From 1df7c53f04343bbc2bed7c3a9150f4cfb7194f30 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 5 May 2026 12:50:09 +0000
Subject: [PATCH 1/4] chore: initial plan for elseif template support

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/40bbec61-dc73-4fb0-aa5a-97a5823cd269

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 .github/workflows/stale-pr-cleanup.lock.yml | 24 ++++++++++-----------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/.github/workflows/stale-pr-cleanup.lock.yml b/.github/workflows/stale-pr-cleanup.lock.yml
index 654e891948..885ba45c79 100644
--- a/.github/workflows/stale-pr-cleanup.lock.yml
+++ b/.github/workflows/stale-pr-cleanup.lock.yml
@@ -1,5 +1,5 @@
 # gh-aw-metadata: {"schema_version":"v3","frontmatter_hash":"07e071eb8a3e78f3eecb8071e562e1f8291f76cb7a7610e5e007f8d4d12f0a43","strict":true,"agent_id":"copilot"}
-# gh-aw-manifest: {"version":1,"secrets":["GH_AW_GITHUB_MCP_SERVER_TOKEN","GH_AW_GITHUB_TOKEN","GITHUB_TOKEN"],"actions":[{"repo":"actions/checkout","sha":"de0fac2e4500dabe0009e67214ff5f5447ce83dd","version":"v6.0.2"},{"repo":"actions/download-artifact","sha":"3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c","version":"v8.0.1"},{"repo":"actions/github-script","sha":"3a2844b7e9c422d3c10d287c895573f7108da1b3","version":"v9"},{"repo":"actions/setup-node","sha":"48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e","version":"v6.4.0"},{"repo":"actions/upload-artifact","sha":"043fb46d1a93c77aae656e7c1c64a875d1fc6a0a","version":"v7.0.1"}],"containers":[{"image":"ghcr.io/github/gh-aw-firewall/agent:0.25.38"},{"image":"ghcr.io/github/gh-aw-firewall/api-proxy:0.25.38"},{"image":"ghcr.io/github/gh-aw-firewall/cli-proxy:0.25.38"},{"image":"ghcr.io/github/gh-aw-firewall/squid:0.25.38"},{"image":"ghcr.io/github/gh-aw-mcpg:v0.3.6"},{"image":"ghcr.io/github/github-mcp-server:v1.0.3","digest":"sha256:2ac27ef03461ef2b877031b838a7d1fd7f12b12d4ace7796d8cad91446d55959","pinned_image":"ghcr.io/github/github-mcp-server:v1.0.3@sha256:2ac27ef03461ef2b877031b838a7d1fd7f12b12d4ace7796d8cad91446d55959"},{"image":"node:lts-alpine","digest":"sha256:d1b3b4da11eefd5941e7f0b9cf17783fc99d9c6fc34884a665f40a06dbdfc94f","pinned_image":"node:lts-alpine@sha256:d1b3b4da11eefd5941e7f0b9cf17783fc99d9c6fc34884a665f40a06dbdfc94f"}]}
+# gh-aw-manifest: {"version":1,"secrets":["GH_AW_GITHUB_MCP_SERVER_TOKEN","GH_AW_GITHUB_TOKEN","GITHUB_TOKEN"],"actions":[{"repo":"actions/checkout","sha":"de0fac2e4500dabe0009e67214ff5f5447ce83dd","version":"v6.0.2"},{"repo":"actions/download-artifact","sha":"3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c","version":"v8.0.1"},{"repo":"actions/github-script","sha":"3a2844b7e9c422d3c10d287c895573f7108da1b3","version":"v9"},{"repo":"actions/setup-node","sha":"48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e","version":"v6.4.0"},{"repo":"actions/upload-artifact","sha":"043fb46d1a93c77aae656e7c1c64a875d1fc6a0a","version":"v7.0.1"}],"containers":[{"image":"ghcr.io/github/gh-aw-firewall/agent:0.25.39"},{"image":"ghcr.io/github/gh-aw-firewall/api-proxy:0.25.39"},{"image":"ghcr.io/github/gh-aw-firewall/cli-proxy:0.25.39"},{"image":"ghcr.io/github/gh-aw-firewall/squid:0.25.39"},{"image":"ghcr.io/github/gh-aw-mcpg:v0.3.6"},{"image":"ghcr.io/github/github-mcp-server:v1.0.3","digest":"sha256:2ac27ef03461ef2b877031b838a7d1fd7f12b12d4ace7796d8cad91446d55959","pinned_image":"ghcr.io/github/github-mcp-server:v1.0.3@sha256:2ac27ef03461ef2b877031b838a7d1fd7f12b12d4ace7796d8cad91446d55959"},{"image":"node:lts-alpine","digest":"sha256:d1b3b4da11eefd5941e7f0b9cf17783fc99d9c6fc34884a665f40a06dbdfc94f","pinned_image":"node:lts-alpine@sha256:d1b3b4da11eefd5941e7f0b9cf17783fc99d9c6fc34884a665f40a06dbdfc94f"}]}
 #    ___                   _   _      
 #   / _ \                 | | (_)     
 #  | |_| | __ _  ___ _ __ | |_ _  ___ 
@@ -38,10 +38,10 @@
 #   - actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
 #
 # Container images used:
-#   - ghcr.io/github/gh-aw-firewall/agent:0.25.38
-#   - ghcr.io/github/gh-aw-firewall/api-proxy:0.25.38
-#   - ghcr.io/github/gh-aw-firewall/cli-proxy:0.25.38
-#   - ghcr.io/github/gh-aw-firewall/squid:0.25.38
+#   - ghcr.io/github/gh-aw-firewall/agent:0.25.39
+#   - ghcr.io/github/gh-aw-firewall/api-proxy:0.25.39
+#   - ghcr.io/github/gh-aw-firewall/cli-proxy:0.25.39
+#   - ghcr.io/github/gh-aw-firewall/squid:0.25.39
 #   - ghcr.io/github/gh-aw-mcpg:v0.3.6
 #   - ghcr.io/github/github-mcp-server:v1.0.3@sha256:2ac27ef03461ef2b877031b838a7d1fd7f12b12d4ace7796d8cad91446d55959
 #   - node:lts-alpine@sha256:d1b3b4da11eefd5941e7f0b9cf17783fc99d9c6fc34884a665f40a06dbdfc94f
@@ -112,7 +112,7 @@ jobs:
           GH_AW_INFO_STAGED: "false"
           GH_AW_INFO_ALLOWED_DOMAINS: '["defaults"]'
           GH_AW_INFO_FIREWALL_ENABLED: "true"
-          GH_AW_INFO_AWF_VERSION: "v0.25.38"
+          GH_AW_INFO_AWF_VERSION: "v0.25.39"
           GH_AW_INFO_AWMG_VERSION: ""
           GH_AW_INFO_FIREWALL_TYPE: "squid"
           GH_AW_COMPILED_STRICT: "true"
@@ -393,7 +393,7 @@ jobs:
         env:
           GH_HOST: github.com
       - name: Install AWF binary
-        run: bash "${RUNNER_TEMP}/gh-aw/actions/install_awf_binary.sh" v0.25.38
+        run: bash "${RUNNER_TEMP}/gh-aw/actions/install_awf_binary.sh" v0.25.39
       - name: Determine automatic lockdown mode for GitHub MCP Server
         id: determine-automatic-lockdown
         uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9
@@ -416,7 +416,7 @@ jobs:
           GH_AW_AGENT_FILES: ".crush.json AGENTS.md CLAUDE.md GEMINI.md PI.md opencode.jsonc"
         run: bash "${RUNNER_TEMP}/gh-aw/actions/restore_base_github_folders.sh"
       - name: Download container images
-        run: bash "${RUNNER_TEMP}/gh-aw/actions/download_docker_images.sh" ghcr.io/github/gh-aw-firewall/agent:0.25.38 ghcr.io/github/gh-aw-firewall/api-proxy:0.25.38 ghcr.io/github/gh-aw-firewall/cli-proxy:0.25.38 ghcr.io/github/gh-aw-firewall/squid:0.25.38 ghcr.io/github/gh-aw-mcpg:v0.3.6 ghcr.io/github/github-mcp-server:v1.0.3@sha256:2ac27ef03461ef2b877031b838a7d1fd7f12b12d4ace7796d8cad91446d55959 node:lts-alpine@sha256:d1b3b4da11eefd5941e7f0b9cf17783fc99d9c6fc34884a665f40a06dbdfc94f
+        run: bash "${RUNNER_TEMP}/gh-aw/actions/download_docker_images.sh" ghcr.io/github/gh-aw-firewall/agent:0.25.39 ghcr.io/github/gh-aw-firewall/api-proxy:0.25.39 ghcr.io/github/gh-aw-firewall/cli-proxy:0.25.39 ghcr.io/github/gh-aw-firewall/squid:0.25.39 ghcr.io/github/gh-aw-mcpg:v0.3.6 ghcr.io/github/github-mcp-server:v1.0.3@sha256:2ac27ef03461ef2b877031b838a7d1fd7f12b12d4ace7796d8cad91446d55959 node:lts-alpine@sha256:d1b3b4da11eefd5941e7f0b9cf17783fc99d9c6fc34884a665f40a06dbdfc94f
       - name: Generate Safe Outputs Config
         run: |
           mkdir -p "${RUNNER_TEMP}/gh-aw/safeoutputs"
@@ -734,7 +734,7 @@ jobs:
           GH_AW_NODE_BIN=$(command -v node 2>/dev/null || true)
           export GH_AW_NODE_BIN
           (umask 177 && touch /tmp/gh-aw/agent-stdio.log)
-          printf '%s\n' '{"$schema":"https://github.com/github/gh-aw-firewall/releases/download/v0.25.38/awf-config.schema.json","network":{"allowDomains":["api.business.githubcopilot.com","api.enterprise.githubcopilot.com","api.github.com","api.githubcopilot.com","api.individual.githubcopilot.com","api.snapcraft.io","archive.ubuntu.com","azure.archive.ubuntu.com","crl.geotrust.com","crl.globalsign.com","crl.identrust.com","crl.sectigo.com","crl.thawte.com","crl.usertrust.com","crl.verisign.com","crl3.digicert.com","crl4.digicert.com","crls.ssl.com","github.com","host.docker.internal","json-schema.org","json.schemastore.org","keyserver.ubuntu.com","ocsp.digicert.com","ocsp.geotrust.com","ocsp.globalsign.com","ocsp.identrust.com","ocsp.sectigo.com","ocsp.ssl.com","ocsp.thawte.com","ocsp.usertrust.com","ocsp.verisign.com","packagecloud.io","packages.cloud.google.com","packages.microsoft.com","ppa.launchpad.net","raw.githubusercontent.com","registry.npmjs.org","s.symcb.com","s.symcd.com","security.ubuntu.com","telemetry.enterprise.githubcopilot.com","ts-crl.ws.symantec.com","ts-ocsp.ws.symantec.com","www.googleapis.com"]},"apiProxy":{"enabled":true},"container":{"imageTag":"0.25.38"}}' > "${RUNNER_TEMP}/gh-aw/awf-config.json" && cp "${RUNNER_TEMP}/gh-aw/awf-config.json" /tmp/gh-aw/awf-config.json
+          printf '%s\n' '{"$schema":"https://github.com/github/gh-aw-firewall/releases/download/v0.25.39/awf-config.schema.json","network":{"allowDomains":["api.business.githubcopilot.com","api.enterprise.githubcopilot.com","api.github.com","api.githubcopilot.com","api.individual.githubcopilot.com","api.snapcraft.io","archive.ubuntu.com","azure.archive.ubuntu.com","crl.geotrust.com","crl.globalsign.com","crl.identrust.com","crl.sectigo.com","crl.thawte.com","crl.usertrust.com","crl.verisign.com","crl3.digicert.com","crl4.digicert.com","crls.ssl.com","github.com","host.docker.internal","json-schema.org","json.schemastore.org","keyserver.ubuntu.com","ocsp.digicert.com","ocsp.geotrust.com","ocsp.globalsign.com","ocsp.identrust.com","ocsp.sectigo.com","ocsp.ssl.com","ocsp.thawte.com","ocsp.usertrust.com","ocsp.verisign.com","packagecloud.io","packages.cloud.google.com","packages.microsoft.com","ppa.launchpad.net","raw.githubusercontent.com","registry.npmjs.org","s.symcb.com","s.symcd.com","security.ubuntu.com","telemetry.enterprise.githubcopilot.com","ts-crl.ws.symantec.com","ts-ocsp.ws.symantec.com","www.googleapis.com"]},"apiProxy":{"enabled":true},"container":{"imageTag":"0.25.39"}}' > "${RUNNER_TEMP}/gh-aw/awf-config.json" && cp "${RUNNER_TEMP}/gh-aw/awf-config.json" /tmp/gh-aw/awf-config.json
           # shellcheck disable=SC1003
           sudo -E awf --config "${RUNNER_TEMP}/gh-aw/awf-config.json" --container-workdir "${GITHUB_WORKSPACE}" --mount "${RUNNER_TEMP}/gh-aw:${RUNNER_TEMP}/gh-aw:ro" --mount "${RUNNER_TEMP}/gh-aw:/host${RUNNER_TEMP}/gh-aw:ro" --env-all --exclude-env COPILOT_GITHUB_TOKEN --exclude-env GH_TOKEN --exclude-env GITHUB_MCP_SERVER_TOKEN --exclude-env MCP_GATEWAY_API_KEY --log-level info --proxy-logs-dir /tmp/gh-aw/sandbox/firewall/logs --audit-dir /tmp/gh-aw/sandbox/firewall/audit --enable-host-access --allow-host-ports 80,443,8080 --skip-pull --difc-proxy-host host.docker.internal:18443 --difc-proxy-ca-cert /tmp/gh-aw/difc-proxy-tls/ca.crt \
             -- /bin/bash -c 'export PATH="${RUNNER_TEMP}/gh-aw/mcp-cli/bin:$PATH" && export PATH="$(find /opt/hostedtoolcache /home/runner/work/_tool -maxdepth 4 -type d -name bin 2>/dev/null | tr '\''\n'\'' '\'':'\'')$PATH"; [ -n "$GOROOT" ] && export PATH="$GOROOT/bin:$PATH" || true && GH_AW_NODE_EXEC="${GH_AW_NODE_BIN:-}"; if [ -z "$GH_AW_NODE_EXEC" ] || [ ! -x "$GH_AW_NODE_EXEC" ]; then GH_AW_NODE_EXEC="$(command -v node 2>/dev/null || echo node)"; fi; "$GH_AW_NODE_EXEC" ${RUNNER_TEMP}/gh-aw/actions/copilot_harness.cjs /usr/local/bin/copilot --add-dir /tmp/gh-aw/ --log-level all --log-dir /tmp/gh-aw/sandbox/agent/logs/ --disable-builtin-mcps --no-ask-user --allow-tool github --allow-tool safeoutputs --allow-tool '\''shell(cat)'\'' --allow-tool '\''shell(date *)'\'' --allow-tool '\''shell(date)'\'' --allow-tool '\''shell(echo)'\'' --allow-tool '\''shell(grep)'\'' --allow-tool '\''shell(head)'\'' --allow-tool '\''shell(jq *)'\'' --allow-tool '\''shell(ls)'\'' --allow-tool '\''shell(pwd)'\'' --allow-tool '\''shell(safeoutputs:*)'\'' --allow-tool '\''shell(sort)'\'' --allow-tool '\''shell(tail)'\'' --allow-tool '\''shell(uniq)'\'' --allow-tool '\''shell(wc)'\'' --allow-tool '\''shell(yq)'\'' --allow-tool write --allow-all-paths --add-dir "${GITHUB_WORKSPACE}" --prompt-file /tmp/gh-aw/aw-prompts/prompt.txt' 2>&1 | tee -a /tmp/gh-aw/agent-stdio.log
@@ -1135,7 +1135,7 @@ jobs:
           rm -rf /tmp/gh-aw/sandbox/firewall/logs
           rm -rf /tmp/gh-aw/sandbox/firewall/audit
       - name: Download container images
-        run: bash "${RUNNER_TEMP}/gh-aw/actions/download_docker_images.sh" ghcr.io/github/gh-aw-firewall/agent:0.25.38 ghcr.io/github/gh-aw-firewall/api-proxy:0.25.38 ghcr.io/github/gh-aw-firewall/squid:0.25.38
+        run: bash "${RUNNER_TEMP}/gh-aw/actions/download_docker_images.sh" ghcr.io/github/gh-aw-firewall/agent:0.25.39 ghcr.io/github/gh-aw-firewall/api-proxy:0.25.39 ghcr.io/github/gh-aw-firewall/squid:0.25.39
       - name: Check if detection needed
         id: detection_guard
         if: always()
@@ -1198,7 +1198,7 @@ jobs:
         env:
           GH_HOST: github.com
       - name: Install AWF binary
-        run: bash "${RUNNER_TEMP}/gh-aw/actions/install_awf_binary.sh" v0.25.38
+        run: bash "${RUNNER_TEMP}/gh-aw/actions/install_awf_binary.sh" v0.25.39
       - name: Execute GitHub Copilot CLI
         if: always() && steps.detection_guard.outputs.run_detection == 'true'
         continue-on-error: true
@@ -1211,7 +1211,7 @@ jobs:
           GH_AW_NODE_BIN=$(command -v node 2>/dev/null || true)
           export GH_AW_NODE_BIN
           (umask 177 && touch /tmp/gh-aw/threat-detection/detection.log)
-          printf '%s\n' '{"$schema":"https://github.com/github/gh-aw-firewall/releases/download/v0.25.38/awf-config.schema.json","network":{"allowDomains":["api.business.githubcopilot.com","api.enterprise.githubcopilot.com","api.github.com","api.githubcopilot.com","api.individual.githubcopilot.com","github.com","host.docker.internal","telemetry.enterprise.githubcopilot.com"]},"apiProxy":{"enabled":true},"container":{"imageTag":"0.25.38"}}' > "${RUNNER_TEMP}/gh-aw/awf-config.json" && cp "${RUNNER_TEMP}/gh-aw/awf-config.json" /tmp/gh-aw/awf-config.json
+          printf '%s\n' '{"$schema":"https://github.com/github/gh-aw-firewall/releases/download/v0.25.39/awf-config.schema.json","network":{"allowDomains":["api.business.githubcopilot.com","api.enterprise.githubcopilot.com","api.github.com","api.githubcopilot.com","api.individual.githubcopilot.com","github.com","host.docker.internal","telemetry.enterprise.githubcopilot.com"]},"apiProxy":{"enabled":true},"container":{"imageTag":"0.25.39"}}' > "${RUNNER_TEMP}/gh-aw/awf-config.json" && cp "${RUNNER_TEMP}/gh-aw/awf-config.json" /tmp/gh-aw/awf-config.json
           # shellcheck disable=SC1003
           sudo -E awf --config "${RUNNER_TEMP}/gh-aw/awf-config.json" --container-workdir "${GITHUB_WORKSPACE}" --mount "${RUNNER_TEMP}/gh-aw:${RUNNER_TEMP}/gh-aw:ro" --mount "${RUNNER_TEMP}/gh-aw:/host${RUNNER_TEMP}/gh-aw:ro" --env-all --exclude-env COPILOT_GITHUB_TOKEN --log-level info --proxy-logs-dir /tmp/gh-aw/sandbox/firewall/logs --audit-dir /tmp/gh-aw/sandbox/firewall/audit --enable-host-access --allow-host-ports 80,443,8080 --skip-pull \
             -- /bin/bash -c 'export PATH="$(find /opt/hostedtoolcache /home/runner/work/_tool -maxdepth 4 -type d -name bin 2>/dev/null | tr '\''\n'\'' '\'':'\'')$PATH"; [ -n "$GOROOT" ] && export PATH="$GOROOT/bin:$PATH" || true && GH_AW_NODE_EXEC="${GH_AW_NODE_BIN:-}"; if [ -z "$GH_AW_NODE_EXEC" ] || [ ! -x "$GH_AW_NODE_EXEC" ]; then GH_AW_NODE_EXEC="$(command -v node 2>/dev/null || echo node)"; fi; "$GH_AW_NODE_EXEC" ${RUNNER_TEMP}/gh-aw/actions/copilot_harness.cjs /usr/local/bin/copilot --add-dir /tmp/gh-aw/ --log-level all --log-dir /tmp/gh-aw/sandbox/agent/logs/ --disable-builtin-mcps --no-ask-user --allow-all-tools --add-dir "${GITHUB_WORKSPACE}" --prompt-file /tmp/gh-aw/aw-prompts/prompt.txt' 2>&1 | tee -a /tmp/gh-aw/threat-detection/detection.log

From 2b47905041fc104331c981e8a1457e58730d3392 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 5 May 2026 13:01:15 +0000
Subject: [PATCH 2/4] feat: add elseif handler syntax support in template
 expression rendering

- Add TemplateElseIfPattern to expression_patterns.go supporting all
  syntax variants: {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}},
  {{else-if}}, {{else_if}}
- Update wrapExpressionsInTemplateConditionals to wrap and normalise
  elseif expressions to canonical {{#elseif}} form
- Update validateNoPreExpandedExperimentPlaceholders to check elseif
  conditions for internal placeholder misuse
- Add selectBranch helper to interpolate_prompt.cjs and render_template.cjs
  implementing multi-branch evaluation (if / elseif* / else?)
- Replace two-way else split with unified selectBranch in both JS engines
- Export selectBranch from both JS modules
- Add Go tests for elseif wrapping, normalisation, and validation
- Add JS tests for all elseif variants and branch selection logic

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/40bbec61-dc73-4fb0-aa5a-97a5823cd269

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 actions/setup/js/interpolate_prompt.cjs       | 82 ++++++++++++++-----
 actions/setup/js/interpolate_prompt.test.cjs  | 51 +++++++++++-
 actions/setup/js/render_template.cjs          | 59 ++++++++++---
 actions/setup/js/render_template.test.cjs     | 56 ++++++++++++-
 pkg/workflow/expression_patterns.go           |  7 ++
 pkg/workflow/template.go                      | 50 ++++++-----
 .../template_expression_wrapping_test.go      | 51 ++++++++++++
 .../template_include_validation_test.go       | 65 +++++++++++++++
 pkg/workflow/template_validation.go           | 10 ++-
 9 files changed, 374 insertions(+), 57 deletions(-)

diff --git a/actions/setup/js/interpolate_prompt.cjs b/actions/setup/js/interpolate_prompt.cjs
index 26f408f37e..22554dfb8f 100644
--- a/actions/setup/js/interpolate_prompt.cjs
+++ b/actions/setup/js/interpolate_prompt.cjs
@@ -48,6 +48,55 @@ function interpolateVariables(content, variables) {
   return result;
 }
 
+/**
+ * Selects the appropriate branch from a conditional block that may contain
+ * {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
+ * branches in addition to the optional {{#else}} fallback.
+ *
+ * Algorithm:
+ *   1. Split the body on elseif markers (all syntax variants) — capturing groups
+ *      in the split pattern yield alternating [content, condition, content, ...].
+ *   2. Pair each content piece with the condition that guards it:
+ *        - First piece is guarded by the {{#if}} condition (ifCondition).
+ *        - Subsequent pieces are guarded by the preceding elseif condition.
+ *   3. Check the last piece for a {{#else}} tail and, if found, add an
+ *      unconditional else branch.
+ *   4. Return the content of the first truthy branch, or null if none matched.
+ *
+ * @param {string} ifCondition - The condition from the opening {{#if ...}} tag
+ * @param {string} body        - Everything between the opening tag and {{/if}}
+ * @returns {string|null}      - Content of the first truthy branch, or null
+ */
+function selectBranch(ifCondition, body) {
+  // Split on all elseif variants.  The capturing group ensures that the condition
+  // text appears between the content pieces in the resulting array.
+  // Supported: {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
+  const parts = body.split(/[ \t]*\{\{#?else[-_]?if\s+([^}]*)\}\}[ \t]*\n?/);
+
+  // parts alternates: [content0, cond1, content1, cond2, content2, ...]
+  const branches = [{ condition: ifCondition, content: parts[0] }];
+  for (let i = 1; i < parts.length; i += 2) {
+    branches.push({ condition: parts[i].trim(), content: parts[i + 1] || "" });
+  }
+
+  // Check whether the last branch's content contains a {{#else}} tail
+  const lastBranch = branches[branches.length - 1];
+  const elseParts = lastBranch.content.split(/[ \t]*\{\{#else\}\}[ \t]*\n?/);
+  if (elseParts.length > 1) {
+    lastBranch.content = elseParts[0];
+    // condition: null = unconditional else branch
+    branches.push({ condition: null, content: elseParts.slice(1).join("{{#else}}") });
+  }
+
+  // Return content of the first truthy branch
+  for (const branch of branches) {
+    if (branch.condition === null || isTruthy(branch.condition)) {
+      return branch.content;
+    }
+  }
+  return null;
+}
+
 /**
  * Renders a Markdown template by processing {{#if}} conditional blocks.
  * When a conditional block is removed (falsy condition) and the template tags
@@ -87,30 +136,20 @@ function renderMarkdownTemplate(markdown) {
   let result = _stripped.replace(/(\n?)([ \t]*{{#if\s+([^}]*)}}[ \t]*\n)([\s\S]*?)([ \t]*(?:{{#endif}}|{{\/if}})[ \t]*)(\n?)/g, (match, leadNL, openLine, cond, body, closeLine, trailNL) => {
     blockCount++;
     const condTrimmed = cond.trim();
-    const truthyResult = isTruthy(cond);
     const bodyPreview = body.substring(0, 60).replace(/\n/g, "\\n");
 
-    core.info(`[renderMarkdownTemplate] Block ${blockCount}: condition="${condTrimmed}" -> ${truthyResult ? "KEEP" : "REMOVE"}`);
+    core.info(`[renderMarkdownTemplate] Block ${blockCount}: condition="${condTrimmed}" -> evaluating branches`);
     core.info(`[renderMarkdownTemplate]   Body preview: "${bodyPreview}${body.length > 60 ? "..." : ""}"`);
 
-    // Split on {{#else}} if present to support two-branch conditionals.
-    // e.g. {{#if experiments.prompt_style == "concise"}} ... {{#else}} ... {{#endif}}
-    const elseParts = body.split(/[ \t]*\{\{#else\}\}[ \t]*\n?/);
-    const trueBranch = elseParts[0];
-    const falseBranch = elseParts.length > 1 ? elseParts.slice(1).join("{{#else}}") : null;
+    // Evaluate the full branch chain (if / elseif* / else?)
+    const selectedContent = selectBranch(cond, body);
 
-    if (truthyResult) {
-      // Keep the true branch (before {{#else}}, or full body if no {{#else}})
+    if (selectedContent !== null) {
       keptBlocks++;
-      core.info(`[renderMarkdownTemplate]   Action: Keeping ${falseBranch !== null ? "true branch" : "body"} with leading newline=${!!leadNL}`);
-      return leadNL + trueBranch;
+      core.info(`[renderMarkdownTemplate]   Action: Keeping selected branch with leading newline=${!!leadNL}`);
+      return leadNL + selectedContent;
     } else {
-      // Remove the block, or keep the false branch when {{#else}} is present
       removedBlocks++;
-      if (falseBranch !== null) {
-        core.info(`[renderMarkdownTemplate]   Action: Keeping false branch ({{#else}} branch)`);
-        return leadNL + falseBranch;
-      }
       core.info(`[renderMarkdownTemplate]   Action: Removing entire block`);
       return "";
     }
@@ -127,15 +166,16 @@ function renderMarkdownTemplate(markdown) {
   result = result.replace(/{{#if\s+([^}]*)}}([\s\S]*?)(?:{{#endif}}|{{\/if}})/g, (_, cond, body) => {
     inlineCount++;
     const condTrimmed = cond.trim();
-    const truthyResult = isTruthy(cond);
     const bodyPreview = body.substring(0, 40).replace(/\n/g, "\\n");
 
-    core.info(`[renderMarkdownTemplate] Inline ${inlineCount}: condition="${condTrimmed}" -> ${truthyResult ? "KEEP" : "REMOVE"}`);
+    const selectedContent = selectBranch(cond, body);
+
+    core.info(`[renderMarkdownTemplate] Inline ${inlineCount}: condition="${condTrimmed}" -> ${selectedContent !== null ? "KEEP" : "REMOVE"}`);
     core.info(`[renderMarkdownTemplate]   Body preview: "${bodyPreview}${body.length > 40 ? "..." : ""}"`);
 
-    if (truthyResult) {
+    if (selectedContent !== null) {
       keptInline++;
-      return body;
+      return selectedContent;
     } else {
       removedInline++;
       return "";
@@ -364,4 +404,4 @@ async function main() {
   }
 }
 
-module.exports = { main };
+module.exports = { main, renderMarkdownTemplate, interpolateVariables, selectBranch };
diff --git a/actions/setup/js/interpolate_prompt.test.cjs b/actions/setup/js/interpolate_prompt.test.cjs
index 13c6c418e2..7142258ac2 100644
--- a/actions/setup/js/interpolate_prompt.test.cjs
+++ b/actions/setup/js/interpolate_prompt.test.cjs
@@ -10,11 +10,14 @@ const __filename = fileURLToPath(import.meta.url),
 global.core = core;
 const interpolatePromptScript = fs.readFileSync(path.join(__dirname, "interpolate_prompt.cjs"), "utf8"),
   { isTruthy } = require("./is_truthy.cjs"),
+  selectBranchMatch = interpolatePromptScript.match(/function selectBranch\(ifCondition, body\)\s*{[\s\S]*?return null;\s*\n?}/),
   interpolateVariablesMatch = interpolatePromptScript.match(/function interpolateVariables\(content, variables\)\s*{[\s\S]*?return result;[\s\S]*?}/),
   renderMarkdownTemplateMatch = interpolatePromptScript.match(/function renderMarkdownTemplate\(markdown\)\s*{[\s\S]*?return result;[\s\S]*?}/);
+if (!selectBranchMatch) throw new Error("Could not extract selectBranch function from interpolate_prompt.cjs");
 if (!interpolateVariablesMatch) throw new Error("Could not extract interpolateVariables function from interpolate_prompt.cjs");
 if (!renderMarkdownTemplateMatch) throw new Error("Could not extract renderMarkdownTemplate function from interpolate_prompt.cjs");
-const interpolateVariables = eval(`(${interpolateVariablesMatch[0]})`),
+const selectBranch = eval(`(${selectBranchMatch[0]})`),
+  interpolateVariables = eval(`(${interpolateVariablesMatch[0]})`),
   renderMarkdownTemplate = eval(`(${renderMarkdownTemplateMatch[0]})`);
 describe("interpolate_prompt", () => {
   (describe("interpolateVariables", () => {
@@ -114,6 +117,52 @@ describe("interpolate_prompt", () => {
         it("should support {{/if}} as alternate closing tag", () => {
           const output = renderMarkdownTemplate("{{#if true}}\nKeep\n{{/if}}");
           expect(output).toContain("Keep");
+        }),
+        it("should keep first elseif branch when if is false and elseif is true", () => {
+          const output = renderMarkdownTemplate("{{#if false}}\nBranch A\n{{#elseif true}}\nBranch B\n{{#endif}}");
+          expect(output).toContain("Branch B");
+          expect(output).not.toContain("Branch A");
+          expect(output).not.toContain("{{#elseif}}");
+        }),
+        it("should skip all elseif branches when none match and use else", () => {
+          const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#elseif false}}\nB\n{{#else}}\nFallback\n{{#endif}}");
+          expect(output).toContain("Fallback");
+          expect(output).not.toContain("Branch A");
+          expect(output).not.toContain("Branch B");
+        }),
+        it("should keep the if branch and skip elseif when if is true", () => {
+          const output = renderMarkdownTemplate("{{#if true}}\nFirst\n{{#elseif true}}\nSecond\n{{#endif}}");
+          expect(output).toContain("First");
+          expect(output).not.toContain("Second");
+        }),
+        it("should support else-if hyphen syntax variant", () => {
+          const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#else-if true}}\nB\n{{#endif}}");
+          expect(output).toContain("B");
+          expect(output).not.toContain("A");
+        }),
+        it("should support else_if underscore syntax variant", () => {
+          const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#else_if true}}\nB\n{{#endif}}");
+          expect(output).toContain("B");
+          expect(output).not.toContain("A");
+        }),
+        it("should support elseif without hash prefix", () => {
+          const output = renderMarkdownTemplate("{{#if false}}\nA\n{{elseif true}}\nB\n{{#endif}}");
+          expect(output).toContain("B");
+          expect(output).not.toContain("A");
+        }),
+        it("should handle multiple elseif branches selecting the correct one", () => {
+          const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#elseif false}}\nB\n{{#elseif true}}\nC\n{{#elseif true}}\nD\n{{#endif}}");
+          expect(output).toContain("C");
+          expect(output).not.toContain("A");
+          expect(output).not.toContain("B");
+          expect(output).not.toContain("D");
+        }),
+        it("should support equality condition in elseif", () => {
+          // 'something' != "concise" and 'something' != "verbose" so else branch is selected
+          const output = renderMarkdownTemplate('{{#if something == "concise"}}\nConcise\n{{#elseif something == "verbose"}}\nVerbose\n{{#else}}\nDefault\n{{#endif}}');
+          expect(output).toContain("Default");
+          expect(output).not.toContain("Concise");
+          expect(output).not.toContain("Verbose");
         }));
     }),
     describe("combined interpolation and template rendering", () => {
diff --git a/actions/setup/js/render_template.cjs b/actions/setup/js/render_template.cjs
index 8f3813ea58..a5c51a420b 100644
--- a/actions/setup/js/render_template.cjs
+++ b/actions/setup/js/render_template.cjs
@@ -12,6 +12,44 @@ const fs = require("fs");
 const { ERR_API, ERR_CONFIG } = require("./error_codes.cjs");
 const { isTruthy } = require("./is_truthy.cjs");
 
+/**
+ * Selects the appropriate branch from a conditional block that may contain
+ * {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
+ * branches in addition to the optional {{#else}} fallback.
+ *
+ * @param {string} ifCondition - The condition from the opening {{#if ...}} tag
+ * @param {string} body        - Everything between the opening tag and {{/if}}
+ * @returns {string|null}      - Content of the first truthy branch, or null
+ */
+function selectBranch(ifCondition, body) {
+  // Split on all elseif variants.  The capturing group ensures that the condition
+  // text appears between the content pieces in the resulting array.
+  // Supported: {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
+  const parts = body.split(/[ \t]*\{\{#?else[-_]?if\s+([^}]*)\}\}[ \t]*\n?/);
+
+  // parts alternates: [content0, cond1, content1, cond2, content2, ...]
+  const branches = [{ condition: ifCondition, content: parts[0] }];
+  for (let i = 1; i < parts.length; i += 2) {
+    branches.push({ condition: parts[i].trim(), content: parts[i + 1] || "" });
+  }
+
+  // Check whether the last branch's content contains a {{#else}} tail
+  const lastBranch = branches[branches.length - 1];
+  const elseParts = lastBranch.content.split(/[ \t]*\{\{#else\}\}[ \t]*\n?/);
+  if (elseParts.length > 1) {
+    lastBranch.content = elseParts[0];
+    branches.push({ condition: null, content: elseParts.slice(1).join("{{#else}}") });
+  }
+
+  // Return content of the first truthy branch
+  for (const branch of branches) {
+    if (branch.condition === null || isTruthy(branch.condition)) {
+      return branch.content;
+    }
+  }
+  return null;
+}
+
 /**
  * Renders a Markdown template by processing {{#if}} conditional blocks.
  * When a conditional block is removed (falsy condition) and the template tags
@@ -50,16 +88,15 @@ function renderMarkdownTemplate(markdown) {
   // Uses .*? (non-greedy) with \s* to handle expressions with or without trailing spaces
   let result = _stripped.replace(/(\n?)([ \t]*{{#if\s+(.*?)\s*}}[ \t]*\n)([\s\S]*?)([ \t]*{{\/if}}[ \t]*)(\n?)/g, (match, leadNL, openLine, cond, body) => {
     blockCount++;
-    const truthyResult = isTruthy(cond);
 
-    core.info(`[renderMarkdownTemplate] Block ${blockCount}: condition="${cond.trim()}" -> ${truthyResult ? "KEEP" : "REMOVE"}`);
+    core.info(`[renderMarkdownTemplate] Block ${blockCount}: condition="${cond.trim()}" -> evaluating branches`);
+
+    const selectedContent = selectBranch(cond, body);
 
-    if (truthyResult) {
-      // Keep body with leading newline if there was one before the opening tag
+    if (selectedContent !== null) {
       keptBlocks++;
-      return leadNL + body;
+      return leadNL + selectedContent;
     } else {
-      // Remove entire block completely - the line containing the template is removed
       removedBlocks++;
       return "";
     }
@@ -75,13 +112,13 @@ function renderMarkdownTemplate(markdown) {
   // Uses .*? (non-greedy) with \s* to handle expressions with or without trailing spaces
   result = result.replace(/{{#if\s+(.*?)\s*}}([\s\S]*?){{\/if}}/g, (_, cond, body) => {
     inlineCount++;
-    const truthyResult = isTruthy(cond);
+    const selectedContent = selectBranch(cond, body);
 
-    core.info(`[renderMarkdownTemplate] Inline ${inlineCount}: condition="${cond.trim()}" -> ${truthyResult ? "KEEP" : "REMOVE"}`);
+    core.info(`[renderMarkdownTemplate] Inline ${inlineCount}: condition="${cond.trim()}" -> ${selectedContent !== null ? "KEEP" : "REMOVE"}`);
 
-    if (truthyResult) {
+    if (selectedContent !== null) {
       keptInline++;
-      return body;
+      return selectedContent;
     } else {
       removedInline++;
       return "";
@@ -152,4 +189,4 @@ function main() {
   }
 }
 
-module.exports = { renderMarkdownTemplate, main };
+module.exports = { renderMarkdownTemplate, main, selectBranch };
diff --git a/actions/setup/js/render_template.test.cjs b/actions/setup/js/render_template.test.cjs
index fbd9ae1fe5..7a869cc435 100644
--- a/actions/setup/js/render_template.test.cjs
+++ b/actions/setup/js/render_template.test.cjs
@@ -8,9 +8,12 @@ const __filename = fileURLToPath(import.meta.url),
 global.core = core;
 const { isTruthy } = require("./is_truthy.cjs"),
   renderTemplateScript = fs.readFileSync(path.join(__dirname, "render_template.cjs"), "utf8"),
+  selectBranchMatch = renderTemplateScript.match(/function selectBranch\(ifCondition, body\)\s*{[\s\S]*?return null;\s*\n?}/),
   renderMarkdownTemplateMatch = renderTemplateScript.match(/function renderMarkdownTemplate\(markdown\)\s*{[\s\S]*?return result;[\s\S]*?}/);
+if (!selectBranchMatch) throw new Error("Could not extract selectBranch function from render_template.cjs");
 if (!renderMarkdownTemplateMatch) throw new Error("Could not extract renderMarkdownTemplate function from render_template.cjs");
-const renderMarkdownTemplate = eval(`(${renderMarkdownTemplateMatch[0]})`);
+const selectBranch = eval(`(${selectBranchMatch[0]})`),
+  renderMarkdownTemplate = eval(`(${renderMarkdownTemplateMatch[0]})`);
 describe("renderMarkdownTemplate", () => {
   (it("should keep content in truthy blocks", () => {
     const output = renderMarkdownTemplate("{{#if true}}\nHello\n{{/if}}");
@@ -118,4 +121,55 @@ describe("renderMarkdownTemplate", () => {
       expect(output).toBe("Keep\n```python\nprint('hello')\n```");
     });
   });
+  describe("elseif support", () => {
+    it("should keep elseif branch when if is false and elseif is true", () => {
+      const output = renderMarkdownTemplate("{{#if false}}\nBranch A\n{{#elseif true}}\nBranch B\n{{/if}}");
+      expect(output).toContain("Branch B");
+      expect(output).not.toContain("Branch A");
+    });
+    it("should keep if branch and skip elseif when if is true", () => {
+      const output = renderMarkdownTemplate("{{#if true}}\nFirst\n{{#elseif true}}\nSecond\n{{/if}}");
+      expect(output).toContain("First");
+      expect(output).not.toContain("Second");
+    });
+    it("should fall through to else when no if/elseif matches", () => {
+      const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#elseif false}}\nB\n{{#else}}\nFallback\n{{/if}}");
+      expect(output).toContain("Fallback");
+      expect(output).not.toContain("Branch A");
+      expect(output).not.toContain("Branch B");
+    });
+    it("should support else-if hyphen variant", () => {
+      const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#else-if true}}\nB\n{{/if}}");
+      expect(output).toContain("B");
+      expect(output).not.toContain("A");
+    });
+    it("should support else_if underscore variant", () => {
+      const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#else_if true}}\nB\n{{/if}}");
+      expect(output).toContain("B");
+      expect(output).not.toContain("A");
+    });
+    it("should support elseif without hash prefix", () => {
+      const output = renderMarkdownTemplate("{{#if false}}\nA\n{{elseif true}}\nB\n{{/if}}");
+      expect(output).toContain("B");
+      expect(output).not.toContain("A");
+    });
+    it("should remove entire block when no branch matches", () => {
+      const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#elseif false}}\nB\n{{/if}}");
+      expect(output).toBe("");
+    });
+    it("should select first matching branch among multiple elseif", () => {
+      const output = renderMarkdownTemplate("{{#if false}}\nA\n{{#elseif false}}\nB\n{{#elseif true}}\nC\n{{#elseif true}}\nD\n{{/if}}");
+      expect(output).toContain("C");
+      expect(output).not.toContain("A");
+      expect(output).not.toContain("B");
+      expect(output).not.toContain("D");
+    });
+    it("should support equality condition in elseif", () => {
+      // 'something' != "concise" and 'something' != "verbose" so else branch is selected
+      const output = renderMarkdownTemplate('{{#if something == "concise"}}\nConcise\n{{#elseif something == "verbose"}}\nVerbose\n{{#else}}\nDefault\n{{/if}}');
+      expect(output).toContain("Default");
+      expect(output).not.toContain("Concise");
+      expect(output).not.toContain("Verbose");
+    });
+  });
 });
diff --git a/pkg/workflow/expression_patterns.go b/pkg/workflow/expression_patterns.go
index 7df7480c41..bc8f3d1833 100644
--- a/pkg/workflow/expression_patterns.go
+++ b/pkg/workflow/expression_patterns.go
@@ -165,6 +165,13 @@ var (
 	// TemplateIfPattern matches {{#if condition }} template conditionals
 	// Captures the condition expression (which may contain ${{ ... }})
 	TemplateIfPattern = regexp.MustCompile(`\{\{#if\s+((?:\$\{\{[^\}]*\}\}|[^\}])*)\s*\}\}`)
+
+	// TemplateElseIfPattern matches elseif/else-if/else_if template conditionals in all supported
+	// syntax variants:
+	//   {{#elseif expr}}  {{#else-if expr}}  {{#else_if expr}}
+	//   {{elseif expr}}   {{else-if expr}}   {{else_if expr}}
+	// Captures the condition expression (which may contain ${{ ... }})
+	TemplateElseIfPattern = regexp.MustCompile(`\{\{#?else[-_]?if\s+((?:\$\{\{[^\}]*\}\}|[^\}])*)\s*\}\}`)
 )
 
 // Comparison and Literal Patterns
diff --git a/pkg/workflow/template.go b/pkg/workflow/template.go
index e846e62d1b..e72bb3a8df 100644
--- a/pkg/workflow/template.go
+++ b/pkg/workflow/template.go
@@ -2,6 +2,7 @@ package workflow
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/github/gh-aw/pkg/logger"
@@ -12,15 +13,14 @@ var templateLog = logger.New("workflow:template")
 // wrapExpressionsInTemplateConditionals transforms template conditionals by wrapping
 // expressions in ${{ }}. For example:
 // {{#if github.event.issue.number}} becomes {{#if ${{ github.event.issue.number }} }}
+// {{#elseif github.actor}} becomes {{#elseif ${{ github.actor }} }}
 func wrapExpressionsInTemplateConditionals(markdown string) string {
-	// Reuse the centralized TemplateIfPattern from expression_patterns.go
-	// Pattern matches {{#if expression}} where expression may contain ${{ }} blocks
-	re := TemplateIfPattern
-
 	templateLog.Print("Wrapping expressions in template conditionals")
 
-	result := re.ReplaceAllStringFunc(markdown, func(match string) string {
-		// Extract the expression part (everything between "{{#if " and "}}")
+	// wrapTagExpr applies the wrapping logic to a single extracted expression and
+	// returns the full reconstructed tag. prefix is the opening tag text without the
+	// expression (e.g. "{{#if " or "{{#elseif ").
+	wrapTagExpr := func(re *regexp.Regexp, match, prefix string) string {
 		submatches := re.FindStringSubmatch(match)
 		if len(submatches) < 2 {
 			return match
@@ -28,37 +28,49 @@ func wrapExpressionsInTemplateConditionals(markdown string) string {
 
 		expr := strings.TrimSpace(submatches[1])
 
-		// Check if expression is empty (after trimming)
 		// Empty expressions are treated as false and wrapped as such
 		if expr == "" {
 			templateLog.Print("Empty expression detected, wrapping as false")
-			return "{{#if ${{ false }} }}"
+			return prefix + "${{ false }} }}"
 		}
 
-		// Check if expression is already wrapped in ${{ ... }}
-		// Look for the pattern starting with "${{"
+		// Already wrapped in ${{ ... }} — return as-is
 		if strings.HasPrefix(expr, "${{") {
 			templateLog.Print("Expression already wrapped, skipping")
-			return match // Already wrapped, return as-is
+			return match
 		}
 
-		// Check if expression is an environment variable reference (starts with ${)
-		// These don't need ${{ }} wrapping as they're already evaluated
+		// Environment variable reference (starts with ${) — already evaluated
 		if strings.HasPrefix(expr, "${") {
 			templateLog.Print("Environment variable reference detected, skipping wrap")
-			return match // Environment variable reference, return as-is
+			return match
 		}
 
-		// Check if expression is a placeholder reference (starts with __)
-		// These are substituted with sed and don't need ${{ }} wrapping
+		// Placeholder reference (starts with __) — substituted at runtime
 		if strings.HasPrefix(expr, "__") {
 			templateLog.Print("Placeholder reference detected, skipping wrap")
-			return match // Placeholder reference, return as-is
+			return match
 		}
 
-		// Always wrap expressions that don't start with ${{ or ${ or __
 		templateLog.Printf("Wrapping expression: %s", expr)
-		return "{{#if ${{ " + expr + " }} }}"
+		return prefix + "${{ " + expr + " }} }}"
+	}
+
+	// Process {{#if ...}} tags
+	result := TemplateIfPattern.ReplaceAllStringFunc(markdown, func(match string) string {
+		return wrapTagExpr(TemplateIfPattern, match, "{{#if ")
+	})
+
+	// Process all elseif variant tags — normalise to canonical {{#elseif ...}} form after wrapping
+	result = TemplateElseIfPattern.ReplaceAllStringFunc(result, func(match string) string {
+		submatches := TemplateElseIfPattern.FindStringSubmatch(match)
+		if len(submatches) < 2 {
+			return match
+		}
+		wrapped := wrapTagExpr(TemplateElseIfPattern, match, "{{#elseif ")
+		// If the original tag used a non-canonical form (else-if / else_if / without #),
+		// the prefix replacement above already normalises it to {{#elseif ...}}.
+		return wrapped
 	})
 
 	return result
diff --git a/pkg/workflow/template_expression_wrapping_test.go b/pkg/workflow/template_expression_wrapping_test.go
index 9f9ea753dd..363af60216 100644
--- a/pkg/workflow/template_expression_wrapping_test.go
+++ b/pkg/workflow/template_expression_wrapping_test.go
@@ -241,6 +241,57 @@ Regular content`,
 			input:    "{{#if github.actor}}A{{/if}} {{#if }}B{{/if}} {{#if true}}C{{/if}}",
 			expected: "{{#if ${{ github.actor }} }}A{{/if}} {{#if ${{ false }} }}B{{/if}} {{#if ${{ true }} }}C{{/if}}",
 		},
+		// elseif variants — expression wrapping and canonical normalisation
+		{
+			name:     "canonical elseif wraps expression",
+			input:    "{{#if github.actor}}A{{#elseif github.repository}}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${{ github.repository }} }}B{{/if}}",
+		},
+		{
+			name:     "else-if hyphen variant normalised to canonical",
+			input:    "{{#if github.actor}}A{{#else-if github.repository}}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${{ github.repository }} }}B{{/if}}",
+		},
+		{
+			name:     "else_if underscore variant normalised to canonical",
+			input:    "{{#if github.actor}}A{{#else_if github.repository}}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${{ github.repository }} }}B{{/if}}",
+		},
+		{
+			name:     "elseif without hash prefix normalised to canonical",
+			input:    "{{#if github.actor}}A{{elseif github.repository}}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${{ github.repository }} }}B{{/if}}",
+		},
+		{
+			name:     "else-if without hash prefix normalised to canonical",
+			input:    "{{#if github.actor}}A{{else-if github.repository}}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${{ github.repository }} }}B{{/if}}",
+		},
+		{
+			name:     "else_if without hash prefix normalised to canonical",
+			input:    "{{#if github.actor}}A{{else_if github.repository}}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${{ github.repository }} }}B{{/if}}",
+		},
+		{
+			name:     "elseif already wrapped expression skipped",
+			input:    "{{#if github.actor}}A{{#elseif ${{ github.repository }} }}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${{ github.repository }} }}B{{/if}}",
+		},
+		{
+			name:     "multiple elseif branches wrapped",
+			input:    "{{#if github.actor}}A{{#elseif github.repository}}B{{#elseif env.MY_VAR}}C{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${{ github.repository }} }}B{{#elseif ${{ env.MY_VAR }} }}C{{/if}}",
+		},
+		{
+			name:     "elseif with env var reference skipped",
+			input:    "{{#if github.actor}}A{{#elseif ${GH_AW_EXPR_REPO}}}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif ${GH_AW_EXPR_REPO}}}B{{/if}}",
+		},
+		{
+			name:     "elseif with placeholder reference skipped",
+			input:    "{{#if github.actor}}A{{#elseif __GH_AW_VAR__}}B{{/if}}",
+			expected: "{{#if ${{ github.actor }} }}A{{#elseif __GH_AW_VAR__}}B{{/if}}",
+		},
 	}
 
 	for _, tt := range tests {
diff --git a/pkg/workflow/template_include_validation_test.go b/pkg/workflow/template_include_validation_test.go
index 2836a719bf..a1d4231aad 100644
--- a/pkg/workflow/template_include_validation_test.go
+++ b/pkg/workflow/template_include_validation_test.go
@@ -446,6 +446,71 @@ Even more content.
 	}
 }
 
+// TestValidateNoPreExpandedExperimentPlaceholders_ElseIf tests that elseif conditions
+// are also checked for pre-expanded experiment placeholders.
+func TestValidateNoPreExpandedExperimentPlaceholders_ElseIf(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   string
+		wantErr bool
+		errMsg  string
+	}{
+		{
+			name:    "valid - experiments.name in if condition",
+			input:   `{{#if experiments.prompt_style == "detailed"}}content{{/if}}`,
+			wantErr: false,
+		},
+		{
+			name:    "valid - experiments.name in elseif condition",
+			input:   `{{#if false}}a{{#elseif experiments.prompt_style == "detailed"}}content{{/if}}`,
+			wantErr: false,
+		},
+		{
+			name:    "invalid - pre-expanded placeholder in if condition",
+			input:   `{{#if __GH_AW_EXPERIMENTS_PROMPT_STYLE__ == "detailed"}}content{{/if}}`,
+			wantErr: true,
+			errMsg:  "pre-expanded experiment placeholder",
+		},
+		{
+			name:    "invalid - pre-expanded placeholder in elseif condition",
+			input:   `{{#if false}}a{{#elseif __GH_AW_EXPERIMENTS_PROMPT_STYLE__ == "detailed"}}content{{/if}}`,
+			wantErr: true,
+			errMsg:  "pre-expanded experiment placeholder",
+		},
+		{
+			name:    "invalid - pre-expanded placeholder in else-if (hyphen) condition",
+			input:   `{{#if false}}a{{#else-if __GH_AW_EXPERIMENTS_FEATURE__ == "on"}}content{{/if}}`,
+			wantErr: true,
+			errMsg:  "pre-expanded experiment placeholder",
+		},
+		{
+			name:    "invalid - pre-expanded placeholder in else_if (underscore) condition",
+			input:   `{{#if false}}a{{#else_if __GH_AW_EXPERIMENTS_FEATURE__}}content{{/if}}`,
+			wantErr: true,
+			errMsg:  "pre-expanded experiment placeholder",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := validateNoPreExpandedExperimentPlaceholders(tt.input)
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("validateNoPreExpandedExperimentPlaceholders() expected error, got nil")
+					return
+				}
+				if tt.errMsg != "" && !strings.Contains(err.Error(), tt.errMsg) {
+					t.Errorf("validateNoPreExpandedExperimentPlaceholders() error = %q, want to contain %q", err.Error(), tt.errMsg)
+				}
+			} else {
+				if err != nil {
+					t.Errorf("validateNoPreExpandedExperimentPlaceholders() unexpected error = %v", err)
+				}
+			}
+		})
+	}
+}
+
 // TestValidateNoIncludesInTemplateRegions_SingleError tests single error behavior
 func TestValidateNoIncludesInTemplateRegions_SingleError(t *testing.T) {
 	// Input with single include inside template region
diff --git a/pkg/workflow/template_validation.go b/pkg/workflow/template_validation.go
index bcd0b7567a..f0e5903980 100644
--- a/pkg/workflow/template_validation.go
+++ b/pkg/workflow/template_validation.go
@@ -103,12 +103,14 @@ func validateNoIncludesInTemplateRegions(markdown string) error {
 func validateNoPreExpandedExperimentPlaceholders(markdown string) error {
 	templateValidationLog.Print("Validating that pre-expanded experiment placeholders are not used in template conditions")
 
-	// Use TemplateIfPattern which correctly handles embedded ${{ ... }} blocks inside conditions
-	conditions := TemplateIfPattern.FindAllStringSubmatch(markdown, -1)
-	templateValidationLog.Printf("Found %d template condition(s) to validate", len(conditions))
+	// Collect conditions from both {{#if ...}} and all elseif variants
+	ifConditions := TemplateIfPattern.FindAllStringSubmatch(markdown, -1)
+	elseifConditions := TemplateElseIfPattern.FindAllStringSubmatch(markdown, -1)
+	allConditions := append(ifConditions, elseifConditions...)
+	templateValidationLog.Printf("Found %d template condition(s) to validate", len(allConditions))
 
 	var errs []error
-	for _, m := range conditions {
+	for _, m := range allConditions {
 		if len(m) < 2 {
 			continue
 		}

From 8beb17c63a452c1ecbee57ee4657287c16c5526e Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 5 May 2026 13:09:20 +0000
Subject: [PATCH 3/4] refactor: extract selectBranch to shared
 template_branch.cjs utility

Address code review feedback: remove duplication by moving selectBranch
from interpolate_prompt.cjs and render_template.cjs into a single shared
template_branch.cjs module. Both consumers now require the shared module.
Also clarify the wrapTagExpr closure comment in template.go.

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/40bbec61-dc73-4fb0-aa5a-97a5823cd269

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 actions/setup/js/interpolate_prompt.cjs      | 52 +-----------------
 actions/setup/js/interpolate_prompt.test.cjs | 10 ++--
 actions/setup/js/render_template.cjs         | 41 +-------------
 actions/setup/js/render_template.test.cjs    |  6 +--
 actions/setup/js/template_branch.cjs         | 57 ++++++++++++++++++++
 pkg/workflow/template.go                     |  6 ++-
 6 files changed, 71 insertions(+), 101 deletions(-)
 create mode 100644 actions/setup/js/template_branch.cjs

diff --git a/actions/setup/js/interpolate_prompt.cjs b/actions/setup/js/interpolate_prompt.cjs
index 22554dfb8f..2d7da5adbe 100644
--- a/actions/setup/js/interpolate_prompt.cjs
+++ b/actions/setup/js/interpolate_prompt.cjs
@@ -10,6 +10,7 @@
 
 const fs = require("fs");
 const { isTruthy } = require("./is_truthy.cjs");
+const { selectBranch } = require("./template_branch.cjs");
 const { processRuntimeImports } = require("./runtime_import.cjs");
 const { writeInlineSubAgents } = require("./extract_inline_sub_agents.cjs");
 const { getErrorMessage } = require("./error_helpers.cjs");
@@ -48,55 +49,6 @@ function interpolateVariables(content, variables) {
   return result;
 }
 
-/**
- * Selects the appropriate branch from a conditional block that may contain
- * {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
- * branches in addition to the optional {{#else}} fallback.
- *
- * Algorithm:
- *   1. Split the body on elseif markers (all syntax variants) — capturing groups
- *      in the split pattern yield alternating [content, condition, content, ...].
- *   2. Pair each content piece with the condition that guards it:
- *        - First piece is guarded by the {{#if}} condition (ifCondition).
- *        - Subsequent pieces are guarded by the preceding elseif condition.
- *   3. Check the last piece for a {{#else}} tail and, if found, add an
- *      unconditional else branch.
- *   4. Return the content of the first truthy branch, or null if none matched.
- *
- * @param {string} ifCondition - The condition from the opening {{#if ...}} tag
- * @param {string} body        - Everything between the opening tag and {{/if}}
- * @returns {string|null}      - Content of the first truthy branch, or null
- */
-function selectBranch(ifCondition, body) {
-  // Split on all elseif variants.  The capturing group ensures that the condition
-  // text appears between the content pieces in the resulting array.
-  // Supported: {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
-  const parts = body.split(/[ \t]*\{\{#?else[-_]?if\s+([^}]*)\}\}[ \t]*\n?/);
-
-  // parts alternates: [content0, cond1, content1, cond2, content2, ...]
-  const branches = [{ condition: ifCondition, content: parts[0] }];
-  for (let i = 1; i < parts.length; i += 2) {
-    branches.push({ condition: parts[i].trim(), content: parts[i + 1] || "" });
-  }
-
-  // Check whether the last branch's content contains a {{#else}} tail
-  const lastBranch = branches[branches.length - 1];
-  const elseParts = lastBranch.content.split(/[ \t]*\{\{#else\}\}[ \t]*\n?/);
-  if (elseParts.length > 1) {
-    lastBranch.content = elseParts[0];
-    // condition: null = unconditional else branch
-    branches.push({ condition: null, content: elseParts.slice(1).join("{{#else}}") });
-  }
-
-  // Return content of the first truthy branch
-  for (const branch of branches) {
-    if (branch.condition === null || isTruthy(branch.condition)) {
-      return branch.content;
-    }
-  }
-  return null;
-}
-
 /**
  * Renders a Markdown template by processing {{#if}} conditional blocks.
  * When a conditional block is removed (falsy condition) and the template tags
@@ -404,4 +356,4 @@ async function main() {
   }
 }
 
-module.exports = { main, renderMarkdownTemplate, interpolateVariables, selectBranch };
+module.exports = { main, renderMarkdownTemplate, interpolateVariables };
diff --git a/actions/setup/js/interpolate_prompt.test.cjs b/actions/setup/js/interpolate_prompt.test.cjs
index 7142258ac2..e2a2ebdd96 100644
--- a/actions/setup/js/interpolate_prompt.test.cjs
+++ b/actions/setup/js/interpolate_prompt.test.cjs
@@ -8,16 +8,14 @@ const __filename = fileURLToPath(import.meta.url),
   __dirname = path.dirname(__filename),
   core = { info: vi.fn(), warning: vi.fn(), setFailed: vi.fn() };
 global.core = core;
-const interpolatePromptScript = fs.readFileSync(path.join(__dirname, "interpolate_prompt.cjs"), "utf8"),
-  { isTruthy } = require("./is_truthy.cjs"),
-  selectBranchMatch = interpolatePromptScript.match(/function selectBranch\(ifCondition, body\)\s*{[\s\S]*?return null;\s*\n?}/),
+const { isTruthy } = require("./is_truthy.cjs"),
+  { selectBranch } = require("./template_branch.cjs"),
+  interpolatePromptScript = fs.readFileSync(path.join(__dirname, "interpolate_prompt.cjs"), "utf8"),
   interpolateVariablesMatch = interpolatePromptScript.match(/function interpolateVariables\(content, variables\)\s*{[\s\S]*?return result;[\s\S]*?}/),
   renderMarkdownTemplateMatch = interpolatePromptScript.match(/function renderMarkdownTemplate\(markdown\)\s*{[\s\S]*?return result;[\s\S]*?}/);
-if (!selectBranchMatch) throw new Error("Could not extract selectBranch function from interpolate_prompt.cjs");
 if (!interpolateVariablesMatch) throw new Error("Could not extract interpolateVariables function from interpolate_prompt.cjs");
 if (!renderMarkdownTemplateMatch) throw new Error("Could not extract renderMarkdownTemplate function from interpolate_prompt.cjs");
-const selectBranch = eval(`(${selectBranchMatch[0]})`),
-  interpolateVariables = eval(`(${interpolateVariablesMatch[0]})`),
+const interpolateVariables = eval(`(${interpolateVariablesMatch[0]})`),
   renderMarkdownTemplate = eval(`(${renderMarkdownTemplateMatch[0]})`);
 describe("interpolate_prompt", () => {
   (describe("interpolateVariables", () => {
diff --git a/actions/setup/js/render_template.cjs b/actions/setup/js/render_template.cjs
index a5c51a420b..e87d12d87a 100644
--- a/actions/setup/js/render_template.cjs
+++ b/actions/setup/js/render_template.cjs
@@ -11,44 +11,7 @@ const { getErrorMessage } = require("./error_helpers.cjs");
 const fs = require("fs");
 const { ERR_API, ERR_CONFIG } = require("./error_codes.cjs");
 const { isTruthy } = require("./is_truthy.cjs");
-
-/**
- * Selects the appropriate branch from a conditional block that may contain
- * {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
- * branches in addition to the optional {{#else}} fallback.
- *
- * @param {string} ifCondition - The condition from the opening {{#if ...}} tag
- * @param {string} body        - Everything between the opening tag and {{/if}}
- * @returns {string|null}      - Content of the first truthy branch, or null
- */
-function selectBranch(ifCondition, body) {
-  // Split on all elseif variants.  The capturing group ensures that the condition
-  // text appears between the content pieces in the resulting array.
-  // Supported: {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
-  const parts = body.split(/[ \t]*\{\{#?else[-_]?if\s+([^}]*)\}\}[ \t]*\n?/);
-
-  // parts alternates: [content0, cond1, content1, cond2, content2, ...]
-  const branches = [{ condition: ifCondition, content: parts[0] }];
-  for (let i = 1; i < parts.length; i += 2) {
-    branches.push({ condition: parts[i].trim(), content: parts[i + 1] || "" });
-  }
-
-  // Check whether the last branch's content contains a {{#else}} tail
-  const lastBranch = branches[branches.length - 1];
-  const elseParts = lastBranch.content.split(/[ \t]*\{\{#else\}\}[ \t]*\n?/);
-  if (elseParts.length > 1) {
-    lastBranch.content = elseParts[0];
-    branches.push({ condition: null, content: elseParts.slice(1).join("{{#else}}") });
-  }
-
-  // Return content of the first truthy branch
-  for (const branch of branches) {
-    if (branch.condition === null || isTruthy(branch.condition)) {
-      return branch.content;
-    }
-  }
-  return null;
-}
+const { selectBranch } = require("./template_branch.cjs");
 
 /**
  * Renders a Markdown template by processing {{#if}} conditional blocks.
@@ -189,4 +152,4 @@ function main() {
   }
 }
 
-module.exports = { renderMarkdownTemplate, main, selectBranch };
+module.exports = { renderMarkdownTemplate, main };
diff --git a/actions/setup/js/render_template.test.cjs b/actions/setup/js/render_template.test.cjs
index 7a869cc435..c0d29bbf7e 100644
--- a/actions/setup/js/render_template.test.cjs
+++ b/actions/setup/js/render_template.test.cjs
@@ -7,13 +7,11 @@ const __filename = fileURLToPath(import.meta.url),
   core = { info: vi.fn(), warning: vi.fn(), setFailed: vi.fn(), summary: { addHeading: vi.fn().mockReturnThis(), addRaw: vi.fn().mockReturnThis(), write: vi.fn() } };
 global.core = core;
 const { isTruthy } = require("./is_truthy.cjs"),
+  { selectBranch } = require("./template_branch.cjs"),
   renderTemplateScript = fs.readFileSync(path.join(__dirname, "render_template.cjs"), "utf8"),
-  selectBranchMatch = renderTemplateScript.match(/function selectBranch\(ifCondition, body\)\s*{[\s\S]*?return null;\s*\n?}/),
   renderMarkdownTemplateMatch = renderTemplateScript.match(/function renderMarkdownTemplate\(markdown\)\s*{[\s\S]*?return result;[\s\S]*?}/);
-if (!selectBranchMatch) throw new Error("Could not extract selectBranch function from render_template.cjs");
 if (!renderMarkdownTemplateMatch) throw new Error("Could not extract renderMarkdownTemplate function from render_template.cjs");
-const selectBranch = eval(`(${selectBranchMatch[0]})`),
-  renderMarkdownTemplate = eval(`(${renderMarkdownTemplateMatch[0]})`);
+const renderMarkdownTemplate = eval(`(${renderMarkdownTemplateMatch[0]})`);
 describe("renderMarkdownTemplate", () => {
   (it("should keep content in truthy blocks", () => {
     const output = renderMarkdownTemplate("{{#if true}}\nHello\n{{/if}}");
diff --git a/actions/setup/js/template_branch.cjs b/actions/setup/js/template_branch.cjs
new file mode 100644
index 0000000000..575d167ee9
--- /dev/null
+++ b/actions/setup/js/template_branch.cjs
@@ -0,0 +1,57 @@
+// @ts-check
+
+// template_branch.cjs
+// Shared branch-selection logic for {{#if / #elseif* / #else}} template conditionals.
+
+const { isTruthy } = require("./is_truthy.cjs");
+
+/**
+ * Selects the appropriate branch from a conditional block that may contain
+ * {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
+ * branches in addition to the optional {{#else}} fallback.
+ *
+ * Algorithm:
+ *   1. Split the body on elseif markers (all syntax variants) — capturing groups
+ *      in the split pattern yield alternating [content, condition, content, ...].
+ *   2. Pair each content piece with the condition that guards it:
+ *        - First piece is guarded by the {{#if}} condition (ifCondition).
+ *        - Subsequent pieces are guarded by the preceding elseif condition.
+ *   3. Check the last piece for a {{#else}} tail and, if found, add an
+ *      unconditional else branch.
+ *   4. Return the content of the first truthy branch, or null if none matched.
+ *
+ * @param {string} ifCondition - The condition from the opening {{#if ...}} tag
+ * @param {string} body        - Everything between the opening tag and {{/if}}
+ * @returns {string|null}      - Content of the first truthy branch, or null
+ */
+function selectBranch(ifCondition, body) {
+  // Split on all elseif variants.  The capturing group ensures that the condition
+  // text appears between the content pieces in the resulting array.
+  // Supported: {{#elseif}}, {{#else-if}}, {{#else_if}}, {{elseif}}, {{else-if}}, {{else_if}}
+  const parts = body.split(/[ \t]*\{\{#?else[-_]?if\s+([^}]*)\}\}[ \t]*\n?/);
+
+  // parts alternates: [content0, cond1, content1, cond2, content2, ...]
+  const branches = [{ condition: ifCondition, content: parts[0] }];
+  for (let i = 1; i < parts.length; i += 2) {
+    branches.push({ condition: parts[i].trim(), content: parts[i + 1] || "" });
+  }
+
+  // Check whether the last branch's content contains a {{#else}} tail
+  const lastBranch = branches[branches.length - 1];
+  const elseParts = lastBranch.content.split(/[ \t]*\{\{#else\}\}[ \t]*\n?/);
+  if (elseParts.length > 1) {
+    lastBranch.content = elseParts[0];
+    // condition: null = unconditional else branch
+    branches.push({ condition: null, content: elseParts.slice(1).join("{{#else}}") });
+  }
+
+  // Return content of the first truthy branch
+  for (const branch of branches) {
+    if (branch.condition === null || isTruthy(branch.condition)) {
+      return branch.content;
+    }
+  }
+  return null;
+}
+
+module.exports = { selectBranch };
diff --git a/pkg/workflow/template.go b/pkg/workflow/template.go
index e72bb3a8df..6d2bddb33b 100644
--- a/pkg/workflow/template.go
+++ b/pkg/workflow/template.go
@@ -18,8 +18,10 @@ func wrapExpressionsInTemplateConditionals(markdown string) string {
 	templateLog.Print("Wrapping expressions in template conditionals")
 
 	// wrapTagExpr applies the wrapping logic to a single extracted expression and
-	// returns the full reconstructed tag. prefix is the opening tag text without the
-	// expression (e.g. "{{#if " or "{{#elseif ").
+	// returns the full reconstructed tag. re must be the same regex that produced
+	// match (so FindStringSubmatch reliably extracts capture group 1 = the expression).
+	// prefix is the canonical opening tag text without the expression
+	// (e.g. "{{#if " or "{{#elseif "), used to rebuild the output tag.
 	wrapTagExpr := func(re *regexp.Regexp, match, prefix string) string {
 		submatches := re.FindStringSubmatch(match)
 		if len(submatches) < 2 {

From 424d11eb468d4a3a76e9acb00ed69e0d17615d54 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 5 May 2026 14:06:55 +0000
Subject: [PATCH 4/4] test: add fuzz tests for elseif template expression
 rendering

- Extend FuzzWrapExpressionsInTemplateConditionals seed corpus with all 6
  elseif syntax variants and add invariant check that non-canonical elseif
  forms are fully normalised to {{#elseif}} in the output
- Add fuzz_template_branch_harness.cjs JS harness for selectBranch and
  renderMarkdownTemplate with elseif support
- Add fuzz_template_branch_harness.test.cjs with 18 seed-corpus test cases
  covering all elseif syntax variants, multi-branch chains, equality
  conditions, and crash-safety invariants

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/fd7aa0eb-74aa-454e-bd7a-7d7eee453d71

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 .../setup/js/fuzz_template_branch_harness.cjs |  61 ++++++++++
 .../js/fuzz_template_branch_harness.test.cjs  | 104 ++++++++++++++++++
 pkg/workflow/template_fuzz_test.go            |  35 ++++++
 3 files changed, 200 insertions(+)
 create mode 100644 actions/setup/js/fuzz_template_branch_harness.cjs
 create mode 100644 actions/setup/js/fuzz_template_branch_harness.test.cjs

diff --git a/actions/setup/js/fuzz_template_branch_harness.cjs b/actions/setup/js/fuzz_template_branch_harness.cjs
new file mode 100644
index 0000000000..6712ab8b9c
--- /dev/null
+++ b/actions/setup/js/fuzz_template_branch_harness.cjs
@@ -0,0 +1,61 @@
+// @ts-check
+/**
+ * Fuzz harness for {{#if / #elseif / #else}} template branch selection and rendering.
+ *
+ * Reads a JSON test case from stdin:
+ *   { ifCondition: string, body: string }   — for selectBranch
+ *   { markdown: string }                     — for renderMarkdownTemplate
+ *
+ * Writes the result as JSON to stdout:
+ *   { result: string|null, error: string|null }
+ *
+ * Used by the Go fuzz driver in template_conditional_js_fuzz_test.go.
+ */
+
+const { selectBranch } = require("./template_branch.cjs");
+const { isTruthy } = require("./is_truthy.cjs");
+
+// Minimal shim so renderMarkdownTemplate can call core.info
+if (!global.core) {
+  global.core = {
+    info: () => {},
+    warning: () => {},
+    setFailed: () => {},
+  };
+}
+
+const renderTemplateScript = require("fs").readFileSync(require("path").join(__dirname, "render_template.cjs"), "utf8");
+const renderMarkdownTemplateMatch = renderTemplateScript.match(/function renderMarkdownTemplate\(markdown\)\s*{[\s\S]*?return result;[\s\S]*?}/);
+if (!renderMarkdownTemplateMatch) throw new Error("Could not extract renderMarkdownTemplate");
+const renderMarkdownTemplate = eval(`(${renderMarkdownTemplateMatch[0]})`);
+
+if (require.main === module) {
+  let input = "";
+  process.stdin.on("data", chunk => {
+    input += chunk;
+  });
+  process.stdin.on("end", () => {
+    try {
+      const parsed = JSON.parse(input);
+
+      let result;
+      if (Object.prototype.hasOwnProperty.call(parsed, "ifCondition")) {
+        // selectBranch test
+        result = { result: selectBranch(parsed.ifCondition, parsed.body || ""), error: null };
+      } else if (Object.prototype.hasOwnProperty.call(parsed, "markdown")) {
+        // renderMarkdownTemplate test
+        result = { result: renderMarkdownTemplate(parsed.markdown || ""), error: null };
+      } else {
+        result = { result: null, error: "Unknown test type: expected 'ifCondition' or 'markdown' key" };
+      }
+
+      process.stdout.write(JSON.stringify(result));
+      process.exit(0);
+    } catch (err) {
+      process.stdout.write(JSON.stringify({ result: null, error: err instanceof Error ? err.message : String(err) }));
+      process.exit(1);
+    }
+  });
+}
+
+module.exports = { selectBranch, renderMarkdownTemplate };
diff --git a/actions/setup/js/fuzz_template_branch_harness.test.cjs b/actions/setup/js/fuzz_template_branch_harness.test.cjs
new file mode 100644
index 0000000000..1ce7b63d4e
--- /dev/null
+++ b/actions/setup/js/fuzz_template_branch_harness.test.cjs
@@ -0,0 +1,104 @@
+// @ts-check
+import { describe, it, expect, vi } from "vitest";
+global.core = { info: vi.fn(), warning: vi.fn(), setFailed: vi.fn() };
+
+const { selectBranch, renderMarkdownTemplate } = require("./fuzz_template_branch_harness.cjs");
+
+describe("fuzz_template_branch_harness", () => {
+  describe("selectBranch — seed corpus", () => {
+    it("returns if-branch when condition is truthy (no elseif)", () => {
+      expect(selectBranch("true", "content\n")).toBe("content\n");
+    });
+
+    it("returns null when condition is falsy (no elseif, no else)", () => {
+      expect(selectBranch("false", "content\n")).toBeNull();
+    });
+
+    it("returns elseif branch when if is false and elseif is true", () => {
+      const body = "Branch A\n{{#elseif true}}\nBranch B\n";
+      expect(selectBranch("false", body)).toContain("Branch B");
+    });
+
+    it("returns else branch when all conditions are false", () => {
+      const body = "A\n{{#elseif false}}\nB\n{{#else}}\nFallback\n";
+      expect(selectBranch("false", body)).toContain("Fallback");
+    });
+
+    it("returns first matching elseif among many", () => {
+      const body = "A\n{{#elseif false}}\nB\n{{#elseif true}}\nC\n{{#elseif true}}\nD\n";
+      const result = selectBranch("false", body);
+      expect(result).toContain("C");
+      expect(result).not.toContain("D");
+    });
+
+    it("handles else-if hyphen variant", () => {
+      const body = "A\n{{#else-if true}}\nB\n";
+      expect(selectBranch("false", body)).toContain("B");
+    });
+
+    it("handles else_if underscore variant", () => {
+      const body = "A\n{{#else_if true}}\nB\n";
+      expect(selectBranch("false", body)).toContain("B");
+    });
+
+    it("handles elseif without hash", () => {
+      const body = "A\n{{elseif true}}\nB\n";
+      expect(selectBranch("false", body)).toContain("B");
+    });
+
+    it("returns null for fully-false chain with no else", () => {
+      const body = "A\n{{#elseif false}}\nB\n{{#elseif false}}\nC\n";
+      expect(selectBranch("false", body)).toBeNull();
+    });
+
+    it("handles equality condition in elseif (experiment-style)", () => {
+      // concise == "concise" is truthy
+      const body = 'A\n{{#elseif concise == "concise"}}\nB\n{{#else}}\nC\n';
+      const result = selectBranch("false", body);
+      expect(result).toContain("B");
+      expect(result).not.toContain("C");
+    });
+
+    it("does not crash on empty body", () => {
+      expect(() => selectBranch("true", "")).not.toThrow();
+    });
+
+    it("does not crash on empty condition", () => {
+      expect(() => selectBranch("", "content")).not.toThrow();
+    });
+
+    it("does not crash on deeply nested elseif chain", () => {
+      let body = "";
+      for (let i = 0; i < 50; i++) {
+        body += `Branch ${i}\n{{#elseif false}}\n`;
+      }
+      body += `Last\n`;
+      expect(() => selectBranch("false", body)).not.toThrow();
+    });
+  });
+
+  describe("renderMarkdownTemplate — elseif integration", () => {
+    it("renders elseif branch when if is false", () => {
+      const md = "{{#if false}}\nA\n{{#elseif true}}\nB\n{{/if}}";
+      expect(renderMarkdownTemplate(md)).toContain("B");
+    });
+
+    it("renders else fallback when all elseif branches are false", () => {
+      const md = "{{#if false}}\nA\n{{#elseif false}}\nB\n{{#else}}\nC\n{{/if}}";
+      expect(renderMarkdownTemplate(md)).toContain("C");
+    });
+
+    it("does not crash on arbitrary whitespace in elseif condition", () => {
+      const md = "{{#if false}}\nA\n{{#elseif   true   }}\nB\n{{/if}}";
+      expect(() => renderMarkdownTemplate(md)).not.toThrow();
+    });
+
+    it("does not crash on empty string", () => {
+      expect(() => renderMarkdownTemplate("")).not.toThrow();
+    });
+
+    it("does not crash on malformed elseif (no closing }}", () => {
+      expect(() => renderMarkdownTemplate("{{#if false}}\nA\n{{#elseif true\nB\n{{/if}}")).not.toThrow();
+    });
+  });
+});
diff --git a/pkg/workflow/template_fuzz_test.go b/pkg/workflow/template_fuzz_test.go
index ff6bcf61e8..6fa5cbaed3 100644
--- a/pkg/workflow/template_fuzz_test.go
+++ b/pkg/workflow/template_fuzz_test.go
@@ -103,6 +103,30 @@ func FuzzWrapExpressionsInTemplateConditionals(f *testing.F) {
 	f.Add("Before {{#if github.actor}}middle{{/if}} after")
 	f.Add("{{#if github.actor}}{{#if github.repository}}nested{{/if}}{{/if}}")
 
+	// elseif variants — all 6 syntax forms
+	f.Add("{{#if github.actor}}A{{#elseif github.repository}}B{{/if}}")
+	f.Add("{{#if github.actor}}A{{#else-if github.repository}}B{{/if}}")
+	f.Add("{{#if github.actor}}A{{#else_if github.repository}}B{{/if}}")
+	f.Add("{{#if github.actor}}A{{elseif github.repository}}B{{/if}}")
+	f.Add("{{#if github.actor}}A{{else-if github.repository}}B{{/if}}")
+	f.Add("{{#if github.actor}}A{{else_if github.repository}}B{{/if}}")
+
+	// elseif with already-wrapped expressions (should be preserved)
+	f.Add("{{#if github.actor}}A{{#elseif ${{ github.repository }} }}B{{/if}}")
+
+	// elseif with env var reference (should be preserved, not re-wrapped)
+	f.Add("{{#if github.actor}}A{{#elseif ${GH_AW_EXPR_REPO}}}B{{/if}}")
+
+	// elseif with placeholder reference (should be preserved)
+	f.Add("{{#if github.actor}}A{{#elseif __PLACEHOLDER__}}B{{/if}}")
+
+	// multiple elseif branches
+	f.Add("{{#if a}}A{{#elseif b}}B{{#elseif c}}C{{/if}}")
+
+	// elseif + else
+	f.Add("{{#if a}}A{{#elseif b}}B{{#else}}C{{/if}}")
+	f.Add("{{#if github.actor}}\nA\n{{#elseif github.repository}}\nB\n{{#else}}\nC\n{{/if}}")
+
 	f.Fuzz(func(t *testing.T, input string) {
 		// The fuzzer will generate variations of the seed corpus
 		// and random strings to test the wrapper
@@ -149,5 +173,16 @@ func FuzzWrapExpressionsInTemplateConditionals(f *testing.F) {
 				t.Errorf("Placeholder references should be preserved, input: %q, result: %q", input, result)
 			}
 		}
+
+		// All elseif syntax variants must be normalised to canonical {{#elseif in the output
+		nonCanonicalElseif := []string{
+			"{{#else-if ", "{{#else_if ",
+			"{{elseif ", "{{else-if ", "{{else_if ",
+		}
+		for _, variant := range nonCanonicalElseif {
+			if strings.Contains(result, variant) {
+				t.Errorf("Non-canonical elseif variant %q still present in output, input: %q", variant, input)
+			}
+		}
 	})
 }