diff --git a/docs/config-catalog.md b/docs/config-catalog.md
index 9a586fa495..dbee6b350f 100644
--- a/docs/config-catalog.md
+++ b/docs/config-catalog.md
@@ -76,6 +76,11 @@ Source: [`packages/ui/acp-agent/src/index.ts:31`](../packages/ui/acp-agent/src/i
 export interface Config {
   /** The agent-loop `agents` list (see dsh-agent-loop's `Config`). */
   agents?: AgentLoopConfig['agents']
+  /**
+   * The factory-wide default concurrent tool-call cap applied to every agent
+   * this bundle creates (see dsh-agent-loop's `Config.maxParallelToolCalls`).
+   */
+  maxParallelToolCalls?: AgentLoopConfig['maxParallelToolCalls']
   /** The deployment persona (see dsh-system-prompt's `Config`). */
   persona?: SystemPromptConfig['persona']
   /** The explicit model-facing tool order (see dsh-system-prompt's `Config`). */
@@ -108,6 +113,16 @@ Requires: `agents` · `sessions` · `llm` · `tools` · `systemPrompt`
 ```ts config-catalog
 /** Plugin configuration for declarative startup agents. */
 export interface Config {
+  /**
+   * Default concurrent tool-call cap applied to every agent this factory
+   * creates (declarative startup agents and factory callers such as the ACP,
+   * stdio, and SDK front doors that go through `create`/`createAgent`/`resume`).
+   * A positive integer; a per-agent `maxParallelToolCalls` overrides it, and an
+   * agent with neither falls back to {@link DEFAULT_MAX_PARALLEL_TOOL_CALLS}.
+   * This is the single `cordis.yml` knob that reaches agents whose front door
+   * does not expose its own cap field.
+   */
+  maxParallelToolCalls?: number
   /** Agents created or resumed at plugin startup. */
   agents: (AgentOptions & {
     /** Registry identity for the live agent. */
@@ -964,7 +979,7 @@ export interface Config {
 export type ToolPresentationMode = 'native' | 'code' | 'both'
 ```
 
-Source: [`packages/core/tools/src/index.ts:391`](../packages/core/tools/src/index.ts)
+Source: [`packages/core/tools/src/index.ts:389`](../packages/core/tools/src/index.ts)
 
 ## `@deepseek-ai/dsh-user-approval`
 
diff --git a/docs/cordis-catalog/services.md b/docs/cordis-catalog/services.md
index 864a89dbfa..830184e804 100644
--- a/docs/cordis-catalog/services.md
+++ b/docs/cordis-catalog/services.md
@@ -19,7 +19,7 @@ async createAgent(ownerCtx: Context, options: CreateAgentOptions): Promise<Agent
 async resume(ownerCtx: Context, options: ResumeAgentOptions): Promise<AgentHandle>
 ```
 
-Source: [`packages/core/agent-loop/src/index.ts:364`](../../packages/core/agent-loop/src/index.ts)
+Source: [`packages/core/agent-loop/src/index.ts:374`](../../packages/core/agent-loop/src/index.ts)
 
 ## `ctx.agents` — `AgentRegistry`
 
@@ -257,7 +257,7 @@ async execute(exec: ToolExecutionInput): Promise<ToolExecutionResult>
 
 Types: [ToolDefinition](../core-data-structures/tools.md) · [ToolExecutionInput](../core-data-structures/tools.md) · [ToolExecutionMode](../core-data-structures/tools.md) · [ToolExecutionResult](../core-data-structures/tools.md)
 
-Source: [`packages/core/tools/src/index.ts:447`](../../packages/core/tools/src/index.ts)
+Source: [`packages/core/tools/src/index.ts:445`](../../packages/core/tools/src/index.ts)
 
 ## `ctx.userInteraction` — `UserInteractionService`
 
diff --git a/docs/core-data-structures/core.md b/docs/core-data-structures/core.md
index 9a9a1706fc..42c11a84f0 100644
--- a/docs/core-data-structures/core.md
+++ b/docs/core-data-structures/core.md
@@ -347,7 +347,7 @@ interface Agent {
 }
 ```
 
-`AgentStatus` is `'idle' | 'running' | 'disposed'`, and `AgentId` is branded. `AgentOptions` is merge-extensible and currently includes `model?`. Persona belongs to `dsh-system-prompt`: an agent-scoped `deployment:persona` may shadow the global default.
+`AgentStatus` is `'idle' | 'running' | 'disposed'`, and `AgentId` is branded. `AgentOptions` is merge-extensible and currently includes `model?` and `maxParallelToolCalls?` (the loop's per-agent concurrent tool-call cap; the owning field, defaulted by `AgentLoop.Config` and, absent that, by `DEFAULT_MAX_PARALLEL_TOOL_CALLS`). Persona belongs to `dsh-system-prompt`: an agent-scoped `deployment:persona` may shadow the global default.
 
 The [event taxonomy](../architecture.md#event) owns the `agent/*` lifecycle, checkpoint, and waterfall contracts. Turn and step boundaries are durable session events rather than agent emits.
 
diff --git a/docs/core-data-structures/tools.md b/docs/core-data-structures/tools.md
index 078e10ac29..5d4973ffe8 100644
--- a/docs/core-data-structures/tools.md
+++ b/docs/core-data-structures/tools.md
@@ -30,20 +30,18 @@ interface ToolDefinition extends ToolSchema {
    *
    * It may inspect the parsed `args` (`unknown` — a hand-rolled definition
    * receives the raw parsed value; `defineTool` schema-validates first and
-   * returns `false` on invalid args, so an eventual `ToolArgsError` is produced
-   * only if the tool actually executes). The check performs no I/O and receives
-   * no live `Agent` or mutable `ToolExecution`.
+   * returns `false` on invalid args). The check performs no I/O and receives no
+   * live `Agent` or mutable `ToolExecution`.
    *
-   * Declaring `true` is a contract: the tool body must NOT mutate the parent
-   * agent's session or other parent-owned async state during `execute` (no
-   * `exec.agent.session.append(...)`, no `agent.inject(...)`). Its only parent-
+   * Declaring `true` is a contract: during `execute` the tool body must NOT
+   * mutate the parent agent's session or other parent-owned async state (no
+   * `exec.agent.session.append(...)`, no `agent.inject(...)`); its only parent-
    * step outputs are the returned content, `meta`, structured error, and
-   * `additionalContext` carried through the loop's ordered post-execute path.
-   * The narrow exception is a synchronous, side-effect-only recorder whose
-   * updates are commutative OR fail closed for concurrent calls by the same
-   * session (the `fs/observed` version recorder is the worked example: its
-   * WeakMap record is last-writer-wins, and a stale observation only makes a
-   * later write/edit fail closed at its in-lock version CAS).
+   * `additionalContext` on the loop's ordered post-execute path. A synchronous,
+   * side-effect-only recorder whose updates are commutative or fail closed for
+   * concurrent same-session calls is the one exception (`fs/observed` is the
+   * worked example). Full contract and rationale: the parallel-tool-call RFC
+   * (docs/rfc/implemented/feature/2026-07-10-parallel-tool-call-execution.md).
    */
   isConcurrencySafe?(args: unknown): boolean
   /**
diff --git a/docs/rfc/implemented/feature/2026-07-10-parallel-tool-call-execution.md b/docs/rfc/implemented/feature/2026-07-10-parallel-tool-call-execution.md
index c8cd96622a..23e0f0d22e 100644
--- a/docs/rfc/implemented/feature/2026-07-10-parallel-tool-call-execution.md
+++ b/docs/rfc/implemented/feature/2026-07-10-parallel-tool-call-execution.md
@@ -45,11 +45,11 @@ A parallel-safe declaration is a contract. The tool body must not mutate the par
 
 The loop waits for the model stream to finish and logs one authoritative `assistant/message` before scheduling tools. Streaming tool execution is out of scope.
 
-For each assistant step, `packages/core/agent-loop/src/tool-calls.ts` parses each call's raw JSON arguments exactly once, creates one distinct `ToolExecution` object per call, asks `ctx.tools.executionMode(exec)`, and partitions calls into ordered groups. A group is either one exclusive call or a run of consecutive parallel calls. `loop.ts` calls the helper so the turn/step lifecycle remains readable.
+For each assistant step, `packages/core/agent-loop/src/tool-calls.ts` parses each call's raw JSON arguments exactly once, creates one distinct `ToolExecution` object per call, asks `ctx.tools.executionMode(exec)`, and partitions calls into ordered groups. A group is either one exclusive call or a run of consecutive parallel calls; grouping classifies each call exactly once. `loop.ts` calls the helper so the turn/step lifecycle remains readable.
 
-Parallelism is per agent. `AgentOptions.maxParallelToolCalls` is a positive integer, defaults to `DEFAULT_MAX_PARALLEL_TOOL_CALLS` (`10`), and is accepted through the config-created agent path. Setting it to `1` preserves serial execution for that agent. Both the TypeScript `AgentOptions` vocabulary and the `AgentLoop.Config` schemastery object validate the cap, so invalid `cordis.yml` values fail during config validation.
+Parallelism is per agent. `AgentOptions.maxParallelToolCalls` is a positive integer, defaults to `DEFAULT_MAX_PARALLEL_TOOL_CALLS` (`10`), and reaches an agent three ways in precedence order: the per-agent option, the factory-wide `AgentLoop.Config.maxParallelToolCalls` applied to every agent the loop creates (declarative startup agents and factory callers such as the ACP, stdio, and SDK front doors), then the built-in default. The factory default is the single `cordis.yml` knob for agents whose front door exposes no cap field of its own. Setting the value to `1` preserves serial execution for that agent. The TypeScript `AgentOptions` vocabulary and both `AgentLoop.Config` fields validate the cap, so invalid `cordis.yml` values fail during config validation.
 
-Within a parallel group, execution uses a rolling pool: start calls in model order up to `maxParallelToolCalls`, and whenever one call settles, start the next unstarted call until the group is exhausted. A group larger than the cap is not truncated; the cap limits simultaneous in-flight calls only.
+Every group runs through the same rolling pool: start calls in model order up to `maxParallelToolCalls`, and whenever one call settles, start the next unstarted call until the group is exhausted. An exclusive group is a pool of one — a barrier — so the loop needs no separate serial path. A group larger than the cap is not truncated; the cap limits simultaneous in-flight calls only.
 
 Only the dispatch/body stage runs concurrently. Generic middleware that can shape ordering-sensitive state remains ordered: `tools/pre-execute` and `tools/post-execute` run in model call order. `@deepseek-ai/dsh-tools` exposes the symbol-keyed internal `TOOL_REGISTRY_SCHEDULER` view so `dsh-agent-loop` can split prepare, dispatch, and finalize without adding named staged service methods to `ctx.tools`; ordinary callers still use the one-call `execute(exec)` API. `tools/execute` around-dispatch listeners run with the dispatch they wrap, so wrappers must be reentrant across distinct `ToolExecution` objects. The shipped timeout policy is per-call: every call owns its mutable `exec` and deadline.
 
diff --git a/packages/core/agent-core/README.md b/packages/core/agent-core/README.md
index fac4f4819a..594c4a8c82 100644
--- a/packages/core/agent-core/README.md
+++ b/packages/core/agent-core/README.md
@@ -39,11 +39,11 @@ This is the [interface/implementation/consumer seam](../../../docs/rfc/implement
 
 ```ts
 import type { Config } from '@deepseek-ai/dsh-agent-core'
-// { agents?, persona?, toolOrder?, tools?, skills? } — the schema intersects the owner schemas,
-// so validation and defaulting can never drift from the owners.
+// { agents?, maxParallelToolCalls?, persona?, toolOrder?, tools?, skills? } — the schema
+// intersects the owner schemas, so validation and defaulting can never drift from the owners.
 ```
 
-The bundle FORWARDS each field to the child that owns it: `agents` to `agent-loop` (default `[]`), so each app supplies its own pre-created agents — a stdio app pre-creates a `main`; the ACP app pre-creates none (it creates agents on demand at `session/new`) — `persona` and `toolOrder` to `dsh-system-prompt`; `tools` to the tool registry for its presentation mode; and `skills.registry`, `skills.local`, and `skills.tool` to the skill registry, local provider, and model-facing consumer. Forwarding is exactly why the owners can live in the shared spine even though the apps disagree on what to configure.
+The bundle FORWARDS each field to the child that owns it: `agents` to `agent-loop` (default `[]`), so each app supplies its own pre-created agents — a stdio app pre-creates a `main`; the ACP app pre-creates none (it creates agents on demand at `session/new`) — `maxParallelToolCalls` to `agent-loop` as the factory-wide default concurrent tool-call cap for every agent it creates; `persona` and `toolOrder` to `dsh-system-prompt`; `tools` to the tool registry for its presentation mode; and `skills.registry`, `skills.local`, and `skills.tool` to the skill registry, local provider, and model-facing consumer. Forwarding is exactly why the owners can live in the shared spine even though the apps disagree on what to configure.
 
 ## Why a code bundle, not a shared YAML include
 
diff --git a/packages/core/agent-core/src/index.ts b/packages/core/agent-core/src/index.ts
index 14ffbd6133..fcb4e87f1e 100644
--- a/packages/core/agent-core/src/index.ts
+++ b/packages/core/agent-core/src/index.ts
@@ -46,6 +46,11 @@ export interface SkillConfig {
 export interface Config {
   /** The agent-loop `agents` list (see dsh-agent-loop's `Config`). */
   agents?: AgentLoopConfig['agents']
+  /**
+   * The factory-wide default concurrent tool-call cap applied to every agent
+   * this bundle creates (see dsh-agent-loop's `Config.maxParallelToolCalls`).
+   */
+  maxParallelToolCalls?: AgentLoopConfig['maxParallelToolCalls']
   /** The deployment persona (see dsh-system-prompt's `Config`). */
   persona?: SystemPromptConfig['persona']
   /** The explicit model-facing tool order (see dsh-system-prompt's `Config`). */
@@ -95,5 +100,8 @@ export function apply(ctx: Context, config: Config): void {
   ctx.plugin(invariants)
   ctx.plugin(toolBash)
   ctx.plugin(toolSkill, config.skills?.tool ?? {})
-  ctx.plugin(AgentLoop, { agents: config.agents ?? [] })
+  ctx.plugin(AgentLoop, {
+    agents: config.agents ?? [],
+    ...config.maxParallelToolCalls !== undefined ? { maxParallelToolCalls: config.maxParallelToolCalls } : {},
+  })
 }
diff --git a/packages/core/agent-core/tests/agent-core.spec.ts b/packages/core/agent-core/tests/agent-core.spec.ts
index 0bf0660364..fe240da8ed 100644
--- a/packages/core/agent-core/tests/agent-core.spec.ts
+++ b/packages/core/agent-core/tests/agent-core.spec.ts
@@ -117,6 +117,16 @@ describe('dsh-agent-core bundle', () => {
     await ctx.fiber.dispose()
   })
 
+  it('forwards the factory-wide maxParallelToolCalls default to agents without a per-agent cap', async () => {
+    const ctx = await mount({
+      agents: [{ id: AgentId('main'), model: 'mock' }],
+      maxParallelToolCalls: 3,
+    })
+    const main = ctx.get('agents')?.get(AgentId('main'))
+    expect(main?.options.maxParallelToolCalls).toBe(3)
+    await ctx.fiber.dispose()
+  })
+
   it('tolerates a schema-bypassing direct apply (the ?? fallbacks fire)', async () => {
     // ctx.plugin validates + defaults the bundle config first; a direct apply
     // skips the schema, so the forwarding `?? []` / `?? ''` are what fire.
diff --git a/packages/core/agent-loop/src/index.ts b/packages/core/agent-loop/src/index.ts
index 17447a0b1d..86df80cd8e 100644
--- a/packages/core/agent-loop/src/index.ts
+++ b/packages/core/agent-loop/src/index.ts
@@ -344,6 +344,16 @@ export { DEFAULT_MAX_PARALLEL_TOOL_CALLS } from './constants.ts'
 
 /** Plugin configuration for declarative startup agents. */
 export interface Config {
+  /**
+   * Default concurrent tool-call cap applied to every agent this factory
+   * creates (declarative startup agents and factory callers such as the ACP,
+   * stdio, and SDK front doors that go through `create`/`createAgent`/`resume`).
+   * A positive integer; a per-agent `maxParallelToolCalls` overrides it, and an
+   * agent with neither falls back to {@link DEFAULT_MAX_PARALLEL_TOOL_CALLS}.
+   * This is the single `cordis.yml` knob that reaches agents whose front door
+   * does not expose its own cap field.
+   */
+  maxParallelToolCalls?: number
   /** Agents created or resumed at plugin startup. */
   agents: (AgentOptions & {
     /** Registry identity for the live agent. */
@@ -366,6 +376,9 @@ export class AgentLoop extends Service implements AgentFactory {
 
   /** Runtime schema for declarative agents. */
   static Config = z.object({
+    // The factory-wide default cap; a per-agent value overrides it. A positive
+    // integer, validated here so a bad cordis.yml value fails at load.
+    maxParallelToolCalls: z.number().step(1).min(1),
     agents: z.array(z.object({
       id: z.string().required(),
       model: z.string(),
@@ -410,6 +423,22 @@ export class AgentLoop extends Service implements AgentFactory {
     }
   }
 
+  /**
+   * Merge the factory-wide default cap into one agent's options. A per-agent
+   * `maxParallelToolCalls` wins; otherwise the `Config.maxParallelToolCalls`
+   * default applies, reaching factory callers (ACP/stdio/SDK front doors) whose
+   * own config does not set a cap. Absent both, the loop falls back to
+   * {@link DEFAULT_MAX_PARALLEL_TOOL_CALLS} at schedule time.
+   * @param options - the caller-supplied agent options.
+   * @returns options with the default cap applied when the caller omitted one.
+   */
+  private withFactoryDefaults(options: AgentOptions): AgentOptions {
+    if (options.maxParallelToolCalls !== undefined || this.config.maxParallelToolCalls === undefined) {
+      return options
+    }
+    return { ...options, maxParallelToolCalls: this.config.maxParallelToolCalls }
+  }
+
   /**
    * Create an agent on a fresh per-run session, owned by the accessing fiber.
    * Constructor-driven config calls use the loop fiber itself.
@@ -419,13 +448,14 @@ export class AgentLoop extends Service implements AgentFactory {
    * @returns the published running agent.
    */
   create(id: AgentId, options: AgentOptions = {}, meta: Pick<SessionHeader, 'cwd'> = {}): ReactLoopAgent {
-    validateAgentOptions(options)
+    const resolved = this.withFactoryDefaults(options)
+    validateAgentOptions(resolved)
     const loopCtx = this.runtime.ctx
     const transaction = new AgentCreationTransaction(loopCtx, this.ctx, this.ownership, id)
     try {
       const sessionId = SessionId(`${id}-session-${randomUUID()}`)
       const session = loopCtx.sessions.prepare(sessionId, { meta })
-      const agent = transaction.prepare(options, session)
+      const agent = transaction.prepare(resolved, session)
       transaction.publish('startup')
       return agent
     } catch (error: unknown) {
@@ -443,7 +473,8 @@ export class AgentLoop extends Service implements AgentFactory {
    * @returns the published handle.
    */
   async createAgent(ownerCtx: Context, options: CreateAgentOptions): Promise<AgentHandle> {
-    validateAgentOptions(options.agentOptions ?? {})
+    const agentOptions = this.withFactoryDefaults(options.agentOptions ?? {})
+    validateAgentOptions(agentOptions)
     const transaction = new AgentCreationTransaction(
       this.runtime.ctx,
       ownerCtx,
@@ -456,7 +487,7 @@ export class AgentLoop extends Service implements AgentFactory {
         ...options.seed === undefined ? {} : { seed: options.seed },
         ...options.meta === undefined ? {} : { meta: options.meta },
       })
-      const agent = transaction.prepare(options.agentOptions ?? {}, session)
+      const agent = transaction.prepare(agentOptions, session)
       await transaction.waitFor(options.setup?.(agent.ctx))
       transaction.assertActive()
       return transaction.publish('startup')
@@ -475,7 +506,6 @@ export class AgentLoop extends Service implements AgentFactory {
    * @returns the published handle.
    */
   async resume(ownerCtx: Context, options: ResumeAgentOptions): Promise<AgentHandle> {
-    validateAgentOptions(options.agentOptions ?? {})
     const persistence = this.runtime.ctx.get('sessionPersistence')
     if (persistence === undefined) {
       throw new Error('cannot resume: session persistence is not configured (load a dsh-session-persistence backend)')
@@ -489,6 +519,8 @@ export class AgentLoop extends Service implements AgentFactory {
     persistence: SessionPersistence,
     options: ResumeAgentOptions,
   ): Promise<AgentHandle> {
+    const agentOptions = this.withFactoryDefaults(options.agentOptions ?? {})
+    validateAgentOptions(agentOptions)
     const transaction = new AgentCreationTransaction(
       this.runtime.ctx,
       ownerCtx,
@@ -508,7 +540,7 @@ export class AgentLoop extends Service implements AgentFactory {
           ...loaded.meta.seedLength === undefined ? {} : { seedLength: loaded.meta.seedLength },
         },
       })
-      const agent = transaction.prepare(options.agentOptions ?? {}, session)
+      const agent = transaction.prepare(agentOptions, session)
       await transaction.waitFor(options.setup?.(agent.ctx))
       transaction.assertActive()
       return transaction.publish('resume')
diff --git a/packages/core/agent-loop/src/tool-calls.ts b/packages/core/agent-loop/src/tool-calls.ts
index 6ee1dc5906..d117823a43 100644
--- a/packages/core/agent-loop/src/tool-calls.ts
+++ b/packages/core/agent-loop/src/tool-calls.ts
@@ -3,8 +3,9 @@
  * the assistant message's `tool-call` blocks; this module parses each call's
  * arguments once, classifies it via `ctx.tools.executionMode`, partitions the
  * calls into ordered groups (one exclusive call, or a run of consecutive
- * parallel-safe calls), and executes each group — a parallel group through a
- * rolling pool bounded by the agent's `maxParallelToolCalls`.
+ * parallel-safe calls), and runs every group through the same rolling pool
+ * bounded by the agent's `maxParallelToolCalls` — an exclusive group is a pool
+ * of one.
  *
  * The session log stays the source of truth and is reconstructable regardless
  * of dispatch timing: each STARTED call appends its own `tool/call` before its
@@ -95,16 +96,13 @@ export async function executeToolCalls(
   // separate ordered groups (no read/write race inside one assistant step).
   const groups = groupByMode(ctx, planned)
 
+  // Every group runs through the same rolling pool: an exclusive call is a
+  // singleton group (pool of one, a barrier), a parallel-safe run is one group
+  // bounded by the cap. `groupByMode` already classified each call, so the loop
+  // does not re-query `executionMode` here.
   const pendingContext: HookContext[] = []
   for (const group of groups) {
-    // Groups are never empty (groupByMode only pushes non-empty runs/singletons).
-    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion -- non-empty group
-    const first = group[0]!
-    if (group.length === 1 && ctx.tools.executionMode(first.exec).kind === 'exclusive') {
-      await runExclusive(ctx, session, turn, step, first, signal, pendingContext)
-    } else {
-      await runParallelGroup(ctx, session, turn, step, group, signal, maxParallel, pendingContext)
-    }
+    await runGroup(ctx, session, turn, step, group, signal, maxParallel, pendingContext)
   }
   return pendingContext
 }
@@ -135,8 +133,8 @@ function parseArguments(raw: string): unknown {
 /**
  * Group planned calls into ordered runs: each exclusive call is a singleton
  * group; consecutive parallel-safe calls coalesce into one group. `executionMode`
- * is queried once per call here and again by the caller to pick the exclusive
- * fast-path — both reads are pure and cheap.
+ * is the sole classification point — the caller runs every group through the
+ * rolling pool without re-querying it. The read is pure and cheap.
  */
 function groupByMode(ctx: Context, planned: PlannedCall[]): PlannedCall[][] {
   const groups: PlannedCall[][] = []
@@ -167,46 +165,19 @@ function assertMaxParallelToolCalls(maxParallel: number): void {
 }
 
 /**
- * The exclusive single-call path keeps the public one-call pipeline sequential:
- * abort-check, `tool/call`, pre/dispatch/post via `ctx.tools.execute`,
- * `tool/result`, buffer context, post-await abort-check.
- */
-async function runExclusive(
-  ctx: Context,
-  session: Session,
-  turn: number,
-  step: number,
-  call: PlannedCall,
-  signal: AbortSignal,
-  pendingContext: HookContext[],
-): Promise<void> {
-  /* v8 ignore next -- signal.reason always set: cancel()/disposal provide a default */
-  if (signal.aborted) throw new Error(String(signal.reason ?? 'aborted'))
-  const callSeq = appendToolCall(session, turn, step, call.block)
-  const result = await ctx.tools.execute(call.exec)
-  appendToolResult(session, turn, step, call.block, result, callSeq)
-  if (result.additionalContext) pendingContext.push(result.additionalContext)
-  // signal CAN flip during the await above (abort() inside a tool); the analyzer
-  // can't see through the await boundary.
-  /* v8 ignore start -- signal.reason default unreachable: cancel()/disposal always set it */
-  // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
-  if (signal.aborted) throw new Error(String(signal.reason ?? 'aborted'))
-  /* v8 ignore stop */
-}
-
-/**
- * The rolling-pool path for a group of parallel-safe calls. Starts calls in
- * model order up to `maxParallel`, and whenever one settles starts the next
- * unstarted call until the group is exhausted. Settled dispatches land in
- * model-order slots; a commit cursor appends `tool/result` (and collects
- * `additionalContext`) only while the next slot is ready, so the log stays
- * model-ordered regardless of completion order.
+ * The rolling-pool path for one ordered group. A singleton exclusive group runs
+ * as a pool of one (a barrier); a parallel-safe run starts calls in model order
+ * up to `maxParallel`, and whenever one settles starts the next unstarted call
+ * until the group is exhausted. Settled dispatches land in model-order slots; a
+ * commit cursor appends `tool/result` (and collects `additionalContext`) only
+ * while the next slot is ready, so the log stays model-ordered regardless of
+ * completion order.
  *
  * Abort: an already-aborted signal starts nothing and throws before any
  * `tool/call`. An abort mid-group stops replenishment, awaits only the started
  * calls, commits their results in order, drops buffered context, and throws.
  */
-async function runParallelGroup(
+async function runGroup(
   ctx: Context,
   session: Session,
   turn: number,
diff --git a/packages/core/agent-loop/tests/tool-calls.spec.ts b/packages/core/agent-loop/tests/tool-calls.spec.ts
index 987b358720..a270ad6da1 100644
--- a/packages/core/agent-loop/tests/tool-calls.spec.ts
+++ b/packages/core/agent-loop/tests/tool-calls.spec.ts
@@ -274,6 +274,48 @@ describe('tool-call scheduler: rolling pool honors maxParallelToolCalls', () =>
     gated.release('2')
     await waitForIdle(ctx, agent)
   })
+
+  it('applies the factory-wide Config default to agents that set no per-agent cap', async () => {
+    const adapter = new MockAdapter([
+      multiCall([{ id: 'c1', name: 'p', args: { id: '1' } }, { id: 'c2', name: 'p', args: { id: '2' } }]),
+      textResponse('done'),
+    ])
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+    await ctx.plugin(SessionStore)
+    await ctx.plugin(SystemPrompt, { persona: '' })
+    await ctx.plugin(ToolRegistry)
+    await ctx.plugin(AgentRegistry)
+    // Factory default of 1 (no per-agent cap set below) must serialize.
+    await ctx.plugin(AgentLoop, { agents: [], maxParallelToolCalls: 1 })
+    ctx.llm.registerAdapter(['mock'], adapter)
+    const gated = gatedParallelTool('p')
+    ctx.tools.register(gated.tool)
+    const agent = ctx.agentLoop.create(AgentId('a1'), { model: 'mock' })
+    expect(agent.options.maxParallelToolCalls).toBe(1)
+
+    agent.send([{ type: 'text', text: 'go' }])
+    await until(() => gated.started.length === 1)
+    await new Promise(r => setTimeout(r, 5))
+    expect(gated.started).toEqual(['1'])
+    gated.release('1')
+    await until(() => gated.started.length === 2)
+    gated.release('2')
+    await waitForIdle(ctx, agent)
+  })
+
+  it('lets a per-agent cap override the factory-wide Config default', async () => {
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+    await ctx.plugin(SessionStore)
+    await ctx.plugin(SystemPrompt, { persona: '' })
+    await ctx.plugin(ToolRegistry)
+    await ctx.plugin(AgentRegistry)
+    await ctx.plugin(AgentLoop, { agents: [], maxParallelToolCalls: 1 })
+    ctx.llm.registerAdapter(['mock'], new MockAdapter([]))
+    const agent = ctx.agentLoop.create(AgentId('a1'), { model: 'mock', maxParallelToolCalls: 4 })
+    expect(agent.options.maxParallelToolCalls).toBe(4)
+  })
 })
 
 describe('tool-call scheduler: ordered middleware and additionalContext', () => {
diff --git a/packages/core/tools/src/index.ts b/packages/core/tools/src/index.ts
index 3575554ac1..4f1741ab39 100644
--- a/packages/core/tools/src/index.ts
+++ b/packages/core/tools/src/index.ts
@@ -142,20 +142,18 @@ export interface ToolDefinition extends ToolSchema {
    *
    * It may inspect the parsed `args` (`unknown` — a hand-rolled definition
    * receives the raw parsed value; `defineTool` schema-validates first and
-   * returns `false` on invalid args, so an eventual `ToolArgsError` is produced
-   * only if the tool actually executes). The check performs no I/O and receives
-   * no live `Agent` or mutable `ToolExecution`.
+   * returns `false` on invalid args). The check performs no I/O and receives no
+   * live `Agent` or mutable `ToolExecution`.
    *
-   * Declaring `true` is a contract: the tool body must NOT mutate the parent
-   * agent's session or other parent-owned async state during `execute` (no
-   * `exec.agent.session.append(...)`, no `agent.inject(...)`). Its only parent-
+   * Declaring `true` is a contract: during `execute` the tool body must NOT
+   * mutate the parent agent's session or other parent-owned async state (no
+   * `exec.agent.session.append(...)`, no `agent.inject(...)`); its only parent-
    * step outputs are the returned content, `meta`, structured error, and
-   * `additionalContext` carried through the loop's ordered post-execute path.
-   * The narrow exception is a synchronous, side-effect-only recorder whose
-   * updates are commutative OR fail closed for concurrent calls by the same
-   * session (the `fs/observed` version recorder is the worked example: its
-   * WeakMap record is last-writer-wins, and a stale observation only makes a
-   * later write/edit fail closed at its in-lock version CAS).
+   * `additionalContext` on the loop's ordered post-execute path. A synchronous,
+   * side-effect-only recorder whose updates are commutative or fail closed for
+   * concurrent same-session calls is the one exception (`fs/observed` is the
+   * worked example). Full contract and rationale: the parallel-tool-call RFC
+   * (docs/rfc/implemented/feature/2026-07-10-parallel-tool-call-execution.md).
    */
   isConcurrencySafe?(args: unknown): boolean
   /**