Custom primary agents rejected by Console free tier (MissingSessionID); built-in agents work

Bug: custom primary agents are rejected by the Console free tier (MissingSessionID) — built-in agents work

Environment

opencode Desktop v1.18.31 (@opencode-aidesktop) on Windows
Provider: opencode (OpenCode Zen), model opencode/big-pickle (keyless free tier)
Custom primary agent hermes (mode: primary, defined both inline in opencode.jsonc and as agent/core/hermes.md; also set as default_agent)

Symptom

Any request sent by the custom primary agent fails immediately, every time:

AI_APICallError: Error from provider (Console): OpenCode's free tier can only be used from within OpenCode

(server error type MissingSessionID — the message string is not present anywhere in the desktop client bundle, so it is produced by the Zen backend)

Evidence

From ~/.local/share/opencode/log/opencode.log, same app run, same provider/model, same session:

agent=hermes mode=primary session.id=ses_f30f79d63ffeat6eneU25KKLnI  -> stream error: "OpenCode's free tier can only be used from within OpenCode"  (2026-09-23 16:10:29)
agent=hermes mode=primary session.id=ses_f30f237edffemZw1IhNHqGeg22  -> stream error: same                                          (2026-09-23 16:16:23)
agent=build   mode=primary session.id=ses_f30f79d63ffeat6eneU25KKLnI  -> OK (repeatedly, right after the failure above)
agent=compaction mode=primary session.id=ses_f30f79d63ffeat6eneU25KKLnI -> OK
agent=coder   mode=subagent session.id=ses_f30df6c1effeq553V0i4zuKtGd -> OK (custom subagent, same model, live probe)
agent=title   mode=primary -> OK

So: built-in primary agents pass, custom primary agents always fail, and custom subagents pass. x-opencode-session is populated for the failing requests too (the client adds it at LLM run for any providerID.startsWith("opencode")).

Expected behavior

Custom primary agents should be admitted on the free tier exactly like built-in primary agents, or fail with a clear, actionable error (e.g., "custom agents require a Zen API key"), rather than the generic free-tier admission refusal.

Workaround

Using a keyed model (e.g. openai/*, google/*, or an OPENCODE_API_KEY) for the custom primary agent avoids the gate.

Reproducible on 2.0.24 with a clean A/B isolation: the only difference is whether the agent is built-in or defined in .opencode/agents/.

Environment

opencode version: 2.0.24 (service + CLI); also failed on 2.0.6 before updating
OS: Windows_NT 10.0.26200.9550 (win32 x64)
Terminal: WarpTerminal (TERM=xterm-256color), client: OpenCode Desktop 1.18.16
Shell: C:\Windows\system32\cmd.exe
Install/channel: npm (@opencode/cli), channel latest
Active plugins: none configured (built-ins only)

Reproduction

Define a custom subagent in .opencode/agents/planner.md (mode: subagent, no model field — inherits the default free-tier model).
From a working built-in primary session, spawn the built-in explore subagent with a trivial prompt → succeeds: EXPLORE OK.
Immediately spawn the custom planner subagent with a trivial prompt → fails with the error below.
Launch a custom mode: primary agent (.opencode/agents/coordinator.md) from the TUI → same error.
Updated everything first: CLI/service 2.0.6 → 2.0.24 (fresh install) and restarted the service → same failure on the new version.

Expected Behavior

Custom agents should behave like built-in agents: same auth, same model, same session → same successful response.

Actual Behavior

AI.Error.Authentication: Error from provider (Console): OpenCode's free tier can only be used from within OpenCode

Server log (repeated for every custom-agent attempt, after the 2.0.24 update):

level=ERROR message="Failed to drain Session" cause="AI.Error: Error from provider (Console):
OpenCode's free tier can only be used from within OpenCode ... [cause]: AI.Error.Authentication"

Evidence

A/B isolation: same service process (pid, v2.0.24), same session, same model, same auth — built-in explore: OK. Custom planner: free-tier error. Custom coordinator (primary, launched from TUI): free-tier error. Built-in primary session: works.
Agent frontmatter has no model override (only description, mode, permissions).
Workarounds tried: repaired broken npm CLI install (postinstall blocked by npm scripts policy), updated 2.0.18 → 2.0.24, restarted background service → still failing.
Frequency: 100% reproducible for custom agents over ~30 min (multiple attempts, 17:20–17:52 UTC).
Related: Custom primary agents rejected by Console free tier (MissingSessionID); built-in agents work #50943 (this issue), Free tier: agent=compaction and agent=title fail with "free tier can only be used from within OpenCode"; agent=build works #49592 (internal agents failing while normal requests work), Error from provider (Console): OpenCode's free tier can only be used from within OpenCode – Official macOS app #49596, Error from provider (Console): OpenCode's free tier can only be used from within OpenCode #49433.

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Custom primary agents rejected by Console free tier (MissingSessionID); built-in agents work #50943

Bug: custom primary agents are rejected by the Console free tier (MissingSessionID) — built-in agents work

Environment

Symptom

Evidence

Expected behavior

Workaround

Environment

Reproduction

Expected Behavior

Actual Behavior

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Custom primary agents rejected by Console free tier (MissingSessionID); built-in agents work #50943

Description

Bug: custom primary agents are rejected by the Console free tier (MissingSessionID) — built-in agents work

Environment

Symptom

Evidence

Expected behavior

Workaround

Activity

jpozasm14 commented on Oct 7, 2026

Environment

Reproduction

Expected Behavior

Actual Behavior

Evidence

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