Keep the stored GitHub token when setup runs again

The secret store outlives the sandbox, so recreating one to change its image
or add a profile does not lose the token. Prompting for a replacement anyway
made --replace impractical and trained the habit of minting tokens that are
never revoked.

Only a token scoped to this sandbox counts. A global one would authenticate
the agent too, but reaching every repository it can reach is what this task
exists to prevent. The token command still always prompts; it is the way to
replace an expired or revoked token.

README.md

@@ -263,8 +263,8 @@ provider "aws" {
 
 | Command | Effect |
 | --- | --- |
-| `setup [options]` | Configure the repository, create the sandbox, open the token form, install AWS profiles, Claude configuration and plugins, and mise |
-| `token` | Replace the GitHub token for this repository — expiry, revocation, permission change |
+| `setup [options]` | Configure the repository, create the sandbox, open the token form if no token is stored yet, install AWS profiles, Claude configuration and plugins, and mise |
+| `token` | Replace the GitHub token for this repository — expiry, revocation, permission change. Always prompts |
 | `run [--launch MODE] [-- args...]` | Refresh AWS credentials and the repository's mise tools, then attach to the agent or to a tmux workspace |
 | `refresh` | Refresh AWS credentials, without attaching |
 | `config` | Re-apply your Claude configuration, plugins and dotfiles after the host changes, without recreating the sandbox |

tasks/ai/sbx

@@ -83,8 +83,10 @@ Usage:
   mise run ai:sbx -- status
   mise run ai:sbx -- remove
 
-Setup opens a pre-filled GitHub token form in your browser. Use "token" on
-its own to replace an expired or revoked token later.
+Setup opens a pre-filled GitHub token form in your browser, unless a token is
+already stored for the sandbox. The secret store outlives the sandbox, so
+recreating one with --replace keeps its token. Use "token" on its own to
+replace an expired or revoked token.
 
 Set AI_SBX_TEMPLATE in your mise config to reuse one custom image across
 every repository without repeating --template.
@@ -242,6 +244,17 @@ read_token() {
     printf '%s' "$token"
 }
 
+# Only a token scoped to this sandbox counts. A global one would authenticate
+# the agent too, but reaching every repository the token can reach is exactly
+# what this task exists to prevent, so it is not treated as satisfying setup.
+sandbox_has_github_token() {
+    sbx secret ls 2>/dev/null |
+        awk -v scope="$SANDBOX_NAME" '
+            $1 == scope && $2 == "service" && $3 == "github" { found = 1 }
+            END { exit !found }
+        '
+}
+
 install_github_token() {
     local url
     url="$(token_url)"
@@ -1354,7 +1367,15 @@ setup_command() {
         create_sandbox
     fi
 
-    install_github_token
+    # The secret store outlives the sandbox, so recreating one to change its
+    # image keeps the token. Prompting anyway would train the habit of minting
+    # replacement tokens and never revoking the old ones.
+    if sandbox_has_github_token; then
+        printf 'Keeping the GitHub token already stored for %s. Replace it with: mise run ai:sbx -- token\n' \
+            "$SANDBOX_NAME"
+    else
+        install_github_token
+    fi
 
     install_sandbox_aws_files
 

tests/github-token.test.sh

@@ -0,0 +1,90 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+TASK="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)/tasks/ai/sbx"
+
+# shellcheck source-path=SCRIPTDIR
+# shellcheck source=tasks/ai/sbx
+source "$TASK"
+
+failures=0
+
+fail() {
+    printf 'FAIL: %s\n' "$1" >&2
+    failures=$((failures + 1))
+}
+
+SANDBOX_NAME=ai-repo-abc123
+
+listing=""
+sbx() {
+    printf '%s\n' "$listing"
+}
+
+with_listing() {
+    listing="$1"
+    sandbox_has_github_token
+}
+
+full_listing() {
+    cat <<'EOF'
+SCOPE                TYPE      NAME        SECRET
+ai-repo-abc123       service   github      (stored)
+(global)             service   anthropic   (oauth configured)
+
+CUSTOM SECRETS
+SCOPE                TARGETS                   ENV                     PLACEHOLDER          SECRET
+ai-repo-abc123       localstack.cloud          LOCALSTACK_AUTH_TOKEN   sbx-cs-0c2f39c1      ls-vOL***
+EOF
+}
+
+with_listing "$(full_listing)" ||
+    fail "a sandbox-scoped github token was not detected"
+
+with_listing "$(
+    cat <<'EOF'
+SCOPE                TYPE      NAME        SECRET
+(global)             service   anthropic   (oauth configured)
+EOF
+)" && fail "no github token stored, yet setup would have been skipped"
+
+with_listing "$(
+    cat <<'EOF'
+SCOPE                TYPE      NAME        SECRET
+(global)             service   github      (stored)
+EOF
+)" && fail "a global github token must not satisfy a per-repository sandbox"
+
+with_listing "$(
+    cat <<'EOF'
+SCOPE                TYPE      NAME        SECRET
+ai-other-sandbox     service   github      (stored)
+EOF
+)" && fail "another sandbox's github token must not count as this one's"
+
+with_listing "$(
+    cat <<'EOF'
+CUSTOM SECRETS
+SCOPE                TARGETS       ENV      PLACEHOLDER     SECRET
+ai-repo-abc123       github.com    github   sbx-cs-abc      gh***
+EOF
+)" && fail "a custom secret must not be mistaken for the stored service token"
+
+with_listing "" &&
+    fail "empty output should mean no token, not a stored one"
+
+grep -q 'if sandbox_has_github_token; then' "$TASK" ||
+    fail "setup no longer guards install_github_token"
+
+awk '/^token_command\(\)/, /^}/' "$TASK" | grep -q 'install_github_token' ||
+    fail "the token command must always prompt; it is the way to replace one"
+
+awk '/^token_command\(\)/, /^}/' "$TASK" | grep -q 'sandbox_has_github_token' &&
+    fail "the token command must not skip when a token exists"
+
+if ((failures)); then
+    printf '%d assertion(s) failed\n' "$failures" >&2
+    exit 1
+fi
+
+printf 'All GitHub token assertions passed.\n'