feat: per-agent Gitea identity resolution (#873)

Closes #873

Mos (id-11) Gate-16 merge: independent APPROVE @4b472a22 (author-blocker dissolved via (a) re-author, identical tree hash to tech-approved head), author id2 != approver id11, clean mosaic-coder commit-author, CI green wp1985. Framework train COMPLETE 6/6.

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

packages/mosaic/framework/tools/git/README.md

@@ -33,3 +33,64 @@ The Gitea API token is **never passed on a curl command line.** An `Authorizatio
 Both `pr-review.sh` and `issue-comment.sh` accept an optional `--login <name>` flag that overrides the automatically detected Gitea login for that single invocation. The override selects **which credential the REST write, the `/user` identity lookup, and the read-back all use** — its token is resolved from the tea config for that login name (`get_gitea_token_for_login`), falling back to the repo host's credential when no login is named. The resolved login is **host- and port-bound**: the login's configured URL host **and effective port** (the scheme's default port — 80 for `http`, 443 for `https` — applies when a port is omitted, symmetrically on both sides) must match the repo remote's, so a login name shared across hosts (or an override configured for a different Gitea, including one on a different port of the same host) can never send one host's credential to another — a host or port mismatch fails closed rather than leaking a cross-host token. Resolving the acting identity and the read-back from the _same_ login that performs the write is essential: a write performed under an overridden login must be verified against that login's identity, not the host default's. Callers who need a different login than the host default should pass `--login <reviewer-login>`.
 
 As a durable successor to this mechanism, consider giving each reviewer/approver slot its own dedicated Gitea login credential, so that author≠reviewer holds at the credential level rather than relying on wrapper-level `--login` bookkeeping. This is a recommendation for future hardening, not something implemented by this flag.
+
+## Per-agent Gitea identity (Gate-16 author≠reviewer)
+
+By default, git push/fetch (via `git-credential-mosaic`) and the API wrappers above (via
+`detect-platform.sh`'s `get_gitea_token`) all authenticate as the single shared Gitea
+account/token configured through `tools/_lib/credentials.sh`. That means every agent in a
+fleet commits, pushes, and opens PRs under one identity — with no cryptographic
+separation between an author and a reviewer.
+
+Both `git-credential-mosaic` and `get_gitea_token()` resolve an optional **per-agent
+identity** before falling back to the shared account:
+
+1. `MOSAIC_GIT_IDENTITY` environment variable, or
+2. `git config --get mosaic.gitIdentity` (set per-worktree; persists on disk across
+   non-persistent shells — `git config mosaic.gitIdentity <agent-id>`), or
+3. (git-credential-mosaic only) the username git itself supplies for the credential
+   request.
+
+If the resolved identity has a token file at
+`~/.config/mosaic/secrets/gitea-tokens/gitea-{usc,mosaicstack}-<agent-id>.token`, that
+identity + token is used. **Nothing configured → nothing changes**: with no per-slot
+token file present, both tools fall through to the existing shared-account path
+unchanged, so this feature is a no-op on any host that hasn't provisioned per-slot
+tokens.
+
+### Enabling it for a clone
+
+The framework installer syncs `git-credential-mosaic` to
+`~/.config/mosaic/tools/git/git-credential-mosaic` (executable) on every install/update,
+but does **not** register it as git's credential helper automatically. Registration is a
+one-time, explicit step:
+
+```bash
+# Per-repo (recommended — scopes the helper to this clone only):
+git config credential.helper "$HOME/.config/mosaic/tools/git/git-credential-mosaic"
+
+# Per-worktree identity pin (Gate-16 separation):
+git config mosaic.gitIdentity <agent-id>
+```
+
+This is deliberately **not** auto-registered on install/update: `credential.helper` is
+global, order-sensitive git config (`~/.gitconfig`) that can already hold an
+operator-chosen credential manager (keychain, `store`, `manager-core`, …) for
+repositories unrelated to Mosaic. Silently inserting an entry on every framework
+install/upgrade risks reordering or shadowing that operator-owned surface across the
+whole host — the same operator-owned config the installer's manifest system is
+otherwise careful never to touch. Because identity is already resolved per-worktree
+(`mosaic.gitIdentity`), the correct granularity for registering the helper is per-clone
+too, so a documented manual step is the right shape here, not a global auto-write.
+
+### PowerShell parity
+
+`detect-platform.ps1`'s Gitea wrappers authenticate through `tea` CLI logins
+(`Get-GiteaLoginForHost`), not a raw-token `get_gitea_token`-equivalent function — there
+is nothing to prepend the identity-resolution block to on the PowerShell side. A native
+PowerShell git-credential helper is also unnecessary: `git-credential-mosaic` is invoked
+by git's credential-helper protocol (stdin/stdout), which works identically under Git for
+Windows' bundled `bash`/`sh` when configured via `credential.helper`, without a `.ps1`
+counterpart. A `tea`-login-based per-agent identity for the PowerShell wrappers is a
+separate, larger design (mapping identities to `tea login` profiles) and is out of scope
+here.

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

@@ -505,6 +505,28 @@ get_gitea_token() {
     script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
     local cred_loader="$script_dir/../_lib/credentials.sh"
 
+    # 0. Per-agent identity (Gate-16 author≠reviewer). If MOSAIC_GIT_IDENTITY, or the
+    #    per-worktree `git config mosaic.gitIdentity`, resolves to an agent that has a
+    #    stored per-slot token for this host, act AS that agent so API tooling
+    #    (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="$(git config --get mosaic.gitIdentity 2>/dev/null || true)"
+    if [[ -n "$_ident" ]]; then
+        local _idpfx=""
+        case "$host" in
+            git.uscllc.com)      _idpfx=gitea-usc ;;
+            git.mosaicstack.dev) _idpfx=gitea-mosaicstack ;;
+        esac
+        if [[ -n "$_idpfx" ]]; then
+            local _idtok="$HOME/.config/mosaic/secrets/gitea-tokens/${_idpfx}-${_ident}.token"
+            if [[ -r "$_idtok" ]]; then
+                cat "$_idtok"
+                return 0
+            fi
+        fi
+    fi
+
     # 1. Mosaic credential loader (host → service mapping, run in subshell to avoid polluting env)
     if [[ -f "$cred_loader" ]]; then
         local token

packages/mosaic/framework/tools/git/git-credential-mosaic

@@ -0,0 +1,69 @@
+#!/bin/bash
+# git-credential-mosaic — git credential helper — resolves Gitea tokens from
+# the Mosaic credential store at runtime so remote URLs never embed secrets.
+#
+# Install (one-time, per clone or globally):
+#   git config credential.helper "$HOME/.config/mosaic/tools/git/git-credential-mosaic"
+#   # or, fleet-wide: git config --global credential.helper "$HOME/.config/mosaic/tools/git/git-credential-mosaic"
+#
+# Per-agent Gate-16 identity (author != reviewer separation):
+#   git config mosaic.gitIdentity <agent-id>   # per-worktree, persists on disk
+#   # or: export MOSAIC_GIT_IDENTITY=<agent-id>
+#
+# Resolution priority: MOSAIC_GIT_IDENTITY env > git config mosaic.gitIdentity
+# (per-worktree, survives across non-persistent shells) > git-supplied username
+# (credential.username / URL). When the resolved identity has a matching
+# per-agent token file, use it instead of the shared account. Backward
+# compatible: nothing resolvable -> shared token (unchanged behavior).
+[ "$1" = "get" ] || exit 0
+host=""; username_in=""
+while IFS= read -r line; do
+  [ -z "$line" ] && break
+  case "$line" in
+    host=*)     host=${line#host=};;
+    username=*) username_in=${line#username=};;
+  esac
+done
+# Per-agent identity resolution (Gate-16 author≠reviewer separation).
+# Priority: MOSAIC_GIT_IDENTITY env  >  git config mosaic.gitIdentity (per-worktree,
+# survives across non-persistent shells)  >  git-supplied username (credential.username
+# / URL). When the resolved identity has a matching per-agent token, use it instead of
+# the shared account. Backward-compatible: nothing resolvable → shared token.
+ident="$MOSAIC_GIT_IDENTITY"
+[ -z "$ident" ] && ident=$(git config --get mosaic.gitIdentity 2>/dev/null)
+[ -z "$ident" ] && ident="$username_in"
+if [ -n "$ident" ]; then
+  case "$host" in
+    git.uscllc.com)      idpfx=gitea-usc;;
+    git.mosaicstack.dev) idpfx=gitea-mosaicstack;;
+    *) idpfx="";;
+  esac
+  if [ -n "$idpfx" ]; then
+    idtok="$HOME/.config/mosaic/secrets/gitea-tokens/${idpfx}-${ident}.token"
+    if [ -r "$idtok" ]; then
+      echo "username=${ident}"
+      echo "password=$(cat "$idtok")"
+      exit 0
+    fi
+  fi
+fi
+case "$host" in
+  git.uscllc.com)      svc=gitea-usc;;
+  git.mosaicstack.dev) svc=gitea-mosaicstack;;
+  *) exit 0;;
+esac
+# Script-relative (not $HOME-absolute) so this resolves correctly regardless
+# of where the framework installer places tools/ under $HOME — mirrors
+# detect-platform.sh's own cred_loader resolution in this same directory.
+script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# shellcheck source=../_lib/credentials.sh
+source "$script_dir/../_lib/credentials.sh"
+load_credentials "$svc" >/dev/null 2>&1 || exit 0
+# GITEA_USER is not populated by load_credentials (it only exports
+# GITEA_URL/GITEA_TOKEN for gitea-*), so this fallback is normally taken. Gitea's
+# git-over-HTTP auth authenticates from the token itself (the password field),
+# not from the username string, so any non-empty placeholder works here — this
+# is deliberately NOT a real account name (framework files must stay
+# operator-agnostic; see tools/quality/scripts/verify-sanitized.sh).
+echo "username=${GITEA_USER:-git}"
+echo "password=$GITEA_TOKEN"

packages/mosaic/framework/tools/git/test-git-credential-mosaic.sh

@@ -0,0 +1,161 @@
+#!/usr/bin/env bash
+# Regression harness for `git-credential-mosaic` — per-agent Gitea identity
+# resolution (Gate-16 author≠reviewer separation).
+#
+# Covers:
+#   1. Identity resolution priority: MOSAIC_GIT_IDENTITY env > git config
+#      mosaic.gitIdentity (per-worktree) > git-supplied username.
+#   2. Correct per-slot token file path chosen per host
+#      (gitea-usc-<id>.token vs gitea-mosaicstack-<id>.token).
+#   3. Per-slot token present -> emits that identity + token.
+#   4. Per-slot token absent -> falls back to the shared account
+#      (backward-compat / no-op for hosts without per-slot tokens).
+#   5. Unknown/unrelated host -> exits 0 with no output (passthrough).
+#
+# Uses stubbed token files under a fake HOME + a real (throwaway) git repo.
+# NEVER reads real secrets or touches the real ~/.config/mosaic/secrets.
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+WORK_DIR="${MOSAIC_TEST_WORK_DIR:-$PWD/.mosaic-test-work/git-credential-mosaic}"
+FAKE_HOME="$WORK_DIR/home"
+REPO_DIR="$WORK_DIR/repo"
+# Mirror the real deployed layout (~/.config/mosaic/tools/{git,_lib}/) under the
+# fake HOME: git-credential-mosaic resolves its credentials.sh sibling via a
+# script-relative path (BASH_SOURCE), so the copy must live next to a stubbed
+# _lib/credentials.sh, not the real one, to keep this test hermetic.
+HELPER="$FAKE_HOME/.config/mosaic/tools/git/git-credential-mosaic"
+
+rm -rf "$WORK_DIR"
+mkdir -p "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens" \
+         "$FAKE_HOME/.config/mosaic/tools/git" \
+         "$FAKE_HOME/.config/mosaic/tools/_lib" \
+         "$REPO_DIR"
+
+cp "$SCRIPT_DIR/git-credential-mosaic" "$HELPER"
+chmod +x "$HELPER"
+
+git -C "$REPO_DIR" init -q
+git -C "$REPO_DIR" config user.email "test@example.invalid"
+git -C "$REPO_DIR" config user.name "Test"
+
+# Fake shared-account credential loader — stands in for
+# tools/_lib/credentials.sh's load_credentials(), scoped to this test only.
+cat > "$FAKE_HOME/.config/mosaic/tools/_lib/credentials.sh" <<'SH'
+load_credentials() {
+  case "$1" in
+    gitea-mosaicstack) GITEA_URL="https://git.mosaicstack.dev"; GITEA_TOKEN="shared-mosaicstack-token"; export GITEA_URL GITEA_TOKEN; return 0 ;;
+    gitea-usc)         GITEA_URL="https://git.uscllc.com"; GITEA_TOKEN="shared-usc-token"; export GITEA_URL GITEA_TOKEN; return 0 ;;
+    *) return 1 ;;
+  esac
+}
+SH
+
+fail=0
+assert_eq() {
+  local desc="$1" expected="$2" actual="$3"
+  if [[ "$expected" != "$actual" ]]; then
+    echo "FAIL: $desc — expected '$expected', got '$actual'" >&2
+    fail=1
+  fi
+}
+
+# Feed "host=<h>\nusername=<u>\n\n" on stdin (mirrors git's credential protocol)
+# and run the helper with the fake HOME, inside REPO_DIR (so `git config
+# mosaic.gitIdentity` resolves per-worktree), plus any extra env passed in $@.
+run_helper() {
+  local host="$1" username_in="$2"; shift 2
+  (
+    cd "$REPO_DIR"
+    env -i HOME="$FAKE_HOME" PATH="$PATH" "$@" bash "$HELPER" get <<EOF
+host=$host
+username=$username_in
+
+EOF
+  )
+}
+
+# ---------------------------------------------------------------------------
+# 1. No identity resolvable anywhere, no per-slot token -> shared fallback
+#    (backward-compat: unchanged behavior when nothing is configured).
+# ---------------------------------------------------------------------------
+git -C "$REPO_DIR" config --unset mosaic.gitIdentity 2>/dev/null || true
+out=$(run_helper "git.mosaicstack.dev" "")
+assert_eq "shared fallback: username" "username=git" "$(echo "$out" | grep '^username=')"
+assert_eq "shared fallback: password" "password=shared-mosaicstack-token" "$(echo "$out" | grep '^password=')"
+
+# ---------------------------------------------------------------------------
+# 2. git-supplied username resolves to an identity WITH a per-slot token ->
+#    that identity + token wins over the shared account.
+# ---------------------------------------------------------------------------
+echo -n "agentA-mosaicstack-token" > "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-mosaicstack-agentA.token"
+out=$(run_helper "git.mosaicstack.dev" "agentA")
+assert_eq "username-resolved identity: username" "username=agentA" "$(echo "$out" | grep '^username=')"
+assert_eq "username-resolved identity: password" "password=agentA-mosaicstack-token" "$(echo "$out" | grep '^password=')"
+
+# ---------------------------------------------------------------------------
+# 3. git config mosaic.gitIdentity (per-worktree) beats git-supplied username.
+# ---------------------------------------------------------------------------
+echo -n "agentB-mosaicstack-token" > "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-mosaicstack-agentB.token"
+git -C "$REPO_DIR" config mosaic.gitIdentity agentB
+out=$(run_helper "git.mosaicstack.dev" "agentA")
+assert_eq "git-config beats username: username" "username=agentB" "$(echo "$out" | grep '^username=')"
+assert_eq "git-config beats username: password" "password=agentB-mosaicstack-token" "$(echo "$out" | grep '^password=')"
+
+# ---------------------------------------------------------------------------
+# 4. MOSAIC_GIT_IDENTITY env beats git config mosaic.gitIdentity.
+# ---------------------------------------------------------------------------
+echo -n "agentC-mosaicstack-token" > "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-mosaicstack-agentC.token"
+out=$(run_helper "git.mosaicstack.dev" "agentA" MOSAIC_GIT_IDENTITY=agentC)
+assert_eq "env beats git-config: username" "username=agentC" "$(echo "$out" | grep '^username=')"
+assert_eq "env beats git-config: password" "password=agentC-mosaicstack-token" "$(echo "$out" | grep '^password=')"
+git -C "$REPO_DIR" config --unset mosaic.gitIdentity
+
+# ---------------------------------------------------------------------------
+# 5. Identity resolves, but no matching per-slot token file -> falls back to
+#    the shared account (per-agent identity is opt-in, not a hard requirement).
+# ---------------------------------------------------------------------------
+out=$(run_helper "git.mosaicstack.dev" "no-such-agent")
+assert_eq "no per-slot token: username" "username=git" "$(echo "$out" | grep '^username=')"
+assert_eq "no per-slot token: password" "password=shared-mosaicstack-token" "$(echo "$out" | grep '^password=')"
+
+# ---------------------------------------------------------------------------
+# 6. Correct per-slot token PATH is chosen per host: same agent id, different
+#    host prefix (gitea-usc- vs gitea-mosaicstack-).
+# ---------------------------------------------------------------------------
+echo -n "agentD-usc-token" > "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-usc-agentD.token"
+out=$(run_helper "git.uscllc.com" "agentD")
+assert_eq "host-scoped token path (usc): username" "username=agentD" "$(echo "$out" | grep '^username=')"
+assert_eq "host-scoped token path (usc): password" "password=agentD-usc-token" "$(echo "$out" | grep '^password=')"
+# agentD has NO mosaicstack token -> must fall back to shared mosaicstack, not
+# leak the usc token across hosts.
+out=$(run_helper "git.mosaicstack.dev" "agentD")
+assert_eq "host-scoped token path (cross-host must not leak): username" "username=git" "$(echo "$out" | grep '^username=')"
+assert_eq "host-scoped token path (cross-host must not leak): password" "password=shared-mosaicstack-token" "$(echo "$out" | grep '^password=')"
+
+# ---------------------------------------------------------------------------
+# 7. Unrelated/unknown host -> exit 0, no output (passthrough for non-Gitea
+#    remotes, e.g. github.com via a different credential helper).
+# ---------------------------------------------------------------------------
+out=$(run_helper "github.com" "agentA")
+assert_eq "unknown host: no output" "" "$out"
+
+# ---------------------------------------------------------------------------
+# 8. Non-"get" verb (store/erase) -> exit 0, no output (git-credential
+#    protocol: this helper only implements get).
+# ---------------------------------------------------------------------------
+store_out=$(cd "$REPO_DIR" && env -i HOME="$FAKE_HOME" PATH="$PATH" bash "$HELPER" store <<EOF
+host=git.mosaicstack.dev
+username=agentA
+password=whatever
+
+EOF
+)
+assert_eq "store verb: no output" "" "$store_out"
+
+if [[ "$fail" -eq 0 ]]; then
+  echo "git-credential-mosaic identity resolution regression passed"
+fi
+
+exit "$fail"

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

@@ -0,0 +1,122 @@
+#!/usr/bin/env bash
+# Regression harness for detect-platform.sh's get_gitea_token() per-agent
+# identity resolution (Gate-16 author≠reviewer separation) — the API-tooling
+# counterpart to git-credential-mosaic, so pr-create.sh/issue-create.sh/etc.
+# open records under the resolved agent identity, not the shared account.
+#
+# Covers:
+#   1. Identity resolution priority: MOSAIC_GIT_IDENTITY env > git config
+#      mosaic.gitIdentity (per-worktree).
+#   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).
+#
+# 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.
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+WORK_DIR="${MOSAIC_TEST_WORK_DIR:-$PWD/.mosaic-test-work/gitea-token-identity}"
+FAKE_HOME="$WORK_DIR/home"
+REPO_DIR="$WORK_DIR/repo"
+CREDENTIALS_FILE="$FAKE_HOME/.config/mosaic/credentials.json"
+
+rm -rf "$WORK_DIR"
+mkdir -p "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens" "$REPO_DIR"
+
+git -C "$REPO_DIR" init -q
+git -C "$REPO_DIR" remote add origin https://git.mosaicstack.dev/mosaicstack/stack.git
+
+cat > "$CREDENTIALS_FILE" <<'JSON'
+{
+  "gitea": {
+    "mosaicstack": {
+      "url": "https://git.mosaicstack.dev",
+      "token": "shared-mosaicstack-token"
+    },
+    "usc": {
+      "url": "https://git.uscllc.com",
+      "token": "shared-usc-token"
+    }
+  }
+}
+JSON
+
+fail=0
+assert_eq() {
+  local desc="$1" expected="$2" actual="$3"
+  if [[ "$expected" != "$actual" ]]; then
+    echo "FAIL: $desc — expected '$expected', got '$actual'" >&2
+    fail=1
+  fi
+}
+
+# Runs get_gitea_token for $1=host inside REPO_DIR (per-worktree git config
+# resolves there) with a fake HOME + the stub credentials.json, plus any
+# extra env passed in $@.
+call_get_gitea_token() {
+  local host="$1"; shift
+  (
+    cd "$REPO_DIR"
+    # shellcheck disable=SC2016 # deliberately deferred: $DETECT_PLATFORM_SH is
+    # expanded by the INNER bash -c (via the exported env var below), not here.
+    env -i HOME="$FAKE_HOME" PATH="$PATH" MOSAIC_CREDENTIALS_FILE="$CREDENTIALS_FILE" \
+      DETECT_PLATFORM_SH="$SCRIPT_DIR/detect-platform.sh" "$@" \
+      bash -c 'source "$DETECT_PLATFORM_SH"; get_gitea_token "$1"' _ "$host"
+  )
+}
+
+# ---------------------------------------------------------------------------
+# 1. No identity resolvable -> shared credential-loader token (unchanged).
+# ---------------------------------------------------------------------------
+git -C "$REPO_DIR" config --unset mosaic.gitIdentity 2>/dev/null || true
+out=$(call_get_gitea_token "git.mosaicstack.dev")
+assert_eq "shared fallback (no identity)" "shared-mosaicstack-token" "$out"
+
+# ---------------------------------------------------------------------------
+# 2. git config mosaic.gitIdentity resolves to an agent WITH a per-slot
+#    token -> that token wins over the shared account.
+# ---------------------------------------------------------------------------
+echo -n "agentA-mosaicstack-token" > "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-mosaicstack-agentA.token"
+git -C "$REPO_DIR" config mosaic.gitIdentity agentA
+out=$(call_get_gitea_token "git.mosaicstack.dev")
+assert_eq "git-config identity token" "agentA-mosaicstack-token" "$out"
+
+# ---------------------------------------------------------------------------
+# 3. MOSAIC_GIT_IDENTITY env beats git config mosaic.gitIdentity.
+# ---------------------------------------------------------------------------
+echo -n "agentB-mosaicstack-token" > "$FAKE_HOME/.config/mosaic/secrets/gitea-tokens/gitea-mosaicstack-agentB.token"
+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).
+# ---------------------------------------------------------------------------
+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" "$out"
+
+# ---------------------------------------------------------------------------
+# 5. Correct per-slot token PATH per host: same agent id, only a usc token
+#    exists -> usc host returns it, mosaicstack host must NOT leak it and
+#    instead falls back to the shared mosaicstack token.
+# ---------------------------------------------------------------------------
+echo -n "agentD-usc-token" > "$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" "$out"
+git -C "$REPO_DIR" config --unset mosaic.gitIdentity
+
+if [[ "$fail" -eq 0 ]]; then
+  echo "get_gitea_token identity resolution regression passed"
+fi
+
+exit "$fail"