diff --git a/README.md b/README.md
index ce4e186..03f8ab2 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ Claude Code as a model provider without an API key.
 | OpenAI-compatible provider | `extensions/Volcanic.AgenticCore.Extensions.OpenAI` | OpenAI, OpenRouter, Groq, Ollama, llama.cpp, vLLM |
 | Claude Code (subscription) provider | `extensions/Volcanic.AgenticCore.Extensions.ClaudeCode` (+ `.Bridge`) | Spawns `claude -p`, MCP "proposal" bridge |
 | Google Calendar (tool + connect commands) | `extensions/Volcanic.AgenticCore.Extensions.GoogleCalendar` | `GOOGLE_CLIENT_ID`, `GOOGLE_CLIENT_SECRET`; one account per chat |
+| Scheduler (reminders, scheduled prompts, watcher scripts) | `extensions/Volcanic.AgenticCore.Extensions.Scheduler` | Cronos; per-chat jobs in `<agent dir>/scheduler/jobs.json`; see [docs/telegram-bot.md](docs/telegram-bot.md#scheduling) |
 | Telegram bot | `hosts/Volcanic.AgenticCore.Telegram` | Chat with the agent from Telegram; long polling, Claude Code, allow-list |
 | Reference headless host | `samples/Volcanic.AgenticCore.Sample.Headless` | Prompt in, JSON events out |
 | Tests | `tests/` | xunit; no test calls a paid API |
diff --git a/docs/superpowers/specs/2026-09-26-scheduler-design.md b/docs/superpowers/specs/2026-09-26-scheduler-design.md
index 240fb18..4f4630d 100644
--- a/docs/superpowers/specs/2026-09-26-scheduler-design.md
+++ b/docs/superpowers/specs/2026-09-26-scheduler-design.md
@@ -61,7 +61,10 @@ same chat.
 - **Scheduled agent prompts are queued as follow-ups, never as steering.** When the chat is idle a prompt job starts a
   run. When a run is active (a user request, or another job), the prompt goes in with `StreamingBehavior.FollowUp`: the
   current work finishes first, then the job's prompt is handled in the same run. A clock-driven prompt shouldn't
-  redirect what the user is doing mid-turn. User messages keep steering as they do today.
+  redirect what the user is doing mid-turn. User messages keep steering as they do today. This also holds when a run
+  starts between `PromptAsync`'s idle check and its run gate: the core's `StartRunAsync` gets the caller's
+  `StreamingBehavior`, and a `FollowUp` prompt joins the active run as a follow-up (with a `QueueUpdate`), not as
+  steering.
 - **Cron parsing uses Cronos** (`Cronos` on NuGet, Hangfire, MIT, no dependencies). It parses standard 5-field
   expressions and macros (`@daily`, `@hourly`, …). `GetNextOccurrence(DateTimeOffset, TimeZoneInfo)` works in a given
   zone and has defined DST semantics: a time skipped when clocks go forward fires at the transition, and an ambiguous
@@ -72,7 +75,10 @@ same chat.
   sets a 1-minute floor for watchers.
 - **Each chat has its own time zone.** It applies to cron, to displayed times, to the session's system prompt, to the
   local-time header on each prompt, and to the `TZ` of the chat's `bash`, watcher and `claude -p` processes (§8). An `at` without an offset is read in the chat's zone, because
-  models often leave the offset out. An `at` with an offset is used as given. The zone is a chat setting, not a
+  models often leave the offset out. An `at` with an offset is used as given. The date is required and only ISO 8601 is
+  accepted (`yyyy-MM-dd`, or `yyyy-MM-dd[T| ]HH:mm[:ss[.fff]]` with an optional `Z`/offset): a bare `09:00` or a culture
+  format such as `09/10/2026` is rejected with a readable error, because it would be resolved against the machine's
+  clock rather than the chat's. The zone is a chat setting, not a
   scheduler setting, because the system prompt and `bash` need it with the scheduler disabled too:
   - **Stored by the host**, in a small per-chat settings store outside every workspace:
     `<AgentDir>/telegram/chat-settings.json` (§7). Not in `jobs.json` (the scheduler can be off) and not in the session
@@ -93,7 +99,9 @@ same chat.
   fires immediately. If it's more than 60 s late, direct text gets `(due <time>, delivered late)` and an agent prompt
   gets `This was due at <time>; the bot was offline.` A cron job's next occurrence is computed strictly after "now".
   Occurrences missed while the bot was down are dropped, which is logged at Information. A one-off is removed only
-  **after** its delivery completes, so a crash mid-fire re-fires it after a restart (at-least-once).
+  **after** its delivery completes, so a crash mid-fire re-fires it after a restart (at-least-once). The same holds for
+  a graceful stop: a delivery cut off by shutdown isn't recorded, so the one-off stays in `jobs.json` and fires late on
+  the next start.
 - **Persistence is one central file:** `<AgentDir>/scheduler/jobs.json` (by default `~/.volcanic/agent/scheduler/`).
   The workspace is deliberately not used: the agent's `bash` can write anywhere there, and a central file is loaded
   without scanning every workspace. The format is `{ "version": 1, "jobs": [...] }` in `VolcanicJson` camelCase.
@@ -153,7 +161,9 @@ watchers. There are at most `MaxJobsPerTarget` (50) jobs per target. Every error
 
 `LoadAsync()` returns the jobs. A missing file means an empty list. A corrupt file is renamed to
 `jobs.json.corrupt-<timestamp>`, logged as an error, and loading starts empty: a bad file must not keep the host down.
-Invalid jobs are dropped with a warning. `SaveAsync(jobs)` writes `jobs.json.<pid>.tmp` and then does
+Invalid jobs are dropped with a warning. A stored cron job whose next occurrence can't be computed on start (for
+example a target the host can't map to a zone) is logged and left unarmed; it never fails `StartAsync`. The Telegram
+delivery's `TimeZoneFor` returns the default zone for a target that isn't a chat id. `SaveAsync(jobs)` writes `jobs.json.<pid>.tmp` and then does
 `File.Move(overwrite: true)`. Writes go through one `SemaphoreSlim`.
 
 ### 3. `ScriptRunner` (`IScriptRunner`, faked in tests)
@@ -189,6 +199,7 @@ public sealed class JobScheduler(SchedulerOptions options, IScriptRunner runner,
     IReadOnlyList<JobView> List(string target);                     // JobView = job + NextRunAt (null = never)
     Task<JobView> CreateAsync(string target, NewJob job, CancellationToken ct);   // throws JobValidationException
     Task<bool> CancelAsync(string target, string id, CancellationToken ct);       // false: unknown, or another target's
+    Task<ScheduledJob?> CancelJobAsync(string target, string id, CancellationToken ct); // the removed job, in one step (tool, /cancel)
     TimeZoneInfo TimeZoneFor(string target);                        // delivery.TimeZoneFor
     Task<ZoneChange> TimeZoneChangedAsync(string target, CancellationToken ct);   // recompute cron, re-arm; counts for the reply
 }
@@ -386,7 +397,11 @@ and Claude Code's `TZ`:
   the allow-list, like its pinned `CLAUDE_CODE_*` flags. Anything Claude Code itself adds about the date then agrees
   with our prompt. It isn't set on Windows (the OS ignores `TZ`, as in the process-environment-hook spec §3), nor for
   `claude auth login`/`auth status` and the doctor's probes, which have no session. `TZ` stays off the inherited
-  allow-list: the host's own `TZ` never leaks through. This goes through the provider, not `IProcessSpawnPolicy`
+  allow-list: the host's own `TZ` never leaks through. When the session has no configured zone, `claude -p` gets the
+  IANA id of `TimeZoneInfo.Local` (it can't inherit `TZ`) while `bash` inherits the host's `TZ` (its `TimeZoneId` is
+  null); both end up in the host's zone. All three id conversions follow one rule, `TimeZoneIds.ToIana` (mirrored by
+  `ClaudeArgs.IanaZoneId` and the scheduler's `ZoneNames.Iana`, since extensions can't reference the core): null unless
+  the id resolves to a system zone, so an unnamed `Local` sets no `TZ`. This goes through the provider, not `IProcessSpawnPolicy`
   (process-environment-hook spec §7). `docs/claude-code-provider.md` (its environment section) is updated with the
   implementation.
 - Headless sample: no change; it gets `TimeZoneInfo.Local` as before, now shown in the prompt.
diff --git a/extensions/Volcanic.AgenticCore.Extensions.ClaudeCode/ClaudeArgs.cs b/extensions/Volcanic.AgenticCore.Extensions.ClaudeCode/ClaudeArgs.cs
index c2308d1..2a928ad 100644
--- a/extensions/Volcanic.AgenticCore.Extensions.ClaudeCode/ClaudeArgs.cs
+++ b/extensions/Volcanic.AgenticCore.Extensions.ClaudeCode/ClaudeArgs.cs
@@ -161,13 +161,17 @@ public static class ClaudeArgs
         return env;
     }
 
-    /// <summary>The IANA id for <c>TZ</c>: the zone's own id, a converted Windows id, or null for an unnamed <c>Local</c> zone.</summary>
+    /// <summary>
+    /// The IANA id for <c>TZ</c>: the zone's own id or a converted Windows id, or null when there is none that resolves
+    /// back to a system zone (an unnamed <c>Local</c> zone). Mirrors the core's <c>TimeZoneIds.ToIana</c> (the extension
+    /// references only the Abstractions); keep the two in step.
+    /// </summary>
     public static string? IanaZoneId(TimeZoneInfo zone)
     {
         ArgumentNullException.ThrowIfNull(zone);
         if (string.Equals(zone.Id, "Local", StringComparison.OrdinalIgnoreCase)) return null;
-        if (zone.HasIanaId) return zone.Id;
-        return TimeZoneInfo.TryConvertWindowsIdToIanaId(zone.Id, out var iana) ? iana : null;
+        var id = zone.HasIanaId ? zone.Id : TimeZoneInfo.TryConvertWindowsIdToIanaId(zone.Id, out var iana) ? iana : null;
+        return id is not null && TimeZoneInfo.TryFindSystemTimeZoneById(id, out _) ? id : null;
     }
 
     /// <summary>The allow-listed environment without the denial check (used by diagnostics that only probe the CLI).</summary>
diff --git a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/JobFormat.cs b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/JobFormat.cs
index d94f220..bfc38a3 100644
--- a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/JobFormat.cs
+++ b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/JobFormat.cs
@@ -27,9 +27,6 @@ public static class JobFormat
 
     public static string ZoneName(TimeZoneInfo zone) => ZoneNames.Name(zone);
 
-    /// <summary><c>UTC+02:00</c> at <paramref name="at"/>.</summary>
-    public static string Offset(TimeZoneInfo zone, DateTimeOffset at) => ZoneNames.Offset(zone.GetUtcOffset(at));
-
     /// <summary><c>exit 1</c>, <c>exit 1, timed out</c>, <c>timed out</c>, or <c>did not start</c>.</summary>
     public static string FailureReason(JobResult result) => result switch
     {
diff --git a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/JobScheduler.cs b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/JobScheduler.cs
index 9737e4d..8eeb7a1 100644
--- a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/JobScheduler.cs
+++ b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/JobScheduler.cs
@@ -33,6 +33,7 @@ public sealed class JobScheduler : IAsyncDisposable
     private DateTimeOffset? _wakeAt;
     private bool _stopped;
     private Task _pendingTick = Task.CompletedTask;
+    private int _firesStarted;
 
     public JobScheduler(SchedulerOptions options, IScriptRunner runner, ISecretRedactor redactor, TimeProvider time, ILogger<JobScheduler> logger)
     {
@@ -53,6 +54,12 @@ public sealed class JobScheduler : IAsyncDisposable
     /// <summary>When the timer fires next (tests).</summary>
     internal DateTimeOffset? NextWakeAt { get { lock (_lock) return _wakeAt; } }
 
+    /// <summary>How many fires have been started (tests: a skipped occurrence doesn't count).</summary>
+    internal int FiresStarted { get { lock (_lock) return _firesStarted; } }
+
+    /// <summary>The latest queued tick, without the fires it started (tests; unlike <see cref="IdleAsync"/> it doesn't wait for held fires).</summary>
+    internal Task PendingTick { get { lock (_lock) return _pendingTick; } }
+
     /// <summary>Load the store, fire overdue one-offs (late), compute cron occurrences strictly after now (no catch-up), arm the timer.</summary>
     public async Task StartAsync(IJobDelivery delivery, CancellationToken cancellationToken)
     {
@@ -69,10 +76,19 @@ public sealed class JobScheduler : IAsyncDisposable
                 if (job.Schedule.At is { } at) entry.Next = at;
                 else
                 {
-                    entry.Next = NextCron(job, now);
-                    var missed = Schedules.NextCron(job.Schedule.Cron!, job.LastRunAt ?? job.CreatedAt, delivery.TimeZoneFor(job.Target));
-                    if (missed is { } m && m < now)
-                        _logger.LogInformation("Job {Id} ({Name}): occurrences missed while the bot was down are skipped; next {Next}", job.Id, job.Name, entry.Next);
+                    try
+                    {
+                        entry.Next = NextCron(job, now);
+                        var missed = Schedules.NextCron(job.Schedule.Cron!, job.LastRunAt ?? job.CreatedAt, delivery.TimeZoneFor(job.Target));
+                        if (missed is { } m && m < now)
+                            _logger.LogInformation("Job {Id} ({Name}): occurrences missed while the bot was down are skipped; next {Next}", job.Id, job.Name, entry.Next);
+                    }
+                    catch (Exception ex)
+                    {
+                        // One bad entry never keeps the host down: it stays listed but unarmed until a zone change recomputes it.
+                        entry.Next = null;
+                        _logger.LogError(ex, "Job {Id} ({Name}): computing the next occurrence on start failed; the job isn't armed", job.Id, job.Name);
+                    }
                 }
                 _jobs[job.Id] = entry;
             }
@@ -148,19 +164,25 @@ public sealed class JobScheduler : IAsyncDisposable
     }
 
     /// <summary>Remove a job of <paramref name="target"/>. A running watcher is killed and its outcome dropped; a prompt run in progress isn't aborted. False: unknown, or another target's.</summary>
-    public async Task<bool> CancelAsync(string target, string id, CancellationToken cancellationToken)
+    public async Task<bool> CancelAsync(string target, string id, CancellationToken cancellationToken) =>
+        await CancelJobAsync(target, id, cancellationToken).ConfigureAwait(false) is not null;
+
+    /// <summary><see cref="CancelAsync"/> returning the removed job (null: unknown, or another target's); looked up and removed in one step.</summary>
+    public async Task<ScheduledJob?> CancelJobAsync(string target, string id, CancellationToken cancellationToken)
     {
         Fire? running;
+        ScheduledJob removed;
         lock (_lock)
         {
-            if (!_jobs.TryGetValue(id, out var entry) || entry.Job.Target != target) return false;
+            if (!_jobs.TryGetValue(id, out var entry) || entry.Job.Target != target) return null;
+            removed = entry.Job;
             _jobs.Remove(id);
             _inFlight.TryGetValue(id, out running);
         }
         if (running is not null) await TryCancelAsync(running.Cancel).ConfigureAwait(false);
         await PersistAsync(cancellationToken).ConfigureAwait(false);
         Arm();
-        return true;
+        return removed;
     }
 
     /// <summary>The target's zone changed: cron jobs get their next occurrence in the new zone (strictly after now), one-offs keep their instant.</summary>
@@ -250,10 +272,13 @@ public sealed class JobScheduler : IAsyncDisposable
         }
     }
 
+    /// <summary>
+    /// Computes the wake time and applies it to the timer under the lock, so two concurrent arms can't apply an older
+    /// wake after a newer one. A synchronous callback from <c>Change</c> (zero delay) is safe: <see cref="Lock"/> is
+    /// re-entrant and <see cref="OnTimer"/> only queues a tick.
+    /// </summary>
     private void Arm()
     {
-        ITimer timer;
-        TimeSpan delay;
         lock (_lock)
         {
             if (_stopped || _timer is null) return;
@@ -262,16 +287,14 @@ public sealed class JobScheduler : IAsyncDisposable
             var wake = soonest is { } s && s - now < MaxTimerDelay ? s : now + MaxTimerDelay;
             if (wake < now) wake = now;
             _wakeAt = wake;
-            timer = _timer;
-            delay = wake - now;
-        }
-        try
-        {
-            timer.Change(delay, Timeout.InfiniteTimeSpan); // outside the lock: a zero delay may call back synchronously
-        }
-        catch (ObjectDisposedException)
-        {
-            // Stopped meanwhile.
+            try
+            {
+                _timer.Change(wake - now, Timeout.InfiniteTimeSpan);
+            }
+            catch (ObjectDisposedException)
+            {
+                // Stopped meanwhile.
+            }
         }
     }
 
@@ -288,6 +311,7 @@ public sealed class JobScheduler : IAsyncDisposable
         var gate = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
         var task = RunFireAsync(gate.Task, job, dueAt, now, cancel);
         _inFlight[job.Id] = new Fire(task, cancel);
+        _firesStarted++;
         gate.SetResult();
     }
 
@@ -324,12 +348,14 @@ public sealed class JobScheduler : IAsyncDisposable
         switch (job.Kind)
         {
             case JobKind.Reminder:
-                await DeliverAsync(job, ct => delivery.SendTextAsync(job.Target, JobMessages.Reminder(job, lateDue, zone), ct)).ConfigureAwait(false);
-                result = new JobResult(true, null, false, null, _time.GetUtcNow());
+                result = await DeliverAsync(job, ct => delivery.SendTextAsync(job.Target, JobMessages.Reminder(job, lateDue, zone), ct)).ConfigureAwait(false)
+                    ? new JobResult(true, null, false, null, _time.GetUtcNow())
+                    : null;
                 break;
             case JobKind.Prompt:
-                await DeliverAsync(job, ct => delivery.RunPromptAsync(job.Target, JobMessages.Prompt(job, lateDue, zone), ct)).ConfigureAwait(false);
-                result = new JobResult(true, null, false, null, _time.GetUtcNow());
+                result = await DeliverAsync(job, ct => delivery.RunPromptAsync(job.Target, JobMessages.Prompt(job, lateDue, zone), ct)).ConfigureAwait(false)
+                    ? new JobResult(true, null, false, null, _time.GetUtcNow())
+                    : null;
                 break;
             default:
                 result = await RunWatcherAsync(job, delivery, zone, scriptToken).ConfigureAwait(false);
@@ -338,7 +364,7 @@ public sealed class JobScheduler : IAsyncDisposable
         if (result is not null) await RecordAsync(job.Id, result).ConfigureAwait(false);
     }
 
-    /// <summary>Null when the run was cancelled (job cancelled or scheduler stopping): the outcome is dropped.</summary>
+    /// <summary>Null when the run or its delivery was cancelled (job cancelled or scheduler stopping): the outcome is dropped.</summary>
     private async Task<JobResult?> RunWatcherAsync(ScheduledJob job, IJobDelivery delivery, TimeZoneInfo zone, CancellationToken scriptToken)
     {
         var timeout = job.TimeoutSeconds is { } seconds ? TimeSpan.FromSeconds(seconds) : _options.DefaultScriptTimeout;
@@ -359,12 +385,14 @@ public sealed class JobScheduler : IAsyncDisposable
         {
             case ScriptOutcome.Output output:
                 // The condition is met: exactly one agent prompt. Redacted: watcher stdout isn't a tool result.
-                await DeliverAsync(job, ct => delivery.RunPromptAsync(job.Target, JobMessages.WatcherMatch(job, _redactor.Redact(output.Text)), ct)).ConfigureAwait(false);
-                return new JobResult(true, 0, false, null, at);
+                return await DeliverAsync(job, ct => delivery.RunPromptAsync(job.Target, JobMessages.WatcherMatch(job, _redactor.Redact(output.Text)), ct)).ConfigureAwait(false)
+                    ? new JobResult(true, 0, false, null, at)
+                    : null;
             case ScriptOutcome.Failed failed:
                 var result = new JobResult(false, failed.ExitCode, failed.TimedOut, _redactor.Redact(failed.StderrTail), at);
-                if (!IsRepeat(LastResult(job.Id), result))
-                    await DeliverAsync(job, ct => delivery.SendTextAsync(job.Target, JobMessages.Failure(job, result), ct)).ConfigureAwait(false);
+                if (!IsRepeat(LastResult(job.Id), result)
+                    && !await DeliverAsync(job, ct => delivery.SendTextAsync(job.Target, JobMessages.Failure(job, result), ct)).ConfigureAwait(false))
+                    return null; // the alert was cut off by shutdown: not recorded, so the next failure alerts again
                 return result;
             default:
                 return new JobResult(true, 0, false, null, at); // silent: nothing but LastRunAt/LastResult
@@ -375,17 +403,27 @@ public sealed class JobScheduler : IAsyncDisposable
     private static bool IsRepeat(JobResult? previous, JobResult current) =>
         previous is { Ok: false } p && p.ExitCode == current.ExitCode && p.TimedOut == current.TimedOut;
 
-    /// <summary>A delivery exception is logged and swallowed; the job's state still advances (no redelivery queue).</summary>
-    private async Task DeliverAsync(ScheduledJob job, Func<CancellationToken, Task> deliver)
+    /// <summary>
+    /// A delivery exception is logged and swallowed; the job's state still advances (no redelivery queue). False only
+    /// when shutdown interrupted the delivery: the fire then isn't recorded, so a one-off stays stored and fires again
+    /// after the next start (at-least-once).
+    /// </summary>
+    private async Task<bool> DeliverAsync(ScheduledJob job, Func<CancellationToken, Task> deliver)
     {
         try
         {
             await deliver(_stopping.Token).ConfigureAwait(false); // a prompt run isn't aborted by a cancel, only by shutdown
+            return true;
+        }
+        catch (OperationCanceledException) when (_stopping.IsCancellationRequested)
+        {
+            _logger.LogInformation("Job {Id} ({Name}): delivery interrupted by shutdown; kept for the next start", job.Id, job.Name);
+            return false;
         }
-        catch (OperationCanceledException) when (_stopping.IsCancellationRequested) { }
         catch (Exception ex)
         {
             _logger.LogError(ex, "Job {Id} ({Name}): delivery to {Target} failed", job.Id, job.Name, job.Target);
+            return true;
         }
     }
 
diff --git a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ScheduleTool.cs b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ScheduleTool.cs
index f109f1b..a5f2355 100644
--- a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ScheduleTool.cs
+++ b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ScheduleTool.cs
@@ -88,9 +88,8 @@ public sealed class ScheduleTool(JobScheduler scheduler, string target) : Tool<S
     {
         var key = id?.Trim().ToLowerInvariant() ?? "";
         if (key.Length == 0) throw Error("cancel needs id (see action=list).");
-        var job = scheduler.List(target).FirstOrDefault(v => v.Job.Id == key)?.Job;
-        if (job is null || !await scheduler.CancelAsync(target, key, cancellationToken).ConfigureAwait(false))
-            throw Error($"No job {key} in this chat.");
+        var job = await scheduler.CancelJobAsync(target, key, cancellationToken).ConfigureAwait(false)
+                  ?? throw Error($"No job {key} in this chat.");
         return ToolResult.Text($"Cancelled {job.Id} ({job.Name}).");
     }
 
diff --git a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/Schedules.cs b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/Schedules.cs
index f30fc0c..1fbdbdd 100644
--- a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/Schedules.cs
+++ b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/Schedules.cs
@@ -38,19 +38,36 @@ public static partial class Schedules
     public static DateTimeOffset? NextCron(string cron, DateTimeOffset after, TimeZoneInfo zone) =>
         ParseCron(cron).GetNextOccurrence(after, zone, inclusive: false);
 
-    /// <summary>ISO 8601. With an offset (or <c>Z</c>) it's used as given; without one it's wall-clock time in <paramref name="zone"/>.</summary>
+    private static readonly string[] WallFormats = ["yyyy-MM-dd'T'HH:mm", "yyyy-MM-dd'T'HH:mm:ss", "yyyy-MM-dd'T'HH:mm:ss.FFFFFFF"];
+
+    /// <summary>
+    /// ISO 8601 only, always with a date: <c>yyyy-MM-dd</c> (local midnight) or <c>yyyy-MM-dd[T| ]HH:mm[:ss[.fff]]</c>, with
+    /// an optional <c>Z</c> or offset. With an offset it's used as given; without one it's wall-clock time in
+    /// <paramref name="zone"/>. A time without a date (<c>09:00</c>) and culture formats (<c>09/10/2026</c>) are rejected:
+    /// they'd be resolved against the machine's clock, not the chat's.
+    /// </summary>
     public static DateTimeOffset ParseAt(string text, TimeZoneInfo zone)
     {
         var trimmed = text?.Trim() ?? "";
-        var hint = $"at \"{trimmed}\" isn't a date-time. Use ISO 8601, e.g. 2026-09-27T09:00 (read in the chat's time zone) or 2026-09-27T09:00+02:00.";
-        if (HasOffset().IsMatch(trimmed))
-        {
-            return DateTimeOffset.TryParse(trimmed, CultureInfo.InvariantCulture, DateTimeStyles.None, out var absolute)
-                ? absolute
-                : throw new JobValidationException(hint);
-        }
-        if (!DateTime.TryParse(trimmed, CultureInfo.InvariantCulture, DateTimeStyles.None, out var wall)) throw new JobValidationException(hint);
+        var hint = $"at \"{trimmed}\" isn't a date-time. Use ISO 8601 with the date, e.g. 2026-09-27T09:00 (read in the chat's time zone) or 2026-09-27T09:00+02:00.";
+        var match = IsoAt().Match(trimmed);
+        if (!match.Success) throw new JobValidationException(hint);
+        var local = match.Groups["date"].Value + (match.Groups["time"].Success ? "T" + match.Groups["time"].Value : "T00:00");
+        if (!DateTime.TryParseExact(local, WallFormats, CultureInfo.InvariantCulture, DateTimeStyles.None, out var wall))
+            throw new JobValidationException(hint);
         wall = DateTime.SpecifyKind(wall, DateTimeKind.Unspecified);
+
+        if (match.Groups["offset"] is { Success: true } group)
+        {
+            try
+            {
+                return new DateTimeOffset(wall, ParseOffset(group.Value));
+            }
+            catch (ArgumentException)
+            {
+                throw new JobValidationException(hint); // an offset beyond ±14:00
+            }
+        }
         // A time skipped by a spring-forward change doesn't exist: move it past the gap (Europe/US gaps are one hour).
         if (zone.IsInvalidTime(wall)) wall = wall.AddHours(1);
         // An ambiguous fall-back time is read as the first of the two (the larger offset).
@@ -58,7 +75,19 @@ public static partial class Schedules
         return new DateTimeOffset(wall, offset);
     }
 
-    /// <summary>A time of day followed by <c>Z</c> or an offset. A bare date such as <c>2026-09-27</c> must not match (its <c>-27</c> isn't an offset).</summary>
-    [GeneratedRegex(@"\d{1,2}:\d{2}(:\d{2}(\.\d+)?)?\s*(Z|[+-]\d{2}(:?\d{2})?)$", RegexOptions.IgnoreCase)]
-    private static partial Regex HasOffset();
+    /// <summary><c>Z</c>, <c>+02</c>, <c>+0200</c> or <c>+02:00</c>.</summary>
+    private static TimeSpan ParseOffset(string text)
+    {
+        if (text.Equals("Z", StringComparison.OrdinalIgnoreCase)) return TimeSpan.Zero;
+        var digits = text[1..].Replace(":", "", StringComparison.Ordinal);
+        var hours = int.Parse(digits[..2], NumberStyles.None, CultureInfo.InvariantCulture);
+        var minutes = digits.Length > 2 ? int.Parse(digits[2..], NumberStyles.None, CultureInfo.InvariantCulture) : 0;
+        if (minutes > 59) throw new ArgumentException("minutes", nameof(text));
+        var offset = new TimeSpan(hours, minutes, 0);
+        return text[0] == '-' ? -offset : offset;
+    }
+
+    /// <summary>A date, optionally a time (after <c>T</c> or a space) and then optionally <c>Z</c> or an offset.</summary>
+    [GeneratedRegex(@"^(?<date>\d{4}-\d{2}-\d{2})(?:[T ](?<time>\d{2}:\d{2}(?::\d{2}(?:\.\d{1,7})?)?)\s*(?<offset>Z|[+-]\d{2}(?::?\d{2})?)?)?$", RegexOptions.IgnoreCase)]
+    private static partial Regex IsoAt();
 }
diff --git a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ScriptRunner.cs b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ScriptRunner.cs
index 6debb35..ff4485c 100644
--- a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ScriptRunner.cs
+++ b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ScriptRunner.cs
@@ -75,7 +75,8 @@ public sealed class ScriptRunner(SchedulerOptions options, IProcessSpawnPolicy p
             Directory.CreateDirectory(spawn.Cwd);
             process.Start();
         }
-        catch (Exception ex) when (ex is Win32Exception or InvalidOperationException or IOException or UnauthorizedAccessException)
+        catch (Exception ex) when (ex is Win32Exception or InvalidOperationException or IOException or UnauthorizedAccessException
+                                       or ArgumentException or NotSupportedException) // e.g. a workspace path that can't be created
         {
             return new ScriptOutcome.Failed(null, $"failed to start {psi.FileName}: {ex.Message}", false);
         }
diff --git a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ZoneNames.cs b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ZoneNames.cs
index 3532278..65834e9 100644
--- a/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ZoneNames.cs
+++ b/extensions/Volcanic.AgenticCore.Extensions.Scheduler/ZoneNames.cs
@@ -1,22 +1,22 @@
-using System.Globalization;
-
 namespace Volcanic.AgenticCore.Extensions.Scheduler;
 
-/// <summary>Zone ids and offsets for display and <c>TZ</c> (the extension can't reference the core's <c>TimeZoneIds</c>).</summary>
+/// <summary>
+/// Zone ids for display and <c>TZ</c>. Mirrors the core's <c>Volcanic.AgenticCore.Hosting.TimeZoneIds</c> (the extension
+/// references only the Abstractions); keep the two in step.
+/// </summary>
 internal static class ZoneNames
 {
-    /// <summary>The IANA id (converting a Windows id), or null for an unnamed <c>Local</c> zone.</summary>
+    /// <summary>
+    /// The IANA id (converting a Windows id), or null when there is none that resolves back to a system zone (an unnamed
+    /// <c>Local</c> zone: <c>TZ=Local</c> would run the script in UTC). Same rule as <c>TimeZoneIds.ToIana</c>.
+    /// </summary>
     public static string? Iana(TimeZoneInfo zone)
     {
         if (string.Equals(zone.Id, "Local", StringComparison.OrdinalIgnoreCase)) return null;
-        if (zone.HasIanaId) return zone.Id;
-        return TimeZoneInfo.TryConvertWindowsIdToIanaId(zone.Id, out var iana) ? iana : null;
+        var id = zone.HasIanaId ? zone.Id : TimeZoneInfo.TryConvertWindowsIdToIanaId(zone.Id, out var iana) ? iana : null;
+        return id is not null && TimeZoneInfo.TryFindSystemTimeZoneById(id, out _) ? id : null;
     }
 
-    /// <summary>The IANA id when there is one, else the zone's own id.</summary>
+    /// <summary>The IANA id when there is one, else the zone's own id (<c>TimeZoneIds.Name</c>).</summary>
     public static string Name(TimeZoneInfo zone) => Iana(zone) ?? zone.Id;
-
-    /// <summary><c>UTC+09:00</c>.</summary>
-    public static string Offset(TimeSpan offset) =>
-        (offset < TimeSpan.Zero ? "UTC-" : "UTC+") + offset.Duration().ToString(@"hh\:mm", CultureInfo.InvariantCulture);
 }
diff --git a/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatCommands.cs b/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatCommands.cs
index 31d9668..1f06336 100644
--- a/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatCommands.cs
+++ b/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatCommands.cs
@@ -3,6 +3,7 @@ using System.Text;
 using Telegram.Bot.Types;
 using Volcanic.AgenticCore.Abstractions.Providers;
 using Volcanic.AgenticCore.Extensions.Scheduler;
+using Volcanic.AgenticCore.Hosting;
 using Volcanic.AgenticCore.Telegram.Rendering;
 using Volcanic.AgenticCore.Telegram.Scheduling;
 
@@ -150,7 +151,7 @@ public sealed class ChatCommands(TelegramSender sender, ChatTimeZoneService? zon
             sb.AppendLine(CultureInfo.InvariantCulture, $"**Context:** {(usage.Tokens is { } t ? t.ToString("N0", CultureInfo.InvariantCulture) : "?")} / {usage.ContextWindow.ToString("N0", CultureInfo.InvariantCulture)} tokens{(usage.Percent is { } p ? $" ({p:0}%)" : "")}");
         if (scheduler is { IsStarted: true })
             sb.AppendLine(CultureInfo.InvariantCulture, $"**Jobs:** {scheduler.List(TelegramJobDelivery.TargetOf(chat.ChatId)).Count}");
-        var zone = zones?.Describe(chat.ChatId) ?? ChatTimeZoneService.Describe(session.TimeZone, DateTimeOffset.UtcNow);
+        var zone = zones?.Describe(chat.ChatId) ?? TimeZoneIds.Name(session.TimeZone); // no service (tests): no clock read
         sb.AppendLine(CultureInfo.InvariantCulture, $"**Time zone:** {zone}");
         sb.AppendLine(CultureInfo.InvariantCulture, $"**Workspace:** `{session.Cwd}`");
         sb.Append(session.IsStreaming ? "**State:** running" : session.IsCompacting ? "**State:** compacting" : "**State:** idle");
@@ -212,8 +213,7 @@ public sealed class ChatCommands(TelegramSender sender, ChatTimeZoneService? zon
         var id = arg.Trim().ToLowerInvariant();
         if (id.Length == 0) return "Usage: /cancel <id> (see /jobs).";
         var target = TelegramJobDelivery.TargetOf(chat.ChatId);
-        var job = scheduler.List(target).FirstOrDefault(v => v.Job.Id == id)?.Job;
-        return job is not null && await scheduler.CancelAsync(target, id, cancellationToken).ConfigureAwait(false)
+        return await scheduler.CancelJobAsync(target, id, cancellationToken).ConfigureAwait(false) is { } job
             ? $"Cancelled {job.Id} ({job.Name})."
             : $"No job {id} in this chat.";
     }
diff --git a/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatRegistry.cs b/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatRegistry.cs
index 08edeeb..97e6e16 100644
--- a/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatRegistry.cs
+++ b/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatRegistry.cs
@@ -117,7 +117,7 @@ public sealed class ChatRegistry(
         if (calendar is not null) extras.Add(GoogleCalendarSetup.Registration(calendar));
         if (zones is not null) extras.Add(ExtensionRegistration.FromInstance(new ChatSettingsExtension(chatId, zones)));
         if (scheduler is not null)
-            extras.Add(ExtensionRegistration.FromInstance(new SchedulerExtension(scheduler, chatId.ToString(System.Globalization.CultureInfo.InvariantCulture))));
+            extras.Add(ExtensionRegistration.FromInstance(new SchedulerExtension(scheduler, Scheduling.TelegramJobDelivery.TargetOf(chatId))));
         AgentSession session;
         try
         {
diff --git a/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatTimeZoneService.cs b/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatTimeZoneService.cs
index cfbe7ae..e105c55 100644
--- a/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatTimeZoneService.cs
+++ b/hosts/Volcanic.AgenticCore.Telegram/Chats/ChatTimeZoneService.cs
@@ -3,6 +3,7 @@ using System.Text;
 using Volcanic.AgenticCore.Extensions.Scheduler;
 using Volcanic.AgenticCore.Features.Agent;
 using Volcanic.AgenticCore.Hosting;
+using Volcanic.AgenticCore.Telegram.Scheduling;
 
 namespace Volcanic.AgenticCore.Telegram.Chats;
 
@@ -13,8 +14,6 @@ namespace Volcanic.AgenticCore.Telegram.Chats;
 /// </summary>
 public sealed class ChatTimeZoneService(ChatSettingsStore store, Func<long, AgentSession?> liveSession, TimeProvider time, JobScheduler? scheduler = null)
 {
-    public TimeZoneInfo TimeZoneFor(long chatId) => store.TimeZoneFor(chatId);
-
     /// <summary>Set (<paramref name="zone"/>) or reset (null) the chat's zone and return the confirmation.</summary>
     public async Task<string> SetAsync(long chatId, TimeZoneInfo? zone, CancellationToken cancellationToken)
     {
@@ -28,7 +27,7 @@ public sealed class ChatTimeZoneService(ChatSettingsStore store, Func<long, Agen
         text.Append(" Now ").Append(JobFormat.DayTime(now, effective)).Append('.');
         if (scheduler is { IsStarted: true })
         {
-            var target = chatId.ToString(CultureInfo.InvariantCulture);
+            var target = TelegramJobDelivery.TargetOf(chatId);
             var change = await scheduler.TimeZoneChangedAsync(target, cancellationToken).ConfigureAwait(false);
             text.Append(JobClause(change, scheduler.List(target), effective));
         }
diff --git a/hosts/Volcanic.AgenticCore.Telegram/Program.cs b/hosts/Volcanic.AgenticCore.Telegram/Program.cs
index af71b28..f949471 100644
--- a/hosts/Volcanic.AgenticCore.Telegram/Program.cs
+++ b/hosts/Volcanic.AgenticCore.Telegram/Program.cs
@@ -34,7 +34,9 @@ var processEnvironment = new ProcessEnvironmentOptions();
 TelegramProcessEnvironment.Configure(processEnvironment, options, processSection, Environment.GetEnvironmentVariable, calendar);
 var mcp = builder.Configuration.GetSection(McpOptions.SectionName).Get<McpOptions>() ?? new McpOptions();
 mcp.ApplyEnvironment(Environment.GetEnvironmentVariable);
-var scheduling = SchedulerSetup.Options(builder.Configuration.GetSection(SchedulerOptions.SectionName), VolcanicPaths.DefaultAgentDir);
+// One agent directory for sessions, chat-settings.json and scheduler/jobs.json.
+var agentDir = VolcanicPaths.DefaultAgentDir;
+var scheduling = SchedulerSetup.Options(builder.Configuration.GetSection(SchedulerOptions.SectionName), agentDir);
 var errors = options.Validate().Concat(processEnvironment.Validate()).Concat(mcp.Validate()).Concat(scheduling.Validate()).ToList();
 if (errors.Count > 0)
 {
@@ -63,6 +65,7 @@ builder.Services.AddSingleton(sp => new ClaudeCodeProviderOptions
 });
 builder.Services.AddAgenticCore(o =>
 {
+    o.AgentDir = agentDir;
     o.DefaultModel = options.Model;
     o.ProcessEnvironment = processEnvironment;
     o.DefaultTimeZone = options.ConfiguredTimeZone();
@@ -75,7 +78,7 @@ builder.Services.AddSingleton<TelegramSender>();
 builder.Services.TryAddSingleton(TimeProvider.System);
 builder.Services.AddSingleton<ChatRegistry>();
 builder.Services.AddSingleton(sp => new ChatSettingsStore(
-    ChatSettingsStore.DefaultPath(sp.GetRequiredService<IOptions<AgenticCoreOptions>>().Value.AgentDir),
+    ChatSettingsStore.DefaultPath(agentDir),
     options.ConfiguredTimeZone() ?? TimeZoneInfo.Local,
     sp.GetRequiredService<ILogger<ChatSettingsStore>>(),
     sp.GetRequiredService<TimeProvider>()));
diff --git a/hosts/Volcanic.AgenticCore.Telegram/Scheduling/TelegramJobDelivery.cs b/hosts/Volcanic.AgenticCore.Telegram/Scheduling/TelegramJobDelivery.cs
index fd7ddc4..086f275 100644
--- a/hosts/Volcanic.AgenticCore.Telegram/Scheduling/TelegramJobDelivery.cs
+++ b/hosts/Volcanic.AgenticCore.Telegram/Scheduling/TelegramJobDelivery.cs
@@ -20,6 +20,9 @@ public sealed class TelegramJobDelivery(ChatRegistry chats, ChatSettingsStore se
 
     public static string TargetOf(long chatId) => chatId.ToString(CultureInfo.InvariantCulture);
 
+    private static bool TryChatIdOf(string target, out long chatId) =>
+        long.TryParse(target, NumberStyles.AllowLeadingSign, CultureInfo.InvariantCulture, out chatId);
+
     public async Task SendTextAsync(string target, string markdown, CancellationToken cancellationToken)
     {
         var chat = await chats.GetAsync(ChatIdOf(target), cancellationToken).ConfigureAwait(false);
@@ -33,10 +36,11 @@ public sealed class TelegramJobDelivery(ChatRegistry chats, ChatSettingsStore se
         var text = MessageContext.TimestampHeader(time.GetUtcNow(), TimeZoneFor(target)) + "\n" + prompt;
         try
         {
-            // Idle: starts a run and returns when it settles. Busy: queued as a follow-up (never steering) and returns at once.
+            // Idle: starts (or joins, as a follow-up) a run and returns when it settles. Busy: queued as a follow-up (never
+            // steering) and returns at once; the job then stays in flight until the run that consumed it settles.
+            var queued = chat.Session.IsStreaming;
             await chat.Session.PromptAsync(text, null, StreamingBehavior.FollowUp, cancellationToken).ConfigureAwait(false);
-            // Queued: the job stays in flight until the run that consumed it settles. Harmless when it already ran.
-            await chat.Session.WaitForIdleAsync(cancellationToken).ConfigureAwait(false);
+            if (queued) await chat.Session.WaitForIdleAsync(cancellationToken).ConfigureAwait(false);
         }
         catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
         {
@@ -53,7 +57,9 @@ public sealed class TelegramJobDelivery(ChatRegistry chats, ChatSettingsStore se
 
     /// <summary>Private chat id = user id: the chat is served while its user is allow-listed.</summary>
     public bool IsDeliverable(string target) =>
-        long.TryParse(target, NumberStyles.AllowLeadingSign, CultureInfo.InvariantCulture, out var chatId) && options.IsAllowed(chatId);
+        TryChatIdOf(target, out var chatId) && options.IsAllowed(chatId);
 
-    public TimeZoneInfo TimeZoneFor(string target) => settings.TimeZoneFor(ChatIdOf(target));
+    /// <summary>An unparsable target (a hand-edited store) gets the default zone rather than an exception.</summary>
+    public TimeZoneInfo TimeZoneFor(string target) =>
+        TryChatIdOf(target, out var chatId) ? settings.TimeZoneFor(chatId) : settings.DefaultZone;
 }
diff --git a/src/Volcanic.AgenticCore/Features/Agent/AgentSession.Host.cs b/src/Volcanic.AgenticCore/Features/Agent/AgentSession.Host.cs
index c358f76..bc9b3b2 100644
--- a/src/Volcanic.AgenticCore/Features/Agent/AgentSession.Host.cs
+++ b/src/Volcanic.AgenticCore/Features/Agent/AgentSession.Host.cs
@@ -22,8 +22,7 @@ public sealed partial class AgentSession : IExtensionHost
     Model? IExtensionHost.Model => _model;
     ThinkingLevel IExtensionHost.ThinkingLevel => _thinkingLevel;
     TimeZoneInfo IExtensionHost.TimeZone => TimeZone;
-    string? IExtensionHost.TimeZoneId =>
-        (_timeZoneOverride ?? _options.TimeZone ?? _coreOptions.DefaultTimeZone) is { } zone ? TimeZoneIds.ToIana(zone) : null;
+    string? IExtensionHost.TimeZoneId => ConfiguredTimeZone is { } zone ? TimeZoneIds.ToIana(zone) : null;
     CancellationToken IExtensionHost.Signal
     {
         get { lock (_stateLock) return _abortCts?.Token ?? CancellationToken.None; }
diff --git a/src/Volcanic.AgenticCore/Features/Agent/AgentSession.Loop.cs b/src/Volcanic.AgenticCore/Features/Agent/AgentSession.Loop.cs
index ef31dda..e3517e7 100644
--- a/src/Volcanic.AgenticCore/Features/Agent/AgentSession.Loop.cs
+++ b/src/Volcanic.AgenticCore/Features/Agent/AgentSession.Loop.cs
@@ -12,18 +12,31 @@ namespace Volcanic.AgenticCore.Features.Agent;
 /// <summary>The agent loop: turns, streaming with retry and overflow recovery, queues, compaction between turns.</summary>
 public sealed partial class AgentSession
 {
-    /// <summary>Starts a run if none is active. When a run is already active the messages must have been queued by the caller.</summary>
-    private async Task StartRunAsync(UserMessage? prompt, IReadOnlyList<ImageContent>? images, CancellationToken cancellationToken)
+    /// <summary>
+    /// Starts a run if none is active. When a run started meanwhile (after the caller's <see cref="IsStreaming"/> check),
+    /// <paramref name="prompt"/> joins it: as a follow-up when <paramref name="behavior"/> is
+    /// <see cref="StreamingBehavior.FollowUp"/>, else as steering. Either way the call returns when that run settles.
+    /// </summary>
+    internal async Task StartRunAsync(UserMessage? prompt, IReadOnlyList<ImageContent>? images, CancellationToken cancellationToken, StreamingBehavior? behavior = null)
     {
         await _runGate.WaitAsync(cancellationToken).ConfigureAwait(false);
         Task run;
+        var queuedFollowUp = false;
         try
         {
             lock (_stateLock)
             {
                 if (_runTask is { IsCompleted: false })
                 {
-                    if (prompt is not null) _steering.Enqueue(prompt);
+                    if (prompt is not null)
+                    {
+                        if (behavior == StreamingBehavior.FollowUp)
+                        {
+                            _followUp.Enqueue(prompt);
+                            queuedFollowUp = true;
+                        }
+                        else _steering.Enqueue(prompt);
+                    }
                     run = _runTask;
                 }
                 else
@@ -34,6 +47,7 @@ public sealed partial class AgentSession
             }
         }
         finally { _runGate.Release(); }
+        if (queuedFollowUp) Emit(new AgentSessionEvent.QueueUpdate(_steering.Texts(), _followUp.Texts()));
         await run.ConfigureAwait(false);
     }
 
diff --git a/src/Volcanic.AgenticCore/Features/Agent/AgentSession.cs b/src/Volcanic.AgenticCore/Features/Agent/AgentSession.cs
index 679ba2c..fc7c48a 100644
--- a/src/Volcanic.AgenticCore/Features/Agent/AgentSession.cs
+++ b/src/Volcanic.AgenticCore/Features/Agent/AgentSession.cs
@@ -102,7 +102,10 @@ public sealed partial class AgentSession : IAsyncDisposable
     public string SessionId => _session.SessionId;
     public string Cwd => _options.Cwd;
     /// <summary>The session's time zone: <see cref="SetTimeZone"/>, else the session option, else the host default, else the machine's zone.</summary>
-    public TimeZoneInfo TimeZone => _timeZoneOverride ?? _options.TimeZone ?? _coreOptions.DefaultTimeZone ?? TimeZoneInfo.Local;
+    public TimeZoneInfo TimeZone => ConfiguredTimeZone ?? TimeZoneInfo.Local;
+
+    /// <summary>The zone set for this session (override, option, host default), or null when none is: then children inherit the host's <c>TZ</c>.</summary>
+    private TimeZoneInfo? ConfiguredTimeZone => _timeZoneOverride ?? _options.TimeZone ?? _coreOptions.DefaultTimeZone;
 
     /// <summary>
     /// Change the session's zone (a host's per-chat setting). Tools and process spawns see it at once; the system prompt
@@ -195,7 +198,8 @@ public sealed partial class AgentSession : IAsyncDisposable
             }
         }
 
-        await StartRunAsync(message, images, cancellationToken).ConfigureAwait(false);
+        // A run may start between the check above and the run gate; behavior then decides how the prompt joins it.
+        await StartRunAsync(message, images, cancellationToken, behavior).ConfigureAwait(false);
     }
 
     /// <summary>Queue a steering message; delivered after the current turn's tools, before the next model call.</summary>
diff --git a/src/Volcanic.AgenticCore/Features/Agent/AgentSessionFactory.cs b/src/Volcanic.AgenticCore/Features/Agent/AgentSessionFactory.cs
index b5a3683..2e990f4 100644
--- a/src/Volcanic.AgenticCore/Features/Agent/AgentSessionFactory.cs
+++ b/src/Volcanic.AgenticCore/Features/Agent/AgentSessionFactory.cs
@@ -34,10 +34,12 @@ public sealed class AgentSessionFactory : IAgentSessionFactory
     private readonly VolcanicPaths _paths;
     private readonly ISecretRedactor _redactor;
     private readonly IProcessSpawnPolicy _processes;
+    private readonly TimeProvider _time;
 
     public AgentSessionFactory(IServiceProvider services, IOptions<AgenticCoreOptions> options, ILoggerFactory loggerFactory,
-        ISecretRedactor redactor, IProcessSpawnPolicy processes)
+        ISecretRedactor redactor, IProcessSpawnPolicy processes, TimeProvider? time = null)
     {
+        _time = time ?? TimeProvider.System;
         _processes = processes;
         _services = services;
         _options = options.Value;
@@ -103,8 +105,9 @@ public sealed class AgentSessionFactory : IAgentSessionFactory
 
         // The builder is created before the session; the zone is read from the session at every render (SetTimeZone).
         AgentSession? owner = null;
-        var time = (TimeProvider?)_services.GetService(typeof(TimeProvider)) ?? TimeProvider.System;
-        var promptBuilder = new SystemPromptBuilder(cwd, () => tools.ActiveTools, time,
+        // The prompt is only rendered by a run, after owner is assigned; the fallback covers an extension rendering it
+        // during activation, and follows the session's own order (AgentSession.TimeZone).
+        var promptBuilder = new SystemPromptBuilder(cwd, () => tools.ActiveTools, _time,
             () => owner?.TimeZone ?? options.TimeZone ?? _options.DefaultTimeZone ?? TimeZoneInfo.Local);
         var compactor = new Compactor(_options.Compaction, models);
 
diff --git a/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/JobFormatTests.cs b/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/JobFormatTests.cs
index 0c2604e..8d32ec4 100644
--- a/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/JobFormatTests.cs
+++ b/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/JobFormatTests.cs
@@ -33,7 +33,6 @@ public sealed class JobFormatTests
         Assert.Equal("14:10", JobFormat.When(new DateTimeOffset(2026, 9, 26, 12, 10, 0, TimeSpan.Zero), Berlin, Now));
         Assert.Equal("27 Sep 00:10", JobFormat.When(new DateTimeOffset(2026, 9, 26, 22, 10, 0, TimeSpan.Zero), Berlin, Now));
         Assert.Equal("Sat 2026-09-26 14:03", JobFormat.Stamp(Now, Berlin));
-        Assert.Equal("UTC+02:00", JobFormat.Offset(Berlin, Now));
         Assert.Equal("exit 1, timed out", JobFormat.FailureReason(new JobResult(false, 1, true, null, Now)));
         Assert.Equal("did not start", JobFormat.FailureReason(new JobResult(false, null, false, "failed to start", Now)));
     }
diff --git a/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/JobSchedulerTests.cs b/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/JobSchedulerTests.cs
index 9d85a15..aebaaaf 100644
--- a/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/JobSchedulerTests.cs
+++ b/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/JobSchedulerTests.cs
@@ -167,8 +167,10 @@ public sealed class JobSchedulerTests
         h.Time.Advance(Minute);
         await Eventually.UntilAsync(() => h.Runner.Requests.Count == 1, "the first run");
         h.Time.Advance(Minute);
+        await h.Scheduler.PendingTick;
         h.Time.Advance(Minute);
-        await Task.Delay(100);
+        await h.Scheduler.PendingTick;
+        Assert.Equal(1, h.Scheduler.FiresStarted); // both occurrences were skipped by their ticks
         Assert.Single(h.Runner.Requests);
 
         h.Runner.Hold.SetResult();
@@ -189,7 +191,8 @@ public sealed class JobSchedulerTests
         h.Time.Advance(Minute);
         await Eventually.UntilAsync(() => h.Delivery.Prompts.Count == 1, "the first prompt");
         h.Time.Advance(Minute);
-        await Task.Delay(100);
+        await h.Scheduler.PendingTick;
+        Assert.Equal(1, h.Scheduler.FiresStarted);
         Assert.Single(h.Delivery.Prompts);
 
         h.Delivery.HoldPrompts.SetResult();
@@ -280,16 +283,60 @@ public sealed class JobSchedulerTests
         h.Time.Advance(Minute);
         await Eventually.UntilAsync(() => h.Runner.Requests.Count == 1, "the run");
 
+        var stoppedAt = h.Time.GetUtcNow();
         var stop = h.Scheduler.StopAsync(CancellationToken.None);
-        await Task.Delay(100);
-        Assert.False(stop.IsCompleted);
-        h.Time.Advance(TimeSpan.FromSeconds(10));
-        await stop.WaitAsync(TimeSpan.FromSeconds(5));
+        Assert.False(stop.IsCompleted); // waiting on the fake clock's grace period
+        // Second by second: the grace timer may be created after the first advances.
+        await Eventually.UntilAsync(() => { h.Time.Advance(TimeSpan.FromSeconds(1)); return stop.IsCompleted; }, "the stop after the grace period");
+        Assert.True(h.Time.GetUtcNow() - stoppedAt >= JobScheduler.StopGrace);
+        await stop;
 
         h.Runner.Hold.SetResult();
         await h.DisposeAsync();
     }
 
+    [Fact]
+    public async Task A_stored_job_whose_zone_lookup_throws_does_not_stop_the_start()
+    {
+        await using var h = new SchedulerHarness();
+        await h.Store.SaveAsync([
+            Stored("bad11", JobKind.Reminder, new JobSchedule(null, "*/10 * * * *"), target: "not-a-chat"),
+            Stored("good1", JobKind.Reminder, new JobSchedule(null, "*/10 * * * *")),
+        ], CancellationToken.None);
+        h.Delivery.BadTargets.Add("not-a-chat");
+
+        await h.StartAsync();
+
+        Assert.True(h.Scheduler.IsStarted);
+        Assert.Null(Assert.Single(h.Scheduler.List("not-a-chat")).NextRunAt); // kept, unarmed
+        Assert.Equal(new DateTimeOffset(2026, 9, 26, 12, 10, 0, TimeSpan.Zero), Assert.Single(h.Scheduler.List("111")).NextRunAt);
+        await h.AdvanceAsync(TimeSpan.FromMinutes(7));
+        Assert.Equal(("111", "⏰ Call the dentist"), Assert.Single(h.Delivery.Texts));
+    }
+
+    [Fact]
+    public async Task A_one_off_whose_delivery_is_cut_off_by_shutdown_is_kept_and_fires_after_the_next_start()
+    {
+        var h = new SchedulerHarness();
+        await h.Store.SaveAsync([Stored("k7m2q", JobKind.Reminder, new JobSchedule(Start.AddSeconds(-30), null))], CancellationToken.None);
+        h.Delivery.HoldTexts = new TaskCompletionSource(); // the send is in flight when the bot stops
+        await h.StartAsync();
+        await Eventually.UntilAsync(() => h.Delivery.Texts.Count == 1, "the reminder send");
+
+        await h.Scheduler.StopAsync(CancellationToken.None).WaitAsync(TimeSpan.FromSeconds(5));
+
+        Assert.Equal("k7m2q", Assert.Single(await h.Store.LoadAsync(CancellationToken.None)).Id);
+        var delivery = new FakeJobDelivery();
+        await using (var restarted = new JobScheduler(h.Options, h.Runner, h.Redactor, h.Time, Microsoft.Extensions.Logging.Abstractions.NullLogger<JobScheduler>.Instance))
+        {
+            await restarted.StartAsync(delivery, CancellationToken.None);
+            await restarted.IdleAsync();
+        }
+        Assert.Equal(("111", "⏰ Call the dentist"), Assert.Single(delivery.Texts));
+        Assert.Empty(await h.Store.LoadAsync(CancellationToken.None));
+        await h.DisposeAsync();
+    }
+
     [Fact]
     public async Task A_zone_change_recomputes_cron_and_leaves_one_offs()
     {
diff --git a/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/ScheduleTests.cs b/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/ScheduleTests.cs
index b537986..b50dffb 100644
--- a/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/ScheduleTests.cs
+++ b/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/ScheduleTests.cs
@@ -54,6 +54,20 @@ public sealed class ScheduleTests
     {
         Assert.Equal(Utc(2026, 9, 27, 4, 0), Schedules.ParseAt("2026-09-27T09:00+05:00", Berlin));
         Assert.Equal(Utc(2026, 9, 27, 9, 0), Schedules.ParseAt("2026-09-27T09:00Z", Tokyo));
+        Assert.Equal(Utc(2026, 9, 27, 7, 0), Schedules.ParseAt("2026-09-27T09:00:00.000+0200", Tokyo));
+        Assert.Equal(Utc(2026, 9, 27, 11, 0), Schedules.ParseAt("2026-09-27 09:00-02", Tokyo));
+    }
+
+    [Theory]
+    [InlineData("09:00")] // no date: would take the machine's date, not the chat's
+    [InlineData("09:00+02:00")]
+    [InlineData("09/10/2026")] // culture formats aren't ISO 8601
+    [InlineData("27.09.2026 09:00")]
+    [InlineData("2026-09-27T09:00+15:00")] // beyond ±14:00
+    public void At_without_a_date_or_not_in_ISO_8601_is_rejected(string at)
+    {
+        var ex = Assert.Throws<JobValidationException>(() => Schedules.ParseAt(at, Berlin));
+        Assert.Contains("ISO 8601 with the date", ex.Message);
     }
 
     [Theory]
diff --git a/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/Support/SchedulerFakes.cs b/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/Support/SchedulerFakes.cs
index d90a2e7..b121fb9 100644
--- a/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/Support/SchedulerFakes.cs
+++ b/tests/Volcanic.AgenticCore.Extensions.Tests/Scheduler/Support/SchedulerFakes.cs
@@ -21,6 +21,8 @@ internal sealed class FakeJobDelivery : IJobDelivery
     public Dictionary<string, TimeZoneInfo> Zones { get; } = new();
     public TimeZoneInfo DefaultZone { get; set; } = TimeZoneInfo.FindSystemTimeZoneById("Europe/Berlin");
     public HashSet<string> Undeliverable { get; } = [];
+    /// <summary>Targets whose <see cref="TimeZoneFor"/> throws (a store entry the host can't map).</summary>
+    public HashSet<string> BadTargets { get; } = [];
     public TaskCompletionSource? HoldTexts { get; set; }
     public TaskCompletionSource? HoldPrompts { get; set; }
     public Exception? FailSends { get; set; }
@@ -59,6 +61,7 @@ internal sealed class FakeJobDelivery : IJobDelivery
     public TimeZoneInfo TimeZoneFor(string target)
     {
         lock (_lock) _calls.Add("TimeZoneFor:" + target);
+        if (BadTargets.Contains(target)) throw new FormatException($"bad target {target}");
         return Zones.GetValueOrDefault(target, DefaultZone);
     }
 }
diff --git a/tests/Volcanic.AgenticCore.Telegram.Tests/ScheduledPromptChatTests.cs b/tests/Volcanic.AgenticCore.Telegram.Tests/ScheduledPromptChatTests.cs
index 8127018..43c1330 100644
--- a/tests/Volcanic.AgenticCore.Telegram.Tests/ScheduledPromptChatTests.cs
+++ b/tests/Volcanic.AgenticCore.Telegram.Tests/ScheduledPromptChatTests.cs
@@ -163,6 +163,23 @@ public sealed class ScheduledPromptChatTests
         Assert.Equal("pasted-code", await ask.WaitAsync(TimeSpan.FromSeconds(5)));
     }
 
+    [Fact]
+    public async Task A_scheduled_prompt_that_fails_is_reported_to_the_chat_and_the_job_still_completes()
+    {
+        var (host, time) = await SchedulerChatTests.StartedAsync();
+        await using var _ = host;
+        var chat = await host.ChatAsync();
+        await chat.Session.DisposeAsync(); // PromptAsync now throws, as any failure to start the run would
+        await host.Scheduler!.CreateAsync(ChatHost.Target, new NewJob("Check", JobKind.Prompt, At: BerlinAt(time, 1), Text: "Check the build"), CancellationToken.None);
+
+        await SchedulerChatTests.AdvanceAsync(host, time, TimeSpan.FromMinutes(1));
+        await chat.Renderer.DrainAsync().WaitAsync(TimeSpan.FromSeconds(5));
+
+        Assert.Contains(host.Texts, t => t.Contains("The scheduled job failed:", StringComparison.Ordinal));
+        Assert.Empty(host.Faux.Requests);
+        Assert.Empty(host.Scheduler.List(ChatHost.Target)); // the one-off completed (no redelivery queue)
+    }
+
     [Fact]
     public async Task Timezone_with_jobs_reports_counts_and_jobs_shows_tokyo_times()
     {
diff --git a/tests/Volcanic.AgenticCore.Telegram.Tests/SchedulerChatTests.cs b/tests/Volcanic.AgenticCore.Telegram.Tests/SchedulerChatTests.cs
index 7cf6fae..8a0a880 100644
--- a/tests/Volcanic.AgenticCore.Telegram.Tests/SchedulerChatTests.cs
+++ b/tests/Volcanic.AgenticCore.Telegram.Tests/SchedulerChatTests.cs
@@ -43,10 +43,12 @@ public sealed class SchedulerChatTests
     {
         var (host, time) = await StartedAsync();
         await using var _ = host;
+        var chat = await host.ChatAsync();
+        var entriesBefore = chat.Session.SessionManager.GetEntries().Count;
+        var leafBefore = chat.Session.SessionManager.LeafId;
         await host.Scheduler!.CreateAsync(ChatHost.Target, new NewJob("Dentist", JobKind.Reminder, At: "2026-09-26T14:05", Text: "Call the **dentist**"), CancellationToken.None);
 
         await AdvanceAsync(host, time, TimeSpan.FromMinutes(2));
-        var chat = await host.ChatAsync();
         await chat.Renderer.DrainAsync().WaitAsync(TimeSpan.FromSeconds(5));
 
         var sent = Assert.Single(host.Bot.Sent);
@@ -54,6 +56,8 @@ public sealed class SchedulerChatTests
         Assert.Equal("⏰ Call the <b>dentist</b>", sent.Text);
         Assert.Empty(host.Faux.Requests);
         Assert.Empty(chat.Session.Messages);
+        Assert.Equal(entriesBefore, chat.Session.SessionManager.GetEntries().Count); // no entry of any kind
+        Assert.Equal(leafBefore, chat.Session.SessionManager.LeafId);
     }
 
     [Fact]
@@ -81,6 +85,7 @@ public sealed class SchedulerChatTests
 
         Assert.Equal(host.WorkspaceOf(), host.Delivery!.WorkspaceFor(ChatHost.Target));
         Assert.Equal("Asia/Tokyo", host.Delivery.TimeZoneFor(ChatHost.Target).Id);
+        Assert.Same(host.Settings.DefaultZone, host.Delivery.TimeZoneFor("not-a-chat")); // a hand-edited store never throws here
         Assert.Null(host.Chats.Find(Updates.AllowedUser));
     }
 
@@ -162,5 +167,10 @@ public sealed class SchedulerChatTests
         await using var host = new ChatHost();
         await host.SendAsync("/jobs");
         Assert.Equal(SchedulerSetup.DisabledReply, host.LastReply());
+        await host.SendAsync("/cancel abcde");
+        Assert.Equal(SchedulerSetup.DisabledReply, host.LastReply());
+        await host.SendAsync("/status");
+        Assert.DoesNotContain("Jobs:", host.LastReply());
+        Assert.Contains("Time zone:", host.LastReply());
     }
 }
diff --git a/tests/Volcanic.AgenticCore.Tests/Features/AgentLoopTests.cs b/tests/Volcanic.AgenticCore.Tests/Features/AgentLoopTests.cs
index 96398f9..cc9d359 100644
--- a/tests/Volcanic.AgenticCore.Tests/Features/AgentLoopTests.cs
+++ b/tests/Volcanic.AgenticCore.Tests/Features/AgentLoopTests.cs
@@ -142,6 +142,29 @@ public class AgentLoopTests
         Assert.Equal(["start", "steer me", "later"], session.Messages.OfType<UserMessage>().Select(m => m.Text));
     }
 
+    [Fact]
+    public async Task A_follow_up_prompt_that_loses_the_race_to_a_run_is_queued_as_a_follow_up_not_steering()
+    {
+        var gate = new TaskCompletionSource();
+        await using var host = new TestHost(null, WithTools(Echo("wait", async v => { await gate.Task; return v; })));
+        host.Faux.Enqueue(FauxTurn.Tool("wait", new { value = "x" }), FauxTurn.Say("after tool"), FauxTurn.Say("after scheduled"));
+        await using var session = await host.CreateSessionAsync();
+
+        var run = session.PromptAsync("user");
+        await WaitUntil(() => session.IsStreaming && host.Events.OfType<AgentSessionEvent.ToolExecutionStart>().Any());
+        // What PromptAsync(FollowUp) does when it saw an idle session just before the user's run took the run gate.
+        var scheduled = session.StartRunAsync(UserMessage.From("scheduled", null), null, CancellationToken.None, StreamingBehavior.FollowUp);
+        await WaitUntil(() => host.Events.OfType<AgentSessionEvent.QueueUpdate>().Any());
+        Assert.Contains(host.Events, e => e is AgentSessionEvent.QueueUpdate { Steering.Count: 0, FollowUp.Count: 1 });
+        gate.SetResult();
+        await run;
+        await scheduled;
+
+        Assert.Equal(3, host.Faux.Requests.Count);
+        Assert.IsType<ToolResultMessage>(host.Faux.Requests[1].Messages[^1]); // not steered into the user's turn
+        Assert.Equal("scheduled", host.Faux.Requests[2].Messages[^1].Text);
+    }
+
     [Fact]
     public async Task Prompt_while_streaming_without_behavior_throws()
     {