feat(observability): optional self-hosted Sentry instrumentation for MCP workflow failures (Closes #606)

Add an env-var-gated, off-by-default Sentry SDK integration so MCP runtime
errors, fail-closed workflow blockers, lease/terminal-lock/stale-runtime
collisions, and recurring watchdog check-ins are visible in a self-hosted
Sentry at https://sentry.prgs.cc/. Gitea stays the source of truth; Sentry is
observe-only.

New module `sentry_observability.py` mirrors the `gitea_audit` conventions
(env-gated, best-effort, redacting):

- Config from MCP_SENTRY_ENABLED / SENTRY_DSN / SENTRY_ENVIRONMENT /
  SENTRY_RELEASE / MCP_SENTRY_TRACES_SAMPLE_RATE / MCP_SENTRY_ENABLE_LOGS.
  Active only when enabled AND a DSN is present; otherwise a hard no-op.
- Fail OPEN for observability (never blocks a tool success path) and fail
  CLOSED for redaction (drop a field rather than risk leaking it).
- `scrub_event` before_send/before_send_log hook + allowlisted tags: no
  tokens/passwords/keychain ids/DSNs/cookies, no raw session-state or full
  prompt bodies (session_id -> 12-char hash), no full filesystem paths
  (worktree path -> coarse category). Reuses incident_bridge + gitea_audit
  scrubbers.
- capture_exception, capture_workflow_blocker (with canonical next action),
  and monitor_checkin with six stable cron slugs (stale lease scan, terminal
  lock scan, allocator health, namespace health, dashboard freshness,
  reconciler cleanup).
- `sentry_sdk` is a lazily-imported optional dependency; the module imports
  and no-ops cleanly when the package is absent.

Wiring in gitea_mcp_server.py (additive, guarded, best-effort):
- init_sentry() in __main__ before mcp.run.
- capture_exception in the `_audited` failure path; capture_workflow_blocker
  in `_audit_pr_result` BLOCKED/FAILED path.
- allocator + namespace-health watchdog check-ins at their MCP tool sites
  (domain modules left pure).

Also: pin `sentry-sdk==2.20.0` (optional), document the six env vars in
`.env.example`, and add `docs/observability/sentry-integration.md` covering
project creation in https://sentry.prgs.cc/, DSN handling, local/dev/prod
config, redaction guarantees, and coexistence with the #612 incident bridge.

Tests: tests/test_sentry_observability.py (36 cases) cover disabled / enabled /
missing-DSN / missing-SDK, redaction, exception capture, workflow-blocker
capture, and cron check-in behaviour. Full suite: 2632 passed, 6 skipped.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

.env.example

@@ -39,6 +39,27 @@ GITEA_AUDIT_LOG=/path/to/gitea-mcp-audit.log
 # only — never the token value. Surfaced by gitea_get_profile.
 GITEA_TOKEN_SOURCE=GITEA_TOKEN
 
+# ── Optional self-hosted Sentry observability (#606) ────────────────────────
+# Emits runtime errors, fail-closed workflow blockers, lease/terminal-lock/
+# stale-runtime collisions, and watchdog cron check-ins to a SELF-HOSTED Sentry
+# (https://sentry.prgs.cc/) — never Sentry Cloud. Gitea stays the source of
+# truth; Sentry is observe-only. OFF by default: with MCP_SENTRY_ENABLED unset
+# or SENTRY_DSN empty, nothing is initialised and no events are sent.
+#
+# Master gate. Truthy = 1/true/yes/on. Both this AND SENTRY_DSN are required.
+MCP_SENTRY_ENABLED=0
+# DSN for the self-hosted project (create a `gitea-tools-mcp` project in
+# https://sentry.prgs.cc/ and copy its DSN). Never commit a real DSN.
+SENTRY_DSN=
+# Deployment environment tag (local/dev/prod). Defaults to "development".
+SENTRY_ENVIRONMENT=development
+# Optional release identifier (e.g. a git SHA or version string).
+SENTRY_RELEASE=
+# Performance-trace sample rate, 0.0–1.0 (clamped). Default 0.0 (traces off).
+MCP_SENTRY_TRACES_SAMPLE_RATE=0.0
+# Set to 1 to forward Python logs to Sentry as structured logs. Default off.
+MCP_SENTRY_ENABLE_LOGS=0
+
 # Optional canonical runtime-profile config (#19). Instead of the fields above,
 # point every LLM launcher at ONE JSON file of named profiles and select one.
 # Secrets are referenced (keychain id / env var name), never inlined. See

docs/observability/sentry-integration.md

@@ -0,0 +1,138 @@
+# Self-hosted Sentry observability for the Gitea MCP server (#606)
+
+Optional, **off-by-default** instrumentation that reports MCP runtime errors,
+fail-closed workflow blockers, lease / terminal-lock / stale-runtime
+collisions, and recurring watchdog check-ins to a **self-hosted** Sentry at
+`https://sentry.prgs.cc/`.
+
+> **Gitea remains the source of truth.** Sentry is observe-only. It never
+> approves, merges, closes, or otherwise mutates Gitea workflow state, and it
+> never bypasses leases, #332, workflow roles, or the MCP gates. Sentry alerts
+> may only feed the *sanctioned* Gitea issue/comment path via the #612 incident
+> bridge — never a direct write.
+
+Implemented by [`sentry_observability.py`](../../sentry_observability.py).
+
+---
+
+## 1. Create the Sentry project
+
+1. Sign in to the self-hosted Sentry at **`https://sentry.prgs.cc/`** (this is
+   **not** Sentry Cloud — do not use `*.ingest.sentry.io`).
+2. Create a new **Python** project named **`gitea-tools-mcp`**.
+3. Open **Settings → Projects → gitea-tools-mcp → Client Keys (DSN)** and copy
+   the DSN. It looks like `https://<publickey>@sentry.prgs.cc/<project-id>`.
+4. **Never commit the DSN.** It is a runtime secret supplied via env var only.
+
+## 2. Configure the environment
+
+All configuration is env-var driven (see [`.env.example`](../../.env.example)):
+
+| Variable | Purpose | Default |
+|----------|---------|---------|
+| `MCP_SENTRY_ENABLED` | Master gate (`1/true/yes/on`). Required. | off |
+| `SENTRY_DSN` | Self-hosted DSN. Required. | *(empty)* |
+| `SENTRY_ENVIRONMENT` | `local` / `dev` / `prod` tag. | `development` |
+| `SENTRY_RELEASE` | Release id (git SHA or version). | *(none)* |
+| `MCP_SENTRY_TRACES_SAMPLE_RATE` | Perf-trace sample rate `0.0–1.0` (clamped). | `0.0` |
+| `MCP_SENTRY_ENABLE_LOGS` | Forward Python logs as structured logs. | off |
+
+**The feature stays completely off unless `MCP_SENTRY_ENABLED` is truthy *and*
+`SENTRY_DSN` is non-empty.** With either missing, `init_sentry()` is a no-op,
+the SDK is never initialised, and no events are sent — existing tool behaviour
+and API-call patterns are unchanged.
+
+### Per-environment examples
+
+```bash
+# local (quiet: capture errors/blockers, no traces)
+export MCP_SENTRY_ENABLED=1
+export SENTRY_DSN="https://<key>@sentry.prgs.cc/<id>"
+export SENTRY_ENVIRONMENT=local
+
+# dev (light tracing + logs)
+export MCP_SENTRY_ENABLED=1
+export SENTRY_DSN="https://<key>@sentry.prgs.cc/<id>"
+export SENTRY_ENVIRONMENT=dev
+export MCP_SENTRY_TRACES_SAMPLE_RATE=0.2
+export MCP_SENTRY_ENABLE_LOGS=1
+
+# prod (errors/blockers + low-rate tracing, release-tagged)
+export MCP_SENTRY_ENABLED=1
+export SENTRY_DSN="https://<key>@sentry.prgs.cc/<id>"
+export SENTRY_ENVIRONMENT=prod
+export SENTRY_RELEASE="$(git rev-parse --short HEAD)"
+export MCP_SENTRY_TRACES_SAMPLE_RATE=0.05
+```
+
+The optional SDK is pinned in [`requirements.txt`](../../requirements.txt)
+(`sentry-sdk==2.20.0`). It is imported lazily: if the package is absent, the
+module still imports and every entry point is a safe no-op.
+
+## 3. What is instrumented
+
+| Signal | Where | Notes |
+|--------|-------|-------|
+| Startup init | `gitea_mcp_server.py` `__main__`, before `mcp.run` | Prints a redaction-safe status line to stderr. |
+| Failing mutations (exceptions) | `_audited(...)` context manager | `capture_exception` with scrubbed tags. |
+| Fail-closed blockers / failed mutations | `_audit_pr_result(...)` (BLOCKED/FAILED) | Structured `capture_workflow_blocker` event incl. the canonical next action when available (criterion 7). |
+| Allocator watchdog check-ins | `gitea_allocate_next_work` tool | `allocator_health`, `stale_lease_scan`, `terminal_lock_scan`. |
+| Namespace-health check-in | `gitea_assess_mcp_namespace_health` tool | `namespace_health`. |
+
+All capture paths are **best-effort / fail open**: a Sentry outage or capture
+error never breaks an MCP tool success path.
+
+## 4. Cron / watchdog monitors
+
+`sentry_observability.MONITOR_SLUGS` defines stable check-in slugs:
+
+| Registry key | Sentry monitor slug | Wired at |
+|--------------|--------------------|----------|
+| `stale_lease_scan` | `gitea-mcp-stale-lease-scan` | allocator run (global lease expiry) |
+| `terminal_lock_scan` | `gitea-mcp-terminal-lock-scan` | allocator run (terminal-lock lookup) |
+| `allocator_health` | `gitea-mcp-allocator-health` | allocator run |
+| `namespace_health` | `gitea-mcp-namespace-health` | namespace-health probe |
+| `dashboard_freshness` | `gitea-mcp-dashboard-freshness` | call `monitor_checkin("dashboard_freshness", ...)` from the dashboard refresh job (#605) |
+| `reconciler_cleanup` | `gitea-mcp-reconciler-cleanup` | call `monitor_checkin("reconciler_cleanup", ...)` from the reconciler cleanup entrypoint |
+
+Create matching Cron monitors in Sentry with those slugs. Emit an
+`in_progress` check-in at job start and `ok`/`error` at completion via
+`sentry_observability.monitor_checkin(slug_key, status)`.
+
+## 5. Redaction guarantees (fail closed)
+
+Redaction fails *closed*: if a field cannot be proven safe it is dropped rather
+than sent. The `before_send` (and `before_send_log`) hook `scrub_event`
+recursively redacts every outgoing event; on any error it drops the event
+entirely. Guarantees, proven by `tests/test_sentry_observability.py`:
+
+- **No** tokens, passwords, keychain IDs, DSNs, cookies, or `user:pass@host`.
+- **No** raw session-state or full prompt/comment bodies — `session_id` is only
+  ever surfaced as a 12-char `session_id_hash`.
+- **No** private config contents or raw credential headers.
+- **No** full local filesystem paths — a worktree path collapses to a coarse
+  `worktree_category` (`author` / `reviewer` / `merger` / `reconciler` /
+  `branches` / `root` / `other`).
+- Only the allowlisted tag keys in `ALLOWED_TAG_KEYS` are ever attached.
+
+## 6. Coexistence with GlitchTip / the #612 incident bridge
+
+This is the **outbound** path (MCP → Sentry SDK). It complements — it does not
+replace — the **inbound** [`incident_bridge.py`](../../incident_bridge.py)
+(#612), which turns Sentry/GlitchTip *observations* into durable Gitea issues
+and `incident_links` rows.
+
+- Prefer **one** observability path per environment. Point the MCP server's
+  `SENTRY_DSN` at the same self-hosted `gitea-tools-mcp` project that the #612
+  bridge reconciles from, so an MCP-reported error and its Gitea issue line up.
+- GlitchTip is Sentry-protocol compatible; if an existing GlitchTip DSN is in
+  use, either migrate it to `https://sentry.prgs.cc/` or document the split
+  (MCP → Sentry, legacy → GlitchTip) explicitly for operators.
+- The bridge remains the **only** sanctioned route from an alert back into
+  Gitea workflow state.
+
+## 7. Non-goals
+
+- Sentry must **not** become the workflow source of truth.
+- Sentry must **not** approve, merge, close, or mutate Gitea workflow state.
+- Sentry must **not** bypass leases, #332, workflow roles, or the MCP gates.

gitea_mcp_server.py

@@ -918,6 +918,7 @@ import allocator_service  # noqa: E402
 import control_plane_db  # noqa: E402
 import lease_lifecycle  # noqa: E402
 import incident_bridge  # noqa: E402
+import sentry_observability  # noqa: E402  (#606 optional Sentry observability)
 import agent_temp_artifacts
 import issue_lock_worktree  # noqa: E402
 import issue_lock_provenance  # noqa: E402
@@ -1777,6 +1778,18 @@ def _audited(action: str, *, host, remote, org=None, repo=None,
                result=gitea_audit.FAILED, reason=_redact(str(exc)),
                request_metadata=request_metadata, issue_number=issue_number,
                pr_number=pr_number, target_branch=target_branch)
+        # #606: best-effort Sentry capture of the failing mutation (fail open).
+        sentry_observability.capture_exception(
+            exc,
+            tags={
+                "mutation_tool": action,
+                "remote": remote,
+                "repo": repo,
+                "org": org,
+                "issue_number": issue_number,
+                "pr_number": pr_number,
+            },
+        )
         raise
     _audit(action, host=host, remote=remote, org=org, repo=repo,
            result=gitea_audit.SUCCEEDED, request_metadata=request_metadata,
@@ -1823,6 +1836,20 @@ def _audit_pr_result(action: str):
                             "merge_method": result.get("merge_method"),
                         },
                     )
+                    # #606: surface fail-closed blockers / failed mutations to
+                    # Sentry as structured events (best-effort, fail open).
+                    if status in (gitea_audit.BLOCKED, gitea_audit.FAILED):
+                        sentry_observability.capture_workflow_blocker(
+                            action,
+                            message="; ".join(reasons) or action,
+                            next_action=result.get("safe_next_action"),
+                            level="error" if status == gitea_audit.FAILED else "warning",
+                            tags={
+                                "mutation_tool": action,
+                                "pr_number": result.get("pr_number"),
+                                "current_head_sha": result.get("head_sha"),
+                            },
+                        )
             except Exception:
                 pass  # best-effort; never break the tool
             return result
@@ -9954,6 +9981,11 @@ def gitea_assess_mcp_namespace_health(
         probe_source=probe_source,
     )
     _record_live_namespace_health(result)
+    # #606: namespace-health watchdog check-in (best-effort, fail open).
+    sentry_observability.monitor_checkin(
+        "namespace_health",
+        "ok" if result.get("healthy", result.get("callable", True)) else "error",
+    )
     return result
 
 
@@ -11881,6 +11913,18 @@ def gitea_allocate_next_work(
     result["inventory_source"] = (
         "candidates_json" if candidates_json else "gitea_live"
     )
+    # #606: watchdog check-ins for the recurring jobs this allocator run
+    # performs — global stale-lease expiry, terminal-lock lookup, and the
+    # allocator itself. Best-effort; a failed selection reports "error".
+    _alloc_ok = bool(result.get("success"))
+    sentry_observability.monitor_checkin(
+        "allocator_health", "ok" if _alloc_ok else "error"
+    )
+    if _alloc_ok:
+        # These two scans complete inside allocate_next_work before selection;
+        # a successful result proves both ran.
+        sentry_observability.monitor_checkin("stale_lease_scan", "ok")
+        sentry_observability.monitor_checkin("terminal_lock_scan", "ok")
     return result
 
 
@@ -12205,4 +12249,10 @@ if __name__ == "__main__":
     # processes (e.g. review_pr.py) can detect and refuse profile
     # side-channel overrides (#199).
     _export_session_profile_lock()
+    # #606: optional self-hosted Sentry observability. No-op unless
+    # MCP_SENTRY_ENABLED is truthy and SENTRY_DSN is set; never blocks startup.
+    _sentry_status = sentry_observability.init_sentry()
+    sys.stderr.write(
+        f"--- Sentry observability: {_sentry_status.get('reason')} ---\n"
+    )
     mcp.run(transport="stdio")

requirements.txt

@@ -31,6 +31,7 @@ python-multipart==0.0.32
 referencing==0.37.0
 rich==15.0.0
 rpds-py==2026.5.1
+sentry-sdk==2.20.0
 shellingham==1.5.4
 sse-starlette==3.4.5
 starlette==1.3.1

sentry_observability.py

@@ -0,0 +1,535 @@
+"""Optional self-hosted Sentry observability for the Gitea MCP server (#606).
+
+Adds env-var-gated Sentry SDK instrumentation so runtime errors, fail-closed
+workflow blockers, lease/terminal-lock/stale-runtime collisions, and recurring
+watchdog check-ins are visible in a *self-hosted* Sentry at
+``https://sentry.prgs.cc/`` — never Sentry Cloud, and never as the workflow
+source of truth (Gitea stays canonical).
+
+Design constraints (mirror ``gitea_audit`` and the #612 incident bridge):
+
+- **Off by default.** With ``MCP_SENTRY_ENABLED`` false/unset *or* ``SENTRY_DSN``
+  empty, ``init_sentry`` is a no-op and no events are ever sent — existing tool
+  behaviour and API-call patterns are unchanged (acceptance criterion 1).
+- **Fail *open* for observability.** A Sentry outage, a missing ``sentry_sdk``
+  package, or any capture error must never break an MCP tool success path. Every
+  public entry point swallows its own exceptions.
+- **Fail *closed* for redaction.** If a field cannot be proven safe it is dropped
+  rather than sent. Tokens, passwords, keychain IDs, DSNs, private config, raw
+  session-state, full prompt bodies, and full filesystem paths never leave here.
+- **No hard dependency.** ``sentry_sdk`` is imported lazily; the module is fully
+  importable and testable without it installed.
+
+Sentry is observe-only: it must not approve, merge, close, or otherwise mutate
+Gitea workflow state, nor bypass leases, #332, or MCP gates. Alerts may only feed
+the sanctioned Gitea issue/comment path via the #612 incident bridge.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import os
+import re
+from dataclasses import dataclass
+from typing import Any
+
+# Reuse the most comprehensive existing scrubber so redaction stays consistent
+# with the #612 incident bridge (tokens, DSNs, cookies, bearer/basic, keychain
+# ids, session ids, user:pass@host).
+from incident_bridge import redact_text as _redact_text
+
+# Second, complementary scrubber: catches bare ``token <value>`` /
+# ``Bearer <value>`` / ``Basic <value>`` prefixes and raw URLs that the
+# incident-bridge delimiter patterns miss.
+from gitea_audit import _redact_str as _redact_prefixes
+
+# ── Optional SDK (lazy, never a hard dependency) ────────────────────────────
+try:  # pragma: no cover - trivial import guard
+    import sentry_sdk  # type: ignore
+except Exception:  # pragma: no cover - absence is a supported state
+    sentry_sdk = None  # type: ignore
+
+
+# ── Env var names (single source of truth) ──────────────────────────────────
+ENV_ENABLED = "MCP_SENTRY_ENABLED"
+ENV_DSN = "SENTRY_DSN"
+ENV_ENVIRONMENT = "SENTRY_ENVIRONMENT"
+ENV_RELEASE = "SENTRY_RELEASE"
+ENV_TRACES_SAMPLE_RATE = "MCP_SENTRY_TRACES_SAMPLE_RATE"
+ENV_ENABLE_LOGS = "MCP_SENTRY_ENABLE_LOGS"
+
+_TRUTHY = frozenset({"1", "true", "yes", "on"})
+
+REDACTED = "[REDACTED]"
+REDACTED_PATH = "[REDACTED_PATH]"
+
+
+# ── Cron / watchdog monitor slugs (acceptance criterion 6) ──────────────────
+# Stable slugs for the recurring/watchdog jobs #606 wants check-ins for. The
+# slug is the durable monitor identity in Sentry; the wiring call sites pass one
+# of these keys (or an explicit slug) to ``monitor_checkin``.
+MONITOR_SLUGS: dict[str, str] = {
+    "stale_lease_scan": "gitea-mcp-stale-lease-scan",
+    "terminal_lock_scan": "gitea-mcp-terminal-lock-scan",
+    "allocator_health": "gitea-mcp-allocator-health",
+    "namespace_health": "gitea-mcp-namespace-health",
+    "dashboard_freshness": "gitea-mcp-dashboard-freshness",
+    "reconciler_cleanup": "gitea-mcp-reconciler-cleanup",
+}
+
+_CHECKIN_STATUSES = frozenset({"in_progress", "ok", "error"})
+
+
+# ── Tag allowlist (issue "Suggested Sentry tags/context") ───────────────────
+# Only these keys are ever attached as Sentry tags. Anything else is dropped so
+# a caller cannot accidentally leak a sensitive value through a tag.
+ALLOWED_TAG_KEYS = frozenset({
+    "role",
+    "profile",
+    "namespace",
+    "repo",
+    "org",
+    "issue_number",
+    "pr_number",
+    "blocker_type",
+    "workflow_hash",
+    "session_id_hash",  # hash only — never the raw session id
+    "pid",
+    "worktree_category",  # category, never the full sensitive path
+    "lease_comment_id",
+    "expected_head_sha",
+    "current_head_sha",
+    "terminal_lock_state",
+    "capability",
+    "mutation_tool",
+})
+
+# Absolute-path shapes that must never be sent verbatim (macOS/Linux + temp).
+_PATH_RE = re.compile(r"(?:/private)?/(?:Users|home|tmp|var|opt|Volumes)/[^\s\"']*")
+
+# ``extra`` keys whose *full* contents are forbidden by the redaction rules
+# (raw session-state, full prompt/comment bodies, private config blobs, raw
+# headers).
+_FORBIDDEN_EXTRA_KEYS = frozenset({
+    "prompt",
+    "prompt_body",
+    "next_prompt",
+    "body",
+    "raw_body",
+    "session_state",
+    "session_state_contents",
+    "config",
+    "config_contents",
+    "private_config",
+    "headers",
+    "authorization",
+})
+
+
+# ── Configuration ───────────────────────────────────────────────────────────
+@dataclass(frozen=True)
+class SentryConfig:
+    """Immutable snapshot of the Sentry env configuration."""
+
+    enabled: bool = False
+    dsn: str | None = None
+    environment: str = "development"
+    release: str | None = None
+    traces_sample_rate: float = 0.0
+    enable_logs: bool = False
+
+    @property
+    def active(self) -> bool:
+        """True only when the operator both opted in *and* supplied a DSN.
+
+        This is the single gate that keeps the feature off by default: enabling
+        the flag without a DSN (or vice versa) sends nothing.
+        """
+        return bool(self.enabled and self.dsn)
+
+    def safe_summary(self) -> dict[str, Any]:
+        """Operator-facing status with **no** DSN value (only presence)."""
+        return {
+            "enabled": self.enabled,
+            "dsn_present": bool(self.dsn),
+            "environment": self.environment,
+            "release": self.release,
+            "traces_sample_rate": self.traces_sample_rate,
+            "enable_logs": self.enable_logs,
+            "active": self.active,
+        }
+
+
+def _env_bool(name: str, env: dict[str, str]) -> bool:
+    return (env.get(name) or "").strip().lower() in _TRUTHY
+
+
+def _env_float(name: str, default: float, env: dict[str, str]) -> float:
+    raw = (env.get(name) or "").strip()
+    if not raw:
+        return default
+    try:
+        val = float(raw)
+    except (TypeError, ValueError):
+        return default
+    # Clamp to Sentry's valid [0.0, 1.0] sample-rate range.
+    if val < 0.0:
+        return 0.0
+    if val > 1.0:
+        return 1.0
+    return val
+
+
+def load_config(env: dict[str, str] | None = None) -> SentryConfig:
+    """Build a :class:`SentryConfig` from the environment (read at call time)."""
+    env = dict(os.environ if env is None else env)
+    dsn = (env.get(ENV_DSN) or "").strip() or None
+    return SentryConfig(
+        enabled=_env_bool(ENV_ENABLED, env),
+        dsn=dsn,
+        environment=(env.get(ENV_ENVIRONMENT) or "").strip() or "development",
+        release=(env.get(ENV_RELEASE) or "").strip() or None,
+        traces_sample_rate=_env_float(ENV_TRACES_SAMPLE_RATE, 0.0, env),
+        enable_logs=_env_bool(ENV_ENABLE_LOGS, env),
+    )
+
+
+def sdk_available() -> bool:
+    """True when the optional ``sentry_sdk`` package is importable."""
+    return sentry_sdk is not None
+
+
+# ── Redaction (fail closed) ─────────────────────────────────────────────────
+def sanitize_path(value: Any) -> str:
+    """Reduce a filesystem path to a non-sensitive *category* token.
+
+    Full local paths must never be sent. We keep only a coarse worktree
+    category derived from the path shape (author/reviewer/merger/reconciler/
+    branches/root/other).
+    """
+    text = "" if value is None else str(value)
+    low = text.lower()
+    if not text:
+        return "unknown"
+    # Order matters: more specific role markers before the generic "branches".
+    if "reconcile" in low:
+        return "reconciler"
+    if "review" in low:
+        return "reviewer"
+    if "merge" in low or "merger" in low:
+        return "merger"
+    if "author" in low or re.search(r"/branches/(?:feat|fix|docs|chore|issue)", low):
+        return "author"
+    if "/branches/" in low:
+        return "branches"
+    if low.rstrip("/").endswith("gitea-tools"):
+        return "root"
+    return "other"
+
+
+def redact_value(value: Any) -> Any:
+    """Recursively redact a JSON-able value: secret text, absolute paths, and
+    known-sensitive dict keys are removed. Fail closed — any error drops the
+    value entirely rather than risk leaking it."""
+    try:
+        if isinstance(value, dict):
+            out: dict[str, Any] = {}
+            for k, v in value.items():
+                key = str(k)
+                low = key.lower()
+                if low in _FORBIDDEN_EXTRA_KEYS or any(
+                    s in low
+                    for s in ("token", "secret", "password", "cookie", "auth", "dsn", "keychain")
+                ):
+                    out[key] = REDACTED
+                    continue
+                out[key] = redact_value(v)
+            return out
+        if isinstance(value, (list, tuple)):
+            return [redact_value(v) for v in value]
+        if isinstance(value, str):
+            scrubbed = _redact_text(value)
+            scrubbed = _redact_prefixes(scrubbed)
+            scrubbed = _PATH_RE.sub(REDACTED_PATH, scrubbed)
+            return scrubbed
+        return value
+    except Exception:
+        return REDACTED
+
+
+def hash_session_id(session_id: Any) -> str:
+    """Short, stable, non-reversible fingerprint of a session id."""
+    digest = hashlib.sha256(str(session_id).encode("utf-8", "replace")).hexdigest()
+    return digest[:12]
+
+
+def build_tags(**kwargs: Any) -> dict[str, str]:
+    """Return a scrubbed, allowlisted tag dict.
+
+    ``session_id`` is accepted but only ever surfaced as ``session_id_hash``.
+    ``worktree_path`` collapses to ``worktree_category``. Any non-allowlisted
+    key, or a value that still contains redacted material after scrubbing, is
+    dropped.
+    """
+    raw: dict[str, Any] = dict(kwargs)
+
+    # Hash the session id — never emit it raw.
+    session_id = raw.pop("session_id", None)
+    if session_id and "session_id_hash" not in raw:
+        raw["session_id_hash"] = hash_session_id(session_id)
+
+    # A full worktree path collapses to a category tag.
+    wt = raw.pop("worktree_path", None)
+    if wt and "worktree_category" not in raw:
+        raw["worktree_category"] = sanitize_path(wt)
+
+    out: dict[str, str] = {}
+    for key, val in raw.items():
+        if key not in ALLOWED_TAG_KEYS:
+            continue
+        if val is None:
+            continue
+        scrubbed = redact_value(val)
+        text = str(scrubbed)
+        if not text or REDACTED in text or REDACTED_PATH in text:
+            continue
+        if len(text) > 200:
+            text = text[:200] + "…"
+        out[key] = text
+    return out
+
+
+def scrub_event(event: Any, hint: Any = None) -> dict[str, Any] | None:
+    """Sentry ``before_send`` / ``before_send_log`` hook.
+
+    Recursively redacts the outgoing event. On *any* failure it returns ``None``
+    so the event is dropped rather than sent unscrubbed (fail closed for
+    redaction).
+    """
+    try:
+        if not isinstance(event, dict):
+            return None
+        scrubbed = redact_value(event)
+        # Drop server_name if it leaked a hostname/path; PID is kept via tags.
+        scrubbed.pop("server_name", None)
+        return scrubbed
+    except Exception:
+        return None
+
+
+# ── Event builders (pure, independently testable) ───────────────────────────
+def build_blocker_event(
+    blocker_type: str,
+    *,
+    message: str | None = None,
+    next_action: str | None = None,
+    level: str = "warning",
+    tags: dict[str, Any] | None = None,
+    extra: dict[str, Any] | None = None,
+) -> dict[str, Any]:
+    """Build a redacted, structured Sentry event for a workflow blocker.
+
+    ``next_action`` maps the issue's "canonical next action when available"
+    requirement (acceptance criterion 7).
+    """
+    merged_tags = dict(tags or {})
+    merged_tags.setdefault("blocker_type", blocker_type)
+    safe_tags = build_tags(**merged_tags)
+
+    safe_extra = redact_value(dict(extra or {}))
+    if next_action:
+        # A short canonical next action is allowed (it is not a full prompt).
+        safe_extra["canonical_next_action"] = redact_value(str(next_action)[:500])
+
+    event: dict[str, Any] = {
+        "message": redact_value(message or blocker_type),
+        "level": level if level in ("debug", "info", "warning", "error", "fatal") else "warning",
+        "logger": "gitea-mcp.workflow",
+        "tags": safe_tags,
+        "extra": safe_extra,
+        "fingerprint": ["workflow-blocker", blocker_type],
+    }
+    return event
+
+
+def build_checkin_payload(
+    monitor: str,
+    status: str,
+    *,
+    check_in_id: str | None = None,
+    duration: float | None = None,
+) -> dict[str, Any]:
+    """Build a Sentry cron check-in payload for one of :data:`MONITOR_SLUGS`.
+
+    ``monitor`` may be a registry key (e.g. ``"stale_lease_scan"``) or an
+    explicit slug. Raises ``ValueError`` on an unknown status so callers cannot
+    silently send a malformed check-in.
+    """
+    if status not in _CHECKIN_STATUSES:
+        raise ValueError(
+            f"invalid check-in status {status!r}; expected one of {sorted(_CHECKIN_STATUSES)}"
+        )
+    slug = MONITOR_SLUGS.get(monitor, monitor)
+    payload: dict[str, Any] = {"monitor_slug": slug, "status": status}
+    if check_in_id:
+        payload["check_in_id"] = str(check_in_id)
+    if duration is not None:
+        try:
+            payload["duration"] = float(duration)
+        except (TypeError, ValueError):
+            pass
+    return payload
+
+
+# ── Runtime init + capture (fail open) ──────────────────────────────────────
+_STATE: dict[str, Any] = {"initialized": False, "config": None}
+
+
+def is_initialized() -> bool:
+    return bool(_STATE.get("initialized"))
+
+
+def active_config() -> SentryConfig | None:
+    return _STATE.get("config")
+
+
+def reset_for_tests() -> None:
+    """Clear module init state. Test-only helper (never called in production)."""
+    _STATE["initialized"] = False
+    _STATE["config"] = None
+
+
+def init_sentry(config: SentryConfig | None = None) -> dict[str, Any]:
+    """Initialise the Sentry SDK if (and only if) enabled + DSN + SDK present.
+
+    Idempotent and never raises. Returns an operator-safe status dict (no DSN
+    value). Behaviour is unchanged when the feature is off.
+    """
+    cfg = config or load_config()
+    status: dict[str, Any] = {"initialized": False, **cfg.safe_summary()}
+    try:
+        if not cfg.active:
+            status["reason"] = "disabled (MCP_SENTRY_ENABLED false or SENTRY_DSN empty)"
+            _STATE["config"] = cfg
+            return status
+        if not sdk_available():
+            status["reason"] = "sentry_sdk not installed"
+            _STATE["config"] = cfg
+            return status
+
+        init_kwargs: dict[str, Any] = {
+            "dsn": cfg.dsn,
+            "environment": cfg.environment,
+            "release": cfg.release,
+            "traces_sample_rate": cfg.traces_sample_rate,
+            "before_send": scrub_event,
+            "send_default_pii": False,
+        }
+        if cfg.enable_logs:
+            # sentry-sdk 2.x captures Python logs as structured logs when the
+            # experimental logs feature is enabled; scrub those too.
+            init_kwargs["_experiments"] = {
+                "enable_logs": True,
+                "before_send_log": scrub_event,
+            }
+        sentry_sdk.init(**init_kwargs)  # type: ignore[union-attr]
+        _STATE["initialized"] = True
+        _STATE["config"] = cfg
+        status["initialized"] = True
+        status["reason"] = "sentry initialised"
+    except Exception as exc:  # fail open: observability must not block startup
+        status["reason"] = f"init failed (ignored): {type(exc).__name__}"
+        _STATE["initialized"] = False
+    return status
+
+
+def _set_scope_tags(scope: Any, tags: dict[str, str]) -> None:
+    for key, val in tags.items():
+        try:
+            scope.set_tag(key, val)
+        except Exception:
+            pass
+
+
+def capture_workflow_blocker(
+    blocker_type: str,
+    *,
+    message: str | None = None,
+    next_action: str | None = None,
+    level: str = "warning",
+    tags: dict[str, Any] | None = None,
+    extra: dict[str, Any] | None = None,
+) -> dict[str, Any]:
+    """Capture a fail-closed workflow blocker as a structured Sentry event.
+
+    Always returns the redacted event dict (so callers/tests can inspect it),
+    and sends it to Sentry only when initialised. Fail open.
+    """
+    event = build_blocker_event(
+        blocker_type,
+        message=message,
+        next_action=next_action,
+        level=level,
+        tags=tags,
+        extra=extra,
+    )
+    try:
+        if is_initialized() and sdk_available():
+            sentry_sdk.capture_event(event)  # type: ignore[union-attr]
+    except Exception:
+        pass
+    return event
+
+
+def capture_exception(
+    exc: BaseException,
+    *,
+    tags: dict[str, Any] | None = None,
+    extra: dict[str, Any] | None = None,
+) -> bool:
+    """Capture a runtime exception with scrubbed tags. Fail open.
+
+    Returns True only when the event was handed to an initialised SDK.
+    """
+    try:
+        if not (is_initialized() and sdk_available()):
+            return False
+        safe_tags = build_tags(**(tags or {}))
+        safe_extra = redact_value(dict(extra or {}))
+        with sentry_sdk.push_scope() as scope:  # type: ignore[union-attr]
+            _set_scope_tags(scope, safe_tags)
+            for key, val in safe_extra.items():
+                try:
+                    scope.set_extra(key, val)
+                except Exception:
+                    pass
+            sentry_sdk.capture_exception(exc)  # type: ignore[union-attr]
+        return True
+    except Exception:
+        return False
+
+
+def monitor_checkin(
+    monitor: str,
+    status: str,
+    *,
+    check_in_id: str | None = None,
+    duration: float | None = None,
+) -> dict[str, Any] | None:
+    """Send a Sentry cron check-in for a watchdog job. Fail open.
+
+    Returns the payload (for inspection/tests), or ``None`` if the status was
+    invalid. Only transmits when initialised.
+    """
+    try:
+        payload = build_checkin_payload(
+            monitor, status, check_in_id=check_in_id, duration=duration
+        )
+    except ValueError:
+        return None
+    try:
+        if is_initialized() and sdk_available() and hasattr(sentry_sdk, "capture_checkin"):
+            sentry_sdk.capture_checkin(**payload)  # type: ignore[union-attr]
+    except Exception:
+        pass
+    return payload

tests/test_sentry_observability.py

@@ -0,0 +1,412 @@
+"""Tests for optional self-hosted Sentry observability (#606).
+
+Covers the pure module (config, redaction, event/check-in builders) and the
+runtime capture paths using a fake ``sentry_sdk``, so nothing ever touches the
+network. Critically proves the feature is a no-op when disabled or DSN-less
+(acceptance criterion 1) and that secrets/paths/session-state are never sent
+(criterion 5).
+"""
+
+import sys
+import contextlib
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+import sentry_observability as so  # noqa: E402
+
+
+# ── Fake SDK ────────────────────────────────────────────────────────────────
+class _FakeScope:
+    def __init__(self):
+        self.tags = {}
+        self.extras = {}
+
+    def set_tag(self, k, v):
+        self.tags[k] = v
+
+    def set_extra(self, k, v):
+        self.extras[k] = v
+
+
+class FakeSentrySDK:
+    """Minimal stand-in exposing the SDK surface sentry_observability uses."""
+
+    def __init__(self):
+        self.init_kwargs = None
+        self.events = []
+        self.exceptions = []
+        self.checkins = []
+        self.last_scope = None
+
+    def init(self, **kwargs):
+        self.init_kwargs = kwargs
+
+    def capture_event(self, event):
+        self.events.append(event)
+
+    def capture_exception(self, exc):
+        self.exceptions.append(exc)
+
+    def capture_checkin(self, **payload):
+        self.checkins.append(payload)
+
+    @contextlib.contextmanager
+    def push_scope(self):
+        self.last_scope = _FakeScope()
+        yield self.last_scope
+
+
+@pytest.fixture(autouse=True)
+def _reset_state():
+    """Isolate module init state between tests."""
+    so.reset_for_tests()
+    yield
+    so.reset_for_tests()
+
+
+@pytest.fixture
+def fake_sdk(monkeypatch):
+    sdk = FakeSentrySDK()
+    monkeypatch.setattr(so, "sentry_sdk", sdk)
+    return sdk
+
+
+# ── Config / gating ─────────────────────────────────────────────────────────
+def test_disabled_by_default_empty_env():
+    cfg = so.load_config(env={})
+    assert cfg.enabled is False
+    assert cfg.active is False
+
+
+def test_enabled_flag_without_dsn_is_not_active():
+    cfg = so.load_config(env={"MCP_SENTRY_ENABLED": "1"})
+    assert cfg.enabled is True
+    assert cfg.dsn is None
+    assert cfg.active is False  # DSN required
+
+
+def test_dsn_without_enabled_flag_is_not_active():
+    cfg = so.load_config(env={"SENTRY_DSN": "https://[email protected]/1"})
+    assert cfg.active is False
+
+
+def test_active_requires_enabled_and_dsn():
+    cfg = so.load_config(
+        env={"MCP_SENTRY_ENABLED": "true", "SENTRY_DSN": "https://[email protected]/1"}
+    )
+    assert cfg.active is True
+
+
+def test_truthy_variants():
+    for val in ("1", "true", "YES", "On"):
+        cfg = so.load_config(env={"MCP_SENTRY_ENABLED": val})
+        assert cfg.enabled is True
+    for val in ("0", "false", "no", "", "off"):
+        cfg = so.load_config(env={"MCP_SENTRY_ENABLED": val})
+        assert cfg.enabled is False
+
+
+def test_traces_sample_rate_parsed_and_clamped():
+    assert so.load_config(env={"MCP_SENTRY_TRACES_SAMPLE_RATE": "0.25"}).traces_sample_rate == 0.25
+    assert so.load_config(env={"MCP_SENTRY_TRACES_SAMPLE_RATE": "5"}).traces_sample_rate == 1.0
+    assert so.load_config(env={"MCP_SENTRY_TRACES_SAMPLE_RATE": "-1"}).traces_sample_rate == 0.0
+    assert so.load_config(env={"MCP_SENTRY_TRACES_SAMPLE_RATE": "junk"}).traces_sample_rate == 0.0
+
+
+def test_safe_summary_has_no_dsn_value():
+    cfg = so.load_config(
+        env={"MCP_SENTRY_ENABLED": "1", "SENTRY_DSN": "https://[email protected]/1"}
+    )
+    summary = cfg.safe_summary()
+    assert summary["dsn_present"] is True
+    assert "secret" not in repr(summary)
+    assert "dsn" not in summary  # only presence, never the value
+
+
+# ── init_sentry ─────────────────────────────────────────────────────────────
+def test_init_noop_when_disabled(fake_sdk):
+    status = so.init_sentry(so.load_config(env={}))
+    assert status["initialized"] is False
+    assert fake_sdk.init_kwargs is None  # no SDK init
+    assert so.is_initialized() is False
+
+
+def test_init_noop_when_enabled_but_missing_dsn(fake_sdk):
+    status = so.init_sentry(so.load_config(env={"MCP_SENTRY_ENABLED": "1"}))
+    assert status["initialized"] is False
+    assert fake_sdk.init_kwargs is None
+
+
+def test_init_reports_missing_sdk(monkeypatch):
+    monkeypatch.setattr(so, "sentry_sdk", None)
+    status = so.init_sentry(
+        so.load_config(
+            env={"MCP_SENTRY_ENABLED": "1", "SENTRY_DSN": "https://[email protected]/1"}
+        )
+    )
+    assert status["initialized"] is False
+    assert "not installed" in status["reason"]
+
+
+def test_init_configures_sdk_with_scrubber(fake_sdk):
+    status = so.init_sentry(
+        so.load_config(
+            env={
+                "MCP_SENTRY_ENABLED": "1",
+                "SENTRY_DSN": "https://[email protected]/1",
+                "SENTRY_ENVIRONMENT": "prod",
+                "MCP_SENTRY_TRACES_SAMPLE_RATE": "0.1",
+            }
+        )
+    )
+    assert status["initialized"] is True
+    assert so.is_initialized() is True
+    kw = fake_sdk.init_kwargs
+    assert kw["dsn"] == "https://[email protected]/1"
+    assert kw["environment"] == "prod"
+    assert kw["traces_sample_rate"] == 0.1
+    assert kw["before_send"] is so.scrub_event
+    assert kw["send_default_pii"] is False
+
+
+def test_init_enable_logs_wires_log_scrubber(fake_sdk):
+    so.init_sentry(
+        so.load_config(
+            env={
+                "MCP_SENTRY_ENABLED": "1",
+                "SENTRY_DSN": "https://[email protected]/1",
+                "MCP_SENTRY_ENABLE_LOGS": "1",
+            }
+        )
+    )
+    exp = fake_sdk.init_kwargs["_experiments"]
+    assert exp["enable_logs"] is True
+    assert exp["before_send_log"] is so.scrub_event
+
+
+def test_init_never_raises_on_sdk_failure(monkeypatch):
+    class Boom:
+        def init(self, **kwargs):
+            raise RuntimeError("sentry down")
+
+    monkeypatch.setattr(so, "sentry_sdk", Boom())
+    status = so.init_sentry(
+        so.load_config(
+            env={"MCP_SENTRY_ENABLED": "1", "SENTRY_DSN": "https://[email protected]/1"}
+        )
+    )
+    assert status["initialized"] is False
+    assert "init failed" in status["reason"]
+
+
+# ── Redaction (fail closed) ─────────────────────────────────────────────────
+def test_build_tags_allowlist_only():
+    tags = so.build_tags(role="author", secret_thing="leak", pid=123)
+    assert tags["role"] == "author"
+    assert tags["pid"] == "123"
+    assert "secret_thing" not in tags
+
+
+def test_build_tags_hashes_session_id():
+    tags = so.build_tags(session_id="prgs-author-20479-cf9ac178")
+    assert "session_id" not in tags
+    assert "session_id_hash" in tags
+    assert tags["session_id_hash"] != "prgs-author-20479-cf9ac178"
+    assert len(tags["session_id_hash"]) == 12
+
+
+def test_build_tags_collapses_worktree_path():
+    tags = so.build_tags(
+        worktree_path="/Users/x/Development/Gitea-Tools/branches/issue-606-sentry-observability"
+    )
+    assert "worktree_path" not in tags
+    assert tags["worktree_category"] == "author"
+
+
+def test_build_tags_drops_value_that_scrubs_to_redacted():
+    # A tag value that is itself a token gets scrubbed then dropped.
+    tags = so.build_tags(capability="token abcdef1234567890")
+    assert "capability" not in tags
+
+
+def test_sanitize_path_categories():
+    assert so.sanitize_path("/repo/branches/review-pr-654") == "reviewer"
+    assert so.sanitize_path("/repo/branches/merge-pr-1") == "merger"
+    assert so.sanitize_path("/repo/branches/reconcile-pr-1") == "reconciler"
+    assert so.sanitize_path("/repo/branches/feat-issue-606") == "author"
+    assert so.sanitize_path("/x/y/Gitea-Tools") == "root"
+
+
+def test_redact_value_scrubs_secrets_and_paths():
+    out = so.redact_value(
+        {
+            "token": "abc123",
+            "note": "Authorization: Bearer sk_live_abcdefgh12345",
+            "path": "/Users/jasonwalker/Development/Gitea-Tools/secret",
+            "dsn": "https://[email protected]/1",
+            "safe": "hello",
+        }
+    )
+    assert out["token"] == so.REDACTED
+    assert out["dsn"] == so.REDACTED
+    assert "sk_live" not in out["note"]
+    assert so.REDACTED_PATH in out["path"]
+    assert "/Users/" not in out["path"]
+    assert out["safe"] == "hello"
+
+
+def test_redact_value_forbidden_prompt_and_session_state():
+    out = so.redact_value(
+        {"prompt": "full body", "session_state": "{...}", "keep": "ok"}
+    )
+    assert out["prompt"] == so.REDACTED
+    assert out["session_state"] == so.REDACTED
+    assert out["keep"] == "ok"
+
+
+def test_scrub_event_redacts_nested_and_drops_server_name():
+    event = {
+        "server_name": "some-host",
+        "message": "boom",
+        "extra": {"token": "leak", "ok": "1"},
+    }
+    scrubbed = so.scrub_event(event)
+    assert "server_name" not in scrubbed
+    assert scrubbed["extra"]["token"] == so.REDACTED
+    assert scrubbed["extra"]["ok"] == "1"
+
+
+def test_scrub_event_drops_non_dict():
+    assert so.scrub_event("not a dict") is None
+    assert so.scrub_event(None) is None
+
+
+# ── Event builders ──────────────────────────────────────────────────────────
+def test_build_blocker_event_structure_and_next_action():
+    event = so.build_blocker_event(
+        "active_foreign_lease",
+        message="blocked by foreign lease",
+        next_action="wait or adopt via allocator",
+        level="warning",
+        tags={"pr_number": 606, "session_id": "s-123"},
+    )
+    assert event["tags"]["blocker_type"] == "active_foreign_lease"
+    assert event["tags"]["pr_number"] == "606"
+    assert "session_id" not in event["tags"]
+    assert event["tags"]["session_id_hash"]
+    assert event["extra"]["canonical_next_action"] == "wait or adopt via allocator"
+    assert event["fingerprint"] == ["workflow-blocker", "active_foreign_lease"]
+
+
+def test_build_blocker_event_invalid_level_defaults_warning():
+    event = so.build_blocker_event("x", level="nonsense")
+    assert event["level"] == "warning"
+
+
+def test_build_checkin_payload_maps_slugs():
+    for key, slug in so.MONITOR_SLUGS.items():
+        payload = so.build_checkin_payload(key, "ok")
+        assert payload["monitor_slug"] == slug
+        assert payload["status"] == "ok"
+
+
+def test_build_checkin_payload_explicit_slug_passthrough():
+    payload = so.build_checkin_payload("custom-slug", "in_progress", duration=1.5)
+    assert payload["monitor_slug"] == "custom-slug"
+    assert payload["duration"] == 1.5
+
+
+def test_build_checkin_payload_rejects_bad_status():
+    with pytest.raises(ValueError):
+        so.build_checkin_payload("allocator_health", "bogus")
+
+
+def test_all_six_monitors_registered():
+    assert set(so.MONITOR_SLUGS) == {
+        "stale_lease_scan",
+        "terminal_lock_scan",
+        "allocator_health",
+        "namespace_health",
+        "dashboard_freshness",
+        "reconciler_cleanup",
+    }
+
+
+# ── Capture paths (fail open) ───────────────────────────────────────────────
+def test_capture_workflow_blocker_noop_when_disabled(fake_sdk):
+    # not initialised
+    event = so.capture_workflow_blocker("some_blocker", message="x")
+    assert isinstance(event, dict)  # still returns redacted event
+    assert fake_sdk.events == []  # but nothing sent
+
+
+def test_capture_workflow_blocker_sends_when_initialised(fake_sdk):
+    so.init_sentry(
+        so.load_config(
+            env={"MCP_SENTRY_ENABLED": "1", "SENTRY_DSN": "https://[email protected]/1"}
+        )
+    )
+    so.capture_workflow_blocker("terminal_lock_occupied", message="held")
+    assert len(fake_sdk.events) == 1
+    assert fake_sdk.events[0]["tags"]["blocker_type"] == "terminal_lock_occupied"
+
+
+def test_capture_exception_noop_when_disabled(fake_sdk):
+    assert so.capture_exception(ValueError("x")) is False
+    assert fake_sdk.exceptions == []
+
+
+def test_capture_exception_sends_scrubbed_tags(fake_sdk):
+    so.init_sentry(
+        so.load_config(
+            env={"MCP_SENTRY_ENABLED": "1", "SENTRY_DSN": "https://[email protected]/1"}
+        )
+    )
+    ok = so.capture_exception(
+        RuntimeError("bad"), tags={"mutation_tool": "gitea_merge_pr", "leaky": "x"}
+    )
+    assert ok is True
+    assert len(fake_sdk.exceptions) == 1
+    assert fake_sdk.last_scope.tags["mutation_tool"] == "gitea_merge_pr"
+    assert "leaky" not in fake_sdk.last_scope.tags
+
+
+def test_capture_exception_never_raises(monkeypatch, fake_sdk):
+    so.init_sentry(
+        so.load_config(
+            env={"MCP_SENTRY_ENABLED": "1", "SENTRY_DSN": "https://[email protected]/1"}
+        )
+    )
+
+    def boom(exc):
+        raise RuntimeError("sdk exploded")
+
+    monkeypatch.setattr(fake_sdk, "capture_exception", boom)
+    # Must swallow the SDK failure (fail open).
+    assert so.capture_exception(ValueError("y")) is False
+
+
+def test_monitor_checkin_noop_when_disabled(fake_sdk):
+    payload = so.monitor_checkin("allocator_health", "ok")
+    assert payload["monitor_slug"] == "gitea-mcp-allocator-health"
+    assert fake_sdk.checkins == []  # not sent while disabled
+
+
+def test_monitor_checkin_sends_when_initialised(fake_sdk):
+    so.init_sentry(
+        so.load_config(
+            env={"MCP_SENTRY_ENABLED": "1", "SENTRY_DSN": "https://[email protected]/1"}
+        )
+    )
+    so.monitor_checkin("stale_lease_scan", "ok")
+    assert fake_sdk.checkins == [
+        {"monitor_slug": "gitea-mcp-stale-lease-scan", "status": "ok"}
+    ]
+
+
+def test_monitor_checkin_invalid_status_returns_none(fake_sdk):
+    assert so.monitor_checkin("allocator_health", "bogus") is None
+    assert fake_sdk.checkins == []