Wall-clock timeout cuts off long deep-research streams

Symptom

Running market-map-profile on lost-in-public/market-maps/Humanoid Robots and their Input Industries.md produced a ~7,500-word draft that terminated mid-sentence inside the Frontier and Open Questions section:

Will the evolution of robot-as-a-service (R

The trailing parenthesis is the last byte written. The Adjacent Concepts and Maps section — the final heading in the template skeleton — never appeared. The frontmatter stamps (cf_last_run, cf_last_run_model) landed correctly, so the run did complete its processFrontMatter post-step; what was lost was the streamed body content that hadn’t yet arrived when the AbortController fired.

The Humanoid Robots run is the first observable instance of this specific cut-off shape, but the pattern is structural — it will reproduce on any sufficiently long deep-research generation run through the directory-template flow.

Diagnosis

Two different streaming primitives live in this codebase, with two different timeout disciplines:

Directory-template flow (src/services/directoryTemplateService.ts streamPerplexityToFile, the function market-map-profile and the four other shipped templates run through):

const controller = new AbortController();
const timer = activeWindow.setTimeout(() => controller.abort(), timeoutMs);

A single wall-clock setTimeout is armed at the moment of fetch. After timeoutMs elapses — regardless of whether the stream is actively producing bytes — controller.abort() fires and the in-flight reader.read() throws. The catch sets truncated = true and falls through to a final flush of whatever streamed so far. The plugin-level default was 600_000 ms (10 min) before today’s fix; analyst-grade deep-research runs routinely run 15-25 min, so the cut-off was inevitable on long templates.

Legacy modal flow (src/services/perplexityService.ts:659, PerplexityModal):

const STREAM_IDLE_TIMEOUT_MS = isDeepResearch ? 270_000 : 90_000;
const readWithIdleTimeout = (): Promise<...> => {
    let timer: number | undefined;
    const timeout = new Promise<never>((_, reject) => {
        timer = window.setTimeout(() => {
            reject(new Error(`stream went idle for ${...}s ...`));
        }, STREAM_IDLE_TIMEOUT_MS);
    });
    return Promise.race([reader.read(), timeout]).finally(() => {
        if (timer !== undefined) window.clearTimeout(timer);
    });
};

Per-chunk idle timeout. A fresh setTimeout is armed and racing each reader.read() call. As long as bytes keep arriving, the timer keeps getting cleared and re-armed. The stream is only killed if it goes quiet for 270 s (deep-research) or 90 s (normal). Total wall-clock duration is unbounded.

The legacy modal moved to this pattern because the same problem hit users there first — but the directory-template flow was forked from an earlier iteration of the streaming code and never received the idle-timeout backport. The legacy PerplexityModal and streamPerplexityToFile now disagree on how to time-bound a Perplexity stream, and the directory-template flow has the strictly weaker discipline.

What we shipped today (partial fix)

Not a structural fix — a pressure-relief valve. Two changes:

1. Bumped the plugin-level default (main.ts:333) from 600_000 ms (10 min) to 1_800_000 ms (30 min). The settings-pane description was updated to call out the override and the cost framing ($10-$50 of analyst time per good output is worth waiting for).
2. Added a per-template override — request-timeout-ms: in the cft block. Resolution code lives in directoryTemplateService.ts just before the streamPerplexityToFile call; accepts number or numeric-string, silently falls back on non-positive / non-numeric values.
3. market-map-profile.md declares request-timeout-ms: 2400000 (40 min) with an inline comment explaining the budget; the other four shipped templates inherit the plugin-level 30-min default.
4. Docs — docs/directory-templates.md gained a Per-template timeout override section with override semantics and a “when to bump” checklist; src/docs/templates/README.md calls out the key in the cft-block list.

This buys headroom. It does not fix the structural problem: any sufficiently long deep-research run will still hit the wall eventually. The 40-min cap is a guess about how long the longest reasonable market-map should take, not a property derived from the stream’s actual behavior.

Why this is only a partial fix

The wall-clock timeout fails in two distinct shapes that the idle-timeout pattern handles correctly:

Shape 1 — slow but healthy stream. Deep-research generations on long templates may sustain a slow trickle of tokens for 30-45 minutes. The wall-clock cap kills them at the ceiling regardless of whether they’re still producing. The idle-timeout pattern lets them complete naturally as long as some byte arrives every N seconds.

Shape 2 — silently stalled stream. Conversely, a stream may go quiet at minute 3 (Perplexity rate-limit, socket close, upstream stall) and the wall-clock cap won’t notice until minute 30. The user stares at an empty file, watching the spinner spin, for 27 unnecessary minutes. The idle-timeout pattern surfaces the failure within STREAM_IDLE_TIMEOUT_MS seconds — fast feedback when something is genuinely wrong.

Both shapes are real. The wall-clock pattern punishes the healthy-but-slow case while tolerating the stalled-but-silent case. The idle-timeout pattern inverts both — slow-but-healthy completes; stalled-but-silent fails fast.

Proposed structural fix

Port the idle-timeout pattern from perplexityService.ts:659-668 into streamPerplexityToFile. Concretely:

1. Replace the single wall-clock setTimeout(controller.abort, timeoutMs) with a per-chunk readWithIdleTimeout() that wraps each reader.read() in a Promise.race against a fresh timeout.
2. Choose idle-timeout values consistent with the existing modal flow: 270_000 ms (4.5 min) for deep-research models, 90_000 ms (1.5 min) for normal models. Detect deep-research from the resolved model name string (/deep-research/i), the same way perplexityService.ts does.
3. Retain the cft-block override key, but rename it to stream-idle-timeout-ms: for accuracy. Templates that have been declaring request-timeout-ms: need a compatibility alias for one release; document the rename in the changelog entry.
4. Optionally retain a generous absolute wall-clock ceiling (60 min or 120 min) as a sanity backstop — but that’s belt-and-suspenders, not load-bearing. The idle timeout is doing the actual safety work.

The diff is moderate — streamPerplexityToFile is ~140 lines today; the refactor touches roughly the first 40 of those (the timer setup and the reader.read() call inside the loop). The post-stream cleanup pipeline (wrapThinkBlocks, processContentWithImages, buildSourcesFooter) is unaffected.

Resolution (2026-05-26)

The structural fix shipped the same day as the issue was filed. See changelog/2026-05-26_02.md for the full ship note.

What landed:

• The port itself. streamPerplexityToFile now wraps each reader.read() in a readWithIdleTimeout() race, ported from perplexityService.ts:659-668. Signature changed from timeoutMs: number to timeouts: { idleMs: number; ceilingMs: number }. AbortController retained for cancel + ceiling.
• Dual-key naming decision. Kept request-timeout-ms: as the legacy key (now semantically the absolute wall-clock ceiling) and added stream-idle-timeout-ms: as the new key (the per-chunk idle timer, primary safety). No rename, no compatibility alias needed — existing template values for request-timeout-ms: still work and now mean exactly what their name suggests.
• Ceiling-vs-idle defaults. Idle defaults match the legacy modal flow: 270s for deep-research models (/deep-research/i on resolved model name), 90s otherwise. Ceiling defaults to settings.requestTimeoutMs (30 min); explicit 0 in either settings or cft disables the ceiling entirely.

Deferred (now their own follow-ups, not blocking):

• Cross-service audit. The same wall-clock pathology may live in the Gemini service, the LM Studio service, and the Claude streaming flows. The idle-timeout discipline should be the house style across all of them. Track as its own issue.
• Settings-pane exposure of idle defaults. Today the 270s/90s values are hardcoded in streamPerplexityToFile (matching perplexityService.ts). Exposing them as plugin settings is a follow-up if we ever need to tune them without a code change.
• Robustness of deep-research detection. /deep-research/i against the resolved model name is the current heuristic — same as perplexityService.ts. Revisit if Perplexity ever ships a long-running model under a different naming convention.

Related

• [[market-map-profile]] — the template that surfaced the bug
• [[Multi-Stage-Cooperative-Claude-and-Perplexity-with-RAG]] — the broader exploration this issue feeds findings back into; the idle-timeout refactor is listed there as an open item
• [[Partials-And-Preambles-For-Perplexed-Templates]] — the architecture-review structure of that issue is the precedent this one follows
• src/services/perplexityService.ts lines 659-668 — the idle-timeout implementation in the legacy modal flow that we’re proposing to port
• src/services/directoryTemplateService.ts streamPerplexityToFile lines 499-635 — the wall-clock implementation in the directory-template flow that the port replaces