Context Firewall

Implement a Context Firewall workflow to prevent the master context from being flooded by large inputs.

Purpose

Route large inputs (big files, logs, PDFs/images, long MCP/tool outputs) through sub-agents that produce compressed, auditable results. Only pass back:

• Structured claims
• Evidence locators (line/symbol/tool-call)
• Coverage statements

When to use

Prefer this workflow when any of the following is true:

• The user wants the "full" content of a large file/log/document.
• Tool output is long/noisy (search results, crawls, API responses).
• The task needs multi-file scanning or cross-file synthesis.
• The output must be verifiable without re-reading everything.

Core contract (Evidence Contract)

For every meaningful claim:

• Attach at least one evidence item.
• Use a locator that enables low-cost verification.

Locator preference order:

1. line_range (default)
2. symbol_range (functions/classes)
3. tool_call (tool-derived facts; include args hash and rerun hint when safe)
4. byte_range/json_path/stack_signature (define, but treat as harder to verify in v1)

Keep quotes short:

• Respect the quote_max_chars constraint.
• Never paste large raw blobs.

Recommended workflow

1) Generate TaskSpec

Create a TaskSpec.v1 that is explicit about:

• Objective
• Inputs (files/tool calls)
• Questions
• must_cover checklist
• Constraints (budget + evidence requirements)
• Risk level

Prefer using the command:

• /cf-spec to generate a schema-valid template.

2) Run Map-Reduce preprocessing

Use /cf-run to:

• Split inputs into shards
• Run cf-fileworker on each shard in parallel
• Merge with cf-aggregator into a final SubResult.v1

Hard requirements for sub-agents:

• Output strict JSON only (no markdown fences, no extra commentary).
• Ensure every claim includes evidence.

3) Verify cheaply

Use /cf-verify to sample-check claims:

• Choose sampling rate by risk_level.
• Re-read only the referenced snippets.
• Produce VerifyReport.v1.

If verification fails:

• Request stronger evidence (more/clearer locators).
• Narrow must_cover.
• Run a second-pass cf-critic to independently review.

Coverage & anti-leak rules

Always include a coverage section that declares:

• Which inputs were scanned
• Which method was used (grep+window, full scan, time-window scan)
• Known gaps (missing archives, not provided inputs)

Never:

• Dump raw input into the master context.
• Hide uncertainty: mark gaps explicitly.

Operational defaults

Default thresholds are configurable in:

• .claude/context-firewall.local.md

Defaults:

• read_warn_bytes: 524288
• tool_output_warn_chars: 20000
• sample_rate: {low:0.05, medium:0.15, high:0.30}

Related resources

• Commands:
  • plugins/context-firewall/commands/cf-spec.md
  • plugins/context-firewall/commands/cf-run.md
  • plugins/context-firewall/commands/cf-verify.md
• Agents:
  • plugins/context-firewall/agents/cf-fileworker.md
  • plugins/context-firewall/agents/cf-aggregator.md
  • plugins/context-firewall/agents/cf-critic.md
• Schemas:
  • plugins/context-firewall/schemas/task-spec.v1.schema.json
  • plugins/context-firewall/schemas/sub-result.v1.schema.json
  • plugins/context-firewall/schemas/verify-report.v1.schema.json
  • plugins/context-firewall/schemas/settings.v1.schema.json
• Settings template:
  • plugins/context-firewall/scripts/settings-frontmatter.md