diff --git a/Cargo.lock b/Cargo.lock
index eee1331392..803dcf1ac8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -993,6 +993,7 @@ version = "0.1.0"
 dependencies = [
  "axum",
  "base64 0.22.1",
+ "buzz-accumulator",
  "buzz-core",
  "buzz-persona",
  "buzz-sdk",
diff --git a/Cargo.toml b/Cargo.toml
index eb40077802..a6a7c76624 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -138,6 +138,7 @@ schemars = { version = "1", default-features = false }
 
 # Internal crates
 buzz-core = { path = "crates/buzz-core" }
+buzz-accumulator = { path = "crates/buzz-accumulator" }
 buzz-conformance = { path = "crates/buzz-conformance" }
 buzz-db = { path = "crates/buzz-db" }
 buzz-deletion = { path = "crates/buzz-deletion" }
diff --git a/crates/buzz-cli/Cargo.toml b/crates/buzz-cli/Cargo.toml
index 59d1bb2cee..bef49bbdf8 100644
--- a/crates/buzz-cli/Cargo.toml
+++ b/crates/buzz-cli/Cargo.toml
@@ -44,6 +44,7 @@ chrono = { workspace = true }
 # Typed event builders for all write operations
 buzz-sdk = { workspace = true }
 buzz-core = { workspace = true }
+buzz-accumulator = { workspace = true }
 
 # Base64 encoding — NIP-98 event serialization for Authorization header
 base64 = "0.22"
diff --git a/crates/buzz-cli/src/commands/folds.rs b/crates/buzz-cli/src/commands/folds.rs
new file mode 100644
index 0000000000..96a0817faf
--- /dev/null
+++ b/crates/buzz-cli/src/commands/folds.rs
@@ -0,0 +1,800 @@
+//! `buzz folds` — the accumulator control plane.
+//!
+//! A fold maintains a small, always-current artifact (digest) over a saved
+//! selection of relay events. All state is signed relay events owned by the
+//! caller's key: specs are kind-30640 addressable events (`d` = fold name,
+//! last-write-wins) and artifact versions are immutable kind-4640 events —
+//! both NIP-44 encrypted to self and author-only at the relay.
+//!
+//! Subcommands:
+//! - `buzz folds set <name> --channel <uuid> …` — create or update a fold spec
+//! - `buzz folds list`                          — list folds with latest-run state
+//! - `buzz folds get <name>`                    — full spec + latest artifact meta
+//! - `buzz folds delete <name>`                 — tombstone a spec (artifacts remain)
+//! - `buzz folds estimate <name>`               — zero-spend preflight: price the exact run
+//! - `buzz folds run <name>`                    — plan, invoke the model, validate, persist
+//! - `buzz folds artifact <name>`               — latest artifact (or `--version`/`--history`)
+//! - `buzz folds share <name> --channel <uuid>` — republish the artifact as a channel message
+//!
+//! Honesty rules carried by the engine (`buzz-accumulator`): estimates never
+//! call a model; coverage records exactly what the model was shown; output
+//! that breaks the artifact contract is refused and nothing persists; prior
+//! log history is spliced back by the engine, so it cannot be rewritten.
+
+use std::collections::{BTreeMap, BTreeSet};
+use std::time::SystemTime;
+
+use buzz_accumulator::{
+    complete_run, plan_run, ArtifactPayload, FoldRunner, FoldSpec, Plan, Selection, Signal,
+    SubprocessRunner,
+};
+use buzz_core::kind::{KIND_FOLD_ARTIFACT, KIND_FOLD_SPEC, KIND_PROFILE};
+use nostr::nips::nip44;
+use nostr::{EventBuilder, Kind, Tag, Timestamp};
+
+use crate::client::BuzzClient;
+use crate::error::CliError;
+use crate::validate::read_or_stdin;
+
+/// Exhaustive-read bound for a fold's artifact chain. The covered-signal set
+/// is the union of `shown_ids` across the chain, so a silently truncated read
+/// would re-show already-folded history; `query_all_bounded` errors instead.
+const MAX_ARTIFACT_CHAIN: u32 = 2_000;
+
+fn now_secs() -> i64 {
+    SystemTime::now()
+        .duration_since(SystemTime::UNIX_EPOCH)
+        .map(|d| d.as_secs() as i64)
+        .unwrap_or(0)
+}
+
+// --- encryption to self ------------------------------------------------------
+
+fn encrypt_to_self(client: &BuzzClient, plaintext: &str) -> Result<String, CliError> {
+    let keys = client.keys();
+    nip44::encrypt(
+        keys.secret_key(),
+        &keys.public_key(),
+        plaintext,
+        nip44::Version::V2,
+    )
+    .map_err(|e| CliError::Other(format!("nip44 encrypt failed: {e}")))
+}
+
+fn decrypt_from_self(client: &BuzzClient, ciphertext: &str) -> Result<String, CliError> {
+    let keys = client.keys();
+    nip44::decrypt(keys.secret_key(), &keys.public_key(), ciphertext)
+        .map_err(|e| CliError::Other(format!("nip44 decrypt failed: {e}")))
+}
+
+// --- spec envelope ------------------------------------------------------------
+
+/// Decrypted content of a kind-30640 event: a live [`FoldSpec`] or a
+/// tombstone. Addressable events cannot be deleted from an append-only store,
+/// so `delete` publishes a `{"deleted":true}` replacement that hides the fold.
+fn parse_spec_envelope(plaintext: &str) -> Result<Option<FoldSpec>, CliError> {
+    let value: serde_json::Value = serde_json::from_str(plaintext)
+        .map_err(|e| CliError::Other(format!("fold spec payload is not JSON: {e}")))?;
+    if value.get("deleted").and_then(|v| v.as_bool()) == Some(true) {
+        return Ok(None);
+    }
+    serde_json::from_value(value)
+        .map(Some)
+        .map_err(|e| CliError::Other(format!("fold spec payload is malformed: {e}")))
+}
+
+/// Monotonic created_at for LWW replacement: strictly newer than the prior
+/// head even when both writes land within one second.
+fn monotonic_created_at(now: i64, prior: Option<i64>) -> i64 {
+    match prior {
+        Some(p) if p >= now => p + 1,
+        _ => now,
+    }
+}
+
+// --- relay reads --------------------------------------------------------------
+
+fn event_field<'a>(ev: &'a serde_json::Value, key: &str) -> Option<&'a str> {
+    ev.get(key).and_then(|v| v.as_str())
+}
+
+/// Tag value for `key` from a raw event JSON value.
+fn event_tag<'a>(ev: &'a serde_json::Value, key: &str) -> Option<&'a str> {
+    ev.get("tags")?.as_array()?.iter().find_map(|t| {
+        let t = t.as_array()?;
+        if t.first()?.as_str()? == key {
+            t.get(1)?.as_str()
+        } else {
+            None
+        }
+    })
+}
+
+/// Fetch the head kind-30640 event for `name` (raw JSON), if any.
+async fn fetch_spec_event(
+    client: &BuzzClient,
+    name: &str,
+) -> Result<Option<serde_json::Value>, CliError> {
+    let me = client.keys().public_key().to_hex();
+    let filter = serde_json::json!({
+        "kinds": [KIND_FOLD_SPEC],
+        "authors": [me],
+        "#d": [name],
+        "limit": 4,
+    });
+    let raw = client.query(&filter).await?;
+    let value: serde_json::Value = serde_json::from_str(&raw)
+        .map_err(|e| CliError::Other(format!("relay returned invalid JSON: {e}")))?;
+    let events = value
+        .as_array()
+        .ok_or_else(|| CliError::Other("relay response is not an array".into()))?;
+    // The relay stores only the NIP-33 head, but pick the newest defensively.
+    Ok(events
+        .iter()
+        .max_by_key(|ev| ev.get("created_at").and_then(|v| v.as_i64()).unwrap_or(0))
+        .cloned())
+}
+
+/// Load the live spec for `name`. `None` when absent or tombstoned.
+async fn load_spec(client: &BuzzClient, name: &str) -> Result<Option<FoldSpec>, CliError> {
+    match fetch_spec_event(client, name).await? {
+        None => Ok(None),
+        Some(ev) => {
+            let content = event_field(&ev, "content")
+                .ok_or_else(|| CliError::Other("spec event has no content".into()))?;
+            parse_spec_envelope(&decrypt_from_self(client, content)?)
+        }
+    }
+}
+
+/// Load every live fold spec owned by this key.
+async fn load_all_specs(client: &BuzzClient) -> Result<Vec<FoldSpec>, CliError> {
+    let me = client.keys().public_key().to_hex();
+    let filter = serde_json::json!({
+        "kinds": [KIND_FOLD_SPEC],
+        "authors": [me],
+        "limit": 500,
+    });
+    let events = client.query_all_bounded(filter, 500).await?;
+    let mut specs = Vec::new();
+    for ev in &events {
+        let Some(content) = event_field(ev, "content") else {
+            continue;
+        };
+        // Skip undecryptable or malformed entries rather than failing the
+        // whole listing; `get` on the specific name surfaces the error.
+        let Ok(plain) = decrypt_from_self(client, content) else {
+            continue;
+        };
+        if let Ok(Some(spec)) = parse_spec_envelope(&plain) {
+            specs.push(spec);
+        }
+    }
+    specs.sort_by(|a, b| a.name.cmp(&b.name));
+    Ok(specs)
+}
+
+/// Load the full artifact chain for `fold`, sorted by version ascending.
+///
+/// Artifact events carry a plaintext `f` tag, but generic-tag filters are not
+/// pushed to storage for regular kinds, so this reads the caller's whole
+/// kind-4640 set (bounded, erroring on overflow rather than silently
+/// truncating the covered-ids union) and filters by payload.
+async fn load_artifacts(client: &BuzzClient, fold: &str) -> Result<Vec<ArtifactPayload>, CliError> {
+    let me = client.keys().public_key().to_hex();
+    let filter = serde_json::json!({
+        "kinds": [KIND_FOLD_ARTIFACT],
+        "authors": [me],
+        "limit": 500,
+    });
+    let events = client.query_all_bounded(filter, MAX_ARTIFACT_CHAIN).await?;
+    let mut artifacts = Vec::new();
+    for ev in &events {
+        // Cheap pre-filter on the plaintext tag; payload is authoritative.
+        if event_tag(ev, "f").is_some_and(|f| f != fold) {
+            continue;
+        }
+        let Some(content) = event_field(ev, "content") else {
+            continue;
+        };
+        let Ok(plain) = decrypt_from_self(client, content) else {
+            continue;
+        };
+        let Ok(payload) = serde_json::from_str::<ArtifactPayload>(&plain) else {
+            continue;
+        };
+        if payload.fold == fold {
+            artifacts.push(payload);
+        }
+    }
+    artifacts.sort_by_key(|a| a.version);
+    Ok(artifacts)
+}
+
+/// Latest artifact + union of shown ids over the whole chain.
+fn chain_state(artifacts: &[ArtifactPayload]) -> (Option<&ArtifactPayload>, BTreeSet<String>) {
+    let covered = artifacts
+        .iter()
+        .flat_map(|a| a.shown_ids.iter().cloned())
+        .collect();
+    (artifacts.last(), covered)
+}
+
+/// Fetch the signals a selection matches over `[since, until_exclusive)`.
+///
+/// One relay query per compiled filter (multi-channel union filters are not
+/// reliable); the engine dedupes and orders during materialization.
+async fn fetch_signals(
+    client: &BuzzClient,
+    selection: &Selection,
+    since: i64,
+    until_exclusive: i64,
+    limit: u32,
+) -> Result<Vec<Signal>, CliError> {
+    let mut signals = Vec::new();
+    for filter in selection.compile_filters(since, until_exclusive, limit as usize) {
+        let events = client.query_paginated(filter, limit).await?;
+        for ev in &events {
+            let (Some(id), Some(pubkey)) = (event_field(ev, "id"), event_field(ev, "pubkey"))
+            else {
+                continue;
+            };
+            signals.push(Signal {
+                id: id.to_string(),
+                pubkey: pubkey.to_string(),
+                kind: ev.get("kind").and_then(|v| v.as_u64()).unwrap_or(0) as u32,
+                created_at: ev.get("created_at").and_then(|v| v.as_i64()).unwrap_or(0),
+                content: event_field(ev, "content").unwrap_or_default().to_string(),
+                channel: event_tag(ev, "h").map(str::to_string),
+            });
+        }
+    }
+    Ok(signals)
+}
+
+/// Resolve display names for transcript lines from kind-0 profiles.
+async fn fetch_names(client: &BuzzClient, pubkeys: &BTreeSet<String>) -> BTreeMap<String, String> {
+    let mut names = BTreeMap::new();
+    if pubkeys.is_empty() {
+        return names;
+    }
+    let filter = serde_json::json!({
+        "kinds": [KIND_PROFILE],
+        "authors": pubkeys.iter().collect::<Vec<_>>(),
+        "limit": pubkeys.len().min(500),
+    });
+    let Ok(raw) = client.query(&filter).await else {
+        return names; // Names are cosmetic; a failed lookup falls back to pubkey prefixes.
+    };
+    let Ok(value) = serde_json::from_str::<serde_json::Value>(&raw) else {
+        return names;
+    };
+    for ev in value.as_array().map(|a| a.as_slice()).unwrap_or_default() {
+        let (Some(pk), Some(content)) = (event_field(ev, "pubkey"), event_field(ev, "content"))
+        else {
+            continue;
+        };
+        let Ok(profile) = serde_json::from_str::<serde_json::Value>(content) else {
+            continue;
+        };
+        let name = profile
+            .get("display_name")
+            .and_then(|v| v.as_str())
+            .filter(|s| !s.is_empty())
+            .or_else(|| profile.get("name").and_then(|v| v.as_str()))
+            .filter(|s| !s.is_empty());
+        if let Some(name) = name {
+            names.insert(pk.to_string(), name.to_string());
+        }
+    }
+    names
+}
+
+// --- relay writes ---------------------------------------------------------------
+
+/// Submit a signed event, mapping a dominated NIP-33 write to
+/// [`CliError::Conflict`] via the shared write-response parser.
+async fn submit_checked(
+    client: &BuzzClient,
+    event: nostr::Event,
+    conflict_msg: &str,
+) -> Result<String, CliError> {
+    let id = event.id.to_hex();
+    let raw = client.submit_event(event).await?;
+    super::parse_write_response(&raw, conflict_msg)?;
+    Ok(id)
+}
+
+/// Publish the spec envelope (live or tombstone) as the new kind-30640 head.
+async fn publish_spec_envelope(
+    client: &BuzzClient,
+    name: &str,
+    plaintext: &str,
+) -> Result<(String, bool), CliError> {
+    let prior = fetch_spec_event(client, name).await?;
+    let replaced = prior.is_some();
+    let prior_ts = prior.and_then(|ev| ev.get("created_at").and_then(|v| v.as_i64()));
+    let created_at = monotonic_created_at(now_secs(), prior_ts);
+    let ciphertext = encrypt_to_self(client, plaintext)?;
+    let tag = Tag::parse(["d", name])
+        .map_err(|e| CliError::Other(format!("failed to build d tag: {e}")))?;
+    let builder = EventBuilder::new(Kind::Custom(KIND_FOLD_SPEC as u16), ciphertext)
+        .tags([tag])
+        .custom_created_at(Timestamp::from_secs(created_at as u64));
+    let event = client.sign_event(builder)?;
+    let id = submit_checked(
+        client,
+        event,
+        "fold spec changed concurrently; re-read and retry",
+    )
+    .await?;
+    Ok((id, replaced))
+}
+
+// --- shared preflight ---------------------------------------------------------
+
+struct Preflight {
+    spec: FoldSpec,
+    prior: Option<ArtifactPayload>,
+    plan: Plan,
+}
+
+/// Load spec + artifact chain, fetch pending signals, and plan the run.
+/// This is the zero-spend half shared by `estimate` and `run`.
+async fn preflight(
+    client: &BuzzClient,
+    name: &str,
+    since: Option<i64>,
+    until: Option<i64>,
+    limit: u32,
+) -> Result<Preflight, CliError> {
+    let spec = load_spec(client, name).await?.ok_or_else(|| {
+        CliError::NotFound(format!("no fold named {name:?} (see `buzz folds list`)"))
+    })?;
+    let artifacts = load_artifacts(client, name).await?;
+    let (prior, covered) = chain_state(&artifacts);
+    let prior = prior.cloned();
+    let since = since.unwrap_or(0);
+    let until_exclusive = until.unwrap_or_else(|| now_secs() + 1);
+    let fetched = fetch_signals(client, &spec.selection, since, until_exclusive, limit).await?;
+    let authors: BTreeSet<String> = fetched.iter().map(|s| s.pubkey.clone()).collect();
+    let names = fetch_names(client, &authors).await;
+    let plan = plan_run(&spec, prior.as_ref(), &covered, fetched, &names)
+        .map_err(|e| CliError::Other(e.to_string()))?;
+    Ok(Preflight { spec, prior, plan })
+}
+
+fn plan_json(name: &str, pre: &Preflight) -> serde_json::Value {
+    match &pre.plan {
+        Plan::Cached => serde_json::json!({
+            "fold": name,
+            "action": "cached",
+            "version": pre.prior.as_ref().map(|p| p.version),
+            "note": "no new signals and the config is unchanged; the latest artifact already answers",
+        }),
+        Plan::Stalled { reason, pending } => serde_json::json!({
+            "fold": name,
+            "action": "stalled",
+            "reason": reason,
+            "pending_signals": pending,
+        }),
+        Plan::Ready(run) => serde_json::json!({
+            "fold": name,
+            "action": "ready",
+            "model": pre.spec.model,
+            "pending_signals": run.pending,
+            "would_show": run.shown.len(),
+            "truncated_to_budget": run.truncated,
+            "est_input_tokens": run.estimate.est_input_tokens,
+            "est_cost_usd": run.estimate.est_cost_usd,
+            "window_fit": run.estimate.window_fit,
+            "next_version": pre.prior.as_ref().map_or(1, |p| p.version + 1),
+        }),
+    }
+}
+
+// --- subcommands ----------------------------------------------------------------
+
+#[allow(clippy::too_many_arguments)]
+async fn cmd_set(
+    client: &BuzzClient,
+    name: String,
+    channels: Vec<String>,
+    authors: Vec<String>,
+    kinds: Vec<u32>,
+    schema: String,
+    model: String,
+    instructions: Option<String>,
+) -> Result<(), CliError> {
+    let instructions = match instructions {
+        Some(value) => read_or_stdin(&value)?,
+        None if schema == buzz_accumulator::schema::CHANNEL_DIGEST_V1.name => {
+            buzz_accumulator::schema::CHANNEL_DIGEST_PROMPT.to_string()
+        }
+        None => {
+            return Err(CliError::Usage(format!(
+                "--instructions is required for schema {schema:?} (only {:?} has a default prompt)",
+                buzz_accumulator::schema::CHANNEL_DIGEST_V1.name
+            )));
+        }
+    };
+    let mut spec = FoldSpec {
+        name: name.clone(),
+        selection: Selection {
+            channels,
+            authors,
+            kinds,
+        },
+        schema,
+        model,
+        instructions,
+    };
+    spec.validate()
+        .map_err(|e| CliError::Usage(e.to_string()))?;
+    let plaintext = serde_json::to_string(&spec)
+        .map_err(|e| CliError::Other(format!("spec serialization failed: {e}")))?;
+    let (event_id, replaced) = publish_spec_envelope(client, &name, &plaintext).await?;
+    println!(
+        "{}",
+        serde_json::json!({
+            "fold": name,
+            "event_id": event_id,
+            "accepted": true,
+            "replaced": replaced,
+            "selection": spec.selection.describe(),
+            "schema": spec.schema,
+            "model": spec.model,
+        })
+    );
+    Ok(())
+}
+
+async fn cmd_list(client: &BuzzClient) -> Result<(), CliError> {
+    let specs = load_all_specs(client).await?;
+    let mut out = Vec::new();
+    for spec in &specs {
+        let artifacts = load_artifacts(client, &spec.name).await?;
+        let (latest, covered) = chain_state(&artifacts);
+        out.push(serde_json::json!({
+            "fold": spec.name,
+            "selection": spec.selection.describe(),
+            "schema": spec.schema,
+            "model": spec.model,
+            "latest_version": latest.map(|a| a.version),
+            "covered_signals": covered.len(),
+            "coverage_until": latest.and_then(|a| a.coverage_until),
+        }));
+    }
+    println!("{}", serde_json::Value::Array(out));
+    Ok(())
+}
+
+async fn cmd_get(client: &BuzzClient, name: String) -> Result<(), CliError> {
+    let spec = load_spec(client, &name)
+        .await?
+        .ok_or_else(|| CliError::NotFound(format!("no fold named {name:?}")))?;
+    let artifacts = load_artifacts(client, &name).await?;
+    let (latest, covered) = chain_state(&artifacts);
+    println!(
+        "{}",
+        serde_json::json!({
+            "fold": spec.name,
+            "selection": spec.selection,
+            "schema": spec.schema,
+            "model": spec.model,
+            "instructions": spec.instructions,
+            "versions": artifacts.len(),
+            "covered_signals": covered.len(),
+            "latest": latest.map(|a| serde_json::json!({
+                "version": a.version,
+                "created_at": a.created_at,
+                "coverage_since": a.coverage_since,
+                "coverage_until": a.coverage_until,
+                "shown_signals": a.shown_ids.len(),
+                "truncated": a.truncated,
+            })),
+        })
+    );
+    Ok(())
+}
+
+async fn cmd_delete(client: &BuzzClient, name: String) -> Result<(), CliError> {
+    if load_spec(client, &name).await?.is_none() {
+        return Err(CliError::NotFound(format!("no fold named {name:?}")));
+    }
+    let (event_id, _) = publish_spec_envelope(client, &name, "{\"deleted\":true}").await?;
+    println!(
+        "{}",
+        serde_json::json!({
+            "fold": name,
+            "event_id": event_id,
+            "accepted": true,
+            "deleted": true,
+            "note": "spec tombstoned; existing artifact versions remain (append-only)",
+        })
+    );
+    Ok(())
+}
+
+async fn cmd_estimate(
+    client: &BuzzClient,
+    name: String,
+    since: Option<i64>,
+    until: Option<i64>,
+    limit: u32,
+) -> Result<(), CliError> {
+    let pre = preflight(client, &name, since, until, limit).await?;
+    println!("{}", plan_json(&name, &pre));
+    Ok(())
+}
+
+async fn cmd_run(
+    client: &BuzzClient,
+    name: String,
+    since: Option<i64>,
+    until: Option<i64>,
+    limit: u32,
+) -> Result<(), CliError> {
+    let pre = preflight(client, &name, since, until, limit).await?;
+    let Plan::Ready(run) = &pre.plan else {
+        // Cached/stalled runs spend nothing and change nothing — report as data.
+        println!("{}", plan_json(&name, &pre));
+        return Ok(());
+    };
+    eprintln!(
+        "running fold {name:?}: {} signal(s), ~{} input tokens{} on {}",
+        run.shown.len(),
+        run.estimate.est_input_tokens,
+        run.estimate
+            .est_cost_usd
+            .map(|c| format!(" (~${c:.4})"))
+            .unwrap_or_default(),
+        pre.spec.model,
+    );
+    let runner = SubprocessRunner::new();
+    let output = runner
+        .run(&run.model_input, &pre.spec.model)
+        .map_err(|e| CliError::Other(e.to_string()))?;
+    // Refusal path: nonconforming output errors here and nothing persists.
+    let artifact = complete_run(&pre.spec, pre.prior.as_ref(), run, &output, now_secs())
+        .map_err(|e| CliError::Other(e.to_string()))?;
+    let plaintext = serde_json::to_string(&artifact)
+        .map_err(|e| CliError::Other(format!("artifact serialization failed: {e}")))?;
+    let ciphertext = encrypt_to_self(client, &plaintext)?;
+    let tags = [
+        Tag::parse(["f", &artifact.fold])
+            .map_err(|e| CliError::Other(format!("failed to build f tag: {e}")))?,
+        Tag::parse(["v", &artifact.version.to_string()])
+            .map_err(|e| CliError::Other(format!("failed to build v tag: {e}")))?,
+    ];
+    let builder = EventBuilder::new(Kind::Custom(KIND_FOLD_ARTIFACT as u16), ciphertext).tags(tags);
+    let event = client.sign_event(builder)?;
+    let event_id = submit_checked(client, event, "artifact write was reported duplicate").await?;
+    println!(
+        "{}",
+        serde_json::json!({
+            "fold": name,
+            "action": "run",
+            "event_id": event_id,
+            "accepted": true,
+            "version": artifact.version,
+            "shown_signals": artifact.shown_ids.len(),
+            "coverage_since": artifact.coverage_since,
+            "coverage_until": artifact.coverage_until,
+            "truncated_to_budget": artifact.truncated,
+            "est_input_tokens": run.estimate.est_input_tokens,
+            "est_cost_usd": run.estimate.est_cost_usd,
+        })
+    );
+    Ok(())
+}
+
+async fn cmd_artifact(
+    client: &BuzzClient,
+    name: String,
+    version: Option<u32>,
+    history: bool,
+    raw: bool,
+) -> Result<(), CliError> {
+    let artifacts = load_artifacts(client, &name).await?;
+    if history {
+        let out: Vec<serde_json::Value> = artifacts
+            .iter()
+            .map(|a| {
+                serde_json::json!({
+                    "version": a.version,
+                    "created_at": a.created_at,
+                    "model": a.model,
+                    "shown_signals": a.shown_ids.len(),
+                    "coverage_since": a.coverage_since,
+                    "coverage_until": a.coverage_until,
+                    "truncated": a.truncated,
+                })
+            })
+            .collect();
+        println!("{}", serde_json::Value::Array(out));
+        return Ok(());
+    }
+    let artifact = match version {
+        Some(v) => artifacts.iter().find(|a| a.version == v),
+        None => artifacts.last(),
+    }
+    .ok_or_else(|| {
+        CliError::NotFound(match version {
+            Some(v) => format!("fold {name:?} has no version {v}"),
+            None => format!("fold {name:?} has no artifact yet (run `buzz folds run {name}`)"),
+        })
+    })?;
+    if raw {
+        println!("{}", artifact.output);
+    } else {
+        println!(
+            "{}",
+            serde_json::to_value(artifact)
+                .map_err(|e| CliError::Other(format!("artifact serialization failed: {e}")))?
+        );
+    }
+    Ok(())
+}
+
+/// The share taint rule: an artifact may be republished into a channel only
+/// when its selection reads from exactly that one channel — then every cited
+/// signal is already visible to the audience by construction. Author/kind
+/// narrowing within the channel is fine; a second channel or a channel-less
+/// selection is not.
+fn share_allowed(selection: &Selection, channel: &str) -> bool {
+    selection.channels.len() == 1 && selection.channels[0] == channel
+}
+
+async fn cmd_share(client: &BuzzClient, name: String, channel: String) -> Result<(), CliError> {
+    let spec = load_spec(client, &name)
+        .await?
+        .ok_or_else(|| CliError::NotFound(format!("no fold named {name:?}")))?;
+    if !share_allowed(&spec.selection, &channel) {
+        return Err(CliError::Usage(format!(
+            "refusing to share: fold {name:?} reads {}, not exactly channel {channel} — \
+             sharing is only allowed into the single channel the fold reads from, so every \
+             cited signal is already visible to the audience",
+            spec.selection.describe(),
+        )));
+    }
+    let artifacts = load_artifacts(client, &name).await?;
+    let artifact = artifacts.last().ok_or_else(|| {
+        CliError::NotFound(format!(
+            "fold {name:?} has no artifact yet (run `buzz folds run {name}`)"
+        ))
+    })?;
+    let channel_uuid = channel
+        .parse::<uuid::Uuid>()
+        .map_err(|e| CliError::Usage(format!("--channel must be a channel UUID: {e}")))?;
+    let content = format!(
+        "{}\n\n—\n_{} v{} · digest of this channel · {} signal(s) this run_",
+        artifact.output,
+        artifact.fold,
+        artifact.version,
+        artifact.shown_ids.len(),
+    );
+    let builder = buzz_sdk::build_message(channel_uuid, &content, None, &[], false, &[])
+        .map_err(|e| CliError::Other(format!("build_message failed: {e}")))?;
+    let event = client.sign_event(builder)?;
+    let event_id = submit_checked(client, event, "share message was reported duplicate").await?;
+    println!(
+        "{}",
+        serde_json::json!({
+            "fold": name,
+            "event_id": event_id,
+            "accepted": true,
+            "shared_to_channel": channel,
+            "version": artifact.version,
+        })
+    );
+    Ok(())
+}
+
+pub async fn dispatch(cmd: crate::FoldsCmd, client: &BuzzClient) -> Result<(), CliError> {
+    use crate::FoldsCmd;
+    match cmd {
+        FoldsCmd::Set {
+            name,
+            channel,
+            author,
+            kind,
+            schema,
+            model,
+            instructions,
+        } => {
+            cmd_set(
+                client,
+                name,
+                channel,
+                author,
+                kind,
+                schema,
+                model,
+                instructions,
+            )
+            .await
+        }
+        FoldsCmd::List => cmd_list(client).await,
+        FoldsCmd::Get { name } => cmd_get(client, name).await,
+        FoldsCmd::Delete { name } => cmd_delete(client, name).await,
+        FoldsCmd::Estimate {
+            name,
+            since,
+            until,
+            limit,
+        } => cmd_estimate(client, name, since, until, limit).await,
+        FoldsCmd::Run {
+            name,
+            since,
+            until,
+            limit,
+        } => cmd_run(client, name, since, until, limit).await,
+        FoldsCmd::Artifact {
+            name,
+            version,
+            history,
+            raw,
+        } => cmd_artifact(client, name, version, history, raw).await,
+        FoldsCmd::Share { name, channel } => cmd_share(client, name, channel).await,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn selection(channels: &[&str], authors: &[&str]) -> Selection {
+        Selection {
+            channels: channels.iter().map(|s| s.to_string()).collect(),
+            authors: authors.iter().map(|s| s.to_string()).collect(),
+            kinds: vec![],
+        }
+    }
+
+    #[test]
+    fn share_requires_exactly_the_target_channel() {
+        assert!(share_allowed(&selection(&["ch1"], &[]), "ch1"));
+        // Author-narrowing within the channel keeps taint ⊆ {channel}.
+        assert!(share_allowed(&selection(&["ch1"], &["pk1"]), "ch1"));
+        assert!(!share_allowed(&selection(&["ch1"], &[]), "ch2"));
+        assert!(!share_allowed(&selection(&["ch1", "ch2"], &[]), "ch1"));
+        assert!(!share_allowed(&selection(&[], &["pk1"]), "ch1"));
+    }
+
+    #[test]
+    fn spec_envelope_roundtrip_and_tombstone() {
+        let spec = FoldSpec {
+            name: "x".into(),
+            selection: selection(&["ch1"], &[]),
+            schema: "channel-digest@v1".into(),
+            model: "haiku".into(),
+            instructions: "do it".into(),
+        };
+        let json = serde_json::to_string(&spec).expect("serialize");
+        assert_eq!(parse_spec_envelope(&json).expect("parse"), Some(spec));
+        assert_eq!(
+            parse_spec_envelope("{\"deleted\":true}").expect("parse"),
+            None
+        );
+        assert!(parse_spec_envelope("not json").is_err());
+    }
+
+    #[test]
+    fn lww_created_at_is_strictly_monotonic() {
+        assert_eq!(monotonic_created_at(100, None), 100);
+        assert_eq!(monotonic_created_at(100, Some(50)), 100);
+        assert_eq!(monotonic_created_at(100, Some(100)), 101);
+        assert_eq!(monotonic_created_at(100, Some(140)), 141);
+    }
+
+    #[test]
+    fn event_tag_reads_first_match() {
+        let ev = serde_json::json!({
+            "tags": [["f", "my-fold"], ["v", "3"], ["h", "chan"]],
+        });
+        assert_eq!(event_tag(&ev, "f"), Some("my-fold"));
+        assert_eq!(event_tag(&ev, "v"), Some("3"));
+        assert_eq!(event_tag(&ev, "x"), None);
+    }
+}
diff --git a/crates/buzz-cli/src/commands/mod.rs b/crates/buzz-cli/src/commands/mod.rs
index 7ed03f9d06..5fa0ce22c4 100644
--- a/crates/buzz-cli/src/commands/mod.rs
+++ b/crates/buzz-cli/src/commands/mod.rs
@@ -5,6 +5,7 @@ pub mod dms;
 pub mod emoji;
 pub mod feed;
 pub mod gifs;
+pub mod folds;
 pub mod issues;
 pub mod mem;
 pub mod messages;
diff --git a/crates/buzz-cli/src/lib.rs b/crates/buzz-cli/src/lib.rs
index 3f2bea7397..ac5f6015b6 100644
--- a/crates/buzz-cli/src/lib.rs
+++ b/crates/buzz-cli/src/lib.rs
@@ -237,6 +237,9 @@ enum Cmd {
     /// Agent engram management — persistent memory per NIP-AE
     #[command(subcommand)]
     Mem(MemCmd),
+    /// Accumulator folds — standing digests over saved relay selections
+    #[command(subcommand)]
+    Folds(FoldsCmd),
     /// Persona pack operations (local, no relay connection needed)
     #[command(subcommand)]
     Pack(PackCmd),
@@ -1824,6 +1827,88 @@ pub enum MediaCmd {
     },
 }
 
+/// Subcommands for `buzz folds` — the accumulator control plane.
+#[derive(Subcommand)]
+pub enum FoldsCmd {
+    /// Create or update a fold spec (last-write-wins by name)
+    Set {
+        /// Fold name: lowercase letters, digits, and inner dashes (≤64 chars)
+        name: String,
+        /// Channel UUID to read from (repeatable)
+        #[arg(long = "channel")]
+        channel: Vec<String>,
+        /// Author pubkey (hex) to read from (repeatable)
+        #[arg(long = "author")]
+        author: Vec<String>,
+        /// Event kind to include (repeatable; default 9 = channel messages)
+        #[arg(long = "kind")]
+        kind: Vec<u32>,
+        /// Artifact schema: channel-digest@v1 or freeform@v1
+        #[arg(long, default_value = "channel-digest@v1")]
+        schema: String,
+        /// Model handed to the fold runner (e.g. haiku, sonnet, opus)
+        #[arg(long, default_value = "haiku")]
+        model: String,
+        /// Fold instructions; pass `-` to read from stdin. Only
+        /// channel-digest@v1 has a built-in default prompt.
+        #[arg(long)]
+        instructions: Option<String>,
+    },
+    /// List folds with latest-run state
+    List,
+    /// Show a fold's full spec and latest artifact metadata
+    Get { name: String },
+    /// Tombstone a fold spec (existing artifact versions remain)
+    Delete { name: String },
+    /// Preflight a run without spending: pending signals, est. tokens, cost
+    Estimate {
+        name: String,
+        /// Only consider signals created at or after this unix timestamp
+        #[arg(long)]
+        since: Option<i64>,
+        /// Only consider signals created strictly before this unix timestamp
+        #[arg(long)]
+        until: Option<i64>,
+        /// Max signals fetched per compiled selection filter
+        #[arg(long, default_value_t = 500)]
+        limit: u32,
+    },
+    /// Run the fold: plan, invoke the model, validate, persist a new version
+    Run {
+        name: String,
+        /// Only consider signals created at or after this unix timestamp
+        #[arg(long)]
+        since: Option<i64>,
+        /// Only consider signals created strictly before this unix timestamp
+        #[arg(long)]
+        until: Option<i64>,
+        /// Max signals fetched per compiled selection filter
+        #[arg(long, default_value_t = 500)]
+        limit: u32,
+    },
+    /// Print an artifact (latest version by default)
+    Artifact {
+        name: String,
+        /// Print a specific version instead of the latest
+        #[arg(long)]
+        version: Option<u32>,
+        /// List version metadata for the whole chain instead
+        #[arg(long, default_value_t = false)]
+        history: bool,
+        /// Print only the artifact's markdown output
+        #[arg(long, default_value_t = false)]
+        raw: bool,
+    },
+    /// Republish the latest artifact as a message in the fold's channel
+    Share {
+        name: String,
+        /// Target channel UUID — must be exactly the one channel the fold
+        /// reads from, so every cited signal is already visible there
+        #[arg(long)]
+        channel: String,
+    },
+}
+
 /// Subcommands for `buzz mem`.
 #[derive(Subcommand)]
 pub enum MemCmd {
@@ -2123,6 +2208,7 @@ async fn run(cli: Cli) -> Result<(), CliError> {
         Cmd::Media(sub) => commands::upload::dispatch_media(sub, &client).await,
         Cmd::Upload(sub) => commands::upload::dispatch(sub, &client).await,
         Cmd::Mem(sub) => commands::mem::dispatch(sub, &client).await,
+        Cmd::Folds(sub) => commands::folds::dispatch(sub, &client).await,
         Cmd::Moderation(sub) => commands::moderation::dispatch(sub, &client, &cli.format).await,
         Cmd::Pack(_) => unreachable!("handled above"),
     }
@@ -2259,6 +2345,7 @@ mod tests {
             "emoji",
             "feed",
             "gifs",
+            "folds",
             "issues",
             "media",
             "mem",
@@ -2361,6 +2448,10 @@ mod tests {
             ]
         );
         assert_eq!(names(&cmd, "canvas"), vec!["get", "set"]);
+        assert_eq!(
+            names(&cmd, "folds"),
+            vec!["artifact", "delete", "estimate", "get", "list", "run", "set", "share"]
+        );
         assert_eq!(names(&cmd, "reactions"), vec!["add", "get", "remove"]);
         assert_eq!(
             names(&cmd, "emoji"),