fix(framework): detect-platform get_gitea_token fail-loud on absent per-slot token (Patch 2b) (#890)

Co-authored-by: jason.woltje <jason@diversecanvas.com>
Co-committed-by: jason.woltje <jason@diversecanvas.com>

packages/mosaic/framework/tools/git/detect-platform.sh

@@ -511,7 +511,11 @@ get_gitea_token() {
     #    (pr-create, issue-create, …) authors under the right identity — matching the
     #    git credential helper. Backward-compatible: nothing resolvable → shared logic below.
     local _ident="${MOSAIC_GIT_IDENTITY:-}"
-    [[ -z "$_ident" ]] && _ident="$(git config --get mosaic.gitIdentity 2>/dev/null || true)"
+    local _ident_src="MOSAIC_GIT_IDENTITY"
+    if [[ -z "$_ident" ]]; then
+        _ident="$(git config --get mosaic.gitIdentity 2>/dev/null || true)"
+        _ident_src="git config mosaic.gitIdentity"
+    fi
     if [[ -n "$_ident" ]]; then
         local _idpfx=""
         case "$host" in
@@ -524,6 +528,15 @@ get_gitea_token() {
                 cat "$_idtok"
                 return 0
             fi
+            # FAIL LOUD: an explicit git identity was requested for a recognized Gitea host,
+            # but no per-slot token exists for THAT identity. Refuse to fall through to the
+            # shared/default credential loader below — silently borrowing another slot's token
+            # would post PRs/issues/reviews under the WRONG agent (e.g. rev2's review attributed
+            # to coder3), corrupting Gate-16 author≠reviewer separation. Hard-stop instead so the
+            # caller aborts loudly rather than acting as the wrong identity.
+            echo "Error: git identity '$_ident' requested (via $_ident_src) for host '$host', but no per-slot token at $_idtok." >&2
+            echo "       Refusing to borrow another slot's token. Provision the per-slot token, or unset the identity to use shared credentials." >&2
+            return 1
         fi
     fi
 

packages/mosaic/framework/tools/git/test-gitea-token-identity.sh

@@ -10,10 +10,19 @@
 #   2. Correct per-slot token file path chosen per host
 #      (gitea-usc-<id>.token vs gitea-mosaicstack-<id>.token).
 #   3. Per-slot token present -> that token is returned (agent-authored calls).
-#   4. Per-slot token absent -> falls back to the shared credential-loader
-#      token (backward-compat / no-op for hosts without per-slot tokens).
-#   5. Unrelated host with no shared credentials configured -> failure
-#      (unchanged, existing behavior).
+#   4. No identity requested -> shared credential-loader token (backward
+#      compat, unchanged).
+#   5. Patch 2b — explicit identity + recognized Gitea host + ABSENT per-slot
+#      token for that identity -> FAIL LOUD (nonzero return, empty stdout, a
+#      stderr diagnostic naming identity/source/host/expected path). Must NOT
+#      fall through to the shared/default token (Gate-16 author≠reviewer
+#      integrity — never silently borrow another slot's credentials). Covered
+#      for both identity sources (git config, MOSAIC_GIT_IDENTITY env) and
+#      for a same-identity cross-host case (token exists for one host, not
+#      the other).
+#   6. Scope containment: identity requested + an UNRECOGNIZED Gitea host (no
+#      per-slot token scheme) -> Patch 2b does not apply; existing
+#      fall-through behavior is unchanged.
 #
 # Uses a stubbed credentials.json + stubbed per-slot token files under a fake
 # HOME. NEVER reads real secrets or touches the real ~/.config/mosaic/secrets.
@@ -95,24 +104,110 @@ out=$(call_get_gitea_token "git.mosaicstack.dev" MOSAIC_GIT_IDENTITY=agentB)
 assert_eq "env beats git-config identity token" "agentB-mosaicstack-token" "$out"
 
 # ---------------------------------------------------------------------------
-# 4. Identity resolves but has no per-slot token for THIS host -> falls back
-#    to the shared token (per-agent identity is opt-in per host).
+# 4. FAIL LOUD (Patch 2b): an identity is explicitly requested (via git config
+#    mosaic.gitIdentity, and separately via MOSAIC_GIT_IDENTITY env) for a
+#    RECOGNIZED Gitea host, but no per-slot token exists for THAT identity.
+#    Must NOT fall through to the shared/default token — silently borrowing
+#    another slot's credentials would post PRs/issues/reviews as the WRONG
+#    agent (Gate-16 author≠reviewer integrity break). Expect: nonzero return,
+#    EMPTY stdout (no token — shared or otherwise — leaked), and a stderr
+#    diagnostic naming the identity, its source, the host, and the expected
+#    per-slot token path.
 # ---------------------------------------------------------------------------
+assert_failloud() {
+  local desc="$1" host="$2" ident="$3" expected_tok_path="$4"; shift 4
+  local stderr_file="$WORK_DIR/stderr.tmp"
+  : > "$stderr_file"
+  set +e
+  local stdout
+  stdout=$(call_get_gitea_token "$host" "$@" 2>"$stderr_file")
+  local rc=$?
+  set -e
+  local stderr
+  stderr=$(cat "$stderr_file")
+  if [[ "$rc" -eq 0 ]]; then
+    echo "FAIL: $desc — expected nonzero return, got 0 (stdout='$stdout')" >&2
+    fail=1
+  fi
+  if [[ -n "$stdout" ]]; then
+    echo "FAIL: $desc — expected empty stdout (no token leaked), got '$stdout'" >&2
+    fail=1
+  fi
+  if [[ "$stderr" != *"$ident"* ]]; then
+    echo "FAIL: $desc — stderr does not name the requested identity '$ident':" >&2
+    echo "$stderr" >&2
+    fail=1
+  fi
+  if [[ "$stderr" != *"$host"* ]]; then
+    echo "FAIL: $desc — stderr does not name the host '$host':" >&2
+    echo "$stderr" >&2
+    fail=1
+  fi
+  if [[ "$stderr" != *"$expected_tok_path"* ]]; then
+    echo "FAIL: $desc — stderr does not name the expected per-slot token path '$expected_tok_path':" >&2
+    echo "$stderr" >&2
+    fail=1
+  fi
+  if [[ "$stderr" == *"shared"*"token"* ]]; then
+    echo "FAIL: $desc — stderr unexpectedly mentions a shared token value:" >&2
+    echo "$stderr" >&2
+    fail=1
+  fi
+}
+
+# 4a. git config mosaic.gitIdentity source, recognized host (mosaicstack),
+#     shared token IS present but must not be borrowed.
 git -C "$REPO_DIR" config mosaic.gitIdentity no-such-agent
-out=$(call_get_gitea_token "git.mosaicstack.dev")
-assert_eq "no per-slot token falls back to shared" "shared-mosaicstack-token" "$out"
+assert_failloud "fail-loud via git-config identity (recognized host)" \
+  "git.mosaicstack.dev" "no-such-agent" \
+  "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-mosaicstack-no-such-agent.token"
+git -C "$REPO_DIR" config --unset mosaic.gitIdentity
+
+# 4b. MOSAIC_GIT_IDENTITY env source (takes priority over git config), same
+#     recognized-host / absent-token scenario -> also fails loud.
+assert_failloud "fail-loud via MOSAIC_GIT_IDENTITY env (recognized host)" \
+  "git.mosaicstack.dev" "no-such-agent-env" \
+  "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-mosaicstack-no-such-agent-env.token" \
+  MOSAIC_GIT_IDENTITY=no-such-agent-env
 
 # ---------------------------------------------------------------------------
 # 5. Correct per-slot token PATH per host: same agent id, only a usc token
-#    exists -> usc host returns it, mosaicstack host must NOT leak it and
-#    instead falls back to the shared mosaicstack token.
+#    exists. usc host returns it (happy path, unchanged). mosaicstack host
+#    has NO per-slot token for this identity -> Patch 2b fail-loud applies
+#    there too (must NOT fall back to the shared mosaicstack token, and must
+#    NOT leak the agent's usc token either).
 # ---------------------------------------------------------------------------
 echo -n "agentD-usc-token" > "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-usc-agentD.token"
 git -C "$REPO_DIR" config mosaic.gitIdentity agentD
 out=$(call_get_gitea_token "git.uscllc.com")
 assert_eq "host-scoped token path (usc)" "agentD-usc-token" "$out"
-out=$(call_get_gitea_token "git.mosaicstack.dev")
-assert_eq "host-scoped token path (no cross-host leak)" "shared-mosaicstack-token" "$out"
+assert_failloud "fail-loud on cross-host absence (no fallback, no cross-host leak)" \
+  "git.mosaicstack.dev" "agentD" \
+  "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-mosaicstack-agentD.token"
+git -C "$REPO_DIR" config --unset mosaic.gitIdentity
+
+# ---------------------------------------------------------------------------
+# 6. Scope containment: identity explicitly requested, but the host is NOT a
+#    recognized Gitea host (no per-slot token scheme at all) -> Patch 2b does
+#    NOT apply; existing fall-through behavior is unchanged (ends in the
+#    pre-existing generic failure since no shared credentials match either,
+#    NOT the fail-loud diagnostic path).
+# ---------------------------------------------------------------------------
+git -C "$REPO_DIR" config mosaic.gitIdentity no-such-agent
+set +e
+out=$(call_get_gitea_token "github.com" 2>"$WORK_DIR/stderr-scope.tmp")
+rc=$?
+set -e
+err=$(cat "$WORK_DIR/stderr-scope.tmp")
+if [[ "$rc" -eq 0 ]]; then
+  echo "FAIL: unrecognized host + identity — expected nonzero (no credentials configured), got 0" >&2
+  fail=1
+fi
+if [[ "$err" == *"no per-slot token at"* ]]; then
+  echo "FAIL: unrecognized host + identity — fail-loud diagnostic must not fire for a host with no per-slot scheme:" >&2
+  echo "$err" >&2
+  fail=1
+fi
 git -C "$REPO_DIR" config --unset mosaic.gitIdentity
 
 if [[ "$fail" -eq 0 ]]; then