diff --git a/.github/agents/self-hosted-runner-doctor.md b/.github/agents/self-hosted-runner-doctor.md
index 1f57aab12..d49d98afa 100644
--- a/.github/agents/self-hosted-runner-doctor.md
+++ b/.github/agents/self-hosted-runner-doctor.md
@@ -80,6 +80,7 @@ Prefer the narrowest match. Examples:
 - credential files such as `~/.aws/credentials`, `~/.ssh/id_rsa`, or `~/.docker/config.json` are visible inside an `--container-runtime sbx` microVM → D9 (older AWF mounted the entire host `$HOME` into sbx; fixed in github/gh-aw-firewall#6336)
 - Copilot CLI exits immediately (exit code 1, ~0.5 s, zero stdout/stderr) after AWF upgrade on Docker or gVisor but not sbx → B14 (`~/.copilot/config.json` incorrectly added to credential deny list; fixed in github/gh-aw-firewall#6374)
 - `copilot: command not found` inside `--container-runtime sbx` when binary is at `~/.local/bin/copilot` → D10 (`bash -lc` login init resets injected PATH in sbx; fixed by wrapping the executed command with `export PATH="$HOME/.local/bin${PATH:+:$PATH}"` in github/gh-aw-firewall#6407)
+- `SIGABRT` / `signal=SIGABRT duration=0s stdout=0B` for Copilot CLI all retries under `--container-runtime gvisor`; or exit 139 / `Segmentation fault` on bash wrapper, often before any model or tool call → D11 (Node.js v22 V8 ESM decode assertion under gVisor; one-shot restart mitigation in github/gh-aw-firewall#6514; underlying Node/gVisor incompatibility unresolved in github/gh-aw-firewall#6558)
 - `TCP_DENIED` in Squid access log for a topology peer or `difcProxyHost` during agent run; in-session MCP/HTTP calls to those hosts fail in network-isolation mode → B13 (topology peer hostnames and `difcProxyHost` not added to `NO_PROXY`; fixed in github/gh-aw-firewall#6189 and github/gh-aw-firewall#6438)
 - `EACCES` + `unlink` on `/tmp/awf-...-chroot-home/<path>` during AWF cleanup (not upload-artifact) → B7 (rootless UID-remapped chroot-home files)
 - `EACCES: permission denied, mkdir '/tmp/gh-aw/...'` before containers start on a persistent runner → B8 (stale root-owned pre-flight dirs)
@@ -124,6 +125,8 @@ D9 / github/gh-aw-firewall#6336 — sbx microVMs previously mounted the entire h
 
 D10 / github/gh-aw-firewall#6407 — On `--container-runtime sbx`, the Copilot CLI installed rootless to `~/.local/bin` was not found because `buildCoreEnvironment()` did not include `~/.local/bin` in the injected PATH and sbx microVMs do not run AWF's `entrypoint.sh` to fix PATH. **Fixed in AWF (PR github/gh-aw-firewall#6407, merged 2026-07-19):** `buildCoreEnvironment()` now prepends `${HOME}/.local/bin` to PATH for all runtimes. Workaround (older AWF): use the non-rootless install or pass `--env PATH=/home/runner/.local/bin:$PATH`.
 
+D11 / github/gh-aw-firewall#6558 — gVisor + Node.js v22 V8 ESM startup crash root cause remains unresolved (`SIGABRT` `StringBytes::Encode` assertion and occasional exit 139). **Mitigated in AWF (PR github/gh-aw-firewall#6514, merged 2026-07-23):** `runAgentCommand()` does a one-shot retry (`MAX_GVISOR_AGENT_RETRIES = 1`) when gVisor exits 134/139 within `GVISOR_STARTUP_CRASH_WINDOW_MS = 30_000`, but this does not prevent the underlying crash.
+
 C7 / #5615 — DIFC proxy enterprise-host awareness for `*.ghe.com` data-residency is not yet implemented in the companion projects; AWF ≥ v0.27.12 provides improved diagnostics (HTTP status + targeted hint) but the underlying cause remains unresolved.
 
 C8 / github/gh-aw-firewall#5872, github/gh-aw-firewall#6237 — Copilot Business `token` prefix short-circuit on GHEC is **fixed** in AWF version including github/gh-aw-firewall#5872. **Additional fix (github/gh-aw-firewall#6237):** `gh-aw`'s offline mode sets `COPILOT_PROVIDER_API_KEY=dummy-byok-key-for-offline-mode` as a sentinel. In AWF before github/gh-aw-firewall#6237, this sentinel was treated as a real BYOK key, suppressing the GitHub-token auth path and producing `400` on Business/Enterprise targets. Fixed by treating `dummy-byok-key-for-offline-mode` as a non-credential sentinel (same class as AWF placeholder tokens).
@@ -239,6 +242,7 @@ Establish these facts before matching a failure mode:
 | D8 | MCP tool calls (`safeoutputs`, `github`) return `403 ERR_ACCESS_DENIED` under `--container-runtime gvisor` or raw `runsc`; agent completes but never writes safe outputs; smoke tests fail at "Validate safe outputs were invoked"; direct `/dev/tcp` connections fail with `No route to host` | gVisor's userspace netstack is isolated from the host network namespace. The iptables DNAT `RETURN` bypass rule (installed by `awf-iptables-init`) that normally lets the agent reach the MCP gateway (`172.30.0.1:8080`) directly never fires under gVisor. MCP requests follow `HTTP_PROXY` into Squid and receive `403 ERR_ACCESS_DENIED` because the MCP gateway IP is not in the domain allowlist. | **Fixed in AWF (PR github/gh-aw-firewall#6401)**: `runtimeUsesIptables()` returns `false` for `gvisor` and its raw `runsc` alias (plus `sbx`); `awf-iptables-init` is skipped for these runtimes (`AWF_SKIP_IPTABLES_INIT=1`); the MCP gateway (`172.30.0.1`) and `host.docker.internal` are added to `NO_PROXY` so proxy-aware MCP clients connect directly. **Caveat:** proxy-unaware tools using raw sockets (e.g. `/dev/tcp`) still get `No route to host` under gVisor — egress requires proxy-aware clients. | Inspect Squid access log for `403` on `172.30.0.1`; check `NO_PROXY` env inside the agent container — should include `172.30.0.1` when runtime is `gvisor` or raw `runsc` on patched AWF | github/gh-aw-firewall#6401, github/gh-aw-firewall#6326 |
 | D9 | On `--container-runtime sbx`, credential files (`~/.aws/credentials`, `~/.ssh/id_rsa`, `~/.docker/config.json`, `~/.kube/config`, `~/.azure/`, `~/.gnupg/`, `~/.netrc`, `~/.config/gh/hosts.yml`, `~/.config/gcloud/`, `~/.cargo/credentials.toml`, `~/.claude/.credentials.json`, `~/.gemini/oauth_creds.json`) are visible to the agent inside the sbx microVM | AWF before PR github/gh-aw-firewall#6336 mounted the entire host `$HOME` (read-write) into the sbx microVM. Unlike compose mode (empty home volume + `/dev/null` overlays), sbx uses virtiofs passthrough where mounts are directory-granular and file-level overlays are not expressible. | **Fixed in AWF (PR github/gh-aw-firewall#6336)**: `sbx-manager.ts` mounts only whitelisted tool/cache + agent-state subdirs (`HOME_TOOL_SUBDIRS` + `.copilot`/`.gemini`). For whitelisted dirs that contain nested credential files (e.g. `~/.config/gh/hosts.yml`, `~/.cargo/credentials.toml`), `scrubHomeCredentials()` moves them aside to `.awf-sbx-cred-backup-<pid>` before `sbx create` and `restoreHomeCredentials()` restores them after teardown. Workaround (older AWF): do not use `--container-runtime sbx` with real credentials in `$HOME`. | `ls $HOME/.aws $HOME/.ssh $HOME/.docker 2>/dev/null` inside the sbx sandbox — if dirs are visible, fix is not applied; confirm AWF version includes github/gh-aw-firewall#6336 | github/gh-aw-firewall#6336 |
 | D10 | On `--container-runtime sbx`, Copilot CLI installed via `install_copilot_cli.sh --rootless` (redirects install to `~/.local/bin`) is **not found** even though `~/.local` is mounted into the microVM; `copilot: command not found` or `ENOENT` at agent startup | sbx executes agent commands via `bash -lc` (login shell), whose profile initialization can reset PATH and discard `--env PATH=...`. The binary is present in the VM but unreachable by name unless PATH is fixed after login init. | **Fixed in AWF (PR github/gh-aw-firewall#6407, merged 2026-07-19):** sbx wraps the executed command with `export PATH="$HOME/.local/bin${PATH:+:$PATH}"` after login initialization (`withLocalBinOnPath()` in `sbx-manager.ts`). Upgrade to the AWF version including github/gh-aw-firewall#6407. Workaround (older AWF): invoke `$HOME/.local/bin/copilot` directly, or prefix the agent command with `export PATH="$HOME/.local/bin${PATH:+:$PATH}"; ...`. | Inside the sbx agent: `which copilot` or `ls ~/.local/bin/copilot` confirms binary presence; on patched AWF, inspect the executed command wrapper in sbx logs and verify it prepends `~/.local/bin` before invoking the agent command | github/gh-aw-firewall#6407 |
+| D11 | Copilot CLI agent starts under `--container-runtime gvisor` but exits immediately with **exit code 139** (`SIGSEGV`) or `SIGABRT` (exit 1); `[copilot-harness]` log shows all retry attempts crashing within ~90 ms (`tokenCount=0`, `stdout=0B`); the outer `bash` wrapper can also segfault, often before any model or tool call is issued. Affects `sandbox.agent.runtime: gvisor` (compose-managed gVisor) at ~8% failure rate; identical workloads on `runc` and `sbx` are unaffected. | Node.js v22 (bundled in the Copilot CLI) can trigger a V8 native assertion (`StringBytes::Encode ... Assertion failed: (written) == (u16size)`) during ESM module translation under gVisor's userspace netstack; gVisor's `mmap`/`madvise` emulation can return unexpected buffer contents to V8's UTF-8 decode path. The `SIGSEGV`/exit 139 variant can also take down the outer `bash` wrapper so the Copilot harness cannot retry. Root cause (gVisor ↔ Node.js v22 incompatibility) is **unresolved** — tracked in github/gh-aw-firewall#6558. | **Mitigated in AWF (PR github/gh-aw-firewall#6514, merged 2026-07-23):** `runAgentCommand()` detects gVisor runtime and automatically retries the agent container **once** (via `docker start awf-agent`) when the exit code is `134` (SIGABRT) or `139` (SIGSEGV) **within the first 30 s** (`GVISOR_STARTUP_CRASH_WINDOW_MS = 30_000`); `MAX_GVISOR_AGENT_RETRIES = 1`. Log reattachment uses `docker logs --since <restart-time> -f awf-agent` to avoid replaying the crashed attempt. Non-gVisor runtimes are unaffected. Root cause remains open; upgrade AWF to include github/gh-aw-firewall#6514 to get the retry mitigation. | Agent logs show `signal=SIGABRT duration=0s stdout=0B` on attempt 1; with github/gh-aw-firewall#6514, a second `docker start awf-agent` log block appears and usually succeeds. Without the fix, all harness retries fail identically. Confirm `containerRuntime: gvisor` in the resolved `docker-compose.redacted.yml`. | github/gh-aw-firewall#6513, github/gh-aw-firewall#6514, github/gh-aw-firewall#6558 |
 
 ## Error-string quick lookup
 
@@ -277,6 +281,7 @@ Establish these facts before matching a failure mode:
 | Credential files (`~/.aws`, `~/.ssh`, `~/.docker/config.json`, `~/.kube`, `~/.config/gh`, `~/.cargo/credentials.toml`, etc.) visible inside sbx microVM under `--container-runtime sbx` | D9 (entire `$HOME` mounted into sbx microVM virtiofs; fixed in github/gh-aw-firewall#6336 with home-whitelist + `scrubHomeCredentials()`) |
 | Copilot CLI exits immediately (exit 1, ~0.5 s, zero stdout/stderr) after AWF upgrade; works in sbx but not Docker/gVisor | B14 (`.copilot/config.json` masked as credential; fixed in github/gh-aw-firewall#6374) |
 | `copilot: command not found` inside sbx microVM when binary is at `~/.local/bin/copilot` | D10 (`bash -lc` login init resets injected PATH; fixed by command wrapper `export PATH="$HOME/.local/bin${PATH:+:$PATH}"` in github/gh-aw-firewall#6407) |
+| `SIGABRT` / `signal=SIGABRT duration=0s stdout=0B` for Copilot CLI all retries under `--container-runtime gvisor`; or exit code 139 with `Segmentation fault` on bash wrapper | D11 (Node.js v22 V8 ESM decode assertion under gVisor; one-shot restart mitigation in github/gh-aw-firewall#6514; underlying Node/gVisor incompatibility unresolved in github/gh-aw-firewall#6558) |
 | `TCP_DENIED` in Squid access log for topology peer or DIFC proxy host during agent run; MCP tool calls silently fail or return connection errors in network-isolation mode | B13 (topology peers and `difcProxyHost` missing from `NO_PROXY`; fixed in github/gh-aw-firewall#6189 and github/gh-aw-firewall#6438) |
 
 ## Known unresolved items
@@ -288,3 +293,4 @@ Flag these explicitly instead of implying there is a complete fix:
 - D4 / #4849 — enterprise header injection extension point
 - C5 / #3937 — full `GH_HOST` leak fix still requires gh-aw changes
 - C7 / #5615 — DIFC proxy enterprise-host awareness for `*.ghe.com` data-residency (root cause unresolved; tracked in github/gh-aw-mcpg#8202 and github/gh-aw#41911)
+- D11 / github/gh-aw-firewall#6558 — gVisor + Node.js v22 V8 ESM startup crash root cause (SIGABRT `StringBytes::Encode`); one-shot retry mitigates (~8% failure rate) but does not prevent the crash
diff --git a/.github/workflows/self-hosted-runner-doctor.lock.yml b/.github/workflows/self-hosted-runner-doctor.lock.yml
index a14770204..5316de922 100644
--- a/.github/workflows/self-hosted-runner-doctor.lock.yml
+++ b/.github/workflows/self-hosted-runner-doctor.lock.yml
@@ -1,4 +1,4 @@
-# gh-aw-metadata: {"schema_version":"v4","frontmatter_hash":"be56d205ed7374bea2d8b19a93bf66a884b9079dc10be8d30dea7e85ae706fef","body_hash":"e3f32a588e015deaaa45dde763e2a9a6758ba8e98266e31e23f5d72424a22335","compiler_version":"v0.83.2","strict":true,"agent_id":"copilot","engine_versions":{"copilot":"1.0.73"}}
+# gh-aw-metadata: {"schema_version":"v4","frontmatter_hash":"be56d205ed7374bea2d8b19a93bf66a884b9079dc10be8d30dea7e85ae706fef","body_hash":"f42565b41a743add222bc66738c2b080f53a5e9fbfac2a78a43a056f6815bb94","compiler_version":"v0.83.2","strict":true,"agent_id":"copilot","engine_versions":{"copilot":"1.0.73"}}
 # gh-aw-manifest: {"version":1,"secrets":["COPILOT_GITHUB_TOKEN","GH_AW_GITHUB_MCP_SERVER_TOKEN","GH_AW_GITHUB_TOKEN","GITHUB_TOKEN"],"actions":[{"repo":"actions/cache","sha":"55cc8345863c7cc4c66a329aec7e433d2d1c52a9","version":"v6.1.0"},{"repo":"actions/cache/restore","sha":"55cc8345863c7cc4c66a329aec7e433d2d1c52a9","version":"v6.1.0"},{"repo":"actions/cache/save","sha":"55cc8345863c7cc4c66a329aec7e433d2d1c52a9","version":"v6.1.0"},{"repo":"actions/checkout","sha":"3d3c42e5aac5ba805825da76410c181273ba90b1","version":"v7.0.1"},{"repo":"actions/download-artifact","sha":"3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c","version":"v8.0.1"},{"repo":"actions/github-script","sha":"3a2844b7e9c422d3c10d287c895573f7108da1b3","version":"v9.0.0"},{"repo":"actions/upload-artifact","sha":"043fb46d1a93c77aae656e7c1c64a875d1fc6a0a","version":"v7.0.1"},{"repo":"github/gh-aw-actions/setup","sha":"39143c7eb25e92c0ab748285770483709db03c05","version":"v0.83.2"}],"containers":[{"image":"ghcr.io/github/gh-aw-firewall/agent:0.27.41","digest":"sha256:053ba306623a1a0d4c3c5ac9a2c3dc3217ce04d44329b61929fe7f8b0dc457f3","pinned_image":"ghcr.io/github/gh-aw-firewall/agent:0.27.41@sha256:053ba306623a1a0d4c3c5ac9a2c3dc3217ce04d44329b61929fe7f8b0dc457f3"},{"image":"ghcr.io/github/gh-aw-firewall/api-proxy:0.27.41","digest":"sha256:a3d33153b6abb2dd39540ef7def8aa8a5020022c11822d88f5b87ebe350276d1","pinned_image":"ghcr.io/github/gh-aw-firewall/api-proxy:0.27.41@sha256:a3d33153b6abb2dd39540ef7def8aa8a5020022c11822d88f5b87ebe350276d1"},{"image":"ghcr.io/github/gh-aw-firewall/squid:0.27.41","digest":"sha256:61d653d372ac417c6e22d5e77becd9e60bde96e6c2d26bb023e3cc3fd60c0920","pinned_image":"ghcr.io/github/gh-aw-firewall/squid:0.27.41@sha256:61d653d372ac417c6e22d5e77becd9e60bde96e6c2d26bb023e3cc3fd60c0920"},{"image":"ghcr.io/github/gh-aw-mcpg:v0.4.5","digest":"sha256:7550c5132d007266b696d77218e8d1b01f29e6e55520875b2431ef4044df71c9","pinned_image":"ghcr.io/github/gh-aw-mcpg:v0.4.5@sha256:7550c5132d007266b696d77218e8d1b01f29e6e55520875b2431ef4044df71c9"},{"image":"ghcr.io/github/gh-aw-node","digest":"sha256:529d02eb970b1161aa25c593a9c3df57fdfad5a8add328cb3b6eccef66f3183b","pinned_image":"ghcr.io/github/gh-aw-node@sha256:529d02eb970b1161aa25c593a9c3df57fdfad5a8add328cb3b6eccef66f3183b"},{"image":"ghcr.io/github/github-mcp-server:v1.6.0","digest":"sha256:2b0c48b070f61e9d3969269ead600f62d00fb237b60ac849ef3d166ee7de9ad3","pinned_image":"ghcr.io/github/github-mcp-server:v1.6.0@sha256:2b0c48b070f61e9d3969269ead600f62d00fb237b60ac849ef3d166ee7de9ad3"}]}
 # This file was automatically generated by gh-aw (v0.83.2). DO NOT EDIT. To debug this workflow, load the skill at https://github.com/github/gh-aw/blob/main/debug.md
 #
diff --git a/.github/workflows/self-hosted-runner-doctor.md b/.github/workflows/self-hosted-runner-doctor.md
index e0d398fdd..08bf79026 100644
--- a/.github/workflows/self-hosted-runner-doctor.md
+++ b/.github/workflows/self-hosted-runner-doctor.md
@@ -109,6 +109,7 @@ Prefer the narrowest match. Examples:
 - credential files such as `~/.aws/credentials`, `~/.ssh/id_rsa`, or `~/.docker/config.json` are visible inside an `--container-runtime sbx` microVM → D9 (older AWF mounted the entire host `$HOME` into sbx; fixed in github/gh-aw-firewall#6336)
 - Copilot CLI exits immediately (exit code 1, ~0.5 s, zero stdout/stderr) after AWF upgrade on Docker or gVisor but not sbx → B14 (`~/.copilot/config.json` incorrectly added to credential deny list; fixed in github/gh-aw-firewall#6374)
 - `copilot: command not found` inside `--container-runtime sbx` when binary is at `~/.local/bin/copilot` → D10 (`bash -lc` login init resets injected PATH in sbx; fixed by wrapping the executed command with `export PATH="$HOME/.local/bin${PATH:+:$PATH}"` in github/gh-aw-firewall#6407)
+- `SIGABRT` / `signal=SIGABRT duration=0s stdout=0B` for Copilot CLI all retries under `--container-runtime gvisor`; or exit 139 / `Segmentation fault` on bash wrapper, often before any model or tool call → D11 (Node.js v22 V8 ESM decode assertion under gVisor; one-shot restart mitigation in github/gh-aw-firewall#6514; underlying Node/gVisor incompatibility unresolved in github/gh-aw-firewall#6558)
 - `TCP_DENIED` in Squid access log for a topology peer or `difcProxyHost` during agent run; in-session MCP/HTTP calls to those hosts fail in network-isolation mode → B13 (topology peer hostnames and `difcProxyHost` not added to `NO_PROXY`; fixed in github/gh-aw-firewall#6189 and github/gh-aw-firewall#6438)
 - `EACCES` + `unlink` on `/tmp/awf-...-chroot-home/<path>` during AWF cleanup (not upload-artifact) → B7 (rootless UID-remapped chroot-home files)
 - `EACCES: permission denied, mkdir '/tmp/gh-aw/...'` before containers start on a persistent runner → B8 (stale root-owned pre-flight dirs)
@@ -159,6 +160,8 @@ C8 / github/gh-aw-firewall#5872 — Copilot Business `token` prefix short-circui
 
 D7 / github/gh-aw-firewall#6260, github/gh-aw-firewall#6261, github/gh-aw-firewall#6276 — Claude Code (Bun/JSC) crashes with `SIGSEGV`/`SIGABRT` under `--container-runtime gvisor` because JSC JIT is incompatible with gVisor's W^X memory restrictions. **AWF (PR github/gh-aw-firewall#6276) automatically sets `BUN_JSC_useJIT=0`** at runtime via `buildToolEnvironment()` when Claude runs under gVisor — no workflow change required. For older AWF builds without github/gh-aw-firewall#6276, pass `--env BUN_JSC_useJIT=0` as a manual fallback.
 
+D11 / github/gh-aw-firewall#6558 — gVisor + Node.js v22 V8 ESM startup crash root cause remains unresolved (`SIGABRT` `StringBytes::Encode` assertion and occasional exit 139). **Mitigated in AWF (PR github/gh-aw-firewall#6514, merged 2026-07-23):** `runAgentCommand()` does a one-shot retry (`MAX_GVISOR_AGENT_RETRIES = 1`) when gVisor exits 134/139 within `GVISOR_STARTUP_CRASH_WINDOW_MS = 30_000`, but this does not prevent the underlying crash.
+
 ### 5. Avoid duplicate triage
 
 Search existing issues before creating a new one. If an open issue already tracks the same failure mode and remediation, add a concise comment to the current thread instead of creating another issue.
diff --git a/.github/workflows/shared/self-hosted-failure-modes.md b/.github/workflows/shared/self-hosted-failure-modes.md
index 25f9c971f..f1d08a2d6 100644
--- a/.github/workflows/shared/self-hosted-failure-modes.md
+++ b/.github/workflows/shared/self-hosted-failure-modes.md
@@ -81,6 +81,7 @@ Establish these facts before matching a failure mode:
 | D8 | MCP tool calls (`safeoutputs`, `github`) return `403 ERR_ACCESS_DENIED` under `--container-runtime gvisor` or raw `runsc`; agent completes but never writes safe outputs; smoke tests fail at "Validate safe outputs were invoked"; direct `/dev/tcp` connections fail with `No route to host` | gVisor's userspace netstack is isolated from the host network namespace. The iptables DNAT `RETURN` bypass rule (installed by `awf-iptables-init`) that normally lets the agent reach the MCP gateway (`172.30.0.1:8080`) directly never fires under gVisor. MCP requests follow `HTTP_PROXY` into Squid and receive `403 ERR_ACCESS_DENIED` because the MCP gateway IP is not in the domain allowlist. | **Fixed in AWF (PR github/gh-aw-firewall#6401)**: `runtimeUsesIptables()` returns `false` for `gvisor` and its raw `runsc` alias (plus `sbx`); `awf-iptables-init` is skipped for these runtimes (`AWF_SKIP_IPTABLES_INIT=1`); the MCP gateway (`172.30.0.1`) and `host.docker.internal` are added to `NO_PROXY` so proxy-aware MCP clients connect directly. **Caveat:** proxy-unaware tools using raw sockets (e.g. `/dev/tcp`) still get `No route to host` under gVisor — egress requires proxy-aware clients. | Inspect Squid access log for `403` on `172.30.0.1`; check `NO_PROXY` env inside the agent container — should include `172.30.0.1` when runtime is `gvisor` or raw `runsc` on patched AWF | github/gh-aw-firewall#6401, github/gh-aw-firewall#6326 |
 | D9 | On `--container-runtime sbx`, credential files (`~/.aws/credentials`, `~/.ssh/id_rsa`, `~/.docker/config.json`, `~/.kube/config`, `~/.azure/`, `~/.gnupg/`, `~/.netrc`, `~/.config/gh/hosts.yml`, `~/.config/gcloud/`, `~/.cargo/credentials.toml`, `~/.claude/.credentials.json`, `~/.gemini/oauth_creds.json`) are visible to the agent inside the sbx microVM | AWF before PR github/gh-aw-firewall#6336 mounted the entire host `$HOME` (read-write) into the sbx microVM. Unlike compose mode (empty home volume + `/dev/null` overlays), sbx uses virtiofs passthrough where mounts are directory-granular and file-level overlays are not expressible. | **Fixed in AWF (PR github/gh-aw-firewall#6336)**: `sbx-manager.ts` mounts only whitelisted tool/cache + agent-state subdirs (`HOME_TOOL_SUBDIRS` + `.copilot`/`.gemini`). For whitelisted dirs that contain nested credential files (e.g. `~/.config/gh/hosts.yml`, `~/.cargo/credentials.toml`), `scrubHomeCredentials()` moves them aside to `.awf-sbx-cred-backup-<pid>` before `sbx create` and `restoreHomeCredentials()` restores them after teardown. Workaround (older AWF): do not use `--container-runtime sbx` with real credentials in `$HOME`. | `ls $HOME/.aws $HOME/.ssh $HOME/.docker 2>/dev/null` inside the sbx sandbox — if dirs are visible, fix is not applied; confirm AWF version includes github/gh-aw-firewall#6336 | github/gh-aw-firewall#6336 |
 | D10 | On `--container-runtime sbx`, Copilot CLI installed via `install_copilot_cli.sh --rootless` (redirects install to `~/.local/bin`) is **not found** even though `~/.local` is mounted into the microVM; `copilot: command not found` or `ENOENT` at agent startup | sbx executes agent commands via `bash -lc` (login shell), whose profile initialization can reset PATH and discard `--env PATH=...`. The binary is present in the VM but unreachable by name unless PATH is fixed after login init. | **Fixed in AWF (PR github/gh-aw-firewall#6407, merged 2026-07-19):** sbx wraps the executed command with `export PATH="$HOME/.local/bin${PATH:+:$PATH}"` after login initialization (`withLocalBinOnPath()` in `sbx-manager.ts`). Upgrade to the AWF version including github/gh-aw-firewall#6407. Workaround (older AWF): invoke `$HOME/.local/bin/copilot` directly, or prefix the agent command with `export PATH="$HOME/.local/bin${PATH:+:$PATH}"; ...`. | Inside the sbx agent: `which copilot` or `ls ~/.local/bin/copilot` confirms binary presence; on patched AWF, inspect the executed command wrapper in sbx logs and verify it prepends `~/.local/bin` before invoking the agent command | github/gh-aw-firewall#6407 |
+| D11 | Copilot CLI agent starts under `--container-runtime gvisor` but exits immediately with **exit code 139** (`SIGSEGV`) or `SIGABRT` (exit 1); `[copilot-harness]` log shows all retry attempts crashing within ~90 ms (`tokenCount=0`, `stdout=0B`); the outer `bash` wrapper can also segfault, often before any model or tool call is issued. Affects `sandbox.agent.runtime: gvisor` (compose-managed gVisor) at ~8% failure rate; identical workloads on `runc` and `sbx` are unaffected. | Node.js v22 (bundled in the Copilot CLI) can trigger a V8 native assertion (`StringBytes::Encode ... Assertion failed: (written) == (u16size)`) during ESM module translation under gVisor's userspace netstack; gVisor's `mmap`/`madvise` emulation can return unexpected buffer contents to V8's UTF-8 decode path. The `SIGSEGV`/exit 139 variant can also take down the outer `bash` wrapper so the Copilot harness cannot retry. Root cause (gVisor ↔ Node.js v22 incompatibility) is **unresolved** — tracked in github/gh-aw-firewall#6558. | **Mitigated in AWF (PR github/gh-aw-firewall#6514, merged 2026-07-23):** `runAgentCommand()` detects gVisor runtime and automatically retries the agent container **once** (via `docker start awf-agent`) when the exit code is `134` (SIGABRT) or `139` (SIGSEGV) **within the first 30 s** (`GVISOR_STARTUP_CRASH_WINDOW_MS = 30_000`); `MAX_GVISOR_AGENT_RETRIES = 1`. Log reattachment uses `docker logs --since <restart-time> -f awf-agent` to avoid replaying the crashed attempt. Non-gVisor runtimes are unaffected. Root cause remains open; upgrade AWF to include github/gh-aw-firewall#6514 to get the retry mitigation. | Agent logs show `signal=SIGABRT duration=0s stdout=0B` on attempt 1; with github/gh-aw-firewall#6514, a second `docker start awf-agent` log block appears and usually succeeds. Without the fix, all harness retries fail identically. Confirm `containerRuntime: gvisor` in the resolved `docker-compose.redacted.yml`. | github/gh-aw-firewall#6513, github/gh-aw-firewall#6514, github/gh-aw-firewall#6558 |
 
 ## Error-string quick lookup
 
@@ -119,6 +120,7 @@ Establish these facts before matching a failure mode:
 | Credential files (`~/.aws`, `~/.ssh`, `~/.docker/config.json`, `~/.kube`, `~/.config/gh`, `~/.cargo/credentials.toml`, etc.) visible inside sbx microVM under `--container-runtime sbx` | D9 (entire `$HOME` mounted into sbx microVM virtiofs; fixed in github/gh-aw-firewall#6336 with home-whitelist + `scrubHomeCredentials()`) |
 | Copilot CLI exits immediately (exit 1, ~0.5 s, zero stdout/stderr) after AWF upgrade; works in sbx but not Docker/gVisor | B14 (`.copilot/config.json` masked as credential; fixed in github/gh-aw-firewall#6374) |
 | `copilot: command not found` inside sbx microVM when binary is at `~/.local/bin/copilot` | D10 (`bash -lc` login init resets injected PATH; fixed by command wrapper `export PATH="$HOME/.local/bin${PATH:+:$PATH}"` in github/gh-aw-firewall#6407) |
+| `SIGABRT` / `signal=SIGABRT duration=0s stdout=0B` for Copilot CLI all retries under `--container-runtime gvisor`; or exit code 139 with `Segmentation fault` on bash wrapper | D11 (Node.js v22 V8 ESM decode assertion under gVisor; one-shot restart mitigation in github/gh-aw-firewall#6514; underlying Node/gVisor incompatibility unresolved in github/gh-aw-firewall#6558) |
 | `TCP_DENIED` in Squid access log for topology peer or DIFC proxy host during agent run; MCP tool calls silently fail or return connection errors in network-isolation mode | B13 (topology peers and `difcProxyHost` missing from `NO_PROXY`; fixed in github/gh-aw-firewall#6189 and github/gh-aw-firewall#6438) |
 
 ## Known unresolved items
@@ -130,3 +132,4 @@ Flag these explicitly instead of implying there is a complete fix:
 - D4 / #4849 — enterprise header injection extension point
 - C5 / #3937 — full `GH_HOST` leak fix still requires gh-aw changes
 - C7 / #5615 — DIFC proxy enterprise-host awareness for `*.ghe.com` data-residency (root cause unresolved; tracked in github/gh-aw-mcpg#8202 and github/gh-aw#41911)
+- D11 / github/gh-aw-firewall#6558 — gVisor + Node.js v22 V8 ESM startup crash root cause (SIGABRT `StringBytes::Encode`); one-shot retry mitigates (~8% failure rate) but does not prevent the crash
diff --git a/containers/api-proxy/token-tracker.http.test.js b/containers/api-proxy/token-tracker.http.test.js
index 5ac50e012..d5f8cf39f 100644
--- a/containers/api-proxy/token-tracker.http.test.js
+++ b/containers/api-proxy/token-tracker.http.test.js
@@ -106,15 +106,31 @@ describe('trackTokenUsage', () => {
     })));
     proxyRes.emit('end');
 
-    setTimeout(() => {
-      expect(fs.existsSync(TOKEN_LOG_FILE)).toBe(true);
-      const lines = fs.readFileSync(TOKEN_LOG_FILE, 'utf8')
-        .split('\n')
-        .filter(Boolean);
-      const matchingLine = lines.find((line) => line.includes('"request_id":"test-incremental-write"'));
-      expect(matchingLine).toBeTruthy();
-      done();
-    }, 20);
+    // The write goes through an async createWriteStream, whose file open +
+    // flush can take longer than a single fixed delay under CI load. Poll for
+    // the record instead of asserting after one short timeout, so the test is
+    // deterministic and fast without being flaky.
+    const deadline = Date.now() + 4000;
+    const poll = () => {
+      const matchingLine = fs.existsSync(TOKEN_LOG_FILE)
+        && fs.readFileSync(TOKEN_LOG_FILE, 'utf8')
+          .split('\n')
+          .filter(Boolean)
+          .find((line) => line.includes('"request_id":"test-incremental-write"'));
+      if (matchingLine) {
+        expect(matchingLine).toBeTruthy();
+        done();
+        return;
+      }
+      if (Date.now() >= deadline) {
+        // Force a clear assertion failure rather than a timeout.
+        expect(matchingLine).toBeTruthy();
+        done();
+        return;
+      }
+      setTimeout(poll, 20);
+    };
+    poll();
   });
 
   test('extracts usage from streaming SSE response', (done) => {
diff --git a/scripts/ci/self-hosted-runner-doctor-workflow.test.ts b/scripts/ci/self-hosted-runner-doctor-workflow.test.ts
index 280bd0605..d29f4b986 100644
--- a/scripts/ci/self-hosted-runner-doctor-workflow.test.ts
+++ b/scripts/ci/self-hosted-runner-doctor-workflow.test.ts
@@ -82,6 +82,12 @@ describe('self-hosted runner doctor workflow config', () => {
       expect(content).toContain('`scrubHomeCredentials()` moves them aside to `.awf-sbx-cred-backup-<pid>`');
       expect(content).toContain('| `403 ERR_ACCESS_DENIED` for MCP tool calls (`safeoutputs`, `github`) to `172.30.0.1/redacted` under `--container-runtime gvisor` or raw `runsc`; agent finishes but safe-output validation fails | D8');
       expect(content).toContain('| Credential files (`~/.aws`, `~/.ssh`, `~/.docker/config.json`, `~/.kube`, `~/.config/gh`, `~/.cargo/credentials.toml`, etc.) visible inside sbx microVM under `--container-runtime sbx` | D9');
+      expect(content).toContain('| D11 | Copilot CLI agent starts under `--container-runtime gvisor` but exits immediately with **exit code 139** (`SIGSEGV`) or `SIGABRT` (exit 1);');
+      expect(content).toContain('often before any model or tool call is issued');
+      expect(content).toContain('`MAX_GVISOR_AGENT_RETRIES = 1`');
+      expect(content).toContain('github/gh-aw-firewall#6513, github/gh-aw-firewall#6514, github/gh-aw-firewall#6558');
+      expect(content).toContain('| `SIGABRT` / `signal=SIGABRT duration=0s stdout=0B` for Copilot CLI all retries under `--container-runtime gvisor`; or exit code 139 with `Segmentation fault` on bash wrapper | D11');
+      expect(content).toContain('- D11 / github/gh-aw-firewall#6558 — gVisor + Node.js v22 V8 ESM startup crash root cause (SIGABRT `StringBytes::Encode`); one-shot retry mitigates (~8% failure rate) but does not prevent the crash');
     }
 
     expect(source).toContain('- `unknown shorthand flag: \'d\' in -d` from `docker compose up -d` → A14 (DinD sidecar missing `docker-compose-plugin`)');
@@ -89,13 +95,17 @@ describe('self-hosted runner doctor workflow config', () => {
     expect(source).toContain('- `EAI_AGAIN` / `ENOTFOUND` resolving a topology-attached DIFC proxy (for example `awmg-cli-proxy`) in network-isolation + topology-attach: if DinD `nslookup` fails, match B12; otherwise B5');
     expect(source).toContain('- `403 ERR_ACCESS_DENIED` for MCP tool calls (`safeoutputs`, `github`) to `172.30.0.1/redacted` under `--container-runtime gvisor` or raw `runsc`; safe-output validation fails even though the agent completed → D8');
     expect(source).toContain('- credential files such as `~/.aws/credentials`, `~/.ssh/id_rsa`, or `~/.docker/config.json` are visible inside an `--container-runtime sbx` microVM → D9');
+    expect(source).toContain('- `SIGABRT` / `signal=SIGABRT duration=0s stdout=0B` for Copilot CLI all retries under `--container-runtime gvisor`; or exit 139 / `Segmentation fault` on bash wrapper, often before any model or tool call → D11');
     expect(source).toContain('B12 / github/gh-aw-firewall#6326, github/gh-aw-firewall#6328 — On ARC/DinD, a topology-attached DIFC proxy addressed by Kubernetes Service name can remain unresolvable from DinD containers even after the ordering fix.');
     expect(source).toContain('D8 / github/gh-aw-firewall#6401, github/gh-aw-firewall#6326 — Under `--container-runtime gvisor` or raw `runsc`, MCP calls to the gateway at `172.30.0.1:8080` could be misrouted through Squid and fail with `403 ERR_ACCESS_DENIED`');
     expect(source).toContain('D9 / github/gh-aw-firewall#6336 — sbx microVMs previously mounted the entire host `$HOME`, exposing credentials such as `~/.aws/credentials`, `~/.ssh/id_rsa`, and `~/.docker/config.json`.');
+    expect(source).toContain('D11 / github/gh-aw-firewall#6558 — gVisor + Node.js v22 V8 ESM startup crash root cause remains unresolved (`SIGABRT` `StringBytes::Encode` assertion and occasional exit 139).');
     expect(portableAgent).toContain('- `unknown shorthand flag: \'d\' in -d` from `docker compose up -d` → A14 (DinD sidecar missing `docker-compose-plugin`)');
     expect(portableAgent).toContain('- `Rootless artifact permission repair failed` on ARC/DinD squid logs → A15 (`dockerHostPathPrefix` not applied to repair bind mount)');
     expect(portableAgent).toContain('- `EAI_AGAIN` / `ENOTFOUND` resolving a topology-attached DIFC proxy (for example `awmg-cli-proxy`) in network-isolation + topology-attach: if DinD `nslookup` fails, match B12; otherwise B5');
     expect(portableAgent).toContain('- `403 ERR_ACCESS_DENIED` for MCP tool calls (`safeoutputs`, `github`) to `172.30.0.1/redacted` under `--container-runtime gvisor` or raw `runsc`; safe-output validation fails even though the agent completed → D8');
     expect(portableAgent).toContain('- credential files such as `~/.aws/credentials`, `~/.ssh/id_rsa`, or `~/.docker/config.json` are visible inside an `--container-runtime sbx` microVM → D9');
+    expect(portableAgent).toContain('- `SIGABRT` / `signal=SIGABRT duration=0s stdout=0B` for Copilot CLI all retries under `--container-runtime gvisor`; or exit 139 / `Segmentation fault` on bash wrapper, often before any model or tool call → D11');
+    expect(portableAgent).toContain('D11 / github/gh-aw-firewall#6558 — gVisor + Node.js v22 V8 ESM startup crash root cause remains unresolved (`SIGABRT` `StringBytes::Encode` assertion and occasional exit 139).');
   });
 });