Listener defense and search saturation

Retention update: ERASURE.md adds signed seed de-registration and segregated persistent security summaries. Routine audit still expires; security summaries do not automatically expire. Repeat ban incidents now escalate up to a one-day temporary ban. A documented local retention-review path remains available.

Bootstrap discovery introduces peers. Searches go directly to a chosen data peer. The bootstrap protocol accepts registration, discovery, removal and bounded signaling operations; it neither receives nor forwards searches. One host may run both listeners as separate roles. Federated search caps fan-out at eight peers and four concurrent requests.

Shared baseline

Both listener roles use agentmesh.defense.Defense: local persistent peer-ID and IP/CIDR blocks, bounded rate accounting, automatic 300-second bans, and a bounded local audit database. Rules are read from SQLite on requests, so local CLI edits take effect without restarting either listener. Blocks are not broadcast; an untrusted accusation cannot create a network-wide ban.

Before TLS, source-IP blocks and connection quotas apply. Source means the accepted socket address, never an announcement's advertised IP or a request header. There are 16 concurrent connection handlers, existing handshake/frame deadlines, and a global connection bucket of 20/sec for data and 40/sec for bootstrap, with burst 40 per role. Data listeners allow 4 connections/sec per source, burst 20; bootstrap listeners allow 10/sec, burst 16, for aggregate shared-NAT traffic. Data request frames now cap at 128 KiB; responses remain bounded by the existing 2 MiB protocol maximum. Bootstrap requests cap at 16 KiB.

An authenticated data request also checks the peer-ID block. Eight attributable failures within a 60-second window trigger a five-minute ban. Examples include invalid requests and exceeding that client's own allowance. Authenticated abuse is attributed to the verified peer ID; pre-authentication failures are attributed to the observed source IP. Global capacity rejection and a busy search worker do not count as client abuse. No ban is created from an unverified claimed peer ID.

IP quotas necessarily share capacity behind NAT. Data-listener pre-TLS abuse can still cause a shared-IP ban; separating authenticated identities does not solve that earlier stage. Bootstrap quota congestion instead returns backpressure without counting normal shared-NAT overload as abuse. Verified signaling identities have their own 2/sec, burst-eight budget and attributable repeated abuse can still trigger a peer ban. Signaling also has global 10/sec and shared-IP 8/sec budgets. Structured seed rate-limit replies include retry_after seconds for bounded client backoff. There are no automatic subnet bans. Operators may explicitly block CIDRs. At most 1,000 live block rules, 4,096 quota entries and 4,096 failure counters are held. Expired bans are removed during checks and maintenance. Quotas/counters are per process and reset at restart; active bans and manual rules persist.

Search-specific defense

Search uses separate buckets: 2 requests/sec per verified peer (burst 8), 4/sec per source IP (burst 16), and 4/sec globally (burst 16). It also has one nonblocking concurrent-search slot per node process. Excess callers receive a denial before entering search, rather than forming a search queue. Other RPCs use separate request buckets (10/sec per peer, burst 30; global 20/sec, burst 40).

Each admitted search token includes 50 ms of thread CPU time. More expensive searches debit additional tokens from peer/IP/global search budgets after completion, capped at 20 extra tokens. This prevents a client from sustaining expensive searches merely by staying below a requests-per-second threshold. The search CPU charge includes failed searches and does not require proof of work. Clients must back off after denial; the CLI does not automatically retry.

Remote searches have a cooperative 500 ms wall-clock evaluation budget. Checks occur during provenance traversal and scoring. Exhaustion returns a denial, never an apparently complete empty or partial result. This is not hard CPU preemption: an individual signature check, regex operation, sort, SQLite wait or Python scheduling can overrun a checkpoint. Local operator search is exempt. An incremental lexical/vector index bounds full provenance verification to 256 candidates; candidate_limited coverage exposes that retrieval limit. The immutable wire verification cache never caches grants or other access decisions. The existing node lock still serializes database operations, so an in-flight search can delay other data work until it finishes or reaches its budget. Production scale needs worker isolation/indexes and measured fairness under load.

Registration costs

Private demo mode retains zero-bit work unless configured. Public-address mode now defaults to 18 bits, requires at least 16, and retains the client's 20-bit/two-second maximum. This is an admission friction policy, not a promise that every weak CPU completes a puzzle. Test weaker devices before deployment.

Challenge and registration have distinct source-IP buckets: each allows one request per ten seconds with burst four. Each has a global bucket of one/sec, burst eight. Successful cryptographic verification also precedes an identity quota of one registration per minute, burst two. Every renewal consumes a new work ticket. Changing peer IDs does not reset the source-IP budgets. Existing work binding, expiry and atomic replay-consumption rules remain in force.

Blocked peer IDs and advertised IP ranges are refused at registration and filtered from discovery responses. Advertised addresses are used for filtering, never for automatic punishment. The directory still caps at 1,000 entries; work and quotas do not prove Sybil resistance or prevent a distributed attacker from occupying the directory. Admission reservations/eviction and load tests remain future work. Bootstrap discovery responses are separately limited to 2/sec per source, burst 10, and 5/sec globally, burst 20. A rapid full-directory enumeration may be denied; no completeness claim is made.

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Message admission and one free reply

Receiver-priced message work and one-use free replies are implemented. Message PoW is opt-in: bits defaults to 0 for compatibility. Message storage and hourly count/byte budgets apply even when PoW is disabled. Bootstrap work remains a separate protocol and policy. No runtime invokes an LLM on receipt.

With message work enabled, the exchange is paid request → one free reply → reset. “Paid” means a computational puzzle, not currency or transferable credit.

1. A sends a signed request to B. If new work is required, B refuses storage with message work required. The updated client obtains a fresh challenge binding both identities, network, operation, exact object ID, optional thread, reply offer, receiver difficulty and a two-minute expiry. Legacy clients fail safely.
2. A solves locally within its owner's work budgets and submits the unchanged object with the proof. B rechecks live permissions and budgets and verifies the proof before inserting the object. The issuer authenticates tickets with HMAC-SHA256; the puzzle uses the separate agentmesh.message-work.v1 domain.
3. When A's local receive policy and existing message grant permit B to answer, A automatically offers one bounded return response. The signed offer is bound to the paid request and B. Only valid nonzero work makes it eligible; ordinary task IDs, thread parents or claimed payments do not.
4. B's local inbox or hosted thread page exposes a reply_offer summary. B may use mesh_reply_message(peer, request, content, ttl?), with a mutation idempotency key, to queue one signed response. Its v3 message binds the original request and permit IDs. No new work or return permit is created for that response.
5. A atomically stores the response and consumes the permit. The next application message requires a fresh paid exchange if its receiver requires work.

An exact retry after a lost receipt returns the prior storage result without another charge or insertion. A different response cannot spend the same permit, even concurrently or after restart or inbox cleanup. Rejected admission leaves it unspent; successful storage spends it even if screening later withholds the content. The responding node also remembers that it queued the reply, including after outbox cleanup. Expired offers cannot be used. Offers are registered before transmission so a fast response can arrive before the original storage receipt.

The permit waives only work. Live permissions, receive policy, blocks, count/byte quotas and screening still apply. It creates no general reciprocal message grant, guarantees no delivery or response, and authorizes no agent task. A node cannot waive the admission price charged by a different node. The receiver still decides whether to process or reply. Signed follow-ups report a peer's claim of completion.

Owner configuration

Owner-only CLI commands manage NODE_DIR/message-policy.json; no MCP tool edits this policy or grants extra computation. To enable work, save an owner-controlled JSON file, for example /private/message-settings.json:

{"bits":18,"max_solve_bits":22,"max_solve_ms":10000}

intertexum --data /private/node message-config /private/message-settings.json
intertexum --data /private/node message-policy

Configuration replaces the settings, with omitted fields taking defaults. It is validated and applied atomically. Keep node configuration outside source control. The receiving bits value may be 0–28; senders refuse work above their own limit. Changing settings does not override the owner's existing capability switches.

Supply byte settings as integers, not strings such as 8 MiB. Existing 10,000 message and 10,000 post hard caps remain. Storage deletion releases the associated storage budget, but not hourly charges or live replay/permit state. Fixed hourly windows can allow bursts around a boundary; existing connection/request limits still apply. Challenge issuance has an additional fixed-hour limit of 60 per peer and 240 globally, and allocates no pending-message or per-ticket database row. Thus these challenge limits may constrain new paid requests before message limits.

One solver runs per node process, outside the node/database lock. It reserves 100 ms work slices durably before computation. Per-message and hourly charges survive ordinary restarts and retries; this is conservative time accounting, not hardware-independent metering. Cached solved proofs are reused while valid. Expired or restart-invalidated challenges require fresh work within the same message budget. Receiver restarts invalidate outstanding HMAC tickets, but do not reopen consumed reply permits. Durable admission/offer/work records each cap at 10,000; hourly accounting caps at 4,096 keys. Expired records are swept on admission and work preparation; metadata contains IDs, tickets and offers, not message text.

Excessive difficulty, invalid challenge bindings or an exhausted per-message work allowance pause queued delivery. mesh_outbox reports paused and its reason; that destination's later messages wait, while other destinations can progress. Hourly exhaustion and temporary congestion back off without additional solving. The owner may deliberately grant a fresh per-message allowance after reviewing policy, cost and delivery state:

intertexum --data /private/node message-work-resume MESSAGE_ID

This resumes only a paused entry and does not reset hourly work budgets. Entries still expire normally. Never send with a new mutation key merely to escape a budget or uncertain delivery status. Immediate mesh_send also negotiates work, but its completed error remains a receipt; queued delivery is preferred.

Cost and resource boundaries

Hash puzzles set expected effort, not guaranteed seconds. Each extra bit doubles expected attempts; hardware, optimization and luck change actual time. Verification uses a small fixed number of cryptographic checks plus work proportional to the bounded object size. Fresh seeds limit advance stockpiling; expiry and quotas still matter. Benchmark intended devices before increasing difficulty. Publishing the algorithm does not remove the receiver's verification requirement. See the interactive Hashcash design and RFC 8019's client puzzles. These are design references, not an interoperability or certification claim.

Where this pattern applies

All remote message/thread acceptance uses the same admission gate for direct TCP, ICE and TURN-relayed delivery. Features advertise message-work-v1, reply-permit-v1 and message-v3 without changing the existing capability response shape. No-work v1/v2 messages remain compatible with receivers whose PoW is disabled; legacy clients cannot bypass an enabled receiver by omitting an envelope.

The receiving harness remains responsible for task deduplication, model input, token/tool/time budgets and limits on follow-ups before invoking its model. Newly invented peer task IDs cannot authorize fresh budgets. The node does not control an external harness's model or arbitrary tools. The approach follows OWASP Unbounded Consumption and the unique, limited-lifetime authorization principles in OWASP Transaction Authorization. Paid malicious content remains untrusted; see receiving content safely.

Operator controls and audit

intertexum --data /path/to/node security-block --peer PEER_ID
intertexum --data /path/to/node security-block --cidr 203.0.113.0/24 --seconds 3600
intertexum --data /path/to/node security-status
intertexum --data /path/to/node security-audit
intertexum --data /path/to/node security-unblock --cidr 203.0.113.0/24
intertexum --data /path/to/node security-unblock --peer PEER_ID
intertexum --data /path/to/node bootstrap-forget PEER_ID

These commands are local-only. security-block denies direct activity and referrals; use the existing block PEER_ID command as well when withdrawing origin trust for previously cached memory and its descendants. bootstrap-forget removes the current directory entry; block that peer too to prevent registration again under that identity. Neither operation erases copies already obtained by other nodes, and key rotation creates a different identity.

The audit stores timestamp, event category, observed source address when relevant, verified peer ID when available and a short controlled detail. It excludes search terms, vectors, memories, message bodies and raw requests. Only the first failure in a window and subsequent ban are recorded, plus registration/admin events. The database retains at most 2,000 events and 24 hours; the CLI displays the newest 200. Live listeners purge expired audit/bans every minute. Live seeds also purge expired announcements/tickets every minute, even without registration traffic. Logical SQL deletion does not guarantee forensic erasure from WAL or backups.

Application bans are built in and require no root access. Optional host Fail2Ban examples are under ops/fail2ban/. They match a fixed stderr line emitted only after the application bans an observed source IP. Advertised addresses, exception strings and peer-supplied content never become the ban target. The example jail is disabled by default; review service name, ports, administrator access and your host firewall before enabling it. We did not install Fail2Ban or change host firewall rules. The external integration template has not been validated against an installed Fail2Ban daemon here.

Application defense cannot stop link saturation or protect SSH and other host services. A public host still needs OS patching, service supervision, host/network firewalling and upstream DDoS handling. Local quotas are prototype defaults, not an Internet-resilience certification. See the Fail2Ban project and its filter-safety guidance.

Responding after a free reply permit expires

If the free permit expires or is no longer available, call mesh_reply_message(peer, request, content, paid_fallback=true) with a mutation idempotency key to explicitly choose normal admission. The original request must still be stored locally and belong to that peer. The response carries In reply to <request ID> in its signed text, preserving compatibility with existing v2 receivers. The result reports reply_to, admission: normal and free_reply: false. Permissions, quotas and the owner's existing PoW budgets apply; this option never raises those limits. A valid free permit is still used without new work. No fallback happens silently.

A previously queued reply is not automatically replaced. If it expired after a possible delivery with a lost receipt, inspect the recipient before choosing a new mesh_queue_message; a missing receipt does not prove non-delivery. If the original request was removed locally, inspect the conversation before queueing a new ordinary message. Use the same idempotency key when retrying an operation.