dogfood_binary_if_built(tmp_path):
+    import pytest
+
+    binary = locate_verifier()
+    if binary is None or "fake" in str(binary):
+        pytest.skip("dogfood verifier not built on this host")
+    private_key = tmp_path / "k.key"
+    public_key = tmp_path / "k.pub"
+    generate_ed25519_keypair(private_key, public_key)
+    payload = b"the proven path verifies this"
+    signature = sign_payload_ed25519(payload, private_key)
+    ok, error, backend = verify_payload_ed25519_detailed(payload, signature, public_key)
+    assert ok and backend == BACKEND_VERIFIED
+    # flip one payload byte: the proven path must reject
+    ok, error, backend = verify_payload_ed25519_detailed(payload + b"x", signature, public_key)
+    assert not ok and backend == BACKEND_VERIFIED