Context Check — Session Context Hygiene

Language-agnostic. Fires on write and review operations regardless of language.

---

Rules

CTX-1 — Stale or Absent SESSION.md

Severity: WARN | Languages: all | Source: CCC

What it prohibits: Starting a non-trivial implementation or review session when .agent/SESSION.md is absent or its last-updated frontmatter field is more than 24 hours old, without first confirming intent with the developer.

Prohibited patterns:

# Absent session file
.agent/SESSION.md does not exist

# Stale session file
last-updated: "2026-01-01T10:00:00Z"   # > 24h ago, session resumed silently

Exemptions:

• Single-file bug fixes or tasks explicitly scoped to < 30 minutes of work
• Sessions where the developer has explicitly stated "start fresh"
• Trivial test runs, formatting, or documentation-only edits

Detection:

1. Read .agent/SESSION.md if it exists; check the last-updated frontmatter field
2. If absent: warn once before proceeding
3. If last-updated is > 24 hours before the current time: warn and ask the developer to confirm the session is intentionally resumed
4. If HANDOFF.json is present and valid, treat it as satisfying the session-state requirement even if SESSION.md is absent or stale

agent_action:

1. Cite: CTX-1 (WARN): No active session state found (SESSION.md absent or stale).
2. Ask: "This looks like a resumed or new session with no recent checkpoint. Should I start fresh, or is there context I should know about?"
3. Do not block — wait for developer confirmation, then proceed

---

CTX-2 — Failed-Hypothesis Budget Exceeded

Severity: WARN | Languages: all | Source: CCC

What it prohibits: Continuing implementation or debugging when ## Failed Hypotheses in .agent/SESSION.md contains 3 or more entries, without a context-hygiene pause to consolidate state and prune dead ends.

Prohibited patterns:

# SESSION.md — too many failed hypotheses without a pause
## Failed Hypotheses
- "Caching layer is the bottleneck"
- "Race condition in auth middleware"
- "Database connection pool exhaustion"
# ^ 3 entries: pause required before forming new hypotheses

Exemptions:

• A context-hygiene pause has already been completed this session (current-phase: "context-hygiene-pause" was set and cleared)
• HANDOFF.json failed-hypotheses array has < 3 entries
• The task is a fresh start with no prior hypotheses

Detection:

1. Read .agent/SESSION.md ## Failed Hypotheses section
2. Count distinct hypothesis entries
3. Warn if count ≥ 3 and no prior pause is recorded in ## Decisions

agent_action:

1. Cite: CTX-2 (WARN): {n} failed hypotheses recorded — context-hygiene pause recommended.
2. Recommend: "Before forming new hypotheses, write a consolidated summary of what is ruled out to .agent/SESSION.md and start fresh with only confirmed facts."
3. Do not block — warn and let developer decide

---

CTX-3 — Missing Codebase Brief for Non-Trivial Implementation

Severity: WARN | Languages: all | Source: CCC

What it prohibits: Beginning a non-trivial implementation task (new module, new service, architectural change) without a recorded codebase brief or scout discovery summary in the session state or task context.

Prohibited patterns:

# Starting "implement new auth service" with:
# - No scout brief
# - No relevant files listed
# - No dependency map
# - SESSION.md Current Task section is empty or generic

Exemptions:

• The task is a single-file change with clear, bounded scope
• A discovery brief has been passed in the agent prompt directly
• The session's ## Current Context section references a prior scout run
• The task is a bug fix, not a new feature or structural change

Detection:

1. Read .agent/SESSION.md ## Current Context section
2. If the current task involves new modules, new services, or architectural changes (infer from task description) AND the context section is empty or lacks file references: warn

agent_action:

1. Cite: CTX-3 (WARN): Non-trivial implementation task with no codebase brief recorded.
2. Recommend: "Run a scout pass first to map relevant files, boundaries, and dependencies before implementing. This prevents scope drift and redundant exploration mid-task."
3. Do not block — warn and let developer decide

---

Report schema: see skills/conductor/shared-contracts.md.