diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
new file mode 100644
index 0000000..1c6de8f
--- /dev/null
+++ b/.github/copilot-instructions.md
@@ -0,0 +1,77 @@
+# Copilot instructions for wolfCOSE
+
+wolfCOSE is a strictly zero-allocation C library implementing CBOR (RFC 8949)
+and COSE (RFC 9052/9053), plus RFC 8230 (RSA keys) and RFC 9964 (ML-DSA), on
+top of wolfCrypt. It runs on constrained and FIPS-bounded targets and parses
+untrusted, attacker-controlled bytes (CBOR/COSE messages and keys).
+
+When reviewing a pull request, act as a security and correctness reviewer
+performing the primary pre-merge gate, in the spirit of a focused
+security-review pass. Prioritize real vulnerabilities and behavioral bugs the
+diff introduces. Be precise, high-confidence, and brief. A short list of solid
+findings is far more useful than a long list of nits.
+
+## How to review
+
+1. Triage the diff by risk. Treat as HIGH RISK anything touching CBOR/COSE
+   parsing of untrusted input, buffer and length handling, key/secret handling,
+   algorithm selection and verification, and error paths. Spend your attention
+   there.
+2. For each changed region, reason about the behavioral delta: what did the
+   code do before, what does it do now, and what new attack surface or weakened
+   check does the change introduce. If the diff removes a check or a previously
+   added security fix, call that out as a likely regression.
+3. Report a finding only when you can name the concrete failure and, where it
+   applies, the input that triggers it. Assign a severity (Critical, High,
+   Medium, Low) and include the relevant CWE.
+
+## What to look for
+
+- Memory safety: out-of-bounds reads and writes, missing or wrong length checks
+  before copies, pointer arithmetic into caller-provided buffers, off-by-one on
+  bstr/array/map lengths (CWE-120, CWE-125, CWE-787).
+- Integer issues: overflow or underflow in size and length math, signed and
+  unsigned confusion, and truncation when casting lengths to `word32` (CWE-190,
+  CWE-191).
+- NULL and uninitialized use: missing NULL checks on parameters and return
+  values, use of a buffer before it is populated (CWE-476).
+- CBOR and COSE parsing of untrusted input: unchecked element counts, lengths,
+  or nesting depth; trusting a header or a decoded length without validating it
+  against the remaining buffer; accepting non-preferred or trailing CBOR.
+- Cryptographic correctness and misuse: nonce or IV reuse, algorithm confusion
+  (dispatching on an unauthenticated `alg`), comparing secrets or MAC tags with
+  non-constant-time `memcmp`, and unchecked crypto return codes (CWE-327,
+  CWE-208, CWE-347).
+- Zeroization: sensitive data (keys, seeds, shared secrets, plaintext, crypto
+  intermediates) must be cleared with `wolfCose_ForceZero` (wolfCOSE's secure
+  scrub helper) on every exit path, including error and early-return paths. Flag
+  missing or wrong-size scrubs and untracked temporary copies.
+- Logic and contracts: inverted conditions, wrong enum or label, copy-paste
+  errors, missing error checks, error paths that skip cleanup, and API misuse
+  (wrong call order, use after a failed call).
+- Spec conformance: deviations from RFC 9052/9053, RFC 8949 deterministic
+  encoding, RFC 8230 (RSA key parameters), or RFC 9964 (ML-DSA / AKP) message
+  and key formats.
+
+## Do not report
+
+These are out of scope here. Other tooling owns them, and raising them adds
+noise rather than safety.
+
+- Style, formatting, naming, or comment-density observations. Code style is
+  enforced by the project's own rules and by cppcheck, clang-tidy, and MISRA
+  checks in CI.
+- Maintainability nits such as "function is too long" or "poorly documented
+  function". Do not flag comment ratios or function length.
+- Any suggestion that introduces dynamic allocation. wolfCOSE is strictly
+  zero-allocation. Never propose `malloc`, `calloc`, `realloc`, `free`, or the
+  `XMALLOC`/`XFREE`/`XREALLOC` wrappers. Large objects use scoped or static
+  storage, never the heap.
+- C++ idioms or constructs outside C89/C99. The library targets C99 and its
+  public headers must also compile as C++.
+- `wolfCose_ForceZero` replaced by `memset` or a plain loop (the project
+  deliberately uses `wolfCose_ForceZero` so the scrub is not optimized away);
+  do not suggest the reverse.
+
+Keep comments few, concrete, and security or correctness focused. If you are
+not confident a finding is real, leave it out.
diff --git a/.github/semgrep-rules.yml b/.github/semgrep-rules.yml
new file mode 100644
index 0000000..f382196
--- /dev/null
+++ b/.github/semgrep-rules.yml
@@ -0,0 +1,66 @@
+# wolfCOSE deterministic security rules (Semgrep).
+#
+# These encode wolfCOSE invariants that are decidable by pattern and currently
+# have zero hits, so they pass today and fail the build on any future
+# violation. Run with: semgrep scan --config .github/semgrep-rules.yml --error
+#
+# Style/maintainability is intentionally out of scope (owned by cppcheck,
+# clang-tidy, and MISRA checks). These rules only enforce security invariants.
+
+rules:
+  - id: wolfcose-no-dynamic-allocation
+    languages: [c]
+    severity: ERROR
+    message: >-
+      wolfCOSE is strictly zero-allocation. Dynamic memory
+      (malloc/calloc/realloc/free, alloca, strdup, or the XMALLOC/XFREE/XREALLOC
+      wrappers) must never appear in the core library. Use a caller-provided
+      buffer or scoped/static storage instead.
+    paths:
+      include:
+        - src/
+        - include/wolfcose/
+    pattern-either:
+      - pattern: malloc(...)
+      - pattern: calloc(...)
+      - pattern: realloc(...)
+      - pattern: free(...)
+      - pattern: aligned_alloc(...)
+      - pattern: alloca(...)
+      - pattern: strdup(...)
+      - pattern: XMALLOC(...)
+      - pattern: XFREE(...)
+      - pattern: XREALLOC(...)
+
+  - id: wolfcose-unsafe-libc
+    languages: [c]
+    severity: ERROR
+    message: >-
+      Unbounded C library function. Use a length-bounded alternative
+      (XMEMCPY/XMEMMOVE with an explicit size, snprintf) so a length cannot run
+      past the destination buffer.
+    paths:
+      include:
+        - src/
+        - include/wolfcose/
+    pattern-either:
+      - pattern: gets(...)
+      - pattern: strcpy(...)
+      - pattern: strcat(...)
+      - pattern: sprintf(...)
+      - pattern: vsprintf(...)
+
+  - id: wolfcose-non-constant-time-compare
+    languages: [c]
+    severity: ERROR
+    message: >-
+      memcmp/XMEMCMP is not constant-time. In the core library, comparing a
+      MAC tag, key, or shared secret with a variable-time compare leaks timing
+      information (CWE-208). Use ConstantCompare for secret-dependent
+      comparisons.
+    paths:
+      include:
+        - src/
+    pattern-either:
+      - pattern: memcmp(...)
+      - pattern: XMEMCMP(...)
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
new file mode 100644
index 0000000..3ab3837
--- /dev/null
+++ b/.github/workflows/codeql.yml
@@ -0,0 +1,71 @@
+name: CodeQL
+
+on:
+  push:
+    branches: [ 'main', 'release/**' ]
+  pull_request:
+    branches: [ '*' ]
+  schedule:
+    - cron: '0 7 * * 1'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+  # Required so CodeQL can upload findings to the Security tab.
+  security-events: write
+
+jobs:
+  analyze:
+    name: CodeQL (C, security)
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y autoconf automake libtool
+
+      # Full-feature wolfSSL so every wolfCOSE code path is compiled and
+      # therefore visible to CodeQL.
+      - name: Build wolfSSL
+        run: |
+          cd ~
+          git clone --depth 1 https://github.com/wolfSSL/wolfssl.git
+          cd wolfssl
+          ./autogen.sh
+          ./configure --enable-ecc --enable-ed25519 --enable-ed448 \
+                      --enable-curve25519 --enable-curve448 \
+                      --enable-aesgcm --enable-aesccm --enable-aescbc \
+                      --enable-sha384 --enable-sha512 \
+                      --enable-keygen --enable-hkdf --enable-aeskeywrap \
+                      --enable-chacha --enable-poly1305 \
+                      --enable-mldsa --enable-rsapss \
+                      --prefix=$HOME/wolfssl-install
+          make -j$(nproc)
+          make install
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: c-cpp
+          build-mode: manual
+          # security-extended runs only the security query suites. The default
+          # "security-and-quality" pack also flags maintainability nits (long
+          # functions, comment density), which we intentionally exclude here.
+          queries: security-extended
+
+      - name: Build wolfCOSE
+        run: |
+          export WOLFSSL_DIR=$HOME/wolfssl-install
+          make CFLAGS="-std=c99 -DHAVE_ANONYMOUS_INLINE_AGGREGATES=1 -Os -Wall -Wextra -Wpedantic -Wshadow -Wconversion -I./include -isystem $WOLFSSL_DIR/include" \
+               LDFLAGS="-L$WOLFSSL_DIR/lib -lwolfssl"
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:c-cpp"
diff --git a/.github/workflows/house-style.yml b/.github/workflows/house-style.yml
new file mode 100644
index 0000000..d3db7c4
--- /dev/null
+++ b/.github/workflows/house-style.yml
@@ -0,0 +1,24 @@
+name: House Style
+
+on:
+  push:
+    branches: [ 'main', 'release/**' ]
+  pull_request:
+    branches: [ '*' ]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  house-style:
+    name: wolfCOSE house-style conventions
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@v4
+      - name: Check conventions (no goto, C-style comments, banner style, no tabs/trailing space)
+        run: sh scripts/check_house_style.sh
diff --git a/.github/workflows/semgrep.yml b/.github/workflows/semgrep.yml
new file mode 100644
index 0000000..6f08f83
--- /dev/null
+++ b/.github/workflows/semgrep.yml
@@ -0,0 +1,34 @@
+name: Semgrep
+
+on:
+  push:
+    branches: [ 'main', 'release/**' ]
+  pull_request:
+    branches: [ '*' ]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  semgrep:
+    name: Semgrep (wolfCOSE security rules)
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.x'
+
+      - name: Install Semgrep
+        run: pip install --quiet semgrep
+
+      # --error makes the job fail on any finding. The rules self-scope via
+      # their `paths:` blocks, so scanning the whole tree is fine.
+      - name: Run wolfCOSE security rules
+        run: semgrep scan --config .github/semgrep-rules.yml --error --quiet .
diff --git a/scripts/check_house_style.sh b/scripts/check_house_style.sh
new file mode 100755
index 0000000..2914b22
--- /dev/null
+++ b/scripts/check_house_style.sh
@@ -0,0 +1,45 @@
+#!/bin/sh
+# wolfCOSE house-style check.
+#
+# Enforces the repo's C conventions across all tracked C sources (the vendored
+# lightpanda tree is excluded). Comment and whitespace conventions are text, not
+# code structure, so git grep is the right tool here. Run from the repo root:
+#   sh scripts/check_house_style.sh
+# Exits non-zero on any deviation.
+
+status=0
+PATHS='*.c *.h :(exclude)lightpanda/'
+tab=$(printf '\t')
+
+report() {
+    matches=$(cat)
+    if [ -n "$matches" ]; then
+        printf '\nFAIL: %s\n' "$1"
+        printf '%s\n' "$matches"
+        status=1
+    fi
+}
+
+# No goto anywhere; new code uses fallthrough cleanup with a single exit.
+git grep -nw goto -- $PATHS | report "goto is banned (use fallthrough cleanup gated on 'if (ret == WOLFCOSE_SUCCESS)')"
+
+# C-style comments only; // line comments are not allowed (URLs in strings/headers excepted).
+git grep -nE '//' -- $PATHS | grep -vE 'https?://|s?ftp://|file://' | report "C++ // comments are banned; use /* ... */"
+
+# Section banners use the /* ----- ... ----- */ style, not ===== / ##### / **** runs.
+git grep -nE '/\*[* ]*(={4,}|#{4,}|\*{4,})' -- $PATHS | report "section banners must use the /* ----- ... ----- */ style"
+
+# Null-check pointers with != NULL, not if (!ptr).
+git grep -nE 'if \(![A-Za-z_]' -- $PATHS | report "null-check pointers with '!= NULL', not 'if (!ptr)'"
+
+# Spaces, no tabs.
+git grep -nE "$tab" -- $PATHS | report "tabs are banned in C sources; use spaces"
+
+# No trailing whitespace.
+git grep -nE ' +$' -- $PATHS | report "trailing whitespace"
+
+if [ "$status" -ne 0 ]; then
+    printf '\nHouse-style check failed.\n'
+    exit 1
+fi
+printf 'House-style check passed.\n'
diff --git a/tests/test_cose.c b/tests/test_cose.c
index 63b42d0..8276bab 100644
--- a/tests/test_cose.c
+++ b/tests/test_cose.c
@@ -13289,10 +13289,8 @@ static void test_force_failure_crypto(void)
 }
 #endif /* WOLFCOSE_FORCE_FAILURE */
 
-/* ========================================================
- * Negative Test Coverage - Phases 1-10
- * Tests for validation/error handling code paths
- * ======================================================== */
+/* ----- Negative Test Coverage - Phases 1-10
+ * Tests for validation/error handling code paths ----- */
 
 /* ----- Phase 1: Buffer Too Small Tests ----- */
 #ifdef WOLFCOSE_HAVE_ES256
@@ -16491,7 +16489,7 @@ int test_cose(void)
     test_cose_key_ecc_public_only();
 #endif
 
-    /* ======== Negative Test Coverage - Phases 1-10 ======== */
+    /* ----- Negative Test Coverage - Phases 1-10 ----- */
     TEST_LOG("\n--- Negative Test Coverage (Phases 1-10) ---\n");
 
     /* Phase 1: Buffer Too Small Tests */